KR20200032101A - Electrolytic copper plating anode and electrolytic copper plating device using the same - Google Patents

Abstract

An object of the present invention is to provide an electrolytic copper plating anode and an electrolytic copper plating apparatus using the same, which can improve plating characteristics such as plating promoting property and via filling without complicating the device structure. To achieve this object, as an anode disposed in an electrolytic treatment tank in which an electrolytic copper plating solution is stored, the electrolytic copper plating solution is an acidic electrolytic copper plating solution containing a disulfide compound, and the anode electrically connects a soluble copper anode and an insoluble anode. An anode for electrolytic copper plating, which is provided in one state, is employed.

Description

Electrolytic copper plating anode and electrolytic copper plating device using the same

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

Conventionally, when forming a conductor on a printed wiring board or the like, electrolytic copper plating treatment is performed. When performing electrolytic copper plating treatment, there are a method of using a soluble copper anode made of a copper material as an anode, and a method of using an insoluble anode made of platinum, titanium, iridium oxide, or the like. Further, an additive such as a brightener or a leveler is added to the electrolytic copper plating solution in order to improve plating properties such as plating promoting properties and via filling properties.

Here, it is currently mainstream to use a soluble copper anode when performing electrolytic copper plating treatment. For this reason, the soluble copper anode can simplify equipment compared to the insoluble anode, and thus does not require maintenance costs, and the anode itself is relatively inexpensive, so that it is possible to realize cost reduction.

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

As for the problem described above, for example, as described in Patent Document 1, attempts have been made to increase the dissolved oxygen concentration in the plating liquid by blowing air into the plating liquid. Specifically, in Patent Document 1, "A plating apparatus for an acid copper having a plating tank provided with an overflow tank, a plating liquid discharging portion provided under the plating tank, a copper anode, and a bar for an object to be plated. An acid copper plating apparatus characterized by providing an air stirring or oxygen stirring means therein.

Japanese Patent Publication No. 2004-143478

However, in the plating apparatus specified in Patent Document 1, it is necessary to separately provide an overflow tank, which has a problem that the structure of the plating apparatus is complicated, and the cost of equipment is high.

From the above, it is an object of the present invention to provide an anode for electrolytic copper plating and an electrolytic copper plating device using the same, which can improve plating properties such as plating promoting property and via filling without complicating the device structure. .

Accordingly, the present inventors have achieved the above object by employing the following method as a result of earnest research.

An anode for electrolytic copper plating according to the present invention is 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, and the anode comprises a soluble copper anode and an insoluble anode. It is characterized in that it is provided in an electrically connected state.

The electrolytic copper plating apparatus according to the present invention is characterized by having the above-mentioned anode for electrolytic copper plating.

According to the positive electrode for electrolytic copper plating and the electrolytic copper plating apparatus according to the present invention, it is possible to improve the plating characteristics such as plating promoting property and via filling without complicating the device structure.

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.
2 is a cross-sectional photograph showing the via filling situation in Example 1 and Comparative Example 1.
3 is a cross-sectional photograph showing the via filling situation 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 while using the drawings. 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 is provided with an anode 1 for electrolytic copper plating according to the present invention. The anode 1 for electrolytic copper plating is an anode disposed in the electrolytic treatment tank 20 in which the electrolytic copper plating solution 21 is stored. In addition, the electrolytic copper plating solution 21 is an acidic electrolytic copper plating solution containing a disulfide compound (for example, SPS), and the anode 1 electrically connects the soluble copper anode 2 and the insoluble anode 3 It is characterized by being provided in one state. Hereinafter, such a configuration will be described.

The electrolytic copper plating apparatus 10 according to the present invention is a state in which the plated member W is immersed in the electrolytic treatment tank 20 storing the electrolytic copper plating solution 21, and the plated member (cathode) W And an anode (anode) 1, which is an apparatus for electrolytically treating the surface to be treated of the plated member W. Here, the plated member 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 an epoxy resin. In addition, those printed wiring boards or wafers can be used having through holes and / or via holes. These through-holes and via-holes are generally micro-diameter holes of about 10 μm to 1000 μm, through which electrical connections between signal layers are made. According to the electrolytic copper plating apparatus 10 according to the present invention, it is possible to perform electrolytic treatment in which copper is filled in these through holes or via holes. On the other hand, the electrolytic copper plating apparatus 10 according to the present invention is to spread the air bubbles in the electrolytic copper plating solution 21 or the nozzle 6 connected to the circulation pipe 5 in order to improve the uniform electrodeposition properties, etc. It is also possible to adopt a configuration in which the electrolytic copper plating solution 21 is stirred, such as blowing high-pressure air from it.

