Книги2 / 1993 Dutton , Yu -Technology CAD_Computer Simulation
.pdfC.l. ID BJT |
359 |
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Title Stanford' BiCMOS-2um Process (npn) |
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Comment |
Start with <100> Silicon. p-doped to 20 |
ohm Resistivity. |
Initialize |
<100> Silicon Boron Concentration-9.0E14 Thickness-6 |
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+Spaces-300
Comment |
Changing Default Coefficients to Prevent Excessive Outdiffusion |
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Wet02 <100> Lin.H.0=2.428e6 Lin.L.0=2.793e4 |
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Segregation Phosph Si |
lOx Mui.O=O.O Model. 1 |
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Segregation Phosph Si lAir Trans.0=1.66e-7 |
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Comment |
Initial Oxidation to 2370 Angstroms |
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Diffusion |
Time=35 |
Temp=BOO |
T.Rate=5.714 |
Diffusion |
Time=10 |
Temp=1000 Dry02 |
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Diffusion |
Time=32 |
Temp=1000 Wet02 |
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Diffusion |
Time=10 |
Temp=1000 Dry02 |
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Diffusion |
Time=30 |
Temp=1000 T.Rate=-6.66 |
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Comment |
n-Well Drive-in |
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Diffusion |
Time=35 |
Temp=800 |
T.Rate=5.7l4 |
Diffusion |
Time=10 |
Temp=1000 Dry02 |
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Diffusion |
Time=30 |
Temp=1000 Wet02 |
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Diffusion |
Time-l0 |
Temp=1000 Dry02 |
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Diffusion |
Time-20 |
Temp=1000 T.Rate=7.5 |
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Diffusion |
Time=960 |
Temp-l1S0 |
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Comment |
Stop Simulation at |
BOO C |
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Diffusion |
Time=65.6 Temp-1150 T.Rate--5.333 |
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Comment |
Masking Oxide Etch after Collector Litho. |
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Etch |
Oxide |
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Comment |
Collector Implant. |
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Grid |
Layer. 1 XdX=0.12 dX=0.005 |
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Implant |
Phosphorus Pearson Dose=3e13 Energy=lOO |
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Comment |
Collector Drive-in |
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Diffusion |
Time=35 |
Temp=800 |
T.Rate=5.7l4 |
Diffusion |
Time=10 |
Temp=lOOO Dry02 |
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Diffusion |
Time=30 |
Temp=lOOO Wet02 |
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Diffusion |
Time=10 |
Temp=1000 Dry02 |
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Diffusion |
Time=20 |
Temp=1000 T.Rate=5.0 |
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Diffusion |
Time=200 |
Temp=ll00 |
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Comment |
Stop Simulation at 800 C |
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Diffusion |
Time=55.7 Temp=llOO T.Rate=-5.385 |
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Comment |
Oxide Etch. |
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Etch |
Oxide |
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C.l. |
lD BJT |
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361 |
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Deposit |
Polysilicon Thickness=O.15 Temp=620 Pressure=O.0004 |
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Comment |
Nitride Deposition |
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Deposit |
Nitride Thickness=O.03 dX=O.005 |
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Comment |
Oxide Deposition |
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Deposit |
Oxide Thickness=O.5 |
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Comment |
Etch LTO Used for the Extrinsic Base Masking |
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Etch |
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Oxide |
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Comment |
Polysilicon Oxidation |
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Grid |
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Layer.2 Dx=O.OOl Xdx=O.015 |
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Diffusion |
Time~20 |
Temp=800 |
T.Rate=5.0 |
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Diffusion |
Time-5 |
Temp=900 |
Dry02 |
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Diffusion |
Time=200 Temp=900 |
Wet02 |
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Diffusion |
Time-5 |
Temp=900 |
Dry02 |
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Diffusion |
Time=13.3 Temp=900 |
T.Rate=-7.5 |
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Comment |
Sidewall Oxidation |
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Diffusion |
Time-5 |
Temp-850 |
Dry02 |
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Diffusion |
Time=6 |
Temp=850 |
Wet02 |
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Diffusion |
Time=5 |
Temp=850 |
Dry02 |
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Comment |
