Metal film deposition equipment

Abstract

To provide an apparatus for depositing a metal film that can suppress the occurrence of film formation defects in a metal film.SOLUTION: A film deposition apparatus 1 includes an anode 11, an electrolyte membrane 13 placed between the anode 11 and a base material W, a housing 15 sealed with the electrolyte film, a tank 17 for housing plating solution L discharged from the housing 15, a pump 18 for pressure-feeding the plating solution L of the tank 17 to the housing, and a power supply 19 for applying a voltage between the anode 11 and the base material W. The anode 11 is composed of the same metal as the metal film F and is soluble to the plating solution, and the film deposition apparatus 1 has a filter 51 between the housing 15 and the tank 17 for filtering the plating solution discharged from the housing 15.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a film forming apparatus for forming a metal film on a surface of a substrate. [Background technology]

[0002] As an example of this type of technology, Patent Document 1 proposes a film-forming apparatus for forming a metal film on the surface of a substrate. This film-forming apparatus includes an anode, an electrolyte membrane disposed between the anode and the substrate serving as a cathode, and a power supply unit for applying a voltage between the anode and the substrate. The film-forming apparatus further includes a container for containing a plating solution between the anode and the electrolyte membrane so that they are in contact with each other.

[0003] The container is formed with a supply passage for supplying the plating solution to the inside of the container and a discharge passage for discharging the plating solution from the inside of the container, and the film forming apparatus further includes a circulation mechanism connected to the supply passage and the discharge passage for circulating the plating solution inside the container. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-169399 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the film forming apparatus shown in Patent Document 1, the plating solution is contained inside the container, so that it does not come into direct contact with the substrate. Therefore, a part of the substrate does not enter the plating solution as an impurity. However, for example, if the anode is made of the same metal as the metal film and is soluble in the plating solution, the surface of the anode may be oxidized during non-film formation, generating an oxide, or a part of the anode may become metal powder and be detached. If such oxides or metal powders exist as impurities in the plating solution, it is expected that the impurities will prevent the formation of a homogeneous metal film, resulting in poor film formation of the metal film.

[0006] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a metal film forming apparatus that can suppress the occurrence of defective formation of a metal film. [Means for solving the problem]

[0007] In view of the above problems, the present invention provides a film formation apparatus for a metal film, the film formation apparatus comprising at least an anode, an electrolyte membrane disposed between the anode and a substrate, a container that contains the anode and a plating solution and has an opening on the substrate side sealed with the electrolyte membrane, a tank that is connected to the container and contains the plating solution discharged from the container, a pressure-feeding device that is connected to the tank and pressure-feeds the plating solution in the tank to the container, and a power supply unit that applies a voltage between the anode and the substrate that serves as a cathode, the film formation apparatus forming a metal film derived from metal ions in the plating solution on a surface of the substrate by applying the voltage with the electrolyte membrane in contact with the substrate, the anode being made of the same metal as the metal film and soluble in the plating solution, and the film formation apparatus is characterized in that a filter that filters the plating solution discharged from the container is provided between the container and the tank.

[0008] According to the present invention, when a voltage is applied between the anode and the substrate in a state where the substrate is in contact with the electrolyte membrane during film formation, metal ions in the plating solution in the container migrate to the substrate side through the electrolyte membrane. When electrons are donated to the metal ions from the surface of the substrate, metal derived from the metal ions in the plating solution is precipitated on the surface of the substrate, and a metal coating made of the precipitated metal can be formed on the surface of the substrate.

[0009] Here, since the anode is a soluble anode, during film formation, the metal constituting the anode dissolves in the plating solution, so that the metal of the anode is consumed and a part of it may be detached from the anode, which may become an impurity in the plating solution. Furthermore, when the film formation is completed, the application of the voltage between the anode and the substrate is released. If such a state is maintained, the surface of the anode may be oxidized by oxygen present in the container, such as oxygen contained in the plating solution. If the surface of the anode is oxidized, it may become an oxide, which may become an impurity in the plating solution. However, according to the present invention, the film formation device is provided with a filter between the container and the tank for filtering the plating solution discharged from the container, so that the impurities contained in the plating solution can be captured by the filter. As a result, the filter is provided on the discharge side of the container, which is close to the source of the impurities, and the plating solution containing the impurities can be purified before it is returned to the tank, so that the occurrence of poor film formation of the metal film due to impurities in the plating solution can be suppressed.

