JP2019127604A - Film deposition apparatus for metallic film - Google Patents

Abstract

To provide a film deposition apparatus capable of easily avoiding formation of a metallic film with reduced gloss.SOLUTION: The film deposition apparatus for forming the metallic film on a surface of a substrate by reducing metal ions derived from an anode on a substrate according to one aspect of the embodiment comprises at least: a solution chamber that is placed between the anode and a solid electrolyte membrane and stores a metal solution; pressing means for relatively pressing the anode and the substrate to bring the substrate and the solid electrolyte membrane into contact with each other; and a power supply unit that applies voltage between the anode and the substrate. The film deposition apparatus has a voltage measurement unit for measuring an immersion potential Vbetween the anode and the substrate when the substrate and the solid electrolyte membrane are brought into contact with each other, and a maximum electrolytic reaction potential Vbetween the anode and the substrate when a constant current is applied, and a control unit that determines whether the potential difference (V-V) between the maximum electrolytic reaction potential Vand the immersion potential Vis equal to or greater than a predetermined set value.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a film forming apparatus for a metal film.

  For example, when an electronic circuit board or the like is manufactured, a metal film is formed on the surface of the substrate in order to form a metal circuit pattern. As a film forming technology of such a metal film, for example, Patent Document 1 discloses a technology of forming a metal film on a surface of a semiconductor substrate such as Si by a plating process such as an electroless plating process. In addition, a technique for forming a metal film by a PVD method such as sputtering is also known.

  In the case of plating treatment such as electroless plating treatment, washing with water after the plating treatment is necessary, and it is also necessary to treat the waste liquid after washing with water. In addition, when a film is formed on the substrate surface by the PVD method, internal stress is generated in the formed metal film, so that there is a limit to increasing the thickness of the metal film. In particular, in the case of sputtering, there is a limitation that a film can be formed only under a high vacuum.

  In view of such a point, for example, Patent Document 2 discloses an anode, a cathode, a solid electrolyte disposed between the anode and the cathode, and a power supply unit that applies a voltage between the anode and the cathode. An apparatus for forming a metal film is disclosed. In the apparatus described in Patent Document 2, the anode is made of a metal material constituting a metal film, and a part of the anode is ionized by applying a voltage to the anode and the cathode. In the device described in Patent Document 2, metal ions generated by ionization of the anode pass through the solid electrolyte and are deposited on the substrate disposed on the cathode side, and a metal film is formed on the substrate surface.

Unexamined-Japanese-Patent No. 2010-037622 Japanese Patent Application Laid-Open No. 05-148681

  Here, when a voltage is applied between the anode and the substrate to continue the film forming process of the metal film, the anode is gradually oxidized to form an oxide film on the surface of the anode. When the oxide film is formed on the anode surface, the anode is not sufficiently dissolved, and the metal ion concentration in the metal solution is lowered. As a result, the gloss of the formed metal film is reduced. When the gloss of the metal film decreases, problems such as a decrease in product value and a change in mechanical properties occur.

  Therefore, in order to prevent the formation of the metal film with reduced gloss, it is conceivable to always grasp the state of the anode, that is, the formation state of the oxide film of the anode during the film forming process or the like. As a method of grasping the state of the anode, for example, a method of directly visualizing the anode can be considered, but since the anode is generally accommodated in the housing, the state of the anode can not be confirmed from the outside. In order to confirm the state of the anode, it is necessary to disassemble the film forming apparatus to make the anode visible and to take out the anode for analysis, which requires labor and cost. Therefore, it is desirable to develop a means capable of easily confirming the thickness of the oxide film at the anode without disassembling the film forming apparatus, and avoiding the formation of a metal film with reduced gloss.

  An object of the present disclosure has been made in view of the above problems, and is to provide a film forming apparatus capable of easily avoiding the formation of a metal film having a reduced gloss.

  One form of this embodiment is as follows.

