JP6802887B2 - 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-scale 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 drive circuit. 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 upper 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. In the top emission type, the display area of the organic light emitting element is used. Instead, the drive circuit described above is formed below it. On the other hand, in the bottom emission type, a drive circuit is formed around 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 configuration in which a drive circuit such as a TFT is formed below almost the entire display area by making it a top emission type is often used. To. On the other hand, the bottom emission type is suitable for large televisions with some allowance between pixels.

The TFT semiconductor used in this drive circuit is formed by film formation of a semiconductor made of amorphous silicon. However, amorphous silicon (amorphous silicon: hereinafter also referred to as a-Si) has low electron mobility, and therefore, when a large amount of current is required, low-temperature polysilicon (low-temperature polycrystalline) is irradiated with laser light. Silicon: Hereinafter used as LTPS). In an organic EL display device, since an organic light emitting element (hereinafter, also referred to as an OLED) is driven by a current, the TFT as the driving element needs to be able to pass a large amount of current. Therefore, it is essential to modify a-Si to LTPS.

Further, when the drive circuit is formed by a TFT or the like, the surface thereof becomes uneven. Since the OLED is formed on the OLED, 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, an inorganic insulating film as a barrier layer is formed after the TFT is formed, and a contact hole for connecting the above-mentioned OLED and the TFT is formed by a photolithography step, and the contact hole is formed on the contact hole. It was obtained by forming a film of the organic insulating film of No. 1 and forming contact holes by a photolithography process and 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, and it is not flattening for forming an OLED on the TFT.

JP-A-2017-11173

As described above, in OLED, a large current flows through the driving element, so that sufficient operation cannot be obtained in a-Si. However, when the LTPS is obtained by irradiating the laser beam, it is difficult to irradiate a large area with the laser beam of uniform intensity. In particular, with the recent increase in the size of display devices and the price reduction of electronic devices, a large number of large mother substrates are formed at one time at the manufacturing stage, and the size of the mother substrate is, for example, a liquid crystal display device. The size has increased from G6 (about 1500 mm × 1850 mm) to G12 at present, and even in G10, it is about 2850 mm × 3050 mm. In order to irradiate such a large mother substrate with laser light, it is necessary to perform partial irradiation while scanning, but even with partial irradiation, the intensity of the laser light is not uniform, let alone scanning. Irradiation with laser light results in very non-uniform irradiation. If the intensity of the laser beam is different, the degree of crystallization will be different, and the drive current will be different even at the same voltage. If the drive current is different for each pixel, there is a problem that the brightness changes depending on the pixel, which causes display unevenness such as brightness unevenness and color unevenness. In this respect, the current-driven OLED is significantly different from the voltage-driven liquid crystal display element.

Further, irradiating a large mother substrate while scanning a laser light source becomes a large-scale device and causes an increase in cost.

In order to eliminate the uneven brightness caused by the pixels as described above, a method of further incorporating a TFT to suppress the display unevenness in a circuit has been considered, but as the number of TFTs increases, the lower side of the light emitting region of the light emitting element There is a problem that unevenness further increases. In order to flatten such unevenness, an organic insulating film is formed on a drive circuit such as a TFT, and an OLED is formed on the organic insulating film. As a result of diligent studies by the present inventors, It has been found that sufficient flatness cannot be obtained by flattening with this organic insulating film, and display unevenness such as luminance unevenness and color unevenness occurs due to the non-flatness.

Further, when the organic light emitting layer of the OLED is not flat, unevenness is also formed in the reflective layer when the light emitting output is increased by providing a layer having a large reflectance on the surface of the organic light emitting layer to form a microcavity. 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. The light emitted from the layer may be flat enough to emit light centered on the front surface.

Furthermore, in the case of the top emission type, in order to improve the light extraction efficiency in the surface direction of the insulating substrate, the anode of the OLED is made of Ag (silver) or APC (silver-palladium-copper alloy) having high reflectance to visible light. Formed by including. Since Ag and APC have low contact resistance with Cu (copper), we would like to use them as a conductor layer connecting between the TFT and OLED, but Cu is difficult to microfabricate using the dry etching method. Therefore, there is also a problem that it is difficult to use as a conductive material for an organic EL display device.

The present invention has been made in view of such a situation, and the cost of the organic EL display device is increased by adopting a TFT structure in which a-Si can obtain a sufficient current without being polysilicon. It is an object of the present invention to provide an organic EL display device having improved display quality and a method for manufacturing the same, by significantly reducing the amount of heat and suppressing the occurrence of color unevenness and / or brightness unevenness with stable quality.

Another object of the present invention is to flatten the surface of the drive circuit even if the structure of the TFT becomes complicated, thereby suppressing color unevenness and / or luminance unevenness of the organic EL display device, thereby improving the display quality. An object of the present invention is to provide an improved organic EL display device and a method for manufacturing the same.

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 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 thin film includes a gate electrode, a drain electrode, a source electrode, and a region serving as a channel of the thin film, and has a semiconductor layer extending along a predetermined direction to form the drain electrode. The first conductor film and the second conductor film are arranged so that a part of each of the first conductor film and the second conductor film constituting the source electrode are alternately arranged along the predetermined direction. The channel is the semiconductor layer sandwiched between a part of the adjacent first conductor film and a part of the second conductor film, and the connection between the drive circuit and the first electrode is established. , The conductor layer is formed through a conductor layer embedded in the contact hole formed in the flattening film, the conductor layer includes a titanium layer and a copper layer or a copper alloy layer, and the surface of the flattening film is formed. It is formed to have an arithmetic average roughness Ra of 50 nm or less.

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 on a substrate and forming an inorganic insulating film and an organic insulating film on the surface of the drive circuit. A step of forming a contact hole reaching the thin film in the organic insulating film and the inorganic insulating film, and forming a titanium layer and a copper layer or a copper alloy layer inside the contact hole and on the surface of the organic insulating film. The step of forming the conductor layer and the step of removing the conductor layer on the surface of the organic insulating film by polishing and further flattening the surface of the organic insulating film by polishing are performed on the conductor layer. The thin film semiconductor includes a step of forming a first electrode on the surface, 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. A gate electrode, a gate insulating film, a semiconductor layer extending along a predetermined direction including a region to be a channel, and a first conductor film as a drain electrode and a second conductor as a source electrode formed by connecting to the semiconductor layer. The first conductor film and the second conductor film are formed by a laminated structure with a film, and a part of each of the first conductor film and the second conductor film is formed so as to be alternately arranged side by side along the predetermined direction. Is the semiconductor layer sandwiched between a part of the adjacent first conductor film and a part of the second conductor film.

