Yt\A t t .

SELECTIVITY FAILURE IN THE CHEMICAL VAPOR DEPOSITION OF

TUNGSTEN

DISSERTATION

Presented to the Graduate Council of the

University of North Texas in Partial

Fulfillment of the Requirements

For the Degree of

DOCTOR OF PHILOSOPHY

By

Roger W. Cheek, B.S.

Denton, Texas

August, 1994

Yt\A t t .

SELECTIVITY FAILURE IN THE CHEMICAL VAPOR DEPOSITION OF

TUNGSTEN

DISSERTATION

Presented to the Graduate Council of the

University of North Texas in Partial

Fulfillment of the Requirements

For the Degree of

DOCTOR OF PHILOSOPHY

By

Roger W. Cheek, B.S.

Denton, Texas

August, 1994

Cheek, Roger, Selectivity Failure in the Chemical Vapor Deposition of Tungsten.

Doctor of Philosophy (Analytical Chemistry), August, 1994, 114 pp., 1 table, 25 figures,

bibliography, 115 titles.

Tungsten metal is used as an electrical conductor in many modern microelectronic

devices. One of the primary motivations for its use is that it can be deposited in thin films

by chemical vapor deposition (CVD). CVD is a process whereby a thin film is deposited

on a solid substrate by the reaction of a gas-phase molecular precursor. In the case of

tungsten chemical vapor deposition (W-CVD) this precursor is commonly tungsten

hexafluoride (WFg) which reacts with an appropriate reductant to yield metallic tungsten.

A useful characteristic of the W-CVD chemical reactions is that while they proceed rapidly

on silicon or metal substrates, they are inhibited on insulating substrates, such as silicon

dioxide (Si02). This selectivity may be exploited in the manufacture of microelectronic

devices, resulting in the formation of horizontal contacts and vertical vias by a self-aligning

process. However, reaction parameters must be rigorously controlled, and even then

tungsten nuclei may form on neighboring oxide surfaces after a short incubation time.

Such nuclei can easily cause a short circuit or other defect and thereby render the device

inoperable. If this loss of selectivity could be controlled in the practical applications of

W-CVD, thereby allowing the incorporation of this technique into production, the cost of

manufacturing microchips could be lowered.

This research was designed to investigate the loss of selectivity for W-CVD in an

attempt to understand the processes which lead to its occurrence. The effects of

passivating the oxide surface with methanol against the formation of tungsten nuclei were

studied. It was found that the methanol dissociates at oxide surface defect sites and blocks

such sites from becoming tungsten nucleation sites. The effect of reactant partial pressure

ratio on selectivity was also studied. It was found that as the reactant partial pressures are

varied there are significant changes in the product partial pressure ratios, which are

associated with gas phase reactions which contribute to the loss of selectivity.

TABLE OF CONTENTS

Page

LIST OF FIGURES v

Chapter

I. INTRODUCTION 1

Microelectronics Applications of Tungsten 1

Tungsten CVD Chemistry 5

Reduction of WF6 by Si 7

Reduction of WF6 by H2 8 Reduction of WF6 by SiEfy 10 Other Reductants 11

Selective Deposition of Tungsten 11

Loss of Selectivity Mechanism 12

Foreign Material 12

Volatile Reaction Products 13

Gas Phase Nucleation 14

Ultra-High Vacuum Techniques 15

Auger Electron Spectroscopy 16

Mass Spectrometry 18

Temperature Programmed Desorption 20

Micro-Volume Mass Spectrometry 20

Chapter References 23

111

II. METHANOL INTERACTIONS WITH SI02 SURFACES 34

Introduction 34

Experimental 35

Results 40

Summary and Conclusions 44

Chapter References 47

III. IN SITU MASS SPECTROMETRY OF A COMMERCIAL TUNGSTEN

CHEMICAL VAPOR DEPOSITION REACTOR 48

Introduction 48

Experimental 49

A model of the sampling capillary 51

Results and Discussion 55

Conclusions 65

Chapter References 67

APPENDIX 69

BIBLIOGRAPHY 105

IV

LIST OF FIGURES

Figure 1. Schematic for using blanket and selective tungsten CVD for metallizing trenches

and vias in a silicon based microelectronic device 2

Figure 2. Schematic of 'step coverage' for a CVD thin film over a high aspect ratio structure 3

Figure 3. Schematic of the Auger process. K, L, and M are the core electron energy levels

for the atom 17

Figure 4. Quadrupole mass filter 18

Figure 5. Schematic of a differentially pumped mass spectrometer attached to a

high pressure chamber 22

Figure 6. Ultra high vacuum chamber for TPD studies 36

Figure 7. Apparatus for dosing a sample in UHV with a controlled amount of gas 37

Figure 8. Auger spectrograph of SiC>2 sample after Ar+ ion sputtering to remove

foriegn material 38

Figure 9. Auger spectrograph of the same SiC>2 sample as in figure 8 after an oxygen anneal 39

Figure 10. TPD spectra (normalized) of methanol from a lightly sputtered SiC>2 surface 41

Figure 11. Mass spectrum of methanol in the UHV chamber at 1 x 1(H* torr 42

Figure 12. TPD spectra of CH4 desorption from an Ar+ sputtered and methanol dosed Si02 surface 43

Figure 13. TPD spectrum of CH4 desorption from a methanol dosed unsputtered

SiC>2 surface 44

Figure 14. Auger spectrograph showing W on SiC>2 after the TPD experiments 45

Figure 15. TPD spectra of WF5+ (characteristic of WFg) from a WFg dosed SiC>2 surface 46

Figure 16. Schematic diagram of the experimental setup used to investigate the reactions in a commercial tungsten CVD reactor 50

Figure 17. Schematic diagram of the capillary sampling system and the differentially pumped mass spectrometer 51

Figure 18. Pressure at the mass spectrometer as a function of the pressure in the CVD chamber for argon 54

Figure 19. Plot of the mass spectrometer response for the CVD reactants, WFg and S1H4,

versus the SiFfy/WFg inlet flow ratio 56

Figure 20. Plot of the mass spectrometer response for four of the mass fractions of SiF4 57

Figure 21. Plot of the mass spectrometer response for four of the mass fractions of SiHF3 59

Figure 22. Mass spectrometer signals as the Siffy/WFg inlet flow ratio is stepped from a selective regime (0.25) to a non-selective regime (3.0) 60

Figure 23. Adding a large amount of Ar to the reaction mixture of Figure 22 decreases the magnitude and location of the maximum signal divergence for the mass 85 and 67 signals 62

Figure 24. SiHF2+/SiF3+ ratios from Figure 22 (low Ar partial pressure) and Figure 23 (high Ar partial pressure) 64

Figure 25. Thermodiffusion results in the depletion of WF6 relative to Ar near a heated surface in the CVD chamber 66

VI

CHAPTER I

INTRODUCTION

Tungsten metal is used as an electrical conductor in many modern microelectronic

devices. One of the primary motivations for its use is that it can be deposited in thin films

by chemical vapor deposition (CVD). This deposition may occur selectively when the

reaction parameters are such that tungsten is deposited only on certain types of surfaces,

usually conducting or semiconducting, to the exclusion of other surfaces, usually

insulating. For selective deposition to be successful then, tungsten must deposit rapidly on

one surface and not at all on a nearby different surface, even though both surfaces are

located in the same reaction environment. This study focused on the chemical reactions

and processes which lead to selectivity failure in tungsten chemical vapor deposition (W-

CVD).

Microelectronics Applications of Tungsten

CVD tungsten (blanket or selective) has many applications in the construction of

silicon based microelectronic devices. There are two main reasons for this usefulness.

First, it is a good electrical conductor, having a bulk resistivity of 5.39 |iQ-cm (7). The

resistivity of thin film CVD tungsten is not generally as low as bulk tungsten since the

CVD process can cause the incorporation of impurities (e.g., silicon or fluorine) and other

defects into the growing tungsten (2-4). This results in electrical resistivities which are at

best approximately 9 n£2-cm (5). This resistivity makes tungsten adequate for many

metallization applications in microelectronics, such as diffusion barriers, via fills, and some

interconnects.

The second reason for CVD tungsten's usefulness is that since deposition is by

heterogeneous reaction of a gas-phase precursor (usually WFg) at a surface, the resulting

thin film can be conformal with any physical structures present in the substrate (6,7). In

microelectronic devices these structures take the form of trenches or vias which may have

lateral dimensions much less than one micron. This deposition may proceed in either a

I -

Dielectric layer with etched grooves and vias

Blanket tungsten CVD

Selective tungsten CVD

Etchback of tungsten

Si or Metal

Figure 1. Schematic for using blanket and selective tungsten CVD for metallizing trenches and vias in a silicon based microelectronic device.

'blanket' mode, with all surfaces receiving a tungsten film, or a 'selective' mode, with

tungsten deposition occurring only on regions of metal or semiconductor, but not on

adjacent insulating surfaces. When blanket deposition is used, it must be followed by a

lithographic etchback step which patterns the metal into useful structures (Figure 1) (8-

10). Selective deposition obviates this lithographic etchback step. The microelectronic

applications of metal CVD in general and tungsten CVD in particular (both selective and

blanket) have been discussed by many authors (11-25).

There are several reasons that tungsten is of interest relative to more conductive

metals such as copper or aluminum (Table 1). First of all, copper and aluminum suffer

from the lack of a reliable CVD technique. These materials can be physically deposited

(sputtered or evaporated) very effectively on low aspect ratio surfaces (where vertical

dimensions are much smaller than horizontal dimensions) (26-28). Unfortunately, ever

shrinking device geometries require that the metal be deposited in trenches or vias with

high aspect ratios. It is difficult to physically deposit films on such structures and maintain

good conformality, or 'step coverage', which for blanket deposition may be defined as the

ratio of the deposited film thickness on the structure sidewall to the film thickness on the

top surface (Figure 2) (29). CVD techniques are far superior to physical deposition

a. b.

Figure 2. Schematic of 'step coverage' for a CVD thin film over a high aspect ratio structure. Step coverage is defined as the ratio of the deposit thickness on the feature sidewall to the thickness on the top surface, a. Step coverage = 1, b. step coverage < 1.

Metal

Property Cu A1 W Si

Coefficient of linear expansion at 25°C

x lO^nCC) - 1 (37)

16.5 23.1 4.5 4.68

Melting Point (°C) (37) 1085 660 3422 1412

Resistivity at 25°C (|iQ-cm) (38) 1.71 2.71 5.39

Table 1. Properties of some metals important to silicon based microelectronics compared to silicon.

techniques for obtaining good step coverages (21). Recent advances have been made in

the CVD of both A1 (30-34) and Cu (35,36), but CVD-W remains a more mature

technology.

The refractory nature of tungsten is another of its advantages over aluminum or

copper (Table 1). Its high melting point means that once a tungsten film or structure is

deposited, it is not likely to be affected by later processing steps which may occur at high

temperatures. The melting point of aluminum and copper are 660°C and 1085°C,

respectively (Table 1) (37), and the temperature at which device structure and

performance are adversely affected is much lower than the melting point. For instance,

once an aluminum layer is added to a device, subsequent process steps which occur at

temperatures greater than approximately 350°C may adversely affect the structure of the

aluminum layer. Tungsten, on the other hand, has a melting point of 3422°C (37), far

above the temperature range required for any potential subsequent process step.

The thermal expansion coefficient of tungsten is very near that of silicon (Table 1)

(37). This is an advantage for reducing film stress where tungsten is deposited on silicon.

The thermal expansion coefficients of copper and aluminum are less closely matched to

silicon (Table 1) (37). This may cause deposited films of these metals to peel away from

the substrate, or may cause stress induced void formation in metal lines {39,40).

Tungsten's electromigration resistance is superior to both aluminum and copper

(41). Electromigration is electronic-current induced atomic diffusion, which results from

the transfer of momentum from electrons to the atoms of the conductor. The result is

movement of the conductive material in the direction of the electron transport, which can

cause a break in the metal line at the cathode end and an accumulation of metal at the

anode end (40). This is important in microelectronic devices where the current density can

be as high as 4 x 10^ A/cnP-, which compares to 100 A/cm^ as the maximum allowed for

house wiring (42). Aluminum suffers from very poor resistance to electromigration

(31,32), while copper has a four orders of magnitude better resistance to electromigration

(41,43), and tungsten suffers virtually no electromigration for the currents ordinarily

encountered in microelectronic devices (41).

Tungsten is also highly inert toward SiC>2, and forms a stable interface with silicon.

Aluminum is known to react chemically with silicon, causing what is commonly referred to

as "spiking" (18,31), that is, long slender "spikes" of aluminum protruding into the

substrate. Copper has a high diffusion coefficient in both silicon and SiC>2 (36). Both of

these effects can sometimes be overcome by using diffusion barriers such as titanium

nitride, tungsten silicide, or Ti-W intermetallic (36,44). Tungsten does not diffuse through

or chemically react with silicon or SiC>2 enough to have a significantly adverse affect on

semiconductor device performance, as long as deposition is carried out under proper

processing conditions.

