METHOD FOR FORMING METAL FILM AND MASK USED IN THE METHOD

Abstract

To provide a film deposition method of a metal film in which the film deposition quality of the metal film deposited partially on a surface of a substrate is improved.SOLUTION: Provided is a film deposition method for depositing a metal film derived from metal ions on a surface of a substrate B with a prescribed pattern by applying a voltage between an anode 11 and the substrate as a cathode in a state that a mask 30 is arranged between an electrolytic film 13 contacting an electrolyte L and the substrate B, the mask 30 having through holes 34a to 34d corresponding to the prescribed pattern, which penetrate from the electrolytic film side toward the substrate side. The method includes the steps of: bringing the electrolytic film into contact with the mask; pressing the mask onto the substrate by raising liquid pressure of the electrolyte; and depositing the metallic film by applying a voltage between the anode and the substrate. The mask has a communication space formed for communicating between the open hole and the outside of the mask at the time of deposition.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for forming a metal film in a predetermined pattern on the surface of a substrate, and a mask used in the method. [Background technology]

[0002] Conventionally, metal has been partially deposited on the surface of a substrate to form a metal coating having a predetermined pattern (for example, Patent Document 1). Patent Document 1 describes a surface treatment device that includes a masking plate that covers an opening formed in a container that contains an electrolytic solution (hereinafter also referred to as electrolytic solution) containing metal ions, a conductive member that is disposed in the container and spaced apart from the masking plate, a solid electrolyte membrane (hereinafter also referred to as electrolyte membrane) that is disposed between the masking plate and the substrate, and a power supply unit that applies a voltage between the conductive member and the substrate, with the conductive member serving as the anode and the substrate serving as the cathode.

[0003] In this surface treatment device, while the electrolyte membrane is pressed against the surface of the substrate, the electrolyte solution contained in the container at a predetermined hydraulic pressure penetrates through the through holes in the masking plate into the part of the electrolyte membrane that corresponds to the shape of the through holes. Then, a voltage is applied between the conductive member and the substrate using a power supply unit. As a result, the metal ions impregnated in the electrolyte membrane move to the substrate in contact with the electrolyte membrane and are reduced on the surface of the substrate. As a result, metal is partially precipitated on the surface of the substrate according to the shape of the through holes in the masking plate, and a metal film is formed on the surface of the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-108586 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when a metal is partially deposited on the surface of a substrate to form a metal coating of a predetermined pattern, an electrolyte membrane may be attached to the container so as to cover the opening of the container, and a masking plate may be disposed between the electrolyte membrane and the substrate. When the liquid pressure of the electrolyte solution contained in the container is increased with the electrolyte membrane in contact with the surface of the masking plate, the electrolyte membrane is pressed against the surface of the masking plate, and the masking plate is pressed against the substrate. At this time, the electrolyte membrane comes into contact with the surface of the substrate in the region of the through-hole of the masking plate, following the shape of the through-hole.

[0006] When the liquid pressure of the electrolyte is increased, the liquid derived from the electrolyte seeps out to the substrate side. When the through-holes of the masking plate are filled with the liquid, the liquid pressure of the electrolyte in the container and the liquid pressure of the liquid in the through-holes of the masking plate may become equal. In this case, the force applied from the electrolyte membrane to the masking plate is reduced, so the force pressing the masking plate against the substrate is also reduced. As a result, during film formation, metal ions that have migrated to the substrate side through the electrolyte membrane may enter between the masking plate and the substrate, making it impossible to form a metal film of the desired pattern.

[0007] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a method for forming a metal coating that improves the film formation quality of a metal coating that is partially formed on the surface of a substrate, and a mask used in the film formation method. [Means for solving the problem]

[0008] In view of the above problems, a method for forming a metal film according to the present invention includes the steps of: disposing a mask having through-holes according to a predetermined pattern, penetrating from the solid electrolyte membrane side toward the substrate side, between a solid electrolyte membrane in contact with an electrolytic solution containing metal ions; applying a voltage between an anode and the substrate serving as a cathode; and reducing the metal ions contained inside the solid electrolyte membrane to form a metal film derived from the metal ions in the predetermined pattern on a surface of the substrate, the method including: covering an opening formed in a container that contains the electrolytic solution; the step of contacting the solid electrolyte membrane with the mask; the step of increasing the liquid pressure of the electrolyte solution contained in the container while the solid electrolyte membrane is in contact with the mask, thereby pressing the mask against the substrate; and the step of applying a voltage between the anode and the substrate while the solid electrolyte membrane is in contact with the mask and while the liquid pressure of the electrolyte solution is increased, thereby depositing the metal coating, wherein the mask used during deposition is a mask in which a communication space is formed that communicates between the through hole and the outside of the mask.

