Effect of Sc concentration on shear wave velocities in ScAlN films measured by micro-Brillouin scattering technique

Ichihashi, Hayato; Yanagitani, Takahiko; Suzuki, Masashi; Takayanagi, Shinji; Matsukawa, Mami

doi:10.1109/ultsym.2014.0629

Cited by 12 publications

(5 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 1 shows the comparisons of calculated BAW velocities in the Sc x Al 1−x N film with published data from [26][27][28]. The calcul ation fits quite well with the experiments for the range from x = 0 to x ~ 0.3, where x stands for the Sc content in the film.…”

Section: Influence Of Sc Content On Acoustic Wave Characteristicssupporting

confidence: 64%

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics

Tang

Han

Zhang

et al. 2016

J. Micromech. Microeng.

View full text Add to dashboard Cite

This paper is aimed at examining the validity of material constants reported for use in surface acoustic wave (SAW) device simulations. First, based on the full set of material constants calculated by first principle, bulk acoustic wave velocities are calculated for ScxAl1−xN and compared with published experimental results. Then, the effects of the ScxAl1−xN material constants with different Sc content on acoustic characteristics are calculated and the influence of shear vibrations on SAW characteristics are recognized. Then, a series of SAW devices are fabricated on ScxAl1−xN film/Si substrate structure with various Cu and ScAlN thicknesses hCu and hScAlN, respectively, and measured variations of phase velocity V and effective electromechanical coupling factor with these parameters are compared with the calculation. The fairly well-agreed results indicate a reliable set of ScxAl1−xN material constants for SAW device simulations.

show abstract

Section: Influence Of Sc Content On Acoustic Wave Characteristicssupporting

confidence: 64%

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics

Tang

Han

Zhang

et al. 2016

J. Micromech. Microeng.

View full text Add to dashboard Cite

show abstract

“…The impedance value | Z | is plotted as a function of frequency in Figure for two devices on the same wafer. The results look at first sight as expected: The longitudinal mode shows up at about twice the frequency of the shear mode resonance, and is much stronger than the latter, because the z ‐axis tilting is expected to be small. Indeed, the experimental coupling for the shear mode was derived as

K_{eff‐S}^{2}

= 0.36% and 0.41% for sample 1 and 2, respectively, and corresponds well to tilting angles in the range from 3.5° to 5° .…”

Section: Device Fabrication and Characterizationsupporting

confidence: 72%

Material Parameter Extraction for Complex AlScN Thin Film Using Dual Mode Resonators in Combination with Advanced Microstructural Analysis and Finite Element Modeling

Parsapour

Pashchenko

Kurz

et al. 2019

Adv Elect Materials

View full text Add to dashboard Cite

rocksalt ScN, exhibits extraordinarily high piezoelectric coefficients for a nitride material. [1,2] Since its discovery by Akiyama and co-workers, many researchers confirmed the increase of piezoelectricity in AlScN with increasing Sc content, [3][4][5][6][7][8][9][10][11] reaching a maximum at the limit of the wurtzite stability somewhere between 40% and 50% of Sc on the cation site. [2,12] The piezoelectric coefficients increase by about a factor of 4 for the case of charge per stress coefficients (d-tensor), and about a factor 2.5 for the case of charge per strain coefficients (e-tensor). Computational modeling in the frame of density functional theory (DFT) confirmed well the increase of the piezoelectric coefficients, accompanied by a decrease of the stiffness with increasing Sc content. [13,14] Even though the obtained piezoelectric coefficients are small as compared to the ones of ferroelectric thin films, AlScN may reach superior performance wherever the dielectric constant (ε) is relevant as well. This is the case for sensors, [15,16] in energy harvesting, [4,17] and in some of the applications governed by a piezoelectric coupling coefficient. [3,5] This is the case in radio frequency (RF) filters for mobile phone communication operating in the lower GHz frequency range. On the market since Accurate property determination of the piezoelectric thin film material Al(1−x)Sc(x)N is necessary for designing the next generation of radio frequency resonators in mobile communication, and for testing results of ab initio calculations. Sound velocity and piezoelectric coupling of both longitudinal and shear mode are evaluated from a single dual mode resonator. This assures a compatible set of coefficients. It is observed that AlScN thin films grew differently on small, isolated bottom electrodes.The investigated film starts growing with a slightly tilted, c-textured microstructure, and switches after 200 nm to a polycrystalline film with irregularly oriented grains having c-axis tilt angles in the range of 35°-70°, as revealed by transmission electron microscope nanodiffraction mapping. Based on this information, a finite element model (FEM) is constructed that properly reproduces the resonance behavior of the resonator. The relevant elastic and piezoelectric constants are derived by curve fitting and yield somewhat lower stiffness and higher piezoelectric coefficients than ab initio calculations published in the literature. The FEM modeling results show that the upper film part with the abnormally oriented grains is overall piezoelectric, i.e., the misoriented grains maintain the polarity projected onto the growth direction from the starting layer. Thin FilmsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

