JPS63242947A - Formation of clear conductive film of tin oxide - Google Patents

Abstract

PURPOSE:To form the title reduced haze film suitable for use as a conductive base for solar cells, at an excellent film formation rate, by pyrolytically oxidizing the vapor of an organotin compound on the heated glass base in the presence of moisture. CONSTITUTION:A glass base, which is, when needed, coated with an alkali barrier such as silica, alumina, zirconia or titania, is heated over 400 deg.C and treated with a vapor of an organotin compound such as (CH3)2SnCl2 or sprayed with the solution thereof in an appropriate organic solvent using a spray gun or a carrier gas. At this time, water at 1-1,000 water/tin molar ratio is mixed in the carrier gas or in the spray solution to effect pyrolytic oxidation of the organotin compound, when it contact with the base surface, to form the title film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improved method for forming a tin oxide transparent conductive film on a glass substrate using a chemical film formation method.

[Prior Art] Conventionally, spray methods, normal pressure CVD methods, low pressure CVD methods, vacuum evaporation methods, sputtering methods, and the like have been known as methods for forming transparent conductive films on glass substrates. Among these, spray methods and CVD methods (hereinafter referred to as chemical film forming methods) are widely used for tin oxide films, and silver tetrachloride or various organic tin compounds are used as raw materials. When silver tetrachloride is used, the film formation rate is fast, but it has the disadvantage that the formed film tends to have a large amount of haze (cloudiness), whereas when an organotin compound is used, haze is less likely to occur. The drawback was that the film formation rate was extremely slow.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the prior art and provides a method for rapidly forming a haze-free tin oxide transparent conductive film. purpose.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. In a method of forming a tin oxide transparent conductive film on a glass substrate surface by an oxidation reaction, moisture is provided during the thermal decomposition oxidation reaction.

The present invention will be explained in more detail below.

As the glass substrate used in the present invention, soda lime silicate glass plates such as ordinary plate glass and float plate glass are generally used, but other glass plates such as aluminosilicate glass plates, borosilicate glass plates, lydium aluminosilicate glass plates, and quartz glass are also used. Boards and other types of glass plates can also be used. In addition, a glass substrate made of glass containing sodium such as soda lime silicate glass,
Or, in the case of a substrate made of glass with a low alkali content, it is necessary to prevent sodium from eluting from the glass surface and have an adverse effect on the transparent conductive film formed on the top surface, such as to prevent haze from occurring, and An alkali barrier coat such as silica, alumina, zirconia, titania, etc. may be applied to the surface of the glass substrate to improve crystallinity and conductivity. Further, the thickness of the glass substrate is not particularly limited, but is suitably 0.5 mm to 5 mm so as not to cause a decrease in light transmittance, an extreme increase in weight, a decrease in strength, and inconvenience in handling.

In the present invention, the method for forming the tin oxide transparent conductive film is the normal pressure CVD method in which the surface of the glass substrate is brought into contact with the vapor of an organic tin compound and the film is formed by a thermal decomposition oxidation reaction, or the low pressure CVD method or the glass substrate surface. A chemical film forming method such as a so-called spray method is applied, in which a liquid of an organic tin compound is sprayed onto the surface and brought into contact with the surface to form a film through a thermal decomposition oxidation reaction.

The organic tin compound used in the present invention includes (C
Ilal 1snclz, (C1lsl 1snc1
．． (C41191zsnclz.

(Cdls) 5snc1. (C4119) asn
cla, (C411915nCIa, (C6116
Organic tin chloride, such as 12SnCIx, (C1la) 5n
Bra, (CIla) xSnBra, (CIla
) asnBr, (Calls) 5snBr, (C1la) m5nFx, (C11
, ) 5snF, (Calls) zsnFa.

(C211s) 5SnF, (Cslls) 5s
Organic tin fluoride such as nF, or (C1ls) Sn
1m, (CILs) 1snlx, (C1ls)
asnl.

(cans) zst++a, (cans) 5sn
Organic tin fluorides such as 1 and various other organic tin fluorides can be preferably used.

In the present invention, when using an organic tin compound, one type may be used, or a plurality of types may be used in combination. In particular, in the atmospheric pressure CVD method, (C)+3
) 1snc1i, (c4ns) 1snclz% and other compounds that have a relatively low temperature and high vapor pressure are particularly preferred.

