Built-In Self-Test of High-Density and Realistic ILV Layouts in Monolithic 3-D ICs

Abstract

Nanoscale interlayer vias (ILVs) in monolithic 3-D (M3D) ICs have enabled high-density vertical integration of logic and memory tiers. However, the sequential assembly of M3D tiers via wafer bonding is prone to variability in the immature fabrication process and manufacturing defects. The yield degradation due to ILV faults can be mitigated via dedicated test and diagnosis of ILVs using built-in self-test (BIST). Prior work has carried out fault localization for a regular 1-D placement of ILVs in the M3D layout where shorts are assumed to arise only between unidirectional ILVs. However, to minimize wirelength in M3D routing, ILVs may be irregularly placed by a place-and-route tool, and shorts can also occur between an up-going ILV and a down-going ILV. To test and localize faults in realistic ILV layouts, we present a new BIST framework that is optimized for test time and PPA overhead. We also present a graph-theoretic approach for representing potential fault sites in the ILVs and carry out inductive fault analysis to drop noncritical sites. We describe a procedure for optimally assigning ILVs to the BIST pins and determining the BIST configuration for test-cost minimization. Evaluation results for M3D benchmarks demonstrate the effectiveness of the proposed framework.