MEMS micro-bridge structure-based process platform fabricated with CMOS Al BEOL compatible process

Abstract

A common MEMS micro-bridge structure-based process was developed on 200 mm standard CMOS Al back end of line. Thick amorphous-Si (alpha-Si) film was developed and used as the sacrificial material with well-controlled film stress to improve the wafer warpage. Anchor/contact structure was formed by a trench first scheme with no metal or dielectric plug in it, and thin Ti/TiN bilayer barrier metal was used as an electrode layer to define the sensing material resistor with improved step coverage on the anchor sidewall. A wet etching process was introduced for electrode layer patterning with almost no damage to the sensing material. The micro-bridge structure-based bolometer device was fabricated and evaluated on this platform. Good electrical performance had been achieved, and after optimized stress engineering the range of the released micro-bridge surface height variation was controlled to less than 10%, which indicated that the process platform can well match the bolometer, micro-lens and related sensor requirements.