JP2008225514A - Liquid crystal display device and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device and a method for manufacturing the same, in which the capacitance of an auxiliary capacitor electrode is increased without reducing the aperture ratio of each pixel and which is suitable to achieve a relatively small pixel area and high definition. <P>SOLUTION: A liquid crystal display device 10 includes: a plurality of signal lines 17 and scan lines arranged on a transparent substrate 11 in a matrix; a plurality of auxiliary capacitor lines provided between the scan lines in parallel; thin film transistors TFTs each provided in a vicinity of an intersection of the signal lines 17 and scan lines; and pixel electrodes 20 arranged in respective positions defined by the signal lines 17 and the scan lines and each electrically connected to a drain electrode D of the thin film transistor TFT; in which the thin film transistor TFT's gate electrode G and the scan line are covered by a gate insulating film formed by an insulating film 25 as a first layer and an insulating layer 26 as a second layer, and the drain electrode D of the thin film transistor TFT extends to overlie an auxiliary capacitor electrode 18a, with the insulating layer 26 as the second layer interposed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a liquid crystal display device and a method for manufacturing the same, and more particularly to a liquid crystal display device suitable for a relatively small pixel area or high definition, in which the capacity of an auxiliary capacitance electrode is increased without decreasing the aperture ratio for each pixel, and the same. It relates to a manufacturing method.

In recent years, liquid crystal display devices are widely used not only in information communication equipment but also in general electric equipment. A liquid crystal display device comprises a substrate made of a pair of glass or the like with electrodes or the like formed on the surface thereof, and a liquid crystal layer formed between the pair of substrates. A liquid crystal is applied by applying a voltage to the electrodes on the substrate. By rearranging the molecules, the light transmittance is changed and various images are displayed.

Such a liquid crystal display device has scanning lines and signal lines formed in a matrix on the surface thereof, and a thin film transistor (switching element for driving liquid crystal) in a region surrounded by both the wirings (
Thin film transistor (TFT), an array substrate on which pixel electrodes for applying a voltage to liquid crystal and auxiliary capacitance lines for forming auxiliary capacitance for holding signals are formed, and red (R), green (on the surface)
G), a blue (B) color filter, and a color filter substrate on which a common electrode and the like are formed, and a configuration in which liquid crystal is sealed between the substrates is provided.

The auxiliary capacity line formed on the array substrate is provided to form an auxiliary capacity for holding a charge of a signal supplied from the signal line for a certain period.
A capacitor is formed by using a drain electrode of the FT or a part of the pixel electrode as an electrode and a gate insulating film covering the gate electrode of the TFT as a dielectric. The auxiliary capacitance line is generally formed from a light-shielding conductive member such as aluminum, molybdenum or chromium.

By the way, it is necessary to increase the capacity of this auxiliary capacitor from the viewpoint of preventing crosstalk or flicker of the liquid crystal display device. However, along with recent technological innovation, miniaturization and higher definition of the liquid crystal display device have progressed. As a result, the size of each pixel has been reduced. Therefore, considering the aperture ratio for each pixel, it is practically difficult to make the auxiliary capacitance line thicker in order to increase the auxiliary capacitance.

In order to solve the above problems, an array substrate 70 of a liquid crystal display device disclosed in Patent Document 1 below will be described with reference to FIG. 9A is a plan view of the array substrate, and FIG. 9B.
FIG. 9B is an IXB-IXB sectional view of FIG. 9A.

As shown in FIGS. 9A and 9B, an array substrate 70 of this liquid crystal display device has a scanning line made of a conductive material such as aluminum, chromium, molybdenum, chromium nitride, molybdenum nitride, or an alloy thereof on a transparent insulating substrate 71. 72, an auxiliary capacitance line 73, and a rectangular auxiliary capacitance pattern 74 are formed. The scanning line 72 is connected to the gate electrode G of the thin film transistor TFT, and the auxiliary capacitance pattern 74 is connected to the auxiliary capacitance line 73.

The insulating substrate 71 has a thickness of 250 made of an insulating material such as silicon nitride or silicon oxide.
A gate insulating film 75 of 0 to 4500 kg covers the scanning line 72, the auxiliary capacitance line 73, and the auxiliary capacitance pattern 74. A semiconductor pattern 76 made of amorphous silicon or the like is formed on the gate insulating film 75 so as to overlap the gate electrode G. On part of the semiconductor pattern 76 and the gate insulating film 75, a signal line 77 and a storage capacitor conductive pattern 78 made of a conductive material are formed. The signal line 77 extends in the vertical direction and doubles as the source electrode S of the TFT.

The auxiliary capacitor conductive pattern 78 is formed in an island shape in the same layer as the signal line 77 and overlaps with the auxiliary capacitor pattern 74 located under the gate insulating film 75 to form an auxiliary capacitor. At this time, the auxiliary capacitor conductive pattern 78 is electrically connected to a pixel electrode 79 described later.

Such signal lines 77, auxiliary capacitance conductive patterns 78, and semiconductor patterns 76 are provided.
Is covered with a protective insulating film 80 having a thickness of 500 to 2000 mm made of an insulating material such as silicon nitride or silicon oxide. In the protective insulating film 80, a contact hole 81 is formed above the drain electrode D, and an opening 82 is provided above the auxiliary capacitor conductive pattern 78. A pixel electrode 79 is formed on the protective insulating film 80, and the pixel electrode 79 and the drain electrode D are electrically connected via the contact hole 81, and a storage capacitor conductive pattern is provided via the opening 82. 78 and the pixel electrode 79 are connected, and as a result, the auxiliary capacitance conductive pattern 78 and the drain electrode D are electrically connected via the pixel electrode 79. The pixel electrode 79 is formed of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide).

In such a conventional technique, the pixel electrode 79 overlaps with the auxiliary capacitance line 73 and the auxiliary capacitance conductive pattern 78, but the auxiliary capacitance line 73 has an auxiliary capacitance interposed between the protective insulating film 80 and the gate insulating film 75. The pixel electrode 79 is electrically connected to the auxiliary capacitance conductive pattern 78, but the auxiliary capacitance conductive pattern 78 forms another auxiliary capacitance with the auxiliary capacitance pattern 74 and the gate insulating film 75 interposed therebetween. To do. In this case, since the gate insulating film 75 interposed between the auxiliary capacitance conductive pattern 78 and the auxiliary capacitance pattern 74 is thin, the auxiliary capacitance pattern 74 overlaps the pixel electrode 79 to form an auxiliary capacitance. Even if it has the same overlapping area, a larger capacitance can be secured. Therefore, in the liquid crystal display device disclosed in Patent Document 1 below, the capacitance can be increased without increasing the areas of the auxiliary capacitance pattern 74 and the auxiliary capacitance line 73, and therefore, the capacitance relative aperture ratio is increased. Can be improved.

However, in the array substrate 70 of the liquid crystal display device disclosed in Patent Document 1 below, the capacitance (auxiliary capacitance) is provided between the auxiliary capacitance conductive pattern 78 and the auxiliary capacitance pattern 74 as electrodes. The gate insulating film 75 is used as a dielectric, and the thickness of the gate insulating film 75 is thin, but the thickness of the gate insulating film 75 is still 2500 to 45.
Therefore, in order to secure a sufficient auxiliary capacity for suppressing display defects such as crosstalk or flicker, the area of the auxiliary capacity pattern 74 made of a light-shielding conductive material must be increased. . That is, in the array substrate 70 of the liquid crystal display device disclosed in Patent Document 1 below, it is possible to increase the auxiliary capacitance by reducing the thickness of the gate insulating film 75, but the thickness of the gate insulating film 75 is not limited. If the thickness itself is made thinner, it becomes difficult to maintain electrical insulation between the gate electrode G and the scanning line 72 covered with the gate insulating film 75 and other members.

