Piezoelectric performance improvement of ScAlN film and two‐port SAW resonator application

Abstract

Highly c-axis-oriented scandium-doped aluminium nitride films (ScAlN) were prepared on platinum substrates by DC magnetron sputtering. The effect of sputtering power on the crystal quality and piezoelectric properties of ScAlN thin film was investigated. The test results show that the piezoelectric properties of the ScAlN film first strengthen and then weaken with the increase of sputtering power, and the optimal piezoelectric properties are obtained under the condition of 180 W. Furthermore, a surface acoustic wave (SAW) resonator with an interdigital transducer width of 500 nm was fabricated by electron beam lithography. The SAW device exhibits a resonant frequency of 1.887 GHz and a quality factor (Q) of 170.8.

Sputtering Process of ScxAl1−xN Thin Films for Ferroelectric Applications

“…Correspondingly, it has been stated that at higher discharge powers the increase of adatom mobility not only improves the crystal quality, but it is also beneficial in preventing the incorporation of impurities from the background gas [34]. Indeed, these phenomena are widely observable in the data available in the literature where the XRD patterns of Sc x Al 1−x N and plots of the rocking curve FWHM are shown to improve initially with increasing power density, and then degrade at higher power densities [10,26,31]. An example of this is shown in Figure 5a,b.…”

“…However, at exceedingly high discharge powers/power densities, the adatoms can harbor (a) Effect on Sputtering Rate and Thickness: Sputtering power density becomes especially important during the process of reactive dual co-sputtering of Sc x Al 1−x N because the variation in power density between the Sc and Al targets allows for the precise control over the concentration of Sc in the alloy [42]. By maintaining a constant power density on the Al target, the Sc concentration can be increased linearly by gradually increasing power density applied to the Sc target [31]. On account of this, most papers employing a dual co-sputtering setup for Sc x Al 1−x N tend to modulate the power density only as a means to dictate the final stoichiometry of the film.…”

“…This helps to promote the rearrangement of atoms to align according to (0002) crystal orienta-tion on the substrate surface, which will contribute to a reduction in surface energy [26]. However, at exceedingly high discharge powers/power densities, the adatoms can harbor an overabundance of kinetic energy that forces the B 2 bonds in wurtzite to disassociate, causing crystal quality deterioration [31]. Correspondingly, it has been stated that at higher discharge powers the increase of adatom mobility not only improves the crystal quality, but it is also beneficial in preventing the incorporation of impurities from the background gas [34].…”

“…Moreover, when the optimum power condition is chosen such that there is a coincidence between the best crystal quality and surface morphology, the maximum piezoelectric response is achieved [26]. When this occurs, the literature has shown that Sc x Al 1−x N thin-films are capable of achieving a piezoelectric response at least 250% greater than that of AlN [31].…”

A brief investigation of one-port SAW resonator for the application in communication systems

“…To enhance the characteristics of the sensor, several overlays, and piezoelectric substrates. In a few cases, these sensors revealed the application of wireless operation, and few cases, the research concentrated on simultaneous identification using sensor arrays [73]. The status of the products currently available for commercial use in different industries is shown in the following table 3.…”