JPH06208134A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device having a high quality of display with a high luminance without the lowering of withstand pressure of a gate insulating film of TFT and the lowering of electric capacity value of the storage capacity. CONSTITUTION:A dielectric 111 is formed on a first electrode 107 through openings of a first layer insulating film 109 and a second layer insulating film 131 respectively opened at a part to be formed with a storage capacity 105. Consequently, since material and film thickness of a gate insulating film 117 of a TFT 113 and the dielectric 111 of the storage capacity 105 can be set separately, dimension of the TFT 113 is reduced and the withstand pressure characteristic thereof can be set optimally, and dimension of the storage capacity 105 is reduced and the capacity value thereof can be set at the optimal value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to an active matrix type liquid crystal display device having a thin film transistor switching element and a light shielding film.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device provided with a switching transistor for each display pixel is widely known as being suitable for high quality display and high speed driving of a liquid crystal display device. A thin film transistor (TFT) made of amorphous silicon (hereinafter abbreviated as a-Si) or polycrystalline silicon (hereinafter abbreviated as poly-Si) is generally used for the switching transistor.

Since a TFT made of a-Si has a feature that it can be formed over a large area on an inexpensive glass substrate, it is particularly suitable for a large-screen liquid crystal display device such as a wall-mounted television or an OA display.

On the other hand, since the poly-Si TFT has a relatively high carrier mobility of several tens to 200 cm ² / Vs, it has a sufficient function as a switching element for driving a pixel of a liquid crystal display element even if the TFT size is small. have. Moreover, since the peripheral drive circuit can be integrally formed on the same substrate and the entire device can be miniaturized, it is suitable for a liquid crystal display device such as a viewfinder of a projection television or a video camera, which is required to have a small size and high definition. is there.

FIG. 7A shows a TFT made of poly-Si.
FIG. 7B is a plan view showing a display pixel portion on the TFT substrate side of a conventional liquid crystal display device using the above, and FIG. The TFT 301 includes an active layer 303 made of the first poly-Si, a gate insulating film 305, and a second low-resistance po layer.
The gate 307 is made of ly-Si. Gate 307
The parts on both sides are the source 309 and drain 3 of the TFT 301.
No. 11 and P (phosphorus), which is an n-type dopant, is implanted and has a low resistance. The drain 311 is connected to the signal line 315 made of Al with the interlayer insulating film 313 sandwiched therebetween, and the gate 307 is integrated with the gate line 317 made of the second poly-Si. Source 309 above
Are connected to the pixel electrode 316 made of ITO with the interlayer insulating film 313 interposed therebetween. Further, the source 309 is connected to the storage capacitor 319. The storage capacity 319 is
It is a MOS capacitor, and its base portion 321 is the first pol.
A second poly is formed on the upper side of a dielectric 323, which is made of y-Si and is integrated with the active layer 303 of the TFT 301 and which is formed simultaneously with the gate insulating film 305.
There is a storage capacitance line 325 made of -Si.

FIG. 8 shows a TFT in which the above-mentioned display pixel is formed.
FIG. 4 is a partially omitted perspective view showing an array substrate 401 and a counter substrate 403. On the counter substrate 403, a light-shielding film 405 called a black matrix (or a black mask) arranged in a matrix and a counter electrode (not shown) made of a transparent electrode such as ITO are formed.

[0007]

Normally, the light-shielding film 405 as the black matrix is formed on the TFT array substrate 40.
1, the gate line 317, the signal line 315, T
The FT 301 is arranged so as to cover the FT 301 and to provide an opening only in the display-related portion of the pixel electrode 316. T
FT301 has an active layer of a-Si or poly-Si
Regardless of the reason, when light is irradiated, the OFF current may increase and malfunction may occur. Therefore, a light-shielding film is necessary to block the incident light that causes such malfunction of the TFT. In the conventional liquid crystal display device having such a configuration,
When assembling the TFT array substrate 401 and the counter substrate 403, highly accurate alignment is required. That is, TF
For example, if the gap between the pixel electrode 316 and the signal line 315 protrudes into the opening of the light-shielding film 405 due to misalignment when the T-array substrate 401 and the counter substrate 403 are arranged in combination, liquid crystal is generated in the gap. This is because, for example, in the case of a normally white mode liquid crystal display element using a TN type liquid crystal, light is always passed through that portion and the contrast ratio of the display pixel becomes low because it is not driven.

