A study of platinum electrode patterning in a reactive ion etcherLi-Hsin Chang, Elizabeth Apen, Mike Kottke, and Clarence Tracy Citation: Journal of Vacuum Science & Technology A 16, 1489 (1998); doi: 10.1116/1.581175 View online: http://dx.doi.org/10.1116/1.581175 View Table of Contents: http://scitation.aip.org/content/avs/journal/jvsta/16/3?ver=pdfcov Published by the AVS: Science & Technology of Materials, Interfaces, and Processing Articles you may be interested in Analyses of chamber wall coatings during the patterning of ultralow- k materials with a metal hard mask:Consequences on cleaning strategies J. Vac. Sci. Technol. B 25, 886 (2007); 10.1116/1.2738482 Dependence of indium–tin–oxide work function on surface cleaning method as studied by ultraviolet and x-rayphotoemission spectroscopies J. Appl. Phys. 87, 295 (2000); 10.1063/1.371859 Metastable-atom-activated growth of an ultrathin carbonaceous resist for reactive ion etching of SiO 2 and Si 3 N4 J. Vac. Sci. Technol. B 16, 1155 (1998); 10.1116/1.590026 Surface processes occurring on TiSi 2 and CoSi 2 in fluorine-based plasmas. Reactive ion etching in CF 4 /CHF3 plasmas J. Vac. Sci. Technol. A 15, 3005 (1997); 10.1116/1.580897 Study of the First Row Transition Metals by X-ray Photoelectron Spectroscopy Surf. Sci. Spectra 4, 316 (1996); 10.1116/1.1247829

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

A study of platinum electrode patterning in a reactive ion etcherLi-Hsin Chang,a) Elizabeth Apen, Mike Kottke, and Clarence TracyMaterials Research and Strategic Technologies, Motorola, Mesa, Arizona 85202

~Received 13 October 1997; accepted 30 March 1998!

This article addresses the problem of Pt electrode etching through the use of a batch load productionreactive ion etch~RIE! tool to study etching characteristics and the cleanliness of patterned filmswith pressure, total gas flow, and percent of Cl2 in Ar as variables, and considers some of theenvironmental, health, and safety issues. The results show that Pt etching is primarily a sputter etchprocess in which the Cl2 percentage has little impact on the Pt removal rate, but does significantlyaffect etch uniformity across the wafer and the surface cleanliness as analyzed with Auger electronspectroscopy. The maximum Pt etch rate achieved was about 5 nm/min with good etch uniformityand surface cleanliness. X-ray photoelectron spectroscopy of the etch by-products shows thepresence of PtCl2 and PtCl4 when the Ar–Cl2 etch chemistry was used. These results provide usefulinformation to address material redeposition, wafer cleaning, and etch chamber cleaning safetyissues, major concerns in the RIE of Pt. ©1998 American Vacuum Society.@S0734-2101~98!60903-9#

I. INTRODUCTION

Materials new to the semiconductor industry are one ofthe keys to fulfilling the demands for shrinking feature sizeand increasing performance in future generations of inte-grated circuits. Currently, there is intense interest in usinghigh-permittivity thin films for storage-node capacitor appli-cations in dynamic random-access memory1–7 and nonvola-tile ferroelectric random-access memory8–10 devices. Suc-cessful integration of these dielectrics requires electrodematerials that will not degrade the properties of the dielec-trics during the device fabrication process. Platinum has beenthe most widely used electrode material for ferroelectric ca-pacitors due to its inertness during high-temperatureprocessing.4,11

High-resolution dry etching of platinum is difficult withthe conventional tools found in manufacturing since volatilereaction products are not likely to form. One often resorts to‘‘physical’’ means such as ion milling12 or high-powersingle-wafer approaches in laboratory-scale reactive ion-etch~RIE! systems13–17 to pattern a limited number of samplesmainly by sputtering. Chlorine is frequently added in thecase of the RIE systems to enhance the sputter rate. In suchprocesses, etch by-products are inevitably redeposited alongthe feature sidewalls as well as on the surfaces of the etchchamber. This poses the need for understanding the typesand properties of the etch by-products so they can be easilyremoved without damaging the device features and, espe-cially in the case of chlorine additions, without introducinghealth hazards during chamber cleaning.

