WAVELET ANALYSIS FOR LASER ULTRASONIC MEASUREMENT OF MATERIAL PROPERTIES

摘要

A laser ultrasonics technique (18) is used to characterize a composite dispersive response signal from a sample under analysis, such as a semiconductor wafer (16). Rather than measuring individual accoustic wa ve velocities at specific frequencies, an entire dispersive response signal (fig. 8) is analyzed. In a presently preferred embodiment of this invention the entire dispersive response signal is analyzed using a wavelet-based technique (figs. 4a, 4b), such as dispersive wavelet transform analysis technique.