JP4617749B2 - Manufacturing method of display device - Google Patents

Description

  The present invention relates to a display device using an organic electroluminescence element (hereinafter referred to as EL) and a manufacturing method thereof.

  In an organic EL display device, there is a step on a surface on which a thin film transistor (hereinafter referred to as TFT) and source / drain wirings are formed, and in order to form an organic EL layer thereon, a planarizing layer is used. It is necessary to provide and eliminate the step. As a planarization method, a method of applying an organic insulating resin such as polyimide or acrylic resin is widely used. However, these organic resins themselves contain a large amount of moisture, and further absorb moisture in the subsequent manufacturing process.

  The organic EL layer is formed on the anode formed on the organic flattening layer, but the moisture in the organic flattening layer diffuses into the organic EL layer, deteriorating the organic EL element and lowering the luminance. was there.

  As a display device that solves the above problems, an inorganic layer such as a silicon oxide layer or a silicon nitride layer is provided on the organic planarization layer by a method such as plasma enhanced chemical vapor deposition (CVD). The thing which prevents the spreading | diffusion of a water | moisture content is proposed (for example, refer patent document 1).

JP 2001-356711 A (FIG. 1)

  In the configuration in which an inorganic layer is provided by plasma CVD on the organic flattening layer as in the above-described organic EL element as a conventional example to prevent moisture diffusion, the organic flattening film is decomposed by plasma ions or organic flattened. Due to the influence of moisture in the layer, a dense inorganic layer cannot be formed, and there is a problem that the shielding property against moisture is not sufficient.

  The present invention has been made in order to solve the above-described problems. An organic EL which is provided with an anode on an organic planarization layer, shields moisture diffused from the organic planarization layer, and is a light-emitting display layer. An object of the present invention is to provide a display device that prevents deterioration of layers due to moisture absorption and suppresses a decrease in luminance over time, and a method for manufacturing the same.

The present invention includes a step of providing an organic flattening layer for flattening unevenness on the upper surface of a drive circuit, a step of providing a metal anode on the surface of the organic flattening layer, and a step of forming an inorganic insulating layer on the surface of the metal anode. A portion corresponding to the light emitting display layer is opened in the inorganic insulating layer, and further, the inorganic insulating layer and the metal anode anode are etched to form a pixel electrode. A step of forming a layer, a step of forming a pixel separation layer in a gap between the light emitting display layer and the moisture shielding layer, and a gap between the moisture shielding layer adjacent to the moisture shielding layer, excluding a portion corresponding to the light emitting display layer, and a pixel A step of providing a light-emitting display layer as an organic EL layer on the exposed metal anode surface of the opening of the separation layer; and covering the light-emitting display layer upper surface, the pixel separation layer upper surface, and the moisture shielding layer upper surface; Providing a cathode to be bonded to Was carried out in order, the light-emitting display layer a method of manufacturing a display device characterized by a structure which is surrounded by a metal anode, water barrier layer and a cathode.

According to the manufacturing method of the display device of the present invention, the light emitting display layer is surrounded by the metal anode, the moisture shielding layer and the cathode, and the organic EL layer which is the light emitting display layer is isolated. It is possible to shield moisture diffused through the pixel separation layer with the inorganic insulating layer and the cathode layer .

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view ((a) and a plan view (b) taken along the line CC of the organic EL element unit 16 of the display device according to the first embodiment of the present invention.
As shown in FIG. 1, a TFT 2 that is a driving circuit is formed on a glass substrate 1. The TFT 2 is covered with a gate insulating layer 3, and an interlayer insulating layer 4 is formed on the gate insulating layer 3. ing. A through hole is formed in the interlayer insulating layer 4, a source / drain wiring 5 connected to the TFT 2 is provided, and a protective insulating layer 6 is formed on the interlayer insulating layer 4. Since the surface of the protective insulating layer 6 in the driving circuit comprising the TFT 2, the gate insulating layer 3, the interlayer insulating layer 4, the source / drain wiring 5 and the protective insulating layer 6 is uneven and not flat, An organic planarization layer 7 is provided, and an anode 10 made of a metal layer is partially opened on the organic planarization layer 7 so as to cover the entire surface. The anode 10 and the source / drain wiring 5 are electrically connected to each other through the through hole 8 provided in the organic planarizing layer 7 and the connection hole 9 b provided in the protective insulating layer 6, and provided in the gate insulating layer 3. The source / drain wiring 5 and the TFT 2 are electrically connected through the connection hole 9a, and the anode 10 and the TFT 2 are electrically connected.

