JP2011240278A - Method for manufacturing filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a filter having the pore diameter of a nano size.SOLUTION: A plurality of carbon nanotubes 15 are selectively formed on a substrate 10. A base material 11 consisting of SOG is successively formed on the substrate 10, and the plurality of carbon nanotubes 15 are retained by the formed base material 11. A plurality of holes 11a by the plurality of carbon nanotubes 15 are successively formed to the base material 11 by oxidizing the plurality of carbon nanotubes 15 to disappear.

Description

  The present invention relates to a method for manufacturing a filter used in a semiconductor manufacturing process or chemical analysis using clean gas or chemicals.

  In the semiconductor manufacturing process, the presence of foreign matters having a diameter of about several tens to 100 nm greatly affects the yield of wafers. At present, there is a filter using a porous material as a filter having a fine pore diameter, but it is difficult to control the diameter of pores through which a gas or a chemical solution passes with a nano size. Therefore, there is a possibility that a foreign substance having a diameter of several tens of nm to 100 nm will pass through, and an improvement in the yield of the manufacturing object cannot be expected.

  In the field of chemical analysis, higher accuracy is required. To meet this demand, it is necessary to supply cleaner reagents.

JP 2005-285821 A JP 2004-315358 A

  As described above, a filter having a fine pore diameter that is generally used at present often uses a porous material. With this porous material, it is difficult to control the pore size with nano-size, and a filter having nano-sized pore size cannot be formed.

  An object of the present invention is to solve the above problems and to form a filter having a nano-sized pore size.

  In order to achieve the above-mentioned object, according to the present invention, a filter manufacturing method uses a carbon nanotube having a nano size as a filter mold.

  Specifically, the method for manufacturing a filter according to the present invention includes a step (a) of selectively forming a plurality of carbon nanotubes on a substrate, a base material formed on the substrate, and the formed base material. A step (b) for holding a plurality of carbon nanotubes, and a step (c) for forming a plurality of holes due to the plurality of carbon nanotubes in the base material by eliminating the plurality of carbon nanotubes after the step (b). And.

  According to the method for manufacturing a filter of the present invention, a plurality of carbon nanotubes are held by the formed base material, and then the plurality of carbon nanotubes are lost, thereby forming a plurality of holes by the plurality of carbon nanotubes in the base material. . That is, by using a plurality of carbon nanotubes as a filter mold, a filter having a nano-sized pore diameter can be produced.

  In the method for producing a filter of the present invention, the base material is liquid glass, and the step (b) preferably includes a step of baking and solidifying the liquid glass holding a plurality of carbon nanotubes.

  In this way, it is possible to obtain a filter having pores having a pore diameter of several nm in a glass in which a plurality of carbon nanotubes are solidified.

  Further, in the filter manufacturing method of the present invention, the base material is silicon nitride, and in the step (b), silicon nitride is preferably formed by a plasma CVD method.

  In this way, a filter having a nano-sized pore diameter can be obtained, and the difference in etching rate between the substrate and the base material can be increased, so that the substrate can be easily removed from the base material. .

  In the method for producing a filter of the present invention, the plurality of carbon nanotubes may be eliminated by performing an oxidation treatment using oxygen plasma or ozone plasma in the step (c).

  The method for producing a filter of the present invention may further include a step (d) of forming a catalyst layer made of a metal on the substrate before the step (a).

  In the filter manufacturing method of the present invention, in the step (a), the carbon nanotubes are preferably oriented in a direction perpendicular to the main surface of the substrate.

  In the method for producing a filter of the present invention, it is preferable that the size of each carbon nanotube is adjusted in step (a).

In the method for producing a filter of the present invention, in step (a), the density of the plurality of carbon nanotubes is 10 ⁹ / cm ² or more and 10 ¹¹ / cm ² or less, and the length is 1 μm or more and 100 μm or less. There may be.

  The method for producing a filter of the present invention may further include a step (e) of removing at least a part of the substrate by chemical etching after the step (c).

  In this case, in step (e), etching may be performed so as to leave the peripheral edge of the substrate.

  In this way, the strength of the filter can be increased.

  The filter manufacturing method of the present invention may further include a step (e) of removing the substrate by a chemical mechanical polishing method after the step (c).

  According to the filter manufacturing method of the present invention, a filter having a nano-sized pore diameter can be produced.

