JP7632360B2 - METHOD FOR FORMING METAL FILM AND MASK USED IN THE METHOD - Google Patents

Description

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.

Conventionally, metal has been partially deposited on the surface of a substrate to form a metal film of 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 spaced apart from the masking plate and disposed in the container, 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 as the anode and the substrate as the cathode.

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 permeates through the through-holes in the masking plate into the portion of the electrolyte membrane that corresponds to the shape of the through-holes. A voltage is then applied between the conductive member and the substrate using a power supply unit. This causes the metal ions impregnated in the electrolyte membrane to migrate 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 coating is formed on the surface of the substrate.

JP 2016-108586 A

When metal is partially deposited on the surface of a substrate to form a metal coating in 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 placed between the electrolyte membrane and the substrate. When the liquid pressure of the electrolyte solution contained in the container is increased while the electrolyte membrane is 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-holes in the masking plate, following the shape of the through-holes.

When the liquid pressure of the electrolyte is increased, liquid derived from the electrolyte seeps out onto the substrate. When the through-holes in 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 in the masking plate may become equal. In this case, the force applied to the masking plate from the electrolyte membrane decreases, and the force pressing the masking plate onto the substrate also decreases. As a result, during film formation, metal ions that have migrated to the substrate side through the electrolyte membrane may get between the masking plate and the substrate, making it impossible to form a metal film in the desired pattern.

The present invention has been made in consideration of these points, and its purpose is to provide a method for forming a metal film that improves the quality of a metal film that is partially formed on the surface of a substrate, and a mask used in the method.

In view of the above-mentioned problems, the method for forming a metal film according to the present invention is a method for forming a metal film on the surface of the substrate in the predetermined pattern by applying a voltage between an anode and the substrate serving as a cathode in a state in which a mask having through holes according to a predetermined pattern is placed between a solid electrolyte membrane in contact with an electrolyte solution containing metal ions and a substrate, the mask penetrating from the solid electrolyte membrane side toward the substrate side, and reducing the metal ions contained inside the solid electrolyte membrane, and forming a metal film derived from the metal ions on the surface of the substrate in the predetermined pattern, the mask covering an opening formed in a container that contains the electrolyte solution. The method includes the steps of: bringing the solid electrolyte membrane into contact with the mask; 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 applying a voltage between the anode and the substrate while the solid electrolyte membrane is in contact with the mask and the liquid pressure of the electrolyte solution is increased, thereby depositing the metal coating. The method is characterized in that the mask used has a communication space formed therein that communicates between the through-hole and the outside of the mask during deposition.

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, so that the mask is pressed against the substrate. At this time, the electrolyte membrane conforms to the shape of the through-holes in the mask in the region of the through-holes, and thus the electrolyte membrane comes into contact with the surface of the substrate. In this way, with the electrolyte membrane in contact with the mask and with the liquid pressure of the electrolyte solution increased, a voltage is applied between the anode and the substrate, and a metal coating of a predetermined pattern is formed on the surface of the substrate.

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 substrate side. In the film formation method according to the present invention, a mask is used during film formation in which a communication space is formed that connects the through-holes of the mask with the outside of the mask. Therefore, 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.

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 that adheres the mask to the substrate can also be maintained. In this way, since the mask can be kept adhered to 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 of the desired pattern can be formed.

In a preferred embodiment, the mask has a groove formed therein that extends from the inner wall surface that forms the through hole to the outer wall surface of the mask, and the communicating space is the space formed in the groove. According to this embodiment, the groove can be easily formed in the mask by cutting or the like.

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 discharged directly 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, the force pressing the electrolyte membrane against the mask can be maintained during film formation, 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.

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.

The present invention also provides a mask for use in the above-mentioned metal film forming method. When the mask is used in the above-mentioned metal film forming method, the through holes of the mask communicate with the outside of the mask through the communication space during film formation. Therefore, the mask can discharge the above-mentioned liquid that has seeped out to the substrate side through the communication space without accumulating 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, the mask continues to adhere to the substrate during film formation. As a result, when the mask is used to form a metal film, 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 film of a desired pattern can be formed.

