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In-situ spectroscopic ellipsometry and structural study of HfO2 thin films deposited by radio frequency magnetron sputtering
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We have investigated the reduction of unwanted interfacial SiO2 layer at HfO2/Si interface brought about by the deposition of thin Hf metal buffer layer on Si substrate prior to the deposition of HfO2 thin films for possible direct contact between HfO2 thin film and Si substrate, necessary for the future generation devices based on high-κ HfO2 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 HfO2 thin films and also to undertake the in-situ characterization of the high-κ HfO2 thin films deposited on n-type 〈100〉 crystalline silicon substrate. The formation of the unwanted interfacial SiO2 layer and its reduction due to the predeposited Hf metal buffer layer as well as the depth profiling and also structure of HfO2 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 HfO2 thin films are crystalline although they were deposited at room temperature.