Method for producing ultrapure indium having a purity of 7n or more

Abstract

The application belongs to the technical field of high-purity material preparation, and discloses a preparation method of ultrahigh-purity indium with a purity of more than 7N. The preparation method comprises the following steps: taking high-purity indium with a purity of more than 6N as a raw material, taking ultrahigh-purity indium with a purity of more than 7N as a seed crystal, and controlling the steps and parameters of a pulling process, so that ultrahigh-purity indium with a purity of more than 7N is prepared, and the content of harmful and difficult-to-remove impurities such as Sn, Sb and Pb in the ultrahigh-purity indium is less than 10 ppbw.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-purity material preparation, and particularly relates to a preparation method of ultrahigh-purity indium. BACKGROUND

[0002] Metal indium is mainly used for manufacturing low-melting alloys, bearing alloys, semiconductors, electric light sources and the like. High-purity indium (purity is above 5N) is mainly used for preparing compound semiconductor materials, thin-film solar cell CIGS and ITO target material. Ultrahigh-purity indium is an important raw material for preparing indium phosphide semiconductor. Indium phosphide crystal has important applications in infrared detection, optical magnetic devices, magnetoresistors and solar energy converters and the like.

[0003] The electronic industry and the semiconductor industry have very high requirements for crystals, and the introduction of trace impurities in raw materials will seriously affect the inherent performance of crystal materials. Generally, the purity of the source material is required to be above 6N or even 7N.

[0004] At present, the preparation methods of high-purity indium and ultrahigh-purity indium mainly include electrolysis, vacuum distillation, zone melting, metal organic compound and low halide compound. These methods mainly remove metal impurities in indium through chemical or physical purification methods, but it is difficult to produce ultrahigh-purity indium with a purity of above 7N, and it is difficult to meet the application needs of high-end semiconductor crystal materials and molecular beam epitaxy ultrahigh-purity metal source materials. SUMMARY

[0005] In view of the problems in the prior art, the purpose of the present application is to provide a preparation method of ultrahigh-purity indium with a purity of above 7N.

[0006] To achieve the above-mentioned purpose, the present application provides the following specific technical solutions.

[0007] A preparation method of ultrahigh-purity indium with a purity of above 7N, comprising the following steps:

[0008] Step S1, high-purity metal indium with a purity of above 6N is loaded into a melting crucible of a pulling single crystal furnace, ultrahigh-purity indium with a purity of above 7N is used as a seed crystal, and the seed crystal is clamped on a seed crystal rod; and an oxygen-free normal pressure environment is ensured in the pulling single crystal furnace;

[0009] Step S2, the pulling single crystal furnace is started, and heated to 200-250 DEG C for a period of time T1;

[0010] Step S3, the pulling single crystal furnace adopts electromagnetic induction heating to fully melt the high-purity metal indium in the melting crucible, and then heated to 800-1000 DEG C for a period of time T2, and hydrogen is introduced into the pulling single crystal furnace during the heat preservation process;

[0011] Step S4, the temperature of the high-purity indium in the smelting crucible is reduced to 160-180℃ and kept constant; during the keeping constant process, the smelting crucible rotates clockwise; after 0.5-3h of keeping constant, the lower end of the seed crystal is inserted into the high-purity indium melt, then the seed crystal is pulled up and rotates counterclockwise, after a period of time T3, the pulling up and rotation of the seed crystal are stopped and paused for a period of time T4, then the pulling up and rotation of the seed crystal are restarted and last for a period of time T5;

[0012] Step S5, after the pulling up, the tail end of the obtained ultrahigh-purity indium rod is cut off, and the remaining part is ultrahigh-purity indium with a purity of 7N or above.

[0013] As a preference, the smelting crucible is selected from one of high-purity graphite crucibles with an ash content of not higher than 20ppm, high-purity boron nitride crucibles with a purity of 6N or above, and titanium metal crucibles with a purity of 4N or above.

[0014] As a preference, the implementation mode for ensuring that the pulling up furnace is in an oxygen-free normal pressure environment is: the door of the pulling up single crystal furnace is closed, the pressure in the furnace is extracted to be less than 10 -2 Pa, and then the inert gas is filled to normal pressure, which is repeated at least three times.

[0015] As a preference, T1 is 30-60min; T2 is 2-4h; T3 is 1-2h; T4 is 1-3h; and T5 is 24-46h.

[0016] As a preference, the flow rate of the hydrogen gas in step S3 is 2-4L / min.

[0017] As a preference, the speed of the clockwise rotation of the smelting crucible is 2-5r / min.

[0018] As a preference, during the time T3, the pulling up speed of the seed crystal is 3-5mm / h, and the rotation speed is 0.5-1.5r / min.

[0019] As a preference, during the time T5, the pulling up speed of the seed crystal is 8-15mm / h, and the rotation speed is 1-2r / min.

