JP6653799B2 - Anode for electrolytic copper plating and electrolytic copper plating apparatus using the same - Google Patents

Description

  The present invention relates to an anode for electrolytic copper plating and an electrolytic copper plating apparatus using the same.

  BACKGROUND ART Conventionally, when a conductor is formed on a printed wiring board or the like, electrolytic copper plating is performed. When performing electrolytic copper plating, there are a method using a soluble copper anode made of a copper material and a method using an insoluble anode made of platinum, titanium, iridium oxide or the like as the anode. In addition, additives such as brighteners and levelers are added to the electrolytic copper plating solution in order to improve plating characteristics such as plating acceleration and via filling.

  Here, in performing the electrolytic copper plating process, it is now mainstream to use a soluble copper anode. The reason is that the soluble copper anode can simplify the equipment compared to the insoluble anode, does not require maintenance costs, the anode itself is relatively inexpensive, and can realize low cost. Can be

  However, when a soluble copper anode is used, bis (3-sulfopropyl) disulfide (B) added as a brightener to the electrolytic copper plating solution is accompanied by a reaction in which the copper electrode is chemically dissolved in the plating solution. Hereinafter, it is known that “SPS” is reduced to 3-mercaptopropane-1-sulfonic acid (hereinafter, simply referred to as “MPS”). If this MPS is present in a certain amount or more in the electrolytic copper plating solution, there is a problem that desired plating characteristics cannot be obtained.

  To solve the above-mentioned problem, for example, as described in Patent Document 1, attempts have been made to increase the dissolved oxygen concentration in the plating solution by blowing air into the plating solution. Specifically, Patent Literature 1 discloses "in a plating apparatus for acidic copper having a plating main tank provided with an overflow tank, a plating solution jet discharge unit provided in a lower part of the plating tank, a copper anode and a bar for a product to be plated. A plating apparatus for acidic copper, characterized in that an air stirring or oxygen stirring means is provided in an overflow tank.

JP-A-2004-143478

  However, in the plating apparatus disclosed in Patent Literature 1, it is necessary to separately provide an overflow tank, and there is a problem in that the structure of the plating apparatus is complicated and equipment cost is increased.

  From the above, the present invention provides an anode for electrolytic copper plating and an electrolytic copper plating apparatus using the same, which can improve plating characteristics such as plating acceleration and via filling without complicating the structure of the apparatus. The purpose is to provide.

  The inventors of the present invention have conducted intensive studies, and as a result, have achieved the above object by employing the following method.

Anode for electrolytic copper plating according to the present invention: An anode disposed in an electrolytic treatment tank in which an electrolytic copper plating solution is stored, wherein the electrolytic copper plating solution is an acidic electrolytic copper plating solution containing a disulfide compound. The anode is provided with a soluble copper anode and an insoluble anode in an electrically connected state.

  Electrolytic copper plating apparatus according to the present invention: An electrolytic copper plating apparatus according to the present invention includes the above-described anode for electrolytic copper plating.

  ADVANTAGE OF THE INVENTION According to the anode for electrolytic copper plating and the electrolytic copper plating apparatus which concern on this invention, it can aim at improvement of plating characteristics, such as plating acceleration and via-filling property, without complicating an apparatus structure.

It is the schematic sectional drawing which illustrated the case where the soluble copper anode which concerns on this invention was used for the electrolytic copper plating apparatus. 4 is a cross-sectional photograph showing a via filling state in Example 1 and Comparative Example 1. 4 is a cross-sectional photograph showing a via filling state in Example 2 and Comparative Example 2.

  Hereinafter, an anode for electrolytic copper plating according to the present invention and an electrolytic copper plating apparatus using the same will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating a case where the soluble copper anode according to the present invention is used in an electrolytic copper plating apparatus.

The electrolytic copper plating apparatus 10 according to the present invention includes the electrolytic copper plating anode 1 according to the present invention. The anode 1 for electrolytic copper plating is an anode installed in an electrolytic treatment tank 20 in which an electrolytic copper plating solution 21 is stored. The electrolytic copper plating solution 21 is an acidic electrolytic copper plating solution containing a disulfide compound (for example, SPS), and the anode 1 is in a state where the soluble copper anode 2 and the insoluble anode 3 are electrically connected. and wherein the kite with in. Hereinafter, these configurations will be described.

