(456a) First Priniciples Calculation Of Atomic Layer Deposition Of HfO2

Hafnium oxide (HfO2) is one of the leading candidates to replace silicon oxide as the gate dielectric for future generation metal-oxide-semiconductor based nanoelectronic devices. Atomic layer deposition (ALD) has recently gained interest because of its suitability for fabrication of conformal films with thicknesses in the nanometer range. This study uses periodic density functional theory (DFT) to investigate the growth reactions of HfO2 on as grown surface. The reactants investigated in this study are Hafnium tetrachloride (HfCl4) and water (H2O). Exchange reaction mechanisms for the two reaction half-cycles were investigated. The energy barrier for the first half-reaction is found to be dependent on the nature of HfCl4 adsorption sites. The activation barrier for the ligand exchange reaction during the water pulse is dependent on the coordination number of hafnium atoms associated with the metal precursor. We found that removal of chlorine at high partial pressure of water is plausible through another mechanism i.e., by solvation. We also offer an explanation of dependence of the growth per cycle on temperature during ALD of HfO2 in terms of stability of the adsorbed metal precursor complex. The increase in the temperature leads to a decrease in the coverage of water due to dehydroxylation. This leads to strongly bound metal precursor species after the metal precursor pulse due to the formation of dative bond between chlorine associated with metal precursor and neighboring under-coordinated surface hafnium atoms. These activation barrier for the remove these chlorine atoms during the water pulse increases and there by effecting the growth per cycle.