The Limits of the Post‐Growth Optimization of AlN Thin Films Grown on Si(111) via Magnetron Sputtering

Abstract

Hexagonal aluminium nitride (AlN) thin films prepared by the reactive magnetron sputtering method usually undergo post‐growth annealing treatment aimed at the improvement of crystalline quality as a principal step for their performance as piezoelectric transducers in micro‐electro‐mechanical systems. Herein, the post‐growth annealing of AlN films deposited on Si(111) is investigated by Raman and Fourier transform infrared spectroscopies, X‐ray diffraction, and scanning probe microscopies. The thermally treated films show a positive trend in stress relaxation via annealing up to 1200 °C; however, it is accompanied by a dewetting of the quasi‐epitaxial layer and the formation of the cubic AlN phase. The critical role is played by the AlN/Si interface being sensitive to oxidation via interstitial oxygen in Si wafers. The piezoelectric performance of the AlN/Si system is found to be inversely proportional to the post‐growth annealing temperature.