JPH05297410A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To produce the liquid crystal display device of a large screen which can be treated at a low temp. at a low cost without impairing its characteristics by providing a hydrophobic mask on the gate line formed on a low melting glass substrate and forming a silicon oxide film by a liquid crystal growth method thereon. CONSTITUTION:The low melting glass substrate 51 into which an alkaline metal is incorporated is first prepd. A gate 52, the gate line 53 integral with the gate, an auxiliary capacity electrode 54 and an auxiliary capacity line integral with the auxiliary capacity electrode 54 are formed. In succession, a resist corresponding to a contact hole 64 is formed and thereafter, the line is anodized to form aluminum oxide 71 on the surface of the line exclusive of a resist forming region. The silicon oxide film 55 is then formed by liquid phase growth while the resist is held masked and thereafter, the resist is removed, by which the contact hole 64 exposed with the Al surface is formed. A transparent electrode material is then deposited over the entire surface and a display electrode 56 and a c6ncluctive line 7 extended a terminal region are formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a liquid crystal display device, which uses a glass substrate having a low melting point and a gate insulating film formed by a liquid phase epitaxy method. It concerns the technology that can be supplied.

[0002]

2. Description of the Related Art In general, it is one of the important subjects to achieve cost reduction of a liquid crystal display device using a-Si or p-Si TFT. On the other hand, as the gate material, C
Various materials such as r, Cu, Au and Al have been adopted or tested. However, considering that the panel will have a large screen in the future, Cr having high resistance is not preferable, and considering stability, only Al or Au remains. Especially Al is Au
Since it is much lower in price than the above, a liquid crystal display device using Al for the gate will be studied in the future.

For example, Japanese Patent Laid-Open No. 3-232274 discloses a device which uses Al as a gate. First, as shown in FIG. 9, a gate terminal (2) made of Cr is formed on a glass substrate (1), and a gate (3) and an auxiliary capacitance electrode (4) are formed of Al. Here, a gate line is formed integrally with the gate, and an auxiliary capacitance line is formed integrally with the auxiliary capacitance electrode.

Subsequently, the photoresist (5) is left on the non-anodized portion such as the gate terminal (2), and as shown in FIG.
The electrodes (3) and (4) are anodized. As a result, aluminum oxide (6) is formed on the surface of the Al electrode.
Further, a silicon nitride film (7) is formed by plasma CVD. Then, as shown in FIG. 11, non-doped a-Si (7) and P-doped N ⁺ -type a-Si (8) are continuously formed by plasma CVD, and subsequently at least the TFT portion is etched by etching. Is left. In addition, the display electrode (9) is made of a transparent electrode material such as indium oxide.
Is formed and is deposited on the portion of the gate terminal.

Finally, as shown in FIG. 12, a drain electrode (10) also serving as a drain line and a source electrode (11) for electrically connecting the source region and the display electrode (9) are formed. Although not shown here, a passivation film and an alignment film are formed. On the other hand, a color filter, a light-shielding film, a counter electrode and an alignment film are provided on the counter substrate, and two glass substrates are set at a predetermined interval via a spacer to seal the periphery and liquid crystal is injected into the inside. ing.

[0006]

In the above process, the glass substrate (1) is made of expensive non-alkali glass in consideration of deterioration of the liquid crystal material and TFT, and the plasma C
Since the silicon nitride film (7) is formed by VD,
There is a problem that throughput is lowered and cost is increased.

There is another method in which a glass substrate having a low melting point mixed with an alkali metal is used in place of the non-alkali glass, a silica film is formed on the surface thereof, and then a TFT is formed on the surface. For example, JP-A-58-16194
Publication No. 4 is an example. However, in both cases, only a silicon nitride film formed by plasma CVD exists between the gate and a-Si, and a silicon nitride film having a conventional thickness is required to prevent a gate short circuit. I was trying.

