JP2001059175A - Tin oxide film, its production and device for producing tin oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tin oxide film small in sheet resistance, high in transmittance, moreover high in hazing rate diffused light quantity/whole transmitted light quantity and uniformly having fine ruggedness on the surface. SOLUTION: In a method for forming a tin oxide film in which tin tetrachloride is brought into reaction with water, a tin oxide film is formed on a glass substrate moving in one direction by a cold pressure CVD method, as to the atmosphere in the case gas contg. tin tetrachloride and water is discharged to the surface of the glass substrate, and the tin oxide film is formed, the concn. of water on the upstream side in the moving direction of the glass substrate is higher than that on the downstream side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tin oxide film and a method for producing the same, and more particularly, to a tin oxide film suitably used as a transparent conductive film for a solar cell substrate and a method for producing the same. Further, the present invention relates to an apparatus for producing a tin oxide film used in the production method.

[0002]

2. Description of the Related Art As a method of forming a tin oxide film, a method of forming a tin oxide film by a normal pressure CVD method utilizing a reaction between tin tetrachloride and water is known. In this method, tin tetrachloride vapor is brought into contact with a heated substrate surface in an oxidizing atmosphere to form a tin oxide film on the substrate surface by a thermal decomposition / oxidation reaction on the substrate surface.

One of the main uses of a tin oxide film is as a transparent conductive film for a solar cell substrate. A tin oxide film used as a transparent conductive film for a solar cell substrate has a low sheet resistance, a high transmittance, and a high energy conversion efficiency (hereinafter, also simply referred to as “conversion efficiency”) of the solar cell, and What has a high haze rate and a uniform thing is desired. Here, the haze ratio is a value obtained by dividing the diffuse transmitted light amount by the total transmitted light amount. When the haze ratio is high, scattering when light passes through the film increases, so that the optical path length in the photoelectric conversion layer of the solar cell increases. Therefore, if the haze ratio can be increased, the light absorptivity in the photoelectric conversion layer increases, and the conversion efficiency of the solar cell becomes excellent. As a technique for increasing the haze ratio, it is known to make the surface of the tin oxide transparent conductive film into a shape having fine irregularities to increase scattering. Currently,
According to the CVD method, the surface can be formed into a shape having fine irregularities.
The VD method is used. In this case, if the haze ratio is uneven over the entire surface of the tin oxide film, adverse effects such as a decrease in conversion efficiency over the entire surface of the tin oxide film occur. The haze ratio becomes non-uniform when the unevenness of the surface is non-uniform. In other words, when the surface is uneven, specifically, when there is a portion having a large convex portion (a portion having a large difference in height between the convex portion and the concave portion), adverse effects such as a decrease in conversion efficiency are caused. Occurs. Therefore, in order to prevent such an adverse effect, it is necessary to have unevenness on the surface uniformly.

As a method of forming a tin oxide film by a CVD method, a method utilizing a reaction of an organic tin compound and a method utilizing a reaction between tin tetrachloride and water are known. The method utilizing the reaction of the organotin compound has a disadvantage that the transmittance of the obtained tin oxide film is low. On the other hand, the method utilizing the reaction between tin tetrachloride and water can increase the transmittance, but has the disadvantage that the unevenness of the surface becomes uneven, that is, the haze ratio becomes uneven.

[0005]

SUMMARY OF THE INVENTION The present invention provides a tin oxide film having a small sheet resistance, a high transmittance, and a high haze ratio, which has fine irregularities uniformly on its surface. The purpose is to do.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a tin oxide film is formed on a glass substrate moving in one direction by reacting tin chloride with water by a normal pressure CVD method. A method for producing a film, in which a gas containing tin tetrachloride and water is discharged onto a glass substrate to form a tin oxide film, the sheet resistance is small, the transmittance is high, the haze is high, and the surface is high. Obtaining a tin oxide film having fine irregularities uniformly on the surface of the glass substrate is required in the initial stage of the formation of the tin oxide film on the glass substrate (that is, at the time of forming the portion of the tin oxide film near the glass substrate surface). They have found that this can be achieved by increasing the proportion of water, and have completed the present invention.

That is, the present invention relates to a method for producing a tin oxide film by forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride with water by atmospheric pressure CVD. The atmosphere at the time of forming a tin oxide film by discharging a gas containing tin chloride and water onto a glass substrate is such that the ratio of water to tin tetrachloride at the time of forming the tin oxide film near the glass surface is lower than that of the glass surface. A method for producing a tin oxide film, characterized in that the atmosphere is larger than the atmosphere at the time of forming a portion far from the tin oxide film.

[0008] Specifically, a tin oxide film is formed on a glass substrate moving in one direction by reacting tin tetrachloride and water under normal pressure CVD.
A method for producing a tin oxide film formed by a method, wherein an atmosphere at the time of discharging a gas containing tin tetrachloride and water onto a glass substrate to form a tin oxide film is on the upstream side in the moving direction of the glass substrate. Is an atmosphere having a higher water concentration than the downstream side.

The present invention relates to a method for producing a tin oxide film by forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride and water by a normal pressure CVD method. A gas containing water and not containing tin tetrachloride, and / or a gas containing tin tetrachloride and water is discharged onto a glass substrate from a plurality of discharge ports arranged in the moving direction. Disclosed is a method for manufacturing a tin oxide film, wherein a gas having a higher water concentration is discharged from a discharge port on an upstream side in a moving direction than a discharge port on a downstream side.

