Sub-nanosecond pulse programming and device design strategy for analog resistive switching in HfOx-based resistive random access memory

Abstract

The analog switching behavior of resistive random access memory (RRAM) is crucial for its application in neuromorphic computing. This paper investigates the switching mechanism of RRAM under sub-nanosecond and nanosecond pulse programming, with selected device materials and structures, using the kinetic Monte Carlo simulation method. The microscopic distribution of oxygen vacancies is simulated in all three spatial dimensions and in the time dimension (four-dimensional). According to the simulation results, thermal effects are a critical factor affecting the switching behavior. The thermal effects inside the HfOx switching layer can be almost completely eliminated by using sub-nanosecond pulses with low voltage, finally leading to good analog behavior. When nanosecond pulses are applied, effective heat insulation is the key to realizing analog characteristics. In general, the switching process is proposed to involve three stages. Having the lowest energy consumption, the first stage shows the greatest potential for achieving analog behavior. The use of heat-isolating structures, like capping layers and side wall materials with lower thermal conductance, could be a solution to improve the analog behavior of RRAM at the first stage when down-scaling the device size.