InGaZnO TFTs on a flexible membrane transferred to a curved surface with a radius of 2 mm

Thin-film transistors have attracted a considerable amount of attention since they enable cost effective and large scale device fabrication. Fabricating TFTs directly on flexible plastic foils enables mechanically flexible transistors [1-3]. However, the mechanical instability of plastic substrates limits the accuracy of the photo mask alignment during the fabrication, and therefore the minimal feature size of the structures and their performance. An alternative way to produce flexible electronic devices is to peal-off a spin-coated polymer layer from a rigid substrate [4], or to spall the thin top layer from a crystalline silicon wafer after device fabrication [5]. These methods in general suffer from high strain applied during the separation process, or a limited flexibility of the final devices. Here, we propose a new approach based on the fabrication of transistors on top of a flexible 1 μm thin parylene membrane deposited on a Si carrier wafer, which can be transferred to nearly any kind of flexible or shaped surfaces. TFTs fabricated on Si and afterwards transferred to a flexible polyimide foil, exhibit transistor functionality even when the polyimide substrate is bent to a tensile radius of 5 mm. Additionally, TFTs are also transferred to a plastic rod with a radius of 2 mm.