Copper film deposition method

Abstract

To provide a film formation method of a copper coating film that can suppress the occurrence of tarnish etc. on a to-be-formed copper coating film and can increase the film formation speed.SOLUTION: In a film formation method of a copper coating film F, an anode 51 and a substrate W are arranged so that the anode 51 and the substrate W exist in an opening part 53a and a film formation area wa of the substrate W exists in an anode area 51a surrounded by the periphery 51d of the anode 51 in the plane view of the substrate W. In the film formation method, the film formation of the copper coating film F is also performed in a state that the relationship of Sa / Sb is satisfied with 1.54-7.14 when Sa is the surface area of the anode area 51a and Sb is the surface area of the film formation area wa of the substrate W in the plane view, with the substrate W pressed by a solid electrolyte membrane 52 and a voltage applied between the anode 51 and the substrate W.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for forming a copper film, which comprises depositing copper on the surface of a substrate by electrolytic plating from copper ions contained in an electrolytic solution, thereby forming a copper film derived from the copper ions on the surface of a substrate. [Background technology]

[0002] For example, Patent Document 1 proposes a method for forming a copper film on the surface of a substrate by electrolytic plating using a solid electrolyte membrane. Specifically, in the method described in Patent Document 1, the electrolyte is passed through the solid electrolyte membrane while the solid electrolyte membrane is pressed against the surface of the substrate from one side by the hydraulic pressure of the electrolyte, and copper ions in the electrolyte that has passed through are precipitated on the surface of the substrate by electrolytic plating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-125087 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when attempting to increase the deposition rate when depositing a copper film on a substrate, there is a risk that the copper film may become discolored, making it difficult to increase the deposition rate.

[0005] The present invention has been made in consideration of these points, and provides a method for forming a copper film that can increase the film formation rate while suppressing the occurrence of burns and the like on the copper film being formed. [Means for solving the problem]

[0006] In view of the above problems, a method for forming a copper film according to the present invention includes disposing a solid electrolyte membrane between an anode and a substrate serving as a cathode, pressing the substrate with the solid electrolyte membrane, applying a voltage between the anode and the substrate, and reducing copper ions contained inside the solid electrolyte membrane to cause copper to precipitate from the copper ions on the surface of the substrate, thereby forming a copper film on the surface of the substrate, the method comprising the steps of: disposing a solid electrolyte membrane between the anode and the substrate; and applying a voltage between the solid electrolyte membrane and the substrate; reducing copper ions contained inside the solid electrolyte membrane to cause copper to precipitate from the copper ions on the surface of the substrate, the method comprising the steps of: disposing a solid electrolyte membrane between the anode and the substrate; the anode is provided as shown in FIG. 2, the solid electrolyte membrane is provided so as to cover an opening formed in the casing, the anode and the substrate are arranged so that, in a plan view of the substrate, the anode and the substrate are present within the opening, and a film formation region of the substrate is present within an anode region surrounded by a periphery of the anode, and the copper film is formed in a state in which Sa / Sb satisfies a relationship of 1.54 to 7.14, where Sa is an area of ​​the anode region in the plan view, and Sb is an area of ​​the film formation region of the substrate.

[0007] According to the present invention, a solid electrolyte film is provided to cover an opening formed in a casing containing an electrolytic solution, and a voltage is applied between an anode in the casing and the substrate. This forms an electric field between the anode and the substrate, and copper ions contained in the electrolytic solution contained in the casing pass through the solid electrolyte film and are reduced on the surface of the base layer. As a result, copper derived from the copper ions is precipitated on the surface of the substrate (specifically, in the film formation area), thereby forming a copper film.

[0008] In the present invention, in forming such a copper film, the anode and the substrate are arranged so that, in a plan view of the substrate, the anode and the substrate are present within the opening surrounded by the periphery of the opening of the casing, and the film formation region of the substrate is present within the anode region surrounded by the periphery of the anode. This allows the film formation region to face the anode through the opening of the casing so as to be contained within the anode region.

