Diffraction grating scanners using polysilicon micromotors

This paper describes polysilicon micromotors with single and pyramidal diff raction grating elements fabricated on the polished surface of large-area r otors for optical scanning applications, While taking full advantage of pla nar processing, such scanners have high-quality scan profiles, good efficie ncy, meter working distances, and multiple out of plane beam diffraction or ders. Chemical-mechanical polishing was used to reduce the 5-mu m-thick pol ysilicon rotors' average surface roughness from 420 Angstrom to below 17 An gstrom, with less than 1500-Angstrom film removal, improving the optical pe rformance of the gratings as well as the definition, delineation, and side wall quality of the device features. Self-assembled monolayers (SAM) were f ound to improve the overall micromotor's dynamic performance. SAM-coated sc anners could operate at voltages as low as 15 V and maximum operational spe eds of 5200 rpm. The gratings were tested optically at 633-nm wavelength an d were verified to have spatial periods of 1.80 and 3.86 mu m, closely matc hing their design values. Stepping and continuous mode dynamic operation of the scanners was demonstrated with visible diffraction orders at meter dis tances away.