Electrical and Structural Properties of TaN Gate Electrodes Fabricated by Wet Etching Using NH_4OH/H_2O_2 Solution and Hf Metal Hard Mask

摘要

We fabricated TaN gate electrodes on SiO_2 film by wet etching using NH_4OH/H_2O_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℃ but increased after annealing at 900℃. 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℃. The increases in Q_(eff) and Φ_(m,eff) are discussed on the basis of the XPS results.