The goal of this work is to address the reactive ion etch-ing related problem through the use of a batch load design,production oriented RIE tool, and to understand the chemis-try of the etch by-products so they can be easily and safelyremoved.

II. EXPERIMENT

An Applied Materials AME-8120 RIE system was used inthis study. The equipment has a hexagon configured cathodetemperature controlled to about 23 °C, which accommodatesa total of 18 150 mm diam wafers per run, with three wafersmounted vertically on each alumina-coated tray by springclips. The stainless-steel wall of the vacuum chamber pro-vides the grounded anode and the separation between thewafer surface and the anode is about 15 cm. The cathode iscapacitively coupled to a 13.56 MHz rf power supplythrough an impedance-matching network. The maximum us-able power during prolonged etching was found to be about1 kW. The system is pumped by mechanical, turbomolecular,and cryogenic vacuum pumps, and there are five processgases ~O2, Cl2, CF4, CHF3, Ar! available. After roughpumping, the cryogenic pump is used to quickly reduce thechamber to the base pressure~0.8 mTorr!, while the me-chanical and turbopumps are utilized during plasma process-ing. Gas flow rates are regulated by mass flow controllers tomaintain the programed gas compositions during the etch.Chamber pressure is controlled independently from gas flowwith a throttle valve.

Auger electron spectroscopy~AES! and x-ray photoelec-tron spectroscopy~XPS! were used to analyze etch products.Auger analysis was carried out in a PHI model 670 scanningAuger system using a 20 keV primary beam. XPS spectrawere obtained in a PHI 5600 XPS system using a MgKasource. The binding energy scale is referenced to the C 1slevels. XPS depth profiling was done with 3 keV Ar ionsusing an AlKa source.

300 nm thick Pt films were sputter deposited at 400 °C on40 nm of TiO2 on oxidized 150 mm silicon substrates. Theseplatinum films were then patterned with photoresist~IX500EL from JSR Electronics, Inc.! to form island struc-tures of various sizes through a conventional photolithogra-phy process. Some wafers went through a resist ‘‘reflow’’process~150 °C hot plate bake! to form sloped sidewall pro-a!Electronic mail: rxfp20@email.sps.mot.com

1489 1489J. Vac. Sci. Technol. A 16 „3…, May/Jun 1998 0734-2101/98/16 „3…/1489/8/$15.00 ©1998 American Vacuum Society

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

files and discourage fence formation.13 The final thickness ofthe resist was about 1.1mm.

For the etching experiments, one photoresist patternedwafer was loaded onto a fixed hexode position in each runand the rest of the positions were filled with thick SiO2

dummy wafers. The depth of etched steps was measured by asurface profilometer and used to calculate Pt etch rate~ER!and etch uniformity across the wafer. Uniformity numbersare determined by $12~ER top–ER center!/ER top%3100%. Optical microscopy, scanning electron microscopy~SEM!, and AES analyses were used to evaluate the surfaceand sidewall cleanliness of etched patterns after an O2

plasma ashing process. The wafers were ranked with clean-liness as a criteria, and arbitrary scales were assigned forcomparison purposes.

To characterize etch by-products, bare silicon couponswere used as witness samples in the RIE chamber duringprocessing and etch by-products were allowed to coat thesurface of the coupons. XPS was used to study the chemicalcomposition of the etch by-products formed from both Arand Ar–Cl chemistries. A summary of the various witnesssamples studied is given in Table I. During etching, the etchstops were determined by color change, implying that asmuch as half of the ‘‘etch stop’’ layer may have been re-moved before the etch process was terminated.

III. RESULTS AND DISCUSSION

A. Pt etch rate and etch uniformity

An initial screening experiment was used to determine thehighest Pt etch rate with reasonable etch selectivity to pho-toresist. The parameters studied were gas type~Ar, Cl2, andCF4 with 8% O2!, total gas flow~30 or 80 sccm!, pressure~5or 20 mTorr!, and bias~2550 or2650 V!. Although high Ptetch rates were achieved in several cells of the experiment,overheating due to prolonged etching at high powers dam-aged the equipment. As a result, the maximum power waslimited to 1 kW.