[0009] According to the present invention, the electrolyte membrane covering the opening of the container is brought into contact with the mask, and the liquid pressure of the electrolyte solution is increased to press the mask against the substrate. At this time, the electrolyte membrane conforms to the shape of the through-hole in the region of the through-hole of the mask, and thus the electrolyte membrane comes into contact with the surface of the substrate. In this manner, a voltage is applied between the anode and the substrate with the electrolyte membrane in contact with the mask and the liquid pressure of the electrolyte solution increased, and a metal coating having a predetermined pattern is formed on the surface of the substrate.

[0010] Here, when the liquid pressure of the electrolyte solution is increased while the electrolyte membrane is in contact with the mask, the liquid derived from the electrolyte solution seeps out to the side of the substrate. In the membrane forming method according to the present invention, a mask having a communication space that connects the through-holes of the mask with the outside of the mask is used during membrane formation, so that the liquid is discharged from the electrolyte membrane through the communication space to the outside of the mask without filling the through-holes of the mask.

[0011] Therefore, when the liquid pressure of the electrolyte solution contained in the container is increased during film formation, the force pressing the electrolyte membrane against the mask can be maintained. Therefore, the force of adhering the mask to the substrate can also be maintained. In this way, since the mask can be kept in close contact with the substrate during film formation, metal ions that have migrated to the substrate side through the electrolyte membrane are prevented from entering between the mask and the substrate, and a metal coating having a desired pattern can be formed.

[0012] In a preferred embodiment, the mask has a groove formed therein, the groove extending from an inner wall surface forming the through hole to an outer wall surface of the mask, and the communicating space is a space formed in the groove. According to this embodiment, the groove can be easily formed in the mask by cutting or the like.

[0013] According to this aspect, when the electrolyte membrane covers the groove, the liquid can be made to seep directly into the groove through the electrolyte membrane. In this case, the liquid is directly discharged from the groove to the outside of the mask without filling the through-holes of the mask. Also, when the substrate covers the groove, the liquid seeps into the through-holes of the mask through the electrolyte membrane. In this case, the liquid is discharged from the groove to the outside of the mask without filling the through-holes of the mask. In this way, during film formation, the force pressing the electrolyte membrane against the mask can be maintained, and the mask can be kept in close contact with the substrate. Therefore, during film formation, metal ions that have migrated to the substrate side through the electrolyte membrane can be prevented from entering between the mask and the substrate, and a metal coating of a desired pattern can be formed.

[0014] In a preferred embodiment, the mask has a communication hole extending from the inner wall surface forming the through hole to the outer wall surface of the mask, and the communication space is a space formed inside the communication hole. According to this embodiment, the liquid seeps into the through hole of the mask through the electrolyte membrane and is discharged from the communication hole to the outside of the mask without filling the through hole. Even if the electrolyte membrane is deformed due to an increase in the liquid pressure of the electrolyte solution, the electrolyte membrane does not narrow the communication space, so the liquid can be reliably discharged to the outside of the mask.

[0015] The present invention also provides a mask used in the above-mentioned metal coating deposition method. When the mask is used in the above-mentioned metal coating deposition method, the through-holes of the mask communicate with the outside of the mask through the communication space during deposition. Therefore, the mask can discharge the liquid that has seeped out to the substrate side through the communication space without storing it in the through-holes of the mask. Therefore, when the electrolyte membrane is in contact with the mask and the liquid pressure of the electrolyte solution is increased, a pressing force is continuously applied to the mask from the electrolyte membrane. Therefore, during deposition, the mask continues to adhere to the substrate. As a result, when the mask is used to deposit a metal coating, it is possible to prevent metal ions that have migrated to the substrate side through the electrolyte membrane from entering between the mask and the substrate, and a metal coating having a desired pattern can be deposited. Effect of the Invention

[0016] According to the present invention, it is possible to improve the quality of the metal coating that is partially formed on the surface of a substrate. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic cross-sectional view showing an example of a film forming apparatus used in a method for forming a metal coating according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the film forming apparatus shown in FIG. 1, showing a state in which an electrolyte solution is poured into a container. [Figure 3A] 2 is a schematic perspective view showing an example of a mask used in the film forming apparatus shown in FIG. [Figure 3B] 3B is a view taken along the arrow A in FIG. 3A. [Figure 3C] 3B is a view taken along the arrow B shown in FIG. 3A. [Figure 4] 1 is a flowchart illustrating an example of a method for forming a metal coating according to an embodiment of the present invention. [Diagram 5] 1. FIG. 4 is a schematic perspective view showing a modified example of a mask used in the film forming apparatus shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] First, a film forming apparatus 1 used in the method for forming a metal film according to an embodiment of the present invention will be described.

