A process for preparing ultra-high purity arsenic single crystal rods by high-pressure liquid-sealed Czochralski method

Abstract

The present invention discloses a process for preparing ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method, which uses 7N high-purity arsenic as raw material, and finally prepares 9N ultra-high purity arsenic single crystal rods for molecular beam epitaxy through six steps of raw material preparation, vacuum deoxidation, heating and chemical processing, Czochralski purification, cooling and furnace discharge, and product processing. The process for preparing 9N ultra-high purity arsenic single crystal rods by a high-pressure liquid-sealed Czochralski method can efficiently achieve the technical indicators of silicon content <1ppb and oxygen content <1ppm, meet the needs of molecular beam epitaxy, and can flexibly adjust product specifications according to customer requirements, without the need for molds of specific specifications, and achieve efficient production.

Description

Technical Field

[0001] This invention patent relates to the field of deep processing of arsenic-containing hazardous waste in non-ferrous metallurgy to prepare high-purity materials, and in particular to a process for preparing ultra-high-purity arsenic single crystal rods by the high-pressure liquid encapsulation Czochralski method. Background Art

[0002] Most non-ferrous metal minerals in nature contain arsenic elements. A large amount of arsenic-containing hazardous waste will be generated during the pyrometallurgical process of arsenic-containing metal minerals. At present, the "rapid cooling and dry arsenic recovery technology for arsenic-containing flue gas in an oxygen-enriched bottom-blown smelting system" can efficiently recover arsenic elements from arsenic-containing complex non-ferrous metal ores and prepare 98% refined arsenic trioxide. The refined arsenic trioxide is then prepared into 99% metallic arsenic by vacuum carbothermal reduction method, realizing the resource utilization of arsenic-containing hazardous waste in non-ferrous metallurgy.

[0003] The metallic arsenic is further processed into 7N high-purity arsenic by the "chlorination-reduction" method, which can be widely used in fields such as gallium arsenide radio frequency chips and gallium arsenide light-emitting diodes. However, due to the existence of impurity elements in the ppb level, higher purity requirements are put forward for high-purity arsenic used in the molecular beam epitaxy field.

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

[0005] The properties of arsenic are relatively special. It sublimes into a gaseous state when heated to 615°C under normal pressure and can only be converted into a liquid state under 36 standard atmospheres, that is, it has a melting point of 817°C at 3.6 Mpa. Therefore, it is impossible to prepare arsenic rods by direct casting, and mechanical processing is likely to introduce impurities and contaminate high-purity arsenic.

[0006] In the industry, a closed quartz tube or quartz ampoule is mostly used to prepare arsenic rods by first converting arsenic into a liquid state and then condensing it under high-temperature and high-pressure conditions. For example, the devices disclosed in Chinese patents CN216838277U "A device for producing ultra-high-purity arsenic rods" and CN112011827A "Device and method for making high-purity arsenic rods" are all like this.

[0007] As proposed in "Ultrapurification of Arsenic by Crystallization" published in the 10th issue of Volume 54 of the journal "Inorganic Materials" in 2018, using 6N high-purity arsenic and other materials as raw materials, a scheme for achieving the ultra-purification and shaping of arsenic in a quartz ampoule by the directional solidification method is proposed. The arsenic ingots obtained are mostly composed of one or two single crystal blocks, and the quality can meet the requirements for application in the molecular beam epitaxy process of III-V compounds. However, it cannot efficiently remove silicon elements deeply. Even in the part with the highest purity of the arsenic ingot, it still contains 10-90 ppb of silicon element impurities.

[0008] As disclosed in the equipment of Chinese Patent CN 115305358 A, "A Device for Forming a Low-Oxygen Ultra-High-Purity Arsenic Rod", by integrating vacuum deoxidation, high-pressure melting, horizontal rotation degassing, and directional solidification in the same device, a 7N5 ultra-high-purity arsenic rod with high density, smooth and flat surface, and oxygen content < 1 ppm for molecular beam epitaxy can be prepared from 7N5 high-purity arsenic as the raw material in a high-purity quartz tube. This can effectively avoid problems such as rough surface and shrinkage cavities in the ingot and high oxygen content in conventional ingot forming. However, it should be noted that the equipment has limited effect on further purifying high-purity arsenic. Instead, through methods such as vacuum deoxidation, horizontal rotation to remove air bubbles, and directional solidification, it mainly serves the forming effect of the arsenic rod and cannot deeply remove silicon elements.

