Ultrasonic Material Characterization System Research Articles

Acoustic properties for Ga–Sn–Zn liquid metal coupler with low melting point and high acoustic impedance

Acoustic properties of Ga–Sn–Zn (GSZ) liquid alloy coupler with high acoustic impedance were investigated to evaluate materials with high acoustic impedance. GSZ liquid alloy was prepared and its longitudinal wave velocity and attenuation coefficient were measured using the plane-wave ultrasonic material characterization system. Density of the GSZ liquid alloy was also measured by a constant volume expansion method. The acoustic impedance of the GSZ was 12 times higher than that of the water. Attenuation coefficient of GSZ is much smaller than that of water, exhibiting 7.6 dB mm−1 for water and 0.5 dB mm−1 for GSZ at 200 MHz. Considering the reflection and transmission coefficients at each medium boundary calculated from the experimentally obtained acoustic impedance, it was suggested that the amplitude of the reflected wave from the back surface of the Ir sample can be made about 30 times larger with the GSZ coupler than with the water coupler.

Optimum measurement condition for V(x) method using the line-focus-beam ultrasonic-material-characterization system

Optimum measurement condition of the V(x) method proposed as a fast scanning technique of the line-focus-beam ultrasonic material characterization system was theoretically investigated to realize more accurate measurement. Through numerical calculation, it was clarified that the appropriate defocus position z m with higher sensitivity used in the V(x) measurement depended on the waveform attenuation of V(z) curves. It was also clarified that the measurement error caused by the focal distance change due to temperature change in the water coupler could be reduced by choosing the lower defocus position as z m. A method for measuring the surface profile of the specimen by applying the V(x) method with z m > 0 was proposed in order to correct measurement error due to warpage of specimen surface.

Propagation properties of leaky surface acoustic wave on water-loaded LiTaO3/quartz bonded structure

Recently, bonded structures such as LiTaO3/quartz structures have been attracting attention as a means of obtaining high-performance surface acoustic wave (SAW) devices. To investigate the possibility of evaluating the acoustical loss in such bonded structures by subtracting the calculated leakage loss into the water from the measured normalized attenuation factor, propagation properties such as the velocity and normalized attenuation factor of leaky SAWs on a water-loaded 36°YX-LiTaO3/AT0°X-quartz bonded structure were investigated using a line-focus-beam ultrasonic material characterization system and were found to be in good agreement with the calculated values for both the 0°X and 90°X propagation directions.

Evaluation of SiO2 Thin films on piezoelectric substrates using line-focus-beam ultrasonic material characterization system

SiO2 thin films deposited on LiNbO3 and LiTaO3 using RF magnetron sputtering were evaluated using a line-focus-beam ultrasonic material characterization (LFB-UMC) system. From the measured velocity of a leaky surface acoustic wave (LSAW), c11 and c44 for a SiO2 film were determined to be 0.755 × 1011 and 0.289 × 1011 N m−2 assuming that the density and dielectric constant of the thin film were bulk values. The measured LSAW velocities are in good agreement with values calculated using determined values. The acoustical loss was evaluated from the difference between the measured propagation attenuation and the calculated leakage loss into water. However, the differences were 0.02–0.27 dB/λ, which were considered to be too large for the acoustical loss of SiO2 thin films. By accurately measuring the density of a thin film and determining its elastic constant, it is possible that the acoustical loss of a thin film can be evaluated using an LFB-UMC system.

Investigation of Material Constants of CaTiO₃ Doped (K,Na)NbO₃ Film by MEMS-Based Test Elements.

A CaTiO3-doped (K,Na)NbO3 (KNN-CT) film is a lead-free piezoelectric film that is expected to substitute Pb(Zr,Ti)O3 (PZT) film in piezoelectric micro electro mechanical systems (MEMS). However, the full set of the material constants (elastic constants, piezoelectric constants and dielectric constants) of the KNN-CT film have not been reported yet. In this study, all the material constants of a sputter-deposited blanket KNN-CT film were investigated by the resonance responses of MEMS-based piezoelectric resonators and the phase velocities of leaky Lamb waves on a self-suspended membrane. The phase velocities measured by a line-focus-beam ultrasonic material characterization (LFB-UMC) system at different frequencies were fitted with theoretical ones, which were calculated from the material constants, including fitting parameters. A genetic algorithm was used to find the best-fitting parameters. All the material constants were then calculated. Although some problems arising from the film quality and the nature of deliquescence are observed, all the material constants were obtained exhibiting accuracy within 16 m/s in the phase velocity of leaky Lamb wave.

