JPWO2019208241A1 - Electrode forming method and electrode forming apparatus for organic thin film transistor, manufacturing method of organic thin film transistor, and organic thin film transistor - Google Patents

Abstract

For the purpose of providing a technique capable of forming an electrode having no step with the surroundings by a simpler manufacturing process, the electrode forming method for an organic thin film and the method for manufacturing an organic thin film according to the present invention are electrically insulating. The step of preparing the base layer formed of the resin material (step S102) and the coating liquid containing the solvent for softening the resin material constituting the base layer and the conductive electrode material are applied in a pattern according to the electrode shape. A step of partially applying the coating liquid to the surface of the base layer (step S104), a step of pressing the uncured coating liquid against the base layer (step S104), and a step of volatilizing the solvent to solidify the coating liquid to form an electrode. The step (step S105) is provided.

Description

The present invention relates to an electrode manufacturing technique suitable for manufacturing an organic thin film transistor.

For example, for the purpose of manufacturing a display device, a touch panel device, or the like, a technique for forming a thin film semiconductor element such as a thin film transistor on the surface of a substrate such as a glass substrate or a resin substrate is being researched. Particularly in recent years, organic semiconductors have been attracting attention as materials for thin film semiconductor devices from the viewpoints that performance and production technology have been remarkably improved and that devices can be manufactured using printing technology depending on the material.

For example, Patent Document 1 describes a technique for forming a thin film transistor using an organic semiconductor material on the surface of a substrate such as a glass substrate, a semiconductor substrate, or a resin substrate. In this technique, when an organic semiconductor layer is formed so as to cover an electrode formed on a substrate, the following is solved in order to solve the problem that a step on the electrode end with the substrate causes an increase in electrical resistance. The manufacturing method is used. That is, in this technique, the electrode material is laminated on the insulating polymer layer in a softened state, the polymer layer and the electrode layer are flattened by pressure, and then the polymer layer is cured. As a result, the electrode is embedded in the polymer layer, and an electrode having no step with the substrate is realized.

Patent Document 1 describes that as a method for realizing a softened polymer layer, a polymer precursor before cross-linking, a polymer before curing treatment, softening by heating, or the like can be used. Further, as a method for forming an electrode, a photolithography method, a lift-off method, etching, laser ablation, a method of patterning with a conductive ink using a printing technique such as inkjet printing or screen printing, and the like are listed.

Japanese Unexamined Patent Publication No. 2008-147346

In the above-mentioned conventional technique, it is necessary to form an electrode in a state where the polymer layer (resin layer) is softened. However, it is necessary that treatments such as transportation between steps, lamination of electrode materials, and flattening by pressurization are performed while maintaining a softened state of the polymer layer (resin layer). From this, it is considered that the actually applicable manufacturing process is limited, and special care is required in handling the substrate having the softened polymer layer. Therefore, there is room for improvement in the above-mentioned prior art in terms of practicality and manufacturing cost.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of forming an electrode having no step with the surroundings by a simpler manufacturing process.

One aspect of the present invention is an electrode forming method for an organic thin film in which an electrode is formed on the surface of a base layer formed of an electrically insulating resin material, and in order to achieve the above object, the base layer is formed. The step of preparing, the step of applying a coating liquid containing a solvent for softening the resin material constituting the base layer and the electrode material to the surface of the base layer in a pattern corresponding to the electrode shape, and the step of unsolidifying the above. It includes a step of pressing the coating liquid against the base layer and a step of volatilizing the solvent and solidifying the coating liquid to form the electrode.

In the invention configured as described above, the coating liquid applied to the base layer contains a solvent that softens the resin material constituting the base layer. Therefore, it is not necessary to soften the base layer in advance. That is, the base layer may have a certain hardness at the time when the coating liquid is applied. Therefore, various coating methods can be applied to the coating of the coating liquid containing the electrode material. Then, by pressing the uncured coating liquid against the base layer softened by the solvent, the coating liquid permeates into the inside of the base layer. By solidifying the coating liquid in this state, it is possible to form an electrode in which the step between the coating liquid and the base layer is eliminated. Hereinafter, the "electrode forming method for an organic thin film transistor" according to the present invention is simply abbreviated as an "electrode forming method", and the "electrode forming device for an organic thin film transistor" is simply abbreviated as an "electrode forming device". There is.

As described above, according to the electrode forming method of the present invention, the process of applying the coating liquid itself becomes a process of softening the base layer by using a solvent having the property of softening the base layer. ing. Therefore, an electrode embedded in the base layer, that is, having no step at the boundary with the base layer, is realized by a relatively simple manufacturing process of applying a coating liquid to a base layer having a certain hardness and pressing the coating liquid. It is possible. Further, the softening of the base layer is limited to the portion where the coating liquid is applied and comes into contact with the solvent, that is, the portion where the electrode should be formed. Therefore, other parts of the base layer are not affected by the disorder of the surface shape or the deterioration of the electrical insulating property, and the shape of the formed electrode is also suppressed from being deformed.

Further, in one aspect of the method for manufacturing an organic thin film transistor according to the present invention, in order to achieve the above object, the step of forming the electrode on the base layer by the above electrode forming method and the step of forming the electrode on the surface of the base layer are described. It includes a step of forming an organic semiconductor layer covering the electrodes. In the invention configured in this way, since the organic semiconductor layer is formed so as to cover the base layer and the electrode without a step, the disorder of crystallinity of the organic semiconductor caused by the step is suppressed. be able to. Therefore, it is possible to manufacture an organic thin film transistor having good performance by suppressing deterioration of the electrical characteristics of the semiconductor due to such disorder of crystallinity.

