The impact of argon admixture on the c-axis oriented growth of direct current magnetron sputtered ScxAl1−xN thin films

Abstract

The piezoelectric properties of wurtzite aluminium nitride (w-AlN) are enhanced by alloying with scandium (Sc), thus offering superior properties for applications in micro electro-mechanical systems devices. ScxAl1−xN thin films have been prepared by DC reactive magnetron sputtering on Si (100) substrates from a single target. When targeting a concentration range from x = 0 up to x = 0.15, the preparation conditions have been optimized by varying the Ar/N2 ratio in the sputtering gas. To incorporate an increasing Sc concentration, a higher Ar/N2 ratio has to be applied during the deposition process. Hence, the argon concentration in the sputtering gas becomes a crucial parameter for microstructure-related parameters. To determine phase purity, degree of c-axis orientation, lattice parameter, and grain size, the ScxAl1−xN thin films were investigated by techniques, such as scanning electron microscopy, transmission electron microscopy, and X-ray diffraction.

Stress controlled pulsed direct current co-sputtered Al1−xScxN as piezoelectric phase for micromechanical sensor applications

“…Their combination then allows to tune the built-in stress of Al 1−x Sc x N over a wide range from strongly tensile to strongly compressive by varying the Ar partial pressure. While increasing the ion bombardment energy during AlN growth was found to increase the piezoelectric response through improving crystallite alignment 24 and the Ar partial pressure was found to determine the degree of c-axis orientation 25 in Al 1−x Sc x N, no such effects were observed here. Instead, the reduction in deposition pressure was accompanied by a decline of e 31,f by up to 20%, despite the c-axis orientation of Al 1−x Sc x N being little affected by the changes in deposition conditions, as expressed by the (0002) rocking curve FWHM of the respective samples [ Fig.…”

Large piezoelectric response of quarternary wurtzite nitride alloys and its physical origin from first principles

“…However, it is well established that physical vapor deposition synthesis, that operates at relatively low temperatures where bulk diffusion is highly limited, strongly promotes formation of disordered solid solutions. For example, several groups reported growth of wurtzite Sc x Al 1−x N alloys [5,28,29] even up to x = 0.5 [7] even though H mix of wurtzite Sc 0.5 Al 0.5 N is 0.35 eV/f.u. Because several of the here considered alloys have lower mixing enthalpies and driving force for phase separation than Sc x Al 1−x N, we envisage the possibility for their synthesis as metastable thin films.…”

Harsh Environmental Surface Acoustic Wave Temperature Sensor Based on Pure and Scandium doped Aluminum Nitride on Sapphire

“…The distance between target and substrate is fixed at 65 mm. The parameters were chosen based on pre-investigations for good caxis orientation [7,11]. The total film thickness h is 2 µm.…”