[0009] According to the present invention, the copper film is formed in a state where Sa / Sb satisfies the relationship of 1.54 to 7.14, where Sa is the area of ​​the anode region in plan view, and Sb is the area of ​​the film formation region of the substrate. By forming the copper film while satisfying such a relationship, it is possible to increase the film formation rate while suppressing scorching of the copper film. Here, if Sa / Sb is less than 1.54, when the applied voltage is increased in an attempt to increase the film formation rate, the amount of copper ions moving from the electrolyte to the substrate is insufficient, and defects such as scorching may occur in the copper film. On the other hand, even if Sa / Sb exceeds 7.14, no further effect can be expected.

[0010] In a further preferred embodiment, the copper film is formed under the condition that L1 / L2 is 3.50 or less, where L1 is the shortest distance between the edge of the anode region and the edge of the film formation region adjacent to each edge in the plan view, and L2 is the inter-electrode distance between the opposing surfaces of the anode and the substrate in a state in which the solid electrolyte membrane is in contact with the substrate. This makes it possible to increase the film formation rate while suppressing discoloration of the peripheral edge of the copper film. Here, if the copper film is formed under the condition that L1 / L2 exceeds 3.50, electric field lines from the anode are concentrated at the peripheral edge of the copper film, which may cause discoloration. Effect of the Invention

[0011] According to the method for forming a copper film of the present invention, it is possible to increase the film formation rate while suppressing the occurrence of scorching or the like on the copper film being formed. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic cross-sectional view illustrating a state in which a substrate is placed in a film formation apparatus used in the copper film formation method according to an embodiment of the present invention. [Diagram 2] 2 is a schematic cross-sectional view illustrating a state in which a copper film is formed on a film formation region of a substrate by the film formation apparatus shown in FIG. 1. [Diagram 3]3(a) is a diagram showing the positional relationship between the anode region, the film formation region, and the opening of the casing in a plan view of the substrate in the state shown in FIG. 2, and (b) is a schematic cross-sectional view for explaining the margin and inter-electrode distance between the anode and the substrate shown in FIG. 2. [Figure 4] 1 is a graph showing the relationship between the maximum deposition rate and Sa / Sb in the copper film deposition methods according to Examples 1 to 3 and Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

[0014] FIG. 1 is a schematic cross-sectional view illustrating a state in which a substrate is placed in a film formation apparatus used in a copper film formation method according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view illustrating a state in which a copper film is formed in a film formation area of ​​a substrate using the film formation apparatus shown in FIG.

[0015] 1. About the W substrate In this embodiment, a copper film F is formed on the surface of a film formation area wa of the substrate W. The substrate W may be a substrate made of metal such as copper, iron, or aluminum, and a metal film such as nickel or copper may be further formed on the film formation area wa of the substrate W. In this embodiment, the entire surface wf facing the substrate W is a metallic surface, and therefore serves as the film formation area wa for forming the copper film F.

[0016] Alternatively, the main body of the substrate W may be an insulating plate material, and a metal film may be formed on the surface of this plate material (main body) by, for example, sputtering, or the surface may be covered with a metal foil. Also, a base layer corresponding to the film formation region may be partially formed on the insulating plate material (main body).

[0017] The main body of the substrate W, which is an insulating plate material, can be, for example, a substrate made of glass epoxy resin, a substrate made of baked glass epoxy resin, a flexible film-like substrate such as a polyimide resin, or a substrate made of glass.

[0018] 2. Film forming apparatus 50 The film forming apparatus 50 is a film forming apparatus (plating apparatus) that forms a copper film F in a film forming area wa of a substrate W by a solid-phase electrodeposition method. As shown in Fig. 1, the film forming apparatus 50 includes a metallic anode 51, a solid electrolyte membrane 52 disposed between the anode 51 and the substrate W which is a cathode, and a power supply unit 54 that applies a voltage between the substrate W. Since the substrate W and a mounting table 56 are electrically connected, applying a voltage between the anode 51 and the mounting table 56 by the power supply unit 54 causes a current to flow between the anode 51 and the substrate W during film formation.

