JP2009085889A - Manufacturing method of microcolumn - Google Patents

Abstract

A microcolumn having a columnar body with a high aspect even when the diameter of the columnar body is uniform from the top to the bottom and the interval between the columnar bodies is narrow.
A step of disposing a base metal layer and an anodized layer on a substrate, and anodizing the anodized layer to form a porous film having holes formed in a direction perpendicular to the substrate. A step of growing an oxide containing an element of the base metal layer from the bottom of the hole of the porous film in the upward direction of the hole to cover the upper surface of the porous film and forming a columnar body and a coating layer; A method for producing a microcolumn, comprising: removing the porous film to obtain a columnar body made of an oxide containing an element of the base metal layer and a hollow structure body having a coating layer on the substrate.
[Selection] Figure 3

Description

  The present invention relates to a method for producing a microcolumn, and more particularly to a method for producing a microcolumn using an oxide hollow structure produced by an anodic oxidation process as a flow path.

  In recent years, microfluidic devices called μTAS (Micro Total Analysis System) have attracted attention. μTAS is a device that mixes, separates and extracts trace samples in a fine flow path, and is effective for analyzing trace amounts of biological materials such as nucleic acids and proteins. In general, μTAS forms fine flow paths and microcolumns on a silicon substrate using semiconductor processing techniques such as photolithography and etching.

In particular, in the case of a microcolumn, in order to analyze a minute sample such as nucleic acid or protein with a size of 100 nm or less with high accuracy, the periodic interval of the separation material of the microcolumn needs to be 100 nm or less. As a technique for producing such a microcolumn, for example, Patent Document 1 discloses a technique for producing a microcolumn made of a columnar body by etching using a resist film having a concavo-convex pattern as a mask.
JP 2004-045357 A

  However, in the technique using etching as disclosed in Patent Document 1, generally, etching becomes more difficult as the depth increases from the processing surface. As a result, the technique using etching has a problem that the cross-sectional shape of the columnar body is wider at the bottom than the top, and the diameter of the columnar body is different between the top and the bottom. This difference becomes more prominent as the diameter of the columnar body is reduced, which causes a decrease in separation ability. Further, in the technique using etching, it becomes difficult to etch to a deeper portion as the interval between the columnar bodies becomes narrower, so that it is difficult to produce a high aspect columnar body.

  The present invention has been made to solve such a problem, and the production of a microcolumn having a columnar body having a high aspect even when the diameter of the columnar body is uniform from the top to the bottom and the interval between the columnar bodies is narrow. Is to provide a method.

The above problem can be solved by the following configuration of the present invention.
A method of manufacturing a microcolumn that solves the above-described problem is a process of disposing a base metal layer and an anodized layer on a substrate, and anodizing the anodized layer to be formed in a direction perpendicular to the substrate A step of forming a porous film having pores, and a columnar body covering an upper surface of the porous film by growing an oxide containing an element of the base metal layer from the bottom of the hole of the porous film in an upward direction of the hole. Forming a covering layer; and removing the porous film to obtain a hollow structure having a columnar body made of an oxide containing the element of the base metal layer and a covering layer on the substrate. It is characterized by.

  ADVANTAGE OF THE INVENTION According to this invention, even if the diameter of a columnar body is uniform from the top part to the bottom part and the space | interval of a columnar body is narrow, the manufacturing method of the microcolumn which has a columnar body with a high aspect can be provided.

Hereinafter, a method for producing a microcolumn according to an embodiment of the present invention will be described in detail.
The method for producing a microcolumn according to the present invention includes the following steps (a) to (d). (A) A step of disposing a base metal layer and an anodized layer on a substrate. (B) a step of anodizing the anodized layer to form a porous film having pores formed in a direction perpendicular to the substrate; (C) A step of growing an oxide containing an element of the base metal layer from the bottom of the hole of the porous film in the upward direction of the hole to cover the upper surface of the porous film to form a columnar body and a coating layer. (D) A step of removing the porous film to obtain a hollow structure having a columnar body made of an oxide containing an element of the base metal layer and a coating layer on the substrate.

