Process for preparing ultra-high-purity arsenic single crystal rod by high-pressure liquid seal czochralski method

Abstract

According to the technology, 7N high-purity arsenic is used as a raw material, and the 9N ultra-high-purity arsenic single crystal rod for molecular beam epitaxy is finally prepared through six steps of raw material preparation, vacuum deoxidation, heating material melting, Czochralski purification, cooling discharging and product treatment. According to the process for preparing the 9N ultra-high-purity arsenic single crystal rod by the high-pressure liquid sealing Czochralski method, the silicon content 1t can be efficiently achieved; the oxygen content is 1ppb, and the oxygen content is lt; the molecular beam epitaxy requirement is met, the product specification can be flexibly adjusted according to the customer requirement, a mold of a specific specification is not needed, and efficient production is achieved.

Description

Technical Field

[0001] The patent of this invention relates to the field of deep processing of non-ferrous metallurgical arsenic-containing hazardous waste to prepare high-purity materials, especially a process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed direct pulling method. Background Art

[0002] Most non-ferrous metal minerals in nature contain arsenic, and a large amount of arsenic-containing hazardous waste will be generated during the pyrometallurgical smelting process. At present, the "arsenic recovery technology of arsenic-containing flue gas quenching in oxygen-enriched bottom-blowing smelting system" can efficiently recover arsenic from complex arsenic-containing non-ferrous metal ores to prepare 98% refined arsenic trioxide, which is then prepared into 99% metallic arsenic through vacuum carbon thermal reduction, realizing the resource utilization of arsenic-containing hazardous waste in non-ferrous metallurgy.

[0003] The metallic arsenic is then processed into 7N high-purity arsenic through the "chlorination-reduction" method, which can be widely used in gallium arsenide RF chips, gallium arsenide light-emitting diodes and other fields. However, because it still contains ppb-level impurity elements, higher purity requirements are placed on the use of high-purity arsenic in the field of molecular beam epitaxy.

[0004] Ultra-high purity arsenic single crystal rod refers to an arsenic single crystal rod with an arsenic mass fraction of not less than 99.9999999% (i.e. 9N), which is currently mainly used in the field of molecular beam epitaxy.

[0005] Arsenic has special properties. It sublimates into gas when heated to 615℃ under normal pressure, and can only be converted into liquid at 36 standard atmospheric pressures, that is, the melting point is 817℃ at 3.6Mpa. Therefore, it is impossible to prepare arsenic rods by direct casting, and mechanical processing is prone to introduce impurities, causing pollution to high-purity arsenic.

[0006] Arsenic rods are usually prepared by converting arsenic into liquid and then condensing it in a sealed quartz tube or quartz ampoule under high temperature and high pressure conditions, such as the equipment disclosed in Chinese patent CN216838277U "A device for producing ultra-high purity arsenic rods" and CN112011827A "Device and method for making high-purity arsenic rods".

[0007] For example, the article Ultrapurification of Arsenic by Crystallization published in the 10th issue of Volume 54 of the journal Inorganic Materials in 2018 proposed a solution to use 6N high-purity arsenic as raw materials and adopt directional solidification method to achieve ultrapurification and molding of arsenic in quartz ampoule. The arsenic ingots produced are mostly composed of one or two single crystal blocks, and the quality can meet the requirements of application in the molecular beam epitaxy process of III-V compounds. However, the silicon element cannot be removed efficiently and deeply, and even in the purest part of the arsenic ingot, it still contains 10~90ppb of silicon impurities.

[0008] For example, the device disclosed in Chinese patent CN 115305358 A “A low-oxygen ultra-high purity arsenic rod forming device” integrates vacuum deoxidation, high-pressure melting, flat rotation degassing, and directional solidification in the same device, thereby using 7N5 high-purity arsenic as a raw material to prepare 7N5 high-purity arsenic rods with high density, smooth surface, and oxygen content <1ppm for molecular beam epitaxy in a high-purity quartz tube. It can effectively avoid the problems of rough ingot surface with shrinkage holes and high oxygen content in conventional ingot forming. However, it should be pointed out that the device is essentially limited in effect on further purification of high-purity arsenic. Instead, it mainly serves the arsenic rod forming effect through vacuum deoxidation, flat rotation degassing, directional solidification, etc., and is unable to deeply remove silicon elements.

[0009] Currently, there is no publicly available process route for preparing ultra-high purity arsenic single crystal rods by the pulling method, nor any other process scheme for achieving deep removal (<1ppb) of all impurity elements including silicon. Summary of the invention

[0010] The present invention provides a process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method. Using 7N high-purity arsenic as a raw material, a 9N ultra-high purity arsenic single crystal rod is prepared by a high-pressure liquid-sealed Czochralski method, which is mainly used in the field of molecular beam epitaxy.