[0010] The present invention also provides a tin oxide film obtained by the above method.

Further, the present invention provides a tin oxide film formed on a glass substrate moving in one direction by reacting tin tetrachloride with water at normal pressure.
An apparatus for producing a tin oxide film formed by a VD method, wherein the gas contains water and does not contain tin tetrachloride, and / or
A plurality of discharge ports for discharging a gas containing tin tetrachloride and water onto the glass substrate are provided in the moving direction of the glass substrate, and the discharge port on the upstream side in the moving direction of the glass substrate is more water than the discharge port on the downstream side. Provided is an apparatus for manufacturing a tin oxide film, which discharges a gas having a high concentration.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a tin oxide film according to the present invention comprises:
A method for producing a tin oxide film in which a tin oxide film is formed by a normal pressure CVD method on a glass substrate moving in one direction by reacting tin tetrachloride and water, wherein a gas containing tin tetrachloride and water is formed. An atmosphere in which a tin oxide film is formed by discharging onto a glass substrate is an atmosphere in which the water concentration is higher on the upstream side in the moving direction of the glass substrate than on the downstream side.

In an atmosphere in which a gas containing tin tetrachloride and water is discharged onto a glass substrate to form a tin oxide film, an atmosphere having a higher water concentration on the upstream side in the moving direction of the glass substrate than on the downstream side. The method is not particularly limited, from a plurality of discharge ports arranged in the moving direction of the glass substrate,
A gas containing water and not containing tin tetrachloride, and / or a gas containing tin tetrachloride and water is discharged onto the glass substrate, and the discharge port on the upstream side in the moving direction of the glass substrate is A method of discharging a gas having a high water concentration from a downstream discharge port is exemplified. As a specific example of the method, a method in which the gas discharged from the most upstream discharge port in the moving direction of the glass substrate is a gas containing tin tetrachloride and water,
A gas containing water and not containing tin tetrachloride. These methods will be described by taking as an example a case where the number of discharge ports arranged in the moving direction of the glass substrate is two.

In the method of (1), a gas containing tin tetrachloride having a high water concentration and water is first blown from the first discharge port on the upstream side to the surface of the glass substrate moving in one direction. A gas having a low water concentration is blown from the second discharge port on the downstream side, and a tin oxide film is generated. In the initial stage of the formation of the tin oxide film, the tin oxide film is formed in an atmosphere of a gas having a high water concentration discharged from the first discharge port. That is, the portion of the tin oxide film which is initially formed on the upstream side in the moving direction of the glass substrate and is close to the glass surface is formed in a state where the ratio of water to tin tetrachloride is large. Next, when a gas having a low water concentration is blown from the second discharge port, the gas having a low water concentration is mixed into the atmosphere of the gas having a high water concentration, so that tetrachloride when the tin oxide film is formed is formed. The ratio of water to tin decreases over time. That is, the portion of the tin oxide film formed on the downstream side in the moving direction of the glass substrate, which is far from the glass surface, is formed in a state where the proportion of water is smaller than that of the portion near the glass surface.

In the method, a gas containing water and not containing tin tetrachloride is blown from a first discharge port to the surface of the glass substrate moving in one direction, and then a second discharge port is formed. A gas containing tin tetrachloride and water is blown from the substrate to form a tin oxide film. In the early stage of tin oxide film formation, tin tetrachloride and tin tetrachloride derived from a gas containing water are mixed into water present in a large amount near the glass surface. The ratio of water to tin tetrachloride is large. That is, the portion near the glass surface of the tin oxide film, which is initially formed on the upstream side in the moving direction of the glass substrate, is formed in an atmosphere in which a large amount of water exists. After that, as the mixing of tin tetrachloride proceeds, the proportion of water in the atmosphere in which the tin oxide film is formed decreases over time. That is, the portion of the tin oxide film formed on the downstream side in the moving direction of the glass substrate, which is far from the glass surface, is formed in an atmosphere with less water than the portion near the glass surface. In the above method, a gas containing water and not containing tin tetrachloride may be discharged through a discharge port connected to the injector, but is used to direct the flow of the gas containing tin tetrachloride and water in a certain direction. It is also possible to make the air of a so-called air curtain contain water and discharge it.

As will be described later, in the present invention, the affinity between the atmosphere and the glass surface in the early stage of the formation of the tin oxide film is important. Therefore, in the present invention, the concentration of water in the atmosphere in the initial stage of the formation of the tin oxide film may be high, and the concentration of water in the atmosphere in a stage following the initial stage may be lower than that in the initial stage. The concentration is not particularly limited. Specifically, among a plurality of discharge ports arranged in the moving direction of the glass substrate, the discharge port at the most upstream position in the moving direction of the glass substrate is the discharge port located at the most upstream side among the discharge ports on the downstream side (upstream side). Second discharge port)
Any method that discharges a gas having a higher water concentration may be used as long as the concentration of water in the atmosphere in the initial stage of the formation of the tin oxide film is lower than the concentration of water in the atmosphere in the subsequent stage. In the case where there is the above, the water concentration of the discharge port further downstream (the third and subsequent discharge ports from the upstream side) is not particularly limited.

