Some typical values
si conductivity 10 -100 S/m
si thickness 250uM
si Erel 11.9
if your design is below 3GHz the above conductivity will have little impact on especially if your Q is low 15 or less.
As the frequency of interest goes up will the concern of substrate conductivity come into play, but this will depend on the height of the metal above it, and the thickness, width, and conductivity of the metal.
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