Another aspect of the present invention is an electrode forming apparatus for an organic thin film, which forms an electrode on the surface of a base layer formed of an electrically insulating resin material, in order to achieve the above object. A flat plate-like coating liquid containing a substrate holding portion that holds a substrate having the base layer, a solvent that softens the resin material constituting the base layer, and an electrode material supports a pattern patterned according to the electrode shape. The carrier holding portion that holds the carrier with the pattern supporting surface close to the surface to be coated of the base layer, the surface of the carrier opposite to the pattern supporting surface, or the coating of the substrate. It is provided with a roller-shaped pressing member that moves along the substrate while pressing the surface opposite to the coated surface.

In the invention configured as described above, the coating liquid can be applied to the base layer by adhering the carrier in which the coating liquid containing the solvent that softens the base layer is patterned to the base layer. Then, the electrode embedded in the base layer can be formed by infiltrating the coating liquid into the base layer whose pressure by the roller-shaped pressing member is softened. That is, the electrode forming apparatus having the above configuration is suitable for carrying out the electrode forming method according to the present invention.

In another aspect of the present invention, the base layer is a coating liquid containing a base layer formed of an electrically insulating resin material, a solvent for softening the resin material constituting the base layer, and an electrode material. By partially applying it to the layer and pressing it against the base layer and then solidifying it, the source electrode and the drain electrode embedded in the base layer are separated from each other and at least a part of the surface is exposed. An organic semiconductor layer that continuously covers the exposed surfaces of the source electrode and the drain electrode, and the surface of the base layer between the source electrode and the drain electrode, an insulating layer that covers the organic semiconductor layer, and the like. It is an organic thin film having a gate electrode that is in contact with an insulating layer, faces the organic semiconductor layer via the insulating layer, and is electrically insulated from the organic semiconductor layer.

In the invention configured in this way, since the source electrode and the drain electrode are embedded in the base layer according to the above principle, the step at the interface with the organic semiconductor layer is small, and therefore the disorder of the crystallinity of the organic semiconductor is suppressed. There is. Therefore, the organic thin film transistor to which the present invention is applied is a transistor having good electrical performance.

As described above, according to the present invention, a solvent having a property of softening the base layer is used as a solvent for the coating liquid. By doing so, it is possible to realize an electrode having no step at the boundary with the base layer by a relatively simple manufacturing process of applying the coating liquid to the base layer having a certain hardness and pressing the coating liquid.

The above and other objectives and novel features of the present invention will become more fully apparent by reading the following detailed description with reference to the accompanying drawings. However, the drawings are for illustration purposes only and do not limit the scope of the invention.

It is a flowchart which shows one Embodiment of the manufacturing method of a semiconductor element. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a figure which shows the structure of the semiconductor element in each manufacturing process. It is a schematic diagram explaining the embedding of an electrode in a transfer process process. It is a schematic diagram explaining the embedding of an electrode in a transfer process process. It is a schematic diagram explaining the embedding of an electrode in a transfer process process. It is a figure which illustrates the structure of the prototype organic thin film transistor. It is a figure which illustrates the structure of the prototype organic thin film transistor. It is a figure which illustrates the structure of the prototype organic thin film transistor. It is a figure which illustrates the structure of the prototype organic thin film transistor. It is a figure which shows the example of the electrical property of the prototype organic thin film transistor. It is a figure which shows typically the cross-sectional structure of the transistor of the comparative example. It is a figure which shows the process of the electrode formation process. It is a figure which shows the process of the electrode formation process. It is a figure which shows the process of the electrode formation process. It is a figure which shows the process of the electrode formation process. It is a schematic diagram which shows the patterning process. It is a schematic diagram which shows the transfer process. It is a figure which shows the other aspect of the electrode formation process.

FIG. 1 is a flowchart showing an embodiment of a method for manufacturing a semiconductor device including the electrode forming method according to the present invention. 2A to 2D and 3A to 3E are diagrams showing the structure of the semiconductor device manufactured by this manufacturing method in each step. This manufacturing method can be used to form a semiconductor element on various flat plates such as a semiconductor substrate, a glass substrate, and a resin substrate. Hereinafter, a process for forming an organic thin film transistor as an example of a semiconductor element on the surface of, for example, a glass plate or a polyimide sheet as the substrate S will be described in detail. However, in addition to this, the following methods and devices can be used for forming various semiconductor elements.

In the following description, a structure in which various functional layers are laminated on the substrate S is referred to as a “work” as a processing target in each step, and is designated by a reference numeral Wk. The structure of such a structure changes sequentially with the progress of the manufacturing process, and all of them are referred to as work Wk. Further, in the following cross-sectional view of the work, since the structural features are clarified, the dimensions and relative thickness of each layer do not always match the actual ones.

First, the substrate to be treated is cleaned with an appropriate detergent (step S101), and the surface of the substrate is cleaned. Then, as shown in FIG. 2A, a resin layer to be the base layer B is formed on one surface Sa of the substrate S (step S102). The base layer B can be formed, for example, by uniformly applying a solution containing a material of a resin (for example, various polymer resins) that exhibits electrical insulation in a cured state to the substrate surface Sa by, for example, a spin coating method. can. The base layer B can be formed by using any forming method capable of forming a uniform layer without being limited to this.

When a method of applying a solution containing the material of the base layer B to the substrate S is used, a firing treatment is performed after the application in order to dry and cure the formed coating film (step S103). As a result, the coating film is cured to form the base layer B in close contact with the substrate surface Sa. In addition, a new layer can be formed on the surface of the cured base layer B. The base layer B has a function of covering the surface of the substrate S with a uniform and stable insulating layer and maintaining the shape of each layer formed in a subsequent step in a stable manner. In particular, since the base layer B functions as a primer layer, it is possible to improve the adhesion of the electrode to the substrate S and effectively prevent the electrode from collapsing or peeling off in the wet treatment described later.

