JP3818984B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflective liquid crystal display device that performs display using reflected light of light incident on a panel surface of a liquid crystal panel, and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, application of liquid crystal display devices to word processors, laptop personal computers, pocket televisions, and the like has been rapidly progressing. Among liquid crystal display devices, in particular, a reflection type liquid crystal display device reflects light incident on the panel surface of the liquid crystal panel from the outside and performs display using the reflected light, so that a backlight is unnecessary. Therefore, the reflective liquid crystal display device has attracted attention because it consumes low power, is thin, and can be reduced in weight.
[0003]
Conventionally, TN (twisted nematic) system and STN (super twisted nematic) system are used for reflective liquid crystal display devices. In these methods, it is necessary to provide a polarizing plate in the liquid crystal display device. This polarizing plate inevitably prevents half of the natural light intensity from being used for display. Therefore, these methods have a problem that the display becomes dark.
[0004]
To solve this problem, a display mode has been proposed in which natural light is effectively used without using a polarizing plate. An example of such a display mode is a phase transition type guest / host system. In this method, a cholesteric-nematic phase transition phenomenon due to an electric field is used. A reflection type multi-color display in which a micro color filter is further combined with this method has been proposed. With such a display mode that does not require a polarizing plate, a bright display can be obtained without causing a decrease in light intensity due to the polarizing plate.
[0005]
Furthermore, in order to obtain a brighter display, it is necessary to increase the intensity of light scattered in a direction perpendicular to the display screen with respect to incident light from a wide angle. For this purpose, it is effective to provide a reflector having optimum reflection characteristics. As an example of a conventional method for manufacturing a reflector, a film is formed on a substrate, an etching method is used to form a plurality of fine irregularities of a predetermined shape on the substrate surface, and further on the film having the irregularities. A method of forming a reflection plate by forming a reflection film such as silver has been proposed.
[0006]
An active matrix reflective liquid crystal display device having such a reflector will be described in more detail. The reflective liquid crystal display device includes an active matrix substrate, a counter substrate (not shown) having a transparent electrode, and a liquid crystal layer (not shown) disposed between these substrates.
[0007]
Hereinafter, the structure of the active matrix substrate used in the reflective liquid crystal display device will be described in more detail with reference to the drawings. 7 is a partial plan view of the active matrix substrate 600, and FIG. 8 is a partial cross-sectional view taken along line Y-Y 'in FIG. Here, a thin film transistor (hereinafter referred to as TFT) is used as an active matrix switching element.
[0008]
As shown in FIGS. 7 and 8, in the active matrix substrate 600, a plurality of gate wirings 66a and source wirings 70a made of chromium, tantalum or the like are substantially parallel to each other on a substrate body 61 such as glass. They are arranged so as to be orthogonal. The gate wiring 66a functions as a scanning line, and the source wiring 70a functions as a signal line. The gate wiring 66a to the gate electrode 66b and the source wiring 70a to the source electrode 70b are branched from each other. As shown in FIG. 8, silicon nitride (SiN) is formed on the entire surface of the substrate body 61 so as to cover the gate electrode 66b._x) And silicon oxide (SiO₂) Etc. are provided. A semiconductor layer 68 made of amorphous silicon is disposed on the gate insulating film 67 and at a position corresponding to the upper side of the gate electrode 66b. On one end portion of the semiconductor layer 68, a source electrode 70 b made of titanium, molybdenum, aluminum, or the like is disposed so as to be partially bonded to the semiconductor layer 68. In addition, a drain electrode 71 made of titanium, molybdenum, aluminum, or the like is disposed at the other end of the semiconductor layer 68 so as to be partially joined to the semiconductor layer 68 in the same manner as the source electrode 70b. The source electrode 70b and the drain electrode 71 are disposed with a space therebetween and are not joined to each other. A first film 62 having a concavo-convex portion is provided on a portion of the substrate body 61 except for the drain electrode 71. Further, a pixel electrode 65 made of a metal such as aluminum or silver is disposed on the first film 62. The pixel electrode 65 is disposed so as to be partially bonded to the semiconductor layer 68 on the end of the drain electrode 71 opposite to the side bonded to the semiconductor layer 68. The pixel electrode 65 also functions as a reflective film. The gate electrode 66b, the gate insulating film 67, the semiconductor layer 68, the source electrode 70b, and the drain electrode 71 constitute a TFT, and this TFT has a function of a switching element.
[0009]
In the reflective liquid crystal display device including the active matrix substrate as described above, external light incident from the counter substrate side is reflected by the pixel electrode (reflective film) 65 of the active matrix substrate, and the reflected light passing through the liquid crystal layer is opposed. Viewed from the substrate side.
[0010]
A process for forming the pixel electrode 65 having such an uneven portion and functioning as a reflective film will be described in detail below. FIG. 9 is a diagram for explaining a manufacturing process of a portion A in FIG. First, as shown in FIG. 9A, the first film 62 is formed on the gate insulating film 67 on the substrate body 61. Next, as shown in FIG. 9B, a photoresist 63 is applied thereon and patterned into a predetermined shape. As shown in FIG. 9C, the first film 62 is etched to form a large number of fine irregularities. Thereafter, as shown in FIG. 9D, the photoresist 63 is peeled off, and a pixel electrode (reflective film) 65 is formed on the first film 62 having an uneven portion. Thus, the pixel electrode 65 having the concavo-convex portions (the convex portions 65a and the concave portions 65b) is formed.
[0011]
If the first film 62 is formed on the substrate 61 on which the TFT is formed as described above, a plurality of fine uneven portions can be easily formed on the first film 62 by using an etching method. By forming the pixel electrode 65 with a metal or the like on the substrate 61 having the uneven portion of the first film 62, the pixel electrode 65 having the uneven portion and functioning as a reflective film can be easily obtained.
[0012]
However, in the reflective film 65 formed by the method as described above, as shown in FIG. 9D, the protrusion 65a formed in the portion where the photoresist 63 was deposited at the time of etching, and the insulating film 62 Are removed by etching and the top surface of the recess 65b formed in the portion where the gate insulating film 67 is exposed is flat and close to a mirror surface state. Therefore, the reflected light reflected by the convex part 65a and the concave part 65b contains many regular reflection components. When there are many specular reflection components, there is a problem that reflected light interferes with each other and good white display cannot be performed.
