CN116065030A - Recovery method of high-purity silver target - Google Patents

Abstract

The invention relates to a recovery method of a high-purity silver target, which comprises the following steps: (1) Heating the sputtered silver target assembly, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target; (2) Pickling the separated silver target obtained in the step (1), and then sequentially carrying out ultrasonic cleaning and drying to obtain a cleaned silver target; (3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) to obtain molten metal, and casting the molten metal to obtain a high-purity silver cast ingot. The recovery method provided by the invention is simple to operate, low in cost and low in impurity content, and meets the requirement of high-purity target sputtering performance.

Description

Recovery method of high-purity silver target

Technical Field

The invention relates to the field of targets, in particular to a recovery method of a high-purity silver target.

Background

The sputtering target material mainly comprises a target blank, a back plate and the like, wherein the target blank is a target material bombarded by high-speed ion beam and belongs to the core part of the sputtering target material. Because the high-purity metal has lower strength, and the sputtering target material needs to be installed in a special machine to finish the sputtering process, the interior of the machine is in a high-voltage and high-vacuum environment, so that the sputtering target blank of the ultra-high-purity metal needs to be jointed with the back plate through different welding processes, and the back plate not only plays a role in fixing the sputtering target material, but also has good electric conduction and heat conduction properties.

The sputtering target material is an extremely important key material necessary for manufacturing the semiconductor chip, and the principle of manufacturing devices by using the sputtering target material is that the physical vapor deposition technology is adopted, and high-pressure accelerated gaseous ions are used for bombarding the target material, so that atoms of the target material are sputtered out and deposited on a silicon wafer in a film form, and finally, a complex wiring structure in the semiconductor chip is formed. The sputtering target material has the advantages of uniformity, controllability and the like of metal coating and is widely applied to the field of semiconductors.

Silver is used in a large amount for producing thin layers of electrodes or reflective layers, such as solar cells, liquid crystal displays, etc., due to its excellent properties such as low resistance and high reflectivity. Because of the high value of silver target raw materials, soldering is typically used in which the silver target blank and copper-chromium alloy backing plate are soldered together by indium solder. In the magnetron sputtering process, the silver target blank does not completely participate in sputtering, and part of silver remains, so that the silver in the sputtered target material needs to be recovered because the silver raw material is high in value.

CN114959271a discloses a recovery method of sputtered silver residual target, the recovery method uses standard silver ingot and silver residual target as raw materials to mix and prepare materials, and the materials are put into an atmospheric smelting furnace to be heated and melted, and plant ash or borax is added into the obtained melt to be stirred, and scum is removed; and after removing the scum, heating, adding charcoal, pouring the obtained molten liquid into a mould, cooling and forming to obtain the raw material for manufacturing the sputtering silver target. However, the purity of the silver obtained by the method is relatively low, the content of gas impurities is relatively high, and the silver is easy to discard in batches of wafers, so that the silver is not suitable for the requirement of high-purity semiconductor sputtering target materials.

Therefore, the recovery method of the high-purity silver target with low impurity content is of great significance.

Disclosure of Invention

Compared with the prior art, the recovery method provided by the invention is simple to operate, low in cost and low in impurity content, and meets the requirements of high-purity target sputtering performance.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

the invention provides a recovery method of a high-purity silver target, which comprises the following steps:

(1) Heating the sputtered silver target assembly, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Pickling the separated silver target obtained in the step (1), and then sequentially carrying out ultrasonic cleaning and drying to obtain a cleaned silver target;

(3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) to obtain molten metal, and casting the molten metal to obtain a high-purity silver cast ingot.

According to the recovery method provided by the invention, through the combined operation of heating, acid leaching, ultrasonic cleaning and vacuum induction melting, firstly, indium solder is melted by heating, a back plate and a silver target are separated, then, the indium solder remained on the surface and other impurities are removed by acid leaching, then, acid liquor is removed by cleaning, and finally, the gas impurities are removed by vacuum induction melting. The vacuum induction smelting adopted by the invention can generate eddy current in the electromagnetic induction process, so that metal is melted, nitrogen, hydrogen, oxygen and carbon dissolved in a silver target can be removed to a lower level than that in normal pressure smelting, and simultaneously impurity elements with higher vapor pressure than silver at the smelting temperature can be removed through volatilization.

In the present invention, the term "high purity" means a purity of 4N or more.

In the invention, a vacuum chuck can be used to separate the silver target from the back plate.

Preferably, the heating temperature in step (1) is 180-200deg.C, and may be, for example, 180deg.C, 182 deg.C, 184 deg.C, 185 deg.C, 186 deg.C, 188 deg.C, 190 deg.C, 192 deg.C, 194 deg.C, 195 deg.C, 198 deg.C or 200 deg.C, but not limited to the values recited, and other values not recited in the range of values are equally applicable.

