JP2004072049A - Organic tft element and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic TFT element which is improved in reliability, reduced in cost, increased in surface area, and applicable to a next-generation display device. <P>SOLUTION: A first organic insulating film 120 is formed on a first base 100, a TFT (thin film transistor) 130 formed of organic semiconductor material is provided thereon, and a second organic insulating film 110 is laminated on the TFT 130 for the formation of the organic TFT element. The organic TFT 130 is sandwiched between the first organic insulating film 120 and the second organic insulating film 110 so as to be inactivated so that the organic TFT element which hardly changes in characteristics with time can be obtained. The organic insulating films 120 and 110 are formed of the same material so that the processes of manufacturing the organic TFT element can be simplified, and the organic TFT element can be reduced in manufacturing cost. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a TFT (thin film transistor) element using an organic semiconductor material, which enhances the reliability of the TFT (thin film transistor), achieves the same constituent material, reduces the manufacturing cost, and further uses the thin film transistor. The present invention relates to an organic TFT element in which an organic TFT is formed on a plastic substrate or the like without restriction on a substrate, and a method for manufacturing the same.
[0002]
[Prior art]
Organic TFT elements, unlike Si semiconductor devices, are inexpensive, can be made larger, can be formed on plastic substrates, and are stable against mechanical shock. Research is being done energetically.
However, the organic TFT element has a problem that the characteristic is significantly deteriorated due to the influence of moisture, oxygen and the like in the atmosphere.
The organic TFT on the glass substrate has been attempted to shield the moisture and oxygen with a passivation film after the device is formed. However, a problem that occurs as the passivation is that the organic layer of the organic TFT has an extremely high temperature (ie, (In general, the temperature exceeds about 100 ° C.), so that an effective passivation film has not been obtained.
[0003]
Japanese Patent Application Laid-Open No. 9-161967 proposes a method of inactivating an organic thin film element formed on a plastic substrate. The present invention proposes a problem inherent to a plastic substrate, that is, inactivation of an organic semiconductor element from permeated oxygen and moisture from the substrate side, which is characterized by arranging a laminated multilayer film of an inorganic substance and an organic substance. . However, this conventional technique involves problems related to the enhancement of the reliability of the laminated film, complexity due to an increase in the number of steps, and an increase in manufacturing cost.
[0004]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and solves the problems of the prior art, improves the reliability of organic TFT elements, achieves large-area fabrication at low cost, and is applied to next-generation display elements. An object of the present invention is to provide an organic TFT element having a structure that can be made possible and a method for manufacturing the same.
[0005]
[Means for Solving the Problems]
As a means for solving the above-mentioned problems, the invention according to claim 1 includes, in an organic TFT element formed on a first substrate, forming a first organic insulating film on the first substrate, A TFT (thin film transistor) made of an organic semiconductor material is formed thereon, and then a second organic insulating film is stacked.
According to a second aspect of the present invention, in the organic TFT element according to the first aspect, the first organic insulating film and the second organic insulating film are formed of the same organic material.
According to a third aspect of the present invention, in the organic TFT device according to the first aspect, the gate insulating film is made of the same material as the first organic material and the second organic material.
According to a fourth aspect of the present invention, there is provided the organic TFT element according to any one of the first to third aspects, wherein the organic insulating film constituting the organic TFT element is formed of an organic material or a chemical vapor deposition using the gas. It is characterized by being an organic film formed by a method.
According to a fifth aspect of the present invention, in the organic TFT element according to any one of the first to fourth aspects, the organic insulating film is made of a parylene material.
[0006]
According to a sixth aspect of the present invention, in the method of manufacturing an organic TFT element according to any one of the first to fifth aspects, a step of forming a first organic insulating film on a first base material is provided. And a step of forming a TFT made of an organic semiconductor material thereon, and a step of laminating a second organic insulating film thereon. In the step of forming the organic insulating film, an organic material or a gas thereof is used. An organic film is formed by the chemical vapor deposition method used.
[0007]
The invention according to claim 7 uses the organic TFT element according to any one of claims 1 to 5, and after bonding the organic TFT element to a second base, the first base and the first base. And the organic TFT is transferred onto the second substrate by peeling off at the interface of the organic insulating film.
