JP6065886B2 - Metal film deposition method - Google Patents

Description

  The present invention relates to a film forming metal solution for forming a nickel film and a film forming method using the same, and in particular, a solid electrolyte film is brought into contact with a substrate to form a metal film on the surface of the substrate. In particular, the present invention relates to a metal film for film formation and a film formation method using the same.

  Conventionally, when manufacturing an electronic circuit substrate or the like, a nickel film is formed on the surface of the substrate to form a nickel circuit pattern. For example, as a technique for forming such a metal film, a metal film is formed on a surface of a semiconductor substrate such as Si by a plating process such as an electroless plating process (for example, see Patent Document 1), sputtering, or the like. A film forming technique for forming a metal film by the PVD method has been proposed.

  However, when a plating process such as an electroless plating process is performed, washing with water after the plating process is necessary, and it is necessary to treat the washed waste liquid. In addition, when a film is formed on the surface of the substrate by a PVD method such as sputtering, internal stress is generated in the coated metal film, so there is a limit to increasing the film thickness. In some cases, the film could only be formed with a high vacuum.

  In view of such a point, for example, as shown in FIG. 4, a solution L containing metal ions on the anode 11 side between the anode 11 made of a porous body and the anode 11 and the base material B serving as the cathode is formed. A film forming apparatus including at least a solid electrolyte membrane 13 disposed so as to be in contact with a power supply unit (not shown) for applying a voltage between the anode 11 and the base material B has been proposed (for example, Patent Document 1).

  Here, the housing 15 of the film forming apparatus is formed with a housing portion 19 for containing the aqueous solution L containing metal ions, and the solid electrolyte membrane 13 is filled with the aqueous solution L containing the metal ions in the housing portion 19 via the anode 11. The anode 11 and the solid electrolyte membrane 13 are disposed so as to be able to be supplied to the battery.

  Using such a film forming apparatus, a voltage is applied between the anode 11 and the base material B at the power supply unit, and metal is supplied from the metal ions contained in the solid electrolyte membrane 13 to the surface of the base material B. By depositing, a metal film F made of metal can be formed on the surface of the base material B.

JP 2010-037622 A International Publication No. 2013/125543

  However, when the technique described in Patent Document 2 is used, hydrogen gas is generated between the solid electrolyte membrane 13 and the substrate B, and the generated hydrogen gas is retained between the solid electrolyte membrane 13 and the substrate B. There was something to do. As shown in FIG. 4, the staying hydrogen gas becomes bubbles and exists between the solid electrolyte membrane 13 and the base material B pressed against the solid electrolyte membrane 13, so that metal deposition is prevented in this portion. was there. As a result, undeposited portions (voids) are formed in the metal film F, and a uniform metal film may not be obtained.

  The present invention has been made in view of the above points, and its object is to suppress the generation of hydrogen gas between the solid electrolyte membrane and the base material in contact with each other. An object of the present invention is to provide a metal film for film formation that can be performed and a film formation method using the same.

  As a result of intensive studies, the inventors have found that when the solvent that dissolves the metal in the ionic state is water, the hydrogen ions (free hydrogen) that exist due to the self-dissociation of water are the It was thought that hydrogen gas was generated by reduction when metal was deposited on the surface. And the new knowledge that generation | occurrence | production of hydrogen gas can be suppressed by using the solvent whose hydrogen ion concentration is smaller than water compared with the case where water is used for a solvent was acquired.

The present invention is based on the inventors' new knowledge, and the metal film-forming solution according to the present invention includes a solid electrolyte membrane disposed between an anode and a base material serving as a cathode. By bringing the electrolyte membrane into contact with the base material, applying a voltage between the anode and the base material, and depositing metal on the surface of the base material from the metal ions contained in the solid electrolyte membrane A metal film for film formation for supplying the metal ions to the solid electrolyte film when forming the metal film made of the metal on the surface of the substrate, the metal film for film formation comprising: And a metal ion solution dissolved in an ionic state in the solvent, wherein a hydrogen ion concentration of the film-forming metal solution is in a range of 0 to 10 ^−7.85 mol / L at 25 ° C. .

