Fully coupled electrothermal simulation of resistive random access memory (RRAM) array

Dear editor, Resistive random access memory (RRAM) is a promising candidate for next generation memory technology [1] and the rapid progress in the threedimensional (3D) integration technology facilitates the design of highly integrated and miniaturized RRAM devices [2]. However, the ever-growing storage density does lead to thermal crosstalk a critical issue as the temperature rise in the victim may induce rupture of conductive filament (CF) and reliability degradation. The electrothermal model given in [3] is employed to describe the electrothermal process in RRAM array. A parallel simulator based on a hybrid finite volume-finite element (FVFE) method and parallel processing technique is developed to numerically study the electrothermal performance in large-scale arrays. Here, a double level parallel scheme base on domain decomposition method (DDM) and the J parallel adaptive unstructured mesh applications infrastructure (JAUMIN) [4] is implemented. Using the developed simulator, the electrothermal properties of a proposed cross-gate vertical RRAM (CGVRRAM) array are investigated. Architecture of the proposed CGVRRAM array. The vertical architecture is one of the most widely used RRAM array structure, and the schematics of a conventional vertical RRAM array and its cell are illustrated in Figures 1(a) and (b). As indicated in [5], thermal crosstalk effects in vertical RRAM array do affect its performance. To improve the thermal management in vertical RRAM array, a novel RRAM (VRRAM) array architecture is proposed as shown in Figure 1(d). We name it CGVRRAM array. Moreover, it also can be seen that compared with the traditional vertical array structure, the proposed one possesses higher integration density. During the operation of the proposed CGVRRAM, the states of word lines, bit lines, and selectors determine the memory chain, while the crossgate lines are used to select the cell in the chain. If there is no cross-gate line chosen, the poly-Si layers can serve as current channels [6]. On the contrary, if one cross-gate line is selected, the channel under it will be TURN OFF, and the current flows through the adjacent cell. Electrothermal model. The electrothermal process taken place in an RRAM consists of ion migration, current transport, and thermal conduction [3]. The electrical simulation can be performed by solving the ion transport equation and current continuity equation, i.e.,