JP2011107476A - Method for manufacturing electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a high-quality electronic device by suppressing damages caused by dissolution of a hole injection layer when a bank is formed by a photolithographic process using an alkali solution on the hole injection layer comprising an oxide of transition metal. <P>SOLUTION: The method for manufacturing an electronic device includes a step of forming an organic resin layer by patterning a photosensitive resin film 82 disposed on a thin film comprising an oxide of transition metal by a photolithographic process. The developing solution used in the photolithographic process is an aqueous solution containing tetraalkylammonium hydroxide and a salt of strong acid and has a pH of 10.5 to 11.5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic device manufacturing method including a step of patterning a resin film using a photolithography process or the like.

  Research and development on various electronic devices such as light-emitting devices, solar cells, and other semiconductor devices are actively conducted. In particular, an organic EL device, which is one of organic electronic devices having an organic functional layer, is expected to be used as a next-generation thin display, and has been actively researched in recent years.

  An organic EL device has a structure in which an organic functional layer including a light emitting layer is sandwiched between an anode and a cathode. Holes from the anode and electrons from the cathode are injected into the light emitting layer, and they are recombined in the light emitting layer. This is a device that takes out light emission. Organic EL devices have high visibility due to self-emission and are completely solid elements, so they have characteristics such as excellent impact resistance, and their use as light-emitting devices in various display devices has attracted attention. (For example, refer to Patent Document 1). Already, the application to various uses including the main display of a cellular phone has begun.

  At the present development and application stage, development of an organic EL device using a low molecular weight organic material as a light emitting layer has preceded. This is because, when a low molecular organic material is used as the light emitting layer, the light emission efficiency is high and the lifetime is long (for example, see Patent Documents 2 and 3). The light emitting layer of the low molecular organic material is manufactured using a vacuum process such as vacuum deposition.

  However, it is difficult to produce a large-sized 100-inch organic EL panel at the mass production level by the organic EL manufacturing technology using this vacuum process. This is because it is difficult to accurately maintain the mask arrangement for each color (for example, R, G, B) used when the light emitting layer is formed by vapor deposition.

  On the other hand, a manufacturing technique for forming an organic functional layer by a printing method is also known. The printing method is advantageous in terms of material use efficiency, production time, and cost of production equipment. In addition, the printing method can apply the pixels arranged in a large-area panel separately in the production of displays, which can cause in-plane non-uniformity problems such as vacuum deposition and deflection of the metal mask used for patterning the deposited layer. No problems arise due to it.

  Therefore, an organic EL device having an organic functional layer formed by using a printing method has been developed (see, for example, Patent Document 4). In Patent Document 4, a hole injection layer made of an aqueous organic substance PEDOT: PSS (3,4 ethylenedioxythiophene: polystyrenesulfonic acid) is formed on an electrode on a substrate by an ink jet method; A hole-transporting material containing an organic solvent is applied and formed into a film, and the film is heat-treated to crosslink and insolubilize; then, a third layer made of a light-emitting organic material is formed into a film with the organic solvent to emit light Finally, the cathode is formed by vapor deposition to form the device. In coating film formation, a material solution is often applied to an area defined by a bank and dried.

  On the other hand, in an organic EL device, a hole injection layer may be disposed between an anode and a light emitting layer. The hole injection layer may be an organic layer such as the aforementioned PEDOT: PSS, but may also be an inorganic layer. There is a concern that the PEDOT: PSS layer may deteriorate device characteristics due to diffusion of sulfonic acid in the light emitting layer. Furthermore, since the electrical conductivity of the PEDOT: PSS layer is too high, the leakage current increases when the PEDOT: PSS layer comes into contact with the cathode. Therefore, an inorganic hole injection layer may be desired.

  As an inorganic hole injection layer, it has been proposed to use a metal oxide layer that has a large ionization potential and is advantageous for hole injection from the viewpoint of energy level (see, for example, Patent Documents 5 to 7). The metal oxide layer as the hole injection layer is required to be easy to inject holes into the organic light emitting layer, and must be a material having a high ionization potential. Suitable materials include molybdenum oxide, tungsten oxide, and an oxide of a mixture of molybdenum and tungsten.

  A cross-sectional view of the structure of the organic EL device disclosed in Patent Document 7 is shown in FIG. FIG. 4 shows an organic EL device disposed on the glass substrate 100. The organic EL element forms a top emission type organic EL device by forming an anode (Al) 111, a molybdenum oxide layer (transition metal oxide layer) 115, a charge blocking layer 116, a light emitting layer 112, and a cathode 113. . That is, the anode 111 and the hole injection layer 115 are formed separately, and the light emitting layer 112 has an opening area defined by the pixel regulation layer 114. The cathode 113 has a two-layer structure of a Ba—Al ultrathin film: 113a and an ITO film: 113b, and is formed in a stripe shape.

JP 2004-171951 A JP 2007-288071 A JP 2002-222695 A Special table 2007-527542 gazette Japanese Patent No. 3369615 JP-A-9-63771 JP 2007-335737 A

  As described above, an oxide film of a transition metal such as tungsten or molybdenum has a hole injecting ability. Therefore, it accepts holes generated from the anode and promotes injection into a layer adjacent to the oxide film. For example, in an organic light emitting device having an anode, an organic light emitting layer, and a cathode, if an oxide film of a transition metal is disposed between the anode and the organic light emitting layer, electrons generated from the anode are injected into the organic light emitting layer. Can be promoted.

  Moreover, the organic functional layer of an electronic device (for example, the organic light emitting layer of an organic EL device) may be formed by a printing method such as inkjet. In order to produce an organic layer by a printing method, a printing region is often defined by a partition called a bank, and an organic layer is formed in the region.

