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We report on the properties of Aluminum Scandium Nitride (AlScN) thin films deposited by pulsed-DC co-sputtering. We present the impact of the nitrogen-to-argon gas ratio on the crystal growth orientation, film stress, surface roughness, scandium concentration, and deposition rate of 760-860 nm thick AlScN thin films on Ti/Pt (111). We utilize the optimized process conditions from this study to deposit thin layers of AlScN and to explore the nucleation and orientation of thin AlScN layers on Ti/Pt (111). We report on the ferroelectric properties of 100 nm thick AlScN materials.

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 0.5–1 at.% 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 = −2.77 C/m2, which is a factor 2.6 higher than in pure AlN thin films.

The discovery of enhanced piezoelectricity in solid solutions of AlN and ScN is certainly one of the most important events in piezoelectric MEMS. As compared to pure AlN, it brought a crucial factor 2 to 3 improvement in a number of figures of merit governing the performance of MEMS devices. The aim of this contribution is to give a short overview on actual topics in processing, properties, and applications in RF filters and sensors.

Scandium doped aluminium nitride (ScAlN) gained much attention during last years, since its piezoelectric response is much enlarged as compared to pure AlN films. Above 30% Sc the films are of high interest for piezoMEMS sensing and actuation, ultrasound generation, as well as energy harvesting applications. In this work, piezo-performance uniformity maps are presented for 20% and 33% Sc containing films, sputter deposited on 200-mm wafers. Furthermore, we employ a new method to determine the electro-mechanical coupling k(t)(2). Coupling results for various Sc/(Sc+Al) concentration (0, 6, 20, 26, 33%) are shown. In addition, the dielectric constant epsilon(r) and dielectric loss tan delta, and the transversal and the longitudinal piezoelectric coefficients, e(31,f) and d(33,f,) were measured. The wafers show a high with-in-wafer uniformity (1 sigma uniformity < 2% for Sc20Al80N and < 1% for Sc33Al67N). The highest coupling k(t)(2) = 21.2% was achieved for a 33% Sc film. The presented Al-Sc property-uniformity maps provide a good foundation for ScAlN based MEMS device design and manufacturing.

Aim To assess patient-reported outcome measures (PROMs), aesthetics and stability of root coverage procedures from a previous 6-month RCT after 1 year. Material & Methods 45 patients (90 recessions) had received a coronally advanced flap (CAF = control) only or a xenogeneic collagen matrix in addition (CAF + CMX = test). Visual analogue scales (VAS) and questionnaires were used for PROMs and the root coverage aesthetic score (RES) for professional aesthetic evaluations. Results VAS scores (patient satisfaction) amounted to 8.58 ± 1.86 (test) versus 8.38 ± 2.46 (control). 6 patients preferred CAF+CMX concerning surgical procedure and aesthetics, 6 preferred CAF and 29 were equally satisfied. RES was 7.85 ± 2.42 for the test group versus 7.34 ± 2.90 for the controls. Root coverage (RC) was 76.28% for test and 75.05% for control defects. The mean increase in keratinized tissue width was higher in test (from 1.97 to 3.02 mm) than in controls (2.00 to 2.64 mm) (p = 0.0413). Likewise, test sites showed more gain in gingival thickness (0.52 mm) than control sites (0.27 mm) (p = 0.0023). Compared to 6 months, clinical outcomes were stable Conclusions Results for PROMs, RES and RC did not significantly differ between treatment groups. Thickness and width of keratinized tissue were enhanced following CAF + CMX compared to CAF alone. This article is protected by copyright. All rights reserved.

The enhancement of the electromechanical coupling coefficient caused by Sc substitution in AlN-based piezoelectric MEMS devices can be exploited successfully only if the dielectric losses remain confined to low values. While the magnitude of the piezoelectric activity in Al 1-x Sc x N thin films has been described widely in the literature, the impact of the Sc content on the loss tangent has not been studied extensively. In this work we discuss the dissipation factor obtained for x=0.095 and x=0.3 on Mo and Pt bottom electrodes, for full capacitor stacks deposited with an EVATEC Clusterline®200–II PVD tool equipped with single alloy targets 304mm in diameter.

