Using current pulses to control the intermediate conductance states in hafnium oxide-based RRAM devices

Artificial synaptic devices used in neuromorphic systems need a high number of reachable conductance levels. Resistive switching devices are promising candidates to implement these devices due to their reachable conductance levels. In this work, we have used TiN/Ti/HfO
₂
/W capacitors to study the control of the intermediate conductance states using current pulses instead of the usual voltage pulses. Unlike the use of voltage pulses, in this case we can control the HRS to LRS transition (potentiation characteristic). The characteristic is clearly linear when applying current pulses with linearly increasing amplitudes. The potentiation characteristic is not affected by the pulse length, even for lengths lower than 1 μs. In terms of peripheral circuitry, it is desirable to use pulses with identical amplitudes, but in this case no accumulative behavior is observed, and one current pulse is enough to carry the device to the final conductance state achieved for the amplitude used. Finally, it is not possible to control the HRS to LRS transition (depression characteristic) using current pulses due to the abrupt reset transition. However, this transition can be well controlled using voltage pulses.