JP2007121793A - Liquid crystal display device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device made to be a small pixel area or high-definition pixel, capable of satisfactorily restraining display defects such as cross talk and flickers, and also provide a manufacturing method thereof. <P>SOLUTION: The liquid crystal display device 10 comprises a plurality of signal lines 17 and scanning lines 16 disposed on a transparent substrate 11 in a matrix, an auxiliary capacitance line 18 disposed in parallel with the scanning lines, a thin film transistor TFT, and a pixel electrode 20 electrically connected to a drain electrode D of the thin film transistor TFT. The portions where the scanning lines 16 and the auxiliary capacitance 18 intersect with the signal line 17 are separated by a gate insulating film 25<SB>1</SB>, 25<SB>2</SB>, and a semiconductor layer 19<SB>1</SB>, 19<SB>2</SB>respectively. The drain electrode D of the thin film transistor TFT extends on the surface of the auxiliary capacitance line 18 at the portion where the pixel electrode 20 is located through an insulating layer 26 of which thickness is smaller than the gate insulating film 25. <P>COPYRIGHT: (C)2007,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 includes a pair of glass substrates having electrodes formed on the surface and a liquid crystal layer formed between the pair of substrates, and a voltage is applied to the electrodes on the substrate. The liquid crystal molecules are rearranged to change the light transmittance and display various images.

  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 (Thin Film Transistor: TFT), which is a switching element for driving liquid crystal, in a region surrounded by both the wirings. An array substrate on which a display electrode for applying a voltage to the electrode and an auxiliary capacitor line for forming an auxiliary capacitor for holding a signal are formed, and color filters such as red (R), green (G), and blue (B) on the surface 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 two substrates is provided.

  The auxiliary capacity line formed on the array substrate is provided to form an auxiliary capacity for holding the charge of the signal supplied from the signal line for a certain period, and the auxiliary capacity is the auxiliary capacity line and the drain electrode of the TFT. Alternatively, a capacitor is formed using 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. 4A is a plan view of the array substrate, and FIG. 4B is a sectional view taken along line XX in FIG. 4A.

  As shown in FIG. 4, an array substrate 70 of this liquid crystal display device includes a scanning line 72 made of a conductive material such as aluminum, chromium, molybdenum, chromium nitride, molybdenum nitride, or an alloy thereof on a transparent insulating substrate 71, and an auxiliary substrate. Capacitor lines 73 and rectangular auxiliary capacitor patterns 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.

  On the insulating substrate 71, a gate insulating film 75 made of an insulating material such as silicon nitride or silicon oxide and having a thickness of 2500 to 4500 mm covers the scanning lines 72, auxiliary capacitance lines 73 and auxiliary capacitance patterns 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.

  The signal line 77, the auxiliary capacitor conductive pattern 78, and the semiconductor pattern 76 are 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.
JP 2005-506575 A (FIGS. 8 and 9, paragraphs [0069] to [0085])

  However, in the array substrate 70 of the liquid crystal display device disclosed in Patent Document 1, 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 a dielectric, and the gate insulating film 75 is thin. However, since the gate insulating film 75 has a thickness of 2500 to 4500 mm, display such as crosstalk or flicker is performed. In order to secure a sufficient auxiliary capacity for suppressing defects, 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, 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 the electrical insulation between the gate electrode G or the scanning line 72 covered with the gate insulating film 75 and the other members, so that it is difficult to adopt it immediately.

  In view of the above problems, the inventors of the present application have studied various methods for increasing the efficiency of a capacitor that forms an auxiliary capacitance, and as a result, an auxiliary capacitance line and a pixel electrode serving as an electrode of the capacitor that forms the auxiliary capacitance. In order to shorten the distance between the drain capacitance electrode and the drain electrode connected to the pixel electrode, the thickness is thinner than the gate insulating film instead of the gate insulating film interposed therebetween. The present inventors have found that if an insulating layer is interposed, the distance between both electrodes can be further reduced, and the capacity of the auxiliary capacitor can be increased, and the present invention has been achieved.

  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.

