JP2001053308A - Manufacture of conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit as much as possible change in film characteristics, such as transmission properties, a resistance value or the like, and to adjust the irregular shapes of film surfaces by forming films having the same quality of the material at a plurality of times by adjusting a film-thickness distribution. SOLUTION: In a substrate for an optoelectric converter, to which a conductive film is formed, a foundation film 1 and a transparent conductive film 2 using tin oxide by forming plural number of times as a main component are formed on a glass pane 5 in this order. Irregularities 3 are formed to the surface of the conductive film 2. The irregularities contribute to the increase of optical confinement effect in a photoelectric conversion layer. When the conductive film 2 having an irregular shape on the surface is formed, the conductive film 2 in a desired film thickness is laminated by film formation by plural number of times. The film-thickness distribution is optimized so that film thickness formed at a plurality of times is formed into an optimum irregular shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminate including a glass plate and a transparent conductive film and used for a thin-film solar cell, and more particularly to a method for controlling the unevenness of the surface of the transparent conductive film.

[0002]

2. Description of the Related Art A laminate in which a transparent conductive film is formed on a glass plate is widely used as a heat-reflective glass, a thin-film solar cell and the like.

As a transparent conductive film, a tin oxide film doped with fluorine is frequently used. This film has better chemical stability such as plasma resistance than a tin-doped indium oxide (ITO) film, and is suitable for forming a photoelectric conversion layer (amorphous silicon layer) to which a plasma CVD method is applied. Less deterioration.

[0004] The tin oxide film is formed by a method involving a thermal decomposition oxidation reaction,
In particular, although a film is formed by a CVD method, it is known that tin oxide of a transparent conductive film formed on a glass plate by a thermal decomposition method on a high-temperature substrate becomes polycrystalline.

[0005] The polycrystalline tin oxide exhibits an uneven shape on the surface due to the growth of the particle size with an increase in the film thickness. In a thin-film solar cell, the unevenness of the surface of the tin oxide film improves the photoelectric conversion characteristics due to the light confinement effect. Therefore, various studies have been made on the uneven shape of the surface of the tin oxide film and the method of forming the same.

For example, Japanese Patent Laid-Open Publication No. 2-503615 discloses a convex portion having a diameter of 0.1 to 0.3 μm and a height / diameter ratio of 0.7 to 1.2 on the surface. There is disclosed a solar cell substrate including a tin oxide film. In that publication,
As a method for producing a tin oxide film, a CVD method using a mixed gas containing tin tetrachloride, water vapor, methanol, nitrogen and the like is disclosed.

[0007] The degree of unevenness formed on the surface of the transparent conductive film can be indicated by a haze ratio. JP-A-63-242947 describes an example in which the haze ratio of a tin oxide film is changed by adjusting the molar ratio of dimethyltin dichloride and water when forming a tin oxide film by a CVD method. Have been.

In each of the above publications, when forming a tin oxide film by the CVD method, the composition of the surface irregularities is adjusted by changing the composition ratio of the supplied source gas. In addition, the unevenness is adjusted for the purpose of improving the characteristics of an amorphous silicon solar cell obtained by depositing an amorphous silicon film as a photoelectric conversion layer on a transparent conductive film.

[0009]

By the way, as a solar cell using a photoelectric conversion material other than amorphous silicon, polycrystalline silicon, silicon containing a microcrystalline phase, or CuI
A crystalline thin-film solar cell using nSe ₂ or the like as a photoelectric conversion layer is given.

In this crystal thin film type solar cell, the crystallinity of the crystal thin film as a photoelectric conversion material is an important factor for obtaining good characteristics. This is because, in a crystalline thin film, the crystallinity determines the characteristics of the thin film, particularly the electrical characteristics. In particular, when a photoelectric conversion material having a crystal structure is formed directly on the surface of the transparent conductive film or via a relaxation layer, the surface of the transparent conductive film needs to have a surface unevenness that does not impair the crystallinity of the photoelectric conversion material.

That is, it is necessary to adjust the surface unevenness shape which has been adjusted for the conventional amorphous silicon solar cell application to the optimum surface unevenness shape for the crystal thin film type solar cell.

Here, conventionally, when forming a tin oxide film by the CVD method, the composition of the supplied source gas is changed to adjust the surface unevenness. However, a transparent conductive film for a thin-film solar cell has a high transmittance,
It is required that the resistance be low, but it is often observed that changing the composition ratio of the source gas impairs this important characteristic.