  According to the present invention, it is possible to reduce the total amount of hydrogen ions (protons) that move from the anode side to the cathode side of the solid electrolyte membrane by suppressing the hydrogen ion concentration of the metal film for film formation within the above-described range. It is possible to suppress the generation of hydrogen gas between the solid electrolyte membrane and the substrate in contact with each other.

Here, the hydrogen ion concentration of 0 mol / L means that the metal film for film formation does not contain hydrogen ions, and the upper limit of the hydrogen ion concentration of 10 ^−7.85 mol / L (at 25 ° C.) is Naturally, the value is lower than the hydrogen ion concentration of 10 ⁻⁷ mol / L in the self-dissociation of water. According to the experiments by the inventors, when the hydrogen ion concentration exceeds 10 ^−7.85 mol / L (at 25 ° C.), a uniform metal film is not formed due to generation of hydrogen gas. I understood it.

  In the present invention, when the metal salt as a solute does not contain hydrogen, the hydrogen ion concentration of the metal solution for film formation matches the hydrogen ion concentration of the solvent, and the case of most metals used for film formation Since the metal salt does not contain hydrogen, the hydrogen ion concentration of the metal solution for film formation matches the hydrogen ion concentration of the solvent.

  Such a solvent is preferably a solvent having a hydrogen ion concentration lower than that of water at the time of self-dissociation, and examples thereof include an aprotic solvent, an alcohol solvent, and the like. Is a solvent that exists in the ionic state (ie, the metal can be dissolved in the ionic state).

  A preferable solvent is an alcohol solvent composed of at least one selected from methanol, ethanol, and propanol (1-propanol or 2-propanol), or a solvent obtained by adding water to the alcohol solvent.

According to this embodiment, methanol, ethanol, and each of the hydrogen ion concentration of propanol is 10 ^-8.35 a ^{mol / L, 10 -8.55 mol /} L, 10 -8.25 mol / L, the above-mentioned 10 ^-7.85 mol / Since the concentration is lower than L (at 25 ° C.), it is difficult for hydrogen gas to be generated between the solid electrolyte membrane and the substrate. Moreover, when methanol, ethanol, and propanol are used, metals such as nickel, tin, and copper can be dissolved in an ionic state. As described above, water may be contained in the alcohol solvent as long as the hydrogen ion concentration satisfies the condition of 10 ^−7.85 mol / L (at 25 ° C.) or less.

  In a more preferred embodiment, the metal dissolved in the solvent is a metal having a greater ionization tendency than hydrogen. Limiting the hydrogen ion concentration as in the present invention is particularly effective because a metal having a higher ionization tendency than hydrogen is likely to generate hydrogen preferentially during its precipitation. Thereby, it is difficult for hydrogen gas to be generated during the deposition of the metal, and a uniform metal film can be formed.

  On the other hand, among the metal species to be precipitated, metals (for example, copper, silver, etc.) having a higher redox potential than hydrogen (small ionization tendency) have a lower ionization tendency than hydrogen, so that the metal is preferentially deposited at the time of deposition. However, since hydrogen gas may be generated depending on the film formation conditions, even such a metal can exert an effect of suppressing the generation of hydrogen gas.

  The metal having a higher ionization tendency than hydrogen is nickel. As is clear from the experiments by the inventors, a uniform nickel film can be obtained by using a solution containing nickel ions that satisfies the above-described hydrogen ion concentration range.

  A method for forming a metal film using the metal film for film formation described above is disclosed below. In this film formation method, a solid electrolyte membrane is disposed between an anode and a base material that becomes a cathode, the solid electrolyte membrane is brought into contact with the base material, and a voltage is applied between the anode and the base material. Then, a metal film made of the metal is formed on the surface of the base material by depositing a metal on the surface of the base material from metal ions contained in the solid electrolyte membrane.

  At this time, by bringing the metal solution for film formation into contact with the solid electrolyte membrane, while supplying the metal ions to the solid electrolyte membrane, a voltage is applied between the anode and the substrate, The metal film is formed on the surface of the substrate.

