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 (PO2) at 920degC. A comparison of N2 and He annealing with controlled PO2 revealed that the optimal PO2 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