JPH0720491A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To prevent the contamination of display electrodes by plasma film formation and photoetching by executing formation of respective patterns in the state of coating the display electrodes with protective films. CONSTITUTION:The protective film 30 formed over the entire surface after the formation of ITO of the display electrodes is self-aligned to source electrodes 19 and is removed by etching and, therefore, remains at the junctures between the display electrodes 14 and the source electrodes 19. Since the protective films 30 are formed on the display electrodes 14, etching rates are equaled in the films and at the boundaries and, therefore, the edges are not formed to a reverse taper shape at the time of forming contact holes in a gate insulating film 15 of an upper layer. Metals, such as Cr, Al and Mo, are used for the material of the protective films 30. The protective films 30 on the display electrodes 14 are etched away simultaneously at the time of patterning if the drain and source wirings and the protective films 30 are formed of the same material by using the Al and Mo.

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 a method for manufacturing the same, and more specifically, to an active matrix liquid crystal display device using a thin film transistor (hereinafter abbreviated as TFT) as a switching element,
The present invention relates to a liquid crystal display device having a two-layer gate insulating film structure in which a gate insulating film is formed in two layers to prevent a short circuit between a wiring crossing portion and a TFT portion, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A conventional liquid crystal display device and a method of manufacturing the same will be described below with reference to FIGS. FIG. 6 is a partial plan view of the liquid crystal display device on the TFT substrate side, and FIG. 7 is a sectional view taken along line AA shown in FIG.
First, on a transparent insulating substrate (10) such as glass, for example, Cr is sputtered and patterned to form a gate electrode (11), an auxiliary capacitance electrode (12), and a gate line (21) integrated with the gate electrode (11). , An auxiliary capacitance line (22) integrated with the auxiliary capacitance electrode (12) is formed. Subsequently, SiO ₂ or SiN _x is deposited as a first gate insulating film (13) on the entire surface by CVD. First
ITO is sputtered on the gate insulating film (13) and patterned to leave it in a predetermined region,
Display electrodes (14) are formed.

Next, a second gate insulating film (15) is formed on the entire surface.
SiO ₂ or SiN _x as a layer is deposited by CVD, followed by non-doped amorphous silicon (hereinafter a-S
abbreviated as i) film (16) and SiN _x are both CV
D is laminated continuously. And the top layer of SiN
_X is removed by etching leaving a predetermined region corresponding to the gate electrode (11) to remove the semiconductor protective film (1
7) is formed.

Further, an amorphous silicon (hereinafter abbreviated as N ⁺ a-Si) film (1) doped with phosphorus on the entire surface is used.
8) is laminated by CVD to form an N ⁺ a-Si film (18) and a-
The shape of the TFT can be obtained by pattern-etching the Si film (16) with the same mask. Subsequently, the second gate insulating film (15) on the display electrode (14) is removed by etching to provide a contact portion with the source electrode (19) which will be formed later.

Then, a drain electrode (20), a drain line (23) and a source electrode (19) are formed by laminating Al and the like and performing a predetermined patterning. Then, the drain electrode (20) and the source electrode (1
The center portion of the N ⁺ a-Si film (18) is removed by etching using 9) as a mask to separate the drain portion and the source portion.

The conventional example described above is disclosed, for example, in Japanese Patent Application Laid-Open No. H3-114028.

[0007]

However, according to the above-mentioned conventional liquid crystal display device and the manufacturing method thereof, as shown in FIG. 8, the second gate insulating film (15), Si, is used.
In the N _x film forming process, the ITO display electrode (14) is exposed. Therefore, when forming a film of SiN _x by CVD, hydrogen (H) contained in the material gas used [eg, silane (SiH4) or ammonia (NH3)]
O was reduced, and the display electrode (14) was colored light brown, which caused problems such as reduction in transmittance and deterioration in display quality.

In general, the ITO film has a property that water or the like is adsorbed on its surface and is easily polluted. Therefore, the ITO display electrode (14) is contaminated by the step of forming the second gate insulating film (15). To be done. The etching rate is high on the surface of the contaminated ITO film. Therefore, when the second gate insulating film (15) on the display electrode (14) is etched, the etching progresses quickly at the interface with the display electrode (14), and thus FIG.
As shown in FIG. 5, the second gate insulating film (15) has an inverse taper shape at the edge portion, film peeling or cracking of the source electrode (19) occurs, and connection failure with the display electrode (14) occurs.

