Influence of deposition temperature during LPCVD on surface properties of ultrathin polysilicon films

Abstract

The selection of the proper materials for the fabrication of the micro electro mechanical systems (MEMS) is a very important issue in the MEMS research. The materials should be adequate for the fabrication process as well as they have to demonstrate in particular good adhesive (to avoid stiction between contacting/sliding components) and frictional/tribological properties. We fabricated ultrathin (50 nm thick) polysilicon films on single crystal silicon wafers at various deposition process conditions and observed the effect of the process parameters on surface topography and adhesive as well as frictional properties of the produced films. The atomic force microscope was used in these studies equipped with special cantilevers. We identified interesting correlations between the process parameters and adhesive/frictional properties of the studied films which enable to optimize the process to decrease adhesion (stiction) and friction between sliding components of MEMS devices and compared them to previous research done at samples with thicker layer. Topography of both samples and cantilevers has been studied in depth to allow later simulation of the interface. Additional measurements of friction in various humidites should be done next in order to assess the influence of its impact on friction coefficient. Further comparison of adhesion to friction in particular environmental properties might also increase our understanding of MEMS surface interactions.