The electrolytic copper plating apparatus 10 according to the present invention is configured such that the member to be plated (cathode) W and the anode (anode) 1 are immersed in the electrolytic processing tank 20 containing the electrolytic copper plating solution 21. And a device for electrolytically treating the surface to be processed of the member to be plated W. Here, the member to be plated W of the present invention can be a printed wiring board or a wafer in which circuit wiring is laminated with an insulating material such as epoxy resin. Further, as these printed wiring boards and wafers, those having through holes and / or via holes can be used. These through holes and via holes are generally holes having a small diameter of about 10 μm to 1000 μm, and electrical connection between signal layers is made through these holes. According to the electrolytic copper plating apparatus 10 according to the present invention, it is possible to perform an electrolytic treatment for filling the inside of these through holes and via holes with copper. The electrolytic copper plating apparatus 10 according to the present invention is designed to diffuse air bubbles into the electrolytic copper plating solution 21 or to supply high-pressure air from the nozzle 6 connected to the circulation pipe 5 in order to improve uniform electrodeposition. May be employed to stir the electrolytic copper plating solution 21 by, for example, jetting out.

  Further, as the electrolytic copper plating solution 21 of the present invention, an acidic electrolytic copper plating solution containing a disulfide compound is used. Usually, the acidic electrolytic copper plating solution 21 is composed of copper sulfate pentahydrate, sulfuric acid, chloride ions and additives. For example, the composition of the acidic electrolytic copper plating solution 21 can be used in the range of 30 g / L to 250 g / L of copper sulfate / pentahydrate, 30 g / L to 250 g / L of sulfuric acid, and 30 mg / L to 75 mg / L of chloride ions. . The temperature of the acidic electrolytic copper plating solution 21 can be usually used in a range of 15 ° C to 60 ° C, and is preferably 20 ° C to 35 ° C. Care must be taken in controlling the concentrations of copper sulfate and pentahydrate since the concentration of copper sulfate and pentahydrate may increase on the copper anode as the concentration of copper sulfate and pentahydrate increases. Here, the concentration of sulfuric acid in the acidic electrolytic copper plating solution 21 is preferably 30 g to 400 g / L. When the sulfuric acid concentration is less than 30 g / L, the conductivity of the acidic electrolytic copper plating solution 21 decreases, and it becomes difficult to supply electricity to the acidic electrolytic copper plating solution 21. On the other hand, when the sulfuric acid concentration exceeds 400 g / L, copper sulfate easily precipitates in the acidic electrolytic copper plating solution, which adversely affects the plating characteristics.

In the electrolytic copper plating apparatus 10 according to the present invention, as described above, the soluble copper anode 2 and the insoluble anode 3 arranged in the electrolytic treatment tank 20 are electrically connected to each other, thereby acting as the anode 1. I do. When performing electrolytic treatment, when the electrolytic copper plating solution 21 containing SPS is used, this SPS is changed to MPS, and this MPS is generated. In the via-fill bath, there is a problem that the filling rate is reduced and plating appearance is poor. Here, it has been confirmed that even when the electrolytic copper plating solution 21 is left after the electrolysis is stopped, SPS is reduced near the anode 1 to generate MPS. The formation of MPS can also cause generation of anode sludge composed of MPS-Cu ⁺ complex. The anode sludge causes a decrease in plating properties such as filling properties and throwing power of vias. However, the anode 1 for electrolytic copper plating according to the present invention is provided in the electrolytic treatment tank 20 in a state where the soluble copper anode 2 and the insoluble anode 3 are electrically connected, so that the insoluble anode 3 Oxygen can be supplied into the liquid 21. Oxygen generated from the insoluble anode 3 oxidizes MPS to SPS, thereby suppressing an increase in the MPS concentration in the electrolytic copper plating solution 21 and eliminating the adverse effect of MPS. Therefore, according to the electrolytic copper plating apparatus 10 of the present invention, even if the electrolytic copper plating solution 21 contains SPS as a brightener, desired plating characteristics can be obtained.

