[SOLVED] Cadence Eldo - Permittivity Model

[Knyquist]

Hello!
I have a quick question.

Is there any particular model for the dielectric permittivity used in cadence? I'm using BSIM3v3 (LEVEL 53) with ELDO Spice in Cadence and I'm not able to identify how and where exactly they define the dielectric permittivity of either silicon or gate oxide.
Where are those parameters defined?

Thanks and best regards.

 

[erikl]

In the BSIM4 manuals version ≧ 4.6.2.

Gate dielectric constant relative to vacuum is EPSROX, default value (if not specified) = 3.9 (SiO₂)
Dielectric constant of substrate relative to vacuum is EPSRSUB, default value (if not specified) = 11.7 (Si)

 

[Knyquist]

Thanks for the reply!

I actually found that manual before, but since I'm using the BSIM3v3 (eldo's level 53 - while BSIM4 is level 60) I thought that definition didn't match what I was searching for and I should have searched it somewhere else.

So you are telling me BSIM3v3 uses simply the default values 3.9 and 11.7?

Thanks and Kind Regards!

 

[erikl]

So you are telling me BSIM3v3 uses simply the default values 3.9 and 11.7?

Yes, I think so. At least I can't remember to ever have seen these parameters in level 53 models. I have seen level 54 models, however, which at least contain epsrox, but given with the default value:

* Customized PTM 90nm NMOS

.model  nmos  nmos  level = 54

+version = 4.0    binunit = 1    paramchk= 1    mobmod  = 0
+capmod  = 2      igcmod  = 1    igbmod  = 1    geomod  = 1
+diomod  = 1      rdsmod  = 0    rbodymod= 1    rgatemod= 1
+permod  = 1      acnqsmod= 0    trnqsmod= 0

* parameters related to the technology node
+tnom = 27    [B]epsrox = 3.9[/B]
+eta0 = 0.0074    nfactor = 1.7    wint = 5e-09
+cgso = 1.9e-10    cgdo = 1.9e-10    xl = -4e-08

* parameters customized by the user
+toxe = 2.05e-09    toxp = 1.4e-09    toxm = 2.05e-09    toxref = 2.05e-09
+dtox = 6.5e-10    lint = 7.5e-09
+vth0 = 0.408    k1 = 0.486    u0 = 0.05383    vsat = 113760
+rdsw = 180    ndep = 2.02e+18    xj = 2.8e-08
...

 

[Knyquist]

Ok then, I agree with you.

But still, I cannot help thinking that there must be a configuration file in eldo where the default value is specified (Maybe hardcoded, maybe not) and that the parameter specified in 54 and so on just overwrites it.

 

[erikl]

I guess it's hard- or softcoded in the called SPICE model:

.model nmos nmos level = xy

 

[Knyquist]

Ok. I agree with your conclusion.

Thanks!