Self-Aligned Bottom-Gate In—Ga—Zn—O Thin-Film Transistor With Source/Drain Regions Formed by Direct Deposition of Fluorinated Silicon Nitride

We developed a bottom-gate and self-aligned In-Ga-Zn-O thin-film transistor (IGZO TFT) with source and drain (S/D) regions that were formed by a direct deposition of fluorinated silicon nitride (SiNx:F) on top of the IGZO film (IGZO/SiNx:F). The resistivity of IGZO/SiN_x:F stack for the S/D regions of the TFT (ρS/D) was highly stable after annealing, and it obtained 4.1 × 10^-3 Qcm after N₂ annealing at 350°C. As a result of thermally stable ρ_S/D, the TFT properties with the IGZO/SiN_x:F S/D regions improved drastically compared with those of IGZO/SiO_x S/D regions. The field effect mobility of 10.6 cm²·V^-1·s-1 and an ON/OFF current ratio of over 10⁸ were obtained after 300°C annealing. The proposed method is essential for making thermally stable S/D regions for self-aligned oxide TFTs.