The present invention can improve the quality of the metal coating that is partially formed on the surface of the substrate.

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. 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. 2 is a schematic perspective view showing an example of a mask used in the film forming apparatus shown in FIG. 1 . FIG. 3B is a view taken along the arrow A in FIG. 3A. 3B is a view taken along the arrow B in FIG. 3A. 2 is a flowchart illustrating an example of a method for forming a metal film according to an embodiment of the present invention. 2 is a schematic perspective view showing a modified example of a mask used in the film forming apparatus shown in FIG. 1. FIG.

First, we will explain the deposition device 1 used in the metal coating deposition method according to an embodiment of the present invention.

Figure 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. Figure 2 is a schematic cross-sectional view of the film forming apparatus 1 shown in Figure 1, showing a state in which an electrolyte L is poured into a container 15. Figure 3A is a schematic perspective view showing an example of a mask 30 used in the film forming apparatus 1 shown in Figure 1. Figure 3B is a view seen from the direction indicated by an arrow A in Figure 3A. Figure 3C is a view seen from the direction indicated by an arrow B in Figure 3A.

As shown in Figures 1 and 2, the film forming device 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 the substrate B, and a container 15 that contains the anode 11 and an electrolyte solution L containing metal ions and has an opening 15d covered with the electrolyte membrane 13. In this embodiment, the mask 30 is placed on the substrate B, and the electrolyte membrane 13 is disposed between the mask 30 and the anode 11.

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.

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

In this embodiment, for convenience of explanation, the positional relationship of the components of the film forming apparatus 1 is specified on the assumption that the electrolyte membrane 13 is placed below the anode 11, and the mask 30 and substrate B are placed further below that. However, as long as a metal film can be formed on the surface of the substrate B, this positional relationship is not limited, 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.

Substrate B functions as a cathode. There are no particular limitations on the material of substrate B as long as it functions as a cathode (i.e., a surface having electrical conductivity). 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.

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 of a predetermined pattern on the surface of the substrate B. The configuration of the mask 30 will be described later.

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.

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.

The electrolyte L is a liquid that contains the metal of the metal film to be formed in an ionic state, and examples of such metals 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 for 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.

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 the metal ions can be reduced on the surface of the substrate B when a voltage is applied by the power supply unit 14, and a metal derived from the metal ions can be precipitated. Examples of materials for the electrolyte membrane 13 include resins with ion exchange functions, such as fluororesins such as Nafion (registered trademark) manufactured by DuPont.

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 electrolyte solution L. The anode 11 is attached to the inner surface of the container 15, which is arranged to surround the periphery of the anode 11. The container 15 also has an opening 15d that opens to the side of the substrate B. The opening 15d opens downward, and the electrolyte membrane 13 is attached to the container 15 so as to cover this opening 15d. As shown in FIG. 2, the container 15 is structured so that the electrolyte solution L contained in the container space 15c comes into direct contact with the anode 11 and the electrolyte membrane 13. The container 15 is made of a material that is insoluble in the electrolyte solution L.

1 and 2, the linear actuator 70 raises and lowers at least one of the housing 15 and the base 110 so that the electrolyte membrane 13 and the mask 30 can be brought into contact with and separated from each other. In this embodiment, the base 110 is fixed, and the housing 15 is raised and lowered by the linear actuator 70. The linear actuator 70 is provided on the upper part of the housing 15. The linear actuator 70 is, for example, an electric actuator that converts the rotational motion of a motor into linear motion by a ball screw or the like (not shown). This linear actuator 70 raises and lowers the housing 15 relative to the base 110, making it possible to bring the electrolyte membrane 13 into contact with and separate from the mask 30 described below. The device for raising and lowering the housing 15 may be a hydraulic or pneumatic cylinder or the like.

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 from above and below between the housing 15 and the frame 17.

The container 15 is formed with a supply flow path 15a that supplies the electrolyte L to the storage space 15c, and a discharge flow path 15b that discharges the electrolyte L from the storage space 15c. The supply flow path 15a and the discharge flow path 15b are holes that communicate 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, which will be described later, and the discharge flow path 15b is fluidly connected to a liquid discharge pipe 52, which will be described later.

