Atomic layer deposition of the aluminum oxide-yttrium oxide pseudo-binary system

The growth of thin films of selected phases from the pseudo-binary Al 2O3-Y2O3 material system was demonstrated using atomic layer deposition (ALD). Specifically ALD growth of Al2O 3, Y2O3, Ce2O3, Y2 Al4O12 (Yttrium Aluminum Monoclinic - YAM), and Y3Al5O12 (Yttrium Aluminum Garnet - YAG) was accomplished. All films were grown using the same precursors: AlCl 3 at 105°C and H2O, Y(thd)3 [thd = 2,2,6,6-tetramethyl-3,5-heptanedione] at 140°C and O3, and Ce(acac)3 [acac = acetylacetonate] at 140°C, and O3. The Al2O3 films were grown at substrate temperatures from 295°C to 515°C. A surface-controlled growth temperature 'window' (ALD window) was found for Al 2O3 between 365°C to 465°C using AlCl3 and H2O. The resultant films grown at all temperatures were amorphous as characterized by X-ray diffraction, and showed a rough surface morphology. The growth rate was determined to be 1 A/cycle within the ALD 'window'. The thickness of films grown in the ALD 'window' varied linearly with the number of cycles. Films up to 1 microm thick were grown (10,000 cycles).;The Y2O3 films were grown at substrate temperatures ranging from 200°C to 500°C. No surface-controlled growth temperature window could be determined using Y(thd)3 and O3. The resultant films were polycrystalline with a cubic structure and a smooth surface morphology. The growth rate was determined to be 3 pm/cycle at 350°C. Films up to 30 nm thick were grown (10,000 cycles).;Atomic layer deposition of Ce2O3 thin films were also studied because Ce3+ is often used as a luminescent rare earth dopant in YAG and YAM. The Ce2O3 films were grown at substrate temperatures from 200°C to 500°C. No surface-controlled growth temperature window could be found using Ce(acac)3 and O 3. The resultant films had a rough surface morphology. Using X-ray photoelectron spectroscopy (XPS), it was determined that the Ce3+ oxidation state was present in the as-deposited films rather than Ce4+. When included in the growth process for YAG and YAM, Ce2O 3 was found to create very rough surfaces.;The ternary oxide phases of YAM and YAG were produced by ALD growth of alternating nano-scaled multilayer stacks of Al2O3 and Y2O3 and subsequent calcinations of these thin nano-scale stack structures. By adjusting the ratio of Al2O 3 deposition cycles to Y2O3 deposition cycles, stoichiometric amounts of material were deposited in an alternating fashion. A 300 nm YAG film was deposited using the ALD method at a substrate growth temperature of 350°C. X-ray diffraction data showed that these films were amorphous as-deposited, but they were transformed to a polycrystalline cubic garnet structure when calcined at 975°C for 12 hrs in air. The surface morphology was uniform and smooth. A 400 nm YAM thin film was also successfully deposited using the ALD method at a growth temperature of 350°C. X-ray diffraction of the YAM film showed an amorphous film as-deposited and a polycrystalline monoclinic structure after calcining at 975°C for 12 hrs in air. The surface morphology of this YAM film was rough and non-uniform.