Chemical vapor deposition of aluminum nitride thin films

Abstract

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 °C with growth rates up to 1500 Å/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 °C and 1.05 ± 0.05 for those deposited at 300–500 °C. Films deposited at 100–200 °C had refractive indexes in the range 1.65–1.80 whereas indexes for films deposited at 300–400 °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 °C to 5.77 eV for those deposited at 500 °C. Films deposited at 100–200 °C were amorphous whereas those deposited at 300–500 °C were polycrystalline.