The base metal layer is preferably a layer containing at least one element selected from Ti, Zr, Nb, Hf, Ta, Mo, and W.
The step of removing the porous film to form a hollow structure having a columnar body and a coating layer is preferably performed by second anodic oxidation.

The electrolytic solution used for the second anodic oxidation is preferably an aqueous ammonium borate solution, an ammonium tartrate solution or an aqueous ammonium citrate solution.
The step of forming the hollow structure having the columnar body and the coating layer by removing the porous film is preferably performed by wet etching.

It is preferable that the anodized layer is anodized after forming a depression that becomes the starting point of anodization in the anodized layer.
The columnar bodies are preferably arranged with a uniform diameter and interval.

Furthermore, it is preferable to include a step of heat-treating the hollow structure having the columnar body and the coating layer in an oxidizing atmosphere.
Next, based on FIG. 3, each process of the manufacturing method of the microcolumn which concerns on this invention is demonstrated sequentially.

FIG. 3 is a process diagram showing one embodiment of a method for producing a microcolumn according to the present invention.
First, as shown in FIG. 3A, a sample is prepared in which a base metal layer is further formed on a substrate, and an anodized layer is further disposed thereon using a thin film forming method such as sputtering. As the base metal layer 13 shown in FIG. 3A, a material containing at least one element selected from Ti, Zr, Nb, Hf, Ta, Mo, and W is disposed. Further, as the anodized layer, Al or an alloy containing Al as a main component is disposed.

  Next, when the sample was anodized using an acidic aqueous solution such as phosphoric acid, oxalic acid, sulfuric acid, etc., as shown in FIG. 3B, a large number of holes 18 grew from the sample surface in the direction perpendicular to the substrate 14. A quality film 17 is obtained. The structure of the porous film 17 includes a minute hole 18 and an oxide 19 of an anodized layer surrounding the hole 18.

  The growth of the holes 18 occurs from random positions on the sample surface. However, as shown in FIG. 3 (a), a minute recess 16 serving as an anodic oxidation starting point is prepared on the surface of the anodized layer of the sample by electron beam drawing, nanoimprinting, FIB (Focused ion beam) method, or the like. In other words, the hole is generated only from the position of the starting point. That is, it is possible to obtain a porous film having pores regularly arranged according to the arrangement pattern of the depressions. At this time, when the anodic oxidation voltage V (Volt) is an anodizing voltage V that satisfies a regular arrangement period (nm) = 2.5 × V, it is preferable to obtain a porous film having highly ordered pores. .

  In order to obtain the porous film as described above, Al is generally used as the anodized film. The reason is that some materials other than Al, such as Si and Ti, form a porous film by anodic oxidation, but the verticality of the holes is not so good, and anodic oxidation of Al such as using hydrofluoric acid as an acidic aqueous solution This is because there are problems and disadvantages compared to. Here, if it is an Al alloy containing at least one element selected from Ti, Zr, Hf, Nb, Ta, Mo, and W, a porous film having pores with good perpendicularity can be formed like Al. . In this case, by alloying Al, it is possible to reduce the roughness of the film surface due to protrusions and grain boundaries formed on the film surface, so that the sample surface has a minute starting point for anodization. It becomes a particularly effective means when preparing a hollow. The amount of element added to Al depends on the type of element to be added, but in order to form a porous film having pores with good perpendicularity as with Al, the amount should be generally in the range of 5 atomic% to 50 atomic%. preferable.

  By continuing the anodic oxidation, the porous film 17 grows from the sample surface toward the substrate, and the holes 18 grow until reaching the base metal layer 13. The diameter of the produced hole 18 can be enlarged (pore wide) by immersing it in a phosphoric acid solution or the like. By this treatment, the diameter of the horizontal cross section of the hole can be arbitrarily controlled.

