Metal film deposition equipment

Abstract

To provide a metallic film deposition apparatus that can suppress damage of a polymer electrolyte even in a state that the polymer electrolyte contacts an anode.SOLUTION: A deposition apparatus 1 comprises: an anode 11; a polymer electrolyte 13 with flexibility, which is spaced apart from the anode 11 and is arranged between the anode 11 and a substrate W; a housing 15 accommodating the anode 11 and a plating solution L and covering an opening 15g opening to the side of the substrate W with the polymer electrolyte 13; and a power supply 19 for applying a voltage between the anode 11 and the substrate W as a cathode. In the deposition apparatus 1, a metallic film F derived from metal ions of the plating solution L is deposited on the surface of the substrate W by applying the voltage in a state that the polymer electrolyte 13 contacts the substrate W. A peripheral part 11b of a surface 11a facing the polymer electrolyte 13 among the surfaces of the anode 11 is covered with a resin-made protective layer 12.SELECTED DRAWING: Figure 1B

Description

[Technical field]

[0001] The present invention relates to a film forming apparatus for forming a metal film on a surface of a substrate. [Background technology]

[0002] As an example of this type of technology, Patent Document 1 proposes a film formation apparatus for forming a metal film on the surface of a substrate. This film formation apparatus includes an anode, an electrolyte membrane disposed between the anode and the substrate with a gap therebetween, and a power supply unit for applying a voltage between the anode and the substrate. In the film formation apparatus, a container for containing a plating solution is provided between the anode and the electrolyte membrane so as to be in contact with them, the container contains the anode and the plating solution, and the open opening of the container is covered with the electrolyte membrane. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-051701 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when forming a film using the film forming apparatus described in Patent Document 1, the electrolyte membrane is flexible and easily deformed. When the electrolyte membrane in contact with the substrate is separated from the substrate, the electrolyte membrane may be deformed toward the anode due to a slight pressure difference that occurs across the electrolyte membrane. If the deformed electrolyte membrane comes into contact with the peripheral portion of the opposing surface of the anode that faces the electrolyte membrane, the electrolyte membrane may be damaged. This phenomenon becomes particularly noticeable when the anode is brought closer to the electrolyte membrane in order to increase the film formation speed, or the electrolyte membrane is enlarged in order to increase the film formation area.

[0005] The present invention has been made in consideration of these points, and its object is to provide a metal coating forming apparatus that can suppress damage to the electrolyte membrane even if the electrolyte membrane comes into contact with the anode. [Means for solving the problem]

[0006] In consideration of the above problems, the metal film forming apparatus of the present invention includes an anode, a flexible electrolyte membrane arranged between the anode and a substrate with a gap between the anode and the substrate, a container that contains the anode and a plating solution and has an opening facing the substrate covered with the electrolyte membrane, and a power supply unit that applies a voltage between the anode and the substrate which serves as a cathode, and is configured to form a metal film derived from metal ions in the plating solution on a surface of the substrate by applying the voltage with the electrolyte membrane in contact with the substrate, and is characterized in that a resin protective layer is provided on the peripheral portion of the surface of the anode that faces the electrolyte membrane. Effect of the Invention

[0007] According to the present invention, even if the electrolyte membrane deforms toward the anode and comes into contact with the peripheral portion of the anode, the peripheral portion of the anode is provided with a resin protective layer, thereby preventing the electrolyte membrane from being damaged. [Brief description of the drawings]

[0008] [Figure 1A] 1 is a schematic cross-sectional view of a metal film forming apparatus according to an embodiment of the present invention. [Figure 1B] 1B is a schematic cross-sectional view illustrating a film formation process of the metal film formation apparatus shown in FIG. 1A, and FIG. 1B is a schematic plan view illustrating a film formation region and a region of an anode covered with a protective layer. [Figure 1C] FIG. 4 is a schematic cross-sectional view for explaining deformation of the electrolyte membrane toward the anode side. [Diagram 2] FIG. 13 is a schematic cross-sectional view for explaining a protective layer of an anode according to a modified example. [Diagram 3]1A is a schematic diagram illustrating a cross section of an anode in a film forming apparatus according to a comparative example, and FIG. 1B is a schematic diagram illustrating a cross section of the anode shown in FIG. 1A over time as the anode is used. [Figure 4] FIG. 1A is a schematic cross-sectional view of a comparative example of a metal film forming apparatus in a film forming process, and FIG. 1B is a schematic cross-sectional view for explaining deformation of the anode side of the electrolyte membrane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a metal film forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

[0010] 1, the film forming apparatus 1 includes an anode 11, a flexible electrolyte membrane 13 disposed between the anode 11 and a substrate W with a gap therebetween, and a container 15 that contains the anode 11 and a plating solution L and has an opening 15g that opens toward the substrate W side covered by the electrolyte membrane 13. The film forming apparatus 1 further includes a power supply unit 19 that applies a voltage between the anode 11 and the substrate W that serves as a cathode, a mounting table 20 on which the substrate W is mounted, and a lifting device 70 that lifts and lowers the container 15.

