JP2008262013A - Display device manufacturing method and TFT array substrate manufacturing method - Google Patents

Abstract

A method of manufacturing a display device and a method of manufacturing a TFT substrate capable of repairing a defective pixel without forming a wiring pattern for repair in advance and without constantly turning off the pixel are provided.
In a manufacturing method of a display device including a pixel circuit having a drive transistor Tr1 and a switching transistor Tr3, when a failure occurs in the switching transistor Tr3, a step of disconnecting a defective portion of the switching transistor Tr3 ′; Contact hole 31a is formed in the passivation film 31 on the drain electrode 23 ′ of the disconnected switching transistor Tr3 ′ and on the drain electrode 23 of the switching transistor Tr3 of the adjacent pixel, and the step of forming the passivation film 31 over the entire area of the substrate 1. A method of manufacturing a display device and a TFT array substrate, comprising: forming and connecting the drain electrodes 23 and 23 ′ to each other with a conductive material through a contact hole 31a.
[Selection] Figure 2

Description

  The present invention relates to a method for manufacturing a display device and a method for manufacturing a TFT (Thin Film Transistor) array substrate, and is particularly suitable for a current-driven display device such as an organic EL (Electro Luminescence) display. The present invention relates to a display device manufacturing method and a TFT array substrate manufacturing method.

  The matrix array provided on the drive substrate side of the display device includes an active matrix array that uses transistors and diodes as drive elements and a passive matrix array that is driven only by a voltage applied between intersecting wirings. As the former, a liquid crystal display or an organic EL display that displays an image using an organic EL phenomenon is well known, and as the latter, a plasma display or a field emission display is well known.

  In recent years, organic EL displays have attracted attention as one of the flat panel displays using the active matrix array described above. The organic EL display has excellent features such as a wide viewing angle and low power consumption because it utilizes the light emission phenomenon of the organic light emitting element itself. Furthermore, since it exhibits high responsiveness to high-definition high-speed video signals, development for practical use is being promoted particularly in the video field.

  One of the promising features of the organic EL display is that it is not necessary to install a backlight, a light guide plate, or the like, which is indispensable for the liquid crystal display, on the back surface of the matrix array, and can be made thinner than the liquid crystal display.

  The active matrix organic EL display has a drive panel provided with a drive element including at least an organic EL element having an organic light emitting material and a TFT for driving the organic EL element. The panel is bonded through an adhesive layer so as to sandwich the organic EL element.

  The active matrix type organic EL display is superior in response speed and resolution as compared with the conventional passive matrix type, and is considered to be a driving method particularly suitable for the organic EL display having the above-described features.

  Further, the TFT array substrate of the active matrix type organic EL display is driven by current, and at least two thin film transistors are required per pixel in order to produce this TFT array substrate. For this reason, the wiring pattern is generally denser than that of a TFT array substrate for liquid crystal, which is made for voltage driving and only requires one thin film transistor per pixel.

  By the way, it is very difficult to manufacture a TFT array substrate in which hundreds of thousands to millions of TFTs are arranged in a matrix without defects, and pixels are defective at a certain rate. The TFT array substrate for organic EL, which has a denser wiring pattern than the TFT array substrate for liquid crystal display devices, has a higher rate of defects due to dust in the air and dust generation during etching than that for liquid crystal. It is a serious problem to significantly reduce. When a pixel has a defect, the pixel is fixed at a certain potential. Therefore, the pixel is always lit or not lit, and not only is it visually recognized as a defect, but also the organic EL element deteriorates, and there is a problem in the lifetime of the element. .

  In recent years, various methods have been proposed as means for improving this problem. For example, by disconnecting the short-circuited part of the wiring that causes bright lines or dark lines with a laser or the like, the defective pixels that are always lit are always turned off, and the non-lighted part is reduced to one pixel. There is a correction method that makes it difficult (see, for example, Patent Document 1).

  In addition, an example of a manufacturing method of an active matrix liquid crystal display device in which a connecting dummy wiring for connecting adjacent pixels is formed is also disclosed (for example, see Patent Document 2).

  Furthermore, a point defect repair pattern formed in the same layer as the gate wiring and an island provided on the point defect repair pattern via the gate insulating film, the transistor portion of the pixel recognized as a point defect is cut, Thereafter, an example of a liquid crystal display device in which a pixel electrode of an adjacent pixel is short-circuited through the point defect repair pattern by irradiating a laser beam has been reported (for example, see Patent Document 3).