The tin oxide film of the present invention obtained by the above-described method for producing a tin oxide film of the present invention has a small sheet resistance,
High transmittance and high haze. This is because the amount of water is increased in the early stage of the formation of the tin oxide film and the affinity is higher than when the tin oxide film is formed on the glass surface using a gas having a smaller content of water than the content of tin tetrachloride. It is conceivable that the tin oxide film is formed more stably on the glass surface when the tin oxide film is formed by increasing the properties and then reducing the amount of water. Further, the tin oxide film of the present invention has a shape having fine irregularities uniformly over the entire surface, and the height of the convex portion (the difference in height between the convex portion and the concave portion) is:
It is about 100 to 200 nm. The reason for such a shape is that the crystal growth of tin oxide is performed stably and the crystal grain size becomes uniform. Since the tin oxide film has the above-mentioned shape and has a high haze ratio and is uniform over the entire surface, the conversion efficiency is increased. Therefore, the tin oxide film of the present invention,
When used as a transparent conductive film for a solar cell substrate, high conversion efficiency can be realized, which is extremely preferable.

The gas containing tin tetrachloride and water (steam) used in the present invention is obtained, for example, by mixing a gas containing tin tetrachloride and a gas containing water. The gas containing tin tetrachloride can be obtained, for example, by vaporizing tin tetrachloride by blowing an inert gas (a gas that does not react with tin tetrachloride), preferably nitrogen, into liquid tin tetrachloride in a bubbler tank. it can. When the gas containing tin tetrachloride contains an inert gas such as nitrogen, the reaction between tin tetrachloride and water is less likely to occur, which is a preferred embodiment. Gases containing water are, for example, those consisting only of water vapor,
Examples include air-containing air.

The gas containing tin tetrachloride and the gas containing water are mixed and maintained preferably at a temperature in the range of 100-240 ° C. When the gas after mixing is maintained in the above temperature range, the reaction between tin tetrachloride and water is suppressed, and no or little reaction occurs. More preferably, the temperature is in the range of 130 to 170C.

When the gas containing tin tetrachloride and the gas containing water are mixed, the gas becomes uniform due to the diffusion phenomenon of gas molecules. However, the gas may be stirred by a gas mixer or the like.

In the case of the method (1), the ratio of tin tetrachloride and water in the gas containing tin tetrachloride and water is 1 mol of tin tetrachloride in the gas discharged from the first discharge port on the upstream side. On the other hand, water is preferably 80 to 200 mol, more preferably 100 to 150 mol. In the gas discharged from the second discharge port on the downstream side, water is 30 to 70 mol per 1 mol of tin tetrachloride.
And more preferably 40 to 60 mol. Within the above range, the ratio of tin tetrachloride and water becomes appropriate in the early stage of the formation of the tin oxide film, and the crystal growth of tin oxide is performed stably. In this case, the ratio of the discharge amount from the first discharge port to the discharge amount from the second discharge port is represented by (the discharge amount from the first discharge port): (the discharge amount from the second discharge port) ) =
The ratio is preferably 1: 5 to 1:20, and 1:10 to 1:
More preferably, it is set to 15. Within the above range, the amounts of tin tetrachloride and water in the initial stage of the formation of the tin oxide film are appropriate, and the production cost can be reduced.

In the case of the above method, the ratio of tin tetrachloride and water in the gas containing tin tetrachloride and water discharged from the second discharge port on the downstream side is based on 1 mol of tin tetrachloride. , Water is preferably 30-70 mol, and 4
More preferably, it is 0 to 60 mol. Within the above range,
In the initial stage of the formation of the tin oxide film, the ratio of tin tetrachloride and water becomes appropriate, and the crystal growth of tin oxide is performed stably. In this case, the discharge amount of the gas containing water and not containing tin tetrachloride discharged from the first discharge port on the upstream side is the first amount with respect to 1 mol of tin tetrachloride discharged from the second discharge port. The amount of water discharged from the discharge port is preferably 50 to 150 mol, and more preferably 60 to 100 mol. Within the above range, the amounts of tin tetrachloride and water in the initial stage of the formation of the tin oxide film are appropriate, and the production cost can be reduced.

Further, an exhaust pipe may be provided between the first discharge port and the second discharge port. This makes it possible to easily adjust the ratio of water to tin tetrachloride at the time of forming the tin oxide film.

The direction in which the gas discharged from each discharge port flows may be the same as the direction in which the glass substrate moves, or may be the opposite direction.

The gas containing tin tetrachloride and water can contain other substances as long as the object of the present invention is not impaired. For example, it may contain hydrogen chloride; a fluorine compound such as hydrogen fluoride and trifluoroacetic acid; a lower alcohol such as methanol and ethanol; and an inert gas such as nitrogen. When the gas containing tin tetrachloride and water contains hydrogen chloride, the reaction between tin tetrachloride and water is less likely to occur, which is a preferred embodiment. When at least one of the gas containing tin tetrachloride and the gas containing water contains hydrogen chloride, the mixture of the two is preferably 45%.
It is performed at a temperature of 0 ° C. or less. The content of hydrogen chloride is preferably at least 1 mol per mol of tin tetrachloride, more preferably 3 to 5 mol. Further, when the gas containing tin tetrachloride and water contains a fluorine compound, the conductivity is high, which is a preferable embodiment. In this case, when a lower alcohol is further contained, fluorine doping is promoted.

The glass used in the present invention is not particularly limited. For example, oxide glass can be used. Examples of the oxide glass include silicate glass, phosphate glass, and borate glass. Examples of the silicate glass include soda lime glass, silicate glass, alkali silicate glass, potassium lime glass, lead (alkali) glass, borosilicate glass, and aluminosilicate glass.

