JP3643065B2 - Liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device including a switching element such as a thin film transistor, and more particularly to a structure of a pixel portion.
[0002]
[Prior art]
FIG. 6 shows a schematic plan view of a liquid crystal display device in which a peripheral drive circuit is formed on a substrate. A gate drive circuit 32, a source drive circuit 33, and a TFT (Thin Film Transistor) array unit 34 are formed on a glass substrate or quartz substrate 31. The gate drive circuit 32 includes a shift register 32a and a buffer 32b. The source drive circuit 33 includes a shift register 33 a, a buffer 33 b, and an analog switch 39 that samples the video line 38. A large number of parallel gate bus lines 116 extending from the gate drive circuit 32 are disposed in the TFT array section 34. A large number of parallel source bus lines 120 extending from the source drive circuit 33 are arranged orthogonal to the gate bus lines 116. An additional capacitance common line 114 is arranged in parallel with the gate bus line 116. A TFT 35, a pixel 36, and an additional capacitor 37 are provided in a rectangular region surrounded by the two gate bus lines 116, the two source bus lines 120, and the additional capacitor common line 114. The gate electrode of the TFT 35 is connected to the gate bus line 116, and the source electrode is connected to the source bus line 120. Liquid crystal is sealed between the pixel electrode connected to the drain electrode of the TFT 35 and the counter electrode on the counter substrate to form a pixel 36. Further, the additional capacitor common line 114 is connected to an electrode having the same potential as the counter electrode.
[0003]
Next, the configuration of the conventional TFT array section 34 of FIG. 6 will be described in more detail with reference to FIGS. FIG. 7 shows a pixel layout pattern in a conventional example. Further, FIG. 8 shows a cross-sectional structure taken along the line AA of FIG. First, a polycrystalline silicon thin film 111 serving as an active layer is formed on the insulating substrate 110 with a thickness of 40 nm to 80 nm. Next, the gate insulating film 113 is formed to a thickness of 80 nm to 150 nm by sputtering or CVD. Next, in the polycrystalline silicon thin film 111, phosphorus ions are implanted at 1 × 10 15 (cm −2) into an additional capacity portion (shown by a hatched portion in FIGS. 7 and 8) where an additional capacity will be formed later.
[0004]
Next, the gate electrode 116 and the additional capacitance common wiring 114 are patterned into a predetermined shape using metal or low resistance polycrystalline silicon. Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are implanted 1 × 10 15 (cm −2) from above the gate electrode 116 to form a channel 112 below the gate electrode 116. Next, a first interlayer insulating film 115 is formed on the entire surface using SiO2 or SiNx, and then a contact hole 118 and a contact hole 119 are provided. Next, the source bus wiring 120 and the drain electrode 121 are formed using a low-resistance metal such as Al. Next, a second interlayer insulating film 124 is formed on the entire surface using SiO2 or SiNx in the same manner as the first interlayer insulating film 115, a contact hole 123 is provided, and then a pixel electrode is formed using a transparent conductive film such as ITO. 125 is formed. When Al is used for the source bus wiring 120 and the drain electrode 121, the barrier metal 126 is formed using Ti, TiW, Mo, MoSi or the like in order to make an ohmic contact between the drain electrode 121 and the pixel electrode 125. Is done.
[0005]
[Problems to be solved by the invention]
However, in the above conventional example, since the film thickness of the first and second interlayer insulating films is an inorganic film, the film thickness is as small as several hundred nm, and the relative dielectric constant is larger than that of a normal organic film, Since the capacitance between the additional capacitance common wiring 114 and other wiring (for example, source bus wiring) is large, it is easily affected by the other wiring. Therefore, when an inorganic material is used for the interlayer insulating film, it is not preferable to form the additional capacitor portion so as to largely overlap with other wiring. In addition, since the additional capacity portion is non-translucent, the aperture ratio is reduced due to the additional capacity portion. Furthermore, since the additional capacitance common wiring 114 is formed in the same layer as the gate bus wiring 116 and the additional capacitance common wiring 114 is non-translucent, the aperture ratio is reduced. For this reason, when the aperture ratio becomes small, there is a problem that the screen becomes dark and difficult to see.