n-Channel SID and n+ Poly Implant |
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Implant |
Arsenic Pearson Dose-le16 Energy-80 |
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Comment |
n-Channel and Emitter Drive-In |
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Diffusion |
Time=25 |
Temp=800 |
T.rate=8.O |
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Diffusion |
Time=10 |
Temp=1000 Dry02 |
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Diffusion |
Time-24 |
Temp=1000 T.rate--8.333 |
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Comment |
Poly Resistor Anneal/Oxidation |
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Diffusion |
Time=25 |
Temp=800 |
T.rate=4.0 |
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Diffusion |
Time=40 |
Temp=900 |
Dry02 |
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Diffusion |
Time=tO Temp=900 T.rate=-10.0 |
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Etch |
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Oxide |
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Etch |
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Nitride |
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Etch |
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Polysilicon |
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Layer |
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Plot |
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Plotdev=xterm Net |
Chemical Xmax=3 |
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Savefile |
Struct |
File=npn.str |
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Savefile |
Export |
File=npn.exp |
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Stop |
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362 APPENDIX C. TEMPLATES FOR PISCES SIMULATION
The output net doping profile from SUPREM III is shown in
Fig. C.2(a), and the actual doping profile used by PISCES is shown in Fig. C.2 (b) in order to put the back contact directly to the collector region. Note that after stripping the polysilicon layer, the depth of the emitter-base junction is about 0.18 j.lm, and that of the base-collector junction is around 0.33 j.lm. In doing PISCES simulation the polysilicon layer can be modeled using the finite surface recombination velocity for the minority carriers (holes in npn transistors) at the emitter contact. In the following we will treat the heavily doped polysilicon layer as a metal contact. The input file for PISCES in order to simulate the Gummel plot and IT vs. VBE for a fixed base-collector bias and at the same time to perform zero-frequency analysis is included below. The so-called "zerofrequency" is actually an asymptotic extreme for low-frequency analysis (J -;. 0). Users can use standard features of ac analysis in PISCES by specifying a low value offrequency (such as freq=l Hz) to get the same, zero-frequency analysis result.
Title npn from Stanford BiCMDS process
option plotdev-xterm
mesh rect nx-2 ny=40l
x.m n=l |
1=0 |
r=1 |
x.m n=2 |
1=1.0 |
r=l |
y.m n=l |
1=0 |
r=1.0 |
y.m n=40l |
1=2.2 r=1.0 |
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region num=l ix.l=l ix.h=2 iy.I=1 iy.h=40l silicon
elec num=1 ix.l=l ix.h=2 iy.l=l iy.h=l elec num=2 ix.l=l ix.h=l iy.l=37 iy.h=39 elec num=3 ix.l=1 ix.h=2 iy.l=401 iy.h=40l
dop |
sup boron |
infil=npn.exp x.l=O |
x.r=l |
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dop |
sup |
arsenic |
infil=npn.exp x.l=O |
x.r=1 |
dop sup |
phosphorus |
infil=npn.exp x.l=O x.r=l |
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contact |
num=2 surf.rec vsurfn=leO vsurfp=le7 |
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symb newton carr=2
364 APPENDIX C. TEMPLATES FOR PISCES SIMULATION
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-e-- |
Zero.freq Analysis |
10' |
--6- Freq·dep AnBtyai8 |
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10'
10' '- ...'-~ o-J'--'-~"""""~~ |
......... |
J.~~----"-~~----"-~~-'--' |
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0.4 |
0.5 |
0.6 |
0.7 |
0.8 |
VB. M
Figure C.3: Comparison between the computed (zero-frequency) and simulated (frequency-dependent ac analysis) iT VS. VEE.
model temp=300 srh auger conmob fldmob bgn method itlimit=15 trap p.tol=1.e-8 c.tol=1.e-8
plot.ld dop x.s=l x.e=1 y.s=O y.e=2.2 log abs
solve ini
log ivfil=npn.iv acfile=npn.ac
solve v2=O.4 v3=1.4 vstep=O.025 nstep=24 elect=23 proj lowf term=2
plot.1d x.a=v2 y.a=i3 log abs min=-12 plot.ld x.a=v2 y.a=i2 log abs unch
end
The computed iT VS. VEE based on the formula
iT = |
gm |
= _g_3_2_ |
(C.l) |
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211"(CEE + CEe) |
21l"C22 |
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where g32 and C22 are obtained from the zero or low frequency analysis (lowf in solve card), are compared to the result from the real, frequency dependent ac analysis. It can be seen that before the high-level injection (HLI) occurs, the agreement is perfect, and after the transistor enters into the HLI operation regime, the computed c's can no longer
C.2. MOS CAPACITORS |
365 |
be considered as the accurate representation of the capacitance as explained in [C.1], and the results from analytical formulation are no more correct. For this particular structure (npn from the triple diffusion), the dip at VBE = 0.9 V is abnormal and is most likely caused by the low doping level at the collector contact.