Further, after forming at least one thin film on a glass substrate by sputtering, vacuum deposition or the like, a tin oxide film can be formed on the thin film according to the present invention to form a multilayer film. Examples of such a thin film include thin films of metals, alloys, oxides, nitrides, and carbides thereof. Specifically, when soda-lime glass is used as a substrate, a silica (SiO ₂ ) film or the like is formed as an undercoat (hereinafter, referred to as an “alkali barrier layer”) for preventing diffusion of an alkali component from the substrate. There is an example of using the above.

The shape and size of the glass substrate are not particularly limited, and may be, for example, a plate having a thickness of 0.2 to 5 mm. The plate-like glass substrate has a width of 10 to 500 c.
m, and may be cut to an appropriate length, or may be in an uncut state (ribbon shape). The geometric thickness (hereinafter, simply referred to as “film thickness”) of the alkali barrier layer can be, for example, 2 to 100 nm. The temperature of the glass substrate is 450-620 ° C
It is preferred that This is because the reaction between tin tetrachloride and water sufficiently occurs within the above range, and the film formation rate is high. The temperature of the glass substrate is more preferably 500 to 600C.

The CVD method is preferably performed at normal pressure (atmospheric pressure).

The thickness (maximum thickness) of the tin oxide film of the present invention is:
It is not particularly limited and can be adjusted according to the application. However, when it is used as a transparent conductive film for a solar cell substrate (electrode for a solar cell), the thickness is preferably 400 to 1000 nm, and 6 nm.
It is more preferably from 00 to 800 nm. The variation width of the thickness (maximum thickness) of the tin oxide film of the present invention is −15 to +15.
%, Especially -10 to + 10%.

The sheet resistance of the tin oxide film of the present invention is not particularly limited and can be adjusted according to the application. However, when used as a transparent conductive film for a solar cell substrate, it is preferably 5 to 15 Ω / □. More preferably, it is 5 to 10 Ω / □.

The visible light transmittance (hereinafter simply referred to as “transmittance”) of the tin oxide film of the present invention is not particularly limited and can be adjusted according to the application. Is preferably 80 to 95%, more preferably 85 to 95%.

The haze ratio of the tin oxide film of the present invention is not particularly limited and can be adjusted according to the application. However, when the tin oxide film is used as a transparent conductive film for a solar cell substrate, it is preferably 3 to 30% on average. More preferably, the average is 10 to 15%. Further, the fluctuation range of the haze ratio is preferably -20 to + 20% with respect to the average value of the haze ratio, and -10
More preferably, it is + 10%.

Although the use of the tin oxide film of the present invention is not particularly limited, the tin oxide film has a low sheet resistance, a high transmittance, a high haze ratio, and has fine irregularities on its surface. It can be used very suitably as a transparent conductive film for a battery substrate. Also, for example, transparent electrodes for liquid crystal displays, EL displays, plasma displays, touch panels, etc .; heat ray reflective films for automobiles and buildings; antistatic films for photomasks and other various applications; CRTs
Electromagnetic shielding film on the surface; various types of transparent heating elements for anti-fogging such as for a freezing showcase; and a substrate for an electrochromic element as a light control glass.

Specific examples in which the tin oxide film of the present invention is used as a transparent conductive film for a solar cell substrate are shown below. The solar cell substrate using the tin oxide film of the present invention is not limited to the following. According to the present invention, a tin oxide film is formed on a glass substrate. Next, a silicon thin film such as an amorphous silicon thin film is formed on the entire surface of the substrate by a plasma CVD method. The amorphous silicon thin film is composed of a p-layer a-SiC film (amorphous silicon carbide film) (thickness of about 10 nm), a b-layer a-SiC film (thickness of about 10 nm), and an i-layer A-Si film (amorphous silicon film) (thickness: about 350 nm) and an n-layer a-Si film (thickness: about 20 nm). Further, a zinc oxide transparent conductive film (about 50 nm in thickness) and a silver film (about 200 nm in thickness) are formed on the entire surface of the substrate as back electrodes by sputtering.

At present, as a method for forming a silicon thin film such as an amorphous silicon thin film as a photoelectric conversion layer of a solar cell on a transparent conductive substrate, a plasma CVD method is mainly used. When the tin oxide film of the present invention is used as a transparent conductive film for a solar cell substrate, a transparent conductive film made of a crystalline thin film such as zinc oxide is formed on the tin oxide film of the present invention in order to impart plasma resistance. It is also a preferred embodiment to use it after overcoating. Therefore, in the above example,
Before forming a silicon thin film such as an amorphous silicon thin film, it is also a preferable example to form a zinc oxide film having a thickness of 20 to 200 nm on the tin oxide film.

Using the tin oxide film of the present invention, 30 cm × 30
cm of the solar cell substrate having the above configuration, the conversion efficiency of the solar cell is 8 to 11%, more preferably 10 to 11%.
%.

The tin oxide film manufacturing apparatus of the present invention is an apparatus for forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride and water by a normal pressure CVD method. A plurality of discharge ports for discharging a gas containing water and not containing tin tetrachloride and / or a gas containing tin tetrachloride and water onto a glass substrate in a moving direction of the glass substrate; The discharge port on the upstream side in the moving direction of the substrate discharges a gas having a higher water concentration than the discharge port on the downstream side. Hereinafter, a specific description will be given with reference to FIGS. Note that the manufacturing apparatus of the present invention is not limited to these.