A subsequent response surface design by Box–Behnkenwith three parameters was used for the more complete study.The three parameters were: total gas flow~60, 70, and 80sccm!, Cl2 in Ar ~10%, 15%, and 20%!, and pressure~10, 15,and 20 mTorr!. Pt etch uniformity and Pt etch rate were themain responses of interest. In addition, Pt etch selectivity tophotoresist, and the surface and the sidewall cleanliness werealso considered in selecting the optimized Pt etch condition.The experimental results and the predicted Pt etch rates fromthe model~value in parentheses! are summarized in Fig. 1~a!

as a three-dimensional display in Å/min. Thex, y, and zaxes correspond to total gas flow, Cl2 in Ar, and pressure,respectively. The value at the origin represents the average ofthree experimental repetitions and the model predicted value.Figure 1~a! shows that low-pressure, low %Cl2, andmedium-to-high total gas flows are desirable for achievingthe highest Pt etch rates. A similar three-dimensional plot ofPt etch uniformities across the wafers is shown in Fig. 1~b!.Pt etch uniformities are best at low pressures and moderate%Cl2, but at either low or high total gas flows. The datashow that low pressure is the most critical parameter neces-sary to achieve high Pt etch rate and good etch uniformityacross the wafer.

A full load of 18 150 mm wafers with 200 nm Pt filmswas etched using the optimized conditions~Ar–15%Cl2, 60sccm, 10 mTorr! to evaluate the etch rate and across loadetch uniformities. The results showed that a repeatable Ptetch rate of about 5 nm/min was achieved and the etch uni-formity from wafer to wafer was about63% ~1s!.

These data are all consistent with a physical sputter re-moval mechanism for the platinum. This has several unpleas-ant implications, among them a predictably slow etch rate,poor selectivities to resist masks, and redeposition on thereactor walls of the removed material, which necessitatesfrequent system cleaning. Reducing the pressure increasesthe etch rate somewhat, but the addition of chlorine de-creases the rate and, as shown below, the etch productschange.

B. Surface and sidewall cleanliness after Pt RIE

The surface and sidewall of the wafers after etch and pho-toresist strip~plasma ashing! were examined with an opticalmicroscope, SEM, and AES. Selected SEM micrographs areshown in Fig. 2. Without the resist reflow step, a thick layerof ‘‘fence’’ about 500 nm tall is produced, as displayed inFig. 2~a!. If only Ar gas is used, the surface of the etched Ptpads became extremely rough@Fig. 2~b!#. These roughenedPt surfaces are thought to be the result of Pt or Al~etchedfrom the chamber! redeposition onto the surface of the resistpattern. These formed micromasks on the resist surface caus-ing the resist to erode nonuniformly. Over-etched resist pat-terns then resulted in the roughened Pt surface. Wafers

TABLE I. Witness sample number and RIE process conditions.

Sample number RIE gas chemistry Etch stop layer

1 Ar–Cl SiO2

2 Ar Pt3 Ar TiO2

4 Ar–Cl TiO2

Blank None None

FIG. 1. Three-dimensional plots of~a! Pt etch rates in Å/min and~b! Pt etchuniformity in percent, by experiment and by model prediction~in parenthe-sis!. Origin: x(total flow)570 sccm, y(Cl2)515%, and z(pressure)515 mTorr. The value at the origin is the average of three replicated ex-periments.

1490 Chang et al. : A study of platinum electrode patterning 1490

J. Vac. Sci. Technol. A, Vol. 16, No. 3, May/Jun 1998

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

etched in Ar with 15% Cl2 and 60 sccm total gas flow at 10mTorr resulted in fairly clean surfaces as shown in Fig. 2~c!.Figure 2~d! is a cross-sectional SEM showing a slope in thePt electrode sidewall of about 33°.

