JP4355552B2 - Manufacturing method of liquid crystal display element - Google Patents

Description

The present invention relates to the production how the liquid crystal display device comprising an active matrix substrate.

  A liquid crystal display element including an active matrix substrate having a thin film transistor (hereinafter referred to as “TFT”) as a switching element of a pixel, which is a minimum unit of an image, has recently been reduced in size and definition and used as a liquid crystal light valve of a liquid crystal projector. It's being used.

  For example, in Patent Documents 1 and 2, in a liquid crystal display element for use in a liquid crystal projector that is used under a large amount of light and has a small area per pixel, means for improving the light resistance of TFT and increasing the aperture ratio of the pixel Is disclosed.

  Such a liquid crystal display element includes an active matrix substrate in which a plurality of pixel electrodes are arranged in a matrix, a counter substrate in which a common electrode is provided so as to face the plurality of pixel electrodes, and a space between the two substrates. And a liquid crystal layer sandwiched between the two.

  By the way, the TFT has a gate electrode, a source electrode, and a drain electrode, and a switching element configured to generate a current between the source electrode and the drain electrode when the gate electrode becomes a high potential. It is.

  In addition, since the drain electrode and the pixel electrode of the TFT are usually formed in different layers, the pixel electrode is connected to the drain electrode through a contact hole.

  FIG. 13 is a schematic cross-sectional view of the periphery of the drain electrode 10a when the pixel electrode 13 is formed in a conventional active matrix substrate. Note that components below the drain electrode 10a are omitted as the base film 8 '.

  In the active matrix substrate shown in FIG. 13A, the drain electrode 10a is provided on the base film 8 ', and the interlayer insulating film 11 is provided so as to cover the drain electrode 10a. A pixel electrode 13 is provided on the interlayer insulating film 11 and is connected to the drain electrode 10 a through the contact hole 12. Further, a pixel electrode forming mask 15 for forming the pixel electrode 13 is provided on the upper layer of the pixel electrode 13.

  In this active matrix substrate, the position of the outer peripheral edge of the pixel electrode 13 is located at the bottom of the contact hole 12, and the manufacturing process such as misalignment and line width variation when the pixel electrode forming mask 15 is formed in a pattern is considered. When the variation occurs, the position of the outer peripheral edge of the pixel electrode 13 varies within the bottom of the contact hole 12. For this reason, the size of the contact area between the pixel electrode 13 and the drain electrode 10a varies, and the contact resistance of both varies. As a result, the charge due to the original image signal cannot be written to the pixel electrode, and the display quality of the image is lowered.

Therefore, as shown in FIG. 13B, a means is employed in which the position of the outer peripheral edge of the pixel electrode 13 is outside the contact hole 12 so that the pixel electrode 13 covers the entire bottom surface of the contact hole 12. .
JP 2002-215064 A JP 2002-49048 A

  In this active matrix substrate, the position of the outer peripheral edge of the pixel electrode 13 is outside the contact hole 12, that is, by providing the pixel electrode 13 with the overlap portion P3, the contact portion P4 between the pixel electrode 13 and the drain electrode 10a. The contact area between the two electrodes is suppressed. However, in manufacturing an active matrix substrate, it is necessary to consider a certain degree of variation in the manufacturing process. However, since a high aperture ratio of the pixel is required, it is difficult to reliably provide the overlap portion P3 in the pixel electrode 13. It is.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a method for manufacturing a liquid crystal display element in which variation in contact resistance between a switching element and a pixel electrode is easily and reliably suppressed, and An object of the present invention is to provide a liquid crystal display element and a liquid crystal projector using the same.

  The method for manufacturing a liquid crystal display element according to the present invention includes a plurality of pixel electrodes provided in a matrix, and provided on the lower layer side through an interlayer insulating film corresponding to each of the plurality of pixel electrodes. A switching element connected to a corresponding pixel electrode through a contact hole formed in a film, and a method of manufacturing a liquid crystal display element having an active matrix substrate, the step of forming the switching element on the substrate Forming an interlayer insulating film so as to cover the switching element; forming a contact hole reaching the switching element in the interlayer insulating film; and forming a pixel electrode so as to cover the interlayer insulating film and the contact hole Forming a conductive film for forming, and forming an insulating layer so as to fill the contact hole; The step of forming the insulating layer includes: forming an insulating coating film so as to cover the conductive film; forming a resist film so as to cover the insulating coating film; and exposing the resist film And a step of forming a pixel electrode forming mask by developing, and a step of etching and removing a portion of the insulating coating film exposed from the pixel electrode forming mask.

