Atomic layer deposition of GdHfOx thin films

GdHfOx thin films were deposited by atomic-layer deposition (ALD) using Tris(isopropyl-cyclopentadienyl) Gadolinium [Gd(i-PrCp)(3)] and HfCl4 in combination with H2O as oxidizer. Growth curves show nearly ideal ALD behavior. The growth per cycle is found to be 0.55 angstrom, independent of Gd/(Gd+Hf) composition in the studied range. This indicates that the amount of HfO2 deposited during an HfCl4/H2O cycle is identical to the amount of Gd2O3 deposited during a Gd(i-PrCp)(3)/H2O cycle. The film composition can therefore be deduced from the HfCl4/Gd(i-PrCp)(3) cycle ratio. The crystallization of GdHfOx with Gd/(Gd+Hf) contents between 9% and 30% was studied. All films crystallize into a cubic/tetragonal HfO2-like phase during spike annealing at 1050 degrees C. Cubic/tetragonal phases are also observed after laser annealing for 1.5 ms up to 1300 degrees C, demonstrating that the cubic/tetragonal phase is thermally stable in this temperature range.