JPH1195234A - Formation of transparent conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for formation of a transparent conductive film which prevents the generation of columnar projections and improves the yield of products, such as liquid crystal panels. SOLUTION: This method for formation consists in washing a substrate 2 and drying this substrate 2 at <=100 deg.C in a baking chamber 12 at the time of forming the transparent conductive film consisting of indium tin oxide on color filters formed on the substrate 2, then forming the transparent conductive film on the color filters by sputtering while heating the substrate 2 at <=150 deg.C in a film forming chamber 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a transparent conductive film, which is preferably performed at the time of manufacturing a liquid crystal panel of a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, in manufacturing a liquid crystal panel of a liquid crystal display device or the like, indium tin oxide (hereinafter, referred to as "ITO") is formed on a color filter using a coloring pigment.
The formation of a transparent conductive film made of such as has been performed.
In the step of forming a transparent conductive film, a color filter is formed on a substrate, the substrate is washed and dried, and then a sputtering method, a CVD method (chemical vapor deposition), a vacuum deposition method, or an ITO solution is used. In this method, a transparent conductive film is formed on a color filter by a method using an organic solvent referred to as a method.

[0003]

However, when a color filter or the like formed by a pigment dispersion method is used in the step of forming the transparent conductive film, as shown in FIG.
In the transparent conductive film 52 formed on the color filter 51 on the substrate 50, many columnar projections 52a were sometimes generated.

In the case of a liquid crystal panel, such columnar projections 52a cause poor alignment of the liquid crystal, resulting in display unevenness or electrical contact with the other substrate constituting the panel. There has been a problem that a failure due to a short circuit occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of forming a transparent conductive film which suppresses and prevents the occurrence of columnar projections and improves the yield of products such as liquid crystal panels. Is to provide.

[0006]

According to a first aspect of the present invention, there is provided a method of forming a transparent conductive film, comprising:
In the method for forming a transparent conductive film formed of a transparent conductive film made of indium tin oxide or the like on a color filter provided on a substrate, the first method includes: drying the substrate at a temperature of 100 ° C. or lower after cleaning the substrate. Process and the substrate at 150 ° C.
A second step of forming the transparent conductive film on the color filter while heating at the following temperature.

According to the above method, the drying temperature in the first step is set to 100 ° C. or less, and the temperature at the time of film formation in the second step is set to 150 ° C. or less.
The generation of columnar projections can be suppressed and prevented.

A transparent conductive film such as an ITO film is usually formed.
The insulating substrate is heated to 250 ° C. to 350 ° C., and the substrate is heated on the heated substrate by means such as a vacuum evaporation method or a sputtering method. However, when a transparent conductive film is formed on a substrate heated in this way, the transparent conductive film grows in a crystal during the film formation process, and the crystal grain size increases.

Therefore, it is considered that the reason why the columnar projections are generated is that the substrate is heated before and during the formation of the transparent conductive film, so that columnar crystal growth occurs during the film formation process.

[0010] Therefore, as in the above-described method, by lowering the set temperatures of the drying temperature after the pre-film-formation cleaning and the substrate heating temperature during the film-formation, columnar crystal growth can be suppressed.

Therefore, a transparent conductive film having a flat surface can be formed on the color filter, and when applied to the production of a liquid crystal panel, etc., poor alignment of the liquid crystal can be prevented and the display quality can be improved. Panel can be obtained.

According to a second aspect of the present invention, there is provided a method of forming a transparent conductive film, the method comprising the steps of: Is set to 25 ° C. or more and 100 ° C. or less.

According to the above method, it is possible to reliably suppress and prevent the occurrence of columnar projections while performing a desired drying treatment.

According to a third aspect of the present invention, there is provided a method for forming a transparent conductive film, wherein the first and second aspects of the invention are to solve the above-mentioned problems.
In the method, the temperature at the time of heating the substrate in the second step is set to 100 ° C. or more and 150 ° C. or less.

According to the above method, a desired film formation process is performed while ensuring good adhesion to the color filter.
It is possible to reliably suppress and prevent the occurrence of columnar projections.

According to a fourth aspect of the present invention, there is provided a method of forming a transparent conductive film, comprising the steps of: It is characterized by.

