Atomic Layer Deposition of Gd-Doped HfO2 Thin Films

Gd x Hf 1-x O y 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 2 0 as an oxidizer. Growth curves showed a nearly ideal ALD behavior. The growth per individual Gd( i PrCp) 3 /H 2 O or HfCl 4 /H 2 O cycle was 0.55 A, independent of the Gd/(Gd + Hf) composition x in the studied range. This indicates that the amount of HfO 2 deposited during a HfCl 4 /H 2 O cycle was essentially identical to the amount of Gd 2 O 3 deposited during a Gd( i PrCp) 3 /H 2 O cycle, assuming identical atomic densities of the films independent of composition. The crystallization of Gd x Hf 1-x O y , with Gd/(Gd + Hf) contents x between 7 and 30% was studied. Films with x ≳ 10% crystallized into a cubic/tetragonal HfO 2 -like phase during spike or laser annealing up to 1300°C, demonstrating that the cubic/tetragonal phase is thermally stable in this temperature range. A maximum dielectric constant of K ~ 36 was found for a Gd/(Gd + Hf) concentration of x ~ 11%.