  According to the above manufacturing method, first, an interlayer insulating film is formed so as to cover the switching element, then a contact hole reaching the switching element is formed in the interlayer insulating film, and then the interlayer insulating film and A conductive film for pixel electrode formation is formed so as to cover the contact hole, and then an insulating coating film is formed so as to cover the conductive film, and then a resist is formed so as to cover the insulating coating film. A film is formed, and then the resist film is exposed and developed to form a pixel electrode forming mask, and then the portion of the insulating coating film exposed from the pixel electrode forming mask is removed by etching. As a result, an insulating coating film can be left in the contact hole. Thereby, an insulating layer made of an insulating coating film can be formed in the contact hole.

  Therefore, when etching the conductive film, the conductive film in the contact hole is not etched because it is covered with the insulating layer, and the contact area between the conductive film and the switching element is substantially the same as the area of the bottom of the contact hole. , Always constant. As a result, fluctuations in contact resistance between the switching element and the pixel electrode formed of the conductive film are easily and reliably suppressed.

  Etching a portion of the conductive film exposed from the pixel electrode formation mask to form a pixel electrode, and removing the pixel electrode formation mask may be further included.

  According to the above manufacturing method, first, a portion of the conductive film exposed from the pixel electrode formation mask is etched to form a pixel electrode, and then the pixel electrode formation mask is removed. Therefore, when the pixel electrode is formed by etching the conductive film, the conductive film in the contact hole is not etched because it is covered with the insulating layer, and the contact area between the conductive film and the switching element is the contact hole. It remains approximately the same as the bottom area. As a result, fluctuations in contact resistance between the switching element and the pixel electrode formed from the conductive film are suppressed.

  In the step of forming the insulating coating film, the insulating coating film may be a non-photosensitive film.

  According to the above manufacturing method, since the insulating coating film is a non-photosensitive film, the insulating coating film can be removed at the same time when the pixel electrode forming mask is removed. Thereby, the insulating coating film can be removed without increasing the number of steps.

  In the step of forming the insulating coating film, the insulating coating film may be formed by a coating method.

  According to the above manufacturing method, since the insulating coating film is formed by the coating method, it is not necessary to increase the film thickness of the insulating coating film in order to fill the contact hole as in the prior art. Thereby, the cost required for forming the insulating coating film and the cost required for removing the unnecessary insulating coating film by etching can be suppressed.

  In the step of forming the pixel electrode forming mask, the pixel electrode forming mask may be formed so that an outer peripheral edge thereof crosses the contact hole.

Conventionally, in order to suppress variation in contact resistance between the switching element and the pixel electrode, the pixel electrode is formed so as to reach the bottom and the other end from one end of the contact hole, and is overlapped from the other end. However, according to the manufacturing method of the present invention, variation in contact resistance between the switching element and the pixel electrode is suppressed, and the pixel electrode forming mask has a contact hole at the outer peripheral end. Therefore, an overlap portion extending from the other end of the contact hole is not formed. Therefore, the size of the switching element connected to the conductive film can be reduced by the overlap portion. Thereby, since the size of the light-shielding switching element is reduced, it is possible to suppress a decrease in the aperture ratio of the pixel .

  As described above, according to the method for manufacturing a liquid crystal display element of the present invention, since the insulating layer is provided on the conductive film in the contact hole, the contact resistance between the switching element and the pixel electrode varies. Deterred.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
The liquid crystal display element according to Embodiment 1 of the present invention will be described below.

  FIG. 1 shows a cross-sectional structure of a liquid crystal display element 100 according to Embodiment 1 of the present invention. FIG. 2 shows a planar structure of an active matrix substrate 50a constituting the liquid crystal display element 100. 1 is a schematic cross-sectional view taken along a cross-section C-C ′ in FIG. 2.

  The liquid crystal display element 100 includes an active matrix substrate 50, a counter substrate 60 provided so as to face the active matrix substrate 50, and a liquid crystal layer 70 provided so as to be sandwiched between the two substrates 50 and 60. And.

  The active matrix substrate 50 includes a plurality of scanning wirings 6 provided so as to extend in parallel with each other, a plurality of signal wirings 10 provided so as to extend in parallel with each other in a direction orthogonal to the scanning wirings 6, and A TFT 22 provided near the intersection of each of the scanning wiring 6 and the signal wiring 10, a pixel electrode 13 provided in a display area surrounded by the pair of scanning wirings 6 and the signal wiring 10 corresponding to each TFT 22, and scanning And a plurality of capacitance lines 6b provided so as to extend in parallel with each other.

  The active matrix substrate 50 has a multilayer laminated structure in which the lower insulating film 3, the gate insulating film 5, the first interlayer insulating film 8, and the second interlayer insulating film 11 are sequentially stacked on the insulating substrate 1.

