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Modeling >> Semiconductor Devices >> BSIM: System of Units
https://designers-guide.org/forum/YaBB.pl?num=1195733555

Message started by tariavo on Nov 22^nd, 2007, 4:12am

Title: BSIM: System of Units
Post by tariavo on Nov 22^nd, 2007, 4:12am

Hi!
What system of units is used in BSIM?
It seems to be MKS (or SI) but there is a strange divergence about Epsilon:
from eq1 (pic1) we can get:
[epsilon] = 1

but from eq2 it resuls in:
[epsilon] = coulomb/v/m

What is wrong?

Title: Re: BSIM: System of Units
Post by tariavo on Nov 22^nd, 2007, 4:13am

equation 1 (pic1):

Title: Re: BSIM: System of Units
Post by tariavo on Nov 22^nd, 2007, 4:14am

eq2 (pic2):

Title: Re: BSIM: System of Units
Post by tariavo on Nov 22^nd, 2007, 4:17am

Oh, in BSIM's manual [EPSROX] = 1, but it should be [EPSROX] = coulomb/v/m and it is necessary to multiply it by 8.85E-12 in all equations.

am i right?

Title: Re: BSIM: System of Units
Post by Geoffrey_Coram on Nov 26^th, 2007, 8:26am

EPSROX is the ratio of the oxide permittivity to that of free space, so it should always appear as EPSROX * Eps0 in equations, eg:

model->BSIM4coxe = epsrox * EPS0 / toxe;

from the source code (b4temp.c). Is there a typo in the equation? Perhaps it used to say EPSOX ( = 3.9 * EPS0 for SiO2) and the equation was changed to EPSROX instead of EPSROX * EPS0 when allowing for other oxides.

Title: Re: BSIM: System of Units
Post by tariavo on Nov 27^th, 2007, 6:52am

thanks! and another question arised about the use of BSIM's code:
http://www.designers-guide.org/Forum/YaBB.pl?num=1196175062