High-quality c-axis oriented Al(Sc)N thin films prepared by magnetron sputtering

Abstract

In order to adapt to the upgrading of wireless communication system, thin film bulk acoustic resonator (FBAR) has become one of the research hotspots in the communication field. The piezoelectric film, such as aluminum nitride (AlN), is the core functional layer of this device. However, previous reports have only focused on specific characteristics of the piezoelectric film, such as preferred orientation, piezoelectric coefficient, residual stress and so on. In this work, AlN and 6% scandium doped AlN films with (002) preferred orientation were deposited on (100) silicon wafers by direct-current magnetron reactive sputtering. We studied the crystallinity, roughness, element distribution, stress and additional characteristics of the films, and compared the quality changes of AlN thin films doped with Sc. Our results showed that all the deposited films had a uniform and dense structure with high crystallinity. But, the doping of Sc significantly reduced the nonuniformity, roughness, and stress of AlN films. Our research is of great significance for the preparation of high-quality piezoelectric thin films to improve the performance of FBAR filters, and ultimately improve the yield of devices.