Surface chemistry of InP ridge structures etched in Cl 2 -based plasma analyzed with angular XPS

Two x-ray photoelectron spectroscopy configurations are proposed to analyze the surface chemistry of micron-scale InP ridge structures etched in chlorine-based inductively coupled plasma (ICP). Either a classical or a grazing configuration allows to retrieve information about the surface chemistry of the bottom surface and sidewalls of the etched features. The procedure is used to study the stoichiometry of the etched surface as a function of ridge aspect ratio for Cl2/Ar and Cl2/H2 plasma chemistries. The results show that the bottom surface and the etched sidewalls are P-rich, and indicate that the P-enrichment mechanism is rather chemically driven. Results also evidence that adding H2 to Cl2 does not necessarily leads to a more balanced surface stoichiometry. This is in contrast with recent experimental results obtained with the HBr ICP chemistry for which fairly stoichiometric surfaces have been obtained.