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 made 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 and pentahydrate, 30 g / L to 250 g / L of sulfuric acid, and 30 mg / L to 75 mg / L of chloride ions. have. In addition, the temperature of the acidic electrolytic copper plating solution 21 can be usually used in a range of 15 ° C to 60 ° C, preferably 20 ° C to 35 ° C. As the concentration of copper sulfate pentahydrate or the concentration of sulfuric acid increases, crystals of copper sulphate pentahydrate may precipitate on the copper anode, so care must be taken in managing both concentrations. 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 is lowered, making it difficult to energize the acidic electrolytic copper plating solution 21. On the other hand, when the sulfuric acid concentration exceeds 400 g / L, copper sulfate is easily precipitated in the acidic electrolytic copper plating solution, which adversely affects the plating properties.

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 disposed in the electrolytic treatment tank 20 are electrically connected to each other, whereby the anode 1 Acts as When electrolytic treatment is performed, when the electrolytic copper plating solution containing SPS 21 is used, the SPS is changed to MPS, and this MPS is generated, resulting in a drop in throwing power in a through-hole bath, poor plating appearance, and a non-fill bath. A problem arises in that the peeling rate is lowered or the appearance of plating is poor. Here, even when the electrolytic copper plating solution 21 was stopped by electrolysis, it was confirmed that SPS is reduced in the vicinity of the anode 1 to generate MPS. The production of this MPS can also be a cause for generating anode sludge composed of MPS-Cu ⁺ complex. This anode sludge causes deterioration in plating characteristics such as filling properties and uniform electrodeposition properties of vias. However, the electrolytic copper plating anode 1 according to the present invention is provided in the electrolytic treatment tank 20 in a state in which the soluble copper anode 2 and the insoluble anode 3 are electrically connected, so that the insoluble anode 3 Oxygen can be supplied to the electrolytic copper plating solution 21. Oxygen generated from the insoluble anode 3 can oxidize MPS to SPS to suppress an increase in the concentration of MPS in the electrolytic copper plating solution 21, thereby eliminating adverse effects of MPS. Therefore, according to the electrolytic copper plating apparatus 10 according to the present invention, even if SPS is included as a brightener in the electrolytic copper plating solution 21, 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 in which the surface area is as large as possible, more copper ions are generated during electrolysis to further increase plating efficiency.

Moreover, it is preferable that the soluble copper anode 2 of this invention consists of a phosphorus containing copper material. When the soluble copper anode 2 is composed of a phosphorus-containing copper member, a film of a compound called “black film” called CuP ₂ is formed on the surface of the phosphorus-containing copper member during electrolysis, and generation of monovalent copper ions occurs. By suppressing, the generation of anode sludge is effectively suppressed, and it becomes possible to prevent the deterioration of plating properties. In further suppressing the generation of anode sludge of the phosphorus-containing copper member, the phosphorus content is preferably about 0.02% to 0.06%. The use of the phosphorus-containing copper member for the soluble copper anode 2 is advantageous in that it is possible to smoothly dissolve copper 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 is of a material that does not elute metal in the electrolytic copper plating solution 21. Examples include, but are not limited to, anodes made of iridium oxide, titanium with platinum, platinum, graphite, ferrite, titanium dioxide coated with lead dioxide and platinum group element oxides, stainless steel, and lead alloys. In addition, the insoluble anode 3 can also be configured by coating a coating on a substrate. In this case, the entire surface of the substrate may be coated, but only a part of the substrate may be coated within a range that 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.

In addition, the shape of the insoluble anode 3 of the present invention is not limited. Since the insoluble anode 3 is a shape and dimension that efficiently generates oxygen without interfering with the dissolution of the soluble copper anode 2 during electrolysis, the MPS present in the electrolytic copper plating solution 21 is rapidly oxidized to SPS. By returning the MPS to suppress the accumulation in the electrolytic copper plating solution 21, it is possible to prevent the deterioration of plating properties.

