JP7506753B2 - Method for manufacturing metal-filled microstructures - Google Patents

Description

The present invention relates to a method for manufacturing a metal-filled microstructure in which a plurality of conductors, which penetrate the thickness direction of an anodized film and are electrically insulated from one another, protrude from at least one surface of the anodized film in the thickness direction, and a resin layer covering the surface of the anodized film from which the conductors protrude is removed after heating, and in particular to a method for manufacturing a metal-filled microstructure in which the resin layer is heated in an atmosphere having an oxygen partial pressure of 10,000 Pa or less.

A structure having a plurality of through holes provided in an insulating substrate filled with a conductive material such as a metal is one of the fields that has attracted attention in recent years in nanotechnology, and is expected to be used, for example, as an anisotropic conductive member.
Anisotropically conductive members are widely used as electrical connection members for electronic components such as semiconductor elements, etc., and as inspection connectors for carrying out functional tests, because electrical connection between the electronic component and the circuit board can be obtained simply by inserting the anisotropically conductive member between the electronic component and the circuit board and applying pressure therebetween.
In particular, electronic components such as semiconductor elements are being significantly downsized. Conventional methods for directly connecting wiring boards, such as wire bonding, flip chip bonding, and thermocompression bonding, may not be able to fully ensure the stability of electrical connections of electronic components, and therefore anisotropic conductive materials have been attracting attention as electronic connection materials.

As a method for manufacturing anisotropically conductive members, for example, Patent Document 1 describes a method for manufacturing a metal-filled microstructure, which includes an anodizing process in which one surface 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 the one surface of the aluminum substrate, a barrier layer removal process in which, after the anodizing process, the barrier layer of the anodized film is removed using an alkaline aqueous solution containing metal M1, which has a higher hydrogen overvoltage than aluminum, a metal filling process in which, after the barrier layer removal process, electrolytic plating is performed to fill the interior of the micropores with metal M2, and a substrate removal process in which, after the metal filling process, the aluminum substrate is removed to obtain a metal-filled microstructure. Patent Document 1 also includes a resin layer formation process in which, after the metal filling process and before the substrate removal process, a resin layer is provided on the surface of the anodized film on the side on which the aluminum substrate is not provided.

Japanese Patent No. 6535098

In the above-mentioned Patent Document 1, a resin layer is provided on the surface of the anodized film on the side where the aluminum substrate is not provided. The metal-filled microstructure is used, for example, to electrically connect two semiconductor chips. In this case, it is necessary to peel off the above-mentioned resin layer. When the metal-filled microstructure of Patent Document 1 is used to electrically connect two semiconductor chips as described above, the electrical conductivity between the semiconductor chips may not be sufficient. A metal-filled microstructure with good electrical conductivity is desired.

The object of the present invention is to provide a method for manufacturing metal-filled microstructures with good electrical conductivity.

In order to achieve the above-mentioned object, one aspect of the present invention provides a method for manufacturing a metal-filled microstructure, the method comprising: a preparation step of preparing a structure having a plurality of conductors penetrating an insulating film in the thickness direction and electrically insulated from one another, the conductors protruding from at least one surface of the insulating film in the thickness direction, and a resin layer covering the surface of the insulating film from which the conductors protrude; a heating step of heating at least the resin layer in an atmosphere having an oxygen partial pressure of 10,000 Pa or less; and a removal step of removing the resin layer heated by the heating step from the insulating film, the resin layer including a thermally peelable adhesive.

In the heating step, the oxygen partial pressure in the atmosphere is preferably 1.0 Pa or less.
In the heating step, the partial pressure of the inert gas in the atmosphere is preferably 85% or more of the total pressure of the atmosphere.
In the heating step, the partial pressure of the reducing gas in the atmosphere is preferably 85% or more of the total pressure of the atmosphere.
In the heating step, the total pressure of the atmosphere is preferably 5.0 Pa or less.

The conductor preferably comprises a base metal.
The plurality of conductors preferably have a cross-sectional area of ²⁰ μm2 or less in a cross section perpendicular to the longitudinal direction of the conductors.
The temperature reached by the resin layer in the heating step is preferably 150° C. or lower.
It is preferable that the conductors protrude from both sides of the insulating film in the thickness direction, and that the resin layers are provided on both sides of the insulating film in the thickness direction.
The insulating film is preferably an anodic oxide film.

According to the present invention, a metal-filled microstructure having good electrical conductivity can be obtained.

1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a step of an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention. 5 is a schematic cross-sectional view showing a step of another example of a method for producing a metal-filled microstructure according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a step of another example of a method for producing a metal-filled microstructure according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a step of another example of a method for producing a metal-filled microstructure according to an embodiment of the present invention. FIG. FIG. 2 is a schematic perspective view showing an example of a supply form of the anisotropically conductive member according to the embodiment of the present invention. FIG. 2 is a schematic perspective view showing an example of a supply form of the anisotropically conductive member according to the embodiment of the present invention. FIG. 1 is a schematic diagram showing an example of a bonded body using a metal-filled microstructure according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a metal-filled microstructure of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
It should be noted that the drawings described below are illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below.
In the following, the term "to" indicating a range of values includes the values written on both sides. For example, if ε _a is a value α _b to a value β _c , the range of ε _a includes the values α _b and β _c , and expressed in mathematical notation, α _b ≦ ε _a ≦ β _c .
Unless otherwise specified, the temperature and time include error ranges generally accepted in the relevant technical field.
In addition, unless otherwise specified, parallelism and the like include an error range generally acceptable in the relevant technical field.

[Metal-filled microstructures]
1 to 8 are schematic cross-sectional views showing an example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention in the order of steps.
8, the metal-filled microstructure 10 has an insulating film 12 having electrical insulation properties, and a plurality of conductors 14 penetrating the insulating film 12 in the thickness direction Dt and electrically insulated from one another. The conductors 14 protrude from at least one surface of the insulating film 12 in the thickness direction Dt. When the conductors 14 protrude from at least one surface of the insulating film 12 in the thickness direction Dt, in a configuration in which the conductors protrude from one surface, it is preferable that the conductors protrude from the front surface 12a or the back surface 12b. In the metal-filled microstructure 10, the insulating film 12 is formed of, for example, an anodic oxide film 15.

The multiple conductors 14 are disposed in the insulating film 12 while being electrically insulated from one another. In this case, for example, the insulating film 12 has multiple pores 13 penetrating in the thickness direction Dt. The conductors 14 are provided in the multiple pores 13. The conductors 14 protrude from a surface 12a of the insulating film 12 in the thickness direction Dt.
The metal-filled microstructure 10 has anisotropic conductivity in which the conductors 14 are arranged in a state in which they are electrically insulated from each other. The metal-filled microstructure 10 has conductivity in the thickness direction Dt, but has sufficiently low conductivity in a direction parallel to the surface 12a of the insulating film 12.

The external shape of the metal-filled microstructure 10 is not particularly limited and may be, for example, a square or a circle. The external shape of the metal-filled microstructure 10 may be a shape according to the application, ease of manufacture, etc.

[Metal-filled microstructure manufacturing method]
In one example of a method for manufacturing a metal-filled microstructure, an insulating film is formed of an anodized aluminum film. In order to form the anodized aluminum film, an aluminum substrate is used. Therefore, in one example of a method for manufacturing a structure, an aluminum substrate 30 is first prepared as shown in FIG.
The size and thickness of the aluminum substrate 30 are appropriately determined depending on the thickness of the insulating film 12 of the metal-filled microstructure 10 (see FIG. 8 ) to be finally obtained, the processing device, etc. The aluminum substrate 30 is, for example, a rectangular plate material. Note that the aluminum substrate is not limited to an aluminum substrate, and any metal substrate capable of forming an electrically insulating insulating film 12 can be used.

Next, one surface 30a (see FIG. 1) of the aluminum substrate 30 is anodized. As a result, one surface 30a (see FIG. 1) of the aluminum substrate 30 is anodized to form an insulating film 12 having a plurality of pores 13 extending in the thickness direction Dt of the aluminum substrate 30, i.e., an anodized film 15, as shown in FIG. 2. A barrier layer 31 exists at the bottom of each pore 13. The above-mentioned anodization process is called an anodization process.
As described above, the insulating film 12 having the plurality of pores 13 has a barrier layer 31 at the bottom of each of the pores 13, but the barrier layer 31 shown in Fig. 2 is removed. As a result, an insulating film 12 having the plurality of pores 13 without the barrier layer 31 (see Fig. 3) is obtained. The step of removing the barrier layer 31 described above is referred to as a barrier layer removal step.
In the barrier layer removal step, an alkaline aqueous solution containing ions of a metal M1 having a higher hydrogen overvoltage than aluminum is used to remove the barrier layer 31 of the insulating film 12, and at the same time, a metal layer 35a (see FIG. 3) made of a metal (metal M1) is formed on a surface 32d (see FIG. 3) of a bottom 32c (see FIG. 3) of the pore 13. As a result, the aluminum substrate 30 exposed in the pore 13 is covered with the metal layer 35a. As a result, when the pore 13 is filled with metal by plating, plating is facilitated, and the pore is prevented from being insufficiently filled with metal, and the pore is prevented from being unfilled with metal, thereby preventing the formation of a defective conductor 14.
The alkaline aqueous solution containing ions of the metal M1 may further contain an aluminum ion-containing compound (sodium aluminate, aluminum hydroxide, aluminum oxide, etc.). The content of the aluminum ion-containing compound, calculated as the amount of aluminum ions, is preferably 0.1 to 20 g/L, more preferably 0.3 to 12 g/L, and even more preferably 0.5 to 6 g/L.