Tungsten CVD Chemistry

Tungsten deposition for microelectronics is normally carried out by the reduction

of tungsten hexafluoride (WFg) by silicon (Si), hydrogen (H2), or silane (Silfy). These

reductants may be used either individually or in some combination. Many other reductants

have also been investigated by various workers {45-47). However, largely for historical

and process integration reasons, these three remain the most widely used and researched

reactions. For the silicon reduction of WFg two reactions have been identified, producing

SiF4 and SiF2 (J1,14,48-50):

2WF6(g) + 3Si(s) -» 2W(s) + 3SiF4 (g) (1)

WF6(g) + 3Si(s) —> W(s) + 3SiF2(g) (2)

The hydrogen reduction is given by (51-54):

WF6(g) + 3H2(g) -> W(s) + 6HF(g) ^

The principal reactions for the silane reduction are (50,55-58):

4WFfi(g) + 3SiH4(g) -> 4W(s) + 3SiF4(g) + 12HF (4)

2WF6(g) + 3SiH4(g) -> 2W(s) + 3SiF4(g) +3H2 (5)

WF6(g) + 2SiH4(g) -> W(s) + 2SiHF3(g) + 3H2 (6)

All of these reactions have WFg as a gas-phase molecular precursor (source of tungsten)

which reacts heterogeneously at an appropriate surface to yield metallic tungsten. The fact

that these reactions are surface catalyzed is the primary reason for their ability to deposit

tungsten films selectively. That is, they proceed rapidly on some surfaces and slowly or

not at all on other surfaces. In order for the deposition to proceed, the substrate must be

capable of either reducing WFg to metallic W, or dissociatively adsorbing WFg and H2

and/or S1H4, Most oxides, including SiC>2, do not readily support these processes (59).

Silicon, however, can reduce WFg directly, and tungsten (and many other conducting and

semiconducting surfaces) supports the necessary dissociation (60). Therefore, the

deposition which results from the above stated chemical reactions are selective for

surfaces of silicon and tungsten versus surfaces of Si02 or other insulators.

Reduction of WFg bv Si

The elementary surface chemical reactions involved in the Si reduction of WF5

have been investigated by Jackman and Foord (61), and others (49,62-64). They found

that when WFg is adsorbed on silicon below 120 K the molecule remains intact (non-

dissociative adsorption). However, at room temperature and above the WF5 adsorbs

dissociatively on surfaces of both Si(100) (55) and Si( l l l ) (62). High-resolution

photoemission experiments (62) demonstrated that WFg adsorption on Si(l 11) at room

temperature results in complete dissociation of the WFg into metallic tungsten and a range

of fluorosilyl compounds SiFx (x=l,2,3). The behavior of WFg on Si(100) is reported to

be quantitatively similar (49). At room temperature, the reaction proceeds no further. The

surface is saturated with tungsten and fluorine species which prevent further dissociative

adsorption of WFg. If the temperature is elevated, however, the deposition of tungsten

may continue by the removal of the SiFx species as volatile reaction products. Yu et al.

(49) used mass spectrometry to identify the reaction products from the silicon reduction

reaction. They found that SLF4 is the principal product (reaction 1) when the reaction

temperature is below approximately 450°C. S1F2 was found to be the principal product

(reaction 2) when the reaction temperature was between approximately 450°C and 700°C.

By removal of these volatile fluorinated species from the surface, the deposition of

tungsten may continue, at least until a monolayer of tungsten is deposited. The silicon

reduction reaction would be expected to become "self-limited" at this point, as the

reductant (silicon) has been physically isolated from the oxidant (WFg). This is not what is

observed. This reaction has been found to become self-limited only after at least 100A to

200A of tungsten has been deposited (25). YarmofF and McFeely (62), and Yu et al. (49)

have identified silicon from the substrate at the surface of the growing tungsten film. This

indicates that silicon from the substrate is diffusing to the surface of the tungsten film

where it can react by the mechanism just described. This diffusion is attenuated as the

tungsten film grows thicker, thus stopping the reaction at the characteristic self-limited

thickness.

The silicon reduction is useful for microelectronics only for tungsten films less than

about 200A thick. One reason is the self-limiting nature just described, but more

importantly, the reaction consumes the silicon substrate. The stoichiometry of reaction 1

indicates that 1.9A of silicon should be consumed for each lA of tungsten deposited (65).

This correlates well to the observation that the ratio of silicon depth consumed to tungsten

thickness deposited is approximately 2:1 (65). This means that tungsten deposition of

more than approximately 200A results in silicon consumption that is near the dimensions

of the active regions in a modern semiconducting device (66). This results in damage to

the device by consuming the silicon substrate which contains the active regions. For

tungsten deposition of greater than a few tens of angstroms thick, another reductant must

be introduced. This is the topic of the next two sections.

Reduction of WF5 by Fb

For tungsten films thicker than approximately 200A, a reductant other than the

silicon substrate must be employed. Hydrogen can act as the reductant on tungsten

surfaces (67). The role of hydrogen on the tungsten surface is qualitatively similar to that

of silicon which has segregated at the surface from the substrate. Whereas in the silicon

reduction, silicon atoms on the tungsten surface react with fluorine from dissociated WFg

to produce SiFx species, in the hydrogen reduction, dissociated hydrogen atoms react with

the fluorine to produce HF (reaction 3) (25):

H2 (g) + 2* <-» 2H(a) (7)

WF6(g) + 6* O W(s) + 6F(a) (8)

F(a) + H(a) —> HF(g) + 2* (9)

where * indicates an empty surface site.

While the hydrogen reduction reaction allows tungsten films on the order of 1 |im

in thickness to be deposited, the effect on the silicon substrate is still problematic. Stacy et

al. (65) and others (69-7J) used scanning electron microscopy to observe the tungsten

films formed from the hydrogen reduction reaction on patterned Si/SiC>2 wafers. They

found that there is significant consumption of the silicon substrate, as well as lateral

encroachment of the tungsten into silicon which is under SiC>2 regions adjacent to growing

tungsten films. Tunnels or "wormholes" with diameters ranging from 20 to 40 nm were

also observed which, in extreme cases, penetrated 1 jum into the silicon substrate. At the

end of each of these tunnels they found a tungsten particle with a diameter approximately

equal to the tunnel diameter. Clearly, such destruction of the structure of the silicon

substrate severely limits the usefulness of this reaction for use in microelectronics.

Apparently, the silicon reduction reaction proceeds quickly relative to the hydrogen

reduction reaction, resulting in the same level of silicon substrate consumption whether

silicon or hydrogen is used as the reductant. Therefore, even though hydrogen reduction

overcomes the self-limiting thickness nature of the silicon reduction reaction, consumption

of the substrate remains a problem.

Despite the problem of substrate damage, much work has been done on the

hydrogen reduction reaction as regards its selectivity. The surface mediated reactions 7

and 8 are not readily supported on oxide surfaces (25) which is presumably the reason that

selective deposition is possible. The mechanism by which selectivity is lost will be

discussed in detail below.

10

Reduction of WFg bv SifiLf

An important and widely researched alternative to hydrogen as a reductant for

tungsten deposition from WFg is silane (SiFfy). Silane is known to undergo complete

dissociative adsorption on clean tungsten surfaces (72,73). The hydrogen atoms on the

surface which result from this dissociative adsorption are readily displaced by silicon

atoms during large silane exposures (72). In this way silane provides a continuous source

of silicon atoms on the tungsten surface. The fluorine which is on the surface as a result of

WFg dissociation (reaction 8) can then react with the silicon to form volatile silicon

fluorides (SiFx), as in the silicon reduction discussed above. The hydrogen atom from the

dissociative adsorption of silane may leave the surface as either H2 or HF, with fluorine

coming from WFg dissociation (reaction 8). Clearly the situation on the tungsten surface is

very complex, and which particular reaction pathways are important is a result of a

dynamic equilibrium which is reached between the adsorption of precursor molecules,

their competitive dissociation, the reaction and interactions of the dissociation products on

the surface, and the subsequent evolution of volatile reaction products. Empirical studies

of the reaction products by mass spectrometry (4,50,55,56,74,75) and Fourier transform

infrared spectroscopy (2,57,58,76-78) have identified H2, SiF4, and SiHF3 as the principal

reaction products. HF was observed to be present in the reaction product mixture only in

small amounts, if at all. This indicates that reactions 5 and 6 above are the likely reaction

pathways for the silane reduction process on tungsten surfaces.

The silane reduction process does not cause damage to the silicon substrate such

as is observed by the hydrogen reduction (74). The silane process does exhibit the

selectivity which is observed for the hydrogen reduction, and it yields a much higher rate

of deposition (79-81). For these reasons the silane reduction of WFg has become the most

widely used process for the chemical vapor deposition of tungsten for microelectronics

11

manufacture. The mechanism by which this process losses selectivity is a central focus of

the present work and will be discussed in detail below.

Other Reductants

Several other reductants have been investigated for CVD of tungsten from WFg.

Germane (Geffy) (46), digermane (Ge2Hg) (82), polysilane (Si2Hg and Si3Hg), diborane

(BiHg), and phosphine (PH3) (45), and dichlorosilane (83) have been studied and

compared to silane as a reductant for WFg. While some of these reductants are reported

to slightly improve on one or more of the characteristics of the silane reduction process,

there has been no impetus to abandon this well characterized and widely employed

process.

Selective Deposition of Tungsten

The selective nature of the CVD-W process has received much interest because of

the potential benefits that selectivity holds for microelectronics (Figure 1) (25). The vast

majority of process steps used in making a microelectronic device are intended to result in

the formation of some form of patterned structure, either within or on top of the silicon

substrate. In broad terms, these structures may be in the form of regions in the silicon with

an excess electron donor (e.g. phosphorus or arsenic) or acceptor (e.g. boron or

aluminum) concentration, or regions which are electrically insulating or conducting. It is

the ability to make these structures in an extremely controlled way for patterns which have

minimum dimensions of much less that one micrometer that has resulted in the so called

'computer revolution' of recent decades (84,85). However, most processes which produce

these regions of varying electrical characteristics do not do so in an area selective manner,

and so do not inherently result in the required patterns. For instance, common

metallization techniques, whether chemical or physical in nature, deposit the metal in a

blanket, or non-selective, fashion. This means that additional process steps are required to

12

produce the required patterns. These additional steps may take the form of etchback as in

Figure 1, or photolithography (86-87). These techniques, while quite reliable, introduce

several process steps to the procedure. Since each added process step has the potential to

introduce errors or defects, and add to the cost of the device, it is desirable to eliminate as

many such steps as possible. Processes which are 'self-aligning' (i.e. area selective) do not

require the etchback or photolithographic steps, and as such are desirable.

Despite the advantages that selective tungsten deposition holds over non-selective

techniques, it has not been widely used in the industrial manufacture of microelectronic

devices. The reason for this is that selectivity is not easily maintained under production

conditions. Selectivity is said to be lost when tungsten is deposited not only on the desired

metal or semiconductor, but on a nearby dielectric material (usually Si(>2). This loss of

selectivity can result in an electrical short circuit or other defect in a microelectronic

device, rendering the device useless. The cause of this loss of selectivity is the subject of

the present work.

Loss of Selectivity Mechanism

Loss of selectivity (i.e., tungsten deposition on SiC>2) can proceed via three routes.

The first is a result of foreign material on the oxide acting as a nucleation site for tungsten

film growth by direct reduction of WFg. The second is the adsorption and

d ispropor t iona te of volatile tungsten containing reaction products on the oxide. The

third is gas phase nucleation of particulates, during the silane reduction process, which fall

on the oxide.

Foreign Material

The physical cleanliness of the oxide surface has a profound effect on selectivity.

The presence of organic residues such as photoresist and bacteria have been shown to act

as nucleation sites for tungsten deposition from WFg (88,89). However, since the surfaces

13

(wafers) that are used in the selective W-CVD are generally handled in clean room

environments, this physical contamination does not pose a serious problem for loss of

selectivity under production conditions.

Volatile Reaction Products

When tungsten is observed to deposit on SiC>2 during the hydrogen reduction

process, the source of tungsten is apparently not WFg but a volatile product of the

reaction of WFg with nearby tungsten or other metal. (WF6 itself is apparently inert on

high quality Si(>2 surfaces at temperatures up to 400 °C (90,91)). The most important

observation which leads to this conclusion is the existence of a proximity effect for loss of

selectivity nucleation. It has been observed by many workers (91-95) that the number of

tungsten nuclei (loss of selectivity nuclei) on an oxide surface decreases exponentially with

distance from a tungsten surface. This phenomenon has been observed even for regions of

tungsten and oxide which are not contiguous, that is, on separate but nearby wafers.

Creighton (96-100) has identified tungsten subfluorides ~ probably WF5 ~ as a volatile

reaction product of the hydrogen reduction reaction which can diffuse through the gas

phase to SiC>2 surfaces and dissociate there, yielding metallic tungsten.

