Metal film forming apparatus and film forming method

Abstract

To provide a film forming device for a metallic film that can form the metallic film with uniform thickness.SOLUTION: A film forming method for a metallic film of the present invention comprises: an anode; a solid electrolyte membrane that is disposed between substrates that serve as both the anode and a cathode; a power supply part that applies a voltage between the anode and the cathode; a solution housing part that houses a metal ion solution containing metal ions between the anode and the solid electrolyte membrane; a pressurizing part that presses the solid electrolyte membrane toward a cathode side with liquid pressure of the metal ion solution; and a mask that is disposed between the solid electrolyte membrane and the substrate, and has an opening part that has a pattern corresponding to a film formation region of a predetermined pattern on an anode side surface of the substrate, wherein an aspect ratio D / W represented by the ratio of depth D to opening width W of the opening part of the mask is 0.67 or more.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to a film forming apparatus and a film forming method for forming a metal film, and more particularly to a film forming apparatus and a film forming method capable of forming a metal film in a film forming region of a predetermined pattern on the surface of a substrate. [Background technology]

[0002] Conventionally, there have been known film formation devices and film formation methods capable of depositing metal ions in a film formation region of a predetermined pattern (e.g., a line pattern of a line-and-space pattern) on the surface of a substrate, thereby forming a metal film in a film formation region of a predetermined pattern on the surface of the substrate. Among these devices and methods, a recent proposal employs solid electrodeposition (SED) technology, which involves disposing a solid electrolyte membrane between an anode and a substrate serving as a cathode, and applying a voltage between the anode and the substrate (cathode) while allowing a solution containing metal ions contained in the space between the anode and the solid electrolyte membrane to permeate from the anode side to the cathode side, thereby depositing the metal ions in the film formation region on the surface of the substrate.

[0003] Specifically, for example, Patent Document 1 describes an apparatus and method for forming a metal coating in a film formation region on the surface of a substrate using a masking plate with through-holes formed in a pattern corresponding to the predetermined pattern of film formation regions on the surface of the substrate. In this apparatus and method, a solid electrolyte membrane is positioned so that its cathode (substrate) side surface contacts the anode side surface of the substrate, and a masking plate is positioned so that its cathode side surface contacts the anode side surface of the solid electrolyte membrane. Then, a solution containing metal ions is supplied from the anode side of the masking plate through the through-holes to the solid electrolyte membrane, causing the solution to seep from the anode side of the solid electrolyte membrane to the cathode side. A voltage is applied between the anode and the substrate (cathode), causing the metal ions to precipitate in the film formation region on the surface of the substrate, thereby forming a metal coating.

[0004] Furthermore, other devices and methods have also been proposed. For example, after forming a resist mask so that openings are provided in a pattern corresponding to the film-forming region on the surface of the substrate (the surface of the underlying layer) where an underlying layer made of copper is provided on the surface of an epoxy substrate, a solution containing metal ions exuded from a solid electrolyte film is supplied to the film-forming region on the surface of the substrate through the openings of the resist mask, whereby a device and a method for forming a metal film have been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a film forming apparatus and a film forming method employing a solid-phase electrolysis method, the film forming speed is improved by shortening the distance between electrodes (the distance between the anode and the cathode (substrate)) to, for example, about 2 mm. However, when the distance between the electrodes is short, the distance over which the lines of electric force are relaxed from the anode to the cathode becomes short. Therefore, on the surface of the substrate (cathode), the number of lines of electric force increases, and the influence of the lines of electric force tends to become large. For this reason, as described above, a method of supplying metal ions to the film forming region on the surface of the substrate by supplying a solution containing metal ions to the solid electrolyte membrane through the through holes (openings) of the masking plate, a method of supplying a solution containing metal ions exuded from the solid electrolyte membrane to the film forming region on the surface of the substrate through the openings of the resist mask, etc. In a film forming apparatus and method for forming a metal film on the film forming region on the surface of the substrate, variations occur in the current density distribution near the opening end on the anode side of the openings of masks such as the masking plate and the resist mask, so that variations may occur in the current density distribution in the film forming region on the surface of the substrate (the bottom surface on the cathode side of the opening of the mask). As a result, the thickness of the metal film formed in the film forming region on the surface of the substrate may become non-uniform. For this reason, when using such a conventional metal film forming apparatus and film forming method to form a wiring layer of a wiring board, problems such as unevenness occurring on the surface of the wiring layer, resulting in an unacceptable increase in the power loss of the wiring board, may occur.

[0007] The present invention has been made in view of such points, and an object thereof is to provide a metal film forming apparatus and a film forming method capable of forming a metal film with a uniform thickness in a film forming region on the surface of a substrate.

Means for Solving the Problems

[0008] To solve the above problems, the metal film forming apparatus of the present invention includes an anode, a solid electrolyte membrane provided between the anode and a base material serving as the anode and the cathode, a power supply unit that applies a voltage between the anode and the cathode, a solution storage unit that stores a metal ion solution containing metal ions between the anode and the solid electrolyte membrane, a pressurizing unit that pressurizes the solid electrolyte membrane toward the cathode side with the hydraulic pressure of the metal ion solution, and a mask provided between the solid electrolyte membrane and the base material and having a pattern in which an opening corresponds to a film forming region of a predetermined pattern on the surface of the base material on the anode side. The aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening of the mask is 0.67 or more. The mask is installed on the surface of the base material such that the opening exposes the film forming region of the base material. In a state where the solid electrolyte membrane is in contact with the surface of the mask on the anode side, the pressurizing unit pressurizes the solid electrolyte membrane toward the cathode side with the hydraulic pressure of the metal ion solution, causing the metal ion solution to ooze out from the solid electrolyte membrane into the opening of the mask. By applying the voltage with the power supply unit, metal ions contained in the metal ion solution oozed out into the opening of the mask are deposited on the film forming region of the base material to form a metal film.

