The HF Vapour Phase Etcher

The 'HF Vapour Phase Etch' machine (a Primaxx uEtch from SPTS) is a single wafer (or pieces) HF vapor etch machine designed for etching sacrificial silicon oxide layers, primarily to release silicon microstructures in MEMS devices. The process uses anhydrous hydrogen fluoride (HF) gas as etchant and ethanol vapor as catalyst. In this way silicon dioxide can be etched in a dry process and the problems associated with wet etching is avoided (small structures collapse when they are underetched due to surface tension of water).

The etch gas and catalyst vapors easily diffuse into "hidden spaces" making e.g. long undercuts, membrane and resonator release etches feasible.