WO2014069487A1

WO2014069487A1 - Method for forming thin film

Info

Publication number: WO2014069487A1
Application number: PCT/JP2013/079322
Authority: WO
Inventors: 誠二東
Original assignee: 旭硝子株式会社
Priority date: 2012-10-31
Filing date: 2013-10-29
Publication date: 2014-05-08
Also published as: JPWO2014069487A1

Abstract

To improve the film formation rate when an alumina thin film is formed on a glass substrate using an atmospheric pressure CVD method. A method for forming an alumina thin film on a glass substrate using an atmospheric pressure CVD method, which is characterized in that an alumina thin film is formed on a glass substrate that is held at a temperature from 500°C to 800°C (inclusive) by supplying, onto the glass substrate, a starting material gas that contains aluminum chloride and an alcohol having 4 or less carbon atoms.

Description

Thin film formation method

The present invention relates to a thin film forming method. Specifically, the present invention relates to a method for forming an alumina thin film on a glass substrate using atmospheric pressure CVD.

Alumina thin films have excellent chemical and mechanical durability and have excellent electrical insulation properties, and are therefore widely used as surface coatings for improving durability and insulating coatings between conductive films.
Moreover, when manufacturing a thin film solar cell, it is also used as an intermediate refractive index layer formed between a glass substrate forming a transparent substrate of the thin film solar cell and a tin oxide film forming a transparent conductive film.

There are a sputtering method, a spray method, a CVD method and the like as a method for forming an alumina thin film. The sputtering method is disadvantageous in terms of equipment cost because it requires a high vacuum, and when the spray method is used, it is difficult to form a dense film and it is difficult to control the film thickness on the order of several nm. On the other hand, the CVD method is suitable for industrial film formation because it can be formed under a wide range of pressure conditions from vacuum to atmospheric pressure, and the formed film is dense and the film thickness can be easily controlled. .

In the case of forming an alumina thin film by a CVD method, conventionally, a mixed gas of aluminum chloride, carbon dioxide, and hydrogen is sprayed onto a heated substrate (see Non-Patent Document 1).
In this method, water is generated by the reaction of carbon dioxide and hydrogen (CO ₂ + H ₂ = H ₂ O + CO) with aluminum chloride to produce aluminum. However, the water generation reaction generally requires a high temperature of about 800 to 1000 ° C., and many glass substrates need to be heated to a higher temperature beyond the softening point, thereby obtaining a good alumina thin film. There are issues that cannot be solved.

Non-patent document 2 proposes a method of forming an alumina thin film by CVD by directly supplying water vapor and aluminum chloride to a substrate of 600 ° C. or lower. However, as disclosed in Patent Document 1, water vapor and aluminum chloride are very reactive, and water vapor and aluminum chloride are used as raw materials for producing alumina fine powder by utilizing the high reactivity. Yes. Therefore, in the method of Non-Patent Document 2, a reaction between water vapor and aluminum chloride occurs before the raw material gas reaches the substrate, forming an alumina fine powder, which significantly reduces the film formation rate. This causes serious problems in production, such as the fact that alumina fine powder is mixed and a dense film cannot be obtained, and the exhaust nozzle of the CVD apparatus is blocked by the alumina fine powder. The above phenomenon is particularly noticeable when the CVD method is performed in an environment with a high pressure such as atmospheric pressure.

International Publication WO01 / 047812

In the present invention, in view of the above-mentioned problems in the prior art, there is a problem of improving the film formation rate when an alumina thin film is formed on a glass substrate using an atmospheric pressure CVD method.

In order to solve the above problems, the present inventors searched for various raw material systems. By using aluminum chloride and predetermined lower alcohols as raw materials, even when film formation was performed by atmospheric pressure CVD, It was found that a film forming process with a high film forming rate and almost no powder generation can be realized.

The present invention has been made on the basis of the above-described knowledge, and is a method for forming an alumina thin film on a glass substrate by using an atmospheric pressure CVD method, and includes a raw material containing aluminum chloride and an alcohol having 4 or less carbon atoms. A thin film forming method is provided, wherein a gas is supplied onto a glass substrate maintained at a temperature of 500 ° C. or higher and 800 ° C. or lower to form an alumina thin film on the glass substrate.