[0019] Fig. 1 is a schematic cross-sectional view showing an example of a film forming apparatus 1 used in a method for forming a metal film according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the film forming apparatus 1 shown in Fig. 1, showing a state in which an electrolytic solution L is poured into a container 15. Fig. 3A is a schematic perspective view showing an example of a mask 30 used in the film forming apparatus 1 shown in Fig. 1. Fig. 3B is a view seen from the direction A shown in Fig. 3A. Fig. 3C is a view seen from the direction B shown in Fig. 3A.

[0020] 1 and 2, the film forming apparatus 1 includes an anode 11, a solid electrolyte membrane (hereinafter also referred to as electrolyte membrane) 13, a power supply unit 14 that applies a voltage between the anode 11 and a substrate B, and a container 15 that contains the anode 11 and an electrolytic solution L containing metal ions and has an opening 15d covered with the electrolyte membrane 13. In this embodiment, a mask 30 is placed on the substrate B, and the electrolyte membrane 13 is disposed between the mask 30 and the anode 11.

[0021] The film forming apparatus 1 may further include a base 110 on which the substrate B is placed, a frame 17 provided on the base 110 so as to surround the substrate B, and a linear actuator 70, as necessary.

[0022] As shown in FIG. 2, the film forming apparatus 1 applies a voltage between the anode 11 and the substrate B using a power supply unit 14 while the electrolyte membrane 13 is in contact with the substrate B, thereby reducing metal ions contained inside the electrolyte membrane 13, thereby forming a metal coating (not shown) on the surface of the substrate B.

[0023] In this embodiment, for convenience of explanation, the positional relationship of the components of the film forming apparatus 1 is specified on the premise that the electrolyte membrane 13 is disposed below the anode 11, and the mask 30 and the substrate B are disposed further below that. However, as long as a metal coating can be formed on the surface of the substrate B, the positional relationship is not limited to this, and for example, the film forming apparatus 1 in FIG. 1 may be upside down. For example, when the film forming apparatus 1 in FIG. 1 is upside down, the mask 30 may be fixed to the frame 17.

[0024] The substrate B functions as a cathode. The material of the substrate B is not particularly limited as long as it functions as a cathode (i.e., a surface having electrical conductivity). The substrate B may be made of a metal material such as aluminum or copper, or the surface of a resin or the like may be coated with a metal layer such as copper.

[0025] The base 110 holds the substrate B below the housing 15 so that the substrate B faces the electrolyte membrane 13. In this embodiment, a mask 30 having a predetermined pattern is placed on the surface of the substrate B. The mask 30 is for forming a metal film having a predetermined pattern on the surface of the substrate B. The configuration of the mask 30 will be described later.

[0026] The base 110 is formed of a conductive material (e.g., metal), for example. In this case, the negative electrode of the power supply unit 14 is electrically connected to the base 110, and thus the substrate B is electrically connected to the negative electrode of the power supply unit 14 via the base 110.

[0027] The anode 11 is, for example, a non-porous (e.g., non-porous) anode made of the same metal as the metal coating, and is a block-shaped or flat anode. Examples of the material of the anode 11 include copper. The anode 11 may be dissolved by applying a voltage using the power supply unit 14, but if the film is formed using only the electrolyte L, the anode 11 does not need to be dissolved. The anode 11 is attached to a container 15 made of, for example, an insulating material. The anode 11 is electrically connected to the positive electrode of the power supply unit 14.

[0028] The electrolyte L is a liquid containing the metal of the metal film to be formed in an ion state, and examples of the metal include copper, nickel, gold, silver, and iron. The electrolyte L is a solution in which these metals are dissolved (ionized) 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 electrolyte L can be an aqueous solution containing copper sulfate, copper pyrophosphate, or the like.

[0029] The electrolyte membrane 13 is a flexible membrane that can be impregnated (contained) with metal ions by contacting it with the electrolytic solution L. The electrolyte membrane 13 is not particularly limited as long as it can reduce metal ions on the surface of the substrate B and precipitate metal derived from the metal ions when a voltage is applied from the power supply unit 14. Examples of materials for the electrolyte membrane 13 include resins having an ion exchange function, such as fluororesins such as Nafion (registered trademark) manufactured by DuPont.