  A lower light shielding film 2 is provided between the insulating substrate 1 and the lower insulating film 3. The lower light-shielding film 2 blocks light incident from the insulating substrate 1 into a channel region 4a of the TFT 22 described later, and suppresses the generation of leakage current due to light.

  A semiconductor film 4 constituting the TFT 22 is provided between the lower insulating film 3 and the gate insulating film 5. The semiconductor film 4 has a channel region 4a corresponding to a gate electrode 6a described later, an LDD region 4b on both sides of the channel region 4a, a source electrode region 4c and a drain electrode region 4d outside the LDD region 4b, Each has. Further, a portion of the drain electrode region 4d facing the capacitor line 6b is an auxiliary capacitor electrode.

  Between the gate insulating film 5 and the first interlayer insulating film 8, a scanning wiring 6 and a capacitor line 6b are provided. The scanning wiring 6 has a gate electrode 6 a that protrudes in the extending direction of the signal wiring 10 corresponding to each TFT 22. The capacitor line 6 b has a protruding portion so as to overlap the signal wiring 10, and constitutes an auxiliary capacitor together with the auxiliary capacitor electrode via the gate insulating film 5.

  Between the first interlayer insulating film 8 and the second interlayer insulating film 11, the signal wiring 10 connected to the source electrode region 4c through the first contact hole 9a and the second contact hole 9b to the drain electrode region 4d are provided. And a drain electrode 10a connected to each other.

  A pixel electrode 13 connected to the drain electrode 10 a through the third contact hole 12 is provided on the second interlayer insulating film 11, and an alignment film 16 is provided on the pixel electrode 13.

  The counter substrate 60 is a multilayer stack in which a color filter layer (not shown), a black matrix (not shown), an overcoat layer (not shown), a common electrode 17 and an alignment film 16 ′ are sequentially stacked on an insulating substrate 1 ′. It has a structure.

  The liquid crystal layer 70 is made of a nematic liquid crystal material having electro-optical characteristics.

  In the liquid crystal display element 100, one pixel is formed for each pixel electrode 13. When a gate signal is sent from the scanning wiring 6 and the TFT 22 is turned on in each pixel, the signal wiring 10 A source signal is sent and a predetermined charge is written into the pixel electrode 22 via the source electrode region 4c and the drain electrode region 4d, and a potential difference is generated between the pixel electrode 13 and the common electrode 17, and the liquid crystal layer A predetermined voltage is applied to the liquid crystal capacitor 70 and the auxiliary capacitor 70. Then, by changing the alignment state of the liquid crystal molecules of the liquid crystal layer 70 according to the applied voltage, the transmittance of light incident from the outside is adjusted to display an image.

  Next, a manufacturing method of the liquid crystal display element according to Embodiment 1 of the present invention will be described.

<Active matrix substrate creation process>
Here, a method for manufacturing the active matrix substrate 50a, which is a feature of the present invention, will be described with reference to FIGS. 3, 4, 5, and 6. FIG.

  FIG. 3 shows a flow of the first half of the manufacturing process in the B-B ′ cross section of the active matrix substrate 50 a of FIG. 2. FIG. 4 shows a flow in the latter half of the production process.

  FIG. 5 shows a flow of the first half of the manufacturing process in the C-C ′ cross section of the active matrix substrate 50 a of FIG. 2. FIG. 6 shows a flow in the latter half of the manufacturing process.

  In addition, the alphabet in the parenthesis in the figure indicates a stage in the manufacturing process, and the alphabet in the parenthesis is between FIG. 3 and FIG. 5 corresponding to each other or between FIG. 4 and FIG. If the same, both indicate the same stage in the fabrication process. For example, FIG. 3B is the same stage as FIG. 5B, and FIG. 4C is the same stage as FIG. 6C.

  First, a polysilicon film (thickness of about 100 nm) doped with phosphorus (P) and a tungsten silicide film (thickness of about 100 nm) are sequentially formed on an insulating substrate 1 such as quartz glass by a CVD (Chemical Vapor Deposition) method. After the film formation, the lower light-shielding film 2 is formed by pattern formation by a photolithography technique (Photo Engraving Process, hereinafter referred to as “PEP technique”).

  Next, a silicon oxide film (having a thickness of about 400 nm) is formed on the entire substrate on the gate line 2 by the CVD method, and the lower insulating film 3 is formed.

Next, a polysilicon film (thickness of about 40 nm) is formed on the lower insulating film 3 by the CVD method, and after pattern formation by the PEP technique, phosphorus (P) is implanted at about 3 × 10 ¹⁵ cm ^−2. As shown in FIGS. 3A and 5A, the semiconductor film 4 is formed. Further, impurity ions may be implanted to adjust the threshold voltage of the TFT 22.

