The initial surface reaction mechanisms of atomic layer depositionTiO2using Ti (OCH3)4and H2O as the precursors are investigated by density functional theory. The ALD process is divided into two half-reactions, i.e., Ti (OCH3)4and H2O half-reactions. The adsorption of Ti (OCH3)4on OH/Si (100)2×1 surface is exothermic. However, the overall reaction of Ti (OCH3)4is endothermic. In addition, H2O half-reactions are endothermic and thermodynamically unfavorable.
The initial surface reaction mechanisms of atomic layer deposition TiO2on H/Si (100 )-2×1 surface using Ti (OCH3)4and H2O as precursors are investigated by density functional theory. The ALD process is divided into two half-reactions, i.e., Ti (OCH3)4and H2O half-reactions. The adsorption energy of Ti (OCH3)4on H/Si (100)2×1 surface is only-2.4 kJ/mol. The overall reaction of Ti (OCH3)4is exothermic, which indicates that Ti (OCH3)4half-reactions are favorable on thermodynamic. Howerver, H2O half-reactions are endothermic and thermodynamically unfavorable.
The competitive reactions in atomic layer deposition (ALD) of HfO2, ZrO2 and Al2O3 on the hydroxylated Si(100) surfaces are investigated by using density functional theory. The surface reactions in ALD of HfO2 and ZrO2 show large similarities in energetics and geometrical structures. However, both of them show discrepancies with the surface reactions in ALD of Al2O3. In addition, by comparing with the self-termination reactions, we could find that the further growth reactions are both kinetically and thermodynamically more favorable in ALD of HfO2, ZrO2 and Al2O3.
The initial growth mechanisms of atomic layer deposition of Hafnium dioxide thin films using Cp2Hf (CH3)2 precursor have been investigated. The calculations show that CH4 elimination reaction is energetically more favorable than CpH elimination reaction. As a result, the two ―CH3 ligands of Cp2Hf (CH3)2 may be dissociated prior to the two ―Cp rings. According to the activation barrier analysis, one CpH elimination may occurs sequentially following the first CH4 elimination reaction. During the pulse of Cp2Hf (CH3)2 precursor, the byproduct CH4 and a small amount of CpH are released.
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