Next, plating is performed from the surface 12a of the insulating film 12 having a plurality of pores 13 extending in the thickness direction Dt. In this case, the metal layer 35a can be used as an electrode for electrolytic plating. The plating uses a metal 35b, and the plating proceeds starting from the metal layer 35a formed on the surface 32d (see FIG. 3) of the bottom 32c (see FIG. 3) of the pore 13. As a result, as shown in FIG. 4, the metal 35b constituting the conductor 14 is filled inside the pore 13 of the insulating film 12. The conductor 14 having electrical conductivity is formed by filling the inside of the pore 13 with the metal 35b. The metal layer 35a and the metal 35b are collectively referred to as the filled metal 35.
The process of filling the pores 13 of the insulating film 12 with the metal 35b is called the metal filling process. As described above, the conductor 14 is not limited to being made of a metal, and a conductive material can be used. Electrolytic plating is used in the metal filling process, and the metal filling process will be described in detail later. The surface 12a of the insulating film 12 corresponds to one side of the insulating film 12.
5, after the metal filling step, the surface 12a of the insulating film 12 on the side where the aluminum substrate 30 is not provided is partially removed in the thickness direction Dt, and the metal 35 filled in the metal filling step is made to protrude from the surface 12a of the insulating film 12. That is, the conductor 14 is made to protrude from the surface 12a of the insulating film 12. In this way, the protruding portion 14a is obtained. The step of making the conductor 14 protrude from the surface 12a of the insulating film 12 is called a surface metal protruding step.

After the surface metal protruding step, a resin layer 16 is formed on the surface 12a of the insulating film 12 on which the protruding portion 14a of the conductor 14 is formed, as shown in Fig. 6. As a result, the surface of the insulating film on which the conductor protrudes is covered with the resin layer, and a structure 18 is obtained. The step of preparing the structure 18 is called a preparation step.
The step of forming the resin layer 16 that covers the surface of the insulating film 12 from which the conductors 14 protrude is referred to as a resin layer forming step. The resin layer 16 contains a heat-peelable adhesive.
After the resin layer forming step, the aluminum substrate 30 is removed from the structure 18 as shown in Fig. 7. The step of removing the aluminum substrate 30 is called a substrate removing step.

Next, at least the resin layer 16 of the structure 18 is heated in an atmosphere having an oxygen partial pressure of not more than 10,000 Pa. The step of heating the resin layer 16 is referred to as a heating step.
In the heating step, a semiconductor wafer heating device used in the manufacture of semiconductor elements can be used.
The heating step is performed, for example, in a metal vessel used for heating semiconductor wafers in a semiconductor manufacturing device. The structure 18 after the substrate removal is placed in the vessel, and the oxygen partial pressure in the vessel is set to 10,000 Pa or less.
The total pressure and partial pressure of the atmosphere in the heating step can be measured, for example, using a pressure gauge. This allows the oxygen partial pressure to be measured. In addition, the partial pressure of the inert gas and the partial pressure of the reducing gas described below can also be measured.
The oxygen partial pressure can be adjusted, for example, by degassing.
The heating step is not limited to an atmosphere having an oxygen partial pressure of 10,000 Pa or less. The temperature reached by the resin layer in the heating step is preferably 150° C. or less. When the temperature reached by the resin layer in the heating step is 150° C. or less, the electrical conductivity is improved.

Next, the resin layer 16 heated in the heating step is removed from the insulating film 12 as shown in Fig. 8. In this way, the metal-filled microstructure 10 is obtained.
The process of removing the resin layer 16 from the insulating film 12 is referred to as a removing process. In the removing process, the method of removing the resin layer 16 is not particularly limited, and for example, the resin layer 16 is removed using a tool such as tweezers. In the removing process, the insulating film 12 may be peeled off from the resin layer 16 using a tool such as tweezers. The atmosphere in the removing process does not need to be the same as the atmosphere in the heating process, and may be, for example, an air atmosphere.

9 to 11 are schematic cross-sectional views showing the steps of another example of a method for manufacturing a metal-filled microstructure according to an embodiment of the present invention.
7, as shown in Fig. 9, the surface of the insulating film 12 on the side where the aluminum substrate 30 was provided after the substrate removal step, i.e., the back surface 12b, may be partially removed in the thickness direction Dt, and the metal 35 filled in the metal filling step, i.e., the conductor 14, may be made to protrude beyond the back surface 12b of the insulating film 12. This provides a protruding portion 14b.
The above-mentioned front surface metal protruding step and rear surface metal protruding step may be both steps, or may be one of the front surface metal protruding step and rear surface metal protruding step. The front surface metal protruding step and rear surface metal protruding step correspond to the "protruding step", and both the front surface metal protruding step and rear surface metal protruding step are protruding steps.
As shown in FIG. 9, the structure 18 may have a configuration having a protrusion 14a and a protrusion 14b in which the conductor 14 protrudes from the front surface 12a and the back surface 12b of the insulating film 12, i.e., from both sides in the thickness direction Dt of the insulating film 12.

As shown in FIG. 10, a resin layer 16 is formed on the rear surface 12b of the insulating film 12 shown in FIG. 9, so that the resin layer 16 is provided on both sides in the thickness direction Dt of the anodic oxide film.
Next, the above-mentioned heating step and the step of removing resin layer 16 are performed on structure 18 to obtain metal-filled microstructure 10 having protrusions 14a and 14b shown in FIG.

In the above-mentioned barrier layer removal step, by removing the barrier layer using an alkaline aqueous solution containing ions of metal M1, which has a higher hydrogen overvoltage than aluminum, not only is the barrier layer 31 removed, but also a metal layer 35a of metal M1, which is less likely to generate hydrogen gas than aluminum, is formed on the aluminum substrate 30 exposed at the bottom of the pores 13. As a result, the in-plane uniformity of the metal filling is improved. This is thought to be because the generation of hydrogen gas by the plating solution is suppressed, making it easier to proceed with metal filling by electrolytic plating.
It has also been found that the uniformity of metal filling during plating is greatly improved by providing a holding step in the barrier layer removal step, in which a voltage (holding voltage) selected from a range of less than 30% of the voltage in the anodizing step is held for a total of 5 minutes or more, and by combining this with the application of an alkaline aqueous solution containing ions of metal M1. For this reason, it is preferable to provide a holding step.
Although the detailed mechanism is unknown, it is believed that in the barrier layer removal process, an alkaline aqueous solution containing ions of metal M1 is used to form a layer of metal M1 at the bottom of the barrier layer, thereby preventing damage to the interface between the aluminum substrate and the anodized film and improving the uniformity of the dissolution of the barrier layer.

In the barrier layer removal step, a metal layer 35a made of a metal (metal M1) is formed at the bottom of the pore 13, but this is not limited to the above. Only the barrier layer 31 is removed, and the aluminum substrate 30 is exposed at the bottom of the pore 13. With the aluminum substrate 30 exposed, it may be used as an electrode for electrolytic plating.

[Anodic oxide film]
As described above, the anodized film is made of aluminum, for example, because it has pores with a desired average diameter and is easy to form a conductor. However, the anodized film is not limited to aluminum, and an anodized film of a valve metal can be used. For this reason, a valve metal is used as the metal substrate.
Here, specific examples of the valve metal include aluminum, as described above, and also tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among these, anodized aluminum film is preferable because it has good dimensional stability and is relatively inexpensive. For this reason, it is preferable to manufacture the structure using an aluminum substrate.
The thickness of the anodic oxide film is the same as the thickness ht of the insulating film 12 described above.

[Metal Substrate]
The metal substrate is used for manufacturing the structure, and is a substrate for forming an anodic oxide film. As the metal substrate, for example, as described above, a metal substrate on which an anodic oxide film can be formed is used, and a substrate made of the valve metal described above can be used. For example, as the metal substrate, an aluminum substrate is used because, as described above, an anodic oxide film can be easily formed as the anodic oxide film.