(1) an anode, a solid electrolyte membrane disposed between the anode and the base material serving as the cathode, a solution chamber disposed between the anode and the solid electrolyte membrane, and containing a metal solution; At least a pressing means for relatively pressing an anode and the base material to bring the base material and the solid electrolyte membrane into contact with each other, and a power supply unit for applying a voltage between the anode and the base material, A film forming apparatus for forming a metal film on the surface of the base material by reducing metal ions derived from the anode on the substrate,
Maximum electrolytic reaction voltage V between the immersion potential V _1, and the anode upon conducting the constant current the substrate between the anode and the substrate when said substrate and said solid electrolyte membrane is in contact A voltage measuring unit that measures ₂ ;
A control unit that determines whether or not a potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ and the immersion potential V ₁ is a predetermined set value or more;
A film forming apparatus comprising:
(2) The film forming apparatus according to (1), wherein the control unit stops energization when the potential difference (V ₂ −V ₁ ) is equal to or greater than a predetermined set value.
(3) The film deposition apparatus according to (1) or (2), wherein the set value is 1.4V.
(4) The film forming apparatus according to any one of (1) to (3), wherein the constant current is energized to form the metal film.
(5) Using an anode, a base material serving as a cathode, a solid electrolyte membrane disposed between the anode and the base material, and a metal solution disposed between the anode and the solid electrolyte membrane, A metal film manufacturing method for forming a metal film on the surface of the base material by reducing metal ions derived from the anode on the substrate,
Relatively pressing the anode and the substrate to bring the solid electrolyte membrane into contact with the substrate;
Measuring the immersion potential V ₁ between the anode and the substrate when the substrate and the solid electrolyte membrane are in contact;
Passing a constant current between the anode and the substrate;
Measuring a maximum electrolytic reaction voltage V ₂ between the anode and the substrate when energized said constant current,
Determining whether a potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ and the immersion potential V ₁ is equal to or greater than a predetermined set value;
Manufacturing method.
(6) The manufacturing method according to (5), wherein energization is stopped when the potential difference (V ₂ −V ₁ ) is equal to or greater than a predetermined set value.
(7) The manufacturing method according to (5) or (6), wherein the set value is 1.4V.
(8) The manufacturing method according to any one of (5) to (7), wherein the constant current is energized to form a metal film.

  According to the present disclosure, it is possible to provide a film forming apparatus that can easily avoid the formation of a metal film having a reduced gloss.

1 is a schematic diagram illustrating a configuration example of a metal film deposition apparatus according to an embodiment. FIG. 2 is a schematic diagram for explaining a film forming method using the metal film forming apparatus shown in FIG. 1. It is a graph showing the relationship between the thickness and the potential difference of the oxide film of the anode obtained in Example (V 2 _{-V 1).} 4 is a time-voltage curve (vertical axis: voltage, horizontal axis: time) when a nickel film is formed using the anode 3 (thickness of oxide film: 0.06 μm). 4 is a time-voltage curve (vertical axis: voltage, horizontal axis: time) when a nickel film is formed using the anode 6 (thickness of oxide film: 0.18 μm). 6 is a time-voltage curve (vertical axis: voltage, horizontal axis: time) when a nickel film is formed using the anode 9 (thickness of oxide film: 3.00 μm).

The present embodiment includes an anode, a solid electrolyte membrane disposed between the anode and the base material serving as the cathode, a solution chamber disposed between the anode and the solid electrolyte membrane, and containing a metal solution, A pressing means for pressing the anode and the base material relatively to bring the base material and the solid electrolyte membrane into contact with each other, and a power supply unit for applying a voltage between the anode and the base material. A film forming apparatus for forming a metal film on the surface of the substrate by reducing metal ions derived from the anode on the substrate, wherein the substrate and the solid electrolyte film are in contact with each other. the immersion potential V ₁ of the between the anode and the substrate, and a voltage measuring unit for measuring the maximum electrolytic reaction voltage V ₂ between the anode and the substrate when energized with a constant current, said maximum electrolyte the potential difference between the reaction potential _{V 2} and the immersion potential _{V 1 (V} 2 _{-V 1)} And a control unit for determining whether equal to or higher than a predetermined value, a film formation apparatus.

