FILM FORMING APPARATUS FOR FORMING METAL FILM

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2022-168657 filed on Oct. 20, 2022, the entire content of which is hereby incorporated by reference into this application.

BACKGROUND
Technical Field

The present disclosure relates to a film forming apparatus for forming a metal film having a predetermine pattern on a surface of a substrate.

Background Art

Conventionally, a film forming apparatus for forming a metal film by depositing metal on a substrate has been proposed (for example, JP 2016-125087 A). In JP 2016-125087 A, the film forming apparatus includes a housing containing a plating solution. The housing has an opening that is sealed with an electrolyte membrane. The film forming apparatus further includes a pressing mechanism that presses the substrate by the electrolyte membrane with a fluid pressure of the plating solution.

Here, when a metallic underlayer having a predetermined pattern on the surface of substrate is formed, the film forming apparatus applies a voltage between the anode and the substrate while pressing the substrate with the fluid pressure of the electrolyte membrane. Thus, the film forming apparatus can form a metal film having the predetermined pattern on the underlayer. However, when an underlayer of the predetermined pattern is not formed on the substrate, it is also conceivable to use, for example, a masking material disclosed in JP 2016-108586 A.

SUMMARY

Here, when a film is formed using a mask structure having a screen mask as the masking material, the mask structure is sandwiched between the substrate and the electrolyte membrane. In this condition, in order to ensure the adhesion between the substrate and the screen mask, the mask structure is pressed by the electrolyte membrane on which the fluid pressure of the plating solution is acting. However, since the frame supports the peripheral edge of the screen mask on a side adjacent to substrate, the electrolyte membrane may be damaged by being pressed against the opening edge of the frame.

The present disclosure has been made in view of the foregoing, and provides a film forming apparatus for forming a metal film capable of suppressing damage to an electrolyte membrane during pressing even when a mask structure is used.

In view of the foregoing, a film forming apparatus for forming a metal film according to the present disclosure is a film forming apparatus for forming a metal film having a predetermined pattern on a substrate by electroplating, with a mask structure sandwiched between an electrolyte membrane and a substrate. The film forming apparatus includes a pressing mechanism that presses the mask structure by the electrolyte membrane with a fluid pressure of a plating solution. The mask structure includes a screen mask in which a penetrating portion corresponding to the predetermined pattern is formed, and a frame that supports a peripheral edge of the screen mask on a side adjacent to the substrate. In the frame, an inner covering portion made of an elastic material softer than a material of the frame is formed along an opening edge contacting the electrolyte membrane.

According to the present disclosure, first, the mask structure is sandwiched between the electrolyte membrane and the substrate, and using the pressing mechanism, the mask structure is pressed by the electrolyte membrane on which a fluid pressure of the plating solution is acting. The peripheral edge of the screen mask is supported by the frame on the side adjacent to the substrate, so that the screen mask can be brought into close contact with the surface of the substrate. By the pressing of the electrolyte membrane, the penetrating portion of the screen mask is filled with an exudation solution (plating solution) exuded from the electrolyte membrane swollen by the plating solution. Since the penetrating portion has a shape corresponding to the predetermined pattern, a metal film having the predetermined pattern can be formed on the surface of the substrate by electroplating.

Here, since the frame supports the peripheral edge of the screen mask on the side adjacent to the substrate, the electrolyte membrane is pressed toward the opening edge of the frame with the fluid pressure of the plating solution. Even in such cases, since the inner covering portion made of an elastic material softer than the material of the frame is formed along the opening edge of the frame, the inner covering portion elastically deforms and the electrolyte membrane can be prevented from being damaged. Note that since the frame is harder than the inner covering portion, even if the frame is pressed by the electrolyte membrane, the shape of the frame is hardly deformed and the adhesion of the screen mask to the substrate can be maintained.

For example, an outer covering portion made of the soft elastic material may be further formed along an outer peripheral edge of the frame facing the electrolyte membrane.

At the time of film formation, the electrolyte membrane may be pressed toward the outer peripheral edge of the frame with the fluid pressure of the plating solution. Even in such cases, since the outer covering portion made of an elastic material softer than the material of the frame is formed along the outer peripheral edge of the frame facing the electrolyte membrane, the outer covering portion elastically deforms and the electrolyte membrane can be prevented from being damaged.

