Interface properties of ultra-thin HfO 2 films grown by atomic layer deposition on SiO 2/Si

Abstract

Ultra-thin (1–8 nm) HfO 2 films, grown on both chemical and thermal SiO 2/Si surfaces by atomic layer deposition, were characterized in terms of interface properties by angle-resolved X-ray photoelectron spectroscopy (ARXPS), high-resolution transmission electron microscopy (HRTEM) and depth profiling techniques such as secondary ion mass spectrometry (SIMS) and Auger electron spectroscopy (AES). ARXPS measurements show, in excellent agreement with HRTEM, that the SiO 2 thickness increases upon HfO 2 deposition, possibly in part as the result of interfacial reactions forming silicates-type bonding states that are evidenced from careful deconvolution of both Hf 4f and Si 2p core-level spectra. SIMS and AES depth profiles exhibit a redistribution of oxidized Hf concentration in the SiO 2 interfacial layer, and also a possible diffusion of Hf into the Si substrate. These results are useful for further understanding of HfO 2/SiO 2 interfaces for the next generation of complementary metal-oxide-semiconductor transistor oxide gates.