MASKING MEMBER AND FILM FORMING APPARATUS FOR METAL FILM

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2023-121226 filed on Jul. 26, 2023, the entire content of which is hereby incorporated by reference into this application.

BACKGROUND
Technical Field

The present disclosure relates to a masking member and a film forming apparatus for a metal film.

Background Art

Conventionally, an invention related to a film forming apparatus for forming a metal film on a surface of a substrate has been known. A film forming apparatus for a metal film described in JP 2016-169398 A applies voltage between an anode and a substrate while pressing a solid electrolyte membrane against the substrate to reduce metallic ions contained in the solid electrolyte membrane so as to form a metal film partially on the substrate.

The aforementioned solid electrolyte membrane has formed thereon a recess so that the solid electrolyte membrane contacts a film forming region where the metal film is formed on the surface of the aforementioned substrate, without contacting the surface excluding the film forming region, the recess being recessed relative to a contact surface contacting the film forming region.

With such a configuration, the contact surface of the solid electrolyte membrane is brought into contact with the film forming region of the substrate, while the solid electrolyte membrane is pressed against the substrate. Simultaneously, the recess of the solid electrolyte membrane faces against the surface excluding the film forming region (i.e., non-film forming region of the substrate where no film is formed), bringing the solid electrolyte membrane in a non-contacting state in the non-film forming region.

When voltage is applied between the anode and the cathode (substrate) with such a state, metallic ions contained in the solid electrolyte membrane move to the film forming region (surface) of the substrate contacting the solid electrolyte membrane to be reduced in the film forming region of the substrate so that metal derived from the metallic ions precipitate. Meanwhile, since in the non-film forming region of the substrate facing against the recess of the solid electrolyte membrane, the solid electrolyte membrane is in a non-contacting state, the metal does not precipitate. As a result, the metal film with a distinct edge portion can be formed in the film forming region of the substrate.

SUMMARY

In solid electro deposition (SED) as mentioned above, a masking member disposed between an electrolyte membrane and a substrate and a film forming apparatus for a metal film using the masking member have been developed. However, when the masking member is disposed between the electrolyte membrane and the substrate and an electrolyte is supplied to the surface of the substrate via the electrolyte membrane and the masking member, air inside a penetrating portion could remain on the surface of the substrate as air bubbles while a plating solution is being filled in the penetrating portion of the masking member. The plating solution does not contact the portion where the air bubbles remain on the surface of the substrate, which could form a defective metal film.

The present disclosure provides a masking member capable of suppressing defects of a metal film caused by air bubbles remaining on a surface of a substrate, and a film forming apparatus for the metal film using the masking member.

An aspect of the present disclosure is a masking member for forming a metal film in a predetermined pattern on a surface of a substrate by electroplating, the masking member disposed between an electrolyte membrane and the substrate, the masking member including: a mesh portion that allows a plating solution for the electroplating to pass therethrough; a mask portion provided on a front side and a back side of the mesh portion and sandwiched between the electrolyte membrane and the substrate; a penetrating portion penetrating the mask portion in accordance with the predetermined pattern so as to expose the mesh portion; and a connecting channel provided in a part of the mask portion sandwiched between the electrolyte membrane and the mesh portion, the connecting channel connecting two of the penetrating portions adjacent to each other or the penetrating portion and a space facing a region where the predetermined pattern is not formed on the substrate so as to allow the plating solution to flow therethrough.

Another aspect of the present disclosure is a film forming apparatus for a metal film provided with the aforementioned masking member, the film forming apparatus including: a container containing the plating solution, with an opening facing the substrate covered with the electrolyte membrane; a moving mechanism configured to move at least one of the container or the substrate from a state in which the container and the substrate are separated from each other so as to sandwich the masking member between the electrolyte membrane and the substrate; a pressure increase mechanism configured to increase a pressure of the plating solution contained in the container; an anode disposed facing the electrolyte membrane inside the container; a power source configured to apply voltage between the anode and the substrate; and the masking member disposed between the electrolyte membrane and the substrate.

