JP2020024930A - Organic el display device and manufacturing method therefor - Google Patents

Abstract

To provide an organic EL display device and a manufacturing method therefor that improve display quality by suppressing color unevenness and/or luminance unevenness of the organic EL display device.SOLUTION: An organic EL display device comprises: a substrate 10 having a surface on which a drive circuit including a TFT 20 is formed; a flattening film 30 that covers the drive circuit to flatten the surface of the substrate 10; and an organic light-emitting element 40 that is formed on a surface of the flattening film 30 and includes a first electrode 41 connected to the drive circuit, an organic light-emitting layer 43 formed on the first electrode 41, and a second electrode 44 formed on the organic light-emitting layer 43. The flattening film 30 includes a first inorganic insulation film 31 and an organic insulation film 32 stacked on the drive circuit. A surface of the organic insulation film 32 is formed so as to have arithmetic plane roughness Ra equal to or smaller than 50 nm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an organic EL display device and a method for manufacturing the same.

  2. Description of the Related Art In recent years, organic EL display devices have tended to be used in large-sized televisions and portable devices. In an organic EL display device, a driving circuit using a thin film transistor (hereinafter, also referred to as a TFT) as an active element such as a switching element and a driving element is formed in an area of each pixel on an insulating substrate, and each pixel is formed thereon. Is formed so as to be connected to the TFT. Organic EL display devices include a top emission type in which a front surface of a light emitting element is a display surface and a bottom emission type in which a back surface of an insulating substrate is a display surface. The top emission type depends on a display area of the organic light emitting element. Instead, the above-described drive circuit is formed below. On the other hand, in the bottom emission type, a drive circuit is formed on the periphery of the display area. Therefore, in a small organic EL display device such as a portable device having a small space for forming a driving circuit, a top emission type, that is, a configuration in which a driving circuit such as a TFT is formed under almost the entire display area is often used. Is done. On the other hand, the bottom emission type is suitable for a large-sized television or the like in which a space between pixels is slightly larger.

  When a driving circuit is formed by a TFT or the like, the surface thereof becomes uneven. Since an organic light emitting element is formed thereon, the planarization film is formed by covering the drive circuit with a resin material or the like. By doing so, the surface is flattened. Conventionally, the flattening film is formed by forming a first inorganic insulating film as a barrier layer after a TFT is formed, and forming a contact hole for connecting the organic light emitting element and the TFT by a photolithography process. A photosensitive organic insulating film is formed thereon, and is obtained by a photolithography process and formation of a contact hole by wet development. By forming the organic insulating film in this way, unevenness on the surface due to the formation of a TFT or the like is flattened.

  Patent Literature 1 discloses a TFT suitable for a switching element for each pixel of an active matrix display device and having both a small occupied area and excellent transistor characteristics, and a method of manufacturing the same. In this method, a plurality of TFTs are integrally formed vertically through an interlayer insulating film whose surface irregularities are reduced to 20 nm or less by a CMP process. That is, when forming a fine TFT, the flatness of the surface of the interlayer insulating film is set to 20 nm or less in order to cope with a shallow depth of focus. In flattening for forming an organic light emitting element on the TFT, Absent.

JP-A-2017-11173

  On the other hand, when visually recognizing the organic EL display device, color unevenness or luminance unevenness may occur depending on the pixel, and the visibility characteristic may be degraded. The present inventor has conducted intensive studies on the cause of the color unevenness or luminance unevenness, and as a result, has found that the cause is the lack of flatness of the surface of the organic light emitting layer. That is, as described above, the organic light-emitting element is formed on a flattening film for flattening the surface on a TFT or the like on which a drive circuit is formed. The surface of the organic insulating film is tentatively flat, and it has conventionally been considered that there is no problem with this. However, as a result of the inventor's intensive studies, the organic insulating film surface has an arithmetic average roughness Ra of about 100 to 300 nm even when a non-photosensitive resin is used. It can be seen that the photosensitive resin used has more irregularities than this, and when the electrodes of the organic light emitting element and the organic light emitting layer are formed on this surface, the surface of the organic light emitting layer has the same surface roughness. Had become. When the surface of the organic light emitting layer has irregularities, the traveling direction of light microscopically varies. Therefore, it has been found that, when the display screen is viewed from the front, light traveling in an oblique direction is hard to be visually recognized, resulting in color unevenness and / or luminance unevenness.

  On the display screen of the display device, even if there is no clear display defect such as a non-lighting area, a constantly lighting area, or a bright line, if display unevenness due to luminance unevenness and / or color unevenness occurs as described above, There is a problem that display quality is deteriorated.

  In addition, it is also possible to increase the light emission output by providing a layer with high reflectivity on the surface of the organic light emitting layer and making it a microcavity, but if there is unevenness on the surface of the organic light emitting layer, unevenness is also formed on the reflective layer In addition, there is a problem that it is not possible to obtain a complete resonator due to irregular reflection, and it is not possible to obtain an increase in output.

  On the other hand, since flatness for manufacturing a fine TFT is not required, even if the surface flatness is not as strict as 20 nm or less as described in the above-mentioned Patent Document 1, the organic light emission is not required. It suffices that the light emitted from the layer is flat so that the light is emitted mainly from the front.

