Highly c-axis-oriented ScAlN thin films deposited using Sc-Al alloy target

ScAlN thin films were deposited by a conventional radiofrequency (RF)-magnetron sputtering system using two Sc-Al alloy metal targets with different Sc/Al ratios. A 10 h deposition time resulted in highly c-axis-oriented ScAlN thin films with Sc concentrations of 32 at% and 22 at% on Sc0.43-Al0.57 and Sc 0.32 -Al 0.68 targets, respectively. C-axis orientation was lost in thin films deposited on the Sc 0.43 -Al 0.57 target after sputtering times of over 50 h. XDS analysis showed a high-Sc-content ScAlN film with an amorphous phase layer near the Si substrate surface. A seed layer of c-axis-oriented ScAIN allowed for > 50 h deposition on the Sc 0.43 -Al 0.57 target to result in highly c-axisoriented ScAlN films. A one-port surface acoustic wave (SAW) resonator based on the ScAlN/Si structure has a K 2 value of 2.7% at 2 GHz, six times larger than for that based on the AlN/Si structure.