Fringe capacitance - how to model it?

[Somashekhar]

Fringe capacitance.

Hi all..
I am new to e-edaboard.com.

I wan know how to model the fringe capacitance??

 

[girih192002]

Re: Fringe capacitance.

Fringe capacitor is capacitance exist between wall of S / D to Gate terminal. in short, it is parasitic capacitor formed between two layer unwarrantably.

 

[Somashekhar]

Re: Fringe capacitance.

Fringe capacitor is capacitance exist between wall of S / D to Gate terminal. in short, it is parasitic capacitor formed between two layer unwarrantably.

Hey i am not discussing about the parasitic in MOSFET..

I need to model fringe capacitance(in MIM capacitance)..that is how to calculate and model the fringe capacince..

I have designed a cap using metal-x and metal-y..two comb structures placed pependicular and compleletely overlaped. I am getting good cap/area.. but i am not getting how to model it??

 

[Braski]

Re: Fringe capacitance.

uhm i don't know how to model it...i think it's not analitically easy because the field lines are not straight outside the plates. However, in a comb structure the fringe effects are not always negligible..you can extimate them with a FEM software if u could use one of them. Sorry, i can't tell you more.
However, they should rise up your capacitance.

 

[Somashekhar]

Re: Fringe capacitance.

uhm i don't know how to model it...i think it's not analitically easy because the field lines are not straight outside the plates. However, in a comb structure the fringe effects are not always negligible..you can extimate them with a FEM software if u could use one of them. Sorry, i can't tell you more.
However, they should rise up your capacitance.

Wat is this FEM software..can u elaborate..

 

[girih192002]

Re: Fringe capacitance.

FEM software is EM solver software use to do momentum simulation to find out parasitic resistance, capacitance of passive components. EM Solver or FEM tool most of time used to find parasitic from Board, of inductor, Capacitance.


You can download some free trial licenses and setup


eagle ware is EM Solver tool from Agilent Technologies. you can get free trial license.


I will let you know some more soon.

 

[Braski]

Re: Fringe capacitance.

Yes, something like that... i meant Finit Element software, but electromagnetic software will work too. I'm not into EM software, so i don't know what to tell you to use. I used some Finit Element simulation software. They're not simple too use, but use energy methods to calculate capacitance or other quantities. Better if someone helps you with advices of EM simulators.

 

[xdmicro]

Fringe capacitance.

you mean a thin metal or the D/S of MOSFET?　in general,they can be seemed as plate capacitor ＋cylindrical capacitor.you can also refer to relative books. that can be found easily.