Interaction of Hf Precursor with H 2 O-terminated Si(001): First Principles Study
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1155-C01-05
Interaction of HfCl4 precursor with H2O terminated Si (001) surface: First principles study Dae-Hyun Kim1, Dae-Hee Kim1, Hwa-Il Seo2, and Yeong-Cheol Kim1 1 Department of Materials Engineering, Korea University of Technology and Education, 1800 Chungjeollo, Byungchun-myun, Chonan, 330-708, Republic of Korea 2 School of Information Technology, Korea University of Technology and Education, 1800 Chungjeollo, Byungchun-myun, Chonan, 330-708, Republic of Korea ABSTRACT We investigated the reaction of HfCl4 molecules with a H2O terminated Si (001)-2×1 surface using density functional theory to understand the initial stage of atomic layer deposition (ALD) of HfO2. Half monolayer of H2O molecules were adsorbed on the buckled-down Si atoms of the Si dimers of the Si (001)-2×1 surface below the dissociation temperature of H2O and were dissociated into H and OH at room temperature. This process could make uniform and wellaligned -H and -OH’s on the Si (001) substrate. The reaction of a HfCl4 molecule was more favorable with -OH than -H. The reaction of the HfCl4 molecule with the -OH generated a HCl molecule, and the remaining HfCl3 was attached to the O atom. The first reaction of the HfCl4 molecule with –OH produced 0.21 eV energy benefit. The reaction of the second HfCl4 molecule with the most adjacent –OH of the first one produced 0.28 eV energy benefit. The third and fourth molecules showed same tendency with the first and second ones. The energy differences of the fifth and sixth HfCl4 reactions were -0.01 eV, 0.06 eV, respectively. Therefore, we found that the saturation Hf coverage was approximately 5/8 of the available –OH’s, which was 2.08 × 1014 Hf /cm2. The result was well-matched with the experimental study of other group. 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 One of the best advantages for SiO2 is that it can be grown by thermal oxidation; whereas, 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 Green et al. studied the efficacy of various underlayers for nucleation and growth of atomic layer deposited HfO2 films. The use of a chemical oxide underlayer led to good HfO2 nucleation with linear growth rate and almost no barrier. In contrast, the growth on H-terminated Si was characterized by a large barrier to nucleation and growth. It in
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