Sasaki Taro, Ueno Keiji, Taniguchi Takashi, Watanabe Kenji, Nishimura Tomonori, Nagashio Kosuke
Department of Materials Engineering, The University of Tokyo, Tokyo, 113-8656, Japan.
Department of Chemistry, Saitama University, Saitama, 338-8570, Japan.
Small. 2020 Nov;16(47):e2004907. doi: 10.1002/smll.202004907. Epub 2020 Nov 3.
The memory window of floating gate (FG) type non-volatile memory (NVM) devices is a fundamental figure of merit used not only to evaluate the performance, such as retention and endurance, but also to discuss the feasibility of advanced functional memory devices. However, the memory window of 2D materials based NVM devices is historically determined from round sweep transfer curves, while that of conventional Si NVM devices is determined from high and low threshold voltages (V s), which are measured by single sweep transfer curves. Here, it is elucidated that the memory window of 2D NVM devices determined from round sweep transfer curves is overestimated compared with that determined from single sweep transfer curves. The floating gate voltage measurement proposed in this study clarifies that the V s in round sweep are controlled not only by the number of charges stored in floating gate but also by capacitive coupling between floating gate and back gate. The present finding on the overestimation of memory window enables to appropriately evaluate the potential of 2D NVM devices.
浮栅（FG）型非易失性存储器（NVM）器件的记忆窗口是一个基本的品质因数，不仅用于评估诸如保持特性和耐久性等性能，还用于讨论先进功能存储器器件的可行性。然而，基于二维材料的NVM器件的记忆窗口历来是根据循环扫描转移曲线确定的，而传统硅NVM器件的记忆窗口是由通过单次扫描转移曲线测量的高阈值电压和低阈值电压（Vs）确定的。在此，阐明了由循环扫描转移曲线确定的二维NVM器件的记忆窗口与由单次扫描转移曲线确定的记忆窗口相比被高估了。本研究中提出的浮栅电压测量表明，循环扫描中的Vs不仅受浮栅中存储的电荷量控制，还受浮栅与背栅之间的电容耦合控制。关于记忆窗口高估的这一发现使得能够适当地评估二维NVM器件的潜力。
