JPH0786620B2 - Manufacturing method of active matrix display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a display device that performs display by applying a drive signal to a display pixel electrode via a switching element, and more particularly to a pixel electrode. The present invention relates to a method of manufacturing a display device of an active matrix drive system in which pixels are arranged in a matrix for high density display.

(Prior Art) Conventionally, in a liquid crystal display device, an EL display device, a plasma display device, etc., a display pattern is formed on a screen by selectively driving picture element electrodes arranged in a matrix. There is. A voltage is applied between the selected pixel electrode and a counter electrode facing the pixel electrode, and the display medium interposed therebetween is optically modulated. This optical modulation is visually recognized as a display pattern. As a driving method of the picture element electrodes, an active matrix driving method is known in which individual picture element electrodes are arranged and a switching element is frozen and driven in each of the picture element electrodes. A TFT (thin film transistor) is used as a switching element for selectively driving the pixel electrodes.
Elements, MIM (metal-insulating layer-metal) elements, MOS transistor elements, diodes, varistors and the like are generally known. The active matrix drive system is capable of high-contrast display, and has been put to practical use in liquid crystal televisions, word processors, terminal display devices of computers, and the like.

(Problems to be Solved by the Invention) When high-density display is performed using such a display device,
It is necessary to arrange a large number of pixel electrodes and switching elements. However, the switching element may be formed as a malfunctioning element when it is formed on the substrate. The pixel electrode frozen in such a defective element causes a pixel defect that does not contribute to display.

A configuration for correcting a picture element defect is disclosed in, for example, Japanese Patent Laid-Open No. 61-1536.
No. 19 is disclosed. In this configuration, the pixel electrode 1
A plurality of switching elements are provided for each. One of the plurality of switching elements is connected to the pixel electrode, and the other is not connected to the pixel electrode. If the switching element connected to the pixel electrode is defective, laser trimmer,
The switching element is separated from the picture element electrode by an ultrasonic cutter or the like, and another switching element is connected to the picture element electrode. The connection between the switching element and the pixel electrode is performed by attaching a minute conductor with a dispenser or the like, or by coating a predetermined portion with Au, Al or the like on the substrate. Furthermore, JP-A-61-56382 and JP-A-5959
Japanese Unexamined Patent Publication No. -101693 discloses a structure in which metal layers are electrically connected to each other by irradiating a laser beam to melt a metal.

The above defect repair must be performed in the state of the active matrix substrate before assembling the display device. The reason is that after the display device is completed, a part of the metal evaporated or melted by laser light irradiation is mixed in the display medium such as liquid crystal present between the pixel electrode and the counter electrode,
This is because the optical characteristics of the display medium are significantly deteriorated.
Therefore, any of the conventional pixel defect corrections described above is applied in the active matrix substrate manufacturing process before the display device is assembled, that is, before the display medium is enclosed.

However, it is extremely difficult to detect a pixel defect at the manufacturing stage of the active matrix substrate. Especially the number of picture elements
In a large-sized display device with 100,000 to 500,000 or more, it is necessary to use extremely high-precision measuring equipment in order to detect the defective switching element by detecting the electrical characteristics of all pixel electrodes. . For this reason, the inspection process becomes complicated, and mass productivity is hindered. Therefore, the cost is increased. For such a reason, in a large-sized display device having a large number of picture elements, the position where the picture element defect is generated is not actually specified in the state of the substrate. Therefore, the pixel defects cannot be corrected by using the laser light described above, and the manufacturing yield cannot be improved.

The present invention has been made to solve such a problem. That is, it is an object of the present invention to provide a method for manufacturing an active matrix display device with a high yield.

(Means for Solving the Problems) A method for manufacturing an active matrix display device of the present invention is
A method for manufacturing an active matrix display device, comprising: a pair of substrates, at least one of which has translucency, and a display medium which is inserted between the substrates and whose optical characteristics are modulated in response to an applied voltage. Picture element electrodes arranged in a matrix on the inner surface of one of the pair of boards, switching elements and preliminary switching elements electrically connected to the picture element electrodes, the switching elements and the preliminary switching elements, respectively. The scanning line connected to the switching element, the signal line connected to the switching element, the extended end of the signal input terminal of the preliminary switching element, and the branch wiring branched from the signal line are not connected via at least the insulating layer. A step of forming a connection part which is placed in close proximity and in a conductive state, a step of covering the display medium side of the connection part with a protective film, and a counter electrode on the other substrate of the pair of substrates. Forming a display medium, inserting the display medium between the pair of substrates, and applying a drive voltage to the display medium through the switching element, the pixel electrode, and the counter electrode, thereby causing a pixel defect. The step of optically detecting, and the connection portion where the branch wiring and the extended end of the signal input terminal of the preliminary switching element connected to the picture element electrode in which the picture element defect is detected are opposed to each other. The step of irradiating light energy to electrically connect the preliminary switching element and the signal line through the connecting portion is included, whereby the above object is achieved.