1 and 2, the mask 30 is placed on the surface of the substrate B and is disposed between the electrolyte membrane 13 and the substrate B, and is flexible. 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, if 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 substrate B. If 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.

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 Figures 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 is 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 changed as appropriate depending on the pattern to be formed on the surface of the substrate B.

Each through hole 34a-34d is defined by an inner wall surface 36a-36d that extends from one surface 32u to the other surface 32l. In each through hole 34a-34d, an internal space 35a-35d is formed by the inner wall surfaces 36a-36d. Each inner wall surface 36a-36d is a surface that perpendicularly intersects with one surface 32u and the other surface 32l.

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

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

As shown in FIG. 1, the liquid tank T contains an electrolyte L. The liquid supply pipe 50 connects the liquid tank T and the container 15. The liquid supply pipe 50 is provided with a pump P that supplies the electrolyte L from the liquid tank T to the container 15.

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

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 storage space 15c. The electrolyte L used during film formation in the storage space 15c 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 storage space 15c can be maintained at a predetermined pressure P1.

With the electrolyte membrane 13 in contact with the mask 30, the liquid pressure of the electrolyte 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, as shown in FIG. 2, the electrolyte membrane 13 conforms to the shapes of the inner wall surfaces 36a-36d of the through holes 34a-34d in the area of the through holes 34a-34d of the mask 30, 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.

Next, a film formation method using the film formation apparatus 1 will be described. FIG. 4 is a flow chart for explaining an example of a film formation method for a metal film according to an embodiment of the present invention. In the film formation method according to this embodiment, a mask 30 is placed between the electrolyte membrane 13 in contact with the electrolytic solution L and the substrate B, the mask 30 having through holes 34a to 34d that penetrate from the electrolyte membrane 13 side toward the substrate B side according to a predetermined pattern, and a voltage is applied between the anode 11 and the substrate B to reduce the metal ions contained inside the electrolyte membrane 13, thereby forming a metal film derived from the metal ions on the surface of the substrate B in a predetermined pattern.

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

Next, a process is carried out in which the electrolyte membrane 13 covering the opening 15d of the container 15 that contains the electrolyte solution L is brought into contact with the mask 30 (S200). In this process, the linear actuator 70 lowers the container 15 relative to the base 110, bringing the electrolyte membrane 13 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.

Then, the pump P is rotated to carry out the process of storing the electrolyte L in the storage space 15c of the storage body 15 (S300). In this process, 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 a 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.

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. This causes the mask 30 to adhere closely to the surface of the substrate B. For example, if the mask 30 is made of silicone rubber (PMDS) or ethylene propylene diene rubber (EPDM), the liquid pressure P1 of the electrolyte solution L compresses and deforms the mask 30, improving the adhesion between the mask 30 and the substrate B.

In addition, when the liquid pressure of the electrolyte solution L is increased while the electrolyte membrane 13 is in contact with the mask 30, as shown in FIG. 2, the electrolyte membrane 13 conforms to the shapes of the inner wall surfaces 36a-36d of the through holes 34a-34d in the areas of the through holes 34a-34d of the mask 30. This causes the electrolyte membrane 13 to come into contact with the surface of the substrate B.

When the liquid pressure of the electrolyte solution L is increased, a liquid derived from the electrolyte solution L (hereinafter also referred to as seepage liquid M) seeps through the electrolyte membrane 13 toward the substrate B. In the film formation method according to this embodiment, a mask is used in which a communication space is formed that communicates the internal space 35a-35d of the through holes 34a-34d of the mask 30 with the external space S of the mask 30 during film formation. Therefore, the seepage 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-34d of the mask 30. The seepage 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.

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, 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.

Here, unlike the film formation method according to this 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, the seepage liquid M cannot be discharged from the through holes 34a-34d of the mask 30 to the external space S, so 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 filling the through holes 34a-34d of the mask 30.