  Next, an oxide containing the element of the base metal layer is grown from the bottom of the hole of the porous film in the upward direction of the hole to cover the upper surface of the porous film to form a columnar body and a coating layer. Specifically, the anodic oxidation is performed by changing from the state of FIG. 3B to an electrolytic solution that can provide a barrier type anodic oxide film such as an aqueous ammonium borate solution, an ammonium tartrate solution, or an aqueous ammonium citrate solution. By this anodic oxidation, as shown in FIG. 3C, the oxide 11 of the base metal layer can be grown while being filled in the holes 18 of the porous film. Therefore, the shape of the oxide 11 of the base metal layer reflects the shape of the hole 18. The diameter of the hole 18 is highly uniform from the top to the bottom, and the columnar body 21 is formed using the hole as a mold. As a result, a structure in which the diameter of the columnar body 21 is uniform from the top to the bottom can be produced. Of the oxide 11 of the base metal layer, a portion filled in the hole 18 is a columnar body 21, and a portion overflowing from the hole 18 is a coating layer 22.

  The height of the columnar body growing in the hole depends on the anodic oxidation voltage, and each columnar body grows at a substantially constant height. On the other hand, when anodic oxidation is performed at a voltage higher than the voltage reaching the upper surface of the porous film 17, growth in the horizontal direction as well as the vertical direction with respect to the substrate starts. Therefore, when anodization is performed at a sufficiently high voltage, the oxide 11 of the base metal layer overflowing from the hole 18 comes into contact with the adjacent hole, and finally the upper surface of the porous film 17 is covered with the oxide 11 of the base metal layer. The coating layer 22 covered with can be formed. Here, when heat treatment is performed in an oxidizing atmosphere, impurities such as bound water in the oxide are removed, and the oxide has a higher oxidation number, thereby increasing etching resistance.

  Next, the porous film is removed to obtain a hollow structure having a columnar body made of an oxide containing an element of the base metal layer and a coating layer on the substrate. Specifically, wet etching is performed by immersing a sample in which the oxide 11 of the base metal layer is grown in an acid or alkali solution. At this time, by utilizing the difference in etching resistance between the porous film 17 containing Al as a main component and the oxide 11 of the base metal layer, only the porous film 17 is selectively dissolved and removed, and the base metal is removed. Etching is performed to leave the oxide 11 of the layer. The etching proceeds from the region where the upper surface of the porous film 17 is not covered with the oxide 11 of the underlying metal layer to the inside so that the etching solution enters the side surface of the porous film 17 and forms the flow path 12. And finally, as shown in FIG.3 (d), the hollow structure 20 which has the columnar body 21 which consists of the base metal layer oxide 11, and the coating layer 22 can be produced.

  FIG. 1 is a schematic view showing a cross section of an example of a microcolumn manufactured by the method of the present invention. As shown in FIG. 1, the periodic interval between adjacent columnar bodies is denoted by P, the diameter of the columnar bodies is denoted by D, and the height of the columnar bodies is denoted by h. As described above, the period interval P is determined by the interval between minute recesses formed by nanoimprinting or FIB (Focused Ion Beam) method. The diameter D of the columnar body is determined by pore wide processing. The height h of the columnar body is determined by the thickness of the anodized layer. From the above, in the present invention, P, D, and h can be determined independently.

  In the microcolumn of the present invention, the period interval P can be set to 30 nm or less, and further can be reduced to 16 nm. The diameter D of the columnar body can be reduced to about 5 nm, and the height h of the columnar body can be increased to 1 μm. By changing the above P, D, and h independently, an appropriate microcolumn can be produced for the analysis sample.

  In addition, since the columnar body constituting the microcolumn according to the present invention is formed using holes as a mold, the diameter of the columnar body is uniform from the top to the bottom. Further, a microcolumn having a high aspect columnar body can be provided even when the interval between the columnar bodies is particularly narrow, such as 50 nm or less. In particular, in order to analyze a minute sample such as nucleic acid or protein with high accuracy, a separation column is necessary in which the periodic interval P is 100 nm or less and the columnar body diameter D is uniform from the top to the bottom. According to the present invention, such a separation column can be produced according to the size of the analysis sample.

  Furthermore, the base metal layer oxide 11 can be made into various oxides by selecting the base metal layer 13 from an element including at least one of Ti, Nb, Zr, Hf, Ta, Mo, and W. . In particular, when Ti or Zr is selected as the base metal layer 13, the base metal layer oxide 11 becomes titanium oxide and zirconium oxide, respectively, and each crystal is formed by heat treatment. Titanium oxide and zirconium oxide are optimal for the analysis of biomaterials because they exhibit excellent properties for separating samples containing phosphate groups such as nucleic acids and proteins.