As the polymer resin material constituting the base layer B, for example, polyurethane, polyimide, polyamideimide, polyvinyl alcohol, polyvinylphenol, polyester, polyethylene and the like can be used. In this case, the firing process for curing the polymer can be performed under the conditions of, for example, 120 ° C. for about 30 minutes. For example, the firing process can be executed by holding the work Wk for a predetermined time in a heating furnace such as an oven whose temperature is adjusted to a predetermined firing temperature. By adopting a polymer material that cures at such a low firing temperature, it is possible to use a resin material that does not have high heat resistance as a substrate. The work Wk may be allowed to stand in the heating furnace, or may be heated while being conveyed in the heating furnace.

A source electrode and a drain electrode constituting the organic semiconductor thin film transistor are formed on the surface of the base layer B thus formed (step S104). Various methods can be adopted for forming these electrodes. Here, as an example thereof, a method applying a printing technique in which an electrode is formed by transferring a preformed electrode pattern to the base layer B will be described.

As shown in FIG. 2B, an electrode pattern PT formed of a conductive material such as metal particles (for example, silver) and a conductive ink containing a solvent is previously formed on the surface of a blanket BL formed of a glass plate, a resin plate, or the like. It is formed. In this example, two electrode pattern PTs separated from each other are supported on the pattern supporting surface (lower surface in the figure) of the blanket BL. These two electrode patterns PT finally function as source electrodes and drain electrodes, respectively.

The blanket BL is arranged close to the work Wk with the pattern supporting surface facing the surface of the base layer B. From this state, as shown in FIG. 2C, the roller member RL is brought into contact with the blanket BL surface on the side opposite to the pattern supporting surface. The roller member RL rolls along the surface of the blanket BL while pushing the blanket BL toward the work WK side. As a result, the electrode pattern PT supported on the blanket BL is pressed against the base layer B and finally transferred to the surface of the base layer B. The pressing force on the blanket BL by the roller member RL can be, for example, 0.05 N / mm ² to 0.3 N / mm ² . The blanket BL after transfer at the time of transfer is carried out from the vicinity of the work Wk.

In order to obtain the conductivity of the transferred electrode pattern PT, the work Wk after transfer is fired (step S105). The firing conditions at this time can be, for example, 120 ° C. for 30 minutes, but it is not essential that the firing conditions are the same as those of the firing process in step S103. In the work Wk at this point, as shown in FIG. 2D, the source electrode Es and the drain electrode Ed formed by curing the transferred electrode pattern are embedded in the base layer B. There is. The principle of such embedding will be described later.

Next, as a process for modifying the surface of the formed electrode, a SAM process of forming a self-assembled monolayer (SAM) on the electrode surface is executed (step S106). Since the principle and method of SAM treatment are known, an example of a method of forming a SAM film by wet treatment will be briefly described here. Work Wk is immersed in a solution of Isopropyl alcohol (IPA) at a concentration of about 0.01 M in Pentafluorobenzenethiol (PFBT) for at least 2 minutes. After that, it is possible to form a SAM film by PFBT by rinsing with IPA and drying. By forming such a SAM film on the electrode surface, the electrical contact between the organic semiconductor layer and the electrode to be laminated thereafter can be made stable with low resistance. In the work Wk after the SAM treatment, as shown in FIG. 3A, a monolayer M made of PFBT is formed on the exposed surfaces of the electrodes Es and Ed in the work Wk.

Next, the organic semiconductor layer is laminated so as to cover the surface of the work Wk on which the electrodes Es and Ed are formed (step S107). The organic semiconductor layer can be formed by using, for example, a known vacuum vapor deposition method. As shown in FIG. 3B, the work Wk at this point is in a state in which the monolayer M covering the electrodes Es and Ed and the surface of the exposed base layer B are continuously covered by the organic semiconductor layer Sc. ing.

Next, a gate insulating layer covering the surface of the organic semiconductor film Sc is formed (step S108). The gate insulating layer is formed, for example, by depositing an electrically insulating material on the surface of the organic semiconductor film Sc using a known chemical vapor deposition (CVD). can do. As shown in FIG. 3C, the work Wk at this point is in a state where the entire surface of the organic semiconductor layer Sc is covered with the continuous gate insulating layer Ig.

Next, a gate electrode is formed on the surface of the gate insulating layer Ig (step S109). For example, the gate electrode can be formed by the same technique as the formation of the source electrode Es and the drain electrode Ed. That is, as shown in FIG. 3D, the blanket BL supporting the electrode pattern PT serving as the gate electrode is arranged close to the work Wk, and the blanket BL is pressed by the roller member RL (FIG. 2C) to gate the electrode pattern PT. Transfer to the surface of the insulating layer Ig. By firing this (step S110), as shown in FIG. 3E, the gate electrode Eg is formed on the surface of the gate insulating layer Ig.

The treatment conditions in the transfer treatment and the firing treatment in this case can also be the same as the treatment conditions at the time of forming the source electrode Es and the drain electrode Ed. For example, the pressing force of the roller member RL during the transfer treatment can be 0.05 N / mm ² to 0.3 N / mm ² , the firing treatment temperature can be 120 ° C., and the firing time can be 30 minutes.

Although not shown, an organic thin film transistor is added by appropriately adding additional steps such as a step of connecting each electrode by wiring and a step of forming a protective layer covering the surface of the formed device. The electronic device including the Tr is completed.

