JP2024085643A - Metal film deposition equipment - Google Patents

Abstract

The present invention provides a metal film forming apparatus capable of forming a uniform metal film and of reducing the size of the apparatus.
[Solution] The film forming apparatus of the present invention comprises an anode made of an insoluble porous body, an electrolyte membrane disposed between a substrate which serves as the anode and the cathode, and a housing having a storage chamber for storing a plating solution containing metal ions between the anode and the electrolyte membrane, and applies a voltage while pressing the substrate with the electrolyte membrane to reduce the metal ions impregnated in the electrolyte membrane and form a metal coating on the substrate. The apparatus further comprises a diaphragm which covers the cathode side of the anode and is attached so as to be in contact with the cathode side of the anode, the diaphragm being permeable to water and hydrogen ions but not to oxygen gas, and the anode is attached so as to block the opening on the side of the housing opposite the cathode side, with the cathode side exposed to the storage chamber via the diaphragm and the side opposite the cathode side exposed to the outside of the housing.
[Selected Figure] Figure 1

Description

The present invention relates to a metal film deposition device, and in particular to a metal film deposition device capable of depositing a metal film on the surface of a substrate.

Conventionally, a film-forming technique has been known in which a metal coating is formed on the surface of a substrate by reducing metal ions contained in a plating solution to precipitate metal derived from the metal ions. In recent years, in such film-forming techniques, a film-forming device has been used that includes an anode, an electrolyte membrane arranged between the substrate serving as the anode and cathode, a power supply device that applies a voltage between the anode and the substrate (cathode), a housing having a storage chamber for storing a plating solution containing metal ions between the anode and the electrolyte membrane, and a pressure device that pressurizes the plating solution. The plating solution applies a voltage between the anode and the substrate while pressing the substrate surface with the electrolyte membrane by the hydraulic pressure of the plating solution, thereby reducing the metal ions contained in the electrolyte membrane to form a metal coating on the substrate surface.

Among such film forming devices, a metal film forming device using an insoluble anode as the anode has attracted attention. However, in a film forming device using an insoluble anode, the water in the plating solution is electrolyzed on the surface of the anode in the storage chamber, generating oxygen gas. As the film formation time passes, the amount of oxygen gas generated increases, causing the oxygen gas to condense and accumulate on the surface of the anode. When the electrolyte membrane presses against the surface of the substrate using the hydraulic pressure of the plating solution during the formation of the metal film as described above, if oxygen gas remains in the storage chamber, it may become difficult to uniformly press the electrolyte membrane against the surface of the substrate because oxygen gas is more compressible than the plating solution. As a result, there is a risk that the metal film cannot be formed uniformly.

In order to address such problems, for example, a film forming apparatus described in Patent Document 1 has been proposed. In the film forming apparatus described in Patent Document 1, a partition member that divides the housing into a first storage chamber on the anode side in which a first electrolytic solution is stored and a second storage chamber on the electrolyte membrane side in which a second electrolytic solution (plating solution) containing metal ions is stored is disposed between the anode and the electrolyte membrane. The partition member is a diaphragm in which a porous body is impregnated with a cation exchange resin. The first storage chamber contains an anode that is insoluble in the first electrolytic solution. The second storage chamber forms an enclosed space in the housing in which the second electrolytic solution is sealed by the electrolyte membrane and the partition member. Therefore, even if the water contained in the first electrolytic solution is electrolyzed on the surface of the anode in the first storage chamber during film formation and oxygen gas is generated, the oxygen gas from the anode does not mix with the second electrolytic solution (plating solution) in the second storage chamber, so the second electrolytic solution can be pressurized without leaving oxygen gas in the second storage chamber. This allows the electrolyte membrane acting on the liquid pressure of the second electrolyte solution to press evenly against the surface of the substrate, allowing the metal coating to be formed evenly.

JP 2020-152987 A

However, for example, in a structure such as the film formation apparatus described in Patent Document 1, it is necessary to provide another storage chamber that contains an insoluble anode and is separated from the first storage chamber by a diaphragm, in addition to the first storage chamber that contains the plating solution. This limits the size of the apparatus and makes it difficult to use in a structure in which the distance between the anode and the substrate is a short distance of about a few mm. Furthermore, when the plating solution is pressurized, if the pressure difference between the first storage chamber that contains the plating solution and the other storage chamber that contains the insoluble anode becomes large, the diaphragm may deform or break, and may not function as a diaphragm.

The present invention was made in consideration of these points, and its purpose is to provide a metal film deposition device that can deposit a metal film uniformly and can be made compact.