The invention according to claim 8 provides a step of manufacturing an organic TFT element by the method of manufacturing an organic TFT element according to claim 6, a step of bonding the organic TFT element to a second base material, and Separating the organic TFT on the second substrate by peeling off at the interface between the first substrate and the first organic insulating film.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In order to solve the above-mentioned problems, in the present invention, as a first embodiment, a first organic insulating film is formed on a first base material, an organic TFT is formed thereon, and a second organic insulating film is formed. Passivation is performed on the film. For the first and second organic insulating films, a material having excellent water and oxygen shielding properties is used, and by using both materials as a common material, the manufacturing apparatus and the process are simplified, and the manufacturing cost is reduced. To achieve a reduction.
A field-effect transistor used for a silicon (Si) device is adopted as the organic TFT of the present invention, and the gate insulating film, which is a transistor constituent part, is made of a material common to the first and second organic insulating films. By doing so, the simplification of the manufacturing apparatus and the simplification of the process can be similarly achieved.
[0009]
Further, as a second embodiment, even when an Si wafer, a glass substrate, or a ceramic substrate is used as the first base material, the element is finally transferred to the plastic substrate by transferring the element to the plastic substrate. The obtained organic TFT element is obtained. The organic TFT element completed in this manner is not destroyed by mechanical shock, and is therefore suitable for a large-screen display sheet.
[0010]
In the present invention, an Si wafer, a glass substrate, a ceramic substrate, or a plastic sheet is used as the first base material. Preferred properties of the first organic insulating film include: excellent shielding properties against permeation of water, oxygen, and the like; excellent resistance to chemicals during TFT fabrication described below; In the second embodiment of the present invention, after the organic TFT element is formed, it is bonded to the second substrate with an adhesive, and then the first substrate is formed under appropriate conditions. Therefore, it satisfies that it has excellent mechanical strength and that it can be easily peeled at the time of peeling. Further, when an organic EL material is used as a display element, it is required to be transparent. When a plastic sheet is used as the second base material, the base material may be deformed by the internal stress of the organic film, so that it is required that the organic film has no internal stress.
[0011]
As a suitable method for forming such an organic insulating film, it is desirable to form a film by a chemical vapor deposition method (chemical vapor deposition method (CVD method)). In this case, a parylene material can be used as a specific material of the organic insulating film.
The parylene film is a coating film made of a polyparaxylylene resin developed by Union Carbide Chemicals and Plastics Co. of the United States by a gas phase synthesis method. This coating film is formed by vaporizing and thermally decomposing a solid diparaxylylene dimer as a raw material, and generating a stable reaction of the stable diradical paraxylylene monomer at the time of adsorption and polymerization on the substrate. This coating film is capable of precision coating that is impossible with conventional liquid coating or powder coating, and can be coated at room temperature regardless of the shape and material of the adherend at the time of coating. Due to its unique properties, it is known as the most suitable conformal coating film, from coating of ultra-precision parts to coating of general-purpose products. Specifically, it can be applied to the coating of insulating film of hybrid IC, prevention of dust generation of disk drive parts, lubrication film of stepping motor, and corrosion prevention film of biomaterial.
[0012]
In the present invention, an organic TFT is formed on such a first organic insulating film. After that, a passivation film (a second organic insulating film) is formed.
The fact that the second organic insulating film can sufficiently cover the steps of the base is added to the properties of the first organic insulating film, and as a result, the second organic insulating film is formed by a chemical vapor deposition method using a parylene material. By performing the first and second organic insulating films with this parylene film, it is possible to achieve each required performance, and furthermore, it is manufactured by a single manufacturing apparatus, thereby simplifying the process and realizing low manufacturing cost. Is done. Needless to say, since the materials are of the same quality, the adhesion between the layers is excellent.
[0013]
The effect described above is further accelerated by forming the gate insulating film, which is a constituent member of the organic TFT element, from this parylene material. The TFT gate insulating film is required to have a high dielectric breakdown voltage and a low dielectric loss, and those values of the parylene material are 3 MV / cm and 0.015 (1 KHz). This value has the same performance as a thermal oxide film of a polycrystalline silicon film formed by thermal CVD on quartz glass.
