12004 MAPLD/138Bytkin Reduction of the Thermo stable Radiation Defects Probability Formation in Si and SiGe as a Physical Basis of the Bipolar npn Transistors

12004 MAPLD/138 Bytkin

Reduction of the Thermo stable Radiation Defects Probability Formation in Si and SiGe as a Physical Basis of the Bipolar npn Transistors Radiation Hardness Increase at the Application of the Radiation & Thermal Processing (RTP-

technology).

S.V. Bytkin

Ukraine, Zaporozhye, [email protected]


I. Introduction

In the previous report the author proposed the combination of the level of the Si doping by isovalent impurity (Ge), level of the preliminary irradiation of bipolar transistors and temperature of their isothermal annealing for the achievement

of the maximal radiation hardness. Actually, experimentally was found technological factor

combination, providing theoretically full radiation hardness: h21E()/h21E(0)=1. Results,which are in

the next slide, are to be explained.


F t z1( ) F t z2( ) F t z5( )

Y= h21E()/h21E(0))

NGe=0

NGe=1,2x1019cm-3

Technological annealing temperature, C

NGe=1,2x1020cm-3

TID of the technological - irradiation, cm-2


Purpose of the work:

-explanation of the various character of npn transistor beta-current gain change after -irradiation for the transistors, subjected to various dozes of a preliminary technological -irradiation and isothermal annealing and manufactured on SiGe with different Ge content;

-description of the main RTP steps;


II. CHOICE OF THE TECHNOLOGICAL - IRRADIATION TID.

The basic purpose of a preliminary technological irradiation of npn transistor is decrease of the radiation defects formation probability, PiV (probability of the vacancy capture

by various impurities) in a material, on which the device was made. Formation of the defects at manufacturing of the device will decrease probability of their formation at the subsequent work of the device in real conditions of its application.


For the definition of PiV were used the empirical equations,

describing accumulation of the radiation defects. Quantity of the defects was measured by DLTS method. Obtained results were

expressed by formulas using STATISTICA 5.0, for example:

Scatterplot (RADDEF.STA 10v*20c)750*x

Alpha-irradiation Dose, cm^-2

Co

nce

ntr

atio

n o

f K

-ce

nte

rs in

SiG

e,

cm^-

3

1e13

3e13

5e13

7e13

9e13

2e14

4e14

6e14

1e10 1e11 1e12


Samples, used for the measurements and obtained results:

For the measurements was used CZ n- Si and n-SiGe (5x1019 cm-3), 35 Ohm x cm test p+n diodes (boron diffusion, depth of p+n junction 5 microns),concentration of oxygen in the initial wafer 7x1017 cm-3, carbon 2x1016 cm-3.

Main difference between Si and SiGe from the technologist’s point of view : the increased values of complexes Ci-Oi-V-V (K – centers) speed formation in SiGe during technological irradiation:


1 1010

1 1011

1 1012

1 1013

1 1012

1 1013

1 1014

1 1015

A-centers concentration in Si A-centers concentration in SiGeE-centers concentration in SiE-centers concentration in SiGeK-centers concentration in SiK-centers concentration in SiGeEv+0.22 eV in SiEv+0.22 eV in SiGeEc-0.22 eV in SiEc-0.22 Ev in SiGe

Integral alpha-particles flow,cm^-2

Co

ncen

trat

ion

of

the r

ad.

def

ect

s,c

m-3

1015

5 1012

f1 i( )

f2 i( )

f3 i( )

f4 i( )

f5 i( )

f6 i( )

f7 i( )

f8 i( )

f9 i( )

f10 i( )

5 10121 10

10 i


For calculation of PiV numerical

values in Si and SiGe use of the received empirical equations and the account of reduction of concentration of oxygen and carbon during an irradiation are necessary. For example:


