A Closed-Loop Controlled CMOS MEMS Biaxial Scanning Mirror for Projection Displays

This work presents a biaxial electromagnetically-drivenpiezoresistivelysensed scanning mirror fabricated in a CMOS (complementary metal oxide semiconductor) process. The structure containing the CMOS metal/dielectric layers and underlying silicon is released after backand front-side etch. The drive coil and piezoresistive sensors are implemented by the metal and polysilicon thin films. Biaxial resonances at 1.13 kHz and 41.5 kHz, and an optical angle of 50° for horizontal scan under a drive current of 12.5 mA are measured. Closed-loop control and oscillation for vertical and horizontal scans are also demonstrated for practical applications.