In addition, an array substrate of the liquid crystal display device 90 disclosed in Patent Document 2 below will be described with reference to FIGS. 10 and 11 as an auxiliary capacitor having a large capacity. 10 is a plan view of several pixels of the array substrate disclosed in Patent Document 2 below, and FIGS. 11A to 11G are FIGS.
It is a fragmentary sectional view which shows the manufacturing process of 0 array substrate in order. First, an auxiliary capacitance line 92 made of ITO (Indium Tin Oxide) is patterned on an insulating substrate 91 made of a glass plate.
Next, a gate metal film 93 is formed and patterned (FIG. 11A).

Further, a gate insulating film 94 made of SiN _x or SiO _{x is} formed by plasma CVD or the like.
Then, an amorphous semiconductor film 95 made of, for example, a-Si as an active layer, and an ohmic contact semiconductor film 96 made of, for example, an n ⁺ a-Si film doped with impurities are successively formed (FIG. 11B). At this time, the film thickness A of the insulating film is sufficiently thick so as not to cause a short circuit between the drain / gate and the source / gate, and is set to, for example, X = 4000 mm.

Next, the ohmic contact semiconductor film 96 and the amorphous semiconductor film 95 are etched into a pattern with the same resist (FIG. 11C). Then, a resist (not shown in FIG. 11) is coated by leaving a portion where the auxiliary capacitance line 92 and the pixel electrode 97 formed in a later process overlap as an opening pattern (a broken line portion in FIG. 10), and gate insulation is performed. Etching is performed by the etchant for the film 94 so as to be as thin as a desired film thickness Y = 2000 mm as an auxiliary capacitor insulating film (
FIG. 11D).

Next, a pixel electrode 97 made of ITO is formed and patterned (FIG. 11E). Further, a drain and source metal film 98 is formed and patterned (FIG. 11F), and the ohmic contact semiconductor film 96 left in the channel portion of the TFT is removed by etching to complete an array substrate for a liquid crystal display device (FIG. 11). 11G). A liquid crystal display device 90 is obtained by disposing the array substrate obtained by such a configuration so as to face the common electrode substrate with a liquid crystal substance interposed therebetween.

In such a conventional technique, the auxiliary capacitance line 92 and the pixel electrode 97 correspond to the electrode of the capacitor, and the gate insulating film 94 existing between the auxiliary capacitance line 92 and the pixel electrode 97 serves as the dielectric of the capacitor. Correspondingly, the thickness X = 400 of the gate insulating film 94 on the gate electrode 93
Although the thickness of the insulating film on the auxiliary capacitance line 92 is 2000 mm while it is 0 mm, the short circuit between the drain and gate and the source and gate is less likely to occur. There is an effect that a necessary auxiliary capacity can be secured without increasing the area.

JP 2005-506575 A (FIGS. 8 and 9, paragraphs [0069] to [0085]) Japanese Patent No. 2584290 (Claims, page 2, column 4, line 30 to page 3, column 5, line 17, FIG. 1, FIG. 2)

In the array substrate of the liquid crystal display device 70 disclosed in Patent Document 1, an auxiliary capacitance pattern having a large area is necessary to secure a sufficient auxiliary capacitance for suppressing display defects, and the aperture ratio is high. Further, since the TFT and the auxiliary capacitance conductive pattern 78 exist as a light shielding member in the pixel, the aperture ratio becomes smaller. Further, in the array substrate of the liquid crystal display device 90 disclosed in Patent Document 2, only the thickness of the gate insulating film on the surface of the auxiliary capacitance line is partially thinned by etching, so that it is covered with the gate insulating film. The auxiliary capacitance is increased while maintaining the electrical insulation between the gate electrode and the scanning line and other members. However, the thickness of the gate insulating film of the auxiliary capacitance line is partially reduced. Therefore, it is difficult to control the etching amount for obtaining a desired thickness, and it is difficult to maintain the film thickness uniformity of the gate insulating film of the auxiliary capacitance line for each liquid crystal display device.

In addition, in the array substrate of the liquid crystal display device 90 disclosed in Patent Document 2 above,
Since the scanning line and the gate electrode are formed by patterning the gate metal film 93 after patterning the auxiliary capacitance line 92 made of ITO on the insulating substrate 91 made of glass plate, man-hours increase. Therefore, it is necessary to increase the distance between the pixel electrode 97 and the source metal film 98 in consideration of reduction in manufacturing efficiency, mask displacement, and the like.
Since the aperture ratio becomes small because the pixel electrode cannot be provided in the FT portion, it can be adopted as a relatively small pixel area or a high-definition auxiliary capacitance forming means for a liquid crystal display device in recent years. Have difficulty.

In view of the above problems, the inventors of the present application make the efficiency of the capacitor that forms the auxiliary capacitance higher, does not particularly increase man-hours, and has a large aperture ratio and a relatively small pixel area or As a result of various studies on auxiliary capacitance forming means that can be used effectively for high-definition liquid crystal display devices, the drain of the TFT is used as an electrode paired with the auxiliary capacitance line that is one electrode of the capacitor forming the auxiliary capacitance. In order to shorten the distance between the storage capacitor line and the drain electrode while extending the electrode, the insulating layer is thinner than the gate insulating film instead of the gate insulating film interposed therebetween In order to complete the present invention, it is found that the capacity of the auxiliary capacitor can be increased without increasing man-hours and lowering the aperture ratio. Is that Tsu.

That is, an object of the present invention is to provide a liquid crystal display device having a small pixel area or a high-definition pixel, which can suppress display defects such as crosstalk and flicker without reducing the aperture ratio of each pixel. It is in providing the manufacturing method.

In order to achieve the first object of the present invention, a liquid crystal display device of the present invention is provided in parallel between a plurality of signal lines and scanning lines arranged in a matrix on a transparent substrate, and the scanning lines. A plurality of storage capacitor lines, a thin film transistor provided in the vicinity of the intersection of the signal line and the scanning line, and a drain electrode of the thin film transistor are disposed at respective positions partitioned by the signal line and the scanning line. In the liquid crystal display device including the connected pixel electrode, the gate electrode and the scanning line of the thin film transistor are covered with a gate insulating film, and an insulating layer thinner than the thickness of the gate insulating film is formed on the auxiliary capacitance line. The drain electrode of the thin film transistor is extended through.

In the liquid crystal display device according to the present invention, the gate insulating film has a multi-layer structure, and the insulating layer is composed of at least one of them.

In the liquid crystal display device according to the present invention, the insulating film is a single layer formed on the most surface side among a plurality of layers constituting the gate insulating film.

In the liquid crystal display device according to the present invention, the insulating layer is a layer formed on the most transparent substrate side among a plurality of layers constituting the gate insulating film.

In the liquid crystal display device according to the present invention, the insulating layer is composed of a thinnest layer among a plurality of layers constituting the gate insulating film.

Further, the invention is characterized in that the edge of the thin portion of the insulating layer on the storage capacitor line is located inside the edge of the storage capacitor line.

According to the present invention, in the liquid crystal display device, the gate insulating film has a thickness of 2500 to 5
The insulating layer has a thickness of 500 to 1500 mm.

According to the present invention, in the liquid crystal display device, an interlayer insulating film is formed between the pixel electrode and the drain electrode, and a contact hole is formed in a portion of the interlayer insulating film located on the auxiliary capacitance line. The pixel electrode and the drain electrode are electrically connected through the contact hole.

In the liquid crystal display device according to the present invention, a reflective film is formed on the front surface or the back surface of the pixel electrode so as to cover the thin film transistor and the auxiliary capacitance line or the entire region corresponding to the pixel electrode. It is characterized by.

Furthermore, in order to achieve the second object of the present invention, a liquid crystal display device manufacturing method according to the present invention includes a plurality of scanning lines and auxiliary capacitance lines connected to a gate electrode on a transparent substrate in parallel with each other. A step of forming a gate insulating film so as to cover the entire surface of the transparent substrate, and a portion of the gate insulating film located on the auxiliary capacitance line is thinned to be thinner than the periphery of the auxiliary capacitance line Forming an insulating layer; and forming a drain electrode of the thin film transistor above the gate insulating film and extending the drain electrode of the thin film transistor so as to cover the insulating layer on the auxiliary capacitance line to form an auxiliary capacitance Including a process.

