WO2025041470A1 - Method for manufacturing structure - Google Patents

Abstract

The present invention addresses the problem of providing a method for manufacturing a structure capable of achieving excellent post-exposure delay stability when used as an anisotropic conductive joining member. The method for manufacturing a structure of the present invention is a method for manufacturing a structure having: an insulating substrate made of an inorganic material; and a plurality of conductive paths made of a conductive member, which are insulated from each other penetrating the insulating substrate in the thickness direction, the method comprising a protruding step for bringing each of the conductive paths into contact with an organic acid-containing composition to form a protruding portion protruding from the surface of the insulating substrate, wherein each of the conductive paths has the protruding portion.

Description

Manufacturing method of the structure

The present invention relates to a method for manufacturing a structure.

Structures (devices) in which fine pores in an insulating substrate are filled with a conductive material are one area of nanotechnology that has attracted attention in recent years, and are expected to be used, for example, as anisotropic conductive bonding members.
This anisotropic conductive bonding member can be inserted between an electronic component such as a semiconductor element and a circuit board and electrically connected to the electronic component and the circuit board simply by applying pressure. Therefore, it is widely used as an electrical connecting member for electronic components such as semiconductor elements, and as an inspection connector for performing functional tests.
In particular, electronic components such as semiconductor elements are being significantly downsized, and conventional methods such as wire bonding, which directly connects wiring boards, flip chip bonding, and thermocompression bonding cannot fully guarantee connection stability. Therefore, anisotropic conductive bonding materials are attracting attention as electronic connection materials.

As an example of a microstructure that can be used for such an anisotropic conductive bonding member, Patent Document 1 describes "a microstructure made of an insulating base material having through micropores with a pore size of 10 to 500 nm at a density of 1 x ¹⁰ to 1 x ¹⁰ / ^mm2 , characterized in that the through micropores are filled with a metal at a filling rate of 30% or more, and at least one surface of the insulating base material is provided with a layer made of a polymer" ([Claim 1]), and describes that natural oxidation of the metal is prevented by configuring the protruding parts of the filled metal (conductive paths) to be covered with a polymer layer ([0038]).

JP 2010-067589 A

The inventors have studied the microstructure described in Patent Document 1 and have found that there is room for improvement in terms of preventing oxidation of the protruding parts of the conductive paths, i.e., in terms of the placement stability when used as an anisotropic conductive joining member.

The present invention aims to provide a method for manufacturing a structure that can achieve excellent placement stability when used as an anisotropic conductive joining member.

As a result of intensive research to achieve the above-mentioned object, the inventors have discovered that a structure having excellent lay-down stability can be produced by forming the protruding portions of each conductive path protruding from the surface of the insulating substrate while contacting the protruding portions with a composition containing an organic acid, and have thus completed the present invention.
That is, the present inventors have found that the above problems can be solved by the following configuration.

[1] A method for producing a structure having an insulating base material made of an inorganic material and a plurality of conductive paths made of a conductive member penetrating the insulating base material in a thickness direction and insulated from one another, comprising:
each conductive path has a protruding portion protruding from a surface of the insulating substrate;
A method for producing a structure, comprising a protruding step of forming protruding portions by contacting a composition containing an organic acid.
[2] The method for producing the structure according to [1], wherein the organic acid includes an organic acid having no nitrogen atom.
[3] The method for producing the structure according to [1] or [2], wherein the organic acid includes an oxycarboxylic acid.
[4] The method for producing the structure according to [3], wherein the oxycarboxylic acid includes at least one selected from the group consisting of lactic acid, malic acid, citric acid, glycolic acid, 2-hydroxymalonic acid, and tartaric acid.
[5] The method for producing a structure according to any one of [1] to [4], wherein the content of the organic acid relative to the total mass of the composition is 0.5 mass% or more.

As described below, the present invention provides a method for manufacturing a structure that can achieve excellent placement stability when used as an anisotropic conductive bonding member.

FIG. 1 is a schematic front view showing an example of a preferred embodiment of a structure produced by the method for producing a structure of the present invention. FIG. 2 is a cross-sectional view taken along the line IB--IB in FIG.

