Wet-Chemical Approaches for Atomic Layer Etching of Semiconductors: Surface Chemistry, Oxide Removal and Reoxidation of InAs (100)

An approach for wet-chemical atomic layer etching (WALE) of semiconductors is described.The surface chemistry of InAs was investigated for HCl/H 2 O 2 solutions suitable for controlled etching in the low etch rate range (<0.1-10 nm min -1 ).Kinetic studies were performed using inductively coupled plasma -mass spectrometry (ICP-MS).As for GaAs and InGaAs, the importance of the Cl -ion for the etching kinetics is demonstrated and a chemical reaction scheme is presented to help understand the surface chemistry.A detailed study of an alternative two-step etching process was performed.A quantitative ICP-MS analysis of the oxide formed in O 3 /H 2 O solution and the dissolution in HCl was performed suggesting that the removal of oxidized In products is the slow step in the dissolution reaction.The reoxidation of oxide-free InAs (100) surfaces in air is discussed.The etch rate range and the surface morphology control after etching show that the investigated wet-chemical approach for atomic-layer etching is a valid candidate for advanced CMOS processing.