Transmission type liquid crystal display device and its production

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a transmissive liquid crystal display device used for a display such as a computer or a television device and provided with a switching element such as a thin film transistor (hereinafter referred to as TFT) as an address element, and a method for manufacturing the same.

【0002】

[Conventional technology]

FIG. 16 is a circuit diagram showing the configuration of a conventional transmissive liquid crystal display device provided with an active matrix substrate.

【0003】

In FIG. 16, a plurality of pixel electrodes 1 are formed in a matrix on the active matrix substrate, and TFT 2 which is a switching element is connected to the pixel electrodes 1 and provided. A gate wiring 3 for supplying a scanning signal is connected to the gate electrode of the TFT 2, and the TFT 2 is driven and controlled by the gate signal input to the gate electrode. Further, a source wiring 4 is connected to the source electrode of the TFT 2 to supply a display signal (data signal), and when the TFT 2 is driven, the data (display) signal is input to the pixel electrode 1 via the TFT 2. The gate wiring 3 and the source wiring 4 pass around the pixel electrodes 1 arranged in a matrix and are provided so as to be orthogonal to each other. Further, the drain electrode of TFT2 is connected to the pixel electrode 1 and the additional capacitance 5, and the counter electrode of the additional capacitance 5 is connected to the common wiring 6, respectively. The additional capacitance 5 is used to hold the voltage applied to the liquid crystal layer. The additional capacitance is provided in parallel with the liquid crystal capacitance including the liquid crystal layer sandwiched between the pixel electrode formed on the active matrix substrate and the counter electrode formed on the counter substrate.

【0004】

FIG. 17 is a cross-sectional view of a TFT portion of an active matrix substrate in a conventional liquid crystal display device.

【0005】

In FIG. 17, a gate electrode 12 connected to the gate wiring 3 of FIG. 16 is formed on the transparent insulating substrate 11, and a gate insulating film 13 is formed over the gate electrode 12 connected to the gate wiring 3 of FIG. Further, a semiconductor layer 14 is formed on the semiconductor layer 14 so as to overlap the gate electrode 12, and a channel protection layer 15 is formed on the central portion thereof. The source electrode 16a and the drain electrode 16b are formed in a state where both ends of the channel protection layer 15 and a part of the semiconductor layer 14 are covered and separated on the channel protection layer 15.⁺A Si layer is formed. One n⁺On the source electrode 16a, which is the Si layer, a metal layer 17a, which is the source wiring 4 of FIG. 16, is formed, and the other n⁺A metal layer 17b connecting the drain electrode 16b and the pixel electrode 1 is formed on the drain electrode 16b, which is a Si layer. Further, an interlayer insulating film 18 is formed so as to cover the upper parts of the TFT 2, the gate wiring 3, and the source wiring 4.

【0006】

A transparent conductive film serving as a pixel electrode 1 is formed on the interlayer insulating film 18, and the transparent conductive film is a metal connected to the drain electrode 16b of TFT2 via a contact hole 19 penetrating the interlayer insulating film 18. Connected to layer 17b.

【0007】

In this way, since the interlayer insulating film 18 is formed between the gate wiring 3 and the source wiring 4 and the transparent conductive film serving as the pixel electrode 1, the pixel electrode 1 overlaps with each of the wirings 3 and 4. Can be made to. Such a structure is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-172685, which can improve the aperture ratio of the liquid crystal display device and shield the electric field caused by the wirings 3 and 4. Discrimination can be suppressed.

【0008】

As the interlayer insulating film 18, conventionally, an inorganic film such as silicon nitride (SiN) has been formed to a film thickness of about 500 nm by a CVD method.

【0009】

[Problems to be Solved by the Invention]

However, SiN, which is a transparent insulating film, is placed on the interlayer insulating film 18._x, SiO₂, TaO_xWhen a film is formed by the CVD method or the sputtering method, the unevenness due to the film thickness of the base film is reflected. Therefore, when the pixel electrode 1 is formed on the film, a step is formed by the step of the base film, and the liquid crystal molecules are formed. There was a problem of causing poor orientation.

【0010】

Further, when a film is formed by applying an organic film such as polyimide to flatten the pixel portion, a mask material is used to form a contact hole for electrically connecting the pixel electrode and the drain electrode. It was necessary to perform patterning, process the contact hole by etching, and finally peel off the unnecessary photoresist. Further, a method of using a photosensitive polyimide film is conceivable in order to shorten the etching and peeling steps, but in this case, the resin after forming the interlayer insulating film appears to be colored, so that the light transmittance is high. In addition, there is a problem that it is not suitable for an interlayer insulating film of a liquid crystal display device that requires transparency.

【0011】

Further, when the interlayer insulating film 18 is formed between the gate wiring 3 and the source wiring 4 and the pixel electrode 1 as in the conventional liquid crystal display device, the pixel electrode 1 overlaps with each of the wirings 3 and 4. The aperture ratio of the liquid crystal display device can be improved. However, when the structure is such that the wirings 3 and 4 and the pixel electrode 1 overlap each other, there is a problem that the capacitance between the wirings 3 and 4 and the pixel electrode 1 increases. In particular, an inorganic film such as a silicon nitride film has a high relative permittivity of 8, and is formed by using the CVD method, and has a film thickness of about 500 nm. With this film thickness, the increase in capacitance between each of the wirings 3 and 4 and the pixel electrode 1 becomes large, and there are problems as shown in (1) and (2) below. In addition, when an attempt is made to form an inorganic film such as a silicon nitride film to a film thickness higher than that, there is a problem that it takes too much time in the manufacturing process.

【0012】

(1) When the structure is such that the source wiring 4 and the pixel electrode 1 overlap, the capacitance between the source wiring 4 and the pixel electrode 1 increases and the signal transmission rate increases, and the pixel electrode during the retention period. The data signal held at 1 will be fluctuated by the potential of the data signal. Therefore, there is a problem that the effective voltage applied to the liquid crystal of the pixel fluctuates, and vertical crosstalk is observed especially for the adjacent pixel in the vertical direction in the actual display.

【0013】

As one of the methods for reducing the influence of the capacitance between the source wiring 4 and the pixel electrode 1 on the display, for example, Japanese Patent Application Laid-Open No. 6-230422 provides data given to the corresponding pixel for each source line. A driving method that inverts the polarity of the signal has been proposed. This driving method was effective for black-and-white display panels that have a high correlation with the display of adjacent pixels, but when the pixel electrodes are arranged in a vertical stripe pattern, as in a normal notebook-type personal computer. (In the case of color display, the shape of the pixel electrode is, for example, a vertical stripe that is a vertically long rectangular shape obtained by dividing a square pixel into three equal parts by R, G, and B). Have different display colors. For this reason, the above-mentioned polarity reversal drive method for each source line was effective in reducing vertical crosstalk in the case of black-and-white display, but was insufficient in reducing crosstalk in the case of general color display. there were.

【0014】

(2) If the pixel electrode 1 and the gate wiring 3 that drives the pixel are overlapped, the capacitance between the gate wiring 3 and the pixel electrode 1 becomes large, and it becomes a switching signal that controls TFT2. As a result, there is a problem that the feed-through of the write voltage to the pixel becomes large.

【0015】

The present invention solves the above-mentioned conventional problems, and can improve the aperture ratio of the liquid crystal display device and suppress the misalignment of the liquid crystal by overlapping the flat pixel electrodes and the respective wirings, and the manufacturing process can be performed. Provided are a transmissive liquid crystal display device and a method for manufacturing the same, which can be simplified and can obtain a good display by further reducing the influence of crosstalk and the like on the display by the capacitance component between each wiring and the pixel electrode. The purpose is.

【0016】

[Means for solving problems]

The transmissive liquid crystal display device of the present invention has a gate wiring, a source wiring, and a switching element provided near the intersection of the gate wiring and the source wiring, and the switching element is connected to the gate wiring. A transmissive liquid crystal display device having a gate, a source connected to the source wiring, and a drain connected to a pixel electrode for applying a voltage to the liquid crystal layer, wherein the switching element, the gate wiring, and the like. An interlayer insulating film made of a highly transparent insulating film is provided above the source wiring, and the pixel electrode and the drain are connected to the pixel electrode and the drain through a contact hole penetrating the interlayer insulating film. It has electrodes that connect at the top of the wiring, thereby achieving the above objectives.

【0017】

The interlayer insulating film is preferably a photosensitive insulating film.

【0018】

It is preferable that the pixel electrode and at least one of the source wiring and the gate wiring are provided so as to overlap each other by 1 μm or more in the wiring width direction.

【0019】

The film thickness of the interlayer insulating film is preferably 1.5 μm or more.

【0020】

It is preferable that the electrode connecting the pixel electrode and the drain is made of a transparent conductive material.

【0021】

It is preferable that the contact hole further has an additional capacitance for holding the voltage applied to the liquid crystal layer, and the contact hole is provided on one electrode of the additional capacitance or above the gate wiring.

