Methods for protecting a surface prior to etching to optimize etch performance

A method for protecting a surface of a ruthenium (Ru) layer to be etched prior to etching the ruthenium layer in a wet atomic layer etching (ALE) process, the method comprising:

• depositing the ruthenium layer on a substrate, wherein a ruthenium surface of the ruthenium layer is exposed on a surface of the substrate;
• depositing a sacrificial metal layer on the ruthenium surface, wherein the sacrificial metal layer comprises a transition metal that differs from the ruthenium layer;
• performing the wet ALE process to remove the sacrificial metal layer from the ruthenium surface;
• and
• continuing the wet ALE process to etch the ruthenium layer once the sacrificial metal layer is removed from the ruthenium surface;
• wherein the wet ALE process exposes the substrate to a halogen-based wet etch chemistry that removes the sacrificial metal layer from the ruthenium surface and etches at least a portion of the ruthenium layer;
• and
• wherein the sacrificial metal layer increases an etch rate of the ruthenium layer during the wet ALE process, compared to an etch rate achieved without the sacrificial metal layer, by preventing formation of at least one of the following:
• (a) an oxidative passivation layer on the ruthenium surface prior to etching the ruthenium layer with the halogen-based wet etch chemistry, and (b) ruthenium dioxide (RuO2) and/or other ruthenium species having oxidation states higher than 3+ on the ruthenium surface while etching the ruthenium layer with the halogen-based wet etch chemistry.