The tungsten subfluoride mechanism for loss of selectivity is intrinsic to the

tungsten CVD process, and as such, can be expected to eventually cause loss of selectivity

whenever WFg is used as the source of tungsten. That selectivity is attainable at all is

apparently due to the differing initial tungsten nucleation rates on silicon or tungsten

relative to SiC>2. There is an initial incubation period on the oxide before loss of selectivity

begins, during which time the deposition proceeds rapidly on the metal surface. This

incubation time before loss of selectivity sets in varies with the condition and genesis of

the oxide surface. It is a function of processing parameters (2,79) and the nature of the

oxide surface (101,102). Some workers have attempted to achieve high degrees of

14

selectivity by repeatedly alternating between tungsten deposition and tungsten etch steps

(103,104), which act to etch the loss of selectivity nuclei and remove them before they

become too large or numerous.

The mechanism for the loss of selectivity for the silane reduction process has not

been investigated to the extent that the hydrogen reduction process has. The silane process

may be affected by the presence of volatile tungsten subfluorides, as in the hydrogen

reduction process. This assumes, however that the surface chemistry is substantially the

same for the two processes. At this time, there is no empirical evidence to support this

assumption. Indeed, silicon subfluorides are products of the silane reduction (50,58,75)

and may be more detrimental for selectivity than tungsten subfluorides (102). The silane

process also can result in gas phase nucleation under some conditions, as will be discussed

in the next section.

Gas Phase Nucleation

A few workers have reported results which indicate that gas phase reactions occur

for the silane reduction process for certain reactant ratios (75,76,105,106). Nakamura et

al. (76), observed that for inlet flow ratios (SiFfy/WFg) in the range of 1.3 to 2.5 visible

luminescence was observed around the gas inlet to the reaction chamber. They further

observed the presence of tungsten powders on the walls of the chamber following the

deposition experiments. These powders were analyzed by x-ray diffraction and scanning

electron microscopy and were found to be polycrystalline (3-phase tungsten. No such

luminescence or particles were observed when the inlet flow ratio was less that 1.3 SCCM

(standard cubic centimeters per second). Mclnerney et al. (106), performed a similar

experiment but used a particle counter on the exhaust port of their chamber as a detector.

They observed the production of particles as the inlet flow ratio became greater than one.

Cheek et al. (75), used mass spectrometry to observe significant changes in the volatile

15

product distribution when the inlet flow ratio was less than one, compared to inlet flow

ratios between 1.2 and 3.0. Many other workers have observed a correlation between the

inlet flow ratio and the selectivity of the process (80,107), with selectivity being lost as the

inlet flow ration becomes greater than approximately 1.0. Kobayashi et al. (58), have

proposed the following homogeneous (gas-phase) reaction:

WF6(g) + 6SiHF3(g) -> W(s) + 6SiF4(g) + 3H2(g) (10)

which can account for the observed phenomena.

The gas-phase production of tungsten particles during the silane reduction process

is a major factor for the loss of selectivity when the inlet flow ratio is greater than

approximately one. The particles are able to land on any surface and, if the temperature is

appropriately high, act as a nucleation site for loss of selectivity.

Ultra-High Vacuum Techniques

Several analytical techniques were used in this study to investigate the phenomena

which lead to loss of selectivity for the tungsten CVD process. As in many surface science

investigations, the techniques are used alone or in various combinations to yield

information about the process in question. Several of the techniques are carried out in

ultra-high vacuum. This is done to prevent contamination of the surface under

investigation by contact with atmospheric gasses or other impurities. The ultra-high

vacuum environment is somewhat analogous to an ultra clean and inert solvent that might

be used in standard "wet" chemistry. UHV is roughly defined as the pressure region from

1q-9 Torr to 10"12 Torr (10"^ Pa to 10"^ Pa) (108). Surface science experiments are

frequently carried out in this pressure range because the rate of collision of gas phase

molecules with surface sites is low enough to allow a surface which has been cleaned in

UHV to remain clean long enough to complete most experiments. Assuming a pressure of

16

7.5 x 10~10 Torr of air at room temperature, it takes approximately 43 minutes for each

surface site to be impacted at least once by a gas phase species. If each impacting

molecule sticks, this is how long it would take to form one monolayer on the surface of

the solid—the so-called "monolayer formation time" (J 09). In practice, it is rare that each

impact results in a new surface species, and pressures are commonly near 2 x 1 0 " ^ Torr.

This means that actual monolayer formation times may be many times longer than the 43

minutes stated above.

Auger Electron Spectroscopy

Auger electron spectroscopy provides elemental analysis of the surface region of a

solid. This is accomplished by directing an electron beam of appropriate energy onto the

surface and analyzing the kinetic energy spectrum of the secondary electrons which are

emitted. This spectrum contains peaks whose position and intensity identify the elements

present in the near surface region of the sample. The Auger process begins when an atom

is ionized by an incident electron, resulting in a core level vacancy. The atom then relaxes

by an electron transition from an outer (lower energy) level. The energy of this transition

may then be released by either photon emission or by ejection of another electron. This

latter electron is called an Auger electron (Figure 3). The kinetic energy of the Auger

electron shown in Figure 3 is given by (110)

E = F - F - F*

Where E*^ is the binding energy for the s level in the presence of a core hole. Each

element has a few characteristic Auger transitions, resulting in electron energy spectra

with peaks at locations and intensities that uniquely identify the element from which the

Auger electron originated. Since Auger peaks are small peaks on a rapidly varying

secondary electron background, it is common to record spectra in a differential mode,

17

dN(E)/dE vs. E. This can be accomplished by analog or digital methods(7/7). Auger

spectra have been carefully studied and examples compiled in reference volumes which are

used to qualitatively determine the elemental composition of a sample {111).

The Auger process is surface sensitive because only electrons which originate near

the surface are likely to escape the solid matrix without losing some kinetic energy to

interactions with the matrix. Loss of energy in this way results in the loss of the

information which leads to elemental identification. Depending on the material, this

"escape depth" is in the range 2-10 atomic layers (112). Auger spectroscopy was used in

this study to verify the elemental composition and cleanliness of the Si and Si02 surfaces

under study.

VAC

E f

M

1-2,3

Li

K

Auger Electron

Initial State Core vacancy resulting from

incident electron

-•—o-

- • — • -

Emission of an Auger electron

Final State

Figure 3. Schematic of the Auger process. K, L, and M are the core electron energy levels for the atom. Ef is the fermi level for the solid, and VAC is the vacuum level where the electrons are removed from the influence of the solid.

18

Mass Spectrometry

Mass spectrometry is an analytical technique which measures the mass to charge

ratio (m/Z) for gas phase analyte species {113). In general, these devices work by ionizing

incoming gas phase species and then electrostatically accelerating them into an area that

performs mass separation, usually by magnetic or electrostatic means. The analyte species,

which may become fragmented by the ionization process, are then detected, usually by

either a Faraday cup or an electron multiplier. There are several design options for each

step of this process—ionization, filtering, and detection. Each option has characteristics

which may be used to optimize the process for a specific application. The mass

spectrometer used in some of the experiments for this study is commonly referred to as a

quadrupole type. The term "quadrupole" actually refers to the mass separation part of the

device. However, since it is nearly always combined with an electron impact ionizer and a

Faraday cup—electron multiplier detector, the single term is usually used to describe the

whole apparatus. In the semiconductor industry this type of mass spectrometer

arrangement is frequently referred to as a "residual gas analyzer" or RGA.

The mass spectrometric process used in the current study begins with electron

impact ionization of the analyte species. This is accomplished using a tungsten filament as

a source of electrons. These electrons are electrostatically accelerated and directed into a

region containing the gas phase analyte species. Some of the electrons impact some of the

analyte species and strip off one or more of their electrons, creating positive ions. These

0 - ) ->

Species in —. from ionizer E x i t t o D e t e c t o r

Figure 4. Quadrupole mass filter.

19

positive ions are electrostatically accelerated and focused into the quadrupole region

which performs the mass separation. The quadrupole mass filter consists of four

cylindrical rods, arranged with their long axes parallel, as shown in Figure 4. Two

opposite rods have a positive direct current potential (dc) applied to them while the other

two rods have a negative dc current applied. Superposed on these dc potentials is a radio

frequency (RF) signal which sets up an electric field in-between the quadrupoles which

varies in time. This field causes ionic species moving along between the quadrupoles to be

jostled back and forth. For a given dc potential and RF value, only particles with a small

range of masses has a stable trajectory from the inlet to the exit of the quadrupole.

Particles with other masses are collected by one of the poles. By changing the dc potential

and RF values, the mass for which a stable trajectory is possible can be changed as a linear

function of time. The species surviving to the exit of the quadrupole are detected by a

combination Faraday cup—electron multiplier detector. A computer controls the

potentials on the quadrupoles and receives the signal from the detector. The computer can

then integrate the signal from the detector over the time that the quadrupoles are set for a

particular mass and thus determine how much of that particular mass is present in the

analyte gas.

The interpretation of the mass spectral data is complicated by several factors. Most

important is the fact that the ionization process results not only in ionizing analyte

molecules, but also can cause the molecules to fragment. This fragmentation results in

mass spectra which contain several peaks of characteristic intensities, the so-called

"cracking pattern", not simply one peak with a mass value of the parent molecule.

Additionally, some fragments may become doubly ionized which may result in the

misinterpretation of the mass as being half of the actual value (the mass spectrometer

measures the mass to charge ratio, m/Z). The presence of various isotopes of some

20

elements adds to the number of peaks in a mass spectrum. For example, tungsten has

isotopes with mass values of 182, 183, 184, and 186 which have natural abundances of

from 14% to 30% {114). Mass spectrometry is a very useful analytical tool if the data are

interpreted carefully.

Temperature Programmed Desorption

Temperature programmed desorption (TPD), also called thermal desorption, is the

process of exposing a solid substrate at low temperature in a vacuum to a gas phase

species, and then heating the substrate in a controlled fashion while observing the volatile

species being evolved with a mass spectrometer. If the pumping speed for the vacuum

chamber is high enough, then the mass spectrometer signal for a given species is

proportional to the rate of desorption of that species at each temperature. It is common

that a species has more than one desorption maxima. This indicates the existence of more

than one adsorption environment on the surface. TPD is a very usefUl technique for

gaining some understanding of the molecular interactions which take place on the surface

of a solid. Since the pioneering work of Redhead (115) many authors have provided useful

applications for TPD (116-119), including detailed analysis of spectra to extract

parameters for desorption kinetics and elucidation of surface structures. This study made

use of TPD to identify chemical species present on an SiC>2 surface.

Micro-Volume Mass Spectrometry

Micro-Volume Mass Spectrometry is the name we have given to the technique of

using a small diameter capillary as a sampling conduit into a vacuum pumped mass

spectrometer. The sampling capillary provides two functions—pressure reduction and

localization of sampling. The pressure reduction is a result of the limited capacitance of

the capillary, and the localized sampling is a result of the fact that the open end of the

sampling capillary is chosen to be on the order of, or larger than, the mean free path of the

21

gaseous species being sampled. The pressure reduction is essential if it is desired to

analyze the gas mixture in a region where the pressure is above approximately 1 * 10~5

Torr, which is the normal maximum operating pressure for a common quadrupole mass

spectrometer.

The pressure reduction that the capillary affords can be approximated by treating it

as a long round tube in molecular flow. Molecular flow is defined as the pressure region

where the mean free path of the gas is long compared to the diameter of the capillary

(J20). In this region the flow of the gas is determined entirely by gas-wall collisions. The

conductance of a gas through a circular tube under molecular flow has been given as {121)

n K d 3

( — y capillary ^ £

where v is the mean velocity of the gas particles, d is the diameter of the capillary, and t is

the length of the capillary, and (122)

8 RT V~inM

whereR is the ideal gas constant, T is the temperature in Kelvin, and M i s the molar mass

of the gas. Combining these two equations leads to

r i - H . capillary " | | ^

where a is a constant.

O'Hanlon (123) analyzed the situation of a differentially pumped mass

spectrometer attached to a chamber with a relatively high pressure by means of a capillary

22

High Pressure Chamber

Mass Spectrometer Vacuum

pump

^Connecting Capillary

Figure 5. Schematic of a differentially pumped mass spectrometer attached to a high pressure chamber.

(Figure 5) and found that the pressure in the spectrometer could be related to the pressure

in the chamber by

P = chamber

spectrometer J + (Sp/C)

where SP is the pumping speed of the pump on the mass spectrometer, and C is the

conductance of the connecting capillary. Inspection of this equation reveals that the

pressure in the spectrometer can be reduced by increasing the pumping speed of the pump

on the spectrometer, or by reducing the conductance of the connecting capillary. In this

study a mass spectrometer was connected to a CVD reaction chamber operating at 300

mTorr via a capillary of 0.53 mm inside diameter and a length of 0.6 m.

