JP2005289767A - Method of manufacturing metal oxide coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a metal oxide coating film having a uniform film thickness even when a metal oxide other than SiO<SB>2</SB>is film-formed by a liquid phase deposition method. <P>SOLUTION: In the method of manufacturing the metal oxide coating film formed by depositing the metal oxide on a base body by dipping the base body in a treating liquid to contain a metallic fluorocomplex and a scavenger for chemically capturing fluorine ion from the metallic fluorocomplex, the oxide of the metal is deposited by adding the metallic fluorocomplex to the treating liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a metal oxide film in which a metal oxide film is deposited on a substrate from a liquid phase.

  As one of the methods for forming metal oxide coatings, liquid phase deposition (Liquid Phase), which allows film formation by simply immersing the substrate in the processing solution, is performed by a self-deposition and growth type film forming reaction The applicants have so far proposed many Deposition (LPD) methods.

  This LPD method is a substance (capturing agent) that forms a more stable fluoro complex by utilizing hydrolysis equilibrium reaction of metal fluoro complex with oxide or oxyhydroxide from the treatment liquid regardless of the base material or shape. (Also referred to as an initiator) to shift the equilibrium to the oxide side in accordance with the law of mass action and to deposit and grow uniformly as a stable metal oxide thin film on the substrate. Such a reaction is represented by the following chemical formula 1 and chemical formula 2, where M is this metal.

(Chemical formula 1)
[MF _6-x (OH) _x ] ² + (6-x) H ₂ O ⇔ [M (OH) ₆ ] ² + (6-x) HF
However, x is usually an integer of 0 to 5, but it may be deviated from the stoichiometric ratio.
(Chemical formula 2)
[M (OH) ₆ ] ^2- ⇒ MO ₂

In the LPD method, first, in Formula 1, when a scavenger is added, hydrogen fluoride is consumed. Therefore, the equilibrium reaction formula of Formula 1 is shifted in the direction in which [M (OH) ₆ ] ²⁻ is generated. Then, this [M (OH) ₆ ] ²⁻ causes a dehydration condensation reaction, and a metal oxide represented by MO ₂ is deposited as shown in Chemical Formula 2.

As this scavenger, boric acid (H ₃ BO ₃ ), FeCl ₂ , FeCl ₃ , NaOH, NH ₃ , Al, Ti, Fe, Ni, Mg, Cu, Zn, Si, SiO ₂ , CaO, B ₂ O ₃ , Al ₂ O ₃ , MgO and the like are known. Even if any of the above-mentioned scavengers is used, a stable fluoro complex compound or fluoride is generated in the treatment liquid, so that precipitation is not hindered. In particular, boric acid is known not to precipitate impurities. In this method, the equilibrium reaction can be controlled by the addition amount (concentration) of the scavenger, and various metal oxides can be precipitated (see, for example, JP-A-4-338136).

  Further, as a method for adding this scavenger, the present applicant has disclosed the following in Japanese Patent Application Laid-Open No. 58-161944. In other words, after the glass is immersed in the treatment liquid, boric acid is added to the treatment liquid to maintain the silica film forming ability of the treatment liquid constant.

In addition, when depositing SiO ₂ , boric acid is continuously added to hydrofluoric acid, and the treatment liquid is circulated while performing the filtering treatment, thereby maintaining the film formation rate and stabilizing the quality. A technique for obtaining a film has been proposed (see, for example, JP-A-3-112806). In this method, continuous film formation is possible, and the waste liquid cost has been successfully reduced.

JP-A-4-338136 JP 58-161944 Japanese Patent Laid-Open No. 3-112806

The above-described LPD method can deposit various metal oxides, but metal oxides other than SiO ₂ generate a considerable amount of precipitates in the liquid due to the inherent properties of the material. If such a material is applied to the continuous film formation process shown in the prior art, a large amount of precipitates are generated not only on the substrate but also in the liquid. However, it was difficult to continuously form a film over a long period of time.

Therefore, in the case of metal oxides other than SiO ₂ , the metal oxide can be precipitated only after the initial mixing of the metal fluoro complex and boric acid until the metal oxide is not deposited in the treatment liquid. There wasn't. For this reason, there has been a problem of high costs.

