JP7616010B2 - METHOD FOR FORMING METAL FILM AND APPARATUS FOR FORMING METAL FILM - Google Patents

Description

The present invention relates to a method and apparatus for forming a metal film, which deposits 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.

For example, Patent Document 1 proposes a method for forming a metal film on the surface of a substrate, in which a solid electrolyte membrane is used as one of the permeable membranes that allows metal ions to pass through, and a metal film is formed by electrolytic plating. In this method, the metal ions are passed through a plating solution containing metal ions while the substrate surface is in contact with the permeable membrane, and the metal ions that have passed through are precipitated on the substrate surface, forming a metal film.

JP 2014-051701 A

However, air can get trapped when the permeable membrane is brought into contact with the substrate. This can prevent a homogeneous metal coating of uniform thickness from being formed.

The present invention has been made in consideration of these points, and provides a metal film deposition method and deposition device that can deposit a homogeneous metal film with a uniform thickness.

In view of the above-mentioned problems, the method for forming a metal film according to the present invention is a method for forming a metal film, which comprises dividing a first storage chamber in which a plating solution is stored so that a space is formed at the top and a second storage chamber arranged below the first storage chamber and in which a substrate is stored, with a permeable membrane through which at least the 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 film is formed on the surface of the substrate from the metal ions that have permeated the permeable membrane, the first storage chamber and the second storage chamber are connected via a communication passage, and the substrate placed on the lifting device is separated from the permeable membrane by the first storage chamber. The method includes at least a water vapor filling step of filling the second storage chamber with water vapor while reducing the pressure of the first storage chamber and the second storage chamber by sucking the air in the space of the container and the second storage chamber; a contact step of bringing the base material placed on the lifting device into contact with the permeable membrane by raising the base material in a state in which the second storage chamber is filled with the water vapor; an opening step of opening the space of the first storage chamber and the second storage chamber, which has been depressurized, to the atmosphere while the base material is in contact with the permeable membrane; and a film forming step of forming the metal film on the surface of the base material while the first storage chamber and the second storage chamber, which have been depressurized, are open to the atmosphere.

According to the present invention, in the water vapor filling step, with the base material placed on the lifting device and the permeable membrane separated, the air in the space of the first storage chamber and the second storage chamber is sucked out, and the first storage chamber and the second storage chamber are depressurized while water vapor is filled into the depressurized second storage chamber. Next, in the contact step, 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 become trapped between the base material and the permeable membrane.

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, no air is 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.

In a more preferred embodiment, 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 placed in the first storage chamber in contact with the plating solution and facing the substrate, and in the film formation step, the metal film 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.

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 the trapped water vapor turns into water and disappears, but this water does not impede the movement of metal ions. Therefore, in the film formation 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, metal precipitation is not hindered by air entrapment, and a homogeneous metal coating with a uniform thickness can be formed.

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 process, 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.

Even in this embodiment, the water vapor trapped between the substrate and the permeable membrane during the opening process turns into water and disappears. It does not impede the movement of metal ions. Therefore, even in this embodiment, the deposition of metal is not hindered by air being trapped, and a homogeneous metal coating with a uniform thickness can be formed.

The present invention discloses a metal film forming apparatus as described below. The metal film forming apparatus according to the present invention comprises 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 raises 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 film forming apparatus that forms a metal film on the surface of the substrate from the permeated metal ions, the first storage chamber and the second storage chamber are connected via a communication passage, and the film forming 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.

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

Even in such a case, the release valve opens the depressurized 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 pressure in the space of the first storage chamber and the second storage chamber to be increased to atmospheric pressure. As a result, the water vapor trapped between the substrate and the permeable membrane is increased in pressure 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.

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 forming device further includes an anode in the first storage chamber that is in contact with the plating solution and is positioned opposite the substrate, and a power supply unit that applies a voltage between the anode and the substrate that serves as a cathode.

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 the trapped water vapor turns into water and disappears, but this water does not impede the movement of metal ions. Therefore, when a voltage is applied from the power supply 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 precipitation of metal being hindered by the entrapment of air.

