how can i deal with the layout?

[longstar]

mim capacitor with shield

I am doing the design of a SR ADC. The charge redistribution architecture is applied in the SR ADC.And the pre-simulation to the ADC is match with the spec.But the post simulation to layout of the capacitor array is terrible because of the coupled capacitor. The results of simulation is very good if the coupled capacitor is not abstracted.I use the SMIC 0.18um MS technology.And the capacitor is MIM(Metal Insulator Metal) capacitor.How can I deal with the layout of capacitor array?Could you give me some ideal?Thank you.
Rgds.
longstar

 

[aomeen]

Hello,

How about using ground shield, by surroending every capacitor with a metal connected to ground, this is very much like a gard ring. thus all your coupling caps will be redirected to ground...

 

[longstar]

yes, it's a good ideal.And I add the ground shield in layout. I use the metal 5 and metal 6 as the ground shield because of the MIM capacitor between metal 5 and metal 6.But it does not work.So any ideal else?
Thanks anyway.
Rgds.
longstar

 

[gpwu]

try match the metal length.
e.g. 1C: M length = x
2C: M length = 2x