Postbond Test of Through-Silicon Vias With Resistive Open Defects

Through-silicon vias (TSVs) technology has attracted industry interest as a way to achieve high bandwidth, and short interconnect delays in nanometer three-dimensional integrated circuits (3-D ICs). However, TSVs are critical elements susceptible to undergoing defects at steps, such as fabrication and bonding or during their lifetime. Resistive open defects have become one of the most frequent failure mechanisms affecting TSVs. They include microvoids, underfilling, misalignment, pinholes in the oxide, or misalignment during bonding, among others. Although considerable research effort has been made to improve the coverage of TSV testing, little attention has been paid to weak (resistive) open defects causing small delays. In this work, a postbond oscillation test strategy to detect such small delay defects is proposed. Variations in the duty cycle of transmitted signals after unbalanced logic gates are shown to help in the detection of weak open defects in TSVs. HSPICE simulations, including process parameter variations, have been considered, and results show the effectiveness of the method in the detection of weak open defects above 1 kΩ. Experimental work on a 65-nm IC also corroborates the detection capability of the proposal.