[0009] Furthermore, the present invention provides a method for forming a metal film, comprising: an installation step of installing a mask on an anode-side surface of a substrate serving as a cathode, the mask having openings corresponding to predetermined patterned film formation regions on the surface of the substrate, the openings exposing the film formation regions of the substrate; a pressurizing step of pressurizing the solid electrolyte membrane toward the cathode side with hydraulic pressure of a metal ion solution containing metal ions contained between the anode and the solid electrolyte membrane, thereby causing the metal ion solution to seep out of the solid electrolyte membrane into the openings of the mask; and a film formation step of applying a voltage between the anode and the cathode, thereby depositing the metal ions contained in the metal ion solution that has seeped out into the openings of the mask in the film formation regions of the substrate, wherein the aspect ratio, represented by D / W, of the openings in the mask, which is the ratio of a depth D to an opening width W, is 0.67 or more. [Effects of the Invention]

[0010] According to the present invention, a metal film can be formed with a uniform thickness. [Brief explanation of the drawings]

[0011]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 4F

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the film forming apparatus and film forming method of the metal film according to the present invention will be described. First, regarding the outline of the embodiment, the film forming apparatus and film forming method of the metal film according to the first embodiment will be exemplified and described. The film forming apparatus and film forming method of the metal film according to the first embodiment are an apparatus and method used in a method for manufacturing a wiring substrate provided with a wiring layer in a line and space pattern (hereinafter referred to as "the method for manufacturing a wiring substrate according to the first embodiment").

[0013] As a premise of the film forming apparatus and film forming method of the metal film according to the first embodiment, the method for manufacturing a wiring substrate according to the first embodiment will be described. FIG. 1 is a flowchart of the method for manufacturing a wiring substrate according to the first embodiment. FIGS. 2A to 2C are process diagrams schematically showing the method for manufacturing a wiring substrate according to the first embodiment. FIGS. 2A(a) and (b) are a cross-sectional view and a top view showing the base material preparation step, and (a) is a cross-sectional view taken along line I-I of (b). FIGS. 2B(a) and (b) are a cross-sectional view and a top view showing the metal film forming step, and (a) is a cross-sectional view taken along line II-II of (b). FIGS. 2C(a) and (b) are a cross-sectional view and a top view showing the underlayer removing step, and (a) is a cross-sectional view taken along line III-III of (b). Note that the cross-sectional views of FIGS. 2A(b), 2B(b), and 2C(b) show a cross-section perpendicular to the longitudinal direction of the line pattern of the wiring layer.

[0014] In the method for manufacturing a wiring substrate according to the first embodiment, first, as shown in FIGS. 1, 2A(a), and (b), a base material 1 for a wiring substrate is prepared (base material preparation step S1). The base material 1 for a wiring substrate includes an insulating substrate 2 and an underlayer 4 provided on the surface 2f on the anode side of the substrate 2.

[0015] Next, by using the film forming apparatus and film forming method of the metal film according to the first embodiment, as shown in FIGS. 1, 2B(a), and (b), a metal film 6 is formed on the film forming region 4fp of the line pattern of the wiring layer on the surface 4f of the underlayer 4 of the base material 1 for a wiring substrate (metal film forming step S2).

[0016] Next, as shown in FIGS. 1, 2C(a) and (b), for example, using a plasma etching method, a chemical etching method, or the like, with the metal film 6 used as an etching mask, an exposed region 4e (shown in FIG. 2B) of the underlying layer 4 where the metal film 6 is not formed on the surface 4f is removed (underlying layer removal step S3). Thereby, a wiring layer 8 composed of the underlying layer 4 and the metal layer 6' (metal film 6) is formed on the surface 2f of the substrate 2, and a wiring substrate 10 including the insulating substrate 2 and the wiring layer 8 having a line and space pattern provided on the surface 2f of the substrate 2 is manufactured.

[0017] The metal film forming apparatus and method according to the first embodiment are an apparatus and method for executing the metal film forming step S2 of the manufacturing method of the wiring substrate according to the above first embodiment. That is, in the metal film forming method according to the first embodiment, using the metal film forming apparatus according to the first embodiment, a metal film 6 is formed on the film forming region 4fp of the line pattern of the wiring layer on the surface 4f of the underlying layer 4 of the base material 1 for the wiring substrate.

[0018] FIG. 3 is a flowchart of the metal film forming method according to the first embodiment. FIGS. 4A to 4F are schematic process diagrams showing the metal film forming method according to the first embodiment. FIGS. 4A(a) and (b) are a cross-sectional view and a top view showing the installation step, where (a) is a cross-sectional view taken along line IV-IV of (b). FIG. 4A(c) is an enlarged view of the X portion shown in FIG. 4A(a), and is a diagram for explaining the aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening of the mask. FIGS. 4B to 4F are cross-sectional views schematically showing the placement step, the contact step, the pressing step, the film forming step, and the removing / removing step, respectively. FIGS. 4A(a) and FIGS. 4B to 4F show a cross-section perpendicular to the longitudinal direction of the line pattern of the wiring layer.

[0019] 3 and 4A(a) and 4A(b), in the method for forming a metal coating according to the first embodiment, first, a mask M is prepared, in which openings MS have a pattern corresponding to the film formation region 4fp on the anode-side surface 4f of the foundation layer 4 of the wiring board substrate 1 (the anode-side surface of the substrate), and the mask M includes shielding portions ML capable of shielding electric field lines. Then, the mask M is placed on the anode-side surface 4f of the foundation layer 4 of the wiring board substrate 1, which will serve as the cathode, so that the openings MS expose the film formation region 4fp of the foundation layer 4 (placement step S21). In this case, a mask M that has been prepared in advance separately from the wiring board substrate 1 is prepared, and the mask M is placed on the surface 4f of the foundation layer 4.

[0020] The mask M is made of rubber such as silicone rubber. As shown in Fig. 4A(c), in a cross section of the mask M perpendicular to the extension direction of the openings MS (the longitudinal direction of the line pattern of the wiring layer) when the mask M is viewed in plan from the anode side, the aspect ratio, represented by the ratio D / W of the depth D to the opening width W of the openings MS of the mask M, is 0.67 or more. Furthermore, as shown in Figs. 4A(a) and (b), the periphery of the openings MS of the mask M is surrounded by wall surfaces Mw of the shielding portion ML perpendicular to the contact surface Mr with the base layer 4.