[0020] Compared with the prior art, the present application has the following obvious beneficial effects:

[0021] By adopting the technical scheme provided by the present application, ultrahigh-purity indium with a purity of 7N or above can be prepared, and the content of harmful and difficult-to-remove impurities such as Sn, Sb, Pb, etc. in the ultrahigh-purity indium is less than 10ppbw. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the following terms are intended to have the meanings presented (unless the context clearly dictates otherwise):

[0024] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0025] The present invention provides a preparation method of ultra-high purity indium with a purity of 7N or more, comprising the following steps:

[0026] Step S1, high-purity indium with a purity of 6N or more is loaded into a melting crucible of a pulling single crystal furnace, ultra-high purity indium with a purity of 7N or more is used as a seed crystal, and the seed crystal is clamped on a seed crystal clamp; ensure that the pulling single crystal furnace is in an oxygen-free normal pressure environment;

[0027] Step S2, turn on the pulling single crystal furnace and heat to 200-250℃ for a period of time T1;

[0028] Step S3, the pulling single crystal furnace adopts electromagnetic induction heating to fully melt the high-purity indium in the melting crucible, then heats to 800-1000℃ for a period of time T2, and hydrogen is introduced into the pulling single crystal furnace during the heat preservation process;

[0029] Step S4, reduce the temperature of the high-purity indium in the melting crucible to 160-180℃ and keep it warm; during the heat preservation process, the melting crucible rotates clockwise; after 0.5-3h of heat preservation, the lower end of the seed crystal is inserted into the high-purity indium melt, then the seed crystal is pulled and rotated counterclockwise, after a period of time T3, the pulling and rotation of the seed crystal are stopped and stagnate for a period of time T4, then the pulling and rotation of the seed crystal are restarted, and the duration is T5;

[0030] Step S5, after the pulling is completed, the tail end of the obtained ultra-high purity indium rod is cut off, and the remaining part is ultra-high purity indium with a purity of 7N or more.

[0031] In step S3 of the present invention, the pulling single crystal furnace adopts electromagnetic induction heating to fully melt the high-purity indium in the melting crucible, and after heating to a certain temperature, heat preservation is carried out, and hydrogen is introduced during the heat preservation process. Induction heating can generate large eddy currents, which can realize induction heating of the crucible and further heat the indium in the crucible. The eddy current can make the indium melt produce micro-movement, so that the trace amount of oxide inclusions in the liquid indium can fully react with hydrogen at high temperature, avoiding the aggregation of impurity elements in the local area during the long pulling process and reducing the generation of inclusions during the pulling process. The electromagnetic induction heating method can further select the intermediate frequency electromagnetic induction heating method commonly used in the art.

[0032] In some embodiments, the smelting crucible is selected from one of high-purity graphite crucible with ash content of no more than 20 ppm, high-purity boron nitride crucible with purity of 6N or above, and titanium metal crucible with purity of 4N or above.

[0033] In some embodiments, the implementation of ensuring an oxygen-free and normal-pressure environment in the pulling furnace is as follows: closing the furnace door of the pulling single crystal furnace, extracting the pressure in the furnace to be less than 10 -2 Pa, and then filling inert gas to normal pressure, repeating at least three times.

[0034] In some embodiments, T1 is 30-60 min, T2 is 2-4 h, T3 is 1-2 h, T4 is 1-3 h, and T5 is 24-46 h.

[0035] In some embodiments, the flow rate of the hydrogen gas in step S3 is 2-4 L / min.

[0036] In some embodiments, the speed of the smelting crucible rotating in the clockwise direction is 2-5 r / min.

[0037] In some embodiments, during the time T3, the pulling speed of the seed crystal is 3-5 mm / h, and the rotating speed is 0.5-1.5 r / min.

[0038] In some embodiments, during the time T5, the pulling speed of the seed crystal is 8-15 mm / h, and the rotating speed is 1-2 r / min.

[0039] The following is further illustrated by specific examples.

[0040] Example 1

[0041] (1) 8 kg of 6N indium was weighed as raw material, and 7N5 high-purity indium was selected to prepare a square seed crystal with a size of 8 mm x 8 mm x 100 mm.

[0042] (2) The raw material was placed in the high-purity graphite crucible of the pulling single crystal furnace, and the seed crystal was clamped on the seed crystal rod. The furnace door of the pulling single crystal furnace was closed, the vacuum system of the device was used to extract the vacuum in the furnace to 5 x 10 -3 Pa, the vacuum system was closed, and 5N high-purity nitrogen was introduced into the furnace to normal pressure, and the process was repeated three times to maintain a normal-pressure high-purity nitrogen atmosphere in the furnace.