[0010] In a more preferred embodiment, the film forming apparatus includes a mounting stage on which the substrate is placed, a lifting device that raises and lowers at least one of the container and the mounting stage so that the electrolyte membrane can be freely attached to and detached from the mounting stage, a replacement mechanism that replaces the plating solution contained in the container with atmosphere, and a control device that controls the lifting and lowering operation of the lifting device and the replacement operation of the replacement mechanism, wherein the control device controls the replacement operation so that the plating solution contained in the container is replaced with atmosphere while the electrolyte membrane is in contact with the substrate, and controls the lifting and lowering operation so that the electrolyte membrane is separated from the substrate after the replacement operation is completed.

[0011] According to this aspect, the control device replaces the plating solution contained in the container with the atmosphere while the electrolyte membrane is in contact with the substrate, and then the electrolyte membrane is separated from the substrate, so that the electrolyte membrane can be prevented from being deformed by the weight of the plating solution. Here, when the atmosphere is present in the container, the surface of the anode is oxidized, and an oxide is generated. When the plating solution is reintroduced into the container during film formation, this oxide is detached from the surface of the anode and becomes sludge or the like and is contained in the plating solution. In this way, even if the control device performs control such that the anode is easily oxidized, the oxide of the anode can be collected by the filter, so that the occurrence of poor film formation of the metal film caused by impurities in the plating solution can be prevented.

[0012] In a more preferred embodiment, the metal of the anode is a metal that is contained in the plating solution as a divalent or higher metal ion, the tank is provided with a bubbling mechanism that bubbles the plating solution with a gas that contains oxygen gas, and a further filter that filters the plating solution is provided between the tank and the pressure-feed device.

[0013] According to this embodiment, divalent or higher metal ions generated during the formation of the metal coating may become monovalent metal ions during the formation of the film, pass through the filter without combining with oxygen, and be returned to the tank. At this time, the monovalent metal ions may become oxides, or may become divalent or higher metal ions and metal (specifically, aggregated metal powder) due to the transfer of electrons between the monovalent metal ions.

[0014] According to this embodiment, by bubbling the plating solution containing such monovalent metal ions with a gas containing oxygen gas, the metal ions are converted into stable divalent or higher metal ions, and the generation of such oxides or metals (metal powder) can be suppressed. Even if oxides or metals (metal powder) are generated in the tank, a further filter is provided between the tank and the pressure-feeding device, so that impurities can be removed from the plating solution before it is supplied to the container. Effect of the Invention

[0015] According to the present invention, the occurrence of defective film formation of a metal film can be suppressed. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view of a metal film forming apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the film forming apparatus shown in FIG. 1, illustrating a state during film formation. [Diagram 3] 2 is a flowchart illustrating control of the film forming apparatus shown in FIG. [Figure 4] FIG. 5 is a schematic cross-sectional view of a metal film forming apparatus according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the film forming apparatus shown in FIG. 4, illustrating a state during film formation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a metal film forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0018] First Embodiment Fig. 1 is a schematic cross-sectional view of a metal coating deposition apparatus 1 according to a first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the deposition apparatus shown in Fig. 1, showing a state during deposition.

[0019] 1 and 2, the film forming apparatus 1 includes an anode 11, an electrolyte membrane 13 disposed between the anode 11 and a substrate W, and a container 15 that contains the anode 11 and a plating solution L and has an opening 15g that opens to the substrate W side sealed with the electrolyte membrane 13. The film forming apparatus 1 further includes a power supply unit 19 that applies a voltage between the anode 11 and the substrate W that serves as a cathode, and may further include a mounting table 20 on which the substrate W is mounted and a lifting device 70, as necessary.

