Effects of energetic negative ions generated from sputtering targets on ScAlN film growth

ScAlN films is attractive for high-frequency piezoelectric devices. In previous study, we demonstrated Sc ingot sputtering in which Sc ingots were set on an Al metal target. Oxidization of Sc ingots was seriously problem because the c-axis orientation of ScAlN films was degraded. In this study, we investigated the energy distributions of O
^-
negative ion which enter the substrate during the deposition. The amount of the O
^-
ion flux decreased with duration, but it remained large. Therefore, the crystalline orientation and the longitudinal mode conversion loss of ScAlN film were inferior to those using a ScAl alloy target. The suppression of the O
^-
generation is required.