METHOD FOR FORMING METAL FILM AND APPARATUS FOR FORMING METAL FILM

Abstract

To provide a metal film deposition method capable of forming a homogeneous metal film with a uniform film thickness.SOLUTION: In a film deposition method, firstly, with a substrate W placed on a lifting device 14 and a permeable membrane 13 separated from each other, the air in a space S of a first housing chamber 11 and the air in a second housing chamber 12 are sucked, and the second housing chamber 12 is filled with water vapor st while decompressing the first housing chamber 11 and the second housing chamber 12. Subsequently, the substrate W mounted on the lifting device 14 is raised to bring the substrate W into contact with the permeable membrane 13. Then, the space S of the decompressed first and second housing chambers 11 and 12 is released to the atmosphere. In this state, a metal film is formed on the surface of the substrate W.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for forming a metal film, which deposits a metal on the surface of a substrate by electrolytic plating or electroless plating from metal ions contained in a plating solution, thereby forming a metal film derived from the metal ions on the surface of the substrate. [Background technology]

[0002] For example, Patent Document 1 proposes a method for forming a metal film on the surface of a substrate by electrolytic plating using a solid electrolyte membrane as one type of permeable membrane that allows metal ions to pass through. In this method, the metal ions are caused to pass through the permeable membrane while the substrate surface is in contact with the permeable membrane via a plating solution containing metal ions, and the permeated metal ions are precipitated on the substrate surface to form a metal film. [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, air may be trapped when the permeable membrane is brought into contact with the substrate, which may prevent the formation of a homogeneous metal coating with a uniform thickness.

[0005] The present invention has been made in view of the above points, and provides a metal film forming method and a film forming apparatus capable of forming a homogeneous metal film with a uniform thickness. [Means for solving the problem]

[0006] In view of the above problems, the present invention provides a method for forming a metal coating, which comprises partitioning a first storage chamber in which a plating solution is stored so that a space is formed at the top from a second storage chamber that is disposed below the first storage chamber and in which a substrate is stored, with a permeable membrane through which at least metal ions contained in the plating solution permeate, and by raising the substrate placed on a lifting device, the substrate is brought into contact with the permeable membrane from below, and a metal coating is formed on a surface of the substrate from the metal ions that have permeated the permeable membrane, the first storage chamber and the second storage chamber are in communication with each other via a communication passage, and the first storage chamber is in communication with the first storage chamber in a state in which the substrate placed on the lifting device and the permeable membrane are separated from each other. The method includes at least a water vapor filling process for filling the second storage chamber with water vapor while reducing the pressure in the first storage chamber and the second storage chamber by sucking in the space of the container and the air in the second storage chamber; a contacting process for bringing the base material placed on the lifting device into contact with the permeable membrane by raising the base material while the second storage chamber is filled with the water vapor; an opening process for opening the space of the first storage chamber and the second storage chamber, which has been reduced in pressure, to the atmosphere while the base material is in contact with the permeable membrane; and a film forming process for forming the metal coating on the surface of the base material while the first storage chamber and the second storage chamber, which have been reduced in pressure, are open to the atmosphere.

[0007] According to the present invention, in the water vapor filling step, the air in the first storage chamber and the second storage chamber is sucked in while the base material placed on the lifting device and the permeable membrane are separated, and the first storage chamber and the second storage chamber are depressurized while filling the second storage chamber in a depressurized state with water vapor. Next, in the contact step, the base material placed on the lifting device is raised in a state in which the second storage chamber is filled with water vapor, thereby bringing the base material into contact with the permeable membrane. Here, when the permeable membrane is brought into contact with the base material, water vapor may be trapped between the base material and the permeable membrane.

[0008] Even in such a case, in the opening step, the depressurized space of the first storage chamber and the second storage chamber are opened to the atmosphere while the substrate is in contact with the permeable membrane, so that the space of the first storage chamber and the second storage chamber are at atmospheric pressure. As a result, the water vapor trapped between the substrate and the permeable membrane is pressurized from the permeable membrane side to atmospheric pressure, and the trapped water vapor turns into water and disappears. As a result, air is not trapped between the substrate and the permeable membrane, and a homogeneous metal coating with a uniform thickness can be formed in the film forming step.