  According to this aspect, while the solid electrolyte membrane and the substrate are in contact with each other, the metal is deposited from the metal ions, while suppressing the generation of hydrogen gas, which is a particular problem that occurs when forming the metal film. A metal film can be formed.

  According to the present invention, it is possible to suppress the generation of hydrogen gas between the solid electrolyte membrane and the substrate in contact with each other.

The typical conceptual diagram of the film-forming apparatus of the metal film which concerns on this embodiment of this invention. FIG. 2 is a schematic cross-sectional view for explaining a film forming method using the metal film forming apparatus shown in FIG. 1. (A) is a photograph of the nickel film according to Example 2, and (b) is a photograph of the nickel film according to Comparative Example 2. The figure for demonstrating the subject at the time of forming into a film with the film-forming apparatus using a solid electrolyte membrane.

  Hereinafter, a film forming apparatus capable of suitably performing the metal film forming method according to the embodiment of the present invention will be described.

  FIG. 1 is a schematic conceptual diagram of a metal film deposition apparatus 1A according to this embodiment of the present invention. FIG. 2 is a schematic cross-sectional view for explaining a film forming method by the film forming apparatus 1A for the metal film F shown in FIG.

  As shown in FIG. 1, a film forming apparatus 1 </ b> A according to the present invention is an apparatus that deposits a metal from metal ions and forms a metal film made of the deposited metal on the surface of a base material B. Here, the base material B uses a base material made of a metal material such as aluminum, or a base material on which a metal underlayer is formed on the treated surface of a resin or silicon base material.

  The film forming apparatus 1A includes a metal anode 11, a solid electrolyte membrane 13 disposed on the surface of the anode 11 between the anode 11 and the base material B serving as the cathode, and a base material B serving as the anode 11 and the cathode. And at least a power supply unit 14 for applying a voltage.

  The anode 11 is accommodated in a housing (metal ion supply unit) 15 that supplies a solution (hereinafter referred to as a metal solution) L containing metal ions for film formation to the anode 11. The housing 15 is formed with a through portion penetrating in the vertical direction, and the anode 11 is accommodated in the internal space. A recess is formed in the solid electrolyte membrane 13 so as to cover the lower surface of the anode 11, and the solid electrolyte membrane 13 covers the lower opening of the through portion of the housing 15 while accommodating the lower portion of the anode 11. Yes.

  Furthermore, a contact pressurizing part (metal punch) 19 for pressing the anode 11 is arranged in contact with the upper surface of the anode 11 in the penetrating part of the housing 15. The contact pressurizing unit 19 pressurizes the surface of the base material B with the solid electrolyte membrane 13 through the anode 11. Specifically, the contact pressure unit 19 applies the surface of the anode 11 corresponding to the film formation region so as to uniformly pressurize the film formation region where the metal film F is formed on the surface of the base material B. Press.

  In this embodiment, the lower surface of the anode 11 has a size that matches the film formation region of the base material B, and the upper surface and the lower surface of the anode 11 have the same size. Therefore, when the upper surface (entire surface) of the anode 11 is pressed by the contact pressurizing unit 19 by the thrust of the pressurizing means 16 described later, the substrate B is formed on the lower surface (entire surface) of the anode 11 via the solid electrolyte membrane 13. The area (all areas) can be uniformly pressurized.

  Furthermore, a solution tank 17 containing a metal solution L is connected to one side of the housing 15 via a supply pipe 17a, and a waste liquid tank 18 for collecting used waste liquid is connected to the other side. Are connected via a waste liquid pipe 18a.

  Here, the supply pipe 17 a is connected to the supply flow path 15 a of the metal solution L in the housing 15, and the waste liquid pipe 18 a is connected to the discharge flow path 15 b of the metal solution L in the housing 15. As shown in FIG. 2, the anode 11 made of a porous material is disposed in the flow path connecting the supply flow path 15 a and the discharge flow path 15 b of the housing 15.