By the above series of processing, a structure in which the substrate S, the base layer B, the source and drain electrodes Es and Ed, the organic semiconductor layer Sc, the monolayer M, the gate insulating layer Ig, and the gate electrode Eg are laminated in this order is formed. Can be formed. Of these, the source and drain electrodes Es and Ed, the organic semiconductor layer Sc, the gate insulating layer Ig, and the gate electrode Eg collectively function as an organic thin film transistor Tr. The substrate S and the base layer B function as a base material that supports the organic thin film transistor Tr. In the actual manufacturing process, many organic thin film transistors Tr having the above-mentioned structure are simultaneously formed on one substrate S in a state of being lined up.

An example of the thickness of each layer is shown, but the thickness is not limited to these values. The thickness of the base layer B is, for example, 100 nm. The thickness of the source and drain electrodes Es and Ed is, for example, 70 nm. The thickness of the organic semiconductor layer Sc is 30 nm. Further, the distance between the source electrode Es and the drain electrode Ed, that is, the channel length is, for example, 50 μm. The thickness of the gate insulating layer Ig and the gate electrode Eg are, for example, 100 nm and 200 nm, respectively.

In order to ensure that the source and drain electrodes Es and Ed are embedded in the base layer B, the thickness of each layer is such that the thickness of the base layer B is larger than the thickness of the electrode pattern PT on the blanket BL. May be set.

One condition for obtaining good electrical characteristics in the organic thin film transistor Tr is that the organic semiconductor layer Sc has good crystallinity. That is, when the organic semiconductor layer Sc is polycrystalline with many grain boundaries, the performance of the organic thin film transistor Tr is limited by the low carrier mobility in the organic semiconductor layer Sc. In order to obtain high carrier mobility, the organic semiconductor layer Sc is required to have good crystallinity close to that of a single crystal.

In order to form an organic semiconductor layer Sc having good crystallinity on the work Wk on which the source and drain electrodes Es and Ed are formed, between the source and drain electrodes Es and Ed on the surface of the work Wk and the base layer B around the source and drain electrodes Es and Ed. Therefore, it is desirable that the surface has a smooth surface with few steps. As shown in FIG. 2D, the structure in which the source and drain electrodes Es and Ed are embedded in the base layer B can meet such a demand. Hereinafter, a configuration for realizing such an embedded structure in the present embodiment will be described.

4A to 4C are schematic views illustrating embedding of electrodes in the transfer processing step. As described above, the source and drain electrodes Es and Ed are formed on the base layer B by transferring the pattern PT formed by the conductive ink containing the electrode material and the solvent to the base layer B. As the solvent contained in the conductive ink, a solvent having a property of softening the cured polymer resin constituting the base layer B is used. Specifically, a solvent having a property of swelling or dissolving the polymer resin is used. For example, when the polymer constituting the base layer B is polyurethane, the solvent is an organic solvent that softens it, particularly a high boiling point solvent used for conductive ink for reverse printing, specifically, for example, butyl carbitol and hexyl carbitol. , Ethylcarbitol acetate, butylcarbitol acetate, 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, 1,3-butylene glycol, octanediol can be used.

As shown in FIG. 4A, when the electrode pattern PT supported on the blanket BL touches the surface of the base layer B, the solvent component contained in the electrode pattern PT permeates the base layer B. As a result, a region (softening region) SR that is swollen or dissolved by the solvent and softened is generated in the upper part of the base layer B. In this state, as shown in FIG. 4B, when the pressing force by the roller member RL is applied, the electrode pattern PT is pushed toward the inside of the softening region SR. As a result, as shown in FIG. 4C, a structure in which the electrode pattern PT is embedded in the base layer B is realized. Further, since the surface of the electrode pattern PT is pressed against the base layer B, it is possible to prevent a step from being generated at the interface between the electrode pattern PT and the surrounding base layer B.

That is, in this manufacturing method, the process itself of transferring the electrode pattern PT to the base layer B is also a process of embedding the electrode pattern PT in the base layer B. Therefore, it is not necessary to embed the electrode pattern PT by pretreatment of the base layer B before transfer, post-processing after transfer, or the like.

5A, 5B, 6A and 6B are diagrams illustrating the structure of the prototype organic thin film transistor. More specifically, FIG. 5A is a microscope (TEM) photograph showing an example of the cross-sectional structure of the organic thin film transistor manufactured by the above manufacturing method, and FIG. 5B is a diagram schematically showing the shape of the drain electrode. .. Further, FIG. 6A is a micrograph showing another example of the cross-sectional structure of the organic thin film transistor manufactured by the above manufacturing method, and FIG. 6B is a diagram schematically showing the shape of the drain electrode. The shape of the source electrode is basically the same.

In the examples shown in FIGS. 5A and 5B, the end portion of the drain electrode Ed is embedded in the base layer B while the thickness of the drain electrode Ed is kept substantially constant. On the other hand, in the cases shown in FIGS. 6A and 6B, the drain electrode Ed is embedded in the base layer B in such a manner that the thickness gradually decreases at the end thereof. In this way, the cross-sectional shape of the electrode varies slightly among the plurality of individuals, but in each case, the drain electrode Ed has a surface shape that gently rises from the surface of the base layer B. The interface with the organic semiconductor layer Sc is a smooth curved surface with no steps. Therefore, it is possible to suppress the disorder of the crystallinity of the organic semiconductor layer Sc caused by the remarkable step and improve the performance of the organic thin film transistor Tr.

When forming the gate electrode Eg, it is not necessary that the electrode pattern PT is embedded in the gate insulating layer Ig because it does not affect the electrical characteristics. Therefore, in the step of forming the gate electrode Eg, no special relationship is required between the solvent component contained in the electrode pattern PT and the material of the gate insulating layer Ig. Rather, from the viewpoint of ensuring the insulating property, the gate insulating layer Ig is preferably formed of a material that does not change with respect to the solvent.