  The soluble copper anode 2 constituting the anode 1 for electrolytic copper plating according to the present invention is used to maintain the concentration of copper ions in the electrolytic copper plating solution 21 consumed during electrolysis at a predetermined concentration. The shape of the soluble copper anode 2 is not limited, but by adopting a shape having a surface area as large as possible, more copper ions can be generated during electrolysis and plating efficiency can be further improved.

Further, it is preferable that the soluble copper anode 2 of the present invention is made of a phosphorous copper material. By forming the soluble copper anode 2 from a phosphorus-containing copper member, a film of a compound called “black film” called Cu ₂ P is formed on the surface of the phosphorus-containing copper member during electrolysis, and monovalent copper ions are formed. The generation of anode sludge can be effectively suppressed by suppressing the generation, and it is possible to prevent the deterioration of plating characteristics. In order to further suppress the generation of anode sludge in the phosphorus-containing copper member, the phosphorus content is preferably set to about 0.02% to 0.06%. The use of a phosphorus-containing copper member for the soluble copper anode 2 is advantageous in that copper can be smoothly dissolved during electrolysis.

As the insoluble anode 3 constituting the anode 1 for electrolytic copper plating according to the present invention, an anode made of any material can be used as long as it does not elute metal in the electrolytic copper plating solution 21. Examples include, but are not limited to, iridium oxide, platinum-clad titanium, platinum, graphite, ferrite, titanium dioxide coated with lead dioxide and platinum group oxides, stainless steel, lead alloys and other materials. . Also, insoluble anodes 3 can be Ri構 formed by the coating the coating to the substrate. In this case, the entire surface of the base material may be coated, but only a part of the base material may be coated as long as it functions as the insoluble anode 3. At this time, the thickness of the coating is not particularly limited, and is preferably 0.1 μm to 10 μm from the viewpoint of durability and cost.

  Further, the shape of the insoluble anode 3 of the present invention is not limited. The insoluble anode 3 has a shape and dimensions that efficiently generate oxygen without disturbing the dissolution of the soluble copper anode 2 during electrolysis, thereby quickly oxidizing MPS present in the electrolytic copper plating solution 21. To return to SPS, so that MPS can be prevented from accumulating in the electrolytic copper plating solution 21 and a decrease in plating characteristics can be prevented.

  The anode 1 for electrolytic copper plating according to the present invention has a surface area ratio of the soluble copper anode 2 and the insoluble anode 3 immersed in the electrolytic copper plating solution 21 of 10: 1 to 1 from the viewpoint of suppressing the generation of MPS. : 10 is preferred. When the area ratio of the surface of the soluble copper anode 2 to the surface of the insoluble anode 3 immersed in the electrolytic copper plating solution 21 is less than 10: 1, the generation of oxygen from the surface of the insoluble anode (for example, iridium oxide member) 3 is extremely small. Therefore, an increase in the MPS concentration in the electrolytic copper plating solution 21 cannot be sufficiently suppressed, and desired plating characteristics cannot be obtained. If the area ratio exceeds 1:10, the generation of oxygen from the surface of the insoluble anode (for example, iridium oxide member) 3 is significantly increased. The consumption amount increases. Further, in this case, supply of copper from the soluble copper anode 2 becomes insufficient, and it is necessary to separately supply a copper source to maintain the copper concentration in the electrolytic copper plating solution 21 at a predetermined concentration. Here, the area ratio of the surface of the soluble copper anode 2 to the surface of the insoluble anode 3 immersed in the electrolytic copper plating solution 21 is more preferably 5: 1 to 1: 5 in order to obtain the above-described effects.