According to the aforementioned aspects of the present disclosure, it is possible to provide a masking member capable of suppressing defects of a metal film caused by air bubbles remaining on a surface of a substrate, and a film forming apparatus for the metal film using the masking member.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 2 is a schematic perspective view showing an embodiment of a masking member according to the present disclosure;

FIG. 3 is a schematic enlarged cross-sectional view of the masking member taken along line III-III of FIG. 2;

FIG. 4 is a schematic enlarged cross-sectional view of the masking member taken along line IV-IV of FIG. 2;

FIG. 5 is a schematic enlarged cross-sectional view of the masking member taken along line V-V of FIG. 2; and

FIG. 6 is a schematic enlarged cross-sectional view of the masking member taken along line VI-VI of FIG. 2.

DETAILED DESCRIPTION

Hereinafter, embodiments of a masking member and a film forming apparatus for a metal film of the present disclosure will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the film forming apparatus for a metal film according to the present disclosure. FIG. 2 is a schematic perspective view showing an embodiment of the masking member according to the present disclosure. A film forming apparatus 1 for a metal film of the present embodiment is an apparatus for forming a metal film on a surface of a substrate B by solid electro deposition (SED) using an electrolyte membrane 11c.

The film forming apparatus 1 includes, for example, a container 11, a moving mechanism 12, a pressure increase mechanism 13, an anode 14, a power source 15, and a masking member 16. Further, the film forming apparatus 1 includes, for example, a mount base 17 and a liquid circulation system 18.

The container 11 includes, for example, a storing space 11a that stores a plating solution L, an opening 11b opening on one side of the storing space 11a and facing the substrate B, the electrolyte membrane 11c covering the opening 11b, and a frame 11d fixing a peripheral edge portion of the electrolyte membrane 11c. The container 11 also includes, for example, a supply channel 11e connected to the storing space 11a and supplied with the plating solution L from the liquid circulation system 18, and a discharge channel 11f connected to the storing space 11a and discharging the plating solution L to the liquid circulation system 18. The container 11 contains the plating solution L, with the opening 11b facing the substrate B covered with the electrolyte membrane 11c. The container 11 also contains and holds the anode 14, for example, in a bottom portion on a side opposite to the opening 11b of the storing space 11a.

The moving mechanism 12 moves at least one of the container 11 or the substrate B from a state in which the container 11 and the substrate B are separated from each other so as to sandwich the masking member 16 between the electrolyte membrane 11c and the substrate B, as shown in FIG. 1. The moving mechanism 12 also moves at least one of the container 11 or the substrate B from a state in which the masking member 16 is sandwiched between the electrolyte membrane 11c and the substrate B so as to separate the container 11 and the substrate B from each other.

In an example shown in FIG. 1, the moving mechanism 12 is composed of a linear motion actuator that raises and lowers the container 11 with respect to the substrate B. The linear motion actuator is, for example, an electric actuator and converts a rotational motion of a motor into a linear motion by means of a ball screw or the like. The moving mechanism 12 may adopt a hydraulic or a pneumatic actuator instead of the electric actuator. The configuration of the moving mechanism 12 is not particularly limited as long as the container 11 and the substrate B can be relatively moved.

The pressure increase mechanism 13 is configured to increase the pressure of the plating solution L contained in the container 11. In the example shown in FIG. 1, the pressure increase mechanism 13 is, for example, a pump provided in a liquid supply pipe 18b of the liquid circulation system 18. Note that the configuration of the pressure increase mechanism 13 is not particularly limited, and may be configured with, for example, a piston and a cylinder capable of increasing the pressure of the plating solution L contained in the container 11. By increasing the pressure of the plating solution L in the storing space 11a of the container 11 by the pressure increase mechanism 13, the masking member 16 can be pressed against the substrate B with the pressure of the plating solution L.

The anode 14 is disposed facing the electrolyte membrane 11c inside the container 11. The anode 14 is, for example, a non-porous electrode, for example, having no pores, made of the same metal as that of the metal film formed on the surface of the substrate B. The anode 14 has, for example, a block-like or a plate-like shape. As the material of the anode 14, copper may be used, for example.