[0030] As shown in FIG. 1, the anode 11 and the electrolyte membrane 13 are attached to the container 15, and the container 15, the anode 11, and the electrolyte membrane 13 form a container space 15c for containing the electrolytic solution L. The anode 11 is attached to the inner surface of the container 15 arranged to surround the periphery of the anode 11. The container 15 also has an opening 15d that opens to the side of the base material B. The opening 15d opens downward, and the electrolyte membrane 13 is attached to the container 15 so as to cover the opening 15d. As shown in FIG. 2, the container 15 has a structure in which the electrolytic solution L contained in the container space 15c directly contacts the anode 11 and the electrolyte membrane 13. The container 15 is made of a material that is insoluble in the electrolytic solution L.

[0031] As shown in FIG. 1 and FIG. 2, the linear actuator 70 raises and lowers at least one of the container 15 and the base 110 so that the electrolyte membrane 13 and the mask 30 can be moved toward and away from each other. In this embodiment, the base 110 is fixed, and the container 15 is raised and lowered by the linear actuator 70. The linear actuator 70 is provided on the upper part of the container 15. The linear actuator 70 is, for example, an electric actuator, and converts the rotational motion of a motor into linear motion by a ball screw or the like (not shown). The linear actuator 70 raises and lowers the container 15 relative to the base 110, making it possible to bring the electrolyte membrane 13 toward and away from the mask 30, which will be described later. The device for raising and lowering the container 15 may be a hydraulic or pneumatic cylinder or the like.

[0032] As shown in Fig. 1, the frame 17 is attached to the base 110 so as to surround the substrate B. As shown in Fig. 2, when the housing 15 is lowered by the linear actuator 70, the electrolyte membrane 13 is sandwiched between the housing 15 and the frame 17 from above and below. As shown in Fig. 2, the frame 17 is disposed at a predetermined distance from the substrate B, thereby forming an external space (outside) S of the mask 30. The frame 17 may be attached to the housing 15 so as to sandwich the electrolyte membrane 13 between the housing 15 from above and below.

[0033] The container 15 is formed with a supply flow path 15a for supplying the electrolytic solution L to the storage space 15c and a discharge flow path 15b for discharging the electrolytic solution L from the storage space 15c. The supply flow path 15a and the discharge flow path 15b are holes communicating with the storage space 15c and are formed on either side of the storage space 15c. The supply flow path 15a is fluidly connected to a liquid supply pipe 50 described later, and the discharge flow path 15b is fluidly connected to a liquid discharge pipe 52 described later.

[0034] As shown in FIG. 1 and FIG. 2, the mask 30 is placed on the surface of the base material B and is disposed between the electrolyte membrane 13 and the base material B, and has flexibility. The material of the mask 30 may be resin, rubber, or metal. This can improve the chemical stability, chemical resistance (not deteriorated by the electrolyte L), and water resistance (not dissolved in water) of the mask 30. For example, when the material of the mask 30 is silicone rubber (PMDS) or ethylene propylene diene rubber (EPDM), the mask is in a film or sheet shape, which makes it easy to give the mask 30 flexibility and compressive deformation, and makes it easy to adhere the mask 30 to the base material B. When a metal is selected as the material of the mask 30, the mask 30 is in a foil shape, and the metal needs to be surface-treated to insulate the mask 30.

[0035] The mask 30 has one surface 32u that faces the electrolyte membrane 13 during film formation, and the other surface 32l that contacts the surface of the substrate B. The mask 30 further has a side surface 32s that connects the one surface 32u and the other surface 32l. As shown in FIGS. 3A to 3C, the mask 30 has four through holes 34a to 34d that penetrate from the one surface 32u to the other surface 32l. In this embodiment, a case will be described in which four through holes 34a to 34d of the same size are provided, but the size, shape, number, etc. of the through holes of the mask 30 may be appropriately changed depending on the pattern of the film to be formed on the surface of the substrate B.

[0036] Each of the through holes 34a to 34d is defined by an inner wall surface 36a to 36d extending from one surface 32u to the other surface 32l. In each of the through holes 34a to 34d, an internal space 35a to 35d is formed by the inner wall surfaces 36a to 36d. Each of the inner wall surfaces 36a to 36d is a surface that perpendicularly intersects with the one surface 32u and the other surface 32l.

[0037] As shown in FIG. 3A and FIG. 3B, the mask 30 has grooves 38a-38d extending from the inner wall surfaces 36a-36d of the through holes 34a-34d to the side surface (outer wall surface) 32s of the mask 30. In this embodiment, the grooves 38a-38d are formed on one surface 32u, recessed from the one surface 32u toward the other surface 32l. Therefore, when the electrolyte membrane 13 contacts the one surface 32u of the mask 30, the grooves 38a-38d are covered by the electrolyte membrane 13. The spaces of the grooves 38a-38d become communication spaces that communicate the internal spaces 35a-35d of the through holes 34a-34d with the external space S of the mask 30 during film formation. The cross-sectional shape of the grooves 38a-38d is not particularly limited, and may include a semicircular shape as shown in FIG. 3A, or may be a rectangular shape, a V-shape, or the like.