[0013]
In order to solve this problem, it is possible to devise etching to increase the area of the slope portion connecting the convex portion 65a and the concave portion 65b. However, such a method cannot completely eliminate the flat portions of the convex portions 65a and the concave portions 65b. Alternatively, etching of the first film can be stopped halfway so that the underlying gate insulating film 67 is not exposed. However, even in this case, the etching cannot be controlled uniformly within the substrate surface, and there arises a problem that the etching shape differs within the surface, and as a result, the reflection characteristics differ within the surface.
[0014]
In order to solve this problem, a reflection type liquid crystal display device in which the shape of the reflection plate is further devised is known (Japanese Patent Laid-Open No. 5-232465). This reflective liquid crystal display device includes a substrate on which a TFT and a reflective plate are disposed, a counter substrate on which a counter electrode is disposed, and a guest / host liquid crystal layer disposed between the substrates.
[0015]
A manufacturing process of a reflector used in such a reflective liquid crystal display device will be described below with reference to FIG. FIG. 10 is a diagram for explaining a manufacturing process of a region corresponding to FIG. 9 (a diagram for explaining a manufacturing process of a portion A in FIG. 8).
[0016]
As shown in FIG. 10A, the first film 62 is formed on the substrate body 61. Next, as shown in FIG. 10B, a photoresist 63 is applied and patterned into a predetermined shape. As shown in FIG. 10C, the first film 62 is etched to form a plurality of fine irregularities. Thereafter, as shown in FIG. 10 (d), the photoresist 63 is peeled off, and a liquid material such as an acrylic resin is applied on the first film 62 having the concavo-convex portion, which is then cured to form the second film 64. Form. Further, as shown in FIG. 10E, the electrode 65 is formed on the second film 64. The electrode 65 functions as a reflecting plate, and thus the reflecting plate 65 is formed.
[0017]
When the acrylic resin is applied in such a thickness that the substrate 61 does not appear, the uneven portion of the first film 62 can be eliminated, and regular reflection of incident light by the reflector can be reduced. . In addition, it is possible to eliminate surface irregularities generated in the uneven portions of the substrate 61 or the first film 62 and uneven reflection due to etching residues. The material of the second film 64 can be applied in a liquid state, and any suitable material that can be cured after application can be used. For example, in addition to the acrylic resin described above, an epoxy resin and the like can be given. As the material of the reflective film 65, aluminum, silver, nickel or the like having high reflection efficiency is used.
[0018]
The reflector 65 manufactured in this way has an advantage that it has a reflection characteristic that is uniform and has good light scattering properties.
[0019]
[Problems to be solved by the invention]
The reflective liquid crystal display device described with reference to FIGS. 9 and 10 employs an inverted staggered TFT. In the reflective liquid crystal display device of FIG. 9, it is necessary to form the first film 62 in order to form the concavo-convex part in the process of forming the reflector 65 after the source bus line is formed. On the other hand, in the reflection type liquid crystal display device of FIG. 10 with improved reflection characteristics, it is necessary to form the first film 62 and the second film 64 in order to form the concavo-convex part, and the reflection type liquid crystal display of FIG. There are many manufacturing processes compared to the device.
[0020]
In contrast to the inverted stagger type TFT, the top gate type TFT can form a gate bus line after forming an active layer (for example, a polycrystalline silicon layer requiring high process temperature) and a gate insulating film. Therefore, after annealing the active layer at a high temperature to improve the characteristics, a metal such as Al that cannot be used at a high process temperature can be used as a gate bus line material. Further, the top gate type TFT has an advantage that it is easy to form a self-aligned source / drain without requiring a resist mask because impurities can be doped into the source / drain using the gate as a mask.
[0021]
When the formation method of the reflector as shown in FIG. 10 is adopted as it is for the top gate type TFT, it is necessary to form a total of three insulating films to form the concavo-convex portion after the source bus line is formed. Therefore, the number of manufacturing steps is further increased. Such an increase in the number of manufacturing steps causes a decrease in yield.
[0022]
Furthermore, the conventional reflective liquid crystal display device can display only by using the reflected light of the incident light. However, there is a demand for a liquid crystal display device capable of bright display even when incident light is dark and sufficient light intensity cannot be obtained.
[0023]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a top gate provided with a reflective plate having a uniform and good light scattering property without increasing the number of manufacturing steps. It is an object of the present invention to provide a reflective liquid crystal display device using a TFT and a method for manufacturing the same. It is another object of the present invention to provide a transflective liquid crystal display device that has the advantages of the above-described reflective liquid crystal display device using a top-gate TFT and can display a transmission mode.
[0024]
[Means for Solving the Problems]
  The liquid crystal display device of the present invention is a liquid crystal display device having a pair of substrates, a liquid crystal layer disposed between the pair of substrates, and a backlight: one of the pair of substrates A semiconductor layer, a gate insulating film, and a gate electrode sequentially disposed on the gate, a gate bus line and an additional capacitor common wiring provided on the one substrate, the one substrate, the semiconductor layer, and the gate insulation A first insulating film disposed on the film, the gate electrode, the gate bus line, and the additional capacitor common wiring and having a contact hole; and the first insulating film on the first insulating film. A source electrode disposed so as to be connected to the semiconductor layer through a contact hole; a second insulating film disposed on the first insulating film so as to cover the source electrode; and the second insulating film And a pixel electrode disposed on the top. The additional capacitor common line is disposed in the pixel region, and the pixel electrode includes a transparent electrode formed of a transparent conductive film and a reflective electrode formed of metal, and the reflective electrode is formed of the additional electrode. Formed on the capacitor common line, one pixel has a non-light-transmitting region that does not transmit light from the backlight by the reflective electrode, and a light-transmitting region that is not shielded by the reflective electrode.