  FIG. 2 shows a plan view of the columnar body of FIG. The sample flows through the flow path 12 between the columns of the oxide 13 of the base metal layer, and is separated according to the sample size. Here, the columnar body of the oxide 13 of the underlying metal layer can be arranged in various arrangements by arbitrarily setting the arrangement pattern of the depressions 16, and can be arranged in a triangular lattice arrangement, a square lattice arrangement, a concentric circle arrangement pattern, or the like. Can be produced. In addition, by arbitrarily setting the processing region of the recess 16, it is possible to form a column at an arbitrary position in the flow path, and it is also possible to provide multistage columns having different sizes on one μTAS chip.

EXAMPLES Hereinafter, although this invention is demonstrated using an Example, it is not limited to the following.
Example 1
This example shows a method for manufacturing a microcolumn of the present invention. Hereinafter, a method for producing a microcolumn in the present embodiment will be described in detail with reference to FIG. A process consists of the process of Fig.3 (a) to (d).

  As shown in FIG. 3A, a 40 nm Nb film was formed as a base metal layer 13 on a Si substrate, and an AlHf layer containing 7 atomic% Hf was formed thereon as a anodic oxidation layer 15 by a 100 nm film by sputtering. . Here, FIB was used as the starting point of anodization, and small depressions 16 of about 2 nm were formed in a square arrangement at 25 nm intervals on the surface of the AlHf layer.

  Next, as shown in FIG. 3B, the AlHf layer is anodized at an applied voltage of 10 V in a 1.0 mol / L sulfuric acid aqueous solution having a bath temperature of 3 ° C. A porous film 17 in which a large number of holes 18 grew in the direction perpendicular to the substrate 14 from the sample surface was obtained. The obtained porous film 17 was immersed in a 5 wt% phosphoric acid aqueous solution having a bath temperature of 20 ° C. to perform a pore size expansion process by wet etching. When the sample surface was observed with FE-SEM, the diameter of the hole 18 was 12 nm.

  Next, as shown in FIG.3 (c), the sample was anodized in the 0.15 mol / L ammonium borate aqueous solution with a bath temperature of 22 degreeC by the applied voltage of 50V. As a result, the growth of the oxide of the base metal layer Nb proceeds and the volume expands, so that the Nb oxide, which is the oxide 11 of the base metal layer, extends from the bottom of the hole to the inside of the hole in the direction perpendicular to the substrate. The anodic oxidation was continued until it was filled and finally overflowed from the top of the hole and completely covered the porous film 17. Thereafter, a heat treatment at 300 ° C. was performed in an air atmosphere.

Next, as shown in FIG.3 (d), the hollow structure 20 which consists of Nb oxide was obtained by removing a porous membrane | film | coat in 25 degreeC 5 wt% phosphoric acid aqueous solution.
As described above, a microcolumn having a period interval between adjacent columnar bodies of P of 25 nm, a columnar body diameter of D of 12 nm, and a columnar body height of h of 300 nm was fabricated.

Example 2
A 40 nm thick Nb film was formed on the Si substrate as a base metal layer, and an AlHf layer containing 7 atomic% Hf was formed thereon by sputtering as the anodic oxidation layer. Next, aluminum alkoxide was applied to the surface of the sample by spin coating to a thickness of 20 nm, baked at 90 ° C. for 20 minutes, and then a depression serving as an anodic oxidation starting point was transferred to the alkoxide surface by nanoimprinting. In this example, protrusions with a height of 15 nm were pressed onto a surface of the alkoxide by pressing a mold having a triangular lattice arrangement at an interval of 50 nm against the alkoxide surface.