【0022】

In the method for manufacturing a transmissive liquid crystal display device of the present invention, a plurality of switching elements are formed in a matrix on a substrate, and the gate wiring connected to the gate of the switching element and the source of the switching element are connected. The step of forming the additional capacitance wiring connected to the drain of the switching element and forming the source wiring so as to intersect each other, and on the switching element, the gate wiring, the source wiring, and the upper part of the additional capacitance wiring. After forming a highly transparent insulating film, the insulating film is patterned to form an interlayer insulating film, and a contact hole penetrating the interlayer insulating film is formed, and on the interlayer insulating film and in the contact hole. , A step of forming a pixel electrode made of a transparent conductive material, and a step of forming an electrode connecting the pixel electrode and the drain through the contact hole at the gate wiring having a light-shielding property or the upper part of the additional capacitance wiring. Including, thereby achieving the above objectives.

【0023】

It is preferable to form the film thickness of the pixel electrode to 50 nm or more.

【0024】

It is preferable that an organic film made of a photosensitive resin is used as the interlayer insulating film, and the patterning of the organic film includes a step of exposing the organic film and developing the exposed organic film.

【0025】

It is preferable to develop the organic film with a tetramethylammonium hydrooxide developer having a concentration of 0.1 to 1.0 mol% to form an interlayer insulating film.

【0026】

The operation of the present invention will be described below.

【0027】

In the present invention, an interlayer insulating film is provided above the switching element, the gate wiring, and the source wiring, a pixel electrode is provided on the interlayer insulating film, and a TFT drain electrode is provided by a connecting electrode through a contact hole penetrating the interlayer insulating film. Is connected to. By connecting the pixel electrode to the drain electrode of the switching element via the connection electrode in this way, even if the TFT becomes small, the connection portion by the contact hole or the like penetrating the interlayer insulating film can be easily formed. It becomes possible to take. That is, since the size of the TFT can be reduced, the aperture ratio can be improved. Further, by providing the interlayer insulating film, each wiring and the pixel electrode can be overlapped with each other, the aperture ratio can be improved, and the poor alignment of the liquid crystal can be suppressed. Moreover, when an organic material such as an acrylic photosensitive resin is used as the interlayer insulating film, a high-quality film having a low relative permittivity and high transparency is produced as compared with the conventionally used inorganic thin films such as silicon nitride. Since it is often obtained, it is possible to increase the film thickness, the capacitance between each wiring and the pixel electrode is reduced, and the signal transmittance is also suppressed, whereby between each wiring and the pixel electrode. A better display can be obtained by further reducing the influence of the capacitance component of the above on the display such as cross talk.

【0028】

This interlayer insulating film can be obtained with good productivity by a simple method of depoting a photosensitive insulating film such as a photosensitive acrylic resin and patterning by exposure and development.

【0029】

Further, when the pixel electrode and each wiring are overlapped by 1 μm or more, the aperture ratio can be maximized and the processing accuracy of each wiring of the pixel electrode may be coarse. That is, even if the processing accuracy is coarse, if the pixel electrode and each wiring overlap, light leakage is blocked by each overlapping wiring.

【0030】

Further, when the film thickness of the interlayer insulating film is 1.5 μm or more, even if the pixel electrode and each wiring overlap by 1 μm or more, the capacitance between each wiring and the pixel electrode becomes sufficiently small and the time constant becomes small. , The influence of the capacitance component on the display such as cross talk is further reduced, and a better display can be obtained.

【0031】

If a transparent conductive film is used for the connection electrode connecting the drain electrode and the pixel electrode of the TFT, the aperture ratio is further improved.

【0032】

Further, if a contact hole penetrating the interlayer insulating film is provided above the light-shielding additional capacitance wiring or the gate wiring, light leakage due to the disordered orientation of the liquid crystal will occur in the light-shielding portion other than the opening. There is no decrease in contrast.

【0033】

Further, by using a relatively thick interlayer insulating film in the present invention, flattening becomes possible, and a step such as a disconnection on the drain side of the pixel electrode, which has conventionally occurred in a step portion due to wiring in the lower layer thereof, etc. The influence of the above is eliminated, and the misalignment due to the step is prevented. In addition, since it is insulated by an interlayer insulating film between the source wiring and the pixel electrodes, defective elements due to electrical leakage between the source wiring and the pixel electrodes are extremely reduced, which makes it possible to improve the manufacturing yield and reduce the manufacturing cost. It can also be reduced. Further, in the present invention, the film formation, the pattern forming step by the photoresist, the etching, the resist peeling, and the cleaning step, which have been conventionally required for forming the interlayer insulating film, can be formed only by the photosensitive insulating film forming step. Therefore, it is possible to shorten and simplify the manufacturing process, and it is also possible to reduce the manufacturing cost.

【0034】

Further, when the film thickness of the pixel electrode is 50 nm or more, it is possible to prevent the chemical solution from entering through the gap between the film surfaces, and the swelling of the resin caused by the chemical solution used for the stripping solution is suppressed.

【0035】

Further, in the present invention, by eliminating the conventionally provided margin between the pixel electrode and each wiring, the pixel electrode becomes large, the display aperture ratio is improved, the brightness is also improved, and the contrast is very good. As a result, it becomes possible to reduce the retardation and widen the viewing angle without deteriorating the contrast, and a great wide viewing angle can be achieved.

【0036】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

【0037】

(Embodiment 1) FIG. 1 is a plan view showing the configuration of one pixel portion of the active matrix substrate in the transmissive liquid crystal display device according to the first embodiment of the present invention.

【0038】

In FIG. 1, a plurality of pixel electrodes 21 are provided in a matrix on the active matrix substrate, and each gate for supplying scanning signals so as to pass around these pixel electrodes 21 and be orthogonal to each other. Wiring 22 and source wiring 23 for supplying display signals are provided. A part of the gate wiring 22 and the source wiring 23 overlaps with the outer peripheral portion of the pixel electrode 21. Further, at the intersection of the gate wiring 22 and the source wiring 23, a TFT 24 as a switching element connected to the pixel electrode 21 is provided. A gate wiring 22 is connected to the gate electrode of the TFT 24, and the TFT 24 is driven and controlled by a signal input to the gate electrode. Further, the source wiring 23 is connected to the source electrode of the TFT 24, and a data signal is input to the source electrode of the TFT 24. Further, the drain electrode of the TFT 24 is connected to the pixel electrode 21 via the connection electrode 25 and the contact hole 26, and is also connected to the additional capacitance electrode 25a which is one of the additional capacitance electrodes via the connection electrode 25. .. The additional capacitance counter electrode 27, which is the other electrode of the additional capacitance, is connected to the common wiring (6 in FIG. 16).

【0039】

FIG. 2 is a cross-sectional view taken along the line A-A'of the active matrix substrate in the transmissive liquid crystal display device of FIG.

【0040】

In FIG. 2, a gate electrode 32 connected to the gate wiring 22 of FIG. 1 is provided on the transparent insulating substrate 31, and a gate insulating film 33 is provided over the gate electrode 32. A semiconductor layer 34 is provided on the semiconductor layer 34 so as to overlap the gate electrode 32, and a channel protection layer 35 is provided on the central portion thereof. Both ends of the channel protection layer 35 and a part of the semiconductor layer 34 are covered, and the source electrode 36a and the drain electrode 36b are formed in a state of being separated on the channel protection layer 35.⁺A Si layer is provided. One n⁺A transparent conductive film 37c and a metal layer 37b are provided on the end of the source electrode 36a, which is a Si layer, to form a source wiring 23 having a two-layer structure. Also, the other n⁺A transparent conductive film 37a'and a metal layer 37b'are provided on the end of the drain electrode 36b, which is a Si layer, and the transparent conductive film 37a'is extended to connect the drain electrode 36b and the pixel electrode 21. In addition, it is a connection electrode 25 connected to the additional capacitance electrode 25a, which is one electrode of the additional capacitance. Further, an interlayer insulating film 38 is provided so as to cover the upper part of the TFT 24, the gate wiring 22, the source wiring 23, and the connection electrode 25.

【0041】

A transparent conductive film serving as the pixel electrode 21 is provided on the interlayer insulating film 38, and the drain electrode 36b of the TFT 24 is provided by the transparent conductive film 37a'which is the connection electrode 25 through the contact hole 26 penetrating the interlayer insulating film 38. Is connected to.

【0042】

As described above, the active matrix substrate of the first embodiment is configured and can be manufactured as follows.

【0043】

First, on a transparent insulating substrate 31 such as a glass substrate, the gate electrode 32, the gate insulating film 33, the semiconductor layer 34, the channel protection layer 35, the source electrode 36a, and the drain electrode 36b are n.⁺The Si layer is formed by sequentially forming a film. The manufacturing process up to this point can be performed in the same manner as the conventional method for manufacturing an active matrix substrate.