[0011] In the film forming apparatus 1, while the electrolyte membrane 13 is brought into contact with the substrate W placed on the mounting table 20 by the lifting device 70, a voltage is applied between the anode 11 and the substrate W by the power supply unit 19 to form a metal coating on the surface of the substrate W. During film formation, metal ions contained in the electrolyte membrane 13 from the plating solution L are reduced on the surface of the substrate W, and metal derived from the metal ions is precipitated, and the precipitated metal forms a metal coating.

[0012] The substrate W functions as a cathode. The material of the substrate W is not particularly limited as long as it functions as a cathode (i.e., a surface having electrical conductivity), and may be made of a metal material such as aluminum or iron, or may be a resin, ceramic, or the like having a surface coated with a metal layer such as copper, nickel, silver, or iron.

[0013] The mounting table 20 is made of a conductive material and is disposed below the container 15 so that the substrate W faces the electrolyte membrane 13. The substrate (specifically, the cathode) W is electrically connected to the negative electrode of the power supply unit 19 via the mounting table 20. When the mounting table 20 is made of an insulating material, the negative electrode of the power supply unit 19 may be directly connected to the substrate W via the conductive terminal 16.

[0014] The anode 11 is attached to a container 15 described later so as to face the mounting table 20 (specifically, the substrate W), and is electrically connected to the positive electrode of a power supply unit 19 via a conductor and a conductive mounting member 18. The anode 11 has a shape corresponding to the film formation area of ​​the substrate W. The film formation area of ​​the substrate W is the surface of the substrate W facing the anode 11 that acts as a cathode. The anode 11 is a non-porous (for example, non-porous) anode made of the same metal as the metal coating, and is a block-shaped or flat anode. The anode 11 is made of the same metal as the metal coating, and may be soluble or insoluble in the plating solution L. In addition, the anode may be a porous anode, a mesh, or a metal ball laid out in a container as long as it has a required surface area.

[0015] When the anode 11 is soluble in the plating solution L, the material thereof may be, for example, copper, nickel, silver, or tin, depending on the composition of the plating solution L. For example, when the plating solution L is a copper sulfate aqueous solution, the anode 11 is made of copper, and the copper anode dissolves in the plating solution L and supplies copper ions to the plating solution L. In this embodiment, the anode 11 is not particularly limited as long as it dissolves when a voltage is applied using the power supply unit 19. When the anode 11 is insoluble in the plating solution L, the material is preferably one that does not dissolve when a voltage is applied, and examples of the material include platinum, stainless steel, titanium, and a titanium alloy.

[0016] As described above, the plating solution (electrolyte) L is a solution containing the metal of the metal film to be formed in an ion state, and examples of the metal include copper, nickel, silver, and tin. The plating solution L is an aqueous solution in which these metals are dissolved (ionized) with an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid. For example, when the metal is nickel, examples of the plating solution L include aqueous solutions of nickel nitrate, nickel phosphate, nickel succinate, nickel sulfate, nickel pyrophosphate, and nickel sulfamate. For example, when the metal is copper, examples of the plating solution L include aqueous solutions containing copper sulfate, copper pyrophosphate, and the like.

[0017] The electrolyte membrane (solid electrolyte membrane) 13 is a flexible membrane that can be impregnated (contained) with metal ions by contacting with the plating solution L described above. The electrolyte membrane 13 is not particularly limited as long as the metal ions can be reduced on the surface of the substrate W when a voltage is applied by the power supply unit 19, and a metal derived from the metal ions can be precipitated. Examples of the material of the electrolyte membrane 13 include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins having an ion exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd. A reinforcing layer may be partially formed on the resin having an ion exchange function.

[0018] 1, the container 15 is made of a material insoluble in the plating solution L, and an anode 11 and an electrolyte membrane 13 are attached to the container 15. In this embodiment, a container space S for containing the plating solution L is formed inside the container 15 by the side wall of the container 15, the anode 11, and the electrolyte membrane 13.