[Aluminum substrate]
The aluminum substrate used to form the insulating film 12 is not particularly limited, and specific examples thereof include a pure aluminum plate; an alloy plate containing aluminum as the main component and trace amounts of other elements; a substrate in which high-purity aluminum is vapor-deposited onto low-purity aluminum (e.g., recycled materials); a substrate in which the surface of a silicon wafer, quartz, glass, or the like is coated with high-purity aluminum by a method such as vapor deposition or sputtering; a resin substrate laminated with aluminum; and the like.

The surface of one side of the aluminum substrate on which the anodized film is formed by anodizing treatment preferably has an aluminum purity of 99.5% by mass or more, more preferably 99.9% by mass or more, and even more preferably 99.99% by mass or more. When the aluminum purity is in the above-mentioned range, the regularity of the micropore arrangement is sufficient.
The aluminum substrate is not particularly limited as long as it is capable of forming an anodized film, and for example, JIS (Japanese Industrial Standards) 1050 material is used.

It is preferable that the surface of one side of the aluminum substrate to be anodized has been previously subjected to heat treatment, degreasing treatment and mirror finishing treatment.
Here, the heat treatment, degreasing treatment and mirror finish treatment can be the same as those described in paragraphs [0044] to [0054] of JP-A-2008-270158.
The mirror finish treatment prior to the anodizing treatment is, for example, electrolytic polishing, and for the electrolytic polishing, for example, an electrolytic polishing solution containing phosphoric acid is used.

[Anodizing process]
The anodization treatment can be carried out by a conventionally known method, but from the viewpoint of increasing the regularity of the micropore arrangement and ensuring the anisotropic conductivity of the structure, it is preferable to use a self-ordering method or a 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 in FIG. 3 of JP-A-2008-270158.

[Holding step]
The method for manufacturing a structure may include a holding step, which is a step of holding the structure for a total of 5 minutes or more at a voltage of 95% to 105% of a holding voltage selected from a range of 1 V or more and less than 30% of the voltage in the anodizing treatment step after the anodizing treatment step. In other words, the holding step is a step of performing an electrolytic treatment for a total of 5 minutes or more at a voltage of 95% to 105% of a holding voltage selected from a range of 1 V or more and less than 30% of the voltage in the anodizing treatment step after the anodizing treatment step.
Here, the "voltage in anodizing treatment" refers to the voltage applied between the aluminum and the counter electrode, and for example, if the electrolysis time in anodizing treatment is 30 minutes, it refers to the average value of the voltage maintained during that 30 minutes.

From the viewpoint of controlling the sidewall thickness of the anodized film, i.e., the thickness of the barrier layer to an appropriate thickness relative to the depth of the pores, it is preferable that the voltage in the holding step be 5% or more and 25% or less of the voltage in the anodizing treatment, and more preferably 5% or more and 20% or less.

Furthermore, in order to further improve the in-plane uniformity, the total holding time in the holding step is preferably 5 minutes or more and 20 minutes or less, more preferably 5 minutes or more and 15 minutes or less, and even more preferably 5 minutes or more and 10 minutes or less.
The holding time in the holding step may be a total of 5 minutes or more, but is preferably 5 minutes or more continuously.

Furthermore, the voltage in the holding step may be set by continuously or stepwise decreasing from the voltage in the anodizing treatment step to the voltage in the holding step, but in order to further improve the in-plane uniformity, it is preferable to set the voltage to 95% or more and 105% or less of the above-mentioned holding voltage within 1 second after the anodizing treatment step is completed.

The above-mentioned holding step can also be carried out consecutively with the above-mentioned anodizing step, for example by lowering the electrolytic potential at the end of the above-mentioned anodizing step.
In the above-mentioned holding step, the same electrolytic solution and treatment conditions as those in the above-mentioned conventionally known anodizing treatment can be adopted, except for the electrolytic potential.
In particular, when the holding step and the anodizing step are carried out successively, it is preferable to carry out the treatments using the same electrolyte.

As described above, an anodized film having multiple micropores has a barrier layer (not shown) at the bottom of the micropores. A barrier layer removal process is included to remove this barrier layer.

[Barrier layer removal process]
The barrier layer removal step is a step of removing the barrier layer of the anodized film using, for example, an alkaline aqueous solution containing ions of a metal M1 having a higher hydrogen overvoltage than aluminum.
By the above-mentioned barrier layer removal step, the barrier layer is removed, and a conductive layer made of metal M1 is formed at the bottom of the micropores.
Here, hydrogen overvoltage refers to the voltage required to generate hydrogen, and for example, the hydrogen overvoltage of aluminum (Al) is −1.66 V (Journal of the Chemical Society of Japan, 1982, (8), pp. 1305-1313). Examples of metals M1 with a higher hydrogen overvoltage than aluminum and their hydrogen overvoltage values are shown below.
<Metal M1 and _Hydrogen (1N _H2SO4 ) Overpotential>
Platinum (Pt): 0.00 V
Gold (Au): 0.02 V
Silver (Ag): 0.08 V
Nickel (Ni): 0.21 V
Copper (Cu): 0.23 V
Tin (Sn): 0.53 V
Zinc (Zn): 0.70 V

In the present invention, it is preferable that the metal M1 used in the above-mentioned barrier layer removal process be a metal having a higher ionization tendency than the metal M2 used in the metal filling process described later, because this will cause a substitution reaction with the metal M2 filled in the anodizing process described later, thereby reducing the effect on the electrical properties of the metal filled inside the micropores.
Specifically, when copper (Cu) is used as the metal M2 in the metal filling process described below, examples of the metal M1 used in the barrier layer removal process include Zn, Fe, Ni, Sn, etc., and among these, it is preferable to use Zn or Ni, and it is more preferable to use Zn.
When Ni is used as the metal M2 in the metal filling step described below, examples of the metal M1 used in the barrier layer removal step include Zn and Fe, and among these, it is preferable to use Zn.

The method for removing the barrier layer using an alkaline aqueous solution containing such metal M1 is not particularly limited, and examples include methods similar to conventional chemical etching processes.

Chemical Etching Treatment
The barrier layer can be removed by chemical etching, for example, by immersing the structure after the above-mentioned anodizing process in an alkaline aqueous solution to fill the inside of the micropores with the 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.

Here, as the alkaline aqueous solution containing the metal M1, 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.
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 alkaline aqueous solution can be appropriately used.

The immersion time in the alkaline aqueous solution is preferably 5 to 120 minutes, more preferably 8 to 120 minutes, even more preferably 8 to 90 minutes, and particularly preferably 10 to 90 minutes. Of these, 10 to 60 minutes is preferable, and 15 to 60 minutes is more preferable.

The pores 13 can also be formed by widening the diameter of the micropores and removing the barrier layer. In this case, a pore widening treatment is used to widen the diameter of the micropores. The pore widening treatment is a treatment in which the anodized film is dissolved by immersing the anodized film in an acidic or alkaline aqueous solution to widen the pore diameter of the micropores. For the pore widening treatment, an aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, or hydrochloric acid or a mixture thereof, or an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, or the like can be used.
The barrier layer at the bottom of the micropores can also be removed by the pore widening treatment. By using an aqueous sodium hydroxide solution in the pore widening treatment, the micropores are enlarged and the barrier layer is removed.

[Metal filling process]
<Metals used in the metal filling process>
In the metal filling step, in order to form a conductor, the metal filled inside the pores 13 as a conductor and the metal constituting the metal layer are preferably materials having an electrical resistivity of 10 ³ Ω·cm or less. Specific examples of the above-mentioned metals include gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), and zinc (Zn).
From the viewpoints of electrical conductivity and formation by a plating method, the conductor is preferably copper (Cu), gold (Au), aluminum (Al), or nickel (Ni), more preferably copper (Cu) or gold (Au), and even more preferably copper (Cu).

<Plating method>
As a plating method for filling the inside of the pores with a metal, for example, an electrolytic plating method or an electroless plating method can be used.
Here, it is difficult to selectively deposit (grow) a metal in a hole with a high aspect ratio using a conventional electrolytic plating method used for coloring, etc. This is thought to be because the deposited metal is consumed in the hole and the plating does not grow even if electrolysis is performed for a certain period of time or more.
Therefore, when filling metal by electrolytic plating, it is necessary to provide a rest period during pulse electrolysis or constant potential electrolysis. The rest period must be 10 seconds or more, and is preferably 30 to 60 seconds.
It is also preferable to apply ultrasonic waves to promote stirring of the electrolyte.

Furthermore, the electrolysis voltage is usually 20 V or less, and preferably 10 V or less, but it is preferable to measure the deposition potential of the target metal in the electrolyte in advance and perform constant-potential electrolysis at a potential within +1 V of that potential. When performing constant-potential electrolysis, it is preferable to use a device that can also be used with cyclic voltammetry, and potentiostat devices such as those from Solartron, BAS Corporation, Hokuto Denko Corporation, and IVIUM can be used.

