Stress relaxation of three dimensional textured AlN films on sapphire substrate by rapid thermal annealing

Abstract 1000 nm high c-axis orientation and three dimensional textured AlN films were deposited on sapphire by reactive ion assisted sputtering and the rapid thermal annealing (RTA) was carried out at 700–900 °C for 5 min to release the film stress. Transmission electron lattice images show that the relationship of the AlN/sapphire interface is [0002]AlN//[0006]sapphire and [11-20]AlN//[1100]sapphire. The Fourier filtered images of the near substrate region suggest a thin buffer layer near the substrate, in which the atomic arrangement changes from matching sapphire lattice to AlN lattice. The buffer layer was disappeared after 900 °C RTA annealing. The Raman spectra shows the in-plane tensile stress of deposited AlN films is released by the RTA. The E2 (high) peak of the sample annealed at 900 °C shifts by 4.4 cm−1 compared to the as-deposited sample, which illustrates the tensile stress relaxation in the annealing process. In order to prevent the occurrence of peeling caused by the long heating time, this work proposed multiple-cycle rapid thermal annealing to anticipate stress relief.