Research progresses of resistive random access memory

Abstract

Resistive random access memory (RRAM) is one of the most promising candidates of next-generation non-volatile memories. Comparing with the traditional floating gate Flash memory, RRAM has advantages in cell structure, operation speed, scalability and ease of 3D integration. In this paper, the RRAM technology is systematically reviewed. The operation principle, technological advantages, development history and fundamental scientific issues of RRAM are introduced. Then several key issues in RRAM are summarized and analyzed in detail, including the materials system, resistive switching mechanism, novel physical effects in RRAM, and 2D/3D integration of RRAM. For the materials system in RRAM, traditional resistive switching films, including solid-electrolyte, complex transition metal oxide, binary metal oxide, are first summarized, following with the analyzing of the recent research progress of the applications of nanowires and 2D materials in RRAM devices. These low-dimensional nanomaterials can be used as the switching dielectrics, planar electrode/nano-electrode/edge electrode and can play active role in the improvement of scalability, switching performances and switching uniformity. Next, we summarize and analyze three resistive switching mechanisms in filamentary RRAM device, i.e. thermochemical mechanism (TCM), electrochemical metallization (ECM) mechanism, valence change mechanism (VCM). Their corresponding SET/RESET switching principles and fundamental electrical characteristics, experimental verifications by transmission electron microscope (TEM) observation are elucidated in detail. Subsequently, based on the resistive switching mechanisms, the novel physical phenomena in RRAM induced by the change of the material microstructure and energy band in the process of resistive switching are elaborated. Three physical effects, including conductance quantization effect, magnetoelectric effect, photoelectric effect, are successively analyzed. At last, considering the integration technology of RRAM, we summarize and analyze the key scientific issues in memory array architecture, 2D/3D integration.