JP6926169B2 - Organic EL display device and its manufacturing method - Google Patents

Description

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

In recent years, organic EL display devices have tended to be adopted in large-sized televisions, portable devices, and the like. In the organic EL display device, a drive circuit using a thin film transistor (hereinafter, also referred to as TFT) as an active element such as a switching element or a drive element is formed in a region of each pixel on an insulating substrate, and each pixel is formed on the thin film transistor (hereinafter, also referred to as TFT). The organic light emitting element of the above is formed so as to be connected to the TFT. The organic EL display device includes a top emission type in which the front surface of the light emitting element is the display surface and a bottom emission type in which the back surface of the insulating substrate is the display surface. Instead, the drive circuit described above is formed below it. On the other hand, in the bottom emission type, a drive circuit is formed at the peripheral edge of the display area. Therefore, in a small organic EL display device such as a mobile device in which a space for forming a drive circuit is small, a top emission type, that is, a configuration in which a drive circuit such as a TFT is formed below almost the entire display area is often used. Will be done. On the other hand, the bottom emission type is suitable for large-sized televisions with a little space between pixels.

When a drive circuit is formed by a TFT or the like, its surface becomes uneven. Since the organic light emitting element is formed on the organic light emitting element, the flattening film is formed by covering the drive circuit with a resin material or the like. By doing so, the surface is flattened. Conventionally, in this flattening film, a first inorganic insulating film as a barrier layer is formed after the TFT is formed, and a contact hole connecting the above-mentioned organic light emitting element and the TFT is formed by a photolithography step. It was obtained by forming a photosensitive organic insulating film on top of it, performing a photolithography process, and forming contact holes by wet development. By forming the organic insulating film in this way, the unevenness of the surface due to the formation of the TFT or the like is flattened.

Patent Document 1 discloses a TFT having both a small occupied area and excellent transistor characteristics, which is suitable for a pixel-by-pixel switching element of an active matrix type display device, and a method for manufacturing the TFT. In this method, a plurality of layers of TFTs are integrally formed vertically through an interlayer insulating film in which the surface irregularities of the TFTs having the same configuration are reduced to 20 nm or less by CMP treatment. 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 correspond to a shallow depth of focus. No.

JP-A-2017-11173

On the other hand, when visually recognizing an organic EL display device, the visibility may be deteriorated due to color unevenness or luminance unevenness depending on the pixels. As a result of repeated studies on the cause of this color unevenness or brightness unevenness, the present inventor has found that it is caused by 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 TFT or the like on which a drive circuit is formed, and on a flattening film that flattens the surface. The surface of this organic insulating film is flat for the time being, and conventionally, it was considered that there was no problem with this. However, as a result of repeated studies by the present inventor, the surface of the organic insulating film has an arithmetic average roughness Ra of about 100 to 300 nm even when a non-photosensitive resin is used, which has been generally used in the past. It was found that the photosensitive resin used had more irregularities than this, and when the electrodes of the organic light emitting element and the organic light emitting layer were formed on the surface, the surface of the organic light emitting layer also had the same surface roughness. It was. When the surface of the organic light emitting layer becomes uneven, the direction in which the light travels microscopically becomes different. Therefore, when the display screen is viewed from the front, it is difficult to visually recognize the light traveling in the oblique direction, and it has been found that the color unevenness and / or the luminance unevenness occurs.

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

Further, it is also possible to increase the light emission output by providing a layer having a high reflectance on the surface of the organic light emitting layer to form a microcavity. However, if the surface of the organic light emitting layer has irregularities, the reflective layer also has irregularities. There is also a problem that it is not possible to obtain a perfect resonator due to diffuse 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, organic light emission is not required even if the surface flatness is not as severe as 20 nm or less as described in Patent Document 1 described above. It suffices if the light emitted by the layer is flat enough to emit light centered on the front surface.

The present invention has been made in view of such a situation, 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 for manufacturing the same. The purpose is.