In order to solve the above problem, the metal coating deposition device of the present invention comprises an anode, an electrolyte membrane disposed between a substrate serving as the anode and the cathode, a housing having a chamber for accommodating a plating solution containing metal ions between the anode and the electrolyte membrane, a power supply device for applying a voltage between the anode and the substrate, and a pressure device for pressurizing the plating solution accommodated in the chamber, the electrolyte membrane being attached so as to cover an opening on the cathode side of the housing that is connected to the chamber, and applying the voltage while pressing the surface of the substrate with the electrolyte membrane, thereby reducing the metal ions impregnated in the electrolyte membrane. , a film-forming apparatus for forming a metal film on the surface of the substrate, the film-forming apparatus further comprising a diaphragm attached so as to cover the cathode side surface of the anode and contact the cathode side surface of the anode, the diaphragm being a membrane that is permeable to water and hydrogen ions but not to oxygen gas, the anode is attached so as to block an opening on the side opposite the cathode side of the housing that is connected to the housing chamber, so that the cathode side surface is exposed to the housing chamber through the diaphragm and the surface opposite the cathode side is exposed to the outside of the housing, and the anode is made of a porous body that is insoluble in the plating solution.

The present invention makes it possible to deposit a uniform metal film and to miniaturize the device.

1 is a schematic cross-sectional view showing a metal film forming apparatus according to one embodiment. 1 is a schematic cross-sectional view for explaining a method for forming a metal film using a metal film forming apparatus according to one embodiment. 1 is a schematic cross-sectional view for explaining the principle of the action and effect of a metal film forming apparatus according to one embodiment, showing a structure between an anode and a plating solution. 1 is a schematic cross-sectional view showing a test system 1 of a metal film forming apparatus. 2 is a schematic cross-sectional view showing a test system 2 of a metal film forming apparatus. FIG. 1 is a graph showing the change in voltage over time at a constant current (10 mA) during deposition of metal films in Reference Examples 1 and 2 and a Comparative Example.

Hereinafter, an embodiment of the metal film forming apparatus of the present invention will be described.
1 is a schematic cross-sectional view showing a metal film forming apparatus according to one embodiment. Hereinafter, the metal film forming apparatus according to one embodiment will be described with reference to FIG.

As shown in FIG. 1, a metal film forming apparatus 1 according to one embodiment includes an anode 11, an electrolyte membrane 13 disposed between the anode 11 and a substrate B serving as a cathode, and a housing 15 having a storage chamber 17. The storage chamber 17 stores a plating solution L containing metal ions between the anode 11 and the electrolyte membrane 13. The film forming apparatus 1 includes a power supply device 16 that applies a voltage between the anode 11 and the substrate B (cathode). The film forming apparatus 1 further includes a plating solution supply pump 21 as a pressure device that pressurizes the plating solution L stored in the storage chamber 17. In the film forming apparatus 1, the direction in which the anode 11 and the substrate B face each other is parallel to the vertical direction. Hereinafter, the vertical direction is referred to as the downward direction, and the opposite direction is referred to as the upward direction.

The substrate B has a conductor B1, which serves as a cathode, partially provided on the surface of an insulating portion B2. The conductor B1 is made of, for example, copper, nickel, silver, iron, etc. The insulating portion B2 is made of, for example, a polymer resin such as epoxy resin, ceramics, etc.

The electrolyte membrane 13 covers the cathode-side opening 15hc of the housing 15 that communicates with the housing chamber 17. The electrolyte membrane 13 is attached to the housing 15 via a seal 19 such as an O-ring. The film forming device 1 pressurizes the plating solution L by the discharge pressure of the plating solution supply pump 21. As a result, the electrolyte membrane 13 is pressed against the cathode side by the liquid pressure of the plating solution L, and the electrolyte membrane 13 can press against the surface of the substrate B. While pressing the surface of the substrate B with the electrolyte membrane 13 in this way, the film forming device 1 applies a voltage between the anode 11 and the substrate B by the power supply device 16. As a result, the metal ions impregnated in the electrolyte membrane 13 are reduced, and the metal derived from the metal ions is precipitated, forming a metal coating containing the metal on the surface of the substrate B (the surface of the conductor portion B1).

The film forming apparatus 1 further includes a diaphragm 18 attached to the housing 15 via a seal material 20 such as an O-ring so as to cover the cathode side surface 11c of the anode 11 and to be in contact with the cathode side surface 11c of the anode 11. The diaphragm 18 is a cation exchange membrane that is permeable to water (H ₂ O) and hydrogen ions (H ⁺ ) but not to oxygen gas (O ₂ ).

