FILM FORMING APPARATUS FOR FORMING METAL FILM

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2022-168689 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, when the screen mask does not sufficiently adhere to the substrate, a metal film having a desired pattern may not occasionally be formed.

Specifically, the screen mask includes a penetrating portion corresponding to a predetermined pattern. At the time of film formation, the penetrating portion is filled with the plating solution (an exudation solution) exuded from the electrolyte membrane and the exudation solution is pressurized by the pressing of the electrolyte membrane. As a result, the exudation solution enters between the screen mask and the substrate, which could fail to form a metal film having a desired pattern.

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 the exuded solution entering between the screen mask and the substrate at the time of film formation.

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 having the predetermined pattern is formed. The screen mask includes a mesh portion having an opening formed in a grid pattern, and a mask portion having the penetrating portion and being fixed to the mesh portion so as to face the substrate. The mask portion includes a core portion that retains the shape of the mask portion, and a seal portion made of an elastic material softer than the material of the core portion and adapted to contact the substrate.

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. By the pressing, the seal portion of the mask portion elastically deformed contacts the surface of the substrate. Consequently, the screen mask can be brought into close contact with the substrate.

Meanwhile, 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. The filled exudation solution is pressurized by the pressing of the electrolyte membrane. As described above, the seal portion of the mask portion elastically deformed contacts the surface of the substrate. Further, the core portion is fixed to the mesh portion and is stiffer than the mask portion. Therefore, with the pressing of the electrolyte membrane, the shape of the penetrating portion can still be retained. 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.

For example, the seal portion may extend along a side wall surface forming the penetrating portion.

According to the example, since the seal portion extends along the side wall surface forming the penetrating portion, the core portion is covered with the seal portion. Therefore, at the time of film formation, the contact of the core portion with the exudation solution filled in the penetrating portion can be suppressed. As a result, deterioration of and damage to the core portion can be suppressed to thus maintain the stiffness of the mask portion.

For example, the core portion includes an opposite surface facing the substrate and the side wall surface forming the penetrating portion, and the seal portion may be formed along a ridgeline formed by the opposite surface and the side wall surface.

According to this example, since the seal portion is formed along the ridgeline of the core portion, the compressive deformability of the seal portion can be increased by the pressing of the electrolyte membrane. As a result, a metal film having a more accurate pattern can be formed.

For example, the hardness of the mask portion may gradually increase from the seal portion toward the core portion.

When the mask structure is repeatedly used, the seal portion repeatedly elastically deforms. This causes the seal portion and the core portion to more easily separate from each other at the interface therebetween. However, according to this example, the difference in hardness locally widened between the seal portion and the core portion is suppressed. As a result, the separation between the core portion and the seal portion can be prevented.

According to the present disclosure, at the time of film formation, the exudation solution entering between the screen mask and the substrate can be suppressed.

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

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;

FIG. 7D is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 4;

FIG. 8A is a schematic view for explaining a method of manufacturing a mask portion of the mask structure of FIG. 7B;

FIG. 8B is a schematic view for explaining a method of manufacturing a mask portion of the mask structure of FIG. 7C;

FIG. 8C is a schematic view for explaining a method of manufacturing a mask portion of the mask structure of FIG. 7D;

FIG. 9A is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 5; and

FIG. 9B is a partial cross-sectional view of a mask structure of a film forming apparatus according to Modification 6.

DETAILED DESCRIPTION

First, a 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 further disposed below the electrolyte membrane 13. However, the positional relation is not limited to this as long as the metal film 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). Examples of the material of the substrate B may include a metal 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. Examples of the anode 11 may include copper or the like. 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, or 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 may include water and alcohol. For example, when the metal is copper, examples of the plating solution L may include 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 film 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 μm 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 housing 15 includes an opening 15d in a position facing the substrate B in the storage space 15a. 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, the liquid supply pipe 50, the 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 frame 61 supports a peripheral edge 62a of the screen mask 62 on the side adjacent to the substrate B (the mount base 40). 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 metal 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.

The mesh portion 64 includes a plurality of openings 64c in a grid pattern. Specifically, as shown in FIG. 3B, the mesh portion 64 is a 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 mesh portion 64 includes the plurality of openings 64c 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 may include metal materials such as stainless steel, and resin materials such as polyester.