  The present invention has been made in view of such circumstances, and provides an organic EL display device having improved display quality by suppressing color unevenness and / or luminance unevenness of the organic EL display device, and a method of manufacturing the same. The purpose is to:

  An organic EL display device according to one embodiment of the present invention includes a substrate having a surface on which a drive circuit including a thin film transistor is formed; a planarization film that covers the drive circuit to planarize the surface of the substrate; A first electrode formed on the surface of the planarization film and connected to the driving circuit; an organic light emitting layer formed on the first electrode; and a second electrode formed on the organic light emitting layer. An organic light-emitting element comprising: a first inorganic insulating film and an organic insulating film laminated on the driving circuit, wherein the surface of the organic insulating film has an arithmetic planar roughness. Ra is formed to 50 nm or less.

  In a method of manufacturing an organic EL display device according to another embodiment of the present invention, a step of forming a drive circuit including a thin film transistor on a substrate, and forming a first inorganic insulating film and an organic insulating film on a surface of the drive circuit Performing a CMP step on the surface of the organic insulating film, forming a contact hole reaching the TFT in the organic insulating film and the first inorganic insulating film, and forming a metal inside the contact hole. Embedding and forming a first electrode in a predetermined region; forming an organic light emitting layer on the first electrode; and forming a second electrode on the organic light emitting layer. In.

  According to the embodiment of the present invention, the organic insulating film is formed on the uneven surface of the drive circuit including the TFT, and the surface is polished by the CMP, so that the surface is flattened to have an arithmetic average roughness Ra of 50 nm or less. It is flattened to a degree. As a result, light traveling microscopically in an oblique direction is greatly suppressed, and the occurrence of color unevenness and / or luminance unevenness is suppressed, and the display quality of the organic EL display device can be significantly improved.

It is a sectional view of an organic EL display of one embodiment of the present invention. 2 is a flowchart showing a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. It is a flowchart explaining the process of FIG. 2A in more detail. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 4 is a cross-sectional view illustrating a manufacturing process of the organic EL display device of Example 1 without the second inorganic insulating film of FIG. 1. FIG. 2 is a cross-sectional view illustrating a manufacturing process of a second embodiment of the organic EL display device in FIG. 1. FIG. 2 is a cross-sectional view illustrating a manufacturing process of a second embodiment of the organic EL display device in FIG. 1. FIG. 2 is a cross-sectional view illustrating a manufacturing process of a second embodiment of the organic EL display device in FIG. 1. FIG. 2 is a cross-sectional view illustrating a manufacturing process of a second embodiment of the organic EL display device in FIG. 1. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the organic EL display device in FIG.

  Next, an organic EL display device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows one pixel of the organic EL display device according to one embodiment (strictly speaking, red, green, and blue sub-pixels in one pixel, but in this specification, one pixel includes these sub-pixels) (Sometimes) is shown in a schematic sectional view.

  An organic EL display device according to an embodiment of the present invention includes a substrate 10 having a surface on which a driving circuit including a TFT 20 is formed, as shown in FIG. A flattening film 30 for flattening the surface of the semiconductor device 10, a first electrode 41 formed on the surface of the flattening film 30 and connected to the driving circuit, an organic light emitting layer 43 formed on the first electrode 41, And an organic light emitting element 40 having a second electrode 44 formed on the organic light emitting layer 43. The planarizing film 30 includes a first inorganic insulating film 31 and an organic insulating film 32 laminated on the driving circuit, and the surface of the organic insulating film 32 is formed to have an arithmetic plane roughness Ra of 50 nm or less. Have been. Further, the organic light emitting layer 43 is formed so as not to be directly above the contact hole 30a.

  That is, in the organic EL display device of the present embodiment, the surface of the substrate 10 is made uneven by the formation of the drive circuit, and the flattening film 30 formed by laminating the inorganic insulating film 31 and the organic insulating film 32 is formed. One characteristic is that, by forming and further polishing the surface by CMP, the surface is formed to have a flatness of 50 nm or less in arithmetic plane roughness Ra. Note that the planarization film 30 can be formed by further forming a second inorganic insulating film 33 on the surface of the organic insulating film 32. In the example shown in FIG. 1, the second inorganic insulating film 33 is also formed. ing. Further, the organic EL display device of the present embodiment has another feature in that the organic light emitting layer 43 is formed in a region that is not directly above the contact hole 30a that connects the drive circuit and the first electrode 41. .

  As described above, the present inventor has conducted intensive studies on the cause of the occurrence of color unevenness and / or luminance unevenness of the organic EL display device. As a result, the surface of the organic light emitting layer 43 of the organic light emitting element 40 has irregularities. Microscopically, the surface of the organic light-emitting layer 43 is not completely flat, and there is a portion that is microscopically inclined. When the surface is inclined, the normal direction of the surface of the organic light-emitting layer 43 is displayed. It will be inclined with respect to the normal direction of the surface. Then, when viewed from a direction perpendicular to the display surface, it is difficult to recognize the light of the pixels in which the emitted light travels in an oblique direction, and the luminance decreases or the color mixture changes. That is, the emitted light has the largest luminance in the normal direction, and the luminance decreases as the light is inclined from the normal direction. In a small display device such as a smartphone, the size of the sub-pixel is as small as several tens μm on one side. Therefore, even if there are slight irregularities, in the sub-pixel having the irregularities on the surface of the organic light-emitting layer 43, the light emission from the front is very weak.

  Conventionally, as a countermeasure against such color unevenness and / or luminance unevenness, a TFT is formed on the outer edge of the display panel, and a pixel having color unevenness and / or luminance unevenness is inspected after the product is manufactured. Brightness is adjusted by a circuit. Therefore, there is also a problem that the driving circuit becomes complicated.