The first object of the present invention can be achieved by the following configuration. That is, the invention of the liquid crystal display device according to claim 1 includes 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, A thin film transistor provided near an intersection of the signal line and the scanning line, 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. In the liquid crystal display device provided,
The intersection of the scanning line and the signal line and the intersection of the storage capacitor line and the signal line are separated by a gate insulating film and a semiconductor layer provided independently of each other,
Further, the drain electrode of the thin film transistor extends on the surface of the auxiliary capacitance line through an insulating layer thinner than the thickness of the gate insulating film.

  The invention according to claim 2 is the liquid crystal display device according to claim 1, wherein the gate insulating film and the insulating layer are made of the same material.

  The invention according to claim 3 is the liquid crystal display device according to claim 1, wherein the gate insulating film has a multilayer structure, and the insulating layer is the same as at least one layer of the gate insulating film having the multilayer structure. It is characterized by comprising the following materials.

According to a fourth aspect of the present invention, in the liquid crystal display device according to the first aspect, the gate insulating film has a thickness of 2500 to 5500 mm, and the insulating layer has a thickness of 500 to 1500 mm. According to a fifth aspect of the present invention, in the liquid crystal display device according to the first aspect, an interlayer insulating film is formed between the pixel electrode and the drain electrode, A contact hole is formed in a portion located on the auxiliary capacitance line, and the pixel electrode and a portion of the drain electrode extending on the auxiliary capacitance line are electrically connected through the contact hole. It is characterized by that.

  According to a sixth aspect of the present invention, in the liquid crystal display device according to any one of the first to fifth aspects, the back surface of the pixel electrode positioned on the thin film transistor and the auxiliary capacitance line, or the entire back surface of the pixel electrode. A reflection plate is formed so as to cover it.

Furthermore, the second object of the present invention can be achieved by the following method. That is, the invention of the manufacturing method of the liquid crystal display device according to claim 7 is:
A step of arranging a plurality of scanning lines and auxiliary capacitance lines connected to the gate electrode of the thin film transistor in parallel with each other on a transparent substrate;
Sequentially forming a gate insulating film and a semiconductor layer so as to cover the entire surface of the transparent substrate;
Selectively removing the semiconductor layer leaving a position corresponding to the surface of the gate electrode, the intersection of the scanning line and the auxiliary capacitance line and the signal line;
Removing a part of the exposed gate insulating film by etching to form an insulating layer thinner than the thickness of the gate insulating film;
A plurality of signal lines are provided in a direction perpendicular to the scanning lines on the surfaces of the semiconductor layer and the insulating layer located on the scanning lines and the auxiliary capacitance lines, and a source electrode of the thin film transistor is provided near the intersection of the scanning lines and the signal lines. Providing a drain electrode and extending the drain electrode so as to cover an insulating layer on the auxiliary capacitance line to form an auxiliary capacitance;
Forming a pixel electrode in each of a plurality of regions surrounded by the scanning line and the signal line, and electrically connecting the pixel electrode to a drain electrode of the thin film transistor;
It is characterized by including.

  The invention according to claim 8 is the method of manufacturing a liquid crystal display device according to claim 7, wherein the gate insulating film has a multilayer structure by changing the substrate temperature for each layer using the same raw material. It is characterized by that.

  According to a ninth aspect of the present invention, in the method for manufacturing a liquid crystal display device according to the eighth aspect, the substrate temperature is highest when the first gate insulating film is formed, and sequentially when further gate insulating films are formed. It is characterized by being lowered.

  According to a tenth aspect of the present invention, in the method of manufacturing a liquid crystal display device according to the seventh aspect, the gate insulating film is composed of the same raw material by changing the components of the surrounding atmospheric gas for each layer. It is characterized by having a multi-layer structure with different.

  The invention according to claim 11 is the method of manufacturing a liquid crystal display device according to claim 7, wherein the gate insulating film has a thickness of 2500 to 5500 mm, and the insulating layer has a thickness of 500 to 1500 mm. It is characterized by.

  According to a twelfth aspect of the present invention, in the method of manufacturing a liquid crystal display device according to the seventh aspect, before forming the pixel electrode, a step of forming an interlayer insulating film over the entire surface of the transparent substrate; Including a step of providing a contact hole in a portion of the interlayer insulating film located on the storage capacitor line, and the drain electrode and the pixel electrode are electrically connected through the contact hole when the pixel electrode is formed. It is characterized by.

