Enhancement of c-Axis Oriented Aluminum Nitride Films via Low Temperature DC Sputtering

• Published in: IEEE sensors journal 2021-08, Vol.21 (16), p.17673-17677
• Main Authors: Chen, Ze-Hui, Li, Chengying, Chen, Yueh-Han, Chu, Shengyuan, Tsai, Cheng-Che, Hong, Cheng-Shong
• Format: Article
• Language: English
• Subjects: Accelerometers; AlN; Aluminum; Aluminum nitride; Cantilever beams; III-V semiconductor materials; Low temperature; Machine tools; MEMS; Microelectromechanical systems; Micromechanical devices; Photoresists; Piezoelectric accelerometer; Piezoelectric films; Preferred orientation; Sputtering; Substrates; Temperature; Temperature measurement
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2021.3077274

In this study, we successfully deposit c-axis oriented aluminum nitride (AlN) piezoelectric films at low temperature (100 °C) via the DC sputtering method with tilt gun. The X-ray diffraction (XRD) observations prove that the deposited films have a c-axis preferred orientation. Effective d 33 value of the proposed films is 5.92 pm/V, which is better than most of the reported data using DC sputtering or other processing methods. It is found that the gun placed at 25° helped the films to rearrange at low temperature and c-axis orientation AlN films were successfully grown at 100 °C. This temperature is much lower than the reported growing temperature. It means the piezoelectric films can be deposited at flexible substrate and the photoresist can be stable at this temperature. The cantilever beam type microelectromechanical systems (MEMS) piezoelectric accelerometers are then fabricated based on the proposed AlN films with a lift-off process. The results show that the responsivity of the proposed devices is 8.12 mV/g, and the resonance frequency is 460 Hz, which indicates they can be used for machine tools.