[0043] (3) Turn on the intermediate frequency induction heating device of the pulling single crystal furnace, heat the crucible to 200°C and keep for 60 min, so that the indium raw material in the crucible is completely melted, after the end of the heat preservation, the temperature in the furnace continues to rise to 800°C, while hydrogen is introduced, the hydrogen flow is 4 L / min, after 4 h of heat preservation, the hydrogen is closed and the temperature in the crucible slowly decreases to 180°C with the furnace and continues to keep for 26 h, the crucible keeps slow rotation in the clockwise direction during the heat preservation process, the rotation speed is 5 r / min.

[0044] (4) After the crucible is kept at 180°C for 0.5 h, the seed crystal rod with the clamped seed crystal is lowered to the lower surface of the seed crystal below the 15 mm of the molten liquid indium and kept for 0.5 h, so that the lower end surface of the seed crystal is slightly melted and fully wetted with the raw material indium liquid, then the seed crystal rod is pulled, the pulling rate is 5 mm / h, the seed crystal rotates counterclockwise at a speed of 1.5 r / m, after 2 h, the pulling and rotation of the seed crystal rod are stopped and paused for 3 h, at this time, the diameter of the lower surface of the seed crystal expands to 15 mm, the pulling and rotation of the seed crystal rod are restarted, the pulling rate is 15 mm / h, the rotation speed is 2 r / min, and the continuous operation time is 20 h, the high-purity indium rod with a weight of 7.78 kg is pulled out, after cutting off the tail end of 3 cm of the indium rod, 6.85 kg of ultra-high-purity indium metal ingot with a purity of 7N is obtained.

[0045] Example 2

[0046] (1) 6 kg of 6N5 indium is weighed as raw material, and 7N5 high-purity indium is selected to prepare a cylindrical seed crystal, and the size of the seed crystal is Φ6 mm x 80 mm.

[0047] (2) The raw material is put into the high-purity titanium metal crucible of the pulling single crystal furnace, and the seed crystal is clamped on the seed crystal rod. Close the furnace door of the pulling single crystal furnace equipment, and extract the vacuum in the furnace to 6.5 x 10 -3 Pa through the self-owned vacuum system of the equipment, close the vacuum system and introduce 5N high-purity argon into the furnace to normal pressure, repeat three times, and keep the furnace at normal pressure and high-purity argon atmosphere.

[0048] (3) Turn on the induction heating device of the pulling single crystal furnace, heat the crucible to 250°C and keep for 30 min, so that the indium raw material in the crucible is completely melted, after the end of the heat preservation, continue to heat to 1000°C, while hydrogen is introduced, the hydrogen flow is 2 L / min, after 2 h of heat preservation, the hydrogen is closed and the temperature in the crucible slowly decreases to 160°C with the furnace and continues to keep for 48 h, the crucible keeps slow rotation in the clockwise direction during the heat preservation process, the rotation speed is 2 r / min.

[0049] (4) The crucible is kept at 160°C for 1 h, then the seed crystal rod with the seed crystal clamped is lowered to make the lower surface of the seed crystal inserted into the molten indium 8 mm below and kept for 1 h, so that the lower end surface of the seed crystal is slightly melted and fully wetted with the raw material indium liquid, then the seed crystal rod is started to be pulled up at a pulling rate of 3 mm / h, the seed crystal rotates counterclockwise at a speed of 0.5 r / m, after 1 h, the pulling and rotation of the seed crystal rod are stopped and paused for 1 h, at this time, the diameter of the lower surface of the seed crystal is expanded to about 10 mm, the pulling and rotation of the seed crystal rod are restarted, the pulling rate is 8 mm / h, the rotation speed is 1 r / min, and the continuous running time is 43 h, the high-purity indium rod with a weight of 5.45 kg is pulled out, after cutting off the tail end of 5 cm of the indium rod, the remaining 4.88 kg of ultra-high-purity indium metal ingot with a purity close to 7N8 is obtained.

[0050] Example 3

[0051] (1) 6.5 kg of 6N5 high-purity indium is weighed as raw material, and 7N5 high-purity indium is selected to prepare a cylindrical seed crystal, the size of which is Φ8 mm x 100 mm.

[0052] (2) The raw material is put into the high-purity titanium metal crucible of the pulling single crystal furnace, and the seed crystal is clamped on the seed crystal rod. The door of the pulling single crystal furnace equipment is closed, the vacuum in the furnace is extracted to 4.3 x 10 -3 Pa by the self-owned vacuum system of the equipment, the vacuum system is closed and 5N high-purity nitrogen is introduced into the furnace to normal pressure, and the process is repeated three times to keep the furnace in a normal pressure high-purity nitrogen atmosphere.