The organic EL display device according to the embodiment of the present invention includes a substrate having a surface on which a drive circuit including a thin film transistor is formed, a flattening film that flattens the surface of the substrate by covering the drive circuit, and the flattening film. A first electrode formed on the surface of the flattening film and connected to the drive circuit, an organic light emitting layer formed on the first electrode, and a second electrode formed on the organic light emitting layer. The flattening film includes a first inorganic insulating film and an organic insulating film laminated on the drive circuit, and the surface of the organic insulating film has an arithmetic plane roughness. It is formed to be 50 nm or less in Ra.

The method for 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 forming a first inorganic insulating film and an organic insulating film on the surface of the drive circuit. Steps, a step of CMP polishing the surface of the organic insulating film, a step of forming contact holes reaching the TFT in the organic insulating film and the first inorganic insulating film, and a step of forming a metal inside the contact holes. It includes a step of forming a first electrode in a predetermined region while embedding, a step of forming an organic light emitting layer on the first electrode, and a step of forming a second electrode on the organic light emitting layer. I'm out.

According to the embodiment of the present invention, an organic insulating film is formed on the uneven surface of the drive circuit including the TFT, and the surface is polished by CMP so that the surface is flat with an arithmetic average roughness Ra of 50 nm or less. It is flattened so that it becomes a degree. As a result, the light traveling in the oblique direction microscopically is significantly suppressed, 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 sectional drawing of the organic EL display device of one Embodiment of this invention. It is a flowchart which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is a flowchart explaining the process of FIG. 2A in more detail. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of the organic EL display device of Example 1 without the 2nd inorganic insulating film of FIG. It is sectional drawing which shows the manufacturing process of Example 2 of the organic EL display device of FIG. It is sectional drawing which shows the manufacturing process of Example 2 of the organic EL display device of FIG. It is sectional drawing which shows the manufacturing process of Example 2 of the organic EL display device of FIG. It is sectional drawing which shows the manufacturing process of Example 2 of the organic EL display device of FIG. It is sectional drawing which shows the manufacturing process of Example 2 of the organic EL display device of 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 of one embodiment (strictly speaking, it is a sub-pixel of red, green, and blue in one pixel, but in the present specification, it is referred to as one pixel including these sub-pixels. A schematic cross-sectional view of the minutes (sometimes) is shown.

The organic EL display device according to the embodiment of the present invention has a substrate 10 having a surface on which a drive circuit including a TFT 20 is formed, and a substrate by covering the drive circuit, as shown in FIG. A flattening film 30 that flattens the surface of 10, a first electrode 41 formed on the surface of the flattening film 30 and connected to a drive circuit, and 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 flattening film 30 includes a first inorganic insulating film 31 and an organic insulating film 32 laminated on the drive circuit, and the surface of the organic insulating film 32 is formed to have an arithmetic plane roughness Ra of 50 nm or less. Has been done. Further, the organic light emitting layer 43 is formed so as to avoid 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 forming the drive circuit, and the flattening film 30 is formed by laminating the inorganic insulating film 31 and the organic insulating film 32. One of the characteristics is that the surface is formed with a flatness of 50 nm or less in terms of arithmetic plane roughness Ra by CMP polishing of the surface. The flattening film 30 can be formed by further forming the second inorganic insulating film 33 on the surface of the organic insulating film 32, and 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 that the organic light emitting layer 43 is formed in a region not directly above the contact hole 30a connecting the drive circuit and the first electrode 41. ..

As described above, as a result of repeated studies on the cause of color unevenness and / or brightness unevenness of the organic EL display device, the present inventor has unevenness on the surface of the organic light emitting layer 43 of the organic light emitting element 40. Microscopically, the surface of the organic light emitting layer 43 is not completely flat, and there is a part that is tilted when viewed microscopically. When it is tilted, the normal direction of the surface of the organic light emitting layer 43 is displayed. It will tilt with respect to the normal direction of the surface. Then, when visually recognizing from the direction perpendicular to the display surface, it becomes difficult to recognize the light of the pixel in which the emitted light travels in the oblique direction, and the brightness is lowered or the color of the mixed color is changed. That is, the light emitted has the highest brightness in the normal direction, and the brightness decreases as the light is inclined from the normal direction. In a small display device such as a smartphone, the size of this sub-pixel is very small, about several tens of μm on each side. Therefore, even if there are slight irregularities, the light emission to the front surface is very weak in the sub-pixels having irregularities on the surface of the organic light emitting layer 43.

