JP2007031164A - Silicon oxide nanostructure body and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon oxide nanostructure body exhibiting nano effects, which is easily and inexpensively obtained by anodically oxidizing a silicon base material by an electrolysis operation. <P>SOLUTION: The silicon oxide nanostructure body is manufactured by an extremely simple process including: a step for arranging a film containing aluminum as a main component on a base body containing silicon as a main component; a step for forming an alumina coat having arrayed pores by anodically oxidizing the film containing aluminum as a main component; and a step for anodically oxidizing the base body containing silicon as a main component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nanostructure obtained by anodizing silicon and a method for producing the same. Specifically, the present invention relates to a silicon oxide nanostructure obtained by anodizing a two-layer structure made of Al / Si in which an aluminum metal film is formed on the surface of a silicon substrate, and a method for manufacturing the same.

  To date, attempts have been made to produce nanostructures made of metal oxides on the surface by anodization using foil materials, plate materials, extruded materials, etc. of valve metals centering on Al, and to provide various uses and applications, Efforts have been made. Through these years of efforts and experience, it can be said that aluminum is a special metal in the production of nanostructures among various valve metals. For metals other than aluminum, nanostructures can be obtained by anodic oxidation. However, only aluminum can be anodized in acid or alkaline solution, and nanostructured porous films and nanostructures such as nanorods, nanofibers, nanotubes, and nanoholes can be easily formed. It has been proposed to be used in various fields (Patent Documents 1 and 2).

  Regarding metals other than Al, the present inventors have succeeded in producing nanostructures regarding Ti, and published them in academic literature (Non-patent Document 1). Moreover, although some information regarding Mg is seen, nanostructure formation like Al has not been succeeded yet. The oxide film obtained by conventional anodization of Mg is not a structure in which the porous structure is neatly arranged like Al, but presents a state where crater-like and sponge-like holes and holes are randomly distributed, Therefore, the actual situation is that it could not be used as a template for producing a nanostructure as in the case of anodic oxidation of Al.

  However, in recent years, in response to the needs for various material designs, the creation of bubble metal oxide nanostructures has been sought. A structure is expected. The same applies to other bubble metals. For example, a technology for nano-structuring these metal oxides is expected for metals such as Ta, Nb, Zr, Y, and Si. However, there are very few reports on these today, and only a few results for the deposited films by physical methods are seen for Nb and Ta.

  Among them, silicon oxide nanostructures are disclosed in patent documents. Although this nanostructure fabrication process is disclosed by anodizing a film in which an aluminum columnar structure is surrounded by silicon (Patent Document 3), it is extremely complicated, and is in terms of production efficiency and cost. It is difficult to say that it is a simple process.

  Silicon oxide is an indispensable material used as one of basic materials in various technical fields such as electric materials, optical materials, catalysts and ceramics. On the other hand, today's technological innovation requires the development of materials that exhibit nano-effects by realizing a form controlled to a nano-level ultrafine structure, and such a request is no exception in silicon oxide. However, the methods proposed so far are as described above, and the manufacturing process is extremely complicated and costly. Therefore, provision of a simple and inexpensive process has been demanded.

The anodization technology by electrolysis can process a large area at once, its electrolysis operation and control are extremely simple, and the cost is low. If it is possible to provide silicon oxide nanostructures simply and inexpensively by electrolytic operation, it is clear that it can greatly contribute to industrial development, and its technical establishment is urgently required.

JP 7-62595 A JP 2003-73859 A JP 2003-266400 A The Electrochemical Society of Japan 2003 Fall Meeting Proceedings P162, Publication Date September 11, 2003

  The present invention is intended to provide an anodizing method capable of meeting the above requirements, and thereby to provide an inexpensive and high-quality silicon oxide nanostructure.