  According to the present embodiment, it is possible to provide a film forming apparatus that can easily avoid the formation of a metal film having a reduced gloss.

  FIG. 1 is a schematic cross-sectional view showing a configuration example of a metal film deposition apparatus 1 according to the present embodiment. As shown in FIG. 1, a film forming apparatus 1 according to the present embodiment is an apparatus for forming a metal film by solid phase electrodeposition, and depositing metal by reducing metal ions derived from a metal solution. A metal film is formed on the surface of the substrate B by

The film forming apparatus 1 includes an anode 11, a solid electrolyte film 13 disposed between the anode 11 and the base material B (cathode), and a power supply unit 16 for applying a voltage between the anode 11 and the base material B It is equipped with. The film forming apparatus 1 further includes a solution chamber 15 for containing the metal solution L. The solution chamber 15 has the solid electrolyte film 13 and the anode such that the metal solution L is in contact with the anode 11 and the solid electrolyte film 13. 11. The solution chamber 15 is formed by the housing 12. Specifically, the housing 12 has a storage space S for storing the metal solution L, and has an opening 12 a on the base material side of the storage space S. The solid electrolyte membrane 13 is attached to the housing 12 so as to seal the opening 12 a of the housing 12. In addition, the film forming apparatus 1 includes a mounting table 40 on which the base material B is mounted. The mounting table 40 is made of, for example, metal. A negative electrode of the power supply unit 16 is connected to the mounting table 40, and a positive electrode of the power supply unit 16 is connected to the anode 11. In addition, the mounting table 40 and the surface (a metal thin film (not shown)) on which the film formation of the base material B is conducted are conducted. Thereby, the surface of the base material B can be functioned as a cathode. Further, the film forming apparatus 1 is further provided with a pressing means 18 on the upper portion of the housing 12 via a buffer member 19 such as a spring. Examples of the pressing means 18 include a hydraulic or pneumatic cylinder. Thereby, the metal film can be formed while pressing the solid electrolyte film 13 against the surface of the base material B. In addition, the solid electrolyte film 13 can be gently pressed against the surface of the base material B by the buffer member 19. The film forming apparatus 1 further includes a voltage measurement unit 50 capable of measuring the potential between the anode 11 and the base material B. Examples of the voltage measuring unit 50 include a voltmeter. The immersion potential V ₁ between the anode 11 and the substrate B when the substrate B and the solid electrolyte film 13 are in contact with each other by the voltage measurement unit 50, and the anode 11 and the substrate B when a constant current is applied. And the maximum electrolytic reaction potential V ₂ between them can be measured. The film forming apparatus 1 further includes a control unit 51. The control unit 51 has a potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ measured by the voltage measurement unit 50 and the immersion potential V ₁ . It is determined whether it is equal to or more than a predetermined set value. In addition, the control unit 51 is connected to the power supply unit 16 via a signal line, and can stop energization when the potential difference (V ₂ −V ₁ ) is equal to or more than a predetermined set value.

  The substrate B is not particularly limited as long as the surface on which the film is formed functions as a cathode (that is, a surface having conductivity). For example, the base material B may be made of a metal material such as aluminum or iron. Further, the base material B may be one in which a metal layer such as copper, nickel, silver or iron is coated on the surface of a polymer resin such as an epoxy resin or ceramics. In FIG. 1, the base material B is a base material in which a resist R is partially formed on the surface of a resin base material, and a metal thin film (not shown) is formed on the surface exposed from the resist R It is done. Therefore, the metal thin film of the base material B functions as a cathode.

  The anode 11 is a soluble anode that contains the same metal as the metal film to be formed and dissolves in the metal solution L. Dissolution of the anode can provide metal ions in the metal solution. The shape of the anode 11 is, for example, block or flat.

