Reaction mechanism of atomic layer deposition of zirconium oxide using tris(dimethylamino)cyclopentadienyl zirconium: experimental and theoretical study†

We investigated the reaction mechanism of atomic layer deposition (ALD) of zirconium oxide (ZrO₂) by integrating experiments and calculations. The ALD process by alternating the supply of tris(dimethylamino)cyclopentadienyl zirconium (CpZr(NMe₂)₃) and ozone (O₃) was examined using an in situ quartz crystal microbalance (QCM) and the successive surface reaction of the Zr precursor was simulated by density functional theory (DFT) calculations. The QCM analysis suggests that two NMe₂ ligands are released during the first half-cycle of ALD. The DFT calculations indicate that the first two NMe₂ ligands are released during the chemisorption of the Zr precursor with low activation energies of 0.22 eV and 0.16 eV. Conversely, the release of the Cp ligand or the third NMe₂ ligand was unfavorable due to its endothermic nature and high activation energy. Upon completion of the chemisorption of the Zr precursor, the resulting surface species would be O₂ZrCp(NMe₂)*, which is in agreement with the QCM results. The integration of the QCM experiment and the DFT calculations is an effective approach to elucidate the ALD reaction mechanism, especially when a heteroleptic precursor is used.