  In the present embodiment, as described above, the cause of the color unevenness and / or the luminance unevenness has been found, and in order to improve the flatness of the surface of the organic light emitting layer 43, the surface of the underlying flattening film 30 has a thickness of 50 nm. In addition to the following, it has been found that color unevenness and / or luminance unevenness hardly occur by forming the organic light emitting layer 43 while avoiding the area directly above the contact hole 30a. Although the surface roughness is preferably as small as possible, it is not necessary to provide a flatness of 20 nm or less, as described in Patent Document 1, and even if the arithmetic average roughness Ra is 20 nm or more, color unevenness or luminance unevenness may occur. Hardly appeared. That is, the lower the surface roughness is, the more preferable it is. Therefore, the lower limit is not set. However, in order to reduce the surface roughness, the polishing operation becomes difficult. Therefore, the surface roughness is preferably 20 nm or more and 50 nm or less.

  Specifically, in the conventional method, the flattening film is formed by forming an inorganic barrier film, forming a contact hole by dry etching, and forming an organic insulating film (photosensitive resin) on the contact hole. A contact hole was formed by etching. That is, as described above, since the organic insulating film is formed by applying a liquid resin, the surface is considered to be flat and no problem occurs. However, even if a non-photosensitive resin is used, the flatness of the surface of the organic insulating film is about 100 to 300 nm in arithmetic average roughness Ra, and is even larger than that of a photosensitive resin. It has been found that this level of planarization is not sufficient. In this case, when a photosensitive resin is used, the surface roughness further increases due to the influence of the photopolymerization initiator mixed therein. As described above, the surface of the organic insulating film 32 is polished by CMP to make the surface roughness 20 nm or more and 50 nm or less in arithmetic average roughness Ra, thereby preventing color unevenness and / or luminance unevenness. It has been found that it can be almost suppressed. In other words, it is not necessary to make the flatness of 20 nm or less as described in the above-mentioned Patent Document 1, but it is necessary to make it about 50 nm or less.

(Structure of the organic EL display device)
Next, the organic EL display device shown in FIG. 1 and its manufacturing method will be specifically described.

  When the substrate 10 is of a bottom emission type in which a display image is visually recognized using the substrate surface as a display surface, it is necessary to transmit light emitted from the organic light-emitting layer 43. Used. Specifically, a glass substrate or a resin film such as polyimide is used. By using the resin film, the organic EL display device can be made flexible and can be attached to a curved surface or the like.

When the substrate 10 is a glass substrate, it is not necessary. However, when the substrate 10 is a resin film such as polyimide, the surface is not crystalline, and it is difficult to directly form a semiconductor layer. Therefore, the base coat layer 11 is formed. The base coat layer 11, for example, 500nm thick / a SiN _x 50 nm thickness / SiO ₂ of 250nm thickness of about laminate SiO ₂ by plasma CVD is formed.

  A drive circuit including the TFT 20 is formed on the base coat layer 11. Although only the cathode wiring 27 is shown in FIG. 1, other gate wirings and signal wirings are formed in the same manner. The TFT 20 is formed thereon. Although FIG. 1 shows only the TFT 20 for driving the light emitting element 40, other TFTs such as other switching TFTs are formed similarly. When the organic EL display device is of a top emission type having a display surface opposite to the substrate 10, the drive circuit can be formed over the entire lower surface of the organic light emitting element 40. However, in the bottom emission type using the substrate 10 as a display surface, a TFT or the like cannot be formed below the light emitting region of the organic light emitting element 40. Therefore, a TFT or the like needs to be formed around a portion overlapping the light emitting region in a plane. In this case, since an inclined surface is formed at the boundary between the area where the surrounding TFTs or wirings are formed and the area below the light emitting area where the TFTs and the like are not formed, irregularities are formed at the periphery of the light emitting area, and the display quality deteriorates. Cause Therefore, the same flatness is required for the bottom emission type. Note that a capacitor is also formed in each pixel, but even if it is formed under a light-emitting region with a large area and a small thickness, it hardly causes fine unevenness.

The TFT 20 includes a semiconductor layer 21 having a source 21s, a channel 21c, and a drain 21d, a gate insulating film 22, a gate electrode 23, an interlayer insulating film 24, a source electrode 25, and a drain electrode 26. The gate insulating film 22 is made of SiO ₂ or the like having a thickness of about 50 nm, and the gate electrode 23 is formed by patterning after forming a film of Mo or the like having a thickness of about 250 nm. An interlayer insulating film 24 made of a SiO ₂ film having a thickness of about 300 nm and a SiN _x film having a thickness of about 300 nm is formed thereon, and a source electrode 25 and a drain electrode 26 are formed so as to be connected to the source 21 s and the drain 21 d. Thus, a drive circuit including the TFT 20 is formed. Before the interlayer insulating film 24 is formed, the electrode connecting portions of the source 21s and the drain 21d are doped with boron to be turned into p ⁺ , and activated by annealing. A more specific structure will be described in a specific example of a manufacturing method described later. In the example shown in FIG. 1, the gate electrode 23 has a top gate structure formed on the side of the semiconductor layer 21 opposite to the substrate 10, but a bottom gate structure in which the gate electrode 23 is formed on the substrate 10. But the same is true.

