Study on c-axis orientation of AlN thin film on the influence Al buffer layer and Ar/N2 gas flow ratio in reactive magnetron sputtering

Abstract

AlN is a piezoelectric material suitable for high temperature dynamic pressure sensing applications. Its piezoelectric coefficient purely depends on its crystal structure and growth direction. Highly c-axis (002) orientation exhibits high piezoelectric coefficient. Deposition of highly (002) oriented AlN thin film poses a challenge since such a growth depends on multiple process parameters and substrate material. In this work, AlN thin film was deposited using reactive radio frequency (RF) magnetron sputtering to correlate the gas flow rate and crystal orientation. AlN deposition was carried out on Si (100) substrate with and without 220 nm Al buffer layer under different Ar/N2 gas flow ratio. The samples were analyzed through X-ray diffraction technique. Results indicated that for the optimized value of 1:1 Ar/N2, (002) AlN intensity at its maximum for both AlN/Si and AlN/Al/Si samples. It is also observed that the use of 220 nm Al buffer layer on Si substrate enhanced the (002) intensity compared to AlN/Si.