The present invention will be described in detail below.
The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits.
In addition, in the present specification, the upper or lower limit value of a certain numerical range in a stepwise described numerical range may be replaced with the upper or lower limit value of another stepwise described numerical range. In addition, the upper or lower limit value of a certain numerical range in the present specification may be replaced with a value shown in the examples.
In the present specification, each component may be used alone or in combination of two or more substances corresponding to each component. When two or more substances are used in combination for each component, the content of the component refers to the total content of the substances used in combination, unless otherwise specified.

[Method of manufacturing structure]
The manufacturing method of the structure of the present invention (hereinafter also abbreviated as "the manufacturing method of the present invention") is a manufacturing method for producing a structure having an insulating base material made of an inorganic material and a plurality of conductive paths made of a conductive member that penetrate the insulating base material in the thickness direction and are insulated from one another (hereinafter also formally abbreviated as "the structure of the present invention").
Furthermore, each conductive path in the structure of the present invention has a protruding portion that protrudes from the surface of the insulating substrate.
The manufacturing method of the present invention further includes a protruding step of forming the protruding portions of each conductive path by contacting the conductive path with a composition containing an organic acid.

In the present invention, as described above, the protruding portions of each conductive path protruding from the surface of the insulating substrate are formed while being in contact with a composition containing an organic acid, thereby making it possible to produce a structure having excellent shelf stability.
Although the details of this mechanism are not clear, it is speculated that it may be as follows.
That is, since the surface of the protruding portion of the conductive path is made of a conductive material, oxidation progresses over time. Note that it is believed that oxidation over time progresses even if the protruding portion of the conductive path is embedded in a polymer layer.
In the present invention, by forming the protruding portion of the conductive path while contacting it with a composition containing an organic acid, an antioxidant film is formed on the surface of the protruding portion of the conductive path by the organic acid simultaneously with or immediately after the formation of the protruding portion of the conductive path, thereby making it possible to suppress oxidation over time. As a result, it is believed that a structure having excellent storage stability can be produced.

Next, the configuration of the structure of the present invention will be described with reference to FIGS.
A structure 1 shown in FIGS. 1 and 2 has an insulating substrate 2 and a plurality of conductive paths 3 made of a conductive material.
As shown in FIGS. 1 and 2 , the conductive paths 3 are insulated from each other and extend through the insulating substrate 2 in a thickness direction Z (Z1: direction from the back surface to the front surface in FIG. 1 , Z2: direction from the front surface to the back surface in FIG. 1 ).
Furthermore, as shown in FIG. 2, the conductive path 3 has protruding portions 3a and 3b protruding from the surfaces 2a and 2b of the insulating substrate 2, and an oxidation prevention film 4 is formed on the surfaces of the protruding portions 3a and 3b.
Here, "insulated from one another" means that the conductive paths present inside (in the thickness direction) of the insulating base material are insulated from one another inside the insulating base material.
In addition, the embodiment in which the antioxidant film 4 is formed on the surfaces of the protruding portions 3a and 3b may be the embodiment shown in FIG. 2, i.e., the antioxidant film 4 is formed on the surfaces of the protruding portions 3a and 3b and on the surfaces 2a and 2b of the insulating substrate 2, but it may also be an embodiment in which the antioxidant film 4 is formed only on the surfaces of the protruding portions 3a and 3b.

[Insulating substrate]
The insulating substrate of the structure of the present invention is not particularly limited as long as it is made of an inorganic material and has an electrical resistivity (about ¹⁰ Ω·cm) similar to that of insulating substrates constituting conventionally known anisotropic conductive films and the like.
Note that the term "made of an inorganic material" does not limit the insulating base material to one made only of an inorganic material, but rather refers to an insulating base material whose main component is an inorganic material (50% by mass or more).

The insulating substrate may be, for example, a metal oxide substrate, a metal nitride substrate, a glass substrate, a ceramic substrate (e.g., silicon carbide, silicon nitride, etc.), a carbon substrate (e.g., diamond-like carbon, etc.), a polyimide substrate, a composite material of these, or a material in which a film is formed on an organic material having through holes with an inorganic material containing 50% by mass or more of a ceramic material or a carbon material.

In the present invention, the insulating substrate is preferably a metal oxide substrate, and more preferably an anodized film of a valve metal, because micropores having a desired average opening diameter are formed as through-holes and the conductive paths described below are easily formed.
Specific examples of the valve metal include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony.
Among these, an anodized aluminum film (substrate) is preferred because it has good dimensional stability and is relatively inexpensive.

