Processing of photosensitive APEX™ glass structures with smooth and transparent sidewalls

Abstract

Improvement of the surface roughness and optical transparency of microstructures lithographically fabricated in APEXTM glass was accomplished through a post-etch anneal. An optimal dose of UV radiation is found to be 24 J g−1 for a wavelength of 280 nm, after which etch rate in HF acid and selectivity saturate. The anneal process, while originally designed to improve the surface roughness by reflowing, can be used to join multiple structures for the creation of optically transparent three-dimensional devices. The resulting glass microstructures demonstrate an average sidewall RMS surface roughness that is reduced from 0.7 µm to 32.7 nm which is adequate for optical signal detection across a wide frequency band that includes the visible spectrum.