JP-A-1-138539 JP 2003-50400 A Japanese Patent Laid-Open No. 9-5785

  However, in the method described in Patent Document 1 described above, since defective pixels are always turned off, it is difficult to visually recognize the pixels as compared to the constant lighting, but it is visually recognized when the number of defects increases. Become.

  In addition, when the method described in Patent Document 2 is applied to an organic EL display device, a pattern of an organic EL TFT array substrate that originally has a dense wiring pattern is prepared by preparing a connecting dummy wiring in advance. The density is further increased. As a result, a serious problem such as a decrease in yield occurs due to an increase in the defect defect generation rate during the fabrication of the TFT array substrate.

  Furthermore, when the method described in Patent Document 3 is applied to an organic EL display device, the pattern density of the organic EL TFT array substrate, which originally has a dense wiring pattern, can be reduced by creating a point defect repair pattern in advance. It gets even higher.

  In view of the above, the present invention provides a method for manufacturing a display device and a method for manufacturing a TFT substrate capable of repairing a defective pixel without forming a wiring pattern for repair in advance or without constantly turning off the pixel. The purpose is to provide.

  In order to achieve the above-described object, a method for manufacturing a display device of the present invention includes a display element arranged on a substrate and a pixel circuit for driving the display element, and the pixel circuit includes the display element. In a manufacturing method of a display device having a driving transistor for driving a transistor and a switching transistor having a first electrode connected to a power supply line and selectively supplying current from the power supply line to the driving transistor, after forming a pixel circuit Thus, when a defect of the switching transistor is detected before forming the display element, the following steps are sequentially performed. First, a step of disconnecting the current path from the power supply line to the switching transistor in which a defect has occurred is performed. Next, a process of forming a passivation film on the substrate in a state of covering the pixel circuit is performed. Subsequently, contact holes are formed in the passivation film on the second electrode of the switching transistor in which the defect is detected and on the second electrode of the switching transistor of the adjacent pixel, and the second electrodes are made of a conductive material through the contact hole. And connecting.

  According to such a method for manufacturing a display device, a defective pixel is repaired by connecting the second electrodes of the switching transistors of adjacent pixels with a conductive material without forming a repair wiring pattern in advance. It is possible. Further, by repairing the defective pixel, it is possible to increase the luminance of the display device as compared with the case where the pixel is always turned off.

  The present invention is also a method for manufacturing a TFT array substrate manufactured by the method described above.

  As described above, according to the method for manufacturing a display device and the method for manufacturing a TFT array substrate of the present invention, it is possible to repair a defective pixel without forming a repair wiring pattern in advance. Since the luminance of the device can be increased, high performance of the display device can be achieved.

  Hereinafter, embodiments of the present invention will be described in detail.

  Next, embodiments of the display device of the present invention will be described in detail with reference to the drawings. Here, an embodiment in which the present invention is applied to an active matrix organic EL display device will be described. This display device includes a display element arranged on a substrate and a pixel circuit for driving the display element.

<Pixel circuit>
In the circuit diagram of the display device of this embodiment, as shown in FIG. 1, a plurality of rows of scanning lines WS and a plurality of columns of signal lines 11 are wired in a matrix, and a current-driven display is provided at each of these intersections. An element, for example, an organic EL element 12 and a pixel circuit that drives the organic EL element 12 are provided.

  The pixel 10 includes the organic EL element 12 as a light emitting element, and has a circuit configuration including a driving transistor Tr1, a writing transistor Tr2, switching transistors Tr3 to Tr5, and a storage capacitor element Cs in addition to the organic EL element 12. It has become.

  In the pixel 10 having such a configuration, N-channel TFTs are used for all of the driving transistor Tr1, the writing transistor Tr2, and the switching transistors Tr3 to Tr5. However, the combination of the conductivity types of the transistors here is only an example, and is not limited to these combinations.

  The organic EL element 12 has a cathode electrode (cathode) connected to the first power supply potential Vcat (here, the ground potential GND). The drive transistor Tr1 is an active element for current-driving the organic EL element 12, and a source electrode is connected to an anode electrode (anode) of the organic EL element 12 to form a source follower circuit.

  The writing transistor Tr2 has a source electrode connected to the signal line 11 (signal voltage Vsig), a drain electrode connected to the gate electrode of the driving transistor Tr1, and a gate electrode connected to the scanning line (WS line).

  The switching transistor Tr3 selectively supplies current to the drive transistor and controls the light emission time of the organic EL element 12. The drain electrode of the switching transistor Tr3 is connected to the second power supply potential Vcc (here, positive power supply potential) (power supply line), the source electrode is connected to the drain electrode of the drive transistor Tr1, and the gate electrode is the drive line ( DS line).

