Lee I-Che, Kuo Hsu-Hang, Tsai Chun-Chien, Wang Chao-Lung, Yang Po-Yu, Wang Jyh-Liang, Cheng Huang-Chung
Department of Electronics Engineering and Institute of Electronics, National Chiao Tung University, Hsinchu 30010, Taiwan.
J Nanosci Nanotechnol. 2012 Jul;12(7):5318-24. doi: 10.1166/jnn.2012.6245.
High-performance bottom-gate (BG) poly-Si polysilicon-oxide-nitride-oxide-silicon (SONOS) TFTs with single grain boundary perpendicular to the channel direction have been demonstrated via simple excimer-laser-crystallization (ELC) method. Under an appropriate laser irradiation energy density, the silicon grain growth started from the thicker sidewalls intrinsically caused by the bottom-gate structure and impinged in the center of the channel. Therefore, the proposed ELC BG SONOS TFTs exhibited superior transistor characteristics than the conventional solid-phase-crystallized ones, such as higher field effect mobility of 393 cm2/V-s and steeper subthreshold swing of 0.296 V/dec. Due to the high field effect mobility, the electron velocity, impact ionization, and conduction current density could be enhanced effectively, thus improving the memory performance. Based on this mobility-enhanced scheme, the proposed ELC BG SONOS TFTs exhibited better performance in terms of relatively large memory window, high program/erase speed, long retention time, and 2-bit operation. Such an ELC BG SONOS TFT with single-grain boundary in the channel is compatible with the conventional a-Si TFT process and therefore very promising for the embedded memory in the system-on-panel applications.
通过简单的准分子激光结晶（ELC）方法，已经证明了具有垂直于沟道方向的单晶界的高性能底栅（BG）多晶硅 - 氧化硅 - 氮化物 - 氧化物 - 硅（SONOS）薄膜晶体管。在适当的激光辐照能量密度下，硅晶粒生长从底栅结构固有产生的较厚侧壁开始，并在沟道中心相遇。因此，所提出的ELC BG SONOS薄膜晶体管表现出比传统固相结晶的晶体管更优异的晶体管特性，例如更高的场效应迁移率393 cm2/V-s和更陡的亚阈值摆幅0.296 V/dec。由于高场效应迁移率，可以有效地提高电子速度、碰撞电离和传导电流密度，从而改善存储性能。基于这种迁移率增强方案，所提出的ELC BG SONOS薄膜晶体管在相对较大的存储窗口、高编程/擦除速度、长保持时间和2位操作方面表现出更好的性能。这种在沟道中具有单晶界的ELC BG SONOS薄膜晶体管与传统的非晶硅薄膜晶体管工艺兼容，因此在面板系统应用中的嵌入式存储器方面非常有前景。