According to the embodiment of the present invention, since the W / L of the thin film transistor is increased, the TFT for driving the organic light emitting element can be configured with a-Si. As a result, the TFT characteristics of each pixel are constant, and color unevenness, brightness unevenness, and the like are unlikely to occur. Further, since the connection between the TFT and the first electrode of the organic light emitting element is made of copper or a copper alloy, stable connection with low resistance can be obtained, and variation in connection resistance is eliminated. Further, since the surface of the flattening film is polished to an arithmetic mean roughness Ra of 50 nm or less, the unevenness of the surface is microscopically eliminated. As a result, uniform light emission can be obtained for each pixel, the occurrence of color unevenness and / or luminance unevenness can be 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 sectional drawing of the staggered structure which made the gate electrode of FIG. 1A a top gate. This is an example of a TFT structure having the same structure as that shown in FIG. 1B and suitable for polysilicon. It is explanatory drawing of the plane explaining the part of the channel of FIG. 1A. It is a figure which shows the other arrangement example of the 1st conductor film and 2nd conductor film of FIG. 2A. It is a figure which shows the other arrangement example of the 1st conductor film and the 2nd conductor film of FIG. 2A. It is a cross-sectional view of IIIA-IIIA of FIG. 2A with the structure of FIG. 1A. It is a cross-sectional view of IIIA-IIIA of FIG. 2A with the structure of FIG. 1B. It is a flowchart which shows the manufacturing process of the organic EL display device of Example 1 of FIG. 1A. It is a flowchart explaining the process of FIG. 4A in more detail. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 1 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 2 of FIG. 1A. It is sectional drawing which shows the manufacturing process of the organic EL display apparatus of Example 2 of FIG. 1A.

Next, an organic EL display device according to an embodiment of the present invention will be described with reference to the drawings. 1A to 1C show 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, one pixel including these sub-pixels is included. A schematic cross-sectional view (sometimes called a pixel) is shown.

The organic EL display device according to the embodiment of the present invention has a drive circuit including a TFT 20 formed so that FIG. 1A shows an explanatory view of a cross section thereof and FIG. 2A shows a plan explanatory view of the structure of the channel portion. A substrate 10 having a surface, a flattening film 30 that flattens the surface of the substrate 10 by covering the drive circuit, and a first electrode 41 formed on the surface of the flattening film 30 and connected to the drive circuit. It includes an organic light emitting layer 43 formed on the first electrode 41, and an OLED 40 having a second electrode 44 formed on the organic light emitting layer 43. The TFT 20 includes a gate electrode 23, a drain electrode 26, a source electrode 25, and a region serving as a channel 21c of the TFT 20, and has a semiconductor layer 21 extending along a predetermined direction P (see FIG. 2A). Further, a part 26a1, 26a2 ... And 25a1, 25a2 ... Of the first conductor film 26a constituting the drain electrode 26 and the second conductor film 25a constituting the source electrode 25, respectively, are in the predetermined direction P. The first conductor film 26a and the second conductor film 25a are arranged so as to be alternately arranged along the above, and the channel 21c is a part 26a1, 26a2 ... Of the adjacent first conductor film 26a and the second conductor film. It is composed of a semiconductor layer 21 sandwiched between a part of 25a, 25a1, 25a2, .... Further, the drive circuit and the first electrode 41 are connected via the conductor layer 410 embedded inside the contact hole 30a formed in the flattening film 30, and the conductor layer 410 is formed by the Ti layer 411 and Cu. A layer (Cu alloy layer) 412 is included. The surface of the conductor layer 410 embedded inside the flattening film 30 and the contact hole 30a is formed to have an arithmetic average roughness Ra of 50 nm or less.

That is, in the organic EL display device of the present embodiment, since the TFT 20 for driving the OLED 40 is formed by using the amorphous semiconductor layer having a small electron mobility, the present inventors have made extensive studies and examined the driving TFT 20. It has been found that a large current can be obtained and the OLED 40 can be driven by increasing the gate width of the TFT. As described above, conventionally, amorphous silicon is irradiated with laser light to make low-temperature polysilicon, so that a large current can flow. However, it is very difficult to uniformly irradiate a large substrate with a laser beam, the cost is very high, and even if the laser beam is irradiated with the utmost care, the large substrate is irradiated with the laser beam. It is difficult to perform the process uniformly at 10, and there are cases where a sufficient current cannot be obtained depending on the pixel. As a result, it causes display unevenness such as color unevenness and brightness unevenness.

In this embodiment, since a large current is obtained by widening the gate width using a-Si, there is no variation in the TFT characteristics based on the irradiation of the laser beam, and the OLED of each pixel is driven with uniform characteristics. can do. As a result, it is possible to obtain an organic EL display device having a very simple manufacturing process, achieving cost reduction, and having stable quality, that is, an excellent display quality with no display unevenness. The specific structure for widening the channel width is described below.

The TFT 20 of the present embodiment can be formed into an inverted staggered structure or a staggered structure as shown in FIGS. 1A to 1C. FIG. 1A shows a TFT 20 having a bottom gate structure with an inverted stagger structure. 1A to 1C are views corresponding to a part of a cross section along a predetermined direction P of FIG. 2A. Note that FIG. 1B is a diagram showing a staggered structure of the top gate, and FIG. 1C is a structure suitable for polysilicon, but is also applicable to a-Si, and is the same in the same portion as in FIG. 1A. A reference is given and the description thereof is omitted.

In the example shown in FIG. 1A, the gate electrode 23 is formed on the substrate 10 via the base coat layer 11. At this time, the cathode wiring 27 and other wirings (not shown) are also formed at the same time. A semiconductor layer 21 made of a gate insulating film 22 and a-Si, a second conductor film 25a constituting the source electrode 25, and a first conductor film 26a forming the drain electrode 26 are laminated and formed on the semiconductor layer 21. There is. In the example shown in FIG. 1A, in order to improve the electrical contact between the semiconductor layer 21, the first conductor film 26a and the second conductor film 25a, and the first conductor film 26a and the second conductor film 25a, respectively. A second semiconductor layer having a high impurity concentration is interposed. However, this is not essential, and impurities may be doped in the connecting portions of the first conductor film 26a and the second conductor film 25a of the semiconductor layer 21. In the present embodiment, the channel 21c (see FIG. 2A) of the semiconductor layer 21 is formed so as to have a wide channel width. That is, as shown in FIG. 2A, a part 26a1, 26a2 ..., 25a1, 25a2 ..., In which the first conductor film 26a and the second conductor film 25a are branched like comb teeth, are formed, respectively. The first conductor film 26a and the second conductor film 25a are formed so that the comb teeth of the above can be engaged with each other.

FIG. 2A is a plan explanatory view of the channel 21c portion, in which the region shown by the broken line is the gate electrode 23, and the semiconductor layer 21 covers the gate electrode 23 via a gate insulating film (not shown). It is formed like this. The first conductor film 26a and the second conductor film 25a are formed by connecting to the semiconductor layer 21. This laminated structure may be an inverted staggered structure as shown in FIG. 1A, or may be a staggered structure shown in FIG. 1B. That is, as shown in FIGS. 3A to 3B, a structural example of a cross section along the first portion 26a1 of FIG. 2A (not an accurate cross-sectional view), a structural example of the inverted stagger is shown in FIG. Is shown in FIG. 3B. In FIGS. 3A to 3B, the same parts as those shown in FIGS. 1A and 2A are designated by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 2A, the first portions 26a1, 26a2, 26a3, 26a4 which are a part of the first conductor film 26 and the second portions 25a1, 25a2, 25a3, 25a4 which are a part of the second conductor film 25. The first conductor film 26a and the second conductor film 25a are formed so that the first conductor film 26a and the second conductor film 25a are alternately arranged along a predetermined direction P.

