Effects of the sputtering deposition process of metal gate electrode on the gate dielectric characteristics

Effects of the N-2-introduced reactive sputtering deposition of metal gate electrodes on the gate leakage current and the dielectric reliability of the W/WNx and W/TiN metal gate MOS capacitors are investigated. The gate dielectric characteristics of W gate MOS capacitor are degraded during the sputtering deposition of the gate electrode. However, the sputtering process-induced degradation of the dielectric characteristics is improved by increasing N-2 how ratio during the deposition of WNx gate electrode. This improvement is considered to be due to the termination of the dangling bonds in the surface-damaged layer in the gate dielectric by the surface nitridation. The nitridation of similar to1.5 at.% is found to effectively improve both gate leakage characteristics and dielectric reliability of the W/WNx gate MOS capacitor to a level comparable to those of the poly-Si gate. The characteristics of W/WNx gate MOS transistors are also improved by the surface nitridation through the decrease of the gate leakage current. However, the surface nitridation enhances the electron trapping probability under substrate injection, which results in the lower activation energy of CVS-Q(bd) of metal gate MOS capacitors. (C) 2001 Elsevier Science Ltd. All rights reserved.