fingering of mosfets

[nishanthpv]

what we need to consider as a rule of thumb while fingering?. What i only know is gate resistance of the finger should be less than inverse transconductance associated with the finger. Is this rule enough? If somebody explains it with an example, i will be happy.
Thanks in advance,
Nishanth

 

[dick_freebird]

Look also at your max DC drain current vs the electromigration
rule for minimum metal; if you can possibly exceed the rule,
then shorten the finger and use more of them.

For RF, you will often make the fingers "stupid short" to get
the best Rgate*Cgd outcome. Like just a few contacts' worth.

 

[bgangur]

Hi,

Making fingers in MOS devices will helpful in following things
1. Reduces the GATE resistance
2. Electro migration issues are minimal by providing multiple Metal tapping
3. matching the first order effects by distributing the fingers/device
4. Layout design become more compact i.e aspect ratio which is good DFM point

Thanks and regards,
Basu