JP5217224B2 - Thin film transistor manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a thin film transistor, a thin film transistor, and an image display device. The present invention relates to a manufacturing method of a thin film transistor used particularly for an image display device, a thin film transistor manufactured by the manufacturing method, and an image display device in which a plurality of the thin film transistors are arranged.

  In recent years, thin film transistors using organic semiconductors (hereinafter simply referred to as “organic TFTs”) have been actively studied from the viewpoints of flexibility, weight reduction, cost reduction, and the like, driving circuits such as organic EL and electronic paper, Application to electronic tags is expected.

  In various devices using organic TFTs, it is important to form an organic semiconductor pattern. For example, a drive circuit for electronic paper has a plurality of organic TFTs arranged in a matrix. By patterning the organic semiconductor and separating the elements, it is possible to suppress a current flowing between adjacent elements, which is a factor that impairs image display quality. Note that element isolation means that an individual element is not bridged by an element adjacent to the element and a semiconductor.

  In general, methods for element separation of organic TFTs include a mask vapor deposition method, a photolithography method, and a lift-off method. Mask vapor deposition, photolithography, lift-off, and the like are not suitable for forming a device having a large number of steps and a large area at low cost. On the other hand, a direct drawing method using an inkjet method has also been reported (see Patent Document 1 and Non-Patent Document 1). In order to suppress wetting and spreading of the organic semiconductor, a step of patterning the surface energy of the base material in advance is necessary (see Patent Document 1), or material process restrictions are large due to restrictions such as ink viscosity (Non-Patent Document 1). See)), and the effectiveness for cost reduction and area increase is limited.

Further, when the semiconductor layer is patterned by the above conventional method, a step is generated between the portion where the semiconductor layer is present and the portion where the semiconductor layer is not present, and there is a problem due to the step when the sealing layer and the interlayer insulating layer are stacked. May occur. In particular, when the lamination of the sealing layer and the interlayer insulating layer is performed by a printing method, the problem is great.
U.S. Pat. No. 6,400,397 K. E. Paul, Appl. Phys. Lett. 2003, Vol. 83, pp. 2070-2072

  The object of the present invention has been made in view of the above-mentioned problems, and a method of manufacturing a thin film transistor capable of element isolation by a simpler manufacturing process, a thin film transistor manufactured by the manufacturing method, and an image in which a plurality of the thin film transistors are arranged It is to provide a display device. Another object of the present invention is to provide a method for manufacturing a thin film transistor that can be easily laminated such as a sealing layer and an interlayer insulating layer, and a thin film transistor and an image display device manufactured by the manufacturing method.

According to a first aspect of the present invention, there is provided a step of forming a pair of main electrode regions disposed on an insulating substrate so that a gate electrode, a gate insulating film, a comb source electrode and a comb drain electrode are engaged with each other. A step of forming an organic semiconductor layer on the entire surface of the insulating substrate including the pair of main electrode regions and a channel region between the organic semiconductor layer and the pair of main electrode regions by a screen printing method. A step of forming a sealing layer so as to penetrate over the source electrode and the drain electrode arranged so as to engage with each other, and a region where the sealing layer of the organic semiconductor layer is not formed using plasma treatment And a step of deactivating the thin film transistor.

  According to the present invention, in a method of manufacturing a thin film transistor using an organic semiconductor, the organic semiconductor can be patterned and elements can be separated by a simpler method compared to the conventional method. In addition, a thin film transistor such as a sealing layer or an interlayer insulating layer can be easily stacked.

  As shown in FIGS. 1A and 1B, the image display device 80 according to the embodiment of the present invention has a plurality of pixels arranged in a matrix. The pixel 50 includes a drain line (video signal line) 7 extending in a first direction (vertical direction in FIG. 1) and a second direction (horizontal direction in FIG. 1) intersecting the first direction. ) Extending to the gate wiring (vertical signal line). The capacitor wiring extends in the second direction in parallel with the gate wiring.

  The pixel 50 is configured by a direct circuit of the thin film transistor 20 and the pixel capacitor 13. As shown in FIGS. 1B and 2, the thin film transistor 20 includes a gate electrode 2, a source electrode 5, a drain electrode 6, an organic semiconductor layer 8, and a sealing layer 10. The pixel capacitor 13 includes a first electrode and a second electrode (not shown) opposite to the first electrode, and a dielectric including the deactivated organic semiconductor layer 9 between both. The capacitor electrode 11 includes a first electrode, a capacitor electrode 11 facing the first electrode and formed of the same layer as the gate electrode 2, and a dielectric between them. The capacitor wiring 12 is made of the same material in the same layer as the capacitor electrode 11.