(Operation) As described above, the inner surface of the active matrix substrate is
Picture element electrode, switching element, preliminary switching element,
Scan lines, signal lines, and connection parts are formed. The connection part is covered with a protective film. A counter electrode is formed on the counter substrate. After the display medium is sealed between the active matrix substrate and the counter substrate, the drive voltage is applied to all the pixel electrodes. By driving all the pixel electrodes, the display medium correspondingly produces optical modulation according to the driving voltage. However, when the switching element is defective, this optical modulation becomes incomplete and is visually recognized as a pixel defect. This pixel defect can be easily identified by using a magnifying lens or the like even on a substrate on which hundreds of thousands of minute pixel electrodes are arranged.

When the pixel defective portion is specified, optical energy such as laser light is applied to the connecting portion from the outside through the transparent substrate. At the connection portion, the extended end of the signal input terminal of the preliminary switching element and the branch wiring branched from the signal are electrically connected to each other by laser light irradiation. In this way, the spare TFT 7 and the signal line are electrically connected via the connecting portion. Further, if necessary, a defective switching element connected to the pixel electrode can be cut by irradiation with light energy to be separated from the pixel electrode. Since the connection portion is covered with the protective film, the molten metal or the like is not mixed in the display medium, and the characteristics of the display medium are not deteriorated. That is, the connection between the above-mentioned preliminary switching element and the signal line is
Since it is performed between the protective film and the substrate that are separated from the display medium, the pixel defects can be corrected without adversely affecting the display medium.

(Examples) The present invention will be described below with reference to Examples. FIG. 1A shows an example of an active matrix substrate constituting a display device manufactured by the manufacturing method of the present invention. The configuration of each cross section along the line B-B and the line C-C in FIG. 1A is shown in FIGS. 1B and 1C.
Shown in the figure. A base coat film 2 made of Ta ₂ O ₅ , Al ₂ O ₃ , Si ₃ N ₄ or the like is formed on a glass substrate 1 with a thickness of 3000Å to 9000Å, and a gate bus wiring 3 for supplying a scanning signal is formed on the base coat film 2.
Source bus lines 4 for supplying data signals are arranged in a grid pattern. Gate bus wiring 3 is generally Ta, Al, Ti, N
It is formed of a single layer such as i or Mo or a multilayer metal of these,
In this embodiment, Ta is used. The source bus line 4 is also made of the same metal, but Ti is used in this embodiment. A base insulating film 11, which will be described later, is interposed at the intersection of the gate bus wiring 3 and the source bus wiring 4. In a rectangular area surrounded by the gate bus wiring 3 and the source bus wiring 4, picture element electrodes 5 made of a transparent conductive film (ITO) are provided to form a picture element pattern in a matrix. The TFT6 is arranged near the corner of the pixel electrode 5, and the TFT6 and the pixel electrode 5
And are electrically connected to each other by the drain electrode 16.
A spare TFT 7 is arranged near the other corner of the picture element electrode 5,
The TFT 7 and the pixel electrode 5 are electrically connected by the drain electrode 16a. The TFT 6 and the spare TFT 7 are arranged side by side on the gate bus wiring 3, and the source electrode 15 of the TFT 6 and the source bus wiring 4 are connected by a branch wiring 8. The source electrode 15a of the spare TFT 7 is connected to the connecting portion 25a by the source electrode extension end 8a.
Be led to. In the connecting portion 25, the source electrode extension end 8a is placed opposite to the branch wiring 8 in a non-conducting state. Therefore, two TFs
Of T6 and 7, only TFT6 is electrically connected to the source bus line 4, and the spare TFT7 is not connected to the source bus line 4. Details of the cross-sectional structure of the connecting portion 25 will be described later.

