Experimental Analysis of Oxide-Based RAM Analog Synaptic Behavior

One of the important features of Resistive RAM (RRAM) is its conductance modulation, which makes it suitable for neuromorphic computing systems. In this paper, the conductance modulation of Oxide-based RAM (OxRAM) devices is evaluated based on experimental data to reveal its inherent analog synaptic behavior. A test chip made of a classical 1T-1R elementary memory array is used to demonstrate the conductance modulation. Using an array of cells, as opposed to an isolated cell, allows to catch temporal as well as spatial variabilities. Thus, the multiple resistance levels capability of OxRAMs is assessed in a more realistic context. Two different programming techniques are used to program the OxRAM cells. The first approach leverages on RESET (RST) voltage control. The second approach relies on compliance current control during the SET operation. In both approaches, although multiple resistance levels can be easily obtained, it is demonstrated that a successful implementation of a reliable conductance modulation scheme mainly depends on the ability to precisely control the impact of variability on the different conductance levels obtained after the programming operation.