The power source 15 applies voltage between the anode 14 and the substrate B. More specifically, for example, the positive electrode of the power source 15 is electrically connected to the anode 14, and the negative electrode of the power source 15 is electrically connected to the substrate B via the mount base 17. The power source 15 applies voltage between the anode 14 and the substrate B with the plating solution L contained in the container 11, so that the metal ions of the anode 14 move via the plating solution L to the surface of the substrate B.

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

The electrolyte membrane 11c contacts the plating solution L supplied to the storing space 11a of the container 11 so as to be impregnated with (contain) the metal ions together with the plating solution L. The electrolyte membrane 11c is flexible. As the material of the electrolyte membrane 11c, for example, a fluorine-based resin having an ion-exchange function, such as Nafion (Registered Trademark) manufactured by Du Pont Corporation, can be used. Note that the material of the electrolyte membrane 11c is not particularly limited as long as the metal ions of the plating solution L can be moved to the substrate B. The film thickness of the electrolyte membrane 11c is, for example, in a range of 20 μm to 200 μm and may be 20 μm to 60 μm.

The masking member 16 is disposed between the electrolyte membrane 11c and the substrate B and is used to form the metal film in a predetermined pattern on the surface of the substrate B by electroplating. The masking member 16 includes, for example, a frame 16a and a screen mask 16b. The frame 16a is, for example, a rectangular frame-like member made of a metallic material or a resin material and having a thickness of around 1 mm to 3 mm.

The screen mask 16b has, for example, a rectangular shape corresponding to an outer shape of the frame 16a. A peripheral edge portion of the screen mask 16b is, for example, fixed to one surface of the frame 16a facing the electrolyte membrane 11c. In this manner, the screen mask 16b covers an opening of the frame 16a. A more detailed configuration of the masking member 16 of the present embodiment will be described later referring to FIG. 2 to FIG. 6.

The mount base 17 is provided with a recess 17b where the substrate B is placed, for example, on an end face 17a facing the container 11. The depth of the recess 17b is, for example, shallower than the thickness of the substrate B. Thus, in a state in which the substrate B is placed on the recess 17b of the mount base 17, a part of the substrate B projects toward the container 11 relative to the end face 17a of the mount base 17. The mount base 17 is made of, for example, a conductive material such as metal.

The substrate B is, for example, a rectangular plate-shaped member that functions as a cathode. The surface facing the electrolyte membrane 11c of the substrate B is, for example, a film forming surface on which the metal film is formed. The material of the substrate B is not particularly limited as long as the film forming surface functions as a cathode. The substrate B may include, for example, a resin insulating substrate and the film forming surface made of metal, such as copper, formed on the surface of the insulating substrate, and may have formed thereon a predetermined pattern by removing the film forming surface by etching after the metal film is formed. Further, the substrate B may be a metallic plate of aluminum, copper, or the like.

The liquid circulation system 18 includes, for example, a tank 18a that stores the plating solution L, a liquid supply pipe 18b connecting the tank 18a and the supply channel 11e of the container 11, and a liquid discharge pipe 18c connecting the discharge channel 11f of the container 11 and the tank 18a. Further, the liquid circulation system 18 includes, for example, a pressure regulating valve 18d provided in the liquid discharge pipe 18c.

In the middle of the liquid supply pipe 18b, for example, a pump as the pressure increase mechanism 13 is provided. By driving the pressure increase mechanism 13, the plating solution L is pumped from the tank 18a to the supply channel 11e of the container 11 via the liquid supply pipe 18b, and the storing space 11a of the container 11 is filled with the plating solution L. Further, the plating solution L is discharged from the storing space 11a of the container 11 via the discharge channel 11f and returned to the tank 18a via the liquid discharge pipe 18c. The pressure regulating valve 18d adjusts the pressure of the plating solution L in the storing space 11a of the container 11 to a predetermined pressure.

