Laser-induced surface acoustic wave spectroscopy of wurtzite AlYN thin films

We present an investigation of aluminum yttrium nitride (AlYN) thin films synthesized via reactive magnetron co-sputtering on 200-mm silicon substrates. While scandium-alloyed aluminum nitride exhibits superior piezoelectric performance, its commercial adoption is limited by scandium’s high costs and supply vulnerabilities. Yttrium offers a promising alternative with similar property enhancements at improved economic viability. This study reports for the first time an experimental determination of the elastic properties of AlYN as a function of Yttrium content by means of laser-induced surface acoustic wave spectroscopy, which demonstrated exceptional sensitivity and measurement reproducibility for determining critical film parameters including Young’s modulus, density, and thickness. Our results confirm theoretical predictions of lattice softening with increasing yttrium concentration, with deviations attributed to microstructural features of sputter-deposited films. Yttrium content was modulated through power density control, affecting film thickness and residual stress. These previously unreported properties provide critical insights for implementing AlYN in microelectromechanical systems, particularly for radio-frequency applications where knowledge of Young’s modulus and acoustic velocity is essential.