An organic EL layer 14 which is a light emitting display layer is provided on the anode 10, and an inorganic insulating layer formed by CVD is patterned so as to surround the organic EL layer 14, and is provided as a moisture shielding layer 11. Yes. A pixel separation layer 12 is formed on the moisture shielding layer 11, between the moisture shielding layer 11 and the organic EL layer 14, and between the adjacent organic EL element units 16. A cathode 15 is provided so as to cover the entire upper surface of the upper surface of the pixel separation layer 12 and the organic EL layer 14 and the moisture shielding layer 11 exposed from the pixel separation layer 12.
That is, the organic EL element unit 16 of the display device according to the present embodiment is formed as described above, is sealed with glass, and is connected to an external control circuit to be a display device (not shown). .

2 and 3 are process diagrams showing a manufacturing process of a display device using an active matrix top emission type organic EL element which is the display device according to the first embodiment.
In the first step shown in FIG. 2A, TFTs 2 (TFTs are simply expressed) are formed in correspondence with the respective pixels on the glass substrate 1. Next, an inorganic insulating layer 4 made of silicon dioxide (SiO ₂ ) is formed so as to cover the TFT ₂ . This inorganic insulating layer 4 is provided with a connection hole 9a formed by photolithography. A metal film having a three-layer structure is formed on the inorganic insulating layer 4. This metal film is formed by successively depositing molybdenum (Mo), aluminum (Al), and molybdenum (Mo) using a DC magnetron sputtering method, and is connected to the TFT 2 through the connection hole 9a. This metal film is patterned by a photoengraving method to form source and drain wirings 5. A protective insulating layer 6 made of a silicon nitride film (SiN _x ) is formed on the inorganic insulating layer 4 so as to cover the wiring 5. A connection hole 9b is formed in the protective insulating layer 6 by photolithography.

In the second step shown in FIG. 2B, an organic flattening layer 7 is formed on the protective insulating layer 6 for the purpose of flattening the steps generated in the device manufacturing process so far. The organic planarizing layer 7 is made of a photosensitive acrylic resin material and is formed by spin coating so as to have a film thickness of about 1500 to 2000 nm. This process can ensure sufficient flatness. This organic planarization layer 7 has photosensitivity, and forms a through hole 8 that communicates with the connection hole 9b by photolithography.
This organic flattening layer 7 is subjected to a baking process at 230 ° C. for 1 hour after the application of the photosensitive resin material, exposure, development, and washing with water using a photolithography method. This baking treatment accelerates the crosslinking reaction of the resin material and dehydrates moisture absorbed during the photolithography process.

  In the third step shown in FIG. 2C, a metal layer serving as the anode 10 is formed on the organic planarizing layer 7 so as to be connected to the wiring (drain) 5 through the through hole 8 and the connection hole 9b. . Here, the metal layer is formed of, for example, molybdenum (Mo) by DC magnetron sputtering. The target is a Mo target and is sputtered with argon (Ar) gas. The sputtering conditions are an Ar gas flow rate of 100 sccm, a pressure of 0.14 Pa, a power of 1.0 kW, a temperature of 100 ° C., and a film thickness of 100 nm. As for the film thickness, a film thickness of 50 nm or more is necessary in order to obtain sufficient reflectivity. However, if the film thickness becomes too thick, protrusions are generated on the film surface and the smoothness deteriorates, so that it is preferably 100 nm or less.

