Effects of negative oxygen ions generated during Sc ingot sputtering on electromechanical coupling of ScAlN film

摘要

ScAlN films are well-researched for GHz acoustic wave devices. Large-area growth techniques of ScAlN films are necessary for the practical application. A single sputtering source with a ScAl alloy metal target is suitable for the film growth from the point of view of the composition stability. However, it is difficult to alloy Al with Sc in the large-size target. Therefore, a mosaic target of Sc and Al metals is reasonable for the large-area growth. In previous study, we demonstrated Sc ingot sputtering deposition [1] in which Sc ingots were set on an Al metal target as similar conditions with the mosaic target. Oxidization of Sc ingots was seriously problem in this method because the c-axis orientation of ScAlN films was degraded by bombardment with O-negative ions generated from the target. In this study, we investigated the effects of the negative ion bombardment on the crystalline orientations and piezoelectric properties.