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High-k materials have received a great deal of attention because of their potential use as alternative gate dielectrics for replacing conventional SiO2 or SiON. Among many candidates, Hf-silicate films have been shown to be superior characteristics due to good thermal stability in contact with Si. Moreover, the incorporation of SiO2 in HfO2 can suppress the crystallization temperature. Above the high temperature of 900°C, however, the phase separation of Hf-silicate films caused by the diffusion of Si and interfacial reaction is observed. Recently, it has been reported that N incorporation into Hf-silicate films improves the thermal stability. However, the effect of incorporated N in band structure has not been considered in detail. This study focused on the change in band alignment of nitrided Hf-silicate as a function of composition and post-nitride anneal using REELS & XPS. Valence band offsets are slightly changed depending on the composition of Hf-silicate films. The SiO2-rich nitrided Hf-silicate films have a smaller band gap than that of the HfO2-rich nitrided Hf-silicate films. In addition post-nitride anneal leads to the increase of band-gap, regardless of the composition of Hf-silicate films. On the basis of these results, the band structures of nitrided Hf-silicate films are configured as a function of composition and post nitride anneal. |