Therefore, in order to absorb the positional deviation of the light-shielding film 405 due to the positional deviation between the TFT array substrate and the counter substrate, a margin of the opening size of the black matrix is provided. The opening area may be reduced.

However, such a method has a problem that the aperture ratio of the portion of the pixel electrode 316 corresponding to the pixel display is reduced and the brightness of the screen is lowered.

On the other hand, although it is conceivable to improve the alignment accuracy itself, the alignment accuracy between the TFT array substrate 401 and the counter substrate 403 actually depends on the screen size, for example, a size of about 5 inches diagonal. It is usually within a range of about ± 2 μm, and within a range of about ± 3 μm for a 10-inch class size, it is extremely difficult to improve the alignment accuracy. Therefore, in the conventional technique, the overlapping part of the light shielding film with the pixel electrode is several μm.
It is designed to take about m, that is, the above-mentioned alignment accuracy.

Further, the TFT array substrate 401 and the counter substrate 403 have different thermal histories in the manufacturing process. p
Maximum 1000 ℃ for TFT array substrate using ol-Si
A maximum of 350 for a TFT array substrate using a-Si
While there is a heating process up to about 200 ° C, it is a heating process up to about 200 ° C for the counter substrate. Therefore,
There is a problem that the degree of expansion and contraction due to heat differs between the TFT array substrate side and the counter substrate side, and the patterns on both substrates have a pitch shift. In order to absorb this, a larger margin must be taken for the size of the opening portion of the light-shielding film. However, if this is done, the opening area of the light-shielding film becomes smaller and the brightness of the screen further decreases.

In order to solve the above problem, it is effective to form a light shielding film on the TFT array substrate side. T
Since the alignment accuracy of the exposure mask used in the manufacturing process of the FT array substrate can be easily set to 1 μm or less, it is not necessary to take a margin for absorbing the misalignment between the counter substrate and the TFT array substrate, and the aperture ratio is large. Is improved.

However, when the definition of the screen becomes higher and the pixel pitch becomes smaller, the TF is increased in order to secure the aperture ratio.
There is no choice but to reduce the size of T and the storage capacity, but this has a limit. That is, in order to match the current characteristics and withstand voltage characteristics of the TFT and the electric capacitance value of the storage capacitor with the specifications required for driving the liquid crystal display device, the dimensions of the TFT and the storage capacitor need to be large to some extent. This is because it cannot be made too small.

In the conventional liquid crystal display device as described above, for example, if an insulating film used as a dielectric of a storage capacitor has a small size and a small thickness to obtain a predetermined electric capacitance, In the liquid crystal display device, since the gate insulating film of the TFT and the dielectric of the storage capacitor are formed in the same process using the same insulating film, the thickness of the gate insulating film of the TFT also becomes thin and the gate withstand voltage of the TFT is reduced. This causes problems such as deterioration and generation of leakage current between the gate and the source. On the contrary, when the thickness of the gate insulating film of the TFT is increased, the thickness of the dielectric of the storage capacitor is also increased, which makes it difficult to secure the predetermined electric capacitance value.

Further, in the conventional liquid crystal display device, the storage capacitor is formed in the MOS structure, and since the storage capacitor is used in the saturation region of the CV curve of this MOS structure,
A large voltage must be applied to the electrode of the storage capacitor, and the electrode must have a sufficiently low resistance. Therefore, in this case, it is devised that the electrode of the storage capacitor is doped with impurity ions such as P (phosphorus) to reduce the resistance of the electrode.

However, if the electrode of the storage capacitor is doped after forming the insulating film on the electrode layer of the storage capacitor, the insulating film is deteriorated by the implanted impurity ions, and its insulating property is deteriorated. Therefore, it suffices to dope only the electrodes of the storage capacitor with impurity ions before forming such an insulating film. In this case, however, the electrode surface of the storage capacitor is thermally oxidized after that to insulate the electrode as the dielectric of the storage capacitor. When a film is formed, the insulating layer swells thicker than the insulating film in other portions, for example, the gate insulating film of the TFT, and there is a problem that it is difficult to control the film thickness of the storage capacitor as a dielectric. .

