Microfabrication and testing of suspended structures compatible with silicon-on-insulator technology

The footing or notching effect arises during the dry overetching of silicon layers on top of dielectric films. The visible consequence of this effect is the resulting etch that propagates along the interface between the underlying dielectric films and the silicon layer. Footing is usually considered an undesirable artifact during etching. Thus, the vast majority of efforts made to date have been oriented towards reducing or eliminating the aforementioned effect. There is, however, another alternative that has not been fully exploited: the application of the notching effect in the microfabrication of released structures. Furthermore, with deep reactive ion etching (DRIE) tools it is also feasible to deposit fluorocarbon films for electrical isolation purposes in situ. Thus, it is possible to microfabricate suspended structures by combining the footing effect with the capabilities offered by DRIE. For this purpose, we have developed, built, and tested suspended electrostatic actuators applying this new microfabrication scheme. The process is well suited for applications involving silicon-on-insulator wafers. Electrostatic actuators microfabricated with this passivation film subsequently underwent 10(5) pull-in cycles without failure. (C) 1999 American Vacuum Society. [S0734-211X(99)07904-4].