SiO2 based conductive bridging random access memory

We present a review on the subject of Conductive Bridging Random Access Memory (CBRAM) based on copper- or silver-doped silicon dioxide. CBRAM is a promising type of resistive non-volatile memory which relies on metal ion transport and redox reactions to form a persistent conducting filament in a high resistance film. This effect may be reversed to return the device to a high resistance state. Such control over resistance can be used to represent digital information (e.g., high =0, low =1) or produce multiple discrete or even continuous analog values as required by advanced storage and computing concepts. Many materials have been used in CBRAM devices but we concentrate in this paper on silicon dioxide as the ion conducting layer. The primary benefits of this approach lie with the CMOS process compatibility and the ubiquity of this material in integrated circuits which greatly lower the barrier for widespread usage and permit integration of memory with silicon-based devices. Our discussion covers materials and electrochemical theory, including the role of counter charge in these devices, as well as the current understanding of the nature of the filament growth. Theory of operation is supported by descriptions of physical and electrical analyses of devices, including in-situ microscopy and impedance spectroscopy. We also provide insight into memory arrays and other advanced applications, particularly in neuromorphic computing. The radiation tolerance of these devices is also described.