Atomic Layer Deposition of Gd-Doped HfO2 Thin Films

Abstract

GdxHf1-xOy thin films were deposited by atomic layer deposition (ALD) using tris(isopropyl-cyclopentadienyl) gadolinium [Gd((PrCp)-Pr-i)(3)] and HfCl4 in combination with H2O as an oxidizer. Growth curves showed a nearly ideal ALD behavior. The growth per individual Gd((PrCp)-Pr-i)(3)/H2O or HfCl4/H2O cycle was 0.55 A degrees, independent of the Gd/(Gd+Hf) composition x in the studied range. This indicates that the amount of HfO2 deposited during a HfCl4/H2O cycle was essentially identical to the amount of Gd2O3 deposited during a Gd((PrCp)-Pr-i)(3)/H2O cycle, assuming identical atomic densities of the films independent of composition. The crystallization of GdxHf1-xOy with Gd/(Gd+Hf) contents x between 7 and 30% was studied. Films with x greater than or similar to 10% crystallized into a cubic/tetragonal HfO2-like phase during spike or laser annealing up to 1300 degrees C, demonstrating that the cubic/tetragonal phase is thermally stable in this temperature range. A maximum dielectric constant of kappa similar to 36 was found for a Gd/(Gd+Hf) concentration of x similar to 11%.