Fabrication of Semi-transparent Resistive Random Access memory and Its Characteristics of Nonvolatile Resistive Switchin
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Fabrication of Semi-transparent Resistive Random Access memory and Its Characteristics of Nonvolatile Resistive Switching Jung Won Seo, Seung Jae Baik, Sang Jung Kang, and Koeng Su Lim Department of Electrical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea ABSTRACT This report covers the resistive switching characteristics of cross-bar type semitransparent (or see-through) resistive random access memory (RRAM) devices based on ZnO. In order to evaluate the transmittance of the devices, we designed the memory array with various electrode sizes and spaces between the electrodes. To prevent read disturbance problems due to sneak currents, we employed a metal oxide based p-NiO/n-ZnO diode structure, which exhibited good rectifying characteristics and high forward current density. Based on these results, we found that the combined metal oxide diode/RRAM device could be promising candidate with suppressed read disturbances of cross-bar type ZnO RRAM device. INTRODUCTION Cross-bar memory array, which configures data storage materials between a set of crossing bottom and top electrodes, provides an attractive architecture due to the simplicity and scalability of structure. This memory array can provide the smallest memory cell size of 4F2 (F is the minimum feature size), thus, it is considered to resolve scaling problems of conventional non-volatile memories. Since adjacent memory cells are connected by the same top electrode (also same way by the bottom electrode), however, cross-bar memory has a problem of read disturbance due to the ‘sneak path’ [1] without certain selection devices. Combination of memory cell with p-n junction diodes [2] and transistors [3] has been widely investigated to eliminate the ‘sneak path’ problem in cross-bar memory. Especially, metal oxide based p-n diodes have been preferred for the following reasons: they have a simpler structure compared with transistor; and they can be fabricated over any kinds of substrate and at low temperature (even room temperature); and they can offer the high current density over Si based diode. Therefore, stacking of metal oxide p-n diodes on cross-bar memory devices is considered to be suitable for preventing undesired ‘sneak path’ current [4]. In this work, we fabricated cross-bar semi-transparent RRAM devices on glass substrate and adopted metal oxide p-NiO/n-ZnO diode stacking structure to block the ‘sneak current path’ among the adjacent memory cells. This metal-oxide p-NiO/n-ZnO diode showed good performance to obstruct the reverse bias current of cross-bar ZnO RRAM device which causes a disturbance or interference between the cells and high forward current density. To confirm the feasibility of semi-transparent memory, we measured the transmittance of devices with different electrode sizes and space between the electrodes. By adding the metal oxide n-ZnO/p-NiO diode to the cross-bar ZnO RRAM, we observed that stable resistive switching in cross-bar ZnO RRAM by blocking th
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