That is, the portion of the semiconductor layer 21 sandwiched between the second portion 25a1 which is a part of the second conductor film 25a and the first portion 26a1 which is a part of the first conductor film 26a is the channel 21c, and the first The portion of the semiconductor layer 21 sandwiched between the portion 26a1 and the second portion 25a2 becomes the channel 21c. The same applies thereafter, and the channels 21c are formed in a portion of the semiconductor layer that is alternately arranged and sandwiched between the adjacent first portion 26an and the second portion 25an. Therefore, the channel 21c is the sum of all the opposing portions of the adjacent first portion 26an and second portion 25an of the meshed comb teeth. Even if the channel 21c is a small display device such as a smartphone, if it is a top emission type, it can be formed on the entire surface of the light emitting region of the organic light emitting element 40, so that many channels 21c can be formed. .. As a result, the channel width can be widened, so that a large current can flow even if the electron mobility is small.

The channel width W of the TFT 20 has a length of a portion where the second portion 25a1 and the first portion 26a1 of the set face each other as W, and if there are n facing portions, it is the sum of all of them. W = n · w. On the other hand, the channel length L is the interval between the second portion 25a1 and the first portion 26a1, and if the intervals between the two portions are all equal, the channel length becomes L. Therefore, the ratio W / L of the channel width W and the channel length L can be increased. Conventionally, the value of this W / L was 2.5, but according to the present embodiment, it could be set to 50 to 500. That is, the current can be increased by increasing the W / L, and the contribution of the increase in the current by changing a-Si to LTPS is about 20 times, whereas according to the present embodiment. For example, it can be increased about 20 to 200 times.

In the structure shown in FIG. 2A, the distance between the portions where the second portion 25a1 and the first portion 26a1 arranged in a predetermined direction face each other (the portion having a length of w) is constant and stably contributes as a channel. However, if the gate electrode 23 is formed large as shown in FIG. 2A, it is between the first conductor film 26a and the second conductor film 25a facing the tip portion of the second portion 25a1 or the first portion 26a1. Channels are also formed in each. Therefore, if this interval is also formed with the minimum necessary channel length L, the channel width is further widened. However, since the contribution of the edge portion of the tip of the first portion 26a1 or the second portion 5a1 as a channel is unclear, the above-mentioned W / L does not include the contribution of this tip portion. Therefore, in reality, the channel width is further increased. From this point of view, when the light emitting region, that is, the region where the channel 21c is formed has a rectangular shape, if the first portion 26a1 and the second portion 25a1 are formed along the long side thereof, as shown in FIG. 2B. , The deterministic length W of the channel width can be increased. In FIG. 2B, the same parts as those in FIG. 2A are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 2C, the first portions 26a1, 26a2 ..., Which are a part of the first conductor film 26a, are not formed in a shape branched from the first conductor film 26a, but are continuously formed in a zigzag pattern. By inserting the second portion 25a1 ... Of the second conductor film 25a between them, the first portion 26a1 ... Of the first conductor film 26a and the second portion 25a1 ... Of the second conductor film 25a ...・ The structure is such that and are arranged alternately. That is, the structure is not limited to the structure in which the comb-shaped comb teeth shown in FIG. 2A and the like are meshed with each other. Also in FIG. 2C, the same parts as those in FIG. 2A are designated by the same reference numerals, and the description thereof will be omitted.

Further, as described above, as a result of intensive studies on the cause of color unevenness and / or luminance unevenness of the organic EL display device, the present inventors have found that the surface of the organic light emitting layer of the OLED is uneven. Microscopically, the surface of the organic light emitting layer is tilted in various directions and is not completely flat, that is, the normal direction of the surface of the organic light emitting layer is in various directions with respect to the normal direction of the display surface. I found that it was caused by tilting. That is, if there is an inclined surface on the light emitting surface, it becomes difficult to recognize the light of the pixel in which the emitted light travels in the diagonal direction when visually recognizing from the direction perpendicular to the display surface, and the brightness decreases or the color of the mixed color changes. become. 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 is a slight unevenness, the light emission to the front surface becomes very weak in the sub-pixel having the uneven surface of the organic light emitting layer.

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.

Further, in detail, the conventional TFT and the first electrode are connected by embedding an ITO film, an Ag film, or the like in the contact holes formed in the flattening film by sputtering, vacuum deposition, or the like. However, this contact hole has a small diameter of about 5 μm. Moreover, the flattening film is formed of at least a two-layer structure of an inorganic insulating film and an organic insulating film, and even if the two layers are etched at the same time, the etching rates of the inorganic insulating film and the organic insulating film are different. Steps or undercuts are likely to occur. Even if the contact holes of the inorganic insulating film and the contact holes of the organic insulating film are formed separately by using a photosensitive resin for the organic insulating film, it is difficult for the contact hole patterns to completely match, and a step is likely to occur. When ITO and Ag, APC, or the like are embedded in the contact holes by sputtering, vacuum deposition, or the like, it becomes difficult for metal to enter the contact holes as the holes become smaller. As a result, the present inventors have found that the number of voids increases and the electrical resistance between the source electrode of the TFT and the first electrode of the OLED may increase. The present inventors have found that the brightness of a pixel in which such an increased electrical resistance is reduced, resulting in uneven brightness.

Further, as described above, the OLED 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 inventors, 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, and is generally used in the past. It was found that the photosensitive resin used was more uneven than this, and when the OLED electrode and the organic light emitting layer were formed on this 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, it has been found that when the display screen is viewed from the front, it becomes difficult to visually recognize the light traveling in the oblique direction, resulting in uneven color and / or uneven brightness. Further, the conductor layer inside the contact hole connecting the TFT of the drive circuit and the first electrode of the OLED is not formed with low resistance, that is, because there is resistance in the connecting portion, the current is reduced and the brightness is reduced. Found to decline.

Therefore, the present inventors form a conductor layer 410 to be embedded in the contact hole 30a by a Ti layer 411 formed by sputtering or the like, and a Cu layer 412 formed by electroplating using the Ti layer 411 as a seed layer. It has been found that the conductor can be completely embedded in the contact hole 30a and the resistance can be reduced. That is, even if the Ti layer 411 is formed in the contact hole 30a by sputtering or the like, the contact hole 30a is also formed large and uniformly because it is an initial stage in which the metal film is formed in the contact hole 30a. Since the Cu layer 412 is electroplated, the plating solution easily permeates even if the contact hole 30a becomes small, and the Cu layer 412 is uniformly formed on the entire surface. The Ti layer 411 has a function of preventing Cu from invading the TFT 20. Further, the Cu constituting the Cu layer 412 may be, for example, a Cu alloy having a composition of Cu—Mo.

