HFSS simulation of on-chip MIM Capacitors

I tried to simulate on-chip MIM capacitors on silicon substrate.
The Si-Sub is low resistivity( 3~8Ohm*cm), a 2um Oxide is formed before the MIM
Cap fabrication(CMOS Backend Process). The insulating layer of MIM is Silicon Nitride, thickness on the ordor of 0.2~0.5um. Two metal plate is Copper.

But in HFSS simulation, I found strange results especially in Q calculations. If I reduced the thickness of two metal plates to 0.1um, the Q results are approximately equal that of 2um thick copper metal case. Any models published on articles would not agree.

I guess this error arises from the simulation setup, can anyone give some tips to simulate this structure accuratley? How to choose mesh and sweep

In view of the computing power, I currently tried interpolating sweep, which is similar to an Spiral Inductor expample in HFSS document.
An early post here mentioned that SONNET might be better for MIM simulation, but my final goal is to simulate and MEMS LC filter structure which mainly a 3D.

Added after 2 minutes:

I forgot to say that , the strange Q factor results remain even if I simulate this MIM structure surrounded by air( exclude silicon substrate effects).

Thank you !

Hi, are those strange simulation results remain the same? You can try to mesh with smaller distance or more triangulars. It's better take discrete points for my opinion though it takes more time.

I am trying to do the CMOS tech as well, could you give me the advice how to set the substrate? My result shows the silicon substrate dosent have such high energy loss than the articles saying..

In HFSS, where can I put the 5ohm*cm resistivity into the material setting? The material I changed was the conductivity. I changed it to 10simens/m. is that correct? Thanks for your help.

is 5ohm*cm corresponding to 20simens/m?