Therefore, it is necessary to readjust not only the irregularities on the surface but also the gas conditions under which the permeability and the resistance value become optimal.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a transparent conductive film in which changes in film characteristics such as permeability and resistance value can be suppressed as much as possible, and the uneven shape of the film surface can be adjusted.

[0015]

In order to achieve the above object, a method of manufacturing a transparent conductive film according to the present invention comprises adjusting the film thickness distribution of a film of the same material in forming a conductive film on a glass substrate. This is a method for producing a conductive film in which a film is formed a plurality of times.

Here, when the film of the same material is sequentially formed n times on the glass substrate by Di (2 ≦ i ≦ n), D1 ≦ D2... ≦ Dn is satisfied. It is desirable to do. Here, D1 is the film thickness at the time of the first film formation, and Di1
Is the film thickness at the time of the i-th film formation from the second time.

The crystal growth process of the conductive film such as tin oxide on the glass substrate and the process of forming the surface irregularities have not been clarified yet. In this case, small, equigranular crystals are generated, and the surface irregularities are considered to be uniform. As the crystal growth further progresses, long columnar crystals are formed.In the case of tin oxide or the like that forms a polycrystal, some crystals grow larger due to the interaction with the adjacent crystal in the growth process. In addition, there are crystals whose crystal growth is suppressed. As a result, it is considered that the surface unevenness becomes non-uniform. If this crystal growth mode is used, it is possible to adjust the surface irregularities.

That is, in order to make the surface unevenness as uniform as possible, a conductive film having a desired film thickness may be formed by performing film formation a plurality of times with the film thickness formed at one time being as small as possible. Become.

Considering that the crystal of the conductive film formed by a plurality of film formations grows in a form following the crystal growth of the conductive film formed by the previous film formation, the (n + 1) th film formation process Is larger than the n-th interaction, it is desirable that the interaction in the n-th film formation be as small as possible. Therefore, in particular, in order to make the surface unevenness uniform, it is desirable that the film thickness formed in the (n + 1) th film be larger than the film thickness formed in the nth film.

According to the method of manufacturing a conductive film of the present invention, the unevenness of the film surface can be adjusted and the unevenness of the surface can be made uniform. It contributes to an increase in the light confinement effect in the photoelectric conversion layer of the used thin-film solar cell, and can increase the photoelectric conversion efficiency.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for producing a conductive film according to the present invention will be described below. FIG. 1 is a cross-sectional view of one embodiment of a photoelectric conversion element substrate on which a conductive film is formed by the method for manufacturing a conductive film of the present invention. In the substrate for a photoelectric conversion element on which a conductive film is formed by the method for producing a conductive film of the present invention, a base film 1 and a transparent conductive film 2 containing tin oxide as a main component obtained by forming a plurality of times are formed on a glass plate 5. The conductive films 2 are formed in this order, and irregularities 3 are formed on the surface of the conductive film 2. This unevenness contributes to an increase in the light confinement effect in the photoelectric conversion layer.

The method of manufacturing a conductive film according to the present invention is a manufacturing method in which a conductive film 2 having a desired film thickness is laminated by a plurality of film formations when forming a conductive film 2 having an uneven surface. This is a method of optimizing the film thickness distribution so that the film thickness formed in a plurality of times has an optimum uneven shape.

Underlayer 1 contains at least one selected from silicon oxide and aluminum oxide as a main component.
The underlayer 1 includes a first underlayer 1a and a second underlayer 1b.
Can be formed as a two-layer film. In this case, the first underlayer 1a preferably contains tin oxide as a main component.
Further, second underlayer 1b preferably contains at least one selected from silicon oxide and aluminum oxide as a main component, and is particularly preferably a silicon oxide film.

The transparent conductive film 2 containing tin oxide as a main component is not particularly limited, but may be a thin film containing tin oxide as a main component to which a predetermined amount of an element such as fluorine is added for improving conductivity. preferable.

The method of forming a conductive film formed by the manufacturing method of the present invention is not particularly limited, but a spraying method in which a raw material liquid is atomized and supplied to the glass ribbon surface, or a raw material is vaporized by vaporizing the raw material liquid, The supplied CVD method can be used. In particular, in the float glass manufacturing process, it is preferable to apply a method of sequentially depositing the above films on the top surface of the glass ribbon by utilizing the heat of the glass ribbon. The reason for this is that it is suitable for film formation at a high temperature and that the heat of the glass ribbon can be used.