[0025]
The liquid crystal display device of the present invention is a liquid crystal display device having a pair of substrates, a liquid crystal layer disposed between the pair of substrates, and a backlight: one of the pair of substrates A semiconductor layer, a gate insulating film, and a gate electrode sequentially disposed on the substrate, a gate bus line and an additional capacitor common wiring provided on the one substrate, the one substrate, the semiconductor layer, A first insulating film disposed on the gate insulating film, the gate electrode, the gate bus line, and the additional capacitor common line and having a contact hole; and the first insulating film on the first insulating film. A source electrode disposed so as to be connected to the semiconductor layer through the contact hole, a second insulating film disposed on the first insulating film so as to cover the source electrode, and the second electrode A pixel electrode disposed on the insulating film; The additional capacitor common line is disposed in the pixel region, and the pixel electrode includes a transparent electrode formed of a transparent conductive film and a rectangular reflective electrode formed of metal, and the reflective electrode An electrode is formed on the additional capacitor common line and the TFT, and one pixel includes a non-translucent area where light from the backlight is not transmitted by the reflective electrode and a translucent area which is not shielded by the reflective electrode. Have.
[0026]
  It is preferable that the additional capacitance common wiring does not transmit light..
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below, but the present invention is not limited thereto. Note that the same reference numerals are given to the same members throughout the respective embodiments and comparative examples.
[0047]
(Embodiment 1)
The reflective liquid crystal display device of this embodiment includes an active matrix substrate, a counter substrate (not shown) provided with a counter electrode, and a liquid crystal layer (not shown) provided between the substrates. . Hereinafter, the active matrix substrate characteristic of the present invention will be mainly described.
[0048]
FIG. 1 is a partial cross-sectional view of an active matrix substrate in the present embodiment in the order of manufacturing steps. The active matrix substrate described with reference to FIGS. 7 to 8 as a conventional technique is an inverted stagger type TFT, whereas in this embodiment, a coplanar type (top gate type) TFT is adopted.
[0049]
Hereinafter, the structure of the active matrix substrate 100 in this embodiment will be described with reference to FIG. A polycrystalline silicon thin film (semiconductor layer) 2, a gate insulating film 3, and a gate electrode 6 are sequentially disposed on the insulating substrate 1. The polycrystalline silicon thin film 2 includes a channel portion 2a that is a non-doped region under the gate insulating film 3, and doped regions 2b and 2c on both sides of the channel portion 2a. A first interlayer insulating film 5 having a concavo-convex pattern portion 20 and contact holes 8 and 9 is disposed on the insulating substrate 1. The concave portion of the first interlayer insulating film 5 is equal to the substrate surface of the insulating substrate 1, and the contact holes 8 and 9 communicate with the doped regions 2 b and 2 c of the polycrystalline silicon thin film 2, respectively. Further, the gate electrode 6 is surrounded by the first interlayer insulating film 5 and the gate insulating film 3. A source bus line (source electrode) 10 and a drain electrode 11 are arranged on the first interlayer insulating film 5 at a distance from each other, and are connected to the doped regions 2b and 2c through the contact holes 8 and 9, respectively. . The gate electrode 6, the gate insulating film 3, the polycrystalline silicon thin film 2, the source bus line 10, and the drain electrode 11 constitute a top gate type TFT. A second interlayer insulating film 14 having a contact hole 13 is disposed on such a structure, and the contact hole 13 communicates with the drain electrode 11. A pixel electrode 15 is disposed on the second interlayer insulating film 14, and the pixel electrode 15 is connected to the drain electrode 11 through the contact hole 13. The pixel electrode 15 also functions as a reflector. In this way, one pixel region is configured. The active matrix substrate 100 has a structure in which a plurality of such pixel regions are arranged in a matrix.
[0050]
Next, with reference to FIGS. 1A to 1F, a method of manufacturing the active matrix substrate 100 in the present embodiment will be described below.
[0051]
First, as shown in FIG. 1A, a polycrystalline silicon thin film 2 serving as an active layer was formed on an insulating substrate 1 with a thickness of about 40 nm to about 80 nm.
[0052]
Next, using sputtering or CVD, etc., SiO₂Or SiN_xA gate insulating film 3 made of or the like was formed with a thickness of about 80 nm. Here, the pattern of the additional capacitor electrode is omitted for simplification. Thereafter, the gate electrode 6 and the gate bus line were formed using Al or polycrystalline silicon. During the patterning of the gate electrode 6, the gate insulating film 3 has the same shape as the gate electrode 6 as shown in FIG.
[0053]
Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are about 1 × 10 from the side opposite to the insulating substrate 1 side (upper side in the figure) with respect to the polycrystalline silicon thin film 2 using the gate electrode 6 as a mask.¹⁵(cm^-2) To form a non-doped channel portion 2 a in the lower region of the gate electrode 6. Both side regions of the channel portion 2a are high-concentration impurity doped regions 2b and 2c. Here, the polycrystalline silicon thin film 2 may have a structure in which a low-concentration impurity region or a non-doped region is provided in the vicinity of the channel portion 2a to reduce leakage current when the TFT is turned off.
[0054]
Next, the first interlayer insulating film 5 is formed on the entire surface of the above substrate using a photosensitive organic material with a thickness of about 0.8 μm to about 5 μm, and then contact holes 8 and 9 are formed. did. In this embodiment, the concavo-convex pattern portion 20 was formed simultaneously with the formation of these contact holes (FIG. 1C). An inorganic material may be used for the first interlayer insulating film 5, but an organic material is preferably used as in the present embodiment.
[0055]
Next, as shown in FIG. 1D, the source bus line 10 and the drain electrode 11 were formed using a low-resistance metal such as Al. Next, as shown in FIG. 1E, a second interlayer insulating film 14 made of a photosensitive organic material was formed by spin coating. The second interlayer insulating film 14 preferably has a thickness of about 0.3 μm to about 1 μm, and is preferably thinner than the thickness of the first interlayer insulating film 5 (that is, the concavo-convex pattern portion 20). An inorganic material may be used for the second interlayer insulating film 14, but an organic material is preferably used as in the present embodiment.
[0056]
Next, as shown in FIG. 1 (f), a contact hole 13 is formed in the second interlayer insulating film 14 so as to communicate with the drain electrode 11, and is connected to the drain electrode 11 through the contact hole 13. The pixel electrode 15 was formed of a highly reflective material such as Al. The pixel electrode 15 is formed at least in the opening of the liquid crystal panel. You may form so that the periphery of the pixel electrode 15 may overlap with a switching element, a gate bus line, and / or a source bus line. The active matrix substrate 100 was produced as described above.