  The switching transistor Tr4 has a drain electrode connected to the other electrode of the write transistor Tr2 (gate electrode of the drive transistor Tr1), a source electrode connected to a third power supply potential Vss1 (here, a positive power supply potential), and a gate The electrode is connected to AZ (Auto Zero) 2 wire.

  The switching transistor Tr5 has a drain electrode connected to the source electrode of the driving transistor Tr1 and an anode electrode of the organic EL element 12, a source electrode connected to the fourth power supply potential Vss2 (here, a negative power supply potential), and a gate electrode. Is connected to the AZ (Auto Zero) 1 line.

  In the present embodiment, the adjacent pixels 10 are arranged so as to have a mirror symmetry in which the switching transistor Tr3 that supplies a potential to the driving transistor Tr1 is arranged adjacent to each other. This is preferable because it becomes easy to connect the drain electrodes of the switching transistor Tr3 in a later step.

  Of the five transistors as described above, the write transistor Tr2 and the switching transistors Tr4 and Tr5 are for controlling on / off of the drive transistor Tr1, and require current characteristics when the switch is on. do not do. Since the on-current characteristics of the transistor depend on the channel width, the write transistor Tr2 and the switching transistors Tr4 and Tr5 may be small.

  On the other hand, since the driving transistor Tr1 and the switching transistor Tr3 directly affect the current force flowing into the organic EL element 12, it is necessary to sufficiently increase the channel width so that on-current characteristics can be obtained. For this reason, the area of the drive transistor Tr1 and the switching transistor Tr3 needs to be made nearly 10 times larger than that of the write transistor Tr2, the switching transistors Tr4 and Tr5.

  By the way, the probability that a transistor is defective due to the influence of dust or the like depends on the surface area of the transistor. For this reason, the drive transistor Tr1 and the switching transistor Tr3 have a high probability of being defective. Therefore, the present invention proposes a correction method when the switching transistor Tr3 is defective.

  First, as shown in FIG. 2A, as described above, the adjacent pixels 10 and 10 ′ on the substrate 1 are mirror-symmetric with the switching transistors Tr3 and Tr3 ′ adjacent to each other. Has been placed. The gate electrodes 21 and 21 ′ of the switching transistors Tr3 and Tr3 ′ are configured by a part of the drive line DS, and the drain electrodes (second electrodes) 22 and 22 ′ are connected to the power supply line 13 (potential Vcc). Has been. The source electrodes (first electrodes) 23 and 23 ′ are provided with contact regions 23 a and 23 a ′ drawn from the source electrodes 23 and 23 ′. Although illustration is omitted here, the other transistors (drive transistor Tr1, write transistor Tr2, switching transistors Tr4, 5) described in FIG. 1 are configured in the same layer as the switching transistor Tr3. To do.

  In a state where the pixel circuit including each of the transistors is provided, a continuity test is usually performed to detect a defective pixel. Here, for example, it is assumed that the switching transistor Tr3 'of the pixel 10' has caused a short circuit S due to dust. In this case, the current path from the power supply line 13 to the switching transistor in which a defect is detected is disconnected (cut line X). Specifically, the drain electrode 22 'of the switching transistor Tr3' is disconnected by laser irradiation. This prevents the pixel 10 'from being constantly lit due to the short circuit S. At this time, by disconnecting the gate electrode 21' of the switching transistor Tr3 ', the drive line DS and the switching transistor Tr3' It is preferable to disconnect the connection.

  Next, as shown in FIG. 2B, a passivation film 31 is formed on the substrate 1 so as to cover the pixel circuit including the switching transistors Tr3 and Tr3 '. Subsequently, a contact hole 31a is formed in the passivation film 31 on the contact region 23a ′ of the source electrode 23 ′ of the switching transistor Tr3 ′ that has failed due to laser irradiation and on the contact region 23a of the source electrode 23 of the adjacent switching transistor Tr3. Form. Next, a wiring pattern 32 is formed by connecting the contact regions 23a and 23a 'with a conductive material through the contact hole 31a.

  As a method for forming the wiring pattern 32, laser CVD (Chemical Vapor Deposition), a metal nano paste coating method using a micro dispenser, or the like is used.

