Method for producing nanoporous copper structure, nanoporous copper structure, and electroless copper-plating solution

Abstract

The present invention is characterized by comprising: a base metal layer formation step (S01) for forming a base metal layer (11) composed of a metal that is less noble than Cu; and a nanoporous Cu layer formation step (S02) for forming a nanoporous Cu layer (12) by subjecting the base metal layer (11) to electroless plating using an electroless copper-plating solution.

Description

Method for manufacturing nanoporous copper structure, nanoporous copper structure, and electroless copper plating solution

[0001] The present invention relates to a method for manufacturing a nanoporous copper structure having a nanoporous copper layer (nanoporous Cu layer) of nanosize, the nanoporous copper structure, and an electroless copper plating solution used for forming the nanoporous Cu layer. This application claims priority based on Japanese Patent Application No. 2025-024827 filed in Japan on February 19, 2025, and incorporates its content herein by reference.

[0002] In recent years, the performance of semiconductor devices has been improving at a high rate, and the importance of micro-joining technology has been increasing. As an IC chip mounting technology, flip-chip mounting is widely used. For example, as shown in Patent Document 1, a method is provided in which a solder layer is formed on a protruding electrode and joined by solder. Further, for example, as shown in Patent Documents 1 and 2, joining technologies such as the TLP method (Transient Liquid Phase Diffusion Bonding) and the SLID method (Solid-Liquid Interdiffusion) that join by mutually diffusing a solid phase and a liquid phase have been proposed.

[0003] As a next-generation mounting technology for a further fine pitch, a technology for solid-phase diffusion bonding of copper members has been proposed. Here, when joining substrates on which a plurality of Cu pillars are erected, it is necessary to precisely align the distances between the Cu pillars to be joined, and it was necessary to process by CMP (chemical mechanical polishing treatment) or the like.

[0004] Further, for example, as shown in Patent Document 4, a technology has been proposed in which a porous copper layer (preform layer) is formed on the joining surface of Cu pillars and the Cu pillars are joined by solid-phase diffusion bonding. When pressure is applied during joining, the porous copper layer (preform layer) functions like a cushion, so that even when there is a variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact and joined.

[0005] Japanese Patent Publication No. 2018-046148 (A) Japanese Patent No. 6061276 (B) Japanese Patent No. 6369620 (B) Japanese Patent Publication No. 2022-133735 (A)

[0006] Incidentally, depending on the material and structure of the components, it may not be possible to conduct electricity, and in such cases, Cu pillars and the like are sometimes manufactured by electroless plating. However, the plating film formed by electroless plating has a dense film structure, and an oxide film is formed on the surface. For this reason, it has been difficult to directly join components using the electroless plating film. Furthermore, conventionally, electroless plating has not been able to form a porous copper layer on the joining surface of Cu pillars, and if there is variation in the height of the Cu pillars, it was necessary to process them using CMP or the like.

[0007] This invention has been made in view of the circumstances described above, and aims to provide a method for manufacturing a nanoporous copper structure, a nanoporous copper structure, and an electroless copper plating solution used when forming a nanoporous Cu layer, which enable the stable formation of a nano-sized porous copper layer (nanoporous Cu layer) even by electroless plating.

[0008] To solve the above problems, the method for manufacturing a nanoporous copper structure according to Embodiment 1 of the present invention is characterized by comprising a base metal layer formation step of forming a base metal layer made of a metal less noble than Cu, and a nanoporous Cu layer formation step of forming a nanoporous Cu layer on the base metal layer by electroless plating using an electroless copper plating solution.

[0009] According to the method for manufacturing a nanoporous copper structure of Embodiment 1 of the present invention, a base metal layer made of a metal less noble than Cu is formed, and by performing electroless plating using an electroless copper plating solution on this base metal layer, it is possible to form a nano-sized porous copper layer (nanoporous Cu layer). Therefore, a nanoporous Cu layer can be formed by electroless plating even on components that cannot conduct electricity. As a result, for example, by forming a nanoporous Cu layer on the joining surface of Cu pillars by electroless plating, it is possible to bring the Cu pillars to be joined into contact and firmly join them together, even if there are variations in the height of the Cu pillars.

[0010] The method for producing a nanoporous copper structure according to Embodiment 2 of the present invention is characterized in that, in the method for producing a nanoporous copper structure according to Embodiment 1, the electroless copper plating solution contains a soluble copper salt, an azole compound, an acid, and water, the copper concentration is 0.1 mol / L or more, and the azole compound concentration is 10 mmol / L or more and 50 mmol / L or less.