The organic tin compound is brought into contact with the glass substrate as a vapor or as a liquid obtained by dissolving the organic tin compound in an appropriate organic solvent.

When applied as a vapor, for example, a method is adopted in which the vapor of the tin compound is fed under pressure using a carrier gas, and this vapor is discharged from the tip of a CVD discharge nozzle toward the glass substrate surface.Also, it is applied as a liquid. In this case, for example, a method is employed in which a liquid of an organic tin compound is sprayed onto the glass substrate surface using a spray gun.

The present invention is characterized in that moisture, that is, water or steam, is present when the organic tin compound undergoes a thermal decomposition reaction.

For example, water vapor may be mixed into the path of the carrier gas that pumps the vapor of the metal tin compound to the glass substrate surface, or it may be supplied through a separate path from the carrier gas at the point where the carrier gas contacts the glass. Water vapor is allowed to be present when the vapor of the compound contacts the glass substrate surface.

Alternatively, the organotin compound spray solution may contain water, or the organotin compound spray solution may be mixed with a water spray solution of a different type, so that the vapor of the organotin compound may come into contact with the glass substrate surface. Moisture may be present at the time of contact. In the case of the normal pressure CVD method, considering the efficiency, it is best to mix organic tin compound vapor and water vapor into a carrier gas such as air or inert gas and discharge it onto the glass substrate surface using the pressure of the carrier gas. be. Although the ratio of water present depends on the equipment used, it is preferable that the ratio of the water supplied to the tin of the organic tin compound supplied to the glass substrate surface, that is, the water/tin (molar ratio), is in the range of about 1 to 1000. In the case of general atmospheric pressure CVD equipment, the water/tin molar ratio is 0 to 100. In the case of a spray method, the optimum range varies widely depending on the equipment, but a range of 10 to 500 is suitable. If the molar ratio of water/tin is lower than 1, the effect of adding water will not be sufficiently expressed, and the film formation rate will be the same as when no water is added, which is undesirable.
Since the film forming rate has reached its upper limit, adding too much does not increase the film forming rate and only increases the haze of the film, which is not preferable. However, for applications such as solar cell substrates, especially for the purpose of forming films with high haze, a water/tinide range of 100 to 1000 can also be used, and in the normal pressure CVD method, a range of 10 to 300 is also usable. The range is appropriate.

The temperature of the glass substrate when forming the tin oxide transparent conductive film on the glass substrate surface is generally preferably 400° C. or higher and lower than the thermal deformation temperature of the glass substrate in terms of reaction efficiency, film deposition efficiency, film performance, etc. In the present invention, in order to adjust the conductivity of the tin oxide film, a fluorine component, an antimony component, etc. may be present during the thermal decomposition oxidation reaction of the organic tin compound.

Specifically, the vapor or liquid of an organic tin compound is mixed with hydrofluoric acid,
Either a dopant-imparting component such as ammonium fluoride, trifluoroacetic acid, antimony pentachloride, or tributyl antimony is mixed and applied to the glass substrate surface, or a dopant-imparting component is directed to the glass substrate surface separately from the vapor or liquid of an organic tin compound. The vapor or liquid and the dopant-imparting component are mixed on a glass substrate, or the like, so that a fluorine component, an antimony component, etc. are allowed to coexist during the thermal decomposition oxidation reaction of the organotin compound.

[Function] In the present invention, the effect of improving the film formation speed without generating haze by intervening moisture when the organic tin compound undergoes a thermal decomposition oxidation reaction is not necessarily clear; In particular, it acts to accelerate the hydrolysis reaction when decomposing organotin compounds containing halogens, thereby increasing the film formation rate, but at the same time, since an organic functional group is also bonded to tin, it is difficult to use tin tetrachloride. It is presumed that the particles will not grow to a gigantic size as in the case.

[Example] Next, examples of the present invention will be described.

Example 1 A glass substrate on which a silicon oxide alkali barrier film with a thickness of about 1000 mm was formed was heated to about 520°C, and dimethyldichlorotin [(C1
13) A tin oxide film was formed by atmospheric pressure CVD using asncIal vapor and water vapor. At this time, carrier gas (C113) is supplied to the glass substrate surface from a CVD nozzle for each sample.
Molar ratio with 1,0 (11,0/(Clla) zsnc
l□) was varied in various ways. The thickness of the tin oxide film formed by this method and the ratio of intervening water, i.e. 1IaO/
(C1la) The relationship between the ratio of zsncla and film thickness is shown in FIG. Similarly, 11□0/ (C1ls) z
The relationship between Snclz ratio and specific resistance is shown in Figure 2, and 11g
The relationship between the ratio of 0/(C1lff)1sncI and haze is shown in FIG.

