Preparation of highly oriented aluminum nitride thin films on polycrystalline substrates by helicon plasma sputtering and annealing

Highly c-axis-oriented aluminum nitride (AIN) thin films were prepared on p olycrystalline Si3N4 and SiC substrates by helicon plasma sputtering. The d ifference in the substrate materials scarcely influenced the crystal struct ures of the films. The full width at half-maximum (FWHM) of the X-ray rocki ng curves of the films was 3.2 degrees, which is the smallest value for AIN thin films deposited on polycrystalline substrates to our knowledge. Annea ling at 800 degreesC in vacuum decreased the FWHM from 3.2 degrees to 2.8 d egrees. The structure of the films was densely packed and consisted of many fibrous grains. The films developed c-axis orientation on the polycrystall ine substrates, because the interaction between the films and substrate sur faces was small, and (100) and (110) AIN planes grew preferentially. The fi lms were piezoelectric and generated electrical signals in response to mech anical stress.