Synaptic behaviors of HfO2 ReRAM by pulse frequency modulation

Abstract

A resistive switching random-access memory (ReRAM) device with TiN/HfO2/SiO2/p(+)-Si stack is analyzed for synaptic behavior. Fabricated RRAM device stack consists of heavily doped p-type silicon bottom electrode (BE), HfO2 as a switching layer, SiO2 as a tunneling barrier layer and TiN as a top electrode (TE). The RRAM cell successfully shows I-V curves including SET and RESET operations in DC sweep mode. By inserting a SiO2 tunneling barrier layer, gradual switching characteristics are obtained by pulse operation. By optimizing the pulse scheme applied to the device, biological synaptic plasticity of long-term potentiation and depression is demonstrated. Finally, spike rate-dependent plasticity (SRDP) learning rule is realized by applying pulses with different frequencies to both terminals of the ReRAM device.