Cross-Coupled Ferroelectric FET-Based Ternary Content Addressable Memory With Energy-Efficient Match Line Scheme

Abstract

Fast communication between networking devices increases the importance of the ternary content addressable memory (TCAM). The demands for low energy in networking devices have accelerated the research on nonvolatile TCAMs that store data without the power supply. Recently, ferroelectric field-effect transistors (FeFETs), nonvolatile three-terminal devices with a high on/off ratio, have been adopted for TCAMs. Although the previous FeFET TCAMs consume low write energy with a significantly compact TCAM cell area, they suffer from write problems: 1) the write scheme cannot afford the saturated polarization switching in FeFETs and 2) the states stored in the unselected TCAM cells are changed during the write operation. In addition, search yield is deteriorated by wide process variations of FeFETs. This paper proposes a novel FeFET TCAM that is free from the write problems of the previous FeFET TCAMs and tolerant to process variations. This paper also proposes a novel match line scheme to improve search energy and time by reducing match line capacitance and the amount of discharged voltage in the match evaluation phase. Industrial-compatible 28 nm technology-based simulation results with the Preisach FeFET model show that the proposed FeFET TCAM achieves the highest search yield.