JP2014043638A - Method for manufacturing an anode material for electroplating and anode for electroplating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an anode material for electroplating capable of improving, by virtue of a more uniform homogenization of the phosphorus distribution within the material, the yield when used for the electrolytic copper plating.SOLUTION: The provided method for manufacturing an anode material for electroplating comprises (a) a step of manufacturing a phosphorus-containing copper metal having, in terms of mass%, a phosphorus content higher than 0 and lower than 0.1 by forming the same via cooling solidification from liquid to solid phases; (b) a quenching step of subjecting, subsequently to the (a) step, the phosphorus-containing copper metal to a homogenizing thermal treatment and of then rapidly cooling the same; and (c) a step of obtaining, after the (b) step, an anode material for electroplating by performing an additional thermomechanical treatment and then quenching once again.

Description

  The present invention relates to a method for producing an anode material, and more particularly to a method for producing an anode material used for electroplating and an anode for electroplating obtained thereby.

  Conventionally, metal copper has been used as an anode in the electrolytic copper plating process. When copper is used as the anode, particles of metallic copper or copper oxide are generated due to the disproportionation reaction of monovalent copper during melting, and the deposition rate of copper is high. However, if the copper content in the plating bath increases too much, the anode mud increases, and extra particles such as copper powder are generated, which adhere to the object to be plated on the cathode side and become contaminated. In addition, the deposited copper surface also has unevenness due to the too high deposition rate on the surface of the deposited copper.

  In order to solve such drawbacks, a method has been devised in which phosphorous copper containing a small amount of phosphorus in metallic copper is used for the anode. According to such an anode, a conductive black film mainly composed of copper, phosphorus, and chlorine is formed on the surface of the phosphorus-containing copper anode during the electroplating process. This black film can suppress the disproportionation reaction of monovalent copper, and thus the generation of copper particles is reduced.

  For example, Japanese Patent Laying-Open No. 2002-275698 (Patent Document 1) discloses a method for producing a phosphorous copper anode for electroplating. According to this, the ingot obtained by adding phosphorus to electrolytic copper is heat-treated and recrystallized to obtain phosphorous-containing copper having a crystal grain size suitable for use as an anode for copper plating. Can do.

  However, the above phosphorus-containing copper anode manufacturing method has the following drawbacks. In other words, the phosphorus element is likely to precipitate in the crystal grain boundaries of copper and the gaps between dendrites (dendrites) in the manufacturing process, so that the distribution of the phosphorus element becomes non-uniform. When a phosphorus-containing copper anode having an uneven phosphorus distribution is used, a black film grows thick and tends to peel off on the anode surface where the phosphorus content is relatively high, while the phosphorus content is low. On a relatively small portion of the anode surface, the formed black film is also relatively thin, so that metallic copper and copper oxide are easily generated. The black film that has fallen off, and the produced metal copper or copper oxide become slime in the plating bath and adhere to the surface of the material to be plated on the cathode side. As a result, plating defects such as protrusions occur, and such plating defects are particularly problematic when the material to be plated is, for example, a semiconductor wafer.

  In view of this, there are also documents that show how to improve the quality of the anode for electroplating. For example, the method disclosed in Japanese Patent Application Laid-Open No. 2011-162875 (Patent Document 2) is as follows. That is, after processing strain is imparted to the phosphorous copper, a recrystallization heat treatment is performed to increase the so-called special grain boundary formation ratio among the crystal grain boundaries on the phosphorous copper anode surface. In addition, since selective dissolution (non-uniform dissolution) hardly occurs at special grain boundaries, peeling of crystal grains not yet dissolved on the surface of the phosphorous copper anode is suppressed, and the thickness of the black film is made uniform. Can be formed. Thereby, peeling of a black film can be prevented and by extension, generation | occurrence | production of the plating defect resulting from an anode slime can be avoided.

JP 2002-275698 A JP 2011-162875 A

  As described above, in the phosphorus-containing copper anode for electroplating, it is shown how the black film can be uniformly formed on the surface of the anode by uniformizing the distribution of phosphorus element in the anode. This is a priority issue for improving the plating quality by suppressing the occurrence.

