Wafer level Demonstration and Characterization of c-Axis Oriented Sc0.3Al0.7N Bilayer Stacks

• Main Authors: Lin, Huamao, Liu, Peng, Chen, Daniel Ssu-Han, Varghese, Binni, Wong, Veronica, Li, Minghua, Hong, Yan, Tsang, Yat Fung, Xin Zhang, Qing, Kee Chang, Peter Hyun, Zakiyyan, Naadaa, Koppisetti, Goutham, Das, Amal, Sim, Dao Hao, Lung Lee, Yee, Leotti, Alberto, Zhu, Yao
• Format: Conference Proceeding
• Language: English
• Subjects: Acoustics; bilayer; bimorph; DBLI; Electrodes; film thickness dependent; Focusing; Frequency control; Microstructure; Piezoelectric films; piezoelectric properties; Sc 0.3 Al 0.7 N; Thickness measurement; X-ray scattering
• ISSN: 2375-0448
• DOI: 10.1109/UFFC-JS60046.2024.10793771

In this study, we investigated c-axis oriented single-layer and bilayer stack of Sc 0.3 Al 0.7 N films, focusing on the film microstructures and piezoelectric properties across various piezoelectric film layer thicknesses. Mo thickness of 2 kÅ was used as the bottom, middle and top electrode layers. Various film stacks with Sc 0.3 Al 0.7 N layer thickness of 1 kÅ, 3 kÅ, 5 kÅ, 7.5 kÅ and 10 kÅ were deposited and characterized. With Sc 0.3 Al 0.7 N thickness varying from 1 kÅ to 10 kÅ, the film texture, (measured from XRD rocking curve FWHM), improved from 2° to 1.3°, the effective piezoelectric coefficients, d 33,f increased from 9.5 pm/V to 11.3 pm/V, e 31,f changed from -1.76 C/m 2 to -2.09 C/m 2 . Comparable or even better ScAlN (0002) orientation can be achieved for the bilayer film stacks. The effective piezoelectric coefficient difference between the first and second Sc 0.3 Al 0.7 N layers is less than 3%.