Film forming apparatus for metal film

Abstract

Provided is a film forming apparatus for a metal film capable of accurately forming the metal film in a predetermined pattern using a masking member including a mask portion made of a rubber material. The masking member of the film forming apparatus includes the mask portion having a penetrating portion formed therein and made of a rubber material. An insulative porous plate is disposed between an electrolyte membrane and the mask portion so as to cover the penetrating portion, the porous plate having formed therein a plurality of pores through which a plating solution passes.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority from Japanese patent application JP 2024-229489 filed on Dec. 25, 2024, the entire content of which is hereby incorporated by reference into this application.BACKGROUNDTechnical Field

[0002] The present disclosure relates to a film forming apparatus for a metal film.Background Art

[0003] As a technique of this type, for example, JP 2024-63738 A proposes a film forming apparatus for a metal film including a masking member that forms the metal film in a predetermined pattern on a surface of a substrate by electroplating. This masking member includes a mask portion in which a penetrating portion corresponding to the predetermined pattern is formed. The mask portion is made of a rubber material.

[0004] At the time of film forming, the mask portion of the masking member is sandwiched between the electrolyte membrane and the substrate, and the electrolyte membrane is pressed against the substrate with the hydraulic pressure of a plating solution. By applying voltage between an anode and the substrate with such a pressed state, the metal film can be formed on the surface of the substrate.SUMMARY

[0005] However, in a case where the mask portion of the masking member shown in JP 2024-63738 A is made of a rubber material, at the time of film forming, when the mask portion is pressed by the electrolyte membrane, the mask portion is non-uniformly comprehensively deformed in some cases. This makes it difficult to form a metal film in a predetermined pattern corresponding to the shape of the penetrating portion.

[0006] The present disclosure has been made in view of the foregoing and provides a film forming apparatus for a metal film capable of accurately forming a metal film in a predetermined pattern using a masking member including a mask portion made of a rubber material.

[0007] In view of the aforementioned problem, a film forming apparatus for a metal film according to the present disclosure is a film forming apparatus for a metal film that forms the metal film in a predetermined pattern on a surface of a substrate by electroplating. The film forming apparatus includes: a container having an opening formed at a position opposing the substrate, the opening covered by an electrolyte membrane with a plating solution contained in the container; a pressing mechanism configured to press the substrate by the electrolyte membrane with a hydraulic pressure of the plating solution contained in the container; an anode disposed inside the container at a position opposing the electrolyte membrane; and a masking member disposed between the electrolyte membrane and the substrate, the masking member having formed therein a penetrating portion in the predetermined pattern. The masking member includes a mask portion having the penetrating portion formed therein and made of a rubber material. A porous plate is disposed between the electrolyte membrane and the mask portion so as to cover the penetrating portion, the porous plate having formed therein a plurality of pores through which the plating solution passes.

[0008] In some aspect, the mask portion includes a first portion facing the electrolyte membrane and a second portion facing the substrate. The masking member includes a mesh portion woven with a wire, the mesh portion being disposed between the first portion and the second portion and retaining the first portion and the second portion.

[0009] In another aspect, the masking member includes a frame that fixes a peripheral edge of the mesh portion. The porous plate is disposed, in an unrestricted state relative to the frame, between the electrolyte membrane and the mask portion.

[0010] In another aspect, the mask portion is fixed on a surface opposing the substrate of opposite surfaces of the porous plate. A mesh woven with a wire is attached at a peripheral edge of the porous plate so as to surround the porous plate. An outer peripheral edge of the mesh is fixed to the frame.

[0011] In further another aspect, the porous plate is made of chemically reinforced glass and the pores are through-holes formed along a thickness direction of the porous plate.