FIG. 1 is a conceptual diagram showing an example of the apparatus for producing a tin oxide film of the present invention. First, the configuration of the tin oxide film manufacturing apparatus of the present invention will be described. The apparatus for producing a tin oxide film of the present invention includes a first injector 1 on the upstream side in the moving direction of the glass substrate and a second injector 2 on the downstream side. FIG. 1 shows a tin oxide film manufacturing apparatus provided with two injectors. However, a manufacturing apparatus provided with one injector connected to two discharge ports for discharging gases having different water concentrations may be used. The manufacturing apparatus may be provided with an injector connected to one of the discharge ports and provided with a so-called air curtain, and discharge a gas containing water from the air curtain. The first injector 1 is supplied with a gas containing vaporized tin tetrachloride and a gas containing water, and the injector body 3 mixes the two, and the injector discharge section 4 discharges the mixed gas.
And The injector body 3 is provided with a jacket 5 for passing a heat medium (oil or the like) therein and keeping the injector body 3 at a constant temperature, and the injector discharge section 4 passes a heat medium (oil or the like) inside to discharge the injector. A jacket 6 is provided for keeping the part 4 at a constant temperature.

The injector body 3 has a conduit 7 to which a gas containing tin tetrachloride is supplied from a bubbler tank. In the bubbler tank, an inert gas such as nitrogen is blown into the liquid tin tetrachloride from a cylinder, and the tin tetrachloride is vaporized to generate a gas containing tin tetrachloride. The bubbler tank is kept at 20 to 100C. The gas containing tin tetrachloride should be 130-130 before mixing with the gas containing water.
It is heated to 170 ° C. and supplied to the injector body 3.

The injector body 3 includes a conduit 8 to which vaporized water (steam) is supplied from a boiler. The boiler supplying water is kept at 100 ° C. or higher. The gas containing water is heated to 130 to 170 ° C. before being mixed with the gas containing tin tetrachloride and supplied to the injector body 3.

In the injector body 3, a gas containing tin tetrachloride supplied from a bubbler tank via a conduit 7 and a gas containing water supplied from a boiler via a conduit 8 are mixed. The internal temperature of the injector body 3 is maintained at 130 to 170 ° C. by passing a heat medium (oil or the like) through the jacket 5. At this time, the mixing ratio of the gas containing tin tetrachloride and the gas containing water supplied from the conduits 7 and 8 can be set to desired values by a flow controller such as a valve (not shown). The injector discharge section 4 discharges a uniformly mixed gas. The internal temperature of the injector discharge section 4 is maintained at 130 to 170 ° C. by passing a heat medium (oil or the like) through the jacket 6.

The second injector can have the same structure as the first injector. The mixing ratio between the gas containing tin tetrachloride and the gas containing water supplied from the conduits 13 and 14, respectively, can also be set to a desired value,
The water concentration of the gas in the injector body 3 is higher than the water concentration of the gas in the injector body 9.

The gas containing tin tetrachloride and water is discharged from the injector discharge sections 4 and 10 to the glass substrate 17 through gas flow paths 15 and 16, respectively. The gas passages 15 and 16 are
8, 19, and 20. The gas containing tin tetrachloride and water discharged on the glass substrate flows in the same direction as the moving direction of the glass substrate, and excess water not used for forming the tin oxide film is discharged from the exhaust pipe 21. The ratio of tin tetrachloride and water in the atmosphere for forming the tin oxide film is adjusted. The water concentration of the gas containing tin tetrachloride and water discharged from the injector onto the glass substrate is higher in the first injector 1 on the upstream side than in the second injector 2 on the downstream side. Therefore, for example, in the first injector 1 on the upstream side, tin tetrachloride: water = 1: 100 to 1:20 in molar ratio in the first injector 1 on the upstream side.
0, and in the second injector 2 on the downstream side,
In a ratio, tin tetrachloride: water = 1: 30 to 1:60. In the apparatus for manufacturing a tin oxide film of FIG. 1, a gas containing water and not containing tin tetrachloride can be discharged from the first injector. In this case, the ratio of tin tetrachloride and water is determined, for example, by using the second injector 2 on the downstream side.
Then, in terms of mol ratio, tin tetrachloride: water = 1: 30 to 1:60
It can be.

The distance between the discharge port at the lower end of the gas flow path 15 and the surface of the glass substrate is preferably 1 to 3 cm. The discharge angle is preferably 45 to 90 degrees with respect to the glass substrate surface (the moving direction of the glass substrate is 0 degree). It is preferable that the distance between the discharge port at the lower end of the gas flow path 16 and the surface of the glass substrate is 1 to 3 cm. The discharge angle is preferably 45 to 90 degrees with respect to the glass substrate surface (the moving direction of the glass substrate is 0 degree).

The distance between the discharge port at the lower end of the gas flow path 15 and the discharge port at the lower end of the gas flow path 16 is not limited because it changes depending on the relationship with the moving speed of the glass substrate. It is preferably 10 to 100 cm, and 20
More preferably, it is set to 80 cm.

