Suppression of thermal interface degradation in high-k film/Si by helium

Abstract

Suppression of thermal interface degradation, especially silicidation, in high-k film (ZrO₂, HfO₂)/Si systems by a helium (He) process, which adds He gas during various annealing processes, was demonstrated. The high-k film/SiO₂/Si thermal interface stability was investigated in terms of N₂, and He gas annealing with controlled oxygen partial pressure (P_O2) at 920degC. A comparison of N₂ and He annealing with controlled P_O2 revealed that the optimal P_O2 ranges in He at which the thermal stability of a layered structure can be achieved are wider than that in N₂. Moreover, regarding the poly-Si/SiO₂/high-k film interface, it was found that He through process consisting of low-temperature SiH ₄ flow diluted by He and high-pressure He post-annealing is the most effective means of suppressing silicidation, whereas a conventional N₂ through process cannot. These results indicate that high-concentration He atoms are indispensable for the upper poly-Si/SiO₂ interface. It is supposed that many He atoms physically obstruct SiO creation through the quenching of atomic vibration at the SiO₂/Si interface, thus impeding the first step of the silicidation reaction