JP2002221735A - Active matrix board, liquid crystal display and method for manufacturing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a liquid crystal display which uses aligmnent marks and does not cause misalignment. SOLUTION: An active matrix board has: a plurality of pixel electrodes disposed as a matrix; a plurality of switching elements; scanning signal supplying lines connected to gate electrodes; and image signal supplying lines connected to source electrodes. A plurality of the switching elements are provided corresponding to a plurality of the pixel electrodes. Each switching element is connected to the gate electrode for controlling an application of a voltage to corresponding pixel electrode, the source electrode that a voltage representing the image signal is applied and the pixel electrode, and has a drain electrode for applying a voltage to the pixel electrode. In the active matrix board, the first alignment mark is provided in a position nearer to the pixel electrode than an end of the scanning signal supplying line, and the second alignment mark is provided in a position nearer to the pixel electrode than an end of the image signal supplying line so as to align positions of the gate and drain electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display, and more particularly to an active matrix type liquid crystal display.

[0002]

2. Description of the Related Art A display device to which liquid crystal is applied has characteristics that are not seen in conventional display devices, such as low power driving and light weight. In particular, an active matrix type liquid crystal display device in which a thin film transistor (hereinafter, referred to as a “TFT”) is disposed as a switching element in each pixel can provide a clear image display with less crosstalk, so that a notebook computer or a car navigation system can be obtained. It is used for displays and the like. In recent years, it has been rapidly used as a large display monitor.

FIG. 1 shows an active matrix substrate 100.
FIG. FIG. 2 is a cross-sectional view of the active matrix substrate 100 along the line AA ′ in FIG. FIG.
The manufacturing process of the active matrix substrate 100 shown in (1) mainly includes (A) a scanning signal supply line 2 (TF
Forming a T gate electrode by etching, (b)
A step of depositing a gate insulating film 3 of the TFT;
Forming the channel portion 4 by etching, (d)
A step of forming the video signal supply line 5 (source electrode of the TFT) and the drain electrode 9 by etching; (e) a step of depositing a passivation insulating film 6 as a protective film;
(F) removing the insulating film 6 and forming the opening 7;
(G) a step of forming the pixel electrode 10 by etching so as to be electrically connected to the drain electrode 9 of the TFT.

A photolithography process is repeatedly performed for patterning each layer. At this time, the alignment (positioning) between the scanning signal supply line 2 and the drain electrode 9 is
In general, patterns are superimposed using an alignment mark and a mask for processing a design pattern in the next step. In recent years, as monitor displays have been increasing in size, improving the overlay accuracy of the scanning signal supply line 2 and the drain electrode 9 has been particularly effective in reducing defects such as luminance unevenness and flicker and improving image uniformity. Connect.

FIG. 6 shows alignment marks 12 and 13. The alignment marks 12 and 13 are
It is provided outside the mounting terminal 14 of the scanning signal supply line 2 and the mounting terminal 15 of the video signal supply line 5 (at a position farther from the pixel array). The alignment mark 12
The alignment mark 13 is provided on the same layer as the scanning signal supply line 2 (gate electrode) and the same layer as the video signal supply line 5 (source electrode) and the drain electrode 9.

[0006]

Even if the scanning signal supply line 2 and the drain electrode 9 are aligned using the alignment marks 12 and 13, a deviation may occur. This is because alignment marks 12 and 13
Is located away from the actual pixel area,
This is because the influence of exposure distortion (distortion) of an exposure apparatus (not shown) increases in the photolithography process. As a result, the overlapping area between the scanning signal supply line 2 and the drain electrode 9 that determines the parasitic capacitance of the pixel is made non-uniform, causing image defects such as flicker and luminance unevenness.

An object of the present invention is to manufacture a liquid crystal display device that does not cause misalignment by using alignment marks.

[0008]

An active matrix substrate according to the present invention comprises a plurality of pixel electrodes arranged in a matrix,
A plurality of switching elements provided corresponding to each pixel electrode, wherein each of the plurality of switching elements controls a voltage applied to a corresponding pixel electrode;
A source electrode to which a voltage representing a video signal is applied, and
A switching element connected to a pixel electrode and having a drain electrode for applying the voltage to the pixel electrode; a scanning signal supply line connected to each gate electrode; and a video signal supply line connected to each source electrode. A first alignment mark is provided at a position closer to a pixel electrode than an end of a scanning signal supply line for alignment of the gate electrode and the drain electrode. An active matrix substrate in which a second alignment mark is provided at a position closer to a pixel electrode than a portion, thereby achieving the above object.