Propagation properties of leaky surface acoustic wave on water-loaded piezoelectric substrate

To evaluate acoustical loss mainly due to Rayleigh scattering loss of a thin film material using a line-focus-beam ultrasonic material characterization system, surface acoustic waves (SAWs) were excited and detected using IDTs, the propagation properties of SAWs with and without water loading were measured, and the acoustical losses of amorphous SiO2 and Ta2O5 thin films deposited on 128°YX-LiNbO3 were evaluated by subtracting the calculated attenuation of leakage loss into water from the measured propagation loss of leaky SAWs (LSAWs) on water-loaded specimens. The results of the evaluation of acoustical losses using LSAWs with the SAW propagation mode of the small leakage loss were in good agreement with the measured propagation loss of the Rayleigh-type SAW corresponding to the acoustical loss.

Chemical composition characterization of Ca3Ta(Ga0.5Al0.5)3Si2O14 single crystal by the line-focus-beam ultrasonic material characterization system

A new method for evaluation of homogeneity of Ca3Ta(Ga0.5Al0.5)3Si2O14 (CTGAS) single crystals was established based on leaky surface acoustic wave (LSAW) velocity measurements performed by the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Three plate specimens cut perpendicular to X-, Y-, and Z-axes were prepared from the CTGAS crystal ingot and LSAW velocity distributions were examined for these specimens. LSAW velocity changes due to Al-substitution effect were successfully extracted by using a relationship between two LSAW velocities propagating along different directions for Ca3TaGa3Si2O14 (CTGS) and Al-substituted CTGS. Comparison of measured LSAW velocities and the results of chemical composition analysis performed by electron probe microanalysis (EPMA) demonstrated that LSAW velocity is mainly affected by Al-content change in CTGAS. Maximum velocity variation was observed in radial direction of the crystal ingot through the Z-axis propagating LSAW velocity measurements for Y-cut CTGAS specimen corresponding to Al-content change of 0.226mol%. Accuracy of evaluation of Al content by velocity measurement for Y-cut Z-propagating LSAW is estimated to be ±0.0047mol% and is superior to that by EPMA.

1Pb-24 Characterization of Polycrystalline Diamond Films by the LFB Ultrasonic Material Characterization System(Poster Session)

1Pb-24 Characterization of Polycrystalline Diamond Films by the LFB Ultrasonic Material Characterization System(Poster Session)

1J2-4 Evaluation of Elastic Inhomogeneity in ZnO Crystals by Means of the Micro-LFB Ultrasonic Material Characterization System(Measurement techniques, Imaging, Nondestructive evaluation II)

1J2-4 Evaluation of Elastic Inhomogeneity in ZnO Crystals by Means of the Micro-LFB Ultrasonic Material Characterization System(Measurement techniques, Imaging, Nondestructive evaluation II)

1J2a-1 Measurement model for propagation characteristics of leaky surface acoustic waves by the line-focus-beam ultrasonic material characterization system(Measurement techniques)

1J2a-1 Measurement model for propagation characteristics of leaky surface acoustic waves by the line-focus-beam ultrasonic material characterization system(Measurement techniques)

Development of superprecise evaluation method for EUVL-grade ultralow-expansion glass using line-focus-beam ultrasonic material characterization system

Development of superprecise evaluation method for EUVL-grade ultralow-expansion glass using line-focus-beam ultrasonic material characterization system

Accurate Velocity Measurement of Periodic Striae of TiO2–SiO2 Glasses by the Line-Focus-Beam Ultrasonic Material-Characterization System

The evaluation of periodic striae layers in TiO2–SiO2 ultra-low-expansion glasses, formed during production, is discussed through the measurement of leaky surface acoustic-wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material-characterization system. The averaging effect associated with an LSAW propagation region interacting with periodic striae on a specimen surface was examined at 225 MHz, taking several specimens prepared with inclination angles of θ=0, 2, 5, 10, 20, and 90° to the plane of striae layers with a periodicity of 0.16 mm. LSAW velocities corresponding to TiO2 concentrations in the glass were properly measured for the specimens with θ less than 10°, and the perpendicular specimen (θ=90°) was suitable for accurate determination of the striae periodicities for LSAW propagation perpendicular to the striae plane.

