Pathfinding for 2.5D Interconnect Technologies

Abstract

As conventional technology scaling becomes harder, 2.5D integration provides a viable pathway to building larger systems at lower cost. Therefore recently, there has been a proliferation of multiple 2.5D integration technologies that offer different interconnect characteristics such as wiring pitch, bump/pad pitch, inter-die distance, etc. All these factors affect the interconnect metrics of bandwidth, latency and energy-per-bit which ultimately determine system performance. There are other factors such as the choice of ESD circuitry, dicing technology and signaling voltage that also influence these interconnect metrics. In this work, we propose a novel pathfinding methodology for 2.5D interconnect technologies, which seeks to identify the trade-offs among the different factors which affect the performance metrics. We show that incessant scaling of the critical dimensions of the interconnect is not very useful. We emphasize the importance of managing ESD and dicing in improving energy efficiency of these interconnects. We also show that a heterogeneous chiplet ecosystem comes with significant I/O energy penalties. Overall, we demonstrate that a holistic approach considering features of 2.5D integration technology, chiplet technology and various other factors need to be considered and optimized simultaneously to maximize the performance and cost benefits of these integration solutions.