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

Abstract

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.

Frequency determination in nondestructive test of semiconductor devices with ultrasound heating

“…14) As an alternative, without the need for decapsulation, the authors propose the ultrasonic beam induced resistance change (SOBIRCH) method by replacing the laser of IR-OBIRCH with ultrasound. [15][16][17][18][19][20] Figure 1 shows a comparison between the conventional IR-OBIRCH and the proposed SOBIRCH. The origin of the signal of IR-OBIRCH is based on the laser heating of faults, with need for the decapsulation of the mold resin.…”

“…In the previous studies, it was suggested that the intensity of the SOBIRCH signal can be significantly improved by appropriately tuning the ultrasound frequency since the ultrasound resonance occurs in the mold resin. 19,20) The resonant frequency in the mold resin is determined by the speed of sound and the thickness of mold resin. However, in some cases of practical fault localization, since both speed of sound and thickness of mold resin are not precisely known, the resonant frequency is not easily obtained.…”