[0019] The anode 11 is attached to the inner surface of the container 15, and an opening 15g that opens toward the substrate W is formed at a position opposite the anode 11. The opening 15g opens downward, and the electrolyte membrane 13 is attached to seal the opening 15g. In this embodiment, the electrolyte membrane 13 is attached to the container 15 by being sandwiched between the main body 15a and the frame 15b of the container 15 at the periphery. The anode 11 and the electrolyte membrane 13 are disposed apart from each other and are in a non-contact state, and the container space S formed between them is filled with the plating solution L during film formation. In this way, the container 15 is structured such that the plating solution L contained in the container space S directly contacts the anode 11 and the electrolyte membrane 13.

[0020] The container 15 is formed with a supply flow path 15c for supplying the plating solution L to the storage space S and a discharge flow path 15d for discharging the plating solution L from the storage space S. The supply flow path 15c and the discharge flow path 15d are in communication with the storage space S. Both the supply flow path 15c and the discharge flow path 15d are in communication with the storage space S near the electrolyte membrane 13.

[0021] The lifting device 70 is a device that lifts and lowers at least one of the container 15 and the mounting table 20 so that the electrolyte membrane 13 and the substrate W can be moved toward and away from each other. In this embodiment, the mounting table 20 is fixed and does not move, and the lifting device 70 lifts and lowers only the container 15. Specifically, as shown in FIG. 1 and FIG. 3, the lifting device 70 includes a device body 71 and a rod 72 that moves linearly relative to the device body 71, and the rod 72 is fixed to the upper part of the container 15. The lifting device 70 may be a known electric actuator that converts the rotation of a motor such as a servo motor into linear motion. As long as the electrolyte membrane 13 can be moved toward and away from the substrate W by linear motion, the lifting device 70 may be provided on the mounting table 20 or may be a hydraulic or pneumatic cylinder.

[0022] The following describes a circulation mechanism for circulating the plating solution L in the film forming apparatus 1. The film forming apparatus 1 includes, as the circulation mechanism, a tank (not shown) connected to the accommodation body 15 for accommodating the plating solution L discharged from the accommodation body 15, and a pump (not shown) connected to the tank for pressure-feeding the plating solution L from the tank to the accommodation body 15.

[0023] The supply flow path 15c of the container 15 is connected to a discharge pipe of the pump, and the discharge flow path 15d of the container 15 is connected to a return pipe toward a tank via a pressure regulating valve (not shown). By providing such a mechanism, the container 15 can hold the plating solution L at a predetermined liquid pressure, and the plating solution L can be used to press the electrolyte membrane 13 against the substrate W, thereby forming a metal film on the substrate W.

[0024] By the way, when the electrolyte membrane 13 and the anode 11 are brought close to each other, a uniform current can be applied to the surface of the substrate W, and by narrowing the distance between the anode 11 and the substrate W (cathode), the liquid resistance can be minimized and a film can be formed at a higher speed. Here, the electrolyte membrane 13 is arranged to separate the substrate W from the plating solution L, but if air bubbles remain between the substrate W and the electrolyte membrane 13 or between the electrolyte membrane 13 and the anode 11, a film cannot be formed uniformly on the substrate W. For this reason, the space separated by the electrolyte membrane 13 is exposed to a vacuum environment or the pressure is controlled to suppress air bubbles, but a slight pressure difference between the spaces may cause the electrolyte membrane 13 to bend toward the anode side, as shown in FIG. 4(a) to FIG. 4(b). In particular, when the film formation area is enlarged, this tendency becomes more pronounced, and precise pressure control is required, so it is difficult to completely eliminate the contact between the anode 11 and the electrolyte membrane 13.

[0025] On the other hand, since the electrolyte membrane 13 is a thin film, has low strength, and is softer than the metal material constituting the anode 11, when the deformed electrolyte membrane 13 comes into contact with the peripheral portion of the facing surface of the anode 11 facing the electrolyte membrane 13, the electrolyte membrane 13 may be damaged. Here, even if the peripheral portion of the facing surface of the anode 11 is rounded as shown in FIG. 3(a), for example, when the anode 11 is a soluble anode, the surface of the anode 11 becomes rough as shown in FIG. 3(b), and as a result, the electrolyte membrane 13 becomes easily damaged. When the damaged electrolyte membrane 13 has a hole on the surface, not only does the plating solution L leak to the substrate W side, but even slight damage increases the permeability of the plating solution L, and the plating solution L seeps out to the substrate W side. In addition, when the anode 11, which is a conductive metal material, comes into contact with the electrolyte membrane 13 due to application of a voltage, metal foreign matter may adhere to the surface of the electrolyte membrane 13, causing uneven film formation.

