Investigation of tetrakis(ethylmethylamido)hafnium adsorption mechanism in initial growth of atomic layer deposited-HfO2 thin films on H-/OH-terminated Si (100) surfaces

Abstract

The continuous scaling down of dynamic random access memory devices has necessitated a comprehensive understanding of the initial growth mechanism in atomic layer deposition. In this study, HfO2 was deposited using tetrakis(ethylmethylamido)hafnium (TEMAHf)-H2O on H-/OH-terminated Si (100) surfaces. By analyzing the Hf-O peak in the FTIR spectra and medium-energy ion scattering measurements, it was determined that a monolayer was formed on the H-Si surface at a rate (10 cycles) lower than that for the OH-Si surface (4 cycles). The ligand variations during each cycle, as determined by FTIR measurements, enabled the suggestion of the initial precursor adsorption mechanism. An analysis of the infrared spectra and secondary ion mass spectrometry depth profiles revealed surface-dependent differences in interfacial bonding. This explained the variation in the rate of formation of 1 Ml. Additionally, theoretical investigations using density functional theory calculations identified the reaction pathway with the lowest energy barrier, thereby validating the experimentally proposed mechanism. This study to elucidate the Si surface and the TEMAHf-H2O reaction mechanism provided insights into the analysis of the initial precursor adsorption mechanism for other types of precursors.