  Next, a silicon oxide film (having a thickness of about 100 nm) is formed on the entire substrate on the semiconductor film 4 by a CVD method to form the gate insulating film 5. The gate insulating film 5 may be formed by using a method of oxidizing a silicon film, or both methods in addition to the above-described CVD method.

  Next, a polysilicon film (thickness of about 150 nm) doped with phosphorus (P) and a tungsten silicide film (thickness of about 150 nm) are sequentially formed on the gate insulating film 5 by the CVD method, and then by the PEP technique. A pattern is formed to form the scanning wiring 6, the gate electrode 6a, and the capacitor line 6b as shown in FIGS. 3 (b) and 5 (b).

Next, about 1 × 10 ¹³ cm ^{−2 is} implanted into the semiconductor film 4 using the gate electrode 6a as a mask.

Next, as shown in FIG. 5C, a first resist 7 is applied so as to cover the gate electrode 6a, and phosphorus is implanted at about 3 × 10 ¹⁵ cm ⁻² using the first resist 7 as a mask. By the implantation of these phosphorus, the channel region 4a is formed in the portion corresponding to the lower layer side of the gate electrode 6a of the semiconductor film 4, and a relatively small amount of phosphorus is applied to the portion covered with the first resist 7 outside thereof. In the implanted LDD region 4b, a source electrode region 4c and a drain electrode region 4d into which a relatively large amount of phosphorus is implanted are formed on both sides of the LDD region 4b.

  Next, after removing the first resist 7, a silicon oxide film (having a thickness of about 400 nm) is formed by CVD on the entire substrate on the scanning wiring 6, the gate electrode 6a, and the capacitor line 6b. 8 is formed.

  Next, portions of the first interlayer insulating film 8 corresponding to the source electrode region 4c and the drain electrode region 4d are removed by etching to form a first contact hole 9a and a second contact hole 9b, respectively.

  Next, a titanium / tungsten film (thickness of about 150 nm), an aluminum film (thickness of about 400 nm), and a titanium / tungsten film (thickness of about 100 nm) are sequentially formed on the entire substrate on the first interlayer insulating film 8 by CVD. After the film formation, a pattern is formed by the PEP technique to form the signal wiring 10 and the drain electrode 10a. Thereby, the signal line 10 is connected to the source electrode region 4c through the first contact hole 9a, and the drain electrode 10a is connected to the drain electrode region 4d through the second contact hole 9b.

  Next, a silicon nitride film (thickness of about 100 nm) and a silicon oxide film (thickness of about 400 nm) are sequentially formed by CVD on the entire substrate on the signal wiring 10 and the drain electrode 10a, and FIG. And as shown in FIG.5 (d), the 2nd interlayer insulation film 11 is formed and a hydrogenation process is performed. If necessary, a film such as a light shielding film, an auxiliary capacitance film, or an electric field shielding film may be formed in the film of the second interlayer insulating film 11.

  Next, the surface of the second interlayer insulating film 11 is planarized by a CMP (Chemical Mechanical Polishing) process. For example, the film thickness of the second interlayer insulating film 11 on the drain electrode 10a is set to about 400 nm by CMP processing.

  Next, a portion of the second interlayer insulating film 11 corresponding to the drain electrode 10a is removed by etching, and a third contact hole 12 is formed.

  Next, an ITO (Indium Tin Oxide) film having a thickness of about 120 nm is formed as a conductive film on the entire substrate on the second interlayer insulating film 11, as shown in FIGS. 3 (e) and 5 (e). Then, the transparent conductive film 13a is formed.

  Next, an insulating coating film 14a (about 500 nm thick) is formed on the entire substrate on the transparent conductive film 13a by a coating method. This insulating coating film 14a is a resist film having no photosensitivity.

  Next, a photosensitive resist film (thickness of about 1000 nm) is formed on the entire substrate on the insulating coating film 14a by a coating method, and the outer peripheral edge thereof crosses the third contact hole 12 by the PEP technique. A pattern is formed, and a pixel electrode forming mask 15 is formed as shown in FIGS. 4 (a) and 6 (a).

  At this time, since the third contact hole 12 is filled with the insulating coating film 14a made of a resist film having no photosensitivity, the insulating coating film 14a in the third contact hole 12 is not patterned.

  Next, using the pixel electrode forming mask 15 as a mask, the exposed portion of the insulating coating film 14a is etched away by anisotropic dry etching, as shown in FIGS. Layer 14 is formed.