7A and 7B are diagrams showing examples of electrical characteristics of the prototype organic thin film transistor. More specifically, FIG. 7A is a graph showing an actual measurement example of electrical characteristics in a prototype organic thin film transistor and a comparative example. Further, FIG. 7B is a diagram schematically showing a cross-sectional structure of a transistor of a comparative example. In addition, in order to facilitate the comparison of the structures, in FIG. 7B, the same reference numerals are given to the configurations having the same functions as the respective configurations of the transistor Tr shown in FIG. 3E.

As shown in FIG. 3E, the organic thin film transistor Tr manufactured by the manufacturing method of the present embodiment is a so-called top gate type transistor in which source and drain electrodes Es and Ed are arranged between layers and gate electrodes Eg appear on the surface of the device. be. On the other hand, the transistor shown in FIG. 7B as a comparative example is a so-called bottom gate type transistor in which the gate electrodes Eg are arranged between layers and the source and drain electrodes Es and Ed appear on the surface of the device. In the comparative example, the gate electrode Eg in which chromium (thickness 3 nm) and gold (thickness 50 nm) are laminated on the glass substrate S, the gate insulating layer Ig having a film thickness of 100 nm by the CVD method, and the organic having a film thickness of 30 nm by the vacuum deposition method. The semiconductor layer Sc, the source and drain electrodes Es and Ed (film thickness 50 nm, channel length 50 μm) by vacuum deposition of gold are laminated in this order.

In the thin film transistor, the portion of the semiconductor layer connecting the source electrode and the drain electrode functions as a channel through which current flows. In a conventional top-gate transistor, the carrier mobility of the organic semiconductor in the channel portion that electrically connects the source electrode and the drain electrode is caused by the disorder of the crystallinity of the organic semiconductor layer around the source and drain electrodes. Is small. Therefore, the electrical characteristics tend to be inferior to those of the bottom gate type transistor in which the organic semiconductor layer can be made into a flat layer.

However, as shown in FIG. 7A, the top gate type transistor manufactured by this embodiment has substantially the same electrical characteristics as the bottom gate type transistor of the comparative example. More specifically, under the measurement condition where the drain voltage is (-5) V, the carrier mobility (field effect mobility) in the saturation region between the transistor manufactured by the present embodiment and the transistor of the comparative example And the maximum drain currents were compared. The result is
-This embodiment:
Field effect mobility 0.283 [cm ² / V · s],
Maximum drain current 8.26 × 10 ^-7 [A]
・ Comparative example:
Field effect mobility 0.297 [cm ² / V · s],
Maximum drain current 7.30 × 10 ^-7 [A]
Met. From this, it can be seen that the organic semiconductor thin film transistor Tr manufactured by the manufacturing method of the present embodiment has substantially the same electrical characteristics as the bottom gate type transistor of the comparative example. Therefore, it can be said that the organic semiconductor layer Sc has good crystallinity.

Next, the method of transferring the electrode pattern PT to the work Wk shown in FIG. 2A in which the base layer B is formed on the substrate S or the work Wk shown in FIG. 3C in which the gate insulating layer Ig is formed to form an electrode is further described. explain in detail. As described above, in this embodiment, the electrodes (source electrode Es, drain electrode Ed, gate electrode Eg) are formed by transferring the conductive ink patterned on the surface of the blanket BL to the work Wk.

Such an electrode forming process can be subdivided into a patterning step of forming an electrode pattern PT with conductive ink on the blanket BL and a transfer step of transferring the formed electrode pattern PT to the work Wk. As described below, the patterning step and the transfer step can be performed using the same processing apparatus. The process described here can be performed by, for example, the transfer apparatus described in JP-A-2016-203518 previously disclosed by the applicant of the present application.

8A to 8D are diagrams showing the process of the electrode forming process. 9A and 9B are schematic views showing a patterning step and a transfer step. In the Cartesian coordinate system shown in FIGS. 8A to 8D, the XY plane represents the horizontal plane. Further, the Z direction represents the vertical direction, and more specifically, the (+ Z) direction represents the vertical upward direction. First, the patterning process will be described with reference to FIGS. 8A to 8D.

In the transfer device 1 that executes the electrode forming process, the upper stage 11 having a vacuum suction surface on the lower surface and the lower stage 12 having a frame shape with a large opening at the center are arranged close to each other in a horizontal posture. There is. The opening size of the opening 121 of the lower stage 12 is larger than the plane size of the upper stage 11. Inside the opening 121, a plurality of elevating hands 13 are arranged so as to be individually supported by an elevating mechanism (not shown).

Further, a cylindrical or cylindrical pressing roller 14 extending in the Y direction is arranged near the (−X) side (left side in the drawing) end of the opening 121. The pressing roller 14 is rotatably supported around the central axis in the Y direction by the support member 15. The support member 15 can move up and down in the Z direction and travel in the X direction by a drive mechanism (not shown). The pressing roller 14 has a function corresponding to the roller member RL shown in FIG. 2C.

In the patterning step, as shown in FIG. 8A, first, a plate PP having a convex pattern obtained by reversing a desired electrode pattern is carried into the transfer device 1 and set on the upper stage 11. The upper stage 11 attracts and holds the plate PP with the pattern forming surface on which the convex pattern is formed facing downward. Further, the blanket BL to which the conductive ink Ik is uniformly applied is carried into the transfer device 1 and set on the lower stage 12. The lower stage 12 attracts and holds the peripheral edge of the blanket BL in a state where the surface coated with the conductive ink Ik faces upward and faces the plate PP.