Next, an inorganic insulating layer to be the moisture blocking layer 11 is formed continuously using a plasma CVD method so as to cover the metal layer to be the anode 10. At this time, the organic planarization layer 7 is not completely exposed to the plasma because it is completely covered with the metal layer serving as the anode 10. As a result, there is no influence of decomposition of the organic component from the organic planarization layer 7, and a dense inorganic insulating layer having a high gas barrier property can be formed. In the present embodiment, a silicon nitride film (Si ₃ N ₄ ) is used for the inorganic insulating layer to be the moisture shielding layer 11. As film formation conditions, silane (SiH ₄ ) 30 sccm, ammonia (NH ₃ ) 30 sccm, and nitrogen (N ₂ ) 1000 sccm were introduced into the reaction chamber, the film formation pressure was 130 Pa, the film formation temperature was 220 ° C., and the high frequency of 13.56 MHz. Was applied to form a film. The film thickness is 800 nm.

In the fourth step shown in FIG. 2 (d), a part of the silicon nitride film to be the moisture shielding layer 11 and a part corresponding to the organic EL light emitting part are opened, so that it is processed by photolithography and dry etching. In the dry etching, etching is performed with 10 sccm of tetrafluoromethane (CF ₄ ), 90 sccm of helium (He), RF power of 200 W, and pressure of ₄ Pa until reaching the lower layer anode 10. Thereafter, in order to remove carbon (C) and freon (F) remaining on the anode surface of the opening and clean the surface, UV ozone treatment is performed.

  In the fifth step shown in FIG. 3E, the silicon nitride film that is the moisture shielding layer 11 and the Mo film of the metal layer that becomes the anode 10 are continuously etched by the photoengraving method, and the anode 10 as the pixel electrode is obtained. Process forming. The etching conditions for the silicon nitride film are the same as described above. Mo is wet etched using a mixed solution of phosphoric acid, nitric acid and acetic acid. Thereby, the moisture shielding layer 11 surrounding the organic EL layer 14 is formed on the anode 10.

  In the sixth step shown in FIG. 3 (f), first, the pixel separation layer 12 is formed on the organic planarization layer 7 so as to cover the anode 10 and the moisture shielding layer 11. The pixel separation layer 12 is formed using a photosensitive polyimide so as to have a film thickness of about 1000 nm by spin coating so as to completely cover the moisture shielding layer 11. Next, the pixel separation layer 12 is opened using a photoengraving method so as to expose the portion where the organic EL layer 14 is formed and the upper side of the moisture blocking layer 11. After opening, baking is performed at 230 ° C. for 1 hour to accelerate the crosslinking reaction of the resin and dehydrate the moisture absorbed during the photolithography process.

  In the seventh step shown in FIG. 3G, the organic EL layer 14 is formed in the opening of the pixel separation layer 12 by vapor deposition using the mask 13. The organic EL layer 14 is formed in a state in which a vacuum state is maintained in the order of the hole transport layer, the light emitting layer, and the electron injection layer. Here, bis [(N-naphthyl) -N-phenyl] benzidine (α-NPD) 20 nm is used as the hole transport layer, 8-quinolinol aluminum complex (Alq) 50 nm is used as the light emitting layer, and bathocuproine 60 nm is used as the electron injection layer. A film was formed. In the present embodiment, the organic EL layer 14 has a three-layer structure, but is not limited to this structure and may have any number of layers.

In the eighth step shown in FIG. 3H, the cathode 15 is formed so as to cover the entire display area. Here, the cathode 15 is a transparent conductive film made of ITO (In ₂ O ₃ + SnO ₂ ) formed by sputtering. The cathode 15 is joined to the moisture shielding layer 11 through the opening of the pixel separation layer 12 to isolate the pixel separation layer 12 and the organic EL layer 14 connected to the organic planarization layer 7. Thereafter, the matrix of the organic EL element unit 16 is sealed with glass and connected to an external control circuit to complete an active matrix type organic EL display device (not shown).