  With this configuration, the metal solution L stored in the solution tank 17 is supplied into the housing 15 through the supply pipe 17a. In the housing 15, the metal solution L passes through the supply channel 15a, and the metal solution L flows into the anode 11 from the supply channel 15a. The metal solution L that has passed through the anode 11 can flow through the discharge passage 15b and be sent to the waste liquid tank 18 via the waste liquid pipe 18a.

  Further, the pressurizing means 16 is connected to the contact pressure unit 19. The pressurizing means 16 pressurizes the solid electrolyte membrane 13 to the film formation region E of the base material B by moving the anode 11 toward the base material B. For example, the pressurizing means 16 may be a hydraulic or pneumatic cylinder. The film forming apparatus 1 </ b> A includes a base 21 that fixes the base material B and adjusts the alignment of the base material B with respect to the anode 11.

  The anode 11 is made of a porous material that allows the metal solution L to pass therethrough and supplies metal ions to the solid electrolyte membrane. As such a porous body, (1) it has corrosion resistance to the metal solution L, (2) has electrical conductivity that can act as an anode, and (3) can pass through the metal solution L, (4) There is no particular limitation as long as it can be pressurized by the pressurizing means 16 via the contact pressurizing unit 19 to be described later. For example, ionization tendency is higher than plating metal ions such as titanium foam. Examples thereof include a metal foam body that is low (or has a high electrode potential) and is composed of open cells having open pores.

  Moreover, as long as the above condition (3) is satisfied, there is no particular limitation. However, when a metal foam body is used, the porosity is about 50 to 95% by volume, the pore diameter is about 50 to 600 μm, and the thickness. The thing of about 0.1-50 mm is preferable.

  The solid electrolyte membrane 13 can be impregnated with metal ions by being brought into contact with the above-described metal solution L, and metal ions derived from metal ions are deposited on the surface of the substrate B when a voltage is applied. If possible, it is not particularly limited. Examples of the material of the solid electrolyte membrane include ion exchange such as fluorine resin such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon resin, polyamic acid resin, and selemion (CMV, CMD, CMF series) manufactured by Asahi Glass. A resin having a function can be mentioned.

  Here, in the present embodiment, the anode 11 is a porous body as an apparatus for forming the metal film F. However, as described later, if metal ions can be supplied to the solid electrolyte film 13, the anode 11 A gap may be provided between the membrane and the solid electrolyte membrane, and the metal solution may flow between them.

  A metal film forming method using such a film forming apparatus 1A will be described below. First, as shown in FIGS. 1 and 2, first, the base material B is arranged on the base 21, the alignment of the base material B is adjusted with respect to the anode 11, and the temperature of the base material B is adjusted. Next, the solid electrolyte membrane 13 is disposed on the surface of the anode 11 made of a porous body, and the solid electrolyte membrane 13 is brought into contact with the base material B.

  Next, the solid electrolyte membrane 13 is pressurized to the film formation region E of the substrate B by moving the anode 11 toward the substrate B using the pressurizing means 16. Thereby, since the solid electrolyte membrane 13 can be pressurized via the anode 11, the solid electrolyte membrane 13 can be made to follow the surface of the base material B in the film formation region uniformly. That is, the metal film F having a more uniform film thickness can be formed while the solid electrolyte membrane 13 is in contact (pressurization) with the base material using the anode 11 pressurized by the contact pressure unit 19 as a backup material. .

  Next, a voltage is applied between the anode 11 and the base material B serving as the cathode by using the power supply unit 14, and metal is deposited on the surface of the base material B from the metal ions contained in the solid electrolyte membrane 13. Let Since the anode 11 is in direct contact with the metal contact pressure unit 19, the anode 11 is electrically connected to the contact pressure unit 19. Therefore, a voltage can be applied between the anode 11 and the base material B by the power supply unit 14.

  At this time, the metal film is formed while flowing the metal solution L inside the anode 11. As a result, by using the anode 11 made of a porous body, the metal solution L can be permeated therein, and the metal solution L can be supplied to the solid electrolyte membrane 13 together with the metal ions. Thereby, at the time of film-forming, the metal solution L can be stably supplied at any time into the anode 11 which is a porous body. The supplied metal solution L passes through the inside of the anode 11 and comes into contact with the solid electrolyte membrane 13 adjacent to the anode 11, and the solid electrolyte membrane 13 is impregnated with metal ions.