For example, an opposing surface formed between the opening edge and the outer peripheral edge and facing the electrolyte membrane may be covered with the soft elastic material such that the inner covering portion and the outer covering portion are continuous.

According to this example, the force that presses the electrolyte membrane toward the frame can be dispersed throughout the soft elastic material. As a result, it is possible to prevent stress from locally acting on the electrolyte membrane.

For example, the film forming apparatus includes a mount base on which the substrate is placed. The mount base includes a first recess for housing the substrate and a second recess for housing the mask structure while the substrate is housed in the first recess. The mount base may include an edge covering portion made of the soft elastic material along an opening edge of the second recess.

At the time of film formation, the electrolyte membrane may be pressed toward the opening edge of the second recess of the mount base with the fluid pressure of the plating solution. Even in such cases, since the edge covering portion is formed in the mount base along the opening edge of the second recess, it is possible to prevent the electrolyte membrane from being damaged.

For example, the screen mask may include a mesh portion in which an opening is formed in a grid pattern, and a mask portion including the penetrating portion, the mask portion being fixed to the mesh portion so as to face the substrate. The mask portion may elastically deform by pressing of the electrolyte membrane.

According to this example, at the time of film formation, the mask portion is pressed by the electrolyte membrane with the fluid pressure of the plating solution. Since the mask portion elastically deforms by the pressing of the electrolyte membrane, the adhesion of the mask portion to the substrate can be maintained.

According to the present disclosure, even when the mask structure is used, it is possible to suppress damage to the electrolyte membrane during pressing.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 2 is a schematic perspective view of a mask structure of the film forming apparatus shown in FIG. 1, and a schematic perspective view of a substrate on which a metal film is formed.

FIG. 3A is a partially enlarged cross-sectional view taken along line A-A shown in FIG. 2;

FIG. 3B is an enlarged cross-sectional view of a portion C of FIG. 3A;

FIG. 4 is a schematic cross-sectional view for explaining film formation by the film forming apparatus shown in FIG. 1.

FIG. 5A is a cross-sectional view of a main portion of FIG. 4;

FIG. 5B is a cross-sectional view at the time of film formation in the portion shown in FIG. 3B;

FIG. 6 is a flow chart for explaining an example of the metal film forming process using the film forming apparatus according to the embodiment of the present disclosure;

FIG. 7A is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 1;

FIG. 7B is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 2;

FIG. 7C is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 3; and

FIG. 8 is a partially enlarged cross-sectional view of a mount base of a film forming apparatus according to Modification 4.

DETAILED DESCRIPTION

First, the film forming apparatus 1 for forming a metal film according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view illustrating an example of the film forming apparatus for forming a metal film according to the embodiment of the present disclosure.

As shown in FIG. 1, the film forming apparatus 1 is a film forming apparatus for forming a metal film F having a predetermined pattern P on a substrate B by electroplating. At the time of film formation, a mask structure 60 is 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 a voltage between the anode 11 and the substrate B.

The film forming apparatus 1 includes a housing 15 containing the anode 11 and a plating solution L, a mount base 40 on which the substrate B is placed, and the mask structure 60. At the time of film formation, the mask structure 60 is placed on the mount base 40 together with the substrate B. The electrolyte membrane 13 is disposed between the mask structure 60 and the anode 11.

The film forming apparatus 1 includes a linear motion actuator 70 for raising and lowering the housing 15. In the present embodiment, for convenience of explanation, the electrolyte membrane 13 is disposed below the anode 11, and the mask structure 60 and the substrate B are disposed below the electrolyte membrane 13. However, the positional relation is not limited to this as long as the metal film F can be formed on the surface of the substrate B.