The present invention has been made to solve such a problem, and an object thereof is to avoid a decrease in withstand voltage of a gate insulating film of a TFT and a decrease in electric capacitance value of a storage capacitor, and An object of the present invention is to provide a liquid crystal display device having a high luminance and a high display quality by miniaturizing a planar size of a storage capacitor and improving an aperture ratio of a pixel.

[0018]

In order to solve the above problems, a liquid crystal display device according to the present invention has a plurality of scanning wirings and a plurality of signal wirings on a substrate, and the scanning wirings and the signal wirings. A switching element array substrate having a switching element connected thereto and a pixel electrode connected to the switching element; and a counter substrate provided with a counter electrode facing the switching element array substrate with a gap. A liquid crystal display device having a liquid crystal composition enclosed between the switching element array substrate and the counter substrate, the first electrode of the storage capacitor formed of a conductive film on the substrate, and An insulating layer formed so as to avoid a portion where the storage capacitor is formed and having an opening formed in the portion where the storage capacitor is formed, and the first electrode on the first electrode through the opening of the insulating layer. And a second electrode of the storage capacitor formed on the dielectric layer and opposed to the first electrode via the dielectric layer. It has a feature.

Alternatively, in the liquid crystal display device according to the present invention, the switching element array substrate has a light blocking film that blocks light incident on the switching element, and the storage capacitor formed of the same conductive material as the light blocking film. A first electrode of
Anodizing the insulating layer formed so as to avoid the portion where the storage capacitor is formed and having an opening in the portion where the storage capacitor is formed, and the first electrode exposed from the opening of the insulating layer. And a second electrode of the storage capacitor, which is formed on the dielectric layer and faces the first electrode through the dielectric layer. Good.

The material of the above-mentioned light-shielding film is T
A high melting point metal such as a, Cr, Ti, W, Al, an alloy thereof, or a compound of them and Si is suitable. As the dielectric layer formed on the first electrode exposed from the opening of the insulating layer, for example, a SiO ₂ film or SiN _x film having a thickness of about several 100 μm formed by using the CVD method is deposited. A film or a film obtained by anodizing the surface of the first electrode is suitable.

[0021]

The interlayer insulating layer used for the gate insulating film of the TFT is formed avoiding the portion where the storage capacitor is formed, and the first insulating layer is formed through the opening of the interlayer insulating layer formed in the portion where the storage capacitor is formed. Since the dielectric layer of the storage capacitor is formed on the electrode of, the dielectric layer can be provided separately from the interlayer insulating layer used for the gate insulating film of the TFT. That is, since the material and thickness of the gate insulating film of the TFT and the dielectric layer of the storage capacitor can be set independently, it is possible to optimize the withstand voltage characteristics while miniaturizing the dimensions of the TFT. In addition, the size of the storage capacitor can be miniaturized and its electric capacitance value can be optimally set.

Further, the first electrode of the storage capacitor is formed of the same conductive material as that of the light-shielding film, and the surface of the first electrode of the storage capacitor exposed from the opening of the insulating layer is subjected to a surface oxidation treatment. If this is applied to form the dielectric layer, the manufacturing process can be simplified.

Particularly, when the dielectric layer is formed by the anodic oxidation method, the insulating layer functions as a mask for forming the pattern, so that only the portion exposed from the opening of the insulating layer is anodized to form the dielectric layer. . Therefore, it is not necessary to additionally use a patterning mask or an etching process using the patterning mask, and the manufacturing process can be further simplified. This is because a film made of a metal material such as Ta or Cr is used as the light shielding film, and these metal films are suitable materials for performing surface oxidation treatment such as anodic oxidation. Moreover, since the dielectric layer formed of the insulating film formed by the anodic oxidation method has very few pinhole defects as compared with the deposition method, it is possible to suppress the occurrence of defects in the storage capacitor. Further, if the light shielding film is provided on the array substrate side and a part of the light shielding film is also used as the first electrode of the storage capacitor, the pattern accuracy (positioning accuracy) of the light shielding film with respect to the pixel can be realized while realizing miniaturization of the pixel. Since it can be further improved, the aperture ratio of the pixel can be further increased.