  Next, the transparent conductive film 13a is etched using the pixel electrode formation mask 15 and the insulating coating layer 14 as a mask to form the pixel electrode 13 as shown in FIGS. 4C and 6C.

  At this time, since the transparent conductive film 13a in the third contact hole 12 is covered with the insulating coating layer 14, it is not etched. As a result, the contact area between the transparent conductive film 13a and the drain electrode 10a is substantially the same as the area of the bottom of the third contact hole 12 and is always constant. Therefore, the pixel electrode and drain formed from the transparent conductive film 13a are constant. Variation in contact resistance with the electrode 10a is suppressed.

  The surface of the insulating coating film 14a is preferably substantially flat as shown in FIGS. 4 (a) and 6 (a), but the third contact hole as shown in FIG. 7 (a). The 12 corresponding portions may be slightly recessed. In this case, in order to leave the insulating coating film 14a at the bottom of the third contact hole 12 when the insulating coating film 14a is removed by etching, as shown in FIG. It is necessary to make the film thickness Tb in the hole 12 thicker than the film thickness Ta outside the contact hole 12.

  Next, the pixel electrode forming mask 15 and the insulating coating layer 14 are removed, and an active matrix substrate 50a as shown in FIGS. 4D and 6D is manufactured.

  At this time, since the pixel electrode forming mask 15 and the insulating coating layer 14 are both resists, they can be simultaneously removed by using O 2 plasma treatment or resist stripping solution. Thereby, it is not necessary to increase the number of steps in order to remove the insulating coating layer 14.

  Further, after a polyimide resin thin film is formed by a printing method, an alignment treatment is performed on the surface by a rubbing method to form an alignment film 19.

  As described above, the active matrix substrate 50 constituting the present invention can be manufactured.

  In the first embodiment, a resist film having no photosensitivity is used as the insulating coating layer 14, but a non-photosensitive SOG (Spin on Glass) film or a resin film (for example, a polyimide resin or an acrylic resin) is used. It is possible. In that case, the insulating coating layer 14 cannot be removed simultaneously with the removal of the pixel electrode forming mask 15, and it is necessary to remove the insulating coating layer 14 in a separate process. It is also effective to leave the insulating coating layer 14 in the hole 12 and form an insulating layer 14 'as shown in FIGS. 8D and 9D of the second embodiment described later. The effectiveness will be described in the second embodiment.

<Opposite substrate manufacturing process>
A chromium thin film having a thickness of about 100 nm is formed on the insulating substrate 1 ′, and then a pattern is formed by the PEP technique to form a black matrix.

  Next, a color filter layer is formed by patterning any one of red, green and blue colored layers with a thickness of about 2 μm between the black matrices.

  Next, an acrylic resin is applied to the entire substrate on the color filter layer with a thickness of about 1 μm to form an overcoat layer.

  Next, a common electrode 17 is formed by forming an ITO (Indium Tin Oxide) film with a thickness of about 100 nm on the entire substrate on the overcoat layer.

  Next, after a thin film of polyimide resin is formed by a printing method, an alignment treatment is performed on the surface by a rubbing method to form an alignment film 16 '.

  As described above, the counter substrate 60 constituting the present invention can be manufactured.

<Liquid crystal display element manufacturing process>
A seal portion made of a thermosetting resin is formed on the active matrix substrate 50 by a printing method, and a counter substrate 60 is bonded together, and then a liquid crystal material is injected between the substrates 50 and 60 by a decompression method and sealed. Then, the liquid crystal layer 70 is formed.

  As described above, the liquid crystal display element 100 of the present invention can be manufactured.

  As described above, according to the manufacturing method of the present invention, when the pixel electrode 13 is formed by etching the transparent conductive film 13a, the insulating coating layer 14 is formed on the transparent conductive film 13a in the third contact hole 12. Will be provided. Therefore, the transparent conductive film 13a in the third contact hole 12 is not etched because it is covered with the insulating coating layer 14, and the contact area between the transparent conductive film 13a and the drain electrode 10a of the TFT 22 is equal to that of the third contact hole 12. It is almost the same as the bottom area and is always constant. Thereby, fluctuations in contact resistance between the drain electrode 10a of the TFT 22 and the pixel electrode 13 formed from the transparent conductive film 13a are suppressed.

  In addition, the variation in contact resistance between the drain electrode 10a of the TFT 22 and the pixel electrode 13 is suppressed, and the pixel electrode forming mask 15 is formed so that the outer peripheral edge thereof crosses the third contact hole 12. The overlap portion P3 extending from the other end of the contact hole 12 that is necessary to suppress the variation in contact resistance between the drain electrode 10a of the TFT and the pixel electrode 13 is not formed. Therefore, the size of the TFT 22 connected to the transparent conductive film 13a can be reduced by the overlap portion. Thereby, since the size of the light-shielding TFT 22 (drain electrode 10a) is reduced, it is possible to suppress a decrease in the aperture ratio of the pixel.