On the surface of the drive circuit including the TFT 20, a first inorganic insulating film 31 made of SiN _x or the like having a thickness of about 200 nm as a barrier layer and an organic insulating film 32 made of, for example, polyimide or acrylic resin are formed to a thickness of about 2 μm. By the CMP polishing, the surface roughness is reduced to 50 nm or less in arithmetic average roughness Ra. This organic insulating film may be a photosensitive organic insulating film mixed with a photopolymerization initiator. In the case of a photosensitive organic insulating film, an organic insulating film 32 is formed after the formation of the first inorganic insulating film 31, and a contact hole 30a is formed by exposure and development in a photolithography process. In this case, CMP polishing may be performed after the contact holes 30a are formed. When the organic insulating film 32 is polished by CMP, even if a polishing slurry of CMP is introduced into the contact hole 30a, the size of the contact hole is much larger than the particle size of the polishing agent (for example, about 50 times), and therefore, it is removed by cleaning. And there is no particular problem. When the organic insulating film 32 is non-photosensitive, the contact hole 30a is formed together with the first inorganic insulating film 31. At this time, the contact hole 30b for forming the second contact 45 for connecting the cathode (second electrode) of the organic EL display device to the cathode wiring 27 is also formed in the flattening film 30 at the same time.

In the example shown in FIG. 1, the second inorganic insulating film 33 of 400nm thickness about made of SiN _x for example, on the organic insulating film 32 is formed. The formation of the second inorganic insulating film 33 is preferable because the organic insulating film can be prevented from being corroded by an etchant during the etching for forming the contact hole 30a. Further, the inorganic insulating film does not need to be polished because the flatness of the base is maintained as it is. After the formation of the second inorganic insulating film 33, the contact holes 30a are formed by etching the three layers at a time.

  Then, for example, by forming a film of ITO and Ag or a metal such as APC and ITO by sputtering or the like, a metal such as Ag is embedded in the contact hole 30a, and the organic insulating film 32 or the second inorganic insulating film 33 ( In the case where the second inorganic insulating film 33 is formed), that is, after the same metal such as Ag or APC and the conductive layer of ITO are formed on the surface of the flattening film 30, the surface and the lowermost layer are formed of the ITO film by patterning. In the meantime, the first electrode (anode) 41 is formed of a laminated film of ITO / Ag or APC / ITO in which Ag or APC is sandwiched. The first electrode 41 is formed continuously with the conductor layer embedded in the contact hole 30a. However, the first electrode 41 is flattened by avoiding a place where the depression is easily formed on the contact hole 30a. It is formed by patterning so as to be located on the surface of the film 30. As a result, the surface of the first electrode 41 has the same flatness as the surface of the flattening film 30, and the surface of the organic light emitting layer 43 thereon has the same flatness.

  The first electrode (anode) 41 preferably has a work function of about 5 eV in relation to the organic light emitting layer 43. In the case of a top emission type, the above materials are used. The ITO film is formed to a thickness of about 10 nm, and Ag or APC is formed to a thickness of about 100 nm. In the case of the bottom emission type, the ITO film is formed to a thickness of about 300 nm to 1 μm. Each pixel is partitioned at the periphery of the first electrode 41, and an insulating bank 42 made of an insulating material for insulating the anode and the cathode is formed, and the first electrode 41 surrounded by the insulating bank 42 is formed. An organic light emitting layer 43 is laminated thereon.

  The organic light emitting layer 43 is stacked on the first electrode 41 exposed by being surrounded by the insulating bank 42. Although the organic light emitting layer 43 is shown as a single layer in FIG. 1 and the like, various materials are laminated to form a plurality of layers. In addition, since the organic light emitting layer 43 is weak to moisture and cannot be patterned after being formed on the entire surface, it is necessary to selectively vaporize the evaporated or sublimated organic material only on a necessary portion using an evaporation mask. Formed by Alternatively, the organic light emitting layer 43 may be formed by printing.

Specifically, for example, as a layer in contact with the first electrode (anode electrode) 41, a hole injection layer made of a material having good ionization energy matching to improve hole injection properties may be provided. On this hole injection layer, a hole transport layer capable of improving the stable transport of holes and confining electrons (energy barrier) to the light emitting layer is formed of, for example, an amine-based material. Further, a light emitting layer selected according to the light emission wavelength is formed thereon by doping red or green organic fluorescent material into Alq ₃ for red and green, for example. As the blue material, a DSA-based organic material is used. On the other hand, when colored by a color filter (not shown), the light emitting layers can be formed of the same material without doping. On the light emitting layer, an electron transporting layer for improving electron injecting property and for stably transporting electrons is formed of Alq ₃ or the like. Each of these layers is laminated on the order of several tens of nm to form a laminated film of the organic light emitting layer 43. Note that an electron injection layer such as LiF or Liq for improving electron injection properties may be provided between the organic light emitting layer 43 and the second electrode 44. Although this is not an organic layer, it is included in the organic light emitting layer 43 in the present specification, as light is emitted by the organic layer.

  As described above, in the light emitting layer of the stacked film of the organic light emitting layer 43, the organic material of the material corresponding to each color of R, G, and B may not be deposited, and a color display device may be formed by a color filter. . That is, the light emitting layers may be formed of the same organic material, and the light emission color may be specified by a color filter (not shown). In addition, it is preferable that the hole transport layer, the electron transport layer, and the like be separately deposited with a material suitable for the light emitting layer, when importance is attached to the light emitting performance. However, in consideration of material cost, the same material may be commonly used for two or three colors of R, G, and B in some cases.