  Further, in a reaction system in which a large amount of precipitates are generated in the liquid, it is difficult to obtain a uniform film because the precipitates in the liquid are taken in when the metal oxide film is formed.

The present invention has been made paying attention to such problems of the prior art. The object is to provide a method for producing a metal oxide film having a uniform film thickness even when a metal oxide other than SiO ₂ is formed in the LPD method.

  As a result of intensive studies, the inventors have been able to keep the deposition rate as constant as possible in the LPD method by adding a metal fluoro complex to the treatment liquid instead of adding a scavenger to the treatment liquid. And it discovered that it could suppress that a metal oxide precipitates in a liquid.

That is, the present invention is the invention according to claim 1,
Manufacture of a metal oxide film in which a substrate is immersed in a treatment solution that may contain a metal fluoro complex and a scavenger that chemically captures fluorine ions from the metal fluoro complex, thereby depositing the metal oxide on the substrate. In the method
It is a method for producing a metal oxide film, wherein the metal oxide is precipitated by adding the metal fluoro complex to the treatment liquid.

As invention of Claim 2,
The method for producing a metal oxide film according to claim 1, wherein the metal fluoro complex is added intermittently and / or continuously.

As invention of Claim 3,
It is a manufacturing method of the metal oxide film of Claim 1 or 2 which adjusts the addition amount of the said metal fluoro complex according to the precipitation amount of the said metal oxide.

As invention of Claim 4,
It is a manufacturing method of the metal oxide film of any one of Claims 1-3 which rock | fluctuate the said base | substrate immersed in the said process liquid.

As invention of Claim 5,
The said rocking | fluctuation is a manufacturing method of the metal oxide film of Claim 4 performed when the said metal fluoro complex is added at least.

As invention of Claim 6,
The method for producing a metal oxide film according to claim 1, wherein the scavenger is boric acid.

As invention of Claim 7,
The method for producing a metal oxide film according to any one of claims 1 to 6, wherein the metal fluoro complex is a fluoro complex of Sn.

  The present invention is characterized in that in the method for producing a metal oxide film by the LPD method, a metal fluoro complex is added to a treatment liquid to deposit a metal oxide film. As a method for adding the metal fluoro complex, it may be added intermittently or continuously. Furthermore, it is good to adjust the addition amount of a metal fluoro complex according to the precipitation amount of a film.

The conventionally known LPD method is a method of adding boric acid as a scavenger to the treatment liquid. In this case, in the case of a metal oxide other than SiO ₂ , the metal oxide is precipitated in the liquid. Could not be suppressed.

Although the details are unknown, the reason is as follows.
First, when the metal fluoro complex and the scavenger coexist, intermediates of the metal fluoro complex in which x of [MF _6-x (OH) _x ] ²⁻ has various values exist. Once this intermediate is in the form of an oxyhydroxide represented by [M (OH) ₆ ] ²⁻ , the reaction of Formula 2 described above becomes dominant. In this case, it is presumed that not only on the target substrate but also in the treatment liquid, a large amount of metal oxide precipitates and becomes a precipitate.

  The difference between the conventional technology and the present invention will be discussed in detail from the viewpoint of the chemical reaction with respect to the generation mechanism of the precipitate.

・ Method of adding scavenger (boric acid) At the beginning of adding boric acid to the treatment liquid, the amount of boric acid added was small, and the reaction to capture fluorine ions from the metal fluorocomplex was not performed sufficiently. There are many metal fluorocomplexes in the treatment liquid. When the amount of boric acid added reaches a certain level, a large amount of oxyhydroxide is generated. As a result, a large amount of the metal oxide is precipitated and becomes a precipitate.

On the other hand, in the method of adding a metal fluoro complex to the treatment liquid of the present invention, a reaction for sufficiently capturing fluorine ions from the metal fluoro complex is performed from the beginning of the addition, and the method is quickly performed. Oxyhydroxide begins to be produced. As a result, it is considered that the metal oxide is constantly and constantly deposited, and no precipitate is generated.
In addition, since there exists a possibility that a precipitate may generate | occur | produce when a large amount of metal fluoro complexes are added at once, it is preferable to adjust the addition amount of a metal fluoro complex.