The substrate B functions as a cathode. The material of the substrate B is not particularly limited as long as the substrate B functions as a cathode (i.e., a conductive surface). The substrate B may be made of, for example, a metallic material such as aluminum or copper. When forming a wiring pattern using the metal film F, for the substrate B, a substrate having an underlayer of copper or the like formed on the surface of the insulating substrate made of a resin or the like may be used. In this case, after the metal film F is formed, the underlayer other than the portion on which the metal film F is formed is removed by etching or the like. In this way, a wiring pattern using the metal film F can be formed on the surface of the insulating substrate.

In one example, the anode 11 is a non-porous anode made of the same metal as the metal of the metal film. The anode 11 has a block shape or a flat plate shape. The anode 11 may be made of copper, for example. The anode 11 dissolves when a voltage is applied by the power supply 14. However, when a film is formed using only metal ions of the plating solution L, the anode 11 is an anode insoluble in the plating solution L. The anode 11 is electrically connected to the positive electrode of the power supply 14. The negative electrode of the power supply 14 is electrically connected to the substrate B via the mount base 40.

The plating solution L is a liquid containing the metal of the metal film to be formed in the state of ions. Examples of the metal may include copper, nickel, gold, silver, iron, and the like. The plating solution L is a solution obtained by dissolving (ionizing) these metals with an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid. Examples of the solvent of the solution include water and alcohol. For example, when the metal is copper, the plating solution L may be an aqueous solution containing copper sulfate, copper pyrophosphate, or the like.

The electrolyte membrane 13 is a membrane that can be impregnated with metal ions (i.e., can contain metal ions therein) together with the plating solution L when brought into contact 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 metal ions of the plating solution L can move toward the substrate B when the power supply 14 applies a voltage. Examples of the material of the electrolyte membrane 13 may include a resin having an ion exchange function such as a fluorine-based resin such as Nafion (registered trademark) available from DuPont. The thickness of the electrolyte membrane may be in the range of 20 μm to 200 μm. Specifically, the film thickness may be in the range of 20 m to 60 μm.

The housing 15 is made of a material insoluble in the plating solution L. The housing 15 includes a storage space 15a for storing the plating solution. The anode 11 is disposed in the storage space 15a of the housing 15. The storage space 15a includes an opening 15d on the side adjacent to the substrate B. The opening 15d of the housing 15 is covered with the electrolyte membrane 13. Specifically, the peripheral edge of the electrolyte membrane 13 is sandwiched between the housing 15 and a frame 17. Accordingly, the plating solution L in the storage space 15a can be sealed with the electrolyte membrane 13.

As shown in FIGS. 1 and 4, the linear motion actuator 70 raises and lowers the housing 15 such that the electrolyte membrane 13 and the mask structure 60 can be brought into contact with and separated from each other. In the present embodiment, the mount base 40 is fixed, and the housing 15 is moved up and down by the linear motion actuator 70. The linear motion actuator 70 is an electric actuator, and converts the rotational motion of the motor into a linear motion by a ball screw or the like (not shown). However, instead of an electric actuator, a hydraulic or pneumatic actuator may be used.

The housing 15 includes a supply port 15b for supplying the plating solution L to the storage space 15a. Further, the housing 15 includes a discharge port 15c for discharging the plating solution L from the storage space 15a. The supply port 15b and the discharge port 15c are holes communicating with the storage space 15a. The supply port 15b and the discharge port 15c are formed with the storage space 15a interposed therebetween. The supply port 15b is connected to a liquid supply pipe 50. The discharge port 15c is fluidly connected to a liquid discharge pipe 52.

The film forming apparatus 1 further includes a liquid tank 90, a liquid supply pipe 50, a liquid discharge pipe 52, and a pump 80. As shown in FIG. 1, the plating solution L is contained in the liquid tank 90. The liquid supply pipe 50 connects the liquid tank 90 and the housing 15. The liquid supply pipe 50 is provided with the pump 80. The pump 80 supplies the plating solution L from the liquid tank 90 to the housing 15. The liquid discharge pipe 52 connects the liquid tank 90 and the housing 15. The liquid discharge pipe 52 is provided with a pressure regulating valve 54. The pressure regulating valve 54 regulates the pressure (fluid pressure) of the plating solution L in the storage space 15a to a predetermined pressure.