In the present invention, the source gas preferably further contains an inert gas.
In the present invention, the source gas supplied onto the glass substrate may be a source gas in which the aluminum chloride and the alcohols are mixed in advance, and the gas containing the aluminum chloride and the alcohols A mixed gas formed by mixing a gas containing the gas immediately above the glass substrate may be used. Hereinafter, a raw material gas in which the aluminum chloride and the alcohols are mixed in advance is referred to as a “premix raw material gas”, and the aluminum chloride-containing gas and the alcohol-containing gas are mixed immediately above the glass substrate. The mixed gas is referred to as “postmix raw material gas”.

In the present invention using the premix source gas, the molar ratio of alcohols to aluminum chloride (alcohol / aluminum chloride) in the premix source gas is preferably 1 or more and 6 or less, and 1.5 or more and 4. More preferably, it is 5 or less.
The aluminum chloride concentration in the premix raw material gas is preferably 0.02 to 6 mol%.
Furthermore, the moisture concentration in the raw material gas is preferably 2 mol% or less.

In the present invention using a postmix source gas, the postmix source gas has an aluminum chloride-containing gas and an alcohol-containing gas in which the molar ratio of alcohol to aluminum chloride (alcohol / aluminum chloride) is 4 or more. A mixed gas formed by mixing at a ratio is preferable, and a mixed gas formed by mixing at a ratio of 4 to 50 is more preferable.
Further, the postmix source gas is preferably a postmix source gas in which an aluminum chloride-containing gas and an alcohol-containing gas are mixed at a ratio such that the aluminum chloride concentration is 0.02 to 6 mol%.
Furthermore, the water concentration of the postmix raw material gas is preferably 2 mol% or less.

In this invention, it is preferable that the temperature of the said glass substrate to which source gas is supplied is 500 degreeC or more and 650 degrees C or less.
In the present invention, the alcohol contained in the raw material gas is preferably at least one selected from the group consisting of methanol, ethanol, isopropanol, and butanol.
Further, the thickness of the alumina thin film formed on the glass substrate is preferably 10 to 100 nm.

According to the present invention, an alumina thin film can be formed on a glass substrate at a high film formation rate by using atmospheric pressure CVD, and a fine alumina thin film can be formed because almost no alumina fine powder is generated.

Hereinafter, the method for forming a thin film of the present invention will be described.

In the method for forming an alumina thin film of the present invention, a raw material gas containing aluminum chloride and an alcohol having 4 or less carbon atoms is maintained at a temperature of 500 ° C. or higher and 800 ° C. or lower using an atmospheric pressure CVD method. An alumina thin film is formed on the glass substrate.
As described above, in the method described in Non-Patent Document 1, when an alumina thin film is formed by CVD, alumina generated by reacting water generated by the reaction of carbon dioxide and hydrogen with aluminum chloride. . However, the water generation reaction generally requires a high temperature of about 800 to 1000 ° C.
In contrast, in the method for forming an alumina thin film of the present invention, alumina is formed by a chemical reaction between aluminum chloride represented by the following formula and alcohols (represented by ROH).
AlCl ₃ + 3ROH = Al (OR) ₃ + 3HCl (1)
Al (OR) ₃ + AlCl ₃ = Al ₂ O ₃ + 3RC1 (2)
The reaction (1) proceeds at 200 ° C. or higher.
On the other hand, the reaction (2) proceeds gradually from around 300 ° C., and the raw material decomposition efficiency becomes almost 100% at 500 ° C. or higher, so that the raw material use efficiency is improved. Therefore, what is necessary is just to hold | maintain a glass substrate to the temperature of 500 to 800 degreeC at the time of implementation of a normal pressure CVD method. In the method described in Non-Patent Document 2 in which water vapor and aluminum chloride are directly supplied and reacted, the reaction rate is very fast and fine alumina powder is generated in the gas phase. In the present invention, the reaction (2) above Hardly progresses on the substrate, so almost no alumina fine powder is generated.
The reason why the glass substrate is held at a temperature of 800 ° C. or lower is that the atmospheric pressure CVD method is performed in a temperature range that does not greatly exceed the softening point of the glass substrate. Therefore, the upper limit of the holding temperature of the glass substrate of atmospheric pressure CVD method changes with glass substrates to be used. For example, when using a soda lime glass substrate, it is preferable to hold | maintain a glass substrate at the temperature of 650 degrees C or less.

