Pre-bond testing of weak defects in TSVs

Through Silicon Vias (TSVs) are critical elements in three dimensional integrated circuits (3-D ICs) and may undergo defects during the fabrication process and also during their life time. The detection of defective TSVs in the earliest process step is of major concern. For this reason, testing TSVs is usually done at different stages of the fabrication process. In fact, effective pre-bond testing is a key factor to prevent stacking yield loss. Extensive research effort has been devoted to develop efficient pre-bond techniques. In this direction, two main approaches have been explored: pre-bond probing and built-in self test (BIST) techniques. Pre-bond probing is challenging since TSVs are too small for standard test probes and the number of probe pads for testing is not affordable. Present BIST proposals have some disadvantages depending on the particular solution considered, namely: the detection of certain types of defects solely, inability to detect weak defects, large area overhead and long test application time. In this context, this work proposes a simple solution, adding low area overhead and fast application test procedure. Simulation results confirm the proposal viability.