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The PMOS and NMOS vs. ESD ZAP

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chang830

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zap test esd

Hi,
Would anyone pls. tell me why the PMOS transistor is more robust under ESD ZAP than NMOS transistor?

Thanks
 

zap esd

For our device just inverse:
NMOS more robust than PMOS.
 

Do you know how to test ESD (ZAP)?
 

Where did u get this statement?
Somehow I don't think absolutely PMOS is more robust than NMOS. I used NMOS only ESD struture in some of my IO designs and it works for over 8kV HBM, so your statement is not always rite, maybe in some particular situation.
What i predict is PMOS is more uniform in current flow, not likely to have current crowding at one spot as PMOS mobility is a lot slower than NMOS, not easily to jam current at one locatio.
 

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    chang830

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hung_wai_ming(at)hotmail.com said:
What i predict is PMOS is more uniform in current flow, not likely to have current crowding at one spot as PMOS mobility is a lot slower than NMOS, not easily to jam current at one locatio.
Click to expand...

This is the third reson I heared to explain the PMOS Tr is more robust than NMOS in most conditions.

Anothet two is

i. The PMOS Tr normally have larger size than the NMOS Tr for thire smaller transcondence. So it will have larger junction area.

ii. The junction P+/NWELL of the PMOS is deeper than the N+/P- of NMOS
 

I think (ii) is more reasonable, as I assume we've got same size as NMOS and PMOS. If the sizes are already different, it's not fair to make comparison.
However, when it comes to a triple WELL process, (ii) is not existed as well. So this statement as far as I concern, may not be always correct in every process technologies. It depends on case by case
 

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    chang830

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