A Reproducible High Etch Rate ICP Process for Etching of Via-Hole Grounds in 200μm Thick GaAs MMICs

Abstract

An inductively coupled plasma etching process to replace an existing slower rate reactive ion etching process for 60 ㎛ diameter via-holes using Cl2/BCl3 gases has been investigated. Process pressure and platen power were varied at a constant ICP coil power to reproduce the RIE etched 200 ㎛ deep via profile, at high etch rate. Desired etch profile was obtained at 40 mTorr pressure, 950 W coil power, 90W platen power with an etch rate ~ 4 ㎛/min and via etch yield >90% over a 3-inch wafer, using 24 ㎛ thick photoresist mask. The etch uniformity and reproducibility obtained for the process were better than 4%. The metallized via-hole dc resistance measured was ~ 0.5 Ω and via inductance value measured was ~ 83 pH.