In the present embodiment, by driving the pump 80, the plating solution L is sucked from the liquid tank 90 into the liquid supply pipe 50. The sucked plating solution L is pressure-fed from the supply port 15b to the storage space 15a. The plating solution L in the storage space 15a is returned to the liquid tank 90 via the discharge port 15c. In this way, the plating solution L circulates in the film forming apparatus 1.

Further, by continuing the driving of the pump 80, the fluid pressure of the plating solution L in the storage space 15a can be maintained at a predetermined pressure by the pressure regulating valve 54. The pump 80 is for pressing the mask structure 60 by the electrolyte membrane 13 on which the fluid pressure of the plating solution L is acting. Therefore, the pump 80 corresponds to a “pressing mechanism” in the present disclosure. However, the pressing mechanism is not particularly limited as long as the mask structure 60 can be pressed by the electrolyte membrane 13. Instead of the pump 80, an injection mechanism composed of a piston and a cylinder for injecting the plating solution may be used.

In one example, the mount base 40 is formed of a conductive material (e.g., metal). The mount base 40 includes a first recess 41 and a second recess 42. The first recess 41 is a recess for housing the substrate B. The second recess is a recess for housing the mask structure 60 while the substrate B is housed in the first recess 41.

FIG. 2 is a schematic perspective view of the mask structure 60 of the film forming apparatus 1 shown in FIG. 1 and a schematic perspective view of the substrate B on which the metal film F is formed. FIG. 3A is a partially enlarged cross-sectional view taken along line A-A of FIG. 2, and FIG. 3B is an enlarged cross-sectional view of the portion C of FIG. 3A.

The mask structure 60 includes a frame 61 and a screen mask 62. The screen mask 62 includes a penetrating portion 68 corresponding to the predetermined pattern P of the metal film F. The screen mask 62 includes a mesh portion 64 and a mask portion 65.

The mesh portion 64 includes a plurality of openings 64c formed in a grid pattern. Specifically, as shown in FIG. 3B, the mesh portion 64 is a mesh-like portion in which pluralities of oriented wires 64a, 64b are woven so as to cross each other. The plurality of wires 64a are arranged at intervals, and the plurality of wires 64b intersecting the plurality of wires 64a are arranged at intervals. As a result, the plurality of openings 64c are formed in the mesh portion 64 in a grid pattern. The material of the wires 64a, 64b is not particularly limited as long as the wires 64a, 64b have corrosion resistance to the plating solution L. Examples of the material of the wires 64a, 64b include metallic materials such as stainless steel, and resin materials such as polyester.

The mask portion 65 is fixed to the mesh portion 64 so as to face the substrate B. The mask portion 65 includes a penetrating portion 68 corresponding to the predetermined pattern P. The mask portion 65 is a portion that comes into close contact with the substrate B at the time of film formation by the pressure from the electrolyte membrane 13. The material of the mask portion 65 is not particularly limited as long as the mask portion 65 can be brought into close contact with the substrate B. The mask portion 65 may be compressed and elastically deform by the pressure from the electrolyte membrane 13. Examples of the material of the mask portion 65 may include a resin material such as an acrylic resin, a vinyl acetate resin, a polyvinyl resin, a polyimide resin, or a polyester resin. The screen mask 62 having the predetermined pattern P can be manufactured by a general silk screen manufacturing technique using an emulsion. Therefore, a detailed description of a method of manufacturing the screen mask 62 will be omitted.

The frame 61 supports a peripheral edge 62a of the screen mask 62 on the side adjacent to the substrate B (the mount base 40) opposite to the frame 61. Specifically, the peripheral edge 62a of the screen mask 62 is fixed to the frame 61. In the present embodiment, the screen mask 62 has a rectangular outer shape. Accordingly, the frame 61 has a rectangular frame-like shape. The material of the frame 61 is not particularly limited as long as the frame 61 can retain the shape of the mask structure 60. Examples of the material of the frame 61 may include a metallic material such as stainless steel, or a resin material such as a thermoplastic resin. The frame 61 is formed by punching a metallic plate, for example, and has a thickness of about 1 mm to 3 mm. Note that, for convenience of explanation, the thickness of the frame 61 is drawn to be thicker than the actual thickness in FIG. 3A and the like.