[0011] The technical solution of the present invention is implemented as follows: A process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method comprises the following process steps: Step 1: Raw material preparation: weigh 3-5 kg ​​of 7N high-purity arsenic in a glove box, put it into a high-purity pyrolytic boron nitride crucible, and then add 0.5-1 kg of high-purity boron oxide to spread on the upper layer of the arsenic material; transfer the crucible out of the glove box and place it in a vertical pulling furnace, install each component in turn and close the furnace body; start the circulating water, start the vacuum pump, use high-purity argon gas to replace the gas in the furnace three times, evacuate the site, and switch the equipment to remote control mode; Step 2: Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10Pa, increase the temperature of the temperature field to 250-300°C, keep the constant temperature for 1h, turn off the vacuum pump, and then use inert gas to increase the pressure to 4.0-5.0MPa; Step 3: Heating and melting the materials: Raise the temperature of the temperature field to 400-500°C, keep the temperature constant for 30 minutes, melt all the boron oxide to form a liquid seal, then raise the temperature of the temperature field to 820-850°C, and after all the raw materials are melted, keep the temperature constant at 800-820°C for 30 minutes, set the crystal rotation speed to 3-20rpm forward, the worm speed to 3-20rpm reverse, and bake the crystal for 10 minutes; Step 4: Direct pulling and purification: manually operate crystal wetting, seeding, necking, and shouldering until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.001-1 mm / s, grow at equal diameters, heat up and neck at 20-40 mm, then adjust the temperature for secondary shouldering to grow at equal diameters of 30 mm, and end at 330-350 mm to separate the arsenic rod from the melt; The direct pulling method is adopted for purification. According to the difference in solubility of different impurity elements in the solid and molten states in the main metal, the impurity distribution is changed. That is, most impurities (Ni, Pb, Mn, Sb, Ga, Zn, Bi, Fe, Cu and Ag) with a distribution coefficient K < 1 in arsenic are concentrated in the bottom material of the melt remaining in the crucible; impurities such as Si and Mg with a distribution coefficient K > 1 in arsenic are concentrated at the head end of the direct pulling rod, thereby achieving the purpose of arsenic purification.

[0012] Step 5: Cool down and take out of the furnace: turn off the crystal rotor and the screw rotor, and stop heating; cool down to 350°C at a rate of 1°C / min, maintain the constant temperature for 30 minutes, then cool naturally to room temperature, turn on the vacuum pump, and use inert gas to replace the gas in the furnace; open the furnace body and take out the arsenic single crystal rod.

[0013] Step 6 Product processing: Transfer the arsenic rod to the cleaning tank in the glove box, use UP-S grade electronic grade ethanol to soak and clean it five times to completely remove the boron oxide remaining on the surface, take the arsenic single crystal rod out of the cleaning chamber and place it in the drying chamber, raise the glove box temperature to 80~100℃ and turn on the cleaning mode, run the process for 1~2h, thoroughly dry the ethanol remaining on the surface, knock off the head end of the arsenic rod, and vacuum package it to finally obtain 9N ultra-high purity arsenic single crystal rod with silicon content <1ppb and oxygen content <1ppm.