[0021] Next, as shown in FIG. 3 and FIGS. 4B to 4E, the metal film forming apparatus 100 according to the first embodiment is used to sequentially carry out the placing step S22 to the removing / removing step S26.

[0022] The metal film forming apparatus 100 according to the first embodiment is a plating apparatus that forms a metal film by solid-phase electrodeposition. The film forming apparatus 100 includes a metal plate-shaped anode 11, a solid electrolyte membrane 13 disposed between the anode 11 and the underlayer 4 of a wiring board substrate 1, which serves as the cathode, a power supply 14 that applies a voltage between the anode 11 and the underlayer 4 (cathode), and a solution container 15 that contains a metal ion solution L containing copper ions, a material for the metal film, in the internal space between the anode 11 and the solid electrolyte membrane 13. The anode 11 is disposed on the upper surface of the internal space of the solution container 15 and is electrically connected to the positive electrode of the power supply 14. A clamper 17 is attached to the cathode side of the solution container 15. The clamper 17 clamps the solid electrolyte membrane 13, which is disposed so as to cover an opening 15d on the cathode side of the solution container 15, between the solution container 15 and the clamper 17, thereby fixing the solid electrolyte membrane 13. The solution storage unit 15 is provided with a supply port 15a and a discharge port 15b. The supply port 15a and the discharge port 15b are connected to a tank 85 and a pump 80 via piping 50. The metal ion solution L delivered from the tank 85 by the pump 80 flows into the internal space of the solution storage unit 15 from the supply port 15a, is discharged from the discharge port 15b, and returns to the tank 85. A pressure adjustment valve 54 is installed on the piping 50 downstream of the discharge port 15b. The pump 80 and the pressure adjustment valve 54 (pressurizing unit) can pressurize the metal ion solution L in the internal space of the solution storage unit 15 to a predetermined pressure, and adjust the liquid pressure of the metal ion solution L to a constant pressure.

[0023] The film forming apparatus 100 further includes an elevating device 70 above the solution storage section 15 for raising and lowering the solution storage section 15. The film forming apparatus 100 further includes a metal pedestal 40 on which the wiring board substrate 1 is placed, and a conductive member 20 for electrically connecting the metal pedestal 40 and the underlying layer 4 of the wiring board substrate 1. The metal pedestal 40 is electrically connected to the negative electrode of the power supply unit 14. The conductive member 20 is a metal plate formed in a partially bent shape so that it can be attached to the metal pedestal 40 and the wiring board substrate 1 so as to simultaneously contact the edges of the metal pedestal 40 and the underlying layer 4 of the wiring board substrate 1. The metal pedestal 40 is electrically connected to the underlying layer 4 (cathode) of the wiring board substrate 1 via the conductive member 20.

[0024] When the placement process S22 to the removal / removal process S26 are sequentially executed using the metal film forming apparatus 100, first, as shown in FIGS. 3 and 4B, the base material 1 for the wiring board is placed together with the mask M at a predetermined position on the surface 40f of the metal pedestal 40 such that the back surface 2r of the substrate 2 contacts the surface 40f of the metal pedestal 40. At the same time, the conductive member 20 is attached to the metal pedestal 40 and the base material 1 for the wiring board so as to simultaneously contact the edges of the metal pedestal 40 and the underlying layer 4 (cathode) of the base material 1 for the wiring board (placement process S22).

[0025] Next, as shown in FIGS. 3 and 4C, the lifting device 70 is used to move the solid electrolyte film 13 together with the solution storage unit 15 toward the base material 1 for the wiring board, so that the surface 13r on the cathode side of the solid electrolyte film 13 contacts the surface Mf on the anode side of the mask M provided on the surface 4f of the underlying layer 4 of the base material 1 for the wiring board (contact process S23).

[0026] Next, as shown in FIGS. 3 and 4D, with the surface 13r on the cathode side of the solid electrolyte film 13 in contact with the surface Mf on the anode side of the mask M, the metal ion solution L in the internal space of the solution storage unit 15 is pressurized at a predetermined pressure by the pump 80 and the pressure regulating valve 54 (pressurizing unit), and the hydraulic pressure of the metal ion solution L is adjusted to a constant pressure. As a result, the solid electrolyte film 13 is uniformly pressurized toward the cathode side by the hydraulic pressure of the metal ion solution L. Thereby, the metal ion solution L oozes out from the solid electrolyte film 13 into the opening MS of the mask M to fill the space closed by the solid electrolyte film 13 in the opening MS of the mask M with the metal ion solution L, and the portion of the solid electrolyte film 13 facing the opening MS of the mask M is deformed so as to protrude toward the cathode side, thereby pressurizing the metal ion solution L that fills the closed space in the opening MS of the mask M (pressurizing process S24).

[0027] Next, as shown in FIGS. 3 and 4E, while pressurizing the metal ion solution L that fills the space closed by the solid electrolyte membrane 13 within the opening MS of the mask M as described above, a voltage is applied between the anode 11 and the underlying layer 4 (cathode) of the base material 1 for the wiring board by the power supply unit 14, causing a current to flow between the anode 11 and the underlying layer 4 (cathode), and depositing the metal ions contained in the metal ion solution L that fills the space within the opening MS onto the film-forming region 4fp of the underlying layer 4 of the base material 1 for the wiring board, thereby forming a metal film 6 on the film-forming region 4fp (film-forming step S25). At this time, after continuously applying the voltage by the power supply unit 14 for a predetermined time, the application of the voltage is terminated, and the pressurization of the metal ion solution L by the pump 80 and the pressure regulating valve 54 is terminated. The thickness of the metal film to be formed can be adjusted by the magnitude of the voltage and the duration of the application.

