Reliability-Ensured and Fast (< 100 ns) Analog Synpase for Training Accelerators: All-Sputtered HfOy/HfO_xRRAM

We reveal that sputtered HfO_x, which has been often neglected in resistive random access memory (RRAM) design, can be an alternative for highly reliable and fast (< 100 ns) analog synapses to accelerate training algorithms. The sub-stoichiometric HfO_x, enables rapid current update owing to the abundant oxygen vacancies (V₀). Additional HfOy layer with increased stoichiometry makes uniformly distributed Vo profile across the entire HfOy/HfO_xRRAM stack, enhancing reliability in dynamic synaptic operation, where multiple pulses are continuously addressed. This not only results in robust device-to-device/cycle-to-cycle uniformity, but also ensures multilevel retention, which is further validated by real-time transient current analysis.