Evaluation method of TiO/sub 2/-SiO/sub 2/ ultra-low-expansion glasses with periodic striae using the LFB ultrasonic material characterization system

Experimental procedures and standard specimens for characterizing and evaluating TiO2-SiO2 ultra-low expansion glasses with periodic striae using the line-focus-beam (LFB) ultrasonic material characterization system are discussed. Two types of specimens were prepared, with specimen surfaces parallel and perpendicular to the striae plane using two different grades of glass ingots. The inhomogeneities of each of the specimens were evaluated at 225 MHz. It was clarified that parallel specimens are useful for accurately measuring velocity variations of leaky surface acoustic waves (LSAWs) excited on a water-loaded specimen surface associated with the striae. Perpendicular specimens are useful for obtaining periodicities in the striae for LSAW propagation perpendicular to the striae plane on a surface and for precisely measuring averaged velocities for LSAW propagation parallel to the striae plane. The standard velocity of Rayleigh-type LSAWs traveling parallel to the striae plane for the perpendicular specimens was numerically calculated using the measured velocities of longitudinal and shear waves and density. Consequently, a reliable standard specimen with an LSAW velocity of 3308.18 +/- 0.35 m/s at 23 degrees C and its temperature coefficient of 0.39 (m/s)/degrees C was obtained for a TiO2-SiO2 glass with a TiO2 concentration of 7.09 wt%. A basis for the striae analysis using this ultrasonic method was established.

Experimental Study for Evaluating Striae Structure of TiO2–SiO2 Glasses Using the Line-Focus-Beam Ultrasonic Material Characterization System

Striae configurations in TiO2–SiO2 ultra-low-expansion glasses caused by variations in TiO2 concentration were investigated through measurement of leaky surface acoustic wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material characterization system. LSAW velocity distributions were measured on the surface of a specimen substrate prepared from a large circular plate glass ingot produced by the direct method using a flame hydrolysis process. A subsequent procedure that included polishing the surface of the specimen to reduce the specimen thickness by 40 µm and measuring the LSAW velocity distributions on the surface was repeated five times in order to examine at least one period of the striae. TiO2 concentration variations were clearly observed in the deposit direction of the glass ingot and in its radial direction. The maximum LSAW velocity difference over the whole examined region was 11.7 m/s, corresponding to 0.70 wt % TiO2 concentration. The three-dimensional striae structure revealed that the striae plane in the examined region was almost parallel to the substrate surface but gently curved down in the radial direction. The plane had a slightly convex-shaped cross section layered with a striae periodicity of about 0.16 mm and a curvature radius of about 440 mm, and also existed in a circular form with a curvature radius of about 450 mm. The ultrasonic method will contribute to improvement of characteristics and homogeneity of glass associated with production-process conditions.

Improvement of Velocity Measurement Accuracy of Leaky Surface Acoustic Waves for Materials with Highly Attenuated Waveform of the V(z) curve by the Line-Focus-Beam Ultrasonic Material Characterization System

Measurement accuracies of leaky surface acoustic wave (LSAW) velocities for materials with highly attenuated waveforms of V(z) curves obtained by the line-focus-beam ultrasonic material characterization (LFB-UMC) system are investigated. Theoretical investigations were carried out and experiments were performed for TiO2–SiO2 glass (C-7972), Li2O–Al2O3–SiO2 glass ceramic (Zerodur®), and (111) gadolinium gallium garnet (GGG) single crystal as specimens. Waveform attenuations of V(z) curves for C-7972 and Zerodur® are greater than those for the (111) GGG single crystal. Frequency dependences of the waveform attenuations were calculated for each specimen by considering the propagation attenuation of LSAWs. The theoretical results revealed that the waveform attenuation dominantly depends upon the acoustic energy loss due to the water loading effect on the specimen surface, and that the waveform attenuation becomes smaller with decreasing frequency. Significant improvement of the measurement precision of LSAW velocities was demonstrated for each specimen using three LFB ultrasonic devices with different curvature radii R of the cylindrical acoustic lenses: R=2.0 mm at 75 MHz, R=1.5 mm at 110 MHz, and R=1.0 mm at 225 MHz; for C-7972, the precisions were improved from ±0.0053% at 225 MHz to ±0.0020% at 75 MHz.

Accurate Calibration Line for Super-Precise Coefficient of Thermal Expansion Evaluation Technology of TiO2-Doped SiO2 Ultra-Low-Expansion Glass Using the Line-Focus-Beam Ultrasonic Material Characterization System

We obtained an accurate relationship between the leaky surface acoustic wave (LSAW) velocities and TiO2 concentrations. Such a relationship is needed for the line-focus-beam ultrasonic material characterization (LFB-UMC) system as a new technology for evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses with extremely high precision. Using commercially available TiO2–SiO2 glass with periodic striae, averaged velocities for LSAW propagation parallel to the striae plane at 225 MHz and averaged TiO2 concentrations by X-ray fluorescence analysis were measured on the surface of seven specimen substrates prepared perpendicular to the striae plane. The obtained sensitivity of LSAW velocity to TiO2 concentration was -0.0601 wt %/(m/s), and the measurement resolution was estimated to be ±0.0084 wt % for ±2 σ (σ: standard deviation) from the LSAW velocity measurement resolution of ±0.14 m/s. The TiO2 concentration for the standard TiO2–SiO2 glass specimen with a LSAW velocity of 3308.18 m/s for system calibration was determined to be 7.09 wt %. This ultrasonic technology will contribute greatly to the development of the ultra-low-expansion glasses needed for extreme ultraviolet lithography (EUVL) systems.