[0006]
The present invention solves the above-described problems, and provides a liquid crystal display device having a high aperture ratio that does not cause a decrease in aperture ratio due to, for example, an additional capacitor common line.
[0007]
[Means for Solving the Problems]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line is formed above the interlayer insulating film, and an additional capacitor portion is formed between the pixel electrode The above object is achieved.
[0008]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is disposed above the interlayer insulating film and overlaps at least the switching element. The additional capacitor portion is formed between the pixel electrode and the pixel electrode, thereby achieving the object.
[0009]
The additional capacitance common line desirably covers at least the PN junction portion of the switching element and functions as a light shielding film.
[0010]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is provided above the interlayer insulating film and at least of a scanning line and a signal line. The additional capacitor portion is formed between the pixel electrode and the pixel electrode so as to achieve the above object.
[0011]
The additional capacitor common line may be formed of a metal for making an ohmic contact between the drain electrode and the pixel electrode.
[0012]
The counter substrate preferably does not have a black matrix.
[0013]
Further, it is desirable that the dielectric constant of the insulating film used as the dielectric of the additional capacitor is larger than the dielectric constant of the organic material used for the interlayer insulating film.
[0014]
An anodic oxide film may be used as the dielectric of the additional capacitor.
[0015]
The operation will be described below.
[0016]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line is formed above the interlayer insulating film, and an additional capacitor portion is formed between the pixel electrode Therefore, the capacitance between the additional capacitance common wiring and the scanning line or the signal line can be ignored, and the additional capacitance common wiring can be formed in an arbitrary shape. For example, the additional capacitance common wiring can be a light shielding film.
[0017]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is disposed above the interlayer insulating film and overlaps at least the switching element. Since the additional capacitor portion is formed between the pixel electrode and the pixel electrode, the aperture ratio is not lowered by the additional capacitor common line.
[0018]
The additional capacitance common wiring covers at least the PN junction in the switching element and functions as a light shielding film, so that the light irradiated to the liquid crystal display device hits the switching element and the display quality deteriorates due to an increase in off-current. Can be prevented.
[0019]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is provided above the interlayer insulating film and at least of a scanning line and a signal line. Since the additional capacitance portion is formed between the pixel electrode and the pixel electrode, the aperture ratio is not lowered by the additional capacitance common wiring.
[0020]
Since the additional capacitance common line is formed of a metal for making an ohmic contact between the drain electrode and the pixel electrode, the additional capacity lower electrode and the additional capacitance common line may be patterned simultaneously with this metal. No patterning process is required for the lower electrode and the additional capacitor common electrode.
[0021]
Since the counter substrate does not have a black matrix, it is not necessary to form a large light shielding pattern for the margin of the light shielding pattern necessary for bonding to the counter substrate, so that the aperture ratio can be increased accordingly. Further, since a transparent conductive film for switching a liquid crystal material or a transparent conductive film and a color filter may be formed on the counter substrate, a process for manufacturing the counter substrate is simplified.
[0022]
Since the dielectric constant of the insulating film used as the dielectric of the additional capacitor is larger than that of the organic material used for the interlayer insulating film, the additional capacitor can be effectively formed in a small area.
[0023]
Since the dielectric of the additional capacitor uses an anodic oxide film, this anodic oxide film has good coverage with respect to the additional capacitor lower electrode and the additional capacitor common wiring. There is no short circuit problem. Moreover, the process of forming an inorganic film by sputtering method or CVD method is not required.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
(Embodiment 1)
FIG. 1 is a layout diagram for one pixel according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. Hereinafter, the present invention will be described with reference to FIGS. 1 and 2. As in the conventional example, a polycrystalline silicon thin film 11 serving as an active layer was formed on the insulating substrate 10 to a thickness of 40 nm to 80 nm. Next, a gate insulating film 13 was formed with a thickness of 80 nm by SiO2 or SiNx by sputtering or CVD. Next, the gate electrode 16 was formed using Al or polycrystalline silicon.
