On-chip testing of blind and open-sleeve TSVs for 3D IC before bonding

Abstract

Pre-bond test is preferred for a three-dimensional integrated circuit (3D IC), since it reduces stacking yield loss and thus saves cost. In this paper, we present two schemes for testing through-silicon vias (TSVs) by performing on-chip screening before wafer thinning and bonding. The first scheme is for blind TSVs, which have one end floating, using a charge-sharing technique commonly seen in DRAM. The second scheme is for open-sleeve TSVs, which have one end shorted to the substrate, using a voltage-dividing technique commonly seen in ROM. By virtue of the inherent capacitive and resistive characteristics, we detect the TSVs out of a specified range as anomalies, taking into account the effects of process variations in the detection circuitry. The statistical design by Monte Carlo simulation using TSMC 65nm low-power process shows that for blind TSVs, the best overkill ratio is below 6%. For open-sleeve TSVs, inherent limitations restrict the applicability, so more work needs to be done in the future. Our implementation enjoys little area overhead, requiring only a simple sense amplifier and a write buffer that are shared among a number of TSVs. Reducing the number of TSVs that share a test module will reduce the test time, but increase the area overhead. For blind TSVs, the parallelism also affects the overkill and escape rates.