  The invention according to claim 13 corresponds to the thin film transistor and auxiliary capacitance line of the pixel electrode before forming the pixel electrode in the method of manufacturing a liquid crystal display device according to any one of claims 7 to 12. The method further includes a step of forming a reflection plate so as to cover the rear surface of the position or the entire rear surface of the pixel electrode.

  By providing the above configuration, the present invention has the following excellent effects. That is, according to the invention according to claim 1 of the present application, the drain electrode connected to the pixel electrode through the insulating layer provided on the surface of the auxiliary capacitance line is provided, and the thickness of the insulating film is Since the thickness of the gate insulating film is smaller than that of the gate insulating film, and this insulating layer forms a dielectric layer of the auxiliary capacitance, the auxiliary capacitance can be dramatically increased. A liquid crystal display device capable of suppressing display defects such as flicker can be obtained.

  That is, 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. In particular, on the gate electrode of the TFT, at the intersection of the scanning line, the auxiliary capacitance line and the signal line, In order to maintain the breakdown voltage, it is impossible to reduce the thickness of the gate insulating film. However, in the invention according to claim 1, at least the thickness of the gate insulating film necessary for maintaining the electrostatic withstand voltage is secured on the gate electrode and at the intersection of the scanning line and the auxiliary capacitance line and the signal line. Since the insulating layer is thinly formed on the surface of the auxiliary capacitance line, the above-described effects can be obtained without adversely affecting other configurations.

  In addition, since a semiconductor is provided on the surface of the gate insulating film at the intersection of the scanning line, the auxiliary capacitance line, and the signal line, the semiconductor layer can be used as a mask during etching, and the presence of this semiconductor layer. Since local concentration of static electricity does not occur, electrostatic withstand voltage is improved. Note that amorphous silicon (a-Si) or polysilicon (p-Si) can be used for the semiconductor layer, but a-Si is better because the formation temperature is low.

  Further, according to the inventions according to claims 2 and 3, since the gate insulating film is formed on the entire transparent substrate as in the conventional example, an insulating layer in which the thickness of the gate insulating film is reduced only at necessary portions can be formed. In particular, a liquid crystal display device that can achieve the effect of the invention according to claim 1 without increasing the number of man-hours can be obtained.

  According to the invention of claim 4, the thickness of the gate insulating film is 2500 to 5500 mm so that the insulation is not impaired, and the insulating layer is as thin as 500 to 1500 mm. Therefore, the auxiliary capacity can be greatly increased compared to the conventional example. Note that the thickness of the gate insulating film is more preferably 2800 mm or more, and the thickness of the insulating layer is more preferably about 1000 mm.

  According to the invention of claim 5, 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.

  According to the invention of claim 6, a transflective liquid crystal display device can be easily obtained by providing a reflector on the back surface of the pixel electrode corresponding to the thin film transistor and the auxiliary capacitance line. If a reflective plate is provided so as to cover the entire back surface of the pixel electrode, a reflective liquid crystal display device can be easily obtained.

  Further, according to the invention according to claim 7, in addition to being able to easily manufacture the liquid crystal display device having the effect of the invention according to claim 1, the gate insulating film and the semiconductor layer are successively and successively formed. Therefore, compared with a method of forming a semiconductor layer after forming a gate insulating film and an etching process, the number of steps of maintaining the periphery of the substrate from a normal pressure state to a vacuum state can be reduced once. In addition, since the semiconductor layer with the insulating layer remaining on the surface of the auxiliary capacitance line can be formed by etching, the lithography process can be reduced once, and contamination generated in the gate insulating film etching process can be reduced. The TFT characteristics are less likely to deteriorate because it is less susceptible to the effects of nations.

  Further, according to the inventions according to claims 8 and 9, when forming the multi-layer gate insulating film, the composition is substantially the same by simply changing the substrate temperature without changing the ambient atmosphere. However, it is possible to form a gate insulating film having a multi-layer structure different from each other and to easily leave only an insulating layer having a predetermined thickness by etching using the difference in physical properties. 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, aluminum oxide or the like can be used as the gate insulating film forming material.