[0012] According to the present disclosure, a metal film in a predetermined pattern can be accurately formed using a masking member having a mask portion made of a rubber material.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic cross-sectional view showing an example of a film forming apparatus for a metal film according to an embodiment of the present disclosure;

[0014] FIG. 2 is a schematic perspective view showing a porous plate, a masking member, and a substrate on which a metal film is formed that are shown in FIG. 1;

[0015] FIG. 3 is a schematic cross-sectional view for explaining film forming using the film forming apparatus shown in FIG. 1;

[0016] FIG. 4 is a schematic cross-sectional view for explaining forming of a metal film using the film forming apparatus shown in FIG. 3;

[0017] FIG. 5A is a schematic cross-sectional view of the film forming apparatus according to a modification of the film forming apparatus shown in FIG. 4;

[0018] FIG. 5B is a schematic cross-sectional view of the film forming apparatus according to another modification;

[0019] FIG. 6 is a schematic perspective view showing a modification of the masking member shown in FIG. 2;

[0020] FIG. 7A is a schematic cross-sectional view of the film forming apparatus using the masking member shown in FIG. 6; and

[0021] FIG. 7B is a schematic cross-sectional view of the film forming apparatus according to another modification.DETAILED DESCRIPTION

[0022] A film forming apparatus 1 for a metal film according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view showing an example of the film forming apparatus for a metal film according to the embodiment of the present disclosure.

[0023] As shown in FIG. 1, the film forming apparatus 1 is a film forming apparatus configured to form a metal film F in a predetermined pattern P on a substrate B by electroplating, with a masking member 60 sandwiched between an electrolyte membrane 13 and the substrate B. Specifically, the film forming apparatus 1 includes an anode 11, the electrolyte membrane 13, and a power supply 14 that applies voltage between the anode 11 and the substrate B.

[0024] The film forming apparatus 1 includes a container 15 that contains the anode 11 and a plating solution L, a mount base 40 on which the substrate B is mounted, and the masking member 60. At the time of film forming, the masking member 60 is mounted on the mount base 40, together with the substrate B. The electrolyte membrane 13 is disposed between the masking member 60 and the anode 11.

[0025] The film forming apparatus 1 includes a linear motion actuator 70 that raises and lowers the container 15. As a matter of convenience for explanation, the present embodiment is based on the premise that the electrolyte membrane 13 is disposed below the anode 11, and the masking member 60 and the substrate B are disposed further below. However, as long as the metal film F can be formed on the surface of the substrate B, the positional relations are not limited to those described above.

[0026] The substrate B functions as a cathode. The substrate B is a plate-like substrate. In the present embodiment, the substrate B is a rectangular board. An opposing surface, which opposes the electrolyte membrane 13 (screen mask 62), of the surfaces of the substrate B, is a film forming surface functioning as the cathode. As long as the substrate B functions as the cathode (i.e., a conductive surface), the material of the substrate B is not particularly limited. The substrate B may be made of, for example, a metal material, such as aluminum or copper.

[0027] In the present embodiment, as shown in FIG. 2, since the pattern (wiring pattern) P is formed from the metal film F, a substrate with a base layer Bb of copper or the like formed on a surface of an insulating board Ba of resin or the like is used as the substrate B. In this case, after forming the metal film F, the base layer Bb excluding a portion where the metal film F was formed is removed by etching or the like. In this manner, the pattern P with the metal film F can be formed on the surface of the insulating board Ba.

[0028] The anode 11 is, as an example, a non-porous anode (for example, having no pores) made of the same metal as that of the metal film. The anode 11 has a block-like or a plate-like shape. Examples of the material of the anode 11 may include copper. The anode 11 is dissolved when voltage is applied by the power supply 14. However, when the film is formed only with metal ions of the plating solution L, the anode 11 is insoluble in the plating solution L. The anode 11 is electrically connected to a positive electrode of the power supply 14. A negative electrode of the power supply 14 is electrically connected to the substrate B via the mount base 40.