  The solid electrolyte film 13 can contain metal ions by being brought into contact with the metal solution L, and when a voltage is applied, the metal ions are reduced to the surface of the base material B, and metal derived from the metal ions is obtained. There is no particular limitation as long as it can be deposited. Examples of the material of the solid electrolyte membrane include ions such as fluorine resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon resins, polyamic acid resins, and selemions (CMV, CMD, CMF series) manufactured by Asahi Glass. A resin having an exchange function can be mentioned.

  The metal solution L is a liquid (electrolytic solution) containing the metal of the metal film to be formed as described above in an ionic state. Examples of such metals include copper, nickel, silver, and iron. The metal solution L is dissolved in an acid such as nitric acid, phosphoric acid, succinic acid, nickel sulfate, or pyrophosphoric acid ( (Ionized) aqueous solution. As the metal solution L, a Watt bath, a wood bath, a sulfamic acid bath, or the like may be used.

  The pH of the metal solution L is preferably 2.0 to 5.0, more preferably 2.5 to 4.5. By setting the pH to such a value, the deposition current efficiency of the metal film can be improved, and the metal film can be easily formed at high speed. In addition, the film-forming speed | rate of a metal film can be adjusted with conditions, such as a metal ion in a metal solution, an electric current value, anode material, an anode area, temperature, etc. besides pH, for example. The metal solution L may contain, for example, a solvent and a pH buffer.

  Examples of the material of the housing 12 include a metal material, but the material is not particularly limited.

The voltage measuring unit 50 is arranged so that the potential between the anode 11 and the base material B can be measured. The voltage measuring unit 50, between the substrate B and the immersion potential V ₁ of the between the anode 11 and the substrate B when solid electrolyte film 13 is in contact, the anode 11 and the substrate B when energized with a constant current The maximum electrolytic reaction potential V ₂ of The voltage measurement unit 50 can monitor the voltage value during film formation.

The control unit 51 determines whether or not the potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ measured by the voltage measurement unit 50 and the immersion potential V ₁ is equal to or greater than a predetermined set value. The control unit 51 is connected to the power supply unit 16 through a signal line, and can stop energization when the potential difference (V ₂ −V ₁ ) is equal to or greater than a predetermined set value. The control unit 51 is configured by, for example, a microcomputer including a ROM, a RAM, a CPU, and the like.

As will be described in detail below, the potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ and the immersion potential V ₁ has a correlation with the thickness of the oxide film formed on the anode, and As the thickness of the oxide film increases, the potential difference (V ₂ −V ₁ ) also increases. Therefore, the thickness of the oxide film on the anode can be indirectly grasped by measuring the potential difference (V ₂ −V ₁ ). Therefore, the threshold value of the thickness of the oxide film on which the metal film with reduced gloss is not formed is confirmed separately, and the potential difference (V ₂ −V ₁ ) corresponding to the threshold value of the oxide film thickness is set as the predetermined value. Keep it. Thereby, when the potential difference (V ₂ -V ₁ ) becomes equal to or greater than the set predetermined value, that is, when the oxide film thickness exceeds the threshold, the control unit 51 can stop the energization, so that the gloss is improved. It can prevent the formation of a reduced metal film.

  Below, the film-forming method using the film-forming apparatus 1 which concerns on this embodiment is demonstrated. FIG. 2 is a schematic cross-sectional view for explaining a state during film formation of the film forming apparatus 1 shown in FIG.

  First, as shown in FIG. 1, a base material B on which a resist R and a metal thin film (not shown) are formed is placed on a mounting table 40 so as to face the solid electrolyte membrane 13. Next, as shown in FIG. 2, the housing 12 is lowered toward the mounting table 40 using the pressing means 18, and the solid electrolyte film 13 is pressed against the surface of the base material B.

Here, the voltage measuring unit 50 measures the immersion potential V ₁ between the anode 11 and the base material B when the base material B and the solid electrolyte membrane 13 are in contact with each other. The immersion potential is also referred to as the natural potential. The measured immersion potential V ₁ can be sent to the control unit 51 and recorded.

