Impacts of substrate and growth temperature on the deposition and etching of c-axis oriented AlN piezoelectric thin films

We studied the impacts of deposition substrate and temperature on the growth and wet etching behavior of AlN piezoelectric thin films. Using Mo substrate as well as optimizing temperature (450 °C), AlN films with high crystalline quality (FWHM =0.9°) and excellent piezoelectric property (d₃₃=6.3pm/V) were achieved by magnetron sputtering. Experiment results suggest that, the substrate predominantly determines the grain size and the formation of columnar structure during the initial growth stage, while the temperature mainly affects the final grain morphology. The better crystalline quality of AlN, the higher its piezoelectricity. Besides, by using TMAH solution for the wet etching of AlN films with different growth condition, it was found that the columnar grain structure is related to the chemical stability of the {10–1–2} planes, which influences the etching morphology. The etching rate shows a trend from fast to slow, and the initial rate is positively correlated with the grain size.