A method for preparing ultra-high purity copper by electrolysis

Abstract

The present invention relates to an electrolytic preparation method for ultra-high purity copper, which solves the problem that the ultra-high purity copper obtained by electrolysis has low purity. The electrolytic preparation method comprises: electrolysis is performed using a copper electrolyte; the copper electrolyte contains citric acid and / or citrate at a concentration of 0.5-5 mg / L. The electrolytic preparation method provided by the present invention realizes the preparation of ultra-high purity copper by introducing a specific citric acid and / or citrate composition into the electrolyte.

Description

Technical Field

[0001] The invention relates to the field of copper electrolytic refining, and in particular to a method for electrolytic preparation of ultra-high purity copper. Background Art

[0002] At present, with the rapid development of VLSI, the size of semiconductor chips has been reduced to the nanometer level. The RC delay and electromigration of metal interconnects have become the main factors affecting chip performance. Traditional aluminum and aluminum alloy interconnects can no longer meet the requirements of VLSI process. Compared with aluminum, copper has higher electromigration resistance and higher conductivity, especially ultra-high purity copper (purity ≥ 6N), which is of great significance for reducing the resistance of chip interconnects and improving their computing speed.

[0003] In order to obtain the above-mentioned ultra-high purity copper, the current method generally uses wet electrolysis to purify high-purity electrolytic copper, and then uses fire smelting to form ingots. Among them, wet purification is particularly important. The purity of electrolytic copper directly determines whether the copper ingot meets the purity requirements of the semiconductor industry.

[0004] For example, CN115505769A discloses a method for preparing an ultra-high purity copper alloy ingot, which comprises: first, cutting and cleaning the ultra-high purity copper alloy head in sequence to obtain a pre-treated head; then, vacuum melting the pre-treated head to obtain an alloy liquid and prepare an analytical ingot, and calculate the loss rate of the alloy element in the analytical ingot; finally, vacuum melting the pre-treated head again, and adding alloy element supplementary material in the vacuum melting process according to the loss rate to obtain an ultra-high purity copper alloy ingot. This solution can control the content of alloy elements in the copper alloy ingot, avoid exceeding the standard of impurity elements, and reduce the loss rate of alloy elements.

[0005] CN107974695A discloses a method for producing ultra-high purity copper by one-time electrolysis, and the specific steps are as follows: a. Prepare a CuSO4 solution by dissolving crude copper sulfate and industrial sulfuric acid; b. Add industrial hydrochloric acid to the copper sulfate solution to adjust the chloride ion concentration, and pre-treat the adjusted solution by filter pressing; c. First, use 4N grade copper as anode and titanium seed plate as cathode for electrolysis, then process the produced copper skin into cathode and put it into the tank, continue to use 4N grade copper as anode and continue electrolysis, and finally obtain 5N grade ultra-high purity copper; d. Scalding; e. Packing and storage. In this scheme, the glass fiber reinforced plastic electrolytic tank is used as the electrolysis carrier, 4N grade high purity copper is used as the raw material, and the electrolyte is circulated from top to bottom to prepare 5N grade ultra-high purity copper by electrolysis. The invention has the characteristics of short process flow, easy acquisition of raw and auxiliary materials, and low production cost. At the same time, the process method of electrolytic refining of sulfuric acid system is adopted to ensure the stability of product quality and the reliability of process operation.

[0006] However, the usual method for preparing electrolytic copper is to use a sulfuric acid electrolyte and add a certain amount of gelatin, thiourea, avildite and other reagents to the electrolyte. The resulting electrolytic copper still cannot meet the requirement of purity ≥ 6N. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for electrolytic preparation of ultra-high purity copper to solve the problem of low purity of ultra-high purity copper obtained by electrolysis.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising: electrolysis using a copper electrolyte;

[0010] The copper electrolyte contains citric acid and / or citrate with a concentration of 0.5-5 mg / L.

[0011] The electrolytic preparation method provided by the present invention realizes the preparation of ultra-high purity copper by introducing specific citric acid and / or citrate composition into the electrolyte.

[0012] In the present invention, the electrolyte is finely filtered before electrolysis, specifically by using membrane filtration with increasing precision, and the membrane porosity ranges from 0.1-5μm, for example, it can be 0.1μm, 1μm, 5μm or 0.5μm, 2μm, 4μm or 0.1μm, 3μm, 5μm, etc.

[0013] In the present invention, the purity of the ultra-high purity copper obtained by electrolysis is ≥6N.

