Helium assisted plasma etching of indium phosphide ridge waveguides at mild condition

Indium phosphide (InP) is a typical III–V group compound semiconductor, which has broad applications in long-wavelength optoelectronic devices and high-frequency communication devices, due to its unique properties, such as high electron mobility, high radiation resistance, high thermal conductivity, and large conduction band discontinuity. The plasma etching is an indispensable process in InP based devices fabrications, and the plasma etching reaction gas of the InP is either halogen based gas system or hydrocarbon based gas system. However, the hydrogen element in the hydrocarbon based gas system is harmful due to the acceptors passivation effect, and the halogen based gas system requires high temperature parts in etch chamber to reduce residuum. Herein, we report a plasma heating method based on helium to realize plasma etching of InP at mild conditions. When helium is further introduced into the main etch step, the by-product formed in the plasma etching process is reduced. The process window for InP etching is investigated, and the footing morphology is optimized by an over etch step. The results show that it is feasible to fabricate InP based ridge waveguides with higher performance and lower cost.