Effective Current-Driven Memory Operations for Low-Power ReRAM Applications
A. Cirera, B. Garrido, Antonio Rubio, Ioannis Vourkas
Abstract
Resistive switching (RS) devices are electronic components which exhibit a resistive state that can be adjusted to different nonvolatile levels via electrical stressing, fueling the development of future resistive memories (ReRAM) and enabling innovative solutions for several applications. Most works so far have used voltage-based driving schemes for both WRITE and READ operations. However, results from current-driven WRITE operations have shown high uniformity in switching performance, and thus constitute a valid alternative to consider, but current-driven READ operations have rarely been explored. In this context, here we tested a current-based READ/WRITE memory driving scheme on commercial self-directed channel (SDC) devices, while operating constantly at low current levels between tenths of nA and 1.5 uA. We propose a novel method to carry out efficient READ operations exploiting the transient response of the voltage on the current-driven ReRAM memory cells. For READ operations performed at 100 nA, we calculated the cumulative probability distribution of the standard deviation of the measured voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{\mathrm {V}}$ </tex-math></inline-formula> ) on the devices and we observed a ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma _{\mathrm {V-HRS}}/\sigma _{\mathrm {V-LRS}} \sim 10\times $ </tex-math></inline-formula> . Moreover, the HRS and LRS states were distinguishable in all the tested devices with less than 0.5% error. Finally, the calculated energy consumption ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{\mathrm {SET}} \approx 10$ </tex-math></inline-formula> nJ, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{\mathrm {RESET}} \approx 30$ </tex-math></inline-formula> nJ, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E_{\mathrm {READ}}$ </tex-math></inline-formula> between 80–400 pJ) was competitive even when the duration of the READ/WRITE current pulses was suboptimal in the millisecond range. Therefore, the presented results validate the promising characteristics and the power-efficiency of the proposed READ method for current-driven ReRAM circuits and applications.