Metal film deposition apparatus

Abstract

The present invention provides a metal film deposition apparatus that can deposit a metal film over a long period of time by pressing the substrate through an electrolyte membrane with a stable plating solution pressure. [Solution] When the pressure measured by the hydraulic pressure gauge 58 falls outside a predetermined range, the metal film control device 30 releases the pressurization by the piston 61 while continuing to apply voltage, and opens the on-off valves 54 and 55, thereby circulating the plating solution L in the container 15 with the circulation pump 80. After the plating solution L has been circulated to the container 15, the on-off valves 54 and 55 are closed, and the plating solution L in the container 15 is pressurized by the piston 61 to the film formation pressure, and the formation of the metal film F continues.

Description

Technical Field

[0001] The present invention relates to a film forming apparatus for a metal film.

Background Art

[0002] Conventionally, a film forming apparatus for forming a metal film on a substrate has been known. The film forming apparatus for a metal film described in Patent Document 1 below applies a voltage between an anode and a substrate while pressing an electrolyte film against the substrate, and reduces metal ions contained inside the electrolyte film, thereby forming a metal film on the surface of the substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when attempting to form a thick metal film, the film forming time becomes long, the hydraulic pressure of the plating solution fluctuates greatly, and there is a risk of poor pressing of the electrolyte film against the substrate. In particular, when the plating solution is pressurized with a piston or the like, this phenomenon becomes prominent.

[0005] The present invention has been made in view of such points, and an object thereof is to provide a film forming apparatus for a metal film that can form a metal film for a long time while pressing a substrate through an electrolyte film with a stable hydraulic pressure of the plating solution.

Means for Solving the Problems

[0006] In view of the above-mentioned problems, the metal film deposition apparatus according to the present invention is a film deposition apparatus that deposits a metal film on the surface of a substrate by electroplating. The film deposition apparatus comprises a container that houses an anode and a plating solution, with an opening facing the substrate covered by an electrolyte membrane; a circulation mechanism having a power supply for applying a voltage between the anode and the substrate and a circulation pump for circulating the plating solution contained in the container; an on-off valve for blocking the movement of the plating solution between the circulation mechanism and the container; a pressurizing mechanism connected to the circulation mechanism and having a piston for pressurizing the plating solution contained in the container when the on-off valve is closed; a pressure gauge for measuring the liquid pressure of the plating solution contained in the container; and a control device for controlling the application of voltage by the power supply, the circulation by the circulation mechanism, the opening and closing of the on-off valve, and the pressurizing by the piston.

[0007] The control device closes the on-off valve while the electrolyte membrane is in contact with the substrate, and uses the piston to pressurize the plating solution in the container to the film formation pressure, and while the plating solution is pressurized, applies the voltage to the power supply to form the metal film. If the pressure measured by the hydraulic pressure gauge falls outside a predetermined range, the control device continues to apply the voltage, releases the pressurization by the piston, and opens the on-off valve, thereby circulating the plating solution in the container with the circulation pump, and after the plating solution has been circulated to the container, closes the on-off valve and continues to pressurize the plating solution in the container to the film formation pressure using the piston, and continues forming the metal film. [Effects of the Invention]

[0008] According to the present invention, a metal film can be formed over a long period of time while pressing the substrate through an electrolyte membrane using a stable plating solution pressure. [Brief explanation of the drawing]

[0009] [Figure 1]Figure 1(a) is a schematic cross-sectional view showing an example of a metal film deposition apparatus according to an embodiment of the present invention, before the metal film is deposited. Figure 1(b) is a cross-sectional view illustrating the process of bringing the electrolyte membrane into contact with the substrate, as shown in Figure 1(a). [Figure 2] Figure 2(a) is a cross-sectional view illustrating the process of supplying the plating solution to the housing of the film deposition apparatus by a circulation mechanism, as shown in Figure 1(b). Figure 2(b) is a cross-sectional view illustrating the process of pressurizing the plating solution in the housing with a piston and then depositing a metal film, as shown in Figure 2(a). [Figure 3] Figure 1 shows the control flow for film deposition using the control device of the film deposition apparatus. [Figure 4] This graph shows the relationship between the film formation time and applied pressure for metal films in the reference examples and reference comparative examples. [Modes for carrying out the invention]

[0010] First, with reference to Figures 1 to 4, a metal film deposition apparatus 1 according to an embodiment of the present invention will be described.