Determination of the true congruent composition for LiTaO/sub 3/ single crystals using the LFB ultrasonic material characterization system

The true congruent composition for LiTaO3 single crystals was determined by measuring the velocities of leaky surface acoustic waves (LSAWs) with the line-focus-beam ultrasonic material characterization (LFB-UMC) system for two 42 degrees YX-LiTa3s crystal ingots. The congruent composition determined here was 48.460 Li2O-mol%, corresponding to the LSAW velocity (42 degrees YX-LiTaO3) of 3125.3 m/s, and the absolute relationship between the LSAW velocity and chemical composition was obtained. Simulations on the variation of the melt and crystal compositions in a mass production of 100 crystals were conducted as a function of the composition of the starting material around the congruent composition. The result showed that the distributions of the melt and crystal compositions within and among the crystals varied largely with the material composition, providing the relationship of the material composition with the maximum composition variation for the 100 crystals. Based on these results, we verified the relationships between the tolerance of the material composition variation and the tolerances for the SH-type SAW velocity, LSAW velocity, and Curie temperature. The material composition needs to be constrained to within +/- 0.007 Li2O-mol% around the congruent composition to mass-produce the crystals with reliable homogeneity, satisfying the tolerance of +/- 0.01% in the SAW velocity. Furthermore, a guideline for the specification of reliable piezoelectric SAW-device wafer substrates was presented with the accurate interrelationships among the chemical composition ratio, LSAW velocity, and Curie temperature.

Ultrasonic microspectroscopy of congruent LiNbO3 crystals

Experimental procedures for evaluating the compositional homogeneity of LiNbO3 single crystals were developed using the line-focus-beam ultrasonic material characterization system, and the true congruent composition was determined. First, the relationships among leaky surface acoustic wave (LSAW) velocities (VLSAW), chemical compositions, Curie temperatures, densities, and lattice constants were investigated for crystal evaluation, using X-, Y-, and Z-cut substrates prepared from three LiNbO3 crystals grown along the crystallographic Z axis with different Li2O contents of 48.0, 48.5, and 49.0mol%. We selected VLSAW for Z-cut Y-axis propagating (ZY) LiNbO3 with the highest sensitivity to chemical composition changes [0.0253Li2Omol%∕(m∕s)], and also VLSAW for Y-cut X-axis propagating (YX) LiNbO3 [0.0464Li2Omol%∕(m∕s)] that was advantageous for detailed evaluation of distributions in the chemical composition along the pulling direction as well as the diameter direction.The congruent composition was estimated to be 48.477Li2Omol%. Next, the homogeneities of the three above-mentioned crystals and a commercially available LiNbO3 crystal with a nominally congruent composition were evaluated using data for YX-LiNbO3 specimens. Consequently, compositional changes were observed clearly as VLSAW changes. The commercial crystal specimen had a gradient of −0.0046(m∕s)∕mm from top to bottom. The VLSAW variations for the entire examined region (60×36mm2) exhibited a maximum change of 0.55m∕s, corresponding to the chemical composition change of 0.025Li2Omol%. The relationships between the chemical compositions and the acoustical physical constants (the elastic, piezoelectric, and dielectric constants, and density) were also provided.

A Super-Precise CTE Evaluation Method for Ultra-Low-Expansion Glasses Using the LFB Ultrasonic Material Characterization System

A super-precise method of evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses for future extreme ultra-violet lithography (EUVL) systems was developed using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Evaluation was demonstrated for two commercial glasses, TiO2-SiO2 glass (C-7971) and Li2O-Al2O3-SiO2 glass ceramic (Zerodur). For the C-7971 specimens, the sensitivity and resolution in the velocity measurement of leaky surface acoustic waves (LSAWs) for the CTE were estimated to be 4.40 (ppb/K)/(m/s) and ±0.77 ppb/K for ±2σ (σ: standard deviation). LSAW velocity differences caused by different TiO2 concentrations and distributions or striae in each specimen were successfully detected and evaluated. For the Zerodur specimens, LSAW velocity differences associated with the chemical compositions and crystallization conditions were observed among different ingots and specimens. This ultrasonic method is expected to be an extremely useful and effective CTE evaluation technology and to contribute to improving and developing EUVL-grade glass materials.

P3-67 Investigation of the thickness of thin liquid layer in the longitudinal acoustic property measurements by the plane-wave ultrasonic material characterization system

P3-67 Investigation of the thickness of thin liquid layer in the longitudinal acoustic property measurements by the plane-wave ultrasonic material characterization system