Experimental Demonstration of Higher-k Phase HfO2 through Non-equilibrium Thermal Treatment

Structural phase transformation of pure-HfO2 films in higher-k phase (cubic or tetragonal phase) was investigated. HfO2/SiO2/Si stacks were annealed at 600oC under various temperature programs. We found that the peak intensity ratio of the higher-k phase to monoclinic one in XRD was enhanced distinctly by increasing the ramping-up rate of temperature, even though the equilibrium phase at 600oC should be the monoclinic. Additionally, the ratio gradually decreased with extending the annealing time, but the higher-k phase was maintained by annealing after deposition of Si capping-layer on HfO2/SiO2/Si stacks