Since the Ti layer 411 is formed by sputtering or the like, it is formed not only inside the contact hole 30a but also on the entire surface of the organic insulating film 32. Therefore, the conductor layer 410 on the surface of the organic insulating film 32 needs to be removed. However, since the Cu layer 412 is chemically stable, it is difficult to etch it. On the other hand, as described above, the present inventors have found that the flatness of the surface of the organic insulating film 32 also causes display unevenness such as luminance unevenness. Therefore, the Cu layer 412 formed on the organic insulating film 32 is removed by polishing, and the organic insulating film 32 exposed by polishing the Cu layer 412 and the Ti layer 411 is also polished. At that time, as described above, the surface of the conductor layer 410 including the portion embedded inside the contact hole 30a so that the surface roughness is 50 nm or less in arithmetic average roughness Ra and the organic insulation on the surface having fine irregularities. By polishing the surface of the film 32, it is possible to suppress color unevenness and / or brightness unevenness due to the surface roughness described above. In other words, in the present embodiment, the metal embedded in the contact hole 30a is formed by the Ti layer 411 and the Cu layer 412, and the surface of the flattening film 30 and the conductor layer 410 embedded in the contact hole 30a is further formed. It is characterized in that it is polished and formed with an arithmetic average roughness Ra of 50 nm or less.

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 the connection resistance is stable even when the arithmetic average roughness Ra is 20 nm or more. It was found that if it is sufficiently small, color unevenness or brightness unevenness hardly appears. That is, the smaller the surface roughness is, the more preferable it is, so the lower limit is not set. However, since the polishing work becomes difficult to reduce the surface roughness, the surface roughness should be 20 nm or more and 50 nm or less in the arithmetic average roughness. Is preferable.

In the present embodiment, the contact hole 30a is further formed in the flattening film 30, and the conductor layer 410 containing Cu or a Cu alloy having a low contact resistance with Ag or APC constituting the first electrode 41 of the OLED 40 is formed in the contact hole. Since it is embedded in 30a, the resistance between the TFT 20 and the OLED 40 is reduced. As a result, the power consumption of the organic EL display device is reduced.

(Structure of organic EL display device)
Next, the organic EL display device shown in FIG. 1A will be specifically described. 1A to 1C show 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, these sub-pixels are also included. A schematic cross-sectional view (sometimes called one pixel) is shown.

In the case of a bottom emission type organic EL display device, the substrate 10 needs to transmit the light emitted by the organic light emitting layer 43, and is a translucent material and an insulating substrate is 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, it is difficult to form a semiconductor layer made of silicon or the like, so that a base coat layer 11 is formed on the surface of the substrate 10. To. As the base coat layer 11, for example, a laminate of SiO ₂ (silicon oxide) having a thickness of 500 nm / SiN _x (silicon nitride) having a thickness of 50 nm / SiO ₂ having a thickness of about 250 nm is formed by a plasma CVD method.

A drive circuit including the TFT 20 is formed on the surface of the base coat layer 11. In FIGS. 1A to 1C, only the cathode wiring 27 is shown, but other gate wiring, signal wiring, and the like are also formed in the same manner. Although only the TFT 20 for driving the OLED 40 is shown in FIGS. 1A to 1C, other TFTs such as other switching TFTs are formed in the same manner. In the case of a top emission type organic EL display device, this drive circuit may be formed over the entire surface below the light emitting region of the OLED 40. However, in the bottom emission type organic EL display device, it is not possible to form a TFT or the like below the light emitting region of the OLED 40, so that the TFT or the like needs to be formed in a portion that does not substantially overlap the light emitting region. In this case, since an inclined surface is formed at the boundary between the region where the TFT or wiring is formed on the peripheral edge of the OLED 40 and the region where the TFT or the like is not formed under the light emitting region, unevenness is formed on the peripheral edge of the light emitting region. It causes deterioration of display quality. Therefore, the same flatness is required for the bottom emission type.

In the structure shown in FIG. 1A, the TFT 20 has a semiconductor layer 21 formed on the gate electrode 23 via a gate insulating film 22. The gate electrode 23 is formed by patterning after forming a film of Mo or the like having a thickness of about 250 nm at the same time as the cathode wiring 27 or the like. The gate insulating film 22 provided on the surfaces of the gate electrode 23 and the base coat layer 11 is made of SiO ₂ or the like having a thickness of about 50 nm, and the semiconductor layer 21 provided on the surface of the gate insulating film 22 is made of a-Si. It is formed to be about 200 nm. In the example shown in FIG. 1A, a second semiconductor layer 211 having a high impurity concentration a-Si is formed on the surface of the semiconductor layer 21. The second semiconductor layer 211 is provided to improve the electrical connection between the semiconductor layer 21 and the second conductor film 25a forming the source electrode 25 and the first conductor film 26a forming the drain electrode 26. Therefore, the corresponding region of the semiconductor layer 21 may be made to have a high impurity concentration by doping or the like without forming the second semiconductor layer 211. By patterning a conductor film made of Ti / Al / Ti or the like on the entire surface after film formation, a second conductor film 25a constituting the source electrode 25 and a first conductor film 26a constituting the drain electrode 26 are formed. Has been done. As described above, the first conductor film 26a and the second conductor film 25a are formed so that the first portion 26a1, ... And the second portion 25a1, ... Are alternately arranged.

After the contact hole 30a is formed so that the flattening film 30 and the second conductor film 25a described later are exposed, the conductor layer 410 embedded inside the contact hole 30a is formed, and the conductor layer 410 forms the source electrode 25. The first conductor film 25a constituting the above is connected to the first electrode 41 of the organic light emitting element 40. The first conductor film 26a constituting the drain electrode 26 is connected to the drive circuit at a portion (not shown).

In the example shown in FIG. 1B, first, the first conductor film 25a and the second conductor film 25a are formed on the surface of the base coat layer 11, and the surfaces of the base coat layer 11, the first conductor film 25a, and the second conductor film 25a are formed. The semiconductor layer 21 is formed on the surface of the semiconductor layer 21, the gate insulating film 22 is formed on the surface of the semiconductor layer 21, and the gate electrode 23 is formed on the surface of the gate insulating film 22, whereby the TFT 20 is formed.

The example shown in FIG. 1C is the same as the structure of the TFT using LTPS, but a-Si can also have the same configuration. That is, the semiconductor layer 21 made of a-Si is formed on the base coat layer 11, and the portions connected to the source electrode 25 and the drain electrode 26 are heavily doped to form the source 21s and the drain 21d. In the meantime, a low concentration doped channel 21c is formed. A gate insulating film 22 and a gate electrode 23 are formed on the gate insulating film 22, and 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 therein. A first conductor film is embedded in the contact hole 24a via the interlayer insulating film 24 to be connected to the source 21s, connected to the second conductor film 25a and the drain 21d to be the source electrode 25, and to be the drain electrode 26. The conductor film 26a is formed. Before the interlayer insulating film 24 is formed, B (boron) ions are doped into p ⁺ at the electrode connection portions of the source 21s and the drain 21d, and the dopant is activated by annealing.