【0044】

Next, the transparent conductive films 37a, 37a'and the metal layers 37b, 37b' constituting the source wiring 23 and the connection electrode 25 are sequentially formed by a sputtering method and patterned into a predetermined shape.

【0045】

Further, a photosensitive acrylic resin is formed on the interlayer insulating film 38 by a spin coating method, for example, with a film thickness of 3 μm. The resin is exposed according to a desired pattern and developed with an alkaline solution. As a result, only the exposed portion is etched by the alkaline solution, and the contact hole 26 penetrating the interlayer insulating film 38 is formed.

【0046】

Then, a transparent conductive film to be the pixel electrode 21 is formed by a sputtering method and patterned. As a result, the pixel electrode 21 is connected to the transparent conductive film 37a'connected to the drain electrode 36b of the TFT 24 via the contact hole 26 penetrating the interlayer insulating film 38. In this way, the active matrix substrate of the first embodiment can be manufactured.

【0047】

Therefore, in the active matrix substrate thus obtained, the interlayer insulating film 38 having a thick film thickness is formed between the gate wiring 22, the source wiring 23 and the TFT 24, and the pixel electrode 21, so that each wiring 22 The pixel electrode 21 can be overlapped with respect to the 23 and the TFT 24, and the surface thereof can be flattened. Therefore, when a transmissive liquid crystal display device in which a liquid crystal is interposed between the active matrix substrate and the opposing substrate is configured, the aperture ratio can be improved and the electric field caused by the wirings 22 and 23 is a pixel electrode. It can be shielded with 21 to suppress dispersion.

【0048】

In addition, the acrylic resin constituting the interlayer insulating film 38 has a relative permittivity of 3.4 to 3.8, which is lower than that of the inorganic film (relative permittivity of silicon nitride 8), and has high transparency, which can be easily applied by the spin coating method. Since the film thickness can be as thick as 3 μm, the capacitance between the gate wiring 22 and the pixel electrode 21 and the capacitance between the source wiring 23 and the pixel electrode 21 can be reduced, resulting in a lower time constant. , The influence of the capacitive component between each of the wirings 22 and 23 and the pixel electrode 21 on the display such as crosstalk can be further reduced, and a good and bright display can be obtained. Further, by performing patterning by exposure and alkaline development, the tapered shape of the contact hole 26 can be improved, and the connection between the pixel electrode 21 and the connection electrode 37a'can be improved. Further, by using a photosensitive acrylic resin, a thin film can be formed by a spin coating method, so that a thin film having a film thickness of several μm can be easily formed, and a photoresist step is not required for patterning. It is advantageous in terms of productivity. Here, the acrylic resin used as the interlayer insulating film 38 is colored before coating, but can be made more transparent by subjecting it to full exposure treatment after patterning. As described above, the transparent treatment of the resin can be performed not only optically but also chemically.

【0049】

For the exposure of the photosensitive resin used as the interlayer insulating film 38 in the present embodiment, the light rays of a mercury lamp including the emission lines of i-line (wavelength 365 nm), h-line (wavelength 405 nm) and g-line (wavelength 436 nm) are used. It is common. As the photosensitive resin, it is preferable to use a photosensitive resin having photosensitivity (absorption peak) on the i-line having the highest energy (shortest wavelength) among these emission lines. It is possible to improve the processing accuracy of the contact hole and minimize the coloring caused by the photosensitizer.

【0050】

Further, short wavelength ultraviolet rays from an excimer laser may be used.

【0051】

In this way, by using the interlayer insulating film without coloring, the transmittance of the transmissive liquid crystal display device can be increased. Therefore, it is possible to reduce the power consumption by increasing the brightness of the liquid crystal display device and suppressing the amount of light from the backlight.

【0052】

Further, since the interlayer insulating film 38 is formed to be thicker than the conventional interlayer insulating film and to a thickness of several μm, it is preferable that the interlayer insulating film has as high a transmittance as possible. However, since the luminosity factor of the human eye is slightly lower for blue than for green and red, the spectral transmittance of the interlayer insulating film is less deteriorated in display quality even if the transmittance for blue light is slightly lower. .. In this embodiment, the film thickness of the interlayer insulating film 38 is set to 3 μm, but the film thickness is not limited to this, and can be appropriately set in consideration of the light transmittance and the dielectric constant. In order to reduce the capacitance sufficiently, the film thickness of the interlayer insulating film is preferably about 1.5 μm or more, and more preferably about 2.0 μm or more.

【0053】

Further, by forming the transparent conductive film 37a'as the connection electrode 25 for connecting the drain electrode 36b of the TFT 24 and the pixel electrode 21, it has the following advantages. That is, in the conventional active matrix substrate, since the connection electrode is formed of a metal layer, the presence of the connection electrode in the opening causes a decrease in the aperture ratio. In order to prevent this, conventionally, a method of forming a connection electrode on the drain electrode of the TFT or TFT, forming a contact hole of an interlayer insulating film on the connection electrode, and connecting the drain electrode of the TFT and the pixel electrode is used. Has been done. However, in this conventional method, especially when the TFT is miniaturized in order to improve the aperture ratio, the contact hole cannot be completely provided on the TFT, which causes a decrease in the aperture ratio. Further, when the interlayer insulating film is formed as thick as several μm, the contact hole needs to be tapered in order for the pixel electrode to contact the connection electrode of the lower layer, and the connection electrode region on the TFT is further formed. It was necessary to take a large amount. For example, when the diameter of the contact hole is 5 μm, the size of the connection electrode needs to be about 14 μm in consideration of the taper region of the contact hole and the alignment accuracy, which is smaller than that of the conventional active matrix substrate. Forming a sized TFT caused a decrease in aperture ratio due to the connecting electrodes. On the other hand, in the active matrix substrate of the first embodiment, since the connection electrode 25 is formed of the transparent conductive film 37a', the aperture ratio does not decrease. In addition, the connection electrode 25 is extended to connect the drain electrode 36b of the TFT and the additional capacitance electrode 25a, which is one of the additional capacitance formed by the transparent conductive film 37a'. Since the extension portion is also formed of the transparent conductive film 37a', the aperture ratio does not decrease due to this wiring.

【0054】

Furthermore, by making the source wiring 23 a two-layer structure, even if a part of the metal layer 37b constituting the source wiring 23 has a film defect, it is electrically connected by a transparent conductive film 37a such as ITO. Therefore, there is an advantage that the disconnection of the source wiring 23 can be reduced.

【0055】

(Embodiment 2) In the second embodiment, another method will be described for the process of producing the interlayer insulating film 38.

【0056】

First, a non-photosensitive organic thin film is formed by a spin coating method. After forming a photoresist on the photoresist and patterning it, an etching process is performed to form a contact hole 26 penetrating the interlayer insulating film 38, and the interlayer insulating film 38 is patterned.

【0057】

Alternatively, the interlayer insulating film 38 may be patterned by laminating a non-photosensitive organic thin film, forming a photoresist on the laminate, and then performing an etching process.

【0058】

As the material of the organic thin film having no photosensitivity, for example, a thermosetting acrylic resin can be used. Specifically, JSS-924 (two-component type) and JSS-925 (one-component type) manufactured by Nippon Synthetic Rubber Co., Ltd. can be used. These resins also have a heat resistance of approximately 280 ° C or higher. Further, by forming the interlayer insulating film using a resin having no photosensitivity, the degree of freedom in designing the resin is increased, and for example, a polyimide resin can be used. The colorless and transparent polyimide resin includes acid dianhydrides such as 2,2-bis (dicarboxyphenyl) hexafluoropropylene acid dianhydride, oxydiphthalic acid anhydride, and biphenyltetracarboxylic acid anhydride, and sulfone groups and /. Alternatively, a polyimide obtained by combining a meta-substituted aromatic diamine having an ether group and a diamine having a hexafluoropropylene group can be mentioned. These polyimide resins are disclosed, for example, in Fujita et al., Nitto Giho, Vol. 29, No. 1, pp. 20-28 (1991). Further, among these colorless transparent polyimide resins, the resin in which both the acid dianhydride and the diamine have a hexafluoropropylene group has high transparency. Fluorine-based resins other than these fluorine-based polyimides can also be used. Fluorine-based materials have excellent colorless transparency, low dielectric constant, and high heat resistance.