[0009] In a more preferred embodiment, an electrolytic plating solution is used as the plating solution, a nonporous solid electrolyte membrane is used as the permeable membrane, an anode is disposed in the first storage chamber in contact with the plating solution and at a position facing the substrate, and in the film forming step, the metal coating is formed on the surface of the substrate by electrolytic plating while applying a voltage between the anode and the substrate which serves as a cathode with the substrate in contact with the permeable membrane.

[0010] According to this embodiment, in the opening step, the water vapor trapped between the substrate and the permeable membrane is increased in pressure from the permeable membrane side to atmospheric pressure, so that the trapped water vapor turns into water and disappears, but this water does not hinder the movement of metal ions. Therefore, in the film forming step, when a voltage is applied between the anode and the substrate serving as the cathode, the metal ions contained in the plating solution pass through the solid electrolyte membrane and are uniformly reduced on the surface of the substrate, causing the metal to precipitate. As a result, the metal precipitation is not hindered by the entrapment of air, and a homogeneous metal coating with a uniform thickness can be formed.

[0011] In another preferred embodiment, an electroless plating solution is used as the plating solution, a porous membrane that is permeable to the plating solution is used as the permeable membrane, and in the membrane formation step, the metal coating is formed on the surface of the substrate by electroless plating while maintaining the substrate in contact with the permeable membrane for a predetermined period of time.

[0012] Even in this embodiment, the water vapor trapped between the substrate and the permeable membrane in the release step turns into water and disappears. The movement of metal ions is not impeded. Therefore, even in this embodiment, the deposition of metal is not inhibited by the trapped air, and a homogeneous metal coating with a uniform thickness can be formed.

[0013] The present invention discloses a metal film forming apparatus as described below. The metal film forming apparatus according to the present invention includes a first storage chamber in which a plating solution containing metal ions is stored so that a space is formed above, a second storage chamber arranged below the first storage chamber in which a substrate is stored, a permeable membrane that separates the first storage chamber from the second storage chamber and is permeable to at least the metal ions contained in the plating solution, and a lifting device on which the substrate stored in the second storage chamber is placed and which lifts and lowers the substrate. The substrate placed on the lifting device is raised to bring the substrate into contact with the permeable membrane, and the permeable membrane is raised while the substrate is kept in contact with the permeable membrane. A metal coating deposition apparatus that deposits a metal coating on a surface of the substrate from the permeated metal ions, the first storage chamber and the second storage chamber being connected via a communication passage, and the film deposition apparatus further includes a suction pump that sucks air from the first storage chamber and the second storage chamber and reduces the pressure of the first storage chamber and the second storage chamber while the substrate is separated from the permeable membrane, a water vapor supply unit that supplies water vapor to the depressurized second storage chamber, and an open valve that opens the depressurized first storage chamber and the second storage chamber to the atmosphere while the substrate is in contact with the permeable membrane.

[0014] According to the present invention, first, the space in the first storage chamber and the air in the second storage chamber are sucked by a suction pump while the base material and the permeable membrane are separated from each other on the lifting device. This allows the water vapor supply unit, which supplies water vapor while depressurizing the first storage chamber and the second storage chamber, to fill the second storage chamber in a depressurized state with water vapor. Next, with the second storage chamber filled with water vapor, the base material placed on the lifting device is raised to bring the base material into contact with the permeable membrane. Here, when the permeable membrane is brought into contact with the base material, water vapor may be trapped between the base material and the permeable membrane.

[0015] Even in such a case, the open valve opens the decompressed space of the first storage chamber and the second storage chamber to the atmosphere while the substrate is in contact with the permeable membrane. This allows the space of the first storage chamber and the second storage chamber to be pressurized to atmospheric pressure. As a result, the water vapor trapped between the substrate and the permeable membrane is pressurized from the permeable membrane side to atmospheric pressure, and the trapped water vapor turns into water and disappears. This allows a homogeneous metal coating with a uniform thickness to be formed without air being trapped between the substrate and the permeable membrane.

