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

Abstract

Suppression of silicidation in polycrystalline-Si (poly-Si)/ high-κ 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 N2 or He, surface silicidation can be suppressed by lowering of initial deposition temperature below 600 and 650°C, respectively, but thin SiO2 films are formed between Si films and these high-κ 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-κ insulator/SiO2∕Si interface but also the silicidation of poly-Si∕SiO2/ high-κ insulator interface, whereas conventional N2 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-κ 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.