According to the above method, even when a transparent conductive film is formed on a color filter by sputtering after the drying treatment in the first step, the generation of columnar projections is suppressed / prevented. A transparent conductive film can be formed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

The method of forming a transparent conductive film according to the present embodiment is a method of forming an ITO film, which is a transparent conductive film, on a color filter formed by using a coloring pigment at the time of manufacturing a liquid crystal panel of a liquid crystal display device. is there. More specifically, the present forming method is used in manufacturing an active matrix type liquid crystal panel provided with an active element such as a TFT (thin film transistor) element for each pixel. After a color filter is formed by a pigment dispersion method on a counter substrate that will form a panel, the counter substrate is washed and dried, and then an ITO film that is a transparent conductive film is formed on the color filter by sputtering. How to

In the manufacture of the active matrix type liquid crystal panel, for example, a TFT substrate 1 provided with a TFT element for each pixel as shown in FIG. 2 and a counter substrate 2 facing the TFT substrate are bonded to each other. Both boards 1 and 2
A panel is manufactured by injecting and sealing liquid crystal between them.

It is necessary to provide an electrode for driving the liquid crystal by applying a voltage to the liquid crystal on each of the substrates 1 and 2. Therefore, the TFT substrate 1 is provided with the pixel electrode 3 for each pixel, while the counter substrate 2 is provided with the counter electrode 4 as an electrode common to all pixels. Further, in a transmissive liquid crystal panel, since the display is performed by controlling the alignment of the liquid crystal and modulating the transmitted light, the electrodes 3 and 4 are required to be translucent electrodes. Therefore, the electrodes 3 and 4 are formed by forming a transparent conductive film such as an ITO film on the substrates 1 and 2.

In the present forming method, a method of forming a transparent filter on a substrate 2 and then forming an ITO film to be a transparent electrode 4 on the color filter will be described.

Referring to FIGS. 3 and 4A and 4B, in step S1, a substrate 2 made of glass or the like is placed.
A color filter 5 is formed. The color filter 5 may be formed directly on the substrate 2 or may be formed after forming an insulating film or the like. The color filter 5 is formed by a pigment dispersion method, in which a colored resist in which a pigment is dispersed in a photosensitive resin is applied onto the substrate 2, and R (red) G (green) B (blue) is formed by photolithography.
The color filter 5 is formed by pattern-forming each color.

After forming the color filter 5, step S2 is performed.
, A washing process of the substrate 2 and a draining and drying process are performed.

In the cleaning process, the surface of the substrate 2 is cleaned with pure water. Cleaning methods include brush scrub, ultrasonic,
A method using megasonic, cavitation jet, bubble jet, or the like can be used.

In the draining / drying process, the substrate 2 is rotated by rotating the substrate 2 at a high speed, or by a method using an air knife that blows high-pressure air onto the surface of the substrate 2.
Drain the surface.

After draining and drying, baking is performed in step S3.

In the baking process, the substrate 2 is placed in a heating chamber (oven) or the like and heated to perform a dehydration / drying process on the substrate 2. In the baking process, the baking process is performed by setting the ambient temperature around the substrate 2 in the heating chamber (hereinafter, referred to as “bake temperature”) to 100 ° C. or less. On the other hand, in the conventional baking process, the baking temperature is set to about 180 ° C. or higher. Therefore, in the present forming method, the baking process is performed at a lower baking temperature than the conventional one.

The time for performing the baking process is preferably in the range of 30 minutes to 60 minutes, but may be set outside this range. For example, the time for performing the baking process may be 60 minutes or more, and a processing time suitable for each manufacturing condition may be selected.

As a heating method in the baking treatment, a heating method using hot air circulation, a heating method using infrared rays, a heating method using a hot plate, or the like can be used.

The baking process may be performed in any of the atmosphere, nitrogen, or vacuum.

After the baking process, in step S4,
As shown in FIG. 4C, an ITO film to be the transparent electrode 4 is formed on the color filter 5.

As a method for forming the ITO film, sputtering is used. Further, in the present forming method, the substrate 2 is heated when the ITO film is formed, and the substrate temperature during the film formation (hereinafter, referred to as “substrate heating temperature”) is set to 150 ° C. or less. . On the other hand, in the conventional film forming method, the substrate heating temperature is set to about 250 ° C. or higher. Therefore, in this forming method, the ITO film is formed at a lower substrate heating temperature than the conventional method. I have.

In this forming method, one of the following two film forming methods is used for forming an ITO film by sputtering.