  Next, in a state where the solid electrolyte membrane 13 is pressed against the surface of the base material B, a voltage is applied between the anode 11 and the base material B by the power supply unit 16. The metal solution L in the solution chamber 15 is in contact with the anode 11 and the solid electrolyte film 13, and the metal ions supplied to the solid electrolyte film 13 move to the exposed surface of the substrate B in contact with the solid electrolyte film 13. Do. The moved metal ions are reduced on the surface of the base material B exposed from the resist R, and the metal derived from the metal ions is deposited on the exposed surface of the base material B. Thereby, a metal film can be formed on the substrate B. Metal ions in the metal solution are replenished by dissolving a part of the anode.

Energization for forming the metal coating is performed by a constant current, the voltage measuring unit 50 measures the maximum electrolytic reaction voltage V ₂ between the anode 11 and the substrate B when energized a constant current. The measured corrosion potential maximum electrolytic reaction voltage V ₂ is sent to the control unit 51 may be recorded. Then, the control unit 51, the potential difference between the maximum electrolytic reaction voltage _{V 2} and the immersion potential _{V 1 (V} 2 -V ₁₎ judging whether equal to or higher than a predetermined value, the potential difference _(V 2 -V ₁ ) Is greater than or equal to a predetermined set value, energization by the power supply unit 16 is stopped. When the potential difference (V ₂ −V ₁ ) is less than the predetermined set value, the current is applied as it is to form a metal film.

The above measurement can be repeated for each substrate. Since the oxide film of the anode becomes thicker as the metal film deposition process is repeated, the set value of the potential difference (V _{2 −} V ₁ ) is set so that the current is automatically stopped when a certain threshold is exceeded. You can choose. The anode can be replaced with a new one if the current ceases.

  In this way, according to the film forming apparatus according to the present embodiment, it is possible to easily avoid the formation of a metal film having a reduced gloss.

  A nickel plate (NI-313520, manufactured by Niraco) was prepared as an anode. This nickel plate was heat-treated with an electric furnace to form an oxide film. The nickel plate was heated at a predetermined temperature (25 ° C., 100 ° C., 200 ° C., 300 ° C., 400 ° C., 500 ° C., 600 ° C., 700 ° C. and 800 ° C.) for 1 hour under an air atmosphere. The thickness of the oxide film was measured by Auger electron spectroscopy. In Table 1, the produced anodes 1 to 9 are shown.

Next, using the anodes 1 to 9, a nickel film was formed on the substrate under the following film forming conditions.
Nickel film thickness: 4 μm
Substrate: Copper sputtered substrate Current density: 100 mA / cm ²
Nickel chloride bath: 1M nickel chloride aqueous solution + acetic acid (pH 4.0)
Temperature: 80 ° C
Pressure: 1.0 MPa
Deposition area: 10mm x 10mm
Electrolyte membrane: ion exchange membrane (N117, manufactured by DuPont)

  The film formation region was produced by forming an opening of 10 × 10 mm square on a substrate using a polyimide tape (650R # 25, Teraoka Seisakusho Co., Ltd.).

In this example, a nickel film was formed on a copper sputter substrate using nickel anodes (anodes 1 to 9) having different oxide film thicknesses using a film forming apparatus as shown in FIG. In the nickel film formation step, the voltage value during film formation is monitored by a voltmeter, and the immersion potential V ₁ between the anode and the substrate when the substrate and the solid electrolyte membrane are in contact with each other. the maximum electrolytic reaction voltage V ₂ between the anode and the substrate when energized current was measured. Table 2 shows the thickness and potential difference (V ₂ −V ₁ ) of the oxide film of the anode, and FIG. 3 shows a graph of the results.

