Some issues on hydrogen and hydrogenation of plasma enhanced chemical vapor deposited films in a-Si:H thin-film transistors
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Several hydrogenation issues related to properties of plasma-enhanced chemical vapor deposited (PECVD) films and the performance of an a-Si : H thin-film transistor (TFT) have been studied. The a-Si : H/a-Si : H interface hydrogen concentration is higher than those of individual a-Si : H films. The small amount of loosely bound hydrogen in the TFT, which can be removed at a temperature lower than the film deposition temperature, is responsible for the major function of the transistor. The plasma hydrogenation process cannot restore all characteristics of de-hydrogenated TFT because of the generation of new types of damages. Plasma hydrogenation of the SiNxsurface includes two mechanisms : passivation of dangling bonds and selective etching of N-containing groups. Depending on the process condition, TFT characteristics can be improved or deteriorated by the interface hydrogenation step. The experimental result is consistent with the deposition-etching mechanism in the PECVD SiNxdeposition process. © 2000 Published by Elsevier Science Ltd.
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