The anode 11 is attached to the housing 15 so as to close the opening 15ha on the side opposite the cathode side of the housing 15 that is connected to the storage chamber 17. The cathode side surface 11c of the anode 11 is exposed to the storage chamber 17 via the diaphragm 18, and the surface 11a opposite the cathode side is exposed to the outside of the housing 15. The anode 11 is made of a flat mesh member (porous body) that is insoluble in the plating solution L. The mesh member is permeable to oxygen gas.

The storage chamber 17 contains plating solution L so that the plating solution L comes into contact with the diaphragm 18 and the electrolyte membrane 13. The storage chamber 17 is sealed by the storage housing 15, the diaphragm 18, and the electrolyte membrane 13 so that the plating solution L can be stably pressurized when forming the metal film. The material of the storage housing 15 is not particularly limited as long as it is corrosion-resistant to the plating solution L, but examples include metal materials such as stainless steel.

The plating solution L is an acidic aqueous solution containing metal ions, and is a conductive electrolyte. When a voltage is applied between the anode 11 and the substrate B (cathode), an electric field for film formation is formed in the plating solution L from the anode 11 toward the substrate B. That is, electric field lines start from the cathode side surface 11c of the anode 11, move toward the substrate B, and reach the surface of the substrate B (the surface of the conductor portion B1).

The film forming apparatus 1 further includes a pressure reducing device 30. The pressure reducing device 30 includes a pressure reducing housing 31. The pressure reducing housing 31 covers the opening 15ha on the side opposite to the cathode side of the housing 15 from the outside of the housing 15, and forms a pressure reducing chamber 33 outside the housing 15. The pressure reducing device 30 further includes an exhaust pipe 35 provided on the upper part of the pressure reducing housing 31, and a vacuum pump 37 (pressure reducing pump) provided in the exhaust pipe 35. The pressure reducing chamber 33 is sealed by the pressure reducing housing 31, the housing 15, and the diaphragm 18 so that the pressure can be reduced stably during the formation of the metal film. The flow path of the exhaust pipe 35 is connected to the pressure reducing chamber 33. The vacuum pump 37 can reduce the pressure of the pressure reducing chamber 33 by exhausting through the flow path of the exhaust pipe 35.

The film forming apparatus 1 further includes a metal mounting table 40 on which the substrate B is placed. The mounting table 40 is connected to the negative pole of the power supply unit 16, and the anode 11 is connected to the positive pole of the power supply unit 16. The mounting table 40 and the conductor portion B1 of the substrate B on which the film is formed are electrically connected. This allows the conductor portion B1 of the substrate B to function as a cathode.

The film forming apparatus 1 further includes a supply source 22 that supplies plating solution L and is provided upstream of the plating solution supply pump 21, a supply pipe 23 that connects the supply source 22 and the plating solution supply pump 21, and a communication pipe 24 that connects the plating solution supply pump 21 and the storage chamber 17. The film forming apparatus 1 further includes a drain pipe 26 that is connected to the storage chamber 17 and drains the plating solution L from the storage chamber 17, and a pressure adjustment valve 27 provided in the drain pipe 26.

In the film forming apparatus 1, the liquid pressure in the storage chamber 17 can be adjusted by the pressure regulating valve 27. Note that in the film forming apparatus 1, an on-off valve may be provided instead of the pressure regulating valve 27. Then, the liquid pressure of the plating solution L in the storage chamber 17 may be controlled by adjusting the discharge pressure of the plating solution supply pump 21 with the on-off valve closed. The drain pipe 26 may be connected to the supply source 22. In this case, the plating solution L used in the storage chamber 17 can be returned to the supply source 22 via the drain pipe 26 and reused during film formation.

The film forming apparatus 1 further includes a lifting device 28 that lifts and lowers the electrolyte membrane 13 together with the housing 15 and the anode 11 in the vertical direction in which the anode 11 and the substrate B face each other, thereby positioning the electrolyte membrane 13. The lifting device 28 has a main body 28b and a movable part 28m. The main body 28b is fixed to the upper fixed part 50. The upper side of the movable part 28m is connected to the main body 28b and moves in the vertical direction relative to the main body 28b. The lower end of the movable part 28m is mechanically connected to the housing 15. In the lifting device 28, during film formation, the movable part 28m is moved downward relative to the main body 28b, thereby lowering the electrolyte membrane 13 together with the housing 15 and the anode 11 from the standby position shown in FIG. 1 to the film forming position shown in FIG. 2 described later, and the electrolyte membrane 13 is brought into contact with the surface of the substrate B. Then, by stopping the movable part 28m at the point when the electrolyte membrane 13 comes into contact with the surface of the substrate B, the electrolyte membrane 13 is positioned in the vertical direction and the vertical position of the electrolyte membrane 13 is fixed. In this way, the electrolyte membrane 13 is brought into contact with the surface of the substrate B, and in this state, a metal film is formed on the surface of the substrate B. After the film is formed, the movable part 28m is moved upward relative to the main body part 28b to raise the electrolyte membrane 13 together with the housing 15 and the anode 11 from the film forming position shown in FIG. 2 to the standby position shown in FIG. 1, and the electrolyte membrane 13 is separated from the surface of the substrate B.