When a thin film containing tin oxide as a main component is formed by the CVD method, tin raw materials include monobutyltin trichloride, tin tetrachloride, dimethyltin dichloride, dibutyltin dichloride, dioctyltin dichloride, and tetramethyltin. No. Organic tin chlorides such as monobutyltin trichloride and dimethyltin dichloride are suitable as tin raw materials. For the oxidation of the tin raw material, oxygen, steam, dry air or the like can be used as the oxidizing raw material. In addition, as a fluorine raw material when fluorine is added to the conductive film, hydrogen fluoride, trifluoroacetic acid, bromotrifluoromethane, chlorodifluoromethane, and the like can be given.

When a thin film containing silicon oxide as a main component is formed by the CVD method, monosilane, disilane, trisilane, monochlorosilane, 1,2-dimethylsilane, 1,1,2-trimethyldisilane, 1 , 1,2,2-tetramethyldisilane, tetramethylorthosilicate, tetraethylorthosilicate and the like.

Examples of the oxidizing material include oxygen, steam, dry air, carbon dioxide, carbon monoxide, nitrogen dioxide, ozone and the like. When a raw material having extremely high reactivity such as monosilane is used, the reactivity may be controlled by adding an unsaturated hydrocarbon gas such as ethylene, acetylene or toluene.

As in the case of silicon oxide, when a film containing aluminum oxide as a main component, which is suitable as the second underlayer, is formed by a CVD method, aluminum materials include trimethylaluminum, aluminum triisopropoxide, and diethyl chloride. Examples include aluminum, aluminum acetylacetonate, and aluminum chloride. In this case, examples of the oxidizing material include oxygen, steam, and dry air.

[0030]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

Example 1 Alkali-free glass having a size of 100 mm × 100 mm and a thickness of 1.1 mm (70 manufactured by Corning Incorporated)
59) was washed and dried to obtain a substrate. On this glass substrate, in a transfer furnace of open-to-atmosphere, by atmospheric pressure CVD,
As the first film formation, a fluorine-containing tin oxide film having a thickness of about 100 nm was formed. The film formation was performed while the glass substrate was transported in a furnace heated to about 600 ° C. using a mesh belt. As a source gas, dimethyltin dichlory, water, oxygen, nitrogen, and trifluoroacetic acid were supplied to form a film.

Next, as a second film formation, using the glass substrate with a fluorine-containing tin oxide film of about 100 nm obtained in the first film formation, on a fluorine-containing tin oxide film of about 100 nm in the same manner as the first film formation Film thickness of about 200nm
Was formed, and a fluorine-containing tin oxide film having a thickness of about 300 nm was formed.

Next, as the third film formation, using the glass substrate with the fluorine-containing tin oxide film of about 300 nm obtained in the second film formation, on the fluorine-containing tin oxide film of about 300 nm in the same manner as the first film formation The thickness is about 300 nm by a simple film formation method
Was formed, and a fluorine-containing tin oxide film having a thickness of about 600 nm was formed.

That is, in this embodiment, the number of times of film formation is three, and a fluorine-containing tin oxide film having a total thickness of about 100 nm, about 200 nm, and about 300 nm is sequentially formed.
A fluorine-containing tin oxide film having a thickness of nm was formed and used as a sample.

(Example 2) Using the same method as in Example 1, the number of times of film formation was three, and was about 300 nm and about 200 n.
m, a fluorine-containing tin oxide film of about 100 nm is sequentially formed,
A fluorine-containing tin oxide film having a total film thickness of about 600 nm was formed as a sample.

The surface irregularities of the conductive film of the specimen thus obtained were evaluated as follows. 1 by atomic force microscope
Within the range of 0 μm × 10 μm, the surface shape profile of the conductive film of the sample was measured, and the maximum unevenness value (the distance between the highest surface convex portion and the lowest surface concave portion) was determined. The value of the maximum unevenness value in Example 1 was 275 nm, and the value of the maximum unevenness value in Example 2 was 277 nm.

Next, based on the data obtained by the above measurement, the area between the maximum height (the highest convex portion on the surface) and the minimum height (the lowest concave portion on the surface) is divided into ten, and the area of each section is obtained. The cross-sectional area distribution in the vertical direction was plotted to obtain a cross-sectional area distribution curve.
The data is shown below. Example 1 Example 2 Depth (nm) Cross-sectional area ratio Depth ( nm) Cross-sectional area ratio------------------------------28 0 27 0 55 0.00006 55 0.00008 83 0.00116 84 0.00065 109 0.00908 111 0.00394 137 0.06574 139 0.02148 165 0.29844 166 0.09190 193 0.70624 195 0.31945 220 0.94827 222 0.69303 247 0 .9888 249 0.95284 275 0.98989 277 0.99839 ------------------------------------------------------------------------ FIG. 2 , Section integral It showed the curve.