A flattening film in which an 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 on the surface of a drive circuit including the TFT 20 to have a thickness of about 2 μm. 30 is formed. A contact hole 30a is formed in the flattening film 30, and a conductor layer 410 is formed in the contact hole 30a. The contact hole 30a may be formed by forming the inorganic insulating film 31 and the organic insulating film 32 together, or as will be described later, after forming the first contact hole 30a1 in the inorganic insulating film 31, photosensitive organic insulation. After the film 32 is formed, the second contact holes 30a2 may be formed so as to overlap with each other by exposure and development to form the contact holes 30a. As will be described later, the organic insulating film 32 is flattened by CMP polishing so that the surface has an arithmetic mean roughness Ra of 50 nm or less. Further, as will be described later, the arithmetic average roughness Ra is preferably 20 nm or more.

The conductor layer 410 is formed of a Ti layer 411 having a thickness of about 25 to 100 nm and a Cu layer 412 having a thickness of about 1000 to 2000 nm. Since the Ti layer 411 is formed on the entire surface by sputtering or the like, it is formed without a gap even if there is a step in the contact hole 30a. The Cu layer 412 is formed by electroplating the Ti layer 411 as a current supply layer (seed layer). Therefore, even if there is a step in the contact hole 30a, the low resistance conductor layer 410 is continuously formed without a break. The Cu constituting the Cu layer 412 may be, for example, a Cu alloy having the above-mentioned composition. Similarly, the second contact 45 for connecting the second electrode (cathode) of the organic EL display device to the cathode wiring 27 is also formed of the Ti layer 411 and the Cu layer 412.

An Ag film 413 is formed on the surface of the flattened film 30 and the conductor layer 410 embedded inside the contact hole 30a to a thickness of about 100 nm by sputtering or the like, and ITO is further formed on the surface of the Ag film 413. After the film 414 is formed, the first electrode (anode) 41 of the OLED 40 is formed by patterning by a photolithography step. This Ag is very compatible with Cu and Cu alloys of the conductor layer 410 and is well bonded, so that the contact resistance between them is reduced. Therefore, the resistance between the TFT 20 and the OLED 40 is also reduced, so that the power consumption of the organic EL display device is reduced. Further, since Ag and the like have high light reflectivity, the light emitted by the OLED 40 is reflected on the opposite surface to the substrate 10, so that the display device can have a high brightness as a top emission type. The Ag constituting the Ag film 413 may be APC, and the same effect as the above-mentioned Ag can be obtained. Further, the ITO constituting the ITO film 413 is a material that is translucent and has a work function of about 5 eV, and improves the hole injection property in relation to the organic light emitting layer 43. Therefore, an ITO film having a thickness of about 10 nm is laminated on the surface of the first electrode 41 made of Ag or APC. In the case of the bottom emission type, the first electrode 41 has an ITO film having 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 first electrode 41 and the second electrode 44 is formed by the insulating bank 42. The organic light emitting layer 43 is laminated on the enclosed first electrode 41.

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 FIGS. 1A to 1C 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 (Tris (8-quinolinolato) aluminum) for red and green with a red or green organic fluorescent material. To. Further, as the blue-based material, a DSA (dystyl-allylene) -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 with a thickness of about several tens of nm. An electron injection layer for improving electron injection such as LiF (lithium fluoride) or Liq (8-hydroxyquinolinate lithium) 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, the second electrode (cathode) 44 is formed on the organic light emitting layer 43. The second electrode 44 is commonly and continuously formed over all the pixels. Further, the second electrode 44 is connected to the cathode wiring 27 via the second contact 45 formed on the flattening film 30 and the first contact 28 formed on the insulating films 22 and 24 of the TFT 20. Further, the second electrode 44 is connected to the cathode wiring 27 via the second contact 45 formed on the flattening film 30. In the example of FIG. 1C, the first contact 28 formed on the insulating films 22 and 24 of the TFT 20 is interposed between the second contact 45 and the cathode wiring 27. The second electrode 44 is formed of a translucent material, for example, a thin film Mg-Ag (magnesium-silver alloy) eutectic film, and is easily corroded by moisture, so that it is covered with a coating layer 46 provided on the surface thereof. There is. 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 (magnesium) 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 (aluminum) also has a small work function of about 4.25 eV, and can be sufficiently used by using LiF as a base. Therefore, in the bottom emission type, Al can be formed thickly on the second electrode 44.

The coating layer 46 is made of, for example, an inorganic insulating film such as SiN _x or SiO _2, or an organic insulating film such as TFE (tetrafluoroethylene), and may be formed of 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 match 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. 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, a method of manufacturing the organic EL display device shown in FIG. 1A will be described with reference to the flowcharts of FIGS. 4A to 4B and the manufacturing process of FIGS. 5A to 5G.

First, as shown in the flowchart of FIG. 4A and FIG. 5A, a drive circuit including the TFT 20 is formed on the substrate 10 (S1 of FIG. 4A). Specifically, as shown in the flowchart in FIG. 4B, the base coat layer 11 is formed on the substrate 10. 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 layers of SiO to a thickness of about 250 nm (S11 in FIG. 4B).

After that, a metal film such as Mo is formed on the surface of the base coat layer 11 by sputtering or the like and patterned to form the gate electrode 23, the cathode wiring 27, and other wiring such as gate wiring and signal wiring ( S12).

After that, a gate insulating film 22 is formed on the entire surface of these (S13). The gate insulating film 22 is formed by forming a SiO ₂ layer having a thickness of about 50 nm by a plasma CVD method.

After that, a semiconductor layer 21 made of an a-Si layer is formed on the surface of the gate insulating film 22 by a plasma CVD method (S14). The semiconductor layer 21 is dehydrogenated by an annealing treatment at, for example, about 350 ° C. for about 45 minutes.

After that, on the surface of the semiconductor layer 21, the second semiconductor layer 211 made of Si having a high impurity concentration is connected to the second conductor film 25a constituting the source electrode 25 and the first conductor film 26a forming the drain electrode 26. Is formed to a thickness of about 10 nm (S15). Impurities may be doped in the portion of the semiconductor layer 21 to which the first conductor film 26a and the second conductor film 25a are connected without forming the second semiconductor layer.

A conductor film having a thickness of about 200 nm to 800 nm is formed on the conductor film by a method such as sputtering, and the first conductor film 26a and the second conductor film 25a are formed by patterning (S16). The first conductor film 26a and the second conductor film 25a are formed by laminating a Ti film of about 300 nm and an Al film of about 300 nm by patterning after sputtering or the like, and by laminating Ti on the film of about 100 nm, for example. , Each is formed into a planar shape as shown in FIG. 2A. Then, the second semiconductor layer 211 sandwiched between the first conductor film 26a and the second conductor film 25a is removed by etching.