Figure 2 is a schematic cross-sectional view for explaining a method for forming a metal film using a metal film forming apparatus according to one embodiment. Hereinafter, a method for forming a metal film using a metal film forming apparatus according to one embodiment (hereinafter, abbreviated as a method for forming a metal film according to one embodiment) will be explained with reference to Figures 1 and 2.

In the method for forming a metal film according to one embodiment, first, as shown in FIG. 1, in the metal film forming apparatus 1 according to one embodiment, the substrate B is placed on the mounting table 40 so that the surface of the substrate B (the surface of the conductor portion B1) faces the electrolyte membrane 13.

2, the lifting device 28 is used to move the movable part 28m downward relative to the main body part 28b, thereby lowering the electrolyte membrane 13 together with the housing 15 and the anode 11, etc., toward the mounting table 40, thereby bringing the electrolyte membrane 13 into contact with the surface of the substrate B (the surface of the conductor part B1). Then, by stopping the movable part 28m at the point when the electrolyte membrane 13 comes into contact with the surface of the substrate B, the electrolyte membrane 13 is positioned in the vertical direction and the vertical position of the electrolyte membrane 13 is fixed. In this way, the electrolyte membrane 13 is brought into contact with the surface of the substrate B.

Next, the plating solution L contained in the storage chamber 17 is pressurized by the discharge pressure of the plating solution supply pump 21. In this case, the pressure of the plating solution L contained in the storage chamber 17 is increased to the pressure set by the pressure adjustment valve 27. The operation of the plating solution supply pump 21 may be stopped at the point when the pressure of the plating solution L contained in the storage chamber 17 is increased to the pressure set by the pressure adjustment valve 27. On the other hand, if the operation of the plating solution supply pump 21 is continued after the point when the pressure of the plating solution L contained in the storage chamber 17 is increased to the pressure set by the pressure adjustment valve 27, the plating solution L continues to be supplied from the supply source 22 to the storage chamber 17, and the pressure of the plating solution L contained in the storage chamber 17 is maintained at the pressure set by the pressure adjustment valve 27. Furthermore, when the plating solution L is pressurized, the pressure reduction chamber 33 is reduced by the pressure reduction device 30.

As described above, when the electrolyte membrane 13 is in contact with the surface of the substrate B, the plating solution L is pressurized, and the electrolyte membrane 13 is pressed toward the cathode side by the liquid pressure of the plating solution L. This allows the electrolyte membrane 13 to press uniformly against the surface of the substrate B. At this time, the metal ions contained in the plating solution L can be impregnated into the electrolyte membrane 13. Furthermore, by pressurizing the plating solution L and pressing the diaphragm 18 toward the anode 11 by the liquid pressure of the plating solution L, and depressurizing the decompression chamber 33 to suck the diaphragm 18 toward the anode 11, the diaphragm 18 can be brought into close contact with the cathode side surface 11c of the anode 11.

Next, the surface of the substrate B is pressed with the electrolyte membrane 13, and the diaphragm 18 is brought into close contact with the cathode side surface 11c of the anode 11. A voltage is then applied between the anode 11 and the substrate B (cathode) by the power supply 16, thereby reducing the metal ions impregnated in the electrolyte membrane 13. This causes the metal derived from the metal ions to precipitate, forming a metal coating F on the surface of the substrate B (the surface of the conductor portion B1).

Figure 3 is a schematic cross-sectional view for explaining the principle of the action and effect of the metal film deposition device according to one embodiment, and shows the structure between the anode and the plating solution. The action and effect of the metal film deposition device 1 according to one embodiment will be explained below.

In the metal coating forming apparatus 1 according to one embodiment, the anode 11 is insoluble in the plating solution L. Therefore, when the metal coating F is formed, water contained in the plating solution L is electrolyzed at the interface between the diaphragm 18 and the anode 11 (the cathode side surface 11c of the anode 11), and oxygen gas is generated by the electrolysis reaction (2H ₂ O→4H ⁺ +O ₂ +4e ⁻ ). If the generated oxygen gas is mixed into the plating solution L and remains in the storage chamber 17, a problem may occur. That is, since oxygen gas is more compressible than the plating solution L, it becomes difficult to uniformly press the surface of the substrate B with the electrolyte membrane 13 by the liquid pressure of the plating solution L by pressurizing the plating solution L. As a result, the metal coating F may not be formed uniformly.