[0024]

Embodiments of the liquid crystal display device of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 1 is a plan view showing a display pixel portion in a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a sectional view taken along the line AA '. For simplification of the description, a TFT array substrate will be mainly described.

A black matrix 103 made of Ta is formed on a quartz substrate 101. The black matrix 103 is not only used as a so-called light-shielding film,
It also serves as the first electrode 107 of the storage capacitor 105 for each pixel portion.

A first interlayer insulating film 109 is formed so as to cover the black matrix 103 and the quartz substrate 101. The first interlayer insulating film 109 is a storage capacitor 1
It is formed so as to avoid the portion where 05 is formed, and therefore an opening is formed in that portion. A dielectric 111 is formed by anodizing the surface of the black matrix 103 exposed from this opening. The dielectric 111 is used as a dielectric layer of the storage capacitor 105.

TF is formed on the first interlayer insulating film 109.
T113 is formed. This TFT 113 has a first
Of the first poly-Si film on the inter-layer insulating film 109, a gate insulating film 117 whose upper surface is a thermal oxide film, and both ends of the gate insulating film 117 and The source electrode 123 and the drain electrode 125, which are respectively connected to the source region 119 and the drain region 121 of the active layer 115 through the contact holes formed in the second interlayer insulating film 131, and the active layer 1
Gate insulating film 1 corresponding to 15 channel regions 127
A gate electrode 129 formed on the first insulating film 17 and a second interlayer insulating film 131 formed so as to cover the gate electrode 129 and contact holes at both ends of the gate insulating film 117. Its main part is composed.

A second electrode 133 is formed by extending the source electrode 123 and is in contact with the upper surface of the dielectric 111. The pixel electrode 1 is formed on a part of the upper surface of the dielectric 111.
It is arranged so that the ends of 35 are in contact with each other.

The gate electrode 129 of the TFT 113 has a second
Of the poly-Si film is integrally formed with the scanning wiring 137. Active layer 11 directly under the gate electrode 129
A source region 119 and a drain region 121 are formed by implanting P (phosphorus), which is an n-type dopant, into the portions on both sides of 5 to reduce the resistance. The signal wiring 139 is C
It is formed integrally with the drain electrode 125 formed in a two-layer structure of r and Al and is connected to the drain region 121.

The storage capacitor 105 is the same as the first electrode 10 described above.
7, the dielectric 111, and the second electrode 133. The thickness of the dielectric 111 of the storage capacitor 105 is about 1000 angstrom. The thickness of this dielectric 111 is independent of the gate insulating film 117 of the TFT 113, the first interlayer insulating film 109, the second interlayer insulating film 131, etc. by changing the anodizing condition of the first electrode 107. Can be controlled.

On the other hand, the gate insulating film 117 of the TFT 113
The thickness was about 600 Å. The gate insulating film 117 is a film formed by thermally oxidizing the surface of the active layer 115, and its film thickness can be controlled independently of the film thickness of the dielectric 111 by changing the conditions of thermal oxidation. it can.

The black matrix 103 is TF
T113 almost the entire surface, the gap between the scanning wiring 137 and the pixel electrode 135, the gap between the signal wiring 139 and the pixel electrode 135,
It covers each part and blocks the light that tries to pass through that part. The portion exposed from the opening of the first interlayer insulating film 109 is used as the first electrode 107 of the storage capacitor 105. Moreover, the dielectric 111 is formed by anodizing the surface of the first electrode 107 in the portion exposed from the opening. Thus, the black matrix 103
Not only as a so-called light-shielding film, but also as a storage capacitor 105.
Since it is also used as the material for forming the first electrode 107 and the dielectric 111, the liquid crystal display device of the present invention has an extremely simple structure and is easy to manufacture.

Next, a method of manufacturing the liquid crystal display device of this embodiment will be described focusing on the pixel portion.

A Ta film is formed on a quartz substrate 101 by a sputtering method and then patterned to form a black matrix 10.
3 is formed. Then, a SiO ₂ film is formed on the entire surface by LPCVD to form a first interlayer insulating film 109.

Subsequently, an undoped first poly-Si film is formed by the LPCVD method and then patterned to form an active layer 115 of the TFT 113. Then, the surface of the active layer 115 is thermally oxidized to form the gate insulating film 117 of the TFT 113. The thickness of the gate insulating film 117 was set to about 600 Å.