23

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(111) Davis, L. E.; MacDonald, N. C.; Palmberg, P. W.; Riach, G. E.; Weber, R. E. Handbook of Auger Electron Spectroscopy, 2nd ed.; Physical Electronics Industries, Inc.: Eden Prairie, MN, 1976.

(112) Briggs, D.; Seah, M. P., Eds. Practical Surface Analysis by Auger and X-ray Photoelectron Spectroscopy; John Wiley & Sons: Chichester, 1983; p. 186.

33

(113) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; chapter 8.

(114) Lide, D. R., Ed. CRC Handbook of Chemistry and Physics, 74th ed.; The Chemical Rubber Company: Dayton, 1993; pp. 1-10.

(115 ) Redhead, P. A. Vacuum 1962,12, 203-211.

(116) Miller, J. B.; Siddiqui, H. R.; Gates, S. M.; Russell, J. N.; Yates, J. T. J.; Tully, J. C.; Cardillo, M. J. J. Chem. Phys. 1987, 57(11), 6725.

(117) King, D. A. Surf Sci. 1975, 47, 384-402.

(118) Madey, T. E.; Yates, J. T. J. Surf Sci. 1977, 63, 203-231.

(119) Yates, J. T. J. In Solid State Physics: Surfaces; Park, R. L.; Lagally, M. G., Eds.; Academic Press, Inc: Orlando, 1985; Vol. 22, pp. 425-464.

(120) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 25.

(121) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 33.

(122) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 9.

(123) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; pp. 142-143.

CHAPTER II

METHANOL INTERACTIONS WITH S I 0 2 SURFACES

Introduction

The interaction of methanol with an Si02 surface was investigated by temperature

programmed desorption (TPD). Methanol was observed to dissociate at oxygen vacancy

sites yielding adsorbed methyl groups. Interactions of WFg with the Si02 surface were

blocked by exposure of the surface to methanol vapor prior to WFg treatment.

Implications of this site blocking for maintaining selectivity for selective CVD tungsten are

discussed.

A demonstrated mechanism for loss of selectivity for tungsten CVD, as stated in

chapter one, is the reaction of volatile reaction products (e.g., tungsten subfluorides, page

13) on Si02- Izumi, et. al. (7), report that pretreatment of Si/Si02 patterned wafers with

methanol prior to tungsten CVD prevents the loss of selectivity. We carried out a series of

TPD and Auger spectrometry experiments directed at gaining an understanding of the

mechanism by which methanol inhibits loss of selectivity on Si02 surfaces. Our TPD

studies showed that methanol dissociates at active sites on the Si0 2 surface to yield

adsorbed methyl groups. These methyl groups were observed to recombine with H and

desorb as methane at approximately 475 K and above. The methane yield at this

temperature was increased by Ar+ sputtering of the surface prior to methanol dosing. Ar+

sputtering is known to produce oxygen deficiencies and partially reduced silicon on Si02

surfaces (2,3). These data indicate that the methanol reacts at surface defect sites which

contain Si in a reduced oxidation state. Our studies also showed that such pre-adsorbed

34

35

methyl groups inhibit the reaction of WF6 with the surface. This suggests that oxygen

vacancy sites are active sites for tungsten nucleation, and are passivated by chemisorbed

methyl groups resulting from exposure to methanol. We note that selective tungsten

deposition begins with the reduction of WFg by Si®, as outlined in chapter one.

Experimental

Six inch diameter single crystal silicon wafers which had been thermally oxidized to

yield a surface oxide film approximately 180 A thick were obtained from Sandia National

Laboratories. These relatively thin oxides were used to avoid charging during Auger

electron spectroscopy (AES). The wafers were cut into one square centimeter samples for

use in these experiments. The samples were lightly etched with dilute (50:1) HF for - 1 0

seconds immediately prior to UHV studies. This procedure parallels typical industry

practice, and thus gives an approximation of surfaces encountered under industrial W-

CVD conditions.

Temperature programmed desorption (TPD) experiments were conducted in a

turbomolecularly pumped multi-port UHV chamber (Figure 6). This chamber is equipped

with a CMA Auger spectrometer (PHI model 10-150), a quadrupole mass analyzer (UTI

model 100C), an argon ion sputter gun (PHI model 04-161), and a leak valve and doser

tube system for controlled exposure of the sample to methanol or WFg vapor. The sample

may be cooled to liquid nitrogen temperatures and heated to > 900 K by resistively heating

the sample holder with a programmable power supply. The thermocouple junction was in

contact with the front surface of the sample near the edge. The power supply and mass

analyzer are simultaneously controlled by a computer which records the analytical signal

from 10 channels of the mass analyzer as a function of sample temperature.

AES was used to determine the elemental composition at the surface of the SiC>2

samples. The Si LMM peak at 76 eV is characteristic of SiC>2 (4). The incident electron

36

beam from the AES was observed to reduce the Si(>2 surface to Si^ unless the beam

energy was kept appropriately high (4 keV in the present experiments) (5). As a further

precaution against disrupting the Si(>2 surface the sample was not subjected to the Auger

e"-beam until after the TPD data were collected.

Initial Auger analysis always revealed the presence of carbon contamination on the

SiC>2 sample. This type of contamination is commonly found on samples before cleaning in

UHV, and is presumably from hydrocarbons on the sample from the laboratory

environment. In this study the samples were cleaned, in situ, first by Ar+ ion sputtering

followed by an O2 anneal. The sputtering was kept as gentle as possible to avoid excessive

disruption of the oxide surface. Typical sputtering parameters were a 15 mA sample

Mass Spectrometer

Doser Tube

Ar+ ion sputter gun Auger

Spectrometer

Sample

Vacuum Pump

AES/TPD Chamber

Turbo Pumped 2x10-10 Torr

Sample: 180A thermally oxidized silicon

Sample Temp. 120K - 900K

Figure 6. Ultra high vacuum chamber for TPD studies.

37

current (as measured by an external picoammeter placed between the sample and ground)

of 0.5 kV Ar+ ions for 5 minutes. This sputtering procedure was sometimes repeated if

subsequent AES analysis revealed continued presence of excessive carbon contamination.

The sputtering causes the volatilization of oxygen from the SiC>2, resulting in the

formation of small amounts of elemental silicon (Si®) at the surface (2) (Figure 8). The

S1O2 surface was recovered by annealing the sample, in situ, at 700 K and lx 10"^ torr

O2 for 15 minutes, followed by 850 K for 1 minute at the system base pressure (typically

3x 10"10 torr). This resulted in a surface of SiC>2 with very little carbon contamination

(approximately 3% C, using the method of ref. 4) (Figure 9).

S1O2 samples thus cleaned were exposed to methanol and tungsten hexafluoride

vapors by means of a UHV dosing system (Figure 7). This consisted of a network of

stainless steel vacuum lines with on/off valves and UHV leak valves arranged so that a

/ UHV

/ Controlled

V Leak Valve

UHV Chamber 10"10 torr

Methanol

On/Off valve

Vacuum Pump UP torr

Figure 7. Apparatus for dosing a sample in UHV with a controlled amount of gas.

38

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controlled amount of the desired gas could be directed onto the Si(>2 surface in the UHV

analytical chamber. The TPD experiments began by cooling the cleaned SiC>2 sample by

liquid nitrogen cooling of the sample holder (sample temperature approximately 100 K to

130 K). The sample was then dosed by opening the appropriate leak valve (methanol or

WFg) for a controlled length of time, while monitoring the UHV chamber pressure. After

the sample was dosed, it was moved in front of the mass spectrometer and the sample

holder was resistively heated at a rate of approximately 5 K to 10 K per second. The

resulting plot of mass spectrometer signal versus sample temperature yields information on

the interaction of the dosed gas with the SiC>2 surface.

Results

Figure 10 shows results of TPD studies with methanol on lightly sputtered (one

minute with A r + ions at 0.5 kV) SiC>2. The mass 32 (methanol) desorption spectra

indicated no significant desorption peaks other than a low temperature ( -250 K) peak.

The mass 15 and 16 spectra show a corresponding low temperature peak, but also a

second peak at approximately 475 K. We attribute the low temperature peak in each

spectrum to the mass spectrometer cracking pattern of methanol (See Figure 11) because

there is a correlation in the TPD spectra between the parent ion (CH30H + ) and the

daughters. The high temperature peaks in the mass 15 and 16 spectra are not from

methanol cracking since there is no corresponding parent ion correlation. The high

temperature peak is also not from OH (yielding 0 + , mass 16, as a mass fraction) since the

mass 15 peak correlates to the mass 16 peak in the TPD, and the mass 15 peak can not

come from OH. We attribute the high temperature peak in the mass 15 and 16 spectra to

CH4 (CH3 + and CH4"1" respectively). This TPD peak at 475 K indicates that CH3OH has

dissociated at active sites on the Si02, yielding adsorbed CH3. The CH3 recombines with

H and desorbs to yield the observed peak at 475 K. The two spectra in Figure 12 show the

41

mass 32 TPD

200 — ,

300 — , —

400 500 600 700 —I

800

1 I m

6

I CO CO in

mass 16 TPD

200 — i —

300 — , —

400 500 600 700 800

mass 15 TPD

200 300 400 500 600 700 I

800

Temperature (K)

Figure 10. TPD spectra (normalized) of methanol from a lightly sputtered Si(>2 surface. Comparing these spectra reveal that the high temperature ( - 475 K) mass 16 peak is due to CH4, not oxygen.

42

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43

effect of Ar + sputtering on the population of adsorbed methyl groups. The dotted curve

(labeled "light sputtering") was sputtered for one minute with Ar + ions at 0.5 kV. The

solid curve (labeled "heavy sputtering") was the same sample sputtered an additional 10

minutes at 1 kV. It is clear from these data that sputtering creates active sites on the SiC>2

for methanol dissociation. This is corroborated by the fact that TPD spectra of SiC>2 which

has not been subjected to AES or ion sputtering showed no desorption above 400 K for

either CH4 or CH3OH (Figure 13).

Figure 15 shows the results of TPD studies with WFg on SiC>2. WFg desorption

was monitored by observing WF54" (281 amu) which is the most abundant mass

spectrometer fragment of WFg. A WFg desorption maximum at approximately 475 K is

fl.B

1 ** 2 p > • A-* a: o

0.2

<1.0

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M e O H o n S10 a

Haavy Sputtflrrng

- - - Lfght SputtBrfnfl

100 200 300 400 500 7am para turn (K)

&00 700 000

Figure 12. TPD spectra of CH4 desorption from an Ar+ sputtered and methanol dosed Si02 surface.

44

1.0 r

"> 0.8

CH4 desorption

800

Temperature (K)

Figure 13. TPD spectrum of CH4 desorption from a methanol dosed unsputtered SiC>2 surface.

observed when no methanol pretreatment is used. AES revealed the presence of tungsten

on the SiC>2 following the TPD cycle (Figure 14). This strongly suggests

disproportionation of tungsten fluoride or subfluorides (WFX), leading to deposition of

tungsten and WF6 desorption (6). The high temperature WFg desorption peak is not

observed when the SiC>2 is lightly dosed with methanol prior to WF5 dosing. The

methanol was dosed at 110 K to give a multilayer, then flashed to 200 K to remove the

multilayer, leaving only actively adsorbed methanol on the surface. The WFg was dosed at

110 K to give a multilayer. These data indicate that WFg, the precursor to CVD tungsten,

adsorbs at active sites on SiC>2 which are deactivated by methanol for WFg adsorption.

45

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Figure 15. TPD spectra ofWF5+ (characteristic ofWFg) from a WF5 dosed Si02 surface. The multilayer peak has been omitted for clarity. A) after Ar+ ion sputtering as described in the text. B) no Ar+ sputtering.

Summary and Conclusions

It is clear that loss of selectivity must be preceded by, among other things,

adsorption of tungsten hexafluoride or subfluoride. Our data indicate that this adsorption

step may be stopped by deactivating the surface with methanol. The methanol dissociates

and leaves a methyl group at the active site rendering it inactive for WFX adsorption,

thereby blocking any loss of selectivity. The nature of these active sites may be inferred

from the observed increase in adsorbed CH3 with sputtering and the fact that Ar+

sputtering is known to produce oxygen deficiencies and partially reduced silicon on Si02

surfaces (2).

47

Chapter References

(1) Izumi, A.; Touei, K.; Yamano, A.; Chong, Y.; Watanabe, N. In Proceedings of the Eleventh International Conference on Chemical Vapor Deposition; Spear, K. E.; Cullen, G. W., Eds.; The Electrochemical Society, Inc: Pennington, NJ, 1990; pp. 425-433.

(2) Thomas, J. H., Ill; Hofmann, S. J. Vac. Sci. Technol. A 1985, 3(5, Sep\Oct), 1921-1928.

(3) McGuire, G. Surf. Sci. 1978, 76, 130.

(4) Davis, L. E.; MacDonald, N. C.; Palmberg, P. W.; Riach, G. E.; Weber, R. E. Handbook of Auger Electron Spectroscopy, 2nd ed.; Physical Electronics Industries, Inc.: Eden Prairie, MN, 1976; p 53

(5) Johannessen, J. S.; Spicer, W. E.; Strausser, Y. E. J. Appl. Phys. 1976, ¥7(7), 3028-3037.

(6) Creighton, J. R. J. Electrochem. Soc. 1989, 136(1), 271-276.

CHAPTER III

IN SITU MASS SPECTROMETRY OF A COMMERCIAL TUNGSTEN

CHEMICAL VAPOR DEPOSITION REACTOR

Introduction

This chapter describes micro-volume mass spectrometry studies which were

carried out in a commercial tungsten chemical vapor deposition reactor. A capillary with

an inside diameter of 0.53 mm was incorporated between the mass spectrometer (which

had its own vacuum pump) and the interior of the CVD reaction chamber (Figure 16). The

capillary created the required pressure difference between the CVD chamber and the mass

spectrometer. It also enabled localized sampling inside the CVD chamber. This novel

application of in situ high pressure mass spectrometry was used to investigate the

observed correlation between the reactant inlet flow ratio (SiH^/WFg) and the loss of

selectivity for tungsten CVD (See "Gas Phase Nucleation", page 14).

The identity of the products of the reaction between SiH4 and WFg on surfaces

has been the subject of some debate (See page 6). H2 and S1F4 have been previously

observed using mass spectrometry (1,2). However, other workers have used FT-IR to

observe that SLHF3 is produced in greater amounts than SiF4 (3). In this study, the

production of both SiF4 and SiHF3 were observed with partial pressure ratios that vary

with the Sffl^/WFg inlet flow ratio.

In this study, the SiF4 and SiHF3 partial pressures were monitored over a tungsten

coated wafer at 320°C as the S i ^ / W F g inlet flow ratio was varied from a selective (0.25)

to a non-selective (3.0) regime (See page 14). We observed the SiHF3/SiF4 product ratio

48

49

to decrease dramatically at reactant ratios associated with the onset of loss of selectivity

(1-1.5). Previous experiments using the same CVD tungsten reactor used in this work

confirm that a transition from selective to blanket tungsten deposition occurs at an inlet

flow ratio between 1 and 1.5. These data provide insight concerning loss of selectivity

mechanisms, and illustrate the potential of this mass spectrometric technique for real-time

in situ process control.

Experimental

In these experiments, we employed an in situ sampling technique in a configuration

novel to CVD studies to investigate the observed relationship between inlet flow ratio and

loss of selectivity. A differentially pumped mass spectrometer was fitted with a fused silica

capillary at its vacuum inlet. A commercial tungsten CVD reactor was modified so that,

with appropriate fittings, the capillary could be fed through the wall of the reactor. This

configuration allowed the mass spectrometer to sample the environment inside the reactor

at discrete locations. CVD processes were then carried out with the mass spectrometer

continuously sampling the environment just above a tungsten coated wafer. The inlet flow

of S1H4 was stepped from 50 to 600 seem with the WFg flow held constant in order to

observe the transition from selective to blanket tungsten deposition.

The experimental apparatus used consisted of a Leybold Inficon quadrupole mass

spectrometer, and a Genus 8720 CVD reactor (a six site deposition system). The mass

spectrometer had an integral 50-L/s turbomolecular pump. The inlet to this mass spectro-

meter was fitted with 1/16 inch Swagelok fittings that could accept a graphite ferrule for a

fused silica capillary (commonly used in gas chromatography). Similar fittings were added

to the chamber wall of the CVD reactor. Two additional small holes (1/32 inch) were

drilled in parts internal to the reactor to provide a direct line-of-site path from the fitting in

50

the reactor wall to the wafer chuck face. This configuration allowed the capillary to be

placed so as to communicate the volatile species near a reacting wafer surface directly to

the mass spectrometer without dilution. The minimum length of capillary required was

approximately 60 cm. The capillary itself did not have an internal stationary phase coating,

such as is commonly used in gas chromatography. Instead, the inner wall of fused silica

had been deactivated by a silanization process performed by the vendor. The capillary is

made sturdy by an external polyimide coating. The internal diameter was 0.53 mm. It was

possible to position the open end of the capillary from less than 1 mm to several

centimeters from the reacting tungsten coated wafer surface.

The total pressure in the chamber was maintained at 300 mTorr by means of a

computer controlled butterfly valve on the chamber pump exhaust. The WFg inlet flow

was kept constant at 200 seem. The wafer temperature was 320°C. The SM4 inlet flow

was varied from 50 to 600 seem in steps, with three minutes at each step to allow

equilibration. Argon was used as a carrier gas and was maintained at 100 seem inlet flow

Sampling Capillary

Mass Spectrometer

0.001 nit

Genus 8720 W-CVD Reactor ( s ix position )

Figure 16. Schematic diagram of the experimental setup used to investigate the reactions in a commercial tungsten CVD reactor.

51

for one set of experiments, and at 2000 seem for another. Complete mass scans in the

range 15 amu to 285 amu were acquired throughout the experiments. The mass

spectrometer was not designed to observe masses below 10 amu.

A model of the sampling capillary

Figure 17 shows a somewhat simplified model (J) of the capillary sampling system.

This treatment allows the estimation of the geometry of the capillary which is required to

achieve the desired pressure differential between the CVD chamber and the mass

spectrometer. The operational pressures in the chamber and the spectrometer vary widely.

CVD pressures range from several 10's of millitorr up to atmospheric pressure. The mass

spectrometer had an upper pressure limit of approximately 1 * 10"4 torr. Here it is assumed

that the CVD chamber has infinite volume, so that the its pressure is not affected by the

removal of gas by the spectrometer's vacuum pump.

The quantity of gas Q (the volume of gas at a known pressure) that flows into the

spectrometer through the capillary is given by (6) :

Qin = C(pc ~ps)

wherePc and Ps are the CVD chamber pressure and the spectrometer pressure,

CVD Chamber

Spectrometer Chamber

Vacuum Pump

Sn

Figure 17. Schematic diagram of the capillary sampling system and the differentially pumped mass spectrometer (4).

52

respectively, and C is the conductance of the capillary, with units of m-Vs or L/s. The

quantity of gas that flows out of the spectrometer through the vacuum pump is given by:

Qou, = S P P S

where Sp is the pumping speed of the vacuum pump on the spectrometer, with the same

units as the conductance, namely m^/s or L/s.

Since at equilibrium the flow into the spectrometer Qin must equal the flow

out Qout, these last two equations may be combined to yield:

P . ' • 1 S

1 + ( s , / c )

The conductance C through long round tubes under molecular flow (where the

mean free path of the gas particles is long compared to the diameter of the tube) has been

derived (7) and is given by:

n (f C = — v —

12 £

where d is the diameter of the capillary, £ is its length, and v is the average velocity of a

gas particle and is given by (<§):

8 RT V~inM

whereR is the ideal gas constant, T is temperature in kelvin, and Mis the molar mass of

the gas. Combining these last two equations and collecting the constants yields:

53

C 3 A m f ^ l = const. I sec. J

and

const. = 3.809 x 10"

when d is in millimeters, t is in meters, T is in kelvins, and M is in grams per mole. By

combining this equation for the conductance of the capillary C with the previous equation

for the pressure in the spectrometer/^, one may estimate the pressure of a particular gas

in the spectrometer by knowing its pressure in the CVD chamber, the geometry of the

sampling capillary, and the speed of the vacuum pump on the spectrometer. These

parameters are easily obtained in most cases.

The conductance C has a mass dependence that varies as M ' ^ 2 . The pumping speed

also has a mass dependence, with the lighter elements, having higher average velocity

being pumped more slowly by the turbomolecular pump than the more massive elements

(P). This means that the mass spectrometer signal is a function of not only the partial

pressure of the analyte gas in the CVD chamber, but also its molecular weight. It is

important to note, however, that the mass spectrometer signal is directly proportional to

the partial pressure of any particular analyte gas in the process chamber (where M does

not vary). The mass dependence of the spectrometer signal may be eliminated by

controlling the conductance between the spectrometer and the vacuum pump ( J O ) , but this

was not attempted in the present study. Experiments with pure argon were conducted to

verify the linear relationship between partial pressure in the process chamber and the

pressure at the spectrometer for a given gas (Figure 18).

54

Experiments were also conducted to verify that the observed species were not an

artifact of the sampling capillary. In the geometry described above, the open end of the

capillary was within a few millimeters of the wafer surface, which was at 320°C. Tungsten

deposition was observed on the polyimide coating of the capillary over approximately the

last four centimeters near the hot wafer. The amount of deposition decreased with distance

from the wafer, apparently as a function of the temperature of the capillary. By

1 2 - i

fc o

3 lifl t U

e £ <U a

R* =0.998

200 400 600 800 1000 Aigon Pressure in CVD Chamber (intoIT)

Figure 18. Pressure at the mass spectrometer as a function of the pressure in the CVD chamber for argon. These data show that there is a linear relationship between the pressure of a gas in the CVD chamber and the pressure of that gas in the mass spectrometer.

55

withdrawing the capillary so that it extended less than one centimeter from the water

cooled wall of the reaction chamber, we were able to repeat the experiment with the end

of the capillary approximately 290°C cooler. The results were essentially unchanged. The

same products were observed to vary in the same way relative to the reactant inlet flow

ratio. This result clearly indicates that the species observed were not artifacts of the

capillary. There were differences in the absolute partial pressures due to the less than

optimum placement of the sampling capillary relative to the wafer surface.

Results and Discussion

The mass spectrum of the gas mixture present in the CVD chamber during process

is very complex. There are several chemical species present, some with complex cracking

patterns. By acquiring complete spectral scans in the range 15 to 285 amu, important

identifications could be made by careful comparison of the data from several mass

channels as the inlet flow of reactants was varied.

Figure 19 shows the mass spectrometer response for the two gas phase reactants,

WFg and Silfy, from the same experiment. This figure clearly indicates that when the

Silfy/WFg inlet flow ratio is low—the selective deposition regime—there is an excess of

unreacted WFg present in the CVD chamber. Conversely, when the Silfy/WFg inlet flow

ratio is high—the non-selective deposition regime—there is excess SiHLj in the CVD

chamber. The WFg signal is only just detectable due to the high molecular weight of WFg

and the mass dependence of the conductance of the capillary (See page 53).

Figure 20 shows the mass spectrometer response for four of the mass fragments of

SiF4 as the inlet flow of S1H4AVF5 was varied from 0.25 (selective) to 3.0 (non-

selective). The signal for the parent ion SiF4+ (top) is especially important in the

identification of SiF4 as the analyte molecule present in the CVD reactor. The other

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Figure 19. Plot of the mass spectrometer response for the CVD reactants, WFg and Siffy, versus the Silfy/WF^ inlet flow ratio.

57

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fragments are identified as daughters of S1F4 because they show the same variations in

intensity as a function of inlet flow ratio.

Figure 21 shows the mass spectrometer response for four mass fragments of

SiHF3 during the same experiment. The identification of SiHF3 as the species giving rise

to these spectra is not as straightforward as the identification of SiF4. The intense mass 67

signal could be from Sff ly^ (m/Z=68) losing a hydrogen, or from SiHF3 (m/Z=86) losing

a fluorine. The situation is not resolved by analysis of the parent ion spectrum, as was

done for SiF4, since there are interfering species with masses of 68 amu (^SiHF2) and 86

amu (29siF3) Therefore, the existence of the 29s; isotope which has the same mass as

2&Si plus H obviates the unambiguous identification of the parent molecule for the spectra

of Figure 21 by considering the mass spectral data alone. There is, however, other

evidence that the m/Z=67 signal is from SiHF3 losing a fluorine. First is by analogy with

the cracking pattern of other fluorinated molecules, which readily lose fluorine (77), as in

SiF4 and WF5 in this study. Second is the data of Kobayashi et al. (3), which identifies

SiHF3 as a product of the silane reduction reaction by in-situ infrared spectroscopy. Other

fluorosilanes, such as SiH2F2 and SiF^F, were not detected in their experiments.

In this study, then, the m/Z=85 channel is used to monitor the SiF4 partial

pressure, and the m/Z=67 is used to monitor the S1HF3 partial pressure. These data

indicate that both SiF4 and SiHF3 are present as products of the SM4 + WFg CVD

reaction (See reactions4, 5, and 6 on page 6), but their relative partial pressures vary as a

function of the SiFfy/WFg inlet flow ratio.

Figure 22 combines the SiF4 most abundant ion (MAI) data from Figure 20 with

the SiHF3 MAI data from Figure 21 and includes the mass spectrometer signal for the

HF+ (m/Z =20) channel. This figure then compares the mass spectrometer response for

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the three principal reaction products from the SH4 + WFg CVD reaction (See reactions

4, 5, and 6 on page 6 ff.) as the Siffy/WFg inlet flow ratio is varied. The qualitatively low

HF signal is consistent with the findings of other workers using mass spectrometry and

in-situ Fourier transform infrared spectroscopy, and HF is not considered further here.

