Development of Ultrasonic Microspectroscopy for Characterization of Layered and Damaged Surfaces on Single Crystal Substrates

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Ultrasonic microspectroscopy technology, using the line-focus-beam (LFB) and plane-wave ultrasonic material characterization system, has been applied to analyze material surface properties introduced by slicing, lapping, and polishing to prepare wafer substrates from single crystal ingots or with very thin layers on the substrates formed by proton-exchanged and ion-implanted methods.1. The reliable LFB system with high accuracy in the velocity measurement of leaky surface-acoustic-waves (LSAWs) on the water-loaded specimen surfaces has been established, operating up to 900 MHz using several LFB ultrasonic devices.2. A method of evaluating material surfaces damaged or roughened by measuring longitudinal-wave reflection coefficients as a function of frequency when the waves are incident normally to the specimen surface through a water couplant has been developed.3. A system of the X-ray diffractometer using the Bond method, combined with a temperature controller to realize highly stabilized measurement environment throughout the whole system, has been developed. The system has been demonstrated with a resolution of better than 【minus-plus】0.0001°, increasing the capability of analyzing single crystal surfaces damaged.4. The following experimental simulations have been conducted using the above-mentioned systems and methods :(1) The LFB system in the measurements of the frequency characteristics of LSAW velocities has been applied to characterize two groups of specimens to demonstrate the high sensitivity and usefulness : five specimens of proton-exchanged layers on Z-cut LiTaOィイD23ィエD2 crystal substrates with the depth of 3-100 nm ; and four specimens ion-implanted layers on (100) Si substrates fabricated with the ion concentrations of 10ィイD113ィエD1-10ィイD116ィエD1 cmィイD11-2ィエD1.(2) The X-ray system has been applied to evaluate the surfaces of several specimens with different levels of roughness to demonstrate the high sensitivity and usefulness.