  The present invention has been made as a result of earnest research on the above problems, and the anode material for electroplating that can improve the yield when used for electrolytic copper plating due to the more uniform phosphorus distribution in the material. One object is to provide a manufacturing method.

  Another object of the present invention is to provide an anode for electroplating that can improve the yield when used in electrocopper plating.

In order to achieve the one object, the present invention provides:
(A) a step of producing a phosphorous copper ingot having a phosphorus content of greater than 0 and less than 0.1 by mass% by cooling and solidifying from a liquid phase to a solid phase;
(B) Subsequent to the step (a), the phosphorous copper ingot is subjected to a homogenization heat treatment and then quenched by quenching;
(C) A process for producing an anode material for electroplating comprising the step of obtaining an anode material for electroplating by subjecting to a further heat treatment after the step (b) and then quenching again. provide.

  The formation in the step (a) is preferably performed using any one of vacuum casting, atmospheric casting, and thermal spraying. The quenching in the step (b) to the step (c) has an average refrigerant temperature. It is preferably performed by water cooling or oil cooling that is 60 ° C. or less.

  Further, the homogenization heat treatment in the step (b) is preferably performed for 5 to 8 hours in a temperature range of 540 ° C. to 1085 ° C., and further in a temperature range higher than 900 ° C. and not exceeding 1050 ° C.

  In addition, it is preferable that the heat treatment in the step (c) is performed by performing an annealing heat treatment after performing any of hot forging, hot rolling, cold rolling, hot pressing, or a combination thereof.

In addition, in order to achieve the other object, the present invention covers a main body made of phosphorus-containing copper having a phosphorus content of greater than 0 and less than 0.1 by mass%, and covering the surface of the main body. There is also provided an anode for electroplating, characterized in that a covering ratio per unit area of 1 cm ² by the black film on the surface of the main body is 98% or more.

  The main body is preferably an anode material for electroplating manufactured by the method for manufacturing an anode material for electroplating.

  According to the above method, the segregation of phosphorus element is prevented in the obtained anode material for electroplating through the homogenization heat treatment and the subsequent quenching, and the heat treatment and the quenching are performed again after the quenching. Thus, the phosphorus distribution can be made more uniform. Moreover, if the anode material for electroplating manufactured in this way is used for electroplating, a black film with a uniform structure is formed, so that peeling of the black film from the anode is prevented, and occurrence of defective plating is avoided. can do.

It is a figure which shows the process in 1st Embodiment of the manufacturing method of the anode material for electroplating which concerns on this invention. It is a figure which shows the process in 2nd Embodiment of the manufacturing method of the anode material for electroplating which concerns on this invention. It is a figure which shows the process in 3rd Embodiment of the manufacturing method of the anode material for electroplating which concerns on this invention. It is a fragmentary sectional view showing the anode for electroplating concerning the present invention. It is a schematic diagram which shows the state by which the anode for electroplating which concerns on this invention is used for electroplating. It is a fragmentary sectional enlarged view which shows the surface of the anode for electroplating which concerns on the specific example of this invention. It is an optical microscope figure which shows the film-forming state of the black film in the anode for electroplating which concerns on the specific example of this invention. In the anode for electroplating which concerns on the comparative example 1, it is a fragmentary sectional enlarged view which shows that the black film is exhibiting dendritic shape. In the anode for electroplating which concerns on the comparative example 1, it is an optical microscope figure which shows that a black film is exhibiting dendritic shape. In the anode for electroplating which concerns on the comparative example 2, it is a fragmentary sectional enlarged view which shows that the dotted | punctate hollow part is scattered in the black film. In the anode for electroplating which concerns on the comparative example 2, it is an optical microscope figure which shows that the dotted | punctate hollow part is scattered in the black film.

  FIG. 1 shows a process in the first embodiment of the method for manufacturing an anode material for electroplating according to the present invention, and this process includes Step S11 and Step S12.

  In step S11, the copper material is formed so as to be cooled and solidified from the liquid phase to the solid phase, thereby producing a phosphorus-containing copper ingot having a phosphorus content of greater than 0 and less than 0.1 by mass%.