[0019] In this embodiment, the film forming apparatus 50 further includes a casing 53, which contains an electrolyte L containing copper ions and an anode 51. In this embodiment, the anode 51 is a flat plate-shaped anode. The anode 51 may be, for example, a soluble anode made of copper, or an insoluble anode made of titanium or a titanium alloy, stainless steel, platinum, or the like. In this specification, soluble and insoluble refer to whether or not the anode dissolves in the electrolyte L as copper ions. Alternatively, the anode may be an insoluble metal cage with multiple copper balls spread inside.

[0020] In this embodiment, the anode 51 and the solid electrolyte membrane 52 are disposed apart from each other, and the electrolytic solution L is in contact between the anode 51 and the solid electrolyte membrane 52 so as to contact the anode 51 and the solid electrolyte membrane 52. In other words, a space for accommodating the electrolytic solution L formed in the casing 53 is formed between the anode 51 and the solid electrolyte membrane 52, and the electrolytic solution L is filled in this space.

[0021] The solid electrolyte membrane 52 is not particularly limited as long as it can be impregnated (contain) copper ions therein by contacting it with the above-mentioned electrolytic solution L and can precipitate copper derived from the copper ions on the surface of the cathode (substrate W) when a voltage is applied.

[0022] The thickness of the solid electrolyte membrane 52 is, for example, about 5 μm to about 200 μm. Examples of materials for the solid electrolyte membrane 52 include fluororesins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon resins, polyamic acid resins, and resins having a cation exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

[0023] The electrolyte L is a liquid containing the copper of the copper film F in an ionic state, and the electrolyte L is obtained by dissolving (ionizing) the copper with an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid.

[0024] Furthermore, the film forming apparatus 50 of this embodiment includes, at an upper portion of the casing 53, an elevator 55 for raising and lowering the casing 53. The elevator 55 may be any device capable of raising and lowering the casing 53, and may be configured, for example, by a hydraulic or pneumatic cylinder, an electric actuator, a linear guide, a motor, or the like.

[0025] The casing 53 is provided with a supply port 53j through which the electrolytic solution L is supplied and a discharge port 53k through which the electrolytic solution L is discharged. The supply port 53j and the discharge port 53k are connected to a tank 61 via piping. The electrolytic solution L pumped out from the tank 61 by the pump 62 flows into the casing 53 from the supply port 53j, is discharged from the discharge port 53k and returns to the tank 61. A pressure regulating valve 63 is provided downstream of the discharge port 53k, and the electrolytic solution L in the casing 53 can be pressurized to a predetermined pressure by the pressure regulating valve 63 and the pump 62.

[0026] Therefore, during film formation, the solid electrolyte film 52 can press the film formation area wa of the substrate W by the liquid pressure of the electrolytic solution L. This allows the copper film F to be formed in the film formation area wa while the film formation area wa is uniformly pressurized by the solid electrolyte film 52.

[0027] The film forming apparatus 50 of this embodiment includes a mounting table 56 on which the substrate W is placed, and a recess 56a for accommodating the substrate W is formed in the mounting table 56. The mounting table 56 is made of a conductive metal material and is electrically connected to the negative electrode of a power supply unit 54, and the positive electrode of the power supply unit 54 is electrically connected to the anode 51 in the casing 53. This allows a voltage to be applied between the anode 51 and the substrate W using the power supply unit 54.

[0028] 3. Copper Film F Deposition Method A method for forming the copper film F will be described below with reference to Figs. 3(a) and (b). Fig. 3(a) is a diagram showing the positional relationship between the anode region 51a, the film formation region wa, and the opening 53a of the casing 53 in a plan view of the substrate W in the state shown in Fig. 2. Fig. 3(b) is a schematic cross-sectional view for explaining the margin (shortest distance) L1 between the anode 51 and the substrate W and the inter-electrode distance L2 shown in Fig. 2.

[0029] In this embodiment, as shown in Fig. 1, the substrate W is placed in a recess 56a of the mounting table 56. Specifically, as shown in Fig. 3(a), the anode 51 and the substrate W are placed such that, in a plan view of the substrate W, the anode 51 and the substrate W are present within the opening 53a of the casing 53, and the film formation region wa of the substrate W is present within an anode region 51a surrounded by a periphery 51d of the anode 51. In this embodiment, since the recess 56a is formed within the opening 53a and the anode region 51a in a plan view of the substrate W, placing the substrate W in the recess 56a satisfies this relationship.

