Chemical reaction at the interface between polycrystalline Si electrodes and HfO2∕Si gate dielectrics by annealing in ultrahigh vacuum

Abstract

We have investigated the chemical reaction at the interface between polycrystalline-Si (poly-Si) electrodes and HfO2∕Si gate dielectrics by photoemission spectroscopy and x-ray absorption spectroscopy depending on the annealing temperature in an ultrahigh vacuum. From Si2p and Hf4f high-resolution core-level photoemission spectra, we revealed that the Hf-silicide formation starts at as low temperature as 700°C and that the Hf-silicate layer is also formed at the interface between poly-Si electrodes and HfO2. Crystallization of the amorphous HfO2 layer even at 700°C was suggested from valence-band and OK-edge absorption spectra. By the annealing at 800°C, the HfO2 layer disappeared completely and the Hf-silicide clusters were formed on the Si substrate. Direct contact between poly-Si electrodes and HfO2 promotes the interfacial reaction compared to the case without poly-Si electrodes.