[0020] The film forming apparatus 1 is an apparatus for forming a metal coating on the surface wa of the substrate W by applying a voltage between the anode 11 and the substrate W by a power supply unit 19 with an electrolyte membrane 13 in contact with the substrate W placed on a mounting table 20. During film formation, metal ions contained inside the electrolyte membrane 13 from the plating solution L are reduced on the surface wa of the substrate W, and metal derived from the metal ions is precipitated, and the precipitated metal forms a metal coating.

[0021] The substrate W functions as a cathode. The material of the substrate W is not particularly limited as long as it functions as a cathode (i.e., a surface having electrical conductivity), and may be made of a metal material such as aluminum or iron, or may be a resin, ceramic, or the like having a surface coated with a metal layer such as copper, nickel, silver, or iron.

[0022] The mounting table 20 is made of a conductive material and is disposed below the container 15 so that the substrate W faces the electrolyte membrane 13. The substrate (specifically, the cathode) W is electrically connected to the negative electrode of the power supply unit 19 via the mounting table 20. When the mounting table 20 is made of an insulating material, the negative electrode of the power supply unit 19 may be directly connected to the substrate W via a wire.

[0023] The anode 11 has a shape corresponding to the film formation region of the substrate W. The film formation region of the substrate W means the portion of the surface wa of the substrate W facing the anode 11. The anode 11 is a non-porous (for example, non-porous) anode made of the same metal as the metal coating, and is a block-shaped or flat anode. The anode 11 is made of the same metal as the metal coating and is soluble in the plating solution L. However, as long as the required surface area is satisfied, the anode may be a porous anode, a mesh, or a metal ball laid out in a container.

[0024] Examples of the material of the anode 11 include copper, nickel, silver, and tin. In this embodiment, the material is not particularly limited as long as the anode 11 dissolves when a voltage is applied using the power supply unit 19. The anode 11 is attached to a container 15 made of, for example, an insulating material, and is electrically connected to the positive electrode of the power supply unit 19 via a positive electrode side conductor.

[0025] As described above, the plating solution (electrolyte) L is a solution containing the metal of the metal film to be formed in an ion state, and examples of the metal include copper, nickel, silver, and tin. The plating solution L is an aqueous solution in which these metals are dissolved (ionized) with an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid. For example, when the metal is nickel, the plating solution L may be an aqueous solution of nickel nitrate, nickel phosphate, nickel succinate, nickel sulfate, nickel pyrophosphate, or nickel sulfamate. Furthermore, when the metal is copper, the plating solution L may be an aqueous solution containing copper sulfate, copper pyrophosphate, or the like.

[0026] The electrolyte membrane (solid electrolyte membrane) 13 is a flexible membrane that can be impregnated (contained) with metal ions by contacting it with the above-mentioned plating solution L. The electrolyte membrane 13 is not particularly limited as long as it can reduce metal ions in the substrate W and precipitate metal derived from the metal ions when a voltage is applied from a power supply unit 19. Examples of the material of the electrolyte membrane 13 include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins having an ion exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

[0027] As shown in FIG. 1, the container 15 is made of a material insoluble in the plating solution L, and the anode 11 and the electrolyte membrane 13 are attached to the container 15. Inside the container 15, a storage space S for storing the plating solution L is formed by the side wall of the container 15, the anode 11, and the electrolyte membrane 13. The anode 11 is attached to the inner surface of the container 15, and an opening 15g that opens to the side of the substrate W is formed at a position facing the anode 11. The opening 15g opens downward, and the electrolyte membrane 13 is attached so as to seal the opening 15g. In this embodiment, the periphery of the electrolyte membrane 13 is attached to the container 15 by being sandwiched between the main body 15a and the frame 15b of the container 15. The anode 11 and the electrolyte membrane 13 are arranged apart from each other and are in a non-contact state, and the storage space S between them is filled with the plating solution L. In this manner, the container 15 has a structure in which the plating solution L contained in the container space S comes into direct contact with the anode 11 and the electrolyte membrane 13.