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

In the present embodiment, as described above, since the cause of color unevenness and / or luminance unevenness has been identified, in order to improve the flatness of the surface of the organic light emitting layer 43, the surface of the flattening film 30 as the base thereof is set to 50 nm. It was found that by forming the organic light emitting layer 43 while avoiding directly above the contact hole 30a, almost no color unevenness and / or luminance unevenness occurs. The smaller the surface roughness is, the more preferable it is. However, as shown in Patent Document 1 described above, it is not necessary to set the flatness to 20 nm or less, and even if the arithmetic average roughness Ra is 20 nm or more, color unevenness or brightness unevenness is required. I found that almost never appeared. That is, the smaller the surface roughness is, the more preferable it is, so the lower limit is not set. However, in order to reduce the surface roughness, the polishing operation becomes difficult, so it is preferable to set the surface roughness to 20 nm or more and 50 nm or less.

Specifically, in the conventional method, the flattening film is wet by forming an inorganic barrier film, forming contact holes by dry etching, and forming an organic insulating film (photosensitive resin) on the contact holes. Contact holes were formed by etching. That is, as described above, since the organic insulating film is formed by applying a liquid resin, the surface becomes flat and it is considered that there is no problem. However, the flatness of the surface of this organic insulating film is about 100 to 300 nm in arithmetic average roughness Ra even when a non-photosensitive resin is used, and is even larger with a photosensitive resin. We found that this level of flattening was not sufficient. In this case, when a photosensitive resin is used, the surface roughness is further increased due to the influence of the photopolymerization initiator mixed in. Then, as described above, by CMP polishing the surface of the organic insulating film 32, the surface roughness is set to 20 nm or more and 50 nm or less in the arithmetic average roughness Ra, thereby causing color unevenness and / or luminance unevenness. It was found that it can be almost suppressed. That is, it is not necessary to make the flatness of 20 nm or less as described in Patent Document 1 described above, but it is necessary to make it about 50 nm or less.

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

In the case of the bottom emission type in which the display image is visually recognized with the substrate surface as the display surface, the substrate 10 needs to transmit the light emitted by the organic light emitting layer 43, and is made of a translucent material and has an insulating substrate. Used. Specifically, a glass substrate or a resin film such as polyimide is used. By using a resin film, the organic EL display device can be made flexible and can be attached to a curved surface or the like.

It is not necessary when the substrate 10 is a glass substrate, but when the substrate 10 is a resin film such as polyimide, the surface is not crystalline and it is difficult to directly form the semiconductor layer, so that 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. In FIG. 1, only the cathode wiring 27 is shown, but other gate wiring, signal wiring, and the like are also formed in the same manner. Then, the TFT 20 is formed on the TFT 20. Although only the TFT 20 that drives the light emitting element 40 is shown in FIG. 1, other TFTs such as other switching TFTs are formed in the same manner. When the organic EL display device is of the top emission type having the surface opposite to the substrate 10 as the display surface, this drive circuit can be formed over the entire surface below the light emitting region of the organic light emitting element 40. However, in the bottom emission type having the substrate 10 side as the display surface, it is not possible to form a TFT or the like below the light emitting region of the organic light emitting element 40. Therefore, the TFT or the like needs to be formed around a portion that partially overlaps the light emitting region. In this case, since an inclined surface is formed at the boundary between the surrounding area where the TFT or wiring is formed and the area under the light emitting area where the TFT or the like is not formed, unevenness is formed at the peripheral edge of the light emitting area, and the display quality is deteriorated. It causes to make. Therefore, the same flatness is required for the bottom emission type. 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 thin thickness, it hardly causes fine irregularities.

The TFT 20 is formed of 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 or the like after film formation of Mo or the like having a thickness of about 250 nm. An interlayer insulating film 24 composed 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 on the interlayer insulating film 24, and a source electrode 25 and a drain electrode 26 are formed so as to be connected to the source 21s and the drain 21d. As a result, a drive circuit including the TFT 20 is formed. Before the interlayer insulating film 24 is formed, the electrode connection portions of the source 21s and the drain 21d are doped with boron to be p ⁺ and activated by annealing. A more specific structure will be described in a specific example of the manufacturing method described later. In the example shown in FIG. 1, the gate electrode 23 has a top gate structure formed on the opposite side of the semiconductor layer 21 to the substrate 10, but the bottom gate structure has the gate electrode 23 formed on the substrate 10. But the same is true.