The positive electrode 1 for electrolytic copper plating according to the present invention has an area ratio of 10% of the surface immersed in the electrolytic copper plating solution 21 of the soluble copper positive electrode 2 and the insoluble positive electrode 3 from the viewpoint of suppressing the production of MPS: It is preferably 1 to 1:10. If the area ratio of the surface immersed in the electrolytic copper plating solution 21 of the soluble copper anode 2 and the insoluble anode 3 is less than 10: 1, from the surface of the insoluble anode (for example, iridium oxide member) 3 Since the generation of oxygen is very small, the increase in the MPS concentration in the electrolytic copper plating solution 21 cannot be sufficiently suppressed, and the desired plating properties cannot be obtained. Moreover, since the generation of oxygen from the surface of the insoluble anode (for example, iridium oxide member) 3 significantly increases when the area ratio exceeds 1:10, the additive contained in the electrolytic copper plating solution 21 is oxidatively decomposed. The consumption of additives increases. Moreover, in this case, the supply of copper from the soluble copper anode 2 becomes insufficient, and it is necessary to separately supply copper sources in order to maintain the copper concentration in the electrolytic copper plating solution 21 at a predetermined concentration. Here, the area ratio of the surface immersed in the electrolytic copper plating solution 21 of the soluble copper anode 2 and the insoluble anode 3 is 5: 1 to 1: 5, and it is more preferable to obtain the above-described effect.

In addition, in the electrolytic copper plating apparatus 10 according to the present invention, it is preferable that the applicable cathode current density is within a range using a phosphorus-containing copper member that is usually used for electrolytic copper plating treatment of a printed wiring board. Specifically, the cathode current density is about 0.1 A / dm ² to 10 A / dm ² , preferably 0.5 A / dm ² to 6 A / dm ² , and more preferably 1 A / dm ² to 5 A / dm ² . The anode current density can usually be used at 0.1 A / dm ² to 3 A / dm ² , but more preferably 1 A / dm ² to 3 A / dm ² . Since the copper concentration in the electrolytic copper plating solution 21 tends to rise when the anode current density is too low and tends to decrease when the anode current density is too high, it is necessary to adjust the anode area according to the cathode current density used. .

Here, when the anode 1 for electrolytic copper plating according to the present invention is used, the effect obtained at the time of electrolysis and at the time of electrolysis stop will be described in more detail. Usually, during electrolysis and electrolysis stop, dissolution occurs in the soluble copper anode 2 as shown in the following formula (1). In addition, during electrolysis, the reaction shown in the following formula (2) of the general formula (1) occurs at the negative electrode to precipitate copper. Then, when the electrolytic copper plating solution 21 contains a disulfide compound, SPS is reduced by electrons released upon dissolution of the soluble copper anode 2, as shown in Formula (3) of Formula 1 below, to generate MPS. do. The resulting MPS is partially oxidized and converted into SPS as in Formula (4) of Formula 1, but Cu (I) MPS combined with monovalent copper ions has MPS as in Formula (5) of Formula 1 below. do.

In Formulas (1) and (3) to (5) of Chemical Formula 1, a process in which MPS is generated that causes a decrease in plating characteristics is shown, but the anode 1 for electrolytic copper plating according to the present invention is an insoluble anode ( By providing 3) in an electrically connected state with the soluble copper anode 2, an increase in the MPS concentration in the electrolytic copper plating solution 21 can be suppressed. That is, during electrolysis, in the insoluble anode 3, electrolysis of water in the electrolytic copper plating solution 21 is performed as in Formula (6) of Formula 1, and MPS is oxidized by oxygen generated at this time to be converted into SPS. MPS can be reduced.

The electrolytic copper plating apparatus 10 according to the present invention has the above-described configuration, whereby the 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 left for a long time as it is, the plating appearance defect is easily It does not occur, and maintenance is unnecessary.

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

Example 1

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

In Example 1, first, a plated member (printed substrate) having a plate thickness of 1.0 mm, a via diameter of 100 µm, and a depth of 80 µm was subjected to a desmear treatment by a Melplate MLB-6001 process (manufactured by Meltex Corporation). Subsequently, electroless copper plating was performed by the Melplate CU-390 process (made by Meltex Corporation). Then, this printed circuit board was subjected to acidic degreasing, water washing and sulfuric acid treatment with 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 is a Lucent Copper SVF-A (manufactured by Meltex Corporation, disulfide system) in a plating solution containing 200 g / L of copper sulfate and pentahydrate, 100 g / L of concentrated sulfuric acid, and 50 mg / L of chloride ions. A 3 L viafill bath adjusted by adding 15 mL / L of mL / L, Lucent Copper SVF-B (manufactured by Meltex Corporation), and 15 mL / L of Lucent Copper SVF-L (manufactured by Meltex Corporation) was used. In addition, 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 placed in a state immersed in the accommodated via fill bath. The positive electrode for electrolytic copper plating was placed in the electrolytic treatment tank with the soluble copper positive electrode (50 mm × 120 mm phosphorus-containing copper plate) and the insoluble positive electrode (50 mm × 120 mm iridium oxide coated plate) electrically connected. In addition, in Example 1, electrolytic treatment was performed while circulating the plating liquid using a pump in the electrolytic treatment tank.