In the present invention, the thickness of the insulating base material (the portion indicated by reference numeral 6 in FIG. 2) is preferably 1 μm to 1000 μm, more preferably 5 μm to 500 μm, and even more preferably 10 μm to 300 μm. When the thickness of the insulating base material is in this range, the insulating base material is easy to handle.
The thickness of the insulating substrate is determined by observing the cross section of the structure with a field emission scanning electron microscope and measuring the thickness at 10 points, averaging the thickness.

In the present invention, the interval between the conductive paths in the insulating base material is preferably 5 nm to 800 nm, more preferably 10 nm to 200 nm, and even more preferably 20 nm to 60 nm. When the interval between the conductive paths in the insulating base material is within this range, the insulating base material functions sufficiently as an insulating partition wall.
Here, the spacing between each conductive path refers to the width between adjacent conductive paths (the portion indicated by reference numeral 7 in FIG. 2), and refers to the average value of the width between adjacent conductive paths measured at 10 points when the cross section of the structure is observed at a magnification of 200,000 times using a field emission scanning electron microscope.

[Conduit]
The plurality of conductive paths in the structure of the present invention are conductive paths made of a conductive material that penetrate the insulating base material in the thickness direction and are insulated from one another.
The conductive paths have protruding portions that protrude from the surface of the insulating base material, and an anti-oxidation film, which will be described later, is formed on the surface of the protruding portion of each conductive path.

<Conductive member>
The conductive member constituting the conductive path is not particularly limited as long as it is a material with an electrical resistivity of 10 ³ Ω·cm or less, and specific examples of suitable materials include gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), indium-doped tin oxide (ITO), etc.
Among these, from the viewpoint of electrical conductivity, copper, gold, aluminum and nickel are preferred, copper and gold are more preferred, and copper is even more preferred.

<Protruding part>
The protruding portion of the conductive path is a portion where the conductive path protrudes from the surface of the insulating base material, and an anti-oxidation film, which will be described later, is formed on the surface of the protruding portion.

In the present invention, when the structure is used as an anisotropic conductive joining member and is connected (joined) to an electrode by a method such as crimping, the aspect ratio of the protruding portion of the conductive path (height of the protruding portion/diameter of the protruding portion) is preferably 0.5 or more and less than 50, more preferably 0.8 to 20, and even more preferably 1 to 10, in order to ensure sufficient insulation in the planar direction in the event that the protruding portion is crushed.

In addition, in the present invention, when the structure is used as an anisotropic conductive bonding member, from the viewpoint of conforming to the surface shape of the semiconductor chip or wiring board to be connected, the height of the protruding portion of the conductive path is preferably 50 nm to 3000 nm, more preferably 100 to 2000 nm, and even more preferably 200 to 1000 nm.
Similarly, the diameter of the protruding portion of the conductive path is preferably more than 5 nm and not more than 10 μm, and more preferably 20 nm to 1000 nm.
The height of the protruding portion of the conductive path herein refers to the average value of the heights of the protruding portions of the conductive path measured at 10 points on a cross section of the structure observed at a magnification of 20,000 times using a field emission scanning electron microscope.
Similarly, the diameter of the protruding portion of the conductive path refers to the average value of the diameters of the protruding portions of the conductive path measured at 10 points on the cross section of the structure observed with a field emission scanning electron microscope.

<Other shapes>
The conductive path is columnar, and its diameter (the portion indicated by reference numeral 8 in FIG. 2) is preferably more than 5 nm and not more than 10 μm, similar to the diameter of the protruding portion, and more preferably 20 nm to 1000 nm.

The conductive paths are insulated from one another by the insulating base material, and their density is preferably 20,000 pieces/mm2 or more, more preferably 2 million pieces/ ^mm2 or more, even more preferably 10 million pieces/ ^mm2 or more, particularly preferably 50 million pieces/ ^mm2 or more, and most preferably 100 million pieces/ ^mm2 or ^more .

Furthermore, the center-to-center distance between adjacent conductive paths (parts indicated by reference numeral 9 in Figures 1 and 2) is preferably 20 nm to 500 nm, more preferably 40 nm to 200 nm, and even more preferably 50 nm to 140 nm.

