In this paper, we present and implement a novel procedure for the accurate simulation of the thermoelectric effects which determine micromachined structures' behavior. This approach is simple to discretize, with rapid numerical convergence properties, and it yields results which are in very good agreement with experimental observations. We employ this procedure in particular to calculate P/sub 1ATM//P/sub VAC/, where P/sub 1ATM/ (resp. A/sub VAC/) denotes heat conducted down the micromachined structure supporting arms at one atmosphere (resp. vacuum) when the device is at the same average temperature. We show that P/sub 1ATM//A/sub VAC/ may not be unity, as had been earlier assumed, but is independent of input current. Finally, for a special class of devices, an analytical formula is obtained for P/sub 1ATM//P/sub VAC/ in terms of device parameters, and this result is also compared with the numerical simulation results.

We have developed a software package that simulates the operation of a silicon micromachined CMOS thermal conductivity gas pressure gauge. The performance of actual devices was compared against the simulated operation and was found to be in good agreement. The 3-dimensional simulation was reduced to two 2-dimensional simulations to reduce complexity. The two equations resulting from steady state energy balance considerations were discretized and an iterative nonlinear Gauss-Seidel procedure applied to solve the system of equations. Temperature profiles and contours were calculated and the effect of geometric and materials modifications was demonstrated.>