  After the stacked film of all the organic light emitting layers 43 including the electron injection layer such as the LiF layer is formed, the second electrode 44 is formed on the surface thereof. Specifically, a second electrode (for example, a cathode) 44 is formed on the organic light emitting layer 43. The second electrode (cathode) 44 is commonly and continuously formed over all pixels. The cathode 44 is connected to the cathode wiring 27 via a second contact 45 formed on the flattening film 30 and a first contact 28 formed on the insulating films 22 and 24 of the TFT 20. The second electrode 44 is formed of a translucent material, for example, a thin Mg-Ag eutectic film, and is easily corroded by moisture. Therefore, the second electrode 44 is covered with a coating layer 46 provided on the surface thereof. As the cathode material, a material having a small work function is preferable, and an alkali metal or an alkaline earth metal may be used. Mg is preferable because it has a small work function of 3.6 eV, but is not stable due to its activity. Therefore, Ag having a work function of 4.25 eV is co-deposited at a rate of about 10% by mass. Al also has a small work function of about 4.25 eV, and can be sufficiently used as a cathode material by using LiF as a base. Therefore, in the bottom emission type, the second electrode 44 can be formed with a thicker Al.

The coating layer (TFE: Thin Film Encapsulation) 46 is made of, for example, an inorganic insulating film such as SiN _x or SiO ₂ , and can be formed by a single layer or a laminated film of two or more layers. For example, it is formed of a laminated film having a thickness of about 0.1 μm to 0.5 μm, preferably about two layers. This coating layer 46 is preferably formed in multiple layers of different materials. Since the coating layer 46 is formed of a plurality of layers, even if pinholes and the like are formed, the pinholes rarely coincide completely in the plurality of layers, and are completely shielded from the outside air. As described above, the coating layer 46 is formed so as to completely cover the organic light emitting layer 43 and the second electrode 44. Note that an organic insulating material may be provided between the two inorganic insulating films.

(Manufacturing method of organic EL display device)
Example 1
Next, a method of manufacturing the organic EL display device without the second inorganic insulating film 33 of the organic EL display device shown in FIG. 1 will be described with reference to the flowcharts of FIGS. 2A to 2B and the manufacturing process diagrams of FIGS. 3A to 3G. Explained.

First, as shown in FIG. 3A, a drive circuit including the TFT 20 is formed on the substrate 10 (S1 in FIG. 2A). Specifically, as shown in the flowchart of FIG. 2B, the base coat layer 11 is formed on the substrate 10 (S11). The base coat layer 11 is formed by, for example, forming an SiO ₂ layer to a thickness of about 500 nm by a plasma CVD method, forming a SiN _x layer to a thickness of about 50 nm thereon to form a lower layer, and further forming an upper layer thereon. It is formed by laminating an SiO ₂ layer to a thickness of about 250 nm.

  Thereafter, a semiconductor layer 21 made of an amorphous silicon (a-Si) layer is formed on the base coat layer 11 by, for example, a low pressure plasma CVD method (S12). Thereafter, by performing an annealing process at about 450 ° C. for about 45 minutes in a nitrogen atmosphere, for example, LTPS (Low Temperature Poly Silicon) is performed (S13).

Next, a resist mask is formed by a photolithography process, and the semiconductor layer 21 is patterned by dry etching or the like, so that a portion of the semiconductor layer 21 to be the TFT 20 and a wiring such as a cathode wiring 27 are formed (S14). Thereafter, the gate insulating film 22 is formed (S15). The gate insulating film 22 is formed by depositing SiO ₂ to a thickness of about 50 nm by a plasma CVD method.

  Thereafter, a metal film such as molybdenum (Mo) is formed to a thickness of about 250 nm by, for example, a sputtering method, and is subjected to dry etching after formation of a resist mask by a photolithography process, whereby patterning is performed to form a gate. The electrode 23 is formed (S16).

After that, a source 21s and a drain 21d are formed in the semiconductor layer 21. Specifically, for example, after doping with boron (B ⁺ ), annealing is performed at about 400 ° C. for about 1 hour to activate the source 21 s and the drain 21 d so as to reduce the resistance. Is performed (S17). Since the gate electrode 23 serves as a mask, boron ions are not implanted into the channel 21c, but are implanted only into the source 21s and the drain 21d to reduce the resistance.

Thereafter, an interlayer insulating film 24 is formed on the entire surface, and a contact hole 24a exposing a part of the source 21s and the drain 21d is formed (S18). The interlayer insulating film 24 is formed by a low-pressure plasma CVD method, for example, as a laminated film of a lower layer mainly made of SiO ₂ and having a thickness of about 300 nm and an upper layer mainly made of SiN _x and having a thickness of about 300 nm. The contact hole 24a is formed by forming a mask by a resist film formation and a photolithography process and performing wet etching.

  Thereafter, by depositing a metal, the metal is buried in the contact hole 24a, and the metal film of the source electrode 25 and the drain electrode 26 is formed on the surface of the interlayer insulating film 24 (S19). The source electrode 25 and the drain electrode 26 are formed, for example, by stacking a Ti film of about 300 nm and an Al film of about 300 nm by sputtering or the like, and stacking Ti of about 100 nm thereon. By patterning the metal film formed on the interlayer insulating film 24 by the same photolithography process and wet etching as described above, the source electrode 25 and the drain electrode 26 connected to the source 21s and the drain 21d of the semiconductor layer 21, respectively. Is formed. The first contact 28 connected to the cathode wiring 27 is formed in the same step as the formation of the source electrode 25 and the drain electrode 26 by the completely same method.

  Through the above steps, a drive circuit including the TFT 20 using the top gate type LTPS of the top gate type, that is, a portion called a back plane is formed. However, the TFT 20 is not limited to this structure, and may be used in other structures such as a top-contact bottom contact structure, a bottom-gate top contact structure, or a bottom-gate bottom contact structure.