  A partition called a bank is often made of a resin, and a photosensitive resin film is often patterned by a photolithography method. More specifically, a photosensitive resin material is applied, and pre-baking for solvent drying is performed to form a resin film; a part of the resin film is selectively irradiated with light (for example, ultraviolet rays). Accelerate the crosslinking reaction of the resin material; dissolve the uncrosslinked portion with a developer to obtain the desired patterning (development); post-bake to increase the strength of the patterned material and form the bank Is done.

  In many cases, an alkaline solution having a pH of about 12 to 13 is used as the developer used in the development process of the photolithography method. In particular, an aqueous solution containing tetramethylammonium hydroxide (hereinafter abbreviated as TMAH) is known as a general alkaline developer.

  Therefore, when an organic light emitting layer of an organic light emitting element having an anode, an organic light emitting layer, a cathode, and an oxide film of a transition metal disposed between the anode and the organic light emitting layer is formed by a printing method In some cases, a bank must be formed on the transition metal oxide film by a photolithography method. In this case, in the process of forming the bank, the transition metal oxide film must be in contact with the developer.

  However, it has been clarified that oxide films of transition metals such as tungsten and molybdenum are easily dissolved by an alkali developer. That is, it was found that when a transition metal oxide film is used as a hole injection layer and a bank is formed thereon, the hole injection layer is dissolved by the developer. Dissolving increases the surface roughness of the hole injection layer, creating pinholes in the organic layer coated and formed on the hole injection layer, and in some cases, as a short circuit between the electrodes. It was found that a problem occurred.

  As described above, in an organic EL device, in a device including a transition metal oxide as a hole injection layer and a bank for forming a functional layer by a printing method, the hole injection layer is used for bank formation. The problem of being dissolved in the developer became clear. Patent Document 7 described above discloses an organic EL device having a transition metal oxide as a hole injection layer and a bank, but the hole injection layer made of the transition metal oxide is dissolved when the bank is formed. The problem of doing is not suggested.

  An object of the present invention is to suppress damage caused by dissolution of a hole injection layer when a bank is formed on a hole injection layer made of an oxide of a transition metal by a photolithography method using an alkaline solution. To do. Thereby, a method for manufacturing a high-quality electronic device is provided.

The present invention relates to a method for manufacturing an electronic device described below.
[1] A method for manufacturing an electronic device, including a step of patterning a photosensitive resin film disposed on a thin film made of an oxide of a transition metal by a photolithography process to form an organic resin layer,
The developing solution used in the photolithography process is an aqueous solution containing tetraalkylammonium hydroxide and a strong acid salt, and has a pH of 10.5 to 11.5.
[2] The method for producing an electronic device according to [1], wherein the tetraalkylammonium hydroxide is tetramethylammonium hydroxide.
[3] The electronic device manufacturing method according to [1] or [2], wherein the strong acid is any one of nitric acid, sulfuric acid, and hydrochloric acid.

  [4] The electronic device manufacturing method according to any one of [1] to [3], wherein the transition metal is tungsten, molybdenum, or a mixture thereof.

[5] The method of manufacturing an electronic device according to any one of [1] to [4], wherein the electronic device is an organic electronic device having an organic functional layer whose region is defined by the organic resin layer.
[6] The electronic device includes a substrate, a first electrode disposed on the substrate, a hole injection layer disposed on the anode, a bank disposed on the hole injection layer, An organic EL device comprising: an organic functional layer defined by a bank and including an organic light emitting layer disposed on a hole injection layer; and a second electrode disposed on the organic functional layer, In any one of [1] to [4], the thin film made of the transition metal oxide in [1] is the hole injection layer, and the organic resin layer in [1] is the bank. Electronic device manufacturing method.

  According to the method for producing an electronic device of the present invention, it is possible to suppress the dissolution of the hole injection layer by appropriately adjusting the pH of the developer for forming the bank. It can be manufactured by a coating method.

1 is a structural cross-sectional view of an active matrix organic EL device in an embodiment of the present invention. It is a structure sectional view of an organic EL device in an embodiment of the invention. It is a figure which shows the flow of the manufacturing method of the organic EL device in embodiment of this invention. It is sectional drawing of an example of the conventional organic EL device.

  The electronic device (electronic device in the present invention) obtained by the production method of the present invention preferably has an organic functional layer and an organic resin layer (that is, a resin bank) that defines a region of the organic functional layer. The organic functional layer is appropriately selected according to the electronic device. That is, in the case of an organic EL device, the organic functional layer is an organic light emitting layer, an intermediate layer (also referred to as an interlayer or a hole transport layer), etc .; in the case of a solar cell, the organic functional layer is a light receiving layer. Etc. The organic functional layer is preferably formed by a coating method, and is formed by providing a solution containing an organic functional material to a region defined by the resin bank. Examples of the coating method include an inkjet method, a dispenser method, a spin coating method, a gravure printing method, a relief printing method, and the like. The organic functional layer may be a single layer or a combination of two or more layers having different functions.

  The surface of the resin bank that defines the region of the organic functional layer is required to have liquid repellency with respect to a solution (ink) containing the organic functional material. There are roughly two types of means for imparting liquid repellency to the resin bank surface. In the first method, after forming the bank, a plasma treatment using fluorine gas is performed, and a fluorine compound is attached to the surface of the bank to make the liquid repellent. In the first method, a small amount of fluorine compound adheres to the pixel region. As a result, the fluorine component may diffuse into the organic functional layer and deteriorate device characteristics.

  The second means for imparting liquid repellency to the bank is a method of forming a bank using a resin material containing a fluorine compound. If a resin material containing a fluorine compound is used, the liquid repellency of the bank surface can be obtained without subjecting the formed bank to a liquid repellency treatment. Therefore, it may be desirable to make the bank liquid repellent by the second method.