The cross-sectional structure near the TFT 6 will be described with reference to FIG. 1B. The configuration of the spare TFT 7 is similar to that of the TFT 6. A gate insulating film 10 made of Ta ₂ O ₃ obtained by anodizing the surface of the gate electrode 9 is formed on the Ta gate electrode 9 formed as a part of the gate bus line 3. From this, a base insulating film 11 of SiN _x (for example, Si ₃ N ₄ ) that also functions as a gate insulating film is deposited over the entire surface of the substrate. An amorphous silicon (a-Si) intrinsic semiconductor layer 12 and a semiconductor layer protective film 13 made of SiN _x for protecting the upper surface of the intrinsic semiconductor layer 12 are sequentially laminated on the base insulating film 11. Further, an n-type semiconductor layer 14 made of a-Si is stacked on the n-type semiconductor layer 14 to obtain ohmic contact with the source electrode and the drain electrode which will be formed later. A source electrode 15 and a drain electrode 16 are formed on the n-type semiconductor layer 14. The source electrode 15 and the drain electrode 16 are made of Ti, Ni, Al or the like.

The pixel electrode 5 is patterned on the base insulating film 11. The thickness of the base insulating film 11 is appropriately 1500Å to 6000Å, but in this embodiment, it is set to 2000Å to 3500Å. Cover the upper surfaces of the TFT 6 and the pixel electrode 5 and cover the entire surface of the substrate with SiN _x.
A protective film 17 composed of is formed, and liquid crystal molecules 18 are formed on the protective film 17.
An alignment layer 19 that controls the alignment of the is deposited. Protective film 17
The appropriate thickness is about 2000Å to 10000Å, but in this embodiment, it is set to about 5000Å. The base insulating film 11 and the protective film 17 may be formed of SiO _x , Ta ₂ O ₅ , Al ₂ O ₃ or other oxides or nitrides other than SiN _x . Instead of forming the protective film 17 on the entire surface of the substrate, it is possible to form a window structure in which only the TFT 6, the spare TFT 7, the bus wiring, and the like that are not directly involved in the display are covered and the central portion of the pixel electrode 5 is removed.

On the inner surface of the other glass substrate 20 facing the glass substrate 1 on which the pixel electrodes 5 are formed, a color filter 21 and a counter electrode are provided.
22 and the alignment layer 23 are formed so as to overlap each other. A black matrix (not shown) is provided around the color filter 21 as needed.

Between the pair of glass substrates 1 and 20 as a display medium,
Twisted nematic liquid crystal molecules 18 are encapsulated. The liquid crystal molecules 18 undergo orientation conversion in response to an applied voltage between the picture element electrode 5 and the counter electrode 22, and are optically modulated. This optical modulation is visually recognized as a display pattern.

The sectional structure of the connecting portion 25 will be described with reference to FIG. 1C. A joint metal layer 24 is formed on the base coat film 2. The shape of the joint metal layer 24 is rectangular in plan view as shown in FIG. 1A. The joint metal layer 24 is Ta, A as in the gate bus wiring 3.
It is made of l, Ti, Ni, Mo, etc., and can be patterned simultaneously with the formation of the gate bus wiring 3. The base insulating film 11 described above is deposited on the joint metal layer 24. On the base insulating film 11, the source electrode extension end 8a connected to the source electrode 15 of the spare TFT 7 and the branch wiring 8 connected to the source bus wiring 4 are placed. The source electrode extension end 8a and the branch wiring 8 are separated from each other and maintain a non-conductive state.
Therefore, the spare TFT 7 is not electrically connected to the source bus line 4. The source electrode extension end 8a and the branch wiring 8 are completely covered with a protective film 17.

The base insulating film 11 located between the joint metal layer 24 and the source electrode extended end 8a and the branch wiring 8 also functions as an interlayer insulating film between these metal layer and wiring. The thickness of the interlayer insulating film is preferably 1000Å to 7000Å, but in this embodiment, since the base insulating film 11 that also functions as the gate insulating film of the TFTs 6 and 7 is used, as described above, 2000Å to 35
It is set to 00Å.

The protective film 17 is for electrically connecting the branch wiring 8 and the source electrode extension end 8a in a state of being separated from the liquid crystal molecules 18 as a display medium. Therefore, the thickness of the protective film 17 is 15
A value of 00Å to 15000Å is appropriate. In this embodiment, since the protective films of the TFTs 6 and 7 are used, the thickness thereof is set to around 5000Å.

