How WPE and STI affect the mobility which is reflected in Spice or Spectre simulator?

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Alex Liao

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Hi,

The two layout dependent effects that cause mobility variation is WPE and STI. The equations are given as follows:
WPE: (Ueff,wpe)

STI: (Ueff,STI)


Beta is the parameter found after simulation and is related to Ueff(effecitive mobility).
Beta = Ueff,final * Coxe * Weff/Leff.

This Beta equation is used in simulator for sure. Is there anyone who knows the relationship between Ueff,final and Ueff,wpe/Ueff,STI?
I know the variance of mobility (Ueff,wpe/STI) is part of Ueff. But is there any equation that clearly describe the relationship between those partial mobility and the final mobility used in simulation?
 

Alex Liao said:
... is there any equation that clearly describe the relationship between those partial mobility and the final mobility used in simulation?
Click to expand...

I (also) didn't find such an equation in the BSIM470 Manual, but I think you can serialize the effects of WPE and STI (i.e. their ratios to µeff,org) :

Code: 
µ[SUB]eff[/SUB](WPE) / µ[SUB]eff,org[/SUB] = (1+KU0WE∙(SCA+WEB∙SCB+WEC∙SCC))                            (15.1)

µ[SUB]eff[/SUB](STI) / µ[SUB]eff,org[/SUB] = ( ... )                                                    (14.5)

µ[SUB]eff[/SUB](WPE+STI) / µ[SUB]eff,org[/SUB] = (µ[SUB]eff[/SUB](STI) / µ[SUB]eff,org[/SUB]) ∙ (µ[SUB]eff[/SUB](WPE) / µ[SUB]eff,org[/SUB])

Of course there are a lot more effects which influence the mobility factor, like, e.g., carrier velocity saturation (mobility reduction due to the longitudinal field), vertical field mobility reduction (VFMR), and, last not least, temperature.
 
Last edited:
Hi Erikl,

So 1. you think Ueff,org is U0 from model card, right?
2. do you think the Mobility Coulomb Scattering Model is such 'the others' that influence the mobility and should have the serialization relationship with previous STI and WPE factor?
3. I am almost agree with you about the serialization relationship but I am currently lack of documents that clearly prove this as well as you, but have you done any experiments to attempt to prove this?

Regards,
Alex
 

Alex Liao said:
1. you think Ueff,org is U0 from model card, right?
Click to expand...
Yes!

Alex Liao said:
2. do you think the Mobility Coulomb Scattering ModelView attachment 101211 is such 'the others' that influence the mobility and should have the serialization relationship with previous STI and WPE factor?
Click to expand...
I think so. But just consider such effects which actually apply in a special application.

Alex Liao said:
3. ... have you done any experiments to attempt to prove this?
Click to expand...
No. Not knowing of a better method, I'd just think this might result in a good (1st order) approximation.

If this is really important for you, I'd suggest to try and contact one of the BSIM authors directly, e.g. Xuemei (Jane) Xi , who's e-mail address is explicitely mentioned in the BSIM4.5.0 Enhancements document: JaneXi@eecs.Berkeley.EDU .
 
Hi Erikl,

Thanks for supporting this. I tried to contact BSIM group by leaving message on their web main page. They never reply. Also I tired to contact Xuemei at: janexi@eecs.berkeley.edu. But the mail system says
It seems they decline email from outside. Do you have an alternative candidate to contact?
 
Last edited:

Hi Erikl,

I have sent each of the group member an email. Let's see what's happened. By the way, I saw your occupation filed: on your own. You are doing IC design on your interest? I guess you must be a professor in a university in Germany years ago.

Alex
 

Hi erikl,

One member of BSIM group have confirmed the multiplication relationship (serialization)
Ueff,final = U0 * Kwpe * K sti * K others
Click to expand...
, Thanks.

Alex
 
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