However, in the film forming apparatus 1, the diaphragm 18, which is permeable to water (H ₂ O) and hydrogen ions (H ⁺ ) but not to oxygen gas (O ₂ ), is attached to cover the cathode side surface 11c of the anode 11 and to contact the cathode side surface 11c of the anode 11. The anode 11 is attached to close the opening 15ha on the opposite side to the cathode side of the housing 15 that communicates with the accommodation chamber 17. As a result, the cathode side surface 11c of the anode 11 is exposed to the accommodation chamber 17 through the diaphragm 18, and the surface 11a on the opposite side to the cathode side is exposed to the outside of the housing 15. The anode 11 is made of a mesh-like member that is permeable to oxygen gas. Furthermore, in the film forming apparatus 1, the diaphragm 18 is brought into close contact with the cathode side surface 11c of the anode 11 when the metal film F is formed.

Therefore, in the film forming apparatus 1, during the formation of the metal film F, as shown in FIG. 3, water, which is one of the components of the plating solution L, can permeate the diaphragm 18, and is successively supplied to the cathode side surface 11c of the anode 11. Therefore, oxygen gas is generated by the electrolysis reaction of water on the cathode side surface 11c of the anode 11. However, the oxygen gas cannot permeate the diaphragm 18, and the diaphragm 18 is in close contact with the cathode side surface 11c of the anode 11. Therefore, the oxygen gas passes through the holes of the mesh member of the anode 11 and is discharged to the outside of the housing 15. This makes it possible to prevent the oxygen gas from remaining in the storage chamber 17, and to suppress the oxygen gas from accumulating at the interface between the diaphragm 18 and the anode 11. Therefore, it is possible to uniformly press the surface of the substrate B with the electrolyte membrane 13, and the metal film can be formed uniformly. Furthermore, it is possible to suppress the occurrence of resistance at the interface between the diaphragm 18 and the anode 11. In addition, hydrogen ions generated simultaneously by the electrolysis reaction can permeate the diaphragm 18 and diffuse into the plating solution L. This prevents excess hydrogen ions from forming around the anode 11. This stabilizes the voltage applied between the anode 11 and the substrate B.

The plating solution L may contain additives such as organic additive components in addition to metal ions, but the additives cannot permeate the diaphragm 18 (cation exchange membrane). Therefore, the additives do not come into direct contact with the anode 11, and decomposition of the additives due to oxidation or the like at the anode 11 can be reduced. This makes it possible to extend the life of the plating solution L. Also, electrons (e ⁻ ) generated by the electrolysis reaction pass through the anode 11 and flow to the positive electrode of the power supply device 16.

Furthermore, in the structure of a conventional film-forming device in which an insoluble anode as described in Patent Document 1 is applied, for example, in order to prevent oxygen gas from remaining in the storage chamber in which the plating solution is stored and to uniformly form a metal film, it is necessary to provide another storage chamber in which an insoluble anode is stored, which is separated from the first storage chamber by a diaphragm, in addition to the first storage chamber in which the plating solution is stored. In contrast, in the film-forming device 1 for a metal film according to one embodiment, oxygen gas is prevented from remaining in the storage chamber 17 in which the plating solution L is stored, and the metal film F can be uniformly formed without providing another storage chamber in which the insoluble anode 11 is stored. Therefore, the metal film F can be uniformly formed and the film-forming device 1 can be miniaturized. By miniaturizing the film-forming device 1, it is possible to use the device in a structure in which the distance between the anode 11 and the substrate B is a short distance of about several mm. This makes it possible to uniformly distribute the density of the electric field lines on the surface of the substrate B, so that the metal film F can be formed even more uniformly. In addition, unlike the structure of the conventional film forming apparatus described above, there is no risk of the pressure difference between one storage chamber and another storage chamber becoming too large, causing deformation or damage to the diaphragm 18.

The configuration of the metal film deposition device according to the embodiment will be described in more detail below.

The anode is not particularly limited as long as it is made of a porous body that is insoluble in the plating solution (a porous body that does not dissolve in the plating solution L). The porous body of the anode is not particularly limited as long as it is insoluble and permeable to oxygen gas, and may be, for example, a mesh-like member or a porous member other than a mesh-like member. The porous body of the anode may have a groove on the cathode side surface of the anode through which oxygen gas can flow, and may have holes penetrating from the inside of the groove to the surface of the anode opposite the cathode side.