The cleanliness of both the etched field areas and the un-etched Pt metal surface from which the resist has beenstripped was analyzed with AES after RIE under variousconditions. Figures 3~a! and 3~b! show Auger spectra repre-senting the Pt surfaces and etched field areas, respectively.The Pt surfaces are oxidized as a result of the O2 plasmaresist strip. Traces of Al and Si are detected on most of the Ptsurfaces and are thought to be coming from slight etching ofthe alumina-coated wafer trays and the SiO2-coated dummywafers. The Ar-only etch shows the highest level of residualAl on the Pt surfaces since without Cl2 there is no volatile Aletch product. In the etched field areas, Auger analysis de-tected TiO2 surfaces with varying levels of residual Pt andalso varying levels of the trace Al and Si contaminants. Forthe etch in Ar–15% Cl2, 60 sccm at 10 mTorr, there was noPt detected in the etched field area.

These data suggest that the combination of resist profile

and the addition of Cl2 to the plasma are helpful in producinga sample with less residue. Tapered resist sidewalls areknown to be useful in ion milling since redeposited materialis exposed to the ion flux, and consequently, removed. Ta-pered resist, however, is not an acceptable solution forsmaller geometries. The reason for the beneficial effect of theCl2 is less clear. Cl2 does enhance the resist etch rate, whichwill likely increase the sidewall taper, but the cause of thereduction in micromasking of the top resist surface is lessobvious. The lack of any increase in Pt etch rate with Cl2

addition does not support even a limited volatility of aPt–Cl2 etch product. This leads us to speculate that the mi-cromasking is caused primarily by the redeposited Al and theCl2 is more effective in removing this contamination. Whilethe addition of chlorine improves the etch characteristics andimmediate postetch wafer appearance, it raises questions asto subsequent wafer cleaning processes and environmental,health, and safety~EHS! issues primarily associated with re-actor cleaning. Thus, it becomes very important to under-stand exactly what the etch by-products are.

FIG. 2. SEM micrographs of etched Pt pads (100mm3100mm) under various RIE conditions after the resist has been oxygen plasma stripped.~a! Ar–15%Cl2 at 80 sccm total gas flow at 10 mTorr pressure without resist reflow.~b! Ar at 70 sccm total gas flow at 10 mTorr pressure with resist reflow.~c! Ar–15%Cl2 at 60 sccm total gas flow at 10 mTorr pressure with resist reflow.~d! Cross-sectional SEM of~c! showing the Pt sidewall to have an angle of about 33°.Low-temperature silicon dioxide was deposited on the sample to facilitate cleaving.

1491 Chang et al. : A study of platinum electrode patterning 1491

JVST A - Vacuum, Surfaces, and Films

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

C. Pt RIE by-product analysis by XPS

Table II shows selected elemental composition ratios forthe surfaces of five silicon coupon witness samples describedearlier. The Cl/Pt ratio is higher for those samples processedin the Ar–Cl chemistry~samples 1 and 4!. The other samples~samples 2 and 3, processed in Ar only! show a smallamount of Cl contamination, probably due to residual Cl inthe background ambient during etching. The Ti/Pt ratio issmall in all cases~Ti concentration was approximately 1%!.TiO2 was the etch stop layer for samples 3 and 4 layer, whilewafer 1 was etched through to the SiO2 layer, which approxi-mately doubles the amount of TiO2 etched. The slightlyhigher Ti/Pt ratio for wafer 1 may be due to an increase in

thickness of the sputtered TiO2 layer. The C/O ratio forsample 2~etched only through the photoresist to Pt! has amuch higher C content relative to O than the other samples.

Figure 4 shows the Pt 4f XP spectra for samples 2 and 3~Ar only process!. The literature values for the Pt 4f 7/2 bind-ing energy for selected Pt compounds are given by the ver-tical lines in Fig. 4. For samples 2 and 3, the Pt 4f 7/2 peak isat 72.1 and 71.8 eV, respectively, both with a full width athalf maximum~FWHM! of 2.0 eV. This large FWHM indi-cates that the peak is most likely the combination of twotypes of Pt with similar binding energies. Literature bindingenergies for both Pt metal and the compound Pt~OH!2 arefound in this region,18–21 indicating that the peak is a com-

FIG. 3. Auger survey spectra of~a! Pt surfaces and~b! etched field areas following various etches.