[0057]
Finally, after forming an alignment film on each of the counter substrate (not shown) on which the counter electrode is formed and the active matrix substrate, the active matrix substrate and the counter substrate are bonded together, and a liquid crystal is formed between these substrates. A liquid crystal layer was formed by encapsulating, thereby producing a reflective liquid crystal display device (not shown). Any appropriate substrate and liquid crystal layer may be used for the counter substrate and the liquid crystal layer.
[0058]
According to the present embodiment, the first interlayer insulating film 5 has the concavo-convex pattern portion 20, and the second interlayer insulating film 14 is provided on the first interlayer insulating film 5, so that the manufacturing process is increased. Accordingly, the flat portion of the pixel electrode 15 formed on the second interlayer insulating film can be eliminated. Here, in order to obtain the pixel electrode 15 having improved light scattering properties and more excellent reflection characteristics, the thickness of the first interlayer insulating film 5 is preferably 0.8 μm or more and 5 μm or less. Furthermore, the thickness of the second interlayer insulating film 14 is preferably smaller than the thickness of the first interlayer insulating film 5 and not less than 0.3 μm and not more than 1 μm.
[0059]
According to the present embodiment, the second interlayer insulating film 14 is formed on the source bus line 10. In the absence of the second interlayer insulating film 14, the pixel electrode 15 needs to be bonded to the drain electrode 13 and disposed so as not to contact other conductive members (such as the source bus line 10). Yes, the area of the pixel electrode is limited to these. On the other hand, according to the present embodiment, since the second interlayer insulating film 14 is formed on the source bus line 10, the pixel electrode 15 can be formed to overlap the TFT and the source bus line 10. it can. Therefore, the size of the pixel electrode 15 contributing to display can be further increased. Further, by providing the second interlayer insulating film 14, the flat portion of the pixel electrode (reflecting plate) 15 formed thereon is eliminated, and thus the reflecting property of the reflecting plate 15 is uniform and the light scattering property is good. Obtainable.
[0060]
In the top gate TFT used in this embodiment, the gate bus line can be formed after the active layer 2 (for example, a polycrystalline silicon layer requiring a high process temperature) and the gate insulating film 3 are formed. Therefore, after annealing the active layer at a high temperature to improve the characteristics, a metal such as Al that cannot be used at a high process temperature can be used as a gate bus line material. Further, since the impurity can be doped into the source / drain using the gate as a mask, a self-aligned source / drain can be easily formed without the need for a resist mask.
[0061]
According to the present embodiment, an organic material is used for the first interlayer insulating film 5. This film made of an organic material has a relative dielectric constant as small as 4 or less, can reduce the capacity of the gate bus line and the source bus line, and can prevent signal propagation delay in each bus line. Furthermore, since the upper portion of the gate bus line is flattened, disconnection of the source bus line due to the step of the gate bus line can be reduced. Furthermore, the organic film can be easily formed into a thick insulating film by using a spin coating method.
[0062]
Furthermore, according to the present embodiment, an organic material is used for the second interlayer insulating film 14. Since the organic film has a relative dielectric constant as small as 4 or less as described above, the capacitance of the pixel electrode can be reduced and the potential fluctuation of the pixel electrode due to the electrode below the pixel electrode can be suppressed. Furthermore, the reverse tilt of the liquid crystal material can be suppressed by reducing the influence of the electric field from the source bus line. Furthermore, since the thickness of the second interlayer insulating film 14 is thinner than the thickness of the first interlayer insulating film 5, similarly to the reflective liquid crystal display device in which a two-layer organic material of a comparative example described later is formed, The light scattering property of the reflecting plate (pixel electrode) 15 can be improved.
[0063]
Further, when a photosensitive material is used for the first interlayer insulating film 5 and / or the second interlayer insulating film 14, there is no need to perform a new etching unlike when an inorganic material is used, and it is easy only by a photo process. An uneven pattern can be formed.
[0064]
Although the coplanar TFT has been described in this embodiment, the present invention can be applied to other top gate TFTs, for example, staggered TFTs.
[0065]
(Comparative example)
As a comparative example, a reflection type liquid crystal display device in which the reflector according to the prior art described with reference to FIG. 10 is used in a coplanar type (top gate type) TFT as in the first embodiment will be described. As in the first embodiment of the present invention, the reflective liquid crystal display device of this comparative example is disposed between an active matrix substrate, a counter substrate (not shown) on which a counter electrode is disposed, and these substrates. A liquid crystal layer (not shown). The active matrix substrate of this comparative example will be described below with a focus on differences from the active matrix substrate characteristic of the present invention. A partial cross-sectional view is shown in FIG.
[0066]
FIG. 2 is a partial cross-sectional view of an active matrix substrate in this comparative example. The active matrix substrate 200 will be described with reference to FIG. 2 in comparison with the active matrix substrate 100 of the first embodiment shown in FIG. In the active matrix substrate 200, the active matrix substrate 100 in the first embodiment shown in FIG. 1F and the first interlayer insulating film 5 do not have the concave / convex pattern portion 20, and instead, the second interlayer insulating film 14. Is different only in that it has an uneven pattern portion 20 and a third interlayer insulating film 17 is provided between the second insulating film 14 and the pixel electrode 15.
[0067]
Next, a method for manufacturing the active matrix substrate 200 in this comparative example will be described below with reference to FIG.
[0068]
First, a polycrystalline silicon thin film 2 serving as an active layer was formed on the insulating substrate 1 with a thickness of about 40 nm to about 80 nm. Next, SiO2 is formed by sputtering or CVD.₂Or SiN_xA gate insulating film 3 made of is formed with a thickness of about 80 nm.
[0069]
Next, a gate electrode 6 made of Al or polycrystalline silicon was formed. Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are about 1 × 10 from the side opposite to the insulating substrate 1 side (upper side in the figure) with respect to the polycrystalline silicon thin film 2 using the gate electrode 6 as a mask.¹⁵(cm^-2The non-doped channel portion 2a is formed in the lower region of the gate electrode 6, and both side regions of the channel portion 2a are made to be highly doped impurity regions 2b and 2c.