[0029] The plating solution L is a solution containing metal in an ionic form of the metal film to be formed. Examples of the metal may include copper, nickel, gold, silver, or iron. The plating solution L is a solution with these metals dissolved (ionized) with acid such as a nitric acid, a phosphoric acid, a succinic acid, a sulfuric acid, or a pyrophosphoric acid. Examples of solvent of the solution may include water or alcohol. When the metal is copper, for example, examples of the plating solution L may include an aqueous solution containing copper sulfate, copper pyrophosphate, and the like.

[0030] The electrolyte membrane 13 is a membrane that can be impregnated with (contain) the metal ions together with the plating solution L by being contacted with the plating solution L. The electrolyte membrane 13 is a flexible membrane. The material of the electrolyte membrane 13 is not particularly limited as long as the metal ions of the plating solution L can be moved toward the substrate B when voltage is applied by the power supply 14. Examples of the material of the electrolyte membrane 13 may include resin having an ion-exchange function, such as a fluorine-based resin, for example, Nafion® manufactured by Du Pont Corporation. The film thickness of the electrolyte membrane 13 may be in a range of 20 μm to 200 μm and may be in a range of 20 μm to 60 μm.

[0031] The container 15 is made of material insoluble in the plating solution L. A storing space 15a that stores the plating solution L is formed in the container 15. The anode 11 is disposed in the storing space 15a of the container 15. An opening 15d is formed on the substrate B side of the storing space 15a. The opening 15d of the container 15 is covered with the electrolyte membrane 13. Specifically, a peripheral edge of the electrolyte membrane 13 is sandwiched between the container 15 and a frame 17. In this manner, the plating solution L in the storing space 15a can be sealed with the electrolyte membrane 13.

[0032] As shown in FIG. 1 and FIG. 3, the linear motion actuator 70 raises and lowers the container 15 so that the electrolyte membrane 13 and the masking member 60 are flexibly contacted and separated. In the present embodiment, the mount base 40 is fixed and the container 15 is raised and lowered by the linear motion actuator 70. The linear motion actuator 70 is an electric actuator and converts a rotational motion of a motor into a linear motion by means of a ball screw or the like (not shown). However, in place of the electric actuator, a hydraulic or a pneumatic actuator may be used.

[0033] In the container 15, a supply flow path 15b for supplying the plating solution L to the storing space 15a is formed. Further, in the container 15, a discharge flow path 15c for discharging the plating solution L from the storing space 15a is formed. The supply flow path 15b and the discharge flow path 15c are holes communicating with the storing space 15a. The supply flow path 15b and the discharge flow path 15c are formed across the storing space 15a. The supply flow path 15b is fluidly connected to a liquid supply pipe 51. The discharge flow path 15c is fluidly connected to a liquid discharge pipe 52.

[0034] The film forming apparatus 1 further includes a liquid tank 90, the liquid supply pipe 51, the liquid discharge pipe 52, and a pump 80. As shown in FIG. 1, the liquid tank 90 contains the plating solution L. The liquid supply pipe 51 connects the liquid tank 90 and the container 15. The liquid supply pipe 51 is provided with the pump 80. The pump 80 supplies the plating solution L from the liquid tank 90 to the container 15. The liquid discharge pipe 52 connects the liquid tank 90 and the container 15. The liquid discharge pipe 52 is provided with a pressure regulating valve 54. The pressure regulating valve 54 adjusts a pressure (hydraulic pressure) of the plating solution L in the storing space 15a to a predetermined pressure.

[0035] In the present embodiment, the plating solution L is sucked into the liquid supply pipe 51 from the liquid tank 90 by driving the pump 80. The sucked plating solution L is pumped through the supply flow path 15b to the storing space 15a. The plating solution L in the storing space 15a is returned to the liquid tank 90 via the discharge flow path 15c. In this manner, the plating solution L circulates inside the film forming apparatus 1.