[0038] The film forming apparatus 1 further includes a liquid tank T, a liquid supply pipe 50, a liquid discharge pipe 52, and a pump P.

[0039] 1, an electrolyte L is contained in a liquid tank T. A liquid supply pipe 50 connects the liquid tank T and the container 15. A pump P that supplies the electrolyte L from the liquid tank T to the container 15 is provided in the liquid supply pipe 50.

[0040] The liquid discharge pipe 52 connects the liquid tank T and the housing 15. The electrolyte L flows through the inside of the liquid discharge pipe 52 from the housing 15 to the liquid tank T. A pressure regulating valve 54 is interposed in the liquid discharge pipe 52. This prevents the pressure (liquid pressure) of the electrolyte L contained in the housing space 15c from exceeding a predetermined pressure.

[0041] By rotating the pump P, the electrolyte L is sucked from the liquid tank T into the liquid supply pipe 50, and the electrolyte L is pumped from the supply flow path 15a to the accommodation space 15c. The electrolyte L used in the accommodation space 15c during film formation is returned to the liquid tank T via the discharge flow path 15b. At this time, by continuing to rotate the pump P, the liquid pressure of the electrolyte L in the accommodation space 15c can be maintained at a predetermined pressure P1.

[0042] With the electrolyte membrane 13 in contact with the mask 30, the liquid pressure of the electrolytic solution L is increased, so that the mask 30 is pressed against the substrate B. At this time, the electrolyte membrane 13 is subjected to the liquid pressure P1, so that the electrolyte membrane 13 conforms to the shapes of the inner wall surfaces 36a-36d of the through holes 34a-34d in the regions of the through holes 34a-34d of the mask 30, as shown in Fig. 2, and thus the electrolyte membrane 13 comes into contact with the surface of the substrate B. In this state, a voltage is applied between the anode 11 and the substrate B using the power supply unit 14, so that a metal film is formed on the surface of the substrate B.

[0043] Next, a film forming method using the film forming apparatus 1 will be described. Fig. 4 is a flow chart for explaining an example of a film forming method of a metal film according to an embodiment of the present invention. In the film forming method according to the present embodiment, a voltage is applied between the anode 11 and the substrate B in a state where a mask 30 having through holes 34a-34d according to a predetermined pattern that penetrates from the electrolyte membrane 13 side toward the substrate B side is placed between the electrolyte membrane 13 in contact with the electrolytic solution L and the substrate B, and a metal film derived from the metal ions is formed on the surface of the substrate B in a predetermined pattern by reducing the metal ions contained inside the electrolyte membrane 13.

[0044] First, in this film formation method, the base material B is placed on the base 110 (S100). At this time, the alignment of the base material B with respect to the anode 11 attached to the container 15 may be adjusted, and the temperature of the base material B may be adjusted.

[0045] Next, a step is performed in which the electrolyte membrane 13 covering the opening 15d of the container 15 that contains the electrolytic solution L is brought into contact with the mask 30 (S200). In this step, the linear actuator 70 lowers the container 15 relative to the base 110, so that the electrolyte membrane 13 is brought into contact with one surface 32u of the mask 30. When the stroke of the linear actuator 70 reaches a predetermined value, the lowering of the container 15 stops.

[0046] Next, a step of storing the electrolyte L in the storage space 15c of the storage body 15 is performed by rotating the pump P (S300). In this step, the electrolyte L sucked from the liquid tank T by the pump P is supplied to the storage body 15 via the liquid supply pipe 50. Since the pressure adjustment valve 54 is interposed in the liquid discharge pipe 52, the liquid pressure of the electrolyte L in the storage space 15c is maintained at a predetermined pressure P1 by continuing to rotate the pump P.

[0047] When the liquid pressure of the electrolyte solution L contained in the container 15 is increased while the electrolyte membrane 13 is in contact with the mask 30, the electrolyte membrane 13 is pressed against the mask 30 by the liquid pressure P1. As a result, the mask 30 adheres closely to the surface of the substrate B. For example, when the mask 30 is made of silicone rubber (PMDS) or ethylene propylene diene rubber (EPDM), the mask 30 is compressed and deformed by the liquid pressure P1 of the electrolyte solution L, improving the adhesion between the mask 30 and the substrate B.

