Application of Plasma Jet Crystallization Technique to Fabrication of Thin-Film Transistor

The crystallization of a-Si films on glass substrates using the plasma jet crystallization (PJC) technique and its application to thin-film transistor fabrication were studied. Amorphous Si (a-Si) films deposited by plasma-enhanced chemical vapor deposition (PECVD) of 50% SiH4 diluted with H2 were crystallized by thermal plasma jet under the power of 1.6 to 2.6 kW input to the plasma source and the substrate scan speed of 170 to 1000 mm/s. The crystallinity of the films was improved by treating the films at a higher input power for a longer duration. Thin-film transistors (TFTs) fabricated using the crystallized films showed good electrical characteristics. By increasing the input power from 1.86 to 2.29 kW in the crystallization, the average field-effect mobility was increased from 42 to 61 cm2·V-1·s-1, and the threshold voltage was decreased from 4.0 to 3.4 V. These results indicate that the PJC technique is a very promising low-temperature process technology.