[0053] (3) The induction heating device of the pulling single crystal furnace is started to heat the crucible to 220°C and keep for 45 min, so that the indium raw material in the crucible is completely melted, after the heat preservation is over, the temperature is continuously increased to 900°C, and hydrogen is introduced at a flow rate of 3 L / min, after 3 h of heat preservation, the hydrogen is closed and the temperature in the crucible is slowly reduced with the furnace to 170°C and kept for 36 h, during the heat preservation process, the crucible is kept rotating in the clockwise direction at a slow speed of 3 r / min.

[0054] (4) The crucible is kept at 170°C for 3 h, then the seed crystal rod with the seed crystal clamped is lowered to make the lower surface of the seed crystal inserted into the molten indium 10 mm below and kept for 1 h, so that the lower end surface of the seed crystal is slightly melted and fully wetted with the raw material indium liquid, then the seed crystal rod is started to be pulled up at a pulling rate of 4 mm / h, the seed crystal rotates counterclockwise at a speed of 0.1 r / m, after 1.5 h, the pulling and rotation of the seed crystal rod are stopped and paused for 2 h, at this time, the diameter of the lower surface of the seed crystal is expanded to about 12 mm, the pulling and rotation of the seed crystal rod are restarted, the pulling rate is 12 mm / h, the rotation speed is 1.5 r / min, and the continuous running time is 30 h, the high-purity indium rod with a weight of 6.15 kg is pulled out, after cutting off the tail end of 4 cm of the indium rod, the remaining 5.75 kg of ultra-high-purity indium metal ingot with a purity of 7N5 is obtained.

[0055] The ultra-high purity indium metal ingots obtained in Examples 1-3 were labeled as Sample 1, Sample 2, and Sample 3, respectively. The impurity content in them was detected, and the results are shown in Table 1.

[0056] Table 1. Impurity content of ultra-high purity indium metal ingots (unit: ppbwt)

[0057]

[0058]

[0059]

[0060] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing ultra-high purity indium with a purity of 7N or higher, characterized in that, Includes the following steps: Step S1: High-purity metallic indium with a purity of 6N or higher is loaded into the melting crucible of the Czochralski single crystal furnace, and ultra-high-purity indium with a purity of 7N or higher is used as a seed crystal, which is then clamped onto the seed crystal rod; ensure that the Czochralski single crystal furnace is an oxygen-free, atmospheric pressure environment; Step S2: Turn on the Czochralski single crystal furnace and heat it to 200~250℃ and hold it for a period of time (T1). Step S3: The Czochralski single crystal furnace fully melts the high-purity metallic indium in the crucible using electromagnetic induction heating, and then heats it to 800~1000℃ and holds it for a period of time T2. During the holding process, hydrogen gas is introduced into the Czochralski single crystal furnace. Step S4: Reduce the temperature of high-purity indium metal in the melting crucible to 160~180℃ and maintain the temperature. During the heat preservation process, the melting crucible is rotated clockwise; after heat preservation for 0.5~3h, the lower end of the seed crystal is inserted into the melt of high-purity indium, and then the seed crystal is pulled up and rotated counterclockwise. After a period of time T3, the pulling and rotation of the seed crystal is stopped and paused for a period of time T4, and then the pulling and rotation of the seed crystal is restarted for a duration of T5. Step S5: After the lifting is completed, the tail end of the obtained ultra-high purity indium rod is cut off, and the remaining part is ultra-high purity indium with a purity of 7N or higher. The content of Sn, Sb, and Pb in the ultra-high purity indium with a purity of 7N or higher is less than 10 ppbw.

2. The preparation method according to claim 1, characterized in that, The smelting crucible is selected from one of the following: a high-purity graphite crucible with an ash content of no more than 20 ppm, a high-purity boron nitride crucible with a purity of 6N or higher, or a titanium metal crucible with a purity of 4N or higher.

3. The preparation method according to claim 1, characterized in that, The method to ensure an oxygen-free, atmospheric pressure environment inside the Czochralski furnace is as follows: close the furnace door and extract the pressure inside the furnace to less than 10. -2 After Pa, inert gas is introduced to atmospheric pressure, and this process is repeated at least three times.

4. The preparation method according to any one of claims 1-3, characterized in that, T1 is 30-60 min; T2 is 2-4 h; T3 is 1-2 h; T4 is 1-3 h; T5 is 24-46 h.

5. The preparation method according to claim 4, characterized in that, In step S3, the hydrogen flow rate is 2~4 L / min.

6. The preparation method according to claim 4, characterized in that, The melting crucible rotates clockwise at a speed of 2~5 r / min.

7. The preparation method according to claim 4, characterized in that, Within time T3, the seed crystal pulling speed is 3~5 mm / h, and the rotation speed is 0.5~1.5 r / min.

8. The preparation method according to claim 4, characterized in that, Within time T5, the seed crystal pulling speed is 8~15mm / h, and the rotation speed is 1~2r / min.

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