JP7130631B2 - Method for producing conductor, method for producing wiring board, and method for producing composition for forming conductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a conductor, a method for producing a wiring board, and a method for producing a composition for forming a conductor.

2. Description of the Related Art In recent years, attention has been paid to a technique called printable electronics, in which elements and wirings of various electronic devices and electrical equipment are formed by a printing method. Conventional methods such as vacuum deposition, sputtering, and CVD require large-scale equipment, which is a major factor in increasing the cost of products. In addition, since these methods generally involve a step of leaving the portion that will become the wiring and removing the other portion by etching or the like, there are problems such as inefficient use of materials and disposal of waste. On the other hand, in printable electronics, a coating liquid containing a wiring material is printed on a substrate and heat-treated to form wiring. Therefore, there are advantages such as no need for expensive equipment and no waste associated with wiring formation.

On the other hand, the use of copper, which is less expensive and does not cause migration, is under consideration as a wiring material in place of precious metals such as gold and silver. However, since copper is a metal that is extremely easily oxidized, it is necessary to take measures to prevent oxidation, such as forming wiring in an inert gas atmosphere, which is one of the factors that hinder cost reduction.

In Non-Patent Document 1, as a method capable of forming a conductor in the atmosphere, a thin film is formed on a substrate by printing using a coating liquid containing a copper complex soluble in a solvent, and then a carbon dioxide gas laser is used to form a desired pattern. A method has been proposed in which copper is deposited in the irradiated region by irradiating a

Materials Sciences and Applications, 2015, 6, 799-808

The method described in Non-Patent Document 1 has advantages such as the ability to form conductors even in the air and direct patterning of conductors.
In view of the above circumstances, an object of the present invention is to provide a method for producing a conductor, a method for producing a wiring board, and a method for producing a composition for forming a conductor, which can be carried out in the atmosphere and can form a conductor with excellent surface smoothness. and

Means for solving the above problems include the following embodiments.
<1> A composition containing a first copper complex formed from a keto acid and a copper ion and a second copper complex formed from a ligand containing a nitrogen atom and a copper ion is applied to a substrate. A method for producing a conductor, comprising the steps of: applying a composition layer to form a composition layer; and irradiating the composition layer with a laser to deposit copper.
<2> The method for producing a conductor according to <1>, wherein the second copper complex is an amine-based copper complex.
<3> The method for producing a conductor according to <1> or <2>, wherein the laser irradiation is performed using a CO ₂ laser or an Er laser.
<4> The method for manufacturing a conductor according to any one of <1> to <3>, wherein the laser irradiation is performed in a pattern.
<5> The method for producing a conductor according to any one of <1> to <4>, which is carried out in the air.
<6> The method for manufacturing a conductor according to any one of <1> to <5>, wherein the substrate is a resin substrate.
<7> A method for producing a wiring substrate comprising a substrate and copper wiring arranged on the substrate, wherein a first copper complex formed from a keto acid and a copper ion and a coordination containing a nitrogen atom and a second copper complex formed from copper ions and a second copper complex formed from copper ions. A method of manufacturing a wiring board, comprising:
<8> The method for producing a wiring board according to <7>, wherein the second copper complex is an amine-based copper complex.
<9> The method for manufacturing a wiring board according to <7> or <8>, wherein the laser irradiation is performed using a CO ₂ laser or an Er laser.
<10> The method for manufacturing a wiring board according to any one of <7> to <9>, wherein the laser irradiation is performed in a pattern.
<11> The method for manufacturing a wiring board according to any one of <7> to <10>, which is carried out in the air.
<12> The method for manufacturing a wiring board according to any one of <7> to <11>, wherein the substrate is a resin substrate.
<13> A conductor-forming composition containing a first copper complex composed of a keto acid and a copper ion, and a second copper complex composed of a ligand containing a nitrogen atom and a copper ion .
<14> The conductor-forming composition according to <13>, wherein the first copper complex is a keto acid copper complex.
<15> The conductor-forming composition according to <13> or <14>, wherein the second copper complex is an amine-based copper complex.

INDUSTRIAL APPLICABILITY According to the present invention, there are provided a method for producing a conductor, a method for producing a wiring board, and a method for producing a conductor-forming composition, which can be carried out in the atmosphere and can form a conductor having excellent surface smoothness.