The signals from the two fluorinated silane products in Figure 22 show interesting

dependencies on the Silfy/WFg inlet flow ratio. For low inlet flow ratios in the range 0.25

to 1.0 the two signals rise in concert, which corresponds to an increased surface reaction

rate. Between inlet flow ratios of 1.1 and 1.2 there is a substantial divergence of the

signals, with the m/Z=85 (SiF3+) signal rising sharply while the m/Z=67 (SiHF2+) signal

drops sharply. This signal divergence goes through a maximum and then decreases until

the m/Z=67 signal becomes slightly higher than the m/Z=85 signal. It is important to note

that for the ratio steps (1.2 to 1.8) the two signals have an inversely related component.

That is, when the m/Z=85 signal increases slightly (as in the 1.5 and 1.8 steps) the increase

is anti-correlated in the m/Z=67 signal. This suggests that the same reaction or reactions

that produce the abrupt rise in the m/Z=85 signal also produce the drop in the m/Z=67

signal.

There are two possible explanations for the divergence observed in Figure 22. One

is that there is a gas phase reaction occurring that has SiHF3 as a reactant and SiF4 as a

product. A second possibility is that there is an abrupt change in the surface chemistry;

from one set of reactions producing both SiF4 and SiHF3 without preference, to a second

set that produces SiF4 in preference to SLHF3. To distinguish between the surface and gas

phase reactions, the experiment was repeated with a substantially increased Ar partial

pressure in order to attenuate any gas phase reactions(/2).

Figure 23 shows the effect of increasing the amount of Ar in the reaction mixture

(from 100 seem to 2000 seem, total pressure maintained at 300 mt). This changes the

62

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0 s u o d s 9 j ' o e d s s s e u i

$ Cm O C5 o o 0

1 d>

1 a

+3 (/> <L>

3 o 0> *T3

CS

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1 O . 1 (U fa B vo • § 1 C i n O 00 t j cfl

I I

• § - I 2 < 2

O o £P I

c

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B i s

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m cs 2

. 1 p i

63

profile of the graphs in two ways. First, the maximum divergence between the mass 85

and 67 signals occurs at the inlet flow ratio of 1.0; a downward shift from 1.3. Second, the

extent of the divergence is diminished. This is clearly seen by comparing the mass 67

signal in Figure 22 and Figure 23. Figure 24 compares the data from the low argon flow

experiment with the data from the high argon flow experiment.

That the magnitude of the divergence is reduced when the Ar partial pressure is

increased indicates that it is caused by a gas phase reaction. With the introduction of high

argon flow, the residence times of the reaction products decrease, thereby reducing the

probability of gas phase interactions. The observed reduction in divergence indicates that

the effect is due to a gas phase reaction that has been attenuated by dilution with argon.

Such a gas phase reaction has been proposed by Kobayashi, et al. (3), and is discussed

above (equation 10 on page 15). Apart from this gas phase reaction, the data show trends

in product ratios from the surface reaction as well. These trends are especially evident

when the argon partial pressure is high (Figure 23). The partial pressure of the more silane

like SiHF3 is observed to rise as the amount of SH4 in the reaction mixture rises. The

more fluorinated SiF4 is the more abundant product when WFg is the dominant reactant

(at low inlet flow ratios) and the surface is presumably highly fluorinated.

The other significant effect that is apparent in Figure 24 is the shift in the maximum

divergence. This can be explained as a result of thermodifiusion (J3). Thermodiffusion is

caused by differences in the diffusion coefficients of the different gases. The result is the

existence of partial pressure gradients resulting from the temperature gradient inside the

CVD reactor (the wall of the reactor is water cooled to 25°C, and the wafer is at 320°C).

The gradients in partial pressures result in the more massive gas (WFg in this case)

becoming rarefied near the heated surface. This means that when the SiFLi/WFg inlet flow

64

Ifl

. 2

P4 £

o PU|

a

vo

r - , Tt a CO

SOI1BH p s u & s / £ J H ! S

£ 3 CO £ Q< 73 • »•*

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2 2 CO £ Cu

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O.

|

O' CN CS CO £ 3> ts S o «h w O • «—4 H +

<T) fe C/3 + (N

^r <s £ . 1 Ph

65

ratio is set at, for instance, one, the actual SiJfy/WFg r a t ' ° a t the hot wafer surface is

something greater than one. If the thermodiffusion effect is increased (e.g., by the

introduction of more of the lighter gas argon) the actual SiHLj/WFg ratio at the surface

increases even more. This means that when the thermodiffusion effects are greater (in the

high Ar partial pressure case), the same surface ratio is reached when the inlet flow ratio is

lower. Hence, the location of the observed divergence in Figure 23 is at a lower

Siffy/WFg inlet flow ratio than in Figure 22 (See also Figure 24).

Conclusions

This study has revealed the presence of a previously unreported relationship in the

SiF4 and SiHF3 product partial pressures as a function of the SiFty/WFg inlet flow ratio.

The ratio of the products changes abruptly when the inlet flow ratio changes from a

regime associated with selective deposition to one associated with non-selective

deposition (Figure 24). For Silfy/WFg inlet flow ratios less than one, both SiF4 and

SiHF3 partial pressure increase with increasing SiPfy partial pressure. As the inlet flow

ratio increases beyond one, the S1HF3 partial pressure is anti-correlated with the SiF4

partial pressure. Dilution with argon demonstrates that this anti-correlation is probably due

to a gas phase reaction between WF5 and SiHF3 which yields solid W and S1F4 as

products (equation 10 on page 15).

Apart from this gas phase reaction, the data from these experiments show trends in

product ratios from the surface reaction as well. These trends are especially evident when

the argon partial pressure is high (Figure 23 and Figure 24). The more silane like SiHF3

partial pressure is observed to rise as the amount of SH4 in the reaction mixture rises.

The more fluorinated SiF4 is the more abundant product when WFg is the dominant

reactant (at low inlet flow ratios) and the surface is highly fluorinated. The SiF4 signal

decreases as Silfy becomes more dominant.

66

Thermodiffusion effects were investigated by introducing a mixture of 10% WF6

in AT into the CVD chamber and recording the mass spectrometer signal for the two

gasses at varying distances from the heated wafer chuck (no Si wafer was used in this

experiment). This was possible because the sampling capillary could be positioned at any

distance above the chuck up to the wall of the CVD chamber. Figure 25 shows the results

of this experiment.

a

0mm 10mm 20mm 30mm 40mm 50mm 60mm 70mm

Distance from hot chuck (420°C)

Figure 25. Thermodiffusion results in the depletion of WF6 relative to Ar near a heated surface in the CVD chamber.

This study also indicates that micro-volume mass spectrometry has significant

potential for real-time process control in commercial CVD reactors. These data

demonstrate that appropriate mass spectrometer monitoring of reaction products permits

the real-time determination of whether the process is operating in the selective or blanket

deposition regimes.

67

Chapter References

(1) Yu, M. L.; Eldridge, B. N.; Joshi, R. V. In Tungsten and Other Refractory Metals for VLSI Applications IV; Blewer, R. S.; McConica, C. M., Eds.; Materials Research Society: Pittsburgh, 1989; pp. 221-230.

(2) Yu, M. L.; Eldridge, B. N. J. Vac. Sci. Technol. A 1989, 7(3, May/June), 625-629.

(3) Kobayashi, N.; Goto, H. J. Appl. Phys. 1991, 69(2), 1013-1019.

(4) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 142.

(5) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; pp. 142-143.

(6) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 27.

(7) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 33.

(8) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 10.

(9) O'Hanlon, J. F. A User's Guide to Vacuum Technology, 2nd ed.; John Wiley & Sons: New York, 1989; chapter 8.

(10) O'Hanlon, J. F. A User's Guide to Vactmm Technology, 2nd ed.; John Wiley & Sons: New York, 1989; p. 143.

68

(11) Bell, D. A.; Zhiming L.; Falconer, J. L.; McConica, C. M. In Tungsten and Other Advanced Metals for ULSI Applications in 1990; Smith, G. C.; Blumenthal, R., Eds.; Materials Research Society: Pittsburgh, 1991; pp. 31-37.

(11) Nakamura, Y.; Kobayashi, N.; Goto, H.; Homma, Y. Extended Abstracts of the 1991 International Conference on Solid State Devices and Materials 1991, 216-218.

(12) Jost, W. Diffusion in Solids, Liquids and Gases; Academic: New York, 1960; pp. 492-501.

APPENDIX

COMPUTER PROGRAM

69

70

The following computer program was written to control, and acquire data from, a

UTI100C quadrupole mass spectrometer () present in an ultra-high vacuum chamber. The

program was written using Asyst (), a commercial version of the computer language

Forth. The data acquisition and control functions are carried out by interface with a

Labmaster DMA computer board (). The analog signal out of the Labmaster board's

DAC(O) channel is used as an input to the UTI lOOC's "external in" connector. A

potential applied to this "external in" connector in the range 0-10 Volts controls the mass

spectrometer's mass selection over the range 1 to 300 amu. The computer program thus

controls the desired mass setting on the mass spectrometer by sending an appropriate

number to DAC(0), which then converts this number to a potential at the "external in"

connector, which causes the mass spectrometer to select the corresponding mass value to

monitor. The Labmaster board's ADC(0) channel then recieves the signal from the "signal

out" connector on the mass spectrometer, which is proportional to the signal from the

mass spectrometer's detector. The program then correlates the mass selection information

with the signal coming from the mass spectrometer to produce a plot of intensity versus

m/Z. The program is menu driven and easy to use.

71

ECHO.OFF

\ MSPEC.ast

\

\ Description: Mass Spectrometer Acqusition and Control

LMDMA LINE.EDIT FORGET.ALL

15 SET.FILE.PARSE

\ ***** Declatation of Menus *****

MENU TOP.MENU

MENU SCAN.MENU

MENU ACQUISITION.MENU

MENU SAVE.FILE.MENU

MENU RETRIEVE.MENU

\ ***** Declaration of Windows *****

{[]DATA} 3 10 18 69 SET.WINDOW {DEF}

{[]PROMPT} 24 0 24 79 SET.WINDOW {DEF}

{[]INSERT} 1 5 1 60 SET.WINDOW {DEF}

{[]STATUS} 1 64 1 79 SET.WINDOW {DEF}

2 10 2 79 WINDOW {[]LABELS}

2 10 5 73 WINDOW {FILE.ERROR.WINDOW}

\ ***** Declaration of Vuports *****

VUPORT SCAN.VUPORT \ Where the M/S scan is displayed

72

NORMAL.COORDS

AXIS.DEFAULTS

0 0 VUPORT.ORIG

1 .81 VUPORT.SIZE

.03 .10 AXIS.ORIG

0 .03 DATA. ORIG

.03 .10 AXIS.POINT

.94 .86 AXIS.SIZE

1 1 DATA. SIZE

15 COLOR

1 VUPORT.COLOR

3 AXIS.COLOR

3 LABEL.COLOR

4 CURSOR.COLOR

HORIZONTAL AXIS.FIT.OFF GRID.OFF LABEL.SCALE.OFF

VERTICAL AXIS.FIT.OFF AXIS.OFF GRID.OFF LABEL.SCALE.OFF

NO.LABELS

\ ***** Declaration of Strings *****

30 STRING HORIZONTAL.LABEL \ Label for horizontal axis

30 STRING SETUP,FILENAME \ Filename of TPD setup file

64 STRING FILE.COMMENTS1

\ ***** Declaration of Tokens *****

73

TOKEN SCAN.IN EXP.MEM> SCAN.IN \ Each element is the ave. for

a channel

\ changed here 9/17

TOKEN CHANNEL.IN exp.mem> channel.in

TOKEN MASS,POINTS EXP.MEM> MASS.POINTS

TOKEN D/A.LOOKUP.ARRAY EXP.MEM> D/A.LOOKUP.ARRAY

TOKEN HIGHMASS.LOCATIONS EXP.MEM> HIGHMASS.LOCATIONS

TOKEN LOWMASS.LOCATIONS EXP.MEM> LOWMASS.LOCATIONS

TOKEN TPD. PARAMETERS. ARRAY EXP.MEM> TPD. PARAMETERS .ARRAY

TOKEN RUN. TIME. ARRAY EXP.MEM> RUN. TIME .ARRAY

TOKEN RUN.TEMP.ARRAY EXP.MEM> RUN.TEMP.ARRAY

\ ***** Declaration of Arrays *****

INTEGER DIM [ 300 ] ARRAY. BECOMES> D/A. LOOKUP .ARPAY

DIM[ 2 , 50 ] ARRAY.BECOMES> HIGHMASS.LOCATIONS

DIM[ 2 , 10 ] ARRAY.BECOMES> LOWMASS.LOCATIONS

DIM[ 16 , 5 ] ARRAY. BECOMES> TPD. PARAMETERS .ARRAY

REAL DIM[ 7500 ] ARRAY PIXBUF \ Used for fast erasure of lines

DIM[ 80 ] ARRAY MASS.LOCATIONS \ Used in calibration

routines

\ ***** Declaration of Scalars *****

INTEGER SCALAR FIRST.MASS

SCALAR FIRST.D/A

74

SCALAR LAST.MASS

SCALAR TOTAL. CHANNELS

SCALAR SAMPLES . PER. CHANNEL

SCALAR MAX. SIGNAL

SCALAR MASS. PEAK. ELEMENT

SCALAR LOWMASS.COUNT

SCALAR HIGHMASS.COUNT

SCALAR #MASSES

SCALAR MASS#

SCALAR SCAN#

SCALAR TEMPORARY

SCALAR MAX.TEMP

SCALAR ICE. PEAK.TEMP

SCALAR CHANNEL.TIME

REAL SCALAR FIRST

SCALAR SECOND

DP. REAL SCALAR TIME. ZERO

\ ***** Declaration of Templates *****

0 0 A/D. TEMPLATE M/S . SIGNAL. IN

0 0 D/A.TEMPLATE M/S.CONTROL.OUT

1 1 A/D.TEMPLATE TEMPERATURE.IN

1 1 D/A.TEMPLATE HEATER.CONTROL.OUT

75

\ ********** Generic Colon Defs *********** ^ *****************************************

\ Makes the foreground text red.

