JP2014143251A - Method for forming plating film and coating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a copper plating film, by which copper plating films 11, 12 having high adhesion can be formed on a glass substrate 10 in an atmosphere and by means of a solution process.SOLUTION: A method for forming a copper plating film of an embodiment includes: a plating step of depositing copper plating films 11, 12 on a glass substrate 10; a protective film forming step of coating a protective film 13 covering the copper plating films 11, 12; a heat treatment step of performing heat treatment at temperature of 500°C in an atmosphere; and a peeling step of peeling the protective film 13.

Description

  The present invention relates to a plating film forming method including a step of performing a heat treatment on a plating film formed on a substrate made of an inorganic material, and a coating solution for forming an oxidation-resistant protective film.

  Since the plating method can be produced by a solution process that does not require the use of a vacuum apparatus or the like, it is inexpensive and excellent in mass productivity. For this reason, the plating method is widely used in the production of printed wiring boards and the like, but in order to obtain strong adhesion strength, the substrate is roughened before plating. However, when the surface roughening treatment is performed, transparency is impaired when the substrate is a glass substrate, and high-frequency transmission characteristics are degraded when the substrate is a wiring board. Therefore, various metal plating methods that do not roughen the substrate have been studied.

  For example, in Japanese Patent Laid-Open No. 10-209584, a 0.1 μm electroless PdP plating film is formed on a non-roughened glass substrate, and a 2 μm electric Ag plating film is further formed. It is disclosed to perform heat treatment. “˜” indicates “above and below”.

  However, Pd and Ag are expensive for use in manufacturing a wiring board. Moreover, since Ag is a migration, it was not easy to apply to wiring materials.

  Therefore, there has been a demand for a method for forming a plating film having high adhesion in the atmosphere and in a solution process, and a coating solution that can be used in the above method to prevent oxidation of the plating film in an atmospheric heat treatment step.

JP 10-209584 A

  Embodiments of the present invention provide a method for forming a plating film having high adhesion in the atmosphere and in a solution process, and a coating solution that can be used in the method to prevent oxidation of the plating film in an atmospheric heat treatment step. Objective.

  The plating film forming method of the embodiment of the present invention includes a plating process for forming a plating film on a substrate made of an inorganic material, a protective film forming process for applying a protective film covering the copper plating film, and 350 ° C. to 550 ° C. A heat treatment step of performing a heat treatment in the atmosphere at a temperature of ° C., and a peeling step of peeling the protective film.

  In another embodiment, the coating solution includes an organic solvent in which alkoxysilane and catechol are dissolved, and a ketone that is a reaction initiator, and forms an oxidation-resistant protective film on the applied metal.

  According to an embodiment of the present invention, a method for forming a plating film with high adhesion in the atmosphere and in a solution process, and the oxidation of the plating film in the atmospheric heat treatment step used in the method can be prevented, and A coating solution that forms a protective film that can be peeled can be provided.

It is a flowchart of the formation method of the copper plating film of embodiment. It is a flowchart of the protective layer formation subroutine of the formation method of the copper plating film of an embodiment. It is sectional drawing for demonstrating the formation method of the copper plating film of embodiment. It is a figure which shows the structure of the precursor solution of the coating solution of embodiment. It is a figure which shows the structure of the coating solution of embodiment. It is a figure which shows the GD-OES analysis result of the protective film / plating film of a comparative example. It is a figure which shows the GD-OES analysis result of the protective film / plating film of embodiment. It is a figure which shows the GD-OES analysis result of the protective film / plating film before heat processing.

<First Embodiment>
Hereinafter, according to the flowchart shown to FIG. 1A and FIG. 1B, the formation method and coating solution of the copper plating film of embodiment are demonstrated.

<Step S11> Substrate Preparation In this embodiment, a transparent glass substrate 10 is used as a substrate made of an inorganic material. As the glass substrate 10, various glass compositions such as sodium glass, borosilicate glass, non-alkali glass, or quartz glass can be used depending on specifications.