In the method of manufacturing a liquid crystal display device according to the present invention, the step of forming the insulating layer includes a step of forming a semiconductor layer on the gate insulating film, and a step of applying a photoresist on the surface of the semiconductor layer. And using a halftone mask, removing the photoresist in the auxiliary capacitance forming portion on the auxiliary capacitance line, leaving a thick photoresist at a position corresponding to the gate electrode and leaving a thin photoresist in other portions, and etching. Then, after the exposed semiconductor layer of the auxiliary capacitance forming portion is removed, a part of the gate insulating film located in the auxiliary capacitance forming portion is further removed to make the insulation thinner than the surrounding gate insulating film A step of forming a layer, a step of removing the thin photoresist and leaving a photoresist only at a position corresponding to the gate electrode, and an exposure. Removing the serial semiconductor layer by etching, characterized in that it comprises a step of removing the remaining of the photoresist.

According to the present invention, in the method for manufacturing a liquid crystal display device, the step of forming the insulating layer includes a step of forming the gate insulating film in a plurality of times and a step of removing at least one of them. Including a process.

In addition, in the method for manufacturing a liquid crystal display device according to the present invention, the step of forming the insulating layer is a step of removing the first formed layer when the gate insulating film is formed into a plurality of layers in a plurality of times. It is characterized by being.

In the method for manufacturing a liquid crystal display device according to the present invention, the step of forming the insulating layer is a step of removing the last layer formed after the gate insulating film is formed into a plurality of layers in a plurality of times. It is characterized by being.

In the method for manufacturing a liquid crystal display device according to the present invention, the gate insulating film having a multilayer structure is formed by changing the substrate temperature for each layer using the same material.

Further, the present invention is characterized in that, in the method for manufacturing a liquid crystal display device, the substrate temperature is highest when the first gate insulating film is formed, and gradually decreases when further gate insulating films are formed. To do.

Further, the present invention is characterized in that, in the above-mentioned method for manufacturing a liquid crystal display device, the gate insulating film having a multilayer structure is formed by using the same material and changing the ambient gas component for each layer. To do.

According to the present invention, in the method of manufacturing the liquid crystal display device, a step of forming an interlayer insulating film so as to cover the drain electrode, and a step of forming a contact hole at a position where the drain electrode and the auxiliary capacitance line overlap with the interlayer insulating film And a step of forming a pixel electrode on the interlayer insulating film so as to be electrically connected to the drain electrode through a contact hole.

According to the present invention, in the method for manufacturing a liquid crystal display device, before or after the formation of the pixel electrode, a full-surface reflector at a position corresponding to the thin film transistor and the auxiliary capacitance line or a position corresponding to the pixel electrode is formed. Including the step of:

By providing the above configuration, the present invention has the following excellent effects. That is, according to the liquid crystal display device of the present invention, the drain electrode connected to the pixel electrode through the insulating layer that is a part of the multi-layered gate insulating film provided on a part of the surface of the auxiliary capacitance line However, the thickness of this insulating film is smaller than the thickness of the gate insulating film covering the periphery of the auxiliary capacitance line, and this insulating layer forms a dielectric layer of the auxiliary capacitance, so that the auxiliary capacitance Thus, a liquid crystal display device can be obtained in which display defects such as crosstalk and flicker can be suppressed without increasing the area of the auxiliary capacitance line.

In other words, the gate insulating film is originally provided with a uniform thickness over the entire transparent substrate for the purpose of maintaining the insulation between the layers. However, the gate insulating film is used to maintain the electrostatic breakdown voltage of the TFT, particularly on the gate electrode serving as one terminal of the TFT. It is impossible to reduce the thickness of the insulating film. However, as in the liquid crystal display device of the present invention, by forming a thin insulating layer which is a part of the gate insulating film having a multilayer structure on the surface of the auxiliary capacitance line, the entire thickness of the gate insulating film is particularly reduced. Since the insulating film on the storage capacitor line can be made thinner without any adverse effect on other configurations, the above-described effects can be achieved. In addition, since the auxiliary capacitance can be formed simply by extending the drain electrode, the light-shielding auxiliary capacitance can be efficiently arranged, and the aperture ratio is improved.

Further, according to the liquid crystal display device of the present invention, when the gate insulating film having a multilayer structure is formed, the insulating layer on the auxiliary capacitance line is formed on one of the plurality of layers, that is, on the most surface side of the gate insulating film. For example, by using a material having different etching characteristics for each layer of the gate insulating film and removing only unnecessary layers by etching, The thin insulating layer described above can be easily formed. Further, if the layer used as the insulating layer is the thinnest layer among the gate insulating films, the capacity of the auxiliary capacitor can be easily increased.

Further, according to the liquid crystal display device of the present invention, since the edge of the thin portion of the insulating layer on the auxiliary capacitance line is positioned inside the edge of the auxiliary capacitance line, the upper electrode and the scanning line constituting the auxiliary capacitance are arranged. It is possible to increase the capacity of the auxiliary capacitor while ensuring a sufficient interval between the upper and lower electrodes, and securing the electrostatic withstand voltage of the upper electrode and the lower electrode constituting the auxiliary capacitor near the edge of the auxiliary capacitor line.

Further, according to the liquid crystal display device of the present invention, the thickness of the gate insulating film is 2500 to 5500 mm, which is a thickness that does not impair the insulation, and the insulating layer is as thin as 500 to 1500 mm. Therefore, the capacity of the capacitor can be increased. The thickness of the gate insulating film is more preferably 2800 mm or more, and the thickness of the insulating layer is more preferably 1
It should be around 000 km.

In addition, according to the liquid crystal display device of the present invention, after various wirings such as scanning lines, signal lines, and thin film transistors are formed, these wirings are covered with the interlayer insulating film. Since the surface is provided, the surface becomes flat. Therefore, the cell gap of the liquid crystal display device can be made uniform, and a liquid crystal display device with good display image quality can be obtained. Further, since the pixel electrode is electrically connected to the drain electrode through a contact hole provided on the auxiliary capacitance line, even if the cell gap on the contact hole is different from the surrounding cell gap, this cell Since the gap portion shields light from the backlight by the light-shielding drain electrode, the display quality is not adversely affected.

Further, according to the liquid crystal display device of the present invention, a transflective liquid crystal display device can be easily obtained by providing a reflective plate on the front surface or back surface of the pixel electrode corresponding to the thin film transistor and auxiliary capacitance line. If a reflector is provided so as to cover the entire surface of the pixel electrode or the entire back surface, a reflective liquid crystal display device can be easily obtained.

Furthermore, according to the method for manufacturing a liquid crystal display device of the present invention, in addition to being able to easily manufacture a liquid crystal display device having the effects of the above invention, a gate insulating film and a semiconductor layer having a multilayer structure are successively formed. Therefore, the number of steps of maintaining the periphery of the substrate from the normal pressure state to the vacuum state is reduced once compared with the method of forming the semiconductor layer after the gate insulating film is formed and etched. In addition, the TFT characteristics are less likely to deteriorate because it is less susceptible to contamination caused by the etching process of the gate insulating film.

According to the method for manufacturing a liquid crystal display device of the present invention, when the gate insulating film having a multilayer structure is formed, one of the plurality of insulating layers formed on the storage capacitor line, that is, the gate insulating film is formed. Since the first formed layer or the last formed layer is removed, an insulating layer having a thickness smaller than that of the gate insulating film can be easily formed.