Therefore, as a result of intensive studies by the present inventors, aluminum was deposited on the surface of a substrate mainly composed of silicon, and this was anodized, whereby the aluminum on the surface of the silicon substrate was converted into porous alumina, and the pores were formed. It was found that the silicon underlayer was anodized through the formation of silicon metal oxide nanoholes, nanodots, and nanorods using the holes as templates. This invention is made | formed based on this knowledge, The structure is as following (1)-(8).
(1) A silicon oxide nanostructure formed by anodizing a substrate mainly composed of silicon.
(2) The silicon oxide nanostructure according to claim 1, wherein the silicon oxide nanostructure is a structure having nanoholes.
(3) The silicon oxide nanostructure according to claim 1, wherein the silicon oxide nanostructure is a structure having nanorods.
(4) disposing a film mainly composed of aluminum on a substrate composed mainly of silicon;
Forming an alumina film in which pores are arranged by anodizing the film containing aluminum as a main component;
Then, anodizing the substrate mainly composed of silicon through an alumina film having pores arranged therein,
A method for producing a silicon oxide nanostructure.
(5) The silicon oxide nanostructure according to claim 4, characterized in that the base body containing silicon as a main component is obtained by physical vapor deposition on an arbitrary substrate. Manufacturing method of structure.
(6) The method for producing a nanostructure according to (5) or (5), wherein the anodic oxidation of the substrate mainly composed of silicon is a constant potential or constant current method.
(7) The nanostructure according to claim 4 or 5, wherein the anodic oxidation of the substrate containing silicon as a main component is a constant potential system, and the electrolytic solution used for the constant potential system anodization is an acidic solution. Manufacturing method of structure.
(8) The anodic oxidation of the substrate containing silicon as a main component is a constant current method, and the electrolytic solution used for the constant current method anodization is an acidic solution. A method for producing a nanostructure.

That is, the present invention is (1) a nanostructure formed by anodizing a substrate mainly composed of silicon.
Here, the substrate containing silicon as a main component can be selected from those obtained by forming silicon on an arbitrary substrate by physical vapor deposition such as vacuum deposition or sputtering, thin films, plate materials, extruded materials, and the like.
Here, the nanostructure is a single structure such as individual nanodots or nanorods separated from the anodized substrate, or remains attached to the substrate without separation from the anodized substrate. Including and including things.

  In addition, the nanostructure of the present invention can be (2) a nanostructure characterized by having nanoholes formed by anodizing a substrate mainly composed of silicon.

  Furthermore, the nanostructure of the present invention can be (3) a nanostructure characterized by having nanodots formed by anodizing a substrate mainly composed of silicon.

  The present invention also includes (4) a step of disposing a film containing aluminum as a main component on a silicon-based substrate, and alumina in which pores are arranged by anodizing the film containing aluminum as a main component. A method for producing a nanostructure, comprising: forming a film; and anodizing a substrate mainly composed of silicon through the alumina film in which the pores are arranged.

  As the substrate mainly composed of silicon, a silicon film formed on a substrate by physical vapor deposition such as sputtering or vacuum deposition, a rolled silicon sheet, or the like can be used, but it is not necessarily in the form of a film. It is not limited to the above, and an appropriate shape can be adopted depending on the application. Further, when the silicon is in the form of a film, although not particularly limited, it is preferably 20 nm to 2000 nm, desirably 50 nm to 1000 nm, and more desirably 100 nm to 500 nm.

  Moreover, the diameter of the pores of the alumina film is not particularly limited as long as it corresponds to the size of the target nanostructure, and specifically, the diameter is 10 nm to 600 nm. Those having a diameter of 20 nm to 200 nm, more preferably 20 nm to 100 nm are more preferable. The thickness (hole depth) depends on the thickness of the aluminum vapor-deposited film before anodic oxidation. Therefore, the heat is not particularly limited, but the thickness corresponds to the diameter of the hole to be formed. The thickness is usually 100 nm to 20 μm, and may be appropriately determined from this range according to the purpose of use. For example, it is desirably 500 nm to 10 μm, more desirably 1 μm to 5 μm. .

  The present invention also includes (5) a step of forming a substrate containing silicon as a main component on an arbitrary substrate by physical vapor deposition, and forming a film containing aluminum as a main component on the surface of the substrate. Forming an alumina film in which pores are arranged by anodizing the aluminum-based film, and anodizing the silicon-based substrate. This is a method for producing a nanostructure.

One of the reasons for forming a film containing aluminum as a main component or a substrate containing silicon as a main component by physical vapor deposition is that a thin film can be formed uniformly by film formation. In addition, unlike bulk metal, film formation by physical vapor deposition is performed by stacking ultrafine particles, there are minute gaps between the stacked ultrafine particles, and ultrafine particles of appropriate size are stacked reasonably densely. Therefore, it is easy to perform control for making the pore diameter and the pore arrangement of the oxide film generated by the electrolyte entering the minute gaps during anodic oxidation appropriate. Although not particularly limited, the thickness of the film mainly composed of aluminum directly affects the thickness of the alumina layer, and the length of the nanostructures generated thereby can be controlled. It may be determined in consideration of the design. When the area | region which can be implemented is illustrated, 200 nm-10 micrometers are normal, and can determine suitably in this range. However, these are examples and are not limited thereto. In addition, it is effective that it is desirably in the range of 500 nm to 5 μm, more desirably 1 μm to 3 μm.

