JP2000247608A - Method for producing metal oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a thin film of a crystallized metal oxide which does not require heat treatment at a high temp. and has a relatively large film thickness, for a remarkably short time as compared to the conventional method. SOLUTION: A process for forming a thin film of a metal oxide precursor sol on the surface of a material to be coated by applying the metal oxide precursor sol obtained by using a metallic alkoxide as a main raw material on the surface of the material to be coated and a process for crystallizing the metal oxide gel by irradiating the thin film of the metal oxide gel with ultraviolet ray having <=360 nm wavelength are repeated on the surface of one material to be treated plural times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thin film of a metal oxide such as an electronic material on the surface of a substrate such as glass, ceramics, metal, and plastics, and more particularly, to a method without performing heat treatment at a high temperature. The present invention relates to a method for producing a metal oxide film for producing a crystallized metal oxide thin film.

[0002]

2. Description of the Related Art Many compounds having excellent functional properties exist in metal oxides. In particular, by forming a metal oxide into a thin film having a thickness of about several μm, for example, titanium oxide (TiO ₂ ) can be used as a material for a protective film, an antireflection film, a catalyst, or the like, and zirconium oxide (ZrO ₂ ) can be used as a material. And tin oxide (SnO ₂ ) and zinc oxide (ZnO) as materials for a protective film and a substrate, and tantalum oxide (Ta ₂ O ₅ ) as a material for a high dielectric film. Also, barium titanate (BaTiO ₃ ) or PZT (Pb (Z
r, Ti) O ₃ ) are used as ferroelectric materials, respectively. These metal oxide thin films are manufactured by a sol-gel method, a sputtering method, an MOCVD method, or the like.

When a metal oxide thin film is manufactured by a sol-gel method, for example, a TiO ₂ film is formed at 400 ° C.
It is known that anatase crystallizes at a temperature of 800 ° C. and further transforms to a rutile phase by heat treatment at a temperature of 800 ° C. The ZrO ₂ film is crystallized by heat treatment at a temperature of 700 ° C. (See Journal of the Ceramic Society of Japan, 94 , 823 (1986)). Also, S
The nO ₂ —Sb ₂ O ₃ film crystallizes at a temperature of 500 ° C. (Thin Solid F)
lms), 295 , 95-100 (1997)), 60 BaO ₃ to form and crystallize a BaTiO ₃ film.
A heat treatment at a temperature of 0 ° C. is required (Material Research Society Symposium Proceedings (Mat. Res. Soc. Symp. Pro)
c. ), Vol. 32, 157-161 (1984)). For the PZT film, a heat treatment at a temperature of 450 ° C. to 600 ° C. is required for the perovskite phase to crystallize (see Procedurals of British Ceramic Society (Proc. Br. Cer.)).
am. Soc. ), 36 , 107-121 (1985).
reference). In _{addition, La} 0.8 _{3 Sr 0.17} Mo ₃ is, 8
By heat treatment at a temperature of 00 ° C. for 2 hours (Japanese Unexamined Patent Publication No.
No. 59022), YBa ₂ Cu ₃ O _7-x is 80
Heat treatment at a temperature of 0 ° C. for 6 hours (Journal of Material Chemistry (J. Mater.
Chem. ), 1 (6), 1031-1034 (199)
1)), respectively.

[0004]

In a conventional method utilizing the conventional sol-gel method, it is possible to apply a precursor sol of a metal oxide onto the surface of an object to be coated by a single coating operation. The film thickness is very small, several tens of nanometers. For this reason, for example, in order to obtain a metal oxide thin film having a thickness of about 1 μm, an operation of applying a precursor sol to the surface of an object to be coated and 30 minutes each time It was necessary to repeat the heat treatment requiring a time of several hours to several tens of times or more.

In order to obtain a metal oxide film having a thickness of about 1 μm by sputtering or MOCVD,
It takes several hours and often requires heat treatment of the substrate.

[0006] The present invention has been made in view of the above circumstances, does not require heat treatment at a high temperature, and
A crystallized metal oxide thin film with a relatively large thickness
An object of the present invention is to provide a method for manufacturing a metal oxide film that can be formed in a much shorter time than in the past.

[0007]

The invention according to claim 1 is
Applying a metal oxide sol or a metal salt precursor sol obtained using a metal salt as a main raw material to the surface of an object to be coated,
A gel film forming step of forming a metal oxide gel thin film on the surface of an object to be coated; and a metal oxide forming a thin film by irradiating the thin film of the metal oxide gel with ultraviolet light having a wavelength of 360 nm or less. A method for producing a metal oxide film including a gel crystallization step of crystallizing a product gel, wherein the gel film forming step and the gel crystallization step are repeatedly performed on the surface of one object to be coated a plurality of times. It is characterized by.