Further, after forming a poly-Si film by the LPCVD method, P is doped as an impurity to form a second poly.
A y-Si film is formed and patterned to form a TFT1.
The gate electrode 129 and the scanning wiring 137 of No. 13 are formed.

Then, by ion implantation, p-MOS-
B (boron) is added to the portion to be formed as a TFT by n-
A source region 119 and a drain region 121 of the TFT 113 are formed by injecting P (phosphorus) into a portion to be formed as a MOS-TFT.

Then, a second interlayer insulating film 131 is formed by depositing SiO ₂ on almost the entire main surface of the substrate by the LPCVD method. The step of forming the second interlayer insulating film 131 also serves to activate the impurities.

Next, the first interlayer insulating film 109 and the second interlayer insulating film 1 corresponding to the portion where the storage capacitor 105 is formed.
31 is removed by etching to provide an opening. Then, the surface of the first electrode 107 exposed from this opening is anodized to form the dielectric 111 of the storage capacitor 105. At this time, the first interlayer insulating film 109 and the second interlayer insulating film 131 act as masking at the time of anodic oxidation, so that they are not covered with the first interlayer insulating film 109 and the second interlayer insulating film 131. Only the surface of the Ta film of the first electrode 107 (exposed from the opening) is anodized. Moreover, the film thickness of the oxide film formed at this time can be adjusted by variously changing the conditions of anodic oxidation. In the present embodiment, the thickness of the anodized dielectric 111 is about 10
It was set to 00 angstrom.

Subsequently, a transparent electrode made of ITO is formed by a sputtering method and then patterned to form a pixel electrode 135. The pixel electrode 135 is formed by partially overlapping the peripheral edge with the peripheral edge of the opening of the black matrix 103, and the portion exposed from the opening of the black matrix 103 becomes a pixel. And this pixel electrode 1
The end of 35 is partially connected to the second electrode 133 and the dielectric 1.
It is formed so as to contact the surface of 11.

Then, contact holes are formed in the gate insulating film 117 and the second interlayer insulating film 131 on the source region 119 and the drain region 121 of the TFT 113.
Then, Cr and Al are sequentially formed by a sputtering method and patterned to form a signal wiring 139, a drain electrode 125 and a source electrode 123 integrally formed with the signal wiring 139, and a second electrode 133 integrally formed with the signal wiring 139.

As is clear from the above description, in the liquid crystal display device of this embodiment, the dielectric 1 of the storage capacitor 105 is used.
Reference numeral 11 is an oxide film formed by anodizing the upper surface of the first electrode 107, and this dielectric 111 is formed independently of the gate insulating film 117 of the TFT 113. As a result, the gate insulating film 117 and the dielectric 111 can be formed such that their respective film thicknesses are independently set to desired desired values. As a result, the characteristics of the TFT 113 and the storage capacitance 1
While setting the characteristics of 05 to the optimum conditions,
The dimensions of 113 and the storage capacitor 105 can be miniaturized.

In addition, in this embodiment, part of the black matrix 103 is also used as the first electrode 107, and the upper surface of the Ta film of the first electrode 107 is further anodized to form the dielectric 111. . Thus T
The dielectric constant of the oxide film formed by anodizing the a film is more than 5 times that of SiO ₂ used as the dielectric layer of the storage capacitor of the conventional liquid crystal display device, and the oxide film formed by the anodization is a pinhole. Since it is a high-quality film with very few defects, it is suitable as a dielectric layer and the storage capacitance can be further reduced, and the effect of using the black matrix 103 also as the first electrode 107 is combined with the aperture ratio of the pixel. It is possible to realize further miniaturization of TFTs and storage capacitors while improving the above.

The first interlayer insulating film 109 and the second
Since the inter-layer insulating film 131 of FIG. 6 is an insulator, it functions as a mask for anodic oxidation, and only the upper surface of the first electrode 107 exposed from the opening is anodized. Therefore, a resist or the like used for anodic oxidation was used. No masking or deposition of a separate dielectric film is required, which simplifies the structure and manufacturing process. As a result, the yield can be improved and the manufacturing cost can be reduced.