[0016] In a more preferred embodiment, the plating solution is an electrolytic plating solution, the permeable membrane is a nonporous solid electrolyte membrane, and the film formation apparatus further includes an anode in the first storage chamber, the anode being in contact with the plating solution and disposed opposite the substrate, and a power supply unit applying a voltage between the anode and the substrate serving as a cathode.

[0017] According to this embodiment, the open valve increases the pressure of the water vapor trapped between the substrate and the permeable membrane from the permeable membrane side to atmospheric pressure, so that the trapped water vapor turns into water and disappears, but this water does not hinder the movement of metal ions. Therefore, when a voltage is applied from the power supply unit between the anode and the substrate serving as the cathode, the metal ions contained in the plating solution pass through the solid electrolyte membrane and are uniformly reduced on the surface of the substrate, causing the metal to precipitate. As a result, a homogeneous metal coating with a uniform thickness can be formed without the metal precipitation being hindered by the trapped air.

[0018] In yet another embodiment, the plating solution is an electroless plating solution, and the permeable membrane is a porous membrane that is permeable to the plating solution.

[0019] In this embodiment, the water vapor trapped between the substrate and the permeable membrane in the open valve turns into water and disappears, and this water does not impede the movement of metal ions. Therefore, the deposition of metal is not hindered by the trapped air, and a homogeneous metal coating with a uniform thickness can be formed. Effect of the Invention

[0020] According to the metal film forming method and film forming apparatus of the present invention, a homogeneous metal film with a uniform thickness can be formed. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view of a metal film forming apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a flow diagram of the film forming method shown in FIG. [Diagram 3] 3 is a view for explaining a water vapor filling step in the film forming method shown in FIG. 2. [Figure 4] 3 is a diagram for explaining a contact step and a film forming step in the film forming method shown in FIG. 2. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a metal film forming apparatus according to a second embodiment of the present invention. [Figure 6] 6A to 6C are diagrams for explaining a film forming process in a film forming method according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, a metal film forming apparatus and a metal film forming method according to a first and second embodiments of the present invention will be described with reference to FIGS. 1 to 6. FIG.

[0023] First Embodiment 1. Metal Coating Deposition Equipment 1 The film forming apparatus 1 according to this embodiment includes a first storage chamber 11, a second storage chamber 12, a permeable membrane 13, and a lifting device 14. The first storage chamber 11 is formed in an upper housing 11A, and stores a plating solution L containing metal ions. The plating solution L is stored in the first storage chamber 11 such that a space S is formed above the plating solution L. A communication passage 20 is connected to the first storage chamber 11 so as to communicate with the space S.

[0024] The second storage chamber 12 is formed in the lower housing 12A. The second storage chamber 12 is disposed below the first storage chamber 11, and the substrate W is stored therein. A permeable membrane 13 is disposed between the first storage chamber 11 and the second storage chamber 12 so as to separate the first storage chamber 11 and the second storage chamber 12. The first storage chamber 11 is sealed by covering the opening of the upper housing 11A with the permeable membrane 13. As a result, the first storage chamber 11 can be partitioned by the permeable membrane 13 into the first storage chamber 11 containing the plating solution L and the second storage chamber 12 containing the substrate W, while the plating solution L is stored in the first storage chamber 11. The lower housing 12A may be provided with an opening / closing door for inserting and removing the substrate W from the second storage chamber 12, and the device configuration is not particularly limited as long as the substrate W after film formation can be removed from the second storage chamber 12 and a new substrate W can be placed in the second storage chamber 12.

[0025] The lifting device 14 is a device for placing the substrate W accommodated in the second accommodation chamber 12 and lifting the substrate W, and a linear-type electric actuator (not shown) or the like is attached to the lower part of the lifting device 14. A placement table 14a for placing the substrate W is formed at the upper end of the lifting device 14. A recess for positioning the substrate W is formed in the placement table 14a.