\ [ - ] < - )

: RED.LETTERS

RED MIX FOREGROUND INTEN.ON

\ Makes the foreground text yellow. \ [ - ] ( - )

: YELLOW.LETTERS

RED GREEN MIX FOREGROUND INTEN.ON

\ Makes the foreground text white.

\ [ - ] ( - )

: WHITE.LETTERS

WHITE MIX FOREGROUND

\ Waits for "Y" or "N" to be entered and repeats if invalid

character

\ Returns a true if "Y" was entered, false if "N".

\ [ - ] ( - T/F)

76

: GET.Y/N

BEGIN

7REL.C0L ?REL.ROW

of error

\ Save col and row in case

repeat

PCKEY NOT

IF

DUP 90 > IF 32 - THEN

DUP 89 = NOT

DUP 78 = NOT AND

ELSE

TRUE

THEN

\ Make lowercase

\ If not "Y" and not "N",

\ If a function key, repeat

WHILE

BELL

DROP

Y or N"

1000 MSEC.DELAY

7REL.COL 3 PICK - 1 +

3 PICK 3 PICK GOTO.XY

SPACES

GOTO.XY

REPEAT

\ Oops! Not a number

\ Drop the key value

\ Print error message

\ and wait a bit

\ Get current col

\ Back up to orig pos

\ Erase entry

\ Return to orig position

77

UNROT 2 *DROP

pos info

89 =

\ Got a good key, so drop

\ Place true on stack, if =

\ Waits for number to be entered and repeats if an invalid entry. \ [ - # ] ( - )

: #INPUT&CHECK

BEGIN

7REL.C0L ?REL.ROW

of error

#INPUT

NOT

WHILE

BELL

7REL.COL 3 PICK - 1 +

3 PICK 3 PICK GOTO.XY

SPACES

GOTO.XY

REPEAT

\ Save col and row in case

\ Get number

\ Valid?

\ Oops! Not a number

\ Get current col

\ Back up to orig pos

\ Erase entry

\ Return to orig position

UNROT 2 *DROP

78

\ Got a good number, so drop

pos info

\ Waits for string to be entered and repeats if a null string.

\ [ ~ ] ( - string )

: "INPUTSCHECK

BEGIN

"INPUT

"LEN 0 =

WHILE

BELL "DROP

start over

REPEAT

\ Get a string

\ Is string length 0 ?

\ Not a good string, so

SEPARATE. ARRAY

DUP XSECT[ 2 , ! ]

SWAP XSECT[ 1 , ! ]

\ ****************************************

\ ***** Show Calibration Definitions ***** \ ****************************************

79

PEAK. AD JUST

SCAN.IN

SUB[ 1 , 2 ; MASS.PEAK.ELEMENT 2 - , 5 ]

XSECT |[ 1 , ! ]

SORT&INDEX

SWAP DROP

[ 5 ] 3 -

PEAK.MAX

XSECT[ ! , MASS.PEAK.ELEMENT PEAK.ADJUST + ]

DUP [ 1 ] MASS.POINTS [ 1 , 1 FIRST.MASS - 1 + ]

[ 2 ] MASS. POINTS [ 2 , 1 FIRST.MASS - 1 + j| : =

SHOW.MASS.POINTS

LAST.MASS 1 + FIRST.MASS

DO

SCAN.IN X.ARRAY

D/A. LOOKUP.ARRAY [ I ]

INDEX.INTERPOLATE DROP

MASS.PEAK.ELEMENT :=

PEAK.MAX

LOOP

MASS. POINTS SEPARATE.ARRAY

80

" +" SYMBOL

XY. DATA. PLOT

CURSOR.OFF

SOLID

\ ******* * *****************************

\ ***** Scan Plotting Definitions ***** ^ *************************************

: ADD. LABELS

NORMAL.COORDS

0 LABEL.DIR 0 CHAR.DIR 0.55 0.05 POSITION

HORIZONTAL.LABEL CENTERED.LABEL

WORLD.COORDS

GET.MAX.SIGNAL

XSECT[ 1 , ! ] []MAX

MAX.SIGNAL :=

SETUP.HORIZONTAL.WORLD

FIRST.D/A DUP TOTAL.CHANNELS +

HORIZONTAL WORLD.SET

81

SETUP. VERTICAL. WORLD

DUP

WORLD.COORDS

GET.MAX.SIGNAL

MAX.SIGNAL DUP .0 100 A/D.SCALE 72 4 GOTO.XY FIX .

-2045 <=

IF

-2049 -2046 VERTICAL WORLD.SET

ELSE

-2049 MAX.SIGNAL DUP 204 8 + 0.05 * + VERTICAL WORLD.SET

THEN

VUPORT.CLEAR

XY.AXIS.PLOT

ADD.LABELS

PIXBUF LINE.BUFFER.ON

: PLOT.THE.SCAN

IF \ First time through scan

INTEGER DIM[ 2 , LAST.MASS FIRST.MASS - 1 + ] ARRAY.BECOMES>

MASS.POINTS

" % Full Scale" 60 4 GOTO.XY "TYPE

SETUP.HORIZONTAL.WORLD

SETUP. VERTICAL. WORLD

82

SEPARATE. ARRAY

XY. DATA. PLOT

SHOW.MASS.POINTS

ELSE

DUP

GET.MAX. SIGNAL

MAX. SIGNAL AYMAX >

IF

SETUP. VERTICAL. WORLD

ELSE

MAX. SIGNAL 2048 + AYMAX 2048 4- 0.70 *

IF

AYMAX -2025 >

IF

SETUP . VERTICAL. WORLD

THEN

THEN

THEN

ERASE.LINES

SEPARATE. ARRAY

XY. DATA. PLOT

SHOW.MASS.POINTS

THEN

83

\ ***** Scanning Definitions *****

: SCANNING.MESSAGE

12 FOREGROUND

26 0 GOTO.XY " Scanning - any key stops" "TYPE

2 FOREGROUND

SCAN.DESCRIPTION \ Finds first, last, and # of channels

D/A.LOOKUP.ARRAY [ LAST.MASS ]

D/A.LOOKUP.ARRAY [ FIRST.MASS ] DUP 7 - FIRST.D/A :=

- 14 + TOTAL.CHANNELS :=

CHANNEL.IN.SIZE

CHANNEL.TIME 0.025 /

SETUP.FOR.SCANNING

RELEASE.OVERLAY

M/S.SIGNAL.IN

CLEAR.TEMPLATE.BUFFERS

INTEGER DIM[ 2 , TOTAL.CHANNELS ] ARRAY.BECOMES> SCAN.IN

DIMf CHANNEL.IN.SIZE ] ARRAY.BECOMES> CHANNEL.IN

84

CHANNEL.IN TEMPLATE.BUFFER CYCLIC

0.025 CONVERSION.DELAY

A/D.INIT

SCAN \ Word for scanning and displaying mass spec

SCANNING.MESSAGE

SCAN.DESCRIPTION

SETUP.FOR.SCANNING

M/S.CONTROL.OUT

D/A. INIT

M/S.SIGNAL.IN

A/D.IN>ARRAY

CHANNEL.TIME 1 + SYNC.PERIOD

ERASE.LINES

TRUE

BEGIN

FIRST.D/A D/A.OUT

5 MSEC.DELAY

TOTAL.CHANNELS 1 + 1

DO

I FIRST.D/A + DUP

D/A. OUT

SYNCHRONIZE

SCAN.IN [ 2 , 1 ] :=

85

CHANNEL.IN MEAN

SCAN.IN [ 1 , 1 ]

LOOP

SCAN.IN

PLOT.THE.SCAN

FALSE

?KEY

UNTIL

PCKEY 7DROP 7DROP DROP

\ CLEAR.TEMPLATE.BUFFERS

\ ***** M/S Calibration Definitions *****

^ -k'k'k-k-k'kiir'k'k-k-Jc'k-k-k-k-k-k'k-Jir-k-k'k-iir'k'k'k-k-k-k'k'k-k^k-k-k'fc-k-k-k

: SAVE. CAL. FILE

LOAD. OVERLAY DATAFILE. SOV

FILE.OPEN CALIB.DAT

D/A. LOOKUP.ARRAY ARRAY>F1LE

FILE.CLOSE

: CALIBRATION

LOAD.OVERLAY MATFIT.SOV

HIGHMASS.LOCATIONS SUB[ 1 , 2 ; 1 , HIGHMASS.COUNT ]

86

SEPARATE. ARRAY

1 \ degree of polynomial fit

LEASTSQ.POLY.FIT

DUP [ 1 ] FIRST :=

DUP [ 2 ] SECOND :=

DROP

301 1

DO

I FIRST * SECOND -t-

D/A. LOOKUP. ARRAY [ I ] : =

LOOP

LOWMASS. COUNT 1 + 1

DO

LOWMASS.LOCATIONS [ 1 , 1 ]

D/A.LOOKUP.ARRAY [ LOWMASS.LOCATIONS [ 2 , 1

LOOP

SAVE. CAL. FILE

0 HIGHMASS.COUNT :=

0 LOWMASS.COUNT :=

ASSIGN.MASSES

#INPUT

IF

DUP 10 >

87

IF HIGHMASS.COUNT 1 + HIGHMASS.COUNT :=

HIGHMASS.LOCATIONS [ 2 , HIGHMASS.COUNT ]

MASS.LOCATIONS [ #READOUTS 2 * 1 - ]

HIGHMASS.LOCATIONS [ 1 , HIGHMASS.COUNT ]

ELSE LOWMASS.COUNT 1 + LOWMASS.COUNT :=

LOWMASS.LOCATIONS [ 2 , LOWMASS.COUNT ] :=

MASS.LOCATIONS [ #READOUTS 2 * 1 - ]

LOWMASS.LOCATIONS [ 1 , LOWMASS.COUNT ] :=

THEN

ELSE NOP

THEN

WAIT.FOR.DEL

BEGIN

PCKEY

IF INTERPRET.KEY FALSE

ELSE DUP 43 = \ + sign is hit

IF 71 INTERPRET.KEY

ASSIGN.MASSES BELL BELL BELL DROP FALSE

ELSE 27 =

THEN

THEN

UNTIL

83 INTERPRET.KEY

88

GET.SCAN.VALUES

0 CURSOR.INCREMENT

12 FOREGROUND

2 2 GOTO.XY " ESC to return to menu " "TYPE

2 FOREGROUND

SCAN.IN SEPARATE.ARRAY

VUPORT.CLEAR

XY. DATA. PLOT

MASS.LOCATIONS READOUT>ARRAY

NORMAL.COORDS

0.5 0.975 READOUT>POSITION

WORLD.COORDS

ARRAY.READOUT

WAIT.FOR.DEL

\ ***** TPD Setup Definitions *****

: SETUP.TPD

LOAD.OVERLAY AR-EDIT.SOV

16 ROWS 5 COLUMNS

89

TPD.PARAMETERS.ARRAY ARRAY.EDIT(MANUAL)

{[]LABELS}

" Mass Pre-ice Post-ice Display? Color"

7 1 GOTO.XY "TYPE {DEF}

INSERT

TPD.PARAMETERS.ARRAY TRANS[ 1 , 2 ] DUP

XSECT[ 1 , ! ] 300 [<=] TRUE.INDICES LOOKUP DUP

XSECT[ 1 , ! ] 1 [>=] TRUE.INDICES LOOKUP DUP

XSECT[ 1 , ! ] SORT&INDEX SWAP DROP LOOKUP

TRANS[ 1 , 2 ]

BECOMES> TPD.PARAMETERS.ARRAY

[]SHAPE DROP #MASSES := DROP DROP

\ ***** TPD Setup File Definitions ***** \ **************************************

: FILE.ERROR.MESSAGE

{FILE.ERROR.WINDOW) 4 BACKGROUND HOME

." Wrong filename or drive is not ready." CR

." Hit any key to try again."