1492 Chang et al. : A study of platinum electrode patterning 1492

J. Vac. Sci. Technol. A, Vol. 16, No. 3, May/Jun 1998

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

bination of these two species, or perhaps a Pt suboxide.18–21

Peak fitting using a mixed Gaussian–Lorentzian line shape~results are not shown here for brevity! and the literaturebinding energies for Pt metal and Pt~OH!2 /Pt suboxideyields a fitted spectrum similar to those obtained experimen-tally for wafers 2 and 3, confirming the assignment.

Samples 1 and 4, etched with the Ar–Cl chemistry, have aPt 4f 7/2 peak at 73.5 eV. This peak is assigned to PtCl2.

18–21

The Pt 4f 7/2 peak for sample 4 has a FWHM of 1.5 eV,indicating that there is essentially one kind of Pt speciespresent in the sample. The Pt 4f 7/2 peak for sample 1, on theother hand, has a FWHM of approximately 1.9 eV, indicat-ing potential contributions from more than one Pt species,including PtCl2 and Pt~OH!x or Pt suboxides. The spectrumfor sample 1 also has a peak at 75.5 eV, in good agreementwith the literature binding energy for PtCl4.

18–21 For longeretch times, the Cl/Pt ratio increases and there is a concurrentgrowth of the 75.5 eV peak and decrease in intensity of the

73.5 eV peak, indicating that some Cl uptake is through theaddition of Cl to PtCl2 forming PtCl4.

Figure 5 shows the XP spectra for the chlorine 2p regionfor various processing conditions. For samples 2 and 3, theCl uptake is mainly from the background (%Cl,5%) and isin the form of Pt–Cl bonding. Pt–Cl binding energies arefound in the 198.8 eV region; however, XPS cannot deter-mine the difference between PtCl2 and PtCl4 from the Cl2p3/2 binding energies.18–21 Sample 4 has a small contribu-tion from Pt–Cl-type bonding in the 198.8 eV region, but themajority of Cl in this sample has a binding energy of 200.0eV. The literature gives the binding energy of Cl in poly~vinyl chloride! and many other organic chlorine containingcompounds in the 200 eV region.18–21 Sample 1 shows anincrease in intensity at 198.8 eV and a concurrent decrease inintensity of ‘‘organic’’ Cl. This increase in Pt–Cl bondingrelative to ‘‘organic’’ Cl is most likely an increase in PtCl4

content, as seen in the Pt 4f 7/2 data above.

FIG. 4. Platinum 4f XP spectra for various processing conditions. The vertical lines designate literature values for the Pt 4f 7/2 binding energies for variouscompounds.

TABLE II. Selected elemental composition ratios for Pt RIE witness samples generated under various processingconditions.

Sample number Conditions Cl/Pt Ti/Pt C/O

1 Ar–Cl to SiO2 2.79 0.136 0.6612 Ar to Pt 0.104 ¯ 1.123 Ar to TiO2 0.0895 0.0246 0.7544 Ar–Cl to TiO2 2.36 0.0511 0.565

Blank None ¯ ¯ 0.177

1493 Chang et al. : A study of platinum electrode patterning 1493

JVST A - Vacuum, Surfaces, and Films

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

FIG. 6. Oxygen 1s XP spectra for various processing conditions. The vertical lines designate the literature values for the O 1s binding energies for variouscompounds.

FIG. 5. Chlorine 2p XP spectra for various processing conditions. The vertical lines designate literature values for the Cl 2p3/2 binding energies for variouscompounds.