A covering portion 66 is formed on the surface of the frame 61. The covering portion 66 is made of an elastic material softer than the material of the frame 61. The covering portion 66 includes an inner covering portion 66A, an outer covering portion 66B, and a planar covering portion 66C.

As shown in FIGS. 3A and 5A, the inner covering portion 66A is formed along an opening edge 61a of the frame 61 contacting the electrolyte membrane 13. The inner covering portion 66A covers the opening edge 61a of the frame 61. Here, the opening edge 61a of the frame 61 is a ridge (edge portion) formed by an opposing surface 61c facing the electrolyte membrane 13 and an inner peripheral surface 61d forming an inner space 69 of the frame 61. The inner covering portion 66A includes an extending portion 66D extending from the opening edge 61a along the inner peripheral surface 61d.

The outer covering portion 66B is formed along an outer peripheral edge 61b of the frame 61 facing the electrolyte membrane 13. The outer covering portion 66B covers the outer peripheral edge 61b of the frame 61. Herein, the outer peripheral edge 61b of the frame 61 is a ridge (edge portion) formed by the opposing surface 61c facing the electrolyte membrane 13 and an outer peripheral surface 61e of the frame 61. The outer covering portion 66B has an extending portion 66E extending from the outer peripheral edge 61b along the outer peripheral surface 61e.

The planar covering portion 66C is formed on the surface (opposing surface) 61c between the opening edge 61a and the outer peripheral edge 61b. The planar covering portion 66C covers the opposing surface 61c. The planar covering portion 66C makes the inner covering portion 66A and the outer covering portion 66B a contiguous part. In the present embodiment, as shown in FIG. 3A, the covering portion 66 is formed in a part except for the surface where the peripheral edge 62a of the screen mask 62 is fixed.

The covering portion 66 is made of an elastic material softer than the material of the frame 61. The material of the covering portion 66 is not particularly limited as long as damage to the electrolyte membrane 13 can be avoided. The covering portion 66 may be compressed and elastically deform by the pressure from the electrolyte membrane 13. For example, the material of the covering portion 66 may be a rubber material such as silicone rubber (PMDS) or ethylene propylene diene rubber (EPDM). The hardness of the rubber material may be HS100 or less, specifically HS50 or less, in Shore A hardness. The “soft elastic material” is, for example, a material having a relatively low hardness measured by a hardness meter of a predetermined standard, and is a material having a low Young's modulus by a tensile test. The thickness of the covering portion 66 is smaller than the thickness of the frame 61. Specifically, the thickness of the covering portion 66 may be in the range of about ⅕ to 1/10 of the thickness of the frame 61.

Referring to FIG. 4 to FIG. 6, a film forming process using the film forming apparatus 1 will be described. First, as shown in FIG. 6, a placement step S1 is performed. In this step, the substrate B and the mask structure 60 are placed on the mount base 40. Specifically, the substrate B is housed in the first recess 41 of the mount base 40, and then the mask structure 60 is housed in the second recess 42. At this time, the alignment of the substrate B with respect to the anode 11 attached to the housing 15 may be adjusted, and the temperature of the substrate B may be adjusted.

Next, a pressing step S2 is performed. In this step, first, the linear motion actuator 70 is driven, and the housing 15 is lowered toward the mask structure 60 from the state shown in FIG. 1 to the state shown in FIG. 4. Next, the pump 80 is driven. As a result, the plating solution L is supplied to the storage space 15a of the housing 15. Since the pressure regulating valve 54 is provided in the liquid discharge pipe 52, the fluid pressure of the plating solution L in the storage space 15a is maintained at a predetermined pressure. Consequently, as shown in FIG. 4, the electrolyte membrane 13 deforms with a fluid pressure toward the inner space 69 of the frame 61, and the mask structure 60 can be sandwiched between the electrolyte membrane 13 and the substrate B. Furthermore, the mask structure 60 can be pressed by the electrolyte membrane 13 on which the fluid pressure of the plating solution L is acting.

