Correlation between the growth-per-cycle and the surface hydroxyl group concentration in the atomic layer deposition of aluminum oxide from trimethylaluminum and water

The growth-per-cycle (GPC) in the trimethylaluminum/water atomic layer deposition (ALD) process is shown to be quantitatively correlated with the surface OH group concentration before the trimethylaluminum reaction. The correlation corresponds to a reaction chemistry, where several types of gas-solid reactions (ligand exchange, dissociation/association) can occur simultaneously, and where steric hindrance by adsorbed methyl groups terminates the trimethylaluminum reaction. The commonly assumed reaction chemistry where one OH group bonds one aluminum atom through ligand exchange does not describe satisfactorily the trimethylaluminum/water process, and should perhaps not be expected to describe other ALD processes either.