_{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 an acrylic resin are formed on the surface of the drive circuit including the TFT 20 by about 2 μm to form a surface. By CMP polishing, the surface roughness is reduced to 50 nm or less in arithmetic average roughness Ra. The organic insulating film may be a photosensitive organic insulating film mixed with a photopolymerization initiator. In the case of a photosensitive organic insulating film, the organic insulating film 32 is formed after the formation of the first inorganic insulating film 31, and the contact holes 30a are formed by exposure and development by a photolithography step. In this case, CMP polishing may be performed after the contact holes 30a are formed. When CMP polishing the organic insulating film 32, even if the CMP abrasive enters the contact hole 30a, the size of the contact hole is much larger than the particle size of the abrasive (for example, about 50 times), so it can be removed by cleaning. It can be done, and no particular problem occurs. 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, a contact hole 30b for forming a 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, a second inorganic insulating film 33 having a thickness of about 400 nm, made of _{, for example, SiN x, is formed on the organic insulating film 32.} The formation of the second inorganic insulating film 33 is preferable because it is possible to prevent corrosion of the organic insulating film by the etchant during etching for forming the contact hole 30a. Further, since the inorganic insulating film maintains the flatness of its base as it is, it does not need to be polished. After the formation of the second inorganic insulating film 33, the contact holes 30a are formed by etching the three layers at once.

Then, for example, when a metal such as ITO and Ag or APC and ITO are formed 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 ( When 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, patterning is performed so that the surface and the bottom layer are ITO films. In the meantime, the first electrode (anode) 41 is formed by an ITO / Ag or APC / ITO laminated film in which Ag or APC is sandwiched. The first electrode 41 is formed continuously with the conductor layer embedded inside the contact hole 30a, but the surface of the first electrode 41 is flattened so as to avoid a place where a dent is likely to occur 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 is made as flat as the surface of the flattening film 30, and the surface of the organic light emitting layer 43 on it is also made as flat as the surface of the flattening film 30.

The first electrode (anode) 41 preferably has a work function of about 5 eV in relation to the organic light emitting layer 43, and in the case of the top emission type, the above material is 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 on the peripheral edge 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. The organic light emitting layer 43 is laminated on the top.

The organic light emitting layer 43 is laminated on the exposed first electrode 41 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. Further, since the organic light emitting layer 43 is vulnerable to moisture and cannot be patterned after being formed on the entire surface, the evaporated or sublimated organic material is selectively deposited only on a necessary portion by using a vapor deposition 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 consistency that improves hole injection may be provided. On the hole injection layer, for example, an amine-based material is formed to improve the stable transport of holes and to confine electrons (energy barrier) to the light emitting layer. Further, a light emitting layer selected according to the emission wavelength is formed on the light emitting layer, for example, _{by doping Alq 3} with a red or green organic fluorescent material for red and green. Further, as the blue-based material, a DSA-based organic material is used. On the other hand, when colored with a color filter (not shown), the light emitting layers can all be formed of the same material without doping. On the light emitting layer, an electron transporting layer that further improves the electron injectability and stably transports electrons is _{formed by Alq 3} or the like. A laminated film of the organic light emitting layer 43 is formed by laminating each of these layers by about several tens of nm. An electron injection layer for improving the injection property of electrons such as LiF and Liq 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 being emitted by the organic layer.

As described above, among the laminated films of the organic light emitting layer 43, the light emitting layer may be made into a color display device by a color filter without depositing organic materials of materials corresponding to each color of R, G, and B. .. That is, the light emitting layer may be formed of the same organic material, and the light emitting color may be specified by a color filter (not shown). Further, the hole transport layer, the electron transport layer, and the like are preferably deposited separately with a material suitable for the light emitting layer, if the light emitting performance is emphasized. However, in consideration of material cost, the same material may be laminated in common for two or three colors of R, G, and B.