[0009] Currently, there is no publicly disclosed process route for preparing ultra-high-purity arsenic single crystal rods by the Czochralski method in the industry, nor any other process solutions that can deeply remove all impurity elements including silicon (< 1 ppb). Summary of the Invention

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

[0011] The technical solution of the present invention is realized as follows: A process for preparing ultra-high-purity arsenic single crystal rods by the high-pressure liquid encapsulation Czochralski method includes the following process steps:

[0012] 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 and spread it on the upper layer of the arsenic material; transfer the crucible out of the glove box, place it in a Czochralski furnace, install each component in sequence, and then close the furnace body; turn on the circulating water, turn on the vacuum pump, replace the gas in the furnace three times with high-purity argon gas, the personnel withdraw from the site, and the equipment switches to the remote control mode;

[0013] Step 2 Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10 Pa, raise the temperature of the heating field to 250 - 300 °C, keep it at a constant temperature for 1 h, turn off the vacuum pump, and then use an inert gas to increase the pressure to 4.0 - 5.0 MPa;

[0014] Step 3 Heating and melting the material: Raise the temperature of the heating field to 400 - 500 °C, keep it at a constant temperature for 30 minutes to completely melt the boron oxide to form a liquid seal, then raise the temperature of the heating field to 820 - 850 °C. After all the raw materials are melted, keep it at a constant temperature of 800 - 820 °C for 30 min, set the crystal rotation speed at 3 - 20 rpm in the forward direction and the snail rotation speed at 3 - 20 rpm in the reverse direction, and bake the crystal for 10 min;

[0015] Step 4 Czochralski purification: Manually perform seeding, crystal pulling, necking, and shoulder releasing until the diameter of the arsenic rod reaches 30 mm. Set the pulling speed to 0.001 - 1 mm / s and perform equal-diameter growth. When it reaches 20 - 40 mm, heat up and neck down, then adjust the temperature to perform secondary shoulder releasing to 30 mm for equal-diameter growth. When it reaches 330 - 350 mm, finish, and separate the arsenic rod from the melt.

[0016] Purification is carried out by the Czochralski method. According to the solubility differences of different impurity elements in the solid and molten states in the host 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 remaining melt bottom material 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 Czochralski rod, thereby achieving the purpose of purifying arsenic.

[0017] Step 5 Cooling and discharging: Turn off the crystal rotation and crucible rotation, and stop heating. Cool down at a rate of 1 °C / min to 350 °C, keep it at a constant temperature for 30 min, then naturally cool 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.

[0018] Step 6 Product treatment: Transfer the arsenic rod to the cleaning tank in the glove box, soak and clean it five times with UP-S grade electronic-grade ethanol to thoroughly remove the residual boron oxide on the surface. Take out the arsenic single crystal rod from the cleaning chamber and place it in the drying chamber. Raise the temperature of the glove box to 80 - 100 °C and turn on the cleaning mode. The process runs for 1 - 2 h to thoroughly dry the residual ethanol on the surface. Knock off the head end of the arsenic rod and vacuum package it. Finally, a 9N ultra-high purity arsenic single crystal rod with a silicon content < 1 ppb and an oxygen content < 1 ppm is obtained.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1) Compared with the existing technology for preparing 7N ultra-high purity arsenic rods for molecular beam epitaxy, the present invention adopts a high-pressure liquid encapsulation Czochralski process, which can efficiently achieve the technical indicators of a silicon content < 1 ppb and an oxygen content < 1 ppm, meeting the needs of downstream users.

[0021] 2) The present invention provides a process for preparing ultra-high purity arsenic single crystal rods by the high-pressure liquid encapsulation Czochralski method. It adopts a secondary "necking - shoulder releasing" process and discards the head end, strengthening the removal effect of impurity elements such as Si and Mg with a distribution coefficient K > 1 in arsenic. At the same time, a high-purity pyrolytic boron nitride crucible is used to avoid Si pollution from equipment sources, achieving deep removal of Si elements in arsenic.

