THREE-DIMENSIONAL ELECTRONIC SURFACES

Novel large-area electronics, such as electronic paper, sensor skin, and electrotextiles, requires building electronic devices on flexible and deformable substrates. Substrates such as organic polymers and stainless steel foils can be deformed into arbitrary shapes, but inorganic semiconductor device materials, such as amorphous silicon and silicon nitride, are brittle, and crack easily when substrates are deformed. Therefore, it is desirable to reduce the strain in such device structure on deformable substrates, and to further understand the relationship between the electrical performance of the devices and the applied mechanical strain for strain below the point where failure occurs. In this thesis, we explore the ability to plastically deform thin film semiconductor structures on deformable substrates to spherical cap shapes without cracking the semiconductor layers. To achieve electronics on a spherical dome, thin-film transistors were first fabricated with conventional processes in islands on a flat polyimide substrate. Next, the substrate was plastically deformed into a spherical dome. With this approach, the strain in the device island was drastically reduced. Interconnects between the device island could be made by lift-off methods. Other interconnect schemes such as direct printing were also discussed. The results demonstrate that the concept of stiff circuit islands fabricated on deformable foil substrates is a promising approach to electronics on surfaces with arbitrary shapes. i