DLC films as anti-stiction coatings for MEMS

Abstract

The stiction of microstructures is still a challenging problem in spite of innovative advances in modern micromachining technology. In this paper, diamond-like carbon films were suggested as a solution for this problem. The microwave electron cyclotron resonance plasma enhanced CVD equipment has been applied to prepare the DLC films. Confocal Raman spectra confirmed the DLC characteristics of the prepared films. Water contact angle increased from <30° on oxide-coated surfaces, to >110° on DLC-coated surfaces. The adhesion force of the DLC films was as low as 3.8nN measured by AFM, whereas the adhesion force of the oxide-coated surfaces was approximately 11.2nN. The polysilicon cantilever beam arrays have been used to determine the success of DLC coating for releasing microstructures. DLC films were prepared under the polysilicon cantilever beams with the sacrificial etching technology. The beam arrays were checked with scanning electron microscope. When the DLC films presented, the average longest detachment length was approximately 145 &mgr;m. While the DLC films didn't present, the average critical detachment length was shorter than 80..m. These results indicated the stiction of polysilicon cantilever beams was effectively restrained with DLC coatings.