Stress analysis of SiO/sub 2//Si bi-metal effect in silicon piezoresistive accelerometers

It is pointed out that stress in a cantilever beam silicon accelerometer, caused by the SiO/sub 2//Si bi-metal effect, can result in a large temperature drift of offset. This has been simulated using a structure analysis program. The distribution of the stress within the beam shows a sharp rise at the SiO/sub 2//Si interface in contrast to an accelerometer-induced stress. The dependence of this stress on the beam structure was investigated, and the calculated value verified experimentally. Using a drift compensation method, involving an additional beam without a seismic mass and subtracting the output from that of the other beam, a reduction of the offset drift of up to 20 fold was obtained for a simple beam structure.<>