  And by applying a voltage between the anode 11 and the base material B which becomes a cathode, the metal ion in the solid electrolyte membrane 13 moves from the anode 11 side to the base material B side, and the solid electrolyte membrane 13 Metal is deposited on the surface of the base material B from the metal ions contained therein. Thereby, the metal film F can be formed on the surface of the base material B.

  Thereby, since the solid electrolyte membrane 13 can uniformly pressurize the film formation region of the base material B, the metal film can be applied to the base material B in a state where the solid electrolyte membrane 13 is made to follow the film formation region of the base material B uniformly. It can be formed into a film. As a result, a uniform film thickness and a uniform metal film with little variation can be formed on the surface of the base material forming region.

By the way, the metal solution L contains a solvent and a metal (metal ion) dissolved in an ionic state in the solvent. In the present embodiment, the hydrogen ion concentration of the metal solution is in the range of 0 to 10 ^−7.85 mol / L at 25 ° C.

  By suppressing the hydrogen ion concentration of the metal solution L within the above-described range, the total amount of hydrogen ions (protons) moving from the anode side to the cathode side of the solid electrolyte membrane 13 can be reduced. Generation of hydrogen gas between the base material B and the base material B can be suppressed.

  Here, the solvent having a hydrogen ion concentration of 0 mol / L is one that does not contain hydrogen ions. Examples of such a solvent include polar aprotic solvents such as tetrahydrofuran (THF), acetonitrile, N, N dimethylformamide (DMF), dimethyl sulfoxide, and the like. Metals such as copper can be included in an ionic state.

Furthermore, an alcohol solvent can be mentioned as a solvent in which the hydrogen ion concentration of the metal solution satisfies 10 ^−7.85 mol / L (at 25 ° C.) or less. In addition, a solvent in which water is added to an alcohol solvent may be used as long as it satisfies the above-described conditions of hydrogen ion concentration.

  Of these alcohol solvents, methanol, ethanol, propanol (1-propanol or 2-propanol), or these can be used as a solvent that can contain metals such as nickel, tin, and copper in an ionic state. The solvent which mixed at least 2 types of these can be mentioned. Moreover, even when a slight amount of water is added to these alcohol solvents, water molecules and alcohol molecules are integrated, and generation of free hydrogen in the solvent can be suppressed.

  Note that the hydrogen ion concentration of the metal solution in the case where nickel, tin, or copper is contained in the metal solution is substantially the same as the hydrogen ion concentration of the alcohol-based solvent (a solvent further containing water in some cases).

  In addition, the metal that dissolves in the solvent in an ionic state is charged into the solvent in the form of an ionizable metal salt and dissolves in the solvent in an ionic state. As the metal, cobalt, iron, nickel, tin And metals such as copper and silver. In particular, among these metals, metals such as nickel and tin, which are metals having a higher ionization tendency than hydrogen, are preferable.

  By using such a metal, when a voltage is applied between the anode 11 and the base material B, a metal having a higher ionization tendency than hydrogen can be deposited on the surface of the base material B. As a result, when forming the metal film F, hydrogen gas is hardly generated, and a uniform metal film F can be obtained.

The invention is illustrated by the following examples.
[Example 1]
Nickel chloride (metal salt) was dissolved in methanol (solvent) to prepare a 0.1M nickel solution (metal solution). After superposing a solid electrolyte (manufactured by DuPont: Nafion N117) and a porous nickel plate on a gold substrate, a 0.1 M nickel solution was dropped onto the porous nickel plate. Thereafter, the porous nickel and the copper substrate were electrically connected, and a constant potential of 2.4 V was applied for 60 seconds to form a nickel film on the copper base material.

[Example 2]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to ethanol.

[Example 3]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to propanol (1-propanol).

[Example 4]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to a mixed liquid of methanol and water (methanol 90 vol%: water 10 vol%).

[Comparative Example 1]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to a mixed liquid of methanol and water (85% by volume of methanol: 15% by volume of water).