Thereafter, as shown in FIG. 3B, a first inorganic insulating film 31 and an organic insulating film 32 are formed on the surface of the drive circuit (S2 in FIG. 2A). The first inorganic insulating film 31 is formed of, for example, SiN _x to a thickness of about 200 nm by a plasma CVD method. This functions as a barrier layer that prevents components of the organic insulating film 32 from entering the TFT 20. Further, the organic insulating film 32 is embedded in a portion having an uneven surface by forming the TFT 20 or the like, and the surface of the organic insulating film 32 is easily flattened by applying a liquid resin. As a coating method, there is a method such as a slit coat or a spin coat, but a slit and spin coat method in which both are combined may be used. The organic insulating film 32 is formed so as to have a thickness of about 2 μm, and for example, a polyimide resin or an acrylic resin can be used. A photosensitive resin in which a photopolymerization initiator is mixed into these resins may be used. However, a non-photosensitive resin containing no photopolymerization initiator is preferable because it has high purity and high surface smoothness. In particular, an acrylic resin is preferable.

Next, as shown in FIG. 3C, the surface of the organic insulating film 32 is polished by CMP (S3). Since the organic insulating film 32 is coated with a liquid resin and dried, the surface is easily flattened. As described above, this surface is formed to have an arithmetic average surface roughness Ra of about 100 to 300 nm. . However, as described above, the present inventor has found that color flatness and / or luminance unevenness appear only with the flatness of the application of the organic insulating film 32 and light emission characteristics cannot be sufficiently satisfied. Therefore, the surface is polished by CMP so that the flatness of the surface is 50 nm or less in arithmetic average roughness Ra. The flatness is preferably as small as possible, but it is not required to have a very flatness of 20 nm or less as shown in Patent Document 1. If it is about 50 nm or less, color unevenness and / or luminance unevenness did not appear to a problem. This CMP polishing is performed, for example, by polishing the surface of the organic insulating film 32 while supplying a ceria (CeO ₂ ) -based slurry or a fumed silica-based slurry together with water and alcohol.

  Thereafter, as shown in FIG. 3D, a contact hole 30a reaching the TFT 20 is formed in the flattening film 30 (S4). The formation of the contact hole 30a is performed by forming a resist mask and performing etching such as dry etching in the same manner as the contact hole 24a described above. In the case where the layers in which the inorganic insulating film and the organic insulating film are mixed are etched together as in the case of the flattening film 30, the etching rates of the two layers are different. This is preferable because a step is hardly generated at the interface between the two. When a step is formed, the metal to be buried in the contact hole 30a is not completely buried, and the problem that the contact resistance with the source electrode 25 or the like is increased easily occurs.

  Thereafter, as shown in FIG. 3E, a metal is buried inside the contact hole 30a, and a first electrode 41 for the organic light emitting element 40 is formed in a predetermined region (S5). Specifically, for example, a lower layer in which an ITO film is stacked on the order of 10 nm and an Ag film or an APC film on the order of 100 nm is formed by sputtering or the like, and an upper layer made of an ITO film having a thickness of about 10 nm is formed. As a result, ITO and metal are buried inside the contact hole 30a, and a laminated film of ITO, metal film, and ITO film is formed on the surface of the flattening film 30. After that, the first electrode 41 is formed by patterning the laminated film of ITO and the metal.

Thereafter, as shown in FIG. 3F, the organic light emitting layer 43 is formed on the first electrode 41 (S6). More specifically, an insulating bank 42 for partitioning each pixel at the peripheral portion of the first electrode 41 and preventing contact between the cathode and the anode is formed. The insulating bank 42 may be an inorganic insulating film such as SiO ₂ or an organic insulating film such as polyimide or acrylic resin. The first electrode 41 is formed on the entire surface so that a predetermined location of the first electrode 41 is exposed. The height of the insulating bank 42 is formed to about 1 μm. As described above, various organic materials are stacked on the organic light emitting layer 43. The organic materials are stacked by, for example, vacuum evaporation. In this case, R, G, B, and the like are passed through the openings of the evaporation mask. Is formed via a vapor deposition mask having openings in desired sub-pixels. On the surface of the organic light emitting layer 43, a layer of LiF or the like for improving the electron injection property may be formed. In addition, it can also be formed by printing by an ink-jet method or the like without using vapor deposition. The reason why Ag or APC is used for the first electrode 41 is to reflect light emitted from the organic light emitting layer 43 and use it as a top emission type.

  Thereafter, as shown in FIG. 3G, a second electrode (cathode) 44 is formed on the organic light emitting layer 43 (S7). The second electrode 44 is formed as a cathode by forming a thin Mg-Ag eutectic film on the entire surface by vapor deposition or the like. The second electrode 44 is also formed on the second contact 45 and is connected to the cathode wiring 27 via the second contact 45 and the first contact 28. Since the Mg-Ag eutectic film has different melting points of Mg and Ag, it is evaporated from separate crucibles and becomes eutectic during film formation. Mg is formed at a rate of about 90% by mass and Ag at a rate of about 10% by weight to a thickness of about 10 to 20 nm.

On the second electrode 44, a coating layer 46 for protecting the second electrode 44 and the organic light emitting layer 43 from moisture or oxygen is formed. The coating layer 46 protects the second electrode 44 and the organic light emitting layer 43 that are weak to moisture or oxygen, and therefore, hardly absorbs moisture and the like, and an inorganic insulating film such as SiO ₂ or SiN _x is formed by a CVD method or the like. . Moreover, the coating layer 46 is formed such that its end is in close contact with an inorganic film such as the second inorganic insulating film 33. This is because, when the inorganic films are joined, they are joined with good adhesion, but with the organic film, it is difficult to obtain perfect adhesion with good adhesion. Therefore, when the second inorganic insulating film 33 shown in FIG. 1 is not provided, it is preferable that a part of the organic insulating film 32 is removed and the organic insulating film 32 is bonded to the underlying first inorganic insulating film. By doing so, penetration of moisture or the like can be completely prevented.