In the present invention, alumina means aluminum oxide (Al ₂ O ₃ ), and the aluminum oxide produced by the atmospheric pressure CVD method is usually amorphous alumina.
In the present invention, the gas of aluminum chloride (AlCl ₃ ) is generated by reacting a vaporized aluminum chloride, an aluminum compound such as metal aluminum or aluminum oxide, and a reactive chlorine compound such as chlorine or hydrogen chloride. Aluminum chloride gas is used.
The alcohol having 4 or less carbon atoms used in the present invention means an organic compound having 4 or less carbon atoms having one or more alcoholic hydroxyl groups, and is preferably a compound having a relatively low boiling point than being used as a gas. The alcohol having 4 or less carbon atoms is preferably an alkanol having 4 or less carbon atoms represented by ROH (R is an alkyl group having 4 or less carbon atoms), and examples thereof include methanol, ethanol, isopropyl alcohol (IPA), and butanol. . Of these, methanol, ethanol, and IPA are particularly preferable because they generate particularly little alumina fine powder and are inexpensive. Two or more types of alcohols having 4 or less carbon atoms in the raw material gas may be used. Hereinafter, unless otherwise specified, alcohols having 4 or less carbon atoms are simply referred to as alcohols.
In the present invention, the inert gas refers to a gas that does not have the possibility of inhibiting the alumina formation reaction and does not have the possibility of being decomposed or altered under conditions such as temperature in the alumina formation reaction. The inert gas may be composed of two or more components. The boiling point of the substance that becomes the inert gas is preferably lower than that of alcohols, and a substance having a boiling point of room temperature or lower is preferable. Examples of the inert gas include nitrogen gas, rare gases such as helium and argon, and air. Nitrogen gas is particularly preferable as the inert gas. Further, as will be described later, it is preferable to use an inert gas having a low water content as the inert gas.

In the present invention, the aluminum chloride-containing gas is preferably a gas obtained by diluting an aluminum chloride gas with an inert gas. Specifically, for example, an aluminum chloride-containing gas is obtained by heating aluminum chloride in a container, introducing an inert gas into the container, and taking out the aluminum chloride gas diluted with the inert gas. The aluminum chloride-containing gas is preferably maintained at a temperature at which aluminum chloride does not condense in a transfer means such as a pipe.
The alcohol-containing gas may be a gas alone, but the alcohol-containing gas is also preferably a gas obtained by diluting an alcohol with an inert gas. Specifically, for example, an alcohol-containing gas can be obtained by bubbling an inert gas through the alcohol in the container and taking out the alcohol gas diluted with the inert gas. The alcohol-containing gas is also preferably maintained at a temperature at which it does not liquefy in a transfer means such as a pipe.

The premix source gas in the present invention is preferably a mixed gas obtained by mixing the aluminum chloride-containing gas and the alcohol-containing gas. This mixed gas may be further diluted with an inert gas. Since it is not preferable that the premix source gas reacts with the aluminum chloride and the alcohol before being supplied onto the glass substrate, the reaction between the two starts at 300 ° C. as described above in the transfer means such as in the pipe. It is preferably maintained at a low temperature and a temperature at which condensation such as aluminum chloride does not occur.

When the premix source gas is used as the source gas in the present invention, the molar ratio of alcohols to aluminum chloride (alcohols / aluminum chloride) in the premix source gas is not particularly limited, and generation of fine alumina powder is suppressed. Is done. However, when the molar ratio is less than 1, the film formation rate is slow, and it is difficult to form a film at a practical speed. On the other hand, when the molar ratio is larger than 6, the film formation rate is slow, and it is difficult to form a film at a practical speed. This is considered to be because the amount of alcohols that do not contribute to the reaction increases to suppress the reaction represented by the formula (1).
Therefore, the molar ratio of alcohol to aluminum chloride in the premix raw material gas is preferably 1 or more and 6 or less, and particularly preferably 1.5 or more and 4.5 or less.

