Dichlorodimethylsilane as an anti-stiction monolayer for MEMS: A comparison to the octadecyltrichlosilane self-assembled monolayer

This paper presents a quantitative comparison of the dichlorodimethylsilane (DDMS) monolayer to the octadecyltrichlorosilane (OTS) self-assembled mono layer (SAM) with respect to the film properties and their effectiveness as anti-stiction coatings for micromechanical structures. Both coatings have b een evaluated in several ways, including atomic force microscopy (AFM), con tact angle analysis (CAA), work of adhesion by cantilever beam array (CBA) technique and coefficient of static friction using a sidewall testing devic e. While water and hexadecane contact angles are comparable, the DDMS coate d microstructures exhibit higher adhesion than OTS coated ones. Furthermore , coefficient of static friction data indicate that the DDMS films are not as effective at lubrication as the OTS SAM's are, although both exhibit muc h improvement over chemical oxide. However, AFM data show that the samples which receive DDMS treatment accumulate fewer particles during processing t han those which receive the OTS SAM treatment. The thermal stability of the DDMS film in air far exceeds the OTS SAM, as the DDMS remains very hydroph obic to temperatures upwards of 400 degreesC.