  As the insulating substrate 1, soda lime glass, quartz, silicon wafer, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cycloolefin polymer, polyimide, polyethersulfone (PES), polymethyl methacrylate (PMMA), polycarbonate, Polyallylate or the like can be used, but is not limited thereto. The insulating substrate 1 is used by selecting a material from the viewpoint of necessary heat resistance.

  As the gate electrode 2 and the capacitor electrode 11 of the thin film transistor 20, a metal such as Al, Cr, Au, Ag, Ni, Cu and Mo, or a transparent conductive film such as ITO can be used. As a manufacturing method, a vacuum deposition method or a sputtering method can be used. A method of forming by etching using a mask formed by a photolithography technique after film formation can be used, but is not limited thereto. The gate wiring 3 is made of the same material in the same layer as the gate electrode 2 of the thin film transistor 20. Similarly, the capacitor wiring 12 is made of the same material in the same layer as the capacitor electrode 11.

The gate insulating film 4 of the thin film transistor 20 can be formed using an inorganic material or an organic material. The inorganic material _can be used _{SiO 2, Ba x Sr (1} -x) TiO 3, BaTi x Zr (1-x) O 3 or the like. As the organic material, polyester / melamine resin paste, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl phenol, polystyrene, cyanoethyl pullulan, and the like can be used. As the production method, for example, a spin coating method, a dip coating method, a screen printing method, a relief printing method, an intaglio printing method, a lithographic printing method, an ink jet method, a vacuum deposition method, a CVD method and the like can be used.

  The source electrode 5 and drain electrode 6 (a pair of main electrode regions) of the thin film transistor 20 and the pixel capacitor 13 can be made of the same material as the gate electrode 2 of the thin film transistor 20 or the like. As for the production method, in addition to the production method similar to the gate electrode 2 of the thin film transistor 20, printing methods such as screen printing method, flexographic printing method, gravure printing method, offset printing method and reverse printing method can be used. Ag ink, Ni ink, Cu ink, or the like can be used in printing formation. The drain wiring 7 is made of the same material in the same layer as the drain electrode 6 of the thin film transistor 20.

  The organic semiconductor layer 8 of the thin film transistor 20 can use an organic semiconductor such as pentacene, polythiophene, polyallylamine, and fluorenebiothiophene copolymer. As the production method, a spin coating method, a dip coating method, a vacuum deposition method, or the like is appropriately selected according to the material. The film thickness of the organic semiconductor layer 8 is 5 nm to 100 nm, preferably 5 nm to 50 nm. If the film thickness is thicker than necessary, it cannot be sufficiently deactivated in the process of deactivating the organic semiconductor layer 8 described later, resulting in insufficient element isolation.

  The sealing layer 10 of the thin film transistor 20 is patterned in the channel region on the organic semiconductor layer 8 (the source electrode 5 and the drain electrode 6, and the portion between the source electrode 5 and the drain electrode 6). In addition to the purpose of preventing the deterioration of the organic semiconductor due to the above, in the step of deactivating the organic semiconductor described later, it serves to protect the organic semiconductor layer 8 in the channel region. In the region where the sealing layer 10 is not formed, the deactivated organic semiconductor layer 8 having the same thickness as the organic semiconductor layer 8 is present.

  The sealing layer 10 of the thin film transistor 20 is not particularly limited as long as the characteristics of the organic semiconductor layer 8 are not impaired. For example, a fluororesin is used. Moreover, the thickness of the sealing layer 10 is 0.5 μm or more, preferably 2 μm or more. If it is thinner than 0.5 μm, a sufficient sealing effect cannot be obtained. As a pattern forming method of the sealing layer 10, various printing methods can be used, but a screen printing method is preferable in terms of resolution and film thickness.