In the first method, a sputtering target obtained by sintering indium oxide mixed with tin oxide at a weight ratio of 5 to 10% by weight to a density of 60 to 98% is used. Then, in a vacuum chamber which is a film forming chamber,
Argon gas or a mixed gas of argon and oxygen was added to 0.1 g.
After introducing to a pressure of 2 to 0.9 Pa, a direct current (D
A glow discharge is generated by a C) method or a high frequency (RF) method to form an ITO film.

In the second method, an alloy of metal indium containing 5 to 10% by weight of metal tin is used as a sputtering target. Then, after introducing a mixed gas of argon and oxygen to a pressure of 0.2 to 0.9 Pa into a vacuum chamber which is a film forming chamber, a glow discharge is generated by a DC method or a high frequency method, and a reaction is performed. An ITO film is formed by reactive sputtering.

In both the first method and the second method, I
The thickness of the TO film is set to about 1000 ° to 2000 °, but an optimum thickness may be selected according to the application.

In both the first method and the second method, the film formation method may be any one of an in-line film formation method, a single-wafer method stationary opposed film formation, and a batch rotation film formation method. May be used.

As described above, in any of the first and second methods, sputtering is performed with the substrate heating temperature kept at 150 ° C. or less, and the IT
An O film is formed. At this time, in consideration of the adhesion between the ITO film and the color filter 5, the substrate heating temperature is set to 100.
It is preferable that the temperature be in the range of 150C to 150C.

After forming the ITO film, in step S5, as shown in FIG. 4D, an alignment film 7 is formed on the ITO film.
To form Thus, the fabrication of the counter substrate 2 is completed.

Next, referring to FIG. 1, an apparatus 10 used in the baking process in S3 and the ITO film forming process in S4.
Will be described.

First, a conventional film forming apparatus will be described in comparison with the apparatus 10 described above. Conventional film forming apparatuses used for sputtering, CVD, and the like generally include a charging chamber 53, a preheating chamber 54, a film forming chamber 55, as shown in FIG.
And a take-out chamber 56, and the substrate 57 is transported in these chambers sequentially in the direction of arrow A. More specifically, when a plurality of substrates 57 are put into the charging chamber 53 in a state of being accommodated in the cassette 58, the substrates 57 are taken out one by one from there, and are passed through the preheating chamber 54 to the film forming chamber 55. After being subjected to the film forming process, it is transported to the cassette 59 in the extraction chamber 56.

The substrate heating temperature when forming a film in the film forming chamber 55 is set at a considerably high temperature in consideration of the film forming speed, the reactivity of the substance, the characteristics of the film formed, and the like. When the ITO film was formed by sputtering, the substrate heating temperature was set to about 250 ° C. Therefore, in order to prevent the substrate 57 from being rapidly exposed to a high temperature from room temperature, the preheating chamber 54 is provided.

The pre-heating step in the pre-heating chamber 54 is set to several minutes in time, and there is not much difference from the film forming speed per substrate.
4, similarly to the film forming chamber 55, the substrates 5 sequentially transferred.
7 were processed one by one.

On the other hand, in the present forming method, as described above, the time for performing the baking process before forming the ITO film is 30 minutes.
Minutes to about 60 minutes, and the film formation time is set to a shorter processing time. Therefore, performing the baking step and the film forming step at the same pace becomes inefficient.
On the other hand, it is conceivable that the baking step and the film forming step are performed by separate apparatuses, but in this case, the occupied area of the apparatus increases.

Therefore, in the baking process and the film forming process in the present forming method, the apparatus 10 shown in FIG. 1 is used.
The apparatus 10 includes a charging chamber 11, a baking chamber 12, and a film forming chamber 1.
3 and an unloading chamber 14, and the substrate 2 is sequentially transported in each of these chambers in the arrow B direction. Here, the bake chamber 12 includes a plurality of substrate holding means (not shown), and is configured to be able to simultaneously bake a plurality of substrates 2 that are sequentially conveyed. Therefore, efficiency can be improved by using the present device 10.

In the following, the baking process in S3 and the film forming process in S4 performed by using the apparatus 10 will be described.

First, at normal temperature and normal pressure, the substrate 2 on which the color filters 5 are formed is loaded into the charging chamber 11 in a state of being stored in the cassette 15.

Next, the substrates 2 are fed into the bake chamber 12 one by one from the cassette 15. The bake chamber 12 is provided with an inlet 12a for the substrate 2 and a sweep port 12b.
The substrate 2 is delivered through the inlet 12a.