[0026] In this embodiment, the plating solution L is an electrolytic plating solution, and the permeable membrane 13 is a nonporous solid electrolyte membrane 13A. In this embodiment, in order to form a metal film by electrolytic plating, an anode 32 and a power supply unit 36 ​​are further provided. The anode 32 is disposed in the first storage chamber 11 at a position in contact with the plating solution L and facing the substrate W.

[0027] The anode 32 may be, for example, either a soluble anode made of the same material as the metal film F (eg, Cu), or an anode made of a material insoluble in the plating solution L (eg, Ti).

[0028] The solid electrolyte membrane 13A is, for example, a membrane of a solid electrolyte having an ion-exchangeable functional group. The solid electrolyte membrane 13A is not particularly limited as long as it can transmit metal ions by contacting with the plating solution L and can precipitate a metal derived from the metal ions on the surface of the substrate W. The solid electrolyte membrane 13A is flexible and preferably has a thickness in the range of 5 μm to 200 μm. Examples of the solid electrolyte include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins having a cation exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

[0029] The plating solution L is a liquid containing the metal of the metal coating in an ionic state, and examples of the metal include Cu, Ni, Ag, and Au. The plating solution L is prepared by dissolving (ionizing) these metals in an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid.

[0030] In this embodiment, the anode 32 is suspended in the first storage chamber 11 by a support 34 and immersed in the plating solution L. A conductor 35 is inserted inside the support 34, one end of the conductor 35 is connected to the anode 32 via a wire, and the other end of the conductor 35 is connected to the positive electrode of a power supply unit 36 ​​via an electric circuit (not shown) such as a switch. The negative electrode of the power supply unit 36 ​​is connected to the substrate W via the mounting table 14a. This allows the power supply unit 36 ​​to apply a voltage between the anode 32 and the substrate W, with the substrate W serving as the cathode.

[0031] The substrate W may be a substrate made of a metal such as copper, iron, or aluminum, and may further have a metal coating such as nickel formed on the surface of the substrate W. Alternatively, the main body of the substrate W may be an insulating plate material made of glass epoxy resin or the like, and a metal film may be formed on the surface of this plate material (main body) by, for example, sputtering, and is not particularly limited as long as the surface of the substrate W acts as a cathode.

[0032] According to the film forming apparatus 1 of the present embodiment, the substrate W placed on the lifting device 14 is raised to bring the substrate W into contact with the solid electrolyte membrane 13A, and then a voltage is applied between the anode 32 and the substrate W (cathode) while the substrate W is kept in contact with the permeable membrane 13. This causes metal ions in the plating solution L contained in the first storage chamber 11 to permeate through the permeable membrane 13, and the permeated metal ions are reduced on the surface of the substrate W. As a result, metal derived from the metal ions is precipitated on the surface of the substrate W, and a metal coating can be formed on the surface of the substrate W.

[0033] Here, in this embodiment, the film forming apparatus 1 further includes a suction pump 17, a water vapor supply unit 18, and an open valve 19. In this embodiment, the first storage chamber 11 and the second storage chamber 12 communicate with each other via a communication passage 20, and the communication passage 20 is connected to the suction pump 17. By suction by the suction pump 17, air in the first storage chamber 11 and the second storage chamber 12 can be sucked through the communication passage 20 while the substrate W is separated from the permeable membrane 13, and the first storage chamber 11 and the second storage chamber 12 can be depressurized.

[0034] The water vapor supply unit 18 is a part that supplies water vapor to the decompressed second storage chamber 12. The water vapor supply unit 18 includes a storage chamber 18a that stores water (hot water) M, and a heating unit 18b that heats the water. The heating unit 18b is, for example, an electric heater. The storage chamber 18a is in communication with the second storage chamber 12 via a communication passage 25, and water vapor generated from the hot water heated by the heating unit 18b is supplied to the second storage chamber 12.

[0035] The release valve 19 is a valve that opens the first storage chamber 11 and the second storage chamber 12, which have been depressurized by the suction pump 17, to the atmosphere with the substrate W in contact with the solid electrolyte membrane 13A. When the release valve 19 is in an open state, it connects the communication passage 20 to the atmosphere, and when the release valve 19 is in a closed state, it blocks the communication passage 20 from the atmosphere. In this embodiment, the release valve 19 is provided at a position branched off from the communication passage 20, but for example, the first storage chamber 11 and the second storage chamber 12 may be opened to the atmosphere by an release valve built into the suction pump 17.