[0011] According to the method for producing a nanoporous copper structure of embodiment 2 of the present invention, the copper concentration is 0.1 mol / L or higher, and the azole compound is contained in a range of 10 mmol / L to 50 mmol / L. Therefore, when electroless plating is performed, the azole compound is adsorbed onto the surface of the base metal layer, which strongly suppresses copper deposition and prioritizes copper nucleation, resulting in the formation of a porous copper layer (nanoporous Cu layer) consisting of copper particles on the surface of the base metal layer. Thus, a nanoporous Cu layer can be reliably formed by electroless plating even on components that cannot conduct electricity.

[0012] The method for producing a nanoporous copper structure according to Embodiment 3 of the present invention is characterized in that, in the method for producing a nanoporous copper structure according to Embodiment 2, the azole compound is represented by the following formulas (1) to (4), having two to three nitrogen atoms in a five-membered ring. In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, or a mercapto group, or any of the following: an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

[0013] According to the method for producing a nanoporous copper structure of embodiment 3 of the present invention, since the azole compound contains the structures shown in formulas (1) to (4) above, copper deposition can be reliably suppressed, and a porous copper layer (nanoporous Cu layer) made of copper particles can be reliably formed on the surface of the base metal layer. Therefore, a nanoporous Cu layer can be reliably formed by electroless plating even on components that cannot conduct electricity.

[0014] The nanoporous copper structure of embodiment 4 of the present invention is characterized by comprising a base metal layer made of a metal less noble than Cu, and a nanoporous Cu layer formed on the base metal layer. According to the nanoporous copper structure of embodiment 4 of the present invention, since the nanoporous Cu layer is formed on the base metal layer made of a metal less noble than Cu, even members that cannot conduct electricity can be provided with a nanoporous Cu layer. For example, even if there is variation in the height of the Cu pillars, it is possible to bring the Cu pillars to be joined into contact and firmly join them together.

[0015] The nanoporous copper structure of aspect 5 of the present invention is the nanoporous copper structure of aspect 4 of the present invention, characterized in that the average porosity of the nanoporous Cu layer is in the range of 5% to 80%. According to the nanoporous copper structure of aspect 5 of the present invention, since the average porosity of the nanoporous Cu layer is in the range of 5% to 80%, the strength of the nanoporous Cu layer can be ensured.

[0016] The electroless plating solution of embodiment 6 of the present invention is an electroless copper plating solution used when forming a nanoporous Cu layer on a base metal layer made of a metal less noble than Cu, and is characterized by containing a soluble copper salt, an azole compound, an acid, and water, having a copper concentration of 0.1 mol / L or more, and the azole compound concentration being 10 mmol / L or more and 50 mmol / L or less.

[0017] According to the electroless plating solution of embodiment 6 of the present invention, the copper concentration is 0.1 mol / L or higher, and the solution contains an azole compound in the range of 10 mmol / L to 50 mmol / L. Therefore, when electroless plating is performed, the azole compound is adsorbed onto the surface of the base metal layer, which strongly suppresses copper deposition and prioritizes copper nucleation, allowing a porous copper layer (nanoporous Cu layer) made of copper particles to be formed on the surface of the base metal layer.

[0018] The electroless plating solution of embodiment 7 of the present invention is characterized in that, in the electroless plating solution of embodiment 6 of the present invention, the azole compound is represented by the following formulas (1) to (4), having two to three nitrogen atoms in a five-membered ring. In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, or a mercapto group, or any of the following: an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

[0019] According to the electroless plating solution of embodiment 7 of the present invention, since it contains an azole compound with the structure shown in formulas (1) to (4) above, it is possible to reliably suppress the deposition of copper and to reliably form a porous copper layer (nanoporous Cu layer) consisting of copper particles on the surface of the base metal layer.

[0020] According to the present invention, it is possible to provide a method for manufacturing a nanoporous copper structure, a nanoporous copper structure, and an electroless copper plating solution used when forming a nanoporous Cu layer, which can be stably formed by electroless plating.