PCKEY

1 BACKGROUND

STACK. CLEAR

90

FILE. EXISTS.MESSAGE

{FILE.ERROR.WINDOW} 4 BACKGROUND HOME

RED.LETTERS

." File already exists. Overwrite? (Y/N)

GET.Y/N

WHITE.LETTERS

1 BACKGROUND

FILE.EXISTS?

DEFER> FILE.SIZES SWAP DROP

0 <>

CREATE.SETUP.FILE

LOAD.OVERLAY DATAFILE.SOV

REGULAR.DATAFILE

FILE.TEMPLATE

1 COMMENTS

INTEGER DIM[ #MASSES , 5 ] SUBFILE

END

SETUP.FILENAME -TRAILING DEFER> FILE.CREATE

SETUP.FILENAME FILE.OPEN

91

FILE.COMMENTS1 1 >COMMENT

TPD. PARAMETERS .ARRAY ARRAY>FILE

FILE.CLOSE

\ Main word for retrieveing files. Executes the menu

RETRIEVE.MENU. Upon

\ leaving RETRIEVE.MENU the number of files tagged for deletion are

on the

\ number stack and the corresponding strings are on the symbol

stack.

\ [ - ] ( - )

: RETRIEVE.SETUP.TPD

STACK. CLEAR

RETRIEVE.MENU MENU.EXECUTE

LOAD. OVERLAY DATAFILE. SOV

DUP 0 =

IF \ If no items tagged drop and do

nothing

DROP

ELSE

DROP

12 "LEFT

-TRAILING DEFER> FILE.OPEN \ Open the tagged file

92

FILE>UNNAMED.ARRAY DUP

FILE.CLOSE

BECOMES> TPD.PARAMETERS.ARRAY

[]SHAPE DROP #MASSES := DROP DROP

THEN VUPORT.CLEAR

SAVE.SETUP.TPD

SAVE.FILE.MENU MENU.EXECUTE

SETUP.FILENAME FILE.EXISTS?

IF

FILE.EXISTS.MESSAGE

IF CREATE.SETUP.FILE

ELSE NOP

THEN

ELSE

CREATE.SETUP.FILE

THEN

ONERR:

?ERROR#

CASE

480 OF FILE.ERROR.MESSAGE ENDOF \ Invalid path or

filename

93

27 OF FILE.ERROR.MESSAGE ENDOF \ Duplicate file or not

found

11 OF FILE.ERROR.MESSAGE ENDOF \ file not found

30 OF FILE.ERROR.MESSAGE ENDOF \ file can't be copied

onto itself

237 OF FILE.ERROR.MESSAGE ENDOF \ drive not ready

58 OF FILE.ERROR.MESSAGE ENDOF \ require unambiguous

filename

25 OF FILE.ERROR.MESSAGE ENDOF

ENDCASE

\ ***** TPD Plotting words *****

^ -k-k "k-k-k-k-k-k-k-k *k-k-k ~k-k ~k-k-k-k k k-k ~k-k-k ~k k-k ~k-k

\ plots the data from the tpd run to the screen in real time

: PLOT.TPD,DATA

NOP

^ •k'k-k'k-k-k-k-k-k-k'k-k-k-k-k-k-k-k-k-kk-k-k-k-k-k-k-k-k-k-kiir-k-k-k'k-k

\ ***** Temperature Control Words *****

^ •k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k-k^c-k'k-k-k-k-k-kk-k-k-k-k-kkr-k

\ Holds sample at a user defined temperature

94

\ run in background so temp can stabalize while

\ other things are set up.

: CONSTANT.TEMP

NOP

\ Ramps sample temperature at user defined rate

: RAMP.TEMP

NOP

\ Displays set point and current sample temperature on screen

: RUN.TEMP

100

^ •k-k'k'k'k-k'k-k'k-k'k'k'k'kic'k'k-k'k-k-k-kic-k'k'k-k'k-k-jc-kic-k

\ ***** TPD Acquisition Words *****

^ •k-ie-k-k-k-k'k-k-k-k'k-k-k-k-k-k-k-k-k-k-k-k-kjc-k-k-kik-k-k-k-k-k

: NEED.SETUP.FILE.MESSAGE

{FILE.ERROR.WINDOW} 4 BACKGROUND HOME

RED.LETTERS

." Please specify a setup file first." CR

. " Hit any key to continue."

95

PCKEY

WHITE.LETTERS

1 BACKGROUND

\ Opens data file for storing TPD run

: CREATE. DATA. FILE

LOAD. OVERLAY DATAFILE. SOV

REGULAR. DATAFILE

FILE.TEMPLATE

3 COMMENTS

\ Puts value of REL.TIME in variable TIME.ZERO

: START.RUN.CLOCK

REL.TIME TIME.ZERO :=

\ Returns the current run time in seconds,

: RUN.TIME

REL.TIME TIME.ZERO - 1000 /

\ Sets mass spec, sensitivity to 10e-6 for moving

\ between masses. This avoids saturating the detector

96

\ if a huge peak is passed.

: SET.SENS.LOW

NOP

\ Sets mass spec, sensitivity to value specified in

\ TPD. PARAMETERS.ARRAY

: SET.SENS.PEAK

DROP

\ calculates the max number of scans possible for 32,768 elements

\ in SCAN.IN

: MAX.#.SCANS

32768 #MASSES /

\ saves the arrays scan.in, run.time.array, and run.temp.array

\ to a disk file.

: SAVE.TPD.RUN

NOP

\ appends the data from the most recent scan to the three arrays

\ scan.in, run.time.array, and run.temp.array

97

: APPEND. SCAN

BELL

NOP

\ Finds the maximum value in the five element array scan.in

\ obtained around the mass of interest

: FIND.MAX

3 MASS.PEAK.ELEMENT :=

SCAN.IN

PEAK.MAX

\ Main word for acquiring the TPD Spectrum

: DO.TPD

TPD.PARAMETERS.ARRAY [ 1 , 1 1 0 =

IF

NEED.SETUP.FILE.MESSAGE

EXIT

THEN

INTEGER DIM [ MAX.#. SCANS ] ARRAY. BE COMES > RUN. TIME .ARRAY

DIM [ MAX.#. SCANS ] ARRAY. BECOMES > RUN. TEMP .ARRAY

DIM[ 2 , #MASSES ] ARRAY.BECOMES> MASS.POINTS

1 SCAN# :=

98

1 FIRST.MASS :=

M/S.CONTROL.OUT

M/S.SIGNAL.IN

A/D.IN>ARRAY{DMA)

CHANNEL.TIME 1 + SYNC.PERIOD

D/A.INIT

SCANNING.MESSAGE

START.RUN.CLOCK

BEGIN \ this loop executes until temp gets to end point

RUN.TIME RUN.TIME.ARRAY [ SCAN# ] :=

RUN.TEMP RUN.TEMP.ARRAY [ SCAN# ] :=

RAMP.TEMP

M/S.CONTROL.OUT

M/S.SIGNAL.IN

#MASSES 1 + 1 \ loops through masses as set by user in

DO \ tpd.parameters.array

SET.SENS.LOW

5 MSEC.DELAY

D/A.LOOKUP.ARRAY [ TPD.PARAMETERS.ARRAY [ 1 , 1 ] ] 2

DUP

FIRST.D/A :=

D/A.OUT

5 MSEC.DELAY

RUN.TEMP ICE.PEAK.TEMP <

IF TPD.PARAMETERS.ARRAY [ 1 , 2 ] SET.SENS.PEAK

99

ELSE TPD. PARAMETERS.ARRAY [ 1 , 3 ] SET.SENS.PEAK

THEN

5 MSEC.DELAY

\ below is loop for acquiring data finding peak max

5 TOTAL.CHANNELS :=

SETUP.FOR.SCANNING

D/A.INIT

6 1 \ five times through the loop

DO

I FIRST.D/A + 1 - DUP

D/A.OUT

SYNCHRONIZE

SCAN.IN [ 2 , 1 ] :=

CHANNEL.IN MEAN

SCAN.IN [ 1 , 1 ] :=

LOOP

FIND.MAX

LOOP

SET.SENS.LOW

PLOT.TPD.DATA

APPEND.SCAN

SCAN# MAX.#.SCANS <

IF SCAN# 1 + SCAN# ;=

ELSE ?KEY.ON

THEN

100

MAX.TEMP RUN.TEMP >= ?KEY OR \ end of loop and experiment

UNTIL

PCKEY 7DROP DROP

SAVE.TPD. RUN

\ ***** Menu Definitions *****

^ -k -k -k-k-k -k -k -k -k -k-k-k-k k -k

\ -k-k-k-k-k TOP.MENU *****

TOP.MENU

" Main Menu" MENU.TITLE

MENU.NO.STORE

1 1 4 79 MENU.SHAPE

1 2 MENU.COLOR

15 MENU.PROMPT.COLOR

1 15 " Scan and Calibrate" MENU.ITEM{ SCAN.MENU )

1 45 " Data Acquisition" MENU.ITEM{ ACQUISITION.MENU

MENU.END

\ ***** SCAN.MENU *****

SCAN.MENU

" Scan and Calibrate"

MENU.STORE.MEMORY

MENU.TITLE

101

1 1 4 79 MENU.SHAPE

1 2 MENU.COLOR

15 MENU.PROMPT.COLOR

0 30 " Begin Scanning" MENU.ITEM{ SCAN }

1 2 " First Mass : " MENU.ITEM{ FIRST.MASS }

1 28 " Last Mass : " MENU.ITEM{ LAST.MASS }

1 50 " Channel Time (ms) : " MENU.ITEM{ CHANNEL.TIME }

2 28 " Calibrate " MENU.ITEM{ GET.SCAN.VALUES }

3 28 " Save New Calibration" MENU.ITEM{ CALIBRATION }

MENU.END

\ ***** ACQUISITION.MENU *****

ACQUISITION.MENU

" Data Acquisition" MENU.TITLE

MENU.STORE.MEMORY

1 1 4 79 MENU.SHAPE

1 2 MENU.COLOR

15 MENU.PROMPT.COLOR

0 1 " Set Sample Temp" MENU.ITEM{ CONSTANT.TEMP }

0 30 " Begin TPD" MENU.ITEMf DO.TPD }

1 1 " Setup Acquisition" MENU.ITEMf SETUP.TPD }

2 1 " Retrieve A Previous Setup" MENU.ITEM{

RETRIEVE.SETUP.TPD }

3 1 " Save The Current Setup" MENU.ITEM{ SAVE.SETUP.TPD }

MENU.END

102

\ ***** SAVE.FILE.MENU *****

SAVE.FILE.MENU

" Save setup file" MENU.TITLE

MENU.NO.STORE

MENU.NO.PROTECT

2 10 5 73 MENU.SHAPE

0 15 MENU.COLOR

1 1 " File name to save to" MENU.ITEM{ SETUP.FILENAME )

2 1 " Comments: " MENU.ITEM{ FILE.COMMENTS1 }

MENU.END

\ ***** RETRIEVE.MENU *****

RETRIEVE.MENU

" Retrieve File - Arrows to Scroll, Enter to choose" MENU.TITLE

MENU.BLOW.UP

MENU.STORE.DISK

3 3 25 55 MENU.SHAPE

4 15 MENU.COLOR

9 MENU.PROMPT.COLOR

1 50 MENU.DISPLAY DIR \ Max taggable Items = 1

MENU.END

Initialize and start the program *****

103

INIT.VALUES

12 FIRST.MASS :=

19 LAST.MASS :=

200 ICE.PEAK.TEMP :=

17 CHANNEL.TIME :=

667 SAMPLES.PER.CHANNEL :=

-2048 MAX.SIGNAL :=

13.826 FIRST :=

-2063.56 SECOND :=

0 HIGHMASS.COUNT :=

0 LOWMASS.COUNT :=

" D/A Channel #" HORIZONTAL.LABEL

" DEFAULT.SET" SETUP.FILENAME ":=

Load.Overlay Datafile.Sov

file.open calib.dat

D/A.LOOKUP.ARRAY FILE>ARRAY

FILE.CLOSE

SYNC.ERROR.OFF

INIT.DISPLAY

GRAPHICS.DISPLAY

{STACK}

15 FOREGROUND

104

SCAN. VUPORT

3 ARRAY. READOUT. TYPE

SCREEN.CLEAR

VUPORT.CLEAR

NEWCAL

STACK. CLEAR

MENU.STACK.CLEAR

INIT.VALUES

INIT.DISPLAY

VUPORT.CLEAR

TOP.MENU MENU.EXECUTE

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