A MEMS micromirror fabricated using CMOS post-process

This work describes the fabrication of a micromachined micromirror by the conventional 0.35 μm CMOS process and a simple maskless post-CMOS process. The micromirror contains a rectangular mirror plate and four pairs of serpentine supported beams, is integrated with a 1 × 4 demultiplexer and a four-stage charge pump circuits on a chip. Maskless dry and wet etching processes are the only requirement to suspend the structure. The primary limitation in the fabrication of microstructures has been overcome by the development of a hybrid processing technique, which combines both an anisotropic dry etch and an isotropic wet etch step. A highly reliable wet etching step with high selectivity between aluminum and sacrificial oxide is also reported. Experimental results reveal that the micromirror has a tilting angle of around 5° at operation voltage of 22.5 V and a dynamic response less than 5 ms. The surface properties of the CMOS micromirror, detailed process flows, measurement set-up and the experimental results are also presented in this work.