As a method for deactivating the organic semiconductor layer 8 of the thin film transistor 20, plasma treatment is preferable. The plasma treatment is preferably performed in an inert gas atmosphere. When the treatment is performed in an active gas, the electrode may be damaged. Other deactivation methods include UV ozone cleaning and corona treatment, but a sufficient deactivation effect cannot be obtained. The deactivated organic semiconductor layer 8 has a resistivity of 1 × 10 ⁻⁶ Ωcm or higher without exhibiting semiconductor characteristics.

  A process chart of a method of manufacturing an image display device according to an embodiment of the present invention will be briefly described with reference to FIG. As shown in FIG. 3A, the gate electrode 2, the gate wiring 3, the capacitor electrode 11 and the capacitor wiring 12 are formed on the insulating substrate 1. Next, a gate insulating film 4 is formed on the gate electrode 2. Next, the source electrode 5, the drain electrode 6, the drain wiring 7, and the pixel capacitor 13 are formed on the gate insulating film 4. Next, as shown in FIG. 3B, the organic semiconductor layer 8 is formed on the entire surface of the source electrode 5, the drain electrode 6, and the pixel capacitor 13 formed on the insulating substrate 1. Next, as shown in FIG. 3C, the sealing layer 10 is pattern-formed on the organic semiconductor layer 8. Next, as shown in FIG. 3D, the organic semiconductor layer 8 in a region where the sealing layer 10 is not formed is deactivated so that element isolation is achieved.

  The thin film transistor and the image display device formed by the method for manufacturing a thin film transistor according to this embodiment of the present invention can be used as a liquid crystal display device and an organic EL display device.

  An image display device 80 shown in FIG. 1A was produced by the steps of FIGS. First, as shown in FIG. 3A, a PEN film is used as the insulating substrate 1, and Al is formed on the PEN film to a thickness of 50 nm by vacuum deposition. After formation, a gate electrode 2, a gate wiring 3, a capacitor electrode 11, and a capacitor wiring 12 were formed by etching using a mask formed by a photolithography technique. Next, the polyvinylphenol solution is spin-coated and then baked at 150 ° C. to form the gate insulating film 4 with a thickness of 1 μm. Next, the source electrode 5, the drain electrode 6, the drain wiring 7, and the pixel capacitor 13 were formed to have a width of 30 μm and a thickness of 500 nm by reverse printing using Ag ink.

  As shown in FIG. 3B, the polythiophene solution was spin-coated on the PEN film on which the various members were formed, and dried at 100 ° C. to form the organic semiconductor layer 8 with a thickness of 30 nm.

  As shown in FIG. 3C, a fluororesin solution was screen-printed and dried at 100 ° C. to form a sealing layer 10 having a thickness of 3 μm on the channel region.

Then, as shown in FIG. 3 (d), this base material is subjected to a plasma treatment for about 1 min in a N ₂ atmosphere under a power of 400 W, and the organic semiconductor layer in the region where the sealing layer 10 is not formed is deactivated. Turned into.

  In the image display device 80 obtained in this way, since there is no step between the portion where the semiconductor is present and the portion where the semiconductor is not present, which occurs in the conventional semiconductor layer forming method, problems in stacking other layers are small.

(A) is sectional drawing of the image display apparatus which concerns on one embodiment of this invention, (b) is a top view of 1 pixel of the image display apparatus shown to (a). It is sectional drawing cut along line AA shown in FIG.1 (b). (A)-(d) is process explanatory drawing explaining the manufacturing method of the image display apparatus which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Gate electrode 3 Gate wiring 4 Gate insulating film 5 Source electrode 6 Drain electrode 7 Drain wiring 8 Organic semiconductor layer 9 Deactivated organic semiconductor layer 10 Sealing layer 11 Capacitor electrode 12 Capacitor wiring 13 Pixel capacity 20 Thin film transistor 50 Pixel 80 image display device

Claims (1)

Forming a pair of main electrode regions disposed on an insulating substrate so that a gate electrode, a gate insulating film, a comb-type source electrode and a comb-type drain electrode are engaged with each other;
Forming an organic semiconductor layer over the entire surface of the insulating substrate including the pair of main electrode regions;
A sealing layer that covers a channel region between the organic semiconductor layer and the pair of main electrode regions is formed by screen printing so as to penetrate over the source electrode and the drain electrode that are arranged to engage with each other. Process,
Inactivating a region of the organic semiconductor layer where the sealing layer is not formed using plasma treatment ;
A method for producing a thin film transistor, comprising:

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