In addition, according to the method for manufacturing a liquid crystal display device of the present invention, the gate insulating film having a multilayer structure is formed by changing the substrate temperature for each layer using the same material, so the ambient atmosphere is changed. By simply changing the substrate temperature, it is possible to form a gate insulating film having a multi-layer structure with substantially the same composition but different physical properties. Only the insulating layer on the surface of the wire can be easily left. Therefore, when the multi-layer gate insulating film is formed, it is not necessary to perform the etching process for each film. Therefore, it is possible not only to avoid contamination of the surface of each film, but also to reduce the predetermined insulating film and gate insulating film in a short time. Can be formed. In this case, silicon nitride, silicon oxide, or the like can be used as the gate insulating film forming material.

In addition, according to the method for manufacturing a liquid crystal display device of the present invention, a multi-layered gate insulating film can be formed by using the same material and changing the ambient gas component for each layer. By using the difference in physical properties based on the difference in composition, only the insulating layer on the surface of the auxiliary capacitance line can be left by etching. Therefore, when the multi-layer gate insulating film is formed, it is not necessary to perform the etching process for each film. Therefore, it is possible not only to avoid contamination of the surface of each film, but also to reduce the predetermined insulating film and gate insulating film in a short time. Can be formed.
The gate insulating film having a multilayer structure composed of thin films having different compositions is preferably composed of a silicon nitride layer and a silicon oxide layer, and more preferably the uppermost layer is composed of a silicon nitride layer.

Hereinafter, the best embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below exemplifies a liquid crystal display device and a manufacturing method thereof for embodying the technical idea of the present invention, and the present invention is specified to the liquid crystal display device and the manufacturing method thereof. And other embodiments within the scope of the claims are equally applicable. Note that a transmissive liquid crystal display device will be described as a liquid crystal display device according to the following embodiment. However, the liquid crystal display device of the present invention is not limited to a transmissive type, but can be applied to a transflective or reflective liquid crystal display device. Obviously it is possible.

1 is an enlarged plan view showing a portion corresponding to one pixel of the liquid crystal display device according to the first embodiment of the present invention, and seeing through the other substrate, for example, a color filter substrate. FIG. 2 is a plan view of FIG. FIG. 3 is a side sectional view showing a state of the liquid crystal display device taken along line II-II, and FIG. 3 and FIG. 4 are sectional views showing manufacturing steps for manufacturing the array substrate of the liquid crystal display device of FIG. 3 and 4 both show a cross-sectional state taken along line II-II in FIG.

In the liquid crystal display device 10 of the first embodiment, the outer peripheral surface of the pair of substrates including the array substrate 13 and the color filter substrate 14 on which various wirings are formed on the transparent substrates 11 and 12 made of glass or the like is used as a sealing material ( (Not shown), and the liquid crystal 15 is injected therein.

Various wirings and the like are formed on the array substrate 13 and the color filter substrate 14 (inner surface side), and among them, the array substrate 13 includes a plurality of scanning lines 16 and signal lines 17 formed in a matrix, A plurality of auxiliary capacitance lines 18 provided between the plurality of scanning lines 16 and parallel to the scanning lines 16, a thin film transistor TFT comprising a source electrode S, a gate electrode G, a drain electrode D, and a semiconductor layer 19, and scanning A pixel electrode 20 that covers a region surrounded by the line 16 and the signal line 17 is provided. As the semiconductor layer 19 of the TFT, polysilicon (p−
Si) or amorphous silicon (a-Si) is usually used, but is not limited to this and may be an active element.

The color filter substrate 14 includes a black matrix 21 provided in a matrix in accordance with the pixel region of the array substrate 13, and red (R), green (G), and blue provided in a region surrounded by the black matrix 21. A color filter 22 such as (B) and a common electrode 23 which is electrically connected to the electrode on the array substrate side and is provided so as to cover the color filter are usually provided. However, the present invention is not limited to this. In the case of the horizontal electric field method, there may be no common electrode, in the case of monochrome display, there may be no color filter, or color complementary color display. In some cases, the color filter may be composed of more kinds of color filters instead of the three primary colors.

In the area surrounded by the array substrate 13, the color filter substrate 14, and the sealant, a plurality of spacers and the like are provided as necessary to make the distance between the substrates uniform, and the liquid crystal 15 is enclosed. Has been.

Next, the manufacturing process of the array substrate of the above-mentioned liquid crystal display device will be described below with reference to FIGS.

First, as shown in FIG. 3A, a conductive material layer 24 made of aluminum, molybdenum, chromium, or an alloy thereof having a predetermined thickness is formed on the transparent substrate 11. Then, as shown in FIG. 3B, by patterning using a well-known photolithography method, a part thereof is removed by etching, and a plurality of scanning lines 16 extending in the lateral direction and the plurality of scanning lines 1
A storage capacitor line 18 is formed between the six. In FIG. 3B, the gate electrode G extending from the scanning line 16 and the auxiliary capacitance line 18a formed by widening a part of the auxiliary capacitance line 18 are widened.
It is shown. The scanning lines 16 and the auxiliary capacitance lines 18 shown here are shown as wirings having a multilayer structure made of aluminum and molybdenum. This has the advantage that aluminum has a small resistance value, but on the other hand, it has disadvantages such as being easily corroded and having high contact resistance with ITO. Such drawbacks can be improved.

Next, a first insulating film 25 having a predetermined thickness is formed so as to cover the transparent substrate 11 on which the scanning lines 16 and the auxiliary capacitance lines 18 are formed by the above process. As the first-layer insulating film 25, a transparent resin material made of silicon nitride or the like is used, and the first-layer insulating film 25 is used.
The thickness is preferably in the range of 2500 to 5500 mm, more preferably 2800 mm or more because it relates to the insulating properties of the scanning line 16 and the gate electrode G. When the first-layer insulating film 25 is formed, as shown in FIG. 3D, only the portion of the first-layer insulating film 25 located on the auxiliary capacitance electrode 18a is removed by etching. A portion 27 is formed.

In addition, after the above steps are completed, as shown in FIG.
A second insulating layer 26 thinner than the insulating film 25 is formed. This second insulating layer 2
6 is formed on the first-layer insulating film 25 and the auxiliary capacitance electrode 18a from which the first-layer insulating film 25 has been removed by the above-described etching. Therefore, the scanning line 16 and the gate electrode G are formed on the first layer. The gate insulating film is composed of both the insulating film 25 of the eye and the insulating layer 26 of the second layer, and the two-layer film. The auxiliary capacitance electrode 18a is covered only with the second insulating layer 26. The material of the second insulating layer 26 is the same material as that of the first insulating film 25.
That is, it may be made of silicon nitride or another insulating film such as silicon oxide. Its thickness is thinner than that of the first insulating film 25, and preferably 50
It is set to 0 to 1500 mm, more preferably around 1000 mm, for example 800 to 1200 mm.

In such a configuration, the thickness of the gate electrode portion in the same manner as the gate insulating film,
That is, since the purpose is to form an insulating film thinner than the peripheral thickness of the auxiliary capacitance line in the main part of the auxiliary capacitance electrode 18a of the auxiliary capacitance line, the second insulating layer 26 may be specially formed. However, it is efficient and the film quality is good that the gate insulating film has a multi-layer structure of 2 to 5 layers, for example, and the insulating layer is composed of at least one of them. In that case, it is possible to change the etching characteristics by changing the film quality or the like to form one layer formed on the surface of the gate insulating film. The most efficient is to form a thick first layer as described above and remove it to the electrode surface by etching.
An insulating layer made of a thin film is formed thereon, and the insulating layer is preferably a single layer formed on the surface side of the gate insulating film. As a result, the insulating layer can be constituted by the thinnest layer among the plurality of layers constituting the gate insulating film, and the auxiliary capacity can be greatly increased.

Next, as shown in FIG. 3F, a silicon layer, for example, aS, is formed on the second insulating layer 26.
i is deposited to a thickness of 1800 mm. Then, as shown in FIG. 3G, the a-Si layer is removed by etching, leaving a portion covering the gate electrode G, thereby forming a semiconductor layer 19 that becomes a part of the TFT. 4A, a conductive material is deposited on the transparent substrate 11, and a plurality of signal lines 17 extending in a direction orthogonal to the scanning lines 16 are extended from the signal lines 17 to the semiconductor. The source electrode S connected to the layer 19 and the drain electrode D which covers the auxiliary capacitance electrode 18a and whose one end is connected to the semiconductor layer 19 are patterned. As a result, a TFT serving as a switching element is located near the intersection of the scanning line 16 and the signal line 17 of the transparent substrate 11.
Is formed.

