JPH0830826B2 - Method for manufacturing 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 method for manufacturing a display device. The present invention relates to a method of manufacturing a display device of an active matrix driving system, in which element electrodes are arranged in a matrix to perform 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 pixel electrodes arranged in a matrix. . A voltage is applied between the selected pixel electrode and a counter electrode facing the pixel electrode, and a display medium such as a liquid crystal interposed between these electrodes 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 connected to each of the picture element electrodes for driving. As a switching element that selectively drives the pixel electrodes, a TFT
(Thin film transistor) 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.

7 and 8 are plan views of an active matrix substrate used in a conventional active matrix type display device. In the substrate of FIG. 7, source bus lines 23 are arranged orthogonal to the gate bus lines 21 arranged in parallel with each other. A pixel electrode 41 is arranged in each rectangular region surrounded by the two gate bus lines 21 and the two source bus lines 23. A TFT 31 that functions as a switching element is formed on the gate bus line 21 near the intersection of the gate bus line 21 and the source bus line 23. A part of the gate bus wiring 21 functions as the gate electrode of the TFT 31. The drain electrode of the TFT 31 is electrically connected to the pixel electrode 41. Saw's bus wiring 2 on the ces electrode of TFT31
The branch line branched from 3 is connected.

The active matrix substrate of FIG. 8 is the same as the substrate of FIG. 7, but the configuration near the TFT 31 is different. That is, TFT
Reference numeral 31 is formed on the gate bus branch line 22 branched from the gate bus wiring 21. A part of the gate bus branch line 22 functions as a gate electrode of the TFT 31.

(Problems to be Solved by the Invention) When high-density display is performed using a display device having such a substrate, it is necessary to arrange a large number of pixel electrodes 41 and TFTs 31. However, the TFT 31 may be formed as a malfunctioning element when it is formed on the substrate. The pixel electrode connected to such a defective element causes a point defect that does not contribute to display. The point defect significantly impairs the image quality of the display device and greatly reduces the product yield.

The main causes of point defects are roughly classified into two types. 1
One is a defect (hereinafter referred to as "on defect") that occurs because the pixel electrode is not sufficiently charged within the time when the pixel electrode is selected by the scanning signal. The other one is a defect (hereinafter referred to as "off defect") in which the charge of the charged pixel electrode leaks within the non-selection time.
The ON failure is caused by the TFT failure. The off failure may be caused by electrical leakage through the TFT or may be caused by electrical leakage between the pixel electrode and the bus wiring. No matter which defect occurs, a necessary voltage is not applied between the pixel electrode and the counter electrode, which causes a point defect. Such a defect appears as a bright spot in the normally white mode in which the light transmittance becomes maximum when the voltage applied between the pixel electrode and the counter electrode is 0V, and when the voltage is 0V, It appears as a black dot in the normally black mode where the light transmittance is the lowest.

Such defects can be corrected by performing laser trimming or the like. However, this defect correction must be performed at the stage of the active matrix substrate before assembling the display device. Although it is easy to detect pixel defects after assembling them as a display device, it is extremely difficult to detect pixel defects at the stage of the active matrix substrate. Especially in a large display device with 100,000 to 500,000 or more picture elements, use an extremely high-precision measuring device to detect the defective TFT by detecting the electrical characteristics of all picture element electrodes. There must be. For this reason, the inspection process becomes complicated and mass productivity is hindered. Therefore, the cost is increased. For this reason, in a large-sized display device having a large number of picture elements, the picture element defect cannot be corrected in the state of the substrate using the laser light described above.

The present invention solves such a problem, and an object of the present invention is to correct a pixel defect due to a defective switching element so that the defect is not noticeable in a state where the display device is assembled. An object of the present invention is to provide a method for manufacturing an active matrix display device to be obtained.