[Anti-oxidation film]
In the structure of the present invention, an oxidation prevention film is formed on the surface of the protruding portion of the conductive path.
Here, the antioxidant film is a film formed from a composition containing an organic acid used in the protruding step described below.
The thickness of the oxidation-preventing film is not particularly limited, but is preferably 0.1 to 10 nm, and more preferably 0.1 to 5 nm.
The thickness of the oxidation-resistant film is determined by observing the cross section of the structure with a transmission electron microscope and measuring the thickness at 10 points, and averaging the measured thickness.

[Each step in the manufacturing method]
The production method of the present invention is not particularly limited as long as it includes a protruding step of forming a protruding portion of each conductive path by contacting a composition containing an organic acid. For example, the production method may include a conductive path forming step of causing a conductive material to be present in a through hole provided in the insulating base material to form a conductive path, and a protruding step of contacting a composition containing an organic acid after the conductive path forming step to partially remove only the surface of the insulating base material to form a protruding portion of the conductive path.

<Preparation of insulating substrate>
The insulating substrate can be, for example, a glass substrate having a through hole (Through Glass Via: TGV) as it is. However, from the viewpoint of keeping the opening diameter of the conductive path and the aspect ratio of the protruding portion within the above-mentioned range, a method of subjecting a valve metal to an anodizing treatment is preferred.
As for the anodizing treatment, for example, when the insulating base material is an anodized aluminum film, the anodizing treatment can be carried out in the order of anodizing the aluminum substrate, and then a perforating treatment for perforating the micropores formed by the anodizing treatment.
In the present invention, the aluminum substrate used in the preparation of the insulating base material and the respective treatment steps applied to the aluminum substrate can be similar to those described in paragraphs [0041] to [0121] of JP-A-2008-270158.

<Conduction Path Forming Process>
The conductive path forming step is a step of causing the conductive material to be present in the through-holes provided in the insulating base material.
Here, examples of the method for causing a metal to be present in the through holes include the methods (electrolytic plating method or electroless plating method) described in paragraphs [0123] to [0126] and [FIG. 4] of JP-A-2008-270158.
In the electrolytic plating method or electroless plating method, it is preferable to previously provide an electrode layer made of gold, nickel, copper, etc. Examples of methods for forming this electrode layer include gas phase processing such as sputtering, liquid phase processing such as electroless plating, and combinations of these.
The metal filling step provides a structure before the protruding portions of the conductive paths are formed.

On the other hand, instead of the method described in JP 2008-270158 A, the conductive path forming process may be a method having steps including an anodizing process in which one surface (hereinafter also referred to as "one side") of an aluminum substrate is anodized to form an anodized film having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores on one side of the aluminum substrate, a barrier layer removal process in which the barrier layer of the anodized film is removed after the anodizing process, a metal filling process in which electrolytic plating is performed after the barrier layer removal process to fill the inside of the micropores with metal, and a substrate removal process in which the aluminum substrate is removed after the metal filling process to obtain a structure.

(Anodizing process)
The anodizing process is a process of performing anodizing on one side of the aluminum substrate to form an anodized film on one side of the aluminum substrate, the anodized film having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores.
The anodizing treatment in the manufacturing method of the present invention can be performed using a conventionally known method, but from the viewpoint of increasing the regularity of the micropore arrangement and ensuring anisotropic conductivity, it is preferable to use a self-ordering method or constant voltage treatment.
Here, the self-ordering method of the anodizing treatment and the constant voltage treatment can be the same as the treatments described in paragraphs [0056] to [0108] and [FIG. 3] of JP-A-2008-270158.

(Barrier layer removal process)
The barrier layer removal step is a step of removing the barrier layer of the anodized film after the anodizing treatment step. By removing the barrier layer, a part of the aluminum substrate is exposed through the micropores.
The method for removing the barrier layer is not particularly limited, and examples thereof include a method for electrochemically dissolving the barrier layer at a potential lower than the potential in the anodizing treatment in the anodizing treatment step (hereinafter also referred to as an "electrolytic removal treatment"); a method for removing the barrier layer by etching (hereinafter also referred to as an "etching removal treatment"); and a combination of these methods (particularly, a method for performing the electrolytic removal treatment and then removing the remaining barrier layer by an etching removal treatment).