C.2 M 0 S Capacitors
The special features to pay attention to with 1D MOS template are (1) the way to put the source region in the simulation region and (2) how to evaluate the integral charge after each solution is found and to assemble the results of charge vs. bias in one data file. The following example shows the process. The purpose of the simulation is to compute the channel charge vs. VGS with VBS as the parameter.
For n-channel capacitor at VBS = -1 V, VGS is ramped from 0 to 1.5 volts with voltage step smaller around where the threshold voltage is expected.
title Simulation of nMOS Capacitor
options plotdev=xterm
mesh rect nx=4 ny=Sl
x.m n=l |
1=0 |
r=l |
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x.m n=2 |
1=0.1 r=l |
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x.m n=3 |
l=S.O |
r=l |
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x.m n=4 |
1=6.0 r=l |
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y.m n=l |
1=0 |
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r=1.0 |
y.m n=2 |
1=0.0418 |
r=1.0 |
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y.m n=3 |
1=0.05 |
r=1.0 |
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y.m n=Sl |
1=4.0 |
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r=1.0S |
region num=l ix.l=l ix.h=4 iy.l=l iy.h=2 oxide region num=2 ix.l=l ix.h=4 iy.l=2 iy.h=Sl silicon
$ Electrodes: 1- Gate, 2- Substrate, 3- Source elec num=l ix.l=l ix.h=4 iy.l=l iy.h=l
elec num=2 iX.l-l ix.h=4 iy.l=Sl iy.h=Sl elec num=3 ix.l=l ix.h=l iy.l=2 iy.h=3
dop suprem3 infil=nchcap.exp boron $ n-type source region
366 APPENDIX C. TEMPLATES FOR PISCES SIMULATION
dop uniform x.left=O x.right=O.l y.top=0.0418 y.bot-O.OS n.typ concz l.e20
$ Specify the gate material to set the work function right contact num=l n.poly
$ For initial solution, solve Poisson's equation only symb newton carr-O
model temp=300 srh
method itlimit=30 p.tol=1.e-8 c.tol=1.e-8 trap
plot.2d grid no.fil bound pause
plot.ld dop x.s=S. x.e=S. y.s=O. y.e=4. log abs pause
solve ini
$ Switch to solving the complete Semiconductor equations symb newton carr=2
$ Using projection scheme for the guess to the next solution
solve v2=-1.0 proj
$ Integral charge of the channel carriers in the substrate
extract ele x.min=S. x.max=6. y.min=0.0418 y.max=4 outfil=nchcap.qn
solve vl=0.2 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=O.4 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn
solve vl=O.S proj
extract ele x.min=5. x.max=6. y.min=0.0418 y.max=4 outfil=nchcap.qn solve vl=O.S5 proj
extract ele x.min=5. x.max=6. y.min=0.0418 y.max=4 outfil=nchcap.qn solve vl-0.6 proj
extract ele x.min=5. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=O.65 proj
extract ele x.min=5. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=O.7 proj
extract ele x.min=S. x.max=6. y.min=0.0418 y.max=4 outfil=nchcap.qn solve vl=O.7S proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve v1=O.8 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve v1=O.8S proj
extract ele x.min=S. x.max=6. y.min=0.0418 y.max=4 outfil=nchcap.qn
solve vl=O.9 proj
extract ele x.min=5. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=1.0 proj
C.2. MOS CAPACITORS |
367 |
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=1.1 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=1.2 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=1.3 proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn solve vl=1.4 proj
extract ele x.min-S. x.max=6. y.mina O.0418 y.max=4 outfil=nchcap.qn solve vl=l.S proj
extract ele x.min=S. x.max=6. y.min=O.0418 y.max=4 outfil=nchcap.qn end
Figure C.4: Template for simulation of n-channel MOS capacitor.
The output of the mesh is shown in Fig. C.5 in which there are four grids in the lateral (x -) direction. The first two grids from the left are only 0.1 JLm apart, and this spacing is served to form a source region. Only one grid spacing (y = 0.0418 '" 0.05 JLm) is assigned to the source region for contacting to the channel after it is formed. The second and third grids should be separated far enough (in this example, it is almost 5 JLm) to buffer the depletion region between the source and substrate from affecting the right-most part of the simulation region. The last spacing between grids 3 and 4 is set to be 1 JLm to ease the computation of the channel charge per square surface area.
The doping profile is shown in Fig. C.6 (a). The curve of Qn vs. Vas can be obtained by manipulating the data file nChcap. qn, and is plotted in Fig. C.6 (b).