CHEMICAL VAPOR-DEPOSITION OF ALUMINUM NITRIDE THIN-FILMS

The atmospheric pressure chemical vapor deposition of aluminum nitride coatings from hexakis(dimethylamido)dialuminum, Al2(N(CH3)2)6, and ammonia precursors is reported. The films were characterized by ellipsometry, transmission electron microscopy, x-ray photoelectron spectroscopy, Rutherford backscattering, and forward recoil spectrometry. The films were deposited at 100-500-degrees-C with growth rates up to 1500 angstrom/min. The films showed good adhesion to silicon, glass, and quartz substrates and were chemically inert. Rutherford backscattering analysis revealed that the N/Al ratio was 1.15 +/- 0.05 for films deposited at 100-200-degrees-C and 1.05 +/- 0.05 for those deposited at 300-500-degrees-C. Films deposited at 100-200-degrees-C had refractive indexes in the range 1.65-1.80 whereas indexes for films deposited at 300-400-degrees-C were 1.86-2.04. The films were transparent in the visible region. The optical bandgap varied from 5.0 eV for films deposited at 100-degrees-C to 5.77 eV for those deposited at 500-degrees-C. Films deposited at 100-200-degrees-C were amorphous whereas those deposited at 300-500-degrees-C were polycrystalline.