  In step S12, subsequent to step S11, the obtained phosphorous copper ingot is subjected to a homogenizing heat treatment, and then quenched by quenching, whereby an electric power composed of phosphorous copper having a uniform phosphorus distribution. An anode material for plating is obtained.

  The first to third embodiments will be specifically described below.

<First Embodiment>
First, step S11 is performed. Specifically, first, phosphorus is added to metallic copper within a range where the phosphorus content does not exceed 0.1% by mass, and then metallic copper is placed in a vacuum furnace and vacuum casting is performed by a vacuum melting method. That is, copper and phosphorus raw materials were put in a vacuum furnace having a degree of vacuum of 10 ⁻² to 10 ⁻⁴ mmHg and dissolved by heating and then solidified by cooling. The advantage of using vacuum melting in this way is that a phosphorus-containing copper ingot having good casting quality can be obtained by preventing oxidation of copper and phosphorus raw materials.

  In addition, as a formation method of the phosphorous copper ingot in step S11, not only vacuum casting as described above, but also atmospheric casting or thermal spraying by an atmospheric melting method may be used. In short, copper and phosphorus are mixed. What is necessary is just to form it so that it may be cooled and solidified after being dissolved. When spraying is used, it is preferable that the spraying distance is within 100 mm, the spraying pressure is 5 to 60 bar, and the hole diameter is 3 to 7 mm.

  Next, following step S11, that is, step S12 is performed directly without intervening other processing. Specifically, the obtained phosphorus-containing copper ingot is subjected to a homogenization heat treatment in a temperature range of 540 ° C. to 1085 ° C. so as to further uniform the phosphorus distribution. The homogenization heat treatment here refers to a high-temperature heat treatment applied to the phosphorous copper ingot for a long time. In this process, the phosphorus element gives a sufficient amount of heat and time for further diffusion in the copper. After the treatment, the phosphorus element in the phosphorous copper ingot is more uniformly distributed. Subsequently, the phosphorous copper ingot in which the phosphorus is more uniformly distributed is produced by immersing the phosphorous copper ingot subjected to the homogenization heat treatment in a refrigerant and quenching, that is, quenching.

  The quenching may be performed by water cooling using water as a coolant, but may be performed by, for example, oil cooling using oil as a coolant. In short, the average temperature of the coolant used may be 60 ° C. or less. . Such a refrigerant is much lower in temperature than the phosphorous copper ingot that has just been subjected to the homogenization heat treatment, and is in direct contact with the phosphorous copper ingot. The temperature of the bullion can be lowered rapidly. In addition, such a cooling method has a much higher temperature drop rate than a method of cooling so that the temperature in the furnace gradually decreases from high temperature to room temperature and reaches a thermal equilibrium state while being left in a vacuum furnace after heating.

  As described above, the purpose of performing the homogenization heat treatment is to make the distribution state uniform by diffusing phosphorus elements that are preferentially deposited on the crystal grain boundaries and dendritic portions of copper due to the segregation phenomenon. Therefore, the homogenization heat treatment in step S12 is desirably performed in a temperature range lower than the melting point of the phosphorous copper ingot and higher than half of the melting point, that is, a temperature range of 540 ° C to 1085 ° C.

  Further, when the temperature range of the homogenization heat treatment exceeds 900 ° C., the phosphorus distribution state becomes more uniform. On the other hand, when the temperature exceeds 1050 ° C., the phosphorus element tends to volatilize. Therefore, the homogenization heat treatment is more preferably performed in a temperature range greater than 900 ° C. and not exceeding 1050 ° C. The heating time is at least 4 hours, preferably 5 to 8 hours.

  In addition, the above quenching is performed promptly after the homogenization heat treatment, so that the phosphorus element can be prevented from segregating in the crystal grain boundaries and dendritic crystal parts during the cooling process. Thereby, an anode material for electroplating made of phosphorous-containing copper in which phosphorus is uniformly distributed after quenching can be obtained.

  Furthermore, it should be noted here that if another processing process is interposed between the step S11 and the step S12, diffusion of phosphorus element is hindered, and as in Comparative Example 1 and Comparative Example 2 described below, Uniform phosphorous distribution is also prevented.

