doubt on MIM capacitor

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srihari465

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Hi all,

What is the purpose of an additional layer as top plate in a mim cap??....plzz explain

________ _topmetal
|| -via
-------- - extra layer(top plate)

************ -dielectric
_________ -bottam plate

Regards

Sreehariii
 

To maximise the capacitance per unit area, the dielectric between the bottom plate (normal metal interconnect layer) and the top plate must be a minimum. To maximise the BV of the capacitor, the dielectric material is usually nitride. So this requires that the dielectric and top metal are not part of the conventional metal stack where there would not be a MIM. The MIM top metal is much closer vertically than the conventional metal layers, so an extra layer just for the capacitor is required.
 
It could be filling the MIM "divot" for planarity in a tall metal
stack. I haven't seen this structure as a requirement in any
processes I've used. I stay far from the bleeding edge though.
 



Thanks for ur reply...after doing some research wat I understood is that , if we are using two different metals there will be some dieletric in b/w them ..which will reduce the capacitance. So inorder to avoid that we are using another layer as top metal that can be placed close to the bottom plate.Correct me if I am wrong.

Can anyone tel wat is the material used in that layer??
Also what does "BV" of a capacitor means???


Regards

Sreeehariiii
 
BV means Break-down Voltage.
 

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