Investigation of high-k/metal gate MOS capacitors annealed by microwave annealing as a post-metal annealing process

Abstract

MOSFETs with high-k and metal gate materials have been adopted nowadays. However, using traditional rapid thermal annealing as the annealing process after metal deposition causes thick SiO2 inter-layers and large flat-band shift. For future processes, an alternative post-metal annealing method has to be found. This study investigated electrical characteristics and physical properties of TiN/Al/TiN/HfO2/Si MOS capacitors annealed with a microwave annealing technique. The results show that samples annealed by microwave annealing at 2700W demonstrate low equivalent oxide thickness, low interface states density and low oxide trapped charge density. Besides, the diffusion of Al into oxides films is also suppressed. As a result, for high-k/metal gate MOS capacitors, high oxide capacitance, high breakdown voltage and low leakage current can be obtained using microwave annealing.