FIG. 1A and FIG. 1B show a filter according to a first embodiment of the present invention, FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view. FIG. 2A to FIG. 2D are cross-sectional views in order of steps showing the method for manufacturing a filter according to the first embodiment of the present invention. FIG. 3A to FIG. 3D are cross-sectional views in order of steps showing the filter manufacturing method according to the first embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a carbon nanotube growth apparatus used for manufacturing a filter according to each embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of an oxidation treatment apparatus used for manufacturing a filter according to each embodiment of the present invention. 6 (a) and 6 (b) show a filter according to a first modification of the first embodiment of the present invention, FIG. 6 (a) is a plan view, and FIG. 6 (b) is a sectional view. It is. 7 (a) and 7 (b) show a filter according to a third modification of the first embodiment of the present invention, FIG. 7 (a) is a plan view, and FIG. 7 (b) is a sectional view. It is. 8A and 8B show a filter according to the second embodiment of the present invention, FIG. 8A is a plan view, and FIG. 8B is a cross-sectional view. FIG. 9A to FIG. 9D are cross-sectional views in order of steps showing a method for manufacturing a filter according to the second embodiment of the present invention. FIG. 10A to FIG. 10C are cross-sectional views in order of steps showing a method for manufacturing a filter according to the second embodiment of the present invention. 11 (a) and 11 (b) show a filter according to a first modification of the second embodiment of the present invention, FIG. 11 (a) is a plan view, and FIG. 11 (b) is a sectional view. It is.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIG.

  As shown in FIGS. 1 (a) and 1 (b), the filter 1 according to the first embodiment has a plurality of holes 11a formed in a base material 11 formed by baking and solidifying liquid glass, for example. . Each hole 11a penetrates in the front and back direction of the base material 11, and is formed by eliminating a plurality of carbon nanotubes. Therefore, the diameter of each hole 11a is adjusted to nano size.

  Hereinafter, a method for manufacturing the filter 1 configured as described above will be described with reference to FIGS.

  First, as shown in FIG. 2A, for example, silicon nitride having a thickness of about 20 nm to 100 nm is formed on the main surface of a substrate 10 made of silicon (Si) by chemical vapor deposition (CVD). A base film 12 is formed.

  Next, as shown in FIG. 2B, a metal thin film 13 made of titanium (Ti) having a thickness of about 1 nm to 15 nm is formed on the base film 12 by sputtering or the like. Here, instead of Ti, molybdenum (Mo), vanadium (V), niobium (Nb), or tungsten (W) can be used for the metal thin film 13.

  Next, as shown in FIG. 2C, a catalyst layer 14 made of cobalt (Co) having a thickness of about 1 nm to 5 nm is formed on the metal thin film 13 by sputtering. The catalyst layer 14 may be made of nickel (Ni) or iron (Fe), or two or more of these alloys including Co instead of Co. Thereafter, the formed catalyst layer 14 is heated to about 300 ° C. to 400 ° C. to agglomerate cobalt to form a plurality of particulate catalyst layers 14. The cobalt aggregation may be performed in a carbon nanotube growth apparatus in the next step.

Next, as shown in FIG. 2D, the substrate 10 is put into the carbon nanotube growth apparatus shown in FIG. 4, and the carbon source, for example, acetylene (C ₂ H ₂ ) and an inert gas, for example, argon ( Ar) is introduced onto the substrate 10. At this time, the substrate 10 is heated to about 350 ° C. to 900 ° C., and the carbon nanotubes 15 having a diameter of 5 nm to 50 nm and a length of about 1 μm to 100 μm are respectively formed from the particulate catalyst layers 14. It grows in a direction substantially perpendicular to the ten main surfaces. Here, the growth density of the carbon nanotubes 15 is set to be about 10 ⁹ / cm ² to 10 ¹¹ / cm ² . The carbon source is not limited to acetylene, and for example, methane (CH ₄ ) can be used.

  Next, as shown in FIG. 3A, liquid glass, for example, SOG (spin-on-glass) is applied so as to embed a plurality of carbon nanotubes 15 on the substrate 10. Thereafter, the applied SOG is baked and hardened at a temperature of about 350 ° C. to 500 ° C. for about 60 to 120 minutes to form a base material 11 made of SOG and holding a plurality of carbon nanotubes 15 therein. At this time, it is necessary that the thickness of the base material 11 does not exceed the height of the carbon nanotube 15.