Preferably, the acid solution of the acid leaching in the step (2) comprises a mixed solution of nitric acid and hydrofluoric acid.

Preferably, the mass ratio of nitric acid, hydrofluoric acid and water in the acid solution is (1-2): 1-3, for example, 1:1:1, 1:2:1, 1:2:2, 1:2:3, 2:1:1 or 2:2:3, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.

In the invention, the acid liquor preferably comprises a mixed solution of nitric acid and hydrofluoric acid, and the mass ratio of the nitric acid to the hydrofluoric acid to the water is controlled to be (1-2) (1-3) within a specific range, so that the impurities remained on the surface can be removed, and the loss of silver is reduced.

Preferably, the acid leaching time is 20-30min, for example, 10min, 22min, 24min, 26min, 28min or 30min, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.

Preferably, the ultrasonic cleaning in the step (2) includes a primary cleaning and a secondary cleaning which are sequentially performed.

Preferably, the washing liquid of the one-time washing in the step (2) comprises water.

Preferably, the time of the one-time washing is 5-10min, for example, 5min, 6min, 7min, 8min, 9min or 10min, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.

Preferably, the wash liquid of the secondary washing in step (2) comprises isopropanol.

Preferably, the time of the secondary cleaning is 5-10min, for example, 5min, 6min, 7min, 8min, 9min or 10min, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.

Preferably, the drying mode in the step (2) comprises vacuum drying.

The vacuum drying temperature is preferably 60 to 80 ℃, and may be 60 ℃, 62 ℃, 64 ℃, 68 ℃, 70 ℃, 72 ℃, 74 ℃, 76 ℃, 78 ℃ or 80 ℃, for example, but is not limited to the recited values, and other non-recited values within the numerical range are equally applicable.

Preferably, the vacuum degree of the vacuum drying is less than 0.01Pa, for example, 0.009Pa, 0.008Pa, 0.007Pa, 0.006Pa or 0.005Pa, but the vacuum degree is not limited to the recited values, and other non-recited values in the numerical range are equally applicable.

Preferably, the drying time is 60-80min, for example, 60min, 62min, 64min, 66min, 68min, 70min, 72min, 74min, 76min, 78min or 80min, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable.

Preferably, the temperature of the vacuum induction melting in the step (3) is 1000-1200 ℃, for example, 1000 ℃, 1020 ℃, 1050 ℃, 1040 ℃, 1080 ℃, 1100 ℃, 1120 ℃, 1140 ℃, 1160 ℃, 1180 ℃ or 1200 ℃, but not limited to the values listed, and other values not listed in the numerical range are equally applicable.

In the invention, the temperature of vacuum induction melting is preferably controlled within a specific range, so that impurity elements contained in the alloy can be effectively removed, and the purity of silver ingots can be further improved.

Preferably, the vacuum degree of the vacuum induction melting is 0.01-0.03Pa, for example, 0.01Pa, 0.012Pa, 0.014Pa, 0.016Pa, 0.018Pa, 0.02Pa, 0.022Pa, 0.024Pa, 0.026Pa, 0.028Pa or 0.03Pa, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable.

In the invention, the vacuum degree of vacuum induction melting is preferably controlled within a specific range, so that impurity elements can be removed more thoroughly, and the purity of silver ingots is further improved.

Preferably, the vacuum induction melting is performed for 30-50min, for example, 30min, 32min, 34min, 36min, 40min, 42min, 44min, 46min, 48min or 50min, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable.

Preferably, the purity of the Gao Chunyin ingot in the step (3) is equal to or greater than 99.995%, for example, 99.995%, 99.996%, 99.997%, 99.998% or 99.999%, but is not limited to the recited values, and other non-recited values in the numerical range are equally applicable.

As a preferred technical scheme of the present invention, the recovery method comprises the following steps:

(1) Heating the sputtered silver target assembly at 180-200 ℃, separating the silver target from the backboard in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Performing acid leaching on the separated silver target obtained in the step (1) by adopting acid liquor with the mass ratio of nitric acid, hydrofluoric acid and water of (1-2) to (1-3) for 20-30min, performing primary cleaning by taking water as a cleaning solution for 5-10min, performing secondary cleaning by taking isopropanol as the cleaning solution for 5-10min, and performing vacuum drying at 60-80 ℃ for 60-80min under the vacuum degree of less than 0.01Pa to obtain the cleaned silver target;

(3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) at the temperature of 1000-1200 ℃ and the pressure of 0.01-0.03Pa for 30-50min to obtain molten metal, and casting the molten metal to obtain a high-purity silver cast ingot, wherein the purity of the Gao Chunyin cast ingot is more than or equal to 99.995%.