[0025]
Next, in order to determine the conductivity type of the thin film transistor, phosphorus ions are implanted 1 × 10 15 (cm −2) from above the gate bus wiring 16 using the gate bus wiring 16 as a mask, and the lower part of the gate bus wiring 16 in the active layer A non-doped channel portion 12 was formed in the region, and a region other than the channel portion 12 was a high concentration impurity region. In the active layer of the TFT, a low concentration impurity region or a non-doped region can be provided in the vicinity of the channel portion 12 so that a leakage current is small when the TFT is turned off. Next, after the first interlayer insulating film 15 was formed on the entire surface, a contact hole 18 and a contact hole 19 were provided. Next, the source bus wiring 20 and the drain electrode 21 were formed using a low resistance metal such as Al. Next, a second interlayer insulating film 24 is formed. In the present invention, a transparent photosensitive organic film is formed by spin coating. If the second interlayer insulating film 24 is photosensitive, a contact hole can be provided only by exposure and development steps, so that the manufacturing process can be simplified.
[0026]
In the present embodiment, since this liquid crystal panel is used as a transmissive liquid crystal display device, a transparent acrylic resin is used as a material for the second interlayer insulating film 24 instead of a colored organic material. This organic film has a small relative dielectric constant of 4 or less and a film thickness of 2 μm or more. Therefore, the reverse tilt of the liquid crystal material can be suppressed, and as a result, the viewing angle of the liquid crystal panel can be increased. Next, exposure and development processes were performed to provide contact holes 23.
[0027]
Next, a barrier metal 26 for forming an ohmic contact between the drain electrode 21 and the pixel electrode 25 formed of ITO in a later step was formed using a metal such as TiW, Ti, Mo, or MoSi. In this embodiment, the additional capacitor lower electrode and the additional capacitor common wiring 26A for forming an additional capacitor with the pixel electrode 25 using this metal are formed in the shape shown in FIG. A metal different from the barrier metal 26 may be used as the additional capacitor lower electrode and the additional capacitor common wiring 26A. Next, an insulating film 27 was formed on the additional capacitor lower electrode and the additional capacitor common line 26A in order to form the pixel electrode 25 and the additional capacitor. If the barrier metal 26 is a material that can be anodized, such as Al or Ta, the insulating film 27 can be formed using an anodizing method. Since this anodic oxide film has a relative dielectric constant larger than that of a normal inorganic film, an additional capacitor can be formed effectively in a small area. Further, since the anodic oxide film has good coverage with respect to the additional capacitor lower electrode and the additional capacitor common wiring 26A, the problem of short circuit between the additional capacitor lower electrode and additional capacitor common wiring 26A and the pixel electrode does not occur. Moreover, the process of forming an inorganic film by sputtering method or CVD method is not required. As described above, in order to effectively form the additional capacitor, the insulating film 27 has a larger relative dielectric material, a smaller thickness material, or a larger relative dielectric constant than the second interlayer insulating film 24. A material with a small film thickness is desirable. Specifically, the relative dielectric constant is 5 or more, preferably 8 or more, and the additional capacitor portion has a film thickness of 500 nm or less.
[0028]
Next, the pixel electrode 25 was formed on the barrier metal 26, the additional capacitor lower electrode, and the additional capacitor common wiring 26A in a shape partially overlapping the gate bus wiring 16 and the source bus wiring 20 as shown in FIG. As described above, since the additional capacitance is formed on the thick interlayer insulating film, the additional capacitance common wiring can be formed at an arbitrary place. As shown in FIG. 1, in the present invention, since the additional capacitance is formed on the thin film transistor, the aperture ratio does not decrease due to the additional capacitance. In addition, since the separation between adjacent pixels is performed on the wiring, the wiring functions as a light shielding film. Further, a non-light-transmitting additional capacitor lower electrode exists on the thin film transistor, and this functions as a light shielding film, so that leakage current due to light irradiation to the PN junction of the thin film transistor can be prevented. In the present embodiment, since the light shielding film is formed on the substrate on the thin film transistor side, it is not necessary to form the light shielding pattern on the counter substrate, and the pattern of the transparent conductive film to be the counter electrode may be formed. Therefore, unlike the case where the light shielding pattern is formed on the counter substrate, it is not necessary to form the light shielding film as large as the bonding margin, and the aperture ratio can be increased.