  FIG. 11 is a schematic configuration diagram of a liquid crystal projector 200 of the present invention.

  The liquid crystal projector 200 includes a reflector 25, a light source 26, a condenser lens 27, the liquid crystal display element 100 of the present invention, a projection lens 28, and a screen 29.

  The reflector 25 is provided with a reflective film on the surface thereof, and efficiently collects the light emitted from the light source 26 and puts it in the condenser lens 27.

  When the liquid crystal projector 200 displays an image, the light emitted from the light source 26 is put into the liquid crystal display element 100 via the condenser lens 27, and the liquid crystal display element 100 creates an image as described above. The enlarged image is displayed on the screen 29 by projecting the image onto the screen 29 via the projection lens 28.

  In the present embodiment, a single-plate type liquid crystal projector is illustrated as the liquid crystal projector 200. However, if the liquid crystal display element 100 is configured except for the color filter layer, the present invention can also be applied to a three-plate type liquid crystal projector. .

  Since the liquid crystal projector 200 is constituted by the liquid crystal display element 100 of the present invention, the area per pixel is small, and the display quality is high even when used under a large amount of light.

<< Embodiment 2 of the Invention >>
The liquid crystal display element according to Embodiment 2 of the present invention will be described below.

  Since the configuration of the liquid crystal display element according to the second embodiment of the present invention is substantially the same as that of the first embodiment, the description thereof is omitted.

  Next, a method for manufacturing a liquid crystal display element according to Embodiment 2 of the present invention will be described.

<Active matrix substrate creation process>
Here, a manufacturing method of the active matrix substrate 50b which is a feature of the present invention will be described with reference to FIGS.

  FIG. 8 shows a flow in the latter half of the manufacturing process corresponding to the B-B ′ cross section of the active matrix substrate 50 a of FIG. 2. FIG. 9 shows a flow of the latter half of the manufacturing process corresponding to the C-C ′ cross section of the active matrix substrate 50 a of FIG. 2.

  The first half of the manufacturing method of the active matrix substrate is the same as the steps shown in FIGS. 3 and 5 used in the first embodiment. That is, the process shown in FIG. 8A follows the process shown in FIG. 3E, and the process shown in FIG. 9A follows the process shown in FIG. . Therefore, detailed description of the first half process is omitted.

  As in the first embodiment, the alphabets in parentheses in the figure indicate stages in the manufacturing process. If the alphabets in parentheses are the same between FIGS. 8 and 9 corresponding to each other, It shows the same stage in the manufacturing process.

  First, an active matrix substrate intermediate shown in FIGS. 3E and 5E is prepared.

  Next, an SOG film is applied to the entire substrate on the transparent conductive film 13a by using a spin coating method as a coating method, and then heat-treated, as shown in FIGS. 8A and 9A. A coating film 14a (thickness of about 500 nm) is formed.

  Next, the insulating coating film 14a is etched away (etched back) as shown in FIGS. 8B and 9B so as to leave a portion where the third contact hole 12 is buried.

  Next, a photosensitive resist film (thickness of about 1000 nm) is formed on the entire substrate on the insulating coating film 14a by a coating method, and the outer peripheral edge thereof crosses the third contact hole 12 by the PEP technique. A pattern is formed, and as shown in FIGS. 8C and 9C, a pixel electrode forming mask 15 is formed.

  Next, the transparent conductive film 13 a is etched using the pixel electrode formation mask 15 as a mask to form the pixel electrode 13.

  Next, the pixel electrode formation mask 15 is removed, and as shown in FIGS. 8D and 9D, an active matrix substrate 50b in which an insulating layer 14 ′ is provided in the third contact hole 12 is manufactured. Is done.

  Next, after a polyimide resin thin film is formed by a printing method, an alignment treatment is performed on the surface by a rubbing method to form an alignment film 19.

  As described above, the active matrix substrate constituting the present invention can be manufactured.

<Opposite substrate manufacturing process>
Since the counter substrate manufacturing process is substantially the same as that of the first embodiment, the description thereof is omitted.

<Liquid crystal display element manufacturing process>
Since the liquid crystal display element manufacturing process is substantially the same as that of the first embodiment, the description thereof is omitted.

  As described above, the liquid crystal display element of the present invention can be manufactured.