In the first injector 1, the discharge amount of the gas containing tin tetrachloride and water is 1 m in width of the glass substrate.
It is preferably 0.025 to 1.4 m ³ / min, and in the second injector 2, it is preferably 0.5 to 7 m ³ / min per 1 m width of the glass substrate. The discharge rate of the gas containing tin tetrachloride and water is preferably 0.1 to 10 m / s in the first injector 1 and 0.5 to 10 m / s in the second injector 2.
It is preferably 20 m / s. When discharging a gas containing water and not containing tin tetrachloride from the first injector, the discharge amount of the gas containing tin tetrachloride and water is:
In the second injector 2, it is preferably 0.5 to 7 m ³ / min per 1 m of the width of the glass substrate. Further, in this case, the discharge speed of the gas is preferably 0.1 to 10 m / s in the first injector 1 and 0.5 to 20 m / s in the second injector 2.
It is preferred that

The moving speed of the glass substrate depends on the discharge amount of the gas containing tin tetrachloride and water. For example, the discharge amount per 1 m width of the glass substrate from the first injector 1 is 0.1 m ^3. / Min, the discharge amount per 1 m width of the glass substrate from the second injector 2 is set to 1.0 m ³ /
When it is set to min, it is preferably set to 1.0 to 2.0 m / min.

The gas containing tin tetrachloride and water may be laminar or turbulent.

FIG. 2 is a conceptual view showing an example of the apparatus for producing a tin oxide film of the present invention. The production apparatus of the tin oxide film of FIG.
It is the same as the apparatus of FIG. 1 in that it has a first injector 26 on the upstream side and a second injector 27 on the downstream side in the moving direction of the glass substrate, but the position of the exhaust pipe 28 is between the two injectors. Some differences. The gas discharged from the first injector 26 flows in the same direction as the direction of movement of the glass substrate, and the gas discharged from the second injector 27 flows in the direction opposite to the direction of movement of the glass substrate. Exhausted. The water concentration in the gas discharged from the injector is such that the upstream first injector 26 is more downstream than the second injector 2.
1 and that a gas containing water and not containing tin tetrachloride can be discharged from the first injector 26 is the same as the apparatus of FIG. Other conditions are the same as those of the apparatus shown in FIG. Note that an exhaust pipe different from the exhaust pipe 28 may be further provided downstream of the second injector 27.

FIG. 3 is a conceptual diagram showing an example of the apparatus for producing a tin oxide film of the present invention. The apparatus for manufacturing a tin oxide film in FIG.
An air curtain 29 is used instead of the first injector of the apparatus shown in FIG. From the air curtain 29, a gas containing water and not containing tin tetrachloride, for example, air containing water vapor is discharged. The concentration of water in the gas can be, for example, 1 to 50%. The gas discharged from the air curtain 29 flows in the same direction as the moving direction of the glass substrate, and the gas discharged from the injector 30 is discharged from the exhaust pipe 31 and the exhaust pipe 32. The gas containing water and not containing tin tetrachloride discharged from the air curtain 29 is exhausted from the exhaust pipe 31, but contains tin tetrachloride and water discharged from the injector 30 near the lower end of the exhaust pipe 31. It mixes with the gas to generate an atmosphere having a higher water concentration than the atmosphere downstream of the exhaust pipe 31. This is similar to the case where the gas containing water and not containing tin tetrachloride is discharged from the first injector 26 in the apparatus of FIG. Other conditions and the like are the same as those of the apparatus of FIG.

FIG. 4 is a conceptual diagram showing an example of the apparatus for producing a tin oxide film of the present invention. The apparatus for manufacturing a tin oxide film shown in FIG.
1 in that it has a first injector 33 on the upstream side and a second injector 34 on the downstream side in the moving direction of the glass substrate, but the position of the exhaust pipe 35 is the same as that of the first injector 33. The difference is that it is on the upstream side.
The gas discharged from the first injector 33 and the second injector 34 flows in the direction opposite to the moving direction of the glass substrate, and is exhausted from the exhaust pipe 35. The water concentration in the gas discharged from the injector is such that the upstream first injector 33 is higher than the downstream second injector 34, and the first injector 33 contains water and contains tin tetrachloride. It is the same as the apparatus of FIG. 1 that a gas not to be discharged can be discharged. Other conditions are the same as those of the apparatus shown in FIG. Note that an exhaust pipe different from the exhaust pipe 35 may be further provided downstream of the second injector 34.

According to the apparatus for producing a tin oxide film of the present invention, a tin oxide film having a small sheet resistance, a high transmittance, a high haze rate and uniform fine irregularities on the surface can be obtained. The apparatus for producing a tin oxide film of the present invention can be cited as an example of an apparatus best suited for implementing the method for producing a tin oxide film of the present invention.

Japanese Patent No. 2,833,797 discloses that a flow of a first reaction gas composed of tin tetrachloride is formed along a glass surface, and a second reaction gas composed of 20% hydrofluoric acid is formed in the flow. A method is described in which a turbulent stream is introduced and a tin oxide layer is deposited by the combined turbulent stream. In the above specification, the second reactant gas is given as a turbulent flow to mix with the first flow already in contact with the glass at a sufficient degree of mixing, thereby depositing a sufficiently uniform tin oxide layer. It states that it can be done. But,
In the method, since the first stream on the upstream side has a lower water concentration than the second stream on the downstream side, the crystal growth of tin oxide is not uniform, and in fact, the first stream is The mixing of the stream and the second stream is not sufficient, and the resulting tin oxide film is not sufficiently uniform. In particular, the haze ratio uniformity is not satisfied at a high level required for a tin oxide film used as a transparent conductive film for a solar cell substrate.
Therefore, a tin oxide film having a small sheet resistance, a high transmittance, a high haze, and uniform fine irregularities on the surface as in the present invention cannot be obtained.

