Self-aligned amorphous silicon thin-film transistors fabricated on clear plastic at 300°C

We fabricated back-channel-cut and back-channelpassivated hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) on clear-plastic (CP) foil substrates using a silicon nitride (SiN_x) deposition temperature of 300°C. The TFTs were fabricated on CP and are as stable under high gate bias as TFTs made on glass substrates. A self-alignment technique was developed to align the channel passivation, the a-Si:H island, and the source/drain (S/D) terminals to the gate. Self-alignment allowed us to fabricate discrete TFTs across 7×7cm² of a free-standing sheet of CP foil to reduce the TFT channel length L to 3 μm and reduce the S/D overlap with the gate L _SD to ∼1μm. To test the self-alignment techniques, we fabricated ring oscillators on the CP substrates. These results show that it is possible to fabricate state-of-the-art self-aligned a-Si:H TFTs and TFT circuits on plastic substrates.