Effects of Mechanical Strain on TFTs on Spherical Domes

In this paper, amorphous-silicon (a-Si:H) thin-film transistors (TFTs) were fabricated on a plastic substrate, which was then permanently deformed into a spherical dome shape after the device fabrication process. The TFTs were patterned in an island structure to prevent cracking in the device films during the substrate deformation. In the majority of the TFTs, the off-current and gate leakage current do not change substantially. Depending on the island structure, the electron mobility either increased or decreased after deformation. This change in mobility was correlated with the mechanical strain in the device islands determined by finite element modeling of the deformation process. Tensile strain caused slightly higher mobility in planar structures. In a mesa-type structure, silicon films on top of the pillars could be in compression after the dome deformation, leading to a slight decrease in mobility.