Monolithic 3D Integration of Analog RRAM-based Computing-in-Memory and Sensor for Energy-Efficient Near-Sensor Computing.

In the era of the Internet of Things, vast amounts of data generated at numerous sensory nodes impose critical challenges on the data-transfer bandwidth and energy efficiency of computing hardware. A near-sensor computing (NSC) architecture places the processing units closer to the sensors such that the generated data can be processed almost in situ with high efficiency. This study demonstrates the monolithic three-dimensional (M3D) integration of a photosensor array, analog computing-in-memory (CIM), and Si complementary metal-oxide-semiconductor (CMOS) logic circuits, named M3D-SAIL. This approach exploits the high-bandwidth on-chip data transfer and massively parallel CIM cores to realize an energy-efficient NSC architecture. The 1 st layer of the Si CMOS circuits served as the control logic and peripheral circuits. The 2 nd layer comprised a 1k-bit one-transistor-one-resistor (1T1R) array with InGaZnO x field-effect transistor (IGZO-FET) and resistive random-access memory (RRAM) for analog CIM. The 3 rd layer comprised multiple IGZO-FET-based photosensor arrays for wavelength-dependent optical sensing. The structural integrity and function of each layer were comprehensively verified. Furthermore, NSC was implemented using the M3D-SAIL architecture for a typical video keyframe-extraction task, achieving a high classification accuracy of 96.7% as well as a 31.5× lower energy consumption and 1.91× faster computing speed compared to its 2D counterpart. This article is protected by copyright. All rights reserved.