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poly to poly and poly to diffusion capacitors

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ALL4HERE

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i need information about poly to poly and poly to diffusion capacitors.
i wan to know about the basic information because i need a presentation on
poly to poly, poly to diffusion and poly to metal capacitors..
i search on the internet but i can not find the exact information...so please help me
 

erikl

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... i can not find the exact information

Exact info is process dependent and company confidential. What exactly do you need? Find here an image with a P-P and a MOS (poly to diff) capacitor:
 

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ALL4HERE

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i need some information to make a presentation on in it...i mean some variation ....
how capacitance is change in between poly to poly and poly to diffusion and some
advantages of these capacitance
 

erikl

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You can't expect exact values if you ask such general questions. So I can give you just general values, e.g. a status-quo & forecast from ITRS resp. MOS & MIM capacitance densities:
 

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dick_freebird

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Your poly-diffusion cap will be a MOSCAP. It may be the standard FET gate,
or it could be field ox. The threshold voltage of the latter can be expected to
vary a lot and its density will be low. Below, or near the VT you can expect a
series depletion capacitance to develop.

Poly depletion in POP caps can be a problem, the silicidation (if any) probably
does not extend to the bottom of the top plate since poly tends to be shot
fairly thick and if the poly is not extremely heavily doped then you can get some
depletion there too.

Depletion capacitance gives you a voltco and it will be nonlinear, causing
distortion / nonlinearity. Audio and RF guys won't be happy.
 

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