The acoustical physical constants (elastic constant, piezoelectric constant, dielectric constant, and density) of commercial surface acoustic wave (SAW)-grade LiNbO(3) and LiTaO(3) single crystals were determined by measuring the bulk acoustic wave velocities, dielectric constants, and densities of many plate specimens prepared from the ingots. The maximum probable error in each constant was examined by considering the dependence of each constant on the measured acoustic velocities. By comparing the measured values of longitudinal velocities that were not used to determine the constants with the calculated values using the previously mentioned constants, we found that the differences between the measured and calculated values were 1 m/s or less for both LiNbO(3) and LiTaO(3) crystals. These results suggest that the acoustical physical constants determined in this paper can give the values of bulk acoustic wave velocities with four significant digits.

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The loss and phase advance due to diffraction are experimentally observed by measuring the amplitude and phase of radio frequency (rf) tone burst signals in the VHF range, in an ultrasonic transmission line consisting of a buffer rod with an ultrasonic transducer on one end, a couplant of water, and a solid specimen of synthetic silica glass. The measured results agree well with the calculated results from the exact integral expression of diffraction. The diffraction effects on the velocity and attenuation measured in this frequency range and their corrections are investigated to realize more accurate measurements. It is shown that attenuation measurements are influenced by diffraction losses and can be corrected by numerical calculations, and that velocity measurements are affected by the phase advance caused by diffraction. This investigation demonstrates that, in complex-mode velocity measurements, in which the velocity is determined from the measured phase of the signals, the true velocity at each frequency can be obtained by correction using the numerical calculation of diffraction. Based on this result, a new correction method in amplitude-mode velocity measurements is also proposed. In this new method, the velocity is determined from the intervals of interference output obtained by sweeping the ultrasonic frequency for the superposed signals generated by the double-pulse method. Velocity may be measured accurately at frequencies in the Fresnel region, and diffraction correction is essential to obtain highly accurate values with five significant figures or more.

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.

Langasite-type single crystal Ca3NbGa3Si2O14 (CNGS) was grown by the Czochralski technique. Dielectric, elastic and piezoelectric constants of CNGS were measured by the resonance-antiresonance method. At room temperature, dielectric constants ε11 T/ε0 and ε33 T/ε0 were 17.8 and 27.9, respectively. Electromechanical coupling coefficients k 12, k 25 and k 26 were also determined as 10.9, 17.3 and 11.9%, respectively. The measurements were carried out in a temperature range from -30 to 80°C. Temperature coefficients of the dielectric, elastic and piezoelectric constants were obtained. The line-focus-beam and plane-wave ultrasonic material characterization system was employed for measuring bulk acoustic velocities, and longitudinal and transverse wave velocities of 7408.4 m/s and 3136.2 m/s, respectively, in the c-direction uncoupled with piezoelectricity at 23°C were obtained. This was in good agreement with the results determined by the resonance-antiresonance method. The density of CNGS was 4125 kg/m3. All the parameters of the CNGS crystal for bulk and surface acoustic wave applications were determined in this research.

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Absolute accuracy of the line-focus-beam (LFB) acoustic microscopy system is investigated for measurements of the leaky surface acoustic wave (LSAW) velocity and attenuation, and a method of system calibration is proposed. In order to discuss the accuracy, it is necessary to introduce a standard specimen whose bulk acoustic properties, (e.g., the independent elastic constants and density) are measured with high accuracy. Single crystal substrates of gadolinium gallium garnet (GGG) are taken as standard specimens. The LSAW propagation characteristics are measured and compared with the calculated results using the measured bulk acoustic properties. Calibration is demonstrated for the system using two LFB acoustic lens devices with a cylindrical concave surface of 1-mm radius in the frequency range 100 to 300 MHz.

Basic acoustic properties of AlN single crystal Y -cut and Z -cut plates, grown by the physical vapor transport method, were evaluated using ultrasonic microspectroscopy (UMS) technology. A method of determining the acoustical physical constants with two specimens was developed by measuring the velocities of longitudinal and shear waves and leaky surface acoustic waves (LSAWs). We obtained accurate bulk-wave velocities, LSAW velocities and their distributions in the specimen surfaces, and the density with great differences compared with the calculated ones using the reported constants. We also determined the corresponding constants. This UMS technology will contribute to the further development of AlN crystals. #