Via-Switch FPGA: 65-nm CMOS Implementation and Evaluation

Offering a combination of low latency, high energy-efficiency, and flexibility, field-programmable gate arrays (FPGAs) suit applications ranging from Internet of Things (IoT) computing to artificial intelligence (AI). The conventional static random access memory (SRAM) FPGAs face severe challenges including large standby power and low logic density due to utilization of SRAM cell and MOS switch for signal routing. In response, researchers have introduced emerging non-volatile (NV) memory technologies to solve standby power issues. However, access transistors used for NV memory cell configuration still consume a large silicon area. In this article, we introduce an NV via-switch (VS) FPGA featuring fully back-end-of-line (BEOL) signal routing and front-end-of-line (FEOL) logic computing for high logic density. The VS fabricated in BEOL is constructed by two Cu atom switches (ASs) for signal routing and two a-Si/SiN/a-Si varistors for AS configuration. We demonstrate the first implementation of the VS-FPGA at 65-nm node and evaluate its performance by various basic applications. 2.6x logic density, 1.5x energy efficiency, and 1.4x operation speed are achieved in comparison with a previous complementary AS (CAS) FPGA in which one access transistor is necessary for each CAS configuration.