(Plating solution)
As the plating solution, a conventionally known plating solution can be used.
Specifically, when copper is precipitated, an aqueous solution of copper sulfate is generally used, and the concentration of the copper sulfate is preferably 1 to 300 g/L, and more preferably 100 to 200 g/L. Precipitation can be promoted by adding hydrochloric acid to the electrolytic solution. In this case, the concentration of hydrochloric acid is preferably 10 to 20 g/L.
When gold is to be deposited, it is preferable to use a sulfuric acid solution of gold tetrachloride and to perform plating by AC electrolysis.

The plating solution preferably contains a surfactant.
Any known surfactant can be used. Sodium lauryl sulfate, which is known as a surfactant conventionally added to plating solutions, can also be used as is. Both surfactants whose hydrophilic portion is ionic (cationic, anionic, zwitterionic) and nonionic (nonionic) can be used, but cationic ray activators are preferred in terms of avoiding the generation of bubbles on the surface of the object to be plated. The concentration of the surfactant in the plating solution composition is preferably 1 mass % or less.
In electroless plating, it takes a long time to completely fill the pores having high aspect ratios with metal, so it is preferable to fill the pores with metal by electrolytic plating.

[Substrate Removal Process]
The substrate removing step is a step of removing the aluminum substrate after the metal filling step. The method for removing the aluminum substrate is not particularly limited, and a suitable example is a method of removing the aluminum substrate by dissolving it.

<Dissolving aluminum substrate>
The above-mentioned aluminum substrate is preferably dissolved using a treatment liquid that does not easily dissolve an anodized film but easily dissolves aluminum.
The dissolution rate of such a treatment solution for aluminum is preferably 1 μm/min or more, more preferably 3 μm/min or more, and even more preferably 5 μm/min or more.Similarly, the dissolution rate of anodized film is preferably 0.1 nm/min or less, more preferably 0.05 nm/min or less, and even more preferably 0.01 nm/min or less.
Specifically, the treatment liquid preferably contains at least one metal compound having a lower ionization tendency than aluminum, and has a pH (hydrogen ion exponent) of 4 or less or 8 or more, more preferably has a pH of 3 or less or 9 or more, and even more preferably has a pH of 2 or less or 10 or more.

The treatment liquid for dissolving aluminum is preferably an acid or alkaline aqueous solution based on which, for example, compounds of manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead, antimony, bismuth, copper, mercury, silver, palladium, platinum, and gold (e.g., chloroplatinic acid), their fluorides, and their chlorides are blended.
Among these, an acid aqueous solution base is preferred, and it is also preferred to blend a chloride.
In particular, a treatment solution in which mercury chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/mercury chloride) and a treatment solution in which copper chloride is blended into an aqueous hydrochloric acid solution (hydrochloric acid/copper chloride) are preferred from the viewpoint of treatment latitude.
The composition of the treatment liquid for dissolving aluminum is not particularly limited, and for example, a bromine/methanol mixture, a bromine/ethanol mixture, aqua regia, etc. can be used.

The acid or alkali concentration of the treatment solution for dissolving aluminum is preferably 0.01 to 10 mol/L, and more preferably 0.05 to 5 mol/L.
Furthermore, the treatment temperature using the treatment liquid that dissolves aluminum is preferably from -10°C to 80°C, and more preferably from 0°C to 60°C.

The aluminum substrate is dissolved by contacting the aluminum substrate after the plating step with the treatment solution. The contact method is not particularly limited, and examples include an immersion method and a spray method. Of these, the immersion method is preferred. The contact time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.

In addition, for example, a support may be provided on the insulating film 12. It is preferable that the support has the same external shape as the insulating film 12. Attaching a support improves handling.

[Projecting process]
To partially remove the insulating film 12, for example, an acidic or alkaline aqueous solution that dissolves the insulating film 12, i.e., aluminum oxide (Al ₂ O ₃ ), without dissolving the metal constituting the conductor 14 is used. The insulating film 12 having the pores 13 filled with metal is brought into contact with the acidic or alkaline aqueous solution to partially remove the insulating film 12. The method for bringing the acidic or alkaline aqueous solution into contact with the insulating film 12 is not particularly limited, and examples include an immersion method and a spray method. Of these, the immersion method is preferred.

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. Among them, an aqueous solution not containing chromic acid is preferable from the viewpoint of excellent safety. The concentration of the aqueous acid solution is preferably 1 to 10 mass %. The temperature of the aqueous acid solution is preferably 25 to 60°C.
In addition, 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 20 to 35° C.
Specifically, for example, a 50 g/L, 40° C. aqueous phosphoric acid solution, a 0.5 g/L, 30° C. aqueous sodium hydroxide solution, or a 0.5 g/L, 30° C. aqueous potassium hydroxide solution are preferably 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. 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.

Furthermore, the metal 35, i.e., the conductor 14, is preferably caused to protrude from the front surface 12a or the back surface 12b of the insulating film 12 by 10 nm to 1000 nm, more preferably by 50 nm to 500 nm. That is, the amount of protrusion of the protrusion 14a from the front surface 12a of the insulating film 12 and the amount of protrusion of the conductor 14 from the back surface 12b of the insulating film 12 by the protrusion 14b are each preferably 10 nm to 1000 nm, more preferably 50 nm to 500 nm.
The height of protrusions 14a, 14b of conductor 14 is the average value of the heights of the conductor protrusions measured at 10 points when the cross section of metal-filled microstructure 10 is observed at 20,000 times magnification using a field emission scanning electron microscope.

When the height of the protruding portion of the conductor 14 is to be strictly controlled, it is preferable to fill the inside of the fine hole 13 with a conductive material such as a metal, process the insulating film 12 and the end of the conductive material such as the metal so as to be flush with each other, and then selectively remove the anodic oxide film.
After the above-mentioned metal filling or protruding step, a heat treatment can be performed in order to reduce distortion in the conductor 14 caused by the metal filling.
The heat treatment is preferably carried out in a reducing atmosphere from the viewpoint of suppressing oxidation of the metal, and more preferably in an atmosphere having an oxygen concentration of 20 Pa or less, and more preferably in a vacuum. Here, the vacuum refers to a state of space in which at least one of the gas density and the air pressure is lower than that of the atmosphere.
Moreover, the heat treatment is preferably performed while applying stress to the insulating film 12 for the purpose of straightening.

[Resin layer forming process]
As described above, this is a step of forming a resin layer that covers the surface of the insulating film from which the conductors protrude. The resin layer is provided to protect the conductors and also to improve transportability.
The resin layer forming step is a step that is carried out after the above-mentioned metal filling step and after the surface metal protruding step, and before the substrate removing step.

The resin layer contains a heat-peelable adhesive as described above. From the viewpoints of transportability and ease of use as an anisotropic conductive member, the resin layer is more preferably a film with an adhesive layer whose adhesiveness is weakened by heat treatment and which becomes peelable.
The method for attaching the above-mentioned adhesive layer-attached film is not particularly limited, and it can be attached using a conventionally known surface protection tape attachment device or laminator.

An example of a film with an adhesive layer that becomes weak in adhesion and peelable by the above-mentioned heat treatment is a film with a thermal peelable resin layer.
Here, the thermal peeling type resin layer has adhesive strength at room temperature and can be easily peeled off simply by heating, and in many cases, foaming microcapsules or the like are used.
Specific examples of the adhesive constituting the adhesive layer include rubber-based adhesives, acrylic-based adhesives, vinyl alkyl ether-based adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, urethane-based adhesives, and styrene-diene block copolymer-based adhesives.

Commercially available products with thermally peelable resin layers include, for example, Intelimer (registered trademark) tapes such as WS5130C02 and WS5130C10 (manufactured by Nitta Corporation); Somatac (registered trademark) TE series (manufactured by Somar Co., Ltd.); No. 3198, No. 3198LS, No. 3198M, No. 3198MS, No. 3198H, No. 3195, No. 3196, No. 3195M, No. 3195MS, No. 3195H, No. 3195HS, No. 3195V, No. 3195VS, No. 319Y-4L, No. 319Y-4LS, No. 319Y-4M, No. and the REVALPHA (registered trademark) series (manufactured by Nitto Denko Corporation), such as No. 319Y-4MS, No. 319Y-4H, No. 319Y-4HS, No. 319Y-4LSC, No. 31935MS, No. 31935HS, No. 3193M, and No. 3193MS.