[0048] 2, when the liquid pressure of the electrolytic solution L is increased while the electrolyte membrane 13 is in contact with the mask 30, the electrolyte membrane 13 conforms to the shapes of the inner wall surfaces 36a-36d of the through holes 34a-34d in the regions of the through holes 34a-34d of the mask 30. As a result, the electrolyte membrane 13 comes into contact with the surface of the substrate B.

[0049] Furthermore, when the liquid pressure of the electrolytic solution L is increased, a liquid derived from the electrolytic solution L (hereinafter, also referred to as an exudation liquid M) exudes through the electrolyte membrane 13 toward the substrate B. In the film forming method according to the present embodiment, a mask is used in which a communication space is formed that communicates the internal spaces 35a to 35d of the through holes 34a to 34d of the mask 30 with the external space S of the mask 30 during film formation. Therefore, the exudation liquid M is discharged from the electrolyte membrane 13 through the communication space of the mask 30 to the external space S of the mask 30 without filling the through holes 34a to 34d of the mask 30. The exudation liquid M flows downward in the external space S while pushing aside the air present in the external space S upward in the external space S.

[0050] Next, with the electrolyte membrane 13 in contact with the mask 30 and with the liquid pressure of the electrolyte solution L increased, a voltage is applied between the anode 11 and the substrate B to form a metal film (S400). As a result, the metal ions contained in the electrolyte membrane 13 migrate to the surface of the substrate B in contact with the electrolyte membrane 13 and are reduced on this surface. As a result, the metal is precipitated on the surface of the substrate B, and a metal film according to the pattern of the mask 30 is formed on the surface of the substrate B.

[0051] Here, unlike the film forming method according to the present embodiment, a case will be considered in which a metal film is formed using a mask that does not have the recessed grooves 38a-38d, i.e., a mask in which the through holes 34a-34d of the mask do not communicate with the external space S of the mask. In this case, since the seepage liquid M cannot be discharged to the external space S from the through holes 34a-34d of the mask 30, the through holes 34a-34d of the mask 30 are filled with the seepage liquid M. When the through holes 34a-34d of the mask 30 are filled with the seepage liquid, the liquid pressure P1 of the electrolyte L contained in the container 15 becomes equal to the liquid pressure (not shown) of the seepage liquid M filled in the through holes 34a-34d of the mask 30.

[0052] In this case, the liquid pressure of the seeping liquid M acts in a direction to reduce the liquid pressure P1 of the electrolyte L, and the force applied from the electrolyte membrane 13 to the mask 30 is reduced. As a result, the force that adheres the mask 30 to the substrate B is reduced. Since the force that adheres the mask 30 to the substrate B is reduced, during film formation, the metal ions that have migrated from the accommodation space 15c of the accommodation body 15 to the substrate B side, together with the electric field lines from the anode 11 toward the surface of the substrate B, are directed toward between the surface of the substrate B and the other surface 32l of the mask 30, and a metal coating having a desired pattern cannot be formed.

[0053] In this respect, according to the film forming method of the present embodiment, the recessed grooves 38a to 38d of the mask 30 are covered with the electrolyte membrane 13, so that the seepage liquid M can be directly seeped into the recessed grooves 38a to 38d through the electrolyte membrane 13. The seepage liquid M is directly discharged from the electrolyte membrane 13 through the recessed grooves 38a to 38d of the mask 30 to the external space S of the mask 30 without filling the through holes 34a to 34d of the mask 30. Therefore, the force pressing the electrolyte membrane 13 against the mask 30 can be maintained during film formation. Therefore, the force pressing the mask 30 against the substrate B is also maintained, so that the mask 30 can be maintained in close contact with the surface of the substrate B. In this way, since the mask 30 can be kept in close contact with the substrate B during film formation, the metal ions that have migrated to the substrate B side through the electrolyte membrane 13 are prevented from entering between the mask 30 and the substrate B, and a metal coating having a desired pattern can be formed.

[0054] In the present embodiment, the grooves 38a-38d are formed on one surface 32u, recessed from the one surface 32u to the other surface 32l. However, the grooves 38a-38d of the mask 30 may be formed on the other surface 32l, recessed from the other surface 32l to the one surface 32u. In this case, when the mask 30 is placed on the surface of the base material B, the grooves 38a-38d are covered by the base material B. Therefore, the seepage liquid M seeps through the electrolyte membrane 13 into the through holes 34a-34d of the mask 30, and is discharged from the communication space formed by the base material B and the grooves 38a-38d to the external space S of the mask. In this case, the grooves 38a-38d of the mask are not covered by the flexible electrolyte membrane 13, so that the spaces of the grooves 38a-38d are not narrowed by the electrolyte membrane 13 during film formation. Therefore, the seeping liquid M can be reliably discharged.

