Methods for wet atomic layer etching of titanium nitride using halogenation

A method of etching, the method comprising:

• receiving a substrate having a titanium nitride (TiN) layer, wherein a TiN surface is exposed on a surface of the substrate;
• exposing the surface of the substrate to a surface modification solution comprising an electrophilic halogenation agent dissolved in a non-aqueous solvent, wherein the electrophilic halogenation agent reacts with the TiN surface to form a titanium halide or titanium oxyhalide passivation layer, which is self-limiting and insoluble in the surface modification solution;
• removing the surface modification solution from the surface of the substrate subsequent to forming the titanium halide or titanium oxyhalide passivation layer;
• exposing the surface of the substrate to a dissolution solution to selectively remove the titanium halide or titanium oxyhalide passivation layer, wherein the dissolution solution reacts with the titanium halide or titanium oxyhalide passivation layer to form soluble species, which are dissolved by the dissolution solution to expose an unmodified TiN surface underlying the titanium halide or titanium oxyhalide passivation layer;
• and
• removing the dissolution solution and the soluble species from the surface of the substrate to etch the TiN layer.