Example 2
2A and 2B and FIGS. 3A to 3G, the planarization film 30 is formed by the first inorganic insulating film 31 and the organic insulating film 32 (the second inorganic film having the structure of FIG. 1). Structure without insulating film 33). Even in such a structure, the surface of the organic insulating film 32 is polished, and the first electrode 41 is formed on the surface. Therefore, the surface of the flattening film 30 is flat and there is no problem. However, when the contact hole 30a is formed, if the wet etching or the like is performed, moisture or the like easily enters the organic insulating film 32, and even if the dry etching is performed, the etching gas or the like easily enters. When water or the like enters, the material of the organic light emitting layer 43 or the second electrode 44 may deteriorate when the light emitting element is formed and operates while the light emitting element is operating. Therefore, it is preferable that the second inorganic insulating film 33 is formed on the surface of the organic insulating film 32, and FIG. 1 shows the structure. The manufacturing method will be described with reference to FIGS.

The steps up to the step shown in FIG. 3C are performed in the same manner as in the first embodiment. That is, the surface of the organic insulating film 32 is planarized by CMP polishing. Thereafter, as shown in FIG. 4A, similarly to the first inorganic insulating film 31, the second inorganic insulating film 33 is formed of SiN _x to a thickness of about 200 nm by plasma CVD or the like. As described above, the second inorganic insulating film 33 is formed by depositing an inorganic material by a method such as plasma CVD and is very thin, so that the flatness of the polished surface of the organic insulating film 32 is maintained as it is. Therefore, the surface of the second inorganic insulating film 33 also has a flatness of 50 nm or less in arithmetic average roughness Ra. That is, in the second embodiment, the flattening film 30 is composed of the first inorganic insulating film 31, the organic insulating film 32, and the second inorganic insulating film 33. It is formed on a flat surface having an average roughness Ra of 50 nm or less.

  The subsequent steps are the same as those in the first embodiment, but a contact hole 30a is formed in the flattening film 30 as shown in FIG. 4B. The forming method is the same as that of the first embodiment, and the description is omitted.

  Thereafter, as shown in FIG. 4C, a metal is embedded in the contact hole 30a, and the first electrode 41 of the organic light emitting element 40 is formed on the surface of the flattening film 30. This method is also the same as the above-described step of FIG. 3E, and the description thereof is omitted.

  Thereafter, as shown in FIG. 4D, after the insulating bank 42 is formed, the organic light emitting layer 43 is formed by a method such as vacuum evaporation. This method is also the same as the step shown in FIG. 3F of the first embodiment, and the detailed description is omitted.

  Thereafter, as shown in FIG. 4E, a second electrode 44 is formed on the entire surface. This step is the same as the step shown in FIG. 3G of the first embodiment, and can be formed by the same method. Thereafter, a coating layer 46 is formed on this surface, whereby the organic EL display device shown in FIG. 1 is obtained.

(Summary)
(1) An organic EL display device according to an embodiment of the present invention includes a substrate having a surface on which a driving circuit including a thin film transistor is formed, and planarization for covering the driving circuit to planarize the surface of the substrate. A film, a first electrode formed on the surface of the planarization film and connected to the driving circuit, an organic light emitting layer formed on the first electrode, and formed on the organic light emitting layer An organic light-emitting element having a second electrode, wherein the flattening film includes a first inorganic insulating film and an organic insulating film laminated on the driving circuit, and the surface of the organic insulating film is Arithmetic plane roughness Ra is formed to be 50 nm or less.

  According to the present embodiment, instead of forming the first electrode of the organic light emitting element while keeping the surface of the flattening film formed of the organic insulating film, the surface of the organic insulating film is formed by CMP polishing. The arithmetic surface roughness Ra is formed to be 50 nm or less, and the organic light emitting layer is formed so as not to be located immediately above the contact hole. As a result, even in a microscopic planar state, there is no unevenness, and the normal direction of the surface of the organic light emitting layer of the small sub-pixel matches the normal direction of the display surface. As a result, the problem that a part of the light of the small sub-pixels travels in the oblique direction is eliminated, and there is no factor such as luminance unevenness and color unevenness that deteriorates the display quality. As a result, an organic EL display device having extremely excellent display quality can be obtained.

  (2) It is preferable that the organic insulating film is made of an acrylic resin or a polyimide resin because it has heat resistance and becomes a stable insulating film.

  (3) It is preferable that the organic insulating film is a non-photosensitive resin because the organic insulating film does not contain a photopolymerization initiator that easily makes the surface uneven, so that the surface flatness can be sufficiently obtained.

  (4) The flattening film has a three-layer structure in which a second inorganic insulating film is formed on the organic insulating film. This is preferable because it can be easily prevented from entering the film.

  (5) Since the contact holes are formed collectively in the three-layer structure, the organic insulating film is not exposed to an etching atmosphere, and the penetration of moisture or the like into the organic insulating film can be suppressed. Is preferred.

