In this study we have investigated the reactive ion etching of 60 mum diam, 200 mm deep holes in 3 in. diam semi-insulating GaAs wafer using a combination of CCl2F2 and CCl4 gases for fabrication of through substrate via holes for grounding in monolithic microwave integrated circuits (MMICs). The effect of process parameters viz. pressure, CCl4/CCl2F2 ratio, and power on GaAs etch rate and resultant etch profile was investigated. Two kind of masks, photoresist and Ni, were used to etch GaAs and their performance was compared by investigating effect on etch rate, etch depth, etch profile, and surface morphology. The etch profile, etch depth, and surface morphology of as-etched samples were characterized by scanning electron microscopy. The desired 200 mum deep strawberry profile, with a top diam = 60 +/- 10 mum and bottom diam = 180 +/- 10 mum, was obtained at 40 mTorr process pressure with an average etch rate similar to1.3 mum/min using Ni mask. The vias were then metallized by depositing a thin seed layer of Ti/Au (1000 Angstrom) using radio frequency sputtering and Au (5 mum) electroplated to connect the front side pad and back side ground plane. The parasitic inductance offered by these vias was; 76 pH. The developed process was then integrated into the MMIC process line and a 16-18 GHz amplifier was fabricated using grounding vias with yield >90%. (C) 2003 The Electrochemical Society.