[0028] Subsequently, the elevating device 70 is used to raise the solid electrolyte membrane 13 together with the solution storage unit 15, and then, as shown in FIGS. 3 and 4F, the base material 1 for the wiring board on which the metal film 6 has been formed is removed together with the mask M (shown in FIG. 4E) from the metal pedestal 40 of the film-forming apparatus 100, and the mask M is removed from the base material 1 for the wiring board (removing / removal step S26). Thus, the metal film forming step S2 of the manufacturing method of the wiring board according to the first embodiment is executed, and a metal film 6 is formed on the film-forming region 4fp of the line pattern of the wiring layer on the surface 4f of the underlying layer 4 of the base material 1 for the wiring board.

[0029] In the film forming apparatus and film forming method of the metal film according to the first embodiment, the aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening MS of the mask M is narrow and deep to such an extent that it is 0.67 or more. Therefore, in order to improve the film forming speed, by shortening the interelectrode distance (the distance between the anode 11 and the cathode (underlayer 4)) to a certain distance, the distance by which the electric lines of force are relaxed from the anode 11 to the cathode becomes shorter. Even if there is a variation in the density distribution (current density distribution) of the electric lines of force near the opening end on the anode side of the opening MS of the mask M, the electric lines of force pass through the opening MS of such a shape and approach the bottom surface on the cathode side (the film forming region 4fp of the surface 4f of the underlayer 4), the density distribution (current density distribution) of the electric lines of force is uniformized. Thereby, it is possible to suppress the occurrence of variations in the current density distribution in the film forming region 4fp of the surface 4f of the underlayer 4 of the base material 1 for the wiring board. Therefore, in the method for manufacturing a wiring board according to the first embodiment, by using the method for forming a metal film according to the first embodiment and executing the metal film forming step S2, the metal film 6 can be formed with a uniform thickness in the film forming region 4fp of the line pattern of the wiring layer on the surface 4f of the underlayer 4 of the base material 1 for the wiring board. Thereby, when manufacturing the wiring board 10 using the method for manufacturing a wiring board according to the first embodiment, the surface of the wiring layer 8 can be formed flat, and a wiring board 10 capable of suppressing power loss can be manufactured.

[0030] Therefore, according to the film forming apparatus and film forming method of the metal film according to the embodiment, for example, as in the first embodiment, it is possible to suppress the occurrence of variations in the current density distribution in the film forming region on the surface of the base material during the film formation of the metal film. Thus, a metal film can be formed with a uniform thickness in the film forming region on the surface of the base material. Thereby, a wiring board capable of suppressing power loss can be manufactured.

[0031] Subsequently, the film forming apparatus and film forming method of the metal film according to the embodiment will be described in detail.

[0032] 1. Film Forming Apparatus for Metal Film The film forming apparatus for a metal film according to the embodiment is a film forming apparatus that employs the solid state electrolysis method (SED), and includes an anode, a solid electrolyte membrane provided between the anode and a substrate that serves as the anode and the cathode, a power supply unit that applies a voltage between the anode and the cathode, a solution storage unit that stores a metal ion solution containing metal ions between the anode and the solid electrolyte membrane, a pressurizing unit that pressurizes the solid electrolyte membrane toward the cathode side with the hydraulic pressure of the metal ion solution, and a mask provided between the solid electrolyte membrane and the substrate and having a pattern whose opening corresponds to a film forming region of a predetermined pattern on the surface of the substrate on the anode side. Hereinafter, each configuration of the film forming apparatus and the like will be described in detail.

[0033] (1) Mask The mask is not particularly limited as long as it has a pattern in which the opening corresponds to a film forming region of a predetermined pattern on the surface of the substrate on the anode side and includes an insulating shielding portion capable of shielding electric lines of force. The opening of the mask usually has a surrounding area of the opening surrounded by the wall surface of the shielding portion perpendicular to the contact surface with the substrate (for example, the underlying layer).

[0034] The pattern of the opening of the mask refers to the shape of the opening when the mask is viewed in a plan view from the anode side. The pattern of the opening of the mask corresponds to the film forming region of a predetermined pattern of the substrate and is not particularly limited as long as it can expose the film forming region on the surface of the substrate. Usually, it has the same shape as the pattern of the film forming region of the substrate. Therefore, for example, as in the first embodiment, when the pattern of the film forming region of the substrate is a line pattern of a line and space pattern, usually, the pattern of the opening of the mask is the same as the line pattern, and the pattern of the shielding portion of the mask is the same as the space pattern of the line and space pattern.

[0035] The aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening of the mask is 0.67 or more. Here, the opening width W of the opening of the mask refers to the opening width of the opening in the cross-section of the mask perpendicular to the extending direction of the opening when the mask is viewed in plan from the anode side, and the depth D of the opening of the mask refers to the depth of the opening in the cross-section. The depth D of the opening of the mask is usually the same as the thickness of the mask. The aspect ratio is not particularly limited. For example, when the pattern in the film formation region of the substrate is a line pattern of a line and space pattern, it is the ratio of the depth D to the opening width W of the opening in the cross-section of the mask perpendicular to the longitudinal direction of the line pattern (the extending direction of the opening when the mask is viewed in plan from the anode side).

[0036] The aspect ratio is not particularly limited as long as it is 0.67 or more, but is preferably 0.67 or more and 3.33 or less. When the aspect ratio is 3.33 or less, in order to form a metal film on the film formation region of the substrate, by applying pressure to the solid electrolyte film with the hydraulic pressure of the metal ion solution, when the metal ion solution is allowed to ooze from the solid electrolyte film into the opening of the mask, the space closed by the solid electrolyte film in the opening of the mask can be easily filled with the metal ion solution, and a metal film with high precision can be formed.

[0037] As the opening width W of the opening of the mask, for example, it is preferably 5 μm or more and 200 μm or less, and particularly preferably 5 μm or more and 50 μm or less. When the opening width W of the opening is within these ranges, a metal film can be formed with a width corresponding to the desired wiring width of the wiring layer (for example, the width of the line pattern of the line and space pattern). As the depth D of the opening of the mask, for example, it is preferably 3.35 μm or more and 666 μm or less, and particularly preferably 3.35 μm or more and 134 μm or less. When the depth D of the opening is within these ranges, when forming a metal film with a width corresponding to the desired wiring width of the wiring layer, it becomes easy to form the metal film with a uniform thickness, and it becomes easy to form a metal film with high precision.