[0036] Further, by continuing driving the pump 80, the hydraulic pressure of the plating solution L in the storing space 15a can be maintained at a predetermined pressure by means of the pressure regulating valve 54. The pump 80 is adapted to press, via a porous plate 30, the masking member 60 by means of the electrolyte membrane 13 on which the hydraulic pressure of the plating solution Lis exerted. However, as long as the masking member 60 can be pressed by the electrolyte membrane 13, the pressing mechanism is not particularly limited. In place of the pump 80, an ejection mechanism including a piston and a cylinder that eject the plating solution L may be adopted.

[0037] The mount base 40 is made of a conductive material (e.g., metal) as an example. A recess 41 is formed in the mount base 40. The recess 41 is a portion recessed from an opposing surface of the mount base 40 for housing the substrate B.

[0038] The masking member 60 includes a frame 61 and the screen mask 62. The frame 61 supports a peripheral edge 62a of the screen mask 62 on the electrolyte membrane 13 side relative to the frame 61. Specifically, the peripheral edge of the screen mask 62 is securely fixed to the frame 61. In the present embodiment, the screen mask 62 has a rectangular outer shape. Therefore, the frame 61 has a rectangular frame-like shape. The material of the frame 61 is not particularly limited, as long as the shape of the masking member 60 can be retained. Examples of the material of the frame 61 may include a metal material such as stainless steel or a resin material such as a thermoplastic resin. The frame 61 is formed by, for example, stamping a metal plate and has a thickness of around 1 mm to 3 mm.

[0039] A penetrating portion 68 corresponding to the predetermined pattern P of the metal film F is formed in the screen mask 62. The screen mask 62 includes a mesh portion 64 and a mask portion 65. The screen mask 62 is a flexible mask having around 50 μm to 400 μm. The screen mask 62 is supported on a surface, which is on the substrate B side, of the surfaces of the frame 61.

[0040] A peripheral edge of the mesh portion 64 is securely fixed to the frame 61. The mesh portion 64 is stretched so as to cover an opening of the frame 61 with a predetermined tension. The mesh portion 64 has a plurality of openings formed in a grid pattern. Specifically, as shown in FIG. 4, the mesh portion 64 is a mesh-like portion (mesh) in which a plurality of oriented wires is woven so as to intersect with each other. The plurality of wires is arranged at intervals from each other, and a plurality of wires intersecting with these wires is arranged at intervals from each other. As a result, the plurality of openings is formed in a grid pattern in the mesh portion 64. The material of the wires is not particularly limited as long as the wires have corrosion resistance against the plating solution L. For example, examples of the material of the wires may include a resin material such as a polyester resin. Other than those described above, the mesh portion 64 may be made of a resin material such as an acrylic resin, a vinyl acetate resin, a polyvinyl chloride resin, a polypropylene resin, a polyethylene resin, a polystyrene resin, a polycarbonate resin, a polyimide resin, or a urethane resin, as long as the wires can be formed.

[0041] The mask portion 65 is retained by the sheet-like mesh portion 64. The penetrating portion 68 corresponding to the predetermined pattern P is formed in the mask portion 65. The mask portion 65 is a portion that closely adheres to the substrate B by being pressed by the electrolyte membrane 13 at the time of film forming. Although the material of the mask portion 65 is not particularly limited as long as it can closely adhere to the substrate B, in the present embodiment, the mask portion 65 is made of a rubber material. Examples of the material of the mask portion 65 may include a rubber material such as silicone rubber (PMDS) or ethylene propylene diene monomer (EPDM). The hardness of the rubber material may be equal to or smaller than HS100, or equal to or smaller than HS50 in Shore A hardness.

[0042] The mask portion 65 is made of an elastic material that is compressively elastically deformed by being pressed by the electrolyte membrane 13. In order to secure the adhesion to the substrate B, the deformation amount in the thickness direction (pressing direction) of the mask portion 65 due to the pressing by means of the electrolyte membrane 13 may be in a range of 5 to 20% of the thickness of the mask portion before deformation. The screen mask 62 having the predetermined pattern P can be manufactured by a typical silk screen manufacturing technique using an emulsion. Therefore, the detailed description of the method for manufacturing the screen mask 62 will be omitted.