The first alignment mark is two rectangular patterns arranged in parallel with each other, and the second alignment mark is a single rectangular pattern, and the two alignment marks are two rectangular patterns of the first alignment mark. It may be arranged in parallel with the rectangular pattern and between the two rectangular patterns.

A liquid crystal display device according to the present invention is characterized in that the active matrix substrate, a counter electrode facing the active matrix substrate, a liquid crystal layer injected into the active matrix substrate and the counter electrode, and an end of each scanning signal supply line. A first drive circuit connected to apply a voltage to the scan signal supply line, and a second drive circuit connected to an end of each video signal supply line and applying a voltage to the video signal supply line.
A liquid crystal display device, which achieves the above object.

In the method for manufacturing an active matrix substrate according to the present invention, a step of providing a substrate, a plurality of gate electrodes, a plurality of scanning signal supply lines connected to the gate electrodes, and a first electrode are provided on the provided substrate. Providing an alignment mark, an insulating film on the gate electrode,
Forming a semiconductor film; providing a source electrode, a drain electrode, a video signal supply line connected to the source electrode, and a second alignment mark so as to be connected to the semiconductor film; Providing a pixel electrode so as to be connected to an electrode, wherein the first alignment mark and the second alignment mark are aligned with the gate electrode and the drain electrode. A method for manufacturing an active matrix substrate provided at a position closer to a pixel electrode than an end of the scanning signal supply line and an end of the video signal supply line. Can be achieved.

The step of providing a first alignment mark is a step of arranging two rectangular patterns in parallel with each other, and the step of providing the second alignment mark is a step of providing the two rectangular patterns in the first alignment mark. The step may be a step of arranging in parallel with the pattern and positioned between the two rectangular patterns.

The method for manufacturing a liquid crystal display device according to the present invention comprises:
Manufacturing an active matrix substrate by the above manufacturing method, forming a counter electrode facing the active matrix substrate, injecting liquid crystal between the active matrix substrate and the counter electrode, and applying a voltage to the scanning signal supply line. Connecting a first drive circuit for applying a voltage to an end of each scanning signal supply line, and connecting a second drive circuit for applying a voltage to the video signal supply line to an end of each video signal supply line And a method of manufacturing a liquid crystal display device, which achieves the above object.

The operation will be described below.

In the present invention, the alignment mark is arranged at a position closer to the pixel electrode than the scanning signal supply line and the video signal supply line, and the scanning signal supply line and the drain electrode are aligned to manufacture an active matrix substrate. Therefore, when lithography is performed using the exposure apparatus after the alignment, the lithography is not affected by the distortion of the exposure apparatus. Since no misalignment occurs, the parasitic capacitance between the scanning signal supply line 2 and the drain electrode is formed uniformly. According to the liquid crystal display device manufactured using such an active matrix substrate 100,
It is possible to reduce defects such as flicker and luminance unevenness and improve the uniformity of an image.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a top view of an active matrix substrate 100 of a liquid crystal display device. The active matrix substrate 100 is a substrate using a thin film transistor (hereinafter, referred to as a “TFT”) as a switching element, and is a main element responsible for an image display operation of a liquid crystal display device. In order to obtain a display panel of a liquid crystal display device, at least another counter substrate (not shown) having a transparent counter electrode and a liquid crystal layer (not shown) sandwiched therebetween are required.

In the following, the active matrix substrate 10
0 will be described. The structure and manufacturing process of the active matrix substrate will be described later with reference to FIG.
First, the active matrix substrate 100 includes a plurality of switching elements and a plurality of corresponding pixel electrodes 10 and common electrodes 8. These are arranged in a matrix.