  According to the invention of claim 10, a multilayer structure comprising thin films having different compositions by simply changing the ambient atmosphere using the same gate insulating film generating material when forming a gate insulating film having a multilayer structure. In addition, only the insulating layer on the surface of the auxiliary capacitance line can be left by etching using the difference in physical properties based on the difference in composition. 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 form a 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.

  Moreover, according to the invention which concerns on Claims 11-13, the liquid crystal display device of the invention which concerns on Claims 4-6 can be manufactured, respectively.

  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.

  FIG. 1 is an enlarged plan view of a portion corresponding to one pixel of an array substrate seen through a color filter substrate of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a plan view of the liquid crystal display device of FIG. FIGS. 3A to 3J are cross-sectional views showing a manufacturing process for manufacturing the array substrate of the liquid crystal display device of FIG. 3A to 3J show the state of the position corresponding to the AA cross section of FIG.

  In the liquid crystal display device 10 of the present 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 (illustrated). And the liquid crystal layer 15 is sealed inside.

  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 in parallel between the plurality of scanning lines 16, a source electrode S, An ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide) provided so as to cover a region surrounded by the TFT composed of the gate electrode G, the drain electrode D, and the semiconductor layer 19 and the scanning line 16 and the signal line 17. And a transparent pixel electrode 20 made of the like. Note that amorphous silicon (a-Si) is usually used as the semiconductor layer 19 of the TFT, but polysilicon (p-Si) may be used in some cases.

  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 provided so as to cover the color filter 22 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, and further, color complementary color display. In this case, the color filter may be composed of more kinds of color filters instead of the three primary colors.

  Next, a manufacturing process of the array substrate 13 of the above-described liquid crystal display device will be described 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, a plurality of scanning lines 16 extending in the lateral direction, the gate electrodes G, and these A storage capacitor line 18 is formed between each of the plurality of scanning lines 16. In FIG. 3B, 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 also 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. 3 (c), the transparent substrate 11 on which the scanning lines 16 and the auxiliary capacitance lines 18 are formed by the above-described process is surfaced by a plasma CVD (Chemical Vapor Deposition) method or the like in a vacuum apparatus according to a conventional method. A gate insulating film 25 made of silicon nitride having a predetermined thickness (for example, 4000 mm) is formed, 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 gate insulating film 25. (For example, an a-Si layer 1800 Å and an n ⁺ a-Si layer 500 Å). Both the gate insulating film 25 and the semiconductor layer 19 can be continuously formed without taking out the transparent substrate 11 from the vacuum apparatus. Note that the thickness of the gate insulating film is preferably 2500 to 5500 mm so as not to cause dielectric breakdown due to static electricity at least on the surface of the gate electrode G of the TFT.

Thereafter, as shown in FIG. 3D, the semiconductor layer is formed on the surface of the gate electrode G of the TFT, the surface of the gate insulating film 25 at the position corresponding to the intersection of the scanning line 16 and the auxiliary capacitance line 18 and the signal line 17, respectively. The semiconductor layer 19 is removed by dry etching so that 19 _G , 19 ₁ and 19 ₂ remain. Next, as shown in FIG. 3 (e), these semiconductor layers 19 _G , 19 ₁ and 19 ₂ are used as etching masks, and the portions not covered by the semiconductor layers 19 _G , 19 ₁ and 19 ₂ are formed. A part of the gate insulating film is removed by wet etching or dry etching with buffered hydrofluoric acid to form an insulating layer 26 having a predetermined thickness (for example, 1000 mm). In this case, since the gate insulating film 25 is a single layer film, the insulating layer 26 having a predetermined thickness can be obtained by controlling the etching time.

Next, after a conductive material is deposited on the transparent substrate 11, as shown in FIG. 3F, a plurality of signal lines 17 extending in a direction orthogonal to the scanning lines 16 are extended from the signal lines 17. a source electrode S connected to the semiconductor layer 19 _G, and is patterned drain electrode D having one end connected to the semiconductor layer 19 _G covers the upper storage capacitor electrode 18a. As a result, a TFT serving as a switching element is formed near the intersection of the transparent substrate 11 with the scanning line 16 and the signal line 17.