[0011] As shown in Figures 1(a) to 2(b), the film deposition apparatus 1 is a film deposition apparatus that deposits a metal film F on a substrate B by electroplating. The film deposition apparatus 1 deposits the metal film F while pressing the substrate B with the liquid pressure of the plating solution L via an electrolyte membrane 13. The film deposition apparatus 1 comprises an anode 11, an electrolyte membrane 13, and a power supply 14 that applies a voltage between the anode 11 and the substrate B.

[0012] The film deposition apparatus 1 includes a housing 15 containing an anode 11 and a plating solution L. The housing 15 contains the anode 11 and the plating solution L with an opening 15d facing the substrate B covered by an electrolyte membrane 13. The film deposition apparatus 1 includes a linear actuator 70 for raising and lowering the housing 15. The linear actuator 70 can be any moving mechanism that moves at least one of the housing 15 and the substrate B so that the electrolyte membrane 13 attached to the housing 15 and the substrate B can move toward and away from each other.

[0013] Substrate B functions as a cathode. Substrate B is a plate-shaped substrate. In this embodiment, substrate B is a rectangular substrate. Of the surfaces of substrate B, the surface facing the electrolyte film 13 is the film-forming surface that functions as a cathode. In this embodiment, substrate B is used in which a metal layer is formed on the surface of an insulating substrate. The insulating substrate is made of a material that is electrically insulating, such as glass, ceramics, resin, or a composite material thereof. The metal layer may be made of a metal such as aluminum or copper.

[0014] The anode 11 may, for example, be a non-porous (e.g., non-porous) anode made of the same metal as the metal film, but in this embodiment, the anode 11 is an insoluble anode that is insoluble in the plating solution L described later. For example, the anode 11 can be titanium, platinum, or gold. The surface of the anode 11 may be coated with one of these metals. The anode 11 has a block-like or flat plate shape. The anode 11 is electrically connected to the positive electrode of the power supply 14. The anode 11 is positioned in the housing space 15a of the housing 15, facing the film-forming surface Ba of the substrate B. The anode 11 is suspended within the housing space 15a via a bracket 19.

[0015] The plating solution L is an aqueous solution containing the metal to be formed into a metal film in an ionic state. Examples of such metals include copper and nickel. The plating solution L is a solution obtained by dissolving (ionizing) these metals in an acidic aqueous solution such as nitric acid, phosphoric acid, or sulfuric acid.

[0016] The electrolyte membrane 13 is a membrane that, when brought into contact with the plating solution L, can impregnate (contain) metal ions together with the plating solution L. The electrolyte membrane 13 is a flexible membrane. The material of the electrolyte membrane 13 is not particularly limited as long as the material allows metal ions from the plating solution L to move to the substrate B side when a voltage is applied by the power supply 14. Examples of materials for the electrolyte membrane 13 include ion-exchange resins such as fluoropolymer resins such as Nafion® manufactured by DuPont. The thickness of the electrolyte membrane 13 is preferably in the range of 20 μm to 200 μm.

[0017] The container 15 is made of a material insoluble in the plating solution L. The container 15 has a containment space 15a for containing the plating solution L. The anode 11 is placed in the containment space 15a of the container 15. An opening 15d is formed in the containment space 15a at a position facing the substrate B. The opening 15d of the container 15 is covered with an electrolyte membrane 13. Specifically, the periphery of the electrolyte membrane 13 is sandwiched between the container 15 and the frame 17. This allows the plating solution L in the containment space 15a to be sealed with the electrolyte membrane 13.