  FIG. 4 is a diagram for explaining a mechanism for preventing the diffusion of moisture to the organic EL element portion in the display device of the first embodiment. As shown in FIG. 4, the moisture absorbed in the organic planarization layer 7 forms a wall that prevents the moisture shielding layer 11 from blocking moisture even if it diffuses into the pixel isolation layer 12 through the moisture diffusion path 17. Therefore, it cannot move to the organic EL layer 14 from the side surface. Moreover, since the metal layer of the anode 10 is blocked on the bottom surface portion of the organic EL layer 14 and the upper surface portion of the organic EL layer 14 is blocked by the inorganic conductive layer of the cathode 15, the organic EL element is prevented from being deteriorated due to moisture absorption. Is done.

  In the first embodiment, an example in which a glass material is used as the substrate has been described. However, other materials such as silicon (Si) or plastic can be applied to the substrate.

  Further, in the first embodiment, the source and drain wiring 5 has been described as having a three-layer structure of molybdenum (Mo), aluminum (Al), and molybdenum (Mo). However, the material is a conductor having low resistance. As long as it is a single layer or a stack of metals such as aluminum (Al), chromium (Cr), tungsten (W), molybdenum (Mo), or a semiconductor material such as polysilicon. There is no particular limitation. In addition, although the film forming method is described using the DC magnetron sputtering method, other film forming methods such as vapor deposition, ion plate, cluster ion beam method, and the like may be used.

In the first embodiment, the metal film of the anode 10 is molybdenum (Mo), but chromium (Cr), silver (Ag), aluminum (Al), palladium (Pd), or other metals may be used. In the case of the bottom emission type, the anode must be a transparent conductive film. In that case, an ITO film, an IZO film (In ₂ O ₃ + ZnO), a ZAO film (ZnO + Al ₂ O ₃ ), or the like may be used.

In the first embodiment, the silicon nitride film is used as the inorganic insulating layer as the moisture shielding layer 11, but the same effect can be obtained even if it is a silicon oxynitride film (SiON). As conditions for forming the silicon oxynitride film, for example, silane (SiH ₄ ) 30 sccm, nitrogen dioxide (NO ₂ ) 300 sccm, and nitrogen (N ₂ ) 700 sccm are introduced, the film forming pressure is 100 Pa, the film forming temperature is 220 ° C. The film is formed to a thickness of 800 nm by applying a high frequency of 56 MHz at 0.8 kW.

  In the first embodiment, the plasma CVD method is shown as the method for forming the inorganic insulating layer as the moisture shielding layer 11. However, any method capable of forming a film at a low temperature by a dry process may be used, and ECR-CVD (electron The thing by cyclotron resonance CVD method etc. can also be used.

  By the way, in the said Embodiment 1, although the thing of the photosensitive acrylic resin material was used as the organic planarization layer 7, other organic insulating materials, such as photosensitive polyimide, may be used. Further, although the spin coating method has been described as the method for forming the organic planarization layer 7, other coating methods such as printing may be used.

  In the first embodiment, photosensitive polyimide is used as the pixel separation layer 12, but the same effect can be obtained by using, for example, a photosensitive organic acrylic resin.

  In Embodiment 1, an ITO film that is a transparent conductive film is used as the cathode 15, but other transparent conductive films such as an IZO film may be used.

  In the first embodiment, the case where an organic EL element is manufactured as a display device has been described. Needless to say, the present invention can be applied to other display elements having a similar structure.

Embodiment 2. FIG.
FIG. 5 is a cross-sectional view showing an organic EL element unit of the display device according to the second embodiment. As shown in FIG. 5, the display device of the second embodiment is formed on the inorganic insulating layer 18 and the inorganic insulating layer 18 instead of the inorganic moisture shielding layer 11 in the organic EL element unit of the first embodiment. A moisture shielding layer 20 is formed as a composite layer with the inorganic conductive layer 19.
The inorganic conductive layer 19 is formed of molybdenum (Mo) under the same conditions as the anode 10. The material of the inorganic conductive layer is not limited to Mo, and may be a metal having high conductivity such as chromium (Cr) or aluminum (Al). Thereafter, Mo is wet etched to open a portion corresponding to the organic EL layer 14 on each pixel by photolithography, and the silicon nitride film is continuously dry etched. The wet etching and dry etching conditions are the same as those described in the first embodiment. Thereafter, in order to remove carbon (C) and freon (F) remaining on the surface of the anode 10 in the connection hole 9b and clean the surface, UV ozone treatment is performed.

