2018 年 138 巻 12 号 p. 1566-1572
In the process of manufacture of silicon wafers, it becomes a problem that microscopic defect called microcrack may occur in a wafer. It is difficult to detect by an image inspection using infrared or a usual ultrasonic inspection because the aperture of microcrack is closed. In this study, as a nondestructive testing for a silicon wafer, we paid attention to inspection method using the nonlinearity of ultrasonic wave. First, a system which detects microcracks by making ultrasonic wave propagate along the surface of a silicon wafer was constructed. However, the ultrasonic wave propagating in a silicon wafer was not identified, and the optimization of the system had been unsolved. Therefore, the propagation analysis of the ultrasonic wave was carried out. As the result, it was suggested that it is a Lamb wave. Finally, by using the characteristic of Lamb wave, it was demonstrated that the proposed inspection method was useful for not only the microcrack inspection which lengthened the propagation distance but also the microcrack inspection in the back surface.
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