<Electrolytic removal treatment>
The electrolytic removal treatment is not particularly limited as long as it is an electrolytic treatment carried out at a potential lower than the potential (electrolytic potential) in the anodizing treatment in the anodizing treatment step.
In the present invention, the electrolytic dissolution treatment can be carried out consecutively with the anodizing treatment, for example, by lowering the electrolytic potential at the end of the anodizing treatment step.

In the electrolytic removal treatment, the same electrolytic solution and treatment conditions as those in the above-mentioned conventionally known anodizing treatment can be used, except for the electrolytic potential.
In particular, when the electrolytic removal treatment and the anodizing treatment are carried out successively as described above, it is preferable to carry out the treatments using the same electrolyte.

The electrolytic potential in the electrolytic removal treatment is preferably lowered continuously or stepwise (in steps) to a potential lower than the electrolytic potential in the anodizing treatment.
Here, the reduction width (step width) when the electrolytic potential is reduced stepwise is preferably 10 V or less, more preferably 5 V or less, and even more preferably 2 V or less, from the viewpoint of the withstand voltage of the barrier layer.
Moreover, the voltage drop rate when the electrolytic potential is lowered continuously or stepwise is preferably 1 V/sec or less, more preferably 0.5 V/sec or less, and even more preferably 0.2 V/sec or less, from the viewpoint of productivity, etc.

Etching Removal Treatment
The etching removal treatment is not particularly limited, but may be a chemical etching treatment in which an acid aqueous solution or an alkali aqueous solution is used to dissolve the film, or may be a dry etching treatment.

The barrier layer can be removed by chemical etching, for example, by immersing the structure after the anodizing process in an acid or alkaline aqueous solution, filling the inside of the micropores with the acid or alkaline aqueous solution, and then contacting the surface of the anodized film on the opening side of the micropores with a pH buffer solution, thereby selectively dissolving only the barrier layer.

When an aqueous acid solution is used, it is preferable to use an aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, or hydrochloric acid, or a mixture thereof. The concentration of the aqueous acid solution is preferably 1 to 10% by mass. The temperature of the aqueous acid solution is preferably 15 to 80°C, more preferably 20 to 60°C, and even more preferably 30 to 50°C.
On the other hand, when an alkaline aqueous solution is used, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The concentration of the alkaline aqueous solution is preferably 0.1 to 5 mass %. The temperature of the alkaline aqueous solution is preferably 10 to 60°C, more preferably 15 to 45°C, and even more preferably 20 to 35°C. The alkaline aqueous solution may contain zinc or other metals.
Specifically, for example, a 50 g/L, 40° C. aqueous phosphoric acid solution, a 0.5 g/L, 30° C. aqueous sodium hydroxide solution, and a 0.5 g/L, 30° C. aqueous potassium hydroxide solution are preferably used.
As the pH buffer solution, a buffer solution corresponding to the above-mentioned acid aqueous solution or alkaline aqueous solution can be appropriately used.

The immersion time in the acid or alkaline aqueous solution is preferably 8 to 120 minutes, more preferably 10 to 90 minutes, and even more preferably 15 to 60 minutes.

In the dry etching process, it is preferable to use a gas species such as a Cl ₂ /Ar mixed gas.

(Metal filling process)
The metal filling step is a step of filling the inside of the micropores in the anodized film with a metal by performing an electrolytic plating process after the barrier layer removal step, and examples of the metal filling step include methods similar to those described in paragraphs [0123] to [0126] and [Figure 4] of JP2008-270158A (electrolytic plating method or electroless plating method).
In the electrolytic plating method or electroless plating method, the aluminum substrate exposed through the micropores after the above-mentioned barrier layer removal step can be used as an electrode.

(Substrate removal process)
The substrate removing step is a step of removing the aluminum substrate after the metal filling step to obtain a structure.
Methods for removing the aluminum substrate include, for example, a method in which a treatment liquid is used to dissolve only the aluminum substrate without dissolving the metal filled inside the micropores in the metal filling step and the anodized film serving as an insulating base material.

Examples of the treatment liquid include aqueous solutions of mercury chloride, bromine/methanol mixtures, bromine/ethanol mixtures, aqua regia, and hydrochloric acid/copper chloride mixtures, with hydrochloric acid/copper chloride mixtures being preferred.
The concentration of the treatment liquid is preferably from 0.01 to 10 mol/L, and more preferably from 0.05 to 5 mol/L.
The treatment temperature is preferably from -10°C to 80°C, more preferably from 0°C to 60°C.