Furthermore, as shown in FIG. 4B, a protective insulating film 28 made of an inorganic insulating material for stabilizing the surface is formed on the transparent substrate 11 so as to cover these various wirings. As shown, an interlayer film 29 made of an organic insulating material for planarizing the surface of the array substrate 13 is formed. A portion of the interlayer film 29 positioned on the auxiliary capacitance electrode 18a is provided with a hole for forming a contact hole 30 for electrically connecting a pixel electrode 20 and a drain electrode D, which will be described later. The position of this hole is not limited to the auxiliary capacitance electrode 18a. However,
The portion where the contact hole 30 is formed is the color filter substrate 1 as the liquid crystal display device 10.
Since the distance between the substrates is different from that of the other portions when bonded to 4, the display quality may vary. Therefore, it is preferably provided on the auxiliary capacitance electrode 18a which is a light shielding material. 4D, after removing the protective insulating film 28 made of an inorganic insulating material exposed from the hole formed in the interlayer film 29, finally, as shown in FIG. 4E, the scanning line 1
6 and the signal line 17 for each pixel region, for example, ITO (Indium Tin Oxide)
A pixel electrode 20 made of is formed. At this time, it is preferable that a part thereof is located on the scanning line 16 and the signal line 17 and the adjacent pixel electrodes 20 are not connected to each other. The array substrate 13 is manufactured through the above steps.

The auxiliary capacitance of the array substrate 13 formed by the manufacturing method described above is that the electrode is the drain electrode D connected to the auxiliary capacitance electrode 18a and the pixel electrode 20, and the dielectric is the second insulating layer having a thickness of 1000 mm. 26 capacitor structure. Therefore, since the dielectric is a thinner insulating film than the gate insulating film of 2500 to 4500 mm as in the prior art, the capacitor capacity can be dramatically increased. In addition, since the gate electrode G and the scanning line 16 are covered with the laminated body of the first-layer insulating film 25 and the second-layer insulating layer 26, the insulating property is ensured.

In addition, by increasing the capacitor capacity, the electrode part constituting the auxiliary capacity can be reduced,
The aperture ratio of the pixel can be increased. Further, since the drain electrode D also serves as an electrode constituting the auxiliary capacitance, the light shielding portion in the pixel can be reduced as compared with the case where an electrode (conductive layer) is provided in addition to the drain electrode D as the auxiliary capacitance electrode. The aperture ratio can be further improved.

In order to increase the capacity of the auxiliary capacitor, it is better to make the insulating film thinner in all the portions forming the auxiliary capacitor. In this embodiment, the insulating film 25 in the auxiliary capacitance portion is thinned by partially removing the first-layer insulating film 25. Therefore, in order to increase the capacitance, the first-layer insulating film 2 is used.
It is better to make the portion where 5 is removed larger than the auxiliary capacitance electrode 18a. That is, the edge of the window portion 27 of the first insulating film 25 may be located outside the edge of the auxiliary capacitance electrode 18a. However, when the drain electrode D also serves as an auxiliary capacitance electrode, the auxiliary capacitance is arranged near the scanning line 16. Therefore, if the insulating film is thinned to the outside of the auxiliary capacitance portion, the distance between the upper electrode (drain electrode D) of the auxiliary capacitance and the scanning line 16 becomes too close, and problems such as parasitic capacitance occur. Therefore, in the case where the drain electrode D also serves as the upper electrode of the auxiliary capacitor, it is necessary to make the insulating film in the auxiliary capacitor portion thin while widening the distance between the upper electrode of the auxiliary capacitor and the scanning line 16. The edge is positioned inside the edge of the auxiliary capacitance electrode 18a. Further, since the insulating film formed on the auxiliary capacitance electrode 18a is likely to be thinner near the edge of the auxiliary capacitance electrode 18a than the other portions, the static capacitance between the auxiliary capacitance electrode 18a and the upper electrode is near the edge of the auxiliary capacitance electrode 18a. In order to ensure the withstand voltage, the auxiliary capacitance electrode 18a
It is better to make the insulating film near the edge of the electrode thicker than the insulating film near the center of the auxiliary capacitance electrode 18a. In this embodiment, the edge of the portion (window portion 27) from which the first-layer insulating film 25 is removed is located inside the auxiliary capacitance electrode 18a, so that the upper electrode (drain electrode D) of the auxiliary capacitance is connected. A sufficient space is provided between the scanning line 16 and the electrostatic withstand voltage between the upper electrode and the auxiliary capacitance electrode is secured.

In this embodiment, as a method of thinning the insulating film in the auxiliary capacitor portion, the first insulating film is first formed, and the portion corresponding to the auxiliary capacitor electrode of the first insulating film is completely formed. A second insulating film that is thinner than the first insulating film is stacked from above. In addition to this, there is another method of thinning the insulating film in the auxiliary capacity part, in which a thicker insulating film is first formed and the insulating film is partially etched to reduce the thickness. However, it is easy to control the thickness of the insulating film in the auxiliary capacitance portion, and an insulating film having a uniform thickness can be formed.

As described above, according to the liquid crystal display device of the present invention, it is possible to increase the capacity of the auxiliary capacitor without increasing the area of the auxiliary capacitor electrode made of a light-shielding material. A portion thereof is located on the scanning line 16 and the signal line 17 and is provided so that adjacent pixel electrodes 20 are not connected to each other, so that the crosstalk, flicker, etc. are not reduced without decreasing the aperture ratio for each pixel. Display defects can be suppressed. In addition, since the pixel electrode 20 is provided on the flat interlayer film 29, the cell gap of the obtained liquid crystal display device 10 can be made uniform, so that the liquid crystal display device 10 with good display image quality can be obtained.

In the case where the liquid crystal display device of the present invention is not a transmissive type but a transflective type, fine irregularities are partially formed on the surface of the interlayer film 29 formed in the region excluding the contact hole 30 of the pixel electrode. At the same time, a reflective film made of a light reflecting material may be formed between the uneven portion and the pixel electrode 20 or on the surface of the pixel electrode 20. In the transflective liquid crystal display device, since the area of the transmissive portion is narrower than that of the transmissive liquid crystal display device, the liquid crystal display device of the present invention that can widen the area of the opening and the manufacturing method thereof are particularly effective. It is. If the liquid crystal display device is to be of a reflective type, a reflective film may be formed between the interlayer film 29 or the entire surface of the pixel electrode 20.

Next, the manufacturing process of the array substrate of the liquid crystal display device 10A of Example 2 will be described with reference to FIGS. An enlarged plan view of a portion corresponding to one pixel of the array substrate seen through the color filter substrate of the liquid crystal display device 10A of the second embodiment is the same as that of the liquid crystal display device 10 of the first embodiment shown in FIG. Similarly, the figure corresponding to the II-II sectional view of FIG. 1 on the array substrate of Example 2 is the same as that of the liquid crystal display device 10 of Example 1 shown in FIG. The description will be made with reference to FIGS. 1 and 2, and the same reference numerals are given to the same parts as those of the liquid crystal display device 10 of the first embodiment. 5A to 5E and FIGS. 6A to 6D are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of the liquid crystal display device 10A of the second embodiment. 5A to 5E and FIGS. 6A to 6D each show a state of a position corresponding to the II-II cross section of FIG.

First, as shown in FIG. 5A, a conductive material layer 24 made of aluminum, molybdenum, chromium, or an alloy thereof having a predetermined thickness is formed on the transparent substrate 11. Then, as shown in FIG. 5B, by patterning using a well-known photolithography method, a part thereof is removed by etching, a plurality of scanning lines 16 extending in the lateral direction, and gate electrodes connected to the scanning lines 16 A storage capacitor line 18 is formed between G and the plurality of scanning lines 16. In FIG. 5B, the gate electrode G extending from the scanning line 16 and the auxiliary capacitance electrode 18a formed by widening a part of the auxiliary capacitance line 18 are shown.