  Further, regarding the lifetime of the treatment liquid, the difference between the conventional technique and the present invention will be considered in detail from the viewpoint of chemical reaction.

-Method of adding the scavenger (boric acid) In this reaction system, the metal fluoro complex is not supplied due to the precipitation of the metal oxide, so that the precipitation stops at a certain point.

-Method of adding a metal fluoro complex In contrast, in the method of the present invention, since the metal fluoro complex consumed by precipitation is supplemented, the deposition efficiency is good and the liquid life can be extended.

  In the present invention, the method for adding the metal fluoro complex may be intermittent or continuous. Moreover, you may combine intermittent addition and continuous addition. For example, at the initial stage of production, the metal fluoro complex may be added intermittently and then continuously.

  Furthermore, in order to improve the precipitation amount and uniformity of the metal oxide, the addition amount may be temporarily increased while continuously adding a certain amount of the metal fluoro complex. Moreover, the timing and amount of addition may be set as appropriate.

  As a specific method of adding a metal fluoro complex, it may be added continuously using a tubing pump or the like, or intermittently added at regular intervals using a tubing pump and a timer. May be.

  The metal fluoro complex used as the raw material for the treatment liquid is not particularly limited as long as it is a material that is stably present in the treatment liquid and can be precipitated by the presence of the scavenger. For example, metal hydrofluoric acid, metal ammonium fluoride salt, or a mixture thereof can be used. Examples of the metal include Ti, Fe, Sn, Zn, V, Zr, W, and In. Among these, when Sn is used, the effect of the present invention can be confirmed particularly remarkably.

  The initial treatment liquid in the present invention may be a mixture of a metal fluoro complex and a scavenger or only a scavenger.

  The substrate used in the present invention is not particularly limited as long as the metal oxide can be deposited on the surface from the metal fluoro complex contained in the treatment liquid. For example, what is necessary is just to select suitably from materials, such as Si, glass, ceramics, and resin, according to a use.

  The substrate is preferably washed in order to remove impurities such as organic substances on the surface before being immersed in the treatment liquid. For example, when glass is used as the substrate, pure water cleaning is preferably performed after alkali cleaning.

  As a means for bringing the substrate into contact with the treatment liquid, a jig having durability against the treatment liquid may be used to fix the substrate directly to the reaction vessel or to hang it from above. Examples of the material having durability include fluorine resin, polyethylene, polypropylene, polycarbonate, or methylpentene resin.

  In order to deposit a metal oxide having a more uniform film thickness, the substrate is preferably shaken in the treatment liquid. At this time, the peristaltic time, distance, and speed are not particularly limited. The timing of peristaltic movement may be adjusted in accordance with the timing of adding the metal fluoro complex.

  Furthermore, in order to make the treatment liquid concentration uniform, stirring or ultrasonic irradiation may be performed. The stirring of the treatment liquid is preferably performed while avoiding a region where the precipitate is deposited so that the precipitate does not approach the substrate. For example, in addition to a method of stirring the upper part of the processing liquid with a propeller or a container in which the substrate is immersed, a sub tank connected to the container by a communication pipe is provided, stirring is performed in the sub tank, and the concentration of the processing liquid is increased by natural diffusion. There is a way to make it uniform.

  According to the present invention, the film formation rate can be kept constant by adding a metal fluoro complex to the treatment liquid in the LPD method. As a result, the method for producing a metal oxide film according to the present invention makes it easy to control the process, and a uniform metal oxide film can be obtained. Also, a relatively thick metal oxide film can be obtained. Furthermore, since unnecessary precipitates in the liquid can be suppressed, the raw material cost can be reduced.

Hereinafter, the manufacturing method of the metal oxide film by this invention is demonstrated using an Example or a comparative example.
[Example 1]
Example 1 is an example in which a SnO ₂ film was formed on a Si substrate as a substrate as a metal oxide film. The manufacturing process of the metal oxide film in the present invention is shown below.