1494 Chang et al. : A study of platinum electrode patterning 1494

J. Vac. Sci. Technol. A, Vol. 16, No. 3, May/Jun 1998

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

Figure 6 shows the oxygen 1s XP spectra for various RIEprocessing times and a blank sample. The blank and samples1 and 4 show oxygen bound to Si~in SiO2! and organicoxygen to higher binding energy. The vertical lines in Fig. 6represent the literature binding energies for selected com-pounds. These samples also have a larger oxygen uptake~relative to carbon content! than samples 2 and 3. Thesamples generated during etching in a Ar-only ambient~2and 3! also show a change in oxygen 1s binding energy witha broadening of the peak. The lower binding-energy compo-nents are contributions from Pt–O and Ti–O bonding. ThePt–O bonding cannot be observed directly in the Pt 4f 7/2

spectra because of the large Pt–Cl component.The XP spectra for the Ti 2p3/2 region are not shown here

for brevity, but all spectra indicate that the Ti that is presentis in an oxidized form.

Figure 7 shows the XPS depth profile data for sample 1.This layerlike structure shown in the XPS depth profile is thereverse of the structure of the etched sample with the excep-tion that no Ti was found on the witness sample due to thevolatility of the Ti containing etch by-products. The profile isdivided by vertical lines delineating the chemical nature ofany Pt containing by-products. The topmost surface is com-posed mainly of PtCl2 and PtCl4, as observed above in thesurface spectra. After approximately 12 min total sputtertime, a region of Pt metal and Pt~OH!2 or Pt suboxide isreached. Further into the film~as the Pt signal dies away!PtCl2 species are detected after approximately 38 min totalsputter time.

The conversion of the etch product into Pt chlorides po-tentially offers benefits. Unlike Pt, which is soluble only in

aqua regia, PtCl2 is known to be soluble in HCl and NH4OH,and PtCl4 is known to be soluble in water and alcohol.22

Thus, not only does the addition of chlorine to argon in theRIE system produce cleaner as-etched wafers, but the solu-bility data strongly suggest further work in postetch wetcleaning with NH4OH and water solutions. From an EHSstandpoint, these are preferable to aqua regia.

An examination of the Material Safety Data Sheets23 forPtCl2 and PtCl4 suggests that reactor cleaning requires onlythe typical protective measures. Both materials are harmfulby inhalation, in contact with skin, and if swallowed, so pro-tective clothing, gloves, and approved respirators must beused. Our experience shows that water seems to be an ad-equate cleaning solution for the reactor surfaces. This is pref-erable to a more aggressive chemical and physical clean thatis expected for an argon-only Pt sputter etch process.

IV. CONCLUSIONS

An etch process for photoresist masked Pt films has beendefined in a batch RIE system commonly used in production.Uniformity is acceptable but the etch rate is slow~approxi-mately 5 nm per min!, resulting in throughputs on the orderof 18 150 mm wafers per hour for Pt films 200 nm in thick-ness. The addition of chlorine to the argon plasma does notenhance the etch rate but does reduce residues on as-etchedwafers and converts the etch products to primarily PtCl2 andPtCl4. Because of the enhanced solubility of these com-pounds relative to Pt, this may offer advantages in both wa-fer and reactor postetch cleaning by allowing the use of morebenign cleaning solutions. The PtCl2 and PtCl4 etch products

FIG. 7. XPS depth profile for sample 1 showing layered structure of witness sample after reactive ion etching of platinum. Headings along the top of the figureindicate the bonding of any Pt which was detected in that portion of the profile.

1495 Chang et al. : A study of platinum electrode patterning 1495

JVST A - Vacuum, Surfaces, and Films

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28

do not appear to introduce any significant new EHS issues.These results will also be applicable to single-wafer RIE pro-cesses that use the same chemistry for patterning Pt.

ACKNOWLEDGMENTS

The authors would like to thank Dan Sullivan and EricEhlert for substrate preparation and Lorraine Johnston for theSEM work.

1D. E. Kotecki, Integr. Ferroelectr.16, 1 ~1997!.2J. Joo, J. Seon, Y. Jeon, K. Oh, J. Roh, and J. Kim, Appl. Phys. Lett.70,3053 ~1997!.

3T. B. Wu, C. M. Wu, and M. L. Chen, Appl. Phys. Lett.69, 2659~1996!.4S. Park, C. Hwang, H. Cho, C. Kang, H. Kang, S. Lee, and M. Lee, Jpn.J. Appl. Phys., Part 135, 1548~1996!.