According to a second aspect of the present invention, a precursor sol of a metal oxide obtained using a metal alkoxide or a metal salt as a main raw material is applied to the surface of an object to be coated, and a metal oxide gel is applied to the surface of the object to be coated. A gel film forming step of forming a thin film, and irradiating a patterned ultraviolet light having a wavelength of 360 nm or less to the thin film of the metal oxide gel to crystallize the metal oxide gel forming the thin film. A gel crystallization step of forming a thin film of metal oxide, and etching the thin film of metal oxide to pattern the thin film of metal oxide by a difference in etching rate between a part irradiated with ultraviolet light and a part not irradiated with ultraviolet light. In the method for producing a metal oxide film including a thin film etching step, the gel film forming step and the gel crystallization step are repeatedly performed on the surface of one object to be coated a plurality of times. And performing thin film etching process.

According to a third aspect of the present invention, in the manufacturing method according to the first or second aspect, the ultraviolet light source for irradiating the thin film of the metal oxide gel is a high-pressure mercury lamp, a low-pressure mercury lamp, an ArF It is an excimer laser, a KrF excimer laser, an excimer lamp, or synchrotron radiation. As the light source, only one type may be used, or two or more types may be used in combination.

According to the method for producing a metal oxide film according to the first aspect of the present invention, in the gel film forming step, a metal oxide sol or a metal oxide precursor sol obtained from a metal alkoxide or a metal salt as a starting material is used as the surface of the object to be coated. By applying to
A thin film of metal oxide gel is formed on the surface of the object to be coated, and in the gel crystallization step, the thin film of metal oxide gel is irradiated with ultraviolet light having a wavelength of 360 nm or less, so that the thin film absorbs ultraviolet light. Then, the metal oxide gel is crystallized by the energy. As described above, a crystallized metal oxide thin film can be obtained without performing high-temperature heat treatment. By repeating the gel film forming step and the gel crystallization step on the surface of one object to be coated a plurality of times, a metal oxide thin film having a desired film thickness can be obtained. In this case, for example, the time required for the operation of applying the precursor sol in the gel film forming step is about several tens of seconds,
Since the ultraviolet light irradiation time in the gel crystallization step is about several seconds to several minutes, it is possible to produce a metal oxide thin film having a thickness of about 1 μm in a short time.

According to the method for producing a metal oxide film according to the second aspect of the present invention, in the gel film forming step, a metal oxide sol obtained from a metal alkoxide or a metal salt as a starting material is used as a starting material. By applying to
A thin film of metal oxide gel is formed on the surface of the object to be coated, and in the gel crystallization step, the thin film of metal oxide gel is irradiated with ultraviolet light having a wavelength of 360 nm or less, so that the thin film absorbs ultraviolet light. The energy promotes the crystallization of the metal oxide gel.However, in the gel crystallization step, the thin film of the metal oxide gel is irradiated with patterned ultraviolet light. A difference occurs in the degree of crystallization between the irradiated portion and the non-irradiated portion, and the metal oxide thin film is patterned. As described above, a crystallized and patterned metal oxide thin film can be obtained without performing high-temperature heat treatment. By repeating the gel film forming step and the gel crystallization step a plurality of times on the surface of one object to be coated, a patterned metal oxide thin film having a desired film thickness can be obtained. In this case, for example, the time required for the coating operation of the precursor sol in the gel film forming step is about several tens of seconds, and the ultraviolet light irradiation time in the gel crystallization step is about several seconds to several minutes. It is possible to manufacture a metal oxide thin film having a thickness of about 1 μm. Then, in the thin film etching step, the metal oxide thin film is etched by etching the thin film of the metal oxide. can get.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

In the method for producing a metal oxide thin film according to the present invention, first, a metal alkoxide or metal salt is used as a starting material, and a solution containing the metal alkoxide or metal salt is hydrolyzed and polymerized to form a metal oxide precursor. Prepare a sol. As the metal oxide, Li, Be, B, Na, M
g, Al, Si, K, Ca, Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Ga, Ge, R
b, Sr, Y, Zr, Nb, Mo, Cd, In, Sn,
Sb, Cs, Ba, La, Hf, Ta, W, Tl, P
b, Bi, Ce, Pr, Nd, Pm, Sm, Eu, G
Among the metals d, Tb, Dy, Ho, Er, Tm, Yb, and Lu, a single oxide of any one of the metals or a composite oxide of a combination of two or more metals may be used. The method for preparing the precursor sol of these metal oxides is not particularly limited, but a thin film of a metal oxide gel (gel film)
When forming, the less the residual organic matter in the film, the more
The lower the crystallization temperature of the gel film by the heat treatment, the more preferable. The method for preparing the metal oxide precursor sol will be described below.