Here, as shown in FIGS. 4 and 5A, since the peripheral edge 62a of the screen mask 62 is supported by the frame 61 on the side adjacent to the substrate B, the screen mask 62 can be brought into close contact with the surface of the substrate B. When the mask portion 65 is formed of a rubber material, the mask portion 65 is compressed and elastically deforms with the fluid pressure of the plating solution L, thereby improving the adhesion between the mask portion 65 and the substrate B.

Further, when the pressing of the electrolyte membrane 13 is continued, as shown in FIGS. 5A and 5B, the penetrating portion 68 formed in the screen mask 62 is filled with an exudation solution (plating solution) La exuded from the electrolyte membrane 13 swollen by the plating solution L.

As shown in FIG. 5A, the peripheral edge 62a of the screen mask 62 is supported on the side adjacent to the substrate B opposite to the frame 61. By this support, when the fluid pressure of the plating solution L acts on the electrolyte membrane 13, the electrolyte membrane 13 is pressed toward the opening edge 61a of the frame 61 and the outer peripheral edge 61b of the frame 61.

Along the opening edge 61a of the frame 61, the inner covering portion 66A made of an elastic material softer than the material of the frame 61 is formed. Further, along the outer peripheral edge 61b of the frame 61 facing the electrolyte membrane 13, the outer covering portion 66B made of an elastic material softer than the material of the frame 61 is formed. As a result, the inner covering portion 66A elastically deforms and the outer covering portion 66B elastically deforms, and the electrolyte membrane 13 can be prevented from being damaged.

In particular, unlike FIG. 5A, when the opposing surface 61c of the frame 61 protrudes toward the electrolyte membrane 13 than an opposing surface 40a of the mount base 40, the electrolyte membrane 13 is easily damaged by the outer peripheral edge 61b of the frame 61. Also when a gap is formed between a side surface 42a of the second recess 42 and the outer peripheral surface 61e of the frame 61, the electrolyte membrane 13 is easily damaged by the outer peripheral edge 61b of the frame 61.

However, as in the present embodiment, by providing the outer covering portion 66B in the frame 61, the outer covering portion 66B elastically deforms and the electrolyte membrane 13 can be prevented from being damaged. Further, when a gap is formed between the side surface 42a of the second recess 42 and the outer peripheral surface 61e of the frame 61, the outer covering portion 66B functions as a sealing member, and it is possible to prevent the plating solution L from entering the gap.

In addition, the opposing surface 61c of the planar covering portion 66C is formed with respect to the electrolyte membrane so that the inner covering portion 66A and the outer covering portion 66B are continuous, and the opposing surface 61c is covered with a soft elastic material. As a result, the force that presses the electrolyte membrane 13 toward the frame 61 can be dispersed throughout the soft elastic material. As a result, it is possible to prevent stress from locally acting on the electrolyte membrane 13.

The frame 61 is harder than the inner covering portion 66A. Therefore, even if the frame 61 is pressed by the electrolyte membrane 13, the shape of the frame 61 is hardly deformed, and the adhesion of the screen mask 62 to the substrate B can be maintained.

Next, a film forming step S3 is performed. In this step, a metal film F is formed while the pressing state by the electrolyte membrane 13 in the pressing step S2 is maintained. Specifically, a voltage is applied between the anode 11 and the substrate B. As a result, metal ions contained in the electrolyte membrane 13 moves through the exudation solution La to the surface of the substrate B, and metal ions are reduced at the surface of the substrate B. Since the exudation solution La filled in the penetrating portion 68 is sealed inside the penetrating portion 68 by the electrolyte membrane 13, the metal film F having the predetermined pattern can be formed on the surface of the substrate B (see FIG. 2). Furthermore, since the exudation solution La is uniformly pressurized by the pressing of the electrolyte membrane 13, it is possible to form a homogeneous metal film F. In manufacturing a wiring pattern using the metal film F, a conductive underlayer formed on the surface of the insulating substrate B may be etched.

FIGS. 7A to 7C are partial cross-sectional views of the mask structure of the film forming apparatus according to Modification 1 to Modification 3. These modifications differ from the embodiment shown in FIG. 3A in the aspect of a covering portion that covers the frame 61 of the mask structure 60. Therefore, differences from the above-described embodiment will be described, and the detailed description of the same configuration will be omitted.

