Methods for wet atomic layer etching of molybdenum

Abstract

Systems and methods are provided for etching molybdenum in a wet ALE process. The methods disclosed herein use a wide variety of techniques and wet etch chemistries to oxidize a molybdenum surface and form a self-limiting, molybdenum oxide passivation layer in a surface modification step of the wet ALE process. For example, the methods use: (a) ultra-violet (UV) photolysis of peroxide oxidizers to create oxidizing radicals, which limit oxidation of the molybdenum surface and provide quasi-self-limiting oxidation behavior, (b) steric hinderance of oxidizers having large reactant molecules to achieve better self-limiting oxidation behavior, and/or (c) ligand-assisted oxidation to change the surface chemistry of the molybdenum oxide passivation layer and ensure self-limiting oxidation behavior. After forming the molybdenum oxide passivation layer using one or more of the oxidation techniques disclosed herein, the passivation layer is selectively removed in a dissolution step of the wet ALE process to etch the molybdenum surface.