Thermal stability of Hf/sub x/Ta/sub y/N metal gate electrodes for advanced MOS devices

In this letter, the composition effects of hafnium (Hf) and tantalum (Ta) in Hf/sub x/Ta/sub y/N metal gate on the thermal stability of MOS devices were investigated. The work function of the Hf/sub x/Ta/sub y/N metal gate can reach a value of /spl sim/4.6 eV (midgap of silicon) by suitably adjusting the Hf and Ta compositions. In addition, with a small amount of Hf incorporated into a TaN metal gate, excellent thermal stability of electrical properties, including the work function, the equivalent oxide thickness, interface trap density and defect generation rate characteristics, can be achieved after a post-metal anneal up to 950/spl deg/C for 45 s. Experimental results indicate that Ta-rich Hf/sub x/Ta/sub y/N is a promising metal gate for advanced MOS devices.