[0043] As shown in FIG. 4, the mask portion 65 includes a first portion 65a facing the electrolyte membrane 13 and a second portion 65b facing the substrate B. The mesh portion 64 is a portion that is disposed between the first portion 65a and the second portion 65b and that retains the first portion 65a and the second portion 65b. That is, the mesh portion 64 is sandwiched between the first portion 65a and the second portion 65b, and the first portion 65a and the second portion 65b are coupled via openings of the mesh portion 64. The force exerted on the mesh portion 64 due to the hydraulic pressure of the plating solution L at the time of film forming can be uniformly dispersed in the second portion 65b. As a result, the deformation of the second portion 65b can be made uniform, so that the sealing property between the mask portion 65 and the substrate B can be stably secured.

[0044] In the present embodiment, the porous plate 30 is disposed between the electrolyte membrane 13 and the mask portion 65. The porous plate 30 is a plate having formed therein a plurality of pores through which the plating solution L passes. The material of the porous plate 30 is not particularly limited as long as the porous plate 30 is electrically insulated from the anode 11, but may be material having a high Young's modulus in the present embodiment, and the example of the material may include a resin material such as polyether ether ketone (PEEK), an acrylic resin, and polytetrafluoroethylene (PTFE), glass such as chemically reinforced glass, and ceramics such as alumina. The porous plate 30 may be those in which the surface of a metal plate body is subjected to insulating treatment. The porous plate 30 may be made of chemically reinforced glass among these materials. Note that the Young's modulus of the chemically reinforced glass is around 76100 MPa.

[0045] As described above, the porous plate 30 has formed therein the plurality of pores through which the plating solution L passes. In addition, at the time of film forming, an electric field toward the substrate B from the anode 11 is formed in the plurality of pores. In the present embodiment, when the porous plate 30 is made of chemically reinforced glass, the pores are through-holes formed along the thickness direction of the porous plate 30. Such pores can be formed by laser machining or the like. In the present embodiment, the pore diameter may be 50 to 100 μm and the pitch of the pores may be 50 to 100 μm. With these ranges satisfied, it is possible to form a film in a homogeneous wiring pattern by supplying the plating solution L to the penetrating portion 68 through the pores of the porous plate 30 while securing the rigidity of the porous plate 30.

[0046] The porous plate 30 is disposed so as to cover the penetrating portion 68 of the mask portion 65. As described above, the masking member 60 includes the frame 61 that fixes the peripheral edge of the mesh portion 64. The porous plate 30 is disposed, in an unrestricted state relative to the frame 61, between the electrolyte membrane 13 and the mask portion 65. In the present embodiment, the porous plate 30 is releasably disposed on a surface, which opposes the electrolyte membrane 13, of the surfaces of the mask portion 65. Note that the porous plate 30 may be fixed integrally with the mask portion 65.

[0047] Referring to FIG. 1 to FIG. 4, a method for film forming using the film forming apparatus 1 will be described. First, a disposing step is performed. In this step, as shown in FIG. 1, the substrate B is disposed on the mount base 40. Specifically, the substrate B is housed in the recess 41 of the mount base 40. In the present embodiment, with the substrate B housed in the recess 41, the surface of the substrate B projects from the opposing surface (surface opposing the electrolyte membrane 13) of the mount base 40. As a result, the mask portion 65 of the masking member 60 can be uniformly contacted to the surface of the substrate B.

[0048] Next, the masking member 60 is disposed in the mount base 40. In doing so, the masking member 60 is housed such that the surface of the substrate B is housed within an internal space of the frame 61 of the masking member 60. Specifically, as shown in FIG. 4, the surface of the substrate B is covered with the mask portion 65 of the masking member 60. Further, the porous plate 30 is disposed so as to cover all the penetrating portions 68 formed in the mask portion 65.