<Second Embodiment>
FIG. 2 shows a process in the second embodiment of the method for manufacturing an anode material for electroplating according to the present invention. This process is in addition to steps S11 and S12 included in the first embodiment. Step S13 is further included.

  The anode material for electroplating obtained through Steps S11 and S12 has improved uniformity of phosphorus distribution as compared with the conventional anode material, but further refines the crystal grains in the anode material to distribute phosphorus. In the present embodiment, step S13 is performed after step S12.

  In step S13, the heat treatment and quenching are performed on the obtained phosphorous copper. The thermomechanical treatment here is a heat treatment that is annealed after hot forging and cold rolling, and the phosphorus distribution state is changed to a first state by quenching the copper-containing copper that has undergone the thermomechanical treatment again by water cooling. It can be made more uniform than that obtained in the embodiment.

  The heat treatment in step S13 is not limited to the high temperature treatment, and external force (for example, mechanical stress) is applied to the phosphorous copper so that the dendrites are crushed and the crystal grains are further refined. By doing so, the processing method which can make a phosphorus distribution state more uniform is included. That is, the heat treatment in step S13 is performed by performing annealing heat treatment after performing any one of hot forging, hot rolling, cold rolling, hot pressing, or a combination thereof in addition to the above-described method. The treatment is not limited to these, and any treatment may be used as long as the dendritic crystals in the phosphorous copper are crushed and the crystal grains are further refined. The quenching in step S13 is not limited to water cooling but may be oil cooling as in step S12, and the phosphorous copper is quenched so as to be in direct contact with a refrigerant having an average temperature of 60 ° C. or less. That's fine.

<Third Embodiment>
FIG. 3 shows a process in the third embodiment of the method for manufacturing an electroplating anode material according to the present invention, which is similar to the second embodiment, but in this process, step S13 is repeatedly performed. Yes. In the following description, an example in which step S13 is performed twice is shown, but the present invention is not limited to this, and step S13 may be performed three or more times.

  As illustrated, this embodiment is performed in the order of step S11 → step S12 → step S13 → step S13.

  Here, the second heat treatment in step S13 is a cold rolling and an annealing heat treatment performed thereafter, and further quenching is performed after the heat treatment. The quenching method is the same as in the first and second embodiments.

  According to the third embodiment, since step S13 is performed once more than in the second embodiment, the distribution of the phosphorus element is further reduced by further refinement of the crystal grains than those obtained in the second embodiment. An anode material for electroplating made of phosphorous copper having a more uniform state can be produced.

  Since the anode material for electroplating obtained by each of the first to third embodiments described above has a much more uniform distribution of phosphorus than the conventional one, if this is used for electroplating, the anode material The black film formed on the surface becomes more uniform and the thickness thereof becomes more uniform.

  FIG. 4 shows a state in which the anode 2 for electroplating obtained by the method for producing an anode material for electroplating according to the present invention has a black film by being used for electroplating. In the figure, 21 is an anode body, and 22 is a black film.

  The anode body 21 has a surface 211 that is immersed in an electrolyte when the anode is used for electroplating. The anode body 21 is obtained in any one of the first to third embodiments of the method for manufacturing an anode material for electroplating according to the present invention described above. The black film 22 is naturally formed on the surface 211 of the anode body 21 during the electroplating process, and is mainly made of copper, phosphorus, chlorine, or the like.

FIG. 5 is a schematic diagram showing a state in which the anode 2 is used for electroplating. As the electrolytic solution 3, it is preferable to use those having concentrations of copper sulfate of 10 to 70 g / L, sulfuric acid of 10 to 300 g / L, and chlorine of 20 to 100 mg / L, respectively. The electrolytic solution 3 in the electrolytic cell is stirred, and the anode 2 and the cathode 4 made of graphite are disposed in the electrolytic cell. Subsequently, a plating process is performed by applying a DC power source having a current density of 1 A / dm ² (ASD) for 15 minutes at room temperature.

  At this time, since the distribution of the phosphorus element in the anode body 21 is uniform, the black film 22 is uniformly formed on the surface 211 of the anode body 21 immersed in the electrolytic solution 3. Thus, the black film 22 uniformly covers the anode main body 21, thereby preventing the generation of particles composed of metallic copper or copper oxide due to the disproportionation reaction of monovalent copper during the plating process. As a result, the cathode side plating object can be prevented from being contaminated by the generated particles.