As switching elements, a gate electrode connected to the scanning signal supply line 2, a source electrode connected to the video signal supply line 5, a drain electrode 9, and a channel between the video signal supply line 5 and the drain electrode 9 Section 4 is included. In FIG. 1, the scanning signal supply line 2 and the gate electrode, and the video signal supply line 5 and the source electrode are formed integrally. Therefore, the scanning signal supply line 2 functions as a gate electrode of the TFT, and the video signal supply line 5 functions as a source electrode of the TFT. The voltage applied to the video signal supply line 5 is also applied to the drain electrode 9 via the channel section 4. The drain electrode 9 is a transparent pixel electrode 10 provided corresponding to the switching element through the opening 7.
Electrically connected to A common electrode 8 is provided below the pixel electrode 10 with an insulating film interposed therebetween. Common electrode 8
Is a pixel electrode 10 at a portion facing the pixel electrode 10.
A storage capacity (holding capacity) is formed between the two. Common electrode 8
Are provided, but are electrically connected to each other via the connection portion 11. As will be described later with reference to FIGS. 3 and 4, the end of the scanning signal supply line 2 is connected to a scanning signal supply line driving circuit via a mounting terminal. A scanning signal (voltage) is applied. The end of the video signal supply line 5 is connected to a video signal supply line drive circuit via a mounting terminal, and a video signal (voltage) is applied from the drive circuit when the pixel is turned on.

Subsequently, the active matrix substrate 100
The operation principle of will be described. As an example, an operation of turning on a pixel formed by a pixel electrode 10 given a reference numeral among a plurality of pixels shown in FIG. 1 will be described. First, when a scanning signal (voltage) is applied to the scanning signal supply line 2 to which the reference numeral is attached, the amorphous silicon semiconductor film 4 of the TFT has a T
An FT channel is formed. One scanning signal supply line 2 also serves as a gate electrode of a plurality of TFTs, and a desired TFT among them is specified by the video signal supply line 5. That is, the source electrode 5 also denoted by the same reference
Is applied with a video signal (voltage).

A video signal (voltage) from the video signal supply line 5
Is applied to the pixel electrode 10 through the channel portion 4, the drain electrode 9, and the opening 7. An electric field is generated by the potential difference between the voltage of the pixel electrode 10 and the voltage supplied to the counter electrode (not shown), and the liquid crystal layer sandwiched between the pixel electrode 10 and the counter electrode (not shown) is excited. You. And
The orientation of liquid crystal molecules contained in the liquid crystal layer is arbitrarily changed.
Thereby, the orientation of the liquid crystal injected between the pixel electrode 10 and the counter electrode can be arbitrarily changed, and the light transmittance can be adjusted. In the case of performing color display, a color filter may be provided for each pixel, and for example, one point may be displayed with three pixels. The display signal written to the pixel electrode (capacitance) is accumulated by the storage capacitor formed between the pixel electrode 10 and the common electrode 8 until the next frame scan, and the potential is maintained. In this manner, for each of the plurality of pixels, the lighting brightness and the like are controlled, and a desired image can be created on the active matrix substrate 100. The operation principle of the active matrix substrate 100 has been described above.

FIG. 2 is a sectional view of the active matrix substrate 100 taken along the line AA ′ of FIG. Next, a manufacturing process of the active matrix substrate 100 will be described with reference to FIG. A liquid crystal display (liquid crystal display panel) is further formed using the manufactured active matrix substrate 100.
In order to manufacture the active matrix substrate 2, a counter substrate having a counter electrode is prepared by a method known to those skilled in the art.
Liquid crystal may be injected between the counter substrate and the counter substrate.

The active matrix substrate 20 shown in FIG.
The manufacturing process 0 mainly includes the following steps (a) to (g).

(A) Glass substrate 1 which is an insulating transparent substrate
The scanning signal supply line 2 and the common electrode 8 (FIG. 1) are formed thereon by etching. Specifically, thin film deposition is performed by a sputtering film forming method, and patterning of the scanning signal supply line 2 and the counter electrode 8 is performed in a photolithography process and an etching process. The scanning signal supply line 2 thus obtained functions as a gate electrode of the TFT. On the other hand, the common electrode 8 (FIG. 1) is an electrode serving as a storage capacitor lower electrode, and forms a storage capacitor via a pixel electrode 10 to be formed later and an insulating film. The connecting portion 11 provided at the same time as the common electrode 8 is provided to supply power to the common electrode 8 from both sides.