[0049] Next, a pressing step is performed. In this step, the substrate B is pressed by the electrolyte membrane 13, via the porous plate 30 and the screen mask 62, with the hydraulic pressure of the plating solution L that has contacted the electrolyte membrane 13. First, the linear motion actuator 70 is actuated, thereby lowering the container 15 toward the porous plate 30 and the masking member 60 from the state shown in FIG. 1 to the state shown in FIG. 3.

[0050] Then, the pump 80 is actuated, thereby supplying the plating solution L to the storing space 15a of the container 15. Since the liquid discharge pipe 52 is provided with the pressure regulating valve 54, the hydraulic pressure of the plating solution L in the storing space 15a is maintained at a predetermined pressure. As a result, the porous plate 30 and the screen mask 62 can be sandwiched between the electrolyte membrane 13 and the substrate B due to the hydraulic pressure of the plating solution L. Further, the screen mask 62 can be pressed by the electrolyte membrane 13 on which the hydraulic pressure of the plating solution L is exerted.

[0051] As shown in FIG. 4, such pressing allows the mask portion 65 to closely adhere to the surface of the substrate B. Since the mask portion 65 is made of a rubber material, the mask portion 65 is compressively elastically deformed due to the hydraulic pressure of the plating solution L, so that the adhesion between the mask portion 65 and the substrate B is improved. Here, in the present embodiment, the porous plate 30 is disposed between the electrolyte membrane 13 and the mask portion 65. Therefore, with the hydraulic pressure of the plating solution L, the electrolyte membrane 13 presses the mask portion 65 via the porous plate 30. Thus, the mask portion 65 can be uniformly, compressively elastically deformed.

[0052] Further, since the porous plate 30 is in an unrestricted state, when pressed, the porous plate 30 can be made to follow the deformation of the mask portion 65. As a result, even when the porous plate 30 is made of a brittle material such as chemically reinforced glass, the stress exerted on the porous plate 30 can be reduced. This can improve the durability of the porous plate 30. When such pressing by means of the electrolyte membrane 13 is continued, the plating solution L is exuded from the electrolyte membrane 13 swollen with the plating solution L. An exuded leachate (plating solution) La passes through the pores of the porous plate 30, and is filled in the penetrating portion 68 formed in the screen mask 62 and pressurized.

[0053] Next, a film forming step is performed. In this step, the metal film F is formed while keeping the pressing state by means of the electrolyte membrane 13. Specifically, voltage is applied between the anode 11 and the substrate B. This causes the metal ions contained in the plating solution L to pass through the electrolyte membrane 13. The metal ions that have passed through the electrolyte membrane 13 move to the surface of the substrate B via the leachate La and are reduced on the surface of the substrate B. As a result, the metal ions of the plating solution L pass through the penetrating portion 68 and the metal ions that have passed are deposited on the surface of the substrate B. In this manner, as shown in FIG. 2, the metal film F in the predetermined pattern P corresponding to the shape of the penetrating portion 68 can be formed on the surface of the substrate B. In this manner, by uniformly deforming the mask portion 65 made of a rubber material, the metal film F in the predetermined pattern P can be accurately, homogeneously formed.

[0054] Now, in the conventional film forming apparatuses, the electrolyte membrane enters the mask portion as the number of times of film forming increases, which deforms the mesh portion up to the surface of the substrate in some cases. As a result, a pattern corresponding to the shape of the mesh portion 64 was formed in the metal film in some cases. However, in the present embodiment, since the porous plate 30 is disposed so as to cover the penetrating portion 68 of the mask portion 65, the electrolyte membrane 13 does not enter the penetrating portion 68. As a result, the homogeneous metal film F can be formed.

[0055] Thereafter, the linear motion actuator 70 raises the container 15 to detach the substrate B from the electrolyte membrane 13 and the substrate B is removed from the mount base 40. Note that when a wire is manufactured with the metal film F, the conductive base layer Bb formed on the surface of the insulating board Ba of the substrate B may be etched so as to maintain a portion where the metal film F is formed.

