Wafer level anti-stiction coatings for MEMS

This paper describes a processing method which allows for the application of a dichlorodimethylsilane (DDMS) anti-stiction monolayer to MEMS devices on a wafer scale from the vapor phase. By utilizing vapor phase processing, many problems associated with liquid processing can be overcome. We have designed and built a reactor system that allows for the vapor phase deposition of a variety of anti-stiction coatings on both die and full 200 mm wafer levels. Contact angle analysis, atomic force microscopy (AFM) and thermal annealing have been used to characterize the film on Si(l 0 0). Film properties such as apparent work of adhesion and coefficient of static friction are obtained from coated micromachine test structures. It is shown that the DDMS monolayer deposited from the vapor phase is as effective at reducing adhesion and friction as the DDMS monolayer deposited from the (conventional) liquid phase. Moreover, it is shown that the DDMS coating can be successfully applied to a 150 mm. wafer of released devices. Post-packaging data show substantial improvement in the stiction behavior of coated devices versus uncoated devices. Published by Elsevier Science B.V.