(B) An insulating film is deposited to form a gate insulating film 3 of the TFT.

(C) An amorphous silicon semiconductor film is deposited on the gate insulating film 3. This amorphous silicon semiconductor film becomes the channel portion 4 of the TFT.

(D) Further, a video signal supply line 5 as a source electrode of the TFT and a drain electrode 9 are formed by etching.

(E) A passivation insulating film 6 is deposited as a protective film covering the TFT. The insulating film 6 is, for example, SiNx, SiO2, acrylic resin, polyimide, polyamide, polycarbonate, or a laminated film thereof.

(F) The insulating film 6 is removed, and an opening 7 is formed. The opening 7 allows the drain electrode 9 and the pixel electrode 10 to be electrically connected. The opening 7 is also called a contact hole.

(G) The pixel electrode 10 is formed by etching so as to be electrically connected to the drain electrode 9 of the TFT. Thereby, the passivation insulating film 6 exists between the pixel electrode 10 and the common electrode 8 (FIG. 1). The passivation insulating film 6 functions as a dielectric when holding the storage capacitor.

Each time a film is deposited at a desired position and shape as shown in FIG. 2 and an electrode or the like is etched, it is necessary to perform photolithography each time. In the above-described steps, only the step (a) is specifically shown, but other steps, for example, (c) and (d) are also required. Photolithography is a technique in which a desired resist pattern is obtained by applying a photoresist and irradiating ultraviolet rays through a photomask having a predetermined shape at a predetermined position. By depositing or etching a film on the resist pattern and then removing the resist pattern, the film can be deposited at a desired position and shape, and the electrodes and the like can be etched.

Next, main features of the present invention will be described with reference to the above step (d). The problem in the above step (d) is that the drain electrode 9 when forming the drain electrode 9 and the scanning signal supply line 2 already obtained on the substrate 1 in the step (a) are problematic. Alignment. In this alignment, an alignment mark provided in each layer of a film is generally superimposed on a mask for processing a design pattern in the next step.

In the present invention, the alignment is performed using the alignment marks provided outside the image area. However, what is greatly different from the related art is the position where the alignment marks are provided. FIG. 3 is a top view showing an arrangement position of the alignment marks 12 and 13 according to the present invention. The alignment marks 12 and 13 are arranged inside the mounting terminals 14 and 15 of the scanning signal supply line 2 and the video signal supply line 5, that is, at positions closer to the pixel electrodes 10 (FIG. 1). More specifically, the alignment marks 12 and 13 are formed by an arrangement of a plurality of mounting terminals 14 corresponding to each of the plurality of scanning signal supply lines 2 and a plurality of mounting terminals 14 corresponding to each of the plurality of video signal supply lines 5. It is provided inside a rectangle having 15 sides as two sides and outside the pixel region. The “pixel region” refers to a region that contributes to display, in which pixel electrodes 10 (FIG. 1) and TFTs formed in a later process are arranged in a matrix on a substrate.

The alignment marks 12 are two rectangular patterns of the same size and arranged in parallel with each other in the same layer as the plurality of scanning signal supply lines 2. On the other hand, the alignment mark 13 is a rectangular pattern arranged in the same layer as the plurality of video signal supply lines 5 in parallel with the rectangular pattern 12 and at the center (between them). The three sets of alignment marks formed by the alignment marks 12 and 13 are provided in two sets at right angles to each other in order to enhance alignment accuracy.
Further, in order to further enhance the alignment accuracy, an alignment mark can be provided in another area (for example, the lower left) outside the pixel area.

In other words, a portion outside the pixel area within a rectangle having the mounting terminals of the plurality of scanning signal supply lines 2 and the mounting terminals of the plurality of video signal supply lines 5 as two sides,
Two rectangular patterns (first alignment marks) of the same size and of the same layer and arranged in parallel with each other are provided. In addition, a rectangular pattern (second alignment mark) formed of the same layer as the plurality of video signal supply lines 5 is provided separately. The first alignment mark and the second alignment mark are arranged in parallel with each other, and such that the second alignment mark is arranged between the first alignment marks. As a set of these three rectangles, to improve accuracy,
Two or more sets are arranged so as to be perpendicular to each other. Using these patterns, the gate electrode layer and the source and drain electrode layers are aligned in a photolithography process using an exposure apparatus. The alignment mark is not limited to a rectangular pattern, and may have another shape.