[0014] The beneficial effects of the present invention are: 1) Compared with the existing 7N ultra-high purity arsenic rod preparation technology for molecular beam epitaxy, the present invention adopts a high-pressure liquid-sealed direct pulling process, which can efficiently achieve the technical indicators of silicon content <1ppb and oxygen content <1ppm, meeting the needs of downstream users; 2) The present invention discloses a process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method, which adopts a secondary "neck shrinkage-shoulder release" process and discards the head end, thereby enhancing the removal effect of impurity elements such as Si and Mg whose distribution coefficient K in arsenic is greater than 1. At the same time, a high-purity pyrolytic boron nitride crucible is used to avoid Si contamination of the equipment source, thereby achieving deep removal of the Si element in arsenic; 3) The present invention provides a process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed direct pulling method, which can flexibly adjust product specifications according to customer requirements, does not require molds of specific specifications, and achieves efficient production. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0016] Example 1: A process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method, comprising the following process steps: Step 1: Raw material preparation: weigh 3 kg of 7N high-purity arsenic in the glove box, put it into a high-purity pyrolytic boron nitride crucible, and then add 0.5 kg of high-purity boron oxide to spread on the upper layer of the arsenic material; transfer the crucible from the glove box and place it in a vertical pulling furnace, install each component in turn and close the furnace body; start the circulating water, start the vacuum pump, use high-purity argon gas to replace the gas in the furnace three times, evacuate the site, and switch the equipment to remote control mode; Step 2: Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10Pa, increase the temperature of the temperature field to 250°C, and keep the constant temperature for 1h; turn off the vacuum pump, and then use inert gas to increase the pressure to 4.0MPa; Step 3: Heating and melting the materials: Raise the temperature of the temperature field to 400°C and keep the temperature constant for 30 minutes to melt all the boron oxide to form a liquid seal, then raise the temperature of the temperature field to 830°C. After all the raw materials are melted, keep the temperature constant at 800°C for 30 minutes, set the crystal rotation speed to 10 rpm forward and the worm speed to 14 rpm reverse, and bake the crystal for 10 minutes; Step 4: Direct pulling and purification: manually operate crystal wetting, seeding, necking, and shouldering until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.013 mm / s, grow at equal diameter, heat up and neck at 20 mm, then adjust the temperature for secondary shouldering to grow at equal diameter of 30 mm, end at 330 mm, and separate the arsenic rod from the melt; Step 5: Cool down and take out of the furnace: turn off the crystal rotor and the screw rotor, stop heating, cool down to 350°C at a rate of 1°C / min, keep the constant temperature for 30 minutes, then cool naturally to room temperature, turn on the vacuum pump, and use inert gas to replace the gas in the furnace; open the furnace body and take out the arsenic single crystal rod; Step 6 Product processing: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, use UP-S grade electronic grade ethanol to immerse and clean it five times to completely remove the boron oxide remaining on the surface, take the arsenic rod out of the cleaning chamber and place it in the drying chamber, raise the glove box temperature to 80°C and turn on the cleaning mode, run the process for 1 hour, thoroughly dry the ethanol remaining on the surface, knock off the head end of the arsenic rod, and vacuum package it to finally obtain a 9N ultra-high purity arsenic single crystal rod with a silicon content of <1ppb and an oxygen content of <1ppm.

[0017] Example 2: A process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method, comprising the following process steps: Step 1: Raw material preparation: weigh 4 kg of 7N high-purity arsenic in the glove box, put it into a high-purity pyrolytic boron nitride crucible, then add 0.75 kg of high-purity boron oxide and spread it on the upper layer of the arsenic material, transfer the crucible out of the glove box, place it in a vertical pulling furnace, install each component in turn, close the furnace body, start the circulating water, start the vacuum pump, use high-purity argon gas to replace the gas in the furnace three times, evacuate the site, and switch the equipment to remote control mode; Step 2: Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10Pa, increase the temperature of the temperature field to 275°C, keep the constant temperature for 1h, turn off the vacuum pump, and then use inert gas to increase the pressure to 4.5MPa; Step 3: Heating and melting the materials: Raise the temperature of the temperature field to 450°C and keep the temperature constant for 30 minutes to melt all the boron oxide to form a liquid seal. Then raise the temperature of the temperature field to 840°C. After all the raw materials are melted, keep the temperature constant at 810°C for 30 minutes. Set the crystal rotation speed to 14 rpm in the forward direction and the worm speed to 18 rpm in the reverse direction. Bake the crystal for 10 minutes. Step 4: Direct pulling and purification: manually operate crystal wetting, seeding, necking, and shouldering until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.005 mm / s, grow at equal diameter, heat up and neck at 30 mm, then adjust the temperature for secondary shouldering to grow at equal diameter of 30 mm, end at 340 mm, and separate the arsenic rod from the melt; Step 5: Cool down and take out of the furnace: turn off the crystal rotor and the screw rotor, stop heating, cool down to 350°C at a rate of 1°C / min, keep the constant temperature for 30 minutes, then cool naturally to room temperature, turn on the vacuum pump, replace the gas in the furnace with inert gas, open the furnace body and take out the arsenic single crystal rod; Step 6 Product processing: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, use UP-S grade electronic grade ethanol to immerse and clean it five times to completely remove the boron oxide remaining on the surface, take the arsenic rod out of the cleaning chamber and place it in the drying chamber, raise the glove box temperature to 90°C and turn on the cleaning mode, run the process for 1.5 hours, thoroughly dry the ethanol remaining on the surface, knock off the head end of the arsenic single crystal rod, and vacuum package it to finally obtain a 9N ultra-high purity arsenic single crystal rod with a silicon content of <1ppb and an oxygen content of <1ppm.