<Projection process>
The protruding process is a process that is carried out after the conductive path forming process, in which a composition containing an organic acid (hereinafter also referred to as a "protruding treatment liquid") is contacted with the insulating substrate to remove only a portion of the surface of the insulating substrate, thereby forming a protruding portion of the conductive path.
Here, the organic acid refers to an organic compound having one or more acidic groups in one molecule, and examples of the acidic group include a carboxy group, a sulfonic acid group, and a phosphoric acid group.

In the present invention, the organic acid preferably contains an organic acid that does not have a nitrogen atom, because this ensures sufficient bonding strength when the structure produced is used as an anisotropic conductive bonding member.

In the present invention, the organic acid preferably contains a hydroxycarboxylic acid because this improves the storage stability.
Here, the oxycarboxylic acid refers to a compound having a carboxy group and a hydroxyl group in one molecule.
As the oxycarboxylic acid, lactic acid, malic acid, citric acid, glycolic acid, 2-hydroxymalonic acid, tartaric acid, and the like are preferably used because they provide better shelf stability. These may be contained alone or in combination of two or more kinds.

Furthermore, in the present invention, the content of the organic acid is preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and even more preferably 0.7% by mass or more, relative to the total mass of the protruding treatment liquid, for the reason that the retention stability is improved.
The upper limit of the content of the organic acid is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the projection treatment liquid.

The composition containing an organic acid (projection treatment liquid) may contain an inorganic acid and/or a base in addition to the organic acid described above, as long as the metal constituting the conductive path is not dissolved.
Specific examples of inorganic acids include sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid.
Specific examples of the base include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide, strontium hydroxide, and barium hydroxide; and the like.
When the protruding treatment liquid contains an inorganic acid, the content of the inorganic acid is preferably 1 to 10% by mass based on the total mass of the protruding treatment liquid.
When the projection treatment liquid contains a base, the content of the base is preferably 1 to 10% by mass based on the total mass of the projection treatment liquid.

The composition containing an organic acid is preferably an aqueous solution containing the above-mentioned organic acid and any inorganic acid and/or base, and more preferably an aqueous solution containing the above-mentioned organic acid and/or base (particularly an alkali metal hydroxide).

The method for contacting the sample with the composition containing an organic acid is not particularly limited, but examples include a method in which the sample after the conductive path forming step is immersed in the composition containing an organic acid.
Here, the immersion time in the organic acid-containing composition is not particularly limited because it varies depending on the height of the protruding portion of the conductive path to be formed, but is preferably 8 to 120 minutes, more preferably 10 to 90 minutes, and even more preferably 15 to 60 minutes. Here, the immersion time refers to the total immersion time when short immersion treatments are repeated. Note that a cleaning treatment may be performed between each immersion treatment.
The temperature of the composition containing an organic acid is not particularly limited, but is preferably 15 to 60°C, more preferably 15 to 50°C, and even more preferably 15 to 40°C.

<Optional Step>
In the manufacturing method of the present invention, when the height of the protruding portion of the conductive path is strictly controlled in the protruding step, it is preferable to process the insulating substrate and the end of the conductive path so as to be flush with each other after the conductive path forming step, and then to contact the insulating substrate with a composition containing an organic acid to remove only a portion of the surface of the insulating substrate.
Here, examples of methods for processing into the same plane include physical polishing (for example, free abrasive polishing, back grinding, surface planing, etc.), electrochemical polishing, and a combination of these.

In the manufacturing method of the present invention, a heat treatment can be carried out after the conductive path forming step or the protruding step in order to reduce distortion in the conductive path caused by filling with metal.
The heat treatment is preferably carried out in a reducing atmosphere from the viewpoint of suppressing oxidation of the metal, and more specifically, is preferably carried out in an oxygen concentration of 20 Pa or less, and more preferably in a vacuum. Here, vacuum refers to a state of space having a lower gas density or air pressure than the atmosphere.
In addition, the heat treatment is preferably carried out while applying pressure to the material for the purpose of straightening.