After the laminated 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. The cathode material is preferably a material having a small work function, and an alkali metal, an alkaline earth metal, or the like can be used. Mg is preferable because it has a small work function of 3.6 eV, but it is not stable due to its activity. Therefore, Ag having a work function of 4.25 eV is co-deposited at a ratio 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 material. Therefore, in the bottom emission type, Al can be formed thickly on the second electrode 44.

The coating layer (TFE: Thin Film Encapsulation) 46 is made of _{an inorganic insulating film such as SiN x} or SiO ₂ , and can be formed by one layer or two or more laminated films. For example, the thickness of one layer is about 0.1 μm to 0.5 μm, and it is preferably formed by a laminated film of about two layers. The coating layer 46 is preferably formed in multiple layers with different materials. Since the coating layer 46 is formed of a plurality of layers, even if pinholes or the like are formed, the pinholes rarely completely coincide with each other in the plurality of layers, and the coating layer 46 is 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. An organic insulating material may be provided between the two layers of the inorganic insulating film.

(Manufacturing method of organic EL display device)
Example 1
Next, the method for manufacturing the organic EL display device without the second inorganic insulating film 33 of the organic EL display device shown in FIG. 1 is described with reference to the flowcharts of FIGS. 2A to 2B and the manufacturing process 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 in FIG. 2B, the base coat layer 11 is formed on the substrate 10 (S11). In the base coat layer 11, for example, a SiO ₂ layer is formed to a thickness of about 500 nm _{by a plasma CVD method, and a SiN x} layer is formed to a thickness of about 50 nm, thereby laminating a lower layer, and further as an upper layer thereof. _{It is formed by laminating two} SiO layers to a thickness of about 250 nm.

After that, a semiconductor layer 21 made of an amorphous silicon (a-Si) layer is formed on the base coat layer 11 by, for example, a reduced pressure plasma CVD method (S12). Then, for example, under a nitrogen atmosphere, an annealing treatment is performed at about 450 ° C. for about 45 minutes to perform polysilicon (LTPS: Low Temperature Poly Silicon) (S13).

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

After that, for example, a metal film such as molybdenum (Mo) is formed to a thickness of about 250 nm by a sputtering method, and dry etching is performed after the resist mask is formed by a photolithography step to pattern the gate. The electrode 23 is formed (S16).

After that, the source 21s and the drain 21d are formed on the semiconductor layer 21. Specifically, for example ^{, after doping with boron (B +} ), it is activated by annealing at about 400 ° C. for about 1 hour to reduce the resistance of the source 21s and the drain 21d. Is done (S17). Since the gate electrode 23 serves as a mask, boron ions are not driven into the channel 21c, but are driven only into the source 21s and the drain 21d to reduce the resistance.

After that, the interlayer insulating film 24 is formed on the entire surface, and the contact holes 24a that expose a part of the source 21s and the drain 21d are formed (S18). The interlayer insulating film 24 is formed by, for example, a vacuum plasma CVD method, in _{which a lower layer mainly composed of SiO 2} and having a thickness of about _{300 nm and an upper layer mainly composed of SiN x} and a thickness of about 300 nm are laminated. The contact holes 24a are formed by forming a resist film, forming a mask by a photolithography step, and performing wet etching.

After that, by forming a metal film, the metal is embedded in the contact hole 24a, and the metal films of the source electrode 25 and the drain electrode 26 are formed on the surface of the interlayer insulating film 24 (S19). The source electrode 25 and the drain electrode 26 are formed by laminating a Ti film of about 300 nm and an Al film of about 300 nm and Ti on the Ti film of about 100 nm, for example, by sputtering or the like. 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 by the same process as the formation of the source electrode 25 and the drain electrode 26 in exactly the same manner.

