Self-Aligned Amorphous Silicon Thin-Film Transistors Fabricated on Clear Plastic at 300 $^{\circ}\hbox{C}$

Abstract

We fabricated back-channel-cut and back-channel-passivated hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) on clear-plastic (CP) foil substrates using a silicon nitride (SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> ) 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 7 × cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of a free-standing sheet of CP foil to reduce the TFT channel length L to 3 m and reduce the S/D overlap with the gate L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SD</sub> to ~1. 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.