4 is an electron micrograph showing the state of the surface of a conductor formed in an example.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention.
In the present disclosure, the term "process" includes a process that is independent of other processes, and even if the purpose of the process is achieved even if it cannot be clearly distinguished from other processes. .
In the present disclosure, the numerical range indicated using "-" includes the numerical values before and after "-" as the minimum and maximum values, respectively.
In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described step by step. . Moreover, in the numerical ranges described in the present disclosure, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples.
In the present disclosure, each component may contain multiple types of applicable substances. When there are multiple types of substances corresponding to each component in the composition, the content rate or content of each component is the total content rate or content of the multiple types of substances present in the composition unless otherwise specified. means quantity.

<Conductor manufacturing method>
The method for producing a conductor of the present disclosure comprises: a first copper complex formed from a keto acid and copper ions; and a second copper complex formed from a ligand containing a nitrogen atom and copper ions. a step of applying a composition containing the composition to a substrate to form a composition layer; and a step of irradiating the composition layer with a laser to deposit copper.

In the above method, copper is deposited by irradiating a composition layer formed on a substrate with a laser. Specifically, when laser irradiation is performed, the irradiated portion is instantaneously heated, and the heat breaks the bonds of the ligands of the copper complex, reducing the copper ions to Cu and depositing copper. In addition, the ligand is decomposed into CO ₂ , CO and H ₂ O by heat and removed as a gas, so that a highly pure conductor can be obtained. The shape of the conductor is not particularly limited, and may be film-like, pattern-like, or any other shape.

In the above method, it is believed that the copper nanoparticles generated by precipitation melt and grow together, forming a conductor in the laser irradiation region. In addition, since this reaction proceeds in an extremely short time, the copper particles are deposited before reacting with oxygen in the air, so it is thought that a good conductor can be formed even in the air. In addition, since the precipitated copper nanoparticles melt at a temperature lower than the melting point of copper, a conductor can be formed with low energy. In addition, since the composition layer outside the laser-irradiated region can be easily removed using a solvent or the like that can dissolve the copper complex, it is advantageous in terms of cost reduction. In addition, since the composition is in a state in which the copper complex is dissolved, problems such as agglomeration and oxidation do not occur unlike materials using metal particles, and the storage stability is excellent.

Furthermore, the conductor formed by the above method has a smoother surface than the conductor formed using the composition containing only the first copper complex. Since the second copper complex is easier to decompose (lower decomposition temperature) than the first copper complex, the deposition of copper from the second copper complex occurs first to form a nucleus, which is used as the basis for It is considered that the growth of the grains is promoted by the copper deposited from the first copper complex. It is believed that a smoother surface of the conductor means a denser structure of the conductor.

The first copper complex used in the above method is not particularly limited as long as it is formed from a keto acid and a copper ion (copper keto acid). Either copper acid or copper γ-keto acid, or a combination thereof may be used.

The second copper complex used in the above method is not particularly limited as long as it is formed from a nitrogen atom-containing ligand and copper ions. For example, monoalkylamine copper complexes such as methylamine copper complexes and ethylamine copper complexes (C _n H _2n+1 NH ₂ Cu: n is an integer), dialkylamine copper complexes, trialkylamine copper complexes, ethylenediamine copper complexes, ethanolamine copper complexes and other amine-based copper complexes. A 2nd copper complex may be used individually by 1 type, or may use 2 or more types together.

The composition containing the first copper complex and the second copper complex may further contain a solvent capable of dissolving these copper complexes. Examples of such solvents include alcohol solvents such as methanol, ethanol and aminoethanol, ketone solvents such as cyclohexanone, amide solvents such as dimethylformamide, terpene solvents such as terpineol, and ester solvents. A solvent may be used individually by 1 type, or may use 2 or more types together.

The content of the first copper complex and the second copper complex in the composition is not particularly limited, but may be, for example, in the range of 90% by mass to 5% by mass of the entire composition, and 80% by mass to 10% by mass. % is preferred.

The molar ratio of the first copper complex to the second copper complex (first copper complex:second copper complex) in the composition is not particularly limited, but is, for example, within the range of 9:1 to 1:9. preferably within the range of 8:2 to 2:8. Further, the molar concentration of copper (total of the first copper complex and the second copper complex) with respect to the entire composition is not particularly limited, but for example, 0.5 M (mol / L) to 3.0 M (mol / L) preferably within the range.