Next, as shown in FIG. 3B, the substrate 10 on which the base material 11 is formed is put into the vacuum vessel 61 of the oxidation processing apparatus shown in FIG. 5, and oxygen (O ₂ ) plasma or ozone (O ₃ ) The carbon nanotubes 15 are oxidized by plasma to be lost as carbon dioxide (CO ₂ ). As a result, as shown in FIG. 3C, the base material 11 is formed with a plurality of holes 11 a formed by the disappearance of the carbon nanotubes 15. Thus, the hole diameter of each hole 11 a depends on the diameter of the carbon nanotube 15.

  Next, as shown in FIG. 3D, the substrate 10 made of silicon is removed by etching using, for example, a sodium hydroxide (NaOH) solution or a potassium hydroxide (KOH) solution. Thereafter, the exposed base film 12 made of silicon nitride is removed by, for example, phosphoric acid bath etching. Subsequently, the exposed metal thin film 13 made of titanium is removed, for example, with hydrochloric acid.

  As described above, the filter 1 having a plurality of nano-sized holes 11a shown in FIG. 1 can be produced.

  The carbon nanotube growth apparatus used in the first embodiment will be described below with reference to FIG.

  As shown in FIG. 4, the carbon nanotube growth apparatus used in the first embodiment includes a vacuum vessel 51, a stage 52 disposed below the vacuum vessel 51 and holding the substrate 10 on the upper surface, The heating unit 53 is disposed on the lower side and heats the stage 52. A source gas and inert gas introduction port 54 is provided in one upper part of the vacuum vessel 51, and a gas exhaust port 55 is provided in the other upper part.

  Next, the oxidation processing apparatus used in the first embodiment will be described with reference to FIG.

  As shown in FIG. 5, the oxidation processing apparatus used in the first embodiment includes a vacuum vessel 61, a stage 62 disposed on the lower portion of the vacuum vessel 61 and holding the substrate 10 on the upper surface, and a lower portion of the stage 62. The heating unit 63 that is disposed on the side and heats the stage 62, and the high-frequency generation unit 64 that is disposed on the top of the vacuum vessel and generates a high frequency with an output of 100 W or more and an oscillation frequency of 13.56 MHz. An oxygen gas or ozone gas introduction port 65 is provided in one upper part of the vacuum vessel 61, and a gas exhaust port 66 is provided in the other upper part.

  Oxygen or ozone introduced into the vacuum vessel 61 from the introduction port 65 is turned into plasma by the high frequency from the high frequency generation unit 64.

(First modification of the first embodiment)
Hereinafter, a first modification of the first embodiment will be described with reference to FIG.

  As shown in FIGS. 6A and 6B, the filter 1 according to the first modification leaves the peripheral portions of the substrate 10, the base film 12, and the metal thin film 13 on the lower surface. Thereby, the strength of the filter 1 itself can be improved.

  The manufacturing method of the filter 1 according to the first modification is as follows. That is, in the substrate removing step shown in FIG. 3D, a resist pattern for masking the peripheral portion of the substrate 10 is formed on the back surface of the substrate 10 by lithography. Subsequently, wet etching is performed on the substrate 10 using the formed resist pattern as a mask. Subsequently, the exposed base film 12 is removed by phosphoric acid bath etching, and the exposed metal thin film 13 is removed with hydrochloric acid.

(Second modification of the first embodiment)
Hereinafter, a second modification of the first embodiment will be described.

  In the second modification, a chemical mechanical polishing (CMP) method is used in place of the method of removing the substrate 10 by wet etching in the substrate removing step shown in FIG. Thereafter, the exposed base film 12 is removed by phosphoric acid bath etching, and the exposed metal thin film 13 is removed with hydrochloric acid.

  Even in this way, the filter 1 shown in FIG. 1 can be obtained.

  If a wet etching method is used for removing the substrate 10, processing with unevenness reflecting the crystal orientation of Si used for the substrate is possible. If the CMP method is used, the crystal orientation of Si used for the substrate is possible. Regardless of this, it is possible to obtain a uniform processed surface.