In the initial state, each elevating hand 13 is positioned at a height such that the upper surface thereof is the same height as the upper surface of the lower stage 12, so that the central portion of the blanket BL in the opened state is maintained in a horizontal posture. .. Further, the pressing roller 14 is positioned below the (−X) side end of the plate PP in the horizontal direction and at a position where the upper end is separated from the lower surface of the blanket BL in the vertical direction.

From this state, the support member 15 raises the pressing roller 14, so that the pressing roller 14 comes into contact with the lower surface of the blanket BL. As the pressing roller 14 continues to rise even after contacting the lower surface of the blanket BL, the blanket BL is pushed up by the pressing roller 14 as shown in FIG. 8B, and finally the upper surface of the blanket BL hits the lower surface of the plate PP. Get in touch. As a result, the ink Ik supported on the upper surface of the blanket BL comes into close contact with the plate PP. Further, the pressing roller 14 pushes up the blanket BL, so that the ink Ik is pressed against the plate PP with a predetermined pressing force.

In this state, the support member 15 moves the pressing roller 14 in the (+ X) direction, so that the pressing roller 14 comes into contact with the lower surface of the blanket BL and travels in the (+ X) direction while being driven to rotate. As a result, the region where the blanket BL and the plate PP are in close contact with each other via the ink Ik expands in the X direction. At this time, as shown in FIG. 8C, each of the plurality of elevating hands 13 sequentially descends with the movement of the support member 15 in order to avoid interference with the traveling pressing roller 14.

As shown in FIG. 8D, when the pressing roller 14 reaches the end position immediately below the (+ X) side end portion of the plate PP, the entire plate PP is in contact with the blanket BL. When the plate PP and the blanket BL are peeled off in this state, the portion of the ink Ik uniformly applied to the blanket BL that corresponds to the convex pattern shifts to the plate PP, and the other portion remains on the blanket BL. .. By doing so, the ink Ik is patterned by the convex pattern, and the inverted pattern of the convex pattern is transferred to the blanket BL as the electrode pattern PT. FIG. 9A is a diagram schematically showing a process in which the ink Ik applied to the blanket BL is patterned by the plate PP to form the electrode pattern PT.

On the other hand, the transfer step of transferring the electrode pattern PT formed on the blanket BL to the work Wk can be explained by replacing the plate PP in the above process with the work Wk and the ink Ik with the electrode pattern PT. That is, the blanket BL on which the electrode pattern PT is supported is held by the lower stage 12, and the work Wk to which the pattern is transferred is held by the upper stage 11 (FIG. 8A).

Then, the pressing roller 14 travels in the X direction while pressing the blanket BL against the work Wk with a predetermined pressing pressure (FIGS. 8B to 8D), so that the blanket BL and the work Wk are brought into close contact with each other via the electrode pattern PT. When the work Wk and the blanket BL are separated, the electrode pattern PT on the blanket BL is transferred to the work Wk.

FIG. 9B is a diagram schematically showing a process (step S104 of FIG. 1) in which the electrode pattern PT is transferred to the work Wk in which the base layer B is formed on the substrate S. The base layer B has already been cured by a prior firing treatment. Therefore, the base layer B is not plastically deformed by the pressing force from the pressing roller 14. On the other hand, the electrode pattern PT is in an undried state and contains a large amount of solvent component. Therefore, the base layer B in contact with the electrode pattern PT is softened by melting or swelling, and the electrode pattern PT is strongly pressed against the base layer B to be embedded in the base layer B.

In each of the above electrode forming treatments, a parallel plate printing technique is applied in which the electrode pattern PT is transferred from the blanket BL to the work Wk by bringing the blanket BL having a flat plate shape and the work Wk into close contact with each other and then peeling them off. It is a thing. However, the method for forming the electrode pattern PT on the work Wk is not limited to this, and various methods can be applied, for example, as illustrated below.

FIG. 10 is a diagram showing another aspect of the electrode forming process. In the transfer device 2 used in this embodiment, the blanket 22 is wound around the surface of the cylindrical blanket body 21. Further, the electrode pattern PT is patterned on the intaglio 23. The electrode pattern PT patterned by the intaglio 23 is transferred to the blanket 22 by moving the intaglio 23 while abutting against the intaglio 22 while rotating the blanket body 21 at a predetermined speed. Subsequently, the electrode pattern PT on the blanket BL is transferred to the work Wk by moving the stage 24 while bringing the work Wk placed on the stage 24 into contact with the blanket BL. The solvent component contained in the electrode pattern PT dissolves or swells the base layer B of the work Wk, so that the electrode pattern PT is embedded in the base layer B. This method corresponds to the offset intaglio printing technique. An electrode can also be formed on the work Wk by such a method.

Alternatively, patterning on a flat or cylindrical blanket may be performed by other methods. For example, the electrode pattern may be formed by partially landing the conductive ink on the blanket surface using a printing technique such as a screen printing method or an inkjet method. For the purpose of transferring the electrode pattern PT to the work Wk, it is conceivable to apply the ink directly to the surface of the work Wk by these printing techniques. However, it does not meet the purpose of embedding the electrode pattern PT in the base layer B by applying pressure while bringing the ink into contact with the work Wk.

However, it is possible to obtain the same effect by adding a separate step for pressing after the ink is applied to the surface of the work Wk by these printing techniques. The above embodiment is particularly effective in that pattern transfer and pressing can be performed simultaneously when compared to such a method.