[0022] 3) The present invention provides a process for preparing ultra-high purity arsenic single crystal rods by the high-pressure liquid encapsulation Czochralski method, which can flexibly adjust the product specifications according to customer requirements without the need for molds of specific specifications, realizing efficient production. Specific embodiments

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with 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.

[0024] Embodiment 1: A process for preparing an ultra-high purity arsenic single crystal rod by the high-pressure liquid encapsulation Czochralski method, comprising the following process steps:

[0025] Step 1 Raw material preparation: Weigh 3 kg of 7N ultra-high purity arsenic in a glove box, put it into a high-purity pyrolytic boron nitride crucible, and then add 0.5 kg of high-purity boron oxide and lay it on the upper layer of the arsenic material; transfer the crucible out of the glove box, place it in a Czochralski furnace, install each component in sequence and then seal the furnace body; turn on the circulating water, turn on the vacuum pump, use high-purity argon gas to displace the gas in the furnace three times, the personnel withdraw from the site, and the equipment switches to the remote control mode;

[0026] Step 2 Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10 Pa, raise the temperature of the heating field to 250 °C, and keep it at a constant temperature for 1 h; turn off the vacuum pump, and then use an inert gas to increase the pressure to 4.0 MPa;

[0027] Step 3 Heating and melting the material: Raise the temperature of the heating field to 400 °C, keep it at a constant temperature for 30 minutes to completely melt the boron oxide to form a liquid seal, then raise the temperature of the heating field to 830 °C, wait for all the raw materials to melt, keep it at a constant temperature of 800 °C for 30 min, set the crystal rotation speed to 10 rpm forward and the crucible rotation speed to 14 rpm reverse, and bake the crystal for 10 min;

[0028] Step 4 Czochralski purification: Manually operate the crystal wetting, crystal seeding, necking, shoulder releasing until the diameter of the arsenic rod reaches 30 mm, set the pulling speed to 0.013 mm / s, grow in the equal diameter stage, raise the temperature and neck at 20 mm, then adjust the temperature to release the shoulder for the second time to 30 mm and grow in the equal diameter stage, and finish at 330 mm, separate the arsenic rod from the melt;

[0029] Step 5 Cooling and discharging: Turn off the crystal rotation and crucible rotation, stop heating, cool down at a rate of 1 °C / min to 350 °C, keep it at a constant temperature for 30 min, then naturally cool to room temperature, turn on the vacuum pump, and use an inert gas to displace the gas in the furnace; open the furnace body and take out the arsenic single crystal rod;

[0030] Step 6 Product treatment: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, soak and clean it five times with UP-S grade electronic grade ethanol to completely remove the residual boron oxide on the surface, take out the arsenic rod from the cleaning chamber and place it in the drying chamber, raise the temperature of the glove box to 80 °C and turn on the cleaning mode, run the process for 1 h to completely dry the residual ethanol on the surface, knock off the head end of the arsenic rod, and vacuum package it. Finally, an ultra-high purity arsenic single crystal rod with a silicon content <1 ppb and an oxygen content <1 ppm is obtained.

[0031] Example 2: A process for preparing an ultra-high purity arsenic single crystal rod by the high-pressure liquid encapsulation Czochralski method, comprising the following process steps:

[0032] Step 1 Raw material preparation: Weigh 4 kg of 7N ultra-high purity arsenic in a 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 Czochralski furnace, install each component in sequence, close the furnace body, turn on the circulating water, turn on the vacuum pump, displace the gas in the furnace three times with high-purity argon gas, the personnel withdraw from the site, and the equipment switches to the remote control mode;

[0033] Step 2 Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10 Pa, raise the temperature of the heating field to 275 °C, keep it constant for 1 h, turn off the vacuum pump, and then increase the pressure to 4.5 MPa with an inert gas;

[0034] Step 3 Heating and melting the material: Raise the temperature of the heating field to 450 °C, keep it constant for 30 minutes to completely melt the boron oxide to form a liquid seal, then raise the temperature of the heating field to 840 °C. After all the raw materials are melted, keep it constant at 810 °C for 30 min, set the crystal rotation speed to 14 rpm in the forward direction and the crucible rotation speed to 18 rpm in the reverse direction, and bake the crystal for 10 min;

