We have grown HfO2 on Si(001) by atomic layer deposition (ALD) using HfCl4 and H2O as precursors. The early stages of the ALD were investigated with high-resolution photoelectron spectroscopy and x-ray absorption spectroscopy. We observed the changes occurring in the Si2p, O1s, Hf4f, Hf4d, and Cl2p core level lines after each ALD cycle up to the complete formation of two layers of HfO2. From the analysis of those variations, we deduced the growth properties of HfO2. The first layer consists of a sparse and Cl-contaminated oxide because of the incomplete oxidation, and the second layer is denser than the first one and with an almost stoichiometric O∕Hf ratio. At the completion of the second layer, the x-ray absorption spectra revealed the change of the Hf-oxide chemical state due to the transition from the thin Hf-oxide to the bulklike HfO2.
Articles you may be interested inInterface quality of Sc2O3 and Gd2O3 films based metal-insulator-silicon structures using Al, Pt, and Ti gates: Effect of buffer layers and scavenging electrodes J. Vac. Sci. Technol. B 31, 01A106 (2013); 10.1116/1.4768678Ultrathin ALD-Al2O3 layers for Ge(001) gate stacks: Local composition evolution and dielectric propertiesThe authors investigated an aluminum oxynitride buffer layer for Pr X O Y / Si metal-insulator-semiconductor stacks. The buffer layer limits unintentional interfacial layer formations and improves the electrical parameters as determined by combined electrical and spectroscopic characterization methods. These benefits are attributed to an interaction of the oxygen of the buffer layer with the Pr X O Y . As essential parameters for the improved performance of the buffer layer the authors find an O:N ratio of 1 and a thickness of 1 nm.
The authors have studied the initial stages of the atomic layer deposition (ALD) of HfO2 onto Si by means of x-ray photoelectron spectroscopy using synchrotron radiation. The ALD was obtained using HfCl4 and H2O as precursors. The investigation was carried out in situ giving the possibility to determine the properties of the grown film after each ALD cycle. The Si 2p, O 1s, and Hf 4d+Cl 2p spectra show the growth of HfO2 in a smooth way until the complete formation of two oxide layers. The averaged growth rate is found to be 0.33 (one layer after three cycles) in accordance with previous works but, within the formation of one oxide layer, each ALD cycle behaves in a distinct way: the oxidation step in the various cycles shows a different efficiency leading to the inclusion of Cl impurities into the Hf oxide. In relation to the experimental results we discuss the origin of the Cl contamination proposing a mechanism based on the adsorption geometry of HfCl4 onto the–OH terminated substrate.
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