Atomic layer deposition of GdHfO_x thin films

摘要

GdHfO_x thin films were deposited by atomic-layer deposition (ALD) using Tris(isopropyl-cyclopentadienyl)Gadolinium [Gd(i-PrCp)_3] and HfCl_4 in combination with H_2O as oxidizer. Growth curves show nearly ideal ALD behavior. The growth per cycle is found to be 0.55 A, independent of Gd/(Gd+Hf) composition in the studied range. This indicates that the amount of HfO_2 deposited during an HfCl_4/H_2O cycle is identical to the amount of Gd_2O_3 deposited during a Gd(i-PrCp)_3/H_2O cycle. The film composition can therefore be deduced from the HfCl_4/Gd(i-PrCp)_3 cycle ratio. The crystallization of GdHfO_x with Gd/(Gd+Hf) contents between 9% and 30% was studied. All films crystallize into a cubic/tetragonal HfO_2/-like phase during spike annealing at 1050°C. Cubic/tetragonal phases are also observed after laser annealing for 1.5 ms up to 1300°C, demonstrating that the cubic/tetragonal phase is thermally stable in this temperature range.