Hereinafter, referring to FIG. 2 to FIG. 6, the configuration of the masking member 16 of the present embodiment will be described in more detail. FIG. 2 is a schematic perspective view of the screen mask 16b showing an embodiment of the masking member 16 according to the present disclosure. FIG. 3 to FIG. 6 are schematic enlarged cross-sectional views of the screen mask 16b taken along lines III-III to VI-VI of FIG. 2, respectively. Note that in the drawings of FIG. 2 to FIG. 6, in order to facilitate understanding of the configuration of the masking member 16 of the present embodiment, the enlargement ratio in the thickness direction of the masking member 16 is increased as compared to the actual thickness.

The screen mask 16b includes, for example, a mesh portion 161, a mask portion 162, a penetrating portion 163, and a connecting channel 164. The mesh portion 161 is, for example, a mesh-like sheet in which a plurality of wires made of metal such as stainless steel or resin such as polyester intersect with each other, and has a plurality of minute openings through which the plating solution L passes.

The mask portion 162 is provided on a front side and a back side of the mesh portion 161, for example, and is sandwiched between the electrolyte membrane 11c covering the opening 11b of the container 11 and the substrate B as shown in FIG. 1. As a material of the mask portion 162, for example, an elastic material such as silicone rubber may be used. The mask portion 162 is provided, for example, in a center portion on an inner side relative to the peripheral edge portion of the mesh portion 161.

Further, the mask portion 162 is provided, for example, in a frame shape on the front and back sides of the mesh portion 161 over the entire peripheral edge portion of the mesh portion 161. In this case, the screen mask 16b is fixed to the surface of the frame 16a facing the electrolyte membrane 11c shown in FIG. 1 via the frame-shaped mask portion 162 provided in the peripheral edge portion of the mesh portion 161. Note that the mask portion 162 may not be provided in the peripheral edge portion of the mesh portion 161. In this case, the peripheral edge portion of the mesh portion 161 is fixed to the surface of the frame 16a facing the electrolyte membrane 11c shown in FIG. 1 via an adhesive or the like.

The penetrating portion 163, for example, penetrates the mask portion 162 in accordance with a predetermined pattern of the metal film formed on the surface of the substrate B so as to expose the mesh portion 161. As shown in FIG. 2, the penetrating portion 163 is formed, for example, in an elongated shape corresponding to the shape of a wiring pattern formed on the surface of the substrate B.

The connecting channel 164 is provided, for example, in a part of the mask portion 162 sandwiched between the electrolyte membrane 11c covering the opening 11b of the container 11 and the mesh portion 161. The connecting channel 164 connects two of the penetrating portions 163 adjacent to each other provided in the mask portion 162 or the penetrating portion 163 and a space S facing a region R where the predetermined pattern is not formed on the substrate B so as to allow the plating solution L to flow therethrough. In the present embodiment, the region R where the predetermined pattern is not formed is, for example, a region on an outer side of the mask portion 162 provided in the center portion of the mesh portion 161 and facing the peripheral edge portion of the mesh portion 161 that is exposed from the mask portion 162.

In addition, in the present embodiment, the connecting channel 164 is a recessed groove provided on a surface of the mask portion 162, the surface facing the electrolyte membrane 11c. The connecting channel 164 has, for example, a rectangular cross-sectional shape. Note that the cross-sectional shape of the connecting channel 164 is not particularly limited, and any shape such as a semicircular shape or a wedge shape can be adopted, for example.

As shown in FIG. 5, a width W of the connecting channel 164 is, for example, equal to or greater than 100 μm and equal to or smaller than 500 μm. Note that the connecting channel 164 is not limited to a recessed groove as long as it connects adjacent two penetrating portions 163 or the penetrating portion 163 and the space S facing the region R of the substrate B where a predetermined pattern is not formed to allow the plating solution L to flow therethrough. The connecting channel 164 may be, for example, a through-hole provided in the mask portion 162.

Hereinafter, the operation of the film forming apparatus 1 for a metal film and the masking member 16 of the present embodiment will be described.