(Means for Solving the Problem) A method for manufacturing an active matrix display device according to the present invention is directed to an insulating substrate, scanning lines and signal lines wired vertically and horizontally on the substrate, and scanning branched from the scanning line. The scanning line is provided with a branch line, a switching element formed by using the tip of the scanning branch line as a gate electrode, and a pixel electrode connected to the switching element. A step of forming an active matrix substrate in which the distance to the line is such that the scanning branch line can be cut by irradiating light energy, and the active matrix substrate and the counter substrate are bonded together to form the active matrix substrate. A step of encapsulating a display medium between the counter substrate and a driving voltage is applied to the picture element electrode from the scanning line and the signal line through the switching element, thereby causing a picture element defect. And a step of detecting light energy in the overlapping portion of the gate electrode and the source electrode of the switching element connected to the defective pixel electrode in which the pixel defect is generated and the overlapping portion of the gate electrode and the drain electrode. Irradiate to electrically connect the defective pixel electrode and the signal line through the gate electrode, and irradiate the scanning branch line of the switching element connected to the defective pixel electrode with light energy to perform the scanning. Separating the branch line from the scan line, whereby the above object is achieved.

(Operation) In the method for manufacturing an active matrix display device of the present invention, a pixel defect due to an ON defect or an OFF defect such as a switching element defect or a weak leak current between a signal line and a pixel electrode is generated. When detected, the pixel defect is corrected with the display device assembled. First, the scanning branch line connected to the picture element electrode having the picture element defect is cut by laser light irradiation or the like. In the method for manufacturing a display device of the present invention, the distance from the side of the switching element on the scanning line side to the scanning line is set to a size capable of irradiating light energy such as laser light to cut the scanning branch line. Because
The scanning branch line can be reliably cut. Next, the electrode connected to the pixel electrode of the switching element and the electrode connected to the signal line are electrically connected by light energy irradiation. As a result, the defective pixel electrode is directly connected to the signal line.

When the switching element is a TFT, this electrical connection is performed by irradiating light energy to the overlapping portion of the source electrode and the gate electrode and the overlapping portion of the drain electrode and the gate electrode, respectively. By irradiating laser light as light energy, holes are formed in spots in these overlapping portions. Around the hole, the source electrode and the gate electrode are electrically connected, and the drain electrode and the gate electrode are electrically connected. In this way, the source electrode and the drain electrode are electrically connected via the gate electrode.

Thus, in the present invention, by using the TFT itself as a pixel short-circuit portion, a TFT for defect correction is provided separately from this TFT as in the conventional case, or the signal line and the pixel electrode are formed of a metal layer. By providing the pixel short-circuit portion that is directly connected, there is no reduction in the aperture ratio for defect correction.

The voltage applied to the picture element electrode (hereinafter referred to as "corrected picture element electrode") connected to the signal line as described above will be described with reference to FIG. In Figure 6,
Gn is the signal voltage of the nth scanning line (vertical axis) and time (horizontal axis)
And Sm represents the relationship between the signal voltage (vertical axis) of the m-th signal line and time (horizontal axis). Pnm represents a voltage applied to a normal pixel electrode connected to the nth scanning line and the mth signal line. P'nm represents the voltage applied to the modified pixel electrode connected to the nth scan line and the mth signal line.

A signal (Vgh) for sequentially selecting switching elements is output to the scanning line for a selection time Ton as shown by Gn and Gn _{+ 1} . The video signal voltage V ₀ is output to the signal line corresponding to the selection time Ton of the scanning line, and this signal voltage V ₀ is held for the non-selection time Toff as indicated by Pnm in the normal pixel electrode. It Then, when the selection signal voltage Vgh is applied next, the video signal of −V ₀ is applied to the signal line.

On the other hand, in the modified pixel electrode, as shown by P'nm,
Since the video signal from the signal line is always applied, the modified pixel electrode cannot function normally. However, the picture element displayed by this modified picture element electrode performs a display corresponding to the effective value of the video signal applied to the signal line during this one cycle when viewed through one cycle. Therefore, this picture element does not become a complete bright spot or a black spot, and the average brightness is displayed along the picture lined up along the signal line. Therefore, this picture area is a picture element defect that is extremely difficult to distinguish.

