Polycide/metal capacitors for high precision A/D converters

The authors present a novel metal-to-silicide-polysilicon capacitor and compare it with metal-to-polysilicon capacitors and conventional polysilicon-to-polysilicon capacitors. Voltage coefficient data for these capacitor structures with oxide, oxide/nitride, oxide/nitride/oxide, and nitride dielectrics are also discussed. It is shown that when metal-to-silicided polysilicon capacitors are used, voltage coefficients of less than 4 p.p.m./V can be attained, which is considerably less than that obtained when metal-to-poly or conventional poly-to-poly capacitors are used. For high-precision A/D converters, this value will make possible accuracies of up to 18 bits through self-calibration.<>