Adsorption and Reaction Behaviors of Hf Precursor with Two Hydroxyls on Si(100): First Principles Study
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1155-C09-14
Adsorption and reaction of Hf precursor with two hydroxyls on Si (100) surface: First principles study Dae-Hyun Kim1, Dae-Hee Kim1, Hwa-Il Seo2, Ki-Young Kim1, and Yeong-Cheol Kim1 Dept. Materials Engineering Korea University of Technology and Education, 1800 Chungjello Byungchun-myun, Chonan, 330-708, Republic of Korea 2 School of Information Technology, Korea University of Technology and Education, 1800 Chungjello Byungchun-myun, Chonan, 330-708, Republic of Korea 1
ABSTRACT Density functional theory was used to investigate the adsorption and reaction of HfCl4 with two hydroxyls on Si (001)-2×1 surface in atomic layer deposition (ALD) process. When H2O molecules are adsorbed on Si (001) surface at room temperature, they are dissociated with hydrogens and hydroxyls. There are two dissociation pathways; inter-dimer dissociation and intra-dimer dissociation. The activation energies of these pathways can be converted to the reaction probabilities. It was approximately 2:1. We prepared a reasonable Si substrate which consisted of six inter-dimer dissociated H2O molecules and two intra-dimer dissociated H2O molecules. The HfCl4 must react with two hydroxyls to be a bulk-like structure. There were five reaction pathways where HfCl4 could react with two hydroxyls; inter-dimer, intra-dimer, crossdimer, inter-row, and cross-row. Inter-row, inter-dimer and intra-dimer were relatively stable among the five reaction pathways based on the energy difference. The electron densities between O and Hf in these three reactions were higher than the others and they had shorter Hf-O and O-O bond lengths than the other two reaction pathways. INTRODUCTION The complementary metal oxide semiconductor (CMOS) device is the most important electronic device in microelectronic industry. Silicon dioxide (SiO2) is used extensively as dielectric materials. However, SiO2 is so thin that the tunneling leakage current becomes too high. 1 High-k materials have received much attention recently in microelectronics because highk gate dielectrics can significantly suppress the tunneling leakage current in CMOS devices. Among various high-k materials, hafnium dioxide (HfO2) is considered to be the most promising candidate due to its relatively high permittivity, good thermal stability, and compatibility with dual metal integration.2 The great advantage of SiO2 is that it can be grown by thermal oxidation. In contrast, high-k oxides must be deposited.2 Atomic layer deposition (ALD) technique is a desirable process to form HfO2 because it shows good conformality and uniformity over large areas.3,4 Willis et al. studied a reaction of HfCl4 with H2O terminated Si (001)-2×1 using density functional theory calculation.5 The model predicted a saturation coverage of (2.05±0.05) × 1014Hf/cm2 and the main factor which limited the reactant coverage was found to be a preferred reaction at two hydroxyl sites. They demonstrated the surface made up of roughly equal numbers of OHfCl3 and (O)2HfCl2. Tang et al. performed density functional theory calculation t
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