2)())(())((

1750)(

SiGeSiGesiiSiGei

SiGe

VCCCAOK NtNNtNN

tP

)()()()()()(2

tNtNtNtNtttNVKEASiGeV SiGeSiGeSiGeSiGe

)lg(10846.110733.1)( 1314 ttNSiGeA

))(2)(2)()((1

)(2

tNtNtNtNt

tSiGeSiGeSiGeSiGe VKEASiGe


Probability of the K-center creation in Si, SiGe

1 103

1 104

1 105

1 106

1 1080

1 1079

1 1078

1 1077

1 1076

1 1075

1 1074

1 1073

1 1072

1 1071

1 1070

1 1069

1 1068

1 1067

1 1066

1 1065

1 1064

1 1063

1 1062

1 1061

1 1060

1 1059

1 1058

1 1057

1 1056

1 1055

1 1054

1 1053

1 1052

1 1051

1 1050

Probability of K-center creation in n-Si The same in n-SiGe

Time of alpha irradiation, s

Pro

bab

ilit

y o

f th

e K

-cen

ter

crea

tion

1 1050

1080

Pksi t( )

Pksige t( )

106

10( )3 t


Practical point of view:

received result specifies necessity of application of a long technological irradiation by -particles, 106s. For =6,4x106 cm-2s-1, 5х1012cm-2.

Initial values of npn transistor beta-current gain should be not less than 200, and their value after an irradiation makes 2…10.


II. CHOICE OF THE TEMPERATURE AND DURATION OF THE TECHNOLOGICAL

ISOTHERMAL ANNEALING.

From the point of view of RTP application, technological -irradiation creates in the recombination area "mix", consisting of the thermo stable and not thermo stable radiation defects. Consequently, the temperature of the annealing must be not less than 350С. It must provide preservation of low PiV of the main radiation defects (EV+0.35eV) at guaranteed stability of npn transistor beta-current gain in all range of working temperatures.


The curve, describing the recovery of the -irradiated transistors during annealing is the following:

0 50 100 150 2000

0.2

0.4

0.6

0.8

1

1.2

npn transistor (Nge=0)npn transistor (Nge=1.3x10^19cm^-3)npn transistor (Nge=1.3x10^20cm^-3)

Duration of the annealing, minutes

Reco

very

of

the b

eta

-curr

ent

gain

1.3

0.01

f1

f2

f3

1650


Practical point of view:

-npn IC transistors after technological irradiation are to be annealed at the temperature not less than 350С.

-duration of the annealing must be determined experimentally for every type of the transistor, but in every case it has to provide stabilization of the beta-current gain.


III. PROVIDING OF THE INVERSE BETA-CURRENT GAIN OF THE OVERLAY TRANSISTOR LOW VALUE DURING OF THE TECHNOLOGICAL ISOTHERMAL

ANNEALING.

Primary goal at realization of the high-temperature annealing is restoration of amplification properties of the output transistor at preservation low, achieved as a result of an irradiation, values of the inverse beta-current gain of the TTL overlay transistor.

Low Ge concentration allows separate recovery of different TTL transistors and produce well-behaved IC (low values of the input current).


Regression equation looks like: q=3,294-2,218x10-20NGe-1,329x10-2+1,17x10-22NGe.

For NGe1x1019cm-3 and =50 min, q=2.5,

where

)0(

)()0(

)(

21

21

21

21

Einverse

Einverse

E

E

h

hh

h

q


RESUME.

1. Physical basis of bipolar npn transistors radiation hardness increase at RTP application is decrease of the basic recombination centers probability formation at realization of technological irradiation. Main level (EV+0.35eV) is thermo stable. Distinction

in probability of K-center formation in Si and SiGe explains previously received results.

2. Long (about 60 min. for the SiGe npn transistors and 150min. for Si devices) annealing at 350С as a part of RTP allows excluding presence in an active transistor base practically all radiation defects which bake out at work in actual conditions will result in instability of the IC performance.

3. Manufacturing of the bipolar devices on SiGe with NGe1x1013cm-3

allows to speed up RTP realization and to make the integrated microcircuits appropriate to standards due to the separation of the annealing of the inverse beta-current gain of the TTL overlay transistor and of the output transistor.

Documents

12004 MAPLD/138Bytkin Reduction of the Thermo stable Radiation Defects Probability Formation in Si and SiGe as a Physical Basis of the Bipolar npn Transistors