A TSV-cross-link-based approach to 3D-clock network synthesis for improved robustness

To obtain high yield for 3D ICs, random open defects, process variations, and thermal induced stress are key issues that must be addressed when synthesizing 3D clock networks. Current research on 3D clock synthesis often focuses on the construction and optimization of a 3D clock tree topology. Moreover, extra circuitry has been proposed to enable pre-bond testing and substitution of through silicon vias (TSVs) with random open defects. However, tree structures inherently have limited robustness to variations and may suffer failures arising from defects and/or process variations. To counter such problems, we propose to use TSVs to add redundancy in a 3D clock network. The proposed 3D network would have a complete 2D clock network on each die, facilitating pre-bond testing. Also, cross links would be inserted within each die using wires and across dies using TSVs to improve timing robustness within each die and across dies, respectively. Moreover, clock buffers are placed outside of zones that have high TSV-induced stress that could influence carrier mobility. Experimental results show that the proposed 3D clock networks have no failures due to random open defects, and on the average have 53% lower skew compared to 3D tree structures.