Further, since the black matrix 103 is formed on the array substrate, highly precise pattern matching between the pixel electrode 135 and the black matrix 103 can be realized, and even if the pixel pitch is reduced to 50 μm or less, the pixel It is possible to avoid a decrease in aperture ratio. By combining the above effects, it is possible to realize high-definition image display with high brightness.

Actually, the aperture ratio of the pixel in the liquid crystal display device of this embodiment is about 55%, which is a significant improvement over the average aperture ratio of the conventional liquid crystal display device of about 40%. did.

Since a current due to the so-called Pool-Frenkel effect easily flows in the oxide film formed by anodic oxidation, the thickness of the dielectric film 111 made of an oxide film is set to about 1000 angstroms or more in the above embodiment. It is desirable to keep. At this time, as described above, since the dielectric constant of the oxide film by anodic oxidation is high, a sufficient capacitance value can be obtained even if the film thickness is increased and the size is reduced.

Needless to say, the entire first electrode 107 of the storage capacitor 105 may be anodized before forming the first interlayer insulating film 109. However, in this case, there is a possibility that the surface of the oxide film formed by the anodic oxidation when the opening is opened is also etched by etching or the like. Further, there is also a problem that a step of patterning a film formed by anodic oxidation is required, which complicates the manufacturing process.

Further, in the above embodiment, the Ta thin film is used as the conductive material for forming the black matrix 103 and the first electrode 107, but the present invention is not limited to this.
In addition to this, for example, a material that can be anodized, such as Cr, Mo—Ta alloy, or Al, can be used. However, Al
When such a low melting point material is adopted, it is difficult to adopt a high temperature process such as when forming the first interlayer insulating film 109 in the above-mentioned embodiment, and it is preferable to use a low temperature process.

The method of forming the dielectric 111 is not limited to the above-mentioned method of forming by anodic oxidation. In addition to this, for example, the upper surface of the first electrode 107 may be thermally oxidized to form an oxide film, which may be used as the dielectric 111.

Alternatively, when a material that is difficult to form a dielectric by surface oxidation is used as the material for the first electrode 107, the first electrode on the first electrode 107 is used.
After an opening is formed in the interlayer insulating film 109 and the second interlayer insulating film 131, a SiO ₂ thin film having a film thickness of about 400 Å is deposited in the opening by LPCVD method or the like, and is patterned by etching or SiN. _The dielectric 111 may be formed by a method of depositing an _x thin film by a plasma CVD method or the like and patterning this by etching. It goes without saying that the film thickness of the dielectric 111 can be adjusted to a desired film thickness independently of the film thickness of the gate insulating film 117 of the TFT 113 also by these deposition methods.

Further, in this embodiment, the black matrix 1
Although 03 is formed on the array substrate, it is not limited to this. For example, as shown in FIGS. 3 and 4, the black matrix 103 is not formed on the array substrate but is formed on the counter substrate side (not shown), and the first electrode 107 of the storage capacitor 105 is formed separately from the black matrix 103. You may do it. In FIGS. 3 and 4, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals for simplification of description. Also in this case, the first interlayer insulating film 109 and the second interlayer insulating film 109
Of the first electrode 10 exposed from the opening of the interlayer insulating film 131 of
The upper surface of 7 is subjected to surface oxidation treatment such as anodic oxidation or thermal oxidation to form the dielectric 111, or a deposited film such as a SiO ₂ thin film is formed to form the dielectric 111, and the dielectric 111 is formed. Of the film thickness of the gate insulating film 117 of the TFT 113
It goes without saying that the desired thickness can be set independently of.

(Embodiment 2) In the first embodiment, an embodiment of an active matrix type liquid crystal display device having a so-called coplanar type poly-Si TFT using a poly-Si film as an active layer will be described. However, in addition to this, the present invention can be applied to an active matrix type liquid crystal display device having a so-called inverted stagger type a-Si TFT using an a-Si (amorphous silicon) film for an active layer. It is possible. As a second embodiment, an embodiment of an active matrix type liquid crystal display device using an inverted stagger type a-Si TFT will be described in the order of manufacturing steps thereof. For simplicity of explanation, especially the TFT
The array substrate will be mainly described.