Further, in the electrolytic copper plating apparatus 10 according to the present invention, it is preferable that the applicable cathode current density is in a range in which a phosphorous copper member which is usually used for electrolytic copper plating of a printed wiring board is used. Specifically, the cathode current ^{density, 0.1A / dm 2 ~10A / dm} 2 , preferably about ^{0.5A / dm 2 ~6A / dm 2} , more preferably ^1A / dm ^{2 ~5A} / dm 2 It is. The anode current density is usable in conventional ^{0.1A / dm 2 ~3A / dm 2} , more preferably ^{1A / dm 2 ~3A / dm 2} . The copper concentration in the electrolytic copper plating solution 21 tends to increase when the anode current density is too low, and tends to decrease when the anode current density is too high. Therefore, it is necessary to adjust the anode area according to the cathode current density used. It is.

  Here, effects obtained at the time of electrolysis and at the time of stopping electrolysis when the anode 1 for electrolytic copper plating according to the present invention is used will be described more specifically. Usually, at the time of electrolysis and at the time of stopping electrolysis, dissolution occurs in the soluble copper anode 2 as in the following formula (1). At the time of electrolysis, a reaction represented by the following formula (2) occurs at the cathode, and copper is deposited. When the electrolytic copper plating solution 21 contains a disulfide compound, the SPS is reduced as shown in the following formula (3) by the electrons released when the soluble copper anode 2 is dissolved, and MPS is generated. I do. The generated MPS is partially oxidized and converted into SPS as shown in the following formula (4), but Cu (I) MPS associated with monovalent copper ion is converted into the following formula (4). It becomes MPS as in 5).

  In the above Chemical Formula 1, (1), (3) to (5) show the process of generating MPS which causes the deterioration of the plating characteristics. However, the anode 1 for electrolytic copper plating according to the present invention uses the insoluble anode 3 instead of the insoluble anode 3. By being provided in a state of being electrically connected to the soluble copper anode 2, an increase in the MPS concentration in the electrolytic copper plating solution 21 can be suppressed. That is, at the time of electrolysis, the water in the electrolytic copper plating solution 21 is electrolyzed at the insoluble anode 3 as shown in the above chemical formula (6), and MPS is oxidized by the oxygen generated at this time to SPS. By being converted, the generated MPS can be reduced.

  Since the electrolytic copper plating apparatus 10 according to the present invention has the above-described configuration, an increase in the concentration of MPS in the electrolytic copper plating solution 21 can be suppressed. Therefore, according to the anode 1 for electrolytic copper plating according to the present invention and the electrolytic copper plating apparatus 10 using the same, even if electrolysis is started using the electrolytic copper plating solution 21 that has been left for a long time, the plating appearance is poor. It hardly occurs, and maintenance-free can be realized.

  As described above, the soluble copper anode according to the present invention and the method for preserving the electrolytic copper plating solution using the same have been described. Hereinafter, examples of the present invention will be described, and the present invention will be described in more detail. The present invention is not limited by these examples.

  In Example 1, a test was performed to confirm the effect when a soluble copper anode and an insoluble anode were used together in an electrically connected state as an anode for electrolytic copper plating.

  In Example 1, first, a desmear treatment was performed on a member to be plated (printed circuit board) having a plate thickness of 1.0 mm, a via diameter of 100 μm, and a depth of 80 μm by a Melplate MLB-6001 process (manufactured by Meltex Corporation). . Next, electroless copper plating was performed by a Melplate CU-390 process (manufactured by Meltex Corporation). Then, the printed circuit board was subjected to acidic degreasing, washing with water, and sulfuric acid treatment using Melplate PC-316 (manufactured by Meltex Co., Ltd.), followed by electrolytic copper plating under the following conditions.

  The acidic electrolytic copper plating solution used in Example 1 was a plating solution containing 200 g / L of copper sulfate pentahydrate, 100 g / L of concentrated sulfuric acid, and 50 mg / L of chloride ion, and was added to Lucent Copper SVF-A (Meltex Co., Ltd.). 3 L prepared by adding 0.4 mL / L, Lucent Copper SVF-B (manufactured by Meltex Corporation) 20 mL / L, and Lucent Copper SVF-L (manufactured by Meltex Corporation) 15 mL / L Was used. The temperature of the acidic electrolytic copper plating solution was 25 ° C.

