Method on surface roughness modification to alleviate stiction of microstructures

Abstract

Modification on surface roughness has been shown to effectively alleviate both release and in-use stiction in the previous literature. However, the modified materials in the previously reported methods were limited to polysilicon or single crystalline silicon with special properties. Here, the proposed modification method not only can apply to silicon without extra property requirements, but also has the potential to modify other materials, such as oxide, nitride, and some metals. The process here combines spin-on photoresist and reactive ion etching. The proposed low temperature process is simple. and no extra mask is needed. Consequently, there is more flexibility to add the roughness modification to the original fabrication process of microdevices. In this study, polysilicon and silicon nitride are demonstrated as the modified materials. Antistiction effects are characterized by calibrating the water contact angles on the modified surfaces and the detachment lengths of released cantilevers. The experimental results show that the detachment length is almost two times longer than the cantilevers without modified substrates, where the interfacial surface energy between solids is reduced about 15 times. (C) 2003 American Vacuum Society.