Through the above steps, a drive circuit including the TFT 20, that is, a portion called a backplane is formed.

After that, as shown in FIG. 5B, an inorganic insulating film 31 is formed on the surface of the drive circuit (returning to FIG. 4A and S2). The 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. Then, the organic insulating film 32 is formed on the surface of the inorganic insulating film 31 (S3). 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 is preferable. 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 with these resins may be used. An example of this will be described later. However, a non-photosensitive resin containing no photopolymerization initiator is preferable because it has high purity and high surface smoothness. In particular, acrylic resin is preferable because it is inexpensive. The flattening film 30 is formed by the inorganic insulating film 31 and the organic insulating film 32.

After that, 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 a layer in which an inorganic insulating film 31 and an organic insulating film 32 coexist together like the flattening film 30, the etching rates of the two are different, so etching is particularly performed by dry etching. Therefore, it is preferable because a step is unlikely to occur at the interface between the two. If a step is formed, the metal to be embedded in the contact hole 30a is not completely embedded, and there is a problem that the contact resistance with the source electrode 25 or the like tends to increase. However, in the present embodiment, since only the thin layer of the Ti layer 411 is provided, even if there is a step, it is sufficiently embedded by electroplating. At this time, the contact hole 30b for forming the second contact 45 connected to the cathode wiring 27 is also formed in the same manner.

Next, as shown in FIG. 5C, a conductor layer 410 composed of a Ti layer 411 and a Cu layer 412 is formed inside the contact hole 30a and on the surface of the organic insulating film 32 (S5). Specifically, the Ti layer 411 is formed to the above-mentioned thickness by a method such as sputtering, and then the Cu layer 412 is formed by electroplating with the Ti layer 411 as a current supply layer (seed layer). As described above, the Cu constituting the Cu layer 412 can be replaced with a Cu alloy.

After that, as shown in FIG. 5D, the conductor layer 410 on the surface of the organic insulating film 32 is removed by polishing, and the surface of the organic insulating film 32 is further flattened by CMP polishing (S6). Since Cu and Cu alloys are chemically stable, they are difficult to etch. Therefore, the conductor layer formed on the surface of the organic insulating film 32 is removed by mechanical polishing. As a result, the surface of the conductor layer 410 embedded in the contact hole 30a and the surface of the organic insulating film 32 are substantially flush with each other, and the surface of the organic insulating film 32 is microscopically flattened. ..

Polishing of the conductor layer 410 is performed by mixing a polishing agent composed of fine particles such as cerium oxide (CeO ₂ ), silica (SiO ₂ ) or alumina (Al ₂ O ₃ ), and a pH adjusting agent in water or alcohol. This is done by polishing with a slurry, and the conductor layer 410 on the organic insulating film 32 is removed. When silica is used, it is preferably fumed silica that has been oxidized and desalted in a flame using SiCl ₄ (silicon tetrachloride) as a raw material. By CMP polishing using such a polishing slurry, as shown in FIG. 3D, the surface roughness is made into a flat surface having an arithmetic average roughness Ra of 50 nm or less. At this time, the second contact 45 for connecting the cathode (second electrode) of the organic EL display device to the cathode wiring 27 is also formed of the Ti layer 411 and the Cu layer 412.

That is, since the organic insulating film 32 is dried by applying a liquid resin by a method such as slit and spin, the surface tends to be flat, and as described above, this surface has an arithmetic mean surface roughness. It is formed to have Ra of about 100 to 300 nm. However, as described above, the present inventors have 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. As described above, since the Cu layer 412 is chemically stable, it is preferably performed by mechanical polishing, but the organic insulating film 32 is preferably polished by CMP using the above-mentioned abrasive. Further, the smaller the surface roughness is, the more preferable it is, so the lower limit is not set, but since the polishing work becomes difficult, it is preferable to set the surface roughness to 20 nm or more and 50 nm or less.

After that, as shown in FIG. 5E, the first electrode 41 of the OLED 40 is formed on the surface of the organic insulating film 32 so as to be connected to the conductor layer 410 formed inside the contact hole 30a (S7). Specifically, for example, by sputtering or the like, a lower layer composed of an Ag film 413 laminated with a thickness of about 100 nm and an upper layer composed of an ITO film 414 with a thickness of about 10 nm are formed, and then a resist film is formed and a photolithography step is performed. The first electrode 41 is formed by forming a mask and performing etching such as wet etching. As a result, the Ag film 413 in close contact with the Cu layer 412 of the conductor layer 410 inside the contact hole 30a is formed, so that the contact resistance between the conductor layer 410 and the first electrode 41 is reduced. Further, by forming the ITO film 414 on the surface of the Ag film 413, the first electrode 41 having good consistency with the organic light emitting layer 43 formed on the ITO film 414 is formed. The Ag constituting the Ag film 413 can be replaced with APC.

After that, as shown in FIG. 5F, the organic light emitting layer 43 is formed on the first electrode 41 (S8). 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, and is formed so that a predetermined location of the first electrode 41 is exposed. The height of the insulation bank 42 is formed to have a thickness of 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 thin-film deposition mask with the desired sub-pixels of. On the surface of the organic light emitting layer 43, a layer such as LiF that improves the electron injectability 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 is used for the first electrode 41 is that the light emitted by the organic light emitting layer 43 is reflected and used as a top emission type.

Then, as shown in FIG. 5G, a second electrode (cathode) 44 is formed on the organic light emitting layer 43 (S9). The second electrode 44 is formed as a cathode by forming a thin film Mg-Ag eutectic film on the entire surface by vapor deposition or the like and patterning it. 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 proportion of about 90% by mass and Ag in an amount of about 10% by mass, and the thickness is about 10 to 20 nm.

On the second electrode 44, 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. 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. .. The coating layer 46 is preferably formed so that its end is in close contact with an inorganic film such as the inorganic insulating film 31. 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, it is preferable to remove a part of the organic insulating film 32 and bond it with the inorganic insulating film 31 under the organic insulating film 32. By doing so, the ingress of moisture and the like can be completely prevented.

Through such a step, the organic EL light emitting device shown in FIG. 1A is manufactured. In this embodiment, the surface of the conductor layer 410 embedded inside the contact hole 30a at the joint with the first electrode 41 is also polished as described above, so that the surface roughness is 50 nm or less. .. Therefore, even if the organic light emitting layer 43 is formed in the region where the contact hole 30a and the conductor layer 410 overlap in a plan view, display unevenness does not occur. Therefore, even a small organic EL display device mounted on a mobile device or the like and having a small space for forming a drive circuit can arrange the organic light emitting elements at a narrower pitch than the conventional one.