  First, pretreatment is performed on the glass substrate 10. In the pretreatment, the foreign substance adsorbed on the surface is removed by immersing the glass substrate 10 in pure water and performing ultrasonic cleaning. Further, the organic matter adsorbed on the surface by ultraviolet irradiation is decomposed, and then immersed in an alkaline degreasing solution containing a surfactant to remove the organic matter. In addition, it is preferable that the solution used for the treatment is previously filtered to remove fine particles. When the substrate is clean, no pretreatment is necessary.

<Step S12> Catalyst Application After immersing the substrate 10 in a 0.2 mg / dm ³ PdCl ₂ containing solution (45 ° C.) for 120 seconds, the substrate 10 is added to a 0.25 mol / dm ³ NaH ₂ PO ₂ containing solution (45 ° C.). It was immersed for 120 seconds, Pd ions were reduced, and used as a catalyst for electroless plating reaction.

For the catalyst application, a known treatment method using various solutions, for example, a two-stage method using a SnCl ₂ solution / PdCl ₂ solution, a PdSn mixed catalyst solution method, or the like may be used.

  Alternatively, the catalyst may be imparted by a method of applying / curing / reducing a catalyst solution containing an organometallic compound and a metal serving as a catalyst for the electroless plating reaction. For example, the following TiCu solution containing organic titanium can be used as the catalyst solution.

Titanium (IV) tetraisopropoxide: Ti (OiPr) ₄ 4.44 mL
1.82 g of copper (II) acetate
1-Hydroxycyclohexyl Phenyl Ketone (HPK) 8.17g
Methoxyethoxyacetic acid 1.14 mL
Ethyl lactate 68.8mL
N, N-dimethylacetamide 17.2 mL

Curing treatment: HP 170 ° C., 60 minutes (in air)
Reduction treatment: immersion of sodium borohydride (SBH) in an aqueous solution (45 ° C.) containing 2 g / L for 2 minutes

  In addition, the photosensitive compounds disclosed in JP 2011-207693 A, for example, 4- (2-nitrobenzyloxycarbonyl) catechol (NBOC-CAT), 1-Hydroxycyclohexyl Phenyl Ketone (HPK) naphthoquinone diazide (NQD), etc. The catalyst film may be patterned by performing ultraviolet exposure after applying the catalyst using a catalyst solution containing the catalyst.

<Step S13> Electroless Copper Plating The electroless copper plating film 11 having a film thickness of 0.1 μm was formed on the substrate by dipping in an electroless copper plating bath shown in Table 1 below. In addition, it is preferable that the electroless copper plating film | membrane 11 film thickness is 0.05 micrometer-5 micrometers. If it is more than the said lower limit, it has a function as a base conductive film in electroplating, and if it is less than the said upper limit, a problem does not arise in productivity.

(Table 1)
Copper sulfate 0.04mol / dm ³
EDTA 0.12mol / dm ³
Formalin 0.15mol / dm ³
Additive appropriate temperature 50 ℃
pH 12.5

  As the electroless plating basic bath, paraformaldehyde or glyoxylic acid can be used as a reducing agent. Glyoxylic acid is similar in structure to formaldehyde and has a small reducing power, but has little effect on the human body.

  In order to accelerate the deposition reaction of electroless copper plating, a thin electroless nickel film may be deposited first, and then the electroless copper plating film may be grown, or a small amount of nickel ions may be added to the electroless copper plating bath. It may be added.

<Step S14> Electrolytic Copper Plating Using an electrolytic copper plating bath shown in the following (Table 2), an electroless copper plating film 12 having a thickness of 20 μm was formed using the electroless copper plating film 11 as a cathode. The film thickness is, for example, 5 μm to 100 μm, and is determined according to the specifications of the wiring board.