From the cross-sectional area distribution curves, it can be understood that the surface irregularities of the samples of Examples 1 and 2 are different. The surface unevenness of the sample of Example 1 is more uniform than that of Example 2, and the shape of the convex portion is more rounded. That is, the surface convex portion of the sample of Example 2 has a sharper tip than the surface convex portion of the sample of Example 1.

When the surface of the transparent conductive film is made uneven, the characteristics of the thin-film solar cell obtained by forming a photoelectric conversion layer on the surface are improved by the light confinement effect and the like. However, when a transparent conductive film having a non-uniform surface unevenness or a large number of convex portions with sharp tips is used, the photoelectric conversion efficiency of the thin-film solar cell is reduced.

The deterioration of such characteristics includes a decrease in step coverage due to a photoelectric conversion layer such as an amorphous silicon layer on a transparent conductive film, and an increase in light absorption at a layer interface due to a decrease in film quality of the photoelectric conversion layer. It is thought that it is affecting. In addition, it is considered that an increase in resistance value due to poor bonding between the photoelectric conversion layer and the transparent conductive film is also a cause of the performance degradation.

In this embodiment, the characteristics of the thin-film solar cell can be greatly improved by adopting the shape of the sample of the first embodiment.

It is needless to say that the present invention can be applied to a case where a thin film is formed on the surface of a glass ribbon in a float method by a CVD method. FIG. 3 shows an embodiment of the apparatus according to the present invention in the float method.

As shown in FIG. 3, in this apparatus, a predetermined number of coaters 16 (shown in FIG. 3) immediately flow out of a glass ribbon 10 which flows out of a melting furnace 11 into a tin float tank 12, is formed into a strip shape in a tin bath 15, and moves. In the form shown, five coaters 16
a, 16b, 16c, 16d, 16e) are arranged. Raw materials that have been adjusted and vaporized in advance are supplied from these coaters, and a film is continuously formed on the surface (top surface; non-tin contact surface) of the glass ribbon 10. Usually, the coater 16a has a first underlayer, the coater 16b has a second underlayer,
The transparent conductive films of tin oxide can be continuously laminated by the coaters 16c, 16d and 16e. In the case where tin oxide, which is a transparent conductive film, is formed using three coaters, the surface roughness of the tin oxide film is adjusted by adjusting the thickness of the tin oxide formed by each coater. It becomes possible to control.

[0044]

As described above, according to the present invention,
It is possible to control the surface unevenness of a transparent conductive film that can be suitably used for a thin film solar cell substrate or the like, that is, to make the surface unevenness uniform. The transparent conductive film manufactured according to the present invention not only has an effect of confining light, but also has a good surface unevenness with a uniform unevenness distribution, so that good bonding with the photoelectric conversion layer can be ensured.

[0045]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a laminate produced by a production method of the present invention.

FIG. 2 is a diagram showing an example of a refractive index distribution curve in a surface layer portion of a transparent conductive film in a laminate produced by the production method of the present invention.

FIG. 3 is a diagram showing a configuration of an apparatus that can be used for manufacturing a laminate by the manufacturing method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Underlayer 1a 1st underlayer 1b 2nd underlayer 2 Transparent conductive film 3 Uniform unevenness which is not relatively sharp 5 Glass plate 10 Glass ribbon 11 Melting furnace 12 Tin float tank 13 Slow cooling furnace 16 Coater 17 Roller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Akira Fujisawa, Inventor 3-5-1-11 Doshomachi, Chuo-ku, Osaka-shi, Osaka Inside Nippon Sheet Glass Co., Ltd. (72) Inventor Masahiro Hirata 3-chome, Doshucho, Chuo-ku, Osaka-shi, Osaka No. 5-11 Nippon Sheet Glass Co., Ltd. F term (reference) 4G059 AA08 AC06 AC11 EA02 EB02 GA01 GA02 GA04 GA12 5F051 CB27 FA03 FA19 FA22 FA24 GA03 GA06 5G323 BA03 BB02 BB03 5H032 AA06 BB10 EE07 EE18 HH04

Claims (2)

[Claims] (1) In forming a conductive film on a glass substrate,
A method for manufacturing a conductive film, comprising forming a film of the same material a plurality of times by adjusting the film thickness distribution. 2. The method for manufacturing a conductive film according to claim 1, wherein each film thickness when sequentially forming a film of the same material n times on the glass substrate is Di (2 ≦ i ≦ n). A method for producing a conductive film that satisfies D1 ≦ D2... ≦ Dn.
Here, D1 is the film thickness at the time of the first film formation, and Di is the film thickness at the time of the second and subsequent i-th film formation.