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Shielding for the MIM capacitor

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shanmei

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Fig. A is the normal MIM capacitor which is formed by metal 4 and metal 5.

Should I add the shield metal 3 as shown in Fig. B to isolate the parasitic capacitance and noise? Thanks.

11.jpg
 

Re: Shileding for the MIM capacitor

Depends on the function of this MIM. And if you need the space below it for other circuitry.
 
Re: Shileding for the MIM capacitor

I prefer the performance, in this case, I have a lot of areas. Thanks.
 

Re: Shileding for the MIM capacitor

shanmei said:
Should I add the shield metal 3 as shown in Fig. B to isolate the parasitic capacitance and noise?
Click to expand...

If you create it as shown, this will increase the capacitive coupling to the substrate.
 
Re: Shileding for the MIM capacitor

Then Fig. A is the better solution, right?

The zero potential voltage of the substrate could decouple the noise, and it is also far away from the metal 4, then less parasitic capacitance from metal 4. Thanks.
 

Re: Shileding for the MIM capacitor

What you draw is normally called MOM (Metal-Oxide-Metal) capacitor - when plates are formed by the "normal" metal layers.
MIM capacitor uses special, thin metal layer(s) in between normal metal layers.
 
Re: Shileding for the MIM capacitor

I'd prefer to add a Patterned and Grounded Polysilicon to increase the Met4-to-SUBS parasitic effects.
It's been using since long time underneath the Coils to decrease the EDDY current effect to increase the Q factor.The same principle may work too..
 
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