Reaction mechanism studies on the zirconium chloride-water atomic layer deposition process

Reaction mechanisms in the zirconium chloride-water atomic layer deposition (ALD) process have been studied with a quartz crystal microbalance (QCM) and quadrupole mass spectrometer (QMS) at 250-500 degreesC The only observed reaction byproduct was HCl. Both the growth rate and the amount of reaction byproduct were the highest at 300 degreesC as measured with QCM and QMS, respectively. The reaction temperature had no major effect on the reaction mechanism: half of the chloride ligands were released during the ZrCl4 pulse and the other half during the water pulse. However, at higher temperatures the process was slowly moving towards a mechanism where only one chlorine is released during the zirconium pulse and the other three during the D2O pulse. This was suggested to be due to a lowered amount of OD groups on the surface at high temperatures. The results were compared with the earlier TiO2, ZrO2 and HfO2 ALD processes.