A driving voltage is applied to all the pixel electrodes 5 via the TFT 6 from all the gate bus wirings 3 and the source bus wirings 4 of the liquid crystal display device having the above structure. In this way, when all the pixel electrodes are driven, the pixel defects can be easily visually recognized. If a pixel defect due to a defective TFT6 has occurred, the connection part 25
Can be easily modified with. FIG. 2 shows a cross-sectional view of the connecting portion 25 used for correcting the picture element defect. As shown by the arrow 26 in FIG. 2, the joint metal layer 24 is irradiated with laser light, infrared rays, an electron beam, and other energy from the outside through the lower glass substrate 1. In this embodiment, YAG laser light is used. In the overlapping portion of the branch wiring 8, the base insulating film 11 and the joint metal layer 24, when the laser light is irradiated, dielectric breakdown of the base insulating film 11 occurs, and the branch wiring 8 and the joint metal layer 24.
And are fused and connected to each other and become conductive. Similarly, dielectric breakdown of the base insulating film 11 occurs even at the overlapping portion of the source electrode extension end 8a, the base insulating film 11 and the joint metal layer 24, and the source electrode extension end 8a and the joint metal layer 24 melt with each other. It is connected and becomes conductive. In this way, the branch line 8 and the source electrode extension end 8a are electrically connected via the joint metal layer 24, and the spare TFT 7 is driven by the source bus line 4.
In the present embodiment, the laser light is applied from the glass substrate 1 side, but any substrate may be applied as long as the laser light is transmitted therethrough.

Even if the pixel defect is corrected by using the laser light as described above, since the protective film 17 is formed above the connection portion 25, the molten metal is not mixed in the liquid crystal which is the display medium. Absent. Further, since the protective film 17 is a transparent insulator, the laser light passes through it. Therefore, the protective film 17 is not destroyed by the laser light. The liquid crystal layer in the vicinity of the portion irradiated with the laser light becomes cloudy, but this cloudiness disappears and is restored to its original state, so that the image quality does not deteriorate.

When it is necessary to separate the TFT 6 from the pixel electrode 5 due to poor insulation of the TFT 6, the drain electrode 16 of the TFT 6 is irradiated with laser light and cut. By separating the TFT6 and the picture element electrode 5, the picture element electrode 5 is a spare TFT7.
Normally driven by.

FIG. 3 shows another example of the active matrix substrate constituting the display device manufactured by the manufacturing method of the present invention. In this example, the positions of the TFT 6 and the spare TFT 7 are opposite to those in the example of FIG. 1A. The connecting portion 25 is provided between the gate bus wiring 3 and the branch wiring 8. Similar to the example of FIG. 1A, the source bus wiring 4 is formed orthogonally to the gate bus wiring 3, and a transparent electrode (ITO) is formed in a rectangular area surrounded by the gate bus wiring 3 and the source bus wiring 4. Is provided with a picture element electrode 5. A TFT 6 and a spare TFT 7 are arranged near two corners of the picture element electrode 5, respectively, and the TFTs 6 and 7 and the picture element electrode 5 are electrically connected by drain electrodes 16 and 16a, respectively. The configuration of TFT6 and 7 is 1B
It is similar to that shown in the figure. The TFT 6 and the spare TFT 7 are juxtaposed on the gate bus wiring 3, and the TFT 6 is connected to the source bus wiring 4 and the branch wiring 8. Source electrode of spare TFT7
15a is guided to the connecting portion 25 by the source electrode extension end 8a. In the connecting portion 25, the source electrode extension end 8a is placed opposite to the branch wiring 8 in a non-conducting state. Therefore, of the TFTs 6 and 7, only the TFT 6 is electrically connected to the source bus line 4,
The spare TFT 7 is not connected to the source bus line 4. A sectional view of the connecting portion 25 taken along the line C'-C 'in FIG. 3 is similar to that in FIG. 1C.

In the case of the present embodiment as well, similar to the example of FIG. 1A, by irradiating the connecting portion 25 with laser light or the like, it is possible to correct a pixel defect due to a defect of the TFT 6.

The structure of the connecting portion 25 may be the structure shown in FIG. 4 or 5 other than the structure shown in FIG. 1C. In the configuration shown in FIG. 4, a through hole 27 is provided in the base insulating film 11, and the joint metal layer 24 and the source electrode extension end 8a are electrically connected beforehand. If a defect occurs in TFT6, branch wiring 8
Only the overlapping portion of the joint metal layer 24 and the joint metal layer 24 is connected using light energy. In the configuration shown in FIG. 5, the joint metal layer 24 is not provided, and the source electrode extension end 8a is arranged immediately above the branch wiring 8 with the base insulating film 11 interposed therebetween. When a defect occurs in the TFT 6, the source electrode extension end 8a and the branch wiring 8 are directly fused and connected by light energy irradiation.

