Enhancements of electrical properties and positive bias instability in self-aligned top-gate a-IGZO TFTs by hydrogen incorporation

Flow rate effects of the silane (SiH4) and ammonia (NH3) on the top gate insulator and the cap layer in self-aligned top-gate amorphous InGaZnO thin film transistors are investigated. The hydrogen density increases with increasing SiH4 and NH3 flow rates. Hydrogen passivation can improve the field-effect mobility, subthreshold swing (S.S.), hysteresis. The positive bias instability is also improved by hydrogen incorporation. However, the overabundance of hydrogen causes the significant negative threshold voltage shift under negative bias illumination stress (NBIS). Moreover, the most deteriorated S.S. and hysteresis shift after NBIS occur in the TFT with the most hydrogen source.