[0030] The plan view of the substrate W refers to a state viewed from a direction in which a voltage is applied between the anode 51 and the substrate W, as shown in Fig. 3(a), and a state viewed from a normal direction of the surface of the substrate W. In this embodiment, as shown in Fig. 3(a), the anode region 51a of the anode 51 is a rectangular region surrounded by a periphery 51d, and corresponds to a surface 51f of the anode 51 that faces the substrate W. The film formation region wa of the substrate W is also a rectangular region surrounded by a periphery wd, and corresponds to the entire surface wf of the substrate W that faces the anode 51 in this embodiment.

[0031] In this embodiment, when the area of ​​the anode region in a plan view of the substrate W is Sa and the area of ​​the film formation region wa of the substrate W is Sb, Sa / Sb satisfies the relationship of 1.54 to 7.14.

[0032] In addition, in this embodiment, the anode 51 and the substrate W are installed so as to satisfy the following condition. As shown in Fig. 3(a), in a plan view of the substrate W, the shortest distance between an edge 51g of the anode region 51a and an edge wg of the film formation region wa adjacent to each edge 51g is defined as L1. As shown in Fig. 3(b), in a state in which the solid electrolyte membrane 52 is in contact with the substrate W, the inter-electrode distance between the opposing surfaces (surfaces) 51f, wf of the anode 51 and the substrate W is defined as L2. At this time, the anode 51 and the substrate W are installed so as to satisfy the condition that L1 / L2 is 3.50 or less.

[0033] With these conditions satisfied, the copper film F is formed on the film formation area wa of the substrate W. Specifically, the casing 53 is lowered to a predetermined height by the lifting device 55, and the solid electrolyte film 52 is brought into contact with the film formation area of ​​the substrate W.

[0034] Next, when the electrolytic solution L is pressurized by the pump 62, the solid electrolyte film 52 conforms to the film formation area wa, which is the surface wf of the substrate W, and the electrolytic solution L in the casing 53 is set to a constant pressure set by the pressure regulating valve 63. That is, the solid electrolyte film 52 can uniformly press the film formation area wa with the regulated liquid pressure of the electrolytic solution L in the casing 53.

[0035] In this pressed state, a voltage is applied between the anode 51 and the substrate W to reduce the copper ions contained in the solid electrolyte film 52, and copper derived from the copper ions is deposited in the film formation region wa. Furthermore, due to the application of the voltage, the copper ions in the electrolyte L in the casing 53 continue to be reduced at the cathode, so that a copper film F is formed on the substrate W as shown in FIG.

[0036] In this manner, the substrate W is pressed by the solid electrolyte membrane 52 provided so as to cover the opening 53a formed in the casing 53 containing the electrolytic solution L, and a voltage is applied between the anode 51 in the casing 53 and the substrate W. As a result, an electric field is formed between the anode 51 and the substrate W, and the copper ions contained in the electrolytic solution L contained in the casing 53 pass through the solid electrolyte membrane and are reduced on the surface wf (film formation region wa) of the substrate W, thereby forming a copper film F.

[0037] In this embodiment, in a plan view of the substrate W, the anode 51 and the substrate W are present within the opening 53a surrounded by the periphery of the opening 53a of the casing 53. Furthermore, a film formation region wa of the substrate W is present within the anode region 51a surrounded by the periphery 51d of the anode 51. This allows the film formation region wa to face the anode 51 via the opening 53a of the casing 53 so as to be contained within the anode region 51a.

[0038] On the premise of such an arrangement relationship, in this embodiment, when the area of ​​the anode region in a plan view of the substrate W is Sa and the area of ​​the film formation region of the substrate is Sb, the copper film F is formed in a state where Sa / Sb satisfies the relationship of 1.54 to 7.14. As a result, as is clear from the experiments of the inventors described later, it is possible to increase the film formation speed while suppressing scorching and the like on the copper film F.