(Table 2)
Copper sulfate 0.8mol / dm ³
Sulfuric acid 0.5 mol / dm ³
Hydrochloric acid 1.4 × 10 ⁻³ mol / dm ³
Additive Appropriate Anode Phosphorus Copper Plate Temperature 25 ° C
Current density 1A / dm ²

<Step S15> Protective Film Formation Subroutine As shown in FIG. 2A, the protective film 13 is formed so as to cover the uppermost electroplated film 12 of the laminate of the glass substrate 10 / electroless plated film 11 / electroplated film 12. Is formed.
As shown in FIG. 1B, the protective film formation subroutine includes steps S21 to S24.

<Step S21> Preparation of Precursor Solution A solution containing 1 mol / L tetraethoxysilane (TEOS) and 1.5 mol / L catechol in toluene as a solvent is heated at 100 ° C. for 1 hour. A precursor solution completely dissolved in toluene is produced.

  As shown in FIG. 3, since TEOS and catechol form a complex, it is considered that catechol is dissolved in toluene. When the liquid before heating is allowed to stand, catechol precipitates. However, the precursor solution after the heat treatment does not precipitate even when left in a colorless to light pink color.

  The precursor solution is stable and can be stored for a long period of time, for example, 5 years or longer.

<Step S22> Preparation of coating solution A coating solution is prepared by adding a ketone, which is a reaction initiator, to the precursor solution. As the ketone, for example, acetylacetone, acetone, methyl ethyl ketone, or the like is used. The addition amount of the ketone which is also a solvent is determined in relation to the concentration of toluene which is the organic solvent in the precursor solution, but is preferably 2 mol or more, particularly preferably 5 mol, with respect to 1 mol of TEOS. That's it.

  As shown in FIG. 4, it is considered that the complex of TEOS and catechol changes to different states by the addition of ketone. As already explained, the precursor solution was colorless to light pink, but the coating solution was yellow-green to green for acetylacetone and brown for acetone and methyl ethyl ketone. In other words, it can be confirmed that TEOS, catechol, and ketone are complexed by changing the color of the solution.

  As described above, the coating solution includes an organic solvent in which alkoxysilane and catechol are complexed and dissolved, and a ketone that is a reaction initiator, and alkoxysilane, catechol, and ketone form a complex. A heat-resistant protective film is formed on the metal.

  In addition, since the coating solution may cause precipitation in a relatively short time (for example, 10 minutes) even at room temperature, it is applied immediately after production.

<Steps S23 and S24> Application / Drying For example, the coating solution is applied so as to cover the electroplating film 12 by spin coating. Thereafter, for example, a drying process for evaporating the solvent at 100 ° C. for 20 minutes is performed using a hot plate or the like, and the protective film 13 is formed. The thickness of the protective film 13 after the drying treatment is preferably 100 nm to 1000 nm, and particularly preferably 400 nm to 800 nm.

  If it is more than the lower limit, there is almost no occurrence of pinholes, and even if it occurs, the oxidation reaction of the plating film starting from the pinhole does not proceed and the oxide layer does not spread. If it has a sufficient function as a protective film and is not more than the above upper limit, cracks and the like are unlikely to occur. In addition, since heat processing is performed subsequently, the heat processing process may serve as the drying process.

  In addition, various known methods can be used for coating / drying.

<Step S16> Heat Treatment A heat treatment is performed in the atmosphere at 500 ° C. for 1 hour. By the heat treatment, the protective film 13 is changed to an Si polymer film, and becomes an oxidation resistant protective film that prevents oxidation of the Cu plating film. At the same time, the adhesion strength between the Cu plating film 11 and the glass substrate 10 is dramatically improved. This is because, as shown in FIG. 2B, a part of the Cu plating film 11 diffuses into the glass substrate 10 and a part of the glass component diffuses into the plating film 11 to form a diffusion layer 19. This is probably because of this. As will be described later, the protective film 13 is changed to a protective layer 13A in which a part of the Cu plating film 11 is diffused by heat treatment.