(Third Modification of First Embodiment)
Hereinafter, a third modification of the first embodiment will be described with reference to FIG.

  As shown in FIGS. 7A and 7B, the filter 1 according to the third modified example has a diameter of the air holes 11a of, for example, about 30 nm to 80 nm, the first embodiment, the first modified example, and It is larger than the second modification.

  The manufacturing method of the filter 1 according to the third modification is as follows. That is, in the step shown in FIG. 2C, the cobalt (Co) film thickness is, for example, about 10 nm to 15 nm, or the heating temperature is, for example, about 450 ° C. to 600 ° C. ) To increase the diameter of the cobalt particles to about 30 nm to 80 nm. The subsequent steps are the same as in the first embodiment.

  Thus, the pore diameter 11a of the filter 1 can be controlled by adjusting the amount of aggregation of the catalyst layer 14, that is, the particle diameter.

  In the third modification, the first modification or the second modification can be applied.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG.

  As shown in FIGS. 8A and 8B, the filter 1 according to the second embodiment has a plurality of holes 21a formed in a base material 21 made of, for example, silicon nitride (SiN). . Each hole 21a penetrates in the front and back direction of the base material 21, and is formed by eliminating a plurality of carbon nanotubes. Therefore, the diameter of each hole 21a is adjusted to nano size.

  Hereinafter, a method for manufacturing the filter 1 configured as described above will be described with reference to FIGS. 9 and 10.

  First, as shown in FIG. 9A, for example, a metal thin film 13 made of titanium (Ti) having a thickness of about 1 nm to 15 nm is formed on the main surface of a substrate 10 made of silicon (Si) by sputtering or the like. Is deposited. Here, instead of Ti, molybdenum (Mo), vanadium (V), niobium (Nb), or tungsten (W) can be used for the metal thin film 13.

  Next, as shown in FIG. 9B, a catalyst layer 14 made of cobalt (Co) having a thickness of about 1 nm to 5 nm is formed on the metal thin film 13 by sputtering. The catalyst layer 14 may be made of nickel (Ni) or iron (Fe), or two or more of these alloys including Co instead of Co. Thereafter, the formed catalyst layer 14 is heated to about 300 ° C. to 400 ° C. to agglomerate cobalt to form a plurality of particulate catalyst layers 14. The cobalt aggregation may be performed in a carbon nanotube growth apparatus in the next step.

Next, as shown in FIG. 9C, the substrate 10 is put into the carbon nanotube growth apparatus shown in FIG. 4, and acetylene (C ₂ H ₂ ) that is a carbon source, for example, an inert gas such as argon ( Ar) is introduced onto the substrate 10. At this time, the substrate 10 is heated to about 350 ° C. to 900 ° C., and the carbon nanotubes 15 having a diameter of 5 nm to 50 nm and a length of about 1 μm to 100 μm are respectively formed from the particulate catalyst layers 14. It grows in a direction substantially perpendicular to the ten main surfaces. Here, the growth density of the carbon nanotubes 15 is set to be about 10 ⁹ / cm ² to 10 ¹¹ / cm ² . The carbon source is not limited to acetylene, and for example, methane (CH ₄ ) can be used.

  Next, as shown in FIG. 9D, a base material 21 made of silicon nitride is formed by plasma CVD so as to embed a plurality of carbon nanotubes 15 on the substrate 10. At this time, it is necessary that the thickness of the base material 21 does not exceed the height of the carbon nanotube 15.

Next, as shown in FIG. 10A, the substrate 10 on which the base material 21 is formed is put into the vacuum vessel 61 of the oxidation processing apparatus shown in FIG. 5, and oxygen (O ₂ ) plasma or ozone (O ₃ ) The carbon nanotubes 15 are oxidized by plasma to be lost as carbon dioxide (CO ₂ ). As a result, as shown in FIG. 10B, the base material 21 is formed with a plurality of holes 21 a formed by the disappearance of the carbon nanotubes 15. Thus, the hole diameter of each hole 21 a depends on the diameter of the carbon nanotube 15.

  Next, as shown in FIG. 10C, the substrate 10 made of silicon is removed by etching, for example, with a sodium hydroxide (NaOH) solution or a potassium hydroxide (KOH) solution. Thereafter, the exposed metal thin film 13 made of titanium is removed, for example, with hydrochloric acid.