[0028] Furthermore, the container 15 is formed with a supply flow path 15c for supplying the plating solution L to the storage space S, and a discharge flow path 15d for discharging the plating solution L from the storage space S. The supply flow path 15c and the discharge flow path 15d are holes communicating with the storage space S, and are formed on either side of the storage space S. The film forming apparatus 1 may have a heating device (not shown) upstream of the supply flow path 15c (for example, in the tank T that stores the plating solution L).

[0029] The lifting device 70 lifts and lowers at least one of the container 15 and the mounting table 20 so that the electrolyte membrane 13 and the substrate W can be moved toward and away from each other. In this embodiment, the mounting table 20 is fixed, and the container 15 is lifted and lowered by the lifting device 70. As shown in Figs. 1 and 2, the lifting device 70 is provided on the upper part of the container 15. The lifting device 70 may be a known electric actuator that converts the rotation of a motor such as a servo motor into linear motion. As long as the electrolyte membrane 13 can be moved toward and away from the substrate W by linear motion, the lifting device 70 may be provided on the mounting table 20 or may be a hydraulic or pneumatic cylinder.

[0030] The following describes a circulation mechanism for circulating the plating solution L in the film forming apparatus 1, and the control device 60. The film forming apparatus 1 includes, as the circulation mechanism, a tank 17 connected to the accommodation body 15 for accommodating the plating solution L discharged from the accommodation body 15, and a pump (pressure-feeding device) 18 connected to the tank 17 for pressure-feeding the plating solution L from the tank 17 to the accommodation body.

[0031] Furthermore, the film forming apparatus 1 is provided, between the container 15 and the tank 17, with a filter (first filter) 51 for filtering the plating solution L discharged from the container 15, and an exchanging mechanism 53A including an air pump 53 for exchanging the plating solution contained in the container 15 with the atmosphere. Furthermore, between the container 15 and the filter 51, a pressure regulating valve 31 for adjusting the liquid pressure of the plating solution L discharged from the container 15 is provided.

[0032] A path from the tank 17 via the pump 18 to the supply flow path 15c is a supply route 41 that supplies the plating solution L to the container 15. A path from the discharge flow path 15d to the tank 17 via the pressure regulating valve 31 and the filter 51 is a discharge route 42 that discharges the plating solution L to the tank 17.

[0033] A circulation mechanism including a supply route 41 and a discharge route 42 allows plating solution L, the metal ion concentration of which has been adjusted to a predetermined concentration in the tank 17, to be supplied to the storage space S, and the plating solution L used during film formation in the storage space S to be returned to the tank 17.

[0034] Incidentally, since the anode 11 is a soluble anode, during film formation, the metal constituting the anode 11 dissolves in the plating solution, and the metal of the anode 11 is consumed and a part of it may be detached from the anode, which may become an impurity in the plating solution. Furthermore, when film formation is completed, the application of the voltage between the anode 11 and the substrate W is released. If this state is maintained, the surface of the anode 11 may be oxidized by oxygen present in the container, such as oxygen contained in the plating solution. When the surface of the anode 11 is oxidized, it becomes an oxide, which may become an impurity in the plating solution.

[0035] From this viewpoint, in this embodiment, as described above, the film forming apparatus 1 includes a filter 51 between the container 15 and the tank 17, which filters the plating solution L discharged from the container 15, as shown in FIG. 1. The filter 51 is for capturing impurities (contamination) contained in the plating solution L, and has a filter or the like provided therein. In this embodiment, the filter 51 collects sludge such as oxides and metal powder derived from metal ions dissolved in the plating solution L, and purifies the plating solution L.

[0036] The filter 51 is not particularly limited in structure for removing sludge such as oxides or metal powder derived from the soluble anode metal generated inside the container 15 from the plating solution L. The filter of the filter 51 is preferably a cartridge type, and the filtration method may be either deep layer filtration or surface filtration. Deep layer filtration is preferable because it has a higher capture rate of foreign matter than surface filtration. Filters include thread-wound type, nonwoven fabric type, pleated type, and membrane type filters, and the filtration accuracy increases in this order. A filter having a size (mesh size) that allows the plating solution L to pass through should be selected in consideration of the pressure loss of the plating solution and the size of the impurities (foreign matter) to be captured.