[0070]
Next, SiO₂After forming the first interlayer insulating film 5 made of etc. over the entire surface, contact holes 8 and 9 were formed.
[0071]
Next, the source bus line 10 and the drain electrode 11 were formed using a low-resistance metal such as Al. Next, a second interlayer insulating film 14 made of a photosensitive organic material was formed by spin coating. Then, the contact hole 13 was formed in the second interlayer insulating film 14 so as to communicate with the drain electrode 11, and the concavo-convex pattern portion 20 was formed in the reflection plate formation region.
[0072]
Next, a third insulating film 17 was formed on the second interlayer insulating film 14 using a photosensitive material at least in the pixel electrode formation region. Here, the third insulating film 17 is not formed in the contact hole 13, and the drain electrode 11 is exposed.
[0073]
Next, the pixel electrode 15 was formed of a highly reflective material such as Al so as to be connected to the drain electrode 11 through the contact hole 13.
[0074]
In this comparative example, after the source bus line is formed, the second interlayer insulating film 14 and the third interlayer insulating film 17 are formed in order to form the reflector (pixel electrode) 15 having no flat portion. It is necessary to form a total of three insulating films. For this reason, the number of manufacturing steps is increased as compared with the first embodiment of the present invention.
[0075]
(Embodiment 2)
In the present embodiment, a transflective liquid crystal display device capable of displaying in a transmissive mode will be described. In this transflective liquid crystal display device, when the external light is bright, the reflective mode is used to reflect the incident light, and when the external light is dark, the display is switched to the transmissive mode and displayed by the backlight. It is possible to perform. Similar to the first embodiment, the transflective liquid crystal display device according to the present embodiment includes an active matrix substrate, a counter substrate (not shown) provided with a counter electrode, and a liquid crystal provided between the substrates. A layer (not shown).
[0076]
Hereinafter, the active matrix substrate characteristic of the present invention will be mainly described. FIG. 3 is a partial plan view of the active matrix substrate 300. 4 is a partial cross-sectional view taken along line A-A ′ in FIG. 3.
[0077]
As shown in FIGS. 3 and 4, the active matrix substrate 300 has a different structure from the active matrix substrate 100 in the first embodiment shown in FIG. The active matrix substrate 300 does not have the drain electrode 11, and the transparent electrode 15 a in which the pixel electrode 15 on the second interlayer insulating film 14 is connected to the polycrystalline silicon thin film 2 through the contact holes 9 and 13, It consists of a reflective electrode 15b disposed on the transparent electrode 15a. Here, the polycrystalline silicon thin film 2 is disposed so as to extend below the concavo-convex pattern portion 20 of the first interlayer insulating film 5. On the polycrystalline silicon thin film 2, the gate insulating film 3 and the gate electrode 6 are arranged. The additional capacitor insulating film 3a and the additional capacitor upper electrode 6a are similarly laminated and spaced from each other. Further, an additional capacitor common wiring for connecting a plurality of additional capacitors is also provided. In this liquid crystal display device, referring to FIG. 3, one pixel is non-transparent so as not to transmit backlight light by a reflective electrode 15b disposed on the upper part of a TFT formation portion, an electrode additional capacitance formation portion or the like. It has a light region (shaded portion in FIG. 3) and a light-transmitting region that is not shielded by the reflective electrode 15b. Only in this non-light-transmitting region, the first interlayer insulating film 5 has a recess (indicated by a dotted circle in FIG. 3). In other regions, the first interlayer insulating film 5 has a flat shape. The transparent electrode 15a is disposed not only in the non-light-transmitting region but also in the light-transmitting region.
[0078]
Next, a method for manufacturing the active matrix substrate 300 in the present embodiment will be described below with reference to FIGS.
[0079]
First, a polycrystalline silicon thin film 2 serving as an active layer was formed on the insulating substrate 1 with a thickness of about 40 nm to about 80 nm. This polycrystalline silicon thin film simultaneously becomes an additional capacitor lower electrode.
[0080]
Next, using sputtering or CVD, etc., SiO₂Or SiN_xA gate insulating film 3 made of or the like was formed with a thickness of about 80 nm. Thereafter, the gate electrode 6, the gate bus line, the additional capacitor upper electrode 6a, and the additional capacitor common wiring were formed using Al or polycrystalline silicon. When patterning the gate electrode 6, the gate bus line, the additional capacitor upper electrode 6a, and the additional capacitor common wiring, the gate insulating film 3 and the additional capacitor insulating film 3a have the same shape as the gate electrode 6 and the additional capacitor upper electrode 6a, respectively. It was.
[0081]
Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are about 1 × 10 from the side opposite to the insulating substrate 1 side (upper side in the figure) with respect to the polycrystalline silicon thin film 2 using the gate electrode 6 as a mask.¹⁵(cm^-2) To form a non-doped channel portion 2 a in the lower region of the gate electrode 6. Both side regions of the channel portion 2a are high-concentration impurity doped regions 2b and 2c. Here, the polycrystalline silicon thin film 2 may have a structure in which a low-concentration impurity region or a non-doped region is provided in the vicinity of the channel portion 2a to reduce leakage current when the TFT is turned off.
[0082]
Next, the first interlayer insulating film 5 is formed on the entire surface of the substrate as described above using a photosensitive organic material so that the gate electrode 6 is not exposed, and then contact holes 8 and 9 are formed. did. In the present embodiment, the concavo-convex pattern portion 20 was formed simultaneously with the formation of these contact holes. The concavo-convex pattern portion 20 was formed in the shaded portion in FIG. 3, that is, the non-light-transmitting region in the liquid crystal display device. An inorganic material may be used for the first interlayer insulating film 5.
[0083]
Next, the source bus line 10 was formed using a low resistance metal such as Al. Next, a second interlayer insulating film 14 made of a photosensitive organic material was formed by spin coating. An inorganic material may be used for the second interlayer insulating film 14.
[0084]
Next, a contact hole 13 is formed in the second interlayer insulating film 14 so as to communicate with the polycrystalline silicon thin film 2 at a position corresponding to the contact hole 9 above the drain region of the TFT. A transparent electrode 15a serving as a pixel electrode was formed of a transparent conductive film so as to be connected to the electrode 11.