As the metal alkoxide used as a starting material, one having an alkoxyl group having 1 to 5 carbon atoms, more preferably one having an alkoxyl group having 2 to 4 carbon atoms is used. Also, as the metal salt,
Inorganic salts such as nitrates and chlorides, organic acid salts such as acetic acid,
Salts of β-diketones such as acetylacetonate are used.

Solvents for dissolving metal alkoxides or metal salts include alcohols such as methanol, ethanol, propanol and butanol, organic acid esters such as ethyl acetate, acetonitrile, ketones such as acetone and methyl ethyl ketone, tetrahydrafuran (TH
F) and cycloethers such as dioxane; acid amides such as formamide (FA) and N, N-dimethylformamide (DMF); hydrocarbons; and aromatics such as toluene.

A solution containing a metal alkoxide is added to a polydentate β-diketone (RCOCH 2 CO 3).
R ′; R and R ′ are an alkyl group or an alkoxyl group),
Alkoxy alcohols, alkanolamines, glycols, glycerin, acetic acid and the like may be included as alkoxide stabilizers. As the β-diketone, acetoacetate such as acetylacetone, ethyl acetoacetate and methyl acetoacetate, and malonate such as diethyl malonate are used. As the alkoxy alcohol, 2-methoxyethanol, 2-ethoxyethanol, 2-methoxy-2-propanol and the like are used. As the alkanolamine, monoethanolamine, diethanolamine, triethanolamine and the like are used. As the glycols, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and monoalkyl ethers and acetates of these compounds are used. These compounds may be used alone or in combination, and the type is selected according to the type of metal or the type of alkoxyl group. Further, it is desirable that these compounds are contained in an amount of 0.1 to 1.5 times by mole of the alkoxide. In addition, alkoxy alcohols can also be used as a solvent.

For the hydrolysis of a solution containing a metal alkoxide or a metal salt, the hydrolysis of the metal alkoxide or the metal salt is carried out.
Water is used in a molar amount of 05 to 2 times, and more preferably 0.5 to 1.5 times the amount of water. For the hydrolysis, an acid catalyst and / or a base catalyst may be used. Preferably, a mineral acid such as hydrochloric acid or an organic acid such as acetic acid is used. Note that, depending on the type of the alkoxide, a diluted solution of the alkoxide is used.
When a metal salt is used as a starting material, the reaction with an alcohol-based solvent is effectively used.

When a precursor sol of a metal oxide is prepared by hydrolysis of a solution containing a metal alkoxide or a metal salt, the precursor sol is applied to the surface of a substrate, and dried to form a metal oxide on the substrate surface. Form a thin film of the product gel.
The method for applying the precursor sol is not particularly limited, and a commonly used dip coating method, spin coating method, flow coating method, bar coating method, ultrasonic spraying method, or the like is used. As described above, the gel film obtained at this time is preferably as small as possible in the amount of residual organic substances in the film and as low as possible in the crystallization temperature when subjected to heat treatment.

When a metal oxide gel thin film is formed on the substrate surface, the gel film is irradiated with ultraviolet light having a wavelength of 360 nm or less. As a light source for ultraviolet light, a wavelength of 3
As long as it can be irradiated with ultraviolet light of 60 nm or less, it is appropriately selected and used according to the target metal oxide thin film, regardless of its type. For example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ArF Excimer lasers, KrF excimer lasers, excimer lamps, synchrotron radiation, and the like are used. It is also possible to use two or more of these light sources in combination.
When irradiating the gel film with ultraviolet light, depending on the purpose,
It is also possible to heat the substrate, place the substrate under reduced pressure, and control the atmosphere (oxidizing atmosphere or non-oxidizing atmosphere). The irradiation intensity of ultraviolet light and the number of shots are appropriately selected according to the type and composition of the gel film.
By irradiating the thin film of the metal oxide gel with ultraviolet light, the metal oxide gel forming the thin film is crystallized, and a thin film of the metal oxide is formed on the surface of the substrate.

