A backside via holes etching technology for indium phosphide MMICs

A wet etching process for backside via holes suitable for use on InP MMICs technologies has been developed for an indium phosphide substrate. PMMA was used to mount the InP wafer onto a glass carrier. Sputtered Ta film was utilized as etch mask. HCl/H/sub 3/PO/sub 4/ solution realised a etch until a depth of 100 /spl mu/m. It has been demonstrated that the wet etching backside process is controllable with large latitudes.