LANGASITE SINGLE CRYSTAL WAFER AND MANUFACTURE OF ELASTIC WAVE DEVICE FROM THE SAME

摘要

PROBLEM TO BE SOLVED: To manufacture a surface acoustic wave device from a langasite single crystal wafer in a good yield and to non-destructively and simply perform judgment on the passfail of a langasite single crystal wafer before forming the wafer from a langasite single crystal by selectively using such a wafer having lattice-constant deviation within the wafer surface of a specified value or lower. SOLUTION: In this manufacturing process, by manufacturing a surface acoustic wave device from a langasite single crystal wafer having <=4×10-5 nm lattice-constant deviation within the wafer surface whose area is >=2.0×10-3 m2, both a low cost and a high yield of the device can concurrently be attained. That is, the device can be manufactured at a low cost and in a high yield by cutting off an X-cut or Z-cut wafer from a part of a grown langasite single crystal, measuring the lattice-constant deviation of the single crystal with the cut wafer as a sample and using only a wafer formed from a langasite single crystal having <=4×10-5 nm lattice-constant deviation. Preferably, the X-cut or Z-cut wafer used for this measurement has a >=50 nm diameter.