The composition may optionally contain components other than the copper complex and the medium. Such components include viscosity modifiers and the like.

The substrate used in the above method is not particularly limited, and a general wiring substrate for electronic component devices can be used. Examples thereof include semiconductor substrates, glass substrates, ceramic substrates, resin substrates, composites thereof, and the like. Further examples include substrates used in paper devices using cellulose nanofibers. Since the conductor is formed by laser irradiation in the above method, the conductor can be formed even if the substrate is made of a material that is not suitable for heat treatment such as firing.

The method of forming the composition layer on the substrate is not particularly limited. For example, a spin coating method, a printing method, and the like can be mentioned. The composition layer may be formed uniformly or patterned on the substrate.

The laser used for laser irradiation in the above method is not particularly limited as long as it causes decomposition of the copper complex and deposition of copper. From the viewpoint of forming good conductors in the atmosphere, infrared lasers and near-infrared lasers are preferred, and CO ₂ lasers and Er lasers are more preferred. The laser irradiation may be performed uniformly or patternwise on the composition layer.

The above method may include a step of removing the composition layer other than the portion where the copper is deposited by laser irradiation. For example, the composition layer may be removed using a solvent capable of dissolving the copper complex contained in the composition layer.

The conductor formed by the above method may be further subjected to a treatment such as electroless copper plating. By applying electroless copper plating, the thickness of the conductor can be increased. In general electroless copper plating, a Pd film is used as a catalyst film for copper deposition, but the above method deposits copper on the conductor, which is advantageous in terms of cost reduction.

The patterned conductor formed by the above method has excellent pattern width uniformity. Therefore, it becomes possible to form finer patterns, and to provide elements (circuits) and wirings with higher performance.

As a method of forming a patterned conductor, a method of directly irradiating a composition layer with a laser in a pattern (direct patterning) can also be used. A conversion method may be used. These methods do not require an etching process for removing unnecessary conductors, and are environmentally friendly because they do not generate etching waste liquid. Examples of methods for forming a patterned composition layer include printing methods such as screen printing and offset printing, which are generally used for forming wiring, and microcontact printing, which can form finer wiring.

As a method of forming a patterned conductor by microcontact printing, for example, a composition deposited on a stamper made of PDMS (polydimethylsiloxane) is transferred to a substrate to form a patterned composition layer, followed by laser irradiation. A method of depositing copper by

Conductors formed by the above method can be used in a variety of applications. For example, it can be suitably used as a method of forming elements or wiring of a wiring substrate used in electronic equipment. In addition, since conductors can be formed with low energy, it can be suitably used for forming conductors on substrates on which it has been difficult to form conductors by conventional methods such as resin films, thin glass plates, and paper devices.

One application example of the above method is the formation of through electrodes in an interposer made of glass (glass interposer). The interposer is a member arranged between the substrate and the semiconductor element, and has through electrodes that electrically connect the substrate and the semiconductor element. Resin, silicon, or the like is generally used as the material of the interposer. Glass interposers are more advantageous than interposers made of resin, silicon, etc. in terms of coefficient of thermal expansion, heat resistance, insulation, manufacturing costs, etc. However, the problem is that the glass interposers are not strong enough to withstand the process of forming through electrodes. There is

According to the above method, the through electrode can be formed without damaging the thin glass plate. Formation of through electrodes in a glass interposer is performed by, for example, forming through holes in a thin glass plate by laser processing, then applying a composition containing a first copper complex and a second copper complex to the inside of the through holes, and applying a laser. It can be carried out by depositing copper by irradiation.

<Method for manufacturing wiring board>
A method for producing a wiring board according to the present disclosure is a method for producing a wiring board including a substrate and copper wiring arranged on the substrate, wherein a first copper complex formed from a keto acid and a copper ion; a second copper complex formed from a ligand containing a nitrogen atom and a copper ion; applying a composition to a substrate to form a composition layer; to deposit copper.

Details and preferred aspects of the materials used in the above method, method of forming the composition layer, laser irradiation conditions, and other items are the same as those in the method of manufacturing the conductor described above.

<Conductor-forming composition>
The conductor-forming composition of the present disclosure comprises a first copper complex composed of a keto acid and copper ions, and a second copper complex composed of a ligand containing a nitrogen atom and copper ions. include.

