Fabrication of low-temperature-polysilicon thin-film transistors on flexible substrates using excimer-laser crystallization

Low-temperature-polysilicon thin-film transistors (LTPS TFTs) were fabricated on polymer substrates using sputtered amorphous-Si (a-Si) films and excimer-laser crystallization. The in-film argon concentration of a-Si films was minimized as low as 1.6% by using an argon/helium gas mixture as the sputtering gas. By employing XeCl excimer-laser crystallization, poly-Si films were successfully fabricated on polymer substrates with an average grain size of 400 nm. With a four-mask process, a poly-Si TFT was fabricated with a fully self-aligned top-gate structure, and the pMOS TFT device showed a field-effect mobility of 63.6 cm²/V-sec, ON/OFF ratio of 10⁵, and threshold voltage of-1.5 V.