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

Abstract

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/Sc0.2Al0.8N composite working at 2.33 GHz is fabricated. The effective electromechanical coupling coefficient Keff2 is calculated to be 6.19%, which has the potential to design high-frequency broadband filters.

Emerging ferroelectric materials ScAlN: applications and prospects in memristors

“…These processes can prepare high-quality ScAlN films with their own characteristics and advantages. [82][83][84][85] For example, PLD and EBPVD techniques can prepare large-area, high-quality ScAlN films, while MOCVD and ALD techniques can achieve better doping and thickness control.…”

Micromachined piezoelectric Lamb wave resonators: a review

“…The circle-shaped apodization, whose signal electrodes approaching the edges were shortened, weakened the electrical excitations at the edges and effectively suppressed the spurious mode. In another work, Nian et al [112] reported an S0 mode Lamb wave resonator utilizing an AlN/Al 0.8 Sc 0.2 N composite thin film, which achieved a k eff 2 of 6.19% at 2.33 GHz (figure 8(a)). They prepared and characterized five types of AlN and Al x Sc 1−x N films as well as AlN/Al x Sc 1−x N composite films.…”

Development of Temperature Sensor Based on AlN/ScAlN SAW Resonators

“…In our previous work, we showed using the same thickness of AlN and ScAlN can improve crystallinity and crystal orientation of ScAlN films, and compared to pure ScAlN, it has lower dielectric loss [20]. A study of AlN/ScAlN composite thin film showed it exhibited higher quality, few defects, low loss, and was a potential application for acoustic devices [21,22]. AlN/ScAlN-based devices have a higher Q-factor, which is a benefit for designing environmental sensors with high sensitivity.…”