  Hereinafter, specific examples of the anode for electroplating according to the present invention and comparative examples will be given and the results of comparative analysis will be shown.

[Concrete example]
(1) A phosphorus-containing copper ingot having a phosphorus content of 0.065% by mass was produced by vacuum casting.
(2) The phosphorous copper ingot was subjected to a homogenization heat treatment at 950 ° C. for 5 hours. Immediately after that, the phosphorous copper ingot was put into water having an average temperature of 60 ° C. or less and quenched to obtain phosphorous copper as an anode material for electroplating.
(3) The obtained anode material for electroplating was hot forged. Then, it annealed at 600 degreeC for 1 hour. Immediately after annealing, the anode material was quenched in water having an average temperature of 60 ° C. or less.
(4) The anode material was cold-rolled. Then, it annealed at 600 degreeC for 1 hour. Immediately after annealing, the anode material was placed in water having an average temperature of 60 ° C. or less and quenched.
(5) The surface of the anode material was polished with No. 300 sandpaper.
(6) A plating solution having a concentration of copper sulfate of 30 g / L, sulfuric acid of 180 g / L, and chlorine of 50 mg / L was placed in a plating tank and stirred. In the plating solution, the anode material was arranged on the anode side, the graphite was arranged on the cathode side, and a plating process was performed by applying a DC power source with a current density of 1 A / dm ² (ASD) for 15 minutes at room temperature. At this time, a black film was formed on the surface of the anode.

[Comparative Example 1]
(1) A phosphorus-containing copper ingot having a phosphorus content of 0.065% by mass was produced by vacuum casting.
(2) The obtained phosphorous copper ingot was preheated at 800 ° C. for 1 hour, hot-pressed by hydraulic pressure, and then cold-rolled.
(3) Then, after performing annealing at 800 degreeC for 1 hour, the anode material for electroplating of the comparative example 1 was obtained by cooling with air.
(4) A plating solution having a concentration of copper sulfate of 30 g / L, sulfuric acid of 180 g / L, and chlorine of 50 mg / L was placed in a plating tank and stirred. In the plating solution, the anode material of Comparative Example 1 is placed on the anode side, graphite is placed on the cathode side, and a DC power supply with a current density of 1 A / dm ² (ASD) is applied for 15 minutes at room temperature to perform the plating treatment. went. At this time, a black film was formed on the surface of the anode.

[Comparative Example 2]
(1) A phosphorus-containing copper ingot having a phosphorus content of less than 0.1% by mass was produced by vacuum casting.
(2) The obtained phosphorous copper ingot was preheated at 800 ° C. for 1 hour and then hot-pressed by hydraulic pressure.
(3) Subsequently, after annealing at 800 ° C. for 1 hour, after air cooling, cold rolling was further performed.
(4) Then, after performing annealing at 700 degreeC for 1 hour, the anode material for electroplating of the comparative example 2 was obtained by cooling with air.
(5) A plating solution having a concentration of copper sulfate of 30 g / L, sulfuric acid of 180 g / L, and chlorine of 50 mg / L was placed in a plating tank and stirred. In the plating solution, the anode material of Comparative Example 2 was placed on the anode side, graphite was placed on the cathode side, and a DC power supply with a current density of 1 A / dm ² (ASD) was applied at room temperature for 15 minutes to perform the plating treatment. went. At this time, a black film was formed on the surface of the anode.

<Analysis results>
Below, the result of having analyzed the black film formed in the anode material surface for electroplating each obtained by said specific example and each comparative example from the viewpoint of film-forming quality is shown.

  The reason for not directly analyzing the phosphorus distribution state of the anode material itself that influences the film formation quality only by analyzing the film formation quality of the black film is that the phosphorus content is 0.1% by mass or less. This is because the energy dispersive X-ray analysis (EDS) and the electron beam microanalyzer (EPMA) are out of the detectable range and cannot be analyzed. Therefore, the phosphorus distribution state of the anode material is estimated from the film formation quality of the black film formed on the anode material surface.