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

After that, as shown in FIG. 3B, the first inorganic insulating film 31 and the organic insulating film 32 are formed on the surface of the drive circuit (returning to FIG. 2A and S2). _{The first inorganic insulating film 31 is formed with SiN x} having a thickness of about 200 nm by, for example, a plasma CVD method. This functions as a barrier layer that prevents the components of the organic insulating film 32 from invading the TFT 20. Further, the organic insulating film 32 is embedded in a portion having irregularities on the surface by forming a 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 are methods such as slit coating and spin coating, but a slit and spin coating method in which both are combined may be used. The organic insulating film 32 is formed 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 with 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 CMP polished (S3). Since the organic insulating film 32 is coated with a liquid resin and dried, the surface tends to be flat, and 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 the flatness of the organic insulating film 32 alone causes color unevenness and / or luminance unevenness, and the light emission characteristics cannot be sufficiently satisfied. Therefore, by CMP polishing, the flatness of the surface is polished so that the arithmetic average roughness Ra is 50 nm or less. The smaller the flatness is, the more preferable it is, but the very flatness of 20 nm or less as shown in Patent Document 1 is not required. If it was about 50 nm or less, color unevenness and / or luminance unevenness did not appear to the extent that it became a problem. This CMP polishing is performed by polishing the surface of the organic insulating film 32 while supplying, for example, a ceria (CeO ₂ ) -based slurry or a fumed silica-based slurry together with water and alcohol.

After that, as shown in FIG. 3D, a contact hole 30a reaching the TFT 20 is formed in the flattening film 30 (S4). The contact hole 30a is formed by forming a resist mask and etching such as dry etching in the same manner as the contact hole 24a described above. When etching layers in which an inorganic insulating film and an organic insulating film coexist, such as the flattening film 30, the etching rates of the two are different. It is preferable because a step is unlikely to occur at the interface between the two. When a step is generated, the metal to be embedded in the contact hole 30a is not completely embedded, and a problem that the contact resistance with the source electrode 25 or the like increases tends to occur.

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

After that, as shown in FIG. 3F, the organic light emitting layer 43 is formed on the first electrode 41 (S6). Specifically, each pixel is partitioned on the peripheral edge of the first electrode 41, and an insulating bank 42 for 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. A film is formed on the entire surface so that a predetermined location of the first electrode 41 is exposed. The height of the insulation bank 42 is formed to be about 1 μm. As described above, various organic materials are laminated on the organic light emitting layer 43, and the organic materials are laminated by, for example, vacuum deposition. In that case, R, G, B, etc. are laminated through the opening of the vapor deposition mask. It is formed through a vapor deposition mask in which the desired sub-pixels of the above are opened. On the surface of the organic light emitting layer 43, a layer such as LiF that improves the injectability of electrons can be formed. It should be noted that it can be formed not by vapor deposition but also by printing by an inkjet method or the like. The reason why Ag or APC is used for the first electrode 41 is to reflect the light emitted by the organic light emitting layer 43 and use it as a top emission type.

Then, 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 used 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 this Mg-Ag eutectic film has different melting points of Mg and Ag, it is evaporated from different crucibles and eutecticized at the time of film formation. Mg is formed in a ratio of about 90% by mass and Ag in a ratio of about 10% by mass to a thickness of about 10 to 20 nm.

A coating layer 46 that protects the second electrode 44 and the organic light emitting layer 43 from moisture, oxygen, or the like is formed on the second electrode 44. Since the coating layer 46 protects the second electrode 44 and the organic light emitting layer 43, which are sensitive to moisture or oxygen, _{an inorganic insulating film such as SiO 2} or SiN _x , which is difficult to absorb moisture or the like, is formed by a CVD method or the like. .. Moreover, the coating layer 46 is formed so that its end is in close contact with an inorganic film such as the second inorganic insulating film 33. This is because if the inorganic films are bonded to each other, they are bonded with good adhesion, but with an organic film, it is difficult to obtain a bond with perfect adhesion. Therefore, when the second inorganic insulating film 33 shown in FIG. 1 is absent, it is preferable to remove a part of the organic insulating film 32 and bond it with the first inorganic insulating film under the organic insulating film 32. By doing so, the ingress of moisture and the like can be completely prevented.