[0036] 2.Metal coating method In this film forming method, a metal film is formed on the surface of the substrate W using the above-mentioned film forming apparatus 1. In this embodiment, as a preparation step before the film formation, the plating solution L is contained in the first storage chamber 11 so that a space S is formed in the upper part of the first storage chamber 11. Furthermore, the substrate W is contained in the second storage chamber 12 so that the substrate W is placed on the mounting table 14a. In this state, the plating solution L is disposed on the upper side of the solid electrolyte membrane 13A so as to be in contact with the solid electrolyte membrane 13A, and the substrate W is disposed on the lower side of the solid electrolyte membrane 13A with a gap therebetween, with the solid electrolyte membrane 13A sandwiched between them. Here, the pressure in the space S in the first storage chamber 11 and the pressure inside the second storage chamber 12 are atmospheric pressure.

[0037] After completing the preparation before the film formation, first, a water vapor filling step S1 shown in Fig. 2 is performed. In this step, in a state in which the substrate W and the solid electrolyte membrane 13A placed on the lifting device 14 are separated from each other, the air in the space S of the first storage chamber 11 and the second storage chamber 12 is sucked, thereby filling the second storage chamber 12 with water vapor st while reducing the pressure in the first storage chamber 11 and the second storage chamber 12.

[0038] Specifically, the water M accommodated in the accommodation chamber 18a of the water vapor supply unit 18 is heated to about 95°C by the heating unit 18b to become hot water, and water vapor st is generated from the surface of the hot water by suction by the suction pump 17. In this embodiment, the water vapor supply unit 18 is also in a state of reduced pressure relative to atmospheric pressure, so that water vapor st is generated from the water M at a lower temperature than in a state of atmospheric pressure. Here, by increasing the temperature of the water M in the water vapor supply unit 18 compared to the temperature of the plating solution L, the water M is evaporated preferentially, and evaporation of the plating solution L during reduced pressure can be suppressed. This can suppress an increase in the concentration of metal ions in the plating solution L and a decrease in the temperature of the plating solution L.

[0039] The generated water vapor st flows into the second storage chamber 12 through the communication passage 25. Furthermore, since the first storage chamber 11 and the second storage chamber 12 are communicated with each other through the communication passage 20, the water vapor st filling the second storage chamber 12 also flows into the first storage chamber 11, and is also filled in the space S of the first storage chamber 11.

[0040] Next, a contact step S2 shown in Fig. 2 is performed. Specifically, as shown in Fig. 4, in a state where the second storage chamber 12 is filled with water vapor st, the substrate W placed on the lifting device 14 is raised to bring the substrate W into contact with the solid electrolyte membrane 13A. When the substrate W comes into contact with the solid electrolyte membrane 13A, suction by the suction pump 17 is stopped. Here, as shown in the partially enlarged view of Fig. 4, when the solid electrolyte membrane 13A is brought into contact with the substrate W, water vapor st may be trapped between the surface Wf of the substrate W and the solid electrolyte membrane 13A.

[0041] 2 is performed. In this step, the depressurized spaces S of the first storage chamber 11 and the second storage chamber 12 are opened to the atmosphere while the substrate W is in contact with the solid electrolyte membrane 13A. Specifically, by opening the release valve 19, the atmosphere enters through the release valve 19, and the first storage chamber 11 and the second storage chamber 12, which are in communication with the communication passage 20, are pressurized from the depressurized state to atmospheric pressure.

[0042] In the opening step S3, the reduced pressure space S of the first storage chamber 11 and the second storage chamber 12 are opened to the atmosphere while the substrate W is in contact with the solid electrolyte membrane 13A, so that the pressure in the space S of the first storage chamber 11 and the second storage chamber 12 becomes atmospheric pressure. As a result, in the contact step, the water vapor st trapped between the surface Wf of the substrate W and the solid electrolyte membrane 13A is increased from the reduced pressure state to atmospheric pressure from the solid electrolyte membrane 13A side, and the trapped water vapor st disappears as water.