  Further, as shown in FIG. 3G, 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 in FIG. 3 (h), after an interlayer film 29 made of an organic insulating material such as polyimide for planarizing the surface of the array substrate 13 is formed, etching is performed as shown in FIG. 3 (i). Contact holes 30 are formed in the interlayer film 29 and the protective insulating film 28 located on the auxiliary capacitance electrode 18a. 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. 3J, 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 manufactured through the above steps.

  The auxiliary capacitance of the array substrate 13 formed by the above-described manufacturing method is such that the auxiliary capacitance electrode 18a and the drain electrode D connected to the pixel electrode 20 correspond to the electrode of the capacitor, and between the auxiliary capacitance electrode 18a and the drain electrode D. The insulating layer 26 disposed on the insulating layer 26 corresponds to the dielectric of the capacitor, and the thickness of the dielectric made of the insulating layer 26 is significantly thinner than the conventionally used thickness of 2500 to 4500 mm of the gate insulating film. Since it is 1000 mm, the auxiliary capacity can be increased dramatically without increasing the area of the auxiliary capacity electrode 18a.

Further, the gate insulating film 25 provided at the surface corresponding to the surface of the gate electrode G of the TFT, the intersection of the scanning line 16 and the auxiliary capacitance line 18 and the signal line 17 is as thick as 2500 to 5500 mm. Therefore, insulation is sufficiently secured. In addition, semiconductor layers 19 ₁ and 19 ₂ are provided between the signal line 17 and the surface of the gate insulating film 25 provided at a position corresponding to the intersection of the scanning line 16 and the auxiliary capacitance line 18 and the signal line 17, respectively. since the signal line 17 is laminated via, for so localize the static electricity is not generated by the presence of the semiconductor layer 19 ₁ and 19 ₂ even static electricity applied to the signal line 17, the electrostatic breakdown voltage is improved .

  As described above, according to the liquid crystal display device of the present invention, the auxiliary capacitance can be increased without increasing the area of the auxiliary capacitance electrode 18a, so that the crosstalk can be reduced without reducing the aperture ratio for each pixel. In addition, display defects such as flicker can be suppressed.

  In addition, according to the method for manufacturing a liquid crystal display device of the present invention, since the gate insulating film and the semiconductor layer are successively formed, the semiconductor layer is formed after the gate insulating film is formed and etched. Compared with the method used, the number of steps of maintaining the periphery of the substrate from the normal pressure state to the vacuum state can be reduced by one time, and the semiconductor layer with the insulating layer remaining on the surface of the auxiliary capacitance line is formed by etching as a mask. Therefore, the lithography process can be reduced once, and the TFT characteristics are less likely to be deteriorated because it is less susceptible to contamination caused by the etching process of the gate insulating film.

  In the present invention, a transflective or reflective liquid crystal display device can be obtained by providing a reflector made of a light reflecting material between the pixel electrode 20 and the interlayer film 29 or on the surface of the pixel electrode 20. . That is, in the case of a transflective liquid crystal display device, it is only necessary to provide the reflector in a region overlapping with the TFT and the auxiliary capacitance electrode 18a in a plan view, and in the case of a reflective liquid crystal display device. In this case, a reflector may be provided in a region overlapping with the pixel electrode. In this case, it is preferable to form fine irregularities on the surface of the interlayer film 29 on which the reflection plate is provided, because the viewing angle of the reflection portion becomes wide.

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

  Furthermore, the gate 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, it is preferable to bring a film having a high etching rate to the uppermost layer, and from the viewpoint of insulation, the uppermost layer is preferably made of a silicon nitride film.

FIG. 3 is an enlarged plan view of one pixel of an array substrate that is seen through a color filter substrate of a liquid crystal display device according to an embodiment of the present invention. It is AA sectional drawing of FIG. FIG. 3A to FIG. 3J are cross-sectional views showing the manufacturing process of the array substrate of the liquid crystal display device of FIG. 4A is a plan view of a conventional array substrate, and FIG. 4B is a cross-sectional view taken along line XX in FIG. 4A.