【0059】

Further, as a photoresist material used for patterning an interlayer insulating film made of a non-photosensitive organic material, it is preferable to use a photoresist containing a silicon element. Etching of the above organic thin film is CF₄, CF₃H and SF₆It is generally performed by a dry etching method using an etching gas containing the above. Since both the interlayer insulating film to be etched and the photoresist functioning as an etching resist are made of an organic material, it is difficult to increase the selection ratio when etching is performed by the above method. In particular, when an interlayer insulating film having a film thickness of 1.5 μm or more is etched as in the present embodiment, the thickness of the interlayer insulating film and the film thickness of the resist layer are almost the same, which is sufficient for the etching rate of the material itself. It is preferable that there is a difference (selection ratio). For example, the selective ratio between the photosensitive acrylic resin of the present embodiment and a normal photoresist (for example, OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is about 1.5. On the other hand, the selectivity of the silicon element-containing photoresist used in the present embodiment and the photosensitive acrylic resin is about 2.0 or more, and high-precision patterning is possible.

【0060】

Further, as another method, after forming a normal photoresist layer containing no silicon element, a silane coupling agent (for example, hexamethyldisilazane) is applied to the surface of the photoresist layer, and this silane coupling agent layer is applied. The etching rate of the photoresist layer can be reduced by treating with oxygen plasma. This is because the silane coupling agent layer becomes a silicon oxide layer by oxygen plasma treatment and functions as a protective layer of the photoresist layer. This method can also be used in combination with a photoresist material containing a silicon element.

【0061】

The method of improving the selectivity by using the above-mentioned silicon element is CF.₄, CF₃H or SF₆A particularly remarkable effect can be obtained in a dry etching method using an etching gas containing.

【0062】

Even in the active matrix substrate in which the interlayer insulating film 38 is formed in this way, it is possible to realize a transmissive liquid crystal display device having a high aperture ratio, similarly to the active matrix substrate of the first embodiment.

【0063】

Further, even if a non-photosensitive organic thin film is used as the interlayer insulating film 38, its relative permittivity is low and its transparency is high, so that a thick film thickness of 3 μm can be obtained. Therefore, the capacitance between the gate wiring 22 and the pixel electrode 21 and the capacitance between the source wiring 23 and the pixel electrode 21 can be reduced by the distance between the electrodes having a low relative permittivity and capacitance.

【0064】

(Embodiment 3) FIG. 3 is a plan view showing the configuration of one pixel portion of the active matrix substrate in the transmissive liquid crystal display device according to the third embodiment of the present invention, and FIG. 4 is a plan view showing the configuration of one pixel portion of the active matrix substrate in the transmissive liquid crystal display device according to the third embodiment. -B'Cross section. The members having the same effects as those in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.

【0065】

In the active matrix substrate of the third embodiment, the additional capacitance counter electrode 27 facing the additional capacitance electrode 25a, which is one electrode of the additional capacitance of the pixel, which is the tip of the connection electrode 25 connected to the drain electrode 36b of the TFT 24. Is connected to the counter electrode formed on the facing substrate through the additional capacitance common wiring 6 in FIG. 16, and the position where the contact hole 26a penetrating the interlayer insulating film 38 is formed is the additional capacitance common wiring. It is formed on the additional capacitance counter electrode 27 and the additional capacitance electrode 25a, which are one ends of 6. That is, the contact hole 26a is provided above the additional capacitance wiring made of a light-shielding metal film.

【0066】

This has the following advantages.

【0067】

For example, when the film thickness of the interlayer insulating film 38 is 3 μm, the thickness is not negligible even when compared with the thickness of the liquid crystal cell of 4.5 μm, so that light leakage occurs around the contact hole 26a due to the disordered orientation of the liquid crystal. .. Therefore, when such a contact hole 26a is formed in the opening of the transmissive liquid crystal display device, the contrast is lowered due to the light leakage. On the other hand, in the active matrix substrate of the third embodiment, the contact hole 26a is formed on the light-shielding metal film upper part of the additional capacitance counter electrode 27 and the additional capacitance electrode 25a, which are one ends of the additional capacitance common wiring 6. Therefore, such a problem does not occur. That is, if the contact hole 26a is provided above the additional capacitance wiring which is a light-shielding metal film, even if light leakage occurs due to the orientation disorder of the liquid crystal, it is a light-shielding part other than the opening and has a contrast. There is no reduction. This also applies to the case where an additional capacitance is formed by using a part of the adjacent gate wiring 22 as an additional capacitance electrode. In this case, the gate is formed by forming the contact hole 26a on the adjacent gate wiring 22. Wiring 22 can block light to prevent a decrease in contrast.

【0068】

Further, since this active matrix substrate forms a transparent conductive film 37a'as a connection electrode 25 for connecting the drain electrode 36b of the TFT 24 and the contact hole 26a, even if the contact hole 26a is formed on the additional capacitance. There is no decrease in aperture ratio.

【0069】

Therefore, since the additional capacitance counter electrode 27 is used to block light at the lower part of the hole, even if the orientation of the liquid crystal is disturbed at that part, the display is not affected, and it is necessary to emphasize the dimensional accuracy for forming the contact hole 26a. The pixel electrodes 21 formed on the interlayer insulating film 38 can be formed smoothly without being cut off at the contact hole 26a, and are better connected to each other, and the yield is also improved.

【0070】

(Embodiment 4) FIG. 5 is a partial cross-sectional view showing the configuration of an active matrix substrate in the transmissive liquid crystal display device according to the fourth embodiment of the present invention.

【0071】

In the active matrix substrate of the fourth embodiment, a contact hole 26b penetrating the interlayer insulating film 38 is formed in the upper part of the additional capacitance common wiring 6, and above the transparent conductive film 37a'formed in the lower part of the contact hole 26b. A metal nitride layer 41 is formed on the surface.

【0072】

This has the following advantages.

【0073】

There is a problem in the adhesion between the resin constituting the interlayer insulating film 38 and the transparent conductive film such as ITO or the metals Ta and Al. For example, in the cleaning step after the opening of the contact hole 26b, there is a problem that the cleaning liquid invades the interface between the resin and the base through the opening of the contact hole 26b, causing the resin film to peel off. On the other hand, in the active matrix substrate of the fourth embodiment, since the metal nitride layer 41 such as TaN or AlN having good adhesion to the resin is formed, there is no problem of adhesion such as film peeling. ..

【0074】

As the metal nitride layer 41, any resin may be used as long as it has good adhesion to the resin constituting the interlayer insulating film 38, the connection electrode 37a'which is a transparent conductive film, and metals such as Ta and Al. However, since it is necessary to electrically connect the connection electrode 37a'and the pixel electrode 21, it is necessary to have good conductivity.

【0075】

(Embodiment 5) In the fifth embodiment, a method of driving the transmissive liquid crystal display device will be described.

【0076】

In the transmissive liquid crystal display device of the present invention, each wiring and the pixel electrode are overlapped by forming an interlayer insulating film. If the pixel electrodes and each wiring do not overlap and there is a gap between them, a region where an electric field is not applied to the liquid crystal is generated. By overlapping the pixel electrodes with each wiring in this way, this region rather than a can Succoth. Further, although an electric field is not applied to the liquid crystal between the adjacent pixel electrodes, light leakage due to the electric field can be blocked by each wiring. Therefore, it is not necessary to form a black mask on the facing substrate in a form in which the bonding of the two substrates is expected to be misaligned, and the aperture ratio can be improved. In addition, since the electric field caused by each wiring can be shielded, there is an advantage that the misalignment of the liquid crystal can be suppressed.

【0077】

However, this overlap width needs to be set in consideration of variations in the actual manufacturing process, and is preferably set to, for example, about 1.0 μm or more.

【0078】

As described above, when the structure is such that the source wiring and the pixel electrodes overlap, there is a problem that crosstalk occurs due to the capacitance between the source wiring and the pixel electrodes, which deteriorates the display quality. there were. In particular, in a liquid crystal panel used in a notebook type personal computer, since the pixels are generally arranged in vertical stripes, the influence on the display of the capacitance between the source wiring and the pixel electrodes is large. The reason for this is that in this arrangement, the shape of the pixel electrodes is a rectangle whose long side is adjacent to the source signal, so that the capacitance between the pixel electrodes and the source wiring is relatively large, and that they are adjacent to each other. Since the display colors of the source wiring are different, it is possible that the signal correlation is small and the influence of capacitance cannot be canceled.

【0079】

In the transmissive liquid crystal display device of the present invention, since the interlayer insulating film is made of an organic thin film, the relative permittivity is small, and the film thickness can be easily increased, so that the capacitance between the pixel electrode and each wiring is reduced. be able to. Furthermore, in addition to this, in order to reduce the influence of the capacitance between the source wiring and the pixel electrodes and sufficiently reduce the vertical crosstalk even in a notebook type personal computer, the following drive method should be used. Can be done.

【0080】

The drive method of the transmissive liquid crystal display device according to the fifth embodiment is a drive method in which the polarity of the data signal is inverted every one horizontal period in order to reduce the influence on the display of the capacitance between the source wiring and the pixel electrodes ( It is driven by using (hereinafter referred to as 1H inversion).

【0081】

In FIG. 6, 1H inversion (Fig. 7a) and a driving method in which the polarity of the data signal is inverted for each field (hereinafter referred to as field inversion) (Fig. 7b) are shown between the source wiring and the pixel electrodes. It shows the effect of capacity on the charge rate of pixels.

