Effects of trap-state density reduction by plasma hydrogenation in low-temperature polysilicon TFT
- 1 March 1989
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Electron Device Letters
- Vol. 10 (3) , 123-125
- https://doi.org/10.1109/55.31689
Abstract
The reduction of trap-state densities by plasma hydrogenation in n-channel polysilicon thin-film transistors (poly-TFTs) fabricated using a maximum temperature of 600 degrees C has been studied. Hydrogenated devices have a mobility of approximately 40 cm/sup 2//V*5, a threshold voltage of approximately 2 V, an inverse subthreshold of approximately 0.55 V/decade, and a maximum on/off current ratio of 5*10/sup 8/. The effective channel length decreases by approximately 0.85 mu m after a short hydrogenation which may be attributed to the activation of donors at trap states near the source/drain junctions. Trap-state densities decrease from 1.6*10/sup 12/ to 3.5*10/sup 11/ cm/sup -2/ after hydrogenation, concomitant with the reduction of threshold voltage. Using the gate lengths at which the trap-state densities deviate from the long-channel values as markets for the leading edge of passivation, the apparent hydrogen diffusivity is found to be 1.2*10/sup -11/ cm/sup 2//s at 350 degrees C in the TFT structure.Keywords
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