High-Performance Junctionless Ferroelectric Thin-Film Transistor for Low-Voltage and High-Speed Nonvolatile Memory Applications

• Published in: IEEE transactions on electron devices 2024-11, p.1-6
• Main Authors: Ma, William Cheng-Yu, Su, Chun-Jung, Kao, Kuo-Hsing, Yen, Yu-Chieh, Yang, Ji-Min, Li, Yi-Han, Chen, Yen-Chen, Lin, Jhe-Yu, Chang, Hui-Wen
• Format: Article
• Language: English
• Subjects: Contracts; Electric fields; Electrons; Endurance; ferroelectric memory; Insulators; junctionless thin-film transistor (JL-TFT); Logic gates; Modulation; Nonvolatile memory; nonvolatile memory (NVM); polycrystalline-silicon (poly-Si) channel; Silicon; Switches; Thin film transistors
• ISSN: 0018-9383
• DOI: 10.1109/TED.2024.3503539

A junctionless ferroelectric thin-film transistor (JL-FeTFT) that combines a highly doped polycrystalline-silicon (poly-Si) channel with a ferroelectric gate insulator is proposed and investigates its nonvolatile memory (NVM) characteristics for application in high-density vertically stacked memory structures in neuromorphic computing. Compared to the conventional inversion mode FeTFT (IM-FeTFT) with undoped poly-Si channel, the JL-FeTFT demonstrates significant advantages. First, the JL-FeTFT operates at a lower voltage due to the higher electron concentration in the channel, resulting in a reduction of the threshold voltage ( V _{{\text{TH}}} ) by 0.522 V. Second, the transconductance of JL-FeTFT is 6.28 times higher than that of IM-FeTFT. Additionally, the V _{{\text{TH}}} modulation in JL-FeTFT is significantly higher than in IM-FeTFT across various pulse widths, particularly excelling under short pulse widths and low operating voltages. Furthermore, the JL-FeTFT exhibits endurance of 2 \times 10 ^{\text{5}} cycles at a 300 ns pulsewidth, substantially surpassing the 5 \times 10 ^{\text{4}} cycles of the IM-FeTFT. The JL-FeTFT also shows better stability and reliability, with a smaller reduction in the memory window (MW) after up to 10 ^{\text{6}} program/erase (PRG/ERS) cycles. Moreover, after 10 ^{\text{6}} PRG/ERS cycles, the JL-FeTFT maintains lower degradation in ON-current, subthreshold swing (SS), and transconductance compared to the IM-FeTFT. Additionally, the JL-FeTFT operates at lower voltages and achieves endurance of 10 ^{\text{5}} cycles at a 100 ns pulsewidth, making it suitable for high-speed and low-voltage NVM applications. Consequently, the JL-FeTFT demonstrates advantages in terms of low operating voltage, high ON-current, excellent endurance, and reliability, positioning it as a promising candi