  An anode may be disposed on one surface of the organic functional layer of the electronic device obtained by the manufacturing method of the present invention, and a cathode may be disposed on the other surface. Each of the anode and the cathode may be disposed in contact with the organic functional layer, or may be disposed through an arbitrary layer. The electronic device according to the present invention is particularly characterized in that a hole injection layer made of an oxide of a transition metal is disposed between the anode and the organic functional layer.

  To place the hole injection layer below the organic functional layer formed in the area defined by the bank, place a resin film made of the resin material of the bank on the surface of the hole injection layer and pattern it Thus, a bank is preferable. If the resin material of the bank is a photosensitive resin, the resin film can be patterned into the bank by a photolithography process. Thereafter, if an organic functional layer is applied and formed in a region defined by the bank, a hole injection layer is disposed below the organic functional layer.

  On the other hand, in order to arrange the hole injection layer below the organic functional layer, after forming the bank, the hole injection layer is formed in a region defined by the bank, and further the organic functional layer is formed. Is also possible. However, in this case, since the hole injection layer is formed on the lyophobic bank, the lyophobicity of the bank is lost and the bank does not function. Therefore, as described above, it is required to form a bank after forming the hole injection layer.

  In order to form the bank, it is preferable to pattern the photosensitive resin film into the bank by a photolithography process. However, the photosensitive resin may be a negative type or a positive type. In any case, the photosensitive resin is preferably an alkali-soluble resin. When the photosensitive resin is a negative photosensitive resin, the non-light-irradiated portion is removed by an alkaline developer; when the photosensitive resin is a positive photosensitive resin The light irradiation part is removed with an alkali developer.

  The pH of the alkali developer is preferably 10.5 to 11.5. The alkali developer preferably contains tetraalkylammonium hydroxide, preferably tetramethylammonium hydroxide (TMAH). Tetraalkylammonium hydroxide is well known as a component of an alkaline developer for lithography and generates an amine in the development process. The concentration of the tetraalkylammonium hydroxide contained in the alkali developer is preferably 0.05% by mass to 2.38% by mass, and more preferably 0.1 to 1.5% by mass. If the concentration of the tetraalkylammonium hydroxide is too low, the development time becomes excessively long and the developability deteriorates. On the other hand, when the concentration of the tetraalkylammonium hydroxide is too high, the development time becomes excessively short, and not only the margin for the development time is reduced, but also excessive development may occur.

  The alkaline developer preferably further contains a strong acid salt. The strong acid refers to an acid having a negative pKa, and examples thereof include sulfuric acid (pKa = -3), hydrochloric acid (pKa = -8) and nitric acid (pKa = -1.32).

  That is, the alkaline developer in the present invention is prepared by adjusting the pH to 10.5 to 11.5 by adding a strong acid to an aqueous solution containing 0.05% by mass to 2.38% by mass of TMAH. sell.

  In the electronic device of the present invention, an oxide thin film of a transition metal is disposed under the resin bank. Therefore, when developing with an alkali developer to form a bank, the alkali developer contacts the transition metal oxide thin film. The present inventor has found that the transition metal oxide thin film may be dissolved by the alkali developer containing tetraalkylammonium hydroxide; however, the pH of the alkali developer containing tetraalkylammonium hydroxide is adjusted. It has been found that the dissolution of the transition metal oxide thin film can be preferably suppressed by containing a strong acid salt.

  The mechanism for suppressing the dissolution of the transition metal oxide film is not limited, but it is considered that the amine generated by the decomposition of the tetraalkylammonium hydroxide reacts with a strong acid to become an “amine strong acid salt”.

  The mechanism for suppressing the dissolution of molybdenum oxide will be specifically described with a developer containing TMAH. With the developer containing TMAH, the molybdenum oxide is dissolved as molybdate ions, and neutralized with TMAH to become a molybdate amine salt. Considering the equilibrium reaction between molybdate ion and molybdate amine salt, an acid stronger than molybdic acid may be added to prevent the equilibrium from proceeding in the direction of the formation of molybdate amine salt. Therefore, the stronger the acid, the lower the generation of molybdate amine salt, thereby reducing the generation of molybdate ions, that is, the amount of molybdenum oxide dissolved is reduced.

  Further, the developer for patterning the photosensitive resin film is required to have a pH of a certain level or more in order to ensure its development performance, and specifically needs to be a pH of 10.5 or more. If the developing performance of the alkaline developer is low, a development residue of the bank is generated. When the development residue of the bank exists on the hole injection layer, the hole injection property is lowered. Further, since the bank material is an insulator, the resistance component increases and the drive voltage of the device increases. This increases the voltage to obtain the same brightness, resulting in a reduced device life.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Specifically, an organic EL device will be described as an example of the electronic device. In the following drawings, components having substantially the same function are denoted by the same reference numerals for the sake of brevity. In addition, this invention is not limited to the following embodiment.

  FIG. 1 shows a structural cross-sectional view of an organic EL device 1 according to an embodiment. The organic EL device 1 shown in FIG. 1 includes a substrate 40, transistor elements 50 (50A, 50B) formed on the substrate 40, and an organic electroluminescence (organic EL) unit 60 formed thereon. It is configured.

  Examples of the substrate 40 include a transparent inorganic substrate (for example, a glass substrate), a non-transparent inorganic substrate (for example, a silicon substrate), a resin substrate (which may be flexible), and the like. The two transistor elements 50 (50A and 50B) disposed on the substrate 40 are thin film transistors (TFTs). Each transistor element 50 (50A and 50B) includes a source / drain electrode 51, a semiconductor layer 52 formed in contact with the source / drain electrode 51, a gate insulating film 53 formed on the semiconductor layer 52, And a gate electrode 54 disposed on the gate insulating film 53. The two transistor elements 50 (50A and 50B) are electrically connected to each other by a wiring 55. With this structure, the organic EL device 1 has an active matrix structure.