[0021] This is a schematic diagram of a nanoporous copper structure according to one embodiment of the present invention. This is a diagram illustrating the nanoporous Cu layer of a nanoporous copper structure according to one embodiment of the present invention. This is a flow chart of a method for manufacturing a nanoporous copper structure according to one embodiment of the present invention. This is a cross-sectional SEM image of the nanoporous copper structure of Example 1 of the present invention in the examples. This is a cross-sectional SEM image of the nanoporous copper structure of Example 1 of the present invention in the examples. This is a cross-sectional SEM image of the nanoporous copper structure of Comparative Example 1 in the examples. This is a cross-sectional SEM image of the nanoporous copper structure of Comparative Example 1 in the examples.

[0022] The following describes, with reference to the drawings, a method for manufacturing a nanoporous copper structure, the nanoporous copper structure, and an electroless copper plating solution, which are embodiments of the present invention.

[0023] The nanoporous copper structure according to this embodiment is formed, for example, on the bonding surface of a plurality of protruding electrodes (Cu pillars) provided on a semiconductor chip or substrate in a semiconductor device, and acts as a buffer layer when bonding the protruding electrodes (Cu pillars) together.

[0024] In this embodiment of the nanoporous copper structure 10, as shown in Figure 1, a base metal layer 11 made of a metal less noble than copper is formed on the bonding surface of the member 1 (Cu pillar), and a nanoporous Cu layer 12 is formed on this base metal layer 11.

[0025] Here, as a metal less base than copper that constitutes the base metal layer 11, for example, Co, Mg, Fe, Zn, etc. can be used. Furthermore, there are no particular restrictions on the thickness of the base metal layer 11, but it is preferably in the range of 10 nm to 1000 nm. The lower limit of the thickness of the base metal layer 11 is more preferably 50 nm or more, and even more preferably 100 nm or more. On the other hand, the upper limit of the thickness of the base metal layer 11 is more preferably 750 nm or less, and even more preferably 500 nm or less.

[0026] As shown in Figure 2, the nanoporous Cu layer 12 is formed in the form of an aggregate of copper particles 15, where copper particles 15 are stacked on top of each other. Here, it is preferable that the average porosity of the nanoporous Cu layer 12 is within the range of 5% to 80%. If the average porosity is 5% or more, copper particles that contribute to the sintering of the nanoporous Cu layer 12 are secured, and the sinterability of the copper particles is improved. If the average porosity is 80% or less, the porosity within the nanoporous Cu layer 12 does not become unnecessarily high, ensuring the strength of the nanoporous Cu layer 12 and ensuring the sinterability of the copper particles. It is more preferable that the lower limit of the average porosity of the nanoporous Cu layer 12 be 10% or more. On the other hand, it is more preferable that the upper limit of the average porosity of the nanoporous Cu layer 12 be 75% or less, and even more preferable that be 70% or less.

[0027] The average porosity of the nanoporous Cu layer 12 is calculated by image analysis of the cross-section of the nanoporous Cu layer 12 using a scanning electron microscope. The arithmetic mean of the porosity (P) obtained by the following formula (A) is taken as the average porosity. Specifically, the measurement is taken by taking three images in different fields of view, and the average value of the calculated porosity is taken as the average porosity. P (%) = (S2 / S1) × 100 (A) However, in formula (A), P is the porosity of the nanoporous Cu layer 12, S1 is the total area of ​​the nanoporous Cu layer 12, and S2 is the area of ​​the vacant portion in the nanoporous Cu layer 12.

[0028] Here, the thickness of the nanoporous Cu layer 12 is preferably in the range of 50 nm to 5000 nm. If the thickness of the nanoporous Cu layer 12 is 50 nm or more, the strength of the nanoporous Cu layer 12 itself is ensured, and handling becomes easier. On the other hand, if the thickness of the nanoporous Cu layer 12 is 5000 nm or less, the nanoporous Cu layer 12 follows the irregularities of each surface of the substrate or electronic component described later during bonding, and the bonding strength of the bonded body is improved. The lower limit of the thickness of the nanoporous Cu layer 12 is more preferably 100 nm or more, and even more preferably 500 nm or more. On the other hand, the upper limit of the thickness of the nanoporous Cu layer 12 is more preferably 4000 nm or less, and even more preferably 3000 nm or less.

[0029] Next, the method for manufacturing the nanoporous copper structure according to this embodiment will be explained using the flow chart in Figure 3. In the method for manufacturing the nanoporous copper structure 10 according to this embodiment, as shown in Figure 3, the method includes a base metal layer formation step S01 in which a base metal layer 11 made of a metal less base than Cu is formed on the surface of the member, and a nanoporous Cu layer formation step S02 in which a nanoporous Cu layer is formed on the base metal layer 11 by electroless plating.

