Properties of Ru-Ta alloys as gate electrodes for NMOS and PMOS silicon devices

This paper describes the characteristics of binary metallic alloys of Ta and Ru for gate electrode applications. The work function of this alloy can be varied from 4.2 eV to 5.2 eV by controlling the composition thereby enabling its use in both NMOS and PMOS devices. Excellent thermal stability up to 1000/spl deg/C was observed in alloy compositions suitable for both NMOS and PMOS devices. It is believed that the Ru/sub 1/Ta/sub 1/ phase of the film and formation of Ru-Ta bonds improves the thermal stability of the gate-dielectric interface while maintaining appropriate work functions.