[0043] In this embodiment, since suction by the suction pump 17 is stopped before the release valve 19 is opened, the first storage chamber 11 and the second storage chamber 12 can be quickly pressurized from a reduced pressure state to atmospheric pressure by opening the release valve 19. However, as long as the pressure in the first storage chamber 11 and the second storage chamber 12 can be maintained at atmospheric pressure by the release valve 19 until the film formation process S4 described below is completed, the suction pump 17 may be operated continuously until the film formation process S4 is completed.

[0044] Next, the film forming step S4 shown in FIG. 2 is performed. In the film forming step S4, a metal film F is formed on the surface of the substrate W in a state in which the first storage chamber 11 and the second storage chamber 12 are opened to the atmosphere under reduced pressure. More specifically, in the first embodiment, as described above, an electrolytic plating solution is used as the plating solution L, and a non-porous solid electrolyte membrane is used as the solid electrolyte membrane 13A. In the first storage chamber 11, the anode 32 is in contact with the plating solution L and is disposed at a position facing the substrate W, and a voltage is applied between the anode 32 and the substrate W serving as the cathode in a state in which the substrate W is in contact with the solid electrolyte membrane 13A. As a result, metal ions contained in the electrolytic plating solution that has permeated the solid electrolyte membrane 13A can be reduced on the surface of the substrate W, and metal derived from the metal ions can be precipitated. As a result, a metal film derived from the metal ions is formed on the surface of the substrate W by utilizing electrolytic plating.

[0045] According to this embodiment, in the opening step S3, the water vapor st trapped between the substrate W and the solid electrolyte membrane 13A is increased in pressure from the solid electrolyte membrane 13A side to atmospheric pressure as the pressure in the space S of the first storage chamber 11 is increased, and the trapped water vapor st turns into water and disappears. Since this water does not prevent the movement of metal ions, when a voltage is applied between the anode 32 and the substrate W serving as the cathode in the film forming step S4, the metal ions contained in the plating solution L pass through the solid electrolyte membrane 13A and are uniformly reduced on the surface of the substrate, and metal is precipitated. As a result, the precipitation of metal is not hindered by the entrapment of air, and a homogeneous metal coating F with a uniform thickness can be formed.

[0046] <Second embodiment> The film formation apparatus 1 and film formation method according to the second embodiment differ from those of the first embodiment in that a metal coating F is formed on the surface of the substrate W by utilizing electroless plating. Specifically, the method for forming a metal coating F and the film formation apparatus 1 of the present embodiment deposit a metal on the surface of the substrate W by electroless plating from metal ions contained in a plating solution L, thereby forming a metal coating F derived from the metal ions on the surface of the substrate W. The same components as those of the film formation apparatus 1 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted, with only the differences being described.

[0047] Here, electroless plating is a method of depositing (forming) a film by a chemical reduction reaction, unlike electrolytic plating, which is electrolytically deposited by a power source. Electroless plating includes displacement plating, which utilizes the difference in ionization tendency between the metal constituting the substrate W and the metal ions contained in the plating solution (electroless plating solution), and autocatalytic reduction plating, which utilizes the reducing ability of a reducing agent.

[0048] When the electroless plating is displacement plating, it is preferable to use a metal material made of a metal (a metal having a high ionization tendency) that is more base than the metal ions contained in the plating solution L as the substrate W. A layer made of a metal that is more base than the metal ions contained in the plating solution L may be formed on the surface of the substrate W body. In this case, a metal material or a resin material that is more noble than the metal ions contained in the plating solution L may be used as the substrate body. An example of such a substrate W is one in which a Ni plating layer is formed on the surface of a substrate made of Cu when the metal ions contained in the plating solution L are Au ions.