The material of the porous anode is not particularly limited as long as it makes the anode insoluble, but for example, platinum, iridium oxide, etc. are preferable because they have a low oxygen overvoltage and enable water electrolysis at a low voltage.

The diaphragm is not particularly limited as long as it is a membrane that allows water and hydrogen ions to pass through and does not allow oxygen gas to pass through. In addition to a cation exchange membrane, a neutral diaphragm is also an example of the diaphragm, but a cation exchange membrane is preferred. This is because it has high hydrogen ion permeability. Nanoscale channels exist in the cation exchange membrane. The cation exchange membrane selectively allows water and hydrogen ions to pass through the nanoscale channels. As the cation exchange membrane, one with a high water content is preferred, specifically, for example, Nafion (registered trademark) manufactured by DuPont is preferred. This is because a large amount of water can be supplied to the anode. A neutral diaphragm is a neutral diaphragm that has no ion selectivity. In cases where there is no problem of the additive deteriorating at the anode, such as when the plating solution does not contain additives or when the additive contained in the plating solution does not permeate the neutral diaphragm depending on the molecular weight, etc., a neutral diaphragm may be used as the diaphragm. A preferred neutral diaphragm is, for example, Y-9207TA manufactured by Yuasa Membrane Systems Co., Ltd. The thickness of the diaphragm is, for example, 10 μm to 200 μm. If the plating solution is a strongly alkaline solution containing metal ions, an anion exchange membrane can also be used as the diaphragm.

The substrate is not particularly limited as long as the surface portion on which the metal film is formed functions as a cathode (a surface portion having electrical conductivity). For example, the substrate may be one in which a conductor portion acting as a cathode is partially provided on the surface of an insulating portion as in one embodiment, or the substrate may be entirely made of a metal material such as aluminum or iron.

The electrolyte membrane is not particularly limited as long as it can be impregnated with metal ions contained in the plating solution by contacting it with the plating solution, and can deposit metal derived from the metal ions on the surface of the substrate by applying a voltage between the anode and the substrate. The electrolyte membrane is usually flexible. The thickness of the electrolyte membrane is, for example, 5 μm to 200 μm. Examples of materials for the electrolyte membrane include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins with ion exchange functions such as Selemion (CMV, CMD, CMF, etc.) manufactured by Asahi Glass Co., Ltd.

The plating solution is a solution that contains metal ions. More specifically, it is a solution that contains the metal contained in the metal film in the form of metal ions. There are no particular limitations on the plating solution as long as it is a solution that contains metal ions, and it may contain additives in addition to the metal ions.

Examples of the metal of the metal ion include copper, nickel, silver, iron, etc. Examples of the plating solution include a solution such as an aqueous solution in which at least one of these metals is dissolved in an acid such as sulfuric acid, nitric acid, phosphoric acid, succinic acid, pyrophosphoric acid, etc. Specifically, when the metal of the metal ion is nickel, examples of the plating solution include a solution such as an aqueous solution of nickel sulfate, nickel nitrate, nickel phosphate, nickel succinate, nickel pyrophosphate, etc. The plating solution may be an acidic solution or an alkaline solution.

The pressurizing device is not particularly limited as long as it can pressurize the plating solution contained in the storage chamber. The pressurizing device may be, for example, a plating solution supply pump or a pressurizing device composed of a cylinder and a piston. The pressurizing device can pressurize and depressurize the plating solution in the storage chamber by connecting the cylinder, which contains the plating solution, to the storage housing so that the cylinder communicates with the storage chamber, and moving the piston forward and backward within the cylinder.

The metal coating forming apparatus preferably further includes a device for adhering the diaphragm to the cathode side surface of the anode. This is because by suppressing the accumulation of oxygen gas or the like at the interface between the diaphragm and the anode and the generation of resistance, a stable current can be passed between the anode and the substrate (cathode), thereby realizing uniform formation of the metal coating. The device for adhering is not particularly limited as long as it can adhere the diaphragm to the cathode side surface of the anode, but a device that can uniformly press the diaphragm to the anode side is preferable, for example, the above-mentioned pressure device is preferable. With the pressure device, the plating solution is pressurized and the diaphragm is pressed to the anode side by the liquid pressure of the plating solution, thereby making the diaphragm adhere to the anode. As a device that can uniformly press the diaphragm to the anode side, for example, a pressure reduction device that reduces the pressure of the space outside the housing where the surface of the anode opposite to the cathode side is exposed is preferable. With the pressure reduction device, the space is reduced in pressure and the diaphragm is sucked to the anode side, making the diaphragm adhere to the anode. The pressure reducing device may be, for example, a device that is composed of a pressure reducing housing, an exhaust pipe, and a pressure reducing pump, and that reduces the pressure in the pressure reducing chamber. As a film forming device, a device that is equipped with both a pressurizing device and a pressure reducing device as a device for bringing the two into contact is preferable. This is because it is possible to sufficiently prevent oxygen gas and the like from accumulating at the interface between the diaphragm and the anode, which causes resistance. The device for bringing the two into contact may be a device that generates a flow from the cathode side to the anode side in the plating solution contained in the container (for example, a device composed of a propeller and a drive device for rotating the propeller).

