Self-Assembled Monlayer Films as Durable Anti-Stiction Coating for Polysilicon Microstructures

Abstract

We present a self-assembled monolayer (SAM) coating process for high-yield release of compliant polysilicon microstructw-es -direct from the water rinse. This process has been used to release cantilever beams up to 1000 microns in length and requires no special sublimation or supercritical drying techniques. Once coated and released, these same microstructures have been used to quantify in-use stiction by electrostatically actuating surfaces into contact. Polysilicon structures coated with SAM films exhibit a work of adhesion of 3 J/m 2 , nearly four orders of magnitude lower than uncoated, hydrophilic structures. These coatings are also thermally stable up to 400 C for 5 minutes in a nitrogen or vacuum ambient, which falls within the range of typical packaging temperature cycles. The SAM-coating process has been further improved to eliminate the use of carbon tetrachloride, an environmentally unfriendly solvent. Using a combination of chloroform and iso-octane in place of the carbon tetrachloride, films have been produced which exhibit equal or better stiction properties than those formed using the carbon tetrachloride process.