Surface-micromachined 2D optical scanners with optically flat single-crystalline silicon micromirrors

We have developed a novel wafer-scale single-crystalline silicon micromirror bonding process to fabricate optically flat micromirrors on polysilicon surface-micromachined 2D scanners. The electrostatically actuated 2D scanner has a mirror area of 450 mum x 450 mum and an optical scan angle of +/-7.5 degrees. Compared to micromirrors made with a standard polysilicon surface-micromachining process, the radius of curvature of the micromirror has been improved by 150 times from 1.8 cm to 265 cm, with surface roughness < 10 nm. Besides, single-crystalline honeycomb micromirrors derived from silicon on insulator (SOI) have been developed to reduce the mass of the bonded mirror.