  (6) In the organic light emitting device, the thin film transistor is not formed in a projection region of the organic light emitting layer, and a bottom emission type light emitting device that extracts light from the substrate side, or the thin film transistor is formed in a projection region of the organic light emitting layer. Any of the structures of the top emission type light emitting element that extracts light from the second electrode can be used. That is, regardless of the structure, due to the flatness of the flattening film, there is no longer a factor of deteriorating the display quality such as luminance unevenness and color unevenness, and an organic EL display device having extremely excellent display quality can be obtained.

  (7) A method of manufacturing an organic EL display device according to another embodiment of the present invention includes a step of forming a drive circuit including a thin film transistor on a substrate, and a step of forming a first inorganic insulating film and an organic insulating film on the surface of the drive circuit. A step of forming a film, a step of polishing the surface of the organic insulating film by CMP, a step of forming a contact hole reaching the TFT in the organic insulating film and the first inorganic insulating film, Forming a first electrode in a predetermined region while embedding a metal in the first electrode, forming an organic light emitting layer on the first electrode, and forming a second electrode on the organic light emitting layer. Includes,

  According to the present embodiment, since the surface of the organic insulating film is polished by CMP, the surface of the flattening film is flat even when viewed microscopically. For this reason, the normal direction of the surface of the organic light emitting layer is different from the normal direction of the display surface, thereby suppressing the occurrence of color unevenness and luminance unevenness.

  (8) Forming a second inorganic insulating film on the organic insulating film, and forming the contact hole in three layers of the second inorganic insulating film, the organic insulating film, and the first insulating film at once. However, this is preferable because not only is the process of forming the contact hole simple, but also because the organic insulating film is protected by the inorganic insulating film, the penetration of moisture and the like can be suppressed.

  (9) The flattening step is performed by supplying a neutral ceria-based abrasive or a fumed silica-based slurry together with water and alcohol, thereby polishing the surface flatness to an arithmetic average roughness Ra of 20 nm or more. Polishing to 50 nm or less is preferable because the organic insulating film can be polished flat.

  (10) It is preferable to form the contact hole by dry etching because etching can be performed without any step at the interface between the inorganic insulating film and the organic insulating film having different etching rates. If a step is formed at the boundary between the inorganic insulating film and the organic insulating film, the metal is not buried cleanly in the contact hole, which tends to increase the contact resistance.

10 substrate 20 TFT
Reference Signs List 21 semiconductor layer 30 flattening film 31 first inorganic insulating film 32 organic insulating film 33 second inorganic insulating film 40 organic light emitting element 41 first electrode (anode)
43 organic light emitting layer 44 second electrode (cathode)

Claims (10)

A substrate having a surface on which a drive circuit including a thin film transistor is formed;
A planarizing film that planarizes the surface of the substrate by covering the driving circuit;
A conductor layer formed on the planarization film and embedded in a contact hole reaching the thin film transistor;
A first electrode formed on the surface of the planarization film and connected to the conductor layer, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. An organic light emitting device having
With
The flattening film includes a first inorganic insulating film, and an organic insulating film formed on the first inorganic insulating film,
The surface of the organic insulating film opposite to the first inorganic insulating film has a surface roughness of not less than 20 nm and not more than 50 nm in arithmetic average roughness Ra,
An organic EL display device, wherein the surfaces of the first electrode and the organic light emitting layer of the organic light emitting element have substantially the same surface roughness as the surface roughness of the planarizing film.   The organic EL display according to claim 1, wherein the surface of the organic insulating film is a polished surface.   The organic EL display device according to claim 1, wherein the surface of the organic light emitting layer is formed without unevenness even in a microscopic planar state.   The organic EL display device according to any one of claims 1 to 3, wherein a normal direction of a surface of the organic light emitting layer in each pixel coincides with a normal direction of a display surface.   The organic EL display according to claim 1, wherein the organic insulating film is an acrylic resin or a polyimide resin.   The organic EL display according to claim 1, wherein the organic insulating film is a non-photosensitive resin.   The flattening film has a three-layer structure by further including a second inorganic insulating film formed on the organic insulating film and having a surface roughness substantially equal to a surface roughness of the organic insulating film. The organic EL display device according to any one of claims 1 to 6.   In the organic light emitting device, the thin film transistor is not formed in the projection region of the organic light emitting layer, but a bottom emission type light emitting device that extracts light from the substrate side, or the thin film transistor is also formed in the projection region of the organic light emitting layer. The organic EL display device according to any one of claims 1 to 7, wherein the organic EL display device is a top emission type light emitting element that extracts light from the second electrode side. Forming a drive circuit including a thin film transistor on a substrate;
Forming a first inorganic insulating film and an organic insulating film on the surface of the driving circuit;
Polishing the surface of the organic insulating film so that the arithmetic average roughness Ra is not less than 20 nm and not more than 50 nm;
Forming a contact hole reaching the thin film transistor in the organic insulating film and the first inorganic insulating film;
A metal is buried inside the contact hole, and the organic material is continuously formed on the surface of the organic insulating film and in the predetermined region where the contact hole is not formed, continuously with the metal buried inside the contact hole. Forming a first electrode having substantially the same surface roughness as the surface roughness of the insulating film;
Forming an organic light emitting layer on the first electrode with a surface roughness substantially the same as the surface roughness of the first electrode;
Forming a second electrode on the organic light emitting layer;
A method for manufacturing an organic EL display device, comprising:   In the polishing step, the surface of the organic insulating film is subjected to a CMP polishing while supplying a neutral ceria-based abrasive or a fumed silica-based slurry together with water and alcohol to an arithmetic average roughness Ra of 20 nm or more. The method according to claim 9, wherein the polishing is performed to a thickness of 50 nm or less.

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