Yang Hyojin, Park Sejun, Yun Sanghyuk, Kim Haesung, Lee Haneul, Park Min-Kyu, Choi Sung-Jin, Kim Dae Hwan, Kim Dong Myong, Kwon Dongseok, Bae Jong-Ho
School of Electrical Engineering, Kookmin University, Seoul 02707, South Korea.
Department of Electrical and Computer Engineering and Inter-University Semiconductor Research Center (ISRC), Seoul National University, Seoul 08826, South Korea.
Nanoscale. 2024 Oct 31;16(42):19856-19864. doi: 10.1039/d4nr02096k.
In this paper, quantitative analysis was performed focusing on the structural effect on the ferroelectric switching of ferroelectric thin-film transistors (FeTFTs). FeTFTs and ferroelectric capacitor (FeCap) test element groups (TEGs) were designed and fabricated, and positive-up-negative-down (PUND) measurements were performed to analyze the switching characteristics of ferroelectric films in various structures constituting an FeTFT. It was verified that TiN/HZO/a-IGZO/Mo (MFSM, FeTFT source/drain contact) mostly contributed to the memory operation of an FeTFT, while TiN/HZO/a-IGZO (MFS, FeTFT channel) exhibits one-time memory operation with irreversible polarization switching. In addition, the switching characteristics of MFSM and MFS were different from those of MFM, especially after a few cycles, related to the oxygen vacancy migration between a-IGZO channels and HZO films. The extracted 2 values for MFS, MFSM and TiN/HZO/Mo (MFM, FeTFT source/drain parasitic capacitor) were 38, 28 and 20 [μC cm], respectively. Based on the operation differences according to the device structure, it was found that irreversible switching in the MFS region (channel) causes a rapid decrease in the memory window after the first switching in an FeTFT and degradation of a-IGZO and HZO films in the MFSM region (contact) including oxygen vacancy exchange and related defect generation causes subthreshold slope increases and negative threshold voltage shifts as cycling stress was applied.
在本文中，进行了定量分析，重点关注铁电薄膜晶体管（FeTFT）中铁电开关的结构效应。设计并制作了FeTFT和铁电电容器（FeCap）测试元件组（TEG），并进行了正向上负向下（PUND）测量，以分析构成FeTFT的各种结构中铁电薄膜的开关特性。结果表明，TiN/HZO/a-IGZO/Mo（MFSM，FeTFT源极/漏极接触）对FeTFT的存储操作贡献最大，而TiN/HZO/a-IGZO（MFS，FeTFT沟道）表现出具有不可逆极化切换的一次性存储操作。此外，MFSM和MFS的开关特性与MFM不同，特别是在几个周期之后，这与a-IGZO沟道和HZO薄膜之间的氧空位迁移有关。提取的MFS、MFSM和TiN/HZO/Mo（MFM，FeTFT源极/漏极寄生电容）的2值分别为38、28和20[μC/cm]。基于器件结构的操作差异，发现MFS区域（沟道）中的不可逆切换会导致FeTFT首次切换后存储窗口迅速减小，而MFSM区域（接触）中的a-IGZO和HZO薄膜退化，包括氧空位交换和相关缺陷产生，会导致施加循环应力时亚阈值斜率增加和负阈值电压偏移。