The aluminum chloride concentration in the premix raw material gas is preferably 0.02 to 6 mol%. If the aluminum chloride concentration is lower than 0.02 mol%, the film formation rate tends to be lowered to a level where it is not practical. On the other hand, when the aluminum chloride concentration is higher than 6 mol%, alumina fine powder is likely to be generated. The aluminum chloride concentration in the premix raw material gas is more preferably 0.02 to 2 mol%, and further preferably 0.02 to 1 mol%.
Furthermore, when the amount of water in the premix raw material gas increases, alumina fine powder is likely to be generated by the reaction between aluminum chloride and water. For this reason, the water content in the premix raw material gas is preferably 2 mol% or less, more preferably 1 mol% or less, and most preferably substantially zero. For this reason, it is preferable to use an inert gas having a low moisture content as well as reducing the moisture contained in the raw materials such as using alcohols having a low moisture content.

The produced premix source gas is transferred to the vicinity of the glass substrate by transfer means such as piping, and is supplied onto the heated glass substrate from supply means such as a nozzle. Further, the premix source gas may be formed in the vicinity of the atmospheric pressure CVD apparatus or in the atmospheric pressure CVD apparatus. Furthermore, the aluminum chloride-containing gas and the alcohol-containing gas may be mixed in an ejection nozzle having a mixing means, and the generated mixed gas may be immediately ejected from the ejection nozzle.
A plurality of supply means such as nozzles may be provided on the glass substrate. For example, when the area of the relatively moving glass substrate is large, the premix raw material gas can be supplied by arranging a plurality of nozzles in a direction perpendicular to the moving direction.

The postmix raw material gas in the present invention is preferably a mixed gas produced by using the aluminum chloride-containing gas and the alcohol-containing gas and mixing the two gases immediately above the glass substrate. The mixing of both gases is preferably performed outside a transfer means such as a pipe. For example, there are two nozzles for ejecting an aluminum chloride-containing gas and nozzles for ejecting an alcohol-containing gas that are installed close to each other so that the gas ejected from these nozzles is mixed by collision mixing or the like. The gases can be mixed outside their transfer means. By mixing the two gases in an open space near the glass substrate, the raw material gas generated by the mixing is immediately supplied onto the heated glass substrate, whereby an alumina thin film is formed on the glass substrate. Can be formed.
As in the case of using the premix source gas, a plurality of supply means such as nozzles may be provided on the glass substrate. For example, when the area of the relatively moving glass substrate is large, a plurality of the two nozzle combinations can be arranged in a direction perpendicular to the moving direction to supply the postmix raw material gas.

When a postmix source gas is used as the source gas in the present invention, the molar ratio of alcohols to aluminum chloride (alcohols / aluminum chloride) in the postmix source gas is not particularly limited, and generation of alumina fine powder is suppressed. The However, the postmix source gas has a shorter mixing time of aluminum chloride and alcohols than the premix source gas, and in many cases the mixing zone is an open system, so that aluminum chloride and alcohols are in the reaction zone. It is easy to deviate without being supplied to (on a heated glass substrate). For this reason, it is preferable to relatively increase the proportion of alcohols, and it is preferable to mix the aluminum chloride-containing gas and the alcohol-containing gas so that the molar ratio is 4 or more. When the molar ratio is less than 4, the film formation rate becomes slow, and it is difficult to form a film at a practical speed.
On the other hand, when the postmix raw material gas is used, the occurrence of problems due to excessive alcohols is less than when the premix raw material gas is used. This is because alcohols are likely to deviate outside the reaction zone as described above, and thus there is less risk of reaction suppression due to excess alcohols. However, a large excess of alcohol no longer contributes to improving the film formation rate or suppressing the generation of alumina fine powder, and the production cost increases due to the use of a large excess of alcohol. In addition, due to the increase in alcohols present in the atmosphere in which the atmospheric pressure CVD method is performed, impurities such as carbon are likely to be generated in the formed alumina thin film. Therefore, the upper limit of the molar ratio is preferably 50. Therefore, when using a postmix raw material gas, it is more preferable to mix the aluminum chloride-containing gas and the alcohol-containing gas so that the molar ratio of the alcohol to the aluminum chloride is 4 or more and 50 or less. It is more preferable to mix so that it becomes.