Further, when the display electrode (14) is contaminated, there is a problem that the contact resistance increases at the connection portion with the source electrode (19).

[0010]

The present invention has been made in view of the above-mentioned problems, and a gate electrode (11), an auxiliary capacitance electrode (12), and a gate line (21) provided on an insulating substrate (10). And the auxiliary capacitance line (22), the first gate insulating film (13) covering them, and the gate insulating film (1
3) A display electrode (14) provided in the upper display area, a second gate insulating film (15) provided on the gate insulating film (13) outside the display area, and a second gate insulating film (15). 15)
The a-Si film (16) formed on the upper part corresponding to the gate electrode (11), the N ⁺ a-Si film (18) and a-Si formed on both ends of the a-Si film (16). Membrane (16)
And a N ⁺ a-Si film (18) between the semiconductor protective film (17), one N ⁺ a-Si film (18) covering the drain electrode (20), the other N ⁺ a-
The source electrode (1) which covers the Si film (18) and is connected to the display electrode (14) through the conductive protective film (30).
9) and a structure comprising a drain line (23) integrated with the drain electrode (20), and covering the gate electrode (11), the gate line (21), the auxiliary capacitance electrode (12) and the auxiliary capacitance line (22). Forming an ITO film and a conductive protective film (30) on the first gate insulating film (13) provided on the insulating substrate (10), and forming the ITO film and the protective film (30). A step of forming a display electrode (14) covered with a protective film (30), which is to be electrically connected to a TFT by patterning with the same mask, and a display covered with the protective film (30). Forming a second gate insulating film (15) on the first gate insulating film (13) including the electrode (14) by utilizing a reducing gas;
A step of forming a semiconductor layer mainly containing Si on the second gate insulating film (15), and the second gate insulating film (on the display electrode (14) covered with the protective film (30) ( 1
5) etching away, a drain electrode (20) covering one end of the semiconductor layer, and a display electrode (14) covering the other end of the semiconductor layer and covered with the protective film (30). A source electrode (19) electrically connected,
And the drain line (2) integrated with the drain electrode (20)
3) and self-aligning with the source electrode (19) to form the protective film (3) on the display electrode (14).
The above problem is solved by a manufacturing method including a step of etching away 0).

[0011]

[Operation] After forming the ITO film, a conductive protective film (3
0) (eg Cr or Mo) to form Si
When the N _x second gate insulating film (15) is formed by CVD, contamination of the ITO due to reduction by hydrogen or adsorption of water is prevented. As a result, it is possible to prevent the problems that the ITO film is discolored to light brown and the transmittance is lowered and the contact resistance is increased. In addition, the display electrode (1
4) When the contact hole is formed by etching the second gate insulating film (15) on the upper side, it is possible to prevent the edge portion from having an inverse taper shape due to the difference in etching rate. Good contact with.

[0012]

EXAMPLES Next, a liquid crystal display device and a method of manufacturing the same according to examples of the present invention will be described. FIG. 1 is a cross-sectional view of a liquid crystal display device showing an embodiment of the present invention, which corresponds to the portion along the line AA of the plan view shown as the conventional example in FIG. , The same symbols are used.

The features of the embodiment shown in FIG. 1 will be apparent from the description of the manufacturing method which will be described later, but a C electrode is formed at the connecting portion between the display electrode (14) and the source electrode (19) made of ITO.
This is the point where a metallic protective film (30) of r, Al, Mo or the like is interposed. That is, immediately after the ITO of the display electrode (14) is formed, the protective film (30) provided on the entire surface is self-aligned with the source electrode (19) and etched away. Source electrode (19)
It is due to remaining in the connection part of. Display electrode (1
4) Since the protective film (30) is coated on the above,
When forming a contact hole in the upper gate insulating film (15), the etching rate becomes equal in the film and at the interface, so that the edge portion does not have an inverse taper shape.

The material of the protective film (30) is Cr or A.
Metals such as l and Mo are used. Cr is excellent in erosion resistance and heat resistance, but has a high specific resistance of 50 μΩ · cm. Therefore, when Cr is used as the protective film (30),
This may cause an increase in contact resistance. On the other hand, Al and M
Although o has a problem in erosion resistance and heat resistance, it has a low specific resistance of 3 μΩ · cm and 20 μΩ · cm, respectively, and can prevent an increase in contact resistance. If the drain and source wirings and the protective film (30) are formed of the same material using Al or Mo, when patterning the drain electrode (20), the drain line (23), and the source electrode (19), At the same time, there is a manufacturing advantage that the protective film (30) on the display electrode (14) can be removed by etching. Also,
In terms of structure, the source electrode (19) and the protective film (30) are not distinguished from each other, and good contact can be obtained.

