STRESS-ANALYSIS OF SIO2/SI BIMETAL EFFECT IN SILICON ACCELEROMETERS AND ITS COMPENSATION

Stress in cantilever beams of silicon accelerometers, caused by the SiO2/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 SiO2/Si interface, in contrast to an acceleration-induced stress. The dependence of this stress on the beam structure is 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 up to 20 fold is obtained for a simple beam structure.