R&D: First Demo of Ferroelectric Tunnel Thin-Film Transistor NVM With Polycrystalline-Silicon Channel and HfZrO Gate Dielectric

IEEE Transactions on Electron Devices has published an article written by William Cheng-Yu Ma, Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan, Chun-Jung Su, Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan, Kuo-Hsing Kao, Department of Electrical Engineering, National Cheng Kung University, Tainan, Taiwan, Yao-Jen Lee, Institute of Pioneer Semiconductor Innovation, National Yang Ming Chiao Tung University, Hsinchu, Taiwan, Ju-Heng Lin, Pin-Hua Wu, Jui-Che Chang, Cheng-Lun Yen, Hsin-Chun Tseng, Hsu-Tang Liao, Yu-Wen Chou, Min-Yu Chiu, and Yan-Qing Chen, Department of Electrical Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan.

Abstract: “In this work, the nonvolatile memory constructed on the tunnel thin-film transistors (tunnel-TFTs) using polycrystalline-silicon channel featuring ferroelectric HfZrOx layer is demonstrated for the first time. When the pulse voltages of program (PG) and erase (ER) are, respectively, 3.5 and −2 V with the pulsewidth of 1 μs , the threshold voltage modulation amount of the ferroelectric tunnel-TFT can reach −0.524 and 0.496 V, respectively. In addition, the endurance behaviors of the ferroelectric tunnel-TFT exhibit a strong PG/ER pulsewidth dependence. The wake-up effect of the ferroelectric layer becomes more pronounced as increasing the PG/ER pulsewidth. Moreover, the increase of the PG/ER pulsewidth also causes the ferroelectric tunnel-TFT to be subjected to the electrical dynamic stress effect, leading to the degradation of the subthreshold swing (SS) and the electron trapping effect. When the pulsewidth is 100 ns, the endurance is mainly dominated by the fatigue effect of the ferroelectric layer and the degradation of the SS. When the pulsewidth increases to 1 μs , the endurance is mainly dominated by the electron trapping effect of the ferroelectric layer in addition to the fatigue effect. The retention of the ferroelectric tunnel-TFT exhibits stable behavior at 50 °C. Consequently, the ferroelectric tunnel-TFT exhibits sufficient electrical performance and can be integrated with display panels and various sensor systems on smart wearable devices for edge computing applications.“