By a single coating operation and ultraviolet light irradiation operation, only a metal oxide thin film having a thickness of about several tens of nm can be obtained. Therefore, in order to obtain a metal oxide thin film having a desired thickness, for example, a metal oxide thin film having a thickness of about 1 μm, the above-described coating step and ultraviolet light irradiation step are repeated as many times as necessary. Thus, a metal oxide thin film having a desired thickness is obtained. in this case,
The time required for one coating operation is about several tens of seconds, and the ultraviolet light irradiation time is about several seconds to several minutes.
Therefore, when the metal oxide gel is crystallized by heat treatment, it takes about 1 μm in a remarkably short time as compared with the conventional method, which requires 30 minutes to several hours for one heat treatment. Thus, a thin film of metal oxide having a film thickness of

In the case of forming a metal oxide thin film having a patterned uneven surface, a metal oxide gel thin film is formed on the substrate surface in the same manner as described above. Ultraviolet light having a wavelength of 360 nm or less is irradiated through a patterned photomask. Then, the coating operation and the pattern irradiation of ultraviolet light are repeated as many times as necessary to obtain a metal oxide thin film having a desired thickness, and then the substrate is immersed in an etching solution such as an aqueous hydrochloric acid solution to perform etching. To do. Thus, a metal oxide thin film having patterned irregularities on the surface can be obtained due to the difference in etching rate between the portion irradiated with ultraviolet light and the portion not irradiated with ultraviolet light.

[0022]

Next, an embodiment to which the present invention is specifically applied will be described.

Examples 1 to 7 A metal alkoxide was dissolved in a solvent so that the solid content of the metal oxide became 3% by weight, and 1N hydrochloric acid was added to the solution to hydrolyze the solution. A liquid (a precursor sol of a metal oxide) was prepared. This coating solution was applied to a spin coater (1,500 rpm ×
15 seconds) to form a coating film (a thin film of a metal oxide gel) on the silicon substrate or the silica substrate, and apply an ArF excimer laser to the obtained coating film. Alternatively, the step of irradiating a KrF excimer laser in the atmosphere was repeated five times. As a result, a crystalline metal oxide thin film was obtained.

Irradiation with laser light was performed at 10 Hz in each case, and one irradiation was completed in about several tens of seconds. Table 1 shows the synthesis conditions such as the type of metal alkoxide used, the type of solvent, the amount of water used for hydrolysis, the irradiation conditions of laser light, and the thickness of the obtained crystalline metal oxide film. Are shown together. In Table 1, the column of "amount" of "stabilizer" indicates the molar ratio of stabilizer / total alkoxide, and the column of "amount of water added" indicates the molar ratio of H2O / total alkoxide. Is shown.

[0025]

[Table 1]

[Comparative Examples 1 to 4]
The coating solutions (precursor sols of metal oxides) obtained in Examples 3 to 5 and Examples 6 and 7 were applied onto a silicon substrate or a silica substrate using a spin coater (1,500 rpm × 15 seconds). And forming a coating film (a thin film of a metal oxide gel) on a silicon substrate or a silica substrate and heating the obtained coating film.
By repeating this process twice, a crystalline metal oxide thin film was formed. In order to crystallize these metal oxide gels, a heat treatment of 30 minutes or more was required each time the coating solution was applied once. Table 2 shows the crystallization temperature of each gel film at this time.

[0027]

[Table 2]

As can be seen from Table 2, a heat treatment at a temperature of 400 ° C. or more was necessary to obtain a crystalline metal oxide thin film.

[0029] In order to obtain Example 8-15] metal oxides ABO _3, A- added alkoxide and B- alkoxide, in a solvent so that the solid concentration of the metal oxide is 3-10 wt% Then, a mixed solution containing A-alkoxide and B-alkoxide in a predetermined ratio is prepared and refluxed, and then water is added to the mixed solution to hydrolyze the solution, thereby obtaining a coating solution (metal oxide ABO). ₃ precursor sol). Table 3 summarizes the synthesis conditions such as the types of A-alkoxide and B-alkoxide used as starting materials, the type of solvent, and the amount of water used for hydrolysis. In Table 3, the column of “amount of water added” shows the molar ratio of H ₂ O / total alkoxide.

[0030]

[Table 3]

The obtained coating solution was applied to a spin coater (1, 5
(00 rpm × 15 seconds), a step of coating a silicon substrate or a platinum (Pt) substrate to form a coating film (a thin film of a metal oxide gel) on the silicon substrate or the Pt substrate, and the obtained coating film Then, the step of irradiating a KrF excimer laser in the air was repeated five times. As a result, a crystalline metal oxide thin film was obtained. Irradiation of laser light was performed at 10 Hz in each case, and one irradiation was completed in about several tens seconds to several minutes. Table 4 shows the irradiation conditions of the laser beam when the crystalline metal oxide thin film was obtained and the thickness of the obtained crystalline metal oxide film.

