vivkr wrote on Jun 22nd, 2009, 2:04am:Hi,
Unless you are doing something wrong (like accidentally placing some large nets on top of your cap), you should see negligible parasitic caps from the top plate (POLY2) to the substrate. The bottom-plate parasitic looks OK.
There may be some problem with the extraction tool setup. Contact your foundry interface, although this design kit should be relatively stable.
Regards,
Vivek
Hi Vivek, thanks for your help... I indeed had a lot of contacts and metal on top of poly2 at first, but since discovering this problem with the parasitic capacitance I went to to even only 1 contact and the parasitics changed very little... Like from 210fF to 208fF.
It does seem that the extractor is summing up the actual capacitance value with the parasitic one for coming up with this total of 210fF of parasitic for a 200fF capacitor. But I have no idea how. I'm using Tanner v13 extractor, and the only configuration file is the extract definition file, which only has layers connections and devices definitions. Would you know any other places where this config could be on?
I know that Tanner v14 has a better parasitic extractor, HiPer PX, but I don't have the design-kit for this version yet...
Well, once again, thanks for your help.
Leo.