  The thickness of the protective film 13 shrinks due to the heat treatment. The thickness of the protective film 13 after the heat treatment is preferably 10 nm to 500 nm, and particularly preferably 50 nm to 100 nm. This range corresponds to the thickness range of the protective film 13 after the drying process described above.

  The heat treatment temperature is 350 ° C to 550 ° C, preferably 350 ° C to 500 ° C. Above the lower limit, there is an effect of improving adhesion, and below the upper limit, the glass substrate 10 is not damaged, and peeling does not occur due to a difference in thermal expansion coefficient between Cu and glass. The heat treatment time is preferably 10 minutes to 10 hours. Above the lower limit, the adhesion is sufficiently improved, and below the upper limit, productivity does not deteriorate.

<Step S17> Protective film peeling As shown in FIG.2 (C), the protective film 13 is peeled with a solution and the plated glass substrate 1 is produced. That is, the protective film 13 after the heat treatment can be peeled off by an acid solution such as 10% sulfuric acid or an alkaline solution such as 10% sodium hydroxide solution. The conditions for the peeling step are, for example, room temperature to 60 ° C. and about 10 seconds to 10 minutes. It may be peeled off by surface polishing or the like. Further, when the protective film is not peeled off, the peeling process is not performed.

<Evaluation>
The adhesion evaluation of the plating film was performed by a cross cut test in which a 2 mm square grid pattern was cut with a cutter and peeling with an adhesive tape was confirmed. In addition, the presence or absence of discoloration and discoloration were confirmed by visual inspection.

  In the method for forming a copper plating film of the embodiment, there was no defect by peeling and visual appearance by a cross cut test. That is, the appearance of the Cu plating film 11 of the plated glass substrate 1 was the same as that of so-called red copper metal copper, which was the same as before the heat treatment.

  On the other hand, when the heat treatment temperature is less than 350 ° C., peeling due to the crosscut test occurs, and when it exceeds 550 ° C., discoloration may occur due to oxidation.

  For the coating solution, various alkoxylanes such as tetramethoxysilane may be used instead of TEOS. The alkoxysilane concentration is preferably 0.5 to 1 mol / L, and the molar concentration of catechol is preferably 1 to 2 times the molar concentration of alkoxylane. As the organic solvent, butyl ether or the like may be used. If it is in the said range, the peeling by a crosscut test and the defect by visual appearance will not generate | occur | produce. Further, catechol is completely dissolved in the precursor solution.

  In addition, when a protective film was formed with the coating solution which does not add catechol, copper oxidized and the plating film was discolored black. In addition, when a protective film is formed with a coating solution added with 4-methylcatechol instead of catechol, the color is slightly changed to black. When a protective film is formed with a coating solution added with 4-t-butylcatechol, As with the non-added coating solution, the color changed to black.

  When the precursor solution was prepared at 25 ° C., no complex was formed even after 5 hours, and catechol was not sufficiently dissolved, resulting in white precipitation. In the protective film formed using the coating solution prepared from the precursor solution not forming the complex, copper was oxidized and the plating film was turned black after the heat treatment.

  On the other hand, when the precursor solution was produced at 80 ° C. for 1 hour or 110 ° C. for 1 hour, a complex in which catechol was dissolved was formed, and the plating film was protected by the protective film 13. .

  Here, FIG. 5, FIG. 6 and FIG. 7 show the results of analysis of Cu and Si in the depth direction of samples prepared under various conditions by glow discharge emission analysis (GD-OED). As shown in FIG. 5, when the coating solution of the comparative example to which catechol was not added was used, Cu was mainly present on the outermost surface because the alkoxylane evaporated before polymerization or peeled off during the heat treatment. It was an ingredient. In contrast, Cu was diffused into the protective film 19 in the protective film made of the coating solution of the embodiment shown in FIG.