  As described above, according to the manufacturing method of the present invention, when the pixel electrode 13 is formed by etching the transparent conductive film 13 a, the insulating layer 14 ′ is formed on the transparent conductive film 13 a in the third contact hole 12. Will be provided. Therefore, the transparent conductive film 13a in the third contact hole 12 is not etched because it is covered with the insulating layer 14 ′, and the contact area between the transparent conductive film 13a and the drain electrode 10a of the TFT 22 is equal to that of the third contact hole 12. It is almost the same as the bottom area and is always constant. Thereby, fluctuations in contact resistance between the drain electrode 10a of the TFT 22 and the pixel electrode 13 formed from the transparent conductive film 13a are suppressed.

  Similarly to the first embodiment, since the pixel electrode forming mask 15 is formed so that the outer peripheral edge thereof crosses the third contact hole 12, conventionally, the contact resistance between the drain electrode 10a of the TFT and the pixel electrode 13 is reduced. The overlap portion P3 extending from the other end of the contact hole 12 necessary for suppressing the fluctuation is not formed. Therefore, the size of the TFT 22 connected to the transparent conductive film 13a can be reduced by an amount corresponding to the overlap portion, and a decrease in the aperture ratio of the pixel can be suppressed.

  Furthermore, since the pixel electrode is generally thinner than the diameter of the contact hole, the upper layer of the contact hole has a shape reflecting the concave shape of the contact hole. Therefore, since the surface of the alignment film in contact with the liquid crystal layer is also uneven, when the alignment treatment is performed by rubbing the surface after applying a polyimide resin or the like on the upper layer of the pixel electrode, the alignment treatment cannot be made uniform. It will be. As a result, the orientation of the liquid crystal molecules in the liquid crystal layer is disturbed, and the light transmittance of that portion becomes higher than that of other portions, which may cause a phenomenon of light leakage.

  Here, light leakage means that the light transmittance at a portion where the orientation of liquid crystal molecules is disturbed is higher than that at other portions. Specifically, in the black display image, the pixel in the portion where the orientation of the liquid crystal molecules is disturbed has a high light transmittance, and the black display of the gradation to be originally displayed is not achieved. Therefore, the liquid crystal display element has a display with insufficient contrast. In particular, in a liquid crystal projector that projects an image of a liquid crystal display element with strong light, a high contrast is desired. Therefore, a phenomenon that causes a decrease in contrast called light leakage is important for maintaining and improving display quality. It is a problem.

  Therefore, a buried metal method as disclosed in JP-A-4-45560 and JP-A-7-106586 has been proposed.

  FIG. 12 is a schematic diagram showing a method for forming the pixel electrode 13 by a buried metal method.

  In this formation method, first, as shown in FIG. 12A, a contact hole 18 reaching the drain electrode 10a is formed in the interlayer insulating film 11, and then a tungsten thin film is formed by using, for example, a blanket tungsten CVD (Chemical Vapor Deposition) method. 21 'is formed.

  Next, as shown in FIG. 12B, the tungsten thin film 21 'is etched back until the interlayer insulating film 11 is exposed on the surface, thereby forming a buried metal 21 made of the tungsten thin film 21'.

  Next, as shown in FIG. 12C, a pixel electrode forming film is formed so as to cover the interlayer insulating film 11 and the buried metal 21, and then a pattern is formed to form the pixel electrode 13.

  As a result, the pixel electrode 13 is connected to the drain electrode 10a via the buried metal 21, and the unevenness caused by the contact hole 18 on the surface thereof is eliminated by the buried metal 21, thereby solving the problem of light leakage.

  In general, the contact hole 18 is filled with a metal film by a sputtering method in which an aluminum thin film 19a is formed in the contact hole 18 as shown in FIG. 10A, or as shown in FIG. 9B. There is a blanket tungsten CVD method for forming a tungsten thin film 19b therein. The sputtering method has a problem in film formation on the side and bottom surfaces of the contact hole 18. On the other hand, in the blanket tungsten CVD method, the tungsten thin film 19 b can be grown vertically from the side surface of the contact hole 18.

  However, even in this blanket tungsten CVD method, in order to fill the contact hole 18, it is necessary to form the tungsten thin film 19 b to a film thickness of ½ or more of the diameter of the contact hole 18. A tungsten thin film 19b having a thickness corresponding to that is formed. Therefore, when the tungsten thin film 19b is removed by etching (etch back process) so as to leave a portion in which the contact hole 12 is buried, there is a problem that the amount of the etch back process increases and the processing time and manufacturing cost increase.

  In the present invention, the contact hole 18 is filled by the coating method shown in FIG. In this case, after forming the coating film 20 ′ so as to fill the contact hole 18, the thickness of the coating film 20 on the upper surface of the contact hole 18 can be reduced by rotating the substrate.