It is necessary that the electric resistance in the portion connected by the light energy irradiation as described above is smaller than the resistance of the switching element in the selected state (hereinafter referred to as “on resistance”). The reason is as follows.
The value of the on-resistance of the switching element is set so that a current enough to charge the pixel electrode flows during the time when the switching element is selected. Therefore, if the resistance in the portion where the above connection is made is larger than the on-resistance, the signal voltage that changes every selection time of the switching element is not surely written in the modified pixel electrode and is applied to the modified pixel electrode. The effective value of voltage becomes small. In such a state, the difference in brightness between the pixel displayed by the modified pixel and the other normal pixel becomes large,
It will be visually recognized as a pixel defect.

(Example) The Example of this invention is described below.

FIG. 1 is a plan view of an active matrix substrate according to the method of manufacturing an active matrix type display device of the present invention. FIG. 3 is a sectional view taken along line III-III in FIG. 1 of a display device using the substrate of FIG. The manufacturing process of the active matrix type display device of the present embodiment will be described. In this example, a transparent glass substrate was used as the insulating substrate. A gate bus wire 21 functioning as a scanning line and a gate bus branch line 22 branching from the gate bus wire 21 were formed on the glass substrate 1. The gate bus wiring 21 and the gate bus branch line 22 are generally formed of a single layer of Ta, Ti, Al, Cr or the like or a multilayer metal thereof, but Ta is used in this embodiment. The gate bus wiring 21 and the gate bus branch line 22 are formed by patterning a Ta metal layer formed by a sputtering method. Before forming the gate bus wiring 21 and the gate bus branch line 22, Ta ₂ O ₅ is formed on the glass substrate 1.
You may form the base coat film which consists of etc. The gate bus branch line 22 will be described later.

SiN on the gate bus wiring 21 and the gate bus branch line 22.
_A base insulating film 11 made of _x was formed on the entire surface. The gate insulating film 11 is formed with a thickness of 3000 Å by the plasma CVD method.

Next, a TFT 31 functioning as a switching element was formed at the end of the gate bus branch line 22. Gate bus branch line 22
A part of this functions as the gate electrode 25 of the TFT 31. After forming the gate insulating film 11 as described above, the channel layer 12 is formed later.
Then, an amorphous silicon (a-Si) layer to be an SiN _x layer to be an etching stopper layer 13 was deposited. a-Si
The layer thickness is 300Å and the SiN _x layer thickness is 2000Å. Next, the SiN _x layer was patterned to form the etching stopper layer 13. Furthermore, the contact layers 1 and 14 will be formed on the entire surface of the a-Si layer and the etching stopper layer 13 later, P
An n ⁺ -type a-Si layer containing (phosphorus) was deposited to a thickness of 800 Å by the plasma CVD method. Next, the a-Si layer and n ⁺
The patterning of the mold a-Si layer was performed simultaneously to form the channel layer 12 and the contact layers 14 and 14.

Next, a source electrode 32, a source bus line 23 functioning as a signal line later, and a Ti metal layer to be the drain electrode 33 were formed. The source bus wiring 23 and the like are generally Ti, Al,
It is formed of a single layer of Mo, Cr, etc., or a multilayer metal of these,
Ti is used in this embodiment. The Ti metal layer was formed by the sputtering method. By patterning this Ti metal layer, the source electrode 32, the source bus line 23, and the drain electrode 33 were formed. The source bus line 23 and the gate bus line 21 cross each other with the gate insulating film 11 interposed therebetween.

Next, as shown in FIG. 1, ITO (Indium) is formed in a rectangular area surrounded by the gate bus wiring 21 and the source bus wiring 23.
A pixel electrode 41 made of tin oxide) was formed. Picture element electrode 4
1 is superimposed on the end of the drain electrode 33 of the TFT 31 and is electrically connected to the drain electrode 33.

Further, a protective film 17 made of SiN _x was deposited on the entire surface of the substrate on which the TFT 31 and the pixel electrode 41 were formed. The protective film 17 is
A window shape removed on the central portion of the pixel electrode 41 may be used. An alignment film 19 was formed on the protective film 17. The counter electrode 3 and the alignment film 9 were formed on the glass substrate 2 facing the glass substrate 1. A liquid crystal layer 18 is enclosed between the substrates 1 and 2.