As described above, the mounting terminal 14 located at a position closer to the pixel, specifically, the end of the scanning signal supply line 2 and the mounting terminal 15 located at the end of the video signal supply line 5 Since alignment of photolithography is performed by providing an alignment mark near the position, the influence of exposure distortion (distortion) of an exposure apparatus (not shown) can be greatly reduced. As a result, highly accurate alignment can be achieved, and therefore, a high image quality free from defects such as uniformity of the parasitic capacitance of the pixel electrode, flicker and uneven brightness can be realized. As an example, in a 15-inch SXGA large-screen high-definition monitor, an alignment deviation range of 1.0 μm or less has been achieved. As a result, it is possible to cope with further miniaturization of the element.

Next, a specific configuration of the liquid crystal display device will be described. FIG. 4 is a top view of the liquid crystal display device 400. The liquid crystal display device 400 includes a liquid crystal display panel 40, a scanning signal supply line drive circuit 42, and a video signal supply line drive circuit 44. The liquid crystal display panel 40 performs the steps (a) to (d) above.
(G) Active matrix substrate 100 obtained
(FIGS. 1-3) and a counter substrate (not shown) having a transparent counter electrode and bonded to face the substrate 100
And a liquid crystal layer (not shown) sandwiched therebetween. Here, the pixel electrode 10, the liquid crystal layer, and the corresponding counter electrode function as pixels representing one dot (dot) at the time of display. When the liquid crystal display panel 40 can perform color display, a filter of three primary colors (red, green, and blue) is provided for each set of three pixels. One point (dot) is represented by these three pixels. Therefore, in this case, three pixels function as one pixel.

The scanning signal supply line driving circuit 42 is a circuit for turning on or off each of the scanning signal supply lines 2 extending in the row direction. The video signal supply line drive circuit 44 is a circuit that turns on or off each of the video signal supply lines 5 extending in the column direction. The drive signals of the scanning signal supply line drive circuit 42 and the video signal supply line drive circuit 44 are supplied to the mounting terminals 14 and 15.
(FIG. 3), only the pixels that need to be turned on and the pixels that need to be turned off can be selectively turned on and off.

FIG. 5 shows a liquid crystal display 500 to which the liquid crystal display device 400 is applied. Liquid crystal display 500
Is connected to a computer, for example, and can display a video signal from the computer. Liquid crystal display 500
Is composed of a liquid crystal display device 400, an arithmetic processing unit (not shown), and a frame 50. The arithmetic processing unit (not shown) receives, for example, a digital or analog video signal from a computer, and calculates which pixel is to be lit at what intensity to display a video. Then, the scanning signal supply line drive circuit 42 and the video signal supply line drive circuit 44 are operated based on the calculation result. The frame 50 includes a power switch, a brightness adjustment button, and the like. The object to which the liquid crystal display device 400 is applied is not limited to the liquid crystal display 500, but may be any image display device for displaying an image. For example, a display unit of a smaller mobile phone.

[0040]

As described above, according to the present invention, the alignment marks are formed by the scanning signal supply line 2 and the video signal supply line 5.
Are arranged inside the mounting terminals 14 and 15, that is, closer to the pixels, and the drain electrode and the scanning signal supply line 2 are aligned by photolithography. As a result, the misalignment between the drain electrode and the scanning signal supply line 2 is greatly reduced, so that the parasitic capacitance is formed uniformly, and image quality free from defects such as flicker and uneven brightness can be obtained. Actually, 15 inches S
An XGA large-screen high-definition monitor has achieved an alignment shift range of 1.0 μm or less. As a result, it is possible to cope with further miniaturization of the element.

[Brief description of the drawings]

FIG. 1 is a top view of an active matrix substrate of a liquid crystal display device.

FIG. 2 is a cross-sectional view of the active matrix substrate taken along line AA ′ of FIG.