Further, since the temperature is high even in plasma CVD,
There is a problem that the low-melting glass substrate is warped or its characteristics are deteriorated. Further, Cr is relatively expensive, and since it is used as a terminal, the number of steps is increased, resulting in high cost. Further, with this structure, the glass substrate (1) is exposed around the terminals, and there is a problem that a glass substrate mixed with an alkali metal, such as soda glass or boron glass, cannot be used. These metals have a problem that when the substrate (1) is put into an etching solution or the like, it is dissolved in the solution to cause deterioration of TFT characteristics, or it is dissolved in the liquid crystal to cause deterioration of the liquid crystal.

[0009]

The present invention has been made in view of the above-mentioned problems, and a gate and a gate line are formed on a glass substrate having a low melting point, and a hydrophobic mask is attached on the gate line near the gate terminal. The problem is solved by forming a silicon oxide film by a liquid phase epitaxy method and connecting the exposed gate line and gate terminal after removing the mask.

Second, the above-mentioned manufacturing method is solved by a method including a step of using Al for the gate and the gate line and anodizing the surface. Thirdly, in the above-described manufacturing method, the step of providing the hydrophobic mask after the anodic oxidation is adopted to solve the problem.
Fourthly, in the first manufacturing method, the electric connection between the gate terminal and the gate line is made of the same material as that of the display electrode, and a method including a step of forming in the same step is solved.

[0011]

In the first and third methods, the low melting point glass is inexpensive, and the silicon oxide film formed by the liquid phase growth method also has a large throughput, so that the cost can be reduced. Further, during liquid phase growth, the silicon oxide film can be selectively grown by covering it with a hydrophobic mask, for example, a resist, and it is possible to cover the entire area except for the region where the resist is provided. Therefore, the impurities in the low melting point substrate will not be eluted into the etching liquid or the liquid crystal.

In the second method, Al is the most suitable in view of the gate resistance and cost in a large screen. Moreover, since the anodic oxidation method, which enables low temperature treatment, is used, the warp of the substrate can be prevented. In the fourth method, the conductive line extending from the gate line to the gate terminal can be formed at the same time as the display electrode. Therefore, in addition to the features of the first method, the process can be further shortened.

Finally, in the first to fourth methods, after a silicon oxide film is formed by a liquid phase epitaxy method, a silicon nitride film,
If a step of continuously forming non-doped a-Si and N ⁺ -type a-Si is adopted, the silicon nitride film is a-
The smallest film that can form Si well, and continuous CVD
Since the film formation can be achieved, the TFT characteristics are not deteriorated.

[0014]

EXAMPLES Before describing the examples of the present invention, the points of the present invention will be described. The first point is that a low melting point glass substrate mixed with an alkali metal is adopted, and / or Al is used as a gate on the glass substrate, and this surface is anodized. The second point is that selective growth is performed on a non-alkali or alkali glass with a hydrophobic mask, and the entire surface of the substrate except this region is covered with a silicon oxide film by a liquid phase epitaxy method. Here, since it also serves as the description of the first point, the description will be made using alkali glass in the examples, but it goes without saying that non-alkali glass also has similar characteristics.

The liquid crystal panel is adopted as a display for computers, word processors, televisions, etc., and is required to have a large screen and a low price. Therefore, the use of expensive non-alkali glass is the opposite, and the technique of using a low-melting glass substrate such as soda glass is considered as an important theme. On the other hand, as the gate electrode, Ta and Cr are mainly used in a normal screen size. However, in order to achieve a large screen, it is not appropriate to use Ta, Cr or the like for the gate line because the resistance value is high, and Al, Cu, Au or the like is preferable. However, Cu easily oxidizes and the oxide film itself is unstable. Also, Au is expensive and must be avoided.
On the other hand, Al has a low price and low resistance, and the oxide film is stable. Also, because it uses a glass substrate with a low melting point,
Also, in order to achieve low cost, anodization and liquid phase growth are important techniques. Both of these techniques allow low-temperature processing and, unlike the plasma CVD apparatus, can increase throughput. Therefore, it is possible to achieve a substrate that is less expensive and that does not warp and that does not elute impurities in the glass substrate.