The configuration near the TFT 31 will be described. An enlarged view around TFT31 is shown in Fig. 2. As described above, the TFT 31 is formed on the gate bus branch line 22 branched from the gate bus line 21. The drain electrode 33 of the TFT 31 is electrically connected to the pixel electrode 41, and the source electrode 32 is electrically connected to the source bus line 23. The distance X from the side of the gate bus wiring 21 side of the TFT 31 to the gate bus wiring 21 is larger than that of the conventional example of FIG. 12 described above, and the gate bus branch line 22 is cut by using light energy such as laser light. It is a size that can be done. It was confirmed that if the distance X is 10 μm or more, the cutting can be reliably performed. If the distance X is small, not only is it impossible to cut the gate bus branch line 22 without damaging the TFT 31, but also the irradiated laser light adversely affects the intersection between the gate bus line 21 and the source bus line 23. This may cause an insulation failure between the bus lines 21 and 23.

After enclosing the liquid crystal layer 18 between the substrates 1 and 2 as described above, the gate bus wiring 21 and the swords bus wiring 23 to the TFT 31
A drive voltage was applied to all the picture element electrodes 41 via the to detect picture element defects. TFT31 becomes defective, source bus wiring 23
When a weak leak current is generated between the pixel electrode 41 and the pixel electrode 41, a pixel defect occurs. After confirming the occurrence position of the generated picture element defect, the correction is performed as follows. First,
The gate bus branch line 22 was cut by irradiating the area 51 shown by the broken line in FIG. 2 with light energy. This allows
The gate bus branch line 22 is electrically insulated from the gate bus wiring 21. In this example, YAG laser light (wavelength 1064 nm) was used as the light energy. As described above, the distance X is set to be sufficiently large, so that the gate bus branch line 22 is reliably cut. The laser light may be emitted from either the substrate 1 or the substrate 2, but the substrate 2 is often provided with a light-shielding film, and in that case, the laser light was emitted from the substrate 1 side. Also in this example, irradiation was performed from the substrate 1 side. Next, areas 52 and 53 indicated by broken lines in FIG. 2, that is, arrows 26 and 53 in FIG.
The portion indicated by 27 was irradiated with laser light. This allows the area
In 52, the source electrode 32 and the gate electrode 25 are electrically connected, and in the region 53, the drain electrode 33 and the gate electrode 25 are electrically connected. Therefore, the source electrode 32 and the drain electrode
It is electrically connected to 33 through the gate electrode 25.

Since the signal of the source bus line 23 is always applied to the picture element electrode 41 (correction picture element electrode) connected to the TFT 31 modified as described above, the correction picture element electrode normally functions. I can't. However, since the picture element displayed by the modified picture element electrode performs display corresponding to the effective value of the signal applied to the source bus line 23, this picture element does not become a complete bright spot or a black spot, The average brightness of the picture elements arranged along the source bus wiring 23 is displayed. Therefore, this picture element becomes a picture element defect that is extremely difficult to distinguish.

Even if laser light irradiation is performed as described above, since the protective film 17 is formed on the gate bus branch line 22 and the TFT 31,
The molten metal or the like does not enter the liquid crystal layer 18 which is a display medium, and does not affect the display. It has also been confirmed that it is possible to perform fusion connection between metal layers and cutting of metal layers by using the same laser light by changing the irradiation conditions of laser light.

The structure of the present invention can be applied to an active matrix type display device having an additional capacitor 42 as shown in FIG. The display device of FIG. 4 is obtained by adding the additional capacitor 42 to the embodiment shown in FIGS. Additional capacity 42
Is an overlapping portion (hatched portion) of the additional capacitance electrode 24 provided in parallel with the gate bus wiring 21 on the substrate 1 and the pixel electrode 41.
Is formed. In the display device shown in FIG. 4, the picture element defect can be corrected in the same manner as the embodiment shown in FIGS.