In FIG. 4, a through hole 27 is provided on the side of the branch wiring 8,
The branch wiring 8 and the joint metal layer 24 may be connected in advance. In this configuration, only the overlapping portion of the source electrode extension end 8a and the joint metal layer 24 is connected by the laser light irradiation.
Further, in FIG. 5, the branch wiring 8 may be formed on the source electrode extension end 8a via the base insulating film 11. Further, in any of the embodiments, the base coat film 2 does not necessarily have to be provided and can be omitted.

In each of the above-described embodiments, the method of manufacturing the transmissive liquid crystal display device is shown, but the present invention can be similarly applied to the manufacture of the reflective display device. Further, in the above-mentioned embodiment, the manufacturing method of the active matrix type liquid crystal display device using the TFT is explained, but the present invention is not limited to this. The present invention can also be applied to the manufacture of a wide range of display devices using various switching elements such as MIM elements, diodes and varistors. Furthermore, as a display medium, a thin film light emitting layer, a dispersion type
It can also be applied to the manufacture of various display devices using EL light emitting layers, plasma light emitters, and the like.

(Effect of the Invention) According to the manufacturing method of the active matrix display device of the present invention, all the picture elements are driven simultaneously from all the wirings, so that the picture element defects can be grasped instantly and the occurrence position of the picture element defects can be easily performed. When the picture element defect can be identified and the switching element is defective, it can be easily corrected, so that the display device can be manufactured with a high yield. Therefore, the cost of the display device can be reduced.

[Brief description of drawings]

FIG. 1A is a plan view of an example of an active matrix substrate constituting a display device manufactured by the manufacturing method of the present invention,
FIGS. 1B and 1C show a display device using the active matrix substrate of FIG. 1A, respectively, taken along line BB and C- of FIG. 1A.
FIG. 2 is a cross-sectional view taken along the line C, FIG. 2 is a cross-sectional view of a connection portion used to correct a pixel defect, and FIG. 3 is another display device manufactured by the manufacturing method of the present invention. Plan views of the active matrix substrate, FIGS. 4 and 5 are cross-sectional views showing other examples of the connecting portion. 1,20 ... Glass substrate, 3 ... Gate bus wiring, 4 ... Source bus wiring, 5 ... Pixel electrode, 6 ... TFT, 7 ... Spare TFT, 8 ... Branch wiring, 8a ... Source Electrode extension end, 9 ...
… Gate electrode, 11 …… Base insulating film, 15,15a …… Source electrode, 16,16a …… Drain electrode, 17 …… Protective film, 18 ……
Liquid crystal molecules, 19,23 ... Alignment layer, 21 ... Color filter, 2
2 …… Counter electrode, 24 …… Coupling metal layer, 25 …… Connection part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takayoshi Nagayasu 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Hidenori Otokoton 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within the Corp. (72) Inventor Ken Kanamori 22-22 Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture Within the Corp. (56) Reference JP-A-62-22455 (JP, A)

Claims (1)

[Claims] 1. A method of manufacturing an active matrix display device, comprising: a pair of substrates, at least one of which is transparent, and a display medium which is inserted between the substrates and whose optical characteristics are modulated in response to an applied voltage. In one of the pair of substrates, the pixel electrodes arranged in a matrix on the inner surface of one of the substrates, a switching element and a preliminary switching element electrically connected to each of the pixel electrodes, and the switching element And a scan line connected to the preliminary switching element, a signal line connected to the switching element, at least an extension end of a signal input terminal of the preliminary switching element and a branch wiring branched from the signal line. A step of forming a connecting part that is placed in close proximity to the film via a film, a step of covering the display medium side of the connecting part with a protective film, and the other of the pair of substrates. Forming a counter electrode on the substrate; inserting the display medium between the pair of substrates; and applying a drive voltage to the display medium via the switching element, the pixel electrode, and the counter electrode. , A step of optically detecting a pixel defect, and the extended end of the signal input terminal of the preliminary switching element connected to the pixel electrode in which the pixel defect is detected, and the branch wiring are opposed to each other. Irradiating the connection portion with light energy to electrically connect the preliminary switching element and the signal line through the connection portion.