JPH06301052A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To prevent the generation of light leak currents of TFTs which are switching elements of the liquid crystal display device which executes active matrix driving and to improve the display characteristics thereof by preventing the incidence of light to these TFTs. CONSTITUTION:This liquid crystal display device is constituted by simultaneously depositing ITO on the upper part of the TFTs 12 as well at the time of formation of pixel electrodes 19 and protecting the ITO of the regions corresponding to the pixel electrodes 19 with a photoresist, then subjecting the resist to a heat treatment for >=1 hours in a reducing atmosphere to reduce the ITO on the upper parts of the TFTs 12 and to precipitate metallic particulates, thereby forming light shielding layers 21 Since the light shielding layers are constituted of the metallic particulates, not only the leak current of the TFTs is prevented but also an electromagnetic shielding effect is obtd. The flickering of the images by a change in the high-frequency potential of signal lines is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix driving liquid crystal display device using a TFT (thin film transistor) as a switching element.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view of a pixel portion of a typical liquid crystal display device of a conventional active matrix type. In the figure, 11 is a first substrate, 12 is a TFT which is a pixel switching element, 13 is a gate electrode, 14 is a source, and 15 is a source.
Is a drain, 16 is an offset source, 17 is an offset drain, 18 is an interlayer insulating layer, 19 is a pixel electrode,
20 is a storage capacitor electrode, 22 is a pixel electrode 19 and the drain 1
Al for connection with 5, signal line 23, interlayer insulating layers 24 to 26, passivation 27, alignment layer 28 for controlling liquid crystal alignment, 30 second substrate, 31 color filter, 32 light shielding layer 33 is a counter electrode, 34 and 35 are interlayer insulating layers, 36 is the same alignment layer as 28, and 40 is a liquid crystal.

In the liquid crystal display device, since the pixel portion needs to be transparent, the first substrate 11 and the second substrate 30 are required.
Is made of a transparent insulating material such as glass or SiO ₂ , and the pixel electrode 19 and the counter electrode 33 are made of ITO (Indium T
in oxide). Also,
The storage capacitor electrode 20 is a member provided to form a storage capacitor of an image signal with the pixel electrode 19, and is usually provided in the peripheral portion of the pixel with polycrystalline Si or the like, or if it is a transparent material such as ITO. It is provided over the entire surface of the display portion, is commonly connected to all pixels, and controls the potential at the peripheral portion of the display portion. On the other hand, the second substrate 30 is provided with a color filter 31 of one of the three primary colors of green, red and blue for each pixel, and a light shielding layer 32 is formed between the pixels. The counter electrode 33 formed on the second substrate 30 is usually formed so as to cover all pixels.

The liquid crystal 40 has alignment films 28 and 3 located on both sides.
6 to the desired angle. The light source is installed on the second substrate side, and the observer observes the light of the light source that has transmitted the liquid crystal from the first substrate side.

[0005]

In the above conventional liquid crystal display device, the light shielding layer 32 prevents the TFT 12 from malfunctioning due to the incidence of light on the TFT 12 from the second substrate side. However, since the light-shielding layer 32 is formed on the second substrate, the light-shielding effect is low with respect to obliquely incident light, and a light leak current is generated in the TFT 12, resulting in deterioration of the contrast of the display image. There was.

[0006]

According to the present invention, a light-shielding layer is provided on the side of a first substrate to reliably shield a TFT from light, and the light-shielding layer is formed of a metal oxide which constitutes a pixel electrode or a storage capacitor electrode. It is easily produced by reducing the metal fine particles.

According to a first aspect of the present invention, a first substrate having a plurality of transistors arranged in a matrix and a pixel electrode made of a metal oxide connected to the output side of each transistor, and a counter electrode are provided. A liquid crystal display device in which a second substrate having the liquid crystal is sandwiched between the substrates, the liquid crystal display device comprising:
A liquid crystal display device is characterized in that it has a light-shielding layer composed of metal fine particles obtained by partially reducing the metal oxide forming the pixel electrode, between the transistor and the liquid crystal.

According to a second aspect of the present invention, there is provided a first substrate having a plurality of transistors arranged in a matrix, a pixel electrode connected to the output side of each transistor, and a second substrate having a counter electrode. A liquid crystal display device arranged to face each other with a liquid crystal sandwiched between the substrates, wherein a storage capacitor electrode made of a metal oxide is provided between the first substrate and the pixel electrode.
In addition, the liquid crystal display device is characterized by having a light-shielding layer composed of metal fine particles formed by partially reducing the metal oxide forming the storage capacitor electrode, between the transistor and the liquid crystal.

A third aspect of the present invention is the method of manufacturing a liquid crystal display device according to the first aspect of the present invention, wherein the metal oxide is deposited on the first substrate to form the pixel electrode, and at the same time, the transistor is formed on the transistor. Also, after depositing the metal oxide layer and covering the pixel electrode with photoresist, 250 to 300 in a reducing atmosphere.
In the method of manufacturing a liquid crystal display device, the heat treatment is performed in the temperature range of ° C for 1 hour or more to reduce the metal oxide layer on the transistor to form a metal fine particle layer to form a light shielding layer.

