Aluminum tri-isopropoxide as an alternative precursor for atomic layer deposition of aluminum oxide thin films

Due to the safety challenges associated with the use of trimethylaluminum as a metal precursor for the deposition of alumina, different chemicals have been investigated over the years to replace it. The authors have investigated the use of aluminum tri-isopropoxide (TIPA) as an alternative alkoxide precursor for the safe and cost-effective deposition of alumina. In this work, TIPA is used as a stable Al source for atomic layer deposition (ALD) of Al₂O₃ when different oxidizing agents including water, oxygen plasma, water plasma, and ozone are employed. The authors have explored the deposition of Al₂O₃ using TIPA in ALD systems operating in vacuum and atmospheric pressure conditions. For thermal and plasma processes in vacuum ALD, a growth rate of 1.1-2 Å/cycle achieved over a range of 140-300 °C is shown. Film density, roughness, and composition have been tested using various characterization techniques confirming comparable film properties to the thermal ALD of trimethylaluminum and water. The thermal water process at atmospheric pressure ALD (AP-ALD) resulted in a growth rate of up to 1.1 Å/cycle with residual carbon below the XPS detection limit. AP-ALD on nanoparticles shows different growth modes on TiO₂ versus SiO₂ nanoparticle surfaces confirmed by transmission electron microscopy analysis. Using TIPA as an ALD precursor would open up the possibility for a safer and cost-effective process for deposition of Al₂O₃ in various applications.