As described above, in this embodiment, in order to prevent a remarkable step at the interface in contact with the organic semiconductor layer when forming an electrode prior to forming the organic semiconductor layer in the semiconductor element (organic thin film transistor), the following is performed. The method like this is adopted. That is, prior to the formation of the electrodes, the base layer B made of the insulating resin material is formed on the substrate S. Then, an ink containing an electrode material and a solvent is partially applied to the surface of the base layer B according to a defined pattern. Here, the solvent is assumed to have a property of softening the resin material constituting the base layer.

When the electrode pattern PT formed on the surface of the base layer B is pressed in an unsolidified state, it permeates into the inside of the base layer B softened by the solvent. Therefore, the electrode formed by solidifying the electrode pattern PT is in a state of being embedded in the base layer B. As a result, in the semiconductor device thus formed, the surface of the electrode laminated on the base layer B and the exposed surface of the base layer form a smooth curved surface. This avoids a significant step at the boundary between the two surfaces.

Therefore, the organic semiconductor layer formed so as to cover them also has a smooth surface. Therefore, it is possible to suppress the deterioration of the electrical characteristics of the organic semiconductor layer due to the disorder of crystallinity caused by the step. That is, according to the manufacturing method of the present embodiment, it is possible to stably manufacture an organic thin film transistor having good electrical characteristics.

Further, since the roller member presses the electrode when the electrode is formed by transferring the electrode pattern PT, it is possible to simultaneously realize the pattern transfer and the embedding of the electrode. Therefore, a processing step for eliminating the step caused by the electrode formation is unnecessary, and the equipment cost and the manufacturing cost of the manufacturing apparatus can be greatly reduced.

As described above, in the method for forming an electrode for an organic thin film transistor and the method for manufacturing an organic thin film transistor including the above embodiment, the conductive ink Ik corresponds to the "coating liquid" of the present invention. The blanket BL and the roller member RL function as the "supporter" and the "roller" of the present invention, respectively.

Further, the transfer device 1 shown in FIG. 8A and the transfer device 2 shown in FIG. 10 function as the "electrode forming device" of the present invention. In the transfer device 1, the upper stage 11 functions as the "substrate holding portion" of the present invention, and the lower stage 12 functions as the "supporter holding portion" of the present invention. Further, the pressing roller 14 functions as the "pressing member" of the present invention. On the other hand, in the transfer device 2, the stage 24 functions as the "board holding portion" of the present invention, and the blanket 22 functions as the "supporter" of the present invention. The blanket body 21 also has functions as a "supporting body holding portion" and a "pressing member" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, the above-described embodiment relates to a method for manufacturing a semiconductor device (specifically, an organic thin film transistor) including the electrode forming method of the present invention. However, the electrode forming method of the present invention can be applied to other than the manufacturing process of semiconductor devices.

Further, for example, the present invention can be applied to the production of various semiconductor devices not limited to the above-mentioned organic thin film transistors. The semiconductor device manufactured by the above method is a top gate / bottom contact type organic thin film transistor, but the present invention may be applied to, for example, the manufacture of a bottom gate / top contact type organic thin film transistor.

Further, in the explanation of the principle of the above embodiment (FIG. 2C), the electrode pattern PT is transferred to the upper surface of the work Wk and is pressed by the roller member RL from above. On the other hand, on the contrary, in the specific transfer device 1, the electrode pattern PT is transferred to the lower surface of the work Wk and receives the pressing roller by the pressing roller 14 from below. However, these are technically equivalent, and the pressing direction with respect to the work Wk is arbitrary. Since the base layer B that receives the transfer of the electrode pattern PT is pre-cured and has no fluidity, there is no particular difference depending on the pressing direction.

Further, in the above embodiment, the electrode pattern PT is transferred to the work Wk in which the base layer B is formed on the surface of the substrate S. However, if the substrate S itself has electrical insulation and has the property of being softened by the solvent of the conductive ink, it is not necessary to form the base layer again. That is, in this case, the substrate S itself has a function as the "base layer" of the present invention.

As described above by exemplifying a specific embodiment, in the electrode forming method for an organic thin film transistor according to the present invention, the solvent may be an organic solvent that swells or dissolves the resin material. According to such a configuration, the coating liquid permeates the base layer that has been swollen or dissolved by the solvent, so that the electrode embedded inside the base layer can be formed.

Further, for example, the base layer may be formed by applying a resin material or a liquid containing a raw material thereof to a substrate and solidifying the substrate. By applying the coating liquid to the already solidified base layer in this way, stable coating is possible, unlike coating to the unsolidified base layer. Then, by softening the once solidified base layer with a solvent, embedding of the electrode in the base layer can be effectively realized.

Further, for example, the resin material may be polyurethane and the solvent may be 2,4-diethyl-1,5-pentanediol. It has been clarified by the experiment of the inventor of the present application that the above-mentioned electrode embedding can be realized by the combination of such a resin material and a solvent.

Further, for example, a pattern of a coating liquid patterned according to the electrode shape is supported on a carrier, and the carrier is pressed against the base layer to transfer the coating liquid to the base layer and press the coating liquid. good. According to such a configuration, since the process itself of transferring the coating liquid to the base layer also serves as the process of pressing the coating liquid, it is not necessary to provide these as separate steps, and the time and cost required for manufacturing can be shortened. It becomes possible to plan.

In this case, the pattern-supporting surface of the carrier is flat, and the pattern-supporting surface is brought close to or in close contact with the surface to be coated of the base layer, and the surface opposite to the pattern-supporting surface of the carrier or the base layer. The surface opposite to the surface to be coated may be pressed by a roller. According to such a configuration, the pattern supported on the carrier can be pressed against the base layer to perform transfer, and at the same time, the pattern can be permeated into the softened base layer.