As apparent from FIG. 3, as the thickness of the anode oxide film increases, the potential difference (V ₂ −V ₁ ) also increases. Therefore, the thickness of the anode oxide film and the potential difference (V ₂ −V ₁ ) Is understood to have a correlation. Therefore, the correlation between the thickness of the oxide film of the anode and the potential difference (V ₂ −V ₁ ) and the threshold value of the thickness of the oxide film at which the metal film with reduced gloss is not formed are confirmed in advance to reduce the gloss. The potential difference (V ₂ −V ₁ ) corresponding to the threshold value of the thickness of the oxide film where the metal film is not formed is set as the predetermined value. Thereby, when the potential difference (V ₂ -V ₁ ) becomes equal to or greater than the set predetermined value, that is, when the oxide film thickness exceeds the threshold, the control unit 51 can stop the energization, so that the gloss is improved. It can prevent the formation of a reduced metal film.

As a representative example of the monitoring result of the voltage value at the time of film formation, anode 3 (thickness of oxide film: 0.06 μm), anode 6 (thickness of oxide film: 0.18 μm), and anode 9 (thickness of oxide film: 3.00) The time-voltage curves obtained in the case of depositing a nickel film using μm) are shown in FIGS. As shown in these figures, in the time-voltage curve at the time of film formation in the constant current method, a constant electric potential (flat potential) appears in the first step about 10 seconds after the electrolyte membrane contacts the substrate. . Potential when the potential became constant is immersion potential V _1. When a constant current is applied with a voltage applied, the voltage rapidly increases and then slowly decreases and approaches a constant value, and a flat voltage at the second stage appears. In the present embodiment, to measure the maximum electrolytic reaction potential V ₂ when a current of a constant current. Maximum electrolytic reaction voltage V ₂ is generally as shown in Figure 4-6, it appears immediately after the load voltage.

Hereinafter, the reason why the potential difference (V ₂ −V ₁ ) increases when the anode having a thick oxide film is used will be considered. In general, the potential difference (V ₂ −V ₁ ) is an activation overvoltage (charge is transferred during discharge / deposition of ions at the cathode and dissolution / ion generation at the anode. Corresponds to the activation energy in the charge transfer process. The electrolysis potential deviates from the equilibrium potential.This deviation is called the activation overvoltage.) Diffusion overvoltage (metal ions near the cathode decrease during electrolysis. Also, in the vicinity of the anode, the concentration of metal ions increases due to dissolution supply. Is higher than the concentration off the nickel bath.The deviation from the equilibrium potential due to the concentration gradient and ion diffusion is called diffusion overvoltage.) And resistance overvoltage (voltage change due to the resistance of the film formed on the electrode surface is resistance overvoltage) It is composed of the sum of In general, in metal plating, metal ions are reduced and metal is deposited at the cathode, and metals are oxidized and metal ions are formed at the anode. Therefore, since the activation energy at which metal ions are generated from the metal oxide on the surface of the anode is higher than the activation energy at which metal ions are generated from the metal when the anode is oxidized, the electrolytic potential is It is considered that the shift, the activation overpotential is increased, and the potential difference (V ₂ −V ₁ ) is increased.

  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 is possible to make changes.

1: Film forming apparatus 11: Anode 12: Housing 12a: Opening 13: Solid electrolyte film 15: Solution chamber 16: Power supply unit 18: Pressing means 19: Buffer member 40: Mounting table 50: Voltage measurement unit 51: Control unit B : Substrate L: Metal solution R: Resist S: Accommodation space

Claims (1)

An anode, a solid electrolyte membrane disposed between the substrate serving as the anode and the cathode, a solution chamber disposed between the anode and the solid electrolyte membrane, containing a metal solution, the anode and the A pressure means that presses the base material relatively to bring the base material and the solid electrolyte membrane into contact with each other; and a power source that applies a voltage between the anode and the base material. A film forming apparatus for forming a metal film on the surface of the substrate by reducing metal ions derived from the substrate on the substrate,
Maximum electrolytic reaction voltage V between the immersion potential V _1, and the anode upon conducting the constant current the substrate between the anode and the substrate when said substrate and said solid electrolyte membrane is in contact A voltage measuring unit that measures ₂ ;
A control unit that determines whether or not a potential difference (V ₂ −V ₁ ) between the maximum electrolytic reaction potential V ₂ and the immersion potential V ₁ is a predetermined set value or more;
A film forming apparatus comprising: