Shrestha Pragya R, Nminibapiel David M, Campbell Jason P, Ryan Jason T, Veksler Dmitry, Baumgart Helmut, Cheung Kin P
Theiss Research, La Jolla, CA USA and the Engineering Physics Division of the NIST, Gaithersburg, MD 20899 USA.
NIST, Gaithersburg, MD 20899 USA and the Department of Electrical and Computer Engineering at Old Dominion University, Norfolk, VA 23529 USA.
IEEE Trans Electron Devices. 2018 Jan;65(1). doi: 10.1109/ted.2017.2776860.
To combat the large variability problem in RRAM, current compliance elements are commonly used to limit the in-rush current during the forming operation. Regardless of the compliance element (1R-1R or 1T-1R), some degree of current overshoot is unavoidable. The peak value of the overshoot current is often used as a predictive metric of the filament characteristics and is linked to the parasitic capacitance of the test structure. The reported detrimental effects of higher parasitic capacitance seem to support this concept. However, this understanding is inconsistent with the recent successes of compliance-free ultra-short pulse forming which guarantees a maximum peak overshoot current. We use detailed circuit analysis and experimental measurements of 1R-1R and 1T-1R structures to show that the peak overshoot is of the parasitic capacitance while the overshoot duration is strongly dependent on the parasitic capacitance. Forming control can be achieved, in ultra-short pulse forming, since the overshoot duration is always less than the applied pulse duration. The demonstrated success of ultra-short pulse forming becomes easier to reconcile after identifying the importance of overshoot duration.
为了应对RRAM中的大变化问题，当前常用电流依从元件来限制形成操作期间的浪涌电流。无论依从元件是1R-1R还是1T-1R，一定程度的电流过冲都是不可避免的。过冲电流的峰值常被用作细丝特性的预测指标，并与测试结构的寄生电容相关联。所报道的较高寄生电容的有害影响似乎支持这一概念。然而，这种理解与最近无依从的超短脉冲形成的成功不一致，后者保证了最大峰值过冲电流。我们通过对1R-1R和1T-1R结构进行详细的电路分析和实验测量，表明峰值过冲与寄生电容有关，而过冲持续时间强烈依赖于寄生电容。在超短脉冲形成中可以实现形成控制，因为过冲持续时间总是小于施加的脉冲持续时间。在认识到过冲持续时间的重要性之后，超短脉冲形成所展示的成功就更容易理解了。
