COMPOSITE SUBSTRATE AND METHOD FOR ESTIMATING THICKNESS TREND OF PIEZOELECTRIC SUBSTRATE

摘要

A composite substrate of the present invention is a composite substrate provided with a support substrate having a diameter of 2 inches or more, and a piezoelectric substrate bonded to the support substrate, the piezoelectric substrate having a thickness of not more than 20 μm and transmitting light, wherein the piezoelectric substrate has a banded thickness distribution, the thickness distribution of the piezoelectric substrate having, in a cross section of the composite substrate taken along a line perpendicular to the bands, a waveform with an amplitude in the thickness direction of not less than 5 nm and not more than 100 nm, and with a pitch in a width direction of not less than 0.5 mm and not more than 20 mm, wherein the pitch of the waveform has a correlation with the width of the bands. In the piezoelectric substrate, the bands may be parallel bands, spiral bands, or concentric bands.