Electrical and Structural Properties of TaN Gate Electrodes Fabricated by Wet Etching Using NH₄OH/H₂O₂ Solution and Hf Metal Hard Mask

We fabricated TaN gate electrodes on SiO 2 film by wet etching using NH 4 OH/H 2 O 2 solution and investigated the electrical and structural properties of the TaN/SiO 2 interfacial layer. Hf metal was used as a hard mask for the wet etching of the TaN film. It was found that the gate patterning of the TaN film was successfully achieved by wet chemical etching, which should be applicable for dual-metal-gate fabrication. The effective fixed charge density ( Q eff ) into the SiO 2 film and the effective work function (Φ m,eff ) of TaN remained constant after N 2 annealing at temperatures of up to 750 °C but increased after annealing at 900 °C. The analysis by X-ray photoelectron spectroscopy (XPS) indicated that Ta oxide was formed near the TaN/SiO 2 interface after the annealing at 900 °C. The increases in Q eff and Φ m,eff are discussed on the basis of the XPS results.