(Example 2)
In the manufacturing method of Example 1 shown in FIGS. 4A to 4B and 5A to 5G, the flattening film 30 is formed by continuously forming the inorganic insulating film 31 and the organic insulating film 32, and the contact holes 30a are collectively formed. However, as the organic insulating film 32, an organic insulating film 32 made of a photosensitive organic material containing a photopolymerization initiator is formed, an inorganic insulating film 31 is formed, and then a first contact hole 30a1 is formed, and then the first contact hole 30a1 is formed. A photosensitive organic insulating film 32 may be formed in, and a second contact hole 30a2 may be formed by exposure and development to form a contact hole 30a. An example is shown in FIGS. 6A-6B.

Specifically, the step shown in FIG. 5A described above is performed in the same manner as in Example 1. Then, as shown in FIG. 6A, after the inorganic insulating film 31 is formed, the first contact hole 30a1 is formed at the position where the contact hole 30a is formed. Similar to the formation of the contact hole 30a described above, the first contact hole 30a1 is formed with an opening in the resist film by a photolithography step after the resist film is formed, and the resist film is used as a mask and etched by dry etching or the like. It is formed by. When the photosensitive organic insulating film is formed, the second contact hole 30a2 can be easily formed, but the addition of the photopolymerization initiator reduces the leveling effect of the organic insulating film, resulting in a rough surface roughness. .. However, since the surface is CMP polished, no problem occurs.

After that, as shown in FIG. 6B, the organic insulating film 32 is formed, and the second contact hole 30a2 is formed at the position of the first contact hole 30a1 of the inorganic insulating film 31 by exposure and development. As a result, the second contact hole 30a2 becomes contact holes 30a and 30b continuously with the first contact hole 30a1. As a result, the structure is the same as that shown in FIG. 5B, and the subsequent steps are the same as in the first embodiment. Therefore, the explanation is omitted. Also in this embodiment, the surface of the conductor layer 410 embedded inside the contact hole 30a at the joint with the first electrode 41 is polished, and the surface roughness thereof is 50 nm or less. Therefore, the contact hole Even if the organic light emitting layer 43 is formed in the region where the 30a and the conductor layer 410 overlap in a plan view, display unevenness does not occur. Therefore, even a small organic EL display device mounted on a mobile device or the like and having a small space for forming a drive circuit can arrange the organic light emitting elements at a narrower pitch than the conventional one.

[Summary]
The organic EL display device according to the first aspect of the present invention includes a substrate having a surface on which a drive circuit including a thin film is formed, a flattening film for flattening 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 thin film includes a gate electrode, a drain electrode, a source electrode, and a region serving as a channel of the thin film, and has a semiconductor layer extending along a predetermined direction to form the drain electrode. The first conductor film and the second conductor film are arranged so that a part of each of the first conductor film and the second conductor film constituting the source electrode are alternately arranged along the predetermined direction. The channel is the semiconductor layer sandwiched between a part of the adjacent first conductor film and a part of the second conductor film, and the connection between the drive circuit and the first electrode is established. , The conductor layer is formed through a conductor layer embedded in the contact hole formed in the flattening film, the conductor layer includes a titanium layer and a copper layer or a copper alloy layer, and the surface of the flattening film is formed. It is formed to have an arithmetic average roughness Ra of 50 nm or less.

According to the configuration of the first aspect of the present invention, since the W / L of the thin film transistor is increased, the thin film transistor having a high current driving ability can be obtained, while the first conductor film and the second conductor film have a complicated shape reflecting the inorganic shape. Concavities and convexities are formed on the surface of the drive circuit including the thin film transistor. However, since the surface flattening film having an arithmetic average roughness Ra of 50 nm or less is formed, the unevenness of the base of the organic light emitting element is microscopically eliminated. As a result, the light traveling in the oblique direction microscopically is 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. Further, since the conductor layer including the copper layer or the copper alloy layer is embedded in the contact holes formed in the flattening film, it is possible to finely form the copper or the copper alloy which is difficult to be etched. As a result, the thin film transistor and the organic light emitting element can be connected to each other via the copper layer or the copper alloy layer, so that the power consumption of the organic EL display device is reduced.

In the organic EL display device according to the second aspect of the present invention, in the first aspect, the surface of the conductor layer embedded in the contact hole may be formed to the arithmetic mean roughness Ra by polishing.

According to the configuration of aspect 2 of the present invention, the embedded conductor layer and the desired arithmetic mean roughness Ra can be easily obtained.

In the organic EL display device according to the third aspect of the present invention, in the above aspect 1 or 2, the first electrode may include a silver film or an APC film and an ITO film.

According to the configuration of aspect 3 of the present invention, the contact resistance between the conductor and the first electrode is reduced. As a result, the consumption electrodes of the organic EL display device are reduced.

In the organic EL display device according to the fourth aspect of the present invention, in the third aspect, the silver film or the APC film is connected to the copper layer or the copper alloy, and the ITO layer is connected to the organic light emitting layer. It may be formed at the interface.

According to the configuration of the fourth aspect of the present invention, since the silver film or the APC film is connected to the copper layer or the copper alloy, the contact resistance between the conductor and the first electrode is reduced. As a result, the consumption electrodes of the organic EL display device are reduced. Further, since the ITO layer is formed at the interface with the organic light emitting layer, it becomes a first electrode having good consistency with the organic light emitting layer.

In the organic EL display device according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the first conductor film and the second conductor film are each formed in a planar shape and in a comb shape. The comb-toothed portions of the first conductor film and the second conductor film may be formed so as to mesh with each other.

According to the configuration of the fifth aspect of the present invention, the W / L of the thin film transistor is further increased, so that the thin film transistor having a higher current driving ability can be obtained.

In the organic EL display device according to the sixth aspect of the present invention, in the fifth aspect, the light emitting region of the light emitting element is formed in a rectangular shape, and the thin film transistor is formed in the lower layer of the light emitting region. A part of the conductor film and a part of the second conductor film facing each other may be formed along the long side of the rectangular shape.

According to the configuration of aspect 6 of the present invention, the first conductor film and the second conductor film can be easily arranged in a rectangular shape within the limited area occupied by the semiconductor layer, so that a thin film transistor having a large W / L can be formed. It can be formed efficiently. Further, since the thin film transistor is arranged so as to sterically overlap with the organic light emitting element, the pixels can be formed small. As a result, the organic EL light emitting device can be manufactured in a small size.

In the organic EL display device according to the seventh aspect of the present invention, in any one of the first to sixth aspects, the region sandwiched between a part of the adjacent first conductor film and a part of the second conductor film is formed. There are a plurality of the semiconductor layers, the semiconductor layer is made of an amorphous semiconductor, and the sum of the plurality of lengths of the portions of the plurality of adjacent first conductor films and the portions of the second conductor films facing each other. Is W, and the distance between the opposing portions is L, W / L may be 50 or more and 500 or less.

According to the configuration of aspect 7 of the present invention, it is possible to obtain a thin film transistor having a current driving ability sufficient to drive the organic light emitting device with a current.

