Characterization of Microcrystalline Silicon Thin Film Transistors Fabricated by Thermal Plasma Jet Crystallization Technique

The electrical characteristics of thin-film transistors (TFTs) fabricated by thermal plasma jet (TPJ)-crystallized microcrystalline Si (µc-Si) films have been investigated. Amorphous Si (a-Si) films were crystallized with the TPJ under the scanning speed (v) of 350 to 550 mm/s, and µc-Si TFTs were successfully fabricated with a 300 °C process. By reducing v, µFE increases from 3.2 to 17.1 cm2 V-1 s-1, and V th and S decrease from 9.2 to 5.2 V and 1.3 to 0.6 V/decade, respectively. The variations of µFE, V th, and S were kept within small values of 1.06 (±4.4%), 0.14 (±1.1%), and 0.04 (±4.0%), respectively. The µc-Si is formed with ∼20-nm-sized randomly oriented small grains, and this isotropic nature results in very small variation of TFT performance. With decreasing v, the fraction of nano sized grains and disordered bonds at the grain boundary decreases, which results in improved TFT performance.