In particular, if a hydrophobic mask is provided in the contact hole region used to electrically connect the terminal and the gate line (auxiliary capacitance line) and then liquid phase growth is performed, the entire surface except this region is covered. A silicon oxide film can be formed. In addition, since this region is covered with ITO or Al, elution of alkali metal is almost eliminated. The liquid phase growth method is
For example, SiO ₂ is saturated with an aqueous solution of H ₂ SiF ₆ , heated to a deposition temperature (about 35 ° C.), and SiO ₂ is supersaturated with an initiator such as H ₃ BO ₃ or CaCl ₂ . Here, the glass substrate is immersed, and SiO ₂ is grown on this. However, when a-Si is formed on this silicon oxide film, the glass substrate is once exposed to the external atmosphere.
The interface with a-Si is contaminated, and only TFTs that are deteriorated due to the denseness of the film can be formed, and the problem remains. Therefore, it has been found that it is necessary to form a silicon nitride film having a minimum film thickness necessary to obtain the characteristics. Therefore, by forming the minimum necessary SiN _x film thickness of about 500Å to 2000Å and forming undoped a-Si and N ⁺ -type a-Si in a sealed atmosphere (in a plasma CVD apparatus), a satisfactory TF can be obtained.
T can be achieved.

Therefore, with these configurations and methods,
It is possible to achieve a low-cost liquid crystal panel with a large screen with good characteristics. First, FIG. 5 shows the configuration of the present liquid crystal display device. All drawings are the same, but the left side broken by wavy lines is TF
It is sectional drawing which showed the part of T and a display electrode, and the right side is a connection part with a gate terminal. The auxiliary capacitance terminal is also basically the same as the right side.

First, there is a low melting point glass substrate (51) mixed with an alkali metal such as soda glass or boron glass, on which a gate (52) using Al, a gate line (53) integrated therewith, There is an auxiliary capacitance electrode (54) and an auxiliary capacitance line integrated therewith. Further, these Al electrodes are provided with an insulating layer (71) made of aluminum oxide on the surface by the anodic oxidation method.

On the almost entire surface of the glass substrate (51) containing these, a silicon oxide film (5
5) is provided with a thickness of about 2000Å to about 3000Å. A display electrode (56) made of a transparent electrode material, such as indium oxide or indium tin oxide, is provided in a region which partially overlaps with the auxiliary capacitance electrode (54) and is surrounded by a gate line (53) and a drain line described later. ), And a TFT (57) is provided near this display electrode.

The TFT (57) has the gate (52) as one structure, and first, about 500Å to about 2000Å, preferably 1∫, on the silicon oxide film (55) corresponding to the structure region.
A silicon nitride film (58) having a thickness of 000 Å or less is provided, and a non-doped a-Si (59) and an N ⁺ -type doped a-Si (60) are provided thereon. This a-S
i is etched into an island shape together with the silicon nitride film (58), and the channel region of the N ⁺ type a-Si (60) is etched to be separated into a source region and a drain region. In addition, N ⁺ type a-Si corresponding to the source region
There is a source electrode (61) for electrically connecting (60) and the display electrode (56), and an N ⁺ type a corresponding to the drain region is provided.
A drain electrode (62) is provided extending from -Si (60) to the drain line and the drain terminal.

Here, the gate line (53) made of anodized Al extends in front of the gate terminal (63), and the gate terminal (63) and the gate line (5).
A contact hole (64) is opened to connect 3). Al is exposed in the hole (64), and a conductive line formed of the same material and in the same process as the display electrode is provided from the exposed portion to the region where the gate terminal is formed. Also in this hole, the source,
An electrode formed in the same step as the drain electrode is provided to prevent disconnection of the line.

