A study of crack detection in silicon wafer using laser generated Lamb wave

In the semiconductor industry, with increasing requirements for high capacity, high reliability and compact components, the crack has been one of the most critical issues in accordance with the growing requirement of the wafer-thinning in recent years. Previous studies presented the crack detection on the silicon wafers with the air-coupled ultrasonic method successfully. However, the high impedance mismatches will be the problem in the industrial field. In this paper, for the crack detection, we propose a laser generated Lamb wave method which is not only non-contact, but reliable for the measurement. The laser-ultrasonic generator and the laser-interferometer are used as a transmitter and a receiver, respectively. We firstly verified the identification of S0 and A0 Lamb wave modes, and then conducted the crack detection. The experimental results showed S0 and A0 modes of Lamb wave were clearly generated and detected, and for the crack detection, the estimated crack size by 6dB drop method was almost equal to the actual crack size. So, the proposed method is expected to make it possible to detect the crack in the silicon wafer in the industrial fields.