The aluminum chloride-containing gas and the alcohol-containing gas are preferably mixed so that the aluminum chloride concentration in the postmix raw material gas is 0.02 to 6 mol%. If necessary, an inert gas can be further mixed to adjust the aluminum chloride concentration to the above range. If the aluminum chloride concentration is lower than 0.02 mol%, the film formation rate tends to be lowered to a level where it is not practical. On the other hand, when the aluminum chloride (AlCl ₃ ) concentration is higher than 6 mol%, fine alumina powder tends to be generated. The aluminum chloride-containing gas and the alcohol-containing gas are more preferably mixed so that the concentration of aluminum chloride in the postmix raw material gas is 0.02 to 2 mol%, and 0.02 to 1 mol%. It is further preferable to mix them.
Furthermore, when the water content in the postmix raw material gas becomes high, alumina fine powder tends to be generated due to the reaction between aluminum chloride and water. For this reason, it is preferable to mix the aluminum chloride-containing gas, the alcohol-containing gas, and, if necessary, an inert gas so that the water content in the postmix raw material gas is 2 mol% or less, and it is 1 mol% or less. It is more preferable to mix so that the moisture content of all the gases is substantially zero, and it is most preferable to mix them. For this reason, it is preferable to use an inert gas having a low moisture content as well as reducing the moisture contained in the raw materials such as using alcohols having a low moisture content.

The glass substrate on which the alumina thin film is formed by the method of the present invention is not particularly limited, and various glass substrates can be used depending on the purpose of forming the alumina thin film.
Specific examples of the glass substrate include glass plates made of soda lime silicate glass, aluminosilicate glass, borate glass, lithium aluminosilicate glass, quartz glass, borosilicate glass, alkali-free glass, and other various glasses. Can be used. The thickness of the glass substrate is not particularly limited, but is preferably 0.2 to 10 mm.
When an alumina thin film is formed as an intermediate refractive index layer formed between a glass substrate forming a transparent substrate of a thin film solar cell and a tin oxide film forming a transparent conductive film, the thickness of the glass substrate is 0. It is preferably from 2 to 6.0 mm from the viewpoint of strength and transmittance.
In the case of a glass substrate made of glass containing sodium such as soda lime silicate glass or a glass substrate made of low alkali content glass, in order to minimize the diffusion of alkali components from the glass, A silica (SiO ₂ ) film, titania (TiO ₂ ) film, tin oxide (SnO ₂ ) film, or the like is preferably formed in advance as an alkali barrier layer with a thickness of about 1 to 100 nm. In addition, when the film formation rate is slow, an alkali barrier layer is formed in advance because the alkali component on the glass substrate, particularly the sodium component, may react with the reaction raw material and the film thickness may not be uniform. It is preferable.

The thickness of the alumina thin film formed by the method of the present invention is preferably 10 to 100 nm, and more preferably selected from this range according to the purpose of forming the alumina thin film. For example, when an alumina thin film is formed as a surface coat for improving durability, the film thickness is preferably 10 to 50 nm. When an alumina thin film is formed as an insulating coat between conductive films, the film thickness is preferably 20 to 100 nm. When an alumina thin film is formed as an intermediate refractive index layer formed between a glass substrate and a tin oxide film forming a transparent conductive film, the film thickness is preferably 50 to 100 nm.

Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to this.