The substrate 2 sent into the bake chamber 12 is held vertically by the above-described substrate holding means and is baked. The substrate holding means is provided in a plurality in the bake chamber 12, and is configured to rotate in the direction of arrow C at a constant cycle. The reason why the substrate holding means holds the substrate 2 vertically is to prevent foreign substances from adhering to the substrate.

Next, the substrate 2 is taken out from the sweep port 12b of the bake chamber 12 and sent to the film forming chamber 13, where a film forming process is performed to form an ITO film on the substrate. The inside of the film forming chamber 13 is in a substantially vacuum state during the processing.

Next, the substrate 2 on which the ITO film has been formed in the film forming step is transported to the unloading chamber 14 and stored in the cassette 16 one by one. When the cassette 16 is completely filled, the substrate 2 is transferred to the next step. It is.

For example, in the above-described baking processing, the baking processing time per substrate is set to 50 minutes, and in the above-described film forming processing, the baking processing time per substrate is set to 5 minutes.
Minutes, 5 minutes from the preparation room 11 to the bake room 12
The number of the substrate holding means may be set so that the substrates 2 are charged at minute intervals, baked in the bake chamber 12 for 50 minutes, and then sent to the film formation chamber 13.

It should be noted that the charging chamber 11 and the unloading chamber 14 are
It is desirable that the pressure in the room can be adjusted. That is, when the cassette 15 is inserted into the charging chamber 11 or when the cassette 16 is removed from the extraction chamber 14,
Although it is exposed to the outside atmosphere, it is preferable that the pressure can be adjusted so that the charging chamber 11 and the unloading chamber 14 have normal pressure in such a case, and have a vacuum when shut off from the outside atmosphere.

When the temperature difference between the charging chamber 11 and the baking chamber 12 increases, a preheating chamber may be provided between the charging chamber 11 and the baking chamber 12.

In the case where an ITO film is formed on the color filter 5 by the above-described present forming method, as shown in Table 1, it is possible to effectively suppress and prevent the occurrence of columnar projections which occur in the conventional method. did it. That is, as shown in FIG. 5, an ITO film to be the transparent electrode 4 could be formed flat on the color filters 5 of R, G, and B provided on the substrate 2.

[0057]

[Table 1]

In the conventional method, an ITO film was formed under the same conditions as the present forming method except that the baking temperature was set at about 180 ° C. and the substrate heating temperature during the formation of the ITO film was set at about 250 ° C. The number of columnar projections was evaluated by counting the number of columnar projections per unit area of the ITO film surface with a scanning microscope.

In the ITO film formed by the conventional method, the number of occurrences of the columnar protrusions on the color filters 5 of R, G, and B is different because the number of occurrences varies depending on the component of the pigment of each color. Conceivable.

Further, the baking temperature and the substrate heating temperature during the formation of the ITO film were changed to various temperatures to form the ITO film, and the generation of columnar projections and the like were evaluated. The results are shown in Tables 2 to 4.

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

[Table 4]

In Table 2, while the baking temperature was changed from room temperature (25 ° C.) to 110 ° C., the substrate heating temperature was 15 ° C.
The graph shows the results of evaluation of the number of columnar protrusions in each ITO film and the display quality of the liquid crystal panel when the ITO films were formed at a constant temperature of 0 ° C.

Table 3 shows that when the baking temperature was kept constant at 90 ° C. and the ITO film was formed while changing the substrate heating temperature in the range of 90 ° C. to 200 ° C.,
The results of evaluation of the number of columnar protrusions in the TO film, the adhesion between the ITO film and the color filter, and the display quality of the liquid crystal panel are shown.

In Table 4, the baking temperature is from room temperature to 110 ° C.
The results of evaluating the display quality of each liquid crystal panel when the ITO film was formed while changing the substrate heating temperature in the range of 90 ° C. to 200 ° C.

As is apparent from these results, by forming the ITO film at a baking temperature of 100 ° C. or less and a substrate heating temperature of 150 ° C. or less, the generation of columnar protrusions can be effectively suppressed and prevented. it can.

The baking temperature is preferably set in the range of 25 ° C. to 100 ° C. at room temperature, and more preferably, in the range of 80 ° C. to 90 ° C.

The substrate heating temperature is preferably in the range of 100 ° C. or more and 150 ° C. or less in consideration of the adhesion between the ITO film and the color filter. However, there is a possibility that desired characteristics can be obtained even if the substrate heating temperature is set to about 170 ° C. in relation to the baking temperature.