The metal film forming apparatus may further include a lifting device. The lifting device is not particularly limited as long as it can raise and lower the electrolyte membrane and position the electrolyte membrane in the opposing direction in which the anode and the substrate face each other. The lifting device may be, for example, a hydraulic or pneumatic actuator composed of a cylinder and a piston, or an electric actuator that is raised and lowered by a motor or the like. Note that the film forming apparatus does not need to include a lifting device as long as it can raise and lower the electrolyte membrane and position the electrolyte membrane in the opposing direction in which the anode and the substrate face each other.

The metal film forming apparatus is not particularly limited, but may be one in which the components are arranged so that the direction in which the anode and the substrate face each other is parallel to the vertical direction. The metal film forming apparatus may be one in which the components are arranged so that the direction in which the anode and the substrate face each other is horizontal. The metal film forming apparatus may be one in which the components are arranged so that the direction in which the anode and the substrate face each other is inclined with respect to the vertical direction.

The metal film deposition device according to the embodiment will be described in more detail below with reference examples and comparative examples.

[Reference Example 1]
First, a test system 1 for a metal film forming apparatus was constructed. The test system 1 simulates the metal film forming apparatus according to the embodiment. Fig. 4 is a schematic cross-sectional view showing the test system 1 for a metal film forming apparatus.

In test system 1, as shown in FIG. 4, the internal space of the housing is divided into a storage chamber and a reduced pressure chamber by an anode and a diaphragm. A substrate that serves as a cathode is stored in the storage chamber. A plating solution is also stored in the storage chamber. A power supply device is also provided to apply a voltage between the anode and the substrate (cathode). A pressure applying device (not shown) is also provided to apply pressure to the plating solution stored in the storage chamber. A pressure reducing device (not shown) is also provided to reduce the pressure in the reduced pressure chamber.

The diaphragm is attached to the housing so as to cover the cathode side surface of the anode and to be in contact with the cathode side surface of the anode. The diaphragm is a cation exchange membrane that is permeable to water and hydrogen ions but not to oxygen gas. The anode is attached to the housing so as to block the communication part connecting the storage chamber and the reduced pressure chamber, with the cathode side surface exposed to the storage chamber through the diaphragm and the surface opposite the cathode side exposed to the reduced pressure chamber. The anode is made of a flat mesh member that is insoluble in the plating solution. The mesh member is permeable to oxygen gas. The substrate is immersed in the plating solution and is in contact with it. The substrate is entirely made of a metal material. The plating solution is an acidic aqueous solution containing metal ions, and is an electrolytic solution that has electrical conductivity.

Next, using test system 1, a metal film was formed on the surface of the substrate. Specifically, the plating solution contained in the storage chamber was pressurized by the pressure device to keep the liquid pressure of the plating solution constant. At the same time, the pressure reduction device reduced the pressure in the reduced pressure chamber to -0.3 atm compared to atmospheric pressure. While maintaining the above state, a constant current (10 mA) was applied between the anode and the substrate (cathode) by the power supply device. This reduced the metal ions contained in the plating solution, forming a metal film on the surface of the substrate.

[Reference Example 2]
A metal film was formed on the surface of the substrate using test system 1 under the same conditions as in Reference Example 1, except that the pressure reduction chamber was not performed. Specifically, the plating solution contained in the storage chamber was pressurized by a pressure device to keep the liquid pressure of the plating solution constant. At the same time, the pressure reduction chamber was not reduced and the pressure was kept at atmospheric pressure. While maintaining the above state, a constant current (10 mA) was applied between the anode and the substrate (cathode) by the power supply device. As a result, the metal ions contained in the plating solution were reduced, and a metal film was formed on the surface of the substrate.

[Comparative Example]
First, a test system 2 of a metal film forming apparatus was constructed. Unlike the embodiment, the test system 2 is a simulation of a metal film forming apparatus that does not have a diaphragm. Fig. 5 is a schematic cross-sectional view showing the test system 2 of the metal film forming apparatus.