[0038] In addition, when the pattern of the opening of the mask is the same as the line pattern of the line and space pattern, and the pattern of the shielding portion of the mask is the same as the space pattern of the line and space pattern, the range of the width of the shielding portion (the width of the shielding portion in the same direction as the width direction of the opening) is, for example, the same as the opening width W of the opening.

[0039] The material of the mask is not particularly limited as long as it is an insulating material capable of shielding electric lines of force, and examples thereof include rubbers such as silicone rubber (PMDS) and ethylene propylene diene rubber (EPDM), and resins such as polyimide, polyethylene terephthalate, and polyethylene naphthalate.

[0040] (2) Anode The anode is not particularly limited as long as it has conductivity capable of acting as an anode. For example, it may be soluble in a metal ion solution or insoluble in a metal ion solution.

[0041] The shape of the anode is not particularly limited, but a plate shape is preferred, and the surface on the cathode side of the anode is parallel to the surface on the cathode side of the solid electrolyte. The material of the anode is not particularly limited and may be a material soluble in a metal ion solution or a material insoluble in a metal ion solution. Examples of the soluble material include the same material as the metal film (for example, copper, etc.), and examples of the insoluble material include titanium, gold, etc.

[0042] (3) Solid electrolyte membrane The solid electrolyte membrane is made of a solid electrolyte and contains metal ions inside by contacting with a metal ion solution. As long as the metal ion solution can be oozed out from the solid electrolyte membrane to the opening of the mask by pressurizing the solid electrolyte membrane to the cathode side with the hydraulic pressure of the metal ion solution, it is not particularly limited. The solid electrolyte membrane usually has flexibility.

[0043] The thickness of the solid electrolyte membrane is not particularly limited, but is, for example, 5 μm to 200 μm. The material of the solid electrolyte membrane is not particularly limited, but examples thereof include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid membranes, and membranes with ion exchange functions such as Selemion (CMV, CMD, CMF, etc.) manufactured by Asahi Glass Co., Ltd.

[0044] (4) Solution storage section The solution storage section is not particularly limited as long as it can store a metal ion solution between the anode and the solid electrolyte membrane.

[0045] The material of the solution storage section is not particularly limited, but is preferably one that is chemically resistant to the metal ion solution and capable of shielding electric field lines. The metal ion solution is a solution containing the metal contained in the metal film in the form of metal ions. The metal of the metal ions is not particularly limited, but examples thereof include copper, nickel, silver, and gold. The metal ion solution is obtained by dissolving the metal of the metal ions in an acid such as nitric acid, phosphoric acid, succinic acid, nickel sulfate, or pyrophosphoric acid.

[0046] The metal film forming device may be, for example, as in the first embodiment, equipped with a clamper for clamping the solid electrolyte membrane on the cathode side of the solution container.

[0047] (5) Power supply and pressure unit The power supply applies a voltage between the anode and the substrate, which serves as the cathode. The positive and negative terminals of the power supply are connected to the anode and the substrate (cathode), respectively.

[0048] The pressurizing unit pressurizes the solid electrolyte membrane toward the cathode side by the liquid pressure of the metal ion solution contained in the solution container. The pressurizing unit is not particularly limited, but examples thereof include, like the pressurizing unit according to the first embodiment, a combination of a pump and a pressure regulating valve that pressurizes the metal ion solution contained in the solution container at a predetermined pressure and adjusts the liquid pressure of the metal ion solution to a constant pressure.

[0049] (6) Other configurations The metal film forming apparatus may further include a lifting device for lifting the solution storage part as in the first embodiment. The lifting device is not particularly limited as long as it can lift the solution storage part. For example, it can be composed of a hydraulic or pneumatic cylinder, an electric actuator, a linear guide, a motor, and the like.

[0050] The metal film forming apparatus may further include a pedestal for placing the substrate as in the first embodiment. The pedestal is not particularly limited. For example, a conductive pedestal such as a metal pedestal made of stainless steel can be mentioned. When the metal film forming apparatus includes a conductive pedestal, the substrate (for example, a conductive underlayer provided on the substrate, a single conductive substrate, etc.) is connected to the negative electrode of the power supply part via the pedestal. The metal film forming apparatus may further include a conductive member for electrically connecting the metal pedestal and the substrate (cathode) as in the first embodiment.

[0051] (7) Metal film forming apparatus The metal film forming apparatus installs the mask on the surface of the substrate so that the opening exposes the film forming region of the substrate, and in a state where the solid electrolyte film is in contact with the surface on the anode side of the mask, the pressure applying part applies pressure to the solid electrolyte film toward the cathode side with the hydraulic pressure of the metal ion solution, so that the metal ion solution oozes out from the solid electrolyte film to the opening of the mask, and by applying the voltage with the power supply part, the metal ions contained in the metal ion solution oozed out to the opening of the mask are deposited on the film forming region of the substrate to form a metal film.

[0052] The metal film forming device is not particularly limited as long as it forms a metal film on the film formation region of the substrate as described above. However, it is preferable that the mask is placed on the surface of the substrate so that the opening exposes the film formation region of the substrate, and the distance between the anode and the substrate (cathode) (hereinafter, sometimes abbreviated as "electrode distance") when the solid electrolyte membrane is in contact with the anode-side surface of the mask is, for example, about 2 mm.

[0053] The metal film forming apparatus is not particularly limited as long as it uses a substrate that functions as a cathode, but it may also use a substrate that includes an insulating substrate and a conductive underlayer (cathode) provided on the surface of the insulating substrate. Examples of such substrates include substrates for wiring boards such as those in the first embodiment, where the insulating substrate is, for example, a substrate made of glass epoxy or the like, and the underlayer is, for example, made of copper or the like. Furthermore, the substrate may also be a single conductive substrate (cathode) such as a metal substrate made of copper or the like.

[0054] The metal film forming apparatus may be, for example, one that forms a metal layer constituting a wiring layer of a wiring board as the metal film, as in the first embodiment. The metal film forming apparatus is preferably, for example, one that forms a metal film by using the metal film forming method according to the embodiment, as in the first embodiment.

