Array of high quality surface micromirrors by chemical mechanical polishing of dielectric and metal

Abstract

The reflective spatial light modulator (SLM) technology of ferroelectric liquid crystal (FLC) on a CMOS VLSI substrate is now relatively mature. In order to optimize the optical performance of such a SLM, the silicon backplane should exhibit the following properties the backplane should be optically flat, both globally (across the backplane) in order to minimize distortion introduced by reflection from its surface and locally (within a pixel) in order to minimize scattering the pixel mirrors should occupy as much of the pixel area as possible, with minimal gaps between mirrors, in order to maximize the amount of reflected light the SLM surface should be microscopically smooth in order to promote good alignment of the FLC molecules. To achieve this we have developed micromachining techniques which are applied (in various combinations) as a post-processing sequence to fully processed wafers from a silicon foundry (such as Alcatel-Mietec or Austria Mikro Systeme). The post processing techniques involve the deposition, polishing and patterning of both dielectric and metal layers on top of the fully processed wafer.