LINEAR-ARRAY OF COMPLEMENTARY METAL-OXIDE-SEMICONDUCTOR DOUBLE-PASS METAL MICROMIRRORS

Low-cost linear arrays of deflectable micromirrors using a CMOS-compat ible process to define both on-chip circuitry and the mirror structure are presented. The mirrors consist of the CMOS second metal layer dep osited in two successive passes in order to establish a thick metal la yer for the stiff mirror plate as well as a thin one for the flexible hinges. The mirrors are released by sacrificial aluminum and oxide etc hing. Supercritical point drying is performed in order to avoid sticki ng of the mirrors to the substrate. The mirrors are electrostatically deflected by biasing the address electrodes implanted into the substra te underneath the mirror plate. Full angular deflection by +/-4.8 deg of a 30 x 40-mu m(2) plate is achieved with a driving voltage of 11 V. On-chip circuitry adjacent to each mirror allows one to address the p ixels with 5-V data pulses. The reflectance of the aluminum surface fo r wavelengths between 400 and 700 nm was measured to be 83% to 89%. Th e mirror surface was further characterized using Auger spectroscopy, s howing that no optically relevant surface modifications occur during p ostprocessing. The surface rms roughness measured by atomic force micr oscopy is on the order of 25 nm. (C) 1997 Society of Photo-Optical ins trumentation Engineers.