(Examples 1 to 12)

(Example 1)
An alumina thin film was formed on a glass substrate coated with a silica film having a thickness of 30 nm by an atmospheric pressure CVD method using an atmospheric pressure CVD apparatus (deposition width 150 mm).
A stainless steel container containing aluminum chloride (AlCl ₃ ) was heated to 150 ° C., and the aluminum chloride gas evaporated by sublimation was diluted with dry nitrogen gas to obtain an aluminum chloride-containing gas, which was conveyed to an atmospheric pressure CVD apparatus. Similarly, a stainless steel container containing ethanol as an alcohol having 4 or less carbon atoms was bubbled with dry nitrogen gas at 25 ° C. to obtain an ethanol-containing gas, which was pressurized and conveyed to an atmospheric pressure CVD apparatus. The water content of these aluminum chloride-containing gas and ethanol-containing gas was substantially zero.
The aluminum chloride-containing gas and the ethanol-containing gas were conveyed to a postmix type source gas supply means installed in an atmospheric pressure CVD apparatus. The postmix type raw material gas supply means includes an aluminum chloride-containing gas jet nozzle and an ethanol-containing gas jet nozzle, and has a structure in which both jetted gases are collided immediately after jetting. This source gas supply means was positioned immediately above the glass substrate in the atmospheric pressure CVD apparatus so that the flow of the mixed gas collided with the glass substrate surface. Further, the glass substrate was moved in one direction at a speed of 0.5 m / min so that an alumina thin film having a width of 150 mm could be uniformly formed on the glass surface.

Supplying the aluminum chloride-containing gas and the ethanol-containing gas to the atmospheric pressure CVD apparatus having the above configuration, mixing both gases immediately above the glass substrate maintained at a substrate temperature of 600 ° C., and supplying the mixture onto the glass substrate, An alumina thin film was formed. The following table shows the AlCl ₃ concentration [mol%] in the aluminum chloride-containing gas, the alcohol concentration [mol%] in the ethanol-containing gas, and the molar ratio of alcohol to AlCl ₃ in the mixed gas (alcohols / AlCl ₃ ). It was shown in 1.
Furthermore, the deposition rate (nm · m / min) of the alumina thin film was measured by the following procedure.
Apply a thin heat-resistant masking agent in advance on a glass substrate coated with a silica film, and after forming an alumina thin film, remove part of the alumina thin film by lift-off and palpate the difference between the removed part and the edge of the alumina thin film. It measured with the type | mold level | step difference meter (DEKTAK). The film formation rate was calculated by multiplying the measured value by 0.5 m / min, which is the glass conveyance speed.
The raw material deposition efficiency (%) was evaluated by the following procedure.
The number of moles of Al deposited per unit time on the glass substrate is calculated from the thickness of the formed alumina thin film, the conveyance speed of the glass substrate, and the width of the glass substrate, and the calculated value is applied to the glass substrate per unit time. Raw material deposition efficiency was evaluated by dividing by the amount (number of moles) of AlCl ₃ sprayed.
The results are shown in Table 1 below.
Moreover, in order to confirm the presence or absence of the generation | occurrence | production of the alumina fine powder at the time of atmospheric pressure CVD method implementation, the atmospheric pressure CVD apparatus was observed from the window of the side part of this apparatus, but generation | occurrence | production of the alumina fine powder was not recognized. Further, after the formation of the alumina thin film, the raw material gas supply means was taken out from the atmospheric pressure CVD apparatus and the state of adhesion of the alumina fine powder to the bottom surface portion was confirmed, and it was confirmed that almost no alumina fine powder was adhered.

(Examples 2 to 14)
AlCl ₃ concentration, the molar ratio of alcohol with respect to alcohol concentration, AlCl ₃ (alcohol / AlCl _3), and, as a condition showing a glass substrate temperature in Table 1, the alumina by atmospheric pressure CVD (Al ₂ O ₃ ) A thin film was formed. Tables 1 and 2 show the thin film formation rate, the raw material deposition efficiency, and the presence or absence of generation of alumina fine powder.
In Examples 10, 13, and 14, IPA was used instead of ethanol as an alcohol having 4 or less carbon atoms, and in Example 11, methanol was used instead of ethanol. In Example 12, water vapor (H ₂ O) was supplied instead of alcohols having 4 or less carbon atoms. For Example 12, the values in the column of alcohol concentration and alcohol / AlCl _{3 in} the table below are the water vapor (H ₂ O) concentration and the molar ratio of water vapor (H ₂ O) to AlCl ₃ .