  A planarizing film 57 is formed on the substrate 40 so as to cover the transistor element 50. The upper surface of the planarizing film 57 is flattened. The substrate 40, the transistor element 50, and the planarizing film 57 constitute a TFT substrate 10 that is a substrate structure.

  On the TFT substrate 10 including the planarizing film 57, the organic EL part 60 is formed. The organic EL unit 60 includes an anode 12, a hole injection layer 13, an intermediate layer 14, an organic light emitting layer 15, a bank layer 16, an electron injection layer 18, a transparent cathode 20, and a transparent sealing film 22. Have

  The organic EL device 1 described in FIG. 1 has a top emission structure. That is, when a voltage is applied to the organic EL unit 60, light emission occurs in the organic light emitting layer 15, and the light 70 is emitted outside (upward) through the transparent cathode 20 and the transparent sealing film 22. Of the light emitted from the organic light emitting layer 15, the light directed toward the TFT substrate 10 is reflected by the anode 12, and is emitted (upward) as light 70 through the transparent cathode 20 and the transparent sealing film 22. . Therefore, it is important that the anode 12 has light reflectivity.

  The organic EL device 1 having the top emission structure can increase the light emission area ratio as compared with the organic EL device having the general bottom emission structure. That is, in the case of the top emission structure, the transistor element 50 and the like can be arranged under the organic EL part 60; whereas in the case of the bottom emission structure, the transistor element 50 and the like are arranged on the same plane as the organic EL part 60. Because it must be.

  The anode 12 is an electrode that is stacked on the surface of the TFT substrate 10 and applies a positive voltage to the organic EL device 1 with respect to the transparent cathode 20. Examples of the anode material constituting the anode 12 include Al, Ag, or an alloy thereof (for example, APC) that is a highly reflective metal. The thickness of the anode 12 is, for example, 100 to 300 nm. The anode 12 is preferably formed by a sputtering film forming method together with a hole injection layer 13 described later. Thereby, the anode 12 and the hole injection layer 13 can be formed by the same vacuum layer, and the manufacturing process can be simplified.

  The hole injection layer 13 is formed on the surface of the anode 12 and has a function of injecting holes into the organic light emitting layer 15 in a stable manner or by assisting generation of holes. Thereby, the drive voltage of the organic EL device 1 is lowered, and the lifetime of the element is extended by stabilizing the hole injection. The hole injection layer 13 is required to have optical transparency and surface flatness in addition to the hole injection property.

  The light transmissivity of the hole injection layer 13 is necessary to transmit light generated in the organic light emitting layer 15 to the anode 12 and light reflected from the anode 12 in the direction of the transparent cathode 20 without loss. That is, if the hole injection layer 13 has high light transmittance, the light emission efficiency of the organic EL device 1 is improved. Since the light transmittance of the hole injection layer 13 decreases as the film thickness increases, the film thickness of the hole injection layer 13 is preferably about 10 nm to 100 nm, for example. The laminated film of the anode 12 and the hole injection layer 13 preferably has a light reflectance in the visible light region of 80% or more.

  The surface flatness of the hole injection layer 13 is required to make the organic light emitting layer 15 (or the intermediate layer 14) formed on the hole injection layer 13 flat and uniform. Thereby, the variation in the thickness of the organic light emitting layer 15 in the pixel is suppressed, and the deviation of the electric field between the two electrodes, the acceleration of deterioration due to this, and the local light emission or short circuit in the pixel can be prevented. .

  The ionization potential (Ip) of the hole injection layer is preferably between the Ip of the adjacent anode 12 and the Ip of the organic light emitting layer 15 (intermediate layer 14 when the intermediate layer 14 is present). Thereby, the hole injection barrier from the anode 12 to the organic light emitting layer 15 (or the intermediate layer 14) can be reduced, and the driving voltage can be lowered.

  As a material meeting the conditions required for such a hole injection layer, an oxide of a transition metal can be given. Examples of the transition metal oxide include molybdenum oxide (MoOx), tungsten oxide (WOx), and a mixture of molybdenum oxide and tungsten oxide.

The reason why molybdenum oxide or tungsten oxide is preferable as the material for the hole injection layer is that these metal oxides each have a high Ip and are excellent in hole injection performance. That is, Ip of tungsten oxide is 5.5 eV, and Ip of molybdenum oxide is 5.6 eV. On the other hand, the Ip of other metal oxide materials such as Ag ₂ O, CuOx, TiOx, ZnOx, RuOx, and VOx are all less than 5.0V. For example, the Ip of Ag ₂ O is 4.6 eV. Furthermore, molybdenum oxide and tungsten oxide are higher than Ip of PEDOT: PSS.

  As described above, the material of the hole injection layer 13 is preferably molybdenum oxide (MoOx), tungsten oxide (WOx), or a mixture of molybdenum oxide and tungsten oxide. Among them, a mixture of molybdenum oxide and tungsten oxide is preferable. There is a case. First, tungsten oxide has lower solubility in water than molybdenum oxide. Therefore, the hole injection layer 13 preferably contains tungsten oxide. On the other hand, a film made of only tungsten oxide tends to have a high surface roughness, but a film made of a mixture of molybdenum oxide and tungsten oxide has a reduced surface roughness. Therefore, the hole injection layer 13 preferably contains molybdenum oxide.

  Thus, the hole injection layer 13 preferably contains a mixture of molybdenum oxide and tungsten oxide. More specifically, a mixture of molybdenum oxide and tungsten oxide is preferably used so that the ratio of molybdenum atoms to the total amount of molybdenum atoms and tungsten atoms is 9 atomic% to 35 atomic%.