In this case, the liquid pressure of the seeping liquid M acts in a direction that reduces the liquid pressure P1 of the electrolyte L, and the force applied to the mask 30 from the electrolyte membrane 13 decreases. As a result, the force that adheres the mask 30 to the substrate B decreases. Because the force that adheres the mask 30 to the substrate B decreases, during film formation, the metal ions that have migrated from the storage space 15c of the storage body 15 to the substrate B side, along with the electric field lines from the anode 11 toward the surface of the substrate B, are directed toward the gap between the surface of the substrate B and the other surface 32l of the mask 30, making it impossible to form a metal film in the desired pattern.

In this respect, according to the film forming method of the present embodiment, the 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 grooves 38a to 38d through the electrolyte membrane 13. The seepage liquid M is directly discharged from the electrolyte membrane 13 through the 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, and 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 of a desired pattern can be formed.

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

If the elapsed time since the voltage application in S400 has not exceeded the predetermined time (NO in S500), the power supply unit 14 continues to apply voltage. 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 exceeded the predetermined time (YES in S500), the power supply unit 14 ends the voltage application (S600). This is because it is determined that the thickness of the metal film on the surface of the substrate B is sufficient.

Next, the rotation of the pump P is stopped, and then 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.

Finally, the substrate B is removed from the base 110 (S800). This completes the series of steps in the film formation method using the film formation apparatus 1.

<Modification>
Fig. 5 is a schematic perspective view showing a modified mask used in the film forming apparatus 1 shown in Fig. 1. The 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 the 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 a description thereof will be omitted, and only different portions will be described.

The mask 40 according to this modified example has communication holes 48a-48d formed therein, which extend from the inner wall surfaces 36a-36d of the through holes 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 surfaces 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 between the internal spaces 35a-35d of the through holes 34a-34d and the external space S of the mask 40.

When forming a metal film using the mask 40 according to this modified example, increasing the liquid pressure of the electrolyte L causes the seepage liquid M to seep through the electrolyte membrane 13 into the through holes 34a-34d of the mask 40, and is discharged from the communication holes 48a-48d into the external space S of the mask 40 without filling the through holes 34a-34d. Because the mask communication holes 48a-48d are not covered by the flexible electrolyte membrane 13, 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.

The present invention is illustrated by the following examples.

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

[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.

<Checking the film formation state>
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).

(Results and Discussion)
In Example 1, since the metal film was formed using a mask with a groove, it is considered that the seepage 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 moved 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 was formed (without bleeding).

On the other hand, in Comparative Example 1, the metal film was formed using a mask without grooves, so the through holes of the mask were filled with the seepage liquid, and it is believed 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. For this reason, it is believed that the liquid pressure of the seepage liquid acts in a direction to reduce the liquid pressure of the electrolyte, reducing the force applied to the mask from the electrolyte membrane and the force that adheres the mask to the substrate. As a result, during film formation, metal ions that migrated from the storage space of the container to the substrate along with the electric field lines from the anode to the substrate surface headed toward the gap between the substrate surface and the mask, and it is believed that a metal film of the desired pattern could not be formed (there was bleeding).

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, but 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.

For example, in the above embodiment, the recessed grooves 38a-38d are formed on one surface 32u or the other surface 32l of the mask 30, and the space formed in the recessed grooves 38a-38d is 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 a communicating space. Also, 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 a communicating space.

For example, in the above embodiment, a case has been described in which grooves 38a to 38d are formed in each of the through holes 34a to 34d. However, it is sufficient to form at least one groove, and as an example, 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 to 34d.

11: Anode, 13: Solid electrolyte membrane, 15: Container, 15d: Opening, 30, 40: Mask, 32s: Side (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: Base material, L: Electrolyte, P1: Liquid pressure of electrolyte, S: External space (outside), M: Seepage liquid (liquid derived from electrolyte)

Claims (4)

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 increasing a liquid pressure of the electrolytic solution contained in the container while the solid electrolyte membrane is in contact with the mask, thereby pressing the mask against the base material;
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 communicates between the through hole and the outside of the mask during film formation. 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. 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. A mask used in the method for forming a metal film according to any one of claims 1 to 3.

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