The fourth aspect of the present invention is the second aspect of the present invention.
The method of manufacturing a liquid crystal display device according to claim 1, wherein when the metal oxide is deposited on the first substrate to form the storage capacitor electrode, at the same time, the metal oxide layer is also deposited on the transistor to form the storage capacitor electrode. 2 in a reducing atmosphere after covering with photoresist
A method of manufacturing a liquid crystal display device, which comprises heat-treating in a temperature range of 50 to 300 ° C. for 1 hour or more to reduce the metal oxide layer on the transistor to form a metal fine particle layer to form a light shielding layer.

[0011]

【Example】

(Embodiment 1) FIG. 1 is a sectional view of a liquid crystal panel of a liquid crystal display device according to a first embodiment of the present invention. The reference numerals in the figure are the same as those in FIG. 9 described above, and the present embodiment is different from the conventional example in that the light shielding layer 21 is provided on the first substrate 11 side. The first substrate 11 is preferably SOI (Silico).
The Si support substrate of the n On Insulator substrate is used to remove the SiO ₂ layer left by wet etching. Therefore, the active layer of the TFT 12 uses the single crystal thin film Si of the SOI substrate. In addition, polycrystalline Si or α (amorphous) -Si is deposited on a conventional glass substrate to form a TFT.
12 may be configured. The TFT 12 has a gate electrode 12,
Source 14 and drain 1 heavily doped with impurities
5, the offset source 16 is doped with impurities at a lower concentration than the source 14, and the offset drain 17 is doped with impurities at a lower concentration than the drain 15. Reference numeral 18 is an interlayer insulating layer, and if it is an SOI substrate,
It is obtained by partially thermally oxidizing the single crystal thin film Si. Reference numeral 19 denotes a pixel electrode made of ITO. In this embodiment, the TFT
The light-shielding layer 21 immediately above 12 is characterized in that it is blackened by reducing ITO to deposit metal fine particles. In this example, as a metal oxide forming a pixel electrode, S added with a small amount of Sb ₂ O ₃ in addition to ITO.
ZnO added with nO ₂ and a small amount of Al ₂ O ₃ can be used.

FIG. 2 shows an active matrix circuit of this embodiment. In the figure, 41 is a vertical shift register, 42 is a horizontal shift register, and 43 is a scanning line.

FIG. 3 shows a step of forming the light shielding layer 21 of this embodiment. First, a TFT is formed on a first substrate by a normal forming process, an interlayer insulating layer 25 is deposited on the entire surface, and polycrystalline Si is deposited to form a storage capacitor electrode 20 (a). Next, an interlayer insulating layer 26 is deposited on the entire surface, and Al22
After forming a contact hole for connecting to the ITO layer and depositing ITO on the entire surface, the ITO layer 37 for forming the pixel electrode 19 and the light shielding layer is patterned using a photoresist (b). Put a photoresist on the entire surface, IT
The photoresist 38 is patterned so that only the O layer 37 is exposed to protect the pixel electrode 19, and 250 to 300
Heat treatment for 1 hour or more in N ₂ gas atmosphere at ℃
The TO layer 37 is reduced and blackened to form the light shielding layer 21. The reduction of ITO at this time is 2In ₂ O ₃ → 4In + 3O ₂ ↑ SnO ₂ → Sn + O ₂ ↑, and the oxides of In and Sn are reduced, and the metal fine particles of In and Sn are precipitated, so that blackening occurs. is there.

After the heat treatment is completed, the photoresist 38
Are removed, and the passivation 27 and the alignment film 28 are provided.

The liquid crystal display device of the present embodiment can effectively shield the light incident on the TFT 12 and prevent the light leak current generated in the TFT 12, so that high contrast display is realized. Further, since the light shielding layer 21 has conductivity, it also has an electromagnetic shielding effect, and the influence of the signal line 23 being shaken during image signal transfer does not affect the pixels, so that high quality display is realized.

(Embodiment 2) FIG. 4 shows a second embodiment of the present invention. The present embodiment is characterized in that the microlens 50 is provided for each pixel on the outside of the second substrate in addition to the structure of the first embodiment. The microlens 50 reduces the oblique light component incident on the TFT 12 and further enhances the light shielding effect of the TFT 12. Further, since the effective aperture area of the pixel is increased by the microlens 50, high brightness display is realized.

(Embodiment 3) A third embodiment of the present invention is shown in FIG. The feature of this embodiment is that the phase shifter 51 is provided outside the second substrate. As shown in FIG. 6, the phase shifter 51 is arranged so as to form a checkerboard pattern by shifting every other pixel in one column and by one pixel in each row. This phase shifter 51
Thus, the light incident on the TFT 12 located between the pixels cancels out the light incident on the adjacent pixel, and as a result, the TFT 1
The generation of the light leakage current of No. 2 is prevented.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention. The feature of the present embodiment is that the storage capacitor electrode 20 is made of ITO, and becomes the light shielding layer of the TFT 12 when the ITO is deposited.
The TO is deposited at the same time.
The substantial effect is the same except that the portion where is located is different. In addition, in the present embodiment, as the metal oxide forming the storage capacitor electrode 20, in addition to ITO, SnO ₂ containing a small amount of Sb ₂ O _{3 or} ZnO containing a small amount of Al ₂ O ₃ may be used. it can.