  A film made of tungsten oxide and a film made of a mixture of molybdenum oxide and tungsten oxide (molybdenum atom ratio is 10 atomic%) are formed by sputtering on a flat ITO substrate (ITO film formed on glass) ) Formed on top. The film thickness was 50 nm in all cases. The sputter deposition conditions were an output of 250 W (Ar flow rate 100 SCCM / O 2 flow rate 100 SCCM, gas pressure 4.5 Pa). The surface roughness (Ra and Rmax) of each film was measured. As a result, Ra of the film made of tungsten oxide was 1.64 nm and Rmax was 21.62 nm; Ra of the film made of a mixture of molybdenum oxide and tungsten oxide was 0.81 nm and Rmax was 10.89 nm.

  A hole injection layer made of molybdenum oxide or tungsten oxide is preferably formed by a sputtering film forming method rather than a vapor deposition film forming method that requires a high vapor deposition temperature. This is from the viewpoint of increasing the panel size and mass productivity.

  The intermediate layer (interlayer) 14 is formed on the surface of the hole injection layer 13. The intermediate layer 14 efficiently transports holes injected from the hole injection layer 13 into the organic light emitting layer 15 and prevents deactivation of excitons at the interface between the organic light emitting layer 15 and the hole injection layer 13. In addition, it functions as a hole transport layer that blocks electrons. The material of the intermediate layer 14 is preferably an organic material having a hole transporting property. The organic material having a hole transporting property is an organic material having a property of transmitting holes generated at the anode by a charge transfer reaction between molecules. An organic material having a hole transporting property is sometimes called a p-type organic semiconductor. The material of the intermediate layer 14 may be a high molecular material or a low molecular material, and examples thereof include triphenylamine and polyaniline.

  The intermediate layer 14 is preferably formed by a printing method. The thickness of the intermediate layer 14 is, for example, about 5 to 50 nm.

  Moreover, it is preferable that the organic material which comprises the intermediate | middle layer 14 is bridge | crosslinked with the crosslinking agent. This is because when the organic light emitting layer 15 which is the upper layer of the intermediate layer 14 is formed by a printing method, the intermediate layer 14 is prevented from being dissolved.

  Although it does not specifically limit as a printing method which forms the intermediate | middle layer 14, The nozzle jet method represented by the inkjet method and the dispenser method can be used. In the ink jet method, the intermediate layer 14 is formed by ejecting an organic film-forming material in ink from the nozzle onto the surface of the hole injection layer 13.

  However, the intermediate layer 14 may be omitted depending on the performance of the hole injection layer 13 and the organic light emitting layer 15 which are adjacent layers.

  The organic light emitting layer 15 is formed on the surface of the intermediate layer 14. Holes and electrons are injected into the organic light emitting layer 15 and have a function of emitting light by generating an excited state by recombination.

  The material of the organic light emitting layer 15 may be a light emitting organic material. The organic light emitting layer 15 is preferably formed by a printing method such as ink jet or spin coating, which enables simple and uniform film formation on a large-screen substrate. The light emitting organic material may be a low molecular weight organic material or a high molecular weight organic material, but is preferably a high molecular weight organic material. By using a polymer organic material, the reliability of the organic light emitting layer can be increased, the device can be driven at a low voltage, and the device structure can be simplified in some cases.

  The polymer organic material constituting the organic light emitting layer 15 may be a π-conjugated polymer having fluorescence and having an aromatic ring or a condensed ring. Specific examples of the polymer light emitting material constituting the organic light emitting layer 15 include polyphenylene vinylene (PPV) or a derivative thereof (PPV derivative), polyfluorene (PFO) or a derivative thereof (PFO derivative), a polyspirofluorene derivative, polythiophene or Its derivatives are included.

  The bank layer 16 is formed on the surface of the hole injection layer 13 and defines the arrangement region of the intermediate layer 14 and the organic light emitting layer 15. That is, the intermediate layer 14 and the organic light emitting layer 15 are formed in the region defined by the bank using a printing method.

The material of the bank layer 16 is not particularly limited, but is preferably a substance having a volume resistivity of 10 ⁵ Ω · cm or more. If the material has a volume resistivity of 10 ⁵ Ω · cm or less, the bank layer 16 causes a leakage current between the anode and the cathode or a leakage current between adjacent pixels, and various problems such as an increase in power consumption. Can occur.

  The material of the bank layer 16 may be either an inorganic substance or an organic resin substance, but the organic resin substance generally has higher liquid repellency and can be used more preferably. Moreover, since the organic resin substance can be patterned by photolithography, the bank layer 16 can be easily manufactured. Examples of the organic resin material include polyimide resin and polyacrylic resin.

  The surface of the bank layer 16 has liquid repellency. If the surface of the bank layer 16 does not have liquid repellency, it is difficult to form the intermediate layer 14 and the organic light emitting layer 15 by a coating method. In order to make the surface of the bank layer 16 liquid repellent, the material of the bank layer itself may be a liquid repellent substance, or the surface of the bank layer may be subjected to a liquid repellent treatment. Examples of the liquid repellent material include organic resins having fluorine atoms introduced into the molecular structure and organic resins containing a fluorine component. Examples of the liquid repellent treatment include a fluorine plasma treatment.

  The thickness of the bank layer 16 may be about 100 to 3000 nm, for example.

  The bank layer 16 is patterned into a predetermined shape, and an area corresponding to the application area is opened. The patterning method is not particularly limited, but it is preferable to form a film made of a photosensitive material into a development pattern by a photolithography method. The present invention is characterized in that the developing solution for development patterning by photolithography is an aqueous solution containing tetraalkylammonium hydroxide and having a pH of 10.5 to 11.5. A specific photolithography flow will be described later.

  The electron injection layer 18 is formed on the organic light emitting layer 15 and has a function of reducing the barrier for electron injection into the organic light emitting layer 15, lowering the driving voltage of the organic EL element 1, and suppressing exciton deactivation. Have Thereby, it is possible to stabilize the electron injection, extend the life of the device, enhance the adhesion with the transparent cathode 20, improve the uniformity of the light emitting surface, and reduce device defects.