FIG. 3 is a top view showing an arrangement position of an alignment mark according to the present invention.

FIG. 4 is a top view of the liquid crystal display device.

FIG. 5 is a diagram showing a liquid crystal display to which a liquid crystal display device is applied.

FIG. 6 is a diagram showing an alignment mark.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Scan signal supply line 3 Gate insulating film 4 Channel part 5 Video signal supply line 6 Passivation insulating film 7 Contact hole 8 Common electrode 9 Drain electrode 10 Pixel electrode 11 Connection part 12 Alignment mark (gate layer) 13 Alignment mark ( (Source layer and drain layer) 14 Scan signal supply line mounting terminal 15 Video signal supply line mounting terminal

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01L 21/336 H01L 29/78 627C F-term (Reference) 2H088 FA16 FA19 HA02 HA08 MA03 MA04 2H090 JC02 LA01 LA04 2H092 GA31 GA33 GA38 JA24 JA27 JA38 JA42 MA13 NA01 NA23 NA24 NA29 PA06 5C094 AA02 AA05 BA03 BA43 CA19 DA14 DA15 EA04 EA07 EA10 EB02 GB01 5F110 AA04 AA28 BB01 CC07 DD02 EE44 GG02 GG15 HL07 NN03 NN05 NN23 NN27 NN27 QNN15

Claims (6)

[Claims] A plurality of pixel electrodes arranged in a matrix and a plurality of switching elements provided corresponding to each pixel electrode, wherein each of the plurality of switching elements is connected to a corresponding pixel electrode. A gate electrode for controlling the application of voltage,
A source electrode to which a voltage representing a video signal is applied, and
A switching element connected to a pixel electrode and having a drain electrode for applying the voltage to the pixel electrode; a scanning signal supply line connected to each gate electrode; and a video signal supply line connected to each source electrode. An active matrix substrate, wherein a first alignment mark is provided at a position closer to a pixel electrode than an end of a scanning signal supply line for alignment of the gate electrode and the drain electrode; An active matrix substrate provided with a second alignment mark at a position closer to a pixel electrode than a portion. 2. The method according to claim 1, wherein the first alignment marks are two rectangular patterns arranged in parallel with each other.
2. The method of claim 1, wherein the second alignment mark is a single rectangular pattern, and is disposed parallel to and between the two rectangular patterns of the first alignment mark. 3. An active matrix substrate as described in the above. 3. The active matrix substrate according to claim 1, a counter electrode facing the active matrix substrate, a liquid crystal layer injected into the active matrix substrate and the counter electrode, and connected to an end of each scanning signal supply line. And a first drive circuit for applying a voltage to the scanning signal supply line, and a second drive circuit connected to an end of each video signal supply line and applying a voltage to the video signal supply line. Display device. Providing a substrate; providing a plurality of gate electrodes, a plurality of scan signal supply lines connected to the gate electrodes, and a first alignment mark on the provided substrate; Forming an insulating film and a semiconductor film on the electrode; a source electrode, a drain electrode, a video signal supply line connected to the source electrode, and a second alignment mark so as to be connected to the semiconductor film. And a step of providing a pixel electrode so as to be connected to the drain electrode, wherein the first alignment mark and the second alignment mark are formed by using the gate electrode And a mark for alignment of the drain electrode, the end of the scanning signal supply line, Beauty, is provided at a position close to the pixel electrode from the end of the video signal supply lines, a method of manufacturing the active matrix substrate. 5. The step of providing a first alignment mark is a step of arranging two rectangular patterns in parallel with each other, and the step of providing the second alignment mark is the step of providing the second alignment mark. The active matrix substrate according to claim 4, wherein the active matrix substrate is a step of arranging the two rectangular patterns in parallel with each other and between the two rectangular patterns. 6. A step of manufacturing an active matrix substrate by the manufacturing method according to claim 4, a step of forming a counter electrode facing the active matrix substrate, and injecting liquid crystal between the active matrix substrate and the counter electrode. And a step of connecting a first drive circuit for applying a voltage to the scan signal supply line to an end of each scan signal supply line, and a second drive circuit for applying a voltage to the video signal supply line. Connecting to the end of each video signal supply line.
A method for manufacturing a liquid crystal display device.