  Here, FIG. 3 shows an enlarged circuit diagram of a main part of region A in FIG. 1 in this state. As shown in this figure, even if a short circuit S occurs in the switching transistor Tr3 ′ of the pixel 10, as described above, the power supply line 13 (see FIG. 2B) reaches the switching transistor in which a defect is detected. The current path is disconnected, and the source electrode 22 of the switching transistor Tr3 of the adjacent pixel 10 and the source electrode 22 ′ of the switching transistor Tr3 ′ are connected by the wiring pattern 32. As a result, the pixel 10 ′ that is not lit when it is disconnected can be corrected by taking in the current from the adjacent switching transistor Tr <b> 3.

  However, as shown in FIG. 4A, the luminance of the pixel 10 having the normal switching transistor Tr3a is determined by the voltage “A” applied to the organic EL element, and as shown in FIG. The luminance when Tr3b is divided into two pixels 10, 10 ′ is determined by the voltage “B”. Therefore, if the voltage drops of the switching transistors Tr3a and Tr3b are the same, “A = B” is obtained, so that the defect is completely corrected, but the voltage drops of the switching transistors Tr3a and Tr3b are made comparable. The condition is necessary.

Here, when the resistance value of the switching transistor Tr3a is Y and the resistance value of the driving transistor Tr1 and the organic EL element is X, the voltage drop of the driving transistor Tr1 of the normal pixel 10 is Y / (X + Y). On the other hand, the voltage drop of the driving transistor Tr1 of the repaired pixel 10 ′ is Y / ((X / 2) + Y). Therefore, in order to make the voltage drop of the switching transistors Tr3a and Tr3b the same, the resistance value of the drive transistor Tr1 and the organic EL element 12 and the resistance value of the switching transistor Tr3b are set so as to satisfy the following formula (1). It may be specified.

  In order to satisfy the formula (1), X in the formula (1) may be made extremely smaller than Y. That is, it is necessary to design the resistance value of the driving transistor Tr1 and the organic EL element 12 to be smaller than the resistance value of the switching transistor Tr3b.

  Specifically, first, when it is assumed that the resistance value of the organic EL element 12 is extremely smaller than the resistance value of the driving transistor Tr1 or the switching transistor Tr3b, the resistance values of the driving transistor Tr1 and the switching transistor Tr3b. Are the same, the voltage drop of the switching transistor Tr3b repaired by the above-described method increases by 33% with respect to the voltage drop of the switching transistor Tr3a that has not been repaired. That is, in this case, the luminance of the restored pixel 10 ′ is 66% of the normal pixel 10.

  However, if the on-state current of the drive transistor Tr1 is set to 5 times the on-state current of the switching transistor Tr3b, the resistance value of the drive transistor Tr1 becomes 1/5 of the resistance value of the switching transistor Tr3b. As a result, the increase in voltage drop of the switching transistor Tr3 before and after the repair can be suppressed to 9%. In this case, the luminance after restoration is 91% of the luminance of normal pixels. At this level, it cannot be recognized as a defect with the naked eye, so it can be said that it has been completely repaired.

  Actually, in order to increase the ON characteristics of the drive transistor Tr1, the gate voltage (Vg-high) of the drive transistor Tr1 is increased, the channel width is increased, and the drive transistor Tr1 having high mobility is manufactured. . If the channel width is made large, there is a trade-off with a decrease in yield, so that a method for improving the mobility of only the drive transistor Tr1 is more optimal.

  As a specific method, when the TFT channel layer is crystallized by excimer laser annealing (ELA) or the like, only the upper portion of the driving transistor Tr1 is covered with an antireflection film, or a CW (Continuous Wave) laser or the like is used. When crystallizing the channel layer of the TFT, a method may be considered in which the crystallization of only the driving transistor Tr1 is further advanced by irradiating only the upper part of the driving transistor Tr1.

  After the repair as described above, a process for forming the next display element is subsequently performed. That is, as shown in FIG. 5, an interlayer insulating film 41 is formed on the passivation film 31 (see FIG. 2B), and the interlayer insulating film 41 is connected to the drive transistor Tr2 via the contact plug. The lower electrode 43 is patterned. Next, after the periphery of the lower electrode 43 is covered with an insulating film pattern 44, an organic layer 45 including at least a light emitting layer is stacked on the lower electrode 43 exposed from the insulating film pattern 44. Next, the upper electrode 46 is formed so as to cover the organic layer 45 and the insulating film pattern 44. Thereby, the organic EL element (display element) 11 connected to the drive transistor Tr2 by the lower electrode 43 is formed.

  As described above, the display device and the TFT array substrate of this embodiment are manufactured. Although illustration is omitted here, the organic EL element 12 may be sealed with a counter substrate with a protective film and a sealing resin.

