JP2004217961A - Anodized porous alumina composite material and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anodized porous alumina composite material and its producing method with which in the case of filling up the other material into the anodized porous alumina fine holes with a vacuum deposition method, the filling structure having high aspect ratio can simply be obtained at a low cost. <P>SOLUTION: This composite material is produced by filling up the other material into the fine holes of the anodized porous alumina. Then, this complex material is produced so as to fill up the other material into the fine holes with the vacuum deposition after expanding the diameters of the opening hole parts of at least fine holes with an etching treatment. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an anodized porous alumina composite in which pores of anodized porous alumina are filled with other substances such as metals, semiconductors, and organic substances, and a method for producing the same.
[0002]
[Prior art]
It is known that a layer of anodized porous alumina can be formed on the surface by anodizing aluminum. This anodized porous alumina is formed with uniform and fine pores oriented perpendicular to the film surface, and by filling other substances such as metals, semiconductors, and organic substances into these pores, A composite having a regular pore structure at the meter scale can be produced, and application to electric / electronic, optical, or magnetic devices is expected.
[0003]
This is because, in anodized porous alumina, it is easy to obtain a pore structure that is oriented perpendicular to the film surface and has a high aspect ratio (pore length / pore diameter ratio). By filling, a composite comprising alumina and a high aspect ratio filling material can be easily obtained. As a typical application example of these composites, there is a perpendicular magnetic recording medium produced by filling a ferromagnetic material (ferromagnetic metal) into pores of anodized porous alumina. In perpendicular magnetic recording media, it is necessary to have perpendicular anisotropy in the plane of the medium. However, ferromagnetic metal is filled in the pores of anodized porous alumina that has a structure in which each pore is oriented perpendicular to the film plane By doing so, a recording medium having perpendicular magnetization anisotropy can be easily obtained.
[0004]
Conventionally, material filling into anodized porous alumina is performed by an electrochemical method, a sol-gel method in which an oxide sol solution is filled and then solidified, or a chemical deposition method based on oxide deposition induced by a change in chemical equilibrium. Are known.
[0005]
On the other hand, there is also known a method of filling a substance into pores based on a so-called vacuum deposition method in which a desired substance is vaporized and then deposited in the pores. According to this method, the substance can be easily filled into the pores without depending on the chemical reaction. However, since the perpendicularity of the pores on the surface of the anode porous alumina is low, a sufficiently high aspect ratio ( (Pore length / pore diameter ratio) was difficult. That is, in the porous alumina produced by the anodization, the oxide film layer formed in the initial stage of the anodization has a lower solubility than the oxide layer formed thereafter. Since the pore diameter of the pore opening is smaller than the pore diameter of the inner part of the pore, and the entrance of the pore is closed, it becomes difficult to fill the deposition material deep. I have. In addition, the pores themselves may be formed by bending from the opening to the back, which also makes it difficult to fill the deposition material with a high aspect ratio.
[0006]
[Non-patent document 1]
Masuda et al., Proceedings of the IEICE Autumn Conference, 2E28 (2001)
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a high-aspect-ratio filling structure that can be easily and inexpensively achieved when filling another substance into the pores of anodized porous alumina by a vacuum deposition method. And a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a method for producing an anodized porous alumina composite according to the present invention is a method for producing a composite by filling other substances into pores of anodized porous alumina, wherein at least an etching process is performed. After the diameter of the opening of the pore is increased, the pore is filled with another substance by vacuum deposition. That is, in the pore opening of the pore structure of anodized porous alumina, a portion formed so as to close the opening is selectively dissolved and removed by etching to secure an opening having a desired pore diameter. This is a method for allowing the deposition material to easily reach the inner part of the pore. Thereby, a composite having a filling structure with a high aspect ratio can be easily obtained.
[0009]
In the method for producing an anodized porous alumina composite according to the present invention, it is preferable that the anodized porous alumina used in this production is produced by another-stage anodization. Another two-stage anodic oxidation makes it possible to form the pores in a higher order.
[0010]
Further, by performing anodic oxidation again after the above-described etching treatment, pores extending further from the bottom of the initially formed pores are formed, and the etching treatment is further performed on the two-stage pores. You can also. Further, the anodic oxidation and the etching treatment can be repeated a plurality of times. By such repetitive processing, the dissolution in the pore opening further progresses, and the diameter expansion processing of the desired pore opening is performed more reliably, and the pore shape that is increased in diameter toward the opening side of the pore. Therefore, during vacuum deposition, the pores can be more easily filled deep into the pores.
[0011]
Further, at the time of vacuum deposition, it is preferable that the deposition beam and the pores have a parallel relationship as much as possible, for sufficient filling, but this is, for example, at the time of vacuum deposition, a deposition source and a substrate. A collimator is installed between the anodized porous alumina to improve the straightness (orthogonality) of the atomic beam (evaporation beam) from the evaporation source, and to make the evaporation beam parallel to the direction in which the pores extend, to remove other substances This can be achieved by making it easier to fill in the pores.
[0012]
The other substance to be filled in the pores may be determined according to the use of the composite. For example, in the case of a perpendicular magnetic recording medium as described above, a ferromagnetic material may be used as another substance to fill the pores.