The oxygen gas barrier property of the parylene film (1 mil per 100 square inches, room temperature, 1 atmosphere, after standing for 24 hours; 1 mil is 1/1000 inch) is 7 cm ^3, which is 5 to 10% of epoxy resin. Equivalent, and as small as about 1/1000 of silicone resin or urea resin.
In the results of the ASTM (American Society for Testing and Material) test D570, the water absorption shows a small value of 0.1% or less (1.4% for polyimide resin).
[0014]
As a second embodiment of the present invention, an element can be formed on any substrate by transferring an organic TFT to a second substrate. For example, a technique of manufacturing an organic TFT on a first base material and transferring the organic TFT to a second base material via an adhesive causes a reduction in adhesion between the first base material and the first organic insulating film interface. This is performed by causing That is, after joining the second base material, it is cut into a desired shape, a new cross section is formed, the liquid phase penetrates into the above-described interface from this cross section, the adhesion is reduced, and then the separation is performed. is there. The liquid phase can be water, alcohol, acetone, or common organic solvents. In order to peel without damaging the organic TFT, it is sufficient that the organic TFT has an adhesion of about 10 g / cm or less in a 90 ° peel test. Since peeling is performed at the interface, damage to the organic TFT is reduced. That is, according to the second embodiment of the present invention, a large substrate, an inexpensive substrate, a light substrate, a substrate that can withstand deformation, and a substrate that does not crack can be used as a substrate finally mounted on a product. Therefore, it is possible to configure an organic TFT element that is inexpensive, lightweight, and excellent in impact resistance and the like.
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
[0015]
[First Embodiment]
FIG. 1 is a schematic cross-sectional view of an essential part of an organic TFT element according to a first embodiment of the present invention, which is a configuration example of an organic TFT element formed on a first base material 100. The feature is that it has a structure in which an organic TFT layer 130 which is easily damaged by water and oxygen is sandwiched between a first organic insulating film 120 and a second organic insulating film 110.
As a method for manufacturing this organic TFT element, first, as shown in FIG. 2, a first organic insulating film 120 is formed on a first base material 100, and a TFT layer 130 made of an organic semiconductor material is formed thereon. I do. Then, as shown in FIG. 1, a second organic insulating film 110 is laminated on the organic TFT layer 130.
Here, as a method for forming the first organic insulating film 120 and the second organic insulating film 110, as described above, an organic material film is formed by a chemical vapor deposition method (CVD method) using a parylene material. .
The organic TFT exemplifies an inverted staggered TFT structure as shown in FIG. 3, and includes an organic semiconductor layer 131, a gate insulating film 132, a gate electrode 133, and a source / drain electrode 134.
[0016]
[Second embodiment]
Next, in the second embodiment of the present invention, as shown in FIG. 4, the second base material 150 is provided on the second organic insulating film 110 of the organic TFT element having the structure shown in FIG. Glue.
Preferred examples of the adhesive constituting the adhesive layer 140 include a reaction-curable adhesive, a thermosetting adhesive, a light-curable adhesive such as an ultraviolet-curable adhesive, and an adhesive such as an anaerobic-curable adhesive. No. The adhesive may be of any composition, for example, epoxy, acrylate, or silicone. The formation of the adhesive layer 140 is performed by, for example, a coating method.
[0017]
Here, when a curable adhesive is used for the adhesive layer 140, for example, an adhesive is applied on the second organic insulating film 110, and the second base material 150 is bonded thereon, and then the adhesive is applied. The adhesive is cured by a curing method according to the characteristics, and the second organic insulating film 110 and the second base material 150 are bonded and fixed.