[0030] (Base metal layer formation step S01) In this base metal layer formation step S01, a base metal layer 11 made of a metal less base than Cu is formed on the surface of the member (for example, the joint surface of a copper pillar). There are no particular limitations on the means of forming the base metal layer 11, and existing methods can be selected and applied depending on the metal that constitutes the base metal layer 11 to be formed. For example, the base metal layer 11 may be formed by electroless plating or by sputtering.

[0031] (Nanoporous Cu layer formation process S02) In this nanoporous Cu layer formation process S02, a nanoporous Cu layer 12 is formed by performing electroless plating on the base metal layer 11 using the electroless copper plating solution of this embodiment.

[0032] The electroless copper plating solution of this embodiment contains a soluble copper salt, an azole compound, an acid, and water, with a copper concentration of 0.1 mol / L or higher, and the concentration of the azole compound being in the range of 5 mmol / L to 100 mmol / L. In addition, the electroless copper plating solution of this embodiment may contain other components as needed, such as brighteners, surfactants, antioxidants, etc. The copper concentration of the electroless copper plating solution may be 0.2 mol / L or higher, or 0.5 mol / L or higher. While not particularly limited, the practical upper limit of the copper concentration of the electroless copper plating solution is 1.0 mol / L or lower. The concentration of the azole compound in the electroless copper plating solution may be 10 mol / L or higher, or 20 mol / L or higher. The concentration of the azole compound in the electroless copper plating solution may be 75 mol / L or lower, or 50 mol / L or lower.

[0033] Specific examples of soluble copper salts include copper sulfate, copper oxide, and copper carbonate; copper alkanesulfonates such as copper methanesulfonate and copper propanesulfonate; copper alkanolsulfonates such as copper isethionate and copper propanolsulfonate; and copper organic acids such as copper acetate, copper citrate, and copper tartrate. These can be used individually or in combination of two or more.

[0034] Examples of acids include organic acids and inorganic acids. These include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; and alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid. These can be used individually or in combination of two or more. Examples of water include deionized water and distilled water.

[0035] Examples of azole compounds include imidazole, 2-aminoimidazole, pyrazole, 3-aminoimidazole, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, and 3-amino-5-methylthio-1H-1,2,4-triazole. These azole compounds are those represented by formulas (1) to (4) above, having two to three nitrogen atoms in a five-membered ring.

[0036] The imidazole mentioned above is a type of azole compound shown in formula (1) above, and is represented by formula (5) below. 2-aminoimidazole is a type of azole compound shown in formula (1) above, and is represented by formula (6) below. Pyrazole is a type of azole compound shown in formula (2) above, and is represented by formula (7) below. 3-aminopyrazole is a type of azole compound shown in formula (2) above, and is represented by formula (8) below. 1,2,3-triazole is a type of azole compound shown in formula (3) above, and is represented by formula (9) below.

[0037]

[0038] 1,2,4-Triazole is a kind of azole compound represented by the above formula (4) and is represented by the following formula (10). 3-Amino-1,2,4-triazole is a kind of azole compound represented by the above formula (4) and is represented by the following formula (11). 3,5-Diamino-1,2,4-triazole is a kind of azole compound represented by the above formula (4) and is represented by the following formula (12). 3-Amino-5-methylthio-1H-1,2,4-triazole is a kind of azole compound represented by the above formula (4) and is represented by the following formula (13).

[0039]

[0040] The azole compound adsorbs on the surface of the base metal layer 11 during electroless plating and has the effect of suppressing copper deposition. Thus, by suppressing copper deposition, copper nucleation is prioritized on the cathode surface, and a porous copper layer composed of copper particles is formed.

[0041] The electroless copper plating solution of the present embodiment can be prepared by mixing the above soluble copper salt, the above-mentioned azole compound, an acid, and water.

[0042] Here, in the prepared electroless copper plating solution, the content of the soluble copper salt is preferably 0.01 mol / L or more. If the content of the soluble copper salt is 0.01 mol / L or more, the nanoporous Cu layer 12 as a copper plating film can be stably formed. In the electroless copper plating solution, the lower limit of the content of the soluble copper salt is more preferably 0.05 mol / L or more, and even more preferably 0.1 mol / L or more. On the other hand, there is no particular limitation on the upper limit of the content of the soluble copper salt, but it is preferably substantially 1 mol / L or less.

