Frequency determination in nondestructive test of semiconductor devices with ultrasound heating

The infrared-optical beam induced resistance change (IR-OBIRCH) method is widely used to localize faults of semiconductor devices. Prior to the fault localization, the IR-OBIRCH generally requires a decapsulation of mold resin that covers the semiconductor devices. As an alternative, without the need for decapsulation, the authors propose the ultrasonic beam induced resistance change (SOBIRCH) method. This research examined a determination method of the optimal ultrasound frequency in order to improve the signal intensity of SOBIRCH even if the speed of sound and the thickness of mold resin are unknown. The resonant frequency estimated by using frequency component of signals of reflected wave agreed with the ultrasound frequency that maximized the intensity of SOBIRCH signal. The frequency dependence of SOBIRCH signal was also estimated. This research demonstrated that the proposed frequency determination method can estimate the resonant frequency on the fault observation of a practical device. (C) 2020 The Japan Society of Applied Physics