Example 2
In the production method of Example 1 shown in FIGS. 2A to 2B and 3A to 3G, the flattening film 30 was 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 wet etching or the like is performed, moisture or the like easily penetrates into the organic insulating film 32, and even if dry etching is performed, there is a problem that etching gas or the like easily penetrates. If water or the like infiltrates, the material of the organic light emitting layer 43 or the second electrode 44 may be deteriorated if the light emitting element exudes while the light emitting element is formed and operates. Therefore, it is preferable that the second inorganic insulating film 33 is formed on the surface of the organic insulating film 32, and the structure thereof is shown in FIG. The manufacturing method will be described with reference to FIGS. 4A-4E.

The steps up to the step shown in FIG. 3C described above are carried out in the same manner as in Example 1. That is, the surface of the organic insulating film 32 is flattened by CMP polishing. After that, as shown in FIG. 4A, the second inorganic insulating film 33 is formed with SiN _x having a thickness of about 200 nm by plasma CVD or the like, similarly to the first inorganic insulating film 31. Since the second inorganic insulating film 33 is formed by depositing an inorganic material by a method such as plasma CVD as described above and is very thin, 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 this 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, but the surface of the flattening film 30 is arithmetically arranged. It is formed on a flat surface having an average roughness Ra of 50 nm or less.

The following steps are the same as in Example 1 described above, but as shown in FIG. 4B, the contact holes 30a are formed in the flattening film 30. The forming method is the same as that of the first embodiment, and the description thereof will be omitted.

After that, 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 step of FIG. 3E described above, and the description thereof will be omitted.

Then, 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 deposition. This method is also the same as the step shown in FIG. 3F of the first embodiment described above, and detailed description thereof will be omitted.

After that, as shown in FIG. 4E, the second electrode 44 is formed on the entire surface. This step is also the same as the step shown in FIG. 3G of Example 1 described above, and can be formed by the same method. After that, by forming the coating layer 46 on this surface, the organic EL display device shown in FIG. 1 is obtained.

(summary)
(1) The organic EL display device according to an embodiment of the present invention flattens a substrate having a surface on which a drive circuit including a thin film transistor is formed, and flattens the surface of the substrate by covering the drive circuit. A film, a first electrode formed on the surface of the flattening film and connected to the drive circuit, an organic light emitting layer formed on the first electrode, and an organic light emitting layer formed on the organic light emitting layer. The flattening film includes an organic light emitting element having a second electrode, and the first inorganic insulating film and the organic insulating film laminated on the drive circuit, and the surface of the organic insulating film is formed. It is formed to have an arithmetic plane roughness Ra of 50 nm or less.

According to the present embodiment, the surface of the organic insulating film is polished by CMP polishing instead of forming the first electrode of the organic light emitting element while the surface of the flattening film is the surface formed of the organic insulating film. The arithmetic plane roughness Ra is formed to be 50 nm or less, and the organic light emitting layer is formed so as to avoid directly above the contact hole. As a result, even in the microscopic flat state, there is no unevenness, and the normal direction of the surface of the organic light emitting layer of the small sub-pixels coincides with 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 the factors such as luminance unevenness and color unevenness that deteriorate the display quality are eliminated. As a result, an organic EL display device having very excellent display quality can be obtained.

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

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

(4) The flattening film has a three-layer structure by forming a second inorganic insulating film on the organic insulating film, so that moisture and the like are organically insulated even when forming contact holes. It is preferable because it easily prevents the invasion of the membrane.

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

(6) The organic light emitting device is a bottom emission type light emitting device in which the thin film transistor is not formed in the projection region of the organic light emitting layer and extracts light from the substrate side, or the thin film transistor is a projection region of the organic light emitting layer. It can be any structure of a top emission type light emitting element that extracts light from the second electrode. That is, in any structure, the flatness of the flattening film eliminates factors that deteriorate 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) The method for 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 first inorganic insulating film and organic insulation on the surface of the drive circuit. A step of forming a film, a step of CMP polishing the surface of the organic insulating film, a step of forming a contact hole reaching the TFT in the organic insulating film and the first inorganic insulating film, and a step of forming a contact hole reaching the TFT, and an inside of the contact hole. A step of embedding a metal in a predetermined region and forming a first electrode in a predetermined region, a step of forming an organic light emitting layer on the first electrode, and a step of forming a second electrode on the organic light emitting layer. , Including.