[0037] In this embodiment, a filter 51 is provided on the discharge side of the container 15, which is close to the source of impurities, and the plating solution L containing impurities can be purified before it is returned to the tank 17. This makes it possible to suppress the occurrence of poor film formation of the metal film F due to impurities in the plating solution L.

[0038] The replacement mechanism 53A is a mechanism for replacing the plating solution L contained in the container 15 with the atmosphere, returning the plating solution L contained in the container 15 to the tank 17, and introducing the atmosphere into the container 15. In this embodiment, an air pump 53 for pumping the atmosphere is connected to the supply flow path 15c of the container 15, and the replacement mechanism 53A is composed of the air pump 53 and a pipe connecting the air pump 53 and the supply flow path 15c of the container 15. The atmosphere contained in the container 15 is replaced with the plating solution L by the pump 18.

[0039] In this embodiment, the plating solution L is replaced with the atmosphere by providing the air pump 53 in the replacement mechanism 53A. However, the present invention is not limited to this, and for example, a relief valve may be provided in the discharge route, and the plating solution L may be sucked from the container 15 and the atmosphere may be introduced through the relief valve by rotating the pump 18 in the reverse direction. Also, a liquid drainage hole may be provided near the bottom of the container 15, and the plating solution L may be discharged by its own weight.

[0040] The control device 60 controls the operation of the lifting device 70, the pump 18, the power supply unit 19, and the air pump 53 of the replacement mechanism 53A, and controls the application of power by the power supply unit 19. Although not shown, the control device 60 includes a storage device (not shown) that stores a control program for executing the following series of steps, and a calculation device (not shown) that executes the control program. The storage device further stores set values ​​such as the start-up time of the pump 18 and the air pump 53, the time for applying power to the power supply unit 19, and the amount of displacement by the lifting device 70. The control device 60 receives inputs such as a signal from a pressure sensor (not shown) that measures the pressure in the storage space S of the storage body 15 via an input device or the like.

[0041] The control flow of the control device 60 will be described with reference to Fig. 3 below. The control device 60 controls a transport device (not shown) and the like to place the substrate W on the mounting table 20 (S1). At this time, the alignment of the substrate W with respect to the anode 11 attached to the container 15 may be adjusted, and the temperature of the substrate W may be adjusted.

[0042] Next, the control device 60 controls the lifting operation of the lifting device 70. Specifically, the control device 60 causes the lifting device 70 to lower the housing 15 at a preset stroke, and brings the electrolyte membrane 13 into contact with the surface wa of the substrate W from above (S2). As a result, the housing 15 and the substrate W are disposed as shown in FIG. 2.

[0043] Next, the control device 60 drives and controls the pump 18 to supply the plating solution L from the tank 17 to the storage space S of the storage body 15 (S3). Since the storage space S is filled with the atmosphere (air) as described later, the atmosphere in the storage body 15 can be replaced with the plating solution L. When the storage body 15 is filled with the plating solution L and the liquid pressure of the plating solution L in the storage space S reaches a predetermined pressure, the plating solution L passes through the pressure regulating valve 31. In this way, the liquid pressure of the plating solution L can be used to uniformly press the substrate W with the electrolyte membrane 13. Note that the fact that the liquid pressure of the plating solution L in the storage space S has reached the predetermined pressure may be detected by a pressure sensor or may be determined by the passage of a preset time.

[0044] Here, after the liquid pressure of the plating solution L in the accommodation space S reaches a predetermined pressure, a voltage may be applied (S4) as described below, but after the predetermined pressure is reached and before the voltage is applied, the pump 18 may be driven to circulate the plating solution L. In this way, for example, oxides formed on the surface of the soluble anode 11 can be discharged from the accommodation body 15 by the circulated plating solution L and collected by the filter 51.