In test system 2, as shown in FIG. 5, the internal space of the same housing as test system 1 is divided into two storage chambers by the same anode as test system 1. One storage chamber is the same as the storage chamber of test system 1, and contains the same substrate as test system 1. Both storage chambers contain the same plating solution as test system 1. In addition, a power supply device is provided to apply a voltage between the anode and the substrate (cathode). A pressure device (not shown) is provided to pressurize the plating solution contained in both storage chambers. The anode is attached to the housing so as to block the communication part connecting both storage chambers, so that the surface on the cathode side is exposed to one storage chamber and the surface opposite the cathode side is exposed to the other storage chamber.

Next, using test system 2, a metal film was formed on the surface of the substrate. Specifically, the plating solution contained in both storage chambers was pressurized by a pressure device, and the liquid pressure of the plating solution was kept constant. While maintaining this state, a constant current (10 mA) was applied between the anode and the substrate (cathode) by a power supply device. This reduced the metal ions contained in the plating solution, forming a metal film on the surface of the substrate.

[evaluation]
In Reference Examples 1 and 2 and the Comparative Example, the voltage (cell voltage) between the anode and the substrate was measured during the formation of the metal film, and the change in voltage over time at a constant current (10 mA) during the formation of the metal film was evaluated. Fig. 6 is a graph showing the change in voltage over time at a constant current (10 mA) during the formation of the metal film in Reference Examples 1 and 2 and the Comparative Example.

As shown in FIG. 6, in Reference Example 1, the voltage rose until a predetermined time had elapsed after the start of current application, and then became constant, and current could be continuously passed at a constant voltage. In Reference Example 1, the pressure reduction chamber was reduced, and the diaphragm was sufficiently attached to the anode, so that air and oxygen gas generated by electrolysis did not accumulate at the interface between the diaphragm and the anode, and the oxygen gas passed through the holes in the anode of the porous body and was discharged to the pressure reduction chamber. It is believed that this made it possible to suppress the occurrence of high resistance at the interface between the diaphragm and the anode. From this, it is believed that under the conditions of Reference Example 1, the reaction resistance of the anode can be suppressed, and therefore the metal film can be formed at a high speed. On the other hand, in Reference Example 2, the voltage continued to rise at a faster rate than in Reference Example 1 after the start of current application, and reached the upper limit of the power supply (20 V). Eventually, the resistance between the anode and the substrate became high, and current could no longer flow. In Reference Example 2, unlike Reference Example 1, the vacuum chamber was not decompressed, so the diaphragm did not adhere sufficiently to the anode, and it is believed that this resulted in high resistance due to air and oxygen gas accumulating at the interface between the diaphragm and the anode. In addition, in the Comparative Example, after the application of current began, the voltage initially rose at a slower rate than in Reference Example 1, and then continued to rise at an increasing rate until it reached the upper limit of the power supply (20 V). In the Comparative Example, it is believed that the anode was continuously covered with oxygen gas, causing the voltage to continue to rise.

The metal film deposition device according to the embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the spirit of the present invention as described in the claims.

1: Metal film forming device, 11: Anode, 13: Electrolyte membrane, 15: Housing, 16: Power supply device, 17: Storage chamber, 18: Diaphragm, 21: Plating solution supply pump (pressurizing device), B: Substrate, L: Plating solution, F: Metal film

Claims (1)

An anode;
an electrolyte membrane disposed between the anode and cathode substrates;
a housing having a chamber between the anode and the electrolyte membrane for accommodating a plating solution containing metal ions;
a power supply device that applies a voltage between the anode and the substrate;
a pressurizing device for pressurizing the plating solution contained in the container;
the electrolyte membrane is attached so as to cover an opening on the cathode side of the accommodating housing that communicates with the accommodating chamber;
A film forming apparatus for forming a metal film on a surface of the substrate by applying the voltage while pressing the surface of the substrate with the electrolyte membrane, thereby reducing the metal ions impregnated in the electrolyte membrane,
the film forming apparatus further includes a diaphragm that covers a surface of the anode on the cathode side and is attached so as to be in contact with the surface of the anode on the cathode side;
The diaphragm is a membrane that is permeable to water and hydrogen ions but not permeable to oxygen gas,
the anode is attached to close an opening of the accommodating housing on an opposite side to the cathode side, the opening communicating with the accommodating chamber, such that a surface on the cathode side is exposed to the accommodating chamber via the diaphragm and a surface on the opposite side to the cathode side is exposed to an outside of the accommodating housing,
The metal film forming apparatus is characterized in that the anode is made of a porous body that is insoluble in the plating solution.

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