[0018] As shown in Figures 1(a) and 1(b), the linear actuator 70 raises and lowers the housing 15 so that the electrolyte membrane 13 and the base material B can move freely into and out of contact. In this embodiment, the mounting base 40 is fixed, and the housing 15 is lowered by the linear actuator 70. The linear actuator 70 is an electrically operated actuator that converts the rotational motion of a motor into linear motion using a ball screw or the like (not shown). However, a hydraulic or pneumatic actuator may be used instead of an electrically operated actuator.

[0019] The container 15 is formed with a supply port 15b for supplying the plating solution L to the accommodation space 15a. The container 15 is formed with a discharge port 15c for discharging the plating solution L from the accommodation space 15a. The supply port 15b and the discharge port 15c are holes communicating with the accommodation space 15a. The supply port 15b and the discharge port 15c are formed with the accommodation space 15a interposed therebetween. The supply port 15b is fluidly connected to the liquid supply pipe 51. The discharge port 15c is fluidly connected to the liquid discharge pipe 52. A pressure gauge 58 for measuring the hydraulic pressure of the plating solution L accommodated in the container 15 is attached to the container 15.

[0020] The film forming apparatus 1 further includes a circulation mechanism 50 and a tank 90. The circulation mechanism 50 includes a liquid supply pipe 51, a liquid discharge pipe 52, and a circulation pump 80. The circulation pump 80 is a pump for circulating the plating solution L accommodated in the container 15. As shown in Fig. 1(a), the tank 90 contains the plating solution L. The liquid supply pipe 51 connects the tank 90 and the container 15. The liquid supply pipe 51 is provided with a circulation pump 80. The circulation pump 80 supplies the plating solution L from the tank 90 to the container 15. The liquid discharge pipe 52 connects the tank 90 and the container 15.

[0021] In this embodiment, by driving the circulation pump 80, the plating solution L is sucked from the tank 90 into the liquid supply pipe 51. The sucked plating solution L is pumped from the supply port 15b into the accommodation space 15a. The plating solution L in the accommodation space 15a is returned to the tank 90 through the discharge port 15c. In this way, the circulation mechanism 50 can circulate the plating solution L in the film forming apparatus 1.

[0022] In this embodiment, the film deposition apparatus 1 is equipped with on-off valves 54 and 55 that block the movement of the plating solution L between the circulation mechanism 50 and the container 15. On-off valve 54 is attached to the liquid discharge pipe 52, and on-off valve 55 is attached to the liquid supply pipe 51. By closing the on-off valves 54 and 55, the plating solution L can be pressurized without causing the plating solution L in the container 15 to flow out. Note that if the movement of the piston 61, which will be described later, can block the flow of the plating solution L from the liquid supply pipe 51 to the container 15, then on-off valve 55 may be omitted.

[0023] In this embodiment, the film deposition apparatus 1 is connected to a circulation mechanism 50 and includes a pressurizing mechanism 60 that pressurizes the plating solution L contained in the housing 15 when the on-off valves 54 and 55 are closed. The pressurizing mechanism 60 has a piston 61 and a cylinder 62. The piston 61 is slidably housed in the cylinder 62, and a liquid supply pipe 51 is connected to the space in the forward direction of the piston 61 so that the plating solution L passes through it. By advancing the piston 61, the liquid pressure of the plating solution L contained in the housing 15 (corresponding to the discharge pressure of the circulation pump 80) can be increased to the film deposition pressure. A motor or the like is connected to the piston 61, and by controlling the motor with a control device 30 (described later), the piston 61 can be moved and the plating solution L can be accurately pressurized to the desired film deposition pressure.

[0024] In this embodiment, a metal ion supplement 11A, which consists of a metal oxide that will form the metal film F, is placed inside the container 15. In this embodiment, the metal ion supplement 11A is in powder form and is placed adjacent to the anode 11. Specifically, the metal ion supplement 11A is placed on the surface of the anode 11 opposite to the surface facing the electrolyte membrane 13. That is, the metal ion supplement 11A is placed between the anode 11 and the inner wall surface of the container 15. In this embodiment, the metal ion supplement 11A is housed in a porous container or the like through which the plating solution L can pass. In this embodiment, since the metal film is a copper film, the metal is copper, and the metal oxide is CuO (copper(II) oxide).

