2.5D Package Modelling for Short Circuit Failure Analysis by High-Resolution Time-domain Reflectometry

Recently, high-resolution time domain reflectometry (TDR) by optical sampling technique has become a popular method in the failure analysis of 2.5D/3D packaged chips. Compared to the conventional electronics-based TDR system with a step waveform, the impulse-waveform based high-resolution TDR can scan a much longer signal time-window with greatly improved time-domain signal resolution. However, long time domain signals are usually challenging to interpret intuitively due to the existence of parasitics and multiple reflections in the circuit network. In this work, a modelling technique is proposed for high-resolution TDR analysis in 2.5D/3D package. One 2.5D chip with short circuit failure has been analyzed by the proposed method with a more accurate localization of the actual failure point.