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Published online by Cambridge University Press: 31 January 2011
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 well-aligned −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.