  Then, in the electrolytic treatment tank, an anode for electrolytic copper plating was installed while being immersed in the contained via-fill bath. The anode for electrolytic copper plating was separated and placed in the electrolytic treatment tank in a state where the soluble copper anode (50 mm × 120 mm phosphorus-containing copper plate) and the insoluble anode (50 mm × 120 mm iridium oxide coated plate) were electrically connected. . In Example 1, the electrolytic treatment was performed in the electrolytic treatment tank while circulating the plating solution using a pump.

In Example 1, the area ratio of the soluble copper anode to the insoluble anode immersed in the electrolytic copper plating solution was 1: 1. In addition, a printed board having electroless copper plating of 50 mm × 130 mm as a cathode was immersed in an electrolytic copper plating solution. Then, the electrolytic treatment was performed at a current density of 2 A / dm ^{2 for} 45 minutes under the conditions of a current flowing amount of the electrolytic copper plating solution of 0 AH / L (new bath), 10 AH / L, 50 AH / L, and 100 AH / L. . Thereafter, the state of plating filling in the via under each of these conditions was observed by a cross-section method. FIG. 2 shows a cross-sectional photograph of the state of filling of plating in the via in Example 1.

  In Example 2, as in Example 1, a test was performed to confirm the effect when a soluble copper anode and an insoluble anode were used in an electrically connected state as an anode for electrolytic copper plating.

  In Example 2, the same member to be plated as in Example 1 was used. Further, in Example 2, the same electrolysis pretreatment conditions and electrolysis treatment conditions as in Example 1 were adopted, except that Lucent Copper SVF-A (0.4 mL / L) was changed to MPS (1 mg / L). Therefore, description of these processing conditions employed in the second embodiment will be omitted.

In Example 2, for the anode for electrolytic copper plating, the area ratio of the soluble copper anode to the insoluble anode in the electrolytic copper plating solution was “10: 1”, “5: 1”, “1: 1”, “ 1: 1 (using platinum-coated titanium as an insoluble anode), "1: 5", and "1:10" were prepared. Then, under the respective conditions of 0 AH / L, 0.5 AH / L, 1 AH / L, 4 AH / L, and 10 AH / L of the electrolytic copper plating solution, as in Example 1, a 50 mm × 130 mm cathode was used. The printed board subjected to the electroless copper plating was immersed in an electrolytic copper plating solution, and subjected to an electrolytic treatment at a current density of 2 A / dm ^{2 for} 45 minutes. Under these conditions, the filling state of the plating in the via was observed by a cross-section method. FIG. 3 shows a cross-sectional photograph of the state of plating filling in the via in Example 2.

Comparative example

[Comparative Example 1]
In Comparative Example 1, a test was performed to confirm the effect when only a soluble copper anode was used as the anode for electrolytic copper plating.

  In Comparative Example 1, the same electrolytic pretreatment conditions and electrolytic treatment conditions as in Example 1 were employed except that only a soluble copper anode was used as the anode for electrolytic copper plating. Therefore, description of these processing conditions employed in Comparative Example 1 will be omitted.

  In Comparative Example 1, the same test as in Example 1 was performed. FIG. 2 shows a cross-sectional photograph of the state of filling of plating in the via in Comparative Example 1 so as to be comparable with Example 1.

[Comparative Example 2]
In Comparative Example 2, as in Comparative Example 1, a test was performed to confirm the effect when only a soluble copper anode was used as the anode for electrolytic copper plating.

  Comparative Example 2 was the same as Example 1 except that only the soluble copper anode was used as the anode for electrolytic copper plating, and that Lucent Copper SVF-A (0.4 mL / L) was changed to MPS (1 mg / L). Electrolysis pretreatment conditions and electrolysis treatment conditions were employed. Therefore, description of these processing conditions employed in Comparative Example 2 is omitted.

  In Comparative Example 2, the same test as in Example 2 was performed. FIG. 3 shows a cross-sectional photograph of the state of plating filling in the vias in Comparative Example 2 so as to be comparable with Example 2.

