how we calculate Cox?

[mohazaga]

cox tox

Hi..
how we can calculte the Cox of CMOS using the parameters of
Pspice CMOS model TSMC 180nm .
thanx[/u]

 

[lavitaebelle]

cox mosfet

you need to use tox(thickness of oxide)
Cox=E0*Er/tox
E0=8.854e-12F/m
Er=3.9 for SiO2
Make sure you use tox in meters to end up with Cox with units F/m^2.
Usually Cox is written as F/(um)^2

 

[mohazaga]

cox cmos

Hi ,
Tox = 4E-9 m from PSpice model of TSMC's 180nm MOSFET process .
E0=8.85E-18 F/um (Jacop Backer : CMOS circuit design ... , pp114)
Er=3.97 , same book
Cox=E0*Er/tox
Cox=8.784E-15F/um²

is that ok
Thanx

 

[omsi]

cox mos

hi,

Cox = Eox/Tox

Eox = er*eo
Tox = thickness of oxide

 

[thuvu]

calculate cox

Hi, I have the following model

.model Mbreakp PMOS
level=2
ld=0.21e-6
kp=28e-6
vto=-0.87
gamma=0.70
phi=0.72
cj=0.62e-3
cjsw=0.26e-9
cgso=0.42e-9
cgdo=0.42e-9
cgbo=0.3e-9
nsub=8.8e16
nfs=1e10
tox=200e-10
xj=0.3e-6
ucrit=1.2e4
uexp=0.063
delta=2
kf=7e-15
af=1.2

and I want to calculate K=1/2 uCox
From the above I can find Cox. But what about u is it constant and what is its value?
(u: mobility)

Thanks

 

[Steven De Bock]

mosfet cox

Hi, I have the following model

.model Mbreakp PMOS
level=2
ld=0.21e-6
kp=28e-6
vto=-0.87
gamma=0.70
phi=0.72
cj=0.62e-3
cjsw=0.26e-9
cgso=0.42e-9
cgdo=0.42e-9
cgbo=0.3e-9
nsub=8.8e16
nfs=1e10
tox=200e-10
xj=0.3e-6
ucrit=1.2e4
uexp=0.063
delta=2
kf=7e-15
af=1.2

and I want to calculate K=1/2 uCox
From the above I can find Cox. But what about u is it constant and what is its value?
(u: mobility)

Thanks

Hi,

If you are using the BSIM3v3 model, than you can use u0 as u. I noticed that u0 isn't defined in your model, so you can use the default values of u0.
For a NMOS: u0 = 670 cm^2/(V*s)
For a PMOS: u0 = 250 cm^2/(V*s)
u0 is defined as the Low-field surface mobility at 'tnom'. So from it's definition it is seen that there is a temperature dependence of u0. However, size of W and L of your transistor also have an influence on the value of u.

I found the default values for u0, by typing the command "spectre -help bsim3v3" on the command line (I'm assuming you are using candence to).

Hope it helps you

 

[thuvu]

how to calculate cox

Thanks Steven

 

[hafizi]

The thickness of gate oxide is obtained from model
parameters given by MOSIS and is 300 Å. For W/L = 8.0 mm/1.6 mm,

300A where the value is obtained

 

[erikl]

The thickness of gate oxide is obtained from model

... where the value is obtained

From the model file. Search for TOX .

 

[dick_freebird]

u0 is a surface mobility, which is different than the well
characterized and fairly consistent bulk mobility. It
depends a lot on surface (underside of gate ox) quality
and this is very process-variable.

For Tox, you may see reported an optical and/or an
electrical Tox in foundry data; electrical Tox may
include things like poly depletion making it generally
larger, but more accurate for device modeling, than
the optical Tox that inline controls tend to observe.