Development of the line-focus-beam ultrasonic materialcharacterization system

摘要

A line-focus-beam ultrasonic material characterization (LFB-UMC)nsystem has been developed to evaluate large diameter crystals and wafersncurrently used in electronic devices. The system enables highly accuratendetection of slight changes in the physical and chemical properties innand among specimens. Material characterization proceeds by measuring thenpropagation characteristics, viz., phase velocity and attenuation, ofnRayleigh-type leaky surface acoustic waves (LSAWs) excited on thenwater-loaded specimen surface. The measurement accuracy depends mainlynupon the translation accuracy of the mechanical stages used in thensystem and the stability of the temperature environment. New precisionnmechanical translation stages have been developed, and the mechanicalnsystem, including the ultrasonic device and the specimen, has beenninstalled in a temperature-controlled chamber to reduce thermalnconvection and conduction at the specimen. A method for preciselynmeasuring temperature and longitudinal velocity in the water couplantnhas been developed, and a measurement procedure for precisely measuringnthe LSAW velocities has been completed, achieving greater relativenaccuracy to better than ±0.002% at any single chosen point andn±0.004% for two-dimensional measurements over a scanning area ofna 200-mm diameter silicon single-crystal substrate. The system wasndeveloped to address various problems arising in science and industrynassociated with the development of materials and device fabricationnprocesses