  As described above, the filter 1 having a plurality of nano-sized holes 21a shown in FIG. 8 can be produced.

  In the second embodiment, since silicon (Si) is used for the substrate 10, an etching rate difference with the base material 21 made of silicon nitride increases when the substrate 10 is removed. The substrate 10 can be easily removed.

(First Modification of Second Embodiment)
Hereinafter, a first modification of the second embodiment will be described with reference to FIG.

  As shown in FIGS. 11A and 11B, the filter 1 according to the first modified example leaves the peripheral portion of the substrate 10 and the metal thin film 13 on the lower surface. Thereby, the strength of the filter 1 itself can be improved.

  The manufacturing method of the filter 1 according to the first modification is as follows. That is, in the substrate removal step shown in FIG. 10C, a resist pattern for masking the peripheral portion of the substrate 10 is formed on the back surface of the substrate 10 by lithography. Subsequently, wet etching is performed on the substrate 10 using the formed resist pattern as a mask. Subsequently, the exposed metal thin film 13 is removed with hydrochloric acid.

(Second modification of the second embodiment)
Hereinafter, a second modification of the second embodiment will be described.

  In the second modification, a chemical mechanical polishing (CMP) method is used in place of the method of removing the substrate 10 by wet etching in the substrate removing step shown in FIG. Thereafter, the exposed metal thin film 13 is removed with hydrochloric acid.

  Even in this way, the filter 1 shown in FIG. 8 can be obtained.

  Also in the second embodiment, in the step shown in FIG. 9D, by increasing the diameter of each particle in which the catalyst layer 14 made of cobalt is aggregated, the first embodiment shown in FIG. The filter 1 equivalent to the three modified examples can be produced.

  The method for producing a filter according to the present invention can produce a filter having a nano-sized pore diameter, and is useful for a semiconductor production process using a clean gas or a chemical or a filter used for chemical analysis.

1 Filter 10 Substrate 11 Base material (SOG)
11a Hole 12 Base film 13 Metal thin film 14 Catalyst layer 15 Carbon nanotube 21 Base material (SiN)
21a Hole 51 Vacuum vessel 52 Stage 53 Heating unit 54 Inlet 55 Exhaust port 61 Vacuum vessel 62 Stage 63 Heating unit 64 High frequency unit 65 Inlet 66 Exhaust port

Claims (11)

A step (a) of selectively forming a plurality of carbon nanotubes on a substrate;
Forming a base material on the substrate and holding the plurality of carbon nanotubes by the formed base material (b);
A step (c) of forming a plurality of pores by the plurality of carbon nanotubes in the base material by eliminating the plurality of carbon nanotubes after the step (b). Filter manufacturing method. The base material is liquid glass,
The method for producing a filter according to claim 1, wherein the step (b) includes a step of baking and solidifying the liquid glass holding the plurality of carbon nanotubes. The base material is silicon nitride;
2. The method for manufacturing a filter according to claim 1, wherein in the step (b), the silicon nitride is formed by a plasma CVD method.   4. The filter according to claim 1, wherein in the step (c), the plurality of carbon nanotubes are eliminated by performing an oxidation treatment using oxygen plasma or ozone plasma. 5. Production method. Prior to step (a),
The method for producing a filter according to claim 1, further comprising a step (d) of forming a catalyst layer made of a metal on the substrate.   6. The filter manufacturing method according to claim 1, wherein, in the step (a), the carbon nanotubes are oriented in a direction perpendicular to a main surface of the substrate.   In the said process (a), the magnitude | size of each said carbon nanotube is adjusted, The filter manufacturing method of any one of Claims 1-6 characterized by the above-mentioned. In the step (a), the density of the plurality of carbon nanotubes is 10 ⁹ / cm ² or more and 10 ¹¹ / cm ² or less, and the length thereof is 1 μm or more and 100 μm or less. The filter manufacturing method of any one of Claims 1-7. After step (c),
The method for manufacturing a filter according to claim 1, further comprising a step (e) of removing at least a part of the substrate by chemical etching.   The method for manufacturing a filter according to claim 9, wherein in the step (e), etching is performed so as to leave a peripheral portion of the substrate. After step (c),
The method for manufacturing a filter according to claim 1, further comprising a step (e) of removing the substrate by a chemical mechanical polishing method.

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