Friction measurement in MEMS using a new test structure

摘要

A MEMS test structure capable of measuring friction between polysilicon surfaces under a variety of test conditions has been refined from previous designs. The device is applied here to measuring friction coefficients of polysilicon surfaces under different environmental, loading, and surface conditions. Two methods for qualitatively comparing friction coefficients ((mu)) using the device are presented. Samples that have been coated with a self- assembled monolayer of the lubricating film perfluorinated-decyltrichorosilane (PFTS) have a coefficient of friction that is approximately one-half that of samples dried using super-critical CO(sub 2) (SCCO(sub 2)) drying. Qualitative results indicate that (mu) is independent of normal pressure. Wear is shown to increase (mu) for both supercritically dried samples and PFTS coated samples, though the mechanisms appear to be different. Super critically dried surfaces appear to degrade continuously with increased wear cycles, while PFTS coated samples reach a steady state friction value after about 10(sup 4) cycles.