Systematic study of InP/InGaAsP heated plasma etching and roughness improvement for integrated optical devices

Indium Phosphide (InP) is one of the most widely commercialized III–V semiconductor materials for making efficient lasers operating in the O-band and C-band. It is also gaining significant attention as a material platform for passive integrated optical devices operating in the telecommunication wavelength range for optical communication networks and sensing. Fabrication of such devices requires a process of lithography for pattern writing followed by plasma etching for transferring the pattern into the semiconductor material. InP is one of the most difficult materials to etch due to the fact that the etching by-products ( InCl x) are not volatile at temperatures less than 150 °C. There have been some studies showing InP etching at lower temperatures and room temperatures. However, after carefully studying these processes using multiple plasma etching tools, we found that the claimed processes are not repeatable because of the low volatility of the by-products at room temperature. In this work, we demonstrate a systematic study of etching InP using methane-hydrogen-based chemistry at low temperatures (60 °C) and chlorine-based chemistry at high temperatures (190 °C).