[0055] 2.Metal coating deposition method The method for forming a metal coating according to the embodiment is a method for forming a metal coating using a solid-phase electrodeposition method, and includes a setting step, a pressurizing step, and a film-forming step. Each step of the method for forming a metal coating will be described in detail below.

[0056] (1) Installation process In the placement process, a mask having openings corresponding to a predetermined pattern of film formation areas on the surface of the substrate, which will serve as a cathode, is placed on the anode side of the substrate so that the openings expose the film formation areas on the substrate.

[0057] As the substrate on which the mask is placed in the placement step, there is no particular limitation as long as it functions as a cathode. The substrate is the same as the substrate used in the film forming apparatus for the metal film according to the embodiment.

[0058] As the placement step, similar to the placement step according to the first embodiment, it may be a step of preparing a mask prepared in advance separately from the substrate and then placing the mask on the surface of the anode side of the substrate. As the placement step, a resist pattern having the shape of the mask may be formed on the surface of the anode side of the substrate by a method such as photolithography, etc., so that the resist pattern is placed as a mask on the surface of the anode side of the substrate. The aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening of the mask is 0.67 or more. The mask is the same as the mask in the film forming apparatus for the metal film according to the embodiment.

[0059] (2) Pressurization step In the pressurization step, with the solid electrolyte membrane in contact with the surface of the anode side of the mask placed on the surface of the substrate, the solid electrolyte membrane is pressurized toward the cathode side by the hydraulic pressure of a metal ion solution containing metal ions accommodated between the anode and the solid electrolyte membrane, so that the metal ion solution oozes out from the solid electrolyte membrane into the opening of the mask.

[0060] Regarding the distance (distance between electrodes) between the anode and the substrate (cathode) in the state where the solid electrolyte membrane is in contact with the surface of the anode side of the mask placed on the surface of the substrate in the pressurization step, it is the same as the distance between electrodes in the film forming apparatus for the metal film according to the embodiment.

[0061] (3) Film forming step In the film forming step, a metal film is formed by applying a voltage between the anode and the cathode to deposit the metal ions contained in the metal ion solution that has oozed out into the opening of the mask onto the film forming region of the substrate.

[0062] Although the film formation process is not particularly limited, usually, in the pressurization process, a voltage is applied between the anode and the cathode while the solid electrolyte membrane is pressurized toward the cathode side by the hydraulic pressure of the metal ion solution. This enables uniform film formation of the metal film.

[0063] (4) Method for forming a metal film The method for forming a metal film includes an installation step, a pressurization step, and a film formation step, and is not particularly limited as long as the aspect ratio is 0.67 or more. For example, like the first embodiment, the metal film may be a metal layer constituting the wiring layer of the wiring board. As the method for forming the metal film, for example, like the first embodiment, it is preferable to use the metal film forming apparatus according to the embodiment to form the metal film.

[0064] 3. Screen mask FIG. 5 is a cross-sectional view schematically showing a screen mask which is another example of the mask in the film forming apparatus and the film forming method according to the embodiment, and shows a cross-section perpendicular to the extending direction of the opening when the screen mask is viewed in plan from the anode side.

[0065] The screen mask S shown in FIG. 5 includes a frame Sf disposed on the outer periphery, an internal mesh Sh (for example, a mesh made of SUS) disposed inside the frame and connected to the frame Sf via a connecting portion Sc (for example, a mesh made of polyester), and a mask portion SM fixed to the cathode-side surface of the internal mesh Sh. The mask portion SM has a pattern in which the opening SMS corresponds to the film formation region of a predetermined pattern on the anode-side surface of the base material, and includes an insulating shielding portion SML capable of shielding the electric lines of force. The aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening SMS of the mask portion SM is 0.67 or more and 3.33 or less.

[0066] As a mask in the film forming apparatus and film forming method of the metal film according to the embodiment, for example, a screen mask as shown in FIG. 5 may be used. In this case, at the time of forming the metal film, the mask portion of the screen mask is installed on the surface of the anode side of the substrate so that the opening of the mask portion exposes the film forming region on the surface of the anode side of the substrate. With the solid electrolyte film in contact with the surface of the inner mesh of the screen mask on the anode side (the surface of the mask on the anode side), the metal ion solution oozes from the solid electrolyte film through the holes of the inner mesh to the opening of the mask portion, and by applying a voltage, metal ions contained in the metal ion solution oozed to the opening of the mask portion are deposited on the film forming region of the substrate to form a metal film. For this reason, since the electric lines of force are interfered by the insulating inner mesh, there is a possibility that a particularly large variation may occur in the current density distribution near the opening end on the anode side of the opening of the mask portion. Therefore, when the aspect ratio (the ratio D / W of the depth D to the opening width W) is 0.67 or more, the effect of suppressing the occurrence of variations in the current density distribution in the film forming region on the surface of the substrate becomes particularly remarkable.

Example

[0067] Hereinafter, the film forming apparatus and film forming method of the metal film according to the embodiment will be described more specifically with reference to examples and comparative examples.

[0068] 1. Current density distribution in the film forming region of the substrate during film formation of the metal film In the examples and comparative examples, a film forming apparatus for a metal film provided with a mask having a pattern in which the opening corresponds to the film forming region of the line pattern of the line and space pattern on the surface of the anode side of the substrate, and with the aspect ratio of the opening of the mask set to each value was used to create a simulation model using the analysis software Fluent manufactured by ANSYS. Then, using the simulation models according to the examples and comparative examples, the current density distribution in the film forming region during film formation of the metal film was evaluated in the film forming region on the surface of the substrate.

[0069] [Example 1] A simulation model of the metal film forming apparatus according to the embodiment was created by using the analysis software Fluent manufactured by ANSYS. Specifically, the finite volume method was applied as the analysis method, and a fluid solver and a potential model were adopted. Then, a simulation model was created under the following conditions. At this time, since the electrical resistance of the solid electrolyte membrane is negligible compared to the electrical resistance of the metal ion solution (electroplating solution), the solid electrolyte membrane was not included in the model.