[0049] When the electroless plating is autocatalytic reduction plating, the substrate W may be made of a metal material, a resin material, or the like, so long as it is a material that has a catalytic effect of promoting the oxidation reaction of the reducing agent. A layer made of a metal that acts as a catalyst may be formed on the surface of the substrate W body. In this case, the substrate W body may be made of a metal material or a resin material that does not have a catalytic effect. An example of such a substrate W is a substrate W having a Pd plating layer that acts as a catalyst formed on the surface of a substrate made of Cu when the metal ions contained in the plating solution (electroless plating solution) L are Ni ions.

[0050] 5, the film forming apparatus 1 according to this embodiment differs from that of the first embodiment in that it does not include an anode 32, a support 34 supporting the anode, a power supply unit 36, etc., and uses a porous membrane 13B instead of a solid electrolyte membrane 13A as a permeable membrane 13. The porous membrane 13B seals the plating solution L contained in the upper housing 11A and is attached to the upper housing 11A so as to face the substrate W (specifically, the mounting table 14a). The porous membrane 13B is a membrane that allows the plating solution L to permeate in the film thickness direction and has a plurality of holes through which the plating solution L can permeate.

[0051] The thickness of the porous membrane 13B is preferably, for example, 5 μm or more and 200 μm or less. The average pore size of the porous membrane 13B may be, for example, 0.1 μm or more and 100 μm or less, and the pore size of the porous membrane 13B is not particularly limited as long as the plating solution L can pass through the membrane in the thickness direction (specifically, the plating solution L can seep out onto the surface of the substrate W) when the membrane comes into contact with the substrate W.

[0052] In this embodiment, the porous membrane 13B may not have an ion exchange functional group (cation exchange functional group or anion exchange functional group) like a solid electrolyte. This allows the porous membrane to have almost no polarity, and metal ions contained in the plating solution L to pass through the pores without being trapped in the porous membrane. Therefore, such a plating solution L can be applied to any case in which the metal ions contained in the plating solution L are cationic, anionic, or nonionic. As such a plating solution L, a polyolefin resin can be used. Examples of the polyolefin resin include polyethylene resin, polypropylene resin, and a resin obtained by mixing these.

[0053] The plating solution (electroless plating solution) L is a solution supplied to one side of the porous membrane 13B, and is a solution containing at least metal ions that are deposited by electroless plating as the metal of the metal film F. The plating solution L for displacement plating or autocatalytic reduction plating may be a plating solution that is generally available commercially.

[0054] When the electroless plating is displacement plating, the metal of the metal ions contained in the plating solution L is a metal that is more noble (has a smaller tendency to ionize) than the material of the substrate W. For example, when the substrate W is made of Cu, examples of the metal of the metal ions include Ag, Pt, and Au.

[0055] When the electroless plating is autocatalytic reduction plating, the plating solution L contains metal ions to be deposited as the metal of the metal film F, and a reducing agent. The metal of the metal ions is not particularly limited as long as it is a metal having catalytic action, and examples thereof include Ag, Pt, and Au. Examples of the reducing agent include hypophosphorous acid, dimethylamine borane, and the like. The plating solution L may further contain a stabilizer, a complexing agent, a reducing agent, and the like.

[0056] In the film formation method according to this embodiment, the same operations as those in the first embodiment are performed from the water vapor filling step S1 to the opening step S3. As shown in Fig. 6, in this embodiment, in the film formation step S4, a metal film F is formed on the surface of the substrate W by electroless plating while the substrate W is kept in contact with the permeable membrane for a predetermined time.

[0057] In the present embodiment, in the release step S3, the water vapor st trapped between the substrate W and the porous membrane 13B turns into water and disappears. This water does not prevent the movement of metal ions, so the precipitation of metal caused by the trapped air is not inhibited. Therefore, the metal ions that have permeated the porous membrane 13B are reduced, and the metal derived from the metal ions is precipitated, so that a homogeneous metal coating F with a uniform thickness can be formed.

[0058] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the spirit of the present invention described in the claims.

