Methods for forming banks and organic thin film transistors comprising such banks

Abstract

Disclosed is a method for forming banks during the fabrication of electronic devices incorporating an organic semiconductor material that includes preparing an aqueous coating composition having at least a water-soluble polymer, a UV curing agent and a water-soluble fluorine compound. This coating composition is applied to a substrate, exposed using UV radiation and then developed using an aqueous developing composition to form the bank pattern. Because the coating composition can be developed using an aqueous composition rather than an organic solvent or solvent system, the method tends to preserve the integrity of other organic structures present on the substrate. Further, the incorporation of the fluorine compound in the aqueous solution provides a degree of control over the contact angles exhibited on the surface of the bank pattern and thereby can avoid or reduce subsequent surface treatments.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The features, elements and steps according to example embodiments will be more clearly understood from the following detailed description when considered in light of the accompanying drawings, in which:

FIG. 1 is a process chart providing a schematic illustration of an example embodiment of a method for forming banks example embodiments;

FIG. 2 is a cross-sectional view illustrating an example embodiment of an organic thin film transistor structure incorporating banks formed by an example embodiment of the disclosed bank formation methods;

FIGS. 3A and 3B are cross-sectional views illustrating the patterning performance according to an example embodiment in reproducing the photomask sizing of FIG. 3A in the bank and source/drain electrode structures FIG. 3B of an organic thin film transistor incorporating banks formed by a method according to an example embodiment, respectively;

FIG. 4 is a photograph illustrating the external shape of example embodiments of organic thin film transistors incorporating banks formed by a method according to an example embodiment of the disclosed methods; and

FIG. 5A is an example embodiment of an ink-jet profile corresponding to example embodiments of organic thin film transistors incorporating banks formed by a method according to an example embodiment of the disclosed methods, and FIG. 5B is an example embodiment of an ink-jet profile corresponding to organic thin film transistors that do not incorporate a bank according to any example embodiments.

It should be noted that these Figures are intended to illustrate the general characteristics of methods and materials of certain example embodiments and to supplement the written description provided below. These drawings are not, however, to scale and may not precisely reflect the precise structural characteristics of any given embodiment, and should not be interpreted as defining or limiting the range of values or properties encompassed by example embodiments. In particular, the relative thicknesses and positioning of layers or regions may be reduced or exaggerated for clarity. The use of similar or identical reference numbers in the various drawings is intended to indicate the presence of a similar or identical element or feature.

Claims

1. A method of forming banks on a substrate comprising: applying an aqueous solution of a water-soluble polymer, a UV curing agent and a water-soluble fluorine compound to the substrate.

2. The method of forming banks according to claim 1, wherein the method further comprises: (1) forming a coating on the substrate from the aqueous solution;(2) irradiating portions of the coating with UV light to form an exposed layer; and(3) developing the exposed layer with an aqueous developing composition to form a bank pattern.

3. The method of forming banks according to claim 1, wherein: the water-soluble fluorine compound is a fluoroalkane.

4. The method of forming banks according to claim 3, wherein: the fluoroalkane contains a silanol group.

5. The method of forming banks according to claim 1, wherein: the water-soluble fluorine compound and the water-soluble polymer are present in the aqueous solution at a ratio of 1:10 to 1:1, based on the solids content.

6. The method of forming banks according to claim 1, wherein: the water-soluble polymer is selected from a group consisting of polyvinyl alcohol, polyvinyl chloride, polyacryl amide, polyethylene glycol, polyethylene oxide, polymethyl vinyl ether, polyethylene imine, polyphenylene vinylene, polyaniline, polypyrrole, mixtures thereof and copolymers thereof.

7. The method of forming banks according to claim 6, wherein: the copolymer includes from 10 to 99% by weight water-soluble polymer.

8. The method of forming banks according to claim 1, wherein: the UV curing agent includes a compound selected from a group consisting of ammonium dichromate, pentaerythritol triacrylate, urethane acrylate and mixtures thereof.

9. The method of forming banks according to claim 1, wherein: the UV curing agent and the water-soluble polymer are present in the aqueous solution at a ratio of 1:100 to 1:20, based on the solids content.

10. The method of forming banks according to claim 1, wherein: applying the aqueous solution includes a method selected from a group consisting of spin coating, dip coating, printing, ink-jet printing and roll coating.

11. The method of forming banks according to claim 1, wherein: irradiating the coating includes exposing portions of the coating to UV radiation at an exposure energy of 300 to 500 W per square centimeter at a wavelength of 340 to 400 nm for an exposure period of 10 to 180 seconds.

12. The method of forming banks according to claim 2, wherein: developing the exposed layer includes treating the exposed layer with deionized water at a developing temperature of about 25° C. for a developing period of 1 to 5 minutes.

13. The method of forming banks according to claim 2, further comprising: drying the aqueous solution to form the coating on the substrate; andbaking the bank pattern.

14. The method of forming banks according to claim 13, wherein: baking the bank pattern includes exposing the bank pattern to a bake temperature of 50 to 200° C. for a bake period of 0.5 to 2 hours.

15. A method of fabricating an organic thin film transistor comprising: preparing a substrate,forming a gate electrode, a gate insulating film, and source/drain electrodes on the substrate;applying an aqueous solution of a water-soluble polymer, a UV curing agent and a water-soluble fluorine compound to the substrateforming a coating on the substrate from the aqueous solution;irradiating portions of the coating with UV light to form an exposed layer; anddeveloping the exposed layer with an aqueous developing composition to form a bank pattern defining discrete semiconductor regions; anddepositing an organic semiconductor material in the semiconductor regions.

16. The method of fabricating an organic thin film transistor according to claim 15, wherein: the bank pattern is formed on the source/drain electrodes.

17. The method of fabricating an organic thin film transistor according to claim 15, wherein: the gate insulating film is made of a material selected from a group consisting of polyvinyl phenol, polymethyl methacrylate, polyacrylate, polyvinyl alcohol, silicon oxynitride, SiNx, wherein 0<x<4, SiO2, Al2O3, and mixtures, combinations and derivatives thereof.

18. The method of fabricating an organic thin film transistor according to claim 15, wherein: the organic semiconductor material is selected from a group consisting of polythiophene, polyaniline, polyacetylene, polypyrrole, polyphenylene vinylene, and combinations, mixtures and derivatives thereof.

19. The method of fabricating an organic thin film transistor according to claim 15, wherein: the gate electrode, the source electrode and the drain electrode each comprise a conductor selected from a group consisting of gold (Au), silver (Ag), aluminum (Al), nickel (Ni), molybdenum (Mo), tungsten (W), indium-tin oxide (ITO), indium-zinc oxide (IZO), metal nitrides, polythiophene, polyaniline, polyacetylene, polypyrrole, polyphenylene vinylene, and polyethylenedioxythiophene (PEDOT)/polystyrenesulfonate (PSS) mixtures and combinations, alloys and mixtures thereof.

20. The method of fabricating an organic thin film transistor according to claim 15, wherein: the substrate is selected from a material selected from a group consisting of glass, silicon, plastic and combinations thereof.

21. An organic thin film transistor comprising: a gate electrode;a source electrode;a drain electrode;an organic semiconductor; anda bank structure surrounding and containing the organic semiconductor, wherein the bank structure includes a quantity of an water-soluble fluorine compound sufficient to produce a contact angle greater than a target value.