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

Abstract

In some cases of the failure analysis of semiconductor devices, package state analysis without decapsulation of mold resin is required. The ultrasonic beam induced resistance change (SOBIRCH) method has been proposed as an alternative without need for the decapsulation. The sensitivity of SOBIRCH depends on the quality of the equipment of its measurement system. After a system is fixed, its sensitivity cannot be upgraded easily. However, if it is possible to improve sensitivity even after the system is fixed, it will be easier to localize faults. By means of numerical analysis, recent research suggested that ultrasound resonance inside the mold resin can improve the sensitivity of SOBIRCH significantly. Our research reported here experimentally verified the ultrasound resonance inside the mold resin improved the sensitivity of SOBIRCH by appropriate tuning of the ultrasound frequency to thinned mold resin. Additionally, this research demonstrated that a fault in a practical device could be more clearly observed by using the expected effect of ultrasound resonance in SOBIRCH observation.