[Heating process]
The heating step is a step for making the resin layer easier to remove. Moreover, when the resin layer is simply heated, some metals constituting the conductor may be oxidized and the electrical resistance may increase. Therefore, when the metal-filled microstructure is used as an anisotropic conductive member to electrically connect a semiconductor chip, the electrical conductivity may decrease. However, by carrying out the heating step in an atmosphere with an oxygen partial pressure of 10,000 Pa or less, the increase in electrical resistance is suppressed, and when the semiconductor chip is electrically connected, the electrical conductivity is improved.
In the heating step, the oxygen partial pressure of the atmosphere is 10,000 Pa or less, and preferably 1.0 Pa or less. If the oxygen partial pressure is 10,000 Pa or less, oxidation of the conductor is suppressed, but a lower oxygen partial pressure is preferable because oxidation is suppressed as much as possible regardless of the metal type of the conductor.

The heating step may be performed in the following atmosphere. For example, when the total pressure of the atmosphere is 100%, the partial pressure of the inert gas in the atmosphere is preferably 85% or more of the total pressure of the atmosphere. If the partial pressure of the inert gas in the atmosphere is 85% or more of the total pressure, the oxygen partial pressure can be relatively small and oxidation of the conductor can be suppressed.
The partial pressure of the inert gas can be adjusted, for example, by adjusting the amount of inert gas supplied into a container in which the heating step is carried out.
In the heating step, for example, when the total pressure of the atmosphere is 100%, the partial pressure of the reducing gas in the atmosphere is preferably 85% or more of the total pressure of the atmosphere. If the partial pressure of the reducing gas in the atmosphere is 85% or more of the total pressure, the oxygen partial pressure can be relatively reduced and oxidation of the conductor can be suppressed. It is preferable that the reducing gas is a gas that is less reactive with the conductor.
The partial pressure of the reducing gas can be adjusted, for example, by adjusting the amount of the reducing gas supplied into the container in which the heating step is carried out.

<Inert gas>
The inert gas is not particularly limited, but may be, for example, a rare gas such as helium gas, neon gas, or argon gas, or nitrogen gas, etc. As the inert gas, the above-mentioned various gases may be used alone, or at least two gases may be mixed.
<Reducing gas>
The reducing gas is not particularly limited, but may be, for example, hydrogen gas, carbon monoxide gas, or a hydrocarbon gas such as CH ₄ , C ₃ H ₈ , or C ₄ H _10. As the reducing gas, the above-mentioned various gases may be used alone, or at least two of the gases may be mixed.
In addition, the total pressure of the atmosphere in the heating step is preferably 5.0 Pa or less. If the total pressure of the atmosphere in the heating step is 5.0 Pa or less, the oxygen partial pressure in the atmosphere is reduced, which is preferable because oxidation of the conductor can be suppressed. The total pressure of the atmosphere can be reduced to 5.0 Pa or less, for example, by using a vacuum pump to reduce the pressure inside the container.

<Atmosphere during heating process>
The atmosphere in the heating step may be one in which the oxygen partial pressure is reduced by degassing as described above, or the air may be replaced with an inert gas or a reducing gas, or the air may be replaced with an inert gas and a reducing gas.
The heating conditions in the heating step are preferably a temperature of 80 to 350°C, more preferably a temperature of 90 to 250°C, and most preferably a temperature of 100 to 200°C. The temperature reached by the resin layer in the heating step is preferably 150°C or lower. If the temperature in the heating step is lower than the above-mentioned temperature range, the resin layer becomes difficult to peel off. On the other hand, if the temperature is high, the oxidation of the filling metal progresses, that is, the oxidation of the conductor progresses, and this causes defects such as cracks or breaks in the structure.

[Removal process]
This is a step of removing the resin layer after the heating step. The removing step is not particularly limited as long as it can remove the resin layer.
The removing step does not have to be performed in the same atmosphere as the heating step, and after the resin layer is heated, for example, it may be removed from the container used in the heating step and performed in an air atmosphere.

<Other manufacturing processes>
A mask layer having a desired shape may be used to anodize a portion of the surface of the aluminum substrate.

[Winding process]
7 from which the substrate has been removed is intended to be supplied in a rolled state wound around a core 21 as shown in FIG 12. For example, when metal-filled microstructure 10 is used as an anisotropically conductive member, the above-mentioned heating step and resin layer 16 removal step are carried out to remove resin layer 16 (see FIG 13). This allows metal-filled microstructure 10 to be used as an anisotropically conductive member, for example.
In order to further improve the transportability of the metal-filled microstructure 10, it is preferable to have a winding process in which the metal-filled microstructure 10 having the above-mentioned resin layer 16 is wound into a roll after the above-mentioned optional resin layer formation process.
Here, the winding method in the winding step is not particularly limited, and for example, a method of winding the film around a winding core 21 (see FIG. 12) having a predetermined diameter and a predetermined width can be mentioned.

From the viewpoint of ease of winding in the winding process described above, the average thickness of the metal-filled microstructure 10 excluding the resin layer 16 (see FIG. 13) is preferably 30 μm or less, and more preferably 5 to 20 μm. The average thickness can be calculated by cutting the metal-filled microstructure 10 excluding the resin layer in the thickness direction with a focused ion beam (FIB), taking a surface photograph (magnification 50,000 times) of the cross section with a field emission scanning electron microscope (FE-SEM), and averaging the results at 10 points.

[Other processing steps]
In addition to the above-mentioned steps, the manufacturing method of the present invention may include a polishing step, a surface smoothing step, a protective film formation treatment, and a water washing treatment described in paragraphs [0049] to [0057] of WO 2015/029881.
From the viewpoint of ease of handling during manufacturing and use of metal-filled microstructure 10 as an anisotropically conductive member, various processes and formats can be applied, as shown below.

<Process example using temporary adhesive>
In the present invention, after the above-mentioned substrate removal step, a step of fixing the metal-filled microstructure on a silicon wafer using temporary bonding materials and thinning the silicon wafer by polishing may be included.
Next, after the thinning step, the surface can be thoroughly cleaned and then the above-mentioned surface metal protrusion step can be carried out.
Next, a temporary adhesive having stronger adhesive strength than the previous temporary adhesive is applied to the surface from which the metal protrudes and fixed onto the silicon wafer, and then the silicon wafer that was adhered with the previous temporary adhesive is peeled off, and the above-mentioned back surface metal protrusion process can be carried out on the surface of the peeled-off metal-filled microstructure.

<Process example using wax>
In the present invention, after the above-mentioned substrate removal step, a step of fixing the metal-filled microstructure on a silicon wafer using wax and thinning the silicon wafer by polishing may be included.
Next, after the thinning step, the surface can be thoroughly cleaned and then the above-mentioned surface metal protrusion step can be carried out.
Next, a temporary adhesive is applied to the surface with the protruding metal and fixed onto the silicon wafer, after which the wax is melted by heating to peel off the silicon wafer, and the above-mentioned backside metal protrusion process can be carried out on the surface of the peeled-off metal-filled microstructure.
Although solid wax may be used, the use of Skycoat (manufactured by Nikka Seiko Co., Ltd.) or the like can improve the uniformity of the coating thickness.

<Process example where substrate removal is performed later>
In the present invention, after the above-mentioned metal filling step and before the above-mentioned substrate removing step, a step may be included in which the aluminum substrate is fixed to a rigid substrate (e.g., a silicon wafer, a glass substrate, etc.) using a temporary adhesive, wax, or a functional adsorbent film, and then the surface of the above-mentioned anodic oxide film on the side where the above-mentioned aluminum substrate is not provided is thinned by polishing.
Next, after the thinning step, the surface can be thoroughly cleaned and then the above-mentioned surface metal protrusion step can be carried out.
Next, a resin material (e.g., epoxy resin, polyimide resin, etc.) which is an insulating material is applied to the surface from which the metal is protruding, and then a rigid substrate can be attached to the surface in the same manner as described above. When attaching using a resin material, a material whose adhesive strength is greater than that of a temporary adhesive or the like is selected, and after attaching using the resin material, the rigid substrate that was attached first is peeled off, and the above-mentioned substrate removal process, polishing process, and backside metal protrusion processing process can be carried out in that order.
As the functional adsorption film, Q-chuck (registered trademark) (manufactured by Maruishi Sangyo Co., Ltd.) or the like can be used.

In the present invention, it is preferable that the metal-filled microstructure is provided as a product in a state where it is attached to a rigid substrate (eg, a silicon wafer, a glass substrate, etc.) by a peelable layer.
In this type of supply form, when the metal-filled microstructure is used as a joining member, the surface of the metal-filled microstructure is temporarily adhered to the surface of a device, the rigid substrate is peeled off, and the device to be connected is placed in an appropriate location and heated and pressed to join the upper and lower devices using the metal-filled microstructure.
The peelable layer may be a thermal peelable layer, or may be a photo-peeling layer in combination with a glass substrate.

In the manufacturing method of the present invention, each of the above-mentioned steps can be performed on a sheet basis, or an aluminum coil can be used as a raw material and a web can be continuously processed.
In the case of continuous treatment, it is preferable to provide appropriate washing and drying steps between each step.