[0039] Here, when Sa / Sb is less than 1.54, if the applied voltage is increased in an attempt to increase the deposition rate of the copper film F, the amount of copper ions moving from the electrolytic solution L to the substrate W may be insufficient, and defects such as scorching may occur in the copper film F. On the other hand, even if Sa / Sb exceeds 7.14, no further effect can be expected.

[0040] Incidentally, assuming that Sa / Sb satisfies the relationship of 1.54 to 7.14, the film formation region wa is disposed inside each edge 51g of the periphery 51d of the anode region 51a in a plan view of the substrate W. At this time, since electric field lines from the anode 51 tend to concentrate on the periphery 51d of the film formation region wa, if an attempt is made to further increase the film formation rate of the copper film F, the periphery of the copper film F may discolor. Note that this discoloration of the copper film F is not as damaging as the above-mentioned scorching of the copper film F, but is at a level that does not cause problems in use.

[0041] From this point of view, as will be clear from the experiments of the inventors described later, by forming the copper film F so that the relationship between the shortest distance L1 between the edge 51g of the anode region 51a and the edge wg of the film-forming region wa and the electrode distance L2 between the anode 51 and the substrate W satisfies L1 / L2≦3.50, it is possible to increase the film-forming rate while suppressing discoloration of the periphery of the copper film F. Here, if the copper film F is formed under conditions where L1 / L2 exceeds 3.50, the shortest distance L1 is too large or the electrode distance L2 is too narrow. Therefore, electric field lines from the anode 51 are concentrated at the edge wg of the film-forming region wa, so that the end of the copper film F may be discolored.

[0042] In this manner, the copper film F is formed, and when the copper film F has been formed to a predetermined thickness, the application of voltage between the anode 51 and the substrate W is stopped, and the pressurization of the electrolytic solution L by the pump 62 is stopped. Thereafter, the casing 53 is raised to a predetermined height, and the substrate W on which the copper film F has been formed is removed from the mounting table 56. In this manner, the copper film F can be formed. EXAMPLES

[0043] The invention is illustrated by the following examples. [Example 1-1] A copper film was formed on the surface of the substrate by the above-mentioned film forming method. A substrate was prepared by attaching copper foil to the surface of a plate-shaped glass epoxy resin. An anode was prepared by spreading copper balls with a diameter of 5 mm on a stainless steel wire mesh anode made of a mesh with a longitudinal length of 3.1 mm and a lateral length of 6 mm. In Example 1, when the substrate was placed in the film forming apparatus, the area of ​​the anode region in the plan view of the substrate / the area of ​​the film forming region of the substrate (Sa / Sb) was 1.54.

[0044] Next, an electrolyte made by mixing 0.2 M sulfuric acid with 1 M copper sulfate aqueous solution and heating it to 70°C was supplied to the casing in which the anode was placed from above the anode. Next, the casing was lowered until the inter-electrode distance became 2 mm, and the electrolyte in the casing was pressurized to 0.6 MPa, and the electrolyte membrane was pressed against the substrate by this pressure increase.

[0045] Next, the current density was changed by changing the voltage applied between the anode and the substrate, and the deposition rate in the thickness direction of the copper film and the presence or absence of fading of the copper film were confirmed. The results are shown in Table 1 and Fig. 4. Fig. 4 is a graph showing the relationship between the maximum deposition rate and Sa / Sb in the deposition methods of Examples 1-1 to 1-3 and Comparative Example 1.

[0046] [Examples 1-2 and 1-3] A copper film was formed in the same manner as in Example 1-1. In Examples 1-2 and 1-3, the size of the substrate was changed so that the area of ​​the anode region in the plan view of the substrate / the area of ​​the film formation region of the substrate (Sa / Sb) was 5.33 and 7.14, respectively, when the substrate was placed in the film formation apparatus. The ratio of the copper balls to the film formation region per unit area was the same in Examples 1-1 to 1-3, and in Comparative Example 1 and Reference Example 1 described later. As in Example 1-1, the voltage applied between the anode and the substrate was changed to change the current density, and the film formation speed in the thickness direction of the copper film and the presence or absence of scorching of the copper film were confirmed. The results are shown in Table 1 and FIG. 4. The maximum film formation speed shown in FIG. 4 is the maximum film formation speed at which scorching did not occur in the copper film.

