Through-Substrate Via Etching and Cleaning for High Volume Production Demands

By the use of multi-level plasma etch experimental designs, an alternative method for post-etch photoresist removal, and development of an automated post-etch veil removal sequence; a reproducible method for through-substrate via processing was integrated into high-volume GaAs manufacturing. For the plasma etch portion, optical microscopy and scanning electron microscopy (SEM) were used to determine defect density and via dimensions. Analysis for post-etch veil removal was accomplished using optical microscopy, SEM, and Auger electron spectroscopy (AES). Through a series of evaluations, a chemistry from General Chemical Corporation was determined to be effective at simultaneously removing both the photo resist mask and the etch residues. The final process developed resulted in a through substrate via with approximately an 80 degree, single-sloped sidewall profile that was clean from post-etch veil materials