5K. Numata, Y. Fukuda, K. Aoki, and A. Nishimura, Jpn. J. Appl. Phys.,Part 134, 5245~1995!.

6K. P. Lee, Y. S. Park, D. H. Ko, C. S. Hwang, C. J. Kang, K. Y. Lee, J.S. Kim, J. K. Park, B. H. Roh, J. Y. Lee, B. C. Kim, J. H. Lee, K. N. Kim,J. W. Park, and J. G. Lee, International Electron Devices Meeting~IEDM! Technical Digest6, 907 ~1995!.

7W. Y. Hsu, J. D. Luttmer, R. Tsu, S. Summerfelt, M. Bedekar, T. Toku-moto, and J. Nulman, Appl. Phys. Lett.66, 2975~1995!.

8K. Torii, H. Kawakami, H. Miki, K. Kushida, T. Itoga, Y. Goto, T.Kumihashi, N. Yokoyama, M. Moniwa, K. Shoji, T. Kaga, and Y.Fujisaki, Integr. Ferroelectr.16, 21 ~1997!.

9J. Lee, H. Jung, O. Auciello, and A. I. Kingon, J. Vac. Sci. Technol. A14,900 ~1996!.

10G. A. C. M. Spierings, G. J. M. Dormans, W. G. J. Moors, M. J. E.Ulenaers, and P. K. Larsen, J. Appl. Phys.78, 1926~1995!.

11J. O. Olowolafe, R. E. Jones, Jr., A. C. Campbell, R. I. Hegde, C. J.Mogab, and R. B. Gregory, J. Appl. Phys.73, 1764~1993!.

12K. Arita, E. Fujii, Y. Shimada, Y. Uemoto, T. Nasu, A. Inoue, A. Mat-suda, T. Otsuki, and N. Suzuoka, Jpn. J. Appl. Phys., Part 133, 5397~1994!.

13C. E. Farrell, K. R. Milkove, C. Wang, and D. E. Kotecki, Integr. Ferro-electr.16, 109 ~1997!.

14W. Yoo, J. Hahm, H. Kim, C. Jung, Y. Koh, and M. Lee, Jpn. J. Appl.Phys., Part 135, 2501~1996!.

15S. Yokoyama, Y. Ito, K. Ishihara, K. Hamada, S. Ohnishi, J. Kudo, andK. Sakiyama, Jpn. J. Appl. Phys., Part 134, 767 ~1995!.

16K. Nishikawa, Y. Kusumi, T. Oomori, M. Hanazaki, and K. Namba, Jpn.J. Appl. Phys., Part 132, 6102~1993!.

17C. Chou and J. Phillips, J. Appl. Phys.68, 2415~1990!.18K. S. Kim, N. Winograd, and R. E. Davis, J. Am. Chem. Soc.93, 6296

~1971!.19J. Escard, B. Pontvianne, and J. P. Contour, J. Electron Spectrosc. Relat.

Phenom.6, 17 ~1975!.20J. S. Hauimond and N. Winograd, J. Electrochem. Electronal. Chem.78,

55 ~1977!.21Handbook of X-ray Photoelectron Spectroscopy,edited by J. Chastain

~Perkin–Elmer, Eden Prairie, MN, 1992! and references cited therein.22Hawley’s Condensed Chemical Dictionary, 12th ed., revised by R. J.

Lewis, Sr.~Van Nostrand Reinhold, New York, 1993!, p. 925.23Material Safety Data Sheets, Chemical Identification Catalog No. 206091,

platinum~II ! chloride, and Catalog No. 37984-0, platinum~IV ! chloride,courtesy of Aldrich Chemical Co., Inc., P.O. Box 355, Milwaukee, WI,53201.

1496 Chang et al. : A study of platinum electrode patterning 1496

J. Vac. Sci. Technol. A, Vol. 16, No. 3, May/Jun 1998

Redistribution subject to AVS license or copyright; see http://scitation.aip.org/termsconditions. Download to IP: 128.138.73.68 On: Sat, 20 Dec 2014 14:35:28