In the ITO film formed at such a temperature setting, the resistance value is slightly increased and the adhesion is slightly weakened, but the characteristics applicable to a wide range are secured. In addition, as shown in FIG. 2B, the present forming method is used for forming the large-area counter electrode 4 which is an electrode common to all pixels, so that the resistance value is slightly increased and the adhesion is slightly increased. The weakness causes almost no problem on the display of the liquid crystal panel.

The method for forming a transparent conductive film of the present invention is not limited to the above-described method of the present embodiment, but can be applied in various fields. However, when an ITO film is formed on a color filter using a color pigment, generation of columnar protrusions can be effectively prevented and suppressed. It is particularly preferred to apply.

[0072]

According to the method for forming a transparent conductive film according to the present invention, as described above, a transparent conductive film formed of indium tin oxide or the like is formed on a color filter provided on a substrate. In the forming method, after the substrate is washed, a first step of drying the substrate at a temperature of 100 ° C. or lower, and while heating the substrate at a temperature of 150 ° C. or lower,
A second step of forming the transparent conductive film on the color filter;
And a step.

As a result, generation of columnar protrusions in the formed transparent conductive film can be suppressed and prevented.

Therefore, a transparent conductive film having a flat surface can be formed on the color filter, and when applied to the production of a liquid crystal panel or the like, poor alignment of the liquid crystal and the like can be prevented to improve the display quality. Panel can be obtained, and the yield of products such as liquid crystal panels can be improved.

In the method for forming a transparent conductive film according to the second aspect of the present invention, the temperature for drying the substrate in the first step is set to 25 ° C.
This is a method of setting the temperature to 100 ° C. or lower.

Thus, while performing the desired drying treatment,
It is possible to reliably suppress and prevent the occurrence of columnar projections.

In the method for forming a transparent conductive film according to the third aspect of the present invention, as described above, in the method of the first or second aspect, in the second step, the temperature at which the substrate is heated is set to 100 degrees. In this method, the temperature is set to not less than 150 ° C. and not more than 150 ° C.

Thus, it is possible to reliably suppress and prevent the occurrence of columnar projections while performing a desired film forming process while ensuring good adhesion to the color filter.

The method of forming a transparent conductive film according to the invention of claim 4 is the method of forming a transparent conductive film by sputtering according to any one of claims 1 to 3, as described above.

Thus, even when the transparent conductive film is formed on the color filter by sputtering after the drying process in the first step, the generation of columnar projections is suppressed and prevented, and a good transparent conductive film is formed. Can be formed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a film forming apparatus used for a method for forming a transparent conductive film according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams schematically showing each substrate constituting an active matrix type liquid crystal panel, FIG. 2A is a diagram showing a TFT substrate, and FIG. 2B is a diagram showing a counter substrate.

FIG. 3 is a flowchart illustrating a method for forming the transparent conductive film.

FIG. 4 is a process chart for explaining a method of forming the transparent conductive film.

FIG. 5 is a view schematically showing a state in which an ITO film is formed by the method for forming a transparent conductive film.

FIG. 6 is an explanatory view showing that columnar projections are formed in an ITO film when an ITO film is formed by a conventional method for forming a transparent conductive film.

FIG. 7 is an explanatory view showing a film forming apparatus used for a conventional preheating process and an ITO film forming process.

[Explanation of symbols]

 2 Substrate 4 Electrode (transparent conductive film) 5 Color filter 7 Alignment film 11 Preparation room 12 Bake room 13 Film formation room 14 Extraction room

Claims (4)

[Claims] 1. A method for forming a transparent conductive film made of indium tin oxide or the like on a color filter provided on a substrate, wherein the substrate is washed at a temperature of 100 ° C. or less after washing the substrate. Forming a transparent conductive film on the color filter while heating the substrate at a temperature of 150 ° C. or less. Method. 2. The method for forming a transparent conductive film according to claim 1, wherein in the first step, a temperature at which the substrate is dried is set to 25 ° C. or more and 100 ° C. or less. 3. The method for forming a transparent conductive film according to claim 1, wherein in the second step, a temperature at which the substrate is heated is set to 100 ° C. or more and 150 ° C. or less. 4. The method for forming a transparent conductive film according to claim 1, wherein the transparent conductive film is formed by sputtering.