【0082】

In FIG. 6, the charge rate difference on the vertical axis is the case where the halftone is uniformly displayed and the case where the black window pattern in which the vertical occupancy is 33% is displayed in the halftone display. Shows the ratio of the effective value difference of the voltage applied to the liquid crystal of the halftone display unit. The capacitance ratio on the horizontal axis is proportional to the voltage fluctuation of the pixel electrode due to the capacitance between the source wiring and the pixel electrode, and is defined by the following equation (1).

【0083】

Capacity ratio = Csd / (Csd + Cls + Cs) (1) However, Csd indicates the capacitance value between the pixel electrode and the source wiring, Cls indicates the capacitance value in the halftone display of the liquid crystal constituting each pixel, and Cs indicates the capacitance value of the additional capacitance constituting each pixel. ing. The halftone display indicates a case where the transmittance is 50%.

【0084】

As is clear from FIG. 6, the driving method of 1H inversion according to the fifth embodiment can be used as an actual liquid crystal even if the capacitance between the source wiring and the pixel electrode is the same as that of the driving method by field inversion. It can be seen that the effect on the applied effective voltage can be reduced to 1/5 to 1/10. The reason for this is that in the case of 1H inversion drive, the polarity of the data signal is inverted in a period sufficiently short for the time of one field during one field, so the + polarity signal and the-polarity signal This is because the effect of is on the display is cancelled.

【0085】

By the way, when a display experiment was conducted on a VGA panel with a diagonal of 26 cm, it was found that crosstalk became prominent when the charge rate difference was 0.6% or more in the halftone, causing a problem in display quality. This spec is shown by the dotted line in the figure of FIG. According to FIG. 6, in order to reduce the charge rate difference to 0.6% or less, the capacity ratio should be set to 10% or less.

【0086】

Fig. 8 shows the amount of overlap between the pixel electrode and the source wiring and the capacitance between the pixel electrode and the source wiring when the thickness of the interlayer insulating film is calculated as a parameter in a VGA panel with a diagonal of 26 cm. Shows the relationship. Here, the interlayer insulating film was the acrylic photosensitive resin (relative permittivity 3.4) used in the first embodiment. At this time, considering the processing accuracy, the overlap width between the pixel electrode and the source wiring needs to be at least 1 μm. According to FIGS. 6 and 8, in order to make the overlap width 1 μm and the charge rate difference 0.6% or less, it can be seen that the film thickness of the interlayer insulating film should be 2.0 μm or more.

【0087】

In this way, when the pixel electrodes overlap with the source wiring, the source line that inverts the signal polarity of the adjacent source wiring by performing 1H inversion drive that inverts the signal polarity every 1 horizontal period. It is possible to obtain a good display in which vertical crosstalk is not recognized even if the reverse drive is not performed, and it is possible to sufficiently support a notebook type personal computer.

【0088】

Further, even if the dot inversion drive in which the polarity of the signal input to the pixel electrodes adjacent in the lateral direction is inverted in the 1H inversion drive is used, the same effect as the above 1H inversion drive can be obtained. Further, the source line inversion drive is also effective when the capacitance between the pixel electrode and the source wiring is sufficiently small. Further, according to the present invention, since the capacitance between the pixel electrode and the source wiring is sufficiently small, it is possible to suppress the occurrence of crosstalk even when performing color display having a low correlation with the signals supplied to the adjacent pixel electrodes. Can be done.

【0089】

(Embodiment 6) In the sixth embodiment, a driving method will be described in which the polarity of the voltage applied to the liquid crystal is inverted for each gate wiring, and the signal applied to the counter electrode is synchronized with the inversion of the polarity of the source signal to drive AC. To do.

【0090】

By driving the counter electrode in this way, the amplitude of the source signal can be suppressed to a small value.

【0091】

FIG. 6 above shows the case where the counter electrode is AC-driven with an amplitude of 5 V at the same time. According to FIG. 6, although the charge rate difference is increased by about 10% by AC driving the counter electrode, the charge rate difference can be sufficiently reduced as compared with the field inversion drive because the 1H inversion drive is performed. Therefore, even with this driving method, it is possible to realize a good display in which vertical crosstalk is not seen.

【0092】

(Embodiment 7) In the seventh embodiment, the flat pixel electrode and each wiring can be overlapped to improve the aperture ratio of the liquid crystal display and suppress the misalignment of the liquid crystal, the manufacturing process can be simplified, and each wiring and the pixel can be simplified. This is a case where a good display can be obtained by further reducing the influence of the capacitance component between the electrode and the display on the display, and in addition to this, after the interlayer insulating film is exposed and developed, the photosensitive transparent acrylic resin is used. This is a case where the entire surface of the substrate is exposed to the photosensitive agent used in the above and the unnecessary photosensitive agent is completely reacted to obtain a highly transparent interlayer insulating film.

【0093】

FIG. 9 is a plan view showing the configuration of one pixel portion of the active matrix substrate in the transmissive liquid crystal display device according to the seventh embodiment of the present invention.

【0094】

In FIG. 9, a plurality of pixel electrodes 51 are provided in a matrix on the active matrix substrate, and the gate wiring 52 and the source wiring 53 pass around the pixel electrodes 51 and are orthogonal to each other. It is provided. A part of the gate wiring 52 and the source wiring 53 overlaps with the outer peripheral portion of the pixel electrode 51. Further, at the intersection of the gate wiring 52 and the source wiring 53, a TFT 54 as a switching element connected to the pixel electrode 51 is provided. A gate wiring 52 is connected to the gate electrode of the TFT 54, and the TFT 54 is driven and controlled by a signal input to the gate electrode. Further, the source wiring 53 is connected to the source electrode of the TFT 54, and a data signal is input to the source electrode of the TFT 54. Further, the drain electrode of the TFT 54 is connected to the pixel electrode 51 via the connection electrode 55 and the contact hole 56, and is also connected to the additional capacitance electrode 55a which is one of the additional capacitance electrodes via the connection electrode 55. .. The additional capacitance counter electrode 57, which is the other electrode of the additional capacitance, is connected to the common wiring.

【0095】

FIG. 10 is a C-C'cross-sectional view of the active matrix substrate in the transmissive liquid crystal display device of FIG.

【0096】

In FIG. 10, a gate electrode 62 connected to the gate wiring 52 of FIG. 9 is provided on the transparent insulating substrate 61, and a gate insulating film 63 is provided over the gate electrode 62. A semiconductor layer 64 is provided on the semiconductor layer 64 so as to overlap the gate electrode 62, and a channel protection layer 65 is provided on the central portion thereof. Both ends of the channel protection layer 65 and a part of the semiconductor layer 64 are covered, and the source electrode 66a and the drain electrode 66b are formed in a state of being separated on the channel protection layer 65.⁺A Si layer is provided. One n⁺A transparent conductive film 67a and a metal layer 67b are provided on the end of the source electrode 66a, which is a Si layer, to form a source wiring 53 having a two-layer structure. Also, the other n⁺A transparent conductive film 67a'and a metal layer 67b' are provided on the end of the drain electrode 66b, which is a Si layer, and the transparent conductive film 67a'is extended to connect the drain electrode 66b and the pixel electrode 51. In addition, it is a connection electrode 55 connected to the additional capacitance electrode 55a, which is one of the additional capacitance electrodes. Further, an interlayer insulating film 68 made of a highly transparent transparent acrylic resin (photosensitive transparent acrylic resin) in which the photosensitive portion dissolves in a developing solution is provided so as to cover the upper part of the TFT 54, the gate wiring 52, the source wiring 53, and the connection electrode 55. Has been done.

【0097】

A transparent conductive film serving as a pixel electrode 51 is provided on the interlayer insulating film 68, and the drain electrode 66b of the TFT 54 is provided by the transparent conductive film 67a'which is the connection electrode 55 through the contact hole 66 penetrating the interlayer insulating film 68. Is connected to.

【0098】

As described above, the active matrix substrate of the seventh embodiment is configured and can be manufactured as follows.

【0099】

First, on a transparent insulating substrate 61 such as a glass substrate, a gate electrode 62 made of Ta, Al, Mo, W, Cr, etc., SiN_x, SiO₂, Ta₂O₅Gate insulating film 63, semiconductor film (i-Si) 64, SiN_x, Ta₂O₅The channel protection film 65, the source electrode 66a, and the drain electrode 66b are n.⁺The Si layer is formed by sequentially forming a film. Further, the transparent conductive films 67a and 67a'consisting of the source wiring 53 and the connection electrode 55 and the metal films 67b and 67b'consisting of Ta, Al, MoW, Cr and the like are sequentially formed by a sputtering method to form a predetermined shape. Pattern. Also in the seventh embodiment, the two-layer structure of the metal film 67b, 67b'constituting the source wiring 53 and the ITO film, which is the transparent conductive film 67a, 67a', is used. This configuration has the advantage that even if the metal films 67b and 67b'constituting the source wiring 53 are defective, the source wiring 53 can be less disconnected because it is electrically connected by the ITO film. There is.

