Effect of Surface Energy on the Wear Process of Bulk-Fabricated MEMS Devices

摘要

Wear phenomena in microelectromechanical systems have been systematically studied in recent years. Novel models are needed to quantitatively describe the wear process at microscales. In this research, a bulk-fabricated microtribotester was used to study the relatively stable wear stage of Si-MEMS devices. Before tested in controlled atmospheres, the rubbing surfaces of some microtribotesters were modified with AgCuTi, NiW, Pt or W coatings by the magnetron sputtering deposition. Test conditions were carefully selected to avoid severe wear during the test period. The major feature of the worn surfaces was the formation of bearing islands. A modified Archard wear model, taking the property of the initial surface morphologies into account, was proposed to analyze the factors affecting the size of such islands. It is found that the surface energy is as important as the material strength to determine the wear process. The contour contact ratio about 20% at the stable wear stage for silicon devices is an intrinsic feature of the tested samples and could not be changed by the working conditions.