The manufacturing process of this embodiment is shown in FIG. Similarly to the first embodiment, the TFT 12 is formed on the first substrate 11 and the interlayer insulating layer 25 is deposited on the entire surface (a). Then, ITO which will be the storage capacitor electrode 20 is extended and deposited on the TFT 12 (b). A region corresponding to the storage capacitor electrode 20 is patterned and protected using a photoresist 38, and the first embodiment is used.
Similarly, heat treatment is performed for 1 hour or more in a reducing atmosphere to reduce the ITO on the light shielding layer 21 to form the light shielding layer 21 (c). After the heat treatment is completed, the photoresist 38 is removed, the interlayer insulating layer 26 is deposited on the entire surface, the contact hole is formed to form and connect the pixel electrode 19, and the passivation 27 and the alignment film 28 are further provided on the entire surface (d). ). The first substrate thus manufactured is arranged so as to face the second substrate, and liquid crystal is sealed therein to form a liquid crystal panel.

As described above, this embodiment is different from the first embodiment only in the layer in which the light shielding layer 21 is located, and in the same manner as the second and third embodiments, the microlens and the phase shifter are installed. The same effect as 2 and 3 can be obtained.

[0021]

As described above, according to the present invention, the TFT for switching the pixel is effectively shielded from light and the generation of the light leak current is reduced, so that the malfunction is prevented and the contrast of the display image is improved. To do. Furthermore, since the light-shielding layer of the present invention is a conductor, it also has an electromagnetic shielding function, and can prevent image flicker due to a high-frequency potential change of the signal line and realize a high-quality image display.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal panel according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an active matrix circuit according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the liquid crystal panel according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a third embodiment of the present invention.

FIG. 6 is a diagram showing an arrangement of phase shifters according to a third embodiment of the present invention.

FIG. 7 is a diagram showing a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a manufacturing process of a liquid crystal panel according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view of a conventional liquid crystal panel.

[Explanation of symbols]

 11 First Substrate 12 TFT 13 Gate Electrode 14 Source 15 Drain 16 Offset Source 17 Offset Drain 18 Interlayer Insulation Layer 19 Pixel Electrode 20 Storage Capacitance Electrode 21 Light-Shielding Layer 22 Al 23 Signal Line 24-26 Interlayer Insulation Layer 27 Passivation 28 Orientation Layer 30 Second substrate 31 Color filter 32 Light-shielding layer 33 ITO 34, 35 Interlayer insulating layer 36 Alignment film 37 IOT layer 38 Photoresist 40 Liquid crystal 41 Vertical shift register 42 Horizontal shift register 43 Scan line 50 Microlens 51 Phase shifter 53 Pixel

Claims (4)

[Claims] 1. A first substrate having a plurality of transistors arranged in a matrix, a pixel electrode made of a metal oxide connected to the output side of each transistor, and a second substrate having a counter electrode. A liquid crystal display device, which is arranged to face each other and has a liquid crystal sandwiched between the substrates, comprising metal fine particles formed by partially reducing a metal oxide forming the pixel electrode between the transistor and the liquid crystal. A liquid crystal display device, comprising a light-shielding layer according to claim 1. 2. A first substrate having a plurality of transistors arranged in a matrix, a pixel electrode connected to the output side of each transistor, and a second substrate having a counter electrode.
A liquid crystal display device in which substrates are arranged to face each other and liquid crystal is sandwiched between the substrates, and a storage capacitor electrode made of a metal oxide is provided between a first substrate and a pixel electrode, and A liquid crystal display device comprising a light-shielding layer composed of fine metal particles formed by partially reducing the metal oxide forming the storage capacitor electrode between the liquid crystal and the liquid crystal. 3. The method for manufacturing a liquid crystal display device according to claim 1, wherein when the metal oxide is deposited on the first substrate to form the pixel electrode, the metal oxide layer is also formed on the transistor at the same time. And the pixel electrode is covered with a photoresist, and then heat-treated in a reducing atmosphere at a temperature range of 250 to 300 ° C. for 1 hour or more to reduce the metal oxide layer on the transistor to form a metal fine particle layer to form a light shielding layer. A method for manufacturing a liquid crystal display device, comprising: 4. The method of manufacturing a liquid crystal display device according to claim 2, wherein when the metal oxide is deposited on the first substrate to form the storage capacitor electrode, the metal oxide is also formed on the transistor at the same time. After depositing a layer and covering the storage capacitor electrode with a photoresist, heat treatment is performed in a temperature range of 250 to 300 ° C. for 1 hour or more in a reducing atmosphere to reduce the metal oxide layer on the transistor to form a metal fine particle layer. A method for manufacturing a liquid crystal display device, which comprises a light-shielding layer.