Micromachined silicon surfaces for maximizing optical absorption at 632.8 nm

Abstract

The optical absorptivity (helium-neon laser illumination, lambda =632.8 nm) of (100)- and (110)-oriented single-crystal silicon wafers was enhanced by synergistically combining anisotropic etching, isotropic etching and anti-reflection coatings (silicon nitride, tantalum pentoxide, titanium dioxide and zirconium dioxide) with four distinct micromachined structures (V-shaped grooves, deep vertical-wall grooves, inverted pyramids and randomly spaced and sized pyramids). The uncoated, deep vertical-wall groove structure and the titanium dioxide coated randomly spaced and sized pyramids yielded the most significant reduction in the bidirectional reflectance distribution function's peak and average values when compared to the performance of an unprocessed silicon wafer control sample.