Further, for example, the thickness of the base layer may be larger than the thickness of the electrode. If the base layer is too thin with respect to the thickness of the electrode, the amount of the electrode embedded in the base layer is limited, and as a result, the step between the surface of the base layer and the surface of the electrode may not be eliminated. If at least the thickness of the base layer is larger than the thickness of the electrode, it is possible to avoid this problem and surely realize the embedding of the electrode.

Further, the method for manufacturing an organic thin film transistor according to the present invention may include, for example, a step of executing a wet treatment for modifying the surface of the electrode after forming the electrode. When the electrodes are provided directly on the substrate, the electrodes formed in such a wet treatment step may be peeled off from the substrate. By providing the base layer in advance, it is possible to effectively prevent the electrode from peeling off in response to such a problem.

Further, in the organic thin film transistor according to the present invention, for example, a self-assembled monolayer may be provided between the exposed surfaces of the source electrode and the drain electrode and the organic semiconductor layer. According to such a configuration, the electrical contact between the electrode and the organic semiconductor layer can be made stable with low resistance.

Although the invention has been described above with reference to specific examples, this description is not intended to be construed in a limited sense. With reference to the description of the invention, various variations of the disclosed embodiments, as well as other embodiments of the present invention, will be apparent to those familiar with the art. Therefore, the appended claims are considered to include such modifications or embodiments within a range that does not deviate from the true scope of the invention.

The present invention can be applied to all electrode forming techniques for forming electrodes on a substrate, but an organic thin film transistor in which disorder of crystallinity caused by a step between the substrate and the electrode causes deterioration of electrical characteristics. It is particularly effective in the production of.

1,2 Transfer device (electrode forming device)
11 Upper stage (board holding part)
12 Lower stage (support holder)
14 Pressing roller (pressing member)
21 Blanket body (support holder, pressing member)
22 Blanket (supporter)
24 stages (board holding part)
B Base layer Ed Drain electrode Eg Gate electrode Es Source electrode Ig Gate insulating layer Ik Conductive ink (coating liquid)
PT Electrode pattern S substrate Sc organic semiconductor layer Tr organic semiconductor thin film transistor Wk workpiece

Claims (12)

An electrode forming method for an organic thin film transistor, in which an electrode is formed on the surface of a base layer formed of an electrically insulating resin material.
The process of preparing the base layer and
A step of applying a coating liquid containing a solvent for softening the resin material constituting the base layer and an electrode material to the surface of the base layer in a pattern corresponding to the electrode shape.
The step of pressing the unsolidified coating liquid against the base layer and
A method for forming an electrode for an organic thin film transistor, comprising a step of volatilizing the solvent and solidifying the coating liquid to form the electrode. The electrode forming method for an organic thin film transistor according to claim 1, wherein the solvent is an organic solvent that swells or dissolves the resin material. The electrode forming method for an organic thin film transistor according to claim 1 or 2, wherein the base layer is formed by applying a liquid containing the resin material or a raw material thereof to a substrate and solidifying the base layer. The electrode forming method for an organic thin film transistor according to any one of claims 1 to 3, wherein the resin material is polyurethane and the solvent is a high boiling point solvent. A pattern of the coating liquid patterned according to the electrode shape is supported on a carrier, and the carrier is pressed against the base layer to transfer the coating liquid to the base layer and press the coating liquid. Item 4. The electrode forming method for an organic thin film transistor according to any one of Items 1 to 4. The pattern-supporting surface of the carrier is flat, and the pattern-supporting surface is brought close to or in close contact with the surface to be coated of the base layer, and the surface of the carrier opposite to the pattern-supporting surface is or The electrode forming method for an organic thin film transistor according to claim 5, wherein the surface of the base layer opposite to the surface to be coated is pressed by a roller. The electrode forming method for an organic thin film transistor according to any one of claims 1 to 6, wherein the thickness of the base layer is larger than the thickness of the electrode. A step of forming the electrode on the base layer by the electrode forming method according to any one of claims 1 to 7.
A method for manufacturing an organic thin film transistor, comprising a step of forming an organic semiconductor layer covering the electrodes on the surface of the base layer. The method for manufacturing an organic thin film transistor according to claim 8, further comprising a step of performing a wet treatment for modifying the surface of the electrode after forming the electrode. An electrode forming device for organic thin film transistors that forms electrodes on the surface of a base layer formed of an electrically insulating resin material.
A substrate holding portion for holding the substrate having the base layer and
A coating liquid containing a solvent for softening the resin material constituting the base layer and an electrode material is a flat-plate-shaped carrier supporting a pattern patterned according to the electrode shape, and the pattern supporting surface is covered with the base layer. A carrier holding portion that holds the coating surface in close contact with each other,
An organic thin film transistor comprising a surface of the carrier opposite to the pattern-supporting surface or a roller-shaped pressing member that moves along the substrate while pressing the surface of the substrate opposite to the surface to be coated. Electrode forming device for. A base layer made of an electrically insulating resin material and
A coating liquid containing a solvent for softening the resin material constituting the base layer and an electrode material is partially applied to the base layer, pressed against the base layer and then solidified to separate them from each other and to solidify the base layer. A source electrode and a drain electrode embedded in the base layer with at least a part of the surface exposed, respectively.
An organic semiconductor layer that continuously covers the exposed surfaces of the source electrode and the drain electrode, and the surface of the base layer between the source electrode and the drain electrode.
An insulating layer covering the organic semiconductor layer and
An organic thin film transistor comprising a gate electrode that is in contact with the insulating layer, faces the organic semiconductor layer via the insulating layer, and is electrically insulated from the organic semiconductor layer. The organic thin film transistor according to claim 11, wherein a self-assembled monolayer is provided between the exposed surface of each of the source electrode and the drain electrode and the organic semiconductor layer.

Images