As is clear from FIG. 1, it is recognized that the thickness of the tin oxide film increases as the amount of water added increases. Furthermore, it is recognized from FIG. 2 that the electrical properties of the tin oxide film as a conductive film do not deteriorate even when water is added.

Note that the Δ mark in FIG. 1 indicates the result when nitrogen was used as the carrier gas, and the O mark indicates the result when air was used. From FIG. 1, there is no difference in the relationship between the film thickness and the water addition ratio between the two. This result shows that the moisture contained in the atmosphere is completely insufficient for adding water.

Figure 3 shows the results of measuring changes in haze value when too much water is added.As is clear from the figure, adding too much water causes an increase in haze, and is generally not Appropriate. However, in recent years, conductive films with a slight haze are sometimes preferred as solar cell substrates, and it is recognized that forming films with the addition of a large excess of water is extremely effective for such applications. .

Example 2 A glass substrate on which a silicon oxide alkali barrier film with a film thickness of about 1000 mm was formed was heated to about 520°C, and dimethyldichlorotin [(CHi
3) zsncl□] and water were dissolved in ethanol and a tin oxide film was formed by a spray method. At this time, for each sample, a carrier gas is supplied to the glass substrate surface from a spray nozzle (C11a) as port CI□ and 11
Ratio to 80 (llzO/ (C1li) aSnCI□
) were varied in various ways. Thickness of tin oxide film formed by this method and percentage of intervening moisture.

That is, the relationship between the ratio of IIJ/(C1la) gsncla and the film thickness is shown in FIG. Similarly, IIaO/ (
C1la) The relationship between the ratio of zsnclg and specific resistance is shown in the sixth
Shown in the figure.

As is clear from FIG. 4, it is recognized that the thickness of the tin oxide film increases as the amount of water added increases. Moreover, it is recognized from FIG. 5 that the electrical properties of the tin oxide film as a conductive film do not deteriorate even if water is added.

[Effects of the Invention] According to the present invention, in a chemical film forming method, an organic tin compound,
In particular, it becomes possible to rapidly form a tin oxide transparent conductive film with low haze on a glass substrate using an organic tin compound containing halogen.

It is also possible to form a film with haze by appropriately changing the amount of water, and by applying this method, it is also possible to form a tin oxide transparent conductive film that is suitable for use in conductive substrates for solar cells. It is.

Furthermore, the effect of the present invention is applied to a mixed system of an organic tin compound and a tin halide that does not contain halogen (for example, a chemical film formation method of a tin oxide film using a mixture of trimethyltin and tin tetrachloride as a starting material), Adding an appropriate amount of water to the system is extremely effective from the viewpoint of increasing the film formation rate.

[Brief explanation of drawings]

Figure 1 is a graph of the relationship between the film thickness of the tin oxide transparent conductive film and the ratio of llgo, / (CHi) *5nCIx by normal pressure CVD method, and Figure 2 is the relationship between the specific resistance of the tin oxide transparent conductive film and the tin transparent conductive film. resistivity and llgo, / (C113) 1snc
Figure 3 is a graph showing the relationship between the haze of the oxidized transparent conductive film and the ratio of 1IaO/(C1lil asnclz), and Figure 4 is the relationship between the film thickness of the tin oxide transparent conductive film made by spraying and the ratio 1120/ (C1l:+l asnc
FIG. 5 shows a graph of the relationship between the specific resistance of the tin oxide transparent conductive film and the ratio of 1+2o,/(Clla)asnclg. 0 700; aη @zO/cs, J, 5n (flJf: 83 countries

Claims (2)

[Claims] (1) In a method of forming a tin oxide transparent conductive film on the glass substrate surface by a thermal decomposition oxidation reaction by bringing vapor and/or liquid of an organic tin compound into contact with the heated glass substrate surface,
A method for forming a tin oxide transparent conductive film, which comprises intervening moisture during the above-mentioned thermal decomposition oxidation reaction. (2) The method for forming a tin oxide transparent conductive film according to claim 1, wherein the organotin compound is an organotin compound containing a halogen.