Influence of carrier gas pressure and flow rate on atomic layer deposition of HfO2 and ZrO2 thin films

Influence of the carrier gas on HfCl₄-H₂O and ZrCl₄-H₂O atomic layer processes was investigated. The growth rates of HfO₂ and ZrO₂ decreased with increasing flow rate and pressure of the N₂ carrier gas. Data of real-time quartz crystal microbalance measurements demonstrated that the effect observed was mainly due to influence of carrier gas on surface reactions and the role of overlapping the precursor pulses was negligible. At the same increase of the carrier gas mass flow, the increase of the linear flow rate led to more significant changes of thin-film properties than the increase of the carrier gas pressure did. Thin films with higher density, higher refractive index and, particularly, lower concentration of residual chlorine were obtained at higher carrier gas flow rates. Increase of the carrier gas flow rate also resulted in a higher concentration of a metastable phase in HfO₂ thin films deposited at 300 °C.