Abstract:
The dependence of the substrate resistance, R[subscript sub], for MOS transistor RF
modeling on transistor biasing and layout is studied from device simulations and
measurements. Though R[subscript sub] is found to be bias dependent, the error incurred by
assuming a constant value equal to the DC resistance is not significant. A scalable
model for R[subscript sub] of multiple gate fingers is developed. This model is simple to extract
and gives good agreement for the output admittance of a MOSFET. The model is
validated by measurements on DC test structures fabricated in a TSMC 0.35 μm
CMOS process. The dependence of Rb on transistor dimensions and the location
of substrate contacts with respect to device active area is also presented. A low
noise amplifier (LNA) is designed and fabricated in the 0.35 μm TSMC process to
show the effect of R[subscript sub] on the performance of a LNA.