As described above, the film forming apparatus 1 for a metal film of the present embodiment includes the container 11, the moving mechanism 12, the pressure increase mechanism 13, the anode 14, the power source 15, and the masking member 16. The container 11 contains the plating solution L, with the opening 11b facing the substrate B covered with the electrolyte membrane 11c. The moving mechanism 12 moves at least one of the container 11 or the substrate B from a state in which the container 11 and the substrate B are separated from each other so as to sandwich the masking member 16 between the electrolyte membrane 11c and the substrate B. The pressure increase mechanism 13 increases the pressure of the plating solution L contained in the container 11. The anode 14 is disposed facing the electrolyte membrane 11c inside the container 11. The power source 15 applies voltage between the anode 14 and the substrate B. The masking member 16 is disposed between the electrolyte membrane 11c and the substrate B.

The masking member 16 of the present embodiment is disposed between the electrolyte membrane 11c and the substrate B and is used to form the metal film in a predetermined pattern on the surface of the substrate B by electroplating. The masking member 16 of the present embodiment includes the mesh portion 161, the mask portion 162, the penetrating portion 163, and the connecting channel 164. The mesh portion 161 allows the plating solution L for electroplating to pass therethrough. The mask portion 162 is provided on the front and back sides of the mesh portion 161 and is sandwiched between the electrolyte membrane 11c and the substrate B. The penetrating portion 163 penetrates the mask portion 162 in accordance with a predetermined pattern of the metal film so as to expose the mesh portion 161. The connecting channel 164 is provided in a part of the mask portion 162 sandwiched between the electrolyte membrane 11c and the mesh portion 161 and connects two of the penetrating portions 163 adjacent to each other or the penetrating portion 163 and the space S facing the region R where the predetermined pattern is not formed on the substrate B so as to allow the plating solution L to flow therethrough.

With such a configuration, in the film forming apparatus 1 for a metal film of the present embodiment, as shown in FIG. 1, the masking member 16 is sandwiched between the electrolyte membrane 11c covering the opening 11b of the container 11 and the substrate B, and the plating solution L is contained in the container 11 and the pressure of the plating solution L is increased to a predetermined pressure by the pressure increase mechanism 13. Thus, as shown in FIG. 3, FIG. 4, and FIG. 6, the electrolyte membrane 11c receives the pressure from the plating solution L in the container 11 so as to deflect along the shape with the recess and projection of the mask portion 162 and the penetrating portion 163 of the masking member 16.

Further, the plating solution L permeates through the electrolyte membrane 11c and the mesh portion 161 exposed in the penetrating portion 163 of the masking member 16 so as to fill the penetrating portion 163. Here, as indicated by a broken line in FIG. 6, air A inside the penetrating portion 163 present near the substrate B permeates through the mesh portion 161 and tends to move toward the electrolyte membrane 11c. However, the electrolyte membrane 11c, for example, receives the pressure of the plating solution L in the container 11 to deflect toward the inner side of the opening of the penetrating portion 163, so that a part of the electrolyte membrane 11c is brought into contact with the mesh portion 161.

Therefore, when the masking member 16 does not have the connecting channel 164, a space between the electrolyte membrane 11c and the mesh portion 161 in the penetrating portion 163 becomes narrow, and the air A near the substrate B indicated by the broken line in FIG. 4 and FIG. 6 may lose a way-out, which could cause air bubbles to remain on the surface of the substrate B. By contrast, the masking member 16 of the present embodiment has the connecting channel 164, so that the plating solution L can be made to flow between the adjacent two penetrating portions 163 or between the penetrating portion 163 and the space S facing the region R of the substrate B where the predetermined pattern is not formed.

Consequently, the air A near the substrate B in the penetrating portion 163 indicated by the broken line in FIG. 4 and FIG. 6 passes through the mesh portion 161 to move to a gap between the mesh portion 161 and the electrolyte membrane 11c, and flows into the connecting channel 164 together with the plating solution L as shown in FIG. 3 and FIG. 5. Further, the air A flowing into the connecting channel 164 moves together with the plating solution L to the adjacent penetrating portion 163 or the space S facing the region R of the substrate B where the predetermined pattern is not formed.

