Computational Associative Memory with Amorphous InGaZnO Channel 3D NAND-Compatible FG Transistors

TL;DR

This paper introduces amorphous InGaZnO channel transistors for 3D NAND and associative memory, achieving high performance, stability, and scalability improvements over traditional poly-Si channels.

Contribution

It demonstrates ultra-scaled a-IGZO FG transistors with superior mobility and uniformity, and experimentally validates a compact, energy-efficient ternary content-addressable memory design.

Findings

Highest ON current of 127 uA/um among a-IGZO flash devices

Achieves at least 240x array scalability in simulations

2.7-fold reduction in search energy compared to existing TCAMs

Abstract

3D NAND enables continuous NAND density and cost scaling beyond conventional 2D NAND. However, its poly-Si channel suffers from low mobility, large device variations, and instability caused by grain boundaries. Here, we overcome these drawbacks by introducing an amorphous indium-gallium-zinc-oxide (a-IGZO) channel, which has the advantages of ultra-low OFF current, back-end-of-line compatibility, higher mobility and better uniformity than poly-Si, and free of grain boundaries due to the amorphous nature. Ultra-scaled floating-gate (FG) transistors with a channel length of 60 nm are reported, achieving the highest ON current of 127 uA/um among all reported a-IGZO-based flash devices for high-density, low-power, and high-performance 3D NAND applications. Furthermore, a non-volatile and area-efficient ternary content-addressable memory (TCAM) with only two a-IGZO FG transistors is experimentally demonstrated. Array-level simulations using experimentally calibrated models show that this design achieves at least 240x array-size scalability and 2.7-fold reduction in search energy than 16T-CMOS, 2T2R, and 2FeFET TCAMs.