Further, the present invention can be applied to the active matrix type display device having the configuration of FIG. This display device eliminates the drawback of the display device of FIG. 4 in that the area of the picture element is reduced due to the portion occupied by the additional capacitance 42. In this display device, the width of the gate bus line 21 is widened and overlapped with a part of the pixel electrode 41. In this configuration, the adjacent non-selected gate bus line 21 can be used as the additional capacitance electrode. Moreover, since there is no gap between the gate bus line 21 and the additional capacitance electrode 24 as shown in FIG. 4, it is possible to suppress the reduction of the area of the picture element. Also in this display device, the picture element defect is corrected as in the embodiment shown in FIGS.

In the above-mentioned embodiment, the example in which the source electrode and the drain electrode are formed above the gate electrode of the TFT 31 is shown, but a TFT of the type in which the gate electrode is formed above and the source electrode and the drain electrode are formed below is shown. It can also be used.

Further, in the above embodiment, the TFT is used as the switching element.
Was used, but by irradiation with light energy such as laser light,
Any switching element capable of electrically connecting the signal line side electrode and the pixel electrode side electrode can be used in the present invention.

(Effect of the Invention) According to the method for manufacturing an active matrix display device of the present invention, a display device in which a pixel defect is corrected so as not to be noticeable in a state of the display device in which the pixel defect can be easily detected. In addition, since the TFT itself is used as a pixel short-circuit portion, it is possible to eliminate the reduction of the aperture ratio due to the provision of a defect correction member separately from the TFT as in the conventional case. Therefore, according to the present invention, a display device can be produced with a high yield, which can contribute to a reduction in the cost of the display device.

[Brief description of drawings]

FIG. 1 is a plan view of an active matrix substrate according to the method for manufacturing a display device of the present invention, FIG. 2 is an enlarged plan view of the vicinity of the TFT of FIG. 1, and FIG. 3 is a display device using the substrate of FIG. A sectional view taken along the line III-III in FIG. 1, FIGS. 4 and 5 are plan views of an active matrix substrate having an additional capacitance according to the manufacturing method of the present invention, and FIG. 6 is a scanning line and a signal. FIG. 7 is a plan view of an active matrix substrate used in a conventional active matrix type display device, showing the relationship between the signal applied to the line and the voltage of the pixel electrode. 1,2 …… Glass substrate, 3 …… Counter electrode, 9,19 …… Alignment film, 11 …… Gate insulating film, 12 …… Channel layer, 13 …… Etching stopper layer, 14 …… Contact layer, 18 ... liquid crystal layer, 21 ... gate bus wiring, 22 ... gate bus branch line,
23 …… Source bus wiring, 24 …… Additional capacitance electrode, 25 ……
Gate electrode, 31 ... TFT, 32 ... source electrode, 33 ... drain electrode, 41 ... pixel electrode, 42 ... additional capacitance.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroaki Kato 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Kozo Yano 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Co., Ltd. (72) Inventor Toshiaki Fujiwara 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Co., Ltd. (56) Reference JP-A-2-124538 (JP, A) JP-A-59-101693 (JP) , A) JP-A-188832 (JP, A)

Claims (1)

[Claims] 1. An insulating substrate, a scanning line and a signal line wired vertically and horizontally on the substrate, a scanning branch line branched from the scanning line, and a switching formed by using a tip portion of the scanning branch line as a gate electrode. An element and a pixel electrode connected to the switching element, and a distance from the side of the switching element on the scanning line side to the scanning line irradiates light energy to form the scanning branch line. A step of forming an active matrix substrate having a size that can be cut, a step of bonding the active matrix substrate and a counter substrate, and enclosing a display medium between the active matrix substrate and the counter substrate, A step of applying a driving voltage from the scanning line and the signal line to the picture element electrode through the switching element to detect a picture element defect; and a step of connecting to the defective picture element electrode in which the picture element defect has occurred. The switching element is electrically connected to the defective pixel electrode and the signal line by irradiating the overlapping portion of the gate electrode and the source electrode and the overlapping portion of the gate electrode and the drain electrode with light energy. And irradiating the scanning branch line of the switching element connected to the defective pixel electrode with light energy to separate the scanning branch line from the scanning line, and a method for manufacturing an active matrix display device. .