In yet another embodiment, the plating solution is an electroless plating solution, and the permeable membrane is a porous membrane that allows the plating solution to permeate.

Even 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.

The metal film deposition method and deposition device of the present invention can deposit a homogeneous metal film with a uniform thickness.

1 is a schematic cross-sectional view of a metal film forming apparatus according to a first embodiment of the present invention. FIG. 2 is a flow diagram of the film forming method shown in FIG. 3 is a diagram for explaining a water vapor filling step in the film forming method shown in FIG. 2 . 3A to 3C are diagrams for explaining a contact step and a film forming step in the film forming method shown in FIG. 2 . FIG. 5 is a schematic cross-sectional view of a metal film forming apparatus according to a second embodiment of the present invention. 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.

Below, the metal film deposition apparatus and the deposition method according to the first and second embodiments of the present invention will be described with reference to Figures 1 to 6.

First Embodiment
1. Regarding the film forming apparatus 1 for forming a metal film 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 an elevating 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.

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 contains the substrate W. 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, while the plating solution L is contained in the first storage chamber 11, the first storage chamber 11 containing the plating solution L and the second storage chamber 12 containing the substrate W can be separated by the permeable membrane 13. 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.

The lifting device 14 is a device that places the substrate W stored in the second storage chamber 12 and raises and lowers the substrate W, and has a linear electric actuator (not shown) or the like attached to its lower part. A placement table 14a on which the substrate W is placed is formed at the upper end of the lifting device 14. A recess is formed in the placement table 14a for positioning the substrate W.

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, an anode 32 and a power supply unit 36 are further provided to form a metal film by electrolytic plating. The anode 32 is disposed in the first storage chamber 11 in a position that contacts the plating solution L and faces the substrate W.

The anode 32 may be, for example, a soluble anode made of the same material as the metal coating F (e.g., Cu), or an anode made of a material that is insoluble in the plating solution L (e.g., Ti).

The solid electrolyte membrane 13A is, for example, a membrane of a solid electrolyte having an ion-exchange 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 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 with cation exchange functions such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

The plating solution L is a liquid that contains the metal of the metal film 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.

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 wiring, 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 as the cathode.

The substrate W may be a metal substrate such as copper, iron, or aluminum, and may have a metal coating such as nickel formed on its surface. 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 there is no particular limitation as long as the surface of the substrate W acts as a cathode.

According to the film forming apparatus 1 of this 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 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.

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 are connected 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 can be sucked from the first storage chamber 11 and the second storage chamber 12 via 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.

The water vapor supply unit 18 is a part that supplies water vapor to the depressurized 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 connected to 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.

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 while the substrate W is 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 it 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.

2. About the film formation method of the metal film In this film formation method, a metal film is formed on the surface of the substrate W by using the above-mentioned film formation apparatus 1. In this embodiment, as a preparation stage 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.

After completing the preparations before film formation, the water vapor filling step S1 shown in FIG. 2 is performed first. In this step, the substrate W placed on the lifting device 14 and the solid electrolyte membrane 13A are separated from each other, and the air in the space S of the first storage chamber 11 and the second storage chamber 12 is sucked in to fill 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.

Specifically, the water M stored in the storage chamber 18a of the water vapor supply unit 18 is heated to about 95°C by the heating unit 18b, 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 water vapor st is generated from the water M at a lower temperature than in a state of atmospheric pressure. Here, by raising 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 suppresses an increase in the concentration of metal ions in the plating solution L, and also suppresses a decrease in the temperature of the plating solution L.

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 connected by the communication passage 20, the water vapor st filled in the second storage chamber 12 also flows into the first storage chamber 11 and fills the space S of the first storage chamber 11.

Next, the contact step S2 shown in FIG. 2 is performed. Specifically, as shown in FIG. 4, with the second storage chamber 12 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, the 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 get caught between the surface Wf of the substrate W and the solid electrolyte membrane 13A.

