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Piezoelectric and structural properties of c-axis textured aluminium scandium nitride thin films up to high scandium content
Partial substitution of aluminium by scandium in the wurtzite structure of aluminium nitride (AlN) leads to a large increase of the piezoelectric response by more than a factor of 2. Therefore, aluminium scandium nitride (ASN) thin films attracted much attention to improve piezoelectric MEMS devices...
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Published in: | Surface & coatings technology 2018-06, Vol.343, p.2-6 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Partial substitution of aluminium by scandium in the wurtzite structure of aluminium nitride (AlN) leads to a large increase of the piezoelectric response by more than a factor of 2. Therefore, aluminium scandium nitride (ASN) thin films attracted much attention to improve piezoelectric MEMS devices such as RF filters, sensors, micro actuators and energy harvesting devices. In this work, process-microstructure-property relationships of ASN thin films containing up to 42% Sc were investigated. Like AlN thin films, ASN films are sputter deposited at 300–350°C with pulsed DC powered magnetrons. The influence of the process parameters on the film structure, the intrinsic stress and the piezoelectric response was investigated in order to achieve optimal piezoelectric coefficients up to high Sc concentrations. X-Ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyse the quality of c-axis texture. The films showed exclusively (002) texture with rocking-curve widths in the range of 1.3–2° (FHWM). The films were further analysed by scanning electron microscopy (SEM). The Sc content was determined by energy-dispersive X-ray spectroscopy (EDX). A good compositional homogeneity in the range of 0.5–1at.% was achieved between border and centre of 200-mm wafers. So far, we obtained ASN films with transversal piezoelectric coefficients of up to e31,f=−2.77C/m2, which is a factor 2.6 higher than in pure AlN thin films.
•Aluminium scandium nitride thin films with 2.6 as large transversal piezoelectric coefficient e31,f than AlN•Largest achieved e31,f=−2.77C/m2 for 42% Sc films•Semiconductor compatible sputtering process for aluminium scandium nitride with high Sc content on industrial cluster tool•C-axis textured films confirmed by XRD and TEM for up to 42% Sc |
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ISSN: | 0257-8972 1879-3347 |
DOI: | 10.1016/j.surfcoat.2018.01.046 |