  From the results shown in FIG. 2, when the anode provided in a state where the soluble copper anode and the insoluble anode are electrically connected to each other is used as the anode disposed in the electrolytic treatment tank in which the electrolytic copper plating solution is stored. Is different from the case where only a soluble copper anode is used, and it is found that there is almost no difference in the filling state of the via even when the amount of current is increased up to 100 AH / L, and that excellent filling properties can be obtained stably.

  From the results shown in FIG. 3, when the anode provided in a state where the soluble copper anode and the insoluble anode were electrically connected to each other was used as the anode disposed in the electrolytic treatment tank in which the electrolytic copper plating solution was stored. It was found that, as compared with the case where only the soluble copper anode was used, even when MPS was contained in the electrolytic copper plating solution at 1 mg / L, the filling property was recovered in a relatively short time. Further, at this time, when the area ratio of the soluble copper anode and the insoluble anode in the electrolytic copper plating solution in Example 2 was “10: 1” and the area ratio was other than that, It was found that the larger the proportion of the soluble anode, the more difficult it was to recover filling properties. On the other hand, as the proportion of the soluble anode becomes smaller, the supply of copper from the soluble copper anode in the electrolytic copper plating solution becomes insufficient, and a separate copper source needs to be supplied to maintain the copper concentration in the electrolytic copper plating solution. It can be assumed that From the above viewpoint, it can be understood that the area ratio of the soluble copper anode to the insoluble anode in the electrolytic copper plating solution is more preferably 5: 1 to 1: 5.

As described above, by using the anode for electrolytic copper plating according to the present invention and the electrolytic copper plating apparatus using the same, it is possible to improve plating characteristics such as plating promotion property and via filling property without complicating the apparatus structure. It turned out that I could do it. Therefore, it matter if the electrolysis treatment was conducted using an electrolytic copper plating anodes according to the invention, it is possible to effectively eliminate the adverse effects associated with elevated concentrations of MPS in the electrolytic copper plating solution Can understand.

ADVANTAGE OF THE INVENTION According to the electrolytic copper plating anode which concerns on this invention, and the electrolytic copper plating apparatus using the same, when using the acidic electrolytic copper plating solution containing the disulfide compound, the density | concentration rise of MPS is suppressed effectively and it is desired. Can be stably obtained. Further, by using the anode for electrolytic copper plating according to the present invention, the structure of the electrolytic copper plating apparatus can be simplified, and the equipment cost can be reduced. Accordingly, the anode for electrolytic copper plating and the electrolytic copper plating apparatus using the same according to the present invention are preferably used particularly when performing an electrolytic copper plating treatment on a printed wiring board or a wafer having through holes and / or via holes. Can be done.

W: Plated member 1: Anode for electrolytic copper plating 2: Soluble copper anode 3 ... Insoluble anode 5: Circulation piping 6: Nozzle 10: Electrolytic copper plating apparatus 20 ... Electrolytic treatment tank 21 ... Electrolytic copper plating solution (acidic electrolytic copper plating solution)

Claims (5)

An anode disposed in an electrolytic treatment tank in which an acidic electrolytic copper plating solution containing a disulfide compound is stored,
An anode for electrolytic copper plating, wherein the anode is provided with a soluble copper anode and an insoluble anode electrically connected.   The anode for electrolytic copper plating according to claim 1, wherein an area ratio of a surface of the soluble copper anode and the insoluble anode immersed in the electrolytic copper plating solution is 10: 1 to 1:10.   The anode for electrolytic copper plating according to claim 2, wherein an area ratio of a surface of the soluble copper anode and the insoluble anode immersed in the electrolytic copper plating solution is 5: 1 to 1: 5. Electrolytic copper plating apparatus, comprising the electrolytic copper plating anode according to any one of claims 1 to 3. The electrolytic copper plating according to claim 4, wherein the member to be plated is a printed wiring board or a wafer having a through hole and / or a via hole, and an electrolytic treatment for filling copper in the through hole and / or the via hole is performed. apparatus.