The mask portion 65 is fixed to a surface facing the substrate B of the surfaces of the mesh portion 64. 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 mask portion 65 has a core portion 65a that retains the shape of the mask portion 65 and a seal portion 65b that is made of an elastic material softer than the material of the core portion and adapted to contact the substrate B.

As shown in FIG. 3B, the core portion 65a is fixed to the mesh portion 64. Of the surfaces of the core portion 65a, a surface (an opposite surface 65c) facing the substrate B is provided with the seal portion 65b. The seal portion 65b is provided on the entire surface of the opposite surface 65c of the core portion 65a. The thickness of the seal portion 65b is smaller than the thickness of the core portion 65a. The thickness of the seal portion 65b may be in the range of around one-fifth to one-tenth of the thickness of the core portion 65a.

Examples of the material of the core portion 65a 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 core portion 65a 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.

In addition, examples of the material of the core portion 65a may include a metal material such as stainless-steel. In this case, the core portion 65a can be formed by attaching a metallic sheet having the penetrating portion 68 to the mesh portion 64. Further, the core portion 65a may have a laminated structure in which a resin layer and a metal layer are laminated.

The material of the seal portion 65b is an elastic material that is softer than the material of the core portion 65a. Specifically, examples of the material of the seal portion 65b may include a rubber material such as a silicone rubber (PMDS) or an ethylene propylene diene rubber (EPDM). However, the material of the seal portion 65b is not particularly limited as long as the seal portion 65b elastically deforms at the time of pressing by the electrolyte membrane 13.

Accordingly, an example of the material of the core portion 65a and an example of the material of the seal portion 65b may be a thermosetting resin or a rubber material. For example, the hardness of the seal portion 65b and the hardness of the core portion 65a may be adjusted by changing the type or the addition ratio of a hardener of these materials. In addition, in manufacturing the screen mask, the hardness of these portions may be adjusted by setting temperature conditions or the like for a cross-linking reaction or a polymerizing reaction.

The hardness of the core portion 65a may be equal to or greater than HS150 and more specifically, may be equal to or greater than H 200 in Shore A hardness. On the other hand, the hardness of the seal portion 65b may be equal to or less than HS90 and more specifically, may be equal to or less than HS50 in Shore A hardness. When the core portion 65a and the seal portion 65b are made of a rubber material, the relation in the hardness of these portions can be determined using a commercially available rubber hardness meter.

Referring to FIGS. 4 to 6, a film forming process using the film forming apparatus 1 will be described. First, as shown in FIG. 6, a placing 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 an 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. By the pressing, the elastically deformed seal portion 65b of the mask portion 65 contacts the surface of the substrate B. Consequently, the screen mask 62 can be brought into close contact with the substrate B.

Meanwhile, by the pressing of the electrolyte membrane 13, the penetrating portion 68 of the screen mask 62 is filled with the exudation solution (plating solution) La exuded from the electrolyte membrane 13 swollen with the plating solution L. By the pressing of the electrolyte membrane 13, the filled exudation solution La is pressurized. As described above, the elastically deformed seal portion 65b of the mask portion 65 contacts the surface of the substrate B. Further, the core portion 65a is fixed to the mesh portion 64 and is stiffer than the mask portion 65. Thus, regardless of the pressing of the electrolyte membrane 13, the shape of the penetrating portion 68 can be retained. Since the penetrating portion 68 has a shape corresponding to the predetermined pattern P, the metal film F having the predetermined pattern can be formed on the surface of the substrate B by electroplating.

Next, a film forming step S3 is performed. In this step, the 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 move through the exudation solution La to the surface of the substrate B, and the 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. Note that 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 7D are partial cross-sectional views of the mask structure of the film forming apparatus according to Modification 1 to Modification 4. These modifications differ from the embodiment shown in FIG. 3A in the form of the mask portion. Therefore, differences from the above-described embodiment will be described, and the detailed description of the same configuration will be omitted.

For example, as shown in FIG. 7A, in Modification 1, the seal portion 65b may extend along a side wall surface 65e of the core portion 65a including the penetrating portion 68. In this way, the core portion 65a is covered with the seal portion 65b. Therefore, it is possible to suppress the core portion 65a contacting the exudation solution La filled in the penetrating portion 68 at the time of film formation. As a result, degradation of and damage to the core portion 65a can be suppressed to thus enable the stiffness of the mask portion 65 to be maintained. In addition, the seal portion 65b can protect the corners including a ridgeline 65f of the core portion 65a. For example, the seal portion 65b is formed by immersing the core portion 65a in a flowable material that forms the seal portion 65b (e.g., a material 6B of FIG. 8B) and then solidifying the material.