[0043] In the prepared electroless copper plating solution, the content of the azole compound is within the range of 10 mmol / L to 50 mmol / L. When the content of the azole compound is 10 mmol / L or more, the effect of suppressing copper deposition can be achieved, and a nanoporous Cu layer 12 as a copper plating film can be stably formed. When the content of the azole compound is 50 mmol / L or less, copper deposition is not excessively suppressed, and the brittleness of the copper plating film can be suppressed. In addition, the azole compound can be sufficiently dissolved in the solution. The lower limit of the azole compound content is more preferably 15 mmol / L or more, and even more preferably 20 mmol / L or more. On the other hand, the upper limit of the azole compound content is more preferably 40 mmol / L or less, and even more preferably 30 mmol / L or less.

[0044] In the prepared electroless copper plating solution, there are no particular restrictions on the concentrations of water, acid, etc., other than the soluble copper salt and azole compound mentioned above. However, it is preferable to adjust the pH of the electroless copper plating solution to be within the range of 0.5 to 4, and more preferably to be within the range of 1 to 3.5.

[0045] According to the manufacturing method of the nanoporous copper structure of this embodiment, which has the above configuration, a base metal layer 11 made of a metal less noble than Cu is formed on the surface of member 1 (Cu pillar), and by performing electroless plating using an electroless copper plating solution on this base metal layer 11, it is possible to form a nano-sized porous copper layer (nanoporous Cu layer 12). Therefore, even for member 1 (Cu pillar) that cannot conduct electricity, a nanoporous Cu layer 12 can be formed by electroless plating. As a result, for example, by forming a nanoporous Cu layer 12 on the joining surface of Cu pillars by electroless plating, it is possible to bring the Cu pillars to be joined into contact and firmly join them together, even if there is variation in the height of the Cu pillars.

[0046] In the method for manufacturing the nanoporous copper structure according to this embodiment, when the electroless copper plating solution contains a soluble copper salt, an azole compound, an acid, and water, and the copper concentration is 0.1 mol / L or more and the concentration of the azole compound is in the range of 10 mmol / L or more and 50 mmol / L or less, when electroless plating is performed, the azole compound is adsorbed on the surface of the base metal layer 11. As a result, the precipitation of copper is strongly suppressed and the nucleation of copper is prioritized, and a porous copper layer (nanoporous Cu layer 12) composed of copper particles is formed on the surface of the base metal layer 11. Therefore, the nanoporous Cu layer 12 can be surely formed on the member 1 that cannot be energized by electroless plating.

[0047] In the method for manufacturing the nanoporous copper structure according to this embodiment, when the azole compound contained in the electroless copper plating solution is one represented by the above formulas (1) to (4) having two or more and three or less nitrogen atoms in the five-membered ring, the precipitation of copper can be surely suppressed, and a porous copper layer (nanoporous Cu layer 12) composed of copper particles can be surely formed on the surface of the base metal layer 11. Therefore, the nanoporous Cu layer 12 can be surely formed on the member 1 that cannot be energized by electroless plating.

[0048] In the nanoporous copper structure 10 according to this embodiment, since it includes a base metal layer 11 made of a metal less noble than Cu and a nanoporous Cu layer 12 formed on the base metal layer 11, even a member 1 that cannot be energized can be provided with the nanoporous Cu layer 12. For example, even when there is a variation in the height of the Cu pillars, the Cu pillars to be joined can be brought into contact with each other and firmly joined.

[0049] In the nanoporous copper structure 10 according to this embodiment, when the average porosity in the nanoporous Cu layer 12 is in the range of 5% or more and 80% or less, the strength of the nanoporous Cu layer 12 can be ensured.

[0050] In this embodiment of the electroless plating solution, the copper concentration is 0.1 mol / L or higher, and the azole compound is contained in a range of 5 mmol / L to 100 mmol / L. Therefore, when electroless plating is performed, the azole compound is adsorbed onto the surface of the base metal layer 11, which strongly suppresses copper deposition and prioritizes copper nucleation, allowing a porous copper layer (nanoporous Cu layer 12) made of copper particles to be formed on the surface of the base metal layer 11.