The method for manufacturing an organic EL display device according to aspect 8 of the present invention includes a step of forming a drive circuit including a thin film on a substrate and a step of forming an inorganic insulating film and an organic insulating film on the surface of the drive circuit. A step of forming contact holes reaching the thin film in the organic insulating film and the inorganic insulating film, and forming a titanium layer and a copper layer or a copper alloy layer inside the contact holes and on the surface of the organic insulating film. Thereby, the step of forming the conductor layer and the step of removing the conductor layer on the surface of the organic insulating film by polishing and further flattening by polishing the surface of the organic insulating film are performed on the surface of the conductor layer. The thin film includes a step of forming a first electrode, 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. A semiconductor layer including an electrode, a gate insulating film, and a region to be a channel, extending along a predetermined direction, and a first conductor film as a drain electrode and a second conductor film as a source electrode formed by connecting to the semiconductor layer. The first conductor film and the second conductor film are formed by a laminated structure with the above, and a part of each of the first conductor film and the second conductor film is formed so as to be arranged alternately along the predetermined direction, and the channel is formed. , The semiconductor layer sandwiched between a part of the adjacent first conductor film and a part of the second conductor film.

According to the configuration of the eighth aspect of the present invention, since the W / L of the thin film transistor is increased, the thin film transistor having a high current driving ability can be obtained, while the first conductor film and the second conductor film have a complicated shape reflecting the inorganic shape. Concavities and convexities are formed on the surface of the drive circuit including the thin film transistor. However, since the base of the organic light emitting element is polished, the unevenness on the surface is microscopically eliminated. As a result, the light traveling in the oblique direction microscopically is 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. Further, since the conductor layer including the copper layer or the copper alloy layer is embedded in the contact holes formed in the flattening film, it is possible to finely form the copper or the copper alloy which is difficult to be etched. As a result, the thin film transistor and the organic light emitting element can be connected to each other via the copper layer or the copper alloy layer, so that the power consumption of the organic EL display device is reduced.

In the method for manufacturing an organic EL display device according to the ninth aspect of the present invention, in the eighth aspect, a silver film or an APC film is formed on the surface of the copper layer or the copper alloy layer in the step of forming the first electrode. After that, the ITO film may be formed and then patterned.

According to the configuration of the ninth aspect of the present invention, since the Cu layer of the conductor and the first electrode and the Ag film are in close contact with each other, the contact resistance between the conductor and the first electrode is reduced. As a result, the consumption electrodes of the organic EL display device are reduced.

In the method for manufacturing an organic EL display device according to aspect 10 of the present invention, in the above aspect 8 or 9, the semiconductor layer is made of an amorphous semiconductor, and between the semiconductor layer and the first conductor film and the second conductor film. A semiconductor layer having a high impurity concentration may be interposed therein.

According to the configuration of aspect 10 of the present invention, the contact resistance between the semiconductor layer made of an amorphous semiconductor and the first conductor film and the second conductor film is reduced by the semiconductor layer having a high impurity concentration, so that the organic EL display The consumption electrodes of the device are reduced.

10 Substrate 20 TFT (Thin Film Transistor)
21 Semiconductor layer 21c channel 23 Gate electrode 25 Source electrode 25a Second conductor film 26 Drain electrode 26a First conductor film 30 Flattening film 30a Contact hole 31 Inorganic insulating film 32 Organic insulating film 40 OLED (organic light emitting element)
41 First electrode (anode)
43 Organic light emitting layer 44 Second electrode (cathode)
410 Conductor layer 413 Ag film 414 ITO film

Claims (8)

A substrate 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,
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. Organic light emitting element with
With
The thin film transistor includes a driving thin film transistor that drives the organic light emitting element, and the driving thin film transistor includes a region that becomes a channel composed of a gate electrode, a drain electrode, a source electrode, and an amorphous semiconductor layer , and extends along a predetermined direction. Has a semiconductor layer,
The first conductor membrane and the second conductor membrane so that a part of each of the first conductor membrane constituting the drain electrode and the second conductor membrane constituting the source electrode are alternately arranged along the predetermined direction. The conductor membrane is arranged,
The channel is provided below the light emitting region of the organic light emitting element , and is formed so as to overlap substantially the entire surface of the light emitting region.
The connection between the drive circuit and the first electrode is performed via a conductor layer embedded in a contact hole formed in the flattening film, and the upper surface of the conductor layer has an arithmetic mean roughness Ra of 20 nm or more. An organic EL display device having a diameter of 50 nm or less and having the first electrode and the organic light emitting layer formed on the conductor layer . The organic EL display device according to claim 1, wherein the surface of the flattening film is formed to have an arithmetic average roughness Ra of 20 nm or more and 50 nm or less. The first conductor film and the second conductor film are each formed in a planar shape in a comb shape, and the comb tooth portions of the first conductor film and the second conductor film are formed so as to mesh with each other. , The organic EL display device according to claim 1 or 2. The comb-shaped portion in which the distance between the tip of each comb-shaped portion of the comb-shaped first conductor film and the second conductor film and the opposite portion of the second conductor film or the first conductor film is in mesh with each other. The organic EL display device according to claim 3, which is formed as a part of the channel by being formed equal to the interval of. The first conductor film is formed in a zigzag, and a part of the second conductor film is formed so as to be inserted into the opposite portion of the first conductor film in the zigzag. The organic EL display device according to claim 1 or 2. Emitting region of the light emitting element is formed in a rectangular shape, a portion of the opposing portions of a part and the second conductor film of the first conductive film is formed along the long sides of the rectangular shape The organic EL display device according to any one of claims 3 to 5. A process of forming a drive circuit including a drive thin film transistor for driving an organic light emitting element on a substrate, and
The process of forming a flattening film on the surface of the drive circuit and
A step of forming the organic light emitting element by sequentially forming a first electrode, an organic light emitting layer, and a second electrode on the surface of the flattening film, and
Including
The thin film transistor includes a gate electrode, a gate insulating film, a region to be a channel, an amorphous semiconductor layer extending along a predetermined direction, and a first conductor film and a source as a drain electrode formed by connecting to the amorphous semiconductor layer. It is formed by a laminated structure with a second conductor film as an electrode.
A part of each of the first conductor film and the second conductor film is formed so as to be arranged alternately along the predetermined direction, and the channel emits light from the organic light emitting element. It is provided below the region and is formed so as to overlap almost the entire surface of the light emitting region.
The channel, Ri said amorphous semiconductor layer der sandwiched between a portion of a portion of an adjacent said first conductive film and the second conductive film,
The connection between the drive circuit and the first electrode is performed via a conductor layer embedded in a contact hole formed in the flattening film, and the upper surface of the conductor layer has an arithmetic mean roughness Ra of 20 nm or more. 50nm is formed below, that has the first electrode and the organic light emitting layer is formed on the conductive layer, a method of manufacturing an organic EL display device. The method for manufacturing an organic EL display device according to claim 7, wherein the surface of the flattening film is polished to an arithmetic mean roughness Ra of 20 nm or more and 50 nm or less, and then the organic light emitting element is formed.

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