The manufacturing method of the present invention, which includes each of these processing steps, can produce a metal-filled microstructure in which metal is filled into the inside of through holes originating from micropores provided in an insulating base material made of an anodized film on an aluminum substrate.
Specifically, by the manufacturing method of the present invention, it is possible to obtain, for example, an anisotropic conductive member described in JP 2008-270158 A, that is, an anisotropic conductive member in which a plurality of conductive paths made of a conductive member (metal) penetrate the insulating base material (an anodized film of an aluminum substrate having micropores) in the thickness direction of the insulating base material while being insulated from one another, and one end of each of the conductive paths is exposed on one surface of the insulating base material, and the other end of each of the conductive paths is exposed on the other surface of the insulating base material.

The configuration of the metal-filled microstructure will now be described in more detail.
[Insulating film]
The insulating film 12 electrically insulates the conductors 14 from one another. The insulating film has electrical insulation properties. The insulating film 12 also has a plurality of pores 13 in which the conductors 14 are formed.
The insulating film is made of, for example, an inorganic material, and may have an electrical resistivity of, for example, about 10 ¹⁴ Ω·cm.
The term "made of inorganic material" is used to distinguish it from polymeric materials, and is not limited to insulating base materials made of only inorganic materials, but is used to refer to insulating base materials whose main component is inorganic material (50 mass % or more). As described above, the insulating film is made of, for example, an anodic oxide film.
The insulating film may also be made of, for example, a metal oxide, a metal nitride, glass, ceramics such as silicon carbide or silicon nitride, a carbon base material such as diamond-like carbon, polyimide, a composite material thereof, etc. In addition to the above, the insulating film may be, for example, a film formed on an organic material having through holes from an inorganic material containing 50 mass % or more of a ceramic material or a carbon material.

The length of the insulating film 12 in the thickness direction Dt, i.e., the thickness of the insulating film 12, is preferably in the range of 1 to 1000 μm, more preferably in the range of 5 to 500 μm, and even more preferably in the range of 10 to 300 μm. When the thickness of the insulating film 12 is in this range, the insulating film 12 becomes easy to handle.
From the viewpoint of ease of winding, the thickness ht of the insulating film 12 is preferably 30 μm or less, and more preferably 5 to 20 μm.
The thickness of the anodic oxide film was calculated as the average value of 10 measurements taken at 10 points by cutting the anodic oxide film in the thickness direction Dt with a focused ion beam (FIB) and taking surface photographs (magnification: 50,000 times) of the cross section with a field emission scanning electron microscope (FE-SEM).
The spacing between the conductors 14 in the insulating film 12 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 spacing between the conductors 14 in the insulating film 12 is within the above range, the insulating film 12 functions sufficiently as an electrically insulating partition for the conductors 14.
Here, the spacing between each conductor refers to the width between adjacent conductors, which is the average value of the widths between adjacent conductors measured at 10 points when the cross section of metal-filled microstructure 10 is observed at a magnification of 200,000 using a field emission scanning electron microscope.

<Average pore diameter>
The average diameter of the pores is preferably 1 μm or less, more preferably 5 to 500 nm, even more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and most preferably 50 to 100 nm. When the average diameter d of the pores 13 is 1 μm or less and within the above-mentioned range, a conductor 14 having the above-mentioned average diameter can be obtained.
The average diameter of the pores 13 is obtained by photographing the surface of the insulating film 12 from directly above at a magnification of 100 to 10,000 times using a scanning electron microscope. At least 20 pores that are connected in a ring shape are extracted from the photographed image, and their diameters are measured to determine the opening diameter. The average of these opening diameters is calculated as the average diameter of the pores.
The magnification can be appropriately selected from the above range so that a captured image can be obtained that can extract 20 or more pores. The opening diameter is measured by measuring the maximum value of the distance between the ends of the pore portion. That is, since the shape of the opening of the pore is not limited to a substantially circular shape, when the shape of the opening is non-circular, the maximum value of the distance between the ends of the pore portion is taken as the opening diameter. Therefore, for example, even in the case of a pore having a shape in which two or more pores are integrated, this is regarded as one pore, and the maximum value of the distance between the ends of the pore portion is taken as the opening diameter.

〔conductor〕
As described above, the multiple conductors 14 are provided in a state where they are electrically insulated from one another by the anodic oxide film.
The plurality of conductors 14 have electrical conductivity. The conductors are made of a conductive material. The conductive material is not particularly limited, and may be a metal. Specific examples of metals include gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), and nickel (Ni). From the viewpoint of electrical conductivity, copper, gold, aluminum, and nickel are preferred, copper and gold are more preferred, and copper is most preferred. Of the metals, copper is a base metal, but a base metal may also be used. Although base metals are easily oxidized in air, in the method for producing a metal-filled microstructure, a metal-filled microstructure with good electrical conductivity can be obtained even if the conductor is made of a base metal.
In addition to metals, oxide conductive materials can be used. Examples of oxide conductive materials include indium-doped tin oxide (ITO). However, metals have superior ductility and other properties compared to oxide conductors, and are easily deformed, and are also easily deformed by compression during bonding, so it is preferable to use metal.
The conductor can also be made of a conductive resin containing nanoparticles of Cu or Ag, for example.
The height H of the conductor 14 in the thickness direction Dt is preferably 10 to 300 μm, and more preferably 20 to 30 μm.

<Conductor shape>
The multiple conductors preferably have a cross-sectional area of ²⁰ μm2 or less in a cross section perpendicular to the longitudinal direction of the conductor, i.e., the thickness direction Dt of the insulating film 12. A conductor having a cross-sectional area of 20 μm2 ^or less has a diameter d of approximately 3.99 μm or less.
Furthermore, the average diameter d of the conductor 14 is more preferably 1 μm or less, even more preferably 5 to 500 nm, even more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and most preferably 50 to 100 nm.
The density of the conductor 14 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 p between adjacent conductors 14 is preferably 20 nm to 500 nm, more preferably 40 nm to 200 nm, and even more preferably 50 nm to 140 nm.
The average diameter of the conductors is measured by photographing the surface of the anodized film from directly above with a scanning electron microscope at a magnification of 100 to 10,000 times. At least 20 conductors that are connected in a ring shape are extracted from the photographed image, and their diameters are measured to determine the opening diameter. The average of these opening diameters is calculated as the average diameter of the conductors.
The magnification can be appropriately selected from the above range so that a captured image can be obtained that can extract 20 or more conductors. The aperture diameter is measured by measuring the maximum value of the distance between the ends of the conductor parts. In other words, the shape of the opening of the conductor is not limited to a substantially circular shape, so when the shape of the opening is non-circular, the maximum value of the distance between the ends of the conductor parts is taken as the aperture diameter. Therefore, for example, even when a conductor has a shape in which two or more conductors are integrated, this is considered as one conductor, and the maximum value of the distance between the ends of the conductor parts is taken as the aperture diameter.

<Protrusion>
The protrusion is a part of the conductor and has a columnar shape. The protrusion is preferably cylindrical in shape because it can increase the contact area with the object to be joined.
The average protrusion length of the protrusions 14a and the average length of the protrusions 14b are preferably 30 nm to 500 nm, and the upper limit is more preferably 100 nm or less.
The average protrusion length of protrusion 14a and the average length of protrusion 14b are the average values obtained by obtaining cross-sectional images of the protrusions using a field emission scanning electron microscope as described above, and measuring the heights of the protrusions at 10 points based on the cross-sectional images.

[Resin Layer]
As described above, the resin layer is provided on at least one of the front and back surfaces of the anodized film, and serves to bury, for example, the protruding portion of the conductor. That is, the resin layer covers the end of the conductor protruding from the anodized film, thereby protecting the protruding portion.
In order to exert the above-mentioned functions, the resin layer preferably exhibits fluidity in a temperature range of, for example, 50° C. to 200° C. and hardens at temperatures of 200° C. or higher. The resin layer will be described in detail later.

The average protruding length of the conductor 14 is preferably less than the average thickness of the resin layer 16. If the average protruding length of the protruding portion 14a of the conductor 14 and the average length of the protruding portion 14b are both less than the average thickness of the resin layer 16, the protruding portions 14a and 14b are both embedded in the resin layer portion 20a of the resin layer 16, and the conductor 14 is protected by the resin layer 16.
The average thickness of the resin layer 16 is the average distance from the surface 12a of the insulating film 12, or the average distance from the back surface 12b of the insulating film 12. The above-mentioned average thickness of the resin layer 16 is obtained by cutting the resin layer in the thickness direction Dt of the metal-filled microstructure 10, observing the cut surface using a field emission scanning electron microscope (FE-SEM), measuring the distance from the surface 12a of the insulating film 12 at 10 points corresponding to the resin layer, and averaging the measured values at 10 points. Also, the average thickness of the resin layer 16 is obtained by measuring the distance from the back surface 12b of the insulating film 12 at 10 points corresponding to the resin layer, and averaging the measured values at 10 points.
The average thickness of the resin layer is preferably 200 to 1000 nm, and more preferably 400 to 600 nm. If the average thickness of the resin layer is 200 to 1000 nm, the effect of protecting the protruding portion of the conductor 14 can be sufficiently exhibited.