[0055] If the elapsed time since the voltage application in S400 has not reached the predetermined time (NO in S500), the voltage application by the power supply unit 14 continues. This is because it is determined that the thickness of the metal film on the surface of the substrate B is insufficient. On the other hand, if the elapsed time since the voltage application has reached the predetermined time (YES in S500), the voltage application by the power supply unit 14 is terminated (S600). This is because it is determined that the thickness of the metal film on the surface of the substrate B is sufficient.

[0056] Next, the rotation of the pump P is stopped, and thereafter, the linear actuator 70 raises the housing 15 relative to the base 110 to separate the electrolyte membrane 13 from the substrate B (S700). When the stroke of the linear actuator 70 reaches a predetermined value, the raising of the housing 15 stops.

[0057] Finally, the substrate B is removed from the base 110 (S800). In this manner, a series of steps in the film formation method using the film formation apparatus 1 is completed.

[0058] <Modification> Fig. 5 is a schematic perspective view showing a modified example of a mask used in the film forming apparatus 1 shown in Fig. 1. A mask 40 according to the modified example differs from the mask 30 according to the above embodiment in that a communicating space is formed by communicating holes 48a to 48d. Hereinafter, components having the same or similar functions as the mask 30 according to the above embodiment will be denoted by the same reference numerals as the mask 30 according to the above embodiment, and descriptions thereof will be omitted, and only different portions will be described.

[0059] The mask 40 according to this modification has communication holes 48a-48d formed therein, each extending from the inner wall surface 36a-36d of the through hole 34a-34d to the side surface (outer wall surface) 32s of the mask 40. One end of the communication holes 48a-48d opens at the inner wall surface 36a-36d, and the other end opens at the side surface (outer wall surface) 32s. The space formed inside the communication holes 48a-48d becomes a communication space that communicates the internal spaces 35a-35d of the through holes 34a-34d with the external space S of the mask 40.

[0060] When forming a metal film using the mask 40 according to this modification, increasing the liquid pressure of the electrolytic solution L causes the seepage liquid M to seep through the through holes 34a-34d of the mask 40 through the electrolyte membrane 13 and is discharged from the communication holes 48a-48d to the external space S of the mask 40 without filling the through holes 34a-34d. The communication holes 48a-48d of the mask are not covered by the flexible electrolyte membrane 13, so the electrolyte membrane 13 does not narrow the spaces of the communication holes 48a-48d. This allows the seepage liquid M to be reliably discharged. EXAMPLES

[0061] The invention is illustrated by the following examples.

[0062] [Example 1] A glass epoxy substrate (ABF substrate manufactured by Ajinomoto Co., Ltd.) made by impregnating a layer of glass fiber cloth with epoxy resin was prepared as a substrate for film formation. Copper foil was formed on the surface of this glass epoxy substrate. Next, a copper film was formed using a film formation apparatus according to the embodiment shown in Figs. 1 and 2. At this time, a mask according to the embodiment shown in Fig. 3 was placed on the surface of the substrate. The mask was made of silicone rubber. An aqueous solution of copper sulfate (Cu-BRITE-SED) manufactured by JCU Corporation was used as the electrolyte, and a Cu plate was used as the anode. The film formation conditions were as follows: the temperature of the electrolyte was 42°C, the solid electrolyte film was brought into contact with the mask, the liquid pressure of the electrolyte was 0.6 MPa, and the current density was 7 A / dm 2 , film forming area 25cm 2 A copper film of 10 μm was formed with a cumulative deposition time of 388 seconds.

[0063] [Comparative Example 1] A copper film was formed in the same manner as in the example. The difference from the example is that a mask without a concave groove was used as the mask placed on the surface of the substrate. In other words, the through holes of the mask in the comparative example are not connected to the outside of the mask.

[0064] <Checking the film formation status> In order to confirm whether or not a metal coating of a desired pattern was formed on the substrate formed as described above, the surface of the substrate was observed by an electron microscope. When a metal coating of a desired pattern was formed, the metal coating showed a sharp outline that matched the outline of the through-hole of the mask (no bleeding). In contrast, when a metal coating of a desired pattern was not formed, the metal coating did not match the outline of the through-hole of the mask (bleeding). The results are shown in Table 1 (Example 1, Comparative Example 1).

