In recent am doing layout of crtmom in 180nm technology node. I found the bulk connection to MOM capacitor. I dont understand the why MOM cap need bulk connection or bulk terminal in design. usually MOM cap are mental on metal. so, why this bulk terminal is given??
The third terminal is required because a MOM capacitor is really two capacitors — the desired capacitance between the two metal terminals, and the parasitic capacitance between the bottom metal and the substrate. The latter is unavoidable, and it is shown explicitly in the schematic so that designers don't forget about it and its effects on the circuit.