According to the present embodiment, since the surface of the organic insulating film is CMP-polished, the surface of the flattening film is flat even when viewed microscopically. Therefore, the normal direction of the surface of the organic light emitting layer is different from the normal direction of the display surface, and it is possible to suppress the cause of color unevenness and brightness unevenness.

(8) A second inorganic insulating film is formed on the organic insulating film, and the contact holes are formed by collectively forming the three layers of the second inorganic insulating film, the organic insulating film and the first insulating film. However, not only the step of forming the contact hole is simple, but also the organic insulating film is protected by the inorganic insulating film, which is preferable in that the invasion of moisture and the like can be suppressed.

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

(10) It is preferable that the contact holes are formed by dry etching because etching can be performed without forming a step at the interface between the inorganic insulating film and the organic insulating film having different etching rates. If a step is formed on the interface between the inorganic insulating film and the organic insulating film, the metal is not neatly embedded in the contact hole, which tends to increase the contact resistance.

10 substrate 20 TFT
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 (8)

A substrate having a surface on which a drive circuit including a thin film transistor having an amorphous silicon layer is formed,
A flattening film that flattens the surface of the substrate by covering the drive circuit,
A conductor layer formed in the flattening film and embedded in a contact hole reaching the thin film transistor,
A first electrode formed on the surface of the flattening 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. With the organic light emitting element
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 20 nm or more and 50 nm or less in arithmetic average roughness Ra.
The first electrode and the organic light emitting layer are arranged so that the surfaces of the first electrode and the organic light emitting layer of the organic light emitting element have a surface shape and surface roughness substantially the same as the surface shape and surface roughness of the flattening film. By being formed, the thickness of the organic light emitting layer becomes substantially uniform in each pixel.
Driving circuit including the thin film transistor is formed over the entire surface of the projection area below the light emitting region of the organic light emitting layer, is a top emission type light emitting device wherein the organic light emitting device extracting light from the second electrode side , Organic EL display device. The organic EL display device 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 or 2, wherein the organic insulating film is an acrylic resin or a polyimide resin. The organic EL display device according to any one of claims 1 to 3, wherein the organic insulating film is a non-photosensitive resin. A claim that 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 the same as the surface roughness of the organic insulating film. The organic EL display device according to any one of 1 to 4. A process of forming a drive circuit including a thin film transistor having an amorphous silicon layer on a substrate, and
The step of forming the first inorganic insulating film and the organic insulating film on the surface of the drive circuit, and
A step of polishing the surface of the organic insulating film so that the arithmetic average roughness Ra is 20 nm or more and 50 nm or less.
A step of forming contact holes reaching the thin film transistor in the organic insulating film and the first inorganic insulating film, and
A metal is embedded in the contact hole, and the metal is continuously physically embedded in the contact hole in a predetermined region on the surface of the organic insulating film and in which the contact hole is not formed. A step of forming a first electrode having a surface shape and surface roughness substantially the same as the surface shape and surface roughness of the organic insulating film and having a substantially uniform thickness in each pixel by physical vapor deposition.
By forming an organic light emitting layer having a surface shape and surface roughness substantially the same as the surface shape and surface roughness of the first electrode on the first electrode by a vacuum deposition method, the thickness of the organic light emitting layer can be adjusted. The process of making the pixels almost uniform and
A step of forming an organic light emitting element together with the first electrode and the organic light emitting layer by forming a second electrode on the organic light emitting layer is included.
Driving circuit including the thin film transistor is formed over the entire surface of the projection area below the light emitting region of the organic light-emitting layer, formed in the top emission type light emitting device wherein the organic light emitting device extracting light from the second electrode side A method of manufacturing an organic EL display device. In the polishing step, CMP polishing is performed while supplying a neutral ceria-based abrasive or a fumed silica-based slurry together with water and alcohol to surface the surface of the organic insulating film with an arithmetic average roughness Ra of 20 nm or more. The production method according to claim 6, wherein the material is polished to 50 nm or less. In the polishing step, the surface of the organic insulating film is polished to 20 nm or more and 50 nm or less with an arithmetic mean roughness Ra by performing CMP polishing while supplying a neutral ceria-based abrasive together with water and alcohol. The manufacturing method according to claim 6.

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