[0018]
When a photocurable adhesive is used for the adhesive layer 140, for example, an adhesive is applied on the second organic insulating film 110, and after bonding the second base material 150 thereon, If the base material 100 is light-transmitting, one of the first base material 100 side, and if the second base material 150 is light-transmitting, from the second base material 150 side. The adhesive is cured by irradiating the adhesive with light from the side, and the second organic insulating film 110 and the second base material 150 are bonded and fixed. The adhesive may be irradiated with light from both the side of the light-transmissive first base material 100 and the side of the light-transmissive second base material 150. As the adhesive used here, an adhesive of an ultraviolet curing type or the like, which hardly affects the second organic insulating film 110 and the TFT element thereunder, is desirable.
[0019]
Instead of forming the adhesive layer 140 on the side of the second organic insulating film 110, the adhesive layer 140 is formed on the side of the second base material 150, and the second organic insulating layer 140 is formed through the adhesive layer 140. The second substrate 150 may be bonded to the film 110. In the case where the second base material 150 itself has an adhesive function, the formation of the adhesive layer 140 may be omitted.
[0020]
As the mechanical properties of the second base material 150, those having a certain degree of rigidity (strength) are used depending on the type of equipment to be manufactured, but may be flexible or elastic.
As the second base material 150, for example, an optimum material depending on the type of equipment to be manufactured, such as an inexpensive glass substrate having a not so high melting point, a thin plastic substrate in a sheet shape, or a considerably thick plastic substrate, is used. Further, the second base material 150 may be not a flat plate but a curved one.
[0021]
When a plastic substrate is used as the second base material 150, the synthetic resin constituting the plastic substrate may be either a thermoplastic resin or a thermosetting resin. For example, polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), cyclic polyolefin, modified polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polyimide, polyamideimide , Polycarbonate, poly- (4-methylbenten-1), ionomer, acrylic resin, polymethyl methacrylate, acryl-styrene copolymer (AS resin), butadiene-styrene copolymer, polio copolymer (EVOH), Polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and precyclohexane terephthalate (PCT), polyether, polyether ketone (PEK), polyether ether ketone (PEEK), polyetherimide, polyacetal (POM), polyphenylene oxide, modified polyphenylene oxide, polyarylate, aromatic polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluororesins, styrene, polyolefin Type, polyvinyl chloride type, polyurethane type, fluoro rubber type, chlorinated polyethylene type etc. various thermoplastic elastomers, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester, silicone resin, polyurethane etc. or these Main copolymers, blends, polymer alloys and the like can be mentioned, and a laminate of one or more of these can be used.
[0022]
When a plastic substrate is used as the second base material 150, the large-sized second base material 150 can be integrally formed. In addition, if the second base material 150 is a plastic substrate, it can be easily manufactured even if it has a complicated shape, such as one having a curved surface or irregularities. Furthermore, if the second base material 150 is a plastic substrate, there is an advantage that material costs and manufacturing costs can be reduced. Therefore, if the second substrate 150 is a plastic substrate, it is advantageous when manufacturing a large and inexpensive device.
[0023]
Next, as shown in FIG. 5, peeling is performed from the interface between the first base material 100 and the first organic insulating film 120. In this step, it is possible to reduce the adhesion of the first organic insulating film 120 by cutting the end of the laminate of FIG. 4 and allowing the liquid layer to enter from the end of the fractured surface. As the liquid layer, water, alcohols, and general organic solvents can be used. Further, these liquid phases may be vapor.
Therefore, by causing the liquid layer to enter the interface between the first base material 100 and the first organic insulating film 120 to reduce the adhesion of the first organic insulating film 120, as shown in FIG. If a force is applied to peel off the first base material 100, the first base material 100 can be easily peeled off at the interface with the first organic insulating film 120.
In addition, by recycling (recycling) the first base material 100 after the separation, manufacturing cost can be reduced.
[0024]
【Example】
[Example 1]
As a specific example of the first embodiment of the present invention, an organic TFT layer 130 was formed on the first base 100 side.
First, a first organic insulating film 120 made of a parylene film is formed on a first base material 100 made of a Si substrate. In this example, a parylene film was formed by a chemical vapor deposition method (CVD method) using a 4-inch Si wafer.
