Suppression of silicidation in polycrystalline-Si/high-kappa insulator/SiO2/Si structure by helium through process

摘要

Suppression of silicidation in polycrystalline-Si (poly-Si)/ high-kappa insulators (ZrO2,HfO2)/SiO2/Si structure by helium (He) through process which adds He gas during a poly-Si gate process was demonstrated. In Si deposition on ZrO2 and HfO2 by SiH4 flow diluted by N-2 or He, surface silicidation can be suppressed by lowering of initial deposition temperature below 600 and 650degreesC, respectively, but thin SiO2 films are formed between Si films and these high-kappa insulator surfaces without being dependent on the dilution gases. Moreover, it is found that He through process of low-temperature SiH4 flow diluted by He and high-pressure He postannealing is the most effective means of suppressing not only the thermal degradation of high-kappa insulator/SiO2/Si interface but also the silicidation of poly-Si/SiO2/ high-kappa insulator interface, whereas conventional N-2 through process cannot suppress both. These results mean that high-concentration He atoms are indispensable for upper and lower SiO2/Si interfaces. It is supposed that many He atoms physically obstruct SiO creation through the quenching of atomic vibration at both SiO2/Si interfaces, thus impeding the first step of silicidation reaction. In addition, by comparing with SiO2 single film, it is found that the suppression efficiency of He atoms in the high-kappa insulator/SiO2/Si system is higher than that in the SiO2/Si system. This phenomenon can be rationalized by presupposing that the efficiency reflected the degradation-prone site density in the interfacial SiO2 layer. (C) 2004 American Institute of Physics.