As described above, it is possible to move, via the connecting channel 164, the air A near the substrate B in the penetrating portion 163 to a portion between the mesh portion 161 of the adjacent penetrating portion 163 and the electrolyte membrane 11c, or the space S facing the region R of the substrate B where the predetermined pattern is not formed. Therefore, according to the masking member 16 and the film forming apparatus 1 for a metal film of the present embodiment, it is possible to suppress the air bubbles remaining on the surface of the substrate B in the penetrating portion 163, and it is possible to suppress the defect of the metal film due to the air bubbles remaining on the surface of the substrate B.

Further, in the masking member 16 of the present embodiment, the connecting channel 164 is a recessed groove provided on the surface of the mask portion 162 facing the electrolyte membrane 11c. Such a configuration can facilitate forming the connecting channel 164 in the mask portion 162 of the masking member 16 by, for example, a typical silk screen manufacturing technique using an emulsion.

Furthermore, in the masking member 16 of the present embodiment, the width W of the connecting channel 164 is equal to or greater than 100 μm and equal to or smaller than 500 μm. With such a configuration, as shown in FIG. 5, for example, it is possible to secure the space for allowing the air A to pass through between the mesh portion 161 and the electrolyte membrane 11c, and to more effectively prevent air bubbles from remaining near the surface of the substrate B.

Although the embodiments of the mask and the film forming apparatus according to the present disclosure have been described in detail with reference to the drawings, the specific configuration is not limited to the embodiments, and any design changes and the like made within the scope without departing from the gist of the present disclosure are included in the present disclosure.

Hereinafter, an example of the masking member according to the present disclosure will be described.

Example

A masking member was produced by forming a mask portion of silicone rubber on the front and back sides of an LCP resin mesh portion having a line width of 20 μm and 420 mesh, and forming a penetrating portion and a recessed groove-like connecting channel on the mask portion. Note that the thickness of the mask portion was set such that the thickness of a portion disposed between the electrolyte membrane and the mesh portion was 20 μm, and the thickness of a portion disposed between the mesh portion and the substrate was 30 μm.

Here, the masking members of Examples 1 to 3 with the connecting channels having widths of 100 μm, 250 μm, and 500 μm, respectively, and a masking member of Comparative Example having no connecting channel were produced. Next, a substrate made of copper (Cu) was prepared, which is in a square shape having a thickness of 0.9 mm and a length of one side of 7.8 cm, and was subjected to cathode electrolytic degreasing at 55° C. for 1 minute using an IC-200RM manufactured by JCU Corporation, and was then washed with pure water for 1 minute. Further, the substrate was immersed in a 10% dilute sulfuric acid at room temperature for 1 minute to be subjected to acid cleaning, and was then washed with pure water for 1 minute.

Thereafter, a metal film having a thickness of 5 μm was formed on the surface of the substrate by solid electro deposition (SED) using a device having the same configuration as that of the film forming apparatus for a metal film described in the aforementioned embodiment. Film forming conditions were: film forming temperature: 42° C., plating solution: 1 mol/l copper sulfate+0.2 mol/l sulfate, anode: phosphorus-containing copper plate, inter-electrode distance of anode-cathode: 2 mm, pressurization: 0.6 MPa, film forming area: 38 cm²/substrate size 61.4 cm², and current: 7 ASD.

The numbers of defective (unprecipitated) portions of the metal films formed using the masking members of Examples 1 to 3 and Comparative Example were counted and the results were summarized in Table 1 below.

TABLE 1

Comparative

Example 1
Example 2
Example 3
Example

Defective
1
2
8
32

portion

(number)

Evaluation
Excellent
Excellent
Excellent
—

The number of defective portions of the metal film formed using the masking member of Comparative Example without the connecting channel was 32. By contrast, the numbers of defective portions of the metal films formed using the masking members of Examples 1 to 3 with the recessed groove-like connecting channels having widths of 100 μm, 250 μm, and 500 μm, respectively, were 1 to 8. That is, use of the masking members of Examples 1 to 3 reduced the number of the defective portions by ¼ to 1/32 as compared to the case of using the masking member of Comparative Example.

MASKING MEMBER AND FILM FORMING APPARATUS FOR METAL FILM

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