[0026] From this viewpoint, in this embodiment, an anode 11 shown in Figs. 1A to 2 is used. The anode 11 according to this embodiment has an opposing surface 11a larger than the film formation region of the substrate W. Specifically, on the opposing surface 11a of the anode 11, an electrode region S1 where electric field lines are formed when a voltage is applied, and a protective layer 12 covering the main body 11A of the anode 11 outside the electrode region S1 are formed. The electrode region S1 is larger than the size of the rectangular film formation region of the substrate W (the hatched portion in Fig. 1C), and the resin protective layer 12 formed so as to surround the electrode region S1 covers the peripheral portion 11b of the opposing surface 11a facing the electrolyte membrane 13 with a width w.

[0027] In this embodiment, protective layer 12 may be formed so as to cover the entire periphery including the side surface of anode 11, or may have a rounded shape so as to cover the ridge line of the periphery of main body 11A of anode 11. Furthermore, as shown in Fig. 2, protective layer 12 may cover only peripheral portion 11b of opposing surface 11a opposing electrolyte membrane 13 so as to protrude from opposing surface 11a of main body 11A of anode 11. Of the surfaces of protective layer 12, the surface opposing substrate W is a flat surface parallel to substrate W, and the corners around it are rounded by rounding treatment.

[0028] The resin constituting the protective layer 12 is preferably softer than the resin constituting the electrolyte membrane 13. The resin constituting the protective layer 12 is preferably a fluororesin such as polytetrafluoroethylene (PTFE), polyether ether ketone resin (PEEK), polyphenylene sulfide resin (PPS), polyether sulfone resin (PES), silicone resin, or the like, and is preferably made of an insulating resin material that has high chemical resistance to the plating solution L.

[0029] The protective layer 12 may be formed by extrusion molding a resin corresponding to the protective layer 12 onto the body 11A of the anode 11, or by insert molding after placing the body 11A of the anode 11 in a mold. By forming the protective layer 12 in this manner, it is possible to smooth the roughness of the surface to the mirror surface level of the mold, and it is possible to prevent the electrolyte membrane 13 from being damaged by the unevenness of the resin surface. In addition, since an injection pressure is applied to the surface of the protective layer 12, it is possible to form the protective layer 12 without any gap between the body 11A of the anode 11 and the protective member. In addition, the protective layer 12 may be formed by applying a resist paint and then curing the paint, or may be formed using a tape such as a resist tape.

[0030] A metal film is formed using the film forming apparatus 1 of this embodiment. A substrate W is placed on a mounting table 20. In Fig. 1A, a plating solution L is contained inside a container 15, but as shown in Fig. 1B, a lifting device 70 may be lowered to bring the electrolyte membrane 13 into contact with the substrate W, and then the plating solution L may be supplied to the container 15.

[0031] Next, after the substrate W comes into contact with the electrolyte membrane 13, the liquid pressure of the plating solution L is increased, the electrolyte membrane 13 presses the substrate W, and a voltage is applied by the power supply unit 19 until the metal coating F reaches a predetermined thickness. Specifically, when a voltage is applied between the anode 11 and the substrate W in a state in which the electrolyte membrane 13 is in contact with the substrate W, metal ions move to the surface side of the substrate W via the electrolyte membrane 13 and are reduced on the surface of the substrate W, causing the metal to precipitate, forming the metal coating F. By applying such a voltage until the metal coating F reaches a predetermined thickness, the metal coating F can be formed to a desired thickness.

[0032] Thereafter, when the liquid pressure of the plating solution L in the container 15 is reduced, depending on the state of the reduced pressure, the electrolyte membrane 13 may be deformed so as to be drawn toward the anode 11, as shown in Fig. 1C. As a result, even if the electrolyte membrane 13 is deformed toward the anode 11 and comes into contact with the peripheral portion 11b of the anode 11, the resin protective layer 12 provided on the peripheral portion 11b of the anode 11 can prevent the electrolyte membrane 13 from being damaged.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as described in the claims. [Explanation of symbols]

[0034] 1: film forming device, 11: anode, 11a: opposing surface, 11b: peripheral portion, 12: protective layer, 13: electrolyte membrane, 15: container, 15g: opening, 19: power supply, W: substrate, L: plating solution

Claims

[Claim 1] An anode; a flexible electrolyte membrane disposed between the anode and a substrate at a distance from the anode; a container that contains the anode and the plating solution and has an opening that opens to the substrate side and is covered with the electrolyte membrane; A power supply unit that applies a voltage between the anode and the base material that serves as a cathode, A film forming apparatus for forming a metal film derived from metal ions in the plating solution on a surface of the substrate by applying the voltage while the electrolyte membrane is in contact with the substrate, a protective layer made of resin is provided on the peripheral portion of the surface of the anode that faces the electrolyte membrane.

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