Micro/Nanotribological Studies of Single-Crystal Silicon and Polysilicon and SiC Films for Use in MEMS Devices

Abstract

MEMS devices are currently made from single-crystal silicon, LPCVD polysilicon films and other ceramic films. For high temperature applications, SiC films are being developed to replace polysilicon films. Tribology in MEMS devices is of importance. Atomic force/friction force microscopy (AFM/FFM) and nanoindentation techniques have been used for tribological studies on microscale on materials of interest. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation and boundary lubrication of bulk and treated silicon, polysilicon films and SiC films. Measurements of microscale and macroscale friction show that friction values on both scales of all the silicon samples are about the same and higher than that of SiC. The microscale values are lower than the macroscale values as there is less ploughing contribution in the microscale measurements. Surface roughness has an effect on friction. Microscratching, microwear and nanoindentation studies indicate that SiC films are superior to coated/treated silicon followed by bare silicon. Chemically bonded lubricants appear to be suitable for MEMS devices.