Method on surface roughness modification to alleviate stiction of microstructures

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.

[1]  A. Adamson.  Physical chemistry of surfaces , 1960 .

[2]  W. Messner,et al.  Effects of elevated temperature treatments in microstructure release procedures , 1995 .

[3]  Weissberger.  Physical methods of chemistry , 1971 .

[4]  T. Chung,et al.  A new organic modifier for anti-stiction , 2001 .

[5]  Roger T. Howe,et al.  Alkene Based Monolayer Films As Anti Stiction Coatings For Polysilicon MEMS , 2001 .

[6]  Guobing Zhang,et al.  A new release process for polysilicon surface micromachining using sacrificial polysilicon anchor and photolithography after sacrificial etching , 1999 .

[7]  R. Howe,et al.  Alkyltrichlorosilane-based self-assembled monolayer films for stiction reduction in silicon micromachines , 1998 .

[8]  Novel prevention method of stiction using silicon anodization for SOI structure , 1999 .

[9]  Chang-Jin Kim,et al.  Polysilicon surface-modification technique to reduce sticking of microstructures , 1996 .

[10]  Carlos H. Mastrangelo,et al.  Elimination of post-release adhesion in microstructures using conformal fluorocarbon coatings , 1997 .

[11]  H. Fujita,et al.  Photoresist-Assisted Release of Movable Microstructures , 1993 .

[12]  R. Maboudian,et al.  Self-assembled monolayers as anti-stiction coatings for MEMS: characteristics and recent developments , 2000 .

[13]  C. Hierold,et al.  A novel method to avoid sticking of surface-micromachined structures , 1996 .

[14]  J. Esteve,et al.  A new process for releasing micromechanical structures in surface micromachining , 1996 .

[15]  Bradley K. Smith,et al.  Thin Teflon-like films for eliminating adhesion in released polysilicon microstructures , 1998 .

[16]  R. Howe,et al.  Critical Review: Adhesion in surface micromechanical structures , 1997 .