[0085]
Next, a reflective electrode 15b serving as a pixel electrode is formed of a highly reflective metal such as Al or Ag in the hatched portion in FIG. The pixel electrode 15 includes a transparent electrode 15a and a reflective electrode 15b. Here, the pixel electrode 15 has a laminated structure of a transparent conductive film 15a and a highly reflective metal 15b. For example, a plurality of TFTs are provided for one pixel, and each TFT has a transparent conductive film and a highly reflective film. It is good also as a structure which connected with other metals. As described above, the active matrix substrate 300 is manufactured.
[0086]
Finally, after forming an alignment film on each of the counter substrate on which the counter electrode is formed and the active matrix substrate, the active matrix substrate and the counter substrate are bonded to each other, and liquid crystal is sealed between these substrates. A display device was produced. This liquid crystal display device includes a backlight.
[0087]
According to the present embodiment, the same effect as described above can be obtained for the same configuration as that of the first embodiment. In addition, according to the present embodiment, since the pixel electrode is composed of a transparent electrode and an electrode having a high reflectance, the incident light is reflected when the external light is bright using the top gate type TFT, and the reflected light When the display is performed and the outside light is dark, it is possible to switch to the transmissive mode and display with the backlight.
[0088]
In the present embodiment, the additional capacitor common wiring and the additional capacitor portion that do not transmit light are formed in the vicinity of the gate bus line, and the reflective electrode 15b that does not transmit light is formed on this portion. When used, loss of light intensity due to light shielding of the reflective electrode 15b can be reduced. Furthermore, since the rectangular reflective electrode 15b is manufactured in accordance with the shapes of the additional capacitor common wiring and the additional capacitor portion, the reflective electrode 15b is not separated and is easy to manufacture. Furthermore, since the reflective electrode 15b and the transparent electrode 15a of the pixel electrode 15 are both formed in a rectangular shape, the pixel electrode 15 can be easily manufactured. In addition, the reflective electrode 15b is formed on the TFT and can block the light irradiated to the TFT, so that deterioration of the TFT characteristics can be prevented.
[0089]
(Embodiment 3)
The reflective liquid crystal display device of this embodiment is a modification of the reflective liquid crystal display device described in the first embodiment. The active matrix substrate used in the reflective liquid crystal display device of this embodiment includes a coplanar type (top gate type) TFT as in the first embodiment. The reflective liquid crystal display device according to the present embodiment differs from the reflective liquid crystal display device according to the first embodiment in that the concavo-convex pattern portion is formed using the material used for TFT formation, the interlayer insulating film, and the like. The active matrix substrate used in the reflective liquid crystal display device of this embodiment will be described below with a focus on differences from the first embodiment. FIG. 5 is a partial cross-sectional view of the active matrix substrate in the present embodiment in the order of the manufacturing process.
[0090]
As shown in FIG. 5E, the active matrix substrate 400 in the present embodiment includes the concavo-convex pattern portion 20 having a laminated structure on the insulating substrate 1. The concavo-convex pattern portion 20 includes pattern layers 2p, 3p, 6p, and 5p made of the same material as the polycrystalline silicon thin film (semiconductor layer) 2, the gate insulating film 3, the gate electrode 6, and the first interlayer insulating film 5, respectively. Are sequentially stacked and patterned in the same shape.
[0091]
Next, with reference to FIGS. 5A to 5E, a method for manufacturing the active matrix substrate 400 in the present embodiment will be described below.
[0092]
First, as shown in FIG. 5A, a polycrystalline silicon thin film 2 serving as an active layer was formed on an insulating substrate 1 with a thickness of about 40 nm to about 80 nm. At the same time, the pattern layer 2p, which later forms the concavo-convex pattern portion 20, was formed using the same material as the polycrystalline silicon thin film 2.
[0093]
Next, using sputtering or CVD, etc., SiO₂Or SiN_xA gate insulating film 3 made of or the like was formed with a thickness of about 80 nm. Here, the pattern of the additional capacitor electrode is omitted for simplification. Thereafter, the gate electrode 6 was formed with a thickness of about 500 nm using Al or polycrystalline silicon. At the time of patterning of the gate electrode 6, the gate insulating film 3 has the same shape as the gate electrode 6 as shown in FIG. Here, simultaneously with the formation of the gate insulating film 3 and the gate electrode 6, the pattern layers 3p and 6p made of the same material as the gate insulating film 3 and the gate electrode 6 were laminated on the pattern layer 2p.
[0094]
Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are about 1 × 10 from the side opposite to the insulating substrate 1 side (upper side in the figure) with respect to the polycrystalline silicon thin film 2 using the gate electrode 6 as a mask.¹⁵(cm^-2) To form a non-doped channel portion 2 a in the lower region of the gate electrode 6. Both side regions of the channel portion 2a are high-concentration impurity doped regions 2b and 2c. Here, the polycrystalline silicon thin film 2 may have a structure in which a low-concentration impurity region or a non-doped region is provided in the vicinity of the channel portion 2a to reduce leakage current when the TFT is turned off.
[0095]
Next, the first interlayer insulating film 5 is made of SiO.₂The contact holes 8 and 9 were formed in the first interlayer insulating film 5 with a thickness of about 500 nm and the entire surface of the substrate. In this embodiment, as shown in FIG. 5C, the first interlayer insulating film 5 formed in the recesses of the pattern layers 2p, 3p, and 6p is removed simultaneously with the formation of the contact holes 8 and 9. Thus, the insulating substrate 1 was partially exposed. Thereby, a pattern layer 5p made of the same material as that of the first interlayer insulating film 5 is laminated on the convex portion of the pattern layer 6p, and the concavo-convex pattern having a laminated structure of the pattern layers 2p, 3p, 6p, and 5p. Part 20 was formed. The uneven pattern portion 20 has a thickness of about 0.8 μm to about 5 μm.
