Designer’s Guide Community

kiran123 Community Member Offline Posts: 42	Question about bisim3v3 parameters Jun 11^th, 2007, 1:19am Hi i am using BISIM3v3 level -11 model parameters and i could not find parameter "phi" which is useful for below equation , *VTH = VT0 + gamma ( sqrt(phi - VBS) - sqrt(phi) )** can anyone help me on how to get this gamma is declared as k1 in models statement Thanks & Regards Kiran
Back to top	IP Logged

Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: Question about bisim3v3 parameters Reply #1 - Jun 11^th, 2007, 4:12am The Berkeley code for BSIM3 has: pParam->BSIM3phi = 2.0 * Vtm0 * log(pParam->BSIM3npeak / ni); where Vtm0 is kT/q (for T=tnom) and BSIM3npeak is entered as the parameter NCH. ni is the intrinsic carrier concentration of Si.
Back to top	If at first you do succeed, STOP, raise your standards, and stop wasting your time. IP Logged

kiran123

Community Member

Offline

Posts: 42

Re: Question about bisim3v3 parameters
Reply #2 - Jun 12^th, 2007, 12:50am

Geoffrey_Coram wrote on Jun 11^th, 2007, 4:12am:

The Berkeley code for BSIM3 has:

pParam->BSIM3phi = 2.0 * Vtm0
� � * log(pParam->BSIM3npeak / ni);

where Vtm0 is kT/q (for T=tnom) and BSIM3npeak is entered as the parameter NCH. �ni is the intrinsic carrier concentration of Si.

Geoffrey,

what is this "pParam->" declaration ? where should i mention this to get "phi" value ?
i understood that the above equation is looks like
"phi" = 2 * kt/q * log( ni / NA)
can i take kT/q = 26mV at 300k
& ni = 1.45* 10^10 cm^-2 otherwise where from i should get ?
NA = nsub or nch ?

Thanks
Kiran

Back to top

IP Logged

Geoffrey_Coram

Senior Fellow

Offline

Posts: 1999
Massachusetts, USA

Re: Question about bisim3v3 parameters
Reply #3 - Jun 12^th, 2007, 4:14am

kiran123 wrote on Jun 12^th, 2007, 12:50am:

what is this "pParam->" declaration ? where should i mention this to get "phi" value ?
i understood that the above equation is looks like
"phi" = 2 * kt/q * log( ni / NA)
can i take kT/q = 26mV at 300k
& ni = 1.45* 10^10 cm^-2 otherwise where from i should get ?
NA = nsub or nch ?

pParam is a data structure in the BSIM3 source code (having to do with sharing values for devices with the same L and W).

You inverted the division in the log, it's log(NCH/ni), and NCH is the parameter.

ni = 1.45e10 * (Tnom / 300.15) * sqrt(Tnom / 300.15) * exp(21.5565981 - Eg0 / (2.0 * Vtm0));

You should double-check that Tnom in the model card is 27.0 C (which would be 300.15 K), else you'll have to adjust ni and kT/q from what you are using; then again, you may not care to be all that exact.

Back to top

If at first you do succeed, STOP, raise your standards, and stop wasting your time.

IP Logged

kiran123

Community Member

Offline

Posts: 42

Re: Question about bisim3v3 parameters
Reply #4 - Jun 21^st, 2007, 12:05am

Geoffrey_Coram wrote on Jun 12^th, 2007, 4:14am:

kiran123 wrote on Jun 12^th, 2007, 12:50am:

� what is this "pParam->" declaration ? where should i mention this to get "phi" value ?
i understood that the above equation is looks like
� �"phi" � �= �2 * kt/q �* log( ni / NA)
can i take kT/q = 26mV at 300k
� & � �ni � �= � 1.45* 10^10 cm^-2 �otherwise where from i should get ?
� NA � = nsub or nch �?

pParam is a data structure in the BSIM3 source code (having to do with sharing values for devices with the same L and W).

You inverted the division in the log, it's log(NCH/ni), and NCH is the parameter.

ni = 1.45e10 * (Tnom / 300.15) * sqrt(Tnom / 300.15) * exp(21.5565981 - Eg0 / (2.0 * Vtm0));

You should double-check that Tnom in the model card is 27.0 C (which would be 300.15 K), else you'll have to adjust ni and kT/q from what you are using; then again, you may not care to be all that exact.

Geoffrey,
Thanks a lot for sharing helpful information on this , if possible can you tell me why should NCH is to be consider instead of nsub, some text boox says it is nsub i.e equivalent SPICE parametr name is NSUB
from the model file information i found below definition for them
NCH: Peak Channel doping concentration
Nsub : substrate doping concentration

thanks
Kiran

Back to top

IP Logged

Geoffrey_Coram Senior Fellow Offline Posts: 1999 Massachusetts, USA	Re: Question about bisim3v3 parameters Reply #5 - Jun 21^st, 2007, 10:18am Have you tried reading the appropriate section of the BSIM3 manual? I assume it's explained there.
Back to top	If at first you do succeed, STOP, raise your standards, and stop wasting your time. IP Logged