In-situ spectroscopic ellipsometry and structural study of HfO_2 thin films deposited by radio frequency magnetron sputtering

摘要

We have investigated the reduction of unwanted interfacial SiO_2 layer at HfO_2/Si interface brought about by the deposition of thin Hf metal buffer layer on Si substrate prior to the deposition of HfO_2 thin films for possible direct contact between HfO_2 thin film and Si substrate, necessary for the future generation devices based on high-κ HfO_2 gate dielectrics. Reactive rf magnetron sputtering system along with the attached in-situ spectroscopic ellipsometry (SE) was used to predeposit Hf metal buffer layer as well as to grow HfO_2 thin films and also to undertake the in-situ characterization of the high-κ HfO_2 thin films deposited on n-type (100) crystalline silicon substrate. The formation of the unwanted interfacial SiO_2 layer and its reduction due to the predeposited Hf metal buffer layer as well as the depth profiling and also structure of HfO_2 thin films were investigated by in-situ SE, Fourier Transform Infrared spectroscopy, and Grazing Incidence X-ray Diffraction. The study demonstrates that the predeposited Hf metal buffer layer has played a crucial role in eliminating the formation of unwanted interfacial layer and that the deposited high-κ HfO_2 thin films are crystalline although they were deposited at room temperature.