[0014] In the present invention, the divalent copper ions in the copper electrolyte are obtained by dissolving copper nitrate or copper sulfate, or by dissolving copper in nitric acid, and the pH value of the electrolyte is 0.5-5.

[0015] In the present invention, the citrate selected in the copper electrolyte may be sodium citrate and / or potassium citrate.

[0016] In the present invention, the copper electrolyte contains citric acid and / or citrate at a concentration of 0.5-5 mg / L, for example, 0.5 mg / L, 0.6 mg / L, 0.8 mg / L, 1 mg / L, 1.2 mg / L, 1.4 mg / L, 1.6 mg / L, 1.8 mg / L, 2 mg / L, 2.2 mg / L, 2.4 mg / L, 2.6 mg / L, 2.8 mg / L, 3 mg / L, 3.2 mg / L, 3.4 mg / L, 3.6 mg / L, 3.8 mg / L, 4 mg / L, 4.2 mg / L, 4.4 mg / L, 4.6 mg / L, 4.8 mg / L or 5 mg / L, etc., but is not limited to the listed values, and other values ​​not listed within the range are equally applicable.

[0017] As a preferred technical solution of the present invention, the anode used in the electrolysis is a high-purity copper material, and the purity can be 4N copper, 5N copper, etc.

[0018] In the present invention, the anode used can be protected by a 0.5-5 μm filter bag to avoid contamination of the electrode by anode mud.

[0019] As a preferred technical solution of the present invention, the anode used in the electrolysis is acid washed before electrolysis.

[0020] In the present invention, after the pickling is completed, water or alcohol is used to clean the acid solution on the surface to avoid affecting the electrolysis process.

[0021] Preferably, the mass concentration of the acid solution used in the pickling is 10-30%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] As a preferred technical solution of the present invention, the cathode used in the electrolysis comprises stainless steel.

[0023] In the present invention, the stainless steel material used for the cathode can be 316L, 304, S32101 and other commonly used steel materials in the art.

[0024] As a preferred technical solution of the present invention, the cathode used in the electrolysis is washed before electrolysis.

[0025] Preferably, the detergent used in the washing comprises water and / or ethanol.

[0026] As a preferred technical solution of the present invention, the concentration of divalent copper ions in the copper electrolyte is 50-100 g / L, for example, it can be 50 g / L, 52 g / L, 54 g / L, 56 g / L, 58 g / L, 60 g / L, 62 g / L, 64 g / L, 66 g / L, 68 g / L, 70 g / L, 72 g / L, 74 g / L, 76 g / L, 78 g / L, 80 g / L, 82 g / L, 84 g / L, 86 g / L, 88 g / L, 90 g / L, 92 g / L, 94 g / L, 96 g / L, 98 g / L or 100 g / L, but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0027] As a preferred technical solution of the present invention, the concentration of gelatin in the copper electrolyte is 1-10 mg / L, for example, it can be 1 mg / L, 1.2 mg / L, 1.4 mg / L, 1.6 mg / L, 1.8 mg / L, 2 mg / L, 2.2 mg / L, 2.4 mg / L, 2.6 mg / L, 2.8 mg / L, 3 mg / L, 3.2 mg / L, 3.4 mg / L, 3.6 mg / L, 3.8 mg / L, 4 mg / L, 4.2 mg / L, 4.4 mg / L, 4.6 mg / L, 4.8 mg / L, 5 mg / L, 5.2 mg / L, 5.4 10mg / L, but not limited to the listed values, other values ​​not listed in this range are also applicable.

[0028] As a preferred technical solution of the present invention, the current density of the electrolysis is 50-200A / m 2 , for example, it can be 50A / m 2 , 55A / m 2 、60A / m 2 、65A / m 2 , 70A / m 2 , 75A / m 2 、80A / m 2 、85A / m 2 、90A / m 2 、95A / m 2 , 100A / m 2 、105A / m 2 , 110A / m 2, 115A / m 2 , 120A / m 2 , 125A / m 2 , 130A / m 2 、135A / m 2 , 140A / m 2 、145A / m 2 , 150A / m 2 、155A / m 2 、160A / m 2 、165A / m 2 、170A / m 2 、175A / m 2 、180A / m 2 、185A / m 2 、190A / m 2 、195A / m 2 or 200A / m 2 The above values ​​are not limited to the above values, and other values ​​not listed in the above values ​​are also applicable.