  Therefore, in this embodiment, since it is necessary to etch back the insulating coating film 14a filling the third contact hole 12, the etching back is performed by using the above-described coating method for forming the insulating coating film 14a. The amount to be processed is reduced, and the processing time and manufacturing cost can be suppressed.

  Further, as in the first embodiment, the liquid crystal projector including the liquid crystal display element having the active matrix substrate 50b has a small area per pixel and high display quality even when used under a large amount of light. become.

  As described above, the present invention is useful for a liquid crystal projector because it has a small area per pixel and high display quality even when used under a large amount of light.

It is a cross-sectional schematic diagram of the liquid crystal display element 100 which concerns on Embodiment 1 of this invention. It is a plane schematic diagram of the active matrix substrate 50a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the first half of the manufacturing process in the B-B 'cross section of the active matrix substrate 50a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the latter half of the manufacturing process in the B-B 'cross section of the active matrix substrate 50a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the first half of the manufacturing process in the C-C 'cross section of the active matrix substrate 50a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the latter half of the manufacturing process in the C-C 'cross section of the active matrix substrate 50a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the film-forming state of the insulating coating film 14a which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the manufacturing process in the B-B 'cross section of the active matrix substrate 50b which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the manufacturing process in the C-C 'cross section of the active matrix substrate 50b which concerns on Embodiment 2 of this invention. It is a schematic diagram which shows the burying method of the contact hole which concerns on the past and embodiment of this invention. 1 is a schematic configuration diagram of a liquid crystal projector 200 according to an embodiment of the present invention. It is a schematic diagram which shows the formation method of the pixel electrode 13 by the conventional embedded metal method. FIG. 10 is a schematic diagram showing a problem related to a conventional pixel electrode 13.

1, 1 'insulating substrate 2 lower light shielding film 3 lower insulating film 4 semiconductor film 4a channel region 4b LDD region 4c source electrode region 4d drain electrode region 5 gate insulating film 6 scanning wiring 6a gate electrode 6b capacitance line 7 first resist 8 first resist 8 1 interlayer insulating film 8 'base film 9a first contact hole 9b second contact hole 10 signal wiring 10a drain electrode 11 (second) interlayer insulating film 12 (third) contact hole 13 pixel electrode 13a transparent conductive film 14 insulating coating layer 14 'insulating layer 14a insulating coating film 15 pixel electrode forming mask 16, 16' alignment film 17 common electrode 18 contact hole 19a aluminum thin film 19b, 21 'tungsten thin film 20, 20' coating film 21, buried metal 25 reflector 26 light source 27 Condenser lens 28 Projection lens 29 Screens 50, 50a, 0b active matrix substrate 60 counter substrate 70 liquid crystal layer 100 liquid crystal display device 200 liquid crystal projector

Claims (5)

A plurality of pixel electrodes provided in a matrix and corresponding to each of the plurality of pixel electrodes via an interlayer insulating film on the lower layer side and corresponding via a contact hole formed in the interlayer insulating film A liquid crystal display element having an active matrix substrate provided with a switching element connected to a pixel electrode.
Forming a switching element on a substrate;
Forming an interlayer insulating film so as to cover the switching element;
Forming a contact hole reaching the switching element in the interlayer insulating film;
Forming a conductive film for forming a pixel electrode so as to cover the interlayer insulating film and the contact hole;
Forming an insulating layer to fill the contact hole,
The step of forming the insulating layer includes
Forming an insulating coating film so as to cover the conductive film;
Forming a resist film so as to cover the insulating coating film;
Forming a pixel electrode forming mask by exposing and developing the resist film; and
And a step of etching and removing a portion of the insulating coating film exposed from the pixel electrode forming mask. In the manufacturing method of the liquid crystal display element described in Claim 1,
Etching a portion of the conductive film exposed from the pixel electrode formation mask to form a pixel electrode;
Removing the pixel electrode forming mask;
A method for producing a liquid crystal display element, further comprising: In the manufacturing method of the liquid crystal display element described in Claim 1,
A method of manufacturing a liquid crystal display element, wherein in the step of forming the insulating coating film, the insulating coating film is a non-photosensitive film. In the manufacturing method of the liquid crystal display element according to claim 1 or 3,
A method of manufacturing a liquid crystal display element, wherein in the step of forming the insulating coating film, the insulating coating film is formed by a coating method. In the manufacturing method of the liquid crystal display element described in Claim 1,
A method of manufacturing a liquid crystal display element, wherein in the step of forming the pixel electrode forming mask, the pixel electrode forming mask is formed so that an outer peripheral edge thereof crosses the contact hole.

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