Highly Selective Etching of Tantalum Electrode to Thin Gate Dielectrics Using SiCl_4-NF_3 Gas Mixture Plasma

摘要

We have developed a new etching technology for a metal gate electrode with high selectivity to thin gate dielectrics. Dry etching of tantalum (Ta) and tantalum nitride (TaN_x) electrodes, not only over thin silicon dioxide (SiO_2) but also over thin silicon nitride (Si_3N_4) gate dielectrics, is achieved by employing an appropriate ratio of silicon tetrachloride (SiCl_4) and nitrogen trifluoride (NF_3) gas mixture plasma. We confirmed that the high selectivity is due to the formation of a deposition layer caused by plasma polymerization based on SiCl_4-NF_3 chemistry. In this paper, we also demonstrate excellent characteristics of metal oxide semiconductor field effect transistor (MOSFET) and metal nitride semiconductor field effect transistor (MNSFET) devices using a low-resistivity TaN_x/bcc-Ta/TaN_x stacked metal gate.