Polysilicon process development for fully integrated surface-micromachined accelerometer with CMOS electronics

In this paper we shall discuss the required polysilicon characteristics to produce foe-standing mechanical structures such as accelerometers, Protection of the metallization and electronics during the removal of the sacrificial oxide will be discussed dong with drying techniques. A process for producing mechanical structures with active CMOS transistors will be presented along with a prototype accelerometer. Tumble-test results for the accelerometer show that even with external, off-chip electronics, these devices can easily distinguish +/- 1g. Capacitance-voltage (CV) curves for the accelerometers are shown as a quick way of checking these devices using standard integrated-circuit test instruments. Analysis of the current-voltage (IV) characteristics of both the n-channel and p-channel transistors shows that the additional processing has no effect on the threshold voltage but does significantly increase the channel shortening. Crown Copyright (C) 1998 Published by Elsevier Science S.A.