[0051] In the electroless plating solution of this embodiment, if the azole compound included is one of those represented by formulas (1) to (4) above, having two to three nitrogen atoms in a five-membered ring, then copper deposition can be reliably suppressed, and a porous copper layer (nanoporous Cu layer 12) made of copper particles can be reliably formed on the surface of the base metal layer 11.

[0052] Although embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified as appropriate without departing from the technical spirit of the invention.

[0053] The following describes the results of confirmation experiments conducted to verify the effectiveness of the present invention. A 50 nm Ti layer was formed on the upper surface of Si glass, and a base metal layer was formed on top of it to form the metal layer shown in Table 1. Then, an electroless plating layer (nanoporous Cu layer) was formed on top of the Ti layer using the electroless plating solution shown in Table 1. In the comparative example, an electroless plating solution that did not contain azole compounds was used. The sample was immersed in the plating solution in a 1 cm square area. The immersion time was 3 min, the solution temperature was room temperature, and there was no agitation during immersion.

[0054] (Voiding) The voiding was measured for the obtained structure using a cross-sectional SEM. Binarization was performed on the voids above the Ti layer at a magnification of 30,000x. The voiding was calculated using the binarization process. Measurements were taken for five samples, and the average value was used as the voiding. The evaluation results are shown in Table 1.

[0055] (Shear Strength) The obtained structure was cut into 5 mm square sections, and the sections were joined together. The joining was performed at 300°C, 15 MPa, for 1 min in a nitrogen atmosphere, and the shear strength was measured. The evaluation results are shown in Table 1.

[0056]

[0057] In the comparative example, an electroless plating layer was formed using an electroless plating solution that did not contain an azole compound, resulting in a porosity of 0% in the electroless plating layer, making it impossible to form a porous Cu layer. Furthermore, it was not possible to join the structures together. In contrast, in Examples 1 to 14 of the present invention, an electroless plating layer was formed on a base metal layer made of a metal less noble than Cu using an electroless plating solution containing an appropriate amount of an azole compound, resulting in a porosity of 11 to 68% in the electroless plating layer, making it possible to form a porous Cu layer with sufficient porosity. Furthermore, the shear strength after joining the structures together was 0.5 MPa or higher.

[0058] Based on the results of the above verification experiments, it has been confirmed that, according to the present invention, it is possible to provide a method for manufacturing a nanoporous copper structure, a nanoporous copper structure, and an electroless copper plating solution used when forming a nanoporous Cu layer, which can be stably formed by electroless plating.

[0059] This invention provides a method for manufacturing a nanoporous copper structure that can stably form a nano-sized porous copper layer (nanoporous Cu layer) even by electroless plating, a nanoporous copper structure, and an electroless copper plating solution used when forming the nanoporous Cu layer.

[0060] 10 Nanoporous copper structure 11 Base metal layer 12 Nanoporous Cu layer

Claims

1. A method for manufacturing a nanoporous copper structure, comprising: a base metal layer formation step of forming a base metal layer made of a metal less base than Cu; and a nanoporous Cu layer formation step of forming a nanoporous Cu layer on the base metal layer by electroless plating using an electroless copper plating solution.

2. A method for producing a nanoporous copper structure, characterized in that the electroless copper plating solution contains a soluble copper salt, an azole compound, an acid, and water, the copper concentration is 0.1 mol / L or higher, and the azole compound concentration is 10 mmol / L or higher and 50 mmol / L or lower.

3. The method for producing a nanoporous copper structure according to claim 2, characterized in that the azole compound is represented by the following formulas (1) to (4) having two to three nitrogen atoms in a five-membered ring. In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, or a mercapto group, or any of the following: an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

4. A nanoporous copper structure characterized by comprising a base metal layer made of a metal less base than Cu, and a nanoporous Cu layer formed on the base metal layer.

5. The nanoporous copper structure according to claim 4, characterized in that the average porosity of the nanoporous Cu layer is in the range of 5% to 80%.

6. An electroless copper plating solution used for forming a nanoporous Cu layer on a base metal layer made of a metal less noble than Cu, comprising a soluble copper salt, an azole compound, an acid, and water, wherein the copper concentration is 0.1 mol / L or higher, and the azole compound concentration is 10 mmol / L or higher and 50 mmol / L or lower.

7. The electroless copper plating solution according to claim 6, characterized in that the azole compound is represented by the following formulas (1) to (4), having two to three nitrogen atoms in a five-membered ring. In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, or a mercapto group, or any of the following: an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

Images