Recent Advances in Electromigration Reliability Modeling and Full-Chip EMinduced IR Analysis

Electromigration (EM) remains the top killer for the copper-based interconnects in current and near-future advanced VLSI technologies. As the technologies scale, the allowable current density continues to decrease due to EM while the required current density to drive the gates increases. 2015 ITRS predicts that EM lifetime of interconnects of VLSI chips will be reduced by half for each generation of technology nodes. The most important observation from our recent study is that EM analysis needs to consider multi-wire segments in the same metal layer to be more accurate and less conservative for all the advanced deep micro techniques. Existing current density-based EM check can lead to significant over-design and loss of design optimization opportunities. Our lab’s recent mission is to change this widely adopted industry design practice to move into new generation EM modeling, assessment, and design techniques. In this talk, I will present recent research works in my research lab (VSCLAB) at UC Riverside. I will cover newly proposed physics-based electromigration (EM) models, especially the physics-based three-phase EM models and full-chip EM-induced IR drop analysis techniques. I will first present the recently proposed three-phase EM model, which much more accurately describes the EM failure process and post-voiding resistance change phenomena. I then introduce two new EM immortality check methods for general multi-segment interconnect wires, which can be viewed as the Blech Product to multi-branch interconnects. Then I will present a novel fast finite difference method (FDM) for EM stress analysis based on frequency domain model order reduction techniques. On top of this, I will present the recently proposed coupled EM-IR drop analysis tool, EMspice, for full-chip EM-induced IR drop analysis of power delivery networks and show how it integrates with Synopsys ICC design flow. EMspice incorporates the latest EM modeling and analysis techniques for multi-segment interconnects, such as EM immortality checks considering both nucleation and incubation phases, the interaction between IR drop, and EM aging effects in the post-void EM phase, EM recovery effects and temporal temperature effects etc. Last, not least, I will present recent work on EM-aware power grid design and optimization, which exploits the recently developed EM modeling and assessment techniques for multi-segment interconnect wires.