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

Suppression of thermal interface degradation, especially silicidation, in high-k film (ZrO
₂
, HfO
₂
)/Si systems by a helium (He) process, which adds He gas during various annealing processes, was demonstrated. The high-k film/SiO
₂
/Si thermal interface stability was investigated in terms of N
₂
, and He gas annealing with controlled oxygen partial pressure (P
_O2
) at 920degC. A comparison of N
₂
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 N
₂
. Moreover, regarding the poly-Si/SiO
₂
/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 N
₂
through process cannot. These results indicate that high-concentration He atoms are indispensable for the upper poly-Si/SiO
₂
interface. It is supposed that many He atoms physically obstruct SiO creation through the quenching of atomic vibration at the SiO
₂
/Si interface, thus impeding the first step of the silicidation reaction