ICP-RIE etching of InP using CH₄/H₂, CH₄/H₂/Cl_2, H₂/Cl₂ and Cl₂: process development and optimization

In this paper, we investigate inductively coupled plasma reactive ion etching of InP. The evolution of the surface/sidewall roughness and anisotropy is comparatively analyzed using different flow rates of CH4/H2, CH4/H2/Cl2, H2/Cl2 and Cl2 gases. In the study, RF bias power (PRIE) and inductive power (PICP) were maintained at 150 W and 400 W, respectively. We have also reported results of the etched structures, including values of roughness average (Ra), inclination angle and etch rates using scanning electron microscopy and 3D profilometer images. Not only hydrocarbon chemistries (CH4/H2) were used for etching InP, but also a certain amount of Cl2 gas was added to CH4/H2 chemistry to investigate the roughness on the surface. It was demonstrated that the smoothest surface structure with roughness average (Ra) of 0.137 mu m and the most anisotropic profile of similar to 90 degrees were obtained without heating by using CH4/H2/Cl2 (10/20/6 sccm) gas mixture with an etch rate of 240 nm min-1.