  The present invention is also characterized in that (6) in the method for producing a nanostructure according to (4) or (5), the anodic oxidation of the substrate mainly composed of silicon is a constant potential or constant current method. This is a method for producing a nanostructure.

The present invention is also directed to (7) the method for producing a nanostructure according to (4) or (5), wherein the anodic oxidation of the substrate mainly composed of silicon is a constant potential method, and the constant potential method anodization is performed. The method for producing a nanostructure is characterized in that the electrolytic solution used in is an acidic solution.

  As the acidic solution, a single inorganic acid, a mixed solution of a plurality of types of inorganic acids, a single organic acid, a mixed solution of a plurality of types of organic acids, or a mixed solution thereof can be used. The inorganic acid is preferably selected from sulfuric acid, phosphoric acid, and chromic acid. The organic acid is preferably selected from malonic acid and oxalic acid. It is also preferable to add at least one kind of salt or acid containing fluorine ions, chloric acid and nitric acid or nitrate to the acidic solution. Furthermore, the electrolytic solution is preferably a strongly acidic electrolytic solution having a pH of 2 or less, and more preferably a strongly acidic electrolytic solution having a pH of 1 or less. By defining the conditions for anodic oxidation in this manner, silicon oxide nanoholes (nanostructures) can be easily formed.

  The present invention is also directed to (8) the method for producing a nanostructure according to (4) or (5), wherein the anodic oxidation of the substrate mainly composed of silicon is a constant current method, and the constant current method anodization is performed. The method for producing a nanostructure is characterized in that the electrolytic solution used in the step is an acidic solution.

As the acidic solution, a single inorganic acid, a mixed solution of a plurality of types of inorganic acids, a single organic acid, a mixed solution of a plurality of types of organic acids, or a mixed solution thereof can be used. Further, it is preferable not to contain F-, Cl- or NO ₃ ^- ions. Moreover, as said inorganic acid, it is preferable that 1 type or multiple types is chosen from a sulfuric acid and phosphoric acid. Moreover, as an organic acid, it is preferable that 1 type or multiple types are chosen from malic acid, tartaric acid, a citric acid, and an oxalic acid. The electrolytic solution is preferably an acidic electrolytic solution having a pH of 3 or more and 6.5 or less.

  By defining the conditions for anodic oxidation in this way, silicon oxide nanodots and nanorods (nanostructures) can be easily formed.

  When a film mainly composed of aluminum is integrally formed on the surface of the substrate based on silicon by physical vapor deposition without exposing the substrate based on silicon to a reactive atmosphere, the silicon as a main component is formed by an anodic oxidation process. This is preferable because the film containing aluminum as a main component on the substrate does not peel off. As the method, a method of forming a film of silicon on a substrate by a sputtering method and subsequently forming a film of aluminum while maintaining a degree of vacuum can be employed.

  According to the method for producing a silicon oxide nanostructure of the present invention, an insulating material in the advanced technology field can be produced in a short process. Moreover, application to a circuit board is possible.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the present invention, as shown in FIG. 4, a step of disposing a film 3 mainly composed of aluminum on the surface of a substrate 2 mainly composed of silicon formed on the substrate 1, and as shown in FIG. The nanostructure is manufactured from the step of forming the alumina film 31 in which the pores 32 are arranged by anodizing the film 3 containing aluminum as a main component and the step of anodizing the substrate 2 containing silicon as a main component. .

  The base body 2 containing silicon as a main component is manufactured, for example, by sputtering or vacuum depositing silicon on the transparent glass substrate 1. Further, the film 3 containing aluminum as a main component is anodized to form an alumina film 31 in which the pores 32 are arranged. These pores 32 need to penetrate substantially from the front surface to the back surface of the alumina coating 31. The meaning of substantially penetrating means that the pores of the alumina coating 31 have electrical properties capable of anodizing silicon.