Although not shown in the drawing, a passivation film is provided on the entire surface if necessary, and an alignment film is provided thereon. On the other hand, in order to inject liquid crystal between the glass substrate and the glass substrate, a counter substrate is provided, and a color filter, a light shielding film, a counter electrode and an alignment film are provided. Spacers are provided to set the two substrates at a predetermined distance, and liquid crystal is injected into the spacers.

This structure is characterized by a low melting point substrate (51) mixed with an alkali metal, a gate (52) made of anodized Al, and a silicon oxide film (5) formed by liquid phase epitaxy.
5) and the silicon nitride film (58) provided on the TFT (57). Low cost can be achieved by low melting point substrate and silicon oxide film by liquid phase epitaxy, and silicon nitride film is formed by plasma CVD method instead of directly forming on silicon oxide film by liquid phase epitaxy method. As a result, a silicon nitride film, non-doped a-Si and N ⁺ -type a-Si can be formed without exposing to the external atmosphere, and stable TFT characteristics can be obtained.

Particularly, by using inexpensive Al and anodizing this surface, the gate resistance of a large screen can be reduced and low temperature treatment is possible. Therefore, the gate having the optimum resistance value for a glass substrate having a low melting point can be obtained. Line, auxiliary capacity line can be achieved. Next, the first manufacturing method will be described with reference to FIGS. First, as shown in FIG. 1, a glass substrate having a low melting point mixed with an alkali metal, for example, soda glass or boron glass (51) is prepared, and a gate (52), a gate line (53) integrated with this gate, and an auxiliary capacitance are provided. Electrode (5
4) Form an auxiliary capacitance line integrated with the auxiliary capacitance electrode. Here, as can be seen from FIG. 5, the gate line and the auxiliary capacitance line extend to the front of the gate terminal and the auxiliary capacitance terminal formed around the glass substrate.

Then, as shown in FIG. 2, after forming a resist (70) in the region corresponding to the contact hole (64), the line is anodized to oxidize the surface of the line except the resist forming region. Form aluminum (71). At this stage, no oxide film is formed by the resist on the surface of the gate line corresponding to the contact hole. As a method, a DC voltage is applied between one end of the gate line and the auxiliary capacitance line and the Pt electrode in the aqueous solution, and the aqueous solution is a mixture of tartaric acid, ammonium and ethylene glycol. The film thickness of this aluminum oxide is at least about 50
About 0Å is formed. In addition, 200 ℃ to improve the film quality
You may heat-process to a degree.

Next, as shown in FIG. 2, the resist (70) is formed.
While being attached as a mask, liquid phase growth is performed to form a silicon oxide film (55) of about 2000Å to about 3000Å. Liquid phase epitaxy enables selective growth of a silicon oxide film by covering a substrate with a hydrophobic material. In general, the resist is hydrophobic and thus selective growth can be achieved. As a method, for example, an aqueous solution of H ₂ SiF ₆ is saturated with SiO ₂ and heated to a precipitation temperature (about 35 ° C.) to obtain H ₃ BO ₃ or Ca.
SiO ₂ is supersaturated with an initiator such as Cl ₂ and the glass substrate is dipped, and SiO ₂ is grown thereon.

Here, the glass substrate is exposed to the external atmosphere in order to carry out this liquid phase growth. Therefore, this glass substrate is contaminated, although there are differences in size. Therefore, if a-Si of the TFT is formed on this, the interface between the silicon oxide film and the a-Si is contaminated, and a TFT having satisfactory characteristics cannot be obtained. Therefore, the following steps are important. As shown in FIG. 3, by removing the resist (70), A
A contact hole (64) whose surface is exposed is formed. After this, a transparent electrode material is deposited on the entire surface to form display electrodes (56) and conductive lines (71) extending to the terminal regions. The conductive line is electrically connected to the gate line and extends as a gate terminal on the silicon oxide film (55) around the substrate.