[Comparative Example 2]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to water.

[Comparative Example 3]
A nickel film was formed in the same manner as in Example 1. The difference from Example 1 is that the solvent is changed to butanol (1-butanol).

<Visual observation of film>
The nickel films of Examples 1 to 4 and Comparative Examples 1 to 3 were visually observed. The results are shown in Table 1. Table 1 also shows values (theoretical values) obtained by calculating the hydrogen ion concentration of the film forming metal solution (solvent) at 25 ° C. in Examples 1 to 4 and Comparative Examples 1 to 3.

(result)
In the case of Examples 1 to 4, when the obtained nickel film was visually confirmed, it was confirmed that nickel precipitation was confirmed and the color tone was uniform and a uniform nickel film was obtained. . FIG. 3A is a photograph of the nickel film according to Example 2.

  On the other hand, in the case of Comparative Example 1, when the obtained nickel film was visually confirmed, precipitation of nickel was confirmed, but the color tone showed a mottled pattern, and the presence of voids was confirmed.

  In the case of Comparative Example 2, when the obtained nickel film was visually confirmed, the color tone showed a mottled pattern, and the presence of voids was confirmed. In addition, it was confirmed that the mottled pattern is remarkable compared with the comparative example 1 (refer FIG.3 (b)).

  The reason for the results as in Comparative Examples 1 and 2 is that there is more free hydrogen than in Examples 1 to 4, so that when a voltage is applied between the anode and the substrate, hydrogen ions (protons) are generated. This is probably because hydrogen gas was generated between the solid electrolyte membrane and the substrate. As a result, hydrogen gas accumulates between the solid electrolyte membrane and the base material, which inhibits nickel deposition, generates voids (undeposited portions), and is considered to be a mottled film.

  In the case of Comparative Example 3, nickel chloride was not dissolved in the solvent, and deposition of a nickel film was not confirmed. This is presumably because the polarity of the molecules decreased as the amount of carbon in the molecules constituting the solvent increased, and nickel became insoluble in the ionic state.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed.

  In the present embodiment, the anode made of a porous body is used as the anode. However, as long as nickel ions can be suitably supplied to the solid electrolyte membrane, the porous body need not be used for the anode. A nickel solution may be supplied between the anode and the solid electrolyte membrane.

DESCRIPTION OF SYMBOLS 1A: Film-forming apparatus, 11: Anode, 13: Solid electrolyte membrane, 14: Power supply part, 15: Housing (metal ion supply part), 15a: Supply flow path, 15b: Discharge flow path, 16: Pressurization means, 17 Solution tank, 17a: supply pipe, 18: waste liquid tank, 18a: waste liquid pipe, 19: contact pressure unit, 21: base, B: substrate (cathode), E: film formation region, L: nickel solution

Claims (1)

A solid electrolyte membrane is disposed between an anode and a base material serving as a cathode, the solid electrolyte membrane is brought into contact with the base material, and a voltage is applied between the anode and the base material, and the solid electrolyte membrane is provided. When the metal film made of the metal is deposited on the surface of the base material by precipitating the metal from the metal ions contained in the base material, the metal ion is applied to the solid electrolyte membrane. A method for forming a metal film using a metal film for film formation to supply ,
The method for forming the metal film is as follows:
Using the anode made of a porous material as the anode, flowing the film-forming metal solution through the anode, and bringing the film-forming metal solution flowing through the anode into contact with the solid electrolyte film, Or film
A gap is provided between the anode and the solid electrolyte membrane, and the film-forming metal solution flowing in the gap is brought into contact with the solid electrolyte film while the film-forming metal solution is allowed to flow through the gap. , To form the metal film,
The film forming metal solution includes a solvent and the metal dissolved in an ionic state in the solvent,
The metal is nickel;
The solvent is an alcohol solvent composed of at least one selected from methanol, ethanol, and propanol, or a solvent obtained by adding water to the alcohol solvent,
The hydrogen ion concentration of the film-forming metal solution, method of forming the metal coating, characterized in range near Rukoto of 0~10 ^-7.85 mol / L at 25 ° C..

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