  The electron injection layer 18 is not particularly limited, but is preferably made of barium, aluminum, phthalocyanine, lithium fluoride, and a barium-aluminum laminate. The thickness of the electron injection layer 18 is, for example, about 2 to 50 nm.

  The transparent cathode 20 is laminated on the surface of the electron injection layer 18, applies a negative voltage to the organic EL device 1 with respect to the anode 12, and injects electrons into the element (specifically, the organic light emitting layer 15). It has a function. The transparent cathode 20 is not particularly limited, but it is preferable to use a substance and structure having a high transmittance. Thereby, a top emission organic EL device with high luminous efficiency can be realized.

  The configuration of the transparent cathode 20 is not particularly limited, but a metal oxide layer is used. Examples of the metal oxide layer include a layer made of indium tin oxide (ITO), a layer made of indium zinc oxide (IZO), and the like. The thickness of the transparent cathode 20 is, for example, about 5 to 200 nm.

  The transparent sealing film 22 is formed on the surface of the transparent cathode 20 and has a function of suppressing moisture and oxygen from entering the device. If the transparent sealing film 22 is not formed, peeling between the electrode and the organic layer proceeds due to moisture or oxygen, and a dot-like or circular non-light-emitting defect called a dark spot (dark defect point) grows. . The transparent sealing film 22 is required to be transparent. Examples of the material of the transparent sealing film 22 include silicon nitride (SiN), silicon nitride oxide (SiON), and transparent organic resin. The thickness of the transparent sealing film 22 is, for example, about 20 to 5000 nm.

  Next, the manufacturing method of the electronic device of the present invention will be described by taking the manufacturing method of the organic EL device as an example. FIG. 2 is a cross-sectional view of the organic EL device according to the embodiment of the present invention, and FIGS. 3A to 3K illustrate a method for manufacturing the organic EL device according to the embodiment of the present invention. FIG.

  First, as shown in FIG. 3A, a TFT substrate 10 is prepared. The TFT substrate 10 is a substrate structure as shown in FIG. 1, that is, a substrate in which the TFT 50 and the planarizing film 57 are disposed on the substrate 40 (for example, a glass substrate).

Next, a metal film 12 ′ to be the anode 12 is formed on the TFT substrate 10 (FIG. 3B). As the metal film 12 ′, for example, a film made of Al, Ag, or an alloy thereof is preferably formed by a sputtering film forming method. The sputtering film forming conditions (film forming conditions) here include, for example, an Ag alloy target and the TFT substrate 10 placed in a chamber; after the chamber is evacuated, argon (Ar) or nitrogen (N ₂ ) introducing a gas such as; applying a voltage between the target and the substrate. Thereby, ions are generated, the ions collide with the Ag alloy target, the target particles are repelled and attached to the substrate, an Ag alloy film is formed, and the metal film 12 ′ is formed.

  A resist mask 81 is formed on the metal film 12 '(FIG. 3C). The resist mask 81 defines the formation region (position / shape) of the anode 12. The resist mask 81 is formed by patterning a photoresist formed on the metal film 12 'by a photolithography method.

  Using the resist mask 81 as a mask, the metal film 12 'is patterned by wet etching to form the anode 12 (FIG. 3D). The wet etching conditions here include, for example, immersing a work-in-process product in an acid-based mixture of phosphoric acid, nitric acid, and acetic acid. Thereby, the metal film 12 'is etched.

  Next, the resist mask 81 is removed (FIG. 3E). The resist mask 81 is removed by, for example, immersing the work-in-process product in acetone, dimethylformamide, or a commercially available resist stripping solution. Thereby, the resist is removed. After removing the resist, the substrate is washed with isopropyl alcohol (IPA) or pure water. In this way, the resist stripping process is executed.

Next, a hole injection layer 13 is formed on the anode 12 by a sputtering film formation method so as to cover the anode 12 (FIG. 3F). The hole injection layer 13 is an oxide layer of a transition metal. Film formation by the sputtering film formation method here is, for example, a transition metal (Mo or W or a mixture of MoW) as a target is placed in a chamber together with a work-in-process product; after the chamber is evacuated, Ar A gas and O ₂ gas are introduced; a voltage is applied between the target and the substrate. Thereby, Ar ions are generated, the ions collide with the target, and the target particles are repelled. It reacts with O ₂ until or after the target particles that have been blown off adhere to the substrate, and a transition metal oxide film (molybdenum oxide film, tungsten oxide film, molybdenum-tungsten oxide film, etc.) is formed on the substrate. Is done.

  The formed hole injection layer 13 may be etched and disposed only in a desired region. Further, a metal film 12 ′ and a hole injection layer 13 are formed, and then a resist mask is disposed, and etching of the hole injection layer 13 and etching of the metal film 12 ′ (FIG. 3D) are performed. You may do it at the same time.

  Next, the bank layer 16 is formed. First, a photosensitive resin for a bank is applied on the TFT substrate 10 so as to cover the hole injection layer 13 by using a slit coating method or a spin coating method to form a photosensitive resin layer 82 (FIG. 3 (g)). Next, pre-baking is performed to remove the solvent contained in the photosensitive resin layer 82.

  Next, the photosensitive resin layer 82 is irradiated with ultraviolet light through a mask (not shown) that defines the opening 85, and the photosensitive resin is photocured (in the case of a negative photosensitive resin). Next, the uncured portion of the material is removed by immersing the substrate in an alkaline developer. Thereby, the photosensitive resin layer 82 is patterned to form an opening 85, thereby forming the bank layer 16 (FIG. 3H).

  Here, as the developer, an aqueous solution containing tetraalkylammonium hydroxide and having a pH adjusted to 10.5 to 11 is used. This is to prevent the hole injection layer 13 from being dissolved by the developer.

  The surface of the bank layer 16 or the hole injection layer 13 may be plasma treated to control wettability. This is because the accuracy of application of an organic material (FIG. 3 (i)) described later is increased.