show abstract

“…In the past, elastic constants of AlScN films have been determined with Brillouin scattering [ 7 , 8 , 9 ] and via electrical excitation of acoustic vibrations, especially with the help of SAW resonators (called resonator method in the following) [ 10 , 11 ] or delay lines [ 12 ] (for a review see for example [ 10 ]). However, preparing SAW or other types of resonators requires advanced fabrication capabilities to obtain the full dispersion curves from multiple test structures (phase velocity as a function of frequency).…”

Section: Introductionmentioning

confidence: 99%

Laser Ultrasound Investigations of AlScN(0001) and AlScN(11-20) Thin Films Prepared by Magnetron Sputter Epitaxy on Sapphire Substrates

et al. 2022

View full text Add to dashboard Cite

The laser ultrasound (LU) technique has been used to determine dispersion curves for surface acoustic waves (SAW) propagating in AlScN/Al2O3 systems. Polar and non-polar Al0.77Sc0.23N thin films were prepared by magnetron sputter epitaxy on Al2O3 substrates and coated with a metal layer. SAW dispersion curves have been measured for various propagation directions on the surface. This is easily achieved in LU measurements since no additional surface structures need to be fabricated, which would be required if elastic properties are determined with the help of SAW resonators. Variation of the propagation direction allows for efficient use of the system’s anisotropy when extracting information on elastic properties. This helps to overcome the complexity caused by a large number of elastic constants in the film material. An analysis of the sensitivity of the SAW phase velocities (with respect to the elastic moduli and their dependence on SAW propagation direction) reveals that the non-polar AlScN films are particularly well suited for the extraction of elastic film properties. Good agreement is found between experiment and theoretical predictions, validating LU as a non-destructive and fast technique for the determination of elastic constants of piezoelectric thin films.

show abstract

Effect of Sc concentration on shear wave velocities in ScAlN films measured by micro-Brillouin scattering technique

Cited by 12 publications

References 14 publications

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics

Material Parameter Extraction for Complex AlScN Thin Film Using Dual Mode Resonators in Combination with Advanced Microstructural Analysis and Finite Element Modeling

Laser Ultrasound Investigations of AlScN(0001) and AlScN(11-20) Thin Films Prepared by Magnetron Sputter Epitaxy on Sapphire Substrates

Contact Info

Product

Resources

About

Effect of Sc concentration on shear wave velocities in ScAlN films measured by micro-Brillouin scattering technique

Cited by 12 publications

References 14 publications

Validity evaluation of ScxAl1−xN material constants based on SAW characteristics

Validity evaluation of ScxAl1−xN material constants based on SAW characteristics

Material Parameter Extraction for Complex AlScN Thin Film Using Dual Mode Resonators in Combination with Advanced Microstructural Analysis and Finite Element Modeling

Laser Ultrasound Investigations of AlScN(0001) and AlScN(11-20) Thin Films Prepared by Magnetron Sputter Epitaxy on Sapphire Substrates

Contact Info

Product

Resources

About

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics

Validity evaluation of Sc_xAl_1−xN material constants based on SAW characteristics