Unless otherwise specified, the size of each part of the metal-filled microstructure 10 is the average value obtained by cutting the metal-filled microstructure 10 in the thickness direction Dt, observing the cross-section of the cut surface using a field emission scanning electron microscope (FE-SEM), and measuring 10 points corresponding to each size.

[Stacked Device]
Fig. 14 is a schematic diagram showing an example of a laminated device using the metal-filled microstructure according to the embodiment of the present invention. The laminated device 40 shown in Fig. 14 uses the above-mentioned metal-filled microstructure 10 (see Figs. 8 and 11) as an anisotropically conductive member 45 exhibiting anisotropic conductivity.
14 is formed by bonding and electrically connecting, for example, a semiconductor element 42, an anisotropically conductive member 45, and a semiconductor element 44 in this order in the stacking direction Ds. In the anisotropically conductive member 45, the conductors 14 (see FIGS. 8 and 11) of the metal-filled microstructure 10 (see FIGS. 8 and 11) are arranged parallel to the stacking direction Ds, and the stacked device 40 is conductive in the stacking direction Ds.
The stacked device 40 has one semiconductor element 42 and one semiconductor element 44 bonded thereto, but is not limited thereto. It may have three semiconductor elements bonded thereto via anisotropic conductive members 45. In this case, the stacked device is constituted by the three semiconductor elements and two anisotropic conductive members 45.
The laminated device 40 is not limited to one having a semiconductor element, but may be a substrate having an electrode. The substrate having an electrode is, for example, a wiring board, an interposer, or the like.
The form of the stacked device is not particularly limited, and examples thereof include SoC (System on a chip), SiP (System in Package), PoP (Package on Package), PiP (Package in Package), CSP (Chip Scale Package), TSV (Through Silicon Via), etc.

The stacked device 40 may include a semiconductor element that functions as an optical sensor. For example, a semiconductor element and a sensor chip (not shown) are stacked in the stacking direction Ds. The sensor chip may be provided with a lens.
In this case, the semiconductor element is one in which a logic circuit is formed, and the configuration is not particularly limited as long as it is capable of processing the signals obtained by the sensor chip.
The sensor chip has an optical sensor that detects light. The optical sensor is not particularly limited as long as it can detect light, and for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor is used.
The lens is not particularly limited in configuration as long as it can focus light on the sensor chip, and for example, what is called a microlens is used.

The above-mentioned semiconductor elements 42, 44, and 46 may have an element region (not shown). The element region will be described later. An element configuration circuit and the like are formed in the element region, and the semiconductor elements are provided with, for example, a rewiring layer (not shown).
In the stacked device, for example, a combination of a semiconductor element having a logic circuit and a semiconductor element having a memory circuit can be used. All the semiconductor elements may have a memory circuit, or all the semiconductor elements may have a logic circuit. The combination of semiconductor elements in the stacked device 40 may be a combination of a sensor, an actuator, an antenna, or the like, a memory circuit, and a logic circuit, and is appropriately determined depending on the application of the stacked device 40.

[Objects to be joined in the structure]
The object to be joined in the structure is, as described above, a semiconductor element, but may be, for example, an object having an electrode or an element region. Examples of objects having electrodes include semiconductor elements that perform a specific function by themselves, but also include objects that perform a specific function when multiple elements are assembled. Furthermore, objects that simply transmit electrical signals, such as wiring members, are also included, and printed wiring boards are also included in objects having electrodes.
The element region is a region in which various element configuration circuits and the like for functioning as electronic elements are formed. The element region is, for example, a region in which a memory circuit such as a flash memory, a logic circuit such as a microprocessor and an FPGA (field-programmable gate array), and a communication module such as a wireless tag and wiring are formed. In addition to the above, a MEMS (Micro Electro Mechanical System) may be formed in the element region. Examples of the MEMS include sensors, actuators, and antennas. Examples of the sensors include various sensors such as acceleration, sound, and light sensors.
As described above, the element region has an element configuration circuit and the like formed therein, and electrodes (not shown) are provided to electrically connect the semiconductor chip to the outside. The element region has an electrode region in which electrodes are formed. The electrodes in the element region are, for example, Cu posts. The electrode region is basically a region that includes all the formed electrodes. However, if the electrodes are provided discretely, the region in which each electrode is provided is also called the electrode region.
The structure may be in the form of an individual piece such as a semiconductor chip, a semiconductor wafer, or a wiring layer.
Furthermore, the structure is joined to an object to be joined, but the object to be joined is not particularly limited to the above-mentioned semiconductor elements, and examples of the object to be joined include semiconductor elements in a wafer state, semiconductor elements in a chip state, printed wiring boards, and heat sinks.

[Semiconductor element]
The above-mentioned semiconductor element 42 and the semiconductor element 44 may be, in addition to those mentioned above, for example, logic LSIs (Large Scale Integration) (for example, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), ASSPs (Application Specific Standard Products), etc.), microprocessors (for example, CPUs (Central Processing Units), GPUs (Graphics Processing Units), etc.), memories (for example, DRAMs (Dynamic Random Access Memory), HMCs (Hybrid Memory Cubes), MRAMs (Magnetic RAMs), PCMs (Phase-Change Memory), ReRAMs (Resistive RAMs), FeRAMs (Ferroelectric RAMs), flash memories (NAND (Not AND) flash), etc.), LEDs (Light Emitting Diodes), (for example, micro flashes for mobile terminals, in-vehicle devices, projector light sources, LCD backlights, general lighting, etc.), power devices, analog ICs (Integrated Circuits), (for example, DCs (Direct Current-DC (Direct Current) converters, insulated gate bipolar transistors (IGBTs), etc.), MEMS (Micro Electro Mechanical Systems), (for example, acceleration sensors, pressure sensors, vibrators, gyro sensors, etc.), wireless (for example, GPS (Global Positioning System), FM (Frequency Modulation), NFC (Nearfield communication), RFEM (RF Expansion Module), MMIC (Monolithic Microwave Integrated Circuit), WLAN (Wireless Local Area Network), etc.), discrete elements, BSI (Back Side Illumination), CIS (Contact Image Sensor), camera modules, CMOS (Complementary Metal Oxide Semiconductor), passive devices, SAW (Surface Acoustic Wave) filters, RF (Radio Frequency) filters, RFIPD (Radio Frequency Integrated Passive Devices), BB (Broadband), etc.
The semiconductor element is, for example, a self-contained device that performs a specific function such as a circuit or a sensor by itself. The semiconductor element may have an interposer function. For example, a logic chip having a logic circuit and a plurality of devices such as a memory chip can be stacked on a device having an interposer function. In this case, the devices can be joined even if the electrode sizes are different for each device.
In addition, the stacked device is not limited to a one-to-multiple configuration in which multiple semiconductor elements are bonded to one semiconductor element, but may be a multiple-to-multiple configuration in which multiple semiconductor elements are bonded to multiple semiconductor elements.

The present invention is basically configured as described above. The manufacturing method of the metal-filled microstructure of the present invention has been described in detail above, but the present invention is not limited to the above-described embodiment, and various improvements or modifications may of course be made within the scope of the gist of the present invention.

The features of the present invention will be described in more detail below with reference to examples. The materials, reagents, amounts and ratios of substances, and operations shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.
In this example, metal-filled microstructures of Examples 1 to 12 and a metal-filled microstructure of Comparative Example 1 were produced. The metal-filled microstructures of Examples 1 to 12 and Comparative Example 1 were evaluated for electrical conductivity. The results of the evaluation of electrical conductivity are shown in Table 1 below. The evaluation of electrical conductivity will be described below.

<Conductivity>
A TEG chip (daisy chain pattern) and an interposer manufactured by Waltz Corporation were prepared, and these were placed above and below a chip bonder, and their alignment was adjusted in advance.
After the alignment adjustment, each of the fabricated metal-filled microstructures was superimposed on the Cu post side of the interposer placed below, and bonded by thermocompression at a temperature of 250° C., 1 minute, and 6 MPa using a room temperature bonding device (WP-100 (model), manufactured by PMT Co., Ltd.). The electrical resistance between the chip wirings of the bonded samples was measured.

Examples 1 to 12 and Comparative Example 1 will be described below.
Example 1
The metal-filled microstructure of Example 1 will be described.
[Metal-filled microstructures]
<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 (Japanese Industrial Standards) 1050 material.
This aluminum substrate was cut to a width of 1030 mm and then subjected to the following treatments.

