Preparation, Characterization, and Application of AlN/ScAlN Composite Thin Films

• Published in: Micromachines (Basel) Vol. 14; no. 3; p. 557
• Main Authors: Nian, Laixia, Qu, Yuanhang, Gu, Xiyu, Luo, Tiancheng, Xie, Ying, Wei, Min, Cai, Yao, Liu, Yan, Sun, Chengliang
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27-02-2023; MDPI
• Subjects: Acoustics; AlN/ScAlN; Aluminum nitride; Approximation; Broadband; Communication; composite film; Coupling coefficients; Dielectric films; first principal calculation; lamb wave resonator; Lamb waves; Piezoelectricity; Resonators; Roughness; Silicon substrates; Stress distribution; Swimming pools; Thin films; first principal calculation; composite film; AlN/ScAlN; lamb wave resonator
• ISSN: 2072-666X; 2072-666X
• DOI: 10.3390/mi14030557

Piezoelectric aluminum nitride (AlN) thin film, as a commonly used material for high-frequency acoustic resonators, has been a research hotspot in the RF field. Doping Sc elements in AlN is one of most effective methods to improve the piezoelectricity of the material. In this work, the first principal calculation and Mori-Tanaka model are used to obtain the piezoelectric constants of AlN, ScAlN, and AlN/ScAlN composites. Then, five types of AlN/ScAlN thin films are prepared on 8 inch silicon substrates. The crystal quality, roughness, and stress distribution are measured to characterize the film quality. The results show that composite film can effectively solve the problem of abnormal grains and reduce the roughness. Finally, a lamb wave resonator with an AlN/Sc
Al
N composite working at 2.33 GHz is fabricated. The effective electromechanical coupling coefficient
is calculated to be 6.19%, which has the potential to design high-frequency broadband filters.