Thursday, July 24, 2008

Printable Thin-Film Transistor for Flexible Electronics

United States Patent Application 20080173865
Kind Code A1
Fink; Richard Lee ; et al. July 24, 2008


Fabrication of thin-film transistor devices on polymer substrate films that is low-temperature and fully compatible with polymer substrate materials. The process produces micron-sized gate length structures that can be fabricated using inkjet and other standard printing techniques. The process is based on microcrack technology developed for surface conduction emitter configurations for field emission devices.

Inventors: Fink; Richard Lee; (Austin, TX) ; Yaniv; Zvi; (Austin, TX)

Assignee Name and Adress: NANO-PROPRIETARY, INC.


1. A thin film transistor (TFT) comprising:a substrate;a source electrode on the substrate;a drain electrode on the substrate positioned a distance from the source electrode;a layer of metal oxide deposited on the substrate between the source and drain electrodes, wherein the layer of metal oxide is reduced to metal to form a microcrack in the layer between the source and drain electrodes, wherein the microcrack separates a first portion of the metal layer contacting the source electrode from a second portion of the metal layer contacting the drain electrode;an active semiconductor material deposited so that it bridges the microcrack, contacting both the first and second portions of the metal layer;a gate dielectric material deposited over the active semiconductor material; anda gate electrode deposited on the gate dielectric material and not contacting the metal layer or the active semiconductor material.

9. A method of manufacturing a TFT comprising:inkjet printing conductive ink on a substrate to form source and drain electrodes spaced apart from each other;inkjet printing a PdO layer on the substrate between the source and drain electrodes;reducing the PdO layer to Pd metal resulting in formation of a microcrack in the Pd metal layer;inkjet printing an active semiconductor on the reduced PdO layer across the microcrack;inkjet printing a gate dielectric over the active semiconductor; andinkjet printing a gate electrode over the gate dielectric.

Advantages of this approach are:

[0041]1. Low cost: All-printing technologies are used to form feedlines and TFT components. Inkjet printing and other printing approaches may he used. Printing is an additive approach and not subtractive, thus in general, the materials cost will be less. In addition, the capital investment for printing equipment is much lower than CVD or vapor deposition equipment needed for a-Si TFT technology or high-performance pentacene transistors.

[0042]2. Low temperature; The fabrication processes are below C.

[0043]3. Compatible with flexible substrates: The fabrication processes are completely compatible with PEN substrates.

[0044]4. Scalable to large area: Ink-jet printers are used now to print billboard signage. 100'' diagonal will be no problem. The fact that Canon, is using this microcrack approach for their SED 36'' diagonal (and larger) displays also demonstrates that arrays of submicron channel TFTs can be fabricated over large areas reliably.

[0045]5. Performance specifications for emissive technologies: The driving currents from this TFT structure are sufficient to drive OLEDs.