Then, as shown in FIG. 4, a silicon nitride film (58), non-doped a-Si (59) and N ⁺ -type doped a-Si (60) are entirely plasma CV.
It is formed continuously by the D method. After that, dry etching is performed using SF ₆ as an etching gas. Here, when the a-Si (59) is formed on the silicon oxide film (55), the glass substrate is once exposed to the external atmosphere and its interface is contaminated, but the silicon nitride film (58) is formed.
Further, since a-Si (59) and (60) can be continuously formed in the CVD apparatus, a TFT having good characteristics without concern about interface contamination can be obtained as usual.

Since it is impossible to use CCl ₄ gas, even if SF ₆ gas is used alone, the etching rate of the silicon oxide film (55) is very small. Not required, and more satisfactory characteristics can be obtained. Finally, as shown in FIG. 5, the electrode material is deposited on the entire surface, and the source electrode (61), the drain line integrated with the drain electrode (62), and the electrode (72) filling the contact hole (64) are patterned. Be converted.

The detailed description of the steps will be simplified below because there is no particular feature, but if necessary, a passivation film and an alignment film are provided on the entire surface. In addition, the counter substrate,
A color filter, a light shielding film, a counter electrode and an alignment film are formed. The stacking order of these formed on the counter substrate is not particularly limited, but it is preferable that the alignment film is on the outermost side. In addition, it is possible to think variously without being limited to the above steps.
For example, FIG. 6 shows that the anodic oxide film (7
In this example, the resist (70) is formed after forming 1). In this case, when the contact hole is filled with the transparent electrode material, an etching process of removing aluminum oxide and exposing Al is added.

FIG. 7 shows an example of forming a silicon nitride film before forming a transparent electrode material. In this case, the silicon nitride film and the a-Si cannot be continuously formed depending on the process, but since the silicon nitride film (58) is formed under the display electrode (56), a short circuit with the auxiliary capacitance electrode is prevented. it can. Here, this can be achieved by using an etchant that selectively etches only a-Si after continuously forming SiNx and a-Si.

Further, as shown in FIG. 8, after the display electrode is formed, a silicon nitride film is formed on the entire surface, and not only the TFT portion as shown in FIG. 4, but the entire surface may be left. You may remove only the display electrode part using a resist.

[0033]

As is apparent from the above description, an inexpensive low melting point glass mixed with an alkali metal is adopted, and the cost is reduced, and the liquid phase growth method is used as a getter of alkali metal except for the contact hole portion. The silicon oxide film formed in 1. is used. As a result, the thickness of the silicon nitride film formed by plasma CVD can be reduced. Plasma C here
The silicon nitride film formed by VD is necessary for forming a-Si, but does not require a sufficiently thick film thickness considering the short circuit between the gate line and the drain line, the auxiliary capacitance electrode and the display electrode, and has characteristics of a-Si. The minimum necessary film thickness required for good formation is sufficient.

Further, by using Al, the resistance value of the gate line can be reduced, and the short circuit can be further prevented because the anodic oxide film is formed. Further, since liquid phase growth is adopted, low-temperature treatment is possible, and it is possible to achieve a display device which is inexpensive and has a large screen and good characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a manufacturing method of the present invention.

FIG. 2 is a cross-sectional view illustrating the manufacturing method of the present invention.

FIG. 3 is a cross-sectional view illustrating the manufacturing method of the present invention.

FIG. 4 is a cross-sectional view illustrating the manufacturing method of the present invention.

FIG. 5 is a cross-sectional view illustrating the manufacturing method of the present invention.

FIG. 6 is a cross-sectional view illustrating another manufacturing method of the present invention.

FIG. 7 is a cross-sectional view illustrating another manufacturing method of the present invention.

FIG. 8 is a cross-sectional view illustrating another manufacturing method of the present invention.

FIG. 9 is a cross-sectional view illustrating a conventional manufacturing method.

FIG. 10 is a cross-sectional view illustrating a conventional manufacturing method.

FIG. 11 is a cross-sectional view illustrating a conventional manufacturing method.