[0045] Next, while the substrate W is pressed against the electrolyte membrane 13 by the hydraulic pressure of the plating solution L, the control device 60 controls the power supply unit 19 to apply a voltage between the anode 11 and the substrate W for a predetermined time (S4). As a result, the metal ions contained in the electrolyte membrane 13 move to the surface wa of the substrate W in contact with the electrolyte membrane 13 and are reduced on the surface wa of the substrate W. As a result, metal is precipitated on the surface of the substrate W, and a metal coating F having a predetermined thickness is formed on the surface wa of the substrate W. At this time, since the plating solution L is contained in the containing space S, metal ions can be constantly supplied to the electrolyte membrane 13.

[0046] Next, the control device 60 controls the replacing operation of the replacing mechanism 53A so that the plating solution L contained in the container 15 is replaced with air while the electrolyte membrane 13 is in contact with the substrate W (S5). Specifically, the air pump 53 is driven to pump air into the container 15, thereby discharging the plating solution L from the container 15. The discharged plating solution L passes through the pressure regulating valve 31, is sent to the filter 51, is filtered, and is returned to the tank 17.

[0047] After the air exchange operation is completed, the control device 60 controls the lifting operation of the lifting device 70 so that the electrolyte membrane 13 is separated from the substrate W. Specifically, the control device 60 causes the lifting device 70 to lift the container 15 at a preset stroke, thereby separating the electrolyte membrane 13 from the surface wa of the substrate W (S6). As a result, the container 15 and the substrate W are disposed as shown in FIG. 1. Finally, the substrate W is removed from the film forming apparatus 1 (S7).

[0048] According to this embodiment, the control device 60 replaces the plating solution contained in the container 15 with the atmosphere while the electrolyte membrane 13 is in contact with the substrate W, and then separates the electrolyte membrane 13 from the substrate W, thereby preventing the electrolyte membrane 13 from deforming due to the weight of the plating solution L itself.

[0049] Here, if air is present in the accommodation space S of the accommodation body 15, the surface of the anode 11 is oxidized, and an oxide is generated. When the plating solution L is reintroduced into the accommodation body 15 during film formation, this oxide is detached from the surface of the anode and becomes sludge or the like, which is contained in the plating solution L. In this way, even if the control device 60 performs control such that the anode 11 is easily oxidized, the filter 51 can collect the oxide from the anode 11, and therefore it is possible to suppress the occurrence of poor film formation of the metal film F caused by impurities in the plating solution L.

[0050] <Second embodiment> FIG. 4 is a schematic cross-sectional view of a film forming apparatus for a metal film according to a second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view of the film forming apparatus shown in FIG. 4, showing a state during film formation. The film forming apparatus 1 according to the second embodiment differs from that of the first embodiment in that a bubbling mechanism 55 and a second filter 52 are provided. The second filter 52 corresponds to the "further filter" as defined in the present invention. The components having the same or similar functions as those of the film forming apparatus 1 according to the first embodiment are denoted by the same reference numerals as those of the film forming apparatus 1 according to the first embodiment, and the description thereof is omitted, and only the different parts are described.

[0051] In the film forming apparatus 1 according to the second embodiment, the anode 11 is also a soluble anode, and the metal of the anode 11 is a metal that is contained in the plating solution as divalent or higher metal ions, such as copper, nickel, tin, and zinc. Here, some of the divalent or higher metal ions generated when forming the metal coating F become monovalent metal ions during film formation and do not bond with oxygen. Those that bond with oxygen become sludge and can be captured by the filter (first filter) 51, but the monovalent metal ions are returned to the tank 17 by the first filter 51.

[0052] In the case where the metal is copper, for example, the monovalent copper ions returned to the tank 17 may become copper hydroxide in the tank 17 (Cu + +H2O→CuOH+H + ) Copper hydroxide is chemically unstable, so it may dehydrate to become copper oxide (I) (2CuOH → Cu2O + H2O), which may precipitate in the tank 17. Also, by transferring electrons between monovalent copper ions, they may become divalent or higher metal ions and metals (2Cu + →Cu+Cu 2+ ), the metals may agglomerate into metal powder and settle in tank 17.