By using the above composition, a conductor having excellent surface smoothness can be formed. The details and preferred aspects of the composition are the same as the details and preferred aspects of the composition used in the method for producing the conductor described above.

Hereinafter, the method for manufacturing the conductor described above will be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

<Example 1>
(Preparation of composition)
The α-keto acid (glyoxylic acid) was neutralized with sodium hydroxide to obtain the sodium salt of the α-keto acid. This α-keto acid sodium salt was dissolved in water and a solution of copper sulfate in water was added. When this mixed solution was stirred, an α-keto acid copper complex was precipitated as a pale blue precipitate. The precipitated α-keto acid copper complex was collected and dissolved in a mixed solvent of aminoethanol and ethanol. To this solution, a solution obtained by dissolving copper formate in a methanol solution of methylamine is added to generate a methylamine copper complex, and α-keto acid copper complex as the first copper complex and α-keto acid copper complex as the second copper complex. A composition comprising: a methylamine copper complex was prepared.
The molar ratio of the α-keto acid copper complex and the methylamine copper complex in the composition is set to 1:1, and the total content of the α-keto acid copper complex and the methylamine copper complex in the entire composition is 1M as a copper concentration ( mol/L).

(Formation of copper wiring on a glass substrate by direct patterning)
The prepared composition was applied onto a glass substrate and irradiated with a CO ₂ laser (laser output: 6 W) in a pattern (pattern width: 200 μm) in the atmosphere. Copper was deposited on the irradiated portion. After irradiation, the substrate was immersed in an aminoethanol solution to remove the composition layer other than the copper-deposited portion. Then, it was dried to obtain a substrate having a conductor formed on its surface.

(Evaluation of conductor surface)
A composition was prepared in the same manner as above except that only the α-keto acid copper complex was contained as the copper complex, and a conductor was formed on the substrate in the same manner as above except that this composition was used. Next, the state of the surfaces of both conductors was observed with an optical microscope. As a result, as shown in FIG. 1, the conductor formed using the composition containing the α-keto acid copper complex and the methylamine copper complex was superior to the conductor formed using the composition containing only the α-keto acid copper complex (left). The surface smoothness of the conductor (right) formed by the method was superior.

<Example 2>
(Preparation of composition)
0.85 g of copper α- ketoate (copper glyoxylate) was dissolved in a mixture of 1 ml of 2-aminoethanol and 2 ml of ethanol to prepare a 1.7 M copper glyoxylate solution. Separately, 1.105 g of copper formate tetrahydrate was dissolved in 3 ml of 40% methylamine methanol to prepare a 1.7 M methylamine copper complex solution. By mixing these two solutions, a composition containing an α-keto acid copper complex as a first copper complex and a methylamine copper complex as a second copper complex was prepared.

(Formation of copper wiring by microcontact printing)
The prepared composition is spin-coated (3000 rpm, 30 seconds) on a slide glass, and a microcontact stamper is pressed to adhere the composition to the stamper, which is then stamped onto an alumina substrate to form a finely patterned composition layer. made. A conductor was obtained by pre-baking at 80° C. for 10 minutes and irradiating with a CO ₂ laser (distance between laser and composition layer: 145 mm, sweep speed: 20 mm/s, output: 8.0 W). Electroless copper plating of the conductor was then performed. Electroless copper plating was carried out at 60° C. for 3, 6, 9 and 15 minutes using “Thrucup ELC-SP” manufactured by Uyemura & Co., Ltd. Thus, a copper wiring with a pattern width of about 5 μm was formed.

<Example 3>
(Preparation of composition)
0.5 g of copper α- ketoate (copper glyoxylate) was dissolved in a mixture of 1 ml of 2-aminoethanol and 2 ml of ethanol to prepare a 1.0 M copper glyoxylate solution. Separately, 0.65 g of copper formate tetrahydrate was dissolved in 3 ml of 40% methylamine methanol to prepare a 1.0 M methylamine copper complex solution. By mixing these two solutions, a composition containing an α-keto acid copper complex as a first copper complex and a methylamine copper complex as a second copper complex was prepared.