  Next, an organic material constituting the organic functional layer is applied to the opening 85 of the bank layer 16. In FIG. 3I, an organic light emitting material is applied to form the organic light emitting layer 15. The organic material is applied using, for example, an inkjet method. The ink jet method is a method of forming a film by ejecting an ink containing a film forming material from a nozzle. The organic light emitting material applied by the inkjet method is dried. Thereby, the organic light emitting layer 15 is formed in the recess or groove defined by the bank layer 16.

  Prior to the formation of the organic light emitting layer 15, the intermediate layer 14 may be similarly formed by coating (see FIG. 1).

  Next, the electron injection layer 18 is formed on the organic light emitting layer 15 (FIG. 3 (j)). The electron injection layer 18 is formed by, for example, a vapor deposition method. The conditions of the vapor deposition method here are as follows. First, for example, Ba raw material is placed in a crucible; placed in a chamber together with a substrate on which a film is formed; then, the crucible is heated after the inside of the chamber is evacuated. Thereby, Ba evaporates and adheres to the substrate to form a Ba film. The crucible heating method at this time includes a resistance heating type, an electron beam type, and a high frequency induction type.

  Next, the transparent cathode 20 is formed on the electron injection layer 18 (FIG. 3 (k)). The transparent cathode 20 is obtained by forming a layer (solid layer) that covers the electron injection layer 18 by vapor deposition or sputtering. The conditions (deposition conditions) for the vapor deposition method here are as follows. First, for example, an ITO raw material is placed in a crucible and placed in a chamber together with a substrate on which a film is to be deposited; An ITO film is formed. Thereafter, predetermined patterning is performed as necessary.

  Finally, when the transparent sealing film 22 is formed on the transparent cathode 20 (see FIG. 1), the organic EL device 1 of the present embodiment is obtained. The transparent sealing film 22 may be formed by forming a layer (solid layer) that covers the transparent cathode 20 by sputtering film formation. The sputtering film forming conditions here (film forming conditions) are, for example, that a SiN target is placed in a chamber together with a substrate to which a film is attached; after the inside of the chamber is evacuated, Ar gas is introduced; A voltage is applied between the substrate and the substrate. Thereby, Ar ions are generated, the ions collide with the target, the target particles are repelled and attached to the substrate, and a SiN film is formed. Thereafter, predetermined patterning is performed as necessary. The patterning is not limited to wet etching but may be dry etching.

  The organic EL device of the present embodiment can be manufactured by the manufacturing method described above. According to the manufacturing method of the present invention, dissolution of the hole injection layer 13 made of an oxide of a transition metal by the developer when forming the bank layer 16 is suppressed. Therefore, an organic EL device having an organic functional layer (for example, an organic light emitting layer) formed by a coating method while having a hole injection layer having high hole injection performance can be produced. By employing the coating method, it becomes easy to produce a large organic EL panel (for example, 100 inch class), and it is possible to produce the large organic EL panel at a mass production level.

  EXAMPLES Next, although this invention is demonstrated in detail with reference to an Example and a comparative example, the scope of the present invention is limited and interpreted by these Examples.

  First, developers shown in Examples 1 and 2 and Comparative Examples 1 to 4 were prepared. The pH of the solution was measured using a digital pH meter PH-201 manufactured by Sato Corporation.

Example 1
In Example 1, a small amount of nitric acid (special grade manufactured by Kanto Chemical Co., Ltd.) was added to a 0.2% by mass TMAH aqueous solution (NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.), and a chemical solution adjusted to pH 11 was used as a developer.
(Example 2)
In Example 2, a chemical solution prepared by adding a small amount of nitric acid to a 0.2% by mass TMAH aqueous solution and adjusting the pH to 11.5 was used as a developer.

(Comparative Example 1)
In Comparative Example 1, a 0.2% by mass TMAH aqueous solution (pH = 12.5) was used as the developer.
(Comparative Example 2)
In Comparative Example 2, a chemical solution prepared by adding a small amount of nitric acid to a 0.2 mass% TMAH aqueous solution and adjusting the pH to 12 was used as a developer.
(Comparative Example 3)
In Comparative Example 3, a chemical solution prepared by adding a small amount of formic acid (special grade manufactured by Kanto Chemical Co., Ltd.) to a 0.2% by mass TMAH aqueous solution and adjusting the pH to 11 was used as a developer.
(Comparative Example 4)
In Comparative Example 4, a chemical solution prepared by adding a small amount of acetic acid (special grade manufactured by Kanto Chemical Co., Ltd.) to a 0.2% TMAH aqueous solution and adjusting the pH to 11 was used as a developer.

  With respect to the developers prepared in Examples 1 and 2 and Comparative Examples 1 to 4, the amount of the hole injection layer dissolved was evaluated.

  The hole injection layer used for evaluation is a molybdenum tungsten mixture film formed on a flat ITO substrate by a reactive sputtering method with an RF power of 500 W (film thickness: 100 nm). The elemental composition of the molybdenum tungsten mixture film was Mo / W = 35/65 (Mo content: 35 atom%). After film formation, a heat treatment was performed at 200 ° C. for 30 minutes to improve chemical resistance. Hereinafter, the formed hole injection layer is referred to as a MoWOx film.

This MoWOx film is immersed in the developer prepared as described above for 30 seconds, washed with pure water (conductivity: about 1 to 10 MΩ · cm) for 10 seconds, and water is removed by blowing N ₂ gas. did. The immersion experiment was performed at room temperature (23 ° C.).

  The dissolution amount of the MoWOx film was calculated by measuring the film thickness before and after immersion in the developer. For measurement of the film thickness, an optical film thickness measuring device, NanoSpec6500A, manufactured by Toago Technology Co., Ltd. was used. However, since the MoWOx film is only slightly dissolved in pure water, the amount dissolved in pure water was ignored in this experiment.