Explanation of symbols

10 liquid crystal display device 11, 12 transparent substrate 13 the array substrate 14 a color filter substrate 15 liquid crystal layer 16 scanning lines 17 signal lines 18 auxiliary capacitance line 18a auxiliary capacitance electrodes 19,19 _{G, 19} 1, _{19 2} semiconductor layer 20 pixel electrode 22 Color Filter 23 Common electrode 24 Conductive material layer 25 Gate insulating film 26 Insulating layer 28 Protective insulating film 29 Interlayer film 30 Contact hole

Claims (13)

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 intersection of the scanning line and the signal line and the intersection of the storage capacitor line and the signal line are separated by a gate insulating film and a semiconductor layer provided independently of each other,
Further, the drain electrode of the thin film transistor is extended on the surface of the auxiliary capacitance line through an insulating layer thinner than the thickness of the gate insulating film.   The liquid crystal display device according to claim 1, wherein the gate insulating film and the insulating layer are made of the same material.   2. The liquid crystal display device according to claim 1, wherein the gate insulating film has a multilayer structure, and the insulating layer is made of the same material as at least one layer of the gate insulating film having the multilayer structure.   2. The liquid crystal display device according to claim 1, wherein the gate insulating film has a thickness of 2500 to 5500 mm, and the insulating layer has a thickness of 500 to 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 a portion of the drain electrode extending on the auxiliary capacitance line are electrically connected.   6. The reflector according to claim 1, wherein a reflection plate is formed so as to cover a back surface of the pixel electrode located on the thin film transistor and the auxiliary capacitance line, or an entire back surface of the pixel electrode. Liquid crystal display device. A step of arranging a plurality of scanning lines and auxiliary capacitance lines connected to the gate electrode of the thin film transistor in parallel with each other on a transparent substrate;
Sequentially forming a gate insulating film and a semiconductor layer so as to cover the entire surface of the transparent substrate;
Selectively removing the semiconductor layer leaving a position corresponding to the surface of the gate electrode, the intersection of the scanning line and the auxiliary capacitance line and the signal line;
Removing a part of the exposed gate insulating film by etching to form an insulating layer thinner than the thickness of the gate insulating film;
A plurality of signal lines are provided in a direction perpendicular to the scanning lines on the surfaces of the semiconductor layer and the insulating layer located on the scanning lines and the auxiliary capacitance lines, and a source electrode of the thin film transistor is provided near the intersection of the scanning lines and the signal lines. Providing a drain electrode and extending the drain electrode so as to cover an insulating layer on the auxiliary capacitance line to form an auxiliary capacitance;
Forming a pixel electrode in each of a plurality of regions surrounded by the scanning line and the signal line, and electrically connecting the pixel electrode to a drain electrode of the thin film transistor;
A method of manufacturing a liquid crystal display device comprising:   8. The method of manufacturing a liquid crystal display device according to claim 7, wherein the gate insulating film has a multilayer structure by changing the substrate temperature for each layer using the same raw material.   9. The method of manufacturing a liquid crystal display device according to claim 8, wherein the substrate temperature is highest when the first gate insulating film is formed and gradually decreases when a further gate insulating film is formed.   8. The method of manufacturing a liquid crystal display device according to claim 7, wherein the gate insulating film has a multi-layer structure having a different composition by changing a component of ambient gas in each layer using the same raw material. .   The method of manufacturing a liquid crystal display device according to claim 7, wherein the gate insulating film has a thickness of 2500 to 5500 mm, and the insulating layer has a thickness of 500 to 1500 mm.   Forming the interlayer insulating film on the entire surface of the transparent substrate before forming the pixel electrode; and providing a contact hole in a portion of the interlayer insulating film located on the auxiliary capacitance line, 8. The method of manufacturing a liquid crystal display device according to claim 7, wherein the drain electrode and the pixel electrode are electrically connected through a contact hole when forming the electrode.   Before forming the pixel electrode, the method further comprises a step of forming a reflector so as to cover the back surface of the pixel electrode corresponding to the thin film transistor and the auxiliary capacitance line or the entire back surface of the pixel electrode. The manufacturing method of the liquid crystal display device in any one of Claims 7-12.

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