FIG. 12 is a cross-sectional view illustrating a conventional manufacturing method.

[Explanation of symbols]

51 low melting point glass substrate 52 gate 53 gate line 55 silicon oxide film by liquid phase growth method 56 display electrode 58 silicon nitride film 59 non-doped a-Si 60 N ⁺ type a-Si 61 source electrode 62 drain electrode 71 anodized film

Claims (4)

[Claims] 1. A step of preparing a glass substrate having a low melting point in which ions are mixed, and a metal is deposited on the glass substrate to form a gate and a gate line integrally formed with the gate and extending to the vicinity of a gate terminal. A step of providing a mask made of a hydrophobic material on the gate line corresponding to the vicinity of the gate terminal, and a silicon oxide layer formed on the entire surface of the glass substrate including the gate, the gate line integrated with the gate and the mask by silicon layer oxidation. A step of forming a film, a step of removing the mask to form a hole in which the gate line is exposed, and a metal of the same material as a source electrode of a TFT having the gate as a constituent is formed in the hole. And the gate line is connected to the gate line. 2. A step of preparing a glass substrate having a low melting point in which ions are mixed, and an Al metal is deposited on the glass substrate to form a gate and a gate line integrally formed with the gate and extending to the vicinity of the gate terminal. And a step of providing a mask made of a hydrophobic material on the gate line corresponding to the vicinity of the gate terminal, a step of anodizing the gate and the surface of the gate line integrated therewith, and the gate and the integrated gate Forming a silicon oxide film on the entire surface of the glass substrate including the gate line and this mask by liquid layer growth; removing the mask to form a hole in which the gate line is exposed; A metal of the same material as the source electrode of a TFT having a gate as one structure is provided in this hole to connect this gate terminal to the gate line. And a method for manufacturing a liquid crystal display device characterized by the above. 3. A step of preparing a glass substrate having a low melting point in which ions are mixed, and an Al metal is deposited on the glass substrate to form a gate and a gate terminal integrally provided with the gate terminal provided around the glass substrate. A step of forming a gate line extending to the vicinity, a step of anodizing the gate and the surface of the gate line integrated with the gate, and a mask made of a hydrophobic material on the gate line corresponding to the vicinity of the gate terminal. The step of providing, the step of forming a silicon oxide film by liquid layer growth on the entire surface of the glass substrate including this gate, the gate line integrated with this gate and this mask, and removing the mask and exposing the hole where the gate line is exposed by etching. A step of forming, and providing in this hole a metal of the same material as the source electrode of the TFT having the gate as one component, A method of manufacturing a liquid crystal display device, characterized in that the gate terminal is connected to the gate line. 4. A step of preparing a glass substrate having a low melting point in which ions are mixed, a metal is deposited on the glass substrate, and a gate and a gate line extending integrally with the gate to the vicinity of the gate terminal are formed by etching. The step of forming, the step of providing a mask made of a hydrophobic material on the gate line corresponding to the vicinity of the gate terminal, and the step of forming a liquid layer on the entire surface of the glass substrate including the gate, the gate line integral with the gate and the mask. A step of forming a silicon oxide film, and a conductive line made of a transparent electrode material, from the hole exposing the gate line by removing the mask to the gate terminal region, and in the vicinity of the formation region of the TFT constituting the gate. And a step of forming a display electrode, a step of forming a silicon nitride film in at least the formation region of the TFT, A non-doped first non-single-crystal silicon film and an impurity-doped second non-single-crystal silicon film are formed on the con-nitride film, and the second non-single-crystal silicon film is a source and a drain and a first non-single-crystal silicon film. A step of etching the single crystal silicon film so as to leave an active region; a source electrode connecting the second non-single crystal silicon film corresponding to the source and the display electrode; and a second non-single crystal corresponding to the drain. A method of manufacturing a liquid crystal display device, which comprises at least a drain electrode connected to a silicon film, a drain line integral with the drain electrode, and a step of forming an electrode filling the hole.