[SOLVED] [MOVED] Technology parameter vs (W/L)

Status
Not open for further replies.
H

harrym

Newbie level 2
Joined
Sep 19, 2014
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Visit site
Activity points
15
Hello,
I am simulating the characteristic of a NMOS transistor with HSPICE, and I am also calculating the technology parameter knowing Id and gm, with the formula
un*Cox=gm^2/2Ids *(L/W) (I am operating in saturation).
Increasing both the W and the L of the transistor of the same ratio (like doubling both L and W), I do not get the same value of k, the difference is almost 50%!
I am using a tcms018 model.

Where am I wrong?

harrym
 

I try to rephrase the question.
I always thought that the technology parameter (un*Cox) was a constant of the circuit (after having doped the semiconductor un is constant, and Cox depends only on the thickness of the insulator), so I cannot understand why I get different values from the simulation. Does un change if I change the transistor W or L?
 

Current gain factor (µCox) depends to biasing conditions due to high values of vertical and lateral electric fields.
In fact You should use this formula:
\[K = \mu ~C_{ox} = \frac{K_0}{[1+(\frac{Vds_{sat}}{E_c L})^\beta]^{1/\beta}[1+V_{od}(\theta+K_0(R_S + R_D)W/L)]}\]
where: K_0 is current gain factor for low fields, beta is equal 1 for holes and 2 for electrons, Ec=0.8MV/m for electrons and 1.95MV/m for holes is critical electric field, theta is parameters depending to technology and is around 1e-7/tox, Rs and Rd are series source and drain resistances (could be quite high for narrow devices).
 
Reactions: harrym

    H

    harrym

    Points: 2
    Helpful Answer Positive Rating
Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…