Ultrasonic beam induced resistance change (SOBIRCH) method for failure analysis of semiconductor devices encapsulated by mold resin

In the process of the failure analysis for semiconductor devices, various optical methods are applied as techniques to localize faults of the semiconductor devices. Conventional optical techniques often require the decapsulation of the mold resin, since the mold resin is not optically transparent. As a new fault localization technique requiring no decapsulation, the authors are proposing the ultrasonic beam induced resistance change (SOBIRCH) method based on a heating by focused ultrasonic beam. In this report, the signal intensity of the SOBIRCH method for the capsulated samples was discussed through the experimental and the theoretical approaches. By comparing the experiment and the numerical analysis, it was suggested that a certain thickness of the thin mold resin can enhance the intensity of the SOBIRCH signal. Additionally, an expected effect of the standing wave in the thin mold resin was calculated, and a method to make use of the standing wave was proposed.