Further, as shown in FIGS. 7B to 7D, in Modification 2 to Modification 4, the core portion 65a includes the opposite surface 65c facing the substrate B and the side wall surface 65e including the penetrating portion 68. The seal portion 65b is formed along the ridgeline 65f formed by the opposite surface 65c and the side wall surface 65e. Note that in these drawings, the ridgeline 65f extends perpendicularly with respect to the face of each drawing. Here, the ridgeline 65f is an opening edge forming the penetrating portion 68 by the core portion 65a. This opening edge is the opening edge on a side opposite to the substrate B (on a side facing the mesh portion 64).

According to these modifications, the seal portion 65b is partially formed along the ridgeline 65f of the core portion 65a. That is, the opposite surface 65c of the core portion 65a is exposed from the seal portion 65b. The pressing of the electrolyte membrane 13 can increase the compressive deformability of the seal portion 65b. As a result, the metal film F having a more accurate pattern can be formed.

Here, in Modification 2 shown in FIG. 7B, the seal portion 65b is formed in an edge area along the ridgeline 65f of the opposite surface 65c of the core portion 65a. In the center area of the opposite surface 65c other than the edge area, the opposite surface 65c is exposed from the seal portion 65b. With the seal portion 65b partially provided in the opposite surface 65c, the compressive deformability of the seal portion 65b can be increased.

The seal portion 65b shown in FIG. 7B can be manufactured as shown in FIG. 8A. The opposite surface 65c of the core portion 65a is brought into contact with a sheet material 6A corresponding to the seal portion 65b (see the drawing at the top of FIG. 8A). With such a state, the sheet material 6A is irradiated with a laser light G1 toward the edge area along the ridgeline 65f of the core portion 65a so that the sheet material 6A is partially fused to the core portion 65a (see the drawing in the middle of FIG. 8A). After that, the sheet material 6A is removed so that the seal portion 65b shown in FIG. 7B can be obtained (see the drawing at the bottom of FIG. 8A).

In Modification 3 shown in FIG. 7C, a recess 65g is formed in the edge area along the ridgeline 65f of the opposite surface 65c of the core portion 65a. The seal portion 65b enters the recess 65g and protrudes toward the substrate B as compared to the exposed opposite surface 65c. In comparison with FIG. 7B, in Modification 3, the compressive deformability of the seal portion 65b can be further increased by increasing the thickness of the seal portion 65b. In addition, the seal portion 65b enters the recess 65g so that the seal portion 65b fits into the core portion 65a. This makes it possible to mechanically restrain the seal portion 65b to the core portion 65a.

The seal portion 65b shown in FIG. 7C can be manufactured as shown in FIG. 8B. The opposite surface 65c of the core portion 65a is brought into contact with a molten rubber or resin material 6B corresponding to the seal portion 65b (see the drawing at the top of FIG. 8B). Specifically, the core portion 65a is brought into contact with the material 6B until reaching a position where the material 6B enters the recess 65g. After that, the core portion 65a is pulled up from the material 6B and then, the material 6B is solidified so that a portion 6C including the seal portion 65b is formed (see the drawing in the middle of FIG. 8B). The area excluding the edge area along the ridgeline 65f of the core portion 65a is irradiated with a laser light G2 to remove the resin. In this way, the seal portion 65b shown in FIG. 7C can be obtained (see the drawing at the bottom of FIG. 8B).

In Modification 4 shown in FIG. 7D, the seal portion 65b is formed in the edge area along the ridgeline 65f of the opposite surface 65c of the core portion 65a. The opposite surface 65c is exposed from the seal portion 65b in the center area of the opposite surface 65c other than the edge area. In addition, the seal portion 65b also extends in the side wall surface 65e of the core portion 65a. With the seal portion 65b partially provided in the opposite surface 65c, the compressive deformability of the seal portion 65b can be increased. In addition, the seal portion 65b can protect the corners including the ridgeline 65f of the core portion 65a.