[0059] In the first and second embodiments, a metal coating is formed on the surface of a single substrate placed on a mounting table. However, for example, multiple substrates may be placed on the mounting table, and metal coatings may be formed on the surfaces of the multiple substrates simultaneously. [Explanation of symbols]

[0060] 1: film forming device, 11: first storage chamber, 12: second storage chamber, 13: permeable membrane, 13A: solid electrolyte membrane, 13B: porous membrane, 14: lifting device, 17: suction pump, 18: water vapor supply unit, 19: release valve, 32: anode, 36: power supply unit, F: metal film, S: space, L: plating solution, W: substrate

Claims

1. A method for forming a metal film, comprising the steps of: dividing a first storage chamber, in which a plating solution is stored so that a space is formed at an upper portion, from a second storage chamber, which is disposed below the first storage chamber and in which a substrate is stored, by a permeable membrane through which at least metal ions contained in the plating solution permeate; raising the substrate placed on a lifting device brings the substrate into contact with the permeable membrane from below, and forming a metal film on a surface of the substrate from the metal ions that have permeated the permeable membrane, The first storage chamber and the second storage chamber are in communication with each other via a communication passage, a water vapor filling step of filling the second storage chamber with water vapor while reducing the pressure in the first storage chamber and the second storage chamber by sucking the air in the space of the first storage chamber and the second storage chamber in a state in which the base material and the permeable membrane placed on the lifting device are separated from each other; a contacting step of bringing the base material into contact with the permeable membrane by raising the base material placed on the lifting device while the second storage chamber is filled with the water vapor; an opening step of opening the decompressed spaces of the first storage chamber and the second storage chamber to the atmosphere while the base material is in contact with the permeable membrane; a film forming step of forming the metal coating on the surface of the base material in a state in which the first storage chamber and the second storage chamber are opened to the atmosphere under reduced pressure; A method for forming a metal film, comprising at least the steps of:

2. An electrolytic plating solution is used as the plating solution, A non-porous solid electrolyte membrane is used as the permeable membrane, an anode is disposed in the first container at a position in contact with the plating solution and facing the substrate; 2. The method for forming a metal coating according to claim 1, wherein in the film formation step, the metal coating is formed on the surface of the substrate by electrolytic plating while applying a voltage between the anode and the substrate serving as a cathode with the substrate in contact with the permeable membrane.

3. An electroless plating solution is used as the plating solution, A porous membrane that allows the plating solution to permeate is used as the permeable membrane, 2. The method for forming a metal film according to claim 1, wherein in the film forming step, the metal film is formed on the surface of the substrate by electroless plating while the substrate is kept in contact with the permeable membrane for a predetermined period of time.

4. a first storage chamber in which a plating solution containing metal ions is stored so that a space is formed at the top; a second storage chamber disposed below the first storage chamber and configured to store a substrate; a permeable membrane that separates the first storage chamber from the second storage chamber and that allows at least metal ions contained in the plating solution to pass through; a lifting device for placing the base material contained in the second storage chamber and lifting the base material, a metal coating forming apparatus for forming a metal coating on a surface of the substrate from metal ions that have permeated the permeable membrane while maintaining a state in which the substrate is in contact with the permeable membrane by raising the substrate placed on the lifting device, The first storage chamber and the second storage chamber are in communication with each other via a communication passage, The film forming apparatus includes: a suction pump that sucks air from the first storage chamber and the second storage chamber and reduces the pressure in the first storage chamber and the second storage chamber while the base material is separated from the permeable membrane; A water vapor supply unit that supplies water vapor to the depressurized second storage chamber; an open valve that opens the first storage chamber and the second storage chamber, the pressure of which has been reduced, to the atmosphere while the base material is in contact with the permeable membrane; The metal film forming apparatus further comprising:

5. The plating solution is an electrolytic plating solution, the permeable membrane is a non-porous solid electrolyte membrane; The film forming apparatus includes: an anode disposed in the first container chamber in contact with the plating solution and facing the substrate; 5. The metal film forming apparatus according to claim 4, further comprising a power supply unit that applies a voltage between the anode and the substrate that serves as a cathode.

6. The plating solution is an electroless plating solution, 5. The metal film forming apparatus according to claim 4, wherein the permeable membrane is a porous membrane that allows the plating solution to permeate.

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