[0065] [Table 1]

[0066] (Results and Discussion) In Example 1, since the metal film was formed using a mask with a groove, it is considered that the seeping liquid was discharged from the electrolyte membrane through the groove to the external space of the mask without filling the through holes of the mask. Therefore, it is considered that the force pressing the mask against the substrate was maintained during film formation, and the mask was maintained in close contact with the surface of the substrate. As a result of the mask being able to continue to be in close contact with the substrate, it is considered that the metal ions that migrated to the substrate side through the electrolyte membrane during film formation did not enter between the mask and the substrate, and a metal film of the desired pattern could be formed (without bleeding).

[0067] On the other hand, in Comparative Example 1, since the metal film was formed using a mask without a groove, the through holes of the mask were filled with the seepage liquid, and it is considered that the liquid pressure of the electrolyte in the container was equal to the liquid pressure of the seepage liquid in the through holes of the mask. Therefore, it is considered that the liquid pressure of the seepage liquid acts in a direction to reduce the liquid pressure of the electrolyte, the force applied to the mask from the electrolyte membrane was reduced, and the force to adhere the mask to the substrate was also reduced. As a result, during the film formation, the metal ions that moved from the storage space of the container to the substrate side along with the electric field lines from the anode to the surface of the substrate were directed to between the surface of the substrate and the mask, and it is considered that the metal film could not be formed in the desired pattern (there was bleeding).

[0068] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the film forming method according to the above embodiment, and includes all aspects included in the concept of the present invention and the scope of the claims. In addition, each configuration may be appropriately and selectively combined to achieve the above-mentioned problems and effects. For example, the shape, material, arrangement, size, etc. of each component in the above embodiment may be appropriately changed depending on the specific aspect of the present invention.

[0069] For example, in the above embodiment, the recessed grooves 38a-38d are formed on the one surface 32u or the other surface 32l of the mask 30, and the space formed in the recessed grooves 38a-38d is defined as a communicating space. However, for example, the mask 30 may have a protruding portion that protrudes from the one surface 32u toward the electrolyte membrane 13, and during film formation, the space between the tip of the protruding portion and the one surface 32u may be defined as a communicating space. In addition, the mask 30 may have a protruding portion that protrudes from the other surface 32l toward the substrate B, and during film formation, the space between the tip of the protruding portion and the other surface 32l may be defined as a communicating space.

[0070] For example, in the above embodiment, the recessed grooves 38a-38d are formed in the through holes 34a-34d, respectively. However, it is sufficient that at least one recessed groove is formed, and as an example, the recessed groove 38a may be formed in one through hole 34a, and grooves or holes (not shown) may be formed to fluidly connect the through hole 34a to the other through holes 34b-34d. [Explanation of symbols]

[0071] 11: anode, 13: solid electrolyte membrane, 15: container, 15d: opening, 30, 40: mask, 32s: side surface (outer wall surface), 34a, 34b, 34c, 34d: through hole, 36a, 36b, 36c, 36d: inner wall surface, 38a, 38b, 38c, 38d: groove, 48a, 48b, 48c, 48d: communication hole, B: substrate, L: electrolyte, P1: liquid pressure of electrolyte, S: external space (outside), M: seepage liquid (liquid derived from electrolyte)

Claims

1. A film formation method comprising: disposing a mask having through-holes according to a predetermined pattern, the through-holes penetrating from the solid electrolyte membrane side toward the substrate side, between a solid electrolyte membrane in contact with an electrolytic solution containing metal ions, and a substrate; applying a voltage between an anode and the substrate serving as a cathode; and reducing the metal ions contained inside the solid electrolyte membrane to form a metal coating derived from the metal ions on a surface of the substrate in the predetermined pattern, the method comprising: bringing the solid electrolyte membrane covering an opening formed in a container for containing the electrolytic solution into contact with the mask; a step of pressing the mask against the substrate by increasing a liquid pressure of the electrolytic solution contained in the container while the solid electrolyte membrane is in contact with the mask; and applying a voltage between the anode and the substrate while the solid electrolyte membrane is in contact with the mask and while the liquid pressure of the electrolyte is increased, thereby forming the metal coating. A method for forming a metal film, comprising the steps of: using as the mask a mask in which a communicating space is formed that connects the through hole with an outside of the mask during film formation.

2. a recessed groove is formed in the mask, the recessed groove extending from an inner wall surface forming the through hole to an outer wall surface of the mask; 2. The method for forming a metal coating according to claim 1, wherein the communicating space is a space formed in the groove.

3. the mask has a communication hole formed therein, the communication hole extending from an inner wall surface forming the through hole to an outer wall surface of the mask; 2. The method for forming a metal coating according to claim 1, wherein the communicating space is a space formed inside the communicating hole.

4. A mask used in the method for forming a metal film according to any one of claims 1 to 3.

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