Fig. 1. Schematic drawing of the SAW resonator on the 42° YX-LT wafer, where We is the width of the IDT, and Nt and Nr are 80 and 15, respectively.

Fig. 2. Schematic drawing of the colorimetry scheme for LT-based wafers. (a) Optical measurement system. (b) CIELAB color space for the wafer evaluation, where the inset denotes measurement points on the wafer. (c) Photograph of the nondestructive colorimetry testing system for the LT-based wafer.

Fig. 3. Simulation of periodic models as a function of frequency and IDT width. (a) Frequency-dependent admittance curves for the 100 nm and 20 nm offsets of We. (b) Normalized stress distributions (S/Smax) of the x–z plane at the resonance frequencies of various SAW resonators.

Fig. 4. Optical spectra of LT-based wafers with double-sided polishing. (a)–(c) LT wafers with various Fe doping densities. (d)–(f) Intrinsic and Fe-doped LT wafers and their partially reduced counterparts.

Fig. 5. Four-inch Fe:LT wafer and its corresponding reduced wafers with different reduction levels.

Fig. 6. (a) L* and (b) ΔEab* as functions of the catalyst ratio and reaction temperature for rFe:LT wafers. (c) Transmittance, (d) absorbance, and (e) reflectance at the wavelength of 365 nm as functions of L* for rLT and rFe:LT wafers. (f) Wafer bending strength for various LT-based wafers. All the rFe:LT wafers have a Fe ion density of 110 ppm.

Fig. 7. (a) Schematic drawing of UV lithography for SAW resonators by using high-L* and low-L* rFe:LT wafers. (b) IDT width as a function of rFe:LT wafer lightness. (c) Nonuniformity of IDT width as a function of rFe:LT on-wafer color difference.

Fig. 8. (a) SEM images of a fabricated SAW resonator for the Band 5 duplexer, where the SAW wavelength is 4.5 μm. (b) Simulated frequency-dependent admittance curves of the SAW resonators for two different IDT widths, which correspond to the measured counterparts for two different L* values. (c) Device resonance and anti-resonance frequency distributions for the rFe:LT wafers with two different L* values. (d) On-wafer resonance and anti-resonance frequency distribution mappings for the rFe:LT wafers with two different ΔEab* values.

Fig. 9. Schematic drawing and photograph of bending strength test for wafers.