Characterization of Dielectric and Piezoelectric Properties of Ferroelectric AlScN Thin Films

Pirro, Michele; Herrera, Bernard; Assylbekova, Meruyert; Giribaldi, Gabriel; Colombo, Luca; Rinaldi, Matteo

doi:10.1109/mems51782.2021.9375427

Cited by 24 publications

(15 citation statements)

References 15 publications

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“…This thickness came from a perspective of ease of fabrication of a high quality film. Particularly for AlScN, a good film quality is more easily obtained after a certain thickness of the film [16], providing ample time for seeding of the crystal columns and proper alignment to take place during deposition. Thicker films usually improve the crystal quality but require longer deposition times, increasing the cost.…”

Section: Methodology a Pmut Array Designmentioning

confidence: 99%

Scandium-Doped Aluminum Nitride PMUT Arrays for Wireless Ultrasonic Powering of Implantables

Herrera

Simeoni

Giribaldi

et al. 2022

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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The present work reports on the novel usage of Scandium-doped Aluminum Nitride (AlScN) PMUT arrays for enhanced power transfer in implantable applications. Optimization considerations were explored for the PMUT array towards high performance. The transmission metric, compared to identical arrays based on Aluminum Nitride (AlN), showed a 25dB increase. Power transfer measurements also confirmed a considerable increase as compared to previous work based on AlN. Different matching strategies were explored to maximize the output power including inductor conjugate matching and matching utilizing resonators in series and parallel topologies. A full characterization of the transferred power versus incident acoustic intensity on the array revealed transmission of power levels of several milliwatts for intensities below the Food and Drug Administration's (FDA) limit. The performance of the array, as compared with other implementations with a range of frequencies, dimensions and input acoustic intensities was bench-marked through the use of the conversion efficiency as the figure-of-merit. The practical applicability of the system, utilizing a realistic tissue phantom as the medium, was proven by interfacing with a commercially available boost converter to obtain a rectified voltage and power levels sufficient for powering and charging intra-body electronics.

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Section: Methodology a Pmut Array Designmentioning

confidence: 99%

Scandium-Doped Aluminum Nitride PMUT Arrays for Wireless Ultrasonic Powering of Implantables

Herrera

Simeoni

Giribaldi

et al. 2022

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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“…According to previous studies, the AlScN films with Sc contents below 27% are prone to break down near the coercive field, and a distinct ferroelectric polarization occurs with a Sc content of more than 27%. As the Sc contents increase, the coercivity, saturation polarization and remanent polarization all decrease [ 8 , 11 , 14 ]. Therefore, we prepared AlScN thin films at a specific Sc content of 30% in this study.…”

Section: Fabrication and Experiments Setupmentioning

confidence: 99%

“…The significantly higher piezoelectric coefficient of AlScN compared to AlN has led to piezoelectric devices based on AlScN with high electromechanical coupling coefficients [ 13 ]. More interestingly, AlScN has been approved to be ferroelectric with a high Sc ratio, and its ferroelectric switching voltage can be flexibly adjusted depending on the Remanent stress and Sc content to meet the needs of ferroelectric thin films in a wide range of application scenarios [ 14 , 15 ]. The two polarization states of AlScN are shown in Figure 1 .…”

Section: Introductionmentioning

confidence: 99%

Characterization of Ferroelectric Al0.7Sc0.3N Thin Film on Pt and Mo Electrodes

et al. 2022

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In the past decade, aluminum scandium nitride (AlScN) with a high Sc content has shown ferroelectric properties, which provides a new option for CMOS-process-compatible ferroelectric memory, sensors and actuators, as well as tunable devices. In this paper, the ferroelectric properties of Al0.7Sc0.3N grown on different metals were studied. The effect of metal and abnormal orientation grains (AOGs) on ferroelectric properties was observed. A coercive field of approximately 3 MV/cm and a large remanent polarization of more than 100 μC/cm2 were exhibited on the Pt surface. The Al0.7Sc0.3N thin film grown on the Mo metal surface exhibited a large leakage current. We analyzed the leakage current of Al0.7Sc0.3N during polarization with the polarization frequency, and found that the Al0.7Sc0.3N films grown on either Pt or Mo surfaces have large leakage currents at frequencies below 5 kHz. The leakage current decreases significantly as the frequency approaches 10 kHz. The positive up negative down (PUND) measurement was used to obtain the remanent polarization of the films, and it was found that the remanent polarization values were not the same in the positive and negative directions, indicating that the electrode material has an effect on the ferroelectric properties.

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“…The ferroelectric switching occurs at coercive fields of 2–5 MV/cm, with higher Sc concentrations showing reduced necessary fields for switching but in turn also lower polarization values from above 100 µC/cm² to around 80 µC/cm². Further research by different groups worldwide is ongoing [ 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

High Rate Deposition of Piezoelectric AlScN Films by Reactive Magnetron Sputtering from AlSc Alloy Targets on Large Area

et al. 2022

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This paper reports on the deposition and characterization of piezoelectric AlXSc1-XN (further: AlScN) films on Si substrates using AlSc alloy targets with 30 at.% Sc. Films were deposited on a Ø200 mm area with deposition rates of 200 nm/min using a reactive magnetron sputtering process with a unipolar–bipolar hybrid pulse mode of FEP. The homogeneity of film composition, structural properties and piezoelectric properties were investigated depending on process parameters, especially the pulse mode of powering in unipolar–bipolar hybrid pulse mode operation. Characterization methods include energy-dispersive spectrometry of X-ray (EDS), X-ray diffraction (XRD), piezoresponse force microscopy (PFM) and double-beam laser interferometry (DBLI). The film composition was Al0.695Sc0.295N. The films showed good homogeneity of film structure with full width at half maximum (FWHM) of AlScN(002) rocking curves at 2.2 ± 0.1° over the whole coating area when deposited with higher share of unipolar pulse mode during film growth. For a higher share of bipolar pulse mode, the films showed a much larger c-lattice parameter in the center of the coating area, indicating high in-plane compressive stress in the films. Rocking curve FWHM also showed similar values of 1.5° at the center to 3° at outer edge. The piezoelectric characterization method revealed homogenous d33,f of 11–12 pm/V for films deposited at a high share of unipolar pulse mode and distribution of 7–10 pm/V for a lower share of unipolar pulse mode. The films exhibited ferroelectric switching behavior with coercive fields of around 3–3.5 MV/cm and polarization of 80–120 µC/cm².

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Characterization of Dielectric and Piezoelectric Properties of Ferroelectric AlScN Thin Films

Cited by 24 publications

References 15 publications

Scandium-Doped Aluminum Nitride PMUT Arrays for Wireless Ultrasonic Powering of Implantables

Scandium-Doped Aluminum Nitride PMUT Arrays for Wireless Ultrasonic Powering of Implantables

Characterization of Ferroelectric Al0.7Sc0.3N Thin Film on Pt and Mo Electrodes

High Rate Deposition of Piezoelectric AlScN Films by Reactive Magnetron Sputtering from AlSc Alloy Targets on Large Area

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