[0055]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. 1. Production of tin oxide film (Example 1) Soda lime glass substrate (30 cm × 30
cm × 3 mm), and after sufficient washing, a silica film having a thickness of about 50 nm was
The tin oxide film was formed by a VD method, and thereafter, a tin oxide film was formed by a hydrolysis reaction with water using tin tetrachloride as a main raw material by a CVD method using the apparatus for manufacturing a tin oxide film of the present invention shown in FIG. Specifically, the procedure was as follows. Tin tetrachloride was put into a bubbler tank maintained at 55 ° C., and nitrogen was introduced from a cylinder to evaporate. Water was supplied from a boiler maintained at 100 ° C. or higher. The cylinder was heated to about 80 ° C. to evaporate hydrogen fluoride gas for lowering the resistance of the film. Further, methanol was placed in a bubbler tank maintained at 30 ° C., and nitrogen was introduced from a cylinder to evaporate. After heating tin tetrachloride and water respectively to 150 ° C., they were transported to the first injector 1 and the second injector 2 via conduits 7, 8, 13 and 14 kept at 150 ° C. After heating the hydrogen fluoride gas and methanol to 150 ° C., respectively, the first injector 1 was heated via a conduit (not shown) kept at 150 ° C.
And transported to the second injector 2. Tin tetrachloride,
Water, hydrogen fluoride gas and methanol were mixed in the injector bodies 3 and 9. In the first injector 1, the mixing ratio (mol ratio) was tin tetrachloride: water = 1: 10.
0, in the second injector 2, tin tetrachloride: water = 1:
50. The temperature of the injector bodies 3 and 9 was maintained at about 150 ° C. by a heating medium (oil).

A gas flow path 15 for discharging a gas having a high water concentration from the first injector 1 to a glass substrate 17 at about 500 ° C., and a gas flow for discharging a gas having a low water concentration from the second injector 2 Passing under the path 16, a tin oxide film was formed on the surface of the glass substrate. The discharge rate ratio is
(Discharge amount from first injector): (Discharge amount from second injector) = 1: 10. Exhaust pipe 2
From 1 onward, excess water was exhausted.

(Example 2) A glass substrate was produced in the same manner as in Example 1 except that steam discharged from the first injector 1 was water instead of a gas containing tin tetrachloride and water. A tin oxide film was formed on the surface.
That is, the gas flow path 15 from which the steam from the first injector 1 is discharged, and the gas flow path from which the gas containing tin tetrachloride and water is discharged from the second injector 2 are passed through the glass substrate 17 at about 500 ° C. Pass under 16,
A tin oxide film was formed on the surface of the glass substrate. The mixing ratio (mol ratio) between tin tetrachloride and water was set to be tin tetrachloride: water = 1: 50 in the second injector 2. In addition, the discharge amount ratio was (a discharge amount from the first injector) :( a discharge amount from the second injector) = 1: 5.

(Comparative Example 1) Except that no gas was discharged from the discharge port 15 and no gas was exhausted from the exhaust pipe 21,
In the same manner as in Example 1, a tin oxide film was formed on the glass substrate surface.

2. Physical Properties of Tin Oxide Film The following physical properties of the obtained tin oxide film were measured and evaluated. The results are shown in Table 1. In addition, apart from Example 1, an attempt was made to form a tin oxide film on a glass substrate surface under the same conditions using the apparatus of FIG. 2 or 4 instead of the apparatus of FIG. A similar tin oxide film could be obtained. Further, apart from the second embodiment, an attempt was made to form a tin oxide film on a glass substrate surface under the same conditions by using the apparatus of FIG. 3 instead of the apparatus of FIG. A film could be obtained. Hereinafter, the results for the tin oxide films obtained in Examples 1 and 2 are shown, but the results for the tin oxide films obtained using the apparatuses of FIGS.

(1) Film thickness The film thickness (maximum film thickness) was measured using a stylus type surface roughness meter. The film of Example 1 was 800 nm, and the film of Example 2 was 70 nm.
0 nm, and the film of Comparative Example 1 had a thickness of 600 nm.

(2) Sheet Resistance The sheet resistance was measured by a four-terminal method. A glass substrate having a film on the surface obtained in each of Examples and Comparative Examples was cut into a square of about 3 cm, and a pair of electrodes having a length of 3 cm was placed on two opposing sides so that the distance between the electrodes was 3 cm. Was mounted in parallel. Next, the resistance (sheet resistance) between the electrodes was measured with a tester. The film of Example 1 was 7Ω / □, the film of Example 2 was 8Ω / □, and the film of Comparative Example 1 was 10Ω / □.

(3) Transmittance The average value of the spectral transmittance at a wavelength of 400 nm to 800 nm is measured by a spectrophotometer using an integrating sphere, and the transmittance is calculated by correcting a decrease in the measured value of the transmittance due to haze. did.
The film of Example 1 was 84%, the film of Example 2 was 85%, and the film of Comparative Example 1 was 83%.

