Via hole formation in semi-insulating InP using wet photoelectrochemical etching

Laser-assisted wet photoelectrochemical etching has been used in conjunction with a metal mask to make via holes in semi-insulating InP. It was found that the incident laser intensity and applied bias can control the degree of sidewall taper in the via holes as well as the vertical and lateral etch rates. It was found that the etch rate is faster for smaller via hole dimensions due to the smaller anode-to-cathode path length. There are however geometric limitations to the overall etched depth for small vias etched at low intensities due to the taper of the sidewalls. This method has demonstrated high etch rates and minimal undercut. Custom tailoring of the etch profile is achievable through adjustment of the etch parameters