The parylene film is sublimated at a temperature of 100 to 170 ° C. under reduced pressure from diX_C manufactured by Daiichi Kasei Co., Ltd. as a raw material, and subsequently introduced into a pyrolysis furnace. After the thermal decomposition temperature is set to 650 ° C. and the dimer is dissociated, it is introduced into a film forming chamber in which a Si wafer is installed, and the film is formed at room temperature. Thus, a parylene film having a thickness of 10 μm is formed.
[0025]
Next, the organic TFT layer 130 is formed on the first organic insulating film (parylene film) 120.
As a method for forming the organic TFT 130 layer, first, a 50 nm-thick Cr metal film is deposited as a gate electrode 133 by a sputtering method, and the gate electrode 133 having a desired pattern is formed by photolithography and etching.
Next, a gate insulating film 132 is formed on the gate electrode 133. This film is formed by spin-coating an organic insulator film. As a specific example, a 100-nm-thick gate insulating film 132 is formed using polyvinyl butyral as the organic insulator film.
Next, the organic semiconductor film 131 is formed over the gate insulating film 132. As a specific example, a polyhexylthiophene organic semiconductor material is formed to a thickness of 80 nm by spin coating.
The patterning of the element and the gate electrode contact are made by photolithography and etching. Further, a certain resist pattern is used as an interlayer insulating film having a contact hole without being removed after the etching step.
Next, source / drain electrodes 134 are formed on the organic semiconductor film 131.
Next, a second organic insulating film 110 serving as a passivation film is formed on the organic TFT layer 130 formed as described above by a chemical vapor deposition method (CVD method) using a parylene material.
[0026]
[Comparative Example 1]
In Example 1, an organic TFT device having a similar configuration was manufactured by replacing the parylene film used for the first and second organic insulating films with a polyimide film, and the characteristics of the organic TFT device over time were compared. The evaluation items are as follows: the source-drain voltage of the transistor static characteristics is 20 V, the current (Ioff) flowing between the source-drain current when a gate voltage of 0 V is applied, and the current (Ion) flowing between the source-drain current when a gate voltage of 20 V is applied. (On / off ratio) was determined, and the change over time in the device shown in Example 1 and the device shown in Comparative Example 1 was obtained. The sample storage conditions are a dark room, a temperature of 50 ° C., and a humidity of 50%.
The initial on / off ratio of the parylene film sample of Example 1 was 5 × 10 ⁴ , and the value after 1000 hours was 3 × 10 ⁴ , which was almost equal to the initial value. On the other hand, in the case of the polyimide film sample of Comparative Example 1, the initial on / off ratio was 5.5 × 10 ⁴ , and the value after 1000 hours was 5 × 10 ³ , a decrease of one digit was observed. This reduction in the on / off ratio was caused by an increase in the off current value.
[0027]
[Example 2]
A parylene film was used for the gate insulating film 132 of the organic TFT 130 of the first embodiment. It was manufactured in the same manner as in Example 1 before the gate insulating film 132 was formed. The parylene material used was a fluorine-containing parylene having excellent film formation controllability due to its low vapor pressure. DiX-F manufactured by Daiichi Kasei Co., Ltd. was used to form a 500-nm thick gate insulating film 132 by chemical vapor deposition. (CVD method).
The on / off ratio of the organic TFT element of Example 2 was 4.5 × 10 ⁴ , which was equivalent to the performance of a conventional product.
[0028]
[Example 3]
In the first and second embodiments, the organic TFT element is formed on the Si substrate. In the present embodiment, an example of manufacturing the organic TFT element on the second substrate by the transfer described in the second embodiment is described. explain.
The method of manufacturing an organic TFT on the first base material 100 is the same as that of the second embodiment. However, the parylene film thickness of the first organic insulating film 120 was 20 μm.
Next, as shown in FIG. 4, an adhesive layer 140 made of epoxy resin is formed as an adhesive layer formed on the second organic insulating film 110 of the organic TFT element. A plastic sheet (second base material) 150 is attached to the element. Next, heat of 80 ° C. or lower is applied to the adhesive layer 140 to cure the epoxy resin, and the second substrate 150 and the side of the organic TFT element are bonded. Note that the adhesive layer 140 may be an ultraviolet-curable adhesive. In this case, the ultraviolet-curable adhesive is cured by irradiating ultraviolet rays from the second substrate 150 side. Next, one end of the first base material 100 is cut to secure a liquid phase entry path to the interface with the first organic insulating film 120, and a peeling step is performed as shown in FIG. Isopropyl alcohol was used for the liquid layer.