For example, when the electrolyte membrane 13 does not come into direct contact with the outer peripheral edge 61b of the frame 61, only the inner covering portion 66A may be formed on the frame 61, as shown in FIG. 7A. Further, as shown in FIG. 7B, the inner covering portion 66A and the outer covering portion 66B may be separately formed on the frame 61. According to Modification 2 of FIG. 7B, in the above-described pressing step S2 and film forming step S3, the inner covering portion 66A and the outer covering portion 66B independently elastically deform by the pressing of the electrolyte membrane 13, so that the electrolyte membrane 13 can be prevented from being damaged.

As shown in FIG. 7C, the covering portion 66 is formed on the entire surface of the frame 61. That is, in Modification 3, a bottom covering portion 66F made of an elastic material softer than the material of the frame 61 is also formed between the frame 61 and the peripheral edge 62a of the screen mask 62. Therefore, since the bottom covering portion 66F elastically deforms by the pressing of the electrolyte membrane 13, the adhesion between the mask structure 60 and the substrate B can be enhanced.

FIG. 8 is a partially enlarged cross-sectional view of the mount base 40 of the film forming apparatus 1 according to Modification 4. In Modification 4, the mount base 40 includes an edge covering portion 48 made of an elastic material softer than the material of the frame 61 along an opening edge 42b of the second recess 42. Accordingly, even if the electrolyte membrane 13 is pressed toward the opening edge 42b of the second recess 42 with the fluid pressure of the plating solution L at the time of film formation, the edge covering portion 48 elastically deforms and the electrolyte membrane 13 can be prevented from being damaged.

In particular, when the opposing surface 40a of the mount base 40 protrudes toward the electrolyte membrane 13 than the opposing surface 61c of the frame 61, the electrolyte membrane 13 is easily damaged by the opening edge 42b of the second recess 42. Therefore, by providing the edge covering portion 48, damage to the electrolyte membrane 13 can be avoided. Further, in the present embodiment, since the edge covering portion 48 and the covering portion 66 are made of the same elastic material, it is possible to suppress wear caused by the contact between the edge covering portion 48 and the outer covering portion 66B.

EXAMPLES

The present disclosure will be described by the following examples.

Example

As a substrate for film formation, a glass epoxy substrate was prepared by impregnating a pile of glass fiber fabric with an epoxy resin. A copper foil was formed on the surface of the glass epoxy substrate. Next, a copper film was formed using the film forming apparatus according to the embodiment shown in FIG. 1. In the mask structure, a frame made of stainless steel was provided with a silicone-rubber covering portion having a Shore A hardness of HS50. As the plating solution, a copper sulfate aqueous solution (Cu-BRITE-SED) manufactured by JCU Corporation was used, and as an anode, a Cu plate was used. Nafion (registered trademark) available from DuPont was used for the electrolyte membrane. A copper film was formed under the electric film formation conditions including: a temperature of 42° C. and a fluid pressure of 1 MPa of the plating solution, a current density of 7 A/dm², and a cumulative pressing time of 500 seconds.

Comparative Example

A copper film was formed in the same manner as in Example. The mask structure differs from that of Example in that the stainless-steel frame is not provided with a covering portion.

Conditions of the electrolyte membranes according to the film forming apparatus of Example and the film forming apparatus of Comparative Example after film formation were checked. The electrolyte membrane of the film forming apparatus according to Example was not damaged. On the other hand, the electrolyte membrane of the film forming apparatus according to Comparative Example was damaged.

While the embodiment of the present disclosure has been described above, the present disclosure is not limited to the film forming apparatus according to the above-described embodiment, and includes all aspects included in the concepts of the present disclosure and the claims. In addition, each configuration may be selectively combined as appropriate so as to achieve the above-described problems to be solved and effects. For example, shapes, materials, arrangements, sizes, and the like of the constituent elements in the above-described embodiment may be appropriately changed according to specific aspects of the present disclosure.

FILM FORMING APPARATUS FOR FORMING METAL FILM

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