Evaluation and selection of LiNbO3 and LiTaO3substrates for SAW devices by the LFB ultrasonic materialcharacterization system

摘要

This paper demonstrates the evaluation and selection ofncommercially available LiNbO3 and LiTaO3 singlencrystals and wafers for surface acoustic wave (SAW) devices using thenline-focus-beam ultrasonic material characterization (LFB-UMC) system.nThis system enables measuring leaky-SAW (LSAW) propagationncharacteristics precisely and efficiently for a number of specimens. Thenwafers are prepared from the top, middle, and bottom parts of fourn128°YX LiNbO3 and seven X-112°Y LiTaO3nsingle crystals. For both series of crystals, the measured LSAWnvelocities increase from top to bottom in the crystals and with thenincreasing crystal growth number. The velocity changes for all wafersnare 0.036% for 128°YX LiNbO3 and 0.035% for X-112°YnLiTaO3, corresponding to changes of 0.038 mol% and 0.075 mol%nin Li2O concentration, respectively. Moreover, theninhomogeneity in the first X-112°Y LiTaO3 single crystalncaused by some undesirable wafer fabrication processes can be detectednprecisely, although it is difficult for the conventional methods tonobtain such information