Computational Associative Memory with Amorphous Metal‐Oxide Channel 3D NAND‐Compatible Floating‐Gate Transistors

3D NAND has been enabling continuous NAND density and cost scaling beyond conventional 2D NAND since sub-20-nm nodes. However, its poly-Si channel suffers from low mobility, instability caused by grain boundaries, and large device-to-device variations in electrical characteristics at highly scaled device dimensions. These drawbacks can be overcome by introducing an amorphous indium-gallium-zinc-oxide (a-IGZO) channel, which has the advantages of ultralow OFF current, back-end-of-line compatibility, higher mobility than poly-Si, and free of grain boundaries due to the amorphous nature. In this work, ultrascaled floating-gate (FG) transistors with a channel length down to 60 nm are reported, achieving the highest ON current of 127 mu A mu m(-1) among all reported a-IGZO-based flash devices for high-density, low-power, and high-performance 3D NAND applications. Furthermore, a nonvolatile and area-efficient ternary content-addressable memory (TCAM) with only two parallel-connected a-IGZO FG transistors is experimentally demonstrated to address the TCAM scalability issue. Experimentally calibrated array-level simulations show that this design achieves at least a 240 x array-size scalability and a 2.7-fold reduction in search energy than TCAMs based on complementary metal-oxide-semiconductor technology using 16 transistors, two-transistor-two-resistive random access memory, and two-ferroelectric field-effect-transistor.