【0100】

Further, a photosensitive acrylic resin is formed on the interlayer insulating film 68 by a spin coating method, for example, with a film thickness of 2 μm. The photosensitive acrylic resin is exposed according to a desired pattern and developed with an alkaline solution. As a result, only the exposed portion is etched by the alkaline solution, and a contact hole 56 or the like penetrating the interlayer insulating film 68 is formed.

【0101】

Then, a transparent conductive film to be the pixel electrode 51 is formed on the interlayer insulating film 68 and the contact hole 56 by a sputtering method, and the transparent conductive film is patterned. As a result, the pixel electrode 51 is connected to the transparent conductive film 67a'connected to the drain electrode 66b of the TFT 54 via the contact hole 56 penetrating the interlayer insulating film 68. In this way, the active matrix substrate of the seventh embodiment can be manufactured.

【0102】

In the seventh embodiment, as a material for forming the interlayer insulating film 68, a highly transparent photosensitive transparent acrylic resin (positive photosensitive acrylic resin) in which the photosensitive portion dissolves in a developing solution is used.

【0103】

As the positive photosensitive acrylic resin, for example, a material obtained by mixing a naphthoquinone diazide positive photosensitive agent with a base polymer composed of a copolymer of methacrylic acid and glycidyl methacrylate is preferable. Since this resin contains a glycidyl group, it can be crosslinked (cured) by heating. As physical properties after curing, a dielectric constant of about 3.4 and a transmittance of 90% or more for light in the wavelength range of 400 nm to 800 nm can be obtained. Moreover, the color can be decolorized in a short time by irradiating with ultraviolet rays of i-line (365 nm). Further, ultraviolet rays other than i-ray can be used for patterning. Since the heat-resistant temperature of the photosensitive acrylic resin used in this embodiment is approximately 280 ° C, a process such as forming a pixel electrode after forming an interlayer insulating film is performed under temperature conditions of about 250 ° C to 280 ° C or less. By doing so, deterioration of the interlayer insulating film can be suppressed.

【0104】

The step of forming the interlayer insulating film 68 with the highly transparent photosensitive transparent acrylic resin described above will be described in more detail below.

【0105】

In the step of forming the interlayer insulating film 68, first, a solution containing a photosensitive transparent acrylic resin material is spin-coated on a substrate, and a series of ordinary photopatterning is performed in the order of prebaking, pattern exposure, alkaline development, and pure water cleaning. Perform in the same way as the process.

【0106】

That is, the interlayer insulating film 68 is formed into a solution containing a photosensitive transparent acrylic resin to a film thickness of 3 μm by a spin coating method. In this case, an acrylic resin having a viscosity of 29.0 cp is applied at a spin rotation speed of 900 to 1100 rpm. By doing so, the pixel electrodes are flattened, the conventional step is eliminated, the poor alignment of the liquid crystal is suppressed, and the display quality is improved. Subsequently, the substrate was heated to about 100 ° C. to dry the solvent of the photosensitive transparent acrylic resin (ethyl lactate, propylene glycol monomethyl ether acetate, etc.). Subsequently, the photosensitive transparent acrylic resin was exposed according to a desired pattern, and developed with an alkaline solution (tetramethylammonium hydrooxide; hereinafter referred to as TMAH) or the like. The exposed portion was etched by this alkaline solution, and a contact hole 56 penetrating the interlayer insulating film 68 could be formed. The concentration of the developer (in the case of TMAH) is preferably 0.1 to 1.0 mol%. When the concentration is 1.0 mol% or more, the amount of decrease in the film thickness of the photosensitive transparent acrylic resin in the unexposed portion is large, and it becomes difficult to control the film thickness. When the developer is used at a high concentration of 2.4 mol%, a deteriorated product of acrylic resin remains in the undeveloped portion, resulting in poor contact. Further, if the concentration is lower than 0.1 mol%, it becomes difficult to control the concentration because the concentration fluctuates greatly in the developing apparatus of the type in which the developing solution is circulated and used repeatedly.

【0107】

Further, the developer remaining on the substrate surface is washed with pure water. Since the photosensitive transparent acrylic resin can be formed by the spin coating method in this way, the film thickness can be easily adjusted by appropriately selecting the rotation speed of the spin coater and the viscosity of the photosensitive transparent acrylic resin even if the film thickness is several μm. It can be formed uniformly. Further, the tapered shape of the contact hole portion can be obtained in a gentle shape by appropriately selecting the exposure amount, the developer concentration and the developing time at the time of pattern exposure.

【0108】

After development, the resin may appear colored depending on the type and amount of the photosensitizer used for the photosensitive transparent acrylic resin (for example, naphthoquinone diazito-based photosensitizer, naphthoquinone diazide-based positive photosensitizer). Therefore, the entire surface of the substrate is exposed to completely react the colored unnecessary photosensitizer contained in the resin to eliminate light absorption in the visible region and to make the acrylic resin transparent. The photosensitizer includes a naphthoxydiazide-based positive photosensitizer and / and a naphthoquinone diazide-based photosensitizer. Here, FIG. 11 shows the change in transmittance before and after exposure when the surface is exposed with respect to the wavelength (nm) of transmitted light after applying a film thickness of 3 μm of acrylic resin. As can be seen from FIG. 11, for example, at a wavelength of transmitted light of 400 nm, when light such as ultraviolet light is not irradiated, the transmittance is 65%, but after light irradiation, the transmittance is 90%. It has been improved above. In this case, the exposure is performed from the front surface of the substrate, but by using the exposure from the back surface together, this process can be completed in a short time, which can contribute to the improvement of the device throughput.

【0109】

Finally, the substrate is heated and the resin is cured by a cross-linking reaction. That is, the substrate is placed on a hot plate or in a clean oven to cure the resin and heated at about 200 ° C.

【0110】

In this way, by using the transparent photosensitive resin, the interlayer insulating film 68 and the pixel electrodes formed on the interlayer insulating film 68 can be obtained only by the photo process without going through the conventional etching and resist peeling steps. A contact hole 56 penetrating the interlayer insulating film 68 for connecting to the drain electrode of the switching element can be formed, which simplifies the manufacturing process. The film thickness of the photosensitive transparent acrylic resin at this time is a required film thickness from 0.05 μm to 10 μm by appropriately selecting the viscosity of the resin solution and the rotation speed of the spin coater at the time of spin application (this embodiment). In the case of 7, it can be uniformly formed to 3 μm, and the thicker the film thickness, the lower the light transmittance and the more the color is formed).

【0111】

Further, ITO is formed on the photosensitive transparent acrylic resin by sputtering to a film thickness of 50 to 150 nm, and patterning is performed to form the pixel electrode 51. If the film thickness of the ITO film, which is the pixel electrode 51, is 50 nm or more, it is possible to prevent the chemical solution from entering through the surface gap of the ITO film, and the resin produced by the chemical solution (dimethyl sulfoxide, etc.) used for the stripping solution. It was effective in suppressing swelling. The active matrix substrate of the seventh embodiment can be produced by the above manufacturing method.

【0112】

Therefore, also in the seventh embodiment, the presence of the interlayer insulating film 68 makes it possible to realize a bright liquid crystal display device having a high light transmittance and a high aperture ratio, which is a pixel opening portion other than the source wiring and the gate wiring portion.

【0113】

Further, the presence of the interlayer insulating film 68 enables flattening, eliminates the influence of the step difference due to the wiring and the switching element in the lower layer, and eliminates the disconnection on the drain side of the pixel electrode, which has conventionally occurred in the step portion. It is possible to reduce defective pixels. In addition, it is possible to prevent the liquid crystal from being misaligned due to this step. Further, since the source wiring 53 and the pixel electrode 51 are insulated with an interlayer insulating film 68 in between, defective picture elements due to an electrical leak between the source wiring 53 and the pixel electrode 51, which has conventionally occurred, are also present. It will decrease.

【0114】

Further, in the present embodiment 7, the film forming, pattern forming step by photoresist, etching step, resist peeling step, and cleaning step, which were conventionally required to form the interlayer insulating film 68, are formed only by the resin forming step. And simplifies the manufacturing process.

【0115】

(Embodiment 8) The eighth embodiment is a case where the adhesiveness between the interlayer insulating film 68 and its underlying film in the seventh embodiment is improved.

