Aging of a fluorinated lubricant on bare and DLC-coated silicon-based MEMS

The aging of Fomblin Zdol® on a silicon-based MEMS device was investigated. The MEMS device used was an electrostatic lateral output motor. Devices freshly coated with Zdol performed exceedingly well compared to uncoated devices, but their performance deteriorated on storage in air. This is apparently due to the decomposition of the fluorinated lubricant in contact with the polysilicon surface for an extended period. XPS and AFM studies show that the composition and morphology of the Zdol-coated polysilicon surface change on aging. A stable, cohesive barrier layer deposited to prevent direct contact of the fluorinated lubricant with polysilicon enhanced the stability of the lubricant. As widely used in hard disk lubrication, a thin film of diamond-like carbon (DLC) acted as an excellent barrier layer extending the life of unlubricated devices and preventing degradation of those lubricated by Zdol.