  That is, the uniform film formation of the black film indicates that the phosphorus distribution in the anode material is also uniform. On the other hand, when the black film is unevenly formed, for example, when the black film has dendritic unevenness or a hollow portion in which metallic copper appears, the phosphorus distribution in the anode material is also uneven. ing.

FIG. 6 is an enlarged partial cross-sectional view of the surface of the anode material according to a specific example of the present invention, and FIG. 7 is an optical microscope view observing the film formation state of the black film on the surface of the anode material. As can be seen from these figures, when the anode material for electroplating produced according to this specific example is used, a black film is uniformly formed on the anode material surface during the electroplating process. Covered. Moreover, the inside of a black film is also substantial and there is no hollow part. As a result of measurement from the above optical micrograph, the coverage per unit area by the black film on the surface of the anode material produced according to the present specific example with a unit area of 1 cm ² was 98% or more.

8 to 11 are diagrams according to the above-described comparative examples, and FIGS. 8 and 10 are partial cross-sectional enlarged views of the anode material surfaces according to comparative example 1 and comparative example 2, respectively. FIG. 4 is an optical microscopic view observing a film formation state of a black film on the surface of each anode material. As can be seen from these figures, when using an anode material that has been processed between casting and subsequent annealing, or when using an anode material that has not been subjected to thermomechanical treatment and quenching after annealing, Since the black film is unevenly formed on the surface of the anode material in the process, the surface of the anode material cannot be uniformly covered with the black film. Moreover, since there is a dendritic hollow portion inside the black film, it can be seen that the black film was formed so as to be biased toward the dendritic crystal portion in the anode material. As a result of measurement from the above optical micrograph, the coverage per unit area by the black film on the surface of the anode material produced according to each comparative example was 1 cm ² as a unit area, far below 98%.

  In summary, in the method for producing an anode material for electroplating according to the present invention, phosphorous copper formed so as to be cooled and solidified from a liquid phase to a solid phase is subjected to heat treatment, specifically homogenization heat treatment and subsequent quenching. By passing through, it is possible to prevent the phosphorus element from segregating to the copper grain boundaries and dendritic crystal parts, and to further crush the dendrites by one or more processing heat treatment and quenching after quenching Can do. As a result, an anode material for electroplating made of phosphorous-containing copper whose phosphorus distribution is made more uniform than before can be produced. In addition, if the anode material produced in this way is used for electroplating, a black film having a uniform structure is formed on the surface of the anode material during the plating process, so that the black film peels off during the electroplating process. Can be prevented. Thereby, generation | occurrence | production of a plating defect can be avoided, ie, the objective of this invention is achieved exactly.

  As mentioned above, although preferable embodiment and the specific example of this invention were described, this invention is not limited to this, It cannot be overemphasized that it can change variously in the range which does not deviate from the summary.

  The method for producing an anode material for electroplating according to the present invention is useful for producing a phosphorous copper anode for use in electrolytic copper plating.

2 Anode 21 Body 211 Surface 22 Black film 3 Electrolyte 4 Cathode

Claims (4)

(A) a step of producing a phosphorous copper ingot having a phosphorus content of greater than 0 and less than 0.1 by mass% by cooling and solidifying from a liquid phase to a solid phase;
(B) Subsequent to the step (a), the phosphorous copper ingot is subjected to a homogenization heat treatment and then quenched by quenching;
(C) After the step (b), a step of obtaining an anode material for electroplating by further performing a heat treatment and then quenching again;
A method for producing an anode material for electroplating, comprising:   The method for producing an anode material for electroplating according to claim 1, wherein the homogenization heat treatment in the step (b) is performed in a temperature range of 540 ° C to 1085 ° C.   The method for producing an anode material for electroplating according to claim 1 or 2, wherein the quenching is performed using a refrigerant having an average temperature of 60 ° C or lower. A main body composed of phosphorus-containing copper having a phosphorus content of greater than 0 and less than 0.1 by mass%; and a black film covering the surface of the main body, and the black film on the surface of the main body An anode for electroplating, wherein the coverage per unit area of 1 cm ² is 98% or more.