  Table 1 shows the amounts of dissolved MoWOx films of Examples 1 and 2 and Comparative Examples 1 to 4, chemical solution (developer) conditions, and pKa values representing the acidity of the added acid (document values). And summarized. pKa is one of the indexes for quantitatively expressing the strength of the acid, and is called an acid dissociation constant or an acidity constant. For a dissociation reaction in which hydrogen ions are released from an acid, the equilibrium constant is called Ka, and the negative common logarithm of the equilibrium constant is called pKa. A larger Ka or a smaller pKa indicates a stronger acid.

  When the MoWOx film was immersed in the developer of Example 1 for 30 seconds, the thickness decreased by 9.5 nm due to dissolution. Table 1 shows the conversion value (18.9 nm / min) of the dissolution amount when the immersion time is 1 minute. Further, the dissolution amount when the MoWOx film was immersed in the developer of Example 2 was 25.0 nm / min.

  On the other hand, when the MoWOx film was immersed in the developer of Comparative Example 1, the film dissolved immediately and disappeared within 1 second. Further, the dissolution amount when the MoWOx film was immersed in the developer of Comparative Example 2 was 120 nm / min.

  Although the MoWOx film is soluble in an alkaline solution, as shown by these results, it is suggested that the amount of dissolution can be reduced by appropriately adjusting the pH value of the alkaline solution.

  In the above examples and comparative examples, the MoWOx film exposed on the ITO substrate is immersed in the developer, so that the contact time between the MoWOx film and the developer is long. On the other hand, if the MoWOx film is covered with a resin film to be developed with a developing solution and immersed in the developing solution, the contact time between the MoWOx film and the developing solution is shortened and the amount of dissolution is also reduced.

  Therefore, as described above, a MoWOx film was formed on the flat ITO substrate, and a resin film (thickness: 1 μm) of an alkali-soluble negative photosensitive acrylic resin (manufactured by Asahi Glass Co., Ltd.) was further formed on the MoWOx film. A sample was prepared. When this sample was immersed in the developers of Examples 1 and 2 (30 seconds), the dissolved amount of the MoWOx film was almost zero. On the other hand, when the same sample was immersed in the developer of Comparative Examples 1 and 2 under the same conditions, dissolution of the MoWOx film was confirmed. That is, it can be seen that the dissolution of the MoWOx film can be suppressed if the pH is 11.5 or less.

  Further, the dissolution amount by the developer of Example 1 was 18.9 nm / min, the dissolution amount by the developer of Comparative Example 3 was 29.8 nm / min, and the dissolution amount by night in the developer of Comparative Example 4 was 36. 0.9 nm / min.

  The developer of Example 1, the developer of Comparative Example 3, and the developer of Comparative Example 4 all have a pH of 11, but the type of acid added is different. The pKa of the nitric acid added in Example 1, the formic acid added in Comparative Example 3, and the acetic acid added in Comparative Example 4 are -1.32, 3.75, and 4.8, respectively, and nitric acid> formic acid> acetic acid. The acidity is high in order. That is, in order to suppress dissolution of the MoWOx film by the developer, it has been found that it is preferable to add a strong acid even if the pH of the developer is the same.

  The alkaline developer has a role of forming a bank by pattern etching of a photosensitive resin. If the pH of the alkaline developer is too low, the development performance is lowered. Therefore, it is generally required that the pH of the developer for pattern development of the photosensitive resin film is 10.5 or more. From the above, it is required that the developer used has a pH of 10.5 to 11.5 in order to ensure both the developability of the bank and the suppression of dissolution of the hole injection layer.

  According to the present invention, reduction in manufacturing cost and increase in area of an organic EL device are realized. It is useful as a pixel light source of a display device, a backlight of a liquid crystal display, and various illumination light sources, and particularly suitable for application to an active matrix organic EL display panel combined with a TFT.

DESCRIPTION OF SYMBOLS 1, 2 Organic EL device 10 TFT substrate 12 Anode 13 Hole injection layer 14 Intermediate layer 15 Organic light emitting layer 16 Bank layer 18 Electron injection layer 20 Transparent cathode 22 Transparent sealing film 40 Substrate 50 Transistor element 50A, 50B TFT
51 Source / Drain Electrode 52 Semiconductor Layer 53 Gate Insulating Film 54 Gate Electrode 55 Wiring 57 Flattening Film 60 Organic EL Part 70 Light 81 Resist Mask 82 Photosensitive Resin Layer 85 Opening

Claims (6)

A method of manufacturing an electronic device, including a step of patterning a photosensitive resin film disposed on a thin film made of an oxide of a transition metal by a photolithography process to form an organic resin layer,
The developing solution used in the photolithography process is an aqueous solution containing tetraalkylammonium hydroxide and a strong acid salt, and has a pH of 10.5 to 11.5.   The method for manufacturing an electronic device according to claim 1, wherein the tetraalkylammonium hydroxide is tetramethylammonium hydroxide.   The method of manufacturing an electronic device according to claim 1, wherein the strong acid is any one of nitric acid, sulfuric acid, and hydrochloric acid.   The method of manufacturing an electronic device according to claim 1, wherein the transition metal is any one of tungsten and molybdenum, or a mixture thereof.   The method of manufacturing an electronic device according to claim 1, wherein the electronic device is an organic electronic device having an organic functional layer having a region defined by the organic resin layer. The electronic device is defined by a substrate, a first electrode disposed on the substrate, a hole injection layer disposed on the anode, a bank disposed on the hole injection layer, and the bank. And an organic functional layer comprising an organic light emitting layer disposed on the hole injection layer, and a second electrode disposed on the organic functional layer,
The thin film made of the transition metal oxide in claim 1 is the hole injection layer, and the organic resin layer in claim 1 is the bank.
The manufacturing method of the electronic device of Claim 1.

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