(Formation of copper wiring on polyimide film by direct patterning)
One side of the polyimide film was irradiated with UV (10 mW/cm ² , distance between polyimide film and UV lamp: 2.0 cm) for 2 minutes. Then, the prepared composition was spin-coated (2000 rpm, 30 seconds) on the UV-irradiated polyimide film, and pre-baked (80° C., 10 minutes) to form a composition layer. Then, a CO ₂ laser was irradiated in a pattern (pattern width: 200 μm) (distance between laser and composition layer: 140 mm, sweep speed: 20 mm/s, output: 2.0 W). After that, the composition layer in the non-irradiated area was removed with pure water and dried with ethanol to obtain a patterned conductor. Electroless copper plating of the conductor was then performed. Electroless copper plating was carried out at 60° C. for 10 minutes using “Thrucup ELC-SP” manufactured by Uyemura & Co., Ltd. Thus, a copper wiring with a pattern width of about 200 μm was formed.

When the cross section of the formed copper wiring was observed with a transmission electron microscope, it was confirmed that the Cu film with a thickness of about 50 nm to 100 nm formed by laser irradiation was thickened to about 500 nm by electroless copper plating. did it. Moreover, the obtained copper wiring had a dense structure.

From the above results, it was found that the method of the present disclosure can be performed in the atmosphere and can form a conductor with excellent surface smoothness. It was also found that the method of the present disclosure is suitable for forming high-definition copper wiring. Further, it was found that the method of the present disclosure can form conductors with excellent surface smoothness even on resin substrates with relatively low heat resistance, and can form high-definition copper wiring.

The disclosure of Japanese Patent Application No. 2017-099366 is incorporated herein by reference in its entirety.
All publications, patent applications and technical standards mentioned herein are to the same extent as if each individual publication, patent application and technical standard were specifically and individually noted to be incorporated by reference. incorporated herein by reference.

Claims (14)

A solution of a first copper complex formed from a keto acid and a copper ion, and a second copper complex formed from a ligand containing a nitrogen atom and a copper ion (provided that it has a piperidine ring or a piperazine ring a polyvalent amino compound excluding those in which copper ions are coordinated) , and a step of mixing a solution to obtain a composition; a step of applying the composition to a substrate to form a composition layer; and a step of depositing copper by irradiating the composition layer with a laser, wherein the molar ratio of the first copper complex to the second copper complex (first copper complex:second copper complex) is 9. : 1 to 1:9 . 2. The method for producing a conductor according to claim 1, wherein the second copper complex is an amine-based copper complex. 3. A method for manufacturing a conductor according to claim 1 or 2, wherein the laser irradiation is performed using a _CO2 laser or an Er laser. The method for manufacturing a conductor according to any one of claims 1 to 3, wherein the laser irradiation is performed in a pattern. 5. The method for manufacturing the conductor according to any one of claims 1 to 4, which is performed in the atmosphere. 6. The method for manufacturing a conductor according to claim 1, wherein the substrate is a resin substrate. A method for manufacturing a wiring substrate comprising a substrate and copper wiring disposed on the substrate, comprising: a solution of a first copper complex formed from a keto acid and copper ions; and a ligand containing a nitrogen atom. and copper ions (excluding polyvalent amino compounds having a piperidine ring or piperazine ring and copper ions coordinated) . A step of applying the composition to the substrate to form a composition layer, and a step of irradiating the composition layer with a laser to deposit copper, wherein the first copper complex and the second copper complex (first copper complex:second copper complex) is in the range of 9:1 to 1:9 . 8. The method for manufacturing a wiring board according to claim 7, wherein the second copper complex is an amine-based copper complex. 9. The method of manufacturing a wiring board according to claim 7, wherein the laser irradiation is performed using a _CO2 laser or an Er laser. 10. The method for manufacturing a wiring board according to claim 7, wherein the laser irradiation is performed in a pattern. 11. The method for manufacturing a wiring board according to any one of claims 7 to 10, which is carried out in the atmosphere. 12. The method for manufacturing a wiring board according to claim 7, wherein the substrate is a resin substrate. A solution of a first copper complex composed of a keto acid and a copper ion, and a second copper complex composed of a ligand containing a nitrogen atom and a copper ion (provided that it has a piperidine ring or a piperazine ring and a solution of a polyvalent amino compound excluding those in which copper ions are coordinated , wherein the molar ratio of the first copper complex to the second copper complex (the first copper complex: A method for producing a conductor-forming composition, wherein the second copper complex) is in the range of 9:1 to 1:9 . 14. The method for producing a conductor-forming composition according to claim 13 , wherein the second copper complex is an amine-based copper complex.

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