Sensitivity improvement of ultrasonic beam induced resistance change (SOBIRCH) method with ultrasound resonance inside mold resin

Frequency determination in nondestructive test of semiconductor devices with ultrasound heating

“…Figure 4 shows the schematic diagram of the measurement system of SOBICH. 21) An ultrasound, its carrier frequency being several tens of MHz, is modulated by a square wave of several kHz. The modulated ultrasound from the transducer stimulates the current path, and induces a small change in its local resistance, leading to a change of current.…”

“…This research examined a determination method of the 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. In the proceeding paper of USE2019, 21) the proposed frequency determination was not applied to the fault observation of practical device. This study demonstrated that the proposed frequency determination method can estimate the resonant frequency in a SOBIRCH observation of a fault in a practical semiconductor device.…”

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

“…Although the ultrasonic wave is expected to pass through optically opaque resin and generate heat near the wiring surface, the wave may be significantly attenuated depending on the resin thickness, leading to the reduction in signal strength. 21) In this study, in order to investigate the influence, we measured the samples with different resin layers and performed a numerical simulation considering the sound field, temperature field and resistance change.…”