  Separately, in a composition analysis performed by XPS, oxygen (O) and carbon (C) were detected from the protective film 19 in addition to Si and Cu as shown below. That is, the protective film 19 after the heat treatment is a SiCu—CO film. In XPS, analysis was performed after removing contaminants on the surface. Note that, as shown in FIG. 7, even in the protective film using the coating solution of the embodiment, Cu is not diffused into the protective film 19 before the heat treatment.

Element Before heat treatment After heat treatment Si 5.3 at. % 14.1 at. %
O 25.7 at. % 55.8 at. %
C 69.0 at. % 25.1 at. %
Cu 0.0 at. % 5.0 at. %

  Here, copper was also diffused into the glass substrate 10 after the heat treatment. That is, the copper of the plating films 11 and 12 diffuses into the protective film 19 and the glass substrate 10 by the heat treatment.

  The SiOC film in which alkoxysilane is polymerized does not dissolve in acid. On the other hand, the reason why the protective film 19 is dissolved in the acid is considered that Cu in the Cu plating film 11 diffuses into the protective film 19.

  In addition, when patterning a Cu plating film as a wiring layer, it is preferable to pattern at least before a protective film formation process. This is because after the heat treatment, copper has diffused in the glass substrate 10 and the insulation resistance between the wirings may be deteriorated.

  Of course, even if copper is diffused in the glass substrate 10, the patterning may be performed after the protective film 13 is peeled off as long as the wiring pattern does not cause a problem in the insulation resistance between the wirings. Further, after patterning, for example, an etching process may be performed with an alkaline solution to melt a glass layer in which copper between wirings is diffused.

  As described above, the entire process of the method for forming a copper plating film of the embodiment is performed in the atmosphere. That is, since it is not necessary to perform in a special environment such as a vacuum or an inert gas atmosphere, a glass substrate having a large area can be processed at low cost.

  That is, the method for forming a copper plating film of the embodiment can form a copper plating film with high adhesion on the glass substrate in the atmosphere and by a solution process. Also, the coating solution of the embodiment is a Thus, a protective film that can be prevented from being oxidized and can be removed with a solution can be formed.

  And since copper is unlikely to cause migration unlike Ag and is inexpensive, the method for forming a copper plating film and the coating solution of the embodiment can be particularly preferably used for manufacturing a wiring board.

  Here, in place of the Cu plating film, the protective film of the embodiment also functions as an oxidation-resistant protective film in a nickel plating film, an iron plating film, or the like.

  The Cu plating film may be an alloy plating film made of a copper alloy containing 50 at% or more of Cu. For example, a CuNiP plating film or a CuSnB plating film can be used as the plating film of the embodiment, particularly as an electroless plating film. Moreover, it cannot be overemphasized that the protective film 13 of embodiment has the thermal oxidation prevention effect of not only the plating film on a board | substrate but copper foil, for example.

Second Embodiment
Next, the formation method of the copper plating film of 2nd Embodiment is demonstrated. Since the method of this embodiment is similar to the method of the first embodiment, description of the same steps and the like is omitted.

  In the method of the first embodiment, the electroplating process of step S14 was performed following the electroless plating process of step S13. In other words, the plating process of step S15 includes an electroless plating process for forming an electroless copper plating film and an electroplating process for forming an electrolytic copper plating film using the electroless copper plating film as a conductive film. It was.

  On the other hand, in the method of this embodiment, the plating process of step S15 is either an electroless plating process or an electroplating process.

  When the plating process is only the electroless plating process, the electroplating process may be performed after the protective film peeling process in step S17.

  When the plating process is only an electroplating process, electroplating is performed by so-called direct plating using the Pd catalyst layer as a conductive layer.

  The formation method of the copper plating film of the second embodiment has the same effect as the formation method of the copper plating film of the first embodiment, and the plating process is simpler and excellent in productivity.

<Third Embodiment>
Next, the formation method of the copper plating film of 3rd Embodiment is demonstrated. Since the method of this embodiment is similar to the method of the first embodiment, the description of the same steps and the like is omitted.