Compared with the prior art, the invention has the following beneficial effects:

(1) According to the recovery method provided by the invention, through the combined operation of heating, acid leaching, ultrasonic cleaning and vacuum induction melting, indium solder, gas elements and other impurities contained in the sputtered silver target are effectively removed, the purity of silver in the high-purity silver ingot can reach more than 4N, the content of gas impurities can reach less than 50ppm, the purity of silver in the high-purity silver ingot can reach more than 4N8 under the better condition, the content of gas impurities can reach less than 12ppm, and the requirement of sputtering performance is met.

(2) The recovery method provided by the invention has low cost and simple operation, and can be industrially applied.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Example 1

The embodiment provides a recovery method of a high-purity silver target, which comprises the following steps:

(1) Heating the sputtered silver target assembly at 190 ℃, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Pickling the separated silver target obtained in the step (1) with an acid solution with the mass ratio of nitric acid to hydrofluoric acid to water being 1.5:1.5:2 for 25min, cleaning for 7min by taking water as a cleaning solution, cleaning for 7min by taking isopropanol as a cleaning solution, and drying in vacuum at 70 ℃ for 70min under the vacuum degree of 0.008Pa to obtain the cleaned silver target;

(3) And (3) carrying out vacuum induction smelting on the cleaned silver target obtained in the step (2) at 1100 ℃ and 0.02Pa for 40min to obtain molten metal, and casting the molten metal to obtain the high-purity silver cast ingot.

Example 2

The embodiment provides a recovery method of a high-purity silver target, which comprises the following steps:

(1) Heating the sputtered silver target assembly at 180 ℃, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Pickling the separated silver target obtained in the step (1) for 30min by adopting acid liquor with the mass ratio of nitric acid, hydrofluoric acid and water being 1:2:1, cleaning for 5min by taking water as a washing liquor, cleaning for 10min by taking isopropanol as a washing liquor for the second time, and then performing vacuum drying for 80min at 60 ℃ under the vacuum degree of 0.009Pa to obtain the cleaned silver target;

(3) And (3) carrying out vacuum induction smelting on the cleaned silver target obtained in the step (2) at 1200 ℃ and 0.01Pa for 50min to obtain molten metal, and casting the molten metal to obtain the high-purity silver cast ingot.

Example 3

The embodiment provides a recovery method of a high-purity silver target, which comprises the following steps:

(1) Heating the sputtered silver target assembly at 200 ℃, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Pickling the separated silver target obtained in the step (1) for 20min by adopting acid liquor with the mass ratio of nitric acid, hydrofluoric acid and water being 2:2:3, cleaning for 10min by taking water as a washing liquor, cleaning for 5min by taking isopropanol as a washing liquor for the second time, and then performing vacuum drying for 60min at 80 ℃ under the vacuum degree of 0.007Pa to obtain the cleaned silver target;

(3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) at 1000 ℃ and 0.03Pa for 30min to obtain molten metal, and casting the molten metal to obtain the high-purity silver cast ingot.

Example 4

The present example provides a recovery method of a high purity silver target, which is different from that of example 1 only in that the total mass of nitric acid, hydrofluoric acid and water is controlled to be unchanged, and the mass ratio of nitric acid, hydrofluoric acid and water is adjusted to be 1.5:1.5:0.5.

Example 5

The present example provides a recovery method of a high purity silver target, which is different from that of example 1 only in that the total mass of nitric acid, hydrofluoric acid and water is controlled to be unchanged, and the mass ratio of nitric acid, hydrofluoric acid and water is adjusted to be 1.5:1.5:4.

Example 6

This example provides a method for recovering a high purity silver target, which differs from example 1 only in that the temperature of vacuum induction melting is 1000 ℃.

Example 7

This example provides a method for recovering a high purity silver target, which differs from example 1 only in that the vacuum induction melting pressure is 0.01Pa.

Example 8

This example provides a method for recovering a high purity silver target, which differs from example 1 only in that the vacuum induction melting pressure is 0.05Pa.

Comparative example 1

The comparative example provides a method for recovering a high purity silver target, which is different from example 1 only in that the acid leaching is not performed, and the separated silver target is sequentially subjected to ultrasonic cleaning and drying, and then subjected to step (3).

The purity of silver and the total content of gaseous impurities in the high purity silver ingots prepared in examples 1 to 8 and comparative example 1 were measured using a Glow Discharge Mass Spectrometer (GDMS), and the results are shown in table 1.

TABLE 1

From table 1, the following points can be seen:

(1) As can be seen from the data of examples 1-8, the recovery method provided by the invention can enable the purity of silver in the high-purity silver cast ingot to be more than 4N, the content of gas impurities to be less than 50ppm, and under the preferred condition, the purity of silver in the high-purity silver cast ingot to be more than 4N8 and the content of the gas impurities to be less than 12 ppm.