[0029] As a preferred technical solution of the present invention, the temperature of the electrolysis is 30-60°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are equally applicable.

[0030] As a preferred technical solution of the present invention, the electrolytic preparation method comprises: using high-purity copper as an anode and a stainless steel plate as a cathode, using a copper electrolyte with a current density of 50-200A / cm 2 Conduct electrolysis at 30-60°C;

[0031] The copper electrolyte comprises: 50-100 g / L of divalent copper ions, 1-10 mg / L of gelatin, and 0.5-5 mg / L of citric acid and / or citrate;

[0032] The anode used in the electrolysis is pickled before electrolysis; the mass concentration of the acid solution used in the pickling is 10-30%; the cathode used in the electrolysis is washed before electrolysis; the washing agent used in the washing includes water and / or ethanol.

[0033] In the present invention, the ethanol used in the washing process can be replaced by other alcohols, such as methanol, propanol, etc.

[0034] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0035] The ultra-high purity copper electrolytic preparation method provided by the present invention realizes the preparation of ultra-high purity copper by adopting an electrolyte with a specific composition and utilizing the synergistic effect of gelatin and citric acid and / or citrate. DETAILED DESCRIPTION

[0036] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0037] Example 1

[0038] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0039] High purity copper (4N) was used as anode and stainless steel (316L) plate was used as cathode. The copper electrolyte was used at a current density of 100A / cm 2 The electrolysis was carried out at 45°C;

[0040] The copper electrolyte is: 60 g / L of divalent copper ions (prepared with copper nitrate), 4 mg / L of gelatin, 2 mg / L of citric acid, and a pH value of 0.5;

[0041] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 12%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is water.

[0042] The purity of the obtained electrolytic copper is shown in Table 1.

[0043] Example 2

[0044] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0045] High purity copper (5N) was used as anode and stainless steel (304) plate was used as cathode. The copper electrolyte was used with a current density of 150A / cm 2 The electrolysis was carried out at 50°C;

[0046] The copper electrolyte is: divalent copper ion (copper nitrate) 70g / L, gelatin 6mg / L, sodium citrate 3mg / L, pH value 1;

[0047] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 16%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is water.

[0048] The purity of the obtained electrolytic copper is shown in Table 1.

[0049] Example 3

[0050] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0051] High purity copper (4N) was used as anode and stainless steel (S32101) plate was used as cathode. Copper electrolyte was used with a current density of 50A / cm 2 The electrolysis was carried out at 30°C;

[0052] The copper electrolyte includes: 100 g / L of divalent copper ions (copper sulfate), 1 mg / L of gelatin, 5 mg / L of citric acid, and a pH value of 2;

[0053] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 10%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is ethanol.

[0054] The purity of the obtained electrolytic copper is shown in Table 1.

[0055] Example 4

[0056] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0057] High purity copper (4N) was used as anode and stainless steel (316L) plate was used as cathode. Copper electrolyte was used with a current density of 200A / cm 2 The electrolysis was carried out at 60°C;

[0058] The copper electrolyte includes: 50 g / L of divalent copper ions (prepared with copper sulfate), 10 mg / L of gelatin, 0.5 mg / L of citric acid, and a pH value of 1.2;

[0059] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 30%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is methanol.

[0060] The purity of the obtained electrolytic copper is shown in Table 1.

[0061] Example 5

[0062] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0063] High-purity copper (4N) was used as the anode and stainless steel (316L) plate was used as the cathode. The copper electrolyte was used at a current density of 75A / cm 2 The electrolysis was carried out at 55°C;

[0064] The copper electrolyte includes: 80 g / L of divalent copper ions (prepared using copper nitrate), 8 mg / L of gelatin, 4 mg / L of potassium citrate, and a pH value of 3;

[0065] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 20%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is water.

[0066] The purity of the obtained electrolytic copper is shown in Table 1.

[0067] Example 6

[0068] This embodiment provides an electrolytic preparation method for ultra-high purity copper, the electrolytic preparation method comprising:

[0069] High purity copper (4N) was used as anode and stainless steel (S32101) plate was used as cathode. Copper electrolyte was used with a current density of 125A / cm 2 The electrolysis was carried out at 40°C;

[0070] The copper electrolyte includes: 90 g / L of divalent copper ions (prepared by dissolving high-purity copper in nitric acid), 2 mg / L of gelatin, 1 mg / L of citric acid, and a pH value of 2;

[0071] The anode used in the electrolysis is pickled before electrolysis and then washed with water until the pH value is 7; the mass concentration of the acid solution used in the pickling is 25%; the cathode used in the electrolysis is washed before electrolysis; and the detergent used in the washing is ethanol.