[0056] With reference to FIGS. 5 to 7, the film forming apparatus according to modifications will be described below. In the film forming apparatus according to FIGS. 1 to 4, the mask portion 65 is retained by the mesh portion 64 of the masking member 60, while in the modifications below, the porous plate 30 retains the mask portion 65. That is, these modifications differ in the configuration of the masking member 60. Therefore, in the modifications below, only the different configurations will be described.

[0057] Specifically, as shown in FIG. 5A and FIG. 5B, in this modification, the porous plate 30 is fixed to the frame 61. In FIG. 5A and FIG. 5B, the mask portion 65 is integrally formed on a surface opposing the substrate B of opposite surfaces of the porous plate 30. Unlike the mesh portion, since the porous plate 30 is not easily deformed by the pressing by means of the electrolyte membrane 13, the forming accuracy of the pattern P of the metal film F to be formed can be improved.

[0058] Further, in FIG. 5B, a cushioning portion 69 corresponding to the shape of the mask portion 65 is formed on a surface opposing the electrolyte membrane 13 of the opposite surfaces of the porous plate 30. The cushioning portion 69 is made of the same material as that of the mask portion 65, but the material is not particularly limited as long as it elastically deforms by the pressing force from the electrolyte membrane 13. With such a cushioning portion 69 provided, a portion where the electrolyte membrane 13 contacts the porous plate 30 at the time of film forming is reduced, thereby being able to suppress damage to the electrolyte membrane 13 due to contact with the porous plate 30.

[0059] In a modification shown in FIG. 6, the mask portion 65 is integrally formed on the surface opposing the substrate B of the opposite surfaces of the porous plate 30. A mesh 32 woven with a wire is attached at a peripheral edge 31 of the porous plate 30 so as to surround the porous plate 30. The mesh 32 is in a rectangular shape and may be made of material and wire that are the same as those illustrated in the aforementioned mesh portion. The center of the mesh 32 opens so as to correspond in size to the rectangular porous plate 30. An inner peripheral edge of an opening (not shown) at the center of the mesh 32 is securely attached with an adhesive or the like to the peripheral edge 31 of the porous plate 30 in an overlapping manner. An outer peripheral edge of the mesh 32 is fixed to a surface 61a of the frame 61 with an adhesive or the like.

[0060] According to the present modification, since the porous plate 30 is in an unrestricted state relative to the frame 61 via the flexible mesh 32, the mesh 32 sags by the pressing by means of the electrolyte membrane 13, thereby enabling the porous plate 30 to follow the deformation of the mask portion 65. The damage due to the deformation of the porous plate 30 is suppressed, so that the durability of the porous plate 30 can be improved. When such pressing by means of the electrolyte membrane 13 is continued, the plating solution L is exuded from the electrolyte membrane 13 swollen with the plating solution L. The exuded leachate (plating solution) La passes through the pores of the porous plate 30, and is filled in the penetrating portion 68 formed in the mask portion 65 and pressurized. Further, since the mask portion 65 is integrally formed with the porous plate 30, as shown in FIG. 7A, a portion other than those in the thickness direction of the mask portion 65 can be deformed. As a result, the forming accuracy of the pattern P of the metal film F can be improved.

[0061] Further, in FIG. 7B, the cushioning portion 69 corresponding to the shape of the mask portion 65 is further formed on the surface opposing the electrolyte membrane 13 of the opposite surfaces of the porous plate 30. The cushioning portion 69 is made of the same material as that of the mask portion 65, but the material is not particularly limited as long as it elastically deforms by the pressing force from the electrolyte membrane 13. With such a cushioning portion 69 provided, a portion where the electrolyte membrane 13 contacts the porous plate 30 at the time of film forming is reduced, thereby being able to suppress damage to the electrolyte membrane 13 due to contact with the porous plate 30. Further, as shown in FIG. 7B, when the mesh 32 is also sandwiched between the mask portion 65 and the cushioning portion 69, leakage of the leachate La exuded from the electrolyte membrane 13 from the vicinity of the frame 61 can be reduced.Example