  According to the manufacturing method of the display device and the manufacturing method of the TFT array substrate as described above, the source electrodes 23 and 23 ′ of the switching transistors of the adjacent pixels 10 and 10 ′ can be connected to each other without forming a wiring pattern for repair in advance. By connecting these with a conductive material, it is possible to repair defective pixels. Further, by repairing the defective pixel, it is possible to increase the luminance of the display device as compared with the case where the pixel is always turned off. Therefore, high performance of the display device can be achieved.

  In the above-described embodiment, the example in which the switching transistor Tr3 is an NMOS transistor has been described. However, when the switching transistor Tr3 is a PMOS transistor, the first electrode connected to the power supply line 13 is the source electrode. Therefore, the drain electrode (second electrode) of the switching transistor Tr3 ′ in which a defect is detected and the drain electrode (second electrode) of the switching transistor Tr3 of the adjacent pixel are connected and repaired.

  In the above-described embodiment, the method for manufacturing a display device having a pixel circuit having five TFTs in one pixel has been described as an example. However, as shown in FIG. 6, three TFTs in one pixel are provided. The present invention can be applied even to a display device having a pixel circuit provided. Further, as shown in FIG. 7, the present invention can be applied even to a display device having a pixel circuit having four TFTs in one pixel.

It is a circuit diagram which shows the pixel circuit to which the manufacturing method of the display apparatus which concerns on embodiment of this invention is applied. It is a manufacturing process figure which shows the manufacturing method of the display apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the manufacturing method of the display apparatus which concerns on embodiment of this invention. FIG. 5 is a circuit diagram (No. 1) illustrating a method for manufacturing a display device according to an embodiment of the present invention. FIG. 6 is a circuit diagram (No. 2) illustrating the method for manufacturing the display device according to the embodiment of the invention. FIG. 10 is a circuit diagram (No. 1) showing another pixel circuit to which the method for manufacturing a display device of the present invention is applied. It is a circuit diagram (the 2) which shows the other pixel circuit to which the manufacturing method of the display apparatus of this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate 10, 10 '... Pixel, 12 ... Organic EL element, 22, 22' ... Drain electrode, 23, 23 '... Source electrode (second electrode), 23a, 23a' ... Contact region, 31 ... Passivation film 31a ... contact hole, Tr1 ... driving transistor, Tr3 ... switching transistor

Claims (6)

A display element arrayed on a substrate and a pixel circuit for driving the display element, the pixel circuit having a driving transistor for driving the display element and a first electrode connected to a power supply line; In a manufacturing method of a display device having a switching transistor that selectively supplies current to the driving transistor from the power supply line,
After detecting the defect of the switching transistor after forming the pixel circuit and before forming the display element,
Disconnecting a current path from the power supply line to the switching transistor in which a defect has occurred;
Forming a passivation film on the substrate in a state of covering the pixel circuit after disconnecting the current path;
Forming a contact hole in the passivation film on the second electrode of the disconnected switching transistor and on the second electrode of the switching transistor of the adjacent pixel, and connecting the second electrodes with a conductive material through the contact hole A method for manufacturing a display device, comprising: In the manufacturing method of the display device according to claim 1,
Adjacent pixels are arranged so as to be mirror-symmetric with the switching transistors adjacent to each other. A method for manufacturing a display device, comprising: In the manufacturing method of the display device according to claim 1,
A contact region is provided in the second electrode of the switching transistor. A method of manufacturing a display device, wherein: In the manufacturing method of the display device according to claim 1,
A method for manufacturing a display device, characterized in that an on-current of the driving transistor is higher than an on-current of the switching transistor. In the manufacturing method of the display device according to claim 1,
The display device is an organic electroluminescent device. A method of manufacturing a display device, wherein: A display element arranged on a substrate and a pixel circuit for driving the display element, the pixel circuit driving a display transistor according to pixel information, and a first electrode supplying power A TFT array substrate having a switching transistor connected to a line and selectively supplying current to the driving transistor from the power supply line.
After detecting the defect of the switching transistor after forming the pixel circuit and before forming the display element,
Disconnecting a current path from the power supply line to the switching transistor in which a defect has occurred;
Forming a passivation film on the substrate in a state of covering the pixel circuit after disconnecting the current path;
Forming a contact hole in the passivation film on the second electrode of the disconnected switching transistor and on the second electrode of the switching transistor of the adjacent pixel, and connecting the second electrodes with a conductive material through the contact hole And a method for manufacturing a TFT array substrate.

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