1. 1. Preparation of treatment solution 2. Preparation of substrate 3. Preparation of initial treatment solution 4. Immerse the substrate in the processing solution 5. Addition of metal fluoro complex to treatment solution 6. Picking up the substrate Substrate cleaning / drying

First, a metal fluoro complex for forming a SnO ₂ film was prepared by the following procedure. The tin fluoride powder was dissolved in hydrogen fluoride water to prepare a metal fluoro complex solution so that the Sn concentration was 1.5 mol / L. As the fluorine ion scavenger, an aqueous boric acid solution prepared at a concentration of 0.5 mol / L was used.

  The prepared metal fluorocomplex solution and boric acid aqueous solution were diluted with an appropriate amount of water to prepare a Sn concentration of 0.01 mol / L and a boric acid concentration of 0.48 mol / L as an initial treatment solution. A metal oxide film was formed on the substrate using the manufacturing apparatus conceptually shown in FIG.

After immersing the Si substrate 2 in the initial treatment liquid 1, the metal fluoro complex solution 5 was sucked up by the tubing pump 4 and added at a constant rate through the pipe 41 every 2 hours. After the substrate 2 was immersed for a predetermined time, it was pulled up, washed with pure water and dried to obtain a Si substrate 2 on which a SnO ₂ film was formed.

In addition, a masking agent is applied to the Si substrate in advance, and after the SnO ₂ film is formed, the masking agent is peeled off, and the step is applied to a stylus type surface roughness meter (Alpha-Step, manufactured by KLA-TENCOR). The thickness of the SnO ₂ film was measured. Further, the relationship between the immersion time and the thickness of the obtained SnO ₂ film was examined by sequentially changing the immersion time of the substrate, and is shown in FIG.

  From FIG. 2, it was found that when a metal fluoro complex was added to the treatment liquid of the present invention, the immersion time and the film thickness were in a directly proportional relationship. Note that when the film thickness exceeds about 800 nm, the boric acid concentration of the scavenger decreases, and even when the metal fluoro complex is added, the reaction for sufficiently capturing the metal fluoro complex cannot be performed, so the film deposition rate is decreased. It was.

  Moreover, SEM observation of the obtained metal oxide film was implemented. The observation conditions were tilted 15 degrees from the fracture surface, the acceleration voltage was 10 kV, the irradiation current was 10 μA, and the imaging magnification was 50,000 times. The obtained SEM photographs are shown in FIGS.

  From the results of FIGS. 3 to 5, it was confirmed that a metal oxide film having a uniform film thickness of 1 μm or less can be obtained.

  When the adhesiveness was evaluated by a method of peeling off vigorously after applying a transparent adhesive tape (5 mm width) to the obtained metal oxide film, the metal oxide film had adhesiveness that would not peel off. It was confirmed.

[Example 2]
Example 2 is an example in which the substrate was swung during film formation. A metal fluoro complex solution and an aqueous boric acid solution were prepared in the same procedure as in Example 1.

  The metal oxide film of Example 2 was produced by the following procedure (see FIG. 6). The initial treatment liquid was the same as in Example 1, and after the Si substrate 2 was immersed in the treatment liquid 1, it was rocked in the vertical direction by the vertical movement mechanism 6. The Si substrate 2 is connected to the shaft 61 of the vertical movement mechanism 6 by a clamp 62. The vertical movement mechanism 6 may be moved up and down by, for example, a gear / crank mechanism or a linear motor.

While the substrate 2 was immersed, the metal fluoro complex solution 5 was sucked up by the tubing pump 4 and added through the pipe 41 at a constant rate every 2 hours. After being immersed for a certain period of time, this was pulled up, washed with pure water and dried to obtain a Si substrate 2 on which a SnO ₂ film was formed.

Further, the film thickness of the obtained SnO ₂ film was measured in the same manner as in Example 1. The obtained film thickness is shown in Table 1 together with the results of Example 1. From Table 1, it was confirmed that in-plane variation was further reduced and a uniform film was obtained in the case of the presence of peristalsis as compared to the case without peristalsis.