[0053] Therefore, in order to suppress such precipitation, it is preferable to convert chemically unstable monovalent metal ions (e.g., copper(I) ions) in the plating solution L in the tank 17 into chemically stable divalent or higher metal ions (e.g., copper(II) ions).

[0054] Therefore, in this embodiment, the tank 17 is provided with a bubbling mechanism 55 that bubbles the plating solution L with a gas containing oxygen gas (for example, air). In this embodiment, the bubbling mechanism 55 is a mechanism in which a pipe is connected so as to supply air from the air pump 53 to the plating solution L contained in the tank 17. As a result, the gas containing oxygen gas is supplied to the tank 17, so that unstable monovalent metal ions can be oxidized to stable divalent or higher metal ions (2Cu + +1 / 2O2+2H + →2Cu 2+ As a result, the monovalent copper ions are allowed to exist stably in the plating solution L, and the generation of sludge such as metal oxides or metal powder caused by the monovalent copper ions can be suppressed.

[0055] Here, monovalent metal ions that are not oxidized to divalent or higher metal ions by the bubbling mechanism 55 become metal oxides or metal powders resulting from monovalent copper ions, and may precipitate in the tank 17. In this state, as shown in Fig. 5, if bubbling by the bubbling mechanism 55 is continued during film formation, impurities such as metal oxides or metal powders that have precipitated in the tank 17 may be stirred up into the plating solution due to the supply of air into the plating solution. If the plating solution in this state is supplied to the container 15, impurities in the plating solution may cause poor film formation.

[0056] Therefore, in this embodiment, a second filter 52 for filtering the plating solution L is provided between the tank 17 and the pump 18. The second filter 52 is capable of capturing the metal oxide and metal powder generated in the tank 17 and filtering the plating solution L, and more preferably, is capable of capturing crystals of metal salts (e.g., CuSO4) contained in the plating solution L.

[0057] The second filter 52 may be configured, like the first filter 51, to include a filter for removing impurities from the plating solution L. For example, since the metal oxide and metal powder generated in the tank 17 have smaller particle sizes than those generated in the container 15, it is preferable that the mesh of the filter of the second filter 52 is finer (smaller) than the mesh of the filter of the first filter 51.

[0058] In this way, even if impurities such as metal oxides or metal powders that have settled in the tank 17 are stirred up into the plating solution due to the supply of air into the plating solution, the impurities can be removed from the plating solution L by the second filter 52 before it is supplied to the container 15, as shown in FIG. 5. EXAMPLES

[0059] The invention is illustrated by the following examples.

[0060] [Example 1] A glass epoxy board (FR-4) was prepared as a substrate for forming a film on its surface, which was made by impregnating a layer of glass fiber cloth with epoxy resin. Copper foil was formed on the surface of this glass epoxy board.

[0061] Next, a copper film was formed using the film forming apparatus according to the first embodiment of FIG. 1 and FIG. 1. A copper sulfate aqueous solution of "1M CuSO4+0.2M H2SO4" was used as the plating solution, and a Cu plate was used as the anode. In addition, a filter capable of filtering out foreign matter with a particle size of 1 μm was used as the filter. The film formation conditions were as follows: the temperature of the plating solution was 70°C, an electrolyte membrane (Nafion (registered trademark): manufactured by DuPont) was attached to the substrate, the liquid pressure of the plating solution was 0.6 MPa, and the current density was 15 A / dm 2 , film forming area 360cm 2 This process was repeated four times according to the flow shown in Figure 3.

[0062] [Example 2] A copper coating was formed in the same manner as in Example 2. The difference from Example 1 is that the copper coating was formed using a coating apparatus further provided with a second filter as shown in the second embodiment. The second filter uses the same filter as the first filter.