[0025] In this embodiment, when an insoluble anode 11 that is insoluble in the plating solution is used as the anode 11 during film formation, electrolysis of water occurs on the surface of the anode 11, generating hydrogen ions. In this embodiment, these hydrogen ions react with the metal oxide of the metal ion supply material 11A to generate metal ions. As a result, even if the amount of metal ions that make up the metal film decreases during film formation, the hydrogen ions generated by the electrolysis of water can be used to replenish the metal ions in the plating solution L. For example, if the metal ion is copper, the metal oxide is CuO (copper(II) oxide), so CuO + 2H + →Cu 2+ A reaction involving +H2O occurs, allowing copper ions to be supplied to the plating solution L.

[0026] Furthermore, in this embodiment, since the metal ion replenishment material 11A is in powder form, the contact area per unit mass with the hydrogen ions can be increased. Also, since the metal ion replenishment material 11A is placed adjacent to the anode 11, it is easier to react with the hydrogen ions. In this way, when the metal film F is formed, the amount of metal ions consumed from the plating solution L inside the container 15 can be replenished from the metal ion replenishment material 11A. As a result, the metal film F can be formed for a long time.

[0027] The film deposition apparatus 1 is further equipped with a control device 30. The control device 30 controls the application of voltage by the power supply 14, circulation by the circulation mechanism 50 (specifically, starting and stopping the circulation pump 80), opening and closing of the on-off valves 54 and 55, pressurization by the piston 61 (specifically, movement of the piston), and raising and lowering of the linear actuator 70. The control device 30 is connected to the power supply 14, the circulation pump 80, the on-off valves 54 and 55, the motor (not shown) connected to the piston 61, and the motor (not shown) of the linear actuator 70, so as to transmit control signals to these devices. Furthermore, the control device 30 is connected to the hydraulic pressure gauge 58 so as to receive a signal of the hydraulic pressure (measured pressure) of the plating solution L from the hydraulic pressure gauge 58.

[0028] Referring to Figure 3 and the like, the method for forming a metal film using the control device 30 will be explained. First, as shown in Figure 1(a), the substrate B is placed on the mounting table 40. In this embodiment, with the substrate B housed in the recess 44, the film-forming surface Ba of the substrate B faces the electrolyte film 13 from the mounting table 40.

[0029] Next, as shown in step S1 of Figure 3 and in Figure 1(b), the control device 30 drives the linear actuator 70 to lower the housing 15 toward the substrate B. This brings the film-forming surface Ba of the substrate B into contact with the electrolyte membrane 13.

[0030] Next, as shown in Figure 2(a) and step S2, the control device 30 drives (starts operation of) the circulation pump 80. Specifically, the control device 30 circulates the plating solution L between the tank 90 and the container 15. At this time, if the on-off valves 54 and 55 are closed, the control device 30 opens the on-off valves 54 and 55. As a result, the container 15 is filled with the plating solution L.

[0031] Next, as shown in Figure 2(b) and step S3, the control device 30 advances the piston 61 of the pressurizing mechanism 60, pressurizing the plating solution L filled inside the container 15 to the film formation pressure. Specifically, the plating solution L in the container 15, which is pressurized by the discharge pressure of the circulation pump 80, is further pressurized by the piston 61. Proceeding to step S4, with the plating solution L pressurized, the control device 30 applies a voltage between the anode 11 and the substrate B using the power supply 14 to form a metal film F. Because the control device 30 pressurizes the plating solution L with the piston 61, it can accurately and completely pressurize the plating solution L in the container 15 to a high liquid pressure (target liquid pressure).

[0032] Next, in step S5, the control device 30 determines whether the thickness of the metal film F has reached the target thickness. Specifically, since the metal film F is formed by electroplating, the control device 30 can manage whether the target thickness has been reached by the time the voltage from the power supply 14 is applied. If it is determined in step S5 that the thickness of the metal film F has reached the target thickness, the formation of the metal film F is terminated. On the other hand, if the thickness of the metal film F has not reached the target thickness, the process proceeds to step S6.