[0096]
Next, as shown in FIG. 5D, the source bus line 10 and the drain electrode 11 were formed using a low-resistance metal such as Al. Next, a second interlayer insulating film 14 made of a photosensitive organic material was formed by spin coating, and a contact hole 13 was formed in the second interlayer insulating film 14 so as to communicate with the drain electrode 11. The second interlayer insulating film 14 has a thickness of about 0.3 μm to about 1 μm, and is preferably thinner than the thickness of the concavo-convex pattern portion 20. An inorganic material may be used for the second interlayer insulating film 14, but an organic material is preferably used as in the present embodiment.
[0097]
Next, as shown in FIG. 5E, the pixel electrode 15 is formed of a highly reflective material such as Al so as to be connected to the drain electrode 11 through the contact hole 13. The pixel electrode 15 is formed at least in the opening of the liquid crystal panel. You may form so that the periphery of the pixel electrode 15 may overlap with a switching element, a gate bus line, and / or a source bus line. The active matrix substrate 400 was manufactured as described above.
[0098]
Finally, in the same manner as in the reflective liquid crystal display device of Embodiment 1, after forming an alignment film on each of a counter substrate (not shown) on which a counter electrode is formed and an active matrix substrate, it faces the active matrix substrate. The substrates were bonded together, and liquid crystal was sealed between these substrates to form a liquid crystal layer, thereby producing a reflective liquid crystal display device (not shown).
[0099]
According to the present embodiment, the same effect as described above can be obtained for the same configuration as that of the first embodiment. In addition, according to this embodiment, the materials used for forming the TFTs are used to form a pattern and are sequentially stacked. Thereby, unlike the first embodiment, even when an inorganic insulating film is used as the first interlayer insulating film, a concavo-convex pattern portion having a thickness of about 0.8 μm to about 5 μm can be formed. . In the coplanar type (top gate type) TFT as in this embodiment, in particular, a thickness of about 0.8 μm or more can be easily obtained by laminating two layers of a thick gate electrode and a first interlayer insulating film. It is possible to form a concavo-convex pattern portion having By forming the second interlayer insulating film on the concavo-convex pattern portion, it is possible to form a reflector with good reflection characteristics by the same number of processes as the number of TFT forming processes without increasing the number of processes. .
[0100]
(Embodiment 4)
The reflective liquid crystal display device of the present embodiment is a modification of the reflective liquid crystal display device described in the third embodiment. Unlike the third embodiment, the active matrix substrate used in the reflective liquid crystal display device according to the present embodiment includes a staggered (top gate type) TFT. The reflective liquid crystal display device according to the present embodiment differs from the reflective liquid crystal display device according to the third embodiment in that the concavo-convex pattern portion is formed using the source, drain electrode material, and gate electrode material used for forming the TFT. . The active matrix substrate used in the reflective liquid crystal display device of this embodiment will be described below with a focus on differences from the third embodiment. FIG. 6 is a partial cross-sectional view of the active matrix substrate in the present embodiment in the order of the manufacturing process.
[0101]
As shown in FIG. 6D, the active matrix substrate 500 in the present embodiment includes an uneven pattern portion 20 having a laminated structure on the insulating substrate 1. The concavo-convex pattern portion 20 includes pattern layers 10p, 2p, 3p made of the same material as the source electrode 10 (and the drain electrode 11), the polycrystalline silicon thin film (semiconductor layer) 2, the gate insulating film 3, and the gate electrode 6, respectively. And 6p are sequentially stacked and patterned in the same shape.
[0102]
Next, with reference to FIGS. 6A to 6D, a method for manufacturing the active matrix substrate 500 in the present embodiment will be described below.
[0103]
First, as shown in FIG. 6A, a source electrode (including a source bus line) 10 and a drain electrode 11 are formed on an insulating substrate 1 using a low-resistance metal such as Al to a thickness of about 500 nm. Formed with. At the same time, the pattern layer 10p, which later configures the concavo-convex pattern portion 20, was formed using the same material as the source electrode 10 and the drain electrode 11.
[0104]
Next, a polycrystalline silicon thin film 2 that becomes an active layer is formed on the insulating substrate 1 with a thickness of about 40 nm to about 80 nm so that both ends thereof are respectively disposed on the source electrode 10 and the drain electrode 11. Formed with. At this time, in order to improve the ohmic property between the active layer 2 and the source electrode 10 and the drain electrode 11, a silicon thin film (not shown) doped with impurities between the active layer 2 and the electrodes 10 and 11 is shown. )).
[0105]
Next, using sputtering or CVD, etc., SiO₂Or SiN_xA gate insulating film 3 made of, for example, was formed with a thickness of about 80 nm, and as shown in FIG. 6B, the polycrystalline silicon thin film 2 and the gate insulating film 3 were etched and patterned. Here, the pattern of the additional capacitor electrode is omitted for simplification. Here, simultaneously with the formation of the polycrystalline silicon thin film 2 and the gate insulating film 3, the patterned layers 2p and 3p made of the same material as the polycrystalline silicon thin film 2 and the gate insulating film 3 were laminated on the pattern layer 10p, respectively.
[0106]
Next, the gate electrode 6 was formed to a thickness of about 500 nm using Al or polycrystalline silicon. Here, at the same time when the gate electrode 6 is formed, a pattern layer 6p made of the same material as the gate electrode 6 is laminated on the pattern layer 3p, and the concavo-convex pattern having a laminated structure of the pattern layers 10p, 2p, 3p, and 6p. Part 20 was formed. The uneven pattern portion 20 has a thickness of about 0.8 μm to about 5 μm.
[0107]
Next, as shown in FIG. 6C, an interlayer insulating film 14 made of a photosensitive organic material was formed by spin coating. The interlayer insulating film 14 has a thickness of about 0.5 μm to about 1 μm, and is preferably thinner than the thickness of the concavo-convex pattern portion 20. An inorganic material may be used for the interlayer insulating film 14, but an organic material is preferably used as in the present embodiment.
[0108]
Next, as shown in FIG. 6D, the contact hole 13 is formed in the interlayer insulating film 14 so as to communicate with the drain electrode 11, and the pixel electrode is connected to the drain electrode 11 through the contact hole 13. 15 was formed of a highly reflective material such as Al. The pixel electrode 15 is formed at least in the opening of the liquid crystal panel. You may form so that the periphery of the pixel electrode 15 may overlap with a switching element, a gate bus line, and / or a source bus line. The active matrix substrate 500 was manufactured as described above.