[0062] A metal film was formed using the film forming apparatus shown in FIG. 1 and the film forming apparatus of a modification of FIG. 5A. A mask portion with a penetrating portion formed therein was formed on both sides of an LCP resin mesh portion having a wire diameter of 20 μm and 420 mesh, using silicone rubber. In this manner, the masking member having the mesh portion and the masking portion was produced. Note that of the thickness of the mask portion, the thickness of the first portion was 30 μm and the thickness of the second portion was 20 μm. Next, as the porous plate, chemically reinforced glass having a thickness of 200 μm, a pore size of 100 μm, and a pitch of 100 μm was prepared. A substrate was prepared in which copper (Cu) was sputtered on a wafer having a square surface with a length of one side of 5 mm.

[0063] Thereafter, a metal film having a thickness of 2.5 μm was formed on the surface of the substrate by solid electro deposition (SED) using a device having the same configuration as that of the film forming apparatus including the porous plate, under an evacuated environment. The film forming conditions were: film forming temperature: 40° C., plating solution: 1 M of copper sulfate and 0.2 M of sulfuric acid, anode: iridium oxide electrode (insoluble anode), inter-electrode distance of anode-cathode: 5 mm, pressurization: 0.6 MPa, retention time: 10 min., and current: 3.5 ASD.

[0064] As a comparative example, film forming was performed without providing the porous plate of the example under the same conditions as those of the example, using the film forming apparatus shown in FIG. 1. Defects of the formed films of the example and the comparative example were checked. The results have shown that no defect was found in the metal film of the example, while in the metal film of the comparative example, a pattern corresponding to the shape of the mesh portion of the masking member was formed. This proved that with the porous plate provided as in the example, a homogeneous metal film is formed.

[0065] The embodiment of the present disclosure has been described above in detail, but the present disclosure is not limited to the aforementioned embodiment, and various design changes can be made within the scope without departing from the spirit of the present disclosure described in the claims.

Claims

1. A film forming apparatus for a metal film that forms the metal film in a predetermined pattern on a surface of a substrate by electroplating, the film forming apparatus comprising:a container having an opening formed at a position opposing the substrate, the opening covered by an electrolyte membrane with a plating solution contained in the container;a pressing mechanism configured to press the substrate by the electrolyte membrane with a hydraulic pressure of the plating solution contained in the container;an anode disposed inside the container at a position opposing the electrolyte membrane; anda masking member disposed between the electrolyte membrane and the substrate, the masking member having formed therein a penetrating portion in the predetermined pattern,whereinthe masking member includes a mask portion having the penetrating portion formed therein and made of a rubber material, anda porous plate is disposed between the electrolyte membrane and the mask portion so as to cover the penetrating portion, the porous plate having formed therein a plurality of pores through which the plating solution passes.

2. The film forming apparatus for a metal film according to claim 1, whereinthe mask portion comprises a first portion facing the electrolyte membrane and a second portion facing the substrate, andthe masking member comprises a mesh portion woven with a wire, the mesh portion being disposed between the first portion and the second portion and retaining the first portion and the second portion.

3. The film forming apparatus for a metal film according to claim 2, whereinthe masking member comprises a frame that fixes a peripheral edge of the mesh portion, andthe porous plate is disposed, in an unrestricted state relative to the frame, between the electrolyte membrane and the mask portion.

4. The film forming apparatus for a metal film according to claim 1, whereinthe mask portion is fixed on a surface opposing the substrate of opposite surfaces of the porous plate,a mesh woven with a wire is attached at a peripheral edge of the porous plate so as to surround the porous plate, andan outer peripheral edge of the mesh is fixed to a frame.

5. The film forming apparatus for a metal film according to claim 1, wherein the porous plate is made of chemically reinforced glass and the pores are through-holes formed along a thickness direction of the porous plate.

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