Highly Selective Etching of Tantalum Electrode to Thin Gate Dielectrics Using SiCl4-NF3 Gas Mixture Plasma

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 (TaNx) electrodes, not only over thin silicon dioxide (SiO2) but also over thin silicon nitride (Si3N4) gate dielectrics, is achieved by employing an appropriate ratio of silicon tetrachloride (SiCl4) and nitrogen trifluoride (NF3) gas mixture plasma. We confirmed that the high selectivity is due to the formation of a deposition layer caused by plasma polymerization based on SiCl4-NF3 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 TaNx/bcc-Ta/TaNx stacked metal gate.