Integration of HfxTayN Metal Gate Electrode with High-k Gate Dielectric in MOS Devices

In this work, the composition effects of hafnium (Hf) and tantalum (Ta) in HfxTayN metal gate on the thermal stability of metal-oxide-semiconductor (MOS) devices were investigated. The work function of the HfxTayN metal gate can reach a value of ~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 (EOT), interface trap density and defect generation rate characteristics, can be achieved after a post-metal anneal up to 950 oC for 45 s. Experimental results indicate that Ta-rich HfxTayN is a promising metal gate for advanced MOS devices.