Diffraction grating scanners using polysilicon micromotors

Abstract

This paper describes polysilicon micromotors with single and pyramidal diffraction grating elements fabricated on the polished surface of large-area rotors for optical scanning applications. While taking full advantage of planar processing, such scanners have high-quality scan profiles, good efficiency, meter working distances, and multiple out of plane beam diffraction orders. Chemical-mechanical polishing was used to reduce the 5-/spl mu/m-thick polysilicon rotors' average surface roughness from 420 /spl Aring/ to below 17 /spl Aring/, with less than 1500-/spl Aring/ film removal, improving the optical performance of the gratings as well as the definition, delineation, and side wall quality of the device features. Self-assembled monolayers (SAM) were found to improve the overall micromotor's dynamic performance. SAM-coated scanners could operate at voltages as low as 15 V and maximum operational speeds of 5200 rpm. The gratings were tested optically at 633-nm wavelength and were verified to have spatial periods of 1.80 and 3.86 /spl mu/m, closely matching their design values. Stepping and continuous mode dynamic operation of the scanners was demonstrated with visible diffraction orders at meter distances away.