In this way, after the peeling phenomenon occurs at the interface between the first base material 100 and the first organic insulating film (parylene film) 120, the first base material 100 is peeled off, and the plastic sheet (the second base material) is removed. The organic TFT is transferred to the material 150. The organic TFT element manufactured in this way has an advantage that it is strong against bending and lightweight, and thus is strong against dropping.
[0029]
【The invention's effect】
As described above, in the present invention, a structure in which an organic TFT is sandwiched by using a first organic insulating film and a second organic insulating film, and the organic TFT having little change with time is made inactive by inactivating the organic TFT. An element can be provided. In addition, since the first and second organic insulating films are made of the same material, the manufacturing process can be simplified, and the manufacturing cost of the device can be reduced. Further, the cost can be further reduced by forming the gate insulating film constituting the organic TFT element from the same material as the first and second organic insulating films. Further, by transferring the organic TFT element from the first base material to the second base material (for example, a plastic base material), the organic TFT element can be manufactured on the plastic base material, and the mechanical strength is excellent. A large-area organic TFT element can be provided. Therefore, according to the present invention, it is possible to improve the reliability of an organic TFT element, achieve large-area fabrication at low cost, and enable application to a next-generation display element.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a principal part of an organic TFT device according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a principal part showing a state where a first organic insulating film and an organic TFT layer are stacked on a first base material.
FIG. 3 is a diagram showing a structural example of an organic TFT.
FIG. 4 is an explanatory view of a second embodiment of the present invention, showing a state in which a second base material is bonded to the organic TFT element having the structure shown in FIG. 1 via an adhesive layer.
FIG. 5 is an explanatory view of a second embodiment of the present invention, showing a state in which the first substrate is peeled from the state of the laminated structure shown in FIG. 4 and the organic TFT is transferred to the second substrate. FIG.
[Explanation of symbols]
100: first base material 110: second organic insulating film 120: first organic insulating film 130: organic TFT layer 131: organic semiconductor 132: gate insulating film 133: gate electrode 134: source / drain electrode 140: adhesion Layer 150: second substrate

Claims (8)

In the organic TFT element formed on the first substrate,
A first organic insulating film is formed on a first base material, a TFT (thin film transistor) made of an organic semiconductor material is formed thereon, and then a second organic insulating film is laminated. Organic TFT element. The organic TFT device according to claim 1,
An organic TFT device, wherein the first organic insulating film and the second organic insulating film are formed of the same organic material. The organic TFT device according to claim 1,
An organic TFT device wherein the gate insulating film is of the same quality as the first organic material and the second organic material. The organic TFT device according to any one of claims 1 to 3,
An organic TFT element, wherein the organic insulating film as a component thereof is an organic material or an organic material film formed by a chemical vapor deposition method using the gas. The organic TFT device according to claim 1, wherein
An organic TFT device, wherein the organic insulating film is made of a parylene material. A manufacturing method for manufacturing the organic TFT element according to claim 1,
A step of forming a first organic insulating film on a first base material, a step of forming a TFT made of an organic semiconductor material thereon, and a step of laminating a second organic insulating film thereon In the method of manufacturing an organic TFT element, in the step of forming the organic insulating film, the organic material film is formed by a chemical vapor deposition method using an organic material or a gas thereof. The organic TFT element according to claim 1, wherein the organic TFT element is bonded to a second substrate, and then peeled off at the interface between the first substrate and the first organic insulating film. An organic TFT element obtained by transferring an organic TFT onto a second base material. 7. A step of producing an organic TFT element by the method for producing an organic TFT element according to claim 6, a step of joining the organic TFT element to a second substrate, and after joining, the first substrate and the first organic substrate. Transferring the organic TFT onto the second substrate by peeling off at the interface of the insulating film.

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