(4) Haze unevenness and haze ratio Haze unevenness was visually observed. Further, at 10 locations distributed over the entire surface of the substrate, the wavelength is 400 nm to 800 nm.
Was measured with a haze meter. In the film of Example 1, uneven haze was not observed on the entire surface of the substrate.
The haze rate averaged 15%, 18% in the high part and 12% in the low part. In the film of Example 2, uneven haze was not observed on the entire surface of the substrate, and the haze ratio was 12% on average.
15% in the high part and 9% in the low part. In the film of Comparative Example 1, haze unevenness of a striped pattern was observed on the entire surface of the substrate, and the haze ratio was 7% on average, 18% in a high portion, and 4% in a low portion.

(5) Concavo-convex shape on film surface The concavo-convex shape on the film surface was observed with a scanning electron microscope (SEM). The films of Examples 1 and 2 had fine pyramid-shaped irregularities uniformly on the surface. The height of the protrusion (the difference in height between the protrusion and the recess) was about 150 to 170 for the film of Example 1.
nm, and that of the film of Example 2 was about 120 to 150 nm.
The film of Comparative Example 1 had uneven surface irregularities, and the heights of the projections (the difference in height between the projections and the depressions) varied widely, from about 80 to 250 nm.

(6) Energy Conversion Efficiency of Solar Cell Substrate in Case of Transparent Conductive Film for Solar Cell Substrate The glass substrate (30 cm × 30 cm) on which the tin oxide film obtained in Examples 1 and 2 and Comparative Example 1 was formed 2), an amorphous silicon thin film was formed on the entire surface by a plasma CVD method. The amorphous silicon thin film is formed from a p-layer a-SiC film (amorphous silicon
Carbide film) (thickness: about 10 nm), b-layer a-SiC
Film (thickness: about 10 nm), i-layer a-Si film (amorphous silicon film) (thickness: about 350 nm), n-layer a-Si
It was composed of a film (about 20 nm thick). Further, a zinc oxide film (about 50 nm in thickness) and a silver film (about 200 nm in thickness) were formed as back electrodes on the entire surface of the substrate by sputtering. About the obtained solar cell substrate, AM (Ai
The energy conversion efficiency was measured using a solar simulator of (r Mass) 1.5. The film of Example 1 is 1
0%, and the film of Example 2 was 9.5%. On the other hand, although the film of Comparative Example 1 was 7%, some of the films obtained in Comparative Example 1 did not exhibit any performance. It is considered that this is because the unevenness of the surface is non-uniform, and short-circuiting occurs at a portion where the height of the convex portion (the height difference between the convex portion and the concave portion) is large.

[0066]

[Table 1]

[0067]

According to the method for producing a tin oxide film of the present invention,
The present invention has a low sheet resistance, a high transmittance, and
A tin oxide film having a high haze ratio and uniform tin oxide film having fine irregularities uniformly on the surface can be obtained. When the tin oxide film of the present invention is used for a transparent conductive film for a solar cell substrate, a solar cell with high energy conversion efficiency can be obtained, which is very suitable. The apparatus for producing a tin oxide film of the present invention is preferably used for carrying out the above method.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a tin oxide film manufacturing apparatus of the present invention.

FIG. 2 is a diagram showing an example of a tin oxide film manufacturing apparatus of the present invention.

FIG. 3 is a diagram showing an example of a tin oxide film manufacturing apparatus of the present invention.

FIG. 4 is a diagram showing an example of a tin oxide film manufacturing apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st injector 2 2nd injector 3, 9 Injector main body 4, 10 Injector discharge part 5, 6, 11, 12 Jacket 7, 8, 13, 14 Conduit 15, 16 Gas flow path 17 Glass substrate 18, 19, 20, 22, 23, 24 Carbon block 21, 25 Exhaust pipe 26 First injector 27 Second injector 28 Exhaust pipe 29 Air curtain 30 Injector 31, 32 Exhaust pipe 33 First injector 34 Second injector 35 Exhaust pipe

Continued on the front page (72) Inventor Makoto Fukawa 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. 4G059 AA01 AC12 EA02 EB01 4K030 AA03 BA45 CA06 EA06 LA01 LA11 5F051 BA14 CA15 CB27 FA03 FA19 FA24 GA03

Claims (4)

[Claims] 1. A method for producing a tin oxide film by forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride and water by a normal pressure CVD method, comprising the steps of: Is characterized in that an atmosphere in which a tin oxide film is formed by discharging a gas containing tin on a glass substrate is an atmosphere having a higher water concentration on the upstream side in the moving direction of the glass substrate than on the downstream side. Manufacturing method of tin film. 2. A method for producing a tin oxide film by forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride and water by a normal pressure CVD method, comprising: A gas containing water and not containing tin tetrachloride and / or a gas containing tin tetrachloride and water is discharged onto a glass substrate from a plurality of discharge ports arranged in the direction of movement of the glass substrate. Characterized in that a gas having a higher water concentration is discharged from a discharge port on the upstream side than a discharge port on the downstream side. 3. A tin oxide film obtained by the method according to claim 1. 4. A tin oxide film manufacturing apparatus for forming a tin oxide film on a glass substrate moving in one direction by reacting tin tetrachloride with water by a normal pressure CVD method. A plurality of discharge ports for discharging a gas containing no tin chloride, and / or a gas containing tin tetrachloride and water onto the glass substrate in a moving direction of the glass substrate,
An apparatus for producing a tin oxide film, wherein a gas having a higher water concentration is discharged from a discharge port on an upstream side in a moving direction of a glass substrate than a discharge port on a downstream side.