  Further, the sample was treated by ashing using ultraviolet rays and ozone at 180 ° C. for 10 minutes, thereby removing the polymer portion in the alkoxide and simultaneously proceeding the oxidation of the aluminum portion to oxidize the alkoxide layer. Thereafter, anodization was performed at an applied voltage of 20 V in a 0.3 mol / L sulfuric acid aqueous solution having a bath temperature of 16 ° C. The oxidized alkoxide layer and aluminum layer were anodized all together. By observing the anodized sample with an FE-SEM (field emission scanning electron microscope), it was confirmed that a porous film having a triangular lattice arrangement was formed in the same manner as the pattern of the protrusions on the mold. The obtained porous coating was immersed in a 5 wt% phosphoric acid aqueous solution having a bath temperature of 20 ° C., thereby carrying out a pore size enlargement process by wet etching. When the sample surface was observed with FE-SEM, the diameter of the hole was 27 nm.

  Next, the sample was anodized at an applied voltage of 80 V in a 0.15 mol / L ammonium borate aqueous solution having a bath temperature of 22 ° C. As a result, the growth of the oxide of the base metal layer Nb proceeds and the volume expands, so that the hole is filled with Nb oxide, which is the oxide of the base metal layer, in the direction perpendicular to the substrate from the bottom of the hole. Anodization was continued until it finally overflowed from the top of the hole and covered the porous film. Thereafter, a heat treatment at 300 ° C. was performed in an air atmosphere. By removing the porous film in a 5 wt% phosphoric acid aqueous solution at 25 ° C., a hollow structure made of Nb oxide was obtained.

  As described above, a microcolumn having a periodic interval P between adjacent columnar bodies of 50 nm, a columnar body diameter of D of 27 nm, and a columnar body height h of 100 nm was fabricated.

  INDUSTRIAL APPLICABILITY The present invention can be used for manufacturing a micro column for μTAS having a columnar body having a high aspect even when the diameter of the columnar body is uniform from the top to the bottom and the interval between the columnar bodies is narrow.

It is a schematic diagram which shows the cross section of an example of the microcolumn manufactured by the method of this invention. It is a schematic diagram which shows the top view of the microcolumn of this invention. It is process drawing which shows one embodiment of the manufacturing method of the microcolumn which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Oxide of base metal layer 12 Flow path 13 Base metal layer 14 Substrate 15 Anodized layer 16 Depression 17 Porous film 18 Hole 19 Oxide of anodized layer 20 Hollow structure 21 Columnar body 22 Covering layer P Adjacent layer Periodic interval of columnar body D Diameter of columnar body h Height of columnar body

Claims (8)

  A method of manufacturing a microcolumn, comprising a step of disposing a base metal layer and an anodized layer on a substrate, and a hole formed in a direction perpendicular to the substrate by anodizing the anodized layer A step of forming a porous film, and an oxide containing an element of the base metal layer is grown from the bottom of the hole of the porous film to the upper direction of the hole to cover the upper surface of the porous film and to form a columnar body and a coating layer And a step of removing the porous film and obtaining a hollow structure having a columnar body made of an oxide containing an element of the base metal layer and a coating layer on the substrate. A method for manufacturing a microcolumn.   2. The method for manufacturing a microcolumn according to claim 1, wherein the base metal layer is a layer containing at least one element selected from Ti, Zr, Nb, Hf, Ta, Mo, and W.   The method for producing a microcolumn according to claim 1 or 2, wherein the step of forming the hollow structure having a columnar body and a covering layer by removing the porous film is performed by second anodic oxidation.   The method for producing a microcolumn according to claim 3, wherein the electrolytic solution used for the second anodic oxidation is an aqueous ammonium borate solution, an ammonium tartrate solution or an aqueous ammonium citrate solution.   The method for producing a microcolumn according to claim 1 or 2, wherein the step of forming the hollow structure having the columnar body and the covering layer by removing the porous film is performed by wet etching.   The microcolumn production according to any one of claims 1 to 5, wherein the anodized layer is anodized after forming a recess as a starting point of anodization in the anodized layer. Method.   The method for manufacturing a microcolumn according to claim 1, wherein the columnar bodies are arranged with a uniform diameter and interval.   The method for manufacturing a microcolumn according to any one of claims 1 to 7, further comprising a step of heat-treating the hollow structure having the columnar body and the coating layer in an oxidizing atmosphere.

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