  As a method for anodizing the substrate 2 containing silicon as a main component, a constant potential or constant current method can be employed. In the case of constant potential anodization, the electrolyte used is preferably an acidic solution. As the acidic solution, a single inorganic acid, a mixed solution of a plurality of types of inorganic acids, a single organic acid, a mixed solution of a plurality of types of organic acids, or a mixed solution thereof can be used. The inorganic acid is preferably selected from sulfuric acid, phosphoric acid, and chromic acid. The organic acid is preferably selected from malonic acid and oxalic acid.

  It is also preferable to add at least one kind of salt or acid containing fluorine ions, chloric acid and nitric acid or nitrate to the acidic solution. Furthermore, the electrolytic solution is preferably a strongly acidic electrolytic solution having a pH of 2 or less, and more preferably a strongly acidic electrolytic solution having a pH of 1 or less. By defining the conditions for anodic oxidation in this way, as shown in FIG. 6, nanoholes 22 (nanostructures) can be easily formed in the substrate 2 mainly composed of silicon. The nanoholes 22 are considered to be formed to selectively and strongly anodize the surface of the substrate 2 mainly composed of silicon through the pores 32 of the alumina layer 31. Further, by removing the alumina film 31 on the surface, a nanohole structure in which the silicon oxide 21 shown in FIG. 7 is exposed on the surface can be obtained.

Moreover, it is preferable that the electrolyte solution used for constant current system anodization is an acidic solution. As the acidic solution, a single inorganic acid, a mixed solution of a plurality of types of inorganic acids, a single organic acid, a mixed solution of a plurality of types of organic acids, or a mixed solution thereof can be used. Further, it is preferable not to contain F ⁻ , Cl ⁻ , or NO ₃ ⁻ ions. Moreover, as said inorganic acid, it is preferable that 1 type or multiple types is chosen from a sulfuric acid and phosphoric acid. Moreover, as an organic acid, it is preferable that 1 type or multiple types are chosen from malic acid, tartaric acid, a citric acid, and an oxalic acid. The electrolytic solution is preferably an acidic electrolytic solution having a pH of 3 or more and 6.5 or less.

  In the present invention, the growth of the silicon oxide product 23 is optimized by adjusting the ratio of the dissolution rate of the base 2 containing silicon as a main component and the rate of oxide formation by determining the conditions for anodic oxidation in this way. Therefore, as shown in FIG. 8, the silicon oxide product 23 can be grown in the pores 32. Silicon nanodots and nanorods (nanostructures) can be formed by adjusting the degree of growth of the silicon oxide product 23. Further, by removing the alumina film 31 on the surface, a nanostructure in which the silicon oxide 23 shown in FIG. 9 is exposed on the surface can be obtained.

  Nanostructures such as nanodots and nanoholes can be manufactured by anodizing a substrate mainly composed of silicon by the above-described method, and controlling the electrolyte, voltage, current, anodic oxidation time, and the like. .

  Here, the shape of silicon is not particularly limited, but usually a film-like shape is preferably employed. Further, “on silicon” means one or both sides of a silicon film when the silicon is in a film form.

  Thinner silicon can form nanostructures more effectively. A method for forming thin silicon is not particularly limited, but it is effective to form a silicon layer on a substrate such as glass, ceramic, or synthetic resin by physical vapor deposition.

  The alumina film having through-holes formed on silicon is preferably formed into an alumina film in which pores are arranged by anodizing aluminum formed on silicon and anodizing the formed aluminum.

Using a transparent coning glass plate, a 300 nm thick silicon layer is formed on the surface by RF (radio frequency) sputtering, and then an Al layer having a thickness of 1.5 μm is RF (radio frequency) without being exposed to air. A sample subjected to ultrasonic cleaning in acetone for 10 minutes as a pretreatment was subjected to anodization using a sputtered substrate. In the anodic oxidation of Al, constant potential electrolysis was performed at 165 V in a 10 vol% phosphoric acid solution, and the electrolysis was stopped when the current density dropped rapidly from the steady state. Thereby, the Al layer was completely oxidized, and a porous alumina film was obtained on silicon. Subsequently, anodization of silicon was performed. Silicon anodic oxidation is performed by dipping in a mixed solution containing 10 vol% sulfuric acid solution as a main component, 2 wt% ammonium fluoride (NH ₄ F) and 1 vol% perchloric acid, and performing constant potential electrolysis at 60 V. I went for a minute. The local anodic oxidation and electrolytic etching of silicon were simultaneously performed through the alumina film. The alumina film was dissolved and removed by immersing this sample in a mixed solution of 5 vol% phosphoric acid and 3 wt% chromic acid at 80 ° C. for 5 minutes to produce a silica nanostructure (nanohole) (FIG. 1).