[0033] Here, if the metal film F is to be deposited with a thickness of 200 μm or more, the voltage application time from the power supply 14 is set to several hours (for example, about 2 to 3 hours). When the deposition of the metal film F is continued for such a long period of time, as metal ions from the plating solution L pass through the electrolyte membrane 13, water from the plating solution L continues to seep out from the electrolyte membrane 13 along with the metal ions. As a result, the amount of plating solution L in the container 15 decreases, the piston 61 of the pressurizing mechanism 60 reaches the stroke end, and the piston 61 is unable to pressurize the plating solution L in the container 15, making it impossible to maintain the optimal liquid pressure of the plating solution L for film deposition. On the other hand, if the anode 11 is, for example, a soluble anode, oxygen gas may be generated as a by-product on the surface of the anode 11 during film deposition, and the pressure of the plating solution L may be excessively increased.

[0034] Therefore, in step S6, the control device 30 determines whether the pressure measured by the hydraulic pressure gauge 58 has fallen outside a predetermined range. This predetermined range is the optimal range of liquid pressure for the plating solution L for forming the metal film F (an experimentally predetermined range). If the pressure falls below this predetermined range, it can be determined that the liquid pressure of the plating solution L has decreased because too much plating solution L has seeped out from the electrolyte membrane 13. On the other hand, assuming that the anode 11 is a soluble anode, if the pressure exceeds this predetermined range, it can be determined that an excessive amount of oxygen gas has been generated and the liquid pressure of the plating solution L has been excessively increased.

[0035] In such a case, that is, if the control device 30 determines YES in step S6, the process proceeds to step S7. Specifically, while continuing to apply voltage, the control device 30 releases the pressurization by the piston 61 and, as shown in Figure 2(a), opens the on-off valves 54 and 55, thereby circulating the plating solution L in the container 15 with the circulation pump 80. Specifically, the control device 30 retracts the piston 61 and opens the on-off valves 54 and 55. Since the circulation pump 80 is continuously operating, the plating solution L is supplied from the circulation pump 80 to the container 15, and the plating solution L in the container 15 is reduced to the discharge pressure of the circulation pump 80 (specifically, a circulation pressure of 0.1 to 0.2 MPa).

[0036] In step S8, the control device 30 maintains the state of step S7 for a certain period of time, thereby completing the exchange of the plating solution L in the container 15 with the plating solution L in the tank 90. ​​This ensures that the volume of plating solution L in the container 15 is maintained by the seepage of the plating solution L, while allowing the incoming air, generated oxygen gas, etc., to be discharged from the container 15.

[0037] In step S9, after circulating the plating solution L to the container 15, the control device 30 closes the on-off valves 54 and 55 and, as shown in Figure 2(b), pressurizes the plating solution L in the container 15 to the film formation pressure using the piston 61. Because the voltage application is continued, the formation of the metal film F can continue. If the control device 30 determines NO in step S6, the process returns to step S4 and the formation of the metal film F continues. In this way, a metal film can be formed for a long time while pressing the substrate through the electrolyte membrane with a stable liquid pressure of the plating solution.

[0038] [Reference Example] In the reference embodiment, a copper film was deposited as a metal film F using the film deposition apparatus 1 shown in Figure 1. The volume of the plating solution L in the container 15 was 2 L, and a soluble anode (an anode made of copper) was used as the anode. A 1.0 mol / L copper sulfate aqueous solution was used for the plating solution L, the current density during film deposition was 5 ASD, and the film deposition area was 100 cm². 2A copper plate was prepared as the substrate, and a film was deposited for 180 minutes (target copper film thickness of 200 μm). In the reference example, instead of the judgment in step S6 of the series of steps shown in Figure 3, steps S7 to S9 were performed at 1000-second intervals, assuming the timing of the judgment in step S6. Figure 4 shows the relationship between the copper film deposition time and the applied pressure (liquid pressure of the plating solution L).

