Improvement of Shear-Mode Electromechanical Coupling of c-Axis Parallel Oriented ZnO Film by Limiting Particle Irradiation Direction During RF Magnetron Sputtering

ZnO films with the crystalline c-axis parallel to the substrate and aligned in one direction can excite shear waves and are suitable for thickness shear-mode resonators. They were obtained by irradiating the substrate with negative ions generated near the ZnO target during RF magnetron sputtering. However, there is a problem that highly oriented films cannot obtain near the anode center by RF magnetron sputtering. To obtain high piezoelectricity, the in-plane direction of c-axis requires alignment in one direction. It was aligned in the radial direction of the anode in the magnetron sputtering with a cylindrical magnet. However, it was difficult to align near the anode center because negative ions were expected to be irradiated from various directions due to the symmetry of the magnet. In this study, improvement of the shear-mode electromechanical coupling of the ZnO film at the center was attempted by installing shields near the substrate to limit the direction of particle irradiation.