[0047] [Comparative Example 1] A copper film was formed in the same manner as in Example 1-1. In Comparative Example 1, the size of the substrate was changed so that the area of ​​the anode region in a plan view of the substrate / the area of ​​the film formation region of the substrate (Sa / Sb) was 0.64 when the substrate was placed in the film formation device. As in Example 1-1, the voltage applied between the anode and the substrate was changed to change the current density, and the film formation speed in the thickness direction of the copper film and the presence or absence of scorching of the copper film were confirmed. The results are shown in Table 1 and FIG. 4.

[0048] [Reference example 1] A copper film was formed in the same manner as in Example 1-1. In Reference Example 1, the size of the substrate was changed so that the area of ​​the anode region in a plan view of the substrate / the area of ​​the film formation region of the substrate (Sa / Sb) was set to 22 when the substrate was placed in the film formation device. As in Example 1-1, the voltage applied between the anode and the substrate was changed to change the current density, and the film formation speed in the thickness direction of the copper film and the presence or absence of scorching of the copper film were confirmed. The results are shown in Table 1.

[0049] In FIG. 4, the ratio of copper balls to the film-formed region per unit area is the same in all of Examples 1-1 to 1-3, and Comparative Example 1 and Reference Example 1 described later.

[0050] [Table 1]

[0051] <Results and Discussion> 4, in Examples 1-1 to 1-3, the film formation speed in the thickness direction can be ensured up to 4.06 μm / min, and it can be said that if a film is formed at this film formation speed, scorching occurs in the copper film in Comparative Example 1. This is because, from Examples 1-1 to 1-3, Sa / Sb satisfies the relationship of 1.54 to 7.14, it is possible to ensure electrolysis (electric lines of force) necessary for film formation for the anode as a whole, and as a result, it is possible to increase the film formation speed to at least 4.06 μm / min while suppressing scorching, etc., of the copper film.

[0052] However, when Sa / Sb is less than 1.54 as in Comparative Example 1, if the applied voltage is increased in an attempt to increase the film formation rate, Sa becomes too small relative to Sb, or Sb becomes too large relative to Sa, and the amount of copper ions moving from the electrolyte to the substrate is not sufficiently secured, which may result in defects such as scorching of the copper film.

[0053] In particular, it was found that in Examples 1-2 and 1-3, the film-thickness direction film-forming speed was at least 5.67 μm / min. This can be said to be because Examples 1-2 and 1-3 satisfy the relationship of Sa / Sb of 5.33 to 7.14, and therefore the film-forming speed could be increased to at least 5.67 μm / min while suppressing the copper film from burning. As can be seen from Reference Example 1 shown in Table 1, when Sa / Sb exceeds 7.14, even if the film-forming speed is increased to 8.00 μm / min, the copper film will burn, and therefore the film-forming speed cannot be increased that much.

[0054] From the above, it can be said that it is necessary for Sa / Sb to satisfy the relationship of 1.54 to 7.14, and it is more preferable for Sa / Sb to satisfy the relationship of 5.33 to 7.14.

[0055] [Example 2-1] A copper film was formed in the same manner as in Example 1-1. In Example 2-1, the size of the anode and the substrate were changed, and while the substrate was placed in the film forming apparatus, the area of ​​the anode region in the plan view of the substrate / the area of ​​the film forming region of the substrate (Sa / Sb) was maintained at 5.33, the position of the substrate was adjusted, and the shortest distance (margin of the non-film forming region) L1 between one edge of the anode region and the edge of the film forming region adjacent to this edge was set to 2.1 mm. Since the electrode distance was 2.0 mm, the shortest distance / electrode distance (L1 / L2) was 1.05. Under these conditions, the film was formed so that the film thickness direction film forming speed was 5.67 μm / min, and the presence or absence of discoloration of the edge of the copper film that satisfied this condition was confirmed. The results are shown in Table 2.

