Simple Fabrication Process for Self-Aligned, High-Performance Microscanners— Demonstrated Use to Generate a 2-D Ablation Pattern

A new, straightforward, complementary metal-oxide-semiconductor (CMOS)-compatible, three-mask process is used to fabricate high-performance torsional microscanners driven by self-aligned, vertically offset comb drives. Both the moving and fixed combs are defined using the same photolithography mask and fabricated in the same device layer, a process allowing the minimum gap between comb fingers to be as small as twice the alignment accuracy of the photolithography process. Our fabricated microscanners have torsional resonant frequencies between 58 Hz and 24 kHz and maximum optical-scanning angles between 8deg and 48deg with actuation voltages ranging from 14.1 to 67.2 V_ac-rms. The yields on two separate fabrication runs have been better than 70%. To demonstrate an application for these scanners, we used them to generate laser-ablation patterns suitable for ocular cornea surgery. We assembled a 2-D scanning system by orienting two identical microscanners at right angles to one another. When driven by two 90deg out-of-phase 6.01-kHz sine waves, the cross-coupled scanners produce circular patterns having radii fixed by the amplitude of the driving voltage. Then, we emulated a small pattern from the surface topography found on a U.S. Roosevelt dime and built up an ablation pattern that compares favorably with similar emulations reported by earlier researchers who used larger, more complicated ablation systems