[0039] [Reference Comparison] In the comparative example, a copper film was formed in the same manner as in the reference example. The difference from the reference example is that steps S6 to S9 were omitted, and the copper film was formed continuously. Figure 4 shows the relationship between the copper film formation time and the applied pressure (liquid pressure of the plating solution L).

[0040] As shown in Figure 4, in the reference embodiment, the plating solution L was replaced periodically, so although the measured pressure of the plating solution L temporarily and briefly decreased only during the circulation timing of steps S7 and S8, the liquid pressure of the plating solution L was able to be stabilized at other times. On the other hand, in the reference comparative example, it can be seen that the liquid pressure of the plating solution L decreased when the film deposition time exceeded 8000 seconds. This is thought to be because, from around 8000 seconds onward, the piston could not pressurize the system due to the leakage of the plating solution L. In both cases, gas (oxygen gas) was generated at the anode during film deposition due to the soluble anode, but it is thought that the gas in the container prevented the liquid pressure of the plating solution from rising excessively. However, when film deposition was continued, oxygen gas accumulated further in the container, and the liquid pressure of the plating solution decreased. On the other hand, in the reference embodiment, it was possible to discharge the gas (oxygen gas) generated from the anode during film formation and accumulated in the container at intervals of 1000 seconds, and to replace and replenish the plating solution, which is thought to have stabilized the liquid pressure of the plating solution in the container.

[0041] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various design modifications can be made without departing from the spirit of the invention as described in the claims. [Explanation of Symbols]

[0042] 1: Film deposition apparatus, 11: Anode, 13: Electrolyte membrane, 14: Power supply, 30: Control device, 50: Circulation mechanism, 54, 55: On / off valves, 58: Hydraulic pressure gauge, 60: Pressurization mechanism (piston), 80: Circulation pump, B: Substrate, F: Metal film, L: Plating solution

Claims

1. A film deposition apparatus for forming a metal film on the surface of a substrate by electroplating, The aforementioned film deposition apparatus is With the opening facing the substrate covered by an electrolyte membrane, a container is provided in which an anode and a plating solution are housed, Between the anode and the substrate, a power supply for applying voltage is provided. A circulation mechanism having a circulation pump for circulating the plating solution contained within the container, A shut-off valve for blocking the movement of the plating solution between the circulation mechanism and the housing, A pressurizing mechanism having a piston connected to the circulation mechanism and pressurizing the plating solution contained in the container when the on / off valve is closed, A pressure gauge for measuring the liquid pressure of the plating solution contained within the container, The system includes a control device that controls the application of voltage by the power supply, circulation by the circulation mechanism, opening and closing of the on / off valve, and pressurization by the piston. The control device is With the electrolyte membrane in contact with the substrate, the on / off valve is closed, and the piston pressurizes the plating solution inside the container to the film formation pressure. The plating solution is pressurized, and the voltage is applied to the power supply to form the metal film. The control device is If the pressure measured by the hydraulic pressure gauge falls outside a predetermined range, the pressurization by the piston is released and the on / off valve is opened while the voltage application continues, thereby circulating the plating solution in the container by the circulation pump. A metal film deposition apparatus characterized by circulating the plating solution into the containment, closing the on / off valve, and continuing to deposit the metal film while pressurizing the plating solution in the containment to the deposition pressure using the piston.

2. The aforementioned plating solution is an aqueous solution containing the metal that will form the metal film in the form of metal ions. The anode is an insoluble anode that is insoluble in the plating solution, The metal film forming apparatus according to claim 1, characterized in that a metal ion supplying material consisting of an oxide of the metal that will become the metal film is arranged inside the containment.

3. The metal film deposition apparatus according to claim 2, characterized in that the metal ion supply material is in powder form and is arranged adjacent to the anode.

4. The metal film deposition apparatus according to claim 2, characterized in that the metal is copper and the oxide of the metal is CuO.

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