FIG. 5 is a sectional view showing a display pixel portion in the liquid crystal display device of the second embodiment according to the present invention. The planar arrangement of each component such as the TFT and the storage capacitor of the liquid crystal display device of the second embodiment is almost the same as that of the first embodiment, and thus the illustration of the planar structure is omitted.

A Ta film is formed on the quartz substrate 101 by a sputtering method and then patterned to form a black matrix 20.
3 is formed. A part of the black matrix 203 is also used as the first electrode 207 of the storage capacitor 205 in each pixel part.

Subsequently, a SiO ₂ film is formed on the entire main surface of the substrate by the LPCVD method to form a first interlayer insulating film 209. The film thickness of the first interlayer insulating film 209 is about 6000.
Angstrom.

Subsequently, a thin film of Mo--Ta alloy is formed by sputtering and patterned to form a gate electrode 211.
And the scanning wiring 137 formed integrally therewith is formed.

Next, SiN _x is formed by a plasma CVD method so as to cover almost the entire main surface of the formed substrate 101.
A film is formed to form a second interlayer insulating film 213. This second interlayer insulating film 213 is formed on the gate insulating film 2 of the TFT 215 at a portion corresponding to the upper surface of the gate electrode 211.
Also used as 17. The film thickness of the gate insulating film 217 was 3500 angstroms.

Then, undoped a is formed by the LPCVD method.
-Si film is formed and then patterned to form a TFT
The active layer 219 of 215 is formed. Then, this active layer 2
After forming the SiN _x by plasma CVD on the 19 and patterned as the SiN _x film is left on the portion to be the channel region of etched active layer 219 to form the etching stopper layer 221 .

Subsequently, an a-Si film is formed by the plasma CVD method, P is doped as an impurity to form a second a-Si film, and this is patterned to form a source electrode 223 and a drain electrode 225 of the TFT 215. To form.

Next, the portions of the second interlayer insulating film 213 and the first interlayer insulating film 209 corresponding to the storage capacitors 205 are
Open the opening by etching. Then, the upper surface of the first electrode 207 made of Ta exposed from this opening is anodized to form the dielectric 227 of the storage capacitor 205. At this time, the first interlayer insulating film 209 and the second interlayer insulating film 2
Since 13 acts as a masking during anodization,
Only the surface of the first electrode 207 exposed from the opening is anodized. Moreover, the film thickness of the oxide film formed at this time can be adjusted by variously changing the conditions of anodic oxidation. In this embodiment, the thickness of the dielectric 227 formed by this anodic oxidation is 1500 angstrom.

Subsequently, a transparent electrode made of ITO is formed by a sputtering method and then patterned to form a pixel electrode 229.

Subsequently, Cr and Al are sequentially formed by a sputtering method and patterned by etching to form a storage capacitor connected to the ends of the source electrode 223 and the pixel electrode 229 and covering the upper surface of the dielectric 227. 205
Forming a second electrode 231 of the drain electrode 225
A signal wiring 233 is formed so as to be connected to.

The liquid crystal display device according to the second embodiment as described above can improve the aperture ratio of the pixel to about 45%. As a result, it was possible to realize good display quality with high screen brightness as in the first embodiment.

In the liquid crystal display device using the inverted stagger type a-SiTFT as in the second embodiment, the black matrix is not formed on the array substrate side as in the first embodiment. It goes without saying that it may be provided on the counter electrode side (not shown) as a separate body from the first electrode 207. This is shown in FIG. In this case, the first interlayer insulating film 209 is omitted.

The method of forming the dielectric 227 is not limited to the above-mentioned method of forming by anodic oxidation. In addition to this, for example, thermal oxidation may be performed on the upper surface of the first electrode 207 to form an oxide film, which may be used as the dielectric 227.

Alternatively, the surface of the dielectric 2 is treated by oxidation.
When a material for which 27 is difficult to form is used as the material for the first electrode 207, the first interlayer insulating film 209 and the second interlayer insulating film 21 on the first electrode 207 are used.
After opening the opening in 3, the SiO ₂ thin film with a film thickness of about 400 Å is deposited on this opening by LPCVD method or the like and is patterned by etching, or the SiN _x thin film is deposited by plasma CVD method or the like. The dielectric 227 may be formed by a method such as patterning by etching. Also in these cases, the film thickness of the dielectric 227 can be adjusted to a desired thickness independently of the film thickness of the gate insulating film 217 of the TFT 215, that is, the film thickness of the second interlayer insulating film 213.