[0056] [Example 2-2] A copper film was formed in the same manner as in Example 1-1. In Example 2-2, the size of the anode and the substrate was changed to maintain Sa / Sb at 5.33 while setting the shortest distance (margin of non-film-formed area) L1 to 7.0 mm. Since the electrode distance was 2.0 mm, the shortest distance / electrode distance (L1 / L2) was 3.50. Under these conditions, the film was formed at a film thickness direction film formation speed of 5.67 μm / min, and the presence or absence of discoloration of the edge of the copper film was confirmed. The results are shown in Table 2.

[0057] [Comparative Examples 2-1 to 2-3] A copper film was formed in the same manner as in Example 1-1. In Comparative Examples 2-1 to 2-3, the size of the anode and the substrate were changed to maintain Sa / Sb at 5.33 while setting the shortest distance (margin of non-film-formed area) L1 to 16.0 mm, 22.0 mm, and 25 mm, respectively. Since the electrode distance was 2.0 mm, the shortest distance / electrode distance (L1 / L2) was 8.00, 11.00, and 12.50, respectively. Under these conditions, in Comparative Examples 2-1 and 2-2, the film was formed so that the film formation speed in the film thickness direction was 5.67 μm / min, and in Comparative Example 2-3, the film was formed so that the film formation speed in the film thickness direction was 5.84 μm / min, and the presence or absence of discoloration of the edge of the copper film was confirmed. The results are shown in Table 2.

[0058] [Table 2]

[0059] <Results and Discussion> As shown in Table 2, discoloration occurred at the edge of the copper film in Comparative Examples 2-1 to 2-3. However, in Examples 2-1 and 2-2, in which L1 / L2 was smaller than in Comparative Examples 2-1 to 2-3, no discoloration occurred at the edge of the copper film.

[0060] This is probably because, in Comparative Examples 2-1 to 2-3, when copper film F was formed under conditions where L1 / L2 exceeded 3.50, the shortest distance was too long or the electrode distance was too narrow, causing electric field lines from the anode to concentrate at the edge of the film formation region, resulting in discoloration of the edge of the copper film. For these reasons, it is considered preferable to ensure that L1 / L2 is 3.50 or less.

[0061] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the spirit of the present invention described in the claims. [Explanation of symbols]

[0062] 50: film forming device, 51: anode, 51a: anode region, 52: solid electrolyte membrane, 53: casing, 53a: opening, L: electrolyte, F: copper film, Sa: area of ​​anode region, Sb: area of ​​film forming region of substrate, L1: shortest distance (margin of non-film forming region), L2: interelectrode distance, W: substrate, wa: film forming region

Claims

1. A method for forming a copper film on a surface of a substrate, the method comprising: disposing a solid electrolyte film between an anode and a substrate serving as a cathode; pressing the substrate with the solid electrolyte film; applying a voltage between the anode and the substrate; and reducing copper ions contained in the solid electrolyte film to cause copper to precipitate from the copper ions on the surface of the substrate, thereby forming a copper film on the surface of the substrate, the method comprising: the anode is provided in a casing that contains an electrolyte solution including copper ions, such that the electrolyte solution is disposed between the anode and the solid electrolyte membrane; the solid electrolyte membrane is provided so as to cover an opening formed in the casing, The anode and the substrate are arranged such that, in a plan view of the substrate, the anode and the substrate are present within the opening, and a film formation region of the substrate is present within an anode region surrounded by a periphery of the anode; The copper film is formed in a state where Sa / Sb satisfies a relationship of 1.54 to 7.14, where Sa is an area of ​​the anode region in the plan view, and Sb is an area of ​​the film formation region of the substrate.

2. In the plan view, the shortest distance between an edge of the anode region and an edge of the film formation region adjacent to each edge is defined as L1, When the solid electrolyte membrane is in contact with the substrate, the inter-electrode distance between the opposing surfaces of the anode and the substrate is L2, 2. The method for forming a copper film according to claim 1, wherein the copper film is formed under the condition that L1 / L2 is 3.50 or less.

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