Gate oxide integrity (GOI) of MOS transistors with W/TiN stacked gate

Abstract

With W/TiN stack gate deposited at high temperature, excellent time-dependent dielectric breakdown (TDDB) characteristics of the gate oxide were obtained in MOS capacitors. In the case of negative gate bias where thin oxide reliability becomes critical, the TiN gate provides a much longer time to breakdown than that of n/sup +/-poly gate due to a larger barrier height and less F-N tunneling current. In spite of skipping the conventional reoxidation process, a breakdown field larger than 10 MV/cm could be obtained in MOS transistors by undercutting TiN with boiling H/sub 2/SO/sub 4/. With a double spacer and undercutting scheme, the short channel effect of NMOS and PMOS transistors could be suppressed up to L/sub gate//spl sim/0.3 /spl mu/m.