[0035] Step 4 Czochralski purification: Manually operate the crystal wetting, crystal seeding, necking, and shoulder releasing until the diameter of the arsenic rod reaches 30 mm. Set the pulling speed to 0.005 mm / s, grow in the equal diameter stage. At 30 mm, raise the temperature for necking, then adjust the temperature for secondary shoulder releasing to 30 mm for equal diameter growth, and finish at 340 mm, separating the arsenic rod from the melt;

[0036] Step 5 Cooling and taking out of the furnace: Turn off the crystal rotation and crucible rotation, stop heating, cool down at a rate of 1 °C / min to 350 °C, keep it constant for 30 min, then naturally cool to room temperature. Turn on the vacuum pump, displace the gas in the furnace with an inert gas, open the furnace body and take out the arsenic single crystal rod;

[0037] Step 6 Product treatment: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, soak and clean it five times with UP-S grade electronic grade ethanol to completely remove the residual boron oxide on the surface. Take out the arsenic rod from the cleaning chamber and place it in the drying chamber. Raise the temperature of the glove box to 90 °C and turn on the cleaning mode. The process runs for 1.5 h to completely dry the residual ethanol on the surface. Knock off the head end of the arsenic single crystal rod and vacuum package it. Finally, an ultra-high purity arsenic single crystal rod with a silicon content <1 ppb and an oxygen content <1 ppm is obtained.

[0038] Example 3: A process for preparing an ultra-high purity arsenic single crystal rod by the high-pressure liquid encapsulation Czochralski method, comprising the following process steps:

[0039] Step 1 Raw material preparation: Weigh 5 kg of 7N high-purity arsenic in a 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 Czochralski furnace, install each component in sequence, then seal the furnace body, turn on the circulating water, turn on the vacuum pump, displace the gas in the furnace three times with high-purity argon gas, the personnel withdraw from the site, and the equipment switches to the remote control mode;

[0040] Step 2 Vacuum deoxidation: Turn on the vacuum pump, evacuate to 10 Pa, raise the temperature of the heating field to 300 °C, keep it at a constant temperature for 1 h, turn off the vacuum pump, and then increase the pressure to 5.0 MPa with an inert gas;

[0041] Step 3 Heating and melting the material: Raise the temperature of the heating field to 500 °C, keep it at a constant temperature for 30 minutes to completely melt the boron oxide to form a liquid seal. Then raise the temperature of the heating field to 850 °C. After all the raw materials are melted, keep it at a constant temperature of 820 °C for 30 min, set the crystal rotation speed at 16 rpm in the forward direction and the crucible rotation speed at 20 rpm in the reverse direction, and bake the crystal for 10 min;

[0042] Step 4 Czochralski purification: Manually operate the crystal wetting, crystal seeding, necking, and shoulder releasing until the diameter of the arsenic rod reaches 30 mm. Set the pulling speed at 0.05 mm / s for equal-diameter growth. When it reaches 40 mm, raise the temperature for necking, and then adjust the temperature for secondary shoulder releasing to 30 mm for equal-diameter growth. When it reaches 350 mm, finish the process and separate the arsenic rod from the melt;

[0043] Step 5 Cooling and discharging: Turn off the crystal rotation and crucible rotation, stop heating, cool down at a rate of 1 °C / min to 350 °C, keep it at a constant temperature for 30 min, then naturally cool to room temperature. Turn on the vacuum pump, displace the gas in the furnace with an inert gas, open the furnace body and take out the arsenic single crystal rod;

[0044] Step 6 Product treatment: Transfer the arsenic single crystal rod to the cleaning tank in the glove box, soak and clean it five times with UP-S grade electronic-grade ethanol to completely remove the residual boron oxide on the surface. Take out the arsenic rod from the cleaning chamber and place it in the drying chamber. Raise the temperature of the glove box to 100 °C and turn on the cleaning mode. The process runs for 2 h to completely dry the residual ethanol on the surface. Knock off the head end of the arsenic single crystal rod and vacuum package it. Finally, a 9N ultra-high-purity arsenic single crystal rod with a silicon content <1 ppb and an oxygen content <1 ppm is obtained.

[0045] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to 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.