Scandium Aluminium Nitride-Based Film Bulk Acoustic Resonators

Schneider, Michael; DeMiguel-Ramos, M.; Flewitt, Andrew J.; Iborra, E.; Schmid, U.

doi:10.3390/proceedings1040305

Cited by 35 publications

(24 citation statements)

References 15 publications

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“…Motivated by industrial interest in the improved performance in AlN-based piezoelectric microelectromechanical systems (piezoMEMS) devices, the breadth of this work was focused on compositions with 0 < x < 0.4, where single-phase textured wurtzite materials could be synthesized. Recent work has focused on incorporation of these alloys into devices such as energy harvesters [16], ultrasonic transducers [17], and primarily in acoustic resonators [18][19][20][21][22][23][24][25], enabling alternative operation modes [26][27][28]. From a deployment perspective, the continued work on processing conditions highlights the difficulty of achieving high-quality materials with x > 0.2, where misoriented grains degrade the macroscopic piezoelectric response [29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Talley

Millican

Mangum

et al. 2018

Phys. Rev. Materials

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An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (Al 1−x Sc x N) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, and therefore composition-and structuredependent mechanisms, underlying property evolution in this system have not been fully described, despite significant recent efforts driven by interest in enhanced piezoelectric performance. Practical realization of these enhanced properties, however, is hindered by the strong driving thermodynamic driving force for phase separation in the system, highlighting the need for increased study into the role of heterostructural alloying on the thermodynamics and composition-structure-property relationships in this system. With this need in mind, ab initio computed alloy thermodynamics and properties are compared to combinatorial thin-film synthesis and characterization to develop a more complete picture of the structure and property evolution across the Al 1−x Sc x N composition space. The combination of structural frustration and a flattened free-energy landscape lead to substantial increases in electromechanical response. The energy scale of alloy metastability is found to be much larger than previously reported, helping to explain difficulties in achieving homogeneous materials with high scandium concentration. Scandium substitution for aluminum softens the wurtzite crystal lattice, and energetic proximity to the competing hexagonal boron-nitride structure enhances the piezoelectric stress coefficient. Overall, this work provides insight into the understanding of the structure-processing-property relationships in the Al 1−x Sc x N system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.

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Section: Introductionmentioning

confidence: 99%

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Talley

Millican

Mangum

et al. 2018

Phys. Rev. Materials

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“…Aluminum nitride (AlN), which has a wurtzite structure, exhibits piezoelectricity which enables it to be used in thin film bulk acoustic wave resonators for wireless telecommunication devices. 1−3 Improvement in the piezoelectric properties of AlN is highly desired for future evolution of communication systems. So far, the highest piezoelectric response has been reported for Sc-doped AlN solid solutions.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Study of Piezoelectric Properties and Bonding Analysis in (Mg, X, Al)N Solid Solutions (X = Nb, Ti, Zr, Hf)

et al. 2019

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The enhancement mechanism of piezoelectric properties by codoping Mg + X (X = Nb, Ti, Zr, Hf) into aluminum nitride (AlN) was investigated by first-principles calculations. Theoretically, the piezoelectric constant (d33) can be increased when the elastic constant (C33) is decreased and the piezoelectric stress constant (e33) is increased. All components of e33, which consists of the clamped e33, the Born effective charge (Z33), and the strain sensitivity (du/dε) of the internal parameter, were improved by the addition of Mg + X into AlN. The decrease in C33 and the increase in du/dε that were observed in Mg + X-codoped AlN indicate the occurrence of elastic softening which was considered to be influenced by changes in the interatomic bond in the wurtzite structure. The bonding analysis of metal–nitrogen (Me–N) pairs in the Mg + X-codoped AlN system which was carried out by crystal orbital Hamilton populations showed that the covalent bonding (Me–N) was weaker than in pure AlN. Therefore, this weaker covalent bond is considered to be one of the origins of the elastic softening. Similar phenomena were also found for Sc-doped AlN which has higher piezoelectric response than that of pure AlN.

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“…It was shown, that piezoelectric coefficient d 33,f gradually increases with increasing Sc concentration in the AlN film [4]. Subsequently, many studies have aimed to improve the piezoelectric properties [4]- [9] and optimize the material deposition process or device design [10]- [12].…”

mentioning

confidence: 99%

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

Bespalova

Österlund

Ross

et al. 2021

J. Microelectromech. Syst.

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Scandium-alloyed aluminum nitride (AlScN) is a potential material for micro-electromechanical systems because of its unique advantages, such as strong piezoelectric effect and high thermal stability. However, issues related to its stability and interaction with other materials in multilayer systems require investigation. The formation of new phases at the interface between piezomaterial and electrode material can lead to the device failure. In this study, multilayer structures Si substrate/AlN/Ti-Mo/Al 0.8 Sc 0.2 N/top electrode (TE) were studied after annealing at a wide range of temperatures and durations. Four different TE materials (i.e. Al, AlSi (1%), Mo/Al, and Mo) were examined to determine the most reliable electrode material for the structure. The phase stability, interfacial quality, and piezoelectric response of the multilayer systems after thermal annealing were investigated. The structure with Mo TE layer was stable after annealing at 800 • C for 300 h and at 1000 • C for 100 h. None of the structures formed any new phases at the interface between the electrode layer and AlScN. The transverse piezoelectric coefficient (e 31,f) was determined for Al 0.8 Sc 0.2 N before and after annealing. The absolute value of the e 31,f was −1.39 C/m 2 for as-deposited structure and −1.67 C/m 2 for the same structure annealed for 300 h at 800 • C.

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Scandium Aluminium Nitride-Based Film Bulk Acoustic Resonators

Cited by 35 publications

References 15 publications

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

First-Principles Study of Piezoelectric Properties and Bonding Analysis in (Mg, X, Al)N Solid Solutions (X = Nb, Ti, Zr, Hf)

Characterization of AlScN-Based Multilayer Systems for Piezoelectric Micromachined Ultrasound Transducer (pMUT) Fabrication

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