[0070] (Conditions for creating the simulation model) 1) Anode Structure: Plate-shaped member Material: Phosphorus-containing copper Conductivity: 5.96×10 7 S / m Width (width in the direction perpendicular to the longitudinal direction of the line pattern on the surface of the cathode side of the anode): 10 mm 2) Substrate (cathode) Structure: Substrate and a substrate provided with an underlayer (cathode) on the surface of the anode side of the substrate Material of the substrate: Glass epoxy Conductivity of the substrate: 2×10 -12 S / m Material of the underlayer: Copper Conductivity of the underlayer: 5.96×10 7 S / m Thickness of the underlayer: 500 nm 3) Inter-electrode distance Inter-electrode distance (distance between the anode and the cathode (underlayer)): 2 mm 4) Metal ion solution (electroplating solution) Material: Copper sulfate Conductivity: 450 S / m 5) Mask Structure: The pattern of the opening part and the pattern of the shielding part are the same as the line pattern and the space pattern of the line and space pattern respectively, and the shielding part of the mask is perpendicular to the contact surface with the substrate Material: Silicone rubber Conductivity: 1×10 -13 S / m Opening width W of the opening part: 30 μm Width of the shielding part (width of the shielding part in the same direction as the width direction of the opening): 30 μm Depth D of the opening (thickness of the mask): 20 μm

[0071] [Examples 2 to 12] Except for setting the depth D of the opening (thickness of the mask) to 32 μm (Example 2), 33 μm (Example 3), 34 μm (Example 4), 100 μm (Example 5), 200 μm (Example 6), 300 μm (Example 7), 400 μm (Example 8), 500 μm (Example 9), 600 μm (Example 10), 700 μm (Example 11), 800 μm (Example 12), a simulation model of the metal film forming apparatus was produced in the same manner as in Example 1.

[0072] [Comparative Example] Except for setting the depth D of the opening (thickness of the mask) to 10 μm, a simulation model of the metal film forming apparatus was produced in the same manner as in Example 1.

[0073] [Analysis of Current Density Distribution] Using the analysis software Fluent manufactured by ANSYS, the current density distribution when forming a metal film in the film forming region on the surface of the anode side (the surface of the anode side of the substrate) of the underlayer (cathode) of the substrate was analyzed using the simulation models of the metal film forming apparatuses according to Examples 1 to 12 and the Comparative Example. FIG. 6(a) is a cross-sectional view schematically showing a cross-section perpendicular to the longitudinal direction of the line pattern in the simulation models according to Examples 1 to 12 and the Comparative Example, and FIG. 6(b) is an enlarged view of the analysis range shown in FIG. 6(a).

[0074] In the analysis of the current density distribution, specifically, as shown in FIGS. 6(a) and (b), A region of 3 cycles with a width of 0.18 mm in the same direction as the width direction of the anode was set as the analysis range, and with both ends in the width direction of the analysis range as symmetric boundaries, a two-dimensional steady-state analysis was performed under the following analysis conditions and boundary conditions.

[0075] (Analysis Conditions and Boundary Conditions) Anode current density: 3.5 A / dm 2 Cathode current density: 7A / dm 2 Potential of the symmetry boundary at the cathode: 0V *Anode current density refers to the current density on the surface of the anode opposite the cathode. *Cathode current density refers to the current density on the surface of the substrate's base layer (cathode) opposite the anode.

[0076] [evaluation] From the analysis results of the current density distribution according to the examples and comparative examples, the current density distribution in the deposition region on the surface of the base layer of the substrate when depositing a metal film was evaluated. In Fig. 7(a), the image on the left shows the analysis results of the current density distribution in the analysis range of a simulation model of a metal film deposition device according to the comparative example (depth D of the opening (thickness of the mask): 10 μm), and the graph on the right is a graph showing the current density at each position in the width direction in the deposition region on the surface of the base layer in the analysis range. In Fig. 7(b), the image on the left shows the analysis results of the current density distribution in the analysis range of a simulation model of a metal film deposition device according to Example 5 (depth D of the opening (thickness of the mask): 100 μm), and the graph on the right is a graph showing the current density at each position in the width direction in the deposition region on the surface of the base layer in the analysis range. In Figs. 7(a) and (b), the current density is expressed in "A / m 2 " units.

[0077] As shown in Figure 7(a), in the simulation model of the metal coating deposition apparatus according to the comparative example (opening depth D (mask thickness): 10 μm), the current density distribution varied near the anode-side opening edge of the mask opening, and there was a large variation in the current density distribution in the width direction in the deposition region on the surface of the base layer (the bottom surface of the mask opening on the cathode side). On the other hand, as shown in Figure 7(b), in the simulation model of the metal coating deposition apparatus according to Example 5 (opening depth D (mask thickness): 100 μm), there was variation in the current density distribution near the anode-side opening edge of the mask opening, but there was no variation in the current density distribution in the width direction in the deposition region on the surface of the base layer.

[0078] Subsequently, from the analysis results of the current density distribution when the depth D of the opening in the simulation model of the metal film forming apparatus according to Examples 1 to 12 and the comparative example was set to each value, the variation in the current density distribution of the film forming region on the surface of the underlayer (the bottom surface on the cathode side of the opening of the mask) with respect to each of the depth D of the opening of the mask and the aspect ratio (the ratio D / W of the depth D to the opening width W) was evaluated. At this time, the variation in the current density distribution of the film forming region on the surface of the underlayer was obtained by the following formula (1).

[0079] [Equation 1] Variation in current density distribution = 100 × (maximum current density - minimum current density) / average current density ···(1)

[0080] FIG. 8(a) is a graph showing the change in the variation of the current density distribution of the film forming region on the surface of the underlayer with respect to the depth D of the opening of the mask, and FIG. 8(b) is a graph showing the change in the variation of the current density distribution of the film forming region on the surface of the underlayer with respect to the aspect ratio of the opening of the mask.

[0081] As shown in FIGS. 8(a) and (b), when the depth D (thickness of the mask) of the opening is 20 μm or more and the aspect ratio is 0.67 or more, the variation in the current density distribution becomes less than 1%. Therefore, in this case, it is considered that a metal film can be formed with a uniform thickness to such an extent that problems such as power loss during the manufacture of the wiring board do not occur.