(Table 1)
──────────────────────
Oscillation film thickness ---------------------
Example 1 None 400 ± 20 nm
Example 2 Available 530 ± 10 nm
──────────────────────

  When the adhesiveness was evaluated by a method of peeling off vigorously after applying a transparent adhesive tape (5 mm width) to the obtained metal oxide film, the metal oxide film had adhesiveness that would not peel off. It was confirmed.

  In comparison with Example 1 and Example 2, the film thickness of Example 2 that was perturbed was larger, but this was because the metal oxide was efficiently deposited in the vicinity of the substrate by the perturbation. it is conceivable that.

[Comparative Example 1]
The manufacturing process of the metal oxide film in Comparative Example 1 is shown below.

1. 1. Preparation of treatment solution 2. Preparation of substrate 3. Preparation of initial treatment solution 4. Immerse the substrate in the processing solution 5. Add boric acid to treatment solution 6. Picking up the substrate Substrate cleaning / drying

A metal fluoro complex and boric acid were prepared in the same procedure as in Example 1.
The metal oxide film of this comparative example was produced by the following procedure. An initial treatment solution was prepared by diluting a metal fluoro complex and boric acid with an appropriate amount of water and adjusting the Sn concentration to 0.03 mol / L and boric acid concentration to 0.28 mol / L. After immersing the Si substrate in the initial treatment solution, boric acid was added in a constant amount every 2 hours by a tubing pump. After immersion for a certain time, the substrate was pulled up, washed with pure water and dried to obtain a Si substrate on which a SnO ₂ film was formed.

Further, the film thickness of the obtained SnO ₂ film was measured in the same manner as in Example 1. The result is shown in FIG. From FIG. 2, when boric acid is added to the treatment liquid, the immersion time and the film thickness are in a proportional relationship, but the linearity is poor and the film thickness is limited to about 300 nm. Thereafter, the film thickness did not increase even when the substrate was continuously immersed in the treatment liquid.

  As described above, it was found from the comparison between Example 1 and Comparative Example 1 that the manufacturing method of the present invention has good film thickness controllability.

It is the schematic explaining typically an example of the manufacturing apparatus which can be used for this invention. It is a figure which shows the film-forming rate of the metal oxide film obtained in Example 1 and Comparative Example 1. 2 is a view showing an SEM photograph of a metal oxide film (film thickness: 100 nm) obtained in Example 1. FIG. It is a figure which shows the SEM photograph of the metal oxide film (film thickness of 300 nm) obtained in Example 1. It is a figure which shows the SEM photograph of the metal oxide film (film thickness of 900 nm) obtained in Example 1. It is a figure which illustrates typically a mode that the board | substrate is rock | fluctuated with the manufacturing apparatus which can be used for Example 2. FIG.

Explanation of symbols

1: treatment liquid,
2: Base (Si substrate),
3: Container,
4: Pump,
41: piping,
5: Metal fluoro complex solution,
6: Vertical movement mechanism,
61: shaft,
62: Clamp,

Claims (7)

Manufacture of a metal oxide film in which a substrate is immersed in a treatment solution that may contain a metal fluoro complex and a scavenger that chemically captures fluorine ions from the metal fluoro complex, thereby depositing the metal oxide on the substrate. In the method
A method for producing a metal oxide film, wherein the metal oxide is precipitated by adding the metal fluoro complex to the treatment liquid.   The method for producing a metal oxide film according to claim 1, wherein the metal fluoro complex is added intermittently and / or continuously.   The manufacturing method of the metal oxide film of Claim 1 or 2 which adjusts the addition amount of the said metal fluoro complex according to the precipitation amount of the said metal oxide.   The method for producing a metal oxide film according to any one of claims 1 to 3, wherein the substrate immersed in the treatment liquid is rocked.   The method for producing a metal oxide film according to claim 4, wherein the rocking is performed at least when the metal fluoro complex is added.   The method for producing a metal oxide film according to claim 1, wherein the scavenger is boric acid.   The method for producing a metal oxide film according to claim 1, wherein the metal fluoro complex is a fluoro complex of Sn.