(Embodiment 2)
In the present embodiment, a case where an additional capacitor is formed on the bus wiring will be described.
[0029]
In the present embodiment, the process is the same as that of the first embodiment until the second interlayer insulating film 24 is formed using an organic film such as an acrylic resin. Since the relative dielectric constant of the organic film is small and the film thickness is as thick as 2 μm or more, the capacitance between the pixel electrode and the bus wiring can be ignored. Therefore, there is no problem even if the pixel electrode is formed on the gate bus wiring. Therefore, as shown in FIG. 3, the pixel electrode 25 is overlapped on the gate bus wiring 16 of the own stage, and the additional capacitor lower electrode and the additional capacitor common wiring 26A are formed on the gate bus wiring 16, and the gate bus wiring 16 and An additional capacitor can be formed above the thin film transistor. In this case, since the additional capacitance is formed not only on the thin film transistor but also on the gate bus wiring 16, the area of the additional capacitance can be increased.
[0030]
Similarly, the pixel electrode can be formed on the source bus wiring. Specifically, as shown in FIG. 4, the pixel electrode 25 is overlapped on the source bus wiring 20 of the own stage, and the additional capacitor lower electrode is formed. The additional capacitance common wiring 26A can be formed on the source bus wiring 20, and an additional capacitance can be formed above the source bus wiring 20 and the thin film transistor. In this case, since the additional capacitance is formed not only on the thin film transistor but also on the source bus wiring 20, the region of the additional capacitance can be increased.
(Embodiment 3)
In the first embodiment, as shown in FIG. 2, the additional capacitor lower electrode and the additional capacitor common line 26A are formed before the pixel electrode 25 is formed. However, as shown in FIG. 5, the pixel electrode 25 is formed. Thereafter, the insulating film 27 and the additional capacitance electrode 28 can be formed. Hereinafter, the third embodiment will be described with reference to FIG. In the same manner as in the first embodiment, a thin film transistor was formed on the insulating substrate 10, a second interlayer insulating film 24 made of an organic material was formed, and a contact hole 23 was provided.
[0031]
Thereafter, only the barrier metal 26 was formed, and the pixel electrode 25 was further formed thereon.
[0032]
Subsequently, the insulating film 27 and the additional capacitor electrode material are formed on the entire surface of the substrate, and the additional capacitor electrode 28 is formed on the thin film transistor, the gate bus wiring 16 or the source bus wiring 20 in the same manner as in the first and second embodiments. Formed. Also in this embodiment, if a material having a large relative dielectric constant or a material having a small film thickness is used as the insulating film 27, an additional capacitor can be formed effectively with a small area.
[0033]
If the insulating film 27 is left at the time of patterning the additional capacitor electrode 28, this insulating film also functions as a protective film. Any metal can be used for the additional capacitance electrode 28. For example, the additional capacitance electrode 28 can be formed of the same material as the gate bus wiring, the source bus wiring, and the pixel electrode. Further, it is not necessary to form an insulating film only on the additional capacitor lower electrode and the additional capacitor common line 26A as in the first embodiment, and the insulating film 27 may be formed on the entire surface of the substrate above the pixel electrode 25. It is not necessary to pattern the insulating film 27.
[0034]
【The invention's effect】
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line is formed above the interlayer insulating film, and an additional capacitor portion is formed between the pixel electrode Therefore, the capacitance between the additional capacitance common wiring and the scanning line or the signal line can be ignored, and the additional capacitance common wiring can be formed in an arbitrary shape. For example, the additional capacitance common wiring can be a light shielding film.
[0035]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is disposed above the interlayer insulating film and overlaps at least the switching element. Since the additional capacitor portion is formed between the pixel electrode and the pixel electrode, the aperture ratio is not lowered by the additional capacitor common line.
[0036]
The additional capacitance common line covers at least the PN junction in the switching element and functions as a light-shielding film. Therefore, the display quality is deteriorated due to the off-current being increased when the light irradiated to the liquid crystal display device hits the switching element. Can be prevented.