[0013]
The anodized porous alumina composite according to the present invention is produced by the above method. Such anodized porous alumina composites can be used, inter alia, to construct electrical, electronic, optical, or magnetic devices.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows the basic concept of the processes of anodic oxidation, vacuum deposition, and smoothing in the present invention. That is, by applying an anodizing treatment to the aluminium material 1, a layer of anodized porous alumina 3 having regular pores 2 is formed. By performing the two-stage anodic oxidation treatment, the uniformity and regularity of the pores 2 can be improved. Another substance, for example, nickel is deposited on the anodized porous alumina 3 by vacuum deposition. The deposition material 4 is filled in the pores 2 of the anodic oxidized porous alumina 3, but is also deposited on surfaces other than the pores 2, and irregularities are formed on the surface. It is chemically removed and the surface is smoothed. By such a method, for example, the structure of the anodized porous alumina composite 5 suitable for a perpendicular magnetic recording medium or the like is completed.
[0015]
In such a basic process, as described above, at the stage of forming the porous alumina 3 by anodic oxidation, as shown in FIG. Since the solubility is lower than that of the material layer, a portion 6 (oxide film portion) having a small hole diameter and having a shape that closes the opening is formed in the opening of the pore 2. If vacuum deposition is performed in this state, as shown in FIG. 3, the deposition material 4 is not uniformly filled in the pores 2 and is unevenly distributed or does not reach the inner part of the pores 2. Invite. Furthermore, the pores 2 themselves may be bent, which also promotes insufficient filling.
[0016]
Therefore, in the present invention, as shown in FIG. 4, prior to material filling based on the vacuum evaporation method, an oxide film portion 6 existing in the opening of the pore 2 is removed by performing an etching process. This ensures a sufficiently large pore opening 7 and then fills the substance 4 by vacuum evaporation. Since the substance 4 is filled in a state in which the pore opening 7 having a sufficiently enlarged diameter is secured, the substance 4 is sufficiently filled in the pore 2 from the inlet to the innermost part as shown in FIG. Filled with honey. After the vapor deposition, the surface is smoothed as described above, and the desired structure of the anodized porous alumina composite 5 is completed.
[0017]
As the etching treatment, in addition to an etching solution for dissolving anodized porous alumina represented by phosphoric acid, a dry etching process such as ion milling can be used.
[0018]
In addition, in the process shown in FIG. 4, only the oxide film portion 6 is mainly removed by the etching process. However, the effect of expanding the diameter of the pore opening by the etching process is more positively utilized. As shown in (1), it is also possible to form the pore opening 8 opened in a trumpet shape so that the substance 4 can be more easily filled. With such a configuration, it is possible to easily control the filling depth (filling amount) of the substance 4 into the pores 2 by vacuum deposition.
[0019]
Further, as shown in FIG. 6, after securing the pore opening 7 whose diameter has been increased by the etching treatment as described above, an anodic oxidation treatment is further performed to further remove the pore from the bottom of the pore 2 formed up to that point. It is also possible to form the elongated pores 9 and to perform an etching process on both the pores 2 and 9. Then, further pores 10 can be added by performing anodic oxidation treatment, and subsequently, etching treatment can be performed. As described above, by repeating the anodic oxidation and the etching treatment, it becomes possible to form the pores 11 close to, for example, an inverted trapezoidal shape as shown in FIG.
[0020]
Also, in order to more easily fill the substance by vacuum deposition and supply it to the depth of the pores more reliably, ensure the straightness of the vapor deposition beam from the deposition source, and extend the pores in the direction perpendicular to the perpendicular direction. It is preferred that the direction of presence is parallel. For this purpose, a collimator may be used as described above.
[0021]
【Example】
Hereinafter, the present invention will be described based on examples.
Example 1
Anodization was performed for 30 seconds at 40 V under the condition of 16 ° C. using 0.3 M oxalic acid as electrolysis. Thereafter, the sample was immersed in 5% by weight, phosphoric acid at 30 ° C. for 10 minutes to perform a pore diameter enlargement process at the pore opening. After washing and drying the sample, metal (Ni) filling was performed by a vacuum evaporation method. In vacuum deposition, Ni was vacuum-deposited using an electron beam melting method under a condition of a pressure of 1.3 × 10 ⁻³ Pa. The vacuum deposition rate at this time was 0.2 nm / s. After evaporating Ni having a thickness of 200 nm, the sample was broken and observed with a scanning electron microscope. As a result, it was confirmed that Ni was sufficiently filled in the pores.
[0022]
Example 2
After anodizing and etching were performed in the same manner as in Example 1, anodizing was performed again for 30 seconds under the same conditions. Thereafter, the sample was immersed in 5% by weight phosphoric acid at 30 ° C. for 10 minutes to perform a pore diameter enlargement treatment. Thereafter, the same anodic oxidation and pore diameter enlargement treatments were again performed for two cycles. In the hole diameter enlargement process in the second cycle, the hole diameter enlargement time was 15 minutes. After washing and drying the sample, metal (Ni) filling was performed under the same conditions as in Example 1. As a result of scanning electron microscope observation, it was confirmed that the pores were sufficiently filled with Ni.