Next, as shown in FIG. 5C, the transparent substrate 11 on which the scanning lines 16 and the auxiliary capacitance lines 18 are formed by the above process is heated in a vacuum apparatus to a high temperature, for example, 350 ° C.
A first insulating film 25 made of silicon nitride having a predetermined thickness (for example, 1000 mm) is formed on the surface by a VD (Chemical Vapor Deposition) method or the like. Thereafter, the temperature of the transparent substrate 11 on which the first insulating film 25 is formed on the surface is lowered to a temperature lower than the initial temperature, for example, 250 ° C., and a predetermined thickness (for example, 3000 mm) is similarly formed by plasma CVD or the like. A second insulating layer 26 made of silicon nitride is formed. The first insulating layer 25 and the second insulating layer 26
Both become gate insulating films. Further, for example, a-Si is formed on the entire surface of the second insulating layer 26.
The semiconductor layer 19 composed of a layer and an n ⁺ a-Si layer has a predetermined thickness (for example, an a-Si layer 1800 mm).
And an n ⁺ a-Si layer 500 Å).

The first insulating film 25, the second insulating layer 26, and the semiconductor layer 19 can all be formed continuously without taking the transparent substrate 11 out of the vacuum apparatus. The first
Since the insulating film 25 in the second layer and the insulating layer 26 in the second layer have different substrate temperatures at the time of forming the insulating films, the hardness of the films differs even if they are made of the same silicon nitride. Since the first insulating film 25 having a higher substrate temperature is harder, the wet etching rate with buffered hydrofluoric acid is lowered. The first insulating film 25 is preferably thin as long as it does not cause a short circuit, and is preferably 500 to 1500 mm. The thickness of both the first insulating film 25 and the second insulating layer 26 is 2500 to 5500 mm in order to prevent dielectric breakdown due to static electricity in the gate electrode G portion of the TFT. It is good to do.

Here, the insulating film having a different etching rate is formed by changing the substrate temperature when the insulating films are stacked, but an insulating film having a different etching rate may be formed by changing the components of the atmospheric gas. For example, when silicon nitride is formed, silane gas and nitrogen gas are used, but when the second layer is formed, the ratio of the silane gas is increased as compared with the case where the first layer is formed. Can be hardened.

Thereafter, as shown in FIG. 5D, the semiconductor layer 19 is removed by dry etching so that the semiconductor layer 19 remains on the surface of the gate electrode G of the TFT, and then the second insulating layer 26 on the surface of the auxiliary capacitance electrode 18a. Is removed by wet etching or dry etching using buffered hydrofluoric acid so that the first insulating film 25 is exposed. At this time, since the etching rate of the first-layer insulating film 25 is slower than the etching rate of the second-layer insulating layer 26, the first-layer insulating film 25 may be left in a state where it is not substantially etched. it can.

Next, after forming a conductive material layer made of aluminum, molybdenum, chromium, or an alloy thereof on the transparent substrate 11, a plurality of signals extending in a direction perpendicular to the scanning line 16 as shown in FIGS. 1 and 5E. The line 17, the source electrode S extending from the signal line 17 and connected to the semiconductor layer 19, and the drain electrode D covering the auxiliary capacitance electrode 18 a and having one end connected to the semiconductor layer 19 are patterned. As a result, a TFT serving as a switching element is formed in the vicinity of the intersection of the transparent substrate 11 with the scanning line 16 and the signal line 17.

Further, as shown in FIG. 6A, a protective insulating film 28 made of an inorganic insulating material (for example, silicon nitride) for surface stabilization is formed on the transparent substrate 11 so as to cover these various wirings, and then 6B, an interlayer film 29 made of an organic insulating material such as polyimide for planarizing the surface of the array substrate 13 is formed, and then the auxiliary capacitance electrode 18a is etched by etching as shown in FIG. 6C. Contact holes 30 are formed in the interlayer film 29 and the protective insulating film 28 located above. The position where the contact hole 30 is formed is not limited to the auxiliary capacitance electrode 18a, but the portion where the contact hole 30 is formed is the distance between the substrates when the liquid crystal display device 10 is bonded to the color filter substrate 14. That is, since the cell gap is different from other parts, there is a possibility that the display quality may vary. Therefore, the cell gap is preferably provided on the auxiliary capacitance electrode 18a which is a light shielding material.

Then, as shown in FIG. 6D, a pixel electrode 20 made of, for example, ITO is formed for each pixel region surrounded by the scanning line 16 and the signal line 17. At this time, in order to prevent light leakage, a part of the pixel electrode 20 is preferably positioned on the scanning line 16 and the signal line 17 and the adjacent pixel electrodes 20 are not connected to each other. The array substrate 13 is obtained by the above process.
Is manufactured.

The array substrate 13 of the liquid crystal display device 10A of Example 2 formed by the manufacturing method described above.
The first auxiliary capacitance is arranged between the auxiliary capacitance electrode 18a and the drain electrode D, the drain electrode D connected to the auxiliary capacitance electrode 18a and the pixel electrode 20 corresponds to the electrode of the capacitor.
The insulating film 25 in the layer corresponds to the dielectric of the capacitor, and this insulating film 25 in the first layer
The thickness of the dielectric composed of the gate insulating film conventionally used is 2500 to 450.
Since it can be 500-1500 mm which is significantly thinner than 0 mm, the auxiliary capacitance electrode 18a
Even if the area is not increased, the auxiliary capacity can be dramatically increased. In addition, since the gate electrode G and the scanning line 16 are covered with a gate insulating film made of a stacked body of the first insulating film 25 and the second insulating layer 26, sufficient insulation is ensured. .

As described above, according to the liquid crystal display device of the second embodiment, the auxiliary capacitance can be increased without increasing the area of the auxiliary capacitance electrode 18a made of a light-shielding material, so that the aperture ratio for each pixel is lowered. Therefore, display defects such as crosstalk and flicker can be suppressed. In addition, since the pixel electrode 20 is provided on the flat interlayer film 29, the cell gap of the obtained liquid crystal display device 10A can be made uniform, so that the liquid crystal display device 10 with good display image quality can be obtained.

In the second embodiment, the example in which both the first insulating film 25 and the second insulating layer 26 are made of silicon nitride has been shown. However, both of them may be made of silicon oxide. In addition, one of the first insulating film 25 and the second insulating layer 26 may be made of silicon oxide and the other may be made of silicon nitride. However, a layer having a high etching rate is preferably the uppermost layer, and in terms of insulation, the second insulating layer 26 is preferably made of silicon nitride. Alternatively, the storage capacitor line can be formed of aluminum, the surface thereof can be anodized to form aluminum oxide, and the film can be used as an insulating layer for the storage capacitor portion.

Next, the manufacturing process of the array substrate of the liquid crystal display device 10B of Example 3 will be described with reference to FIGS. An enlarged plan view of a portion corresponding to one pixel of the array substrate seen through the color filter substrate of the liquid crystal display device 10B of the third embodiment is the same as the case of the liquid crystal display device 10 of the first embodiment shown in FIG. Similarly, the figure corresponding to the II-II sectional view of FIG. 1 on the array substrate of Example 3 is the same as that of the liquid crystal display device 10 of Example 1 shown in FIG. The description will be made with reference to FIGS. 1 and 2, and the same reference numerals are given to the same parts as those of the liquid crystal display device 10 of the first embodiment. 7A to 7F and FIGS. 8A to 8E are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of the liquid crystal display device 10B of the third embodiment. 7A to 7F and FIGS. 8A to 8E all show the state of the position corresponding to the II-II cross section of FIG.

