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

Abstract

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 , µ FE increases from 3.2 to 17.1 cm 2 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 µ FE , 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.