Fabrication and characterization of a dynamically flat high resolution micro-scanner

We present an ultra flat high frequency micro-scanner for high resolution laser projection applications. The scanner is fabricated in silicon-on-insulator wafers with a 30 mu m thick device layer. A backside island is constructed behind the mirror plate to improve the rigidity. The backside island is done with a deep reactive ion etching (DRIE)-tetramethylammonium hydroxide (TMAH) combination process to achieve a height of 86 mu m with good uniformity (4% within-wafer non-uniformity). The dynamic deformation is measured with a stroboscopic interferometer. The 1 mm diameter mirror plate has a root-mean-square deformation of less than 27 nm if operated at 30.84 kHz and a mechanical scan angle of +/- 10 degrees.. The dynamic flatness performance of the device exceeds the optical quality requirement of <lambda/10 deformation. The modulation transfer function of the scanner is calculated to demonstrate the resolution improvement from a scanner without backside reinforcement. With a diameter-scan angle product of 10 and a good dynamic flatness, the scanner is capable of performing the horizontal scanning (800 pixels) for an SVGA quality laser projection display.