  As in Example 1, a transparent coning glass plate was used, and a substrate in which a 300 nm thick silicon layer and a 1.5 μm thick Al layer were RF (radio frequency) sputtered on the surface was used as a pretreatment in acetone. The sample which was ultrasonically cleaned for 10 minutes was subjected to anodization. First, the sample was subjected to constant potential electrolysis at 165 V in a 10 vol% phosphoric acid solution at 0 ° C., and anodized until the current reached a value close to zero. Next, this sample was immersed in a mixed solution of 5 vol% phosphoric acid and 3 wt% chromic acid at 80 ° C. for 5 minutes to dissolve and remove the alumina film, thereby producing a silica nanostructure (nanodot) (FIG. 2).

Using a transparent coning glass plate, a substrate having a surface of 300 nm thick silicon layer and 1.5 μm thick Al layer RF (radio frequency) sputtered was used and ultrasonically cleaned in acetone for 10 minutes as a pretreatment. The sample was subjected to anodization. The sample was subjected to constant potential electrolysis at 20 V in a 10 wt% sulfuric acid solution at 15 ° C., and anodization of Al was performed until the current became a value close to zero. Subsequently, anodization was performed up to 250 V at a constant current of 10 A / m ^{2 in} the same solution.
Next, this sample was immersed in a mixed solution (75 ° C.) of 5 vol% phosphoric acid and 3 wt% chromic acid for 5 minutes to dissolve and remove the alumina film, thereby producing a silica nanostructure (nanodot) (FIG. 3). .

  Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration of the present invention is not limited to these embodiments, and the present invention can be changed even if there is a design change or the like without departing from the gist of the present invention. include.

In the present invention, silica nanostructures that are directly bonded and arranged on a substrate have a high specific surface area, and are excellent in chemical strength and physical strength such as heat resistance (heat insulation) and wear resistance (hardness), Furthermore, it can make a great contribution to the development of piezoelectric elements, semiconductor elements, various electronic devices, gate insulating films, optical fiber connectors, etc., consisting of nanostructures with excellent electrical properties such as semiconductor properties, dielectric properties, and piezoelectricity. it can.

It is an electron micrograph of the nanostructure (nanohole) of this invention. It is an electron micrograph of the other nanostructure (nanodot) of this invention. It is an electron micrograph of the other nanostructure (nanodot) of this invention. It is sectional drawing for demonstrating the manufacturing method of the nanostructure of this invention. FIG. 5 is a cross-sectional view for explaining a step following the step in FIG. 4. It is sectional drawing for demonstrating the manufacturing method of the nanohole of this invention. FIG. 7 is a cross-sectional view for explaining a step following the step in FIG. 6. It is sectional drawing for demonstrating the manufacturing method of the nanorod of this invention. FIG. 9 is a cross-sectional view for explaining a step following the step in FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Base body mainly composed of silicon 21 Oxide silicon 22 Nanohole 23 Silicon oxide product 3 Film mainly composed of aluminum 31 Alumina coating 32 Pore

Claims (8)

  A silicon oxide nanostructure formed by anodizing a substrate mainly composed of silicon.   The silicon oxide nanostructure according to claim 1, wherein the silicon oxide nanostructure is a structure having nanoholes.   The silicon oxide nanostructure according to claim 1, wherein the silicon oxide nanostructure is a structure having nanorods. Disposing a film composed mainly of aluminum on a substrate composed mainly of silicon;
Forming an alumina film in which pores are arranged by anodizing the film containing aluminum as a main component;
And a step of anodizing the substrate containing silicon as a main component through an alumina film in which pores are arranged, and a method for producing a silicon oxide nanostructure.   5. The silicon oxide nanostructure according to claim 4, wherein the silicon-based substrate is obtained by physical vapor deposition on an arbitrary substrate. Production method.   6. The method for producing a nanostructure according to claim 5, wherein the anodic oxidation of the substrate mainly composed of silicon is a constant potential or constant current method.   6. The nanostructure according to claim 4, wherein the anodic oxidation of the substrate containing silicon as a main component is a constant potential method, and the electrolytic solution used for the constant potential method anodization is an acidic solution. Production method. 6. The nanostructure according to claim 4 or 5, wherein the anodic oxidation of the substrate containing silicon as a main component is a constant current method, and the electrolytic solution used for the constant current method anodization is an acidic solution. Manufacturing method.

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