  In the present embodiment, a glass glaze alumina substrate is used as the substrate made of an inorganic material. The glass glaze alumina substrate has a glass glaze layer formed on the surface by applying a glass paste containing glass powder and a binder to the alumina substrate and baking it.

  Glass glaze ceramic substrates such as a glass glaze alumina substrate and a glass glaze AlN substrate can form a copper plating film in the same process as the case where the glass substrate 10 described in the first embodiment is used. Can be obtained.

  Even if a ceramic substrate or the like on which a glass glaze layer is not formed, for example, a silicon wafer, an alumina substrate, a SiC ceramic substrate, or the like is used, the same effects as the copper plating film forming method of the first embodiment can be obtained. In this case, since Cu hardly diffuses into the substrate, it is preferable to perform heat treatment at a higher temperature. However, when the heat treatment temperature is high, problems such as blistering may occur due to a difference in thermal expansion coefficient between Cu and ceramic. For this reason, the heat treatment temperature is preferably 550 ° C. or lower.

  Moreover, although the copper plating film was demonstrated in the above description, the same effect can be acquired also in an electroless nickel plating film. The electroless nickel plating is made of a nickel alloy such as NiP or NiB.

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Plated glass substrate 10 ... Glass substrate 11 ... Electroless plating film 12 ... Electroplating film 13 ... Protective film 19 ... Diffusion layer

Claims (15)

A plating step of forming a plating film on a substrate made of an inorganic material;
A protective film forming step of applying a protective film covering the plating film;
A heat treatment step of performing an air heat treatment at a temperature of 350 ° C. to 550 ° C. or less;
And a peeling step of peeling off the protective film.   The method for forming a plating film according to claim 1, wherein the substrate is a glass substrate or a glass glaze ceramic substrate.   3. The plating film forming method according to claim 2, wherein in the protective film forming step, a coating solution containing alkoxysilane, catechol, an organic solvent, and a ketone as a reaction initiator is applied.   The method for forming a plating film according to claim 3, wherein in the peeling step, the protective film is dissolved using a solution. The alkoxysilane is tetraethoxysilane;
A precursor solution preparation step of heating a solution containing 1 mol to 2 mol of catechol with respect to 1 mol of tetraethoxysilane to prepare a precursor solution in which catechol is dissolved;
The method for forming a plating film according to claim 4, further comprising a coating solution preparation step of adding a ketone to the precursor solution before the protective film formation step.   The method for forming a plating film according to claim 5, further comprising a patterning step of patterning the plating film before the protective film forming step.   The plating process includes an electroless plating process for forming an electroless copper plating film, and an electroplating process for forming an electrolytic copper plating film using the electroless copper plating film as a conductive film. The method for forming a plating film according to claim 6.   The plating film according to claim 6, wherein the plating process is either an electroless plating process for forming an electroless copper plating film or an electroplating process for forming an electrolytic copper plating film. Forming method.   A coating solution comprising an organic solvent in which alkoxysilane and catechol are dissolved, and a ketone as a reaction initiator, and forming an oxidation-resistant protective film on the applied metal. The alkoxysilane is tetraethoxysilane;
The coating solution according to claim 9, wherein the catechol is 1 mol to 2 mol with respect to 1 mol of tetraethoxysilane.   The coating solution according to claim 10, wherein the solution is prepared by heating a solution containing tetraethoxysilane, catechol and an organic solvent, and adding the ketone to a precursor solution in which the catechol is dissolved.   The coating solution according to claim 11, wherein the metal is copper, a copper alloy, or a nickel alloy.   The coating solution according to claim 12, wherein the protective film prevents oxidation of the metal from heat treatment in the air at 350 ° C. to 550 ° C.   The coating solution according to claim 13, wherein the protective film after the heat treatment is dissolved by the solution.   15. The coating solution according to claim 14, wherein the metal is a plating film formed on a glass substrate or a glass glaze ceramic substrate.

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