[0037]
According to the present invention, a plurality of scanning lines and signal lines are provided in a matrix on the substrate, a switching element is provided at an intersection of the scanning lines and the signal line, and the switching element is made of an organic material. In a liquid crystal display device in which an interlayer insulating film is provided and a pixel electrode is provided on the interlayer insulating film, an additional capacitor common line corresponding to the pixel electrode is provided above the interlayer insulating film and at least of a scanning line and a signal line. Since the additional capacitance portion is formed between the pixel electrode and the pixel electrode, the aperture ratio is not lowered by the additional capacitance common wiring.
[0038]
Since the additional capacitor common line is formed of a metal for making an ohmic contact between the drain electrode and the pixel electrode, the additional capacitor lower electrode and the additional capacitor common line may be patterned simultaneously with this metal. A new patterning process for the electrode and the additional capacitor common wiring is not required.
[0039]
Since the counter substrate does not have a black matrix, a transparent conductive film for switching the liquid crystal material or a transparent conductive film and a color filter may be formed on the counter substrate, which simplifies the process of manufacturing the counter substrate.
[0040]
Since the dielectric constant of the insulating film used as the dielectric of the additional capacitor is larger than that of the organic material used for the interlayer insulating film, the additional capacitor can be effectively formed in a small area.
[0041]
Since the anodic oxide film is used as the dielectric of the additional capacitor, the anodic oxide film has good coverage with respect to the additional capacitor lower electrode and the additional capacitor common wiring. There is no short circuit problem. Moreover, the process of forming an inorganic film by sputtering method or CVD method is not required.
[Brief description of the drawings]
FIG. 1 is a layout diagram of a pixel according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a pixel according to the first embodiment of the present invention.
FIG. 3 is a layout diagram of a pixel according to a second embodiment of the present invention.
FIG. 4 is a layout diagram of a pixel according to a second embodiment of the present invention.
FIG. 5 is a cross-sectional view of a pixel according to a third embodiment of the present invention.
FIG. 6 is a diagram schematically showing a configuration of a liquid crystal display device in which a driver is integrally formed.
FIG. 7 is a layout diagram of pixels in a conventional example.
FIG. 8 is a cross-sectional view of a pixel in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Insulating substrate 11 Polycrystalline silicon thin film 12 Channel part 13 Gate insulating film 15 1st interlayer insulating film 16 Gate bus wiring 18 Contact hole 19 Contact hole 20 Source bus wiring 21 Drain electrode 23 Contact hole 24 2nd interlayer insulating film 25 pixel electrode 26 barrier metal 26A additional capacity lower electrode and additional capacity common wiring 28 additional capacity electrode

Claims (5)

A plurality of scanning lines and signal lines are provided in a matrix on a substrate, a thin film transistor is provided at an intersection of the scanning lines and the signal line, an interlayer insulating film made of an organic material is provided above the thin film transistor, and the interlayer In a liquid crystal display device in which a pixel electrode is provided on an insulating film,
An additional capacitor electrode and an additional capacitor insulating film made of an additional capacitor common wiring are provided on the interlayer insulating film, and an additional capacitor portion is formed in which an additional capacitor insulating film is disposed between the pixel electrode and the additional capacitor electrode .
A liquid crystal display device, wherein the additional capacitor portion is provided on at least one of a PN junction portion and a scanning line or a signal line in a thin film transistor.   2. The liquid crystal display device according to claim 1, wherein an additional capacitor electrode, an additional capacitor insulating film, and a pixel electrode are provided in this order on the interlayer insulating film.   2. The liquid crystal display device according to claim 1, wherein a pixel electrode, an additional capacitor insulating film, and an additional capacitor electrode are provided in this order on the interlayer insulating film.   4. The liquid crystal display device according to claim 1, wherein the additional capacitor common line is formed of a metal for making an ohmic contact between a drain electrode and a pixel electrode of the thin film transistor.   5. The liquid crystal display device according to any one of 1 to 4, wherein the additional capacitor insulating film has a relative dielectric constant higher than that of the interlayer insulating film.

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