[0023]
Example 3
Using 0.3 M sulfuric acid as an electrolysis, anodic oxidation was performed at 25 V for 30 seconds at 0 ° C. Thereafter, the sample was immersed in 5% by weight phosphoric acid at 30 ° C. for 10 minutes to perform a pore diameter enlargement treatment. Thereafter, the same anodic oxidation and pore diameter enlargement treatments were again performed for two cycles. In the hole diameter enlargement process in the second cycle, the hole diameter enlargement time was 15 minutes. After washing and drying the sample, Ni was charged by a vacuum deposition method in the same manner as in Example 1. After Ni deposition, the sample was broken and observed with a scanning electron microscope. As a result, it was confirmed that the pores were sufficiently filled with Ni.
[0024]
Example 4
In the same manner as in Example 1, the pores of the anodic oxidized porous alumina were filled with Co using a vacuum evaporation method. The degree of vacuum, deposition rate, and deposited film thickness are the same as those in Example 1. After that, scanning electron microscope observation was performed, and it was confirmed that the pores were sufficiently filled with Co.
[0025]
Example 5
In the same manner as in Example 1, the pores of the anodized porous alumina were filled with Si using a vacuum deposition method. The degree of vacuum, deposition rate, and deposited film thickness are the same as those in Example 1. After that, scanning electron microscope observation was performed, and it was confirmed that the pores were sufficiently filled with Si.
[0026]
Example 6
In the same manner as in Example 1, the pores of anodized porous alumina were filled with phthalocyanine using a vacuum evaporation method. As the evaporation source, a thermal evaporation source made of tungsten was used. The degree of vacuum, deposition rate, and deposited film thickness are the same as those in Example 1. After that, scanning electron microscope observation confirmed that phthalocyanine was sufficiently filled in the pores.
[0027]
Example 7
After anodizing was performed in the same manner as in Example 1, Ni was filled in the pores by performing vacuum deposition of Ni. At this time, a collimator having a perpendicular pore with a high aspect ratio was provided between the evaporation source and the sample. It was confirmed that the use of a collimator at the time of vapor deposition makes it possible to fill Ni into the pores.
[0028]
Example 8
After anodization was performed in the same manner as in Example 1, the surface was etched by ion milling. The ion milling was performed using argon as an etching gas at a pressure of 5 × 10 ⁻³ Pa and an acceleration voltage of 5.0 kV for 8 minutes. Thereafter, Ni was filled under the same conditions as in Example 1, and as a result, it was confirmed that the metal could be sufficiently filled.
[0029]
【The invention's effect】
As described above, according to the anodized porous alumina composite and the method of manufacturing the same according to the present invention, the composite in which the substance is easily and densely filled in the pores of the anodized porous alumina, compared to the conventional method. A body can be manufactured, and as a result, a high-performance device can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a basic concept of a process in a method according to the present invention.
FIG. 2 is a schematic cross-sectional view showing a pore morphology at a stage of producing anodized porous alumina.
FIG. 3 is a schematic cross-sectional view showing a state in which vapor deposition is performed in the state of FIG.
FIG. 4 is a schematic structural view showing a process for producing an anodized porous alumina composite including an etching treatment in the present invention.
FIG. 5 is a schematic configuration diagram showing another example of an etching process for a pore opening.
FIG. 6 is a schematic configuration diagram showing an example of a case where anodic oxidation and etching are repeated.
7 is a conceptual diagram of a pore shape formed by the process of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Aluminum material 2 Pores 3 Anodized porous alumina 4 Deposition material 5 Anodized porous alumina composite 6 Portion with small pore size (oxide film portion)
7 Large-pore opening 8 Large-pore opening 9 opened in a trumpet shape Further extending pore 10 Further pore 11 Fine pore close to inverted trapezoidal shape

Claims (8)

In a method of manufacturing a composite by filling other substances into the pores of anodized porous alumina, after expanding at least the opening of the pores by etching, filling the pores with another substance by vacuum evaporation A method for producing an anodized porous alumina composite, comprising: The method for producing an anodized porous alumina composite according to claim 1, wherein the anodized porous alumina to be used is produced by two-stage anodization. The anodic oxidation is performed again after the etching to form pores extending from the bottom of the initially formed pores, and the etching is further performed on the two-stage pores. A method for producing the anodized porous alumina composite according to 1 or 2. 4. The method for producing an anodized porous alumina composite according to claim 3, wherein the anodizing and etching are repeated a plurality of times. The method for producing an anodized porous alumina composite according to any one of claims 1 to 4, wherein the other substance is filled in the pores by using a collimator at the time of vacuum deposition and making the deposition beam parallel. The method for producing an anodized porous alumina composite according to any one of claims 1 to 5, wherein a ferromagnetic material is used as the other substance filled in the pores. An anodized porous alumina composite produced by the method according to claim 1. An electric / electronic, optical, or magnetic device formed using the anodized porous alumina composite according to claim 7.

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