Addition of Si-Containing Gases for Anisotropic Etching of III–V Materials in Chlorine-Based Inductively Coupled Plasma

We discuss the possibility of obtaining high-aspect-ratio etching of InP materials in Cl2- and HBr-based inductively coupled plasmas (ICP) with the addition of Si-containing gases (SiH4or SiCl4). A vertical and smooth etching profile is demonstrated in SiCl4/H2plasma. The effect of adding of a small amount of SiH4to a previously optimised Cl2/H2chemistry is presented, and new SiH4/Cl2and SiH4/HBr chemistries are proposed.Ex-situenergy-dispersive X-ray spectroscopy coupled to transmission electron microscopy (EDX–TEM) is used to analyze the composition of the thin passivation layer deposited on the etched sidewalls. We show that it consists of a Si-rich silicon oxide (Si/O∼1) in Cl2/H2/SiH4chemistry, and is changed to nano-crystalline (nc-) Si in SiH4/Cl2chemistry depending on the SiH4percentage. Moreover, we show that deep anisotropic etching of InP independent of the electrode coverplate material can be obtained via a SiOxpassivation mechanism with the addition of Si-containing gases.