[0063] [Comparative Example 1] A copper film was formed in the same manner as in Example 1. The difference from Example 1 is that the copper film was formed using a film forming apparatus that did not have the first and second filters.

[0064] <Checking the film formation status> The state of the copper film formed by the film forming apparatus according to Example 1 and Comparative Example 1 was confirmed. The results are shown in Table 1 below. Here, "X" in Table 1 indicates "a state in which the surface of the copper film was discolored" or "a state in which the electrolyte film was stuck to the copper film during film formation," and "◯" indicates a state in which such a state did not occur and the film was formed satisfactorily.

[0065] [Table 1]

[0066] (Results and Discussion) In Examples 1 and 2, copper films were formed well in all film formations, but in Comparative Example 1, defects occurred in film formation from the third time onwards. This is believed to be because impurities in the plating solution were removed by providing a filter in Examples 1 and 2. It is also believed that the amount of impurities increases as the number of film formations increases, and in the film formation devices of Examples 1 and 2, impurities were captured in the first and second filters. Since the impurities (sludge) captured by these filters were copper oxides or copper powder, it is believed that the sludge was impurities caused by the soluble anode.

[0067] Furthermore, in Examples 1 and 2, the amount of sludge captured by the filter of the first filter was approximately the same, and in Example 2, the amount of sludge captured by the filter of the second filter was less than the amount of sludge captured by the first filter. From this, it is considered that the sludge captured by the filter of the second filter in Example 2 is the plating solution generated in the tank, and that the first filter collects the sludge generated in the container, and the second filter collects the sludge generated in the tank. However, since the sludge generated in the tank is in a state of settling in the tank unless bubbling is performed, it is considered that the second filter is not necessary in the film forming apparatus of Example 1.

[0068] 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 design modifications can be made without departing from the spirit of the present invention as described in the claims.

[0069] In the first and second embodiments, a sampling tank for sampling the plating solution may be further provided downstream of the filter in order to check the filtering state of the plating solution. [Explanation of symbols]

[0070] 1: film forming device, 11: anode, 13: electrolyte membrane, 15: container, 15g: opening, 17: tank, 18: pressure delivery device (pump), 19: power supply unit, 20: mounting table, 51: first filter (filter), 52: second filter (further filter), 53A: replacement mechanism, 55: bubbling mechanism, 60: control device, 70: lifting device, W: substrate, L: plating solution

Claims

1. An anode; an electrolyte membrane disposed between the anode and a substrate; a container that contains the anode and the plating solution and has an opening on the substrate side sealed with the electrolyte membrane; a tank connected to the container for storing the plating solution discharged from the container; a pressure-feeding device connected to the tank for pressure-feeding the plating solution in the tank to a container; A power supply unit that applies a voltage between the anode and the substrate serving as a cathode, A film forming apparatus for forming a metal film derived from metal ions in the plating solution on a surface of the substrate by applying the voltage while an electrolyte membrane is in contact with the substrate, the film forming apparatus comprising: the anode is made of the same metal as the metal coating and is soluble in the plating solution; the film forming apparatus is provided with a filter between the container and the tank, the filter filtering the plating solution discharged from the container; The film forming apparatus includes: A mounting table on which the base material is placed; a lifting device that lifts and lowers at least one of the container and the mounting table so that the electrolyte membrane can be moved toward and away from the mounting table; a replacement mechanism for replacing the plating solution contained in the container with the atmosphere; A control device for controlling the lifting operation of the lifting device and the replacement operation of the replacement mechanism, The control device controls the replacement operation so that the plating solution contained in the container is replaced with air while the electrolyte membrane is in contact with the substrate, and controls the lifting operation so that the electrolyte membrane is separated from the substrate after the replacement operation is completed.

2. The metal of the anode is a metal that is contained in a plating solution in the form of a divalent or higher metal ion, The tank is provided with a bubbling mechanism for bubbling the plating solution with a gas containing oxygen gas, 2. The metal film forming apparatus according to claim 1, further comprising a filter for filtering the plating solution, the filter being disposed between the tank and the pressure-feeding device.

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