First, as shown in FIG. 7A, a conductive material layer 24 made of aluminum, molybdenum, chromium, or an alloy thereof having a predetermined thickness is formed on the transparent substrate 11. Then, as shown in FIG. 7B, by patterning using a well-known photolithography method, a part thereof is removed by etching, a plurality of scanning lines 16 extending in the lateral direction, and gate electrodes connected to the scanning lines 16 A storage capacitor line 18 is formed between G and the plurality of scanning lines 16. In FIG. 7B, the gate electrode G extending from the scanning line 16 and the auxiliary capacitance electrode 18a formed by widening a part of the auxiliary capacitance line 18 are shown. Further, the scanning line 16 and the auxiliary capacitance line 18 shown here have a multilayer structure made of aluminum and molybdenum in order to make a junction contact with the pixel electrode.

Next, as shown in FIG. 7C, plasma CVD (Chemical Vapor Deposition) is formed on the surface of the transparent substrate 11 on which the scanning lines 16 and the auxiliary capacitance lines 18 are formed by the above-described process.
An insulating film 25 made of silicon nitride having a predetermined thickness (for example, 4000 mm) is formed on the surface by a method or the like, and a semiconductor layer 19 made of, for example, an a-Si layer and an n ⁺ a-Si layer is formed on the entire surface of the insulating film 25. Are formed to a predetermined thickness (for example, an a-Si layer 1800 Å and an n ⁺ a-Si layer 500 Å).

Both the insulating film 25 ′ and the semiconductor layer 19 can be continuously formed without removing the transparent substrate 11 from the vacuum apparatus. The thickness of the insulating film 25 ′ is 2500 to 5500 mm so as not to cause dielectric breakdown due to static electricity at the gate electrode G portion of the TFT.
It is good to do.

Thereafter, as shown in FIG. 7D, a positive photoresist 31 is formed on the entire surface of the transparent substrate 11.
Are provided so as to have a uniform thickness, and the photoresist 31 is exposed using a halftone mask 32. This halftone mask 32 has a portion 3 corresponding to the gate electrode G of the TFT.
3 is completely light-shielding, the portion 34 corresponding to the auxiliary capacitance electrode 18a is translucent, and the other portion 35 is semi-transmissive. Therefore, when the photoresist 31 is developed after exposure, FIG.
As shown in E, the thick photoresist 31 ₁ remains on the surface of the gate electrode G, the photoresist does not exist on the surface of the auxiliary capacitance electrode 18a, and the semiconductor layer 19 is exposed, and the remaining portion has the gate electrode Photoresist 31 ₂ having a thickness smaller than that of photoresist 31 ₁ on the surface of G remains.

In this state, as shown in FIG. 7F, the semiconductor layer 19 on the surface of the auxiliary capacitance electrode 18a is removed by dry etching to expose the insulating film 25 ′, and the insulating film exposed on the surface of the auxiliary capacitance electrode 18a. A part of 25 'is wet-etched or dry-etched with buffered hydrofluoric acid so that an insulating layer 26' having a predetermined thickness (for example, 1000 mm) remains. Next, FIG. 8A
As shown in, thin photoresist layer 31 _{and second} semiconductor layer 19 is removed by ashing
To expose. At this time, a thick photoresist layer 31 ₁ positioned on the gate electrode G,
Since part of the film is ashed, the thickness is reduced, but the semiconductor layer 19 remains covered. Thereafter, as shown in FIG. 8B, the semiconductor layer 1 exposed by dry etching.
9 is removed.

Thereafter, a thick photoresist layer 31 ₁ positioned on the gate electrode G is removed by ashing, aluminum on a transparent substrate 11, after forming molybdenum, chromium or conductive material layer made of such an alloy, FIG. 1 8C, a plurality of signal lines 17 extending in a direction orthogonal to the scanning line 16, a source electrode S extending from the signal line 17 and connected to the semiconductor layer 19, and an auxiliary capacitance electrode 18a The drain electrode D that covers the top and has one end connected to the semiconductor layer 19 is patterned. As a result, a TFT serving as a switching element is formed in the vicinity of the intersection of the transparent substrate 11 with the scanning line 16 and the signal line 17. Further, a protective insulating film 28 made of an inorganic insulating material (for example, silicon nitride) for stabilizing the surface is formed on the transparent substrate 11 so as to cover these various wirings, and then the surface of the array substrate 13 is formed. An interlayer film 29 made of an organic insulating material such as polyimide for flattening is formed.

Then, as shown in FIG. 8D, contact holes 30 are formed in the interlayer film 29 and the protective insulating film 28 located on the auxiliary capacitance electrode 18a by etching. The position where the contact hole 30 is formed is not limited to the auxiliary capacitance electrode 18a, but the portion where the contact hole 30 is formed is the distance between the substrates when the liquid crystal display device 10 is bonded to the color filter substrate 14. That is, since the cell gap is different from other parts, there is a possibility that the display quality may vary. Therefore, the cell gap is preferably provided on the auxiliary capacitance electrode 18a which is a light shielding material.

Then, as shown in FIG. 8E, a pixel electrode 20 made of, for example, ITO or IZO is formed for each pixel region surrounded by the scanning line 16 and the signal line 17. At this time, in order to prevent light leakage, a part of the pixel electrode 20 is preferably positioned on the scanning line 16 and the signal line 17 and the adjacent pixel electrodes 20 are not connected to each other. The array substrate 13 of the liquid crystal display device 10B of Example 3 is manufactured through the above steps.

In the auxiliary capacitance of the array substrate 13 formed by the manufacturing method of the third embodiment described above, the auxiliary capacitance electrode 18a and the drain electrode D connected to the pixel electrode 20 correspond to the electrode of the capacitor, and the auxiliary capacitance electrode 18a and the drain electrode. Insulating layer 26 'disposed between D and D corresponds to the dielectric of the capacitor, and the thickness of the dielectric composed of this insulating layer 26' is the thickness of a conventionally used gate insulating film 2500-500. Since the thickness can be 500-1500 mm, which is significantly thinner than 4500 mm, the auxiliary capacity can be dramatically increased without increasing the area of the auxiliary capacity electrode 18a. Further, since the gate electrode G and the scanning line 16 are covered with the gate insulating film made of the insulating film 25 ′ having a thickness larger than that of the insulating layer 26 ′, sufficient insulation is ensured.

In the above-described third embodiment, the insulating film 25 ′ is composed of a single silicon nitride layer. In such a case, the insulating film 25 ′ is homogeneous, so that the insulating film 25 ′ is formed. When the thin insulating layer 26 ′ is formed by wet etching using buffered hydrofluoric acid, it is necessary to strictly control the etching time. However, if the insulating film 25 ′ has a multi-layer structure made of materials with different etching rates, the etching conditions can be made more flexible and the manufacture becomes easier. For example, after the temperature of the transparent substrate 11 is first increased and a hard silicon nitride film is provided,
If a soft silicon nitride film is laminated by lowering the temperature of the transparent substrate 11, the soft silicon nitride film has a high etching rate due to buffered hydrofluoric acid, so even if there is some etching time error, Since the hard silicon nitride film is hardly etched, the insulating layer 26 having an accurate thickness can be obtained.

Furthermore, the insulating film 25 ′ can be composed of a single layer of silicon oxide, and further can be composed of a multilayer structure of a silicon nitride layer and a silicon oxide layer. However, from the viewpoint of insulation, the uppermost layer is preferably made of a silicon nitride film.

In Example 3 described above, the insulating film 25 ′ and the insulating layer 26 ′ are both made of silicon nitride. However, both of them can be made of silicon oxide or the like. One of the insulating film and the second insulating layer can be made of silicon oxide and the other can be made of silicon nitride.