The seal portion 65b shown in FIG. 7D can be manufactured as shown in FIG. 8C. The opposite surface 65c of the core portion 65a is brought into contact with the molten rubber or resin material 6B corresponding to the seal portion 65b (see the drawing at the top of FIG. 8C). After that, the core portion 65a is pulled up from the material 6B and then, the material 6B is solidified so that a portion 6D including the seal portion 65b is formed (see the drawing in the middle of FIG. 8C). The area excluding the edge area along the ridgeline 65f of the core portion 65a is irradiated with the laser light G2 to remove the resin. In this way, the seal portion 65b shown in FIG. 7D can be obtained (see the drawing at the bottom of FIG. 8C).

FIGS. 9A and 9B are partial cross-sectional views of the mask structure of the film forming apparatus according to Modification 5 and Modification 6. These modifications differ from the embodiment shown in FIG. 3A in the form of the mask portion. Therefore, differences from the above-described embodiment will be described, and the detailed description of the same configuration will be omitted.

In Modification 5 and Modification 6, the hardness of the mask portion 65 gradually increases from the seal portion 65b toward the core portion 65a. When the mask structure 60 is repeatedly used, the seal portion 65b repeatedly elastically deforms. This causes the seal portion 65b and the core portion 65a to more easily separate from each other at the interface therebetween. However, according to these examples, the difference in hardness locally widened between the seal portion 65b and the core portion 65a is suppressed. As a result, the separation between the core portion 65a and the seal portion 65b can be prevented.

In Modification 5 shown in FIG. 9A, the seal portion 65b is formed only on the side contacting the substrate B, and the hardness of the mask portion 65 gradually changes along the thickness direction of the mask portion 65. Specifically, the mask portion 65 gradually becomes harder from the seal portion 65b side toward the core portion 65a on the mesh portion 64 side. In Modification 5, in the mask portion 65, the portion to be compressed and elastically deformed by the pressing of the electrolyte membrane 13 is the seal portion 65b. The other portion is the core portion 65a. The hardness of the mask portion 65 may be changed as follows. Specifically, in producing the mask portion 65, the degree of the crosslinking reaction or the polymerization reaction of the resin material or the rubber material is changed by heating with a temperature gradient in the thickness direction using a heater.

In Modification 6 shown in FIG. 9B, the seal portion 65b is formed so as to surround the core portion 65a. That is, in Modification 6, unlike Modification 5, the seal portion 65b extends to the side wall surface 65e forming the penetrating portion 68. As a result, it is possible to suppress the exposure of the core portion 65a. The hardness of the mask portion 65 may be changed as follows. Specifically, in producing the mask portion 65, the degree of the crosslinking reaction or the polymerization reaction of the resin material or the rubber material is changed by heating with a temperature gradient from the center to the periphery thereof using microwaves.

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. As the mask structure, the mask structure shown in FIG. 9B was prepared. Specifically, the surface of the mask portion was swollen to adjust the Shore A hardness of the seal portion to H540. Note that the Shore A hardness of the core portion is HS600. 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 film formation conditions including: a temperature of the plating solution of 42° C., a fluid pressure of 1 MPa of the electrolytic solution, a current density of 7 A/dm², and a film forming time of 500 seconds.

Comparative Example 1

A copper film was formed in the same manner as in Example. The difference from Example is that polyethylene terephthalate (PET) having a thickness of 100 μm was used as the mask portion of the mask structure.

Comparative Example 2

A copper film was formed in the same manner as in Example. The difference from Example is that a silicone rubber having a Shore A hardness of HS50 with a thickness of 100 μm was used as the mask portion of the mask structure.

In Example and Comparative Examples 1 and 2 after film formation, the shapes of the formed metal films were checked. In Comparative Example 1, the plating solution (exudation solution) entering between the mask portion and the substrate was confirmed. In Example and Comparative Example 2, there was no such phenomenon. This is because the material of the mask portion of Comparative Example 1 was hard and thus, the adhesion between the mask portion and the substrate was insufficient.

Meanwhile, the structural analysis was performed on the mask portions of Example and Comparative Examples 1 and 2 by pressing of the electrolyte membrane. It was found that the mask portion of Comparative Example 2 significantly deformed, with the cross-sectional area of the penetrating portion reduced by about 5% after pressing. Note that in Example and Comparative Example 1, there was almost no change before and after pressing.

These results can confirm that a metal film having a desired pattern and a desired cross-sectional shape can be formed by providing the core portion in the mask portion and providing the seal portion made of an elastic material softer than the material of the core portion and contacting the substrate.

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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