In each of Examples 1 to 3, Example 5 to 9, and Examples 13 to 14, almost no alumina fine powder was generated. Among them, Examples 1 to 3, Examples 5 to 6, Examples 10 to 11, and Examples 13 to 14 all have a high film formation rate of 15 nm · m / min or more, and the material deposition efficiency is 10% or more. It was high. Almost no alumina fine powder was generated.
In Example 4 where the substrate temperature was lower than 500 ° C., the film formation rate and the raw material deposition efficiency were low. In Example 12 in which water vapor (H ₂ O) was supplied instead of alcohols having 4 or less carbon atoms, a large amount of alumina fine powder was generated.

(Example 15 to Example 19)
In Examples 15 to 19, an atmospheric pressure CVD apparatus having the same configuration as the atmospheric pressure CVD apparatus described in Example 1 using the same postmix raw material as in Example 1 and having a film forming width of 300 mm was used. Also, instead of directly heating and vaporizing the stainless steel container containing aluminum chloride, it is diluted with dry nitrogen gas by blowing chlorine gas to a Hastelloy container packed with aluminum pellets heated to 300 ° C. to produce AlCl _3. A gas containing aluminum chloride was produced. In Example 19, alcohols having 4 or less carbon atoms were not supplied.
AlCl ₃ concentration, the molar ratio of alcohol with respect to alcohol concentration, AlCl ₃ (alcohol / AlCl _3), and, the glass substrate temperature conditions shown in Table 3, were formed of alumina thin film by atmospheric pressure CVD It was. Table 3 shows the results of the film formation rate, raw material deposition efficiency, and the presence or absence of generation of alumina fine powder.

In each of Examples 15 to 18, the film formation rate was as high as 15 nm · m / min or more, and the material deposition efficiency was as high as 10% or more. Almost no alumina fine powder was generated. In Example 19 where no alcohol having 4 or less carbon atoms was supplied, an alumina thin film was not formed.

(Example 20 to Example 26)
In Examples 20 to 26, an atmospheric pressure CVD apparatus having a film forming width of 300 mm similar to that described in Example 1 was used. Also, instead of directly heating and vaporizing a stainless steel container containing aluminum chloride, a method of generating AlCl ₃ by blowing chlorine gas to a Hastelloy container packed with aluminum pellets heated to 300 ° C. Manufactured.
The aluminum chloride-containing gas and the ethanol-containing gas were mixed by a mixer installed in an atmospheric pressure CVD apparatus, and the mixed gas was ejected from a nozzle and supplied onto the substrate.
AlCl ₃ concentration, the molar ratio of alcohol with respect to alcohol concentration, AlCl ₃ (alcohol / AlCl _3), and, the glass substrate temperature conditions shown in Table 4, were formed in the alumina thin film by atmospheric pressure CVD It was. Table 4 shows the results of the film formation rate, raw material deposition efficiency, and the presence or absence of generation of alumina fine powder.

In all of Examples 20 to 26, the film forming rate was as high as 15 nm · m / min or more, and almost no alumina fine powder was generated. Furthermore, in all of Examples 20 to 25, the material deposition efficiency was 10% or more.

(Example 27 to Example 30)
In Examples 27 to 30, an atmospheric pressure CVD apparatus having a film formation width of 150 mm similar to that described in Example 1 was used. The aluminum chloride-containing gas was supplied by heating a stainless steel container containing AlCl ₃ to directly vaporize it and diluting with dry nitrogen gas. In addition, the aluminum chloride-containing gas and the alcohol-containing gas were mixed by a mixer installed in the atmospheric pressure CVD apparatus as in Examples 20 to 26, and the mixed gas was ejected from a nozzle and supplied onto the substrate. .
AlCl ₃ concentration, the molar ratio of alcohol with respect to alcohol concentration, AlCl ₃ (alcohol / AlCl _3), and, the glass substrate temperature conditions shown in Table 5, were formed in the alumina thin film by atmospheric pressure CVD It was. Table 5 shows the results of the film formation rate, raw material deposition efficiency, and the presence or absence of generation of alumina fine powder. In Example 27, IPA was used as an alcohol having 4 or less carbon atoms instead of ethanol, and in Examples 28 to 30, methanol was used instead of ethanol.