【0116】

Depending on the material of the base film, the adhesion to the photosensitive transparent acrylic resin used as the interlayer insulating film 68 may not be good. In this case, before the application of the photosensitive transparent acrylic resin in the above embodiment 7 of FIG. M-type mercury lamp (860W) on the surface of the gate insulating film 63, channel protective film 65, source electrode 66a, drain electrode 66b, transparent conductive film 67a, 67a'and metal film 67b, 67b' as the base film on the substrate surface. ) Is used to irradiate the surface with ultraviolet light in an oxygen atmosphere to roughen the surface, and then an interlayer insulating film 68 made of a photosensitive transparent acrylic resin is formed on the roughened surface. In other forming steps, an active matrix substrate is produced by the same method as in the seventh embodiment. By this forming method, in order to improve the adhesion between the base film having a rough surface and the photosensitive transparent acrylic resin, for example, some kind of surface is formed at the interface between the base film and the interlayer insulating film 68 made of the photosensitive transparent acrylic resin. The conventional problem that film peeling occurs between these films due to the invasion of chemicals such as a mixed solution of hydrochloric acid and iron chloride that etch ITO, is eliminated.

【0117】

By irradiating the substrate surface before forming the interlayer insulating film 68 with ultraviolet light in this way, the adhesion between the interlayer insulating film 68 and its underlying film is improved, and it is stable against processing during the process. Device can be realized.

【0118】

Further, in the present invention, as a method of improving the adhesion between the interlayer insulating film 68 and its underlying film, the surface of the underlying film is silane coupled before the resin for forming the interlayer insulating film 68 is applied. There is a method of surface treatment with an agent. Among the silane coupling agents, hexamethyldisilazane, dimethyldiethoxysilane, n-butyltrimethoxysilane and the like are particularly effective in improving adhesion. For example, when a silicon nitride film was used as the base film, the adhesion strength was improved by about 10% by performing the silane coupling agent treatment as compared with the case without the treatment. In addition, the phenomenon that the resin pattern shifts due to the internal stress associated with the cross-linking reaction of the resin, which occurs when the adhesion between the resin and the base film is low, can be completely prevented by performing the silane coupling agent treatment. It was.

【0119】

The silane coupling agent may be applied to the base film as described above, may be blended in the resin material forming the interlayer insulating film, or may be used in combination. For example, by adding 1 wt% of dimethylethoxysilane to the photosensitive acrylic resin, the adhesion strength with the silicon nitride film was improved by 70%.

【0120】

(Embodiment 9) The ninth embodiment is a case where the adhesion between the interlayer insulating film 68 and the pixel electrode material formed on the interlayer insulating film 68 in the seventh embodiment is improved.

【0121】

In the above embodiment 7 of FIG. 9, after the interlayer insulating film 68 is formed of the photosensitive transparent acrylic resin, it is incinerated from the surface of the interlayer insulating film 68 to a film thickness of 100 to 500 nm by oxygen plasma using a dry etching apparatus. Processing was performed. In this ashing treatment, a parallel plate type plasma etching apparatus is used to ash the surface of the acrylic resin under the conditions of RF power 1.2KW, pressure 800mTorr, oxygen flow rate 300sccm, temperature 70 ° C, and RF application time 120sec. .. At this time, it is carried out in oxygen plasma, and the surface thereof becomes rough due to the oxidative decomposition of organic matter causing water and carbon dioxide to escape and exit.

【0122】

After that, the ITO film to be the pixel electrode 51 is subjected to this ashing treatment by sputtering to form a film with a film thickness of 50 to 150 nm on a photosensitive transparent acrylic resin having a rough surface, and patterning is performed to form the pixel electrode 51. By forming, an active matrix substrate is produced. By performing this ashing treatment, the adhesion between the pixel electrode 51 and the interlayer insulating film 68 made of the photosensitive transparent acrylic resin whose surface is roughened as the underlying film thereof is greatly improved, and ultrasonic waves are applied when cleaning the substrate. There was no film peeling between these films. Regarding the above-mentioned ashing treatment film thickness, if it is thinner than 100 nm, no effect can be obtained, and if it is thicker than 500 nm, the film loss of the photosensitive transparent acrylic resin is too large, so that the film is reduced in the substrate. The film thickness of the photosensitive transparent acrylic resin varies too much, which causes a display problem. The above dry etching apparatus has an effect of improving adhesion regardless of the barrel method, the RIE method, or the like.

【0123】

In this way, by incinerating the surface of the pixel electrode material on the interlayer insulating film 68 with oxygen plasma before forming the pixel electrode material, between the interlayer insulating film 68 and the pixel electrode material formed on the interlayer insulating film 68. Adhesion is improved, and a more stable device can be realized for processing during the process. Further, by performing this ashing treatment, the residue in the contact hole portion can be removed, so that there is also an effect of suppressing the occurrence of connection failure in the contact hole portion.

【0124】

In the present embodiment, the ashing treatment was performed after the cross-linking treatment of the resin forming the interlayer insulating film. Since the cross-linking reaction of the resin involves the generation of gas, there is an effect that the ashing treatment is stabilized by performing the ashing treatment after the cross-linking treatment rather than performing the ashing treatment before the cross-linking treatment of the resin.

【0125】

(Embodiment 10) FIG. 14 shows the configuration of one pixel portion of the active matrix substrate of the transmissive liquid crystal display device according to the tenth embodiment of the present invention. Further, FIG. 15 shows a cross-sectional view of the active matrix substrate of FIG. 14 along D-D'. The members having the same functions as those in FIGS. 1 and 2 are designated by the same reference numerals, and the description thereof will be omitted.

【0126】

In the active matrix substrate of the present embodiment, the contact between the TFT 24 and the pixel electrode 21 and the contact between the additional capacitance electrode 25a and the pixel electrode 21 are made through the contact holes 26a and 26b, respectively. Further, the source wiring 23 was formed of a single layer made of metal. Of course, a multi-layer structure having two or more layers may be used. The additional capacitance electrode 25a was formed in the same process using the same material as the source wiring 23, as in the previous embodiments. The contact holes 26a and 26b penetrating the interlayer insulating film 38 were formed at the upper part of the metal electrode 23b and the additional capacitance electrode 25a formed so as to partially overlap the drain electrode 36b, respectively. That is, the contact holes 26a and 26b are both formed on a metal electrode having a light-shielding property.

【0127】

The transmissive liquid crystal display device according to the present embodiment has the following advantages. The film thickness of the interlayer insulating film 38 used in the present invention is much thicker than that of the conventional one, for example, 3 μm. Since this thickness is equivalent to the typical liquid crystal layer thickness (cell gap) of 4.5 μm, light leakage occurs around the contact holes 26a and 26b due to the disordered orientation of the liquid crystal molecules. Therefore, when the contact holes 26a and 26b are formed in the opening of the transmissive liquid crystal display device, the contrast is lowered due to light leakage. On the other hand, in the active matrix substrate of the present embodiment, the additional capacitance electrode 25a, which is one of the electrodes forming the additional capacitance, blocks the vicinity of the contact hole 26b, and the metal electrode 23b shields the vicinity of the contact hole 26a. Therefore, the problem of contrast deterioration due to the contact holes 25a and 25b can be prevented. Further, the aperture ratio can be further improved by forming the additional capacitance counter electrode 27 so as not to protrude from the additional capacitance electrode 25a.

【0128】

Although the Cs-Common method has been described in this embodiment, the same effect can be obtained with the Cs-on-Gate method.

【0129】

In each of the above embodiments 1 to 10, the pixel electrodes and the wirings can be overlapped to improve the aperture ratio of the liquid crystal display and suppress the misalignment of the liquid crystal, and the manufacturing process can be simplified. It is possible to obtain a good display by further reducing the influence of the capacitance component between the wiring and the pixel electrode on the display such as cross talk. In addition to this, a wide viewing angle can be achieved.

【0130】

The reason why this wide viewing angle is achieved is that the surface of the pixel electrode is flat so that the orientation of the liquid crystal is not disturbed, the dispersion line due to the wiring electric field is eliminated, and the adjacent openings. By forming an interlayer insulating film on a thick film of several μm, the oblique light from the backlight can be effectively used, and the contrast is increased. That (1: 300 or more for 10.4 inch SVGA). Therefore, it has become possible to reduce the value of retardation, which is the refractive index anisotropy (Δn) × cell thickness (d) of the liquid crystal. Here, the cell thickness d is mainly changed. Generally, when Δn × d is made smaller, the viewing angle becomes wider, but the contrast becomes worse. However, in the present invention, by eliminating the margin conventionally provided between the pixel electrode and each wiring, the pixel electrode becomes larger. For example, in 10.4 inch VGA, the aperture ratio becomes 65% to 85%. It increased by 20 points (about 30%), and its brightness was more than 1.5 times. Also, with 12.1-inch XGA, the aperture ratio will be significantly improved from 55% to 80%. For example, in the conventional configuration, if the source wiring width is 6 μm, the distance between the source wiring and the element electrode is 3 μm, and the bonding accuracy is 5 μm, 22 μm or more is required as the distance between adjacent openings. On the other hand, if the configuration in which the picture element electrodes are superimposed on the source wiring is used, the distance between the adjacent openings can be set to 6 μm in the width of the source wiring, so that the area of the region that does not contribute to the display can be significantly reduced. Can be greatly improved.