Scandium doped aluminium nitride (ScAlN) exhibits an overall greater piezoelectric response as compared to pure aluminium nitride (AlN). Films with a Sc/(Sc+Al)content above 30% or more are of high interest for MEMS sensing and actuation, ultrasound generation, and energy harvesting applications. In this work we present the uniformity of the material properties of (002)-axis oriented $\text{Sc}_{33}\text{A}1_{67}\text{N}$ films deposited on 200-mm wafers. For this purpose, the dielectric constant $\varepsilon_{\text{r}}$ and dielectric loss tanδ, as well as the transversal and the longitudinal piezoelectric coefficients, $e_{31,\text{f}}$ and $d_{33,\text{f}}$ , were measured. Wafers exhibiting a great in-wafer uniformity of the piezoelectric coefficients up to $d_{33,\text{f}}=11.8\text{pm}/\text{V}$ and $e_{31,\text{f}}=-2.3 \text{C}/\text{m}^{2}$ were obtained ( $1\sigma$ uniformity $\approx$ 1-2%). The results are very promising for the fabrication and designing of devices, as well as for volume manufacturing.

Aluminium scandium nitride (ASN) exhibits a largely enhanced piezoelectric response as compared to aluminium nitride (AlN), which makes it an upcoming piezoelectric material for use in next generation RF filters, sensors, actuators and energy harvesting devices. In this work, process-microstructure-property relationships of such sputtered ASN films containing up to 42 at% Sc were investigated. Hereby, the influence of the process parameters on the film structure, the intrinsic stress and the piezoelectric response were carefully investigated. A high piezoelectric response (e(31),(f) = -2.67 C/m(2) and d(33,f) = 10.3 pm/V) was measured for films with 42 at% and 34 at% Sc, respectively. The results are very promising towards industrial applications.

Recent literature has focused on improving piezoelectric coupling coefficients by alloying aluminum nitride (AlN) with scandium (Sc). Akiyama et al. showed the highest d_33 piezoelectric coefficient increase of >4x at a 41% Sc substitution for Al. Thus far, studies mainly focus on material measurements such as x-ray diffraction or piezoelectric constants to assess the material quality. Although these measurements are useful to assess the improvement in the piezoelectric performance of the material, they do not address improvements in the figure-of-merit (FOM) of resonators (i.e., coupling coefficient times quality factor). Resonator structures are needed to directly extract these key performance parameters for film assessment. Fabrication integration, however, must be minimized to avoid obscuring film performance by extrinsic device effects.

Recent literature has focused on improving piezoelectric coupling coefficients by alloying aluminum nitride (AlN) with scandium (Sc). Akiyama et al. showed the highest piezoelectric coefficient increase of nearly four times for a 41% Sc substitution for Al. Thus far, studies mainly focus on material measurements such as x-ray diffraction or piezoelectric constants to assess the material quality. Although these measurements are useful to assess the improvement in the piezoelectric performance of the material, they do not address changes in the coupling coefficient and quality factor. Resonator structures are needed to directly extract these key performance parameters for film assessment. Fabrication integration, however, must be minimized to avoid obscuring film performance by extrinsic device effects. In this work, we assess a film evaluation tool using contour mode resonators (CMRs) to directly extract resonator performance for film comparison. Resonators formed from AlN, Sc 0.06 Al 0.94 N, and Sc 0.125 Al 0.875 N films are compared to demonstrate the method.

Aluminium scandium nitride (Al 1−x Sc x N) with its strongly enhanced piezoelectric response is the upcoming piezoelectric material of choice in next generation RF filters, sensors, actuators and energy harvesting devices. This paper will concentrate on the deposition technology for Al 1−x Sc x N films with high Sc content. Films with Sc concentrations close to 43 at% have been grown on 200-mm substrates using a cluster type sputter deposition tool. The piezoelectric response will be discussed and correlated with the deposition parameters and film structural properties. The steps required to deliver a high-volume production solution for high Sc concentration will be described.

Organic passivated silicon wafers, composite substrates such as silicon on glass or Fan-out Wafer-Level Package (FOWLP) technology all pose new challenges for UBM and RDL processes [1]-[5]. Materials used in these substrates must be adequately degassed for subsequent plasma processing under vacuum but their heat-sensitive nature necessitates careful thermal management. Selecting the proper technology for each individual step enables the definition of a high yield process, minimizing contamination from the organic materials. This paper discusses the preferred degas principles for different substrates and applications. Temperature simulation data and experimental results are presented for various heating methods including single wafer and batch processes. It illustrates the effectiveness of an atmospheric batch degasser for removal of volatile water and organic compounds (VC) at moderate temperatures below 150°C. The results will be compared with standard vacuum degas technologies and the resulting contact resistance (Rc) values after subsequent low temperature ICP etch will be reported. The paper also addresses the etch process requirements to ensure efficient pumping of remaining volatile contaminants, the required temperature management of the substrates and the particle containment and cleanliness of the process environment.