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 ?eld effect mobility of 393 cm 2 /V-s and steeper subthreshold swing of 0.296 V/dec. Due to the high ?eld 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.
- Bottom-Gate (BG)
- Excimer Laser Crystallization (ELC)
- Nonvolatile Memory (NVM)
- Thin Film Transistor (TFT)