[0018] Example 3: A process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method, comprising the following process steps: Step 1: Raw material preparation: weigh 5 kg of 7N high-purity arsenic in the glove box, put it into a high-purity pyrolytic boron nitride crucible, then add 1 kg of high-purity boron oxide and spread it on the upper layer of the arsenic material, transfer the crucible out of the glove box, place it in a vertical pulling furnace, install each component in turn, close the furnace body, start the circulating water, start the vacuum pump, use high-purity argon gas to replace the gas in the furnace three times, evacuate the site, and switch the equipment to remote control mode; Step 2: Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10Pa, increase the temperature of the temperature field to 300°C, keep the constant temperature for 1h, turn off the vacuum pump, and then use inert gas to increase the pressure to 5.0MPa; Step 3: Heating and melting the materials: Raise the temperature of the temperature field to 500°C and keep the temperature constant for 30 minutes to melt all the boron oxide to form a liquid seal. Then raise the temperature of the temperature field to 850°C. After all the raw materials are melted, keep the temperature constant at 820°C for 30 minutes. Set the crystal rotation speed to 16 rpm in the forward direction and the worm speed to 20 rpm in the reverse direction. Bake the crystal for 10 minutes. Step 4: Direct pulling and purification: manually operate crystal wetting, seeding, necking, and shouldering until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.05 mm / s, grow at equal diameter, heat up and neck at 40 mm, then adjust the temperature for secondary shouldering to grow at equal diameter of 30 mm, end at 350 mm, and separate the arsenic rod from the melt; Step 5: Cool down and take out of the furnace: turn off the crystal rotor and the screw rotor, stop heating, cool down to 350°C at a rate of 1°C / min, keep the constant temperature for 30 minutes, then cool naturally to room temperature, turn on the vacuum pump, replace the gas in the furnace with inert gas, open the furnace body and take out the arsenic single crystal rod; Step 6 Product processing: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, use UP-S grade electronic grade ethanol to immerse and clean it five times to completely remove the boron oxide remaining on the surface, take the arsenic rod out of the cleaning chamber and place it in the drying chamber, raise the glove box temperature to 100°C and turn on the cleaning mode, run the process for 2 hours, thoroughly dry the ethanol remaining on the surface, knock off the head end of the arsenic single crystal rod, and vacuum package it to finally obtain a 9N ultra-high purity arsenic single crystal rod with a silicon content of <1ppb and an oxygen content of <1ppm.

[0019] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A process for preparing ultra-high purity arsenic single crystal rods by high pressure liquid seal Czochralski method, characterized in that The process steps include: Step 1: Raw material preparation: weigh 3-5 kg ​​of 7N high-purity arsenic in a glove box, put it into a high-purity pyrolytic boron nitride crucible, and then add 0.5-1 kg of high-purity boron oxide to spread on the upper layer of the arsenic material; transfer the crucible out of the glove box and place it in a vertical pulling furnace, install each component in turn and close the furnace body; start the circulating water, start the vacuum pump, use high-purity argon gas to replace the gas in the furnace three times, evacuate the site, and switch the equipment to remote control mode; Step 2: Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10Pa, increase the temperature of the temperature field to 250-300°C, keep the constant temperature for 1h, turn off the vacuum pump, and then use inert gas to increase the pressure to 4.0-5.0MPa; Step 3: Heating and melting the materials: Raise the temperature of the temperature field to 400-500°C, keep the temperature constant for 30 minutes, melt all the boron oxide to form a liquid seal, then raise the temperature of the temperature field to 820-850°C, and after all the raw materials are melted, keep the temperature constant at 800-820°C for 30 minutes, set the crystal rotation speed to 3-20rpm forward, the worm speed to 3-20rpm reverse, and bake the crystal for 10 minutes; Step 4: Direct pulling and purification: manually operate crystal wetting, seeding, necking, and shouldering until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.001-1 mm / s, grow at equal diameters, heat up and neck at 20-40 mm, then adjust the temperature for secondary shouldering to grow at equal diameters of 30 mm, and end at 330-350 mm to separate the arsenic rod from the melt; Step 5: Cool down and take out of the furnace: turn off the crystal rotor and the screw rotor, stop heating, cool down to 350°C at a rate of 1°C / min, keep the constant temperature for 30 minutes, then cool naturally to room temperature, turn on the vacuum pump, replace the gas in the furnace with inert gas, open the furnace body and take out the arsenic single crystal rod; Step 6 Product processing: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, use UP-S grade electronic grade ethanol to immerse and clean it five times to completely remove the boron oxide remaining on the surface, take the arsenic rod out of the cleaning chamber and place it in the drying chamber, raise the glove box temperature to 80~100℃ and turn on the cleaning mode, run the process for 1~2h, thoroughly dry the ethanol remaining on the surface, knock off the head end of the arsenic rod, and vacuum package it to finally obtain a 9N ultra-high purity arsenic single crystal rod with a silicon content of <1ppb and an oxygen content of <1ppm.