The composition and interfacial properties of annealed AlN films deposited on 4H-SiC by atomic layer deposition

We have investigated and compared the influence of annealing temperature on composition and interfacial properties of AlN thin films deposited on 4H-SiC substrates by atomic layer deposition using trimethylaluminum (TMA) and ammonia as precursors at 400 °C. Those as-deposited films were annealed by rapid thermal annealing at 700 °C, 800 °C, 900 °C and 1000 °C for 1 min in N2 atmosphere, respectively. As the annealing temperature increased, the thickness of AlN films decreased and the refractive index increased due to the densification and compositional changes in the films. The roughness of films decreased as the films became denser after annealing. In addition, the deposited AlN film is not amorphous structure and the intensity of the (0002) diffraction of the AlN films enhanced in the annealed films. N-O-Al bond broke down and the intensity of Al-N bond increased with the increase of annealing temperature. Moreover, the interface between AlN and SiC was mainly a transition layer containing Al-O-Si, and the intensity of Al-O-Si was enhanced after annealing at 1000 °C. And the annealing process reduced the negative charge and the density of interface trap of the AlN annealed film in the MIS capacitor. These results provide a significant reference for AlN as a gate dielectric for SiC-based MOS devices in the future.