[0109]
Finally, in the same manner as in the reflective liquid crystal display device of Embodiment 3, an alignment film is formed on each of the counter substrate (not shown) on which the counter electrode is formed and the active matrix substrate, and then the active matrix substrate is opposed. The substrates were bonded together, and liquid crystal was sealed between these substrates to form a liquid crystal layer, thereby producing a reflective liquid crystal display device (not shown).
[0110]
According to the present embodiment, the same effect as described above can be obtained for the same configuration as that of the third embodiment. In addition, according to this embodiment, the materials used for forming the TFTs are used to form a pattern and are sequentially stacked. Thereby, unlike the first embodiment, even when an inorganic insulating film is used as the first interlayer insulating film, a concavo-convex pattern portion having a thickness of about 0.8 μm to about 5 μm can be formed. . In the stagger type (top gate type) TFT as in this embodiment, the source electrode, the drain electrode, and the gate electrode can be formed of a thick film made of Al or polycrystalline silicon. By laminating the layers, it is possible to easily form a concavo-convex pattern portion having a thickness of about 0.8 μm or more. By forming an interlayer insulating film on the concavo-convex pattern portion, it is possible to form a reflector with good reflection characteristics by the same number of processes as the TFT formation process without increasing the number of processes. The present embodiment can be similarly applied to a case where an inverted stagger type TFT is used instead of a stagger type TFT.
[0111]
When a staggered TFT is used as in the present embodiment, it is not necessary to use the first interlayer insulating film for the uneven pattern portion as in the third embodiment using a coplanar TFT. That is, in the third embodiment, the first and second interlayer insulating films are used. However, according to the present embodiment, since only one interlayer insulating film is required, the manufacturing process is further reduced.
[0112]
【The invention's effect】
According to the present invention, it is possible to provide a reflective liquid crystal display device including a reflective plate having a reflection characteristic that is uniform and has good light scattering properties without increasing the number of manufacturing steps, and a method for manufacturing the same. Further, it is possible to provide a transmissive / reflective liquid crystal display device that has the advantages of the above-described reflective liquid crystal display device using a top-gate TFT and is capable of displaying a transmissive mode. Furthermore, the present invention can be applied to a reflection type liquid crystal display device of various display modes using scattering of a reflection plate.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view of an active matrix substrate of a reflective liquid crystal display device according to Embodiment 1. FIG.
FIG. 2 is a partial cross-sectional view of an active matrix substrate of a reflective liquid crystal display device according to a comparative example.
FIG. 3 is a partial plan view of an active matrix substrate of a transflective liquid crystal display device according to a second embodiment.
4 is a cross-sectional view taken along line A-A ′ in FIG. 3;
5 is a partial cross-sectional view of an active matrix substrate of a reflective liquid crystal display device according to Embodiment 3. FIG.
6 is a partial cross-sectional view of an active matrix substrate of a reflective liquid crystal display device according to Embodiment 4. FIG.
FIG. 7 is a partial plan view of an active matrix substrate of a conventional reflective liquid crystal display device.
8 is a cross-sectional view taken along line Y-Y ′ of FIG. 7;
FIG. 9 is a diagram for explaining a manufacturing process of a reflector in a conventional reflective liquid crystal display device.
FIG. 10 is a diagram for explaining a manufacturing process of a reflector in another conventional reflective liquid crystal display device.
[Explanation of symbols]
1 Insulating substrate
2, 2a, 2b, 2c Polycrystalline silicon layer (semiconductor layer)
3 Gate insulation film
5 First interlayer insulating film
6 Gate electrode
8 Contact hole
9 Contact hole
10 Source bus line (source electrode)
11 Drain electrode
13 Contact hole
14 Second interlayer insulating film
15 Pixel electrode
100 active matrix substrate

Claims (3)

A liquid crystal display device having a pair of substrates, a liquid crystal layer disposed between the pair of substrates, and a backlight :
A semiconductor layer, a gate insulating film, and a gate electrode sequentially disposed on one of the pair of substrates, a gate bus line and an additional capacitance common wiring provided on the one substrate,
The one substrate, the semiconductor layer, the gate insulating film, the gate electrode is disposed on the gate bus lines and said additional capacitor common wiring, a first insulating film having a contact hole,
On the first insulating film, a source electrode disposed so as to be connected to the semiconductor layer through the contact holes of the first insulating film,
A second insulating film disposed on the first insulating film so as to cover the source electrode;
A pixel electrode disposed on the second insulating film,
The additional capacitance common wiring is disposed in the pixel region;
The pixel electrode has a transparent electrode formed by a transparent conductive film, and a reflective electrode formed by a metal,
The reflective electrode is formed on the additional capacitor common line,
1. A liquid crystal display device in which one pixel has a non-light-transmitting region in which light from the backlight is not transmitted by the reflective electrode and a light-transmitting region that is not shielded by the reflective electrode . A liquid crystal display device having a pair of substrates, a liquid crystal layer disposed between the pair of substrates, and a backlight :
A semiconductor layer, a gate insulating film, and a gate electrode sequentially disposed on one of the pair of substrates, a gate bus line and an additional capacitance common wiring provided on the one substrate,
The one substrate, the semiconductor layer, the gate insulating film, the gate electrode is disposed on the gate bus lines and said additional capacitor common wiring, a first insulating film having a contact hole,
On the first insulating film, a source electrode disposed so as to be connected to the semiconductor layer through the contact holes of the first insulating film,
A second insulating film disposed on the first insulating film so as to cover the source electrode;
A pixel electrode disposed on the second insulating film,
The additional capacitance common wiring is disposed in the pixel region;
The pixel electrode has a transparent electrode formed by a transparent conductive film, and a rectangular reflective electrode formed by a metal,
The reflective electrode is formed on the additional capacitor common line and the TFT,
1. A liquid crystal display device in which one pixel has a non-light-transmitting region in which light from the backlight is not transmitted by the reflective electrode and a light-transmitting region that is not shielded by the reflective electrode . The additional capacitor common line is a liquid crystal display device according to claim 1 or 2 does not transmit light.

Images