Further, FIG. 1 shows a drain auxiliary line (24) which is another embodiment. The drain auxiliary line (24) is provided for the purpose of relief when the drain line (23) is broken due to manufacturing reasons, for example, dust, and the second auxiliary gate insulating film (15).
It is connected to the lower part of the drain line (23) by the contact line formed in. The drain auxiliary line (24) has a two-layer structure of ITO and a metal that is the same material as the protective film (30) coated on the ITO, and is formed at the same time as the display electrode (14) and the protective film (30). It Although ITO has a high specific resistance of 200 to 300 μΩ · cm and is not suitable for wiring, it can be used for wiring by covering the upper layer with a metal to form two layers.

The manufacturing method of the embodiment shown in FIG. 1 will be described below.
Will be described with reference to FIGS. 2 to 5. (Explanation of FIG. 2) On an insulating substrate (10) such as glass,
For example, Cr is sputtered to a thickness of about 1000Å,
By patterning, the gate electrode (11)
Integrated with the storage capacitor electrode (12) and the gate electrode (11)
Integrated with the gate line (21) and auxiliary capacitance electrode (12)
Auxiliary capacitance line (22) is formed. Next, SiN
_XOr SiO₂2000-4000 liters by CVD
This is used as a first gate insulating film (13).

Next, I which is the material of the display electrode (14)
Cr, which is the material of TO and the protective film (30), is continuously formed by sputtering. This step is a feature of the present invention, in which the protective film (30) is formed on the ITO, and since the protective film (30) is formed immediately after the ITO is deposited, the subsequent step follows. Contamination of ITO in the process is prevented. The material of the protective film (30) is not limited to Cr,
As described above, Al, Mo or the like may be used. (Description of FIG. 3) By patterning Cr and ITO with the same mask, the protective film (3) is left in the display region and the region where the drain line (23) is to be formed.
The display electrode (14) covered with 0) and the drain auxiliary line (24) are formed.

Next, a second gate insulating film (15) is formed on the entire surface.
SiN _x or SiO ₂ is used for about 200 by CVD
The layers are laminated to a thickness of 0 to 4000 Å, and subsequently, an a-Si film (16) is continuously formed to a thickness of about 1000 Å and SiN _x to a thickness of about 2500 Å by CVD. Then, by performing a predetermined patterning on the uppermost SiN _x , the TFT
The semiconductor protective film (17) is formed. (Explanation of FIG. 4) Next, 500 N ⁺ a-Si film (18) is formed.
After the CVD film is formed to a film thickness of about Å, the N ⁺ a-Si film (1
8) and the a-Si film (16) are subjected to the same patterning and left in the TFT section. (Explanation of FIG. 5) Subsequently, the second gate insulating film (15) on the display electrode (14) and the drain auxiliary line (24).
Are removed by etching, and the display electrode (14) covered with the protective film (30) and the drain auxiliary line (2
4) is exposed. The drain auxiliary line (24) is contacted with a drain line (23) which will be formed later.

Next, as a wiring material, for example, Al is 800
By forming and patterning with a film thickness of 0Å, N ⁺
The drain electrode (2 which covers one end of the a-Si film (18)
0), the source electrode (19) and the drain electrode (20) which are connected to the display electrode (14) which covers the other end of the N ⁺ a-Si film (18) and is covered with the protective film (30). A drain line (23) is formed. As the wiring material, the lower layer is 1000 Å Mo and the upper layer is 7,000 Å Al
It may have a two-layer structure.

Then, the protective film (3
The display electrode (14) is exposed by self-aligning 0) with the source electrode (19) and etching away. In addition, the drain electrode (20) and the source electrode (1
9) is used as a mask to remove the center portion of the N ⁺ a-Si film (18) by etching, thereby separating the drain portion and the source portion to obtain the structure shown in FIG.

[0021]

As is apparent from the above description, ITO
When the display electrode is formed at a relatively early stage of manufacturing the substrate, each pattern is formed with the display electrode covered with the protective film, so that the display electrode is prevented from being contaminated due to plasma film formation or photoetching. Further, by this, when the insulating film is etched to form the contact hole, the etching rate at the interface with the protective film is prevented from increasing, so that the edge portion does not have a reverse taper shape and the film peeling of the source electrode occurs. Cracks are prevented. Further, the poor contact between the source electrode and the display electrode caused by the contamination of ITO is improved.