[0032]

[Table 4]

[Comparative Examples 5 to 12] The above Examples 8 to 1
5 was applied to a spin coater (1,500 rpm × 15).
Second) to form a coating film (thin film of metal oxide gel) on the silicon substrate or Pt substrate, and heat-treat the obtained coating film. Is repeated five times,
A crystalline metal oxide thin film was prepared. In order to crystallize these metal oxide gels, a heat treatment of 50 minutes or more was required for each application of the coating solution. Table 4 shows the crystallization temperature of each gel film at this time.

As can be seen from Table 4, even with SrTiO ₃ or PZT having the lowest crystallization temperature, a heat treatment at a temperature of 600 ° C. was necessary to confirm the crystallization.

The present invention is not limited to the formation of the metal oxide thin film shown in the above embodiment, but forms a thin film of a metal oxide other than the above to a desired thickness without heat treatment. It goes without saying that the present invention is also applicable to the case. As described above, a crystalline metal oxide thin film having a desired film thickness can be formed without performing a heat treatment. A metal oxide thin film can be formed on a substrate having poor heat resistance.

[0036]

According to the method for manufacturing a metal oxide film according to the first aspect of the present invention, a crystallized metal oxide thin film having a relatively large film thickness can be formed in a plastic material in a much shorter time than in the past. It can also be formed on a substrate that is inferior in heat resistance, such as metal.

According to the method for manufacturing a metal oxide film according to the second aspect of the present invention, a crystallized metal oxide thin film having a relatively large film thickness and having irregularities patterned on the surface can be formed as compared with the conventional method. It can be formed on a substrate having poor heat resistance, such as plastics, in a much shorter time.

In the manufacturing method according to the third aspect of the present invention, the metal oxide gel can be crystallized by the energy of ultraviolet light without performing heat treatment at a high temperature.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C01G 23/047 C01G 23/047 25/02 25/02 30/00 30/00 45/00 45/00 C23C 26/00 C23C 26/00 E // C23C 18/12 18/12 20/08 20/08 F term (reference) 4G042 DA01 DA02 DB11 DB15 DB27 DC01 DC03 DD02 DE04 DE09 DE14 4G047 CA02 CA05 CA07 CA08 CB06 CC02 CC03 CD02 4G048 AA02 AA05 AB02 AC02 AC04 AC08 AD02 AE06 AE08 4K022 AA01 AA02 AA03 AA04 AA05 BA02 BA04 BA06 BA07 BA08 BA10 BA11 BA12 BA14 BA15 BA17 BA20 BA22 BA23 BA24 BA25 BA26 BA27 BA28 BA33 DA08 DB04 DB06 DB07 4K11 A13A13 A13A13 A13A13 A13A13A BC14 CA41 CA53

Claims (3)

[Claims] 1. A gel film in which a precursor sol of a metal oxide obtained using a metal alkoxide or a metal salt as a main raw material is applied to the surface of an object to be coated to form a thin film of a metal oxide gel on the surface of the object. A metal oxide comprising: a forming step; and a gel crystallization step of irradiating the thin film of the metal oxide gel with ultraviolet light having a wavelength of 360 nm or less to crystallize the metal oxide gel forming the thin film. A method for producing a metal oxide film, comprising: repeating the gel film forming step and the gel crystallization step on a surface of one object to be coated a plurality of times. 2. A gel film in which a precursor sol of a metal oxide obtained using a metal alkoxide or a metal salt as a main raw material is applied to the surface of an object to be coated to form a thin film of a metal oxide gel on the surface of the object. Forming step, irradiating a patterned ultraviolet light having a wavelength of 360 nm or less to the thin film of the metal oxide gel to crystallize the metal oxide gel forming the thin film, A gel crystallization step of forming a thin film, and a thin film etching step of etching the thin film of the metal oxide, and patterning the thin film of the metal oxide by a difference in etching rate between a portion irradiated with ultraviolet light and a portion not irradiated with ultraviolet light. The method for producing a metal oxide film, comprising: repeating the gel film forming step and the gel crystallization step on the surface of one object to be coated a plurality of times; A method for producing a metal oxide film. 3. A high-pressure mercury lamp, a low-pressure mercury lamp, and an ultraviolet light source for irradiating a thin film of metal oxide gel with ultraviolet light.
The method for producing a metal oxide film according to claim 1 or 2, wherein the method is an rF excimer laser, a KrF excimer laser, an excimer lamp, or synchrotron radiation.