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

Example 2

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

In Example 2, the same plated member as in Example 1 was used. In addition, in Example 2, the same electrolytic pretreatment conditions and electrolytic treatment conditions as in Example 1 were employed 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 Example 2 is omitted.

In Example 2, with respect to the positive electrode for electrolytic copper plating, the area ratio of the soluble copper positive electrode and the insoluble positive electrode in the electrolytic copper plating solution was "10: 1", "5: 1", "1: 1", and "1: 1". (Titanium with platinum is used as an insoluble anode). Those made of "1: 5" and "1:10" were prepared. Then, under the conditions of the energized amount of the electrolytic copper plating solution of 0AH / L, 0.5AH / L, 1AH / L, 4AH / L, 10AH / L, 50 mm × 130 mm electroless copper plating was used as a cathode as in Example 1. The printed substrate was immersed in an electrolytic copper plating solution, and electrolytic treatment was performed at a current density of 2 A / dm ² for 45 minutes. The plating filling condition in the via under each of these conditions was observed by the cross section method. Fig. 3 shows a cross-sectional photograph of the plating filling condition in the via in Example 2.

Comparative example

[Comparative Example 1]

In Comparative Example 1, a test was conducted to confirm the effect of using only a soluble copper anode as an 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 is omitted.

In addition, in Comparative Example 1, the same test as in Example 1 was performed. Fig. 2 shows a cross-sectional photograph of the plating filling condition in the via in Comparative Example 1, as can be compared with Example 1.

[Comparative Example 2]

In Comparative Example 2, as in Comparative Example 1, a test was conducted to confirm the effect of using only a soluble copper anode as an anode for electrolytic copper plating.

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

In addition, in Comparative Example 2, the same test as in Example 2 was performed. Fig. 3 shows a cross-sectional photograph of the plating filling condition in the via in Comparative Example 2, as can be compared with Example 2.

From the results shown in Fig. 2, when an electrolytic copper plating solution is used in which a soluble copper anode and an insoluble anode are electrically connected as an anode disposed in the electrolytic treatment tank, the amount of electricity applied is different from the case where only the soluble copper anode is used. It was found that even when the size was increased to 100AH / L, there was almost no difference in the via filling condition, and it was stable and excellent filling properties were obtained.

From the results shown in FIG. 3, when an electrode having a soluble copper anode and an insoluble anode electrically connected as an anode disposed in the electrolytic treatment tank in which the electrolytic copper plating solution is stored is used, the electrolysis is compared with the case where only the soluble copper anode is used. It was found that even in the case where MPS was included in 1 mg / L in the copper plating solution, the recovery of filling properties was achieved in a relatively short time. In this case, when the area ratio in the electrolytic copper plating solution of the soluble copper anode and the insoluble anode in Example 2 was "10: 1" and the other area ratio, the larger the proportion of the soluble anode occupied It tended to be difficult to recover the chargeability. On the other hand, as the proportion occupied by the soluble anode decreases, the supply of copper from the soluble copper anode in the electrolytic copper plating solution becomes insufficient, and it can be assumed that additional supply of a copper source is required to maintain the copper concentration in the electrolytic copper plating solution. From the above viewpoint, it can be understood that it is more preferable that the area ratio of the soluble copper anode and the insoluble anode in the electrolytic copper plating solution is 5: 1 to 1: 5.

From the above, it is understood that by using the positive electrode for electrolytic copper plating according to the present invention and the electrolytic copper plating apparatus using the same, it is possible to improve the plating characteristics such as plating acceleration and via filling without complicating the device structure. Could. From this, it can be understood that when the electrolytic treatment is performed using the positive electrode for electrolytic copper plating according to the present invention, the adverse effect accompanying the increase in the concentration of MPS in the electrolytic copper plating solution can be effectively excluded.

According to the anode for electrolytic copper plating according to the present invention and an electrolytic copper plating apparatus using the same, when using an acidic electrolytic copper plating solution containing a disulfide compound, the increase in the concentration of MPS can be effectively suppressed, and desired plating properties can be stably obtained. . In addition, by using the positive electrode for electrolytic copper plating according to the present invention, the structure of the electrolytic copper plating device can be simplified and the cost of equipment can be reduced. Therefore, the positive electrode for electrolytic copper plating according to the present invention and the electrolytic copper plating apparatus using the same can be particularly preferably used when electrolytic copper plating is applied to a printed wiring board or wafer having through-holes and / or via-holes.

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)

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

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