c-Axis-tilted ScAlN films grown on silicon substrates for surface acoustic wave devices

Abstract

ScAlN films are currently being investigated for their potential use in surface acoustic wave (SAW) devices for next-generation mobile networks because of their high piezoelectricity. This paper describes the numerical simulation of SAW propagation in c-axis-tilted ScAlN films on silicon substrates and a fabrication technique for preparing c-axis-tilted ScAlN films on silicon substrates. The electromechanical coupling coefficient K 2 of SAW propagating in the ScAlN film/silicon substrate increased due to the c-axis tilt angle. The maximum K 2 value is approximately 3.90%. This value is 2.6 times the maximum K 2 value of the c-axis-oriented ScAlN film/silicon substrate structure. The c-axis-tilted ScAlN films with an Sc concentration of 40% were prepared on a silicon substrate via RF magnetron sputtering based on the self-shadowing effect, and the maximum c-axis tilt angle was 57.4°. These results indicate that this device structure has potential for SAW device applications with well-established micromachining technology derived from silicon substrates.

Sputtering Process of ScxAl1−xN Thin Films for Ferroelectric Applications

“…The trends for rocking curve FWHM values for different sputtering pressures coincide with the trends for the piezoelectric constant (d 33 ) at different sputtering pressures [34]. For this reason, there is a consensus in the literature that the ideal piezoelectric response is achieved when the greatest degree of c-axis texturing occurs [6,28,34,36,39]. Furthermore, by optimizing the sputtering pressure to reach the maximum c-axis orientation, the greatest piezoelectric response can be achieved, paving the way for the creation of piezoelectric sensors and SAW devices [39].…”

“…Sputtering atmosphere consists of both the chamber pressure and the proportion of argon to nitrogen gas [6]. There have been several studies conducted that examine how the variation in sputtering atmosphere affects parameters such as crystal quality, sputtering rate, residual stress, and the electric properties of the film [6,28,34,36,39]. Because sputtering atmosphere is one of the parameters that directly impacts the energy for adatoms to bombard the surface of the substrate, it is especially pertinent to optimize the sputtering atmosphere to achieve desired film quality and the subsequent electric properties [47].…”

Analysis of longitudinal leaky surface acoustic waves on piezoelectric thin plates bonded to diamond substrate

“…The research and development of SAW propagation modes and piezoelectric materials for high-performance SAW devices have been actively conducted in Japan and overseas. [1][2][3][4][5][6][7][8][9][10][11][12][13] In particular, 5 GHz bands, called the Sub-6 band in 5G communication systems, are approximately 1.5-2 times higher than those of 4G communication systems. Hence, there is a significant demand for higher frequencies in SAW filters.…”

Contribution of Ribbon-Structured SiO2 Films to AlN-Based and AlN/Diamond-Based Lamb Wave Resonators

“…In recent years, surface acoustic wave (SAW) devices have been extensively used for very numerous applications such as mobile and wireless communications [ 1 , 2 , 3 ]. These devices are most often based on piezoelectric substrates whose phase velocity is usually low, like lithium niobate and quartz.…”