The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[Example 1]
<Preparation of Aluminum Substrate>
A molten metal was prepared using an aluminum alloy containing 0.06 mass% Si, 0.30 mass% Fe, 0.005 mass% Cu, 0.001 mass% Mn, 0.001 mass% Mg, 0.001 mass% Zn, 0.001 mass% Ti, and the remainder being Al and unavoidable impurities. The molten metal was treated and filtered, and an ingot having a thickness of 500 mm and a width of 1,200 mm was produced by DC (Direct Chill) casting.
Next, the surface was scraped off by an average thickness of 10 mm using a facing machine, and then the plate was soaked at 550° C. for about 5 hours. When the temperature was lowered to 400° C., the plate was rolled into a 2.7 mm thick plate using a hot rolling machine.
Further, the sheet was heat-treated at 500° C. using a continuous annealing machine, and then cold-rolled to a thickness of 1.0 mm to obtain an aluminum substrate of JIS 1050 material.
This aluminum substrate was cut to a width of 1,030 mm and then subjected to the following treatments.

<Electrolytic polishing treatment>
The aluminum substrate was subjected to electrolytic polishing treatment using an electrolytic polishing solution having the following composition under conditions of a voltage of 25 V, a solution temperature of 65° C., and a solution flow rate of 3.0 m/min.
The cathode was a carbon electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.) The flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).
(Electrolytic polishing solution composition)
85% by weight phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) 660 mL
・160mL of pure water
・150mL sulfuric acid
・30mL ethylene glycol

<Anodizing process>
Next, the aluminum substrate after the electrolytic polishing treatment was subjected to anodizing treatment by a self-ordering method according to the procedure described in JP-A-2007-204802.
The aluminum substrate after electrolytic polishing was subjected to a pre-anodizing treatment for 5 hours in an electrolytic solution of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a solution temperature of 16° C., and a solution flow rate of 3.0 m/min.
Thereafter, the aluminum substrate after the pre-anodizing treatment was subjected to a film removing treatment by immersing it in a mixed aqueous solution of 0.2 mol/L chromic anhydride and 0.6 mol/L phosphoric acid (liquid temperature: 50° C.) for 12 hours.
Thereafter, re-anodization was performed for 3 hours and 45 minutes in an electrolyte of 0.50 mol/L oxalic acid under conditions of a voltage of 40 V, a liquid temperature of 16° C., and a liquid flow rate of 3.0 m/min, to obtain an anodized film with a thickness of 30 μm.
In both the pre-anodizing treatment and the re-anodizing treatment, the cathode was a stainless steel electrode, and the power source was GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.). The cooling device was NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.), and the stirring and heating device was Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.). Furthermore, the flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).

<Barrier Layer Removal Step>
Next, after the anodizing treatment step, an etching treatment was performed by immersing the aluminum substrate in an alkaline aqueous solution in which zinc oxide was dissolved in an aqueous sodium hydroxide solution (50 g/l) to a concentration of 2000 ppm at 30° C. for 150 seconds, thereby removing the barrier layer at the bottom of the micropores of the anodized film and simultaneously depositing zinc on the exposed surface of the aluminum substrate.
The average thickness of the anodic oxide film after the barrier layer removal step was 30 μm.

<Metal filling process>
Next, electrolytic plating was carried out by using the aluminum substrate as the cathode and platinum as the anode.
Specifically, a copper plating solution having the composition shown below was used and constant current electrolysis was performed to produce a structure in which nickel was filled inside the micropores.
Here, the constant current electrolysis was performed using a plating device manufactured by Yamamoto Plating Tester Co., Ltd. and a power supply (HZ-3000) manufactured by Hokuto Denko Corporation. After cyclic voltammetry was performed in the plating solution to confirm the deposition potential, the treatment was performed under the conditions shown below.
(Copper plating solution composition and conditions)
・Copper sulfate 100g/L
Sulfuric acid 50g/L
Hydrochloric acid 15g/L
Temperature: 25℃
・Current density 10A/dm ²

<Protrusion process (surface)>
The structure after the metal filling process was immersed in a protrusion treatment liquid prepared by dissolving citric acid at 1 mass % in an aqueous potassium hydroxide solution (concentration: 5 mass %, liquid temperature: 20°C). The immersion time was adjusted so that the height of the protruding parts was 400 nm, and the surface of the anodized film of the aluminum was selectively dissolved, causing the filling metal, copper, to protrude, thereby producing a structure in which an oxidation prevention film was formed on the surface of the protruding copper parts.