As described above, according to the liquid crystal display device 10B of the third embodiment, since the auxiliary capacitance can be increased without increasing the area of the auxiliary capacitance electrode 18a, the aperture ratio for each pixel is not reduced. Display defects such as crosstalk and flicker can be suppressed. In addition, according to the method for manufacturing the liquid crystal display device 10B of Example 3, since the gate insulating film and the semiconductor layer were sequentially formed in succession, the semiconductor layer was formed after the gate insulating film was formed and etched. Compared with the conventional method of forming a film, the step of maintaining the periphery of the substrate from the normal pressure state to the vacuum state can be reduced once, and the photoresist left around the auxiliary capacitance line by the halftone mask The semiconductor layer located on the surface of the auxiliary capacitance line can be removed by etching using the layer as a mask, and the TFT characteristics are deteriorated because it is less susceptible to contamination generated in the gate insulating film etching process. Less. In addition, according to the method of manufacturing the liquid crystal display device 10B of Example 3, after etching the semiconductor layer on the surface of the storage capacitor line, the insulating layer is formed by etching using the remaining photoresist layer and semiconductor layer as a mask. Since the number of steps for etching the semiconductor layer is increased after the insulating layer is formed, it is not necessary to provide a photolithography step particularly when the insulating layer is formed.

3 is an enlarged plan view of a portion corresponding to one pixel of the liquid crystal display device according to the first exemplary embodiment, with a color filter substrate seen through. FIG. It is a sectional side view which shows the state cut | disconnected by the II-II line | wire of the liquid crystal display device of FIG. 3A to 3G are cross-sectional views showing manufacturing steps for manufacturing the array substrate of FIG. 4A to 4E are cross-sectional views showing manufacturing steps for manufacturing the array substrate of FIG. 1 following FIG. 3G. 5A to 5E are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of the second embodiment. 6A to 6D are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of Example 2 subsequent to FIG. 5E. 7A to 7F are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of the third embodiment. 8A to 8E are cross-sectional views illustrating manufacturing steps for manufacturing the array substrate of Example 3 subsequent to FIG. 7F. 9A is a plan view of the array substrate of the first conventional example, and FIG. 9B is a cross-sectional view taken along the line IXB-IXB in FIG. 9A. FIG. 10 is a plan view of several pixels of the array substrate of the second conventional example. 11A to 11G are partial cross-sectional views sequentially showing manufacturing steps of the array substrate of FIG.

Explanation of symbols

10, 10A, 10B ... Liquid crystal display device, 11, 12 ... Transparent substrate, 13 ... Array substrate, 1
4 ... color filter substrate, 15 ... liquid crystal, 16 ... scanning line, 17 ... signal line, 18 ... auxiliary capacitance line, 18a ... auxiliary capacitance electrode, 19 ... semiconductor layer, 20 ... pixel electrode, 22 ... color filter, 2
DESCRIPTION OF SYMBOLS 3 ... Common electrode, 24 ... Conductive material layer, 25 ... 1st insulating film, 25 '... Insulating film, 26 ... 2nd insulating layer, 26' ... Insulating layer, 27 ... Window part, 28 ... Protective insulating film, 29 ... interlayer film, 30 ... contact hole.

Claims (19)

A plurality of signal lines and scanning lines arranged in a matrix on a transparent substrate, a plurality of auxiliary capacitance lines provided in parallel between the scanning lines, and a thin film transistor provided near the intersection of the signal lines and the scanning lines And a pixel electrode disposed at each position partitioned by the signal line and the scanning line and electrically connected to the drain electrode of the thin film transistor,
The gate electrode of the thin film transistor and the scanning line are covered with a gate insulating film, and the drain electrode of the thin film transistor extends on the storage capacitor line through an insulating layer thinner than the thickness of the gate insulating film. A liquid crystal display device. The liquid crystal display device according to claim 1, wherein the gate insulating film has a multi-layer structure, and the insulating layer includes at least one of them. 3. The liquid crystal display device according to claim 2, wherein the insulating film is a single layer formed on the most surface side among a plurality of layers constituting the gate insulating film. The liquid crystal display device according to claim 2, wherein the insulating layer is a single layer formed on the most transparent substrate side among a plurality of layers constituting the gate insulating film. The liquid crystal display device according to claim 2, wherein the insulating layer is formed of a thinnest layer among a plurality of layers constituting the gate insulating film. The liquid crystal display device according to claim 1, wherein an edge of a thin portion of the insulating layer on the auxiliary capacitance line is located inside an edge of the auxiliary capacitance line. The gate insulating film has a thickness of 2500 to 5500 mm, and the insulating layer has a thickness of 500 to 500.
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is 1500 mm. An interlayer insulating film is formed between the pixel electrode and the drain electrode, and a contact hole is formed in a portion of the interlayer insulating film located on the storage capacitor line, via the contact hole. The liquid crystal display device according to claim 1, wherein the pixel electrode and the drain electrode are electrically connected. 9. The reflective film is formed on the front surface or the back surface of the pixel electrode so as to cover the entire area of the thin film transistor and the auxiliary capacitance line or a position corresponding to the pixel electrode. Liquid crystal display device. A step of arranging a plurality of scanning lines and auxiliary capacitance lines parallel to each other on a transparent substrate;
Forming a gate insulating film so as to cover the entire surface of the transparent substrate;
Thinning a portion of the gate insulating film located on the auxiliary capacitance line to form an insulating layer having a smaller thickness than the periphery of the auxiliary capacitance line;
Forming a storage capacitor by forming a drain electrode of the thin film transistor above the gate insulating film and extending the drain electrode of the thin film transistor so as to cover the insulating layer on the storage capacitor line; A method for manufacturing a liquid crystal display device. The step of forming the insulating layer includes
Forming a semiconductor layer on the gate insulating film;
Applying a photoresist to the surface of the semiconductor layer;
Using a halftone mask, removing the photoresist of the auxiliary capacitance forming portion on the auxiliary capacitance line, leaving a thick photoresist at a position corresponding to the gate electrode and leaving a thin photoresist in the other portions;
After the exposed semiconductor layer of the auxiliary capacitance forming portion is removed by etching, a part of the gate insulating film located in the auxiliary capacitance forming portion is further removed to make the thickness thinner than the surrounding gate insulating film Forming an insulating layer;
Removing the thin photoresist to leave the photoresist only in a position corresponding to the gate electrode;
Removing the exposed semiconductor layer by etching;
The method of manufacturing a liquid crystal display device according to claim 10, further comprising a step of removing the remaining photoresist. 11. The liquid crystal according to claim 10, wherein the step of forming the insulating layer includes a step of forming the gate insulating film into a plurality of layers in a plurality of times and a step of removing at least one of them. Manufacturing method of display device. 13. The liquid crystal display according to claim 12, wherein the step of forming the insulating layer is a step of removing a layer formed first when the gate insulating film is formed into a plurality of layers divided into a plurality of times. Device manufacturing method. 13. The liquid crystal display device according to claim 12, wherein the step of forming the insulating layer is a step of removing the last formed layer after the gate insulating film is formed into a plurality of layers divided into a plurality of times. Manufacturing method. 13. The method of manufacturing a liquid crystal display device according to claim 12, wherein the multi-layer gate insulating film is formed by changing the substrate temperature for each layer using the same material. 16. The method of manufacturing a liquid crystal display device according to claim 15, wherein the substrate temperature is highest when the first gate insulating film is formed, and gradually decreases when further gate insulating films are formed. 13. The method of manufacturing a liquid crystal display device according to claim 12, wherein the multi-layered gate insulating film is formed by using the same material and changing the ambient gas component for each layer. Forming an interlayer insulating film so as to cover the drain electrode;
Forming a contact hole at a position where the drain electrode and the auxiliary capacitance line overlap the interlayer insulating film;
The method of manufacturing a liquid crystal display device according to claim 10, further comprising: forming a pixel electrode on the interlayer insulating film so as to be electrically connected to the drain electrode through a contact hole. 19. The method according to claim 18, further comprising a step of forming a reflection plate on a whole surface at a position corresponding to the thin film transistor and the auxiliary capacitance line or a position corresponding to the pixel electrode before or after the pixel electrode is formed. Liquid crystal display device manufacturing method.

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