Improving RF Magnetron Sputter Parameters for a Piezoelectric AlN Thin Film Deposition

This paper reports on the parameters that affect the crystalline quality of Aluminium Nitride (AlN) thin film grown using the RF magnetron sputtering process. AlN film of 1-micron thickness is the piezoelectric material of choice in the fabrication of a high-frequency resonating structure. Substrate temperature, RF power, gas-ratios were fine tuned in various experimental trials to obtain a <002> c-axis oriented AlN thin film. Least obtained FWHM from the XRD plots were 0.44∘. In Atomic Force Microscopy (AFM) surface roughness of the best quality AlN thin film was 11.1nm. Using Piezo response Force Microscopy (PFM) butterfly loops were constructed and effective piezoelectric co-efficient of 7.28 pm/V was obtained. This co-efficient value is accounting for both the d33 of the piezoelectric material and the substrate bending for the released membrane structure.