<Resin substrate formation process>
A thermally peelable resin substrate with an adhesive layer (REVALPHA 3195MS, manufactured by Nitto Denko Corporation) was attached to the surface on the side where the aluminum substrate was not provided. This resin substrate was a substrate for supporting the structure produced in the above-mentioned "protruding step (surface)" during the "substrate removing step" described later.

<Substrate Removal Process>
Next, the aluminum substrate was dissolved and removed by immersion in a mixed solution of copper chloride/hydrochloric acid to prepare a structure having an average thickness of 30 μm.
The diameter of the conductive paths in the fabricated structure was 60 nm, the pitch between the conductive paths was 100 nm, and the density of the conductive paths was 57.7 million/mm 2 .

<Protrusion process (back side)>
The structure after the substrate removal process was immersed in a protrusion treatment solution prepared by dissolving citric acid at 1 mass % in an aqueous sodium hydroxide solution (concentration: 5 mass %, liquid temperature: 20°C). The immersion time was adjusted so that the height of the protruding parts was 400 nm, thereby selectively dissolving the surface of the anodized film of the aluminum, causing the filling metal, copper, to protrude, and producing a structure in which an oxidation prevention film was formed on the surface of the protruding copper parts.

<Thermal peeling process>
After the protruding step (rear surface), the substrate was heated at 110° C. for 1 minute in air to peel off the resin substrate, thereby preparing a structure.

[Examples 2 to 8 and Comparative Example 1]
A structure was produced in the same manner as in Example 1, except that the type and concentration of the organic acid in the protrusion treatment solution used in the protrusion process (front surface) and the protrusion process (rear surface) were changed to those shown in Table 1 below.

[Placement stability]
Each of the fabricated structures was left at 35° C. in an air environment for one month.
Then, the cross section of each structure was cut out by FIB (focused ion beam) to obtain ultra-thin slices. The obtained ultra-thin slices were observed by TEM (transmission electron microscope) to measure the thickness of the oxide film at the protruding part of the conductive path. From the thickness of the oxide film, the drag stability was evaluated according to the following criteria.
<Evaluation criteria>
A: The thickness of the oxide film is 5 nm or less. B: The thickness of the oxide film is more than 5 nm and less than 10 nm. C: The thickness of the oxide film is more than 10 nm and less than 20 nm. D: The thickness of the oxide film is more than 20 nm.

From the results shown in Table 1 above, it was found that when a composition containing an organic acid was not used in the protrusion step, the thickness of the oxide film exceeded 20 nm, and the dragging stability was poor (Comparative Example 1).
In contrast, when a composition containing an organic acid was used in the protruding step, the thickness of the oxide film was 20 nm or less, and it was found that the dragging stability was poor (Examples 1 to 8).
In particular, comparison of Examples 1, 2, and 4 to 8 reveals that when the organic acid is an oxycarboxylic acid, the storage stability is improved.
Furthermore, a comparison between Example 1 and Example 3 revealed that the retention stability was improved when the content of the organic acid was 0.5 mass % or more relative to the total mass of the ejection treatment liquid.

REFERENCE SIGNS LIST 1 Structure 2 Insulating substrate 2a, 2b Surface of insulating substrate 3 Conductive path 3a, 3b Protruding portion of conductive path 4 Antioxidant film 6 Thickness of insulating substrate 7 Distance between conductive paths 8 Diameter of conductive path 9 Center-to-center distance (pitch) of conductive paths

Claims (5)

A method for producing a structure having an insulating base material made of an inorganic material and a plurality of conductive paths made of a conductive member penetrating the insulating base material in a thickness direction and insulated from one another, comprising:
each of the conductive paths has a protruding portion protruding from a surface of the insulating substrate;
A method for producing a structure, comprising a protruding step of forming the protruding portion by contacting a composition containing an organic acid. The method for producing the structure according to claim 1, wherein the organic acid includes an organic acid that does not have a nitrogen atom. The method for producing the structure according to claim 1, wherein the organic acid includes an oxycarboxylic acid. The method for producing the structure according to claim 3, wherein the oxycarboxylic acid includes at least one selected from the group consisting of lactic acid, malic acid, citric acid, glycolic acid, 2-hydroxymalonic acid, and tartaric acid. The method for producing a structure according to any one of claims 1 to 4, wherein the content of the organic acid relative to the total mass of the composition is 0.5 mass% or more.