[0082] 2. Amount of metal ion solution oozing out during film formation of metal film The amount of metal ion solution oozing out during film formation of the metal film in the actual machine of the metal film forming apparatus according to the embodiment was measured, and based on the amount of oozing, the upper limit of the depth D (thickness of the mask) of the opening of the mask was examined.

[0083] [Example 13] An actual machine of a metal film forming apparatus (SED apparatus) according to an embodiment was fabricated with a general configuration. At this time, the size of the surface on the anode side of the substrate (cathode) was set to 10 cm × 10 cm, which is assumed to be a general size. The ratio of the film forming area on the surface on the anode side of the substrate was set to 60%, which is assumed to be a general ratio. The pattern of the film forming area on the surface on the anode side of the substrate was set to a line pattern (width: 30 μm) of a line and space pattern. Then, the pattern of the opening and the pattern of the shielding part were made the same as the line pattern and the space pattern of the line and space pattern, respectively, and the opening width W of the opening was set to 30 μm. The opening of the mask was such that the periphery of the opening was surrounded by the wall surface of the shielding part perpendicular to the contact surface with the substrate. Further, the depth D (thickness of the mask) of the opening was set to 130 μm. Also, the material of the metal ion solution was copper sulfate. Furthermore, the other configurations of the actual machine were appropriately set according to the configurations described above.

[0084] Subsequently, in the fabricated actual machine, the pressurization step in the metal film forming method according to the embodiment was executed under general conditions. In the pressurization step, the solid electrolyte membrane was pressurized to the cathode side at 0.6 MPa, which is assumed to be a general liquid pressure of the metal ion solution, so that the amount of seepage of the metal ion solution when the metal ion solution seeped out from the solid electrolyte membrane into the above-mentioned opening of the mask was measured. The measured value of the seepage amount was 640 mm 3 It was. Since this measured value was measured when the pressurization step in the metal film forming method according to the embodiment was executed under general conditions with an actual machine having a general configuration of the metal film forming apparatus according to the embodiment, it is considered to be a general seepage amount.

[0085] [Evaluation of the upper limit of the depth D of the opening of the mask] FIG. 9 is a graph showing the change in the volume of the opening of the mask with respect to the depth D (thickness of the mask) of the opening of the mask provided in the actual machine of the metal film forming apparatus according to Example 13.

[0086] As is clear from the graph of FIG. 9, in the actual machine of the film forming apparatus for a metal film according to Example 13, when the depth D (thickness of the mask) of the opening of the mask is 100 μm or less, the volume of the opening of the mask is 600 mm 3 or less, and it does not exceed 640 mm 3 which is considered to be the general amount of seepage as described above. Therefore, if the depth D of the opening of the mask is 100 μm or less, that is, if the aspect ratio (ratio D / W of the depth D to the opening width W) of the mask is 3.33 (100 μm / 30 μm) or less, in the pressurizing step in the method for forming a metal film according to the embodiment, the space inside the opening of the mask can be filled with the metal ion solution, and it is considered that a highly accurate metal film can be formed.

[0087] As described above, the film forming apparatus and the film forming method for a metal film according to the embodiment of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the spirit of the present invention described in the claims.

Explanation of Reference Numerals

[0088] 1 Base material for wiring board (base material) 2 Insulating substrate 2f Surface 2r Back surface 4 Underlayer 4f Surface 6 Metal film 6´ Metal layer 8 Wiring layer 10 Wiring board 100 Film forming apparatus 11 Anode 13 Solid electrolyte membrane 14 Power supply unit 15 Solution storage unit L Metal ion solution 20 Conductive member 80 Pump 54 Pressure regulating valve M Mask MS Opening ML Shielding portion

Claims

1. a power supply unit that applies a voltage between the anode and the cathode; a solution storage unit that stores a metal ion solution containing metal ions between the anode and the solid electrolyte membrane; a pressure unit that presses the solid electrolyte membrane toward the cathode by hydraulic pressure of the metal ion solution; and a mask that is provided between the solid electrolyte membrane and the substrate, the mask having openings that have a pattern corresponding to a predetermined pattern of film formation regions on the anode-side surface of the substrate, an aspect ratio, expressed as a ratio D / W of a depth D to an opening width W of the opening of the mask, of 0.67 or more; the mask is placed on the surface of the substrate so that the opening exposes the film formation region of the substrate; the solid electrolyte membrane is in contact with the anode-side surface of the mask; and the pressure unit presses the solid electrolyte membrane toward the cathode side with the hydraulic pressure of the metal ion solution, causing the metal ion solution to seep out of the solid electrolyte membrane into the opening of the mask; and the power supply unit applies the voltage, causing the metal ions contained in the metal ion solution that has seeped out into the opening of the mask to deposit on the film formation region of the substrate, thereby forming a metal coating.

2. 2. The metal film forming apparatus according to claim 1, wherein the aspect ratio is 0.67 or more and 3.33 or less.

3. a setting step of setting a mask having openings corresponding to predetermined patterned film formation regions on the surface of the substrate that will become the cathode on the anode side, so that the openings expose the film formation regions of the substrate; a pressurizing step in which, in a state in which a solid electrolyte membrane is in contact with the anode-side surface of the mask placed on the surface of the base material, the solid electrolyte membrane is pressed toward the cathode side by hydraulic pressure of a metal ion solution containing metal ions accommodated between the anode and the solid electrolyte membrane, thereby causing the metal ion solution to seep out from the solid electrolyte membrane into the opening of the mask; a film-forming process in which a voltage is applied between the anode and the cathode to cause the metal ions contained in the metal ion solution that has seeped into the openings of the mask to precipitate on the film-forming region of the substrate, thereby forming a metal film; The method for forming a metal film is characterized in that the aspect ratio represented by the ratio D / W of the depth D to the opening width W of the opening of the mask is 0.67 or more.

4. The method for forming a metal film according to claim 3, wherein the aspect ratio is 0.67 or more and 3.33 or less.

Images