Solution based etching of titanium carbide and titanium nitride structures

Abstract

Provided are methods for fabricating transistors using a gate last approach. These methods involve etching of titanium nitride and titanium carbide structures while preserving high k-dielectric structures. The titanium carbide structures may also include aluminum. Etching may be performed in one or more etching solutions, each including hydrogen peroxide. Titanium nitride and titanium carbide structures can be etched simultaneously (non-selectively) in the same etching solution that also includes hydrochloric acid, in addition to hydrogen peroxide, and maintained at about 25° C. and 85° C. In some embodiments, titanium nitride structures and titanium carbide structures may be etched separately (selectively) in different operations and using different etching solutions. The titanium nitride structures may be etched in a diluted hydrogen peroxide solution maintained at about 25° C. and 85° C. The titanium carbide structures may be etched in a solution that also includes ammonium hydroxide, in addition to hydrogen peroxide, and maintained at about 25° C.