In each of Examples 27 to 30, the film formation rate was as high as 15 nm · m / min or more, and the material deposition efficiency was as high as 10% or more. Almost no alumina fine powder was generated.

The alumina thin film formed by the present invention has excellent properties such as a durable surface coat, an insulating coat between conductive films, and an intermediate refractive index layer formed between a glass substrate and a tin oxide film forming a transparent conductive film. Thus, the glass substrate with an alumina thin film obtained by the present invention is suitably used as a substrate for a thin film solar cell, a protective plate for a display device, a glass substrate for a semiconductor device, and the like.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2012-239864 filed on October 31, 2012 are incorporated herein as the disclosure of the specification of the present invention. It is.

Claims

A method for forming an alumina thin film on a glass substrate using an atmospheric pressure CVD method, wherein a source gas containing aluminum chloride and an alcohol having 4 or less carbon atoms is maintained at a temperature of 500 ° C. or higher and 800 ° C. or lower. And forming an alumina thin film on the glass substrate.
The method for forming a thin film according to claim 1, wherein the source gas further contains an inert gas.
The method for forming a thin film according to claim 1 or 2, wherein the source gas supplied onto the glass substrate is a source gas obtained by mixing the aluminum chloride and the alcohols in advance.
The method for forming a thin film according to claim 3, wherein a molar ratio of the alcohol to the aluminum chloride in the source gas (alcohol / aluminum chloride) is 1 or more and 6 or less.
The method for forming a thin film according to claim 3 or 4, wherein a molar ratio of the alcohol to the aluminum chloride in the source gas (alcohol / aluminum chloride) is 1.5 or more and 4.5 or less.
The method for forming a thin film according to any one of claims 3 to 5, wherein the concentration of aluminum chloride in the raw material gas is 0.02 to 6 mol%.
The method for forming a thin film according to any one of claims 3 to 6, wherein the moisture concentration in the source gas is 2 mol% or less.
The said source gas supplied on the glass substrate is a mixed gas formed by mixing the gas containing the said aluminum chloride, and the gas containing the said alcohol directly on the said glass substrate. Method for forming a thin film.
The mixed gas is a mixed gas in which the aluminum chloride-containing gas and the alcohol-containing gas are mixed at a ratio of a molar ratio of the alcohol to the aluminum chloride (alcohol / aluminum chloride) of 4 or more. The method for forming a thin film according to claim 8.
The mixed gas is a mixture in which the aluminum chloride-containing gas and the alcohol-containing gas are mixed at a ratio such that the molar ratio of the alcohol to the aluminum chloride (alcohol / aluminum chloride) is 4 or more and 50 or less. The method for forming a thin film according to claim 8 or 9, wherein the method is a gas.
The mixed gas according to any one of claims 8 to 10, wherein the mixed gas is a mixed gas in which the aluminum chloride-containing gas and the alcohol-containing gas are mixed at a ratio of aluminum chloride concentration of 0.02 to 6 mol%. The method for forming a thin film according to claim 1.
The method for forming a thin film according to any one of claims 8 to 11, wherein a moisture concentration of the mixed gas is 2 mol% or less.
The method for forming a thin film according to any one of claims 1 to 12, wherein a temperature of the glass substrate is 500 ° C or higher and 650 ° C or lower.
The method for forming a thin film according to any one of claims 1 to 13, wherein the alcohol contained in the source gas is at least one selected from the group consisting of methanol, ethanol, isopropanol, and butanol.
The method for forming a thin film according to any one of claims 1 to 14, wherein the alumina thin film formed on the glass substrate has a thickness of 10 to 100 nm.