(2) As can be seen from a combination of the data of examples 1 and examples 4-5, the mass ratio of nitric acid, hydrofluoric acid and water in example 1 is 1.5:1.5:2, and the purity of silver and the content of gaseous impurities in example 1 are significantly lower than those in examples 4-5 compared with 1.5:1.5:0.5 and 1.5:1.5:4, respectively, so that the preferred control of the mass ratio of nitric acid, hydrofluoric acid and water in the present invention can further improve the purity of silver, contributing to the reduction of the content of impurities.

(3) As can be seen from a combination of the data of examples 1 and examples 6-8, the temperature of the vacuum induction melting in example 1 was 1100 c, the pressure of the vacuum induction melting in example 1 was 0.02Pa, compared to 1000 c in example 6, and the purity of silver and the content of gaseous impurities in example 1 were significantly lower than in examples 6-8, compared to 0.01Pa and 0.05Pa, respectively, in examples 7-8, whereby it can be seen that the invention preferably controls the temperature and pressure of the vacuum induction melting, and the purity of silver can be further improved.

(4) From the data of comparative example 1 and comparative example 1, it can be seen that the comparative example 1 is different from example 1 only in that no pickling is performed, the purity of silver in example 1 can reach 4N9, while only silver alloy can be obtained in comparative example 1, high purity silver cannot be obtained, the purity can reach only 2N, and the content of gas impurities is also high, and thus, according to the present invention, impurities in recovered silver targets can be effectively removed by the combined operation of heating, pickling, ultrasonic cleaning and vacuum induction melting, and high purity silver ingots can be obtained.

In conclusion, the recovery method provided by the invention is simple to operate, low in cost and low in impurity content, and meets the requirement of high-purity target sputtering performance.

The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.

Claims (10)

1. A method for recovering a high purity silver target, the method comprising the steps of:

(1) Heating the sputtered silver target assembly, separating the silver target from the back plate in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Pickling the separated silver target obtained in the step (1), and then sequentially carrying out ultrasonic cleaning and drying to obtain a cleaned silver target;

(3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) to obtain molten metal, and casting the molten metal to obtain a high-purity silver cast ingot.

2. The recovery method according to claim 1, wherein the heating temperature in step (1) is 180 to 200 ℃.

3. The recovery method according to claim 1 or 2, wherein the acid liquid of the acid leaching in the step (2) comprises a mixed solution of nitric acid and hydrofluoric acid;

preferably, the mass ratio of nitric acid, hydrofluoric acid and water in the acid liquor is (1-2) (1-3);

preferably, the acid leaching time is 20-30min.

4. A recovery method according to any one of claims 1 to 3, wherein the ultrasonic cleaning of step (2) comprises a primary cleaning and a secondary cleaning performed in sequence.

5. The recovery method according to claim 4, wherein the washing liquid of the one-time washing in the step (2) includes water;

preferably, the time of the one-time washing is 5-10min.

6. The recovery method of claim 4, wherein the secondary cleaning wash liquid of step (2) comprises isopropyl alcohol;

preferably, the time of the secondary washing is 5-10min.

7. The recovery method according to any one of claims 1 to 6, wherein the drying means of step (2) comprises vacuum drying;

preferably, the temperature of the vacuum drying is 60-80 ℃;

preferably, the vacuum degree of the vacuum drying is less than 0.01Pa;

preferably, the drying time is 60-80min.

8. The recovery method according to any one of claims 1 to 7, wherein the temperature of the vacuum induction melting in step (3) is 1000 to 1200 ℃;

preferably, the vacuum degree of the vacuum induction smelting is 0.01-0.03Pa;

preferably, the vacuum induction melting is carried out for 30-50min.

9. The recovery method according to any one of claims 1 to 8, wherein the purity of the Gao Chunyin ingot in step (3) is not less than 99.995%.

10. The recycling method according to any one of claims 1 to 9, characterized in that the recycling method comprises the steps of:

(1) Heating the sputtered silver target assembly at 180-200 ℃, separating the silver target from the backboard in the target assembly after the solder is melted, removing indium solder on the welding surface of the silver target, and cooling to obtain a separated silver target;

(2) Performing acid leaching on the separated silver target obtained in the step (1) by adopting acid liquor with the mass ratio of nitric acid, hydrofluoric acid and water of (1-2) to (1-3) for 20-30min, performing primary cleaning by taking water as a cleaning solution for 5-10min, performing secondary cleaning by taking isopropanol as the cleaning solution for 5-10min, and performing vacuum drying at 60-80 ℃ for 60-80min under the vacuum degree of less than 0.01Pa to obtain the cleaned silver target;

(3) And (3) carrying out vacuum induction melting on the cleaned silver target obtained in the step (2) at the temperature of 1000-1200 ℃ and the pressure of 0.01-0.03Pa for 30-50min to obtain molten metal, and casting the molten metal to obtain a high-purity silver cast ingot, wherein the purity of the Gao Chunyin cast ingot is more than or equal to 99.995%.