Then, after the TFT is formed, the protective film is removed by etching to expose the display electrode, whereby a liquid crystal display device in which deterioration of display quality and increase in power consumption are prevented can be obtained. Further, the drain auxiliary line connected to the drain line can be formed without increasing the number of masks, and defects due to disconnection can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a method of manufacturing a liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the method of manufacturing the liquid crystal display device according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the method of manufacturing the liquid crystal display device according to the embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the method of manufacturing the liquid crystal display device according to the embodiment of the present invention.

FIG. 6 is a plan view of a conventional liquid crystal display device.

7 is a sectional view taken along the line AA of FIG.

FIG. 8 is a cross-sectional view showing a method of manufacturing a conventional liquid crystal display device.

FIG. 9 is a cross-sectional view showing a method of manufacturing a conventional liquid crystal display device.

[Explanation of symbols]

10 Transparent Insulating Substrate 11 Gate Electrode 12 Auxiliary Capacitance Electrode 13 First Gate Insulating Film 14 Display Electrode 15 Second Gate Insulating Film 16 a-Si Film 17 Semiconductor Protective Film 18 N ⁺ a-Si Film 19 Source Electrode 20 Drain electrode 21 Gate line 22 Auxiliary capacitance line 23 Drain line 24 Drain auxiliary line 30 Protective film

Claims (5)

[Claims] 1. A plurality of gate lines provided on a transparent insulating substrate, a plurality of drain lines provided to intersect the gate lines, and an intersection of the gate lines and the drain lines. A thin film transistor including a gate electrode, a drain electrode, a source electrode and a semiconductor layer, and a liquid crystal display device electrically connected to the source electrode and including a transparent conductive display electrode, wherein the display electrode and the source electrode are: A liquid crystal display device, wherein the liquid crystal display device is connected through a conductive protective film. 2. A drain auxiliary line electrically connected to the drain line is provided below the drain line, and the drain auxiliary line includes the same transparent conductive material as the display electrode and the protective film. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is made of the same conductive material. 3. A step of forming a plurality of gate electrodes and a gate line integrated with the gate electrodes on a transparent insulating substrate; a step of forming a first gate insulating film on the entire surface; and an ITO film on the entire surface. A step of forming a coating, a step of forming a conductive protective film on the ITO film, and a step of patterning the ITO film and the protective film with the same mask to form a display electrode covered with the protective film. A step of forming a second gate insulating film on the entire surface, a step of forming a semiconductor layer on a region of the second gate insulating film corresponding to the gate electrode, and a step of forming the second gate insulating film, A step of etching and removing at least a part of the display electrode covered with the protective film, a step of forming a metal layer on the entire surface, and a patterning of the metal layer to form a drain line crossing the gate line. Source, which is integrated with the drain line and electrically connected to a drain electrode covered at one end of the semiconductor layer, and a display electrode covered with the protective film, and a source covered at another end of the semiconductor layer. A method for manufacturing a liquid crystal display device, which comprises at least a step of forming an electrode, and a step of self-aligning with the source electrode to remove the protective film by etching to expose the display electrode. 4. A step of forming a plurality of gate electrodes and a gate line integrated with the gate electrodes on a transparent insulating substrate; a step of forming a first gate insulating film on the entire surface; and an ITO film on the entire surface. A step of forming a coating, a step of forming a conductive protective film on the ITO film, a patterning of the ITO film and the protective film with the same mask, a display electrode covered with the protective film, and the gate. Forming a drain auxiliary line that intersects with the line, forming a second gate insulating film on the entire surface, and forming a semiconductor layer in a region corresponding to the gate electrode on the second gate insulating film A step of etching and removing at least a part of the second gate insulating film on the display electrode covered with the protective film and at least a part of the drain auxiliary line, and A step of forming a layer by coating, a pattern of the metal layer, a drain line connected to the drain auxiliary line and intersecting with the gate line, and a drain electrode integrally formed with the drain line at one end of the semiconductor layer And a source electrode that is electrically connected to the display electrode covered with the protective film to cover another end of the semiconductor layer, and the protective film is self-aligned with the source electrode. A method of manufacturing a liquid crystal display device, which comprises at least a step of removing the display electrode by etching. 5. The liquid crystal display device according to claim 3, wherein the protective film is made of the same material as the source electrode and is removed by etching at the same time when the metal layer is patterned. Method.