Improved polysilicon surface-micromachined micromirror devices using chemical-mechanical polishing

Surface polysilicon micromachined micromirrors require ultra-flat surfaces for advance optical applications such as adaptive optics. This paper details the planarization of micromirrors using chemical-mechanical polishing. We show that the increase in topography is due to a high temperature anneal step downstream From the CMP process itself. Two process alternatives were investigated: (I) perform a CMP step after the high temperature anneal step, and (2) perform a CMP step on the final polysilicon mirror surface. Both process alternatives produced acceptable flatness requirements for micromirror applications.