  Further, the molybdenum film (Mo), the silicon nitride film, and the molybdenum film (Mo) are successively etched using a photoengraving method to form the anode (pixel electrode) 10. At this stage, an inorganic insulating layer 18 and an inorganic conductive layer 19 are formed on the anode 10 so as to surround the organic EL layer 14, thereby forming a moisture shielding layer 20.

  Next, a pixel separation layer 12 is provided on the organic planarization layer 7 so as to cover the anode 10 and the moisture shielding layer 20 of the composite layer, and this pixel separation layer 12 corresponds to an organic EL element by photolithography. An opening is made so that the portion and the upper side of the inorganic conductive layer 19 are exposed. Thereafter, the organic EL layer 14 and the cathode 15 are formed as in the first embodiment, and the cathode 15 and the inorganic conductive layer 19 are joined. As a result, even if moisture absorbed in the organic planarization layer 7 diffuses into the pixel separation layer 12, it is blocked by the moisture shielding layer 20 of the composite layer and cannot move to the organic EL layer. Similarly, deterioration due to moisture absorption of the organic EL element is prevented.

  In the second embodiment, since the inorganic conductive layer 19 acts as an auxiliary electrode for the cathode 15, not only the effect of blocking moisture but also the effect of suppressing shading. Shading means that a transparent conductive film has a resistance several tens of times higher than that of a metal film, so that a voltage drop is likely to occur, and the cathode voltage drop becomes more conspicuous from the outer edge of the display area toward the center, and sufficient electrons are generated. As a result of not being supplied, it means a phenomenon in which light emission is weakened and darkened. As a countermeasure, a voltage drop is suppressed by partially using a low resistance metal or the like as an auxiliary electrode.

They are sectional drawing (a) which shows the organic EL element unit of the display apparatus of Embodiment 1, and a top view (b) in CC plane. FIG. 6 is a process diagram showing the first half of a manufacturing process of a display device using an active matrix top emission organic EL element which is the display device in the first embodiment. FIG. 6 is a process diagram showing the second half of a manufacturing process of a display device using an active matrix top emission type organic EL element which is the display device in the first embodiment. 3 is a diagram illustrating a mechanism for preventing moisture from diffusing into an organic EL element portion in the display device of Embodiment 1. FIG. 6 is a cross-sectional view showing an organic EL element unit of a display device according to Embodiment 2. FIG.

Explanation of symbols

2 TFT
7 Organic flattening layer 10 Anode 11, 20 Moisture shielding layer 12 Pixel separation layer 14 Organic EL layer 15 Cathode 19 Inorganic conductive layer

Claims (2)

Providing an organic flattening layer for flattening irregularities on the upper surface of the drive circuit;
Providing a metal anode on the surface of the organic planarization layer;
Forming an inorganic insulating layer on the surface of the metal anode;
A portion corresponding to the light emitting display layer is opened in the inorganic insulating layer, and the inorganic insulating layer and the metal anode anode are etched to form a pixel electrode, and a region to be the light emitting display layer is formed on the metal anode. Forming a surrounding moisture shielding layer;
Forming a pixel separation layer in a gap between the light-emitting display layer and the moisture shielding layer, and a gap between the moisture shielding layer and the moisture shielding layer, excluding a portion corresponding to the light-emitting display layer;
Providing a light emitting display layer that is an organic EL layer on the exposed metal anode surface of the opening of the pixel separation layer;
Providing a cathode that covers the upper surface of the light emitting display layer, the upper surface of the pixel separation layer, and the upper surface of the moisture shielding layer, and is bonded to the light emitting display layer and the moisture shielding layer;
In order,
The method for manufacturing a display device, wherein the light-emitting display layer has a structure surrounded by the metal anode, the moisture shielding layer, and the cathode. 2. The display according to claim 1, wherein the moisture shielding layer is a composite layer in which an inorganic insulating layer formed by CVD and an inorganic conductive layer continuously formed on the inorganic insulating layer are laminated. Device manufacturing method.

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