A 7-nm 4-GHz Arm¹-Core-Based CoWoS¹ Chiplet Design for High-Performance Computing

Abstract

We present a dual-chiplet interposer-based system-in-package (SiP) octo-core processor using Chip-on-Wafer-on-Substrate (CoWoS) technology. Each of the two identical chiplets is implemented in 7-nm CMOS with 15 metal layers and has four Arm Cortex-A72 processor cores operating at 4.0 GHz. A bidirectional mesh bus with 2-mm flop-to-flop distance is distributed throughout the chiplet for high-speed on-die data transport above 4.0 GHz. The chiplets communicate with each other through ultrashort reach (0.5 mm long) interposer channels using a Low-voltage-In-Package-INterCONnect (LIPINCON) clock-forwarded parallel interface. The scalable link module offers 320 GB/s of aggregate bandwidth, operating at 8.0 Gb/s/pin and 0.3-V transmitter swing without receiver termination to achieve 0.56-pJ/bit energy efficiency and 1.6-Tb/s/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> bandwidth density. Measurements of the fabricated SiP validate the functionality and performance of the cores, on-die data bus, and inter-chiplet link. The built-in LIPINCON eye-scan feature validates inter-chiplet connectivity at 8.0 Gb/s with an eye opening of 244 mV and 0.69 UI.