Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

how we calculate Cox?

Status
Not open for further replies.

mohazaga

Full Member level 2
Joined
Aug 18, 2005
Messages
141
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,397
cox tox

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

lavitaebelle

Member level 4
Joined
Jan 26, 2006
Messages
75
Helped
24
Reputation
48
Reaction score
12
Trophy points
1,288
Activity points
2,131
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

Full Member level 2
Joined
Aug 18, 2005
Messages
141
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
2,397
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

Member level 5
Joined
Jan 24, 2006
Messages
93
Helped
7
Reputation
14
Reaction score
4
Trophy points
1,288
Location
London
Activity points
2,105
cox mos

hi,

Cox = Eox/Tox

Eox = er*eo
Tox = thickness of oxide
 

thuvu

Member level 3
Joined
Jan 3, 2006
Messages
65
Helped
9
Reputation
18
Reaction score
3
Trophy points
1,288
Activity points
1,819
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

Junior Member level 3
Joined
Mar 16, 2006
Messages
25
Helped
4
Reputation
8
Reaction score
3
Trophy points
1,283
Activity points
1,650
mosfet cox

thuvu said:
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

Member level 3
Joined
Jan 3, 2006
Messages
65
Helped
9
Reputation
18
Reaction score
3
Trophy points
1,288
Activity points
1,819
how to calculate cox

Thanks Steven
 

hafizi

Newbie level 1
Joined
Jun 8, 2013
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
4
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
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
6,961
Helped
2,037
Reputation
4,078
Reaction score
1,883
Trophy points
1,393
Location
USA
Activity points
55,795
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.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top