【0131】

In the above-described embodiments 3 and 4, a transmissive liquid crystal display device having a structure in which one electrode of the additional capacitance (additional capacitance electrode) is connected to the counter electrode through the additional capacitance common wiring has been described. The same effect can be obtained with a structure in which the gate wiring 22 of adjacent pixels is used. This case is shown in the Cs-on-Gate type liquid crystal display device of FIGS. 12 and 13. This Cs-on-Gate method is a method in which the immediately preceding or next gate wiring 22 and the pixel electrode 21 are overlapped to form an additional capacitance Cs. At this time, it is desirable that the pixel electrode 21 is placed only slightly on the self-stage gate, and is placed larger on the immediately preceding or next gate.

【0132】

Further, in each of the above-described embodiments 1 to 10, after applying a highly transparent photosensitive transparent acrylic resin by a spin coating method, the photosensitive transparent acrylic resin is patterned and then patterned to form an interlayer insulating film, and the interlayer insulating film is penetrated to form the connection. A contact hole that reaches the electrodes is used, but it is not limited to the spin coating method, but other coating methods, such as the roll coating method (between a roll with irregularities and a belt, with the coating surface on the roll side) are used. The thickness to be applied is determined by the degree of this unevenness.) And the slot coating method (the substrate is passed under the discharge port. The width of this discharge port determines the thickness to be applied.) Even so, the effect of the present invention can be achieved.

【0133】

Further, in the above embodiments 7 and 8, the shortest wavelength of the i-line (wavelength 365 nm), h-line (wavelength 405 nm), and g-line (wavelength 436 nm), which are the emission lines of ultraviolet rays generally used in the exposure process. i-ray (wavelength 365 nm) is used. As a result, the light irradiation time can be shortened, the decolorization efficiency of the seventh embodiment is high, and the efficiency of roughening the surface of the eighth embodiment is also high.

【0134】

[Effect of the invention]

As described above, according to the present invention, if the pixel electrode is connected to the drain electrode of the switching element via the connection electrode, a contact hole or the like penetrating the interlayer insulating film can be formed even when the TFT becomes small. It is possible to easily take the connection part by. That is, since the size of the TFT can be reduced, the aperture ratio can be improved. Further, by providing the interlayer insulating film, each wiring and the pixel electrode can be overlapped with each other, the aperture ratio can be improved, and poor alignment of the liquid crystal can be suppressed. When an organic thin film is used as the interlayer insulating film, the relative permittivity is lower than that of the inorganic thin film, and the film thickness can be easily increased, so that the capacitance between each wiring and the pixel electrode can be reduced. Therefore, vertical crosstalk due to the capacitance between the source wiring and the pixel electrode can be reduced, and the feedthrough of the write voltage to the picture element due to the capacitance between the pixel electrode and the gate wiring and the manufacturing process Variation can be reduced.

【0135】

Further, this interlayer insulating film can be obtained with good productivity by a simple method of depoting a photosensitive insulating film such as a photosensitive acrylic resin and patterning by exposure and development. Therefore, it is possible to realize a transmissive liquid crystal display device having a high aperture ratio without significantly increasing the production cost.

【0136】

Further, the aperture ratio can be further improved by forming the connection electrode connecting the drain electrode and the pixel electrode of the TFT with a transparent conductive film. In this transparent conductive film, the source wiring can be formed at the same time as a two-layer structure, and if the source wiring has a two-layer structure, disconnection of the source wiring can be prevented.

【0137】

Further, by forming the contact hole penetrating the interlayer insulating film on the additional capacitance wiring or the gate wiring, light leakage is shielded at the additional capacitance portion and the contrast ratio can be improved.

【0138】

Further, when the pixel electrode and the source wiring are overlapped by 1 μm or more, the aperture ratio can be improved and the processing accuracy is also good. Further, when the thickness of the interlayer insulating film is 1.5 μm (preferably 2.0 μm) or more, the capacitance between the source wiring and the pixel electrode is sufficiently reduced even if the pixel electrode and the source wiring overlap by 1 μm or more. It is possible to obtain a good display.

【0139】

Further, by using a relatively thick interlayer insulating film in the present invention, flattening becomes possible, and a step such as a disconnection on the drain side of the pixel electrode, which has conventionally occurred in a step portion due to wiring in the lower layer thereof, etc. The influence of the above is eliminated, and the misalignment due to the step is prevented. In addition, since it is insulated by an interlayer insulating film between the source wiring and the pixel electrodes, defective elements due to electrical leakage between the source wiring and the pixel electrodes are extremely reduced, which makes it possible to improve the manufacturing yield and reduce the manufacturing cost. It can also be reduced. Further, in the present invention, the film formation, the pattern forming step by the photoresist, the etching, the resist peeling, and the cleaning step, which have been conventionally required for forming the interlayer insulating film, can be formed only by the photosensitive insulating film forming step. Therefore, it is possible to shorten and simplify the manufacturing process, and it is also possible to reduce the manufacturing cost.

【0140】

Further, when the film thickness of the pixel electrode is 50 nm or more, it is possible to prevent the chemical solution from entering through the gap between the film surfaces and suppress the swelling of the resin caused by the chemical solution used for the stripping solution.

【0141】

Furthermore, since the aperture ratio of the display can be improved, its brightness can also be improved, and the retardation can be reduced and the viewing angle can be widened without deteriorating the contrast, resulting in a large wide viewing angle. Can be achieved.

[Simple explanation of drawings]

[Figure 1]

It is a top view which shows the structure of 1 pixel part of the active matrix substrate in the transmissive liquid crystal display device of Embodiment 1 of this invention.

[Figure 2]

It is AA'cross-sectional view of the active matrix substrate in the transmissive liquid crystal display device of FIG.

[Fig. 3]

It is a top view which shows the structure of 1 pixel part of the active matrix substrate in the transmissive liquid crystal display device of Embodiment 3 of this invention.

[Fig. 4]

It is a B-B'cross-sectional view of the active matrix substrate in the transmissive liquid crystal display device of FIG.

[Fig. 5]

It is a partial cross-sectional view of the active matrix substrate in the transmissive liquid crystal display device of Embodiment 4 of this invention.

[Fig. 6]

It is a figure which shows the relationship between the charge rate difference and the capacity ratio of the liquid crystal in the transmissive liquid crystal display device of Embodiments 5 and 6 of this invention, and the conventional liquid crystal display device.

[Fig. 7]

(a) is a waveform diagram of the data signal in the case of 1H inversion in embodiments 5 and 6 of the present invention, and (b) is a waveform diagram of the data signal in the case of conventional field inversion.

[Fig. 8]

It is a figure which shows the relationship between the capacity ratio of the liquid crystal and the overlap width in the transmissive liquid crystal display device of Embodiment 5 of this invention.

[Fig. 9]

It is a top view which shows the structure of 1 pixel part of the active matrix substrate in the transmissive liquid crystal display device of Embodiment 7 of this invention.

[Fig. 10]

FIG. 9 is a C-C'cross-sectional view of an active matrix substrate in the transmissive liquid crystal display device of FIG.

[Fig. 11]

It is a figure which shows the change of the transmittance before and after exposure with respect to the wavelength (nm) of the transmitted light of the acrylic resin in the transmissive liquid crystal display apparatus of Embodiment 7 of this invention.

[Fig. 12]

It is a circuit diagram which shows the structure of the liquid crystal display device of the Cs-on-Gate system.

[Fig. 13]

It is a top view which shows the structure of one pixel part of the active matrix substrate when the structure of Embodiment 3 of this invention is applied to the liquid crystal display device of FIG.

[Fig. 14]

It is a top view which shows the structure of 1 pixel part of the active matrix substrate in the transmissive liquid crystal display device of Embodiment 10 of this invention.

[Fig. 15]

It is a D-D'cross-sectional view of the active matrix substrate in the transmissive liquid crystal display device of FIG.

[Fig. 16]

It is a circuit diagram which shows the structure of the conventional liquid crystal display device provided with an active matrix substrate.

[Fig. 17]

It is sectional drawing of the TFT part of the active matrix substrate in the conventional liquid crystal display device.

[Explanation of symbols]

6 Common wiring for additional capacity 21,51 pixel electrodes 22,52 Gate wiring 23,53 Source wiring 24,54 TFT 25,55 Connection electrode 26,26a, 26b, 56 Contact holes 31,61 Transparent insulating substrate 32,62 Gate electrode 36a, 66a Source electrode 36b, 66b Drain electrode 37a, 37a', 67a, 67a'Transparent conductive film 37b, 37b', 67b, 67b'metal layer 38,68 interlayer insulating film 41 Titanium nitride layer