Fine-pitch 3D System Integration and Advanced CMOS nodes: Technology and System Design Perspective

Advanced CMOS SoCs with more cores and more complex memory hierarchies are hitting the memory wall, especially in intermediate cache levels (L2, L3). Managing the memory wall thus represent major challenge in the design of future systems and should include memory tech tuning, macro design & Logic-to-Memory interconnect optimization using multi-die packages & different 3D structures. To understand the benefits of 3D interconnects on Memory-on-Logic partitioning we analyze four different partitioning options of intermediate (L2) cache assuming high density CuCu hybrid bonding. We observe that, the partitioning of the complete sub-system (memory macros & controller logic) is less beneficial with respect to reference 2D integration when compared to memory macro only partitioning schemes. Further, more memory macros are moved from the logic die, better the gains are (up to 40% total wirelength reduction). Such gains come at the expense of higher 3D pin count, motivating finer 3D pitches. Finally, we demonstrate design enablement of 3D aware IR-drop analysis for micro- and nano-TSVs with Buried Power Rail for Back Side power delivery.