Next, the opening step S3 shown in FIG. 2 is performed. In this step, the space S of the first storage chamber 11 and the second storage chamber 12, which has been reduced in pressure, is opened to the atmosphere while the substrate W is in contact with the solid electrolyte membrane 13A. Specifically, by opening the opening valve 19, the atmosphere enters through the opening valve 19, and the first storage chamber 11 and the second storage chamber 12, which are connected to the communication passage 20, are pressurized from a reduced pressure state to atmospheric pressure.

In the opening step S3, the depressurized 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 space S of the first storage chamber 11 and the second storage chamber 12 are at 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 pressurized from the depressurized state to atmospheric pressure from the solid electrolyte membrane 13A side, and the trapped water vapor st disappears as water.

In this embodiment, suction by the suction pump 17 is stopped before the release valve 19 is opened, so that 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, if 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.

Next, the film formation step S4 shown in FIG. 2 is performed. In the film formation step S4, a metal film F is formed on the surface of the substrate W with the first storage chamber 11 and the second storage chamber 12, which have been reduced in pressure, open to the atmosphere. 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, which serves as the cathode, with the substrate W in contact with the solid electrolyte membrane 13A. As a result, the 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 using electrolytic plating.

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 impede the movement of metal ions, when a voltage is applied between the anode 32 and the substrate W, which serves 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, causing the metal to precipitate. As a result, a homogeneous metal coating F with a uniform thickness can be formed without the metal precipitation being hindered by the entrapment of air.

Second Embodiment
The film forming apparatus 1 and film forming method according to the second embodiment differ from those of the first embodiment in that electroless plating is used to form a metal coating F on the surface of the substrate W. Specifically, the method for forming a metal coating F and the film forming apparatus 1 of the present embodiment deposit 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 forming 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.

Here, electroless plating is a method of depositing (forming) a film by a chemical reduction reaction, unlike electrolytic plating, which is electrolytically deposited using a power source. Electroless plating includes substitution plating, which utilizes the difference in ionization tendency between the metal that constitutes 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.

When the electroless plating is displacement plating, it is preferable to use a metal material made of a metal (a metal with 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 also be formed on the surface of the substrate W body. In this case, the substrate body may be made of a metal material or a resin material that is more noble than the metal ions contained in the plating solution L. An example of such a substrate W is one in which a Ni plating layer is formed on the surface of a substrate body made of Cu when the metal ions contained in the plating solution L are Au ions.

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 catalytic metal may also 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 catalytic Pd plating layer formed on the surface of a Cu body when the metal ions contained in the plating solution (electroless plating solution) L are Ni ions.

As shown in FIG. 5, unlike the first embodiment, the film forming apparatus 1 according to this embodiment 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 pass through in the film thickness direction, and has a plurality of holes through which the plating solution L can pass.

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.

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 can pass through the pores without being trapped in the porous membrane. Therefore, such a plating solution L can be applied when 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 polyolefin resins include polyethylene resins, polypropylene resins, and resins made by mixing these.

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

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.

When the electroless plating is autocatalytic reduction plating, the plating solution L contains metal ions to be precipitated 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 has catalytic activity, and examples of the metal include Ag, Pt, and Au. Examples of the reducing agent include hypophosphorous acid and dimethylamine borane. The plating solution L may further contain a stabilizer, a complexing agent, a reducing agent, and the like.

In the film forming method according to this embodiment, the same operations as in the first embodiment are performed from the water vapor filling step S1 to the opening step S3. As shown in FIG. 6, in the film forming step S4 in this embodiment, 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.

In this embodiment, too, in the opening 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 impede the movement of metal ions, so the precipitation of metal caused by 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 precipitates, forming a homogeneous metal coating F with a uniform thickness.

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 as described in the claims.

In the first and second embodiments, a metal coating is formed on the surface of one substrate placed on a mounting table, but, 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.

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: Open valve, 32: Anode, 36: Power supply unit, F: Metal film, S: Space, L: Plating solution, W: Substrate

Claims (6)

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: 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. 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,
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. 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: 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. 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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