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I am modeling a transistor in IC-CAP using the spice level 3 simulator. I extracted these parameters and tried importing them as a spice model in LT spice, but the output current is less than half and the curves look different. Any suggestions on what am I missing? Here is the .model:

.MODEL PlanarFET NMOS (LEVEL=3
+UO=117.8 VTO=2 NFS=0 TOX=30n NSUB=2.44E19 NSS=0 VMAX=48.69K 
+RS=19.77K RD=22.51K RSH=0 CBD=0 CBS=0 CJ=0 MJ=0.5 
+CJSW=0 MJSW=0.33 IS=164.2E-12 PB=0.8 FC=0.5 KAPPA=4.537 XJ=0 LD=0 DELTA=0 THETA=0 ETA=0)

The IC-CAP software is using a level three spice simulation based initially on this model, which the parameters are being fitted as shown below in the screenshot.

M1 1=D 2=G 3=S 4=B MOSMOD L=2u W=10u AD=100p AS=100p PD=104u PS=104u
.MODEL MOSMOD NMOS
+ LEVEL     = 3
+ UO        = 600
+ VTO       = 0
+ NFS       = 0
+ TOX       = 100n
+ NSUB      = 1.00e+15
+ NSS       = 0
+ VMAX      = 1MEG
+ RS        = 0
+ RD        = 0
+ RSH       = 0
+ CBD       = 0
+ CBS       = 0
+ CJ        = 0
+ MJ        = 0.5
+ CJSW      = 0
+ MJSW      = 0.33
+ IS        = 1.0E-14
+ PB        = 0.8
+ FC        = 0.5
+ XJ        = 0
+ LD        = 0
+ DELTA     = 0
+ THETA     = 0
+ ETA       = 0
+ KAPPA     = 0.2

enter image description here

Ste Kulov
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Barlo67
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    Might be a good idea to post your .model as text so people don't have to type it out from your picture in case they want to try it. I'm a loser and did it anyway, and I don't even get the same exact results as you (my currents are even lower). Couple things I noticed are that CJSW and MJSW are mixed up and don't match the chart. Also IS doesn't match the chart. These aren't the cause of your discrepancy, but it's worth noting at least. – Ste Kulov Oct 16 '22 at 08:19
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    RD is also slightly wrong. I tested the same circuit in ngspice and received the same exact results as I did in LTspice. I don't know how you're getting different results than me. Are you leaving anything out of your screenshots? Please try to include as much information as possible. What are the Vgs steps you're using in the IC-CAP screenshot? What does the label for the vertical axis that's cut-off say? – Ste Kulov Oct 16 '22 at 17:02
  • Opps yeah apparently RD is slightly off and IS is E14 vs E12, though fixing that doesn't give me the same current. The IC-CAP data is 6 steps of 2V each going from 0 to 10V, Where the current on the y-axis is given in uA. The level three spice model in LT spice with this parameters doesn't capture the current or the challenge length modulation, though level 3 doesn't utilize lambda? – Barlo67 Oct 16 '22 at 17:18
  • Added the the code on which the initial plotting is done, where editing of the model's parameters as shown in the screenshot is done in order to match the data. – Barlo67 Oct 16 '22 at 17:21
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    @Barlo67Did you use the L, W, AD, ... parameters? – a concerned citizen Oct 16 '22 at 17:35
  • So adding in AD, AS, PD, PS has no impact. For L, W I think I can either specify that in the model, or it is overridden if in LTspice I specify a different L/W within the part? I simulated it in IC-CAP with L=2u W=10u, then LTspice having L=2u W=10u in the model or defining it within in the part doesn't seem to make a difference :( Ofc manually adjusting the L/W gives a different current, however it should be matched. – Barlo67 Oct 16 '22 at 18:16
  • What's that program you're using at the bottom? – Shredder Oct 16 '22 at 18:45
  • The bottom program is called IC-CAP which is for modeling devices and extracting parameters. This is performing a spice model fitting of raw data which I am trying to use these parameters to put into LTspice. – Barlo67 Oct 16 '22 at 19:32
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    Thanks. The missing info about L and W explains why I was not getting the same plots as you. I am unable to figure out the discrepancy, but I suspect it's on the IC-CAP side. LTspice and ngspice seem to be reproducing exactly what they're told to do. Very few of us have access to IC-CAP,, so you might not be able to get someone here who can explore that side for you. Since you're paying a ton of money for that software, shouldn't you be able to ask for support from Keysight? Lastly, your question about channel length modulation: KAPPA is used in LEVEL3, instead of LAMBDA for LEVEL1 and LEVEL2. – Ste Kulov Oct 17 '22 at 07:09

1 Answers1

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Apparently IC-CAP stopped supporting these older spice models and it seems like there was an internal error with the program. I think it may have had something to do with setting the wrong L and W internally. Making use of pspice in IC-CAP or a newer model seems to work fine.

Thanks for the inputs though!

Barlo67
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