<Electrolytic polishing treatment>
The above-mentioned 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 purified 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, a stainless steel electrode was used as the cathode, and a GP0110-30R (manufactured by Takasago Manufacturing Co., Ltd.) was used as the power source. A NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.) was used as the cooling device, and a Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.) was used as the stirring and heating device. 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 prepared by dissolving zinc oxide 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 (fine pores) 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 metal-filled microstructure in which nickel was filled into the micropores was fabricated by constant current electrolysis using a copper plating solution having the composition shown below. Here, constant current electrolysis was performed using a plating device manufactured by Yamamoto Plating Tester Co., Ltd. and a power source (HZ-3000) manufactured by Hokuto Denko Corporation. After confirming the deposition potential by performing cyclic voltammetry in the plating solution, 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/ ^dm2

The surface of the anodized film after filling the micropores with metal was observed with an FE-SEM to determine whether 1,000 micropores were sealed with metal. The sealing rate (number of sealed micropores/1,000) was calculated to be 98%.
In addition, after filling the micropores with metal, the anodized film was cut in the thickness direction using an FIB, and the cross section was photographed with an FE-SEM (magnification 50,000x) to check the inside of the micropores. It was found that the inside of the sealed micropores was completely filled with metal.

<Surface metal protrusion process>
The structure after the metal filling step was immersed in an aqueous sodium hydroxide solution (concentration: 5 mass%, liquid temperature: 20°C) and the immersion time was adjusted so that the height of the protruding parts was 400 nm, thereby selectively dissolving the surface of the anodized aluminum film, and producing a structure with protruding copper, the filling metal.

<Resin layer forming 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 not provided with the aluminum substrate.

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

<Back surface metal protrusion process>
The structure after the metal filling step was immersed in an aqueous sodium hydroxide solution (concentration: 5 mass%, liquid temperature: 20°C) and the immersion time was adjusted so that the height of the protruding parts was 400 nm, thereby selectively dissolving the surface of the anodized aluminum film, and producing a structure with protruding copper, the filling metal.

<Heating step and removal step>
The structure was placed in the container. Thereafter, the partial pressure of each gas was set to 80% nitrogen and 20% oxygen, and the total pressure of the atmosphere in the container was set to 4.0×10 ⁻² Pa, assuming a total pressure of 100%. The resin layer was heated at a temperature of 120° C. for 2 minutes using a heater, and then the resin layer was peeled off. The pressure in the container was reduced using a vacuum pump to adjust the total pressure.
The mixed gas was injected so that the gas ratio was the same as the desired total pressure. For example, if the gas ratio was _N2 : _O2 = 80:20 and the total pressure was 4.0 Pa, _N2 was purged (nitrogen purged), the pressure was reduced to 3.2 Pa using a vacuum pump, and then _O2 gas was injected to make the total pressure 4.0 Pa.
The resin layer was peeled off in the air.

Example 2
Example 2 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 80% nitrogen and 20% oxygen, and the total pressure was 4.0 Pa, assuming a total pressure of 100%.
Example 3
Example 3 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 80% nitrogen and 20% oxygen, and the total pressure was 1.0×10 ⁴ Pa, assuming a total pressure of 100%.
Example 4
Example 4 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.8% nitrogen and 0.2% oxygen, and the total pressure was 1.0×10 ⁶ Pa, assuming the total pressure to be 100%.
Example 5
Example 5 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.8% argon and 0.2% oxygen, and the total pressure was 1.0×10 ⁶ Pa, assuming the total pressure to be 100%.

Example 6
Example 6 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.8% hydrogen and 0.2% oxygen, and the total pressure was 1.0×10 ⁶ Pa, assuming the total pressure to be 100%.

(Example 7)
Example 7 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.998% nitrogen and 0.002% oxygen, and the total pressure was 4.0 Pa, assuming the total pressure to be 100%.

(Example 8)
Example 8 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.998% argon and 0.002% oxygen, and the total pressure was 4.0 Pa, assuming the total pressure to be 100%.

Example 9
Example 9 was prepared in the same manner as Example 1, except that the partial pressure of each gas in the heating step was 99.998% hydrogen and 0.002% oxygen, and the total pressure was 4.0 Pa, assuming the total pressure to be 100%.
Example 10
In Example 10, the thermal peelable adhesive layer-attached resin substrate was changed to REVALPHA (registered trademark) 3195VS (manufactured by Nitto Denko Corporation) in the resin layer forming step. Regarding the atmosphere in the heating step, when the total pressure was 100%, the partial pressure of each gas was 80% nitrogen and 20% oxygen, and the total pressure was 1.0 x 10 ⁴ Pa. The resin layer was heated at a temperature of 170°C for 2 minutes, and the resin layer was peeled off, but the resin layer was produced in the same manner as in Example 1.

(Example 11)
Example 11 was prepared in the same manner as Example 10, except that the partial pressure of each gas in the heating step was 99.998% nitrogen and 0.002% oxygen, and the total pressure was 4.0 Pa, assuming a total pressure of 100%.
Example 12
Example 12 was prepared in the same manner as in Example 3, except that in the resin layer forming step, the thermal peelable resin substrate with an adhesive layer was changed to Somatac TE PS-2021TE (manufactured by Somar Co., Ltd.).
(Comparative Example 1)
Comparative Example 1 was produced in the same manner as in Example 12, except that the total pressure of the atmosphere in the heating step was 1.0×10 ⁶ Pa.

As shown in Table 1, compared to Comparative Example 1, Examples 1 to 12 had lower electrical resistance and better electrical conductivity.
In Comparative Example 1, the oxygen partial pressure in the atmosphere during the heating step exceeded 10,000 Pa, and the electrical resistance increased.
In Examples 1, 2, 7 to 9, and 11, the oxygen partial pressure was 1.0 Pa or less, the electrical resistance was smaller, and the electrical conductivity was better.
From Examples 1 to 3, it was found that the lower the total pressure, the smaller the electrical resistance and the better the electrical conductivity.
From Examples 3 and 10 and Examples 7 and 11, it was found that the lower the heating temperature, the smaller the electrical resistance and the better the electrical conductivity.

REFERENCE SIGNS LIST 10 Metal-filled microstructure 12 Insulating film 12a Surface 12b Back surface 13 Pore 14 Conductor 14a Protrusion 14b Protrusion 15 Anodic oxide film 16 Resin layer 18 Structure 21 Winding core 30 Aluminum substrate 30a Surface 31 Barrier layer 32c Bottom 32d Surface 35 Metal 35a Metal layer 35b Metal 40 Laminated device 42 Semiconductor element 44 Semiconductor element 45 Anisotropically conductive member Ds Lamination direction Dt Thickness direction H Height d Average diameter ht Thickness p Center-to-center distance

Claims (10)

a preparation step of preparing a structure having an insulating film and a plurality of conductors penetrating the insulating film in a thickness direction and electrically insulated from one another, the conductors protruding from at least one surface of the insulating film in the thickness direction, and a resin layer covering the surface of the insulating film from which the conductors protrude;
a heating step of heating at least the resin layer in an atmosphere having an oxygen partial pressure of 10,000 Pa or less;
a removing step of removing the resin layer heated in the heating step from the insulating film,
The resin layer comprises a heat-releasable adhesive. The method for manufacturing a metal-filled microstructure according to claim 1, wherein the oxygen partial pressure in the atmosphere during the heating step is 1.0 Pa or less. The method for manufacturing a metal-filled microstructure according to claim 1 or 2, wherein the partial pressure of the inert gas in the atmosphere during the heating step is 85% or more of the total pressure of the atmosphere. The method for manufacturing a metal-filled microstructure according to any one of claims 1 to 3, wherein the partial pressure of the reducing gas in the atmosphere during the heating step is 85% or more of the total pressure of the atmosphere. The method for manufacturing a metal-filled microstructure according to any one of claims 1 to 4, wherein the total pressure of the atmosphere during the heating step is 5.0 Pa or less. The method for manufacturing a metal-filled microstructure according to any one of claims 1 to 5, wherein the conductor includes a base metal. 6. The method for producing a metal-filled microstructure according to claim 1, wherein the plurality of conductors have a cross-sectional area of ²⁰ μm2 or less in a cross section perpendicular to the longitudinal direction of the conductors. The method for manufacturing a metal-filled microstructure according to any one of claims 1 to 7, wherein the temperature reached by the resin layer in the heating step is 150°C or less. the conductor protrudes from both sides of the insulating film in the thickness direction,
9. The method for producing a metal-filled microstructure according to claim 1, wherein the resin layer is provided on each of both sides of the insulating film in the thickness direction. The method for manufacturing a metal-filled microstructure according to any one of claims 1 to 9, wherein the insulating film is an anodic oxide film.