In addition, the materials and film thicknesses of various films used for the TFT, or the planar arrangement of the pixel electrodes, the scanning wirings, the signal wirings, the black matrix, etc. can be appropriately changed without departing from the scope of the present invention. Needless to say.

[0069]

As is clear from the detailed description above, according to the present invention, the flatness of the TFT and the storage capacitor can be avoided while avoiding a decrease in the breakdown voltage of the gate insulating film of the TFT and a decrease in the electric capacitance value of the storage capacitor. It is possible to provide a liquid crystal display device having high luminance and high display quality by miniaturizing the target size and improving the aperture ratio of pixels.

[Brief description of drawings]

FIG. 1 is a plan view showing a display pixel portion in a liquid crystal display device according to a first embodiment.

FIG. 2 is a sectional view taken along the line AA ′ of the display pixel portion in the liquid crystal display device of the first embodiment.

FIG. 3 is a plan view showing a display pixel portion when a black matrix is not formed on the array substrate side in the liquid crystal display device of the first embodiment.

FIG. 4 is a cross-sectional view showing a display pixel portion when a black matrix is not formed on the array substrate side in the liquid crystal display device of the first embodiment.

FIG. 5 is a sectional view showing a display pixel portion in the liquid crystal display device of the second embodiment.

FIG. 6 is a cross-sectional view showing a display pixel portion when a black matrix is not formed on the array substrate side in the liquid crystal display device of the second embodiment.

FIG. 7 is a diagram showing a display pixel portion on the TFT substrate side of a conventional liquid crystal display device using a poly-Si TFT.

FIG. 8 is a partially omitted perspective view showing a TFT array substrate and a counter substrate of a conventional active matrix type liquid crystal display device.

[Explanation of symbols]

101 ... Quartz substrate, 103 ... Black matrix, 10
5 ... Storage capacitor, 107 ... First electrode, 109 ... First interlayer insulating film, 111 ... Dielectric material, 113 ... TFT, 115 ...
Active layer 117, gate insulating film 119, source region,
121 ... Drain region, 123 ... Source electrode, 125 ...
Drain electrode, 127 ... Channel region, 129 ... Gate electrode, 131 ... Second interlayer insulating film, 133 ... Second electrode, 135 ... Pixel electrode, 137 ... Scan wiring, 139 ... Signal wiring

Claims (2)

[Claims] 1. A switching element array substrate having a plurality of scanning wirings and a plurality of signal wirings on a substrate, a switching element connected to the scanning wirings and the signal wirings, and a pixel electrode connected to the switching element. And a counter substrate provided with counter electrodes that are arranged to face the switching element array substrate with a gap, and a liquid crystal composition sealed between the switching element array substrate and the counter substrate. In a liquid crystal display device, the first of the storage capacitors formed of a conductive film on the substrate.
Electrode, an insulating layer which is formed avoiding a portion where the storage capacitor is formed, and has an opening formed in a portion where the storage capacitor is formed, and the first electrode which is exposed from the opening of the insulating layer. The storage capacitor has a dielectric layer formed thereon, and a second electrode of the storage capacitor formed on the dielectric layer and facing the first electrode through the dielectric layer. A liquid crystal display device characterized by the above. 2. A plurality of scanning wirings and a plurality of signal wirings on a substrate, a switching element connected to the scanning wirings and the signal wirings, a pixel electrode connected to the switching element, and a pixel electrode connected to the pixel electrode. A storage element having a storage capacitor and a light-shielding film that blocks light incident on the switching element, and a counter substrate provided with a counter electrode facing the switching element array substrate with a gap. A liquid crystal display device having a liquid crystal composition sealed between the switching element array substrate and the counter substrate, the first electrode of the storage capacitor being formed of the same conductive material as the light shielding film; An insulating layer formed so as to avoid a portion where the storage capacitor is formed and having an opening formed in a portion where the storage capacitor is formed; and an insulating layer exposed from the opening of the insulating layer. A dielectric layer of the storage capacitor formed by anodizing the first electrode, and a first storage capacitor formed on the dielectric layer and facing the first electrode through the dielectric layer. A liquid crystal display device comprising two electrodes.