CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2019-084847 filed on Apr. 26, 2019, the content of which is hereby incorporated by reference into this application.

BACKGROUND

Technical Field

The present disclosure relates to a film forming apparatus for forming a metal film on a surface of a substrate.

Background Art

Conventionally, a metal film is formed by depositing metal (by reducing metal ions) on a surface of a substrate. For example, JP 2017-88918 A proposes a film forming apparatus including an anode, an electrolyte membrane disposed between the anode and a substrate serving as a cathode, a liquid housing portion that houses a metal solution containing metal ions, and a power supply unit that applies a voltage across the anode and the substrate. The film forming apparatus further includes a pressure device that pressurizes the electrolyte membrane against the substrate. The liquid housing portion is attached to the pressure device via an elastic body that can elastically deform in the pressurization direction of the pressure device.

In such a film forming apparatus, when the electrolyte membrane is pressurized against the substrate, the elastic body elastically deforms in the pressurized direction of the substrate, and thus, the surface of the substrate can be pressurized with the electrolyte membrane due to a restoring force of the elastic body that has elastically deformed. At this time, the fluid pressure of the metal solution in the liquid housing portion increases due to a reaction force of the substrate acting on the electrolyte membrane. Consequently, the surface of the substrate can be uniformly pressurized with the electrolyte membrane due to the increased fluid pressure of the metal solution. In such a pressurized state, a voltage is applied across the anode and the substrate so that metal ions contained in the electrolyte membrane are reduced and a uniform metal film can thus be formed on the surface of the substrate.

SUMMARY

However, in the film forming apparatus according to JP 2017-88918 A, when metal films are concurrently formed on a plurality of portions of a substrate using a plurality of electrolyte membranes, for example, it may be impossible to uniformly pressurize the surface of the substrate with the electrolyte membranes. In particular, when the distance between each electrolyte membrane and the surface of the substrate before a pressure is applied thereto differs from one another, such a phenomenon becomes prominent. Consequently, it may be impossible to form a uniform metal film on a portion of the surface of the substrate in contact with each electrolyte membrane.

The present disclosure has been made in view of the foregoing, and provides a film forming apparatus for forming a metal film, capable of forming a uniform metal film on a surface of a substrate by uniformly pressurizing an electrolyte membrane against the surface of the substrate.

Accordingly, the film forming apparatus for forming a metal film according to the present disclosure is a film forming apparatus for forming a metal film on a surface of a substrate by (chemically) reducing metal ions, including a plurality of film forming units each including an anode, an electrolyte membrane disposed between the anode and the substrate, and a liquid housing portion having the electrolyte membrane attached thereto, the liquid housing portion being adapted to house a metal solution containing the metal ions such that the metal solution is sealed in the liquid housing portion and the metal solution is in contact with the electrolyte membrane; a pressure device including a coupling portion and a pressure unit, the coupling portion being adapted to couple the film forming units together, and the pressure unit being adapted to pressurize the substrates with the electrolyte membranes of the respective film forming units via the coupling portion; and a power supply unit adapted to apply a voltage across each anode and each substrate so that metal derived from the metal ions with which each electrolyte membrane is impregnated are deposited on a surface of the substrate in a state in which the electrolyte membrane of each film forming unit is in contact with the substrate, in which each film forming unit is coupled to the coupling portion via a first elastic body, the first elastic body being adapted to elastically deform in a pressurization direction of the pressure unit.

According to the present disclosure, when a metal film is formed on a surface of a substrate, the electrolyte membrane of each film forming unit is pressurized against the substrate by the pressure unit of the pressure device via the coupling unit. At this time, the first elastic body of each film forming unit, which is coupled to the coupling portion of the pressure device, elastically deforms in the direction of compression. Accordingly, the electrolyte membrane of each film forming unit can be independently displaced in the pressurization direction with respect to the single coupling portion. Consequently, even when the distance between each electrolyte membrane and the surface of each substrate differs from one another before a pressure is applied, for example, such a difference in the distance can be absorbed through elastic deformation of each first elastic body, so that the surface of each substrate can be uniformly pressurized with the electrolyte membrane of each film forming unit.

In this manner, when a voltage is applied across the anode of each film forming unit and each substrate by the power supply unit while the surface of the substrate is uniformly pressurized with the electrolyte membrane of each film forming unit, metal ions contained in the electrolyte membrane are reduced on the surface of the substrate. Accordingly, a uniform metal film can be formed on the surface of the substrate.

Further, in some embodiments, the electrolyte membrane is attached to the liquid housing portion via a second elastic body, the second elastic body being adapted to elastically deform in the pressurization direction, and the spring constant of the first elastic body in the pressurization direction is smaller than that of the second elastic body in the pressurization direction.

According to such an embodiment, since the spring constant of the first elastic body in the pressurization direction is smaller than that of the second elastic body in the pressurization direction, the first elastic body can be compressively deformed more than the second elastic body in each film forming unit when a pressure is applied. Consequently, when the distance between each electrolyte membrane and the surface of each substrate is different from one another before a pressure is applied, for example, such a difference in the distance can be absorbed through elastic deformation of each first elastic body. Further, the electrolyte membrane of each film forming unit can be allowed to uniformly follow the surface of each substrate through elastic deformation of the second elastic body.

Herein, the state of the pressure unit and the coupling portion attached together is not particularly limited as long as the pressure unit can pressurize the surface of each substrate with each electrolyte membrane via the coupling portion. However, in some embodiments, the coupling portion is pivotally attached to the pressure unit so that the coupling portion pivots when each first elastic body has elastically deformed in response to a pressure applied by the pressure unit.

According to such an embodiment, since the coupling portion is pivotally attached to the pressure unit, even when the distance between each electrolyte membrane and its corresponding substrate differs from one another, the coupling portion pivots by an amount corresponding to the difference in the distance, and thus, the amount of compressive deformation of each first elastic body can be made closer to each other. Accordingly, a pressure applied with the electrolyte membrane of each film forming unit can be made more uniform.

According to the present disclosure, it is possible to form a uniform metal film on a surface of a substrate by uniformly pressurizing an electrolyte membrane against the surface of the substrate.