[0072] The purity of the obtained electrolytic copper is shown in Table 1.

[0073] Comparative Example 1

[0074] The only difference from Example 1 is that the citric acid is replaced by an equal amount of hydrochloric acid. The purity of the obtained electrolytic copper is shown in Table 1.

[0075] Comparative Example 2

[0076] The only difference from Example 1 is that the citric acid is replaced by oxalic acid. The purity of the obtained electrolytic copper is shown in Table 1.

[0077] Comparative Example 3

[0078] The only difference from Example 1 is that the citric acid is replaced by tartaric acid. The purity of the obtained electrolytic copper is shown in Table 1.

[0079] Comparative Example 4

[0080] The only difference from Example 1 is that the citric acid is replaced by sodium tartrate. The purity of the obtained electrolytic copper is shown in Table 1.

[0081] Comparative Example 5

[0082] The only difference from Example 1 is that gelatin is replaced by an equal amount of thiourea. The purity of the obtained electrolytic copper is shown in Table 1.

[0083] Comparative Example 6

[0084] The only difference from Example 1 is that the concentration of citric acid is 0.1 mg / L. The purity of the obtained electrolytic copper is shown in Table 1.

[0085] Comparative Example 7

[0086] The only difference from Example 1 is that the concentration of citric acid is 10 mg / L. The purity of the obtained electrolytic copper is shown in Table 1.

[0087] Comparative Example 8

[0088] The only difference from Example 1 is that the concentration of gelatin is 0.5 mg / L. The purity of the obtained electrolytic copper is shown in Table 1.

[0089] Comparative Example 9

[0090] The only difference from Example 1 is that the concentration of gelatin is 20 mg / L. The purity of the obtained electrolytic copper is shown in Table 1.

[0091] Comparative Example 10

[0092] The only difference from Example 1 is that the citric acid is replaced by an equal amount of thiourea. The purity of the obtained electrolytic copper is shown in Table 1.

[0093] Comparative Example 11

[0094] The only difference from Example 1 is that citric acid is not added. The purity of the obtained electrolytic copper is shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] It can be seen from the results of the above examples and comparative examples that the electrolytic preparation method provided by the present invention achieves the preparation of ultra-high purity copper by introducing a specific citric acid and / or citrate composition into the electrolyte.

[0099] It is stated that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0100] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0101] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0102] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing ultra-high purity copper by electrolysis, characterized in that: The electrolytic preparation method comprises: electrolysis using a copper electrolyte; The copper electrolyte contains citric acid and / or citrate at a concentration of 0.5-5 mg / L; The anode used in the electrolysis is high-purity copper; The cathode used in the electrolysis comprises stainless steel; The concentration of divalent copper ions in the copper electrolyte is 50-100 g / L; The concentration of gelatin in the copper electrolyte is 1-10 mg / L.

2. The electrolytic preparation method according to claim 1, characterized in that: The anode used in the electrolysis is acid-washed before electrolysis.

3. The electrolytic preparation method according to claim 2, characterized in that: The mass concentration of the acid solution used in the pickling is 10-30%.

4. The electrolytic preparation method according to claim 1, characterized in that: The cathode used in the electrolysis is washed before electrolysis.

5. The electrolytic preparation method according to claim 4, characterized in that: The detergent used in the washing includes water and / or ethanol.

6. The electrolytic preparation method according to claim 1, characterized in that: The current density of the electrolysis is 50-200A / m 2 .

7. The electrolytic preparation method according to claim 1, characterized in that: The temperature of the electrolysis is 30-60°C.

8. The electrolytic preparation method according to any one of claims 1 to 7, characterized in that: The electrolytic preparation method comprises: High-purity copper is used as anode, stainless steel plate is used as cathode, copper electrolyte is used with current density of 50-200A / cm 2 Conduct electrolysis at 30-60°C; The copper electrolyte comprises: 50-100 g / L of divalent copper ions, 1-10 mg / L of gelatin, and 0.5-5 mg / L of citric acid and / or citrate; The anode used in the electrolysis is pickled before electrolysis; the mass concentration of the acid solution used in the pickling is 10-30%; the cathode used in the electrolysis is washed before electrolysis; the washing agent used in the washing includes water and / or ethanol.

Images