A Hierarchical 3-D Physical Design Method for Ultralarge-Scale Logic-on-Memory CGRA Chip

Abstract

Face-to-face bonded 3-D (F2F 3D) technology, with the potential to significantly reduce chip area while enhancing performance, stands as one of the most promising ways to extend Moore’s Law. However, current 3-D physical design flows are often modifications of 2-D design flows and rely on technical personnel to manually modify technical files. Furthermore, existing research on 3-D design flow primarily focuses on module implementation, with very few studies addressing hierarchical design methods for large-scale chips. In this article, we first introduce a 3-D physical design flow which concurrently optimizes the timing of both the logic tier and the memory tier, achieving synchronized physical design for both tiers. Then, we develop a bottom-up hierarchical 3-D physical design flow to extend the 3-D design flow to large-scale chip design. Through coordinated power planning, clock tree design, and interconnect unit design, we enhance the power, performance, and area (PPA) metrics of the entire chip. Using our RTL-to-GDS physical design flow, we successfully implemented a 28-nm CMOS logic-on-memory (LoM) 3-D coarse-grained reconfigurable architecture (CGRA) chip with over 50 million gates. Experimental results demonstrate that our 3-D flow improves timing by 16.1% while reducing voltage drop by 38.6% compared to the 2-D design. In addition, the power-delay product (PDP) of the 3-D chip decreases by 10.2%, showcasing better performance.