Wear characteristics of microscopic bushings for MEMS applications investigated by an AFM

The wear characteristics of silicon-based materials that are widely utilized in MEMS applications were investigated. Silicon (1 0 0), silicon oxide, silicon nitride and polysilicon specimens with microscopic bushings were fabricated for the wear tests performed under 100 νN normal force. The wear tests were conducted for a relatively long sliding distance of 5.6-187 km. Following the sliding experiment, the wear characteristics of the bushings were assessed by using an atomic force microscope. It was found that the wear rate was highest for the silicon oxide specimens and decreased in the order of polysilicon, silicon (1 0 0) and silicon nitride. Observation of the wear region showed that the scratches due to wear particles were often formed on the silicon (1 0 0), silicon oxide and polysilicon specimens. However, silicon nitride specimens showed signs of burnishing wear. The wear coefficients of the specimens were in the order of 10^-8 to 10^-7. Based on the wear characteristics and the wear debris behavior, the application of microgrooves for wear debris removal at the contacting interface was proposed.