CN111074346A - Device and method for preparing high-purity monocrystalline germanium by pulling method - Google Patents
Device and method for preparing high-purity monocrystalline germanium by pulling method Download PDFInfo
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- CN111074346A CN111074346A CN202010028713.4A CN202010028713A CN111074346A CN 111074346 A CN111074346 A CN 111074346A CN 202010028713 A CN202010028713 A CN 202010028713A CN 111074346 A CN111074346 A CN 111074346A
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- 238000000034 method Methods 0.000 title claims abstract description 45
- 239000013078 crystal Substances 0.000 claims abstract description 180
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- 239000002184 metal Substances 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 229910052741 iridium Inorganic materials 0.000 claims description 3
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 3
- 230000007547 defect Effects 0.000 abstract description 8
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- 238000004458 analytical method Methods 0.000 description 4
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/08—Germanium
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/14—Heating of the melt or the crystallised materials
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/30—Mechanisms for rotating or moving either the melt or the crystal
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- Engineering & Computer Science (AREA)
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- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
本发明公开了一种提拉法制备单晶锗的装置及方法，该装置包括腔内设有坩埚的锗单晶生长炉，坩埚周围设有加热装置，加热装置在单晶提拉方向的截面形状为“<>”形对称结构，将坩埚包围在中间，加热装置分为上部加热器和下部加热器，上部加热器和下部加热器的夹角为110°～160°，上部加热器和下部加热器内均设置有由上到下均布的若干个高频涡流感应线圈，以控制单晶周围温度场的轴向和径向梯度。本发明装置可以根据生产需要对制备单晶锗过程调控，具有极高的操作灵活性和自动化潜力。本发明所制备得到的晶体结晶性能良好，晶体无开裂、位错、气泡、夹杂、散射等缺陷，单晶重复率较高，达到了良好的长晶效果。
The invention discloses a device and method for preparing single crystal germanium by pulling method. The device comprises a germanium single crystal growth furnace with a crucible in the cavity, a heating device is arranged around the crucible, and the cross section of the heating device in the single crystal pulling direction The shape is a "<>" symmetrical structure, which surrounds the crucible in the middle. The heating device is divided into an upper heater and a lower heater. The angle between the upper heater and the lower heater is 110° to 160°. The upper heater and the lower heater Several high-frequency eddy current induction coils are arranged in the heater evenly distributed from top to bottom to control the axial and radial gradients of the temperature field around the single crystal. The device of the invention can regulate and control the process of preparing single crystal germanium according to production needs, and has extremely high operational flexibility and automation potential. The crystals prepared by the invention have good crystallinity, no defects such as cracks, dislocations, bubbles, inclusions, scattering, etc., and the single crystal repetition rate is high, and a good crystal growth effect is achieved.
Description
Technical Field
The invention relates to a germanium purification technology, in particular to a device and a method for preparing high-purity single crystal germanium by a pulling method.
Background
Germanium is an important semiconductor material, and germanium and compounds thereof are widely applied in the fields of electronic industry, infrared optics, optical fiber communication, chemical catalysts and the like, and are one of the most important metals in modern information industry.
At present, the growth methods of germanium single crystals mainly comprise a single crystal pulling method, a horizontal Bridgman method and a VGF method. The horizontal Bridgman method has the advantages of high crystal growth speed, low cost and the like, but because the crystal is D-type, the utilization rate is low, and the germanium single crystal with larger size is difficult to grow. The crystal diameter of the VGF method is the same as that of the crucible, and a germanium single crystal with a larger size can be theoretically grown. However, in this method, the junction between the crucible and the crystal is liable to cause parasitic nucleation, and the crystal grown by the VGF method is mostly a concave interface, and it is difficult to ensure the crystal yield.
The single crystal pulling method has the advantages of high growth speed, less pollution, good integrity of the cultivated single crystal and the like. However, because the thermal conductivity of the germanium single crystal material is small, and the critical shear stress ratio for generating dislocation is small, heat in the crystal is difficult to dissipate in the single crystal growth process, thermal stress is easy to generate, so that dislocation is generated and added, and when the crystal is grown by the pulling method, the crystal needs to be pulled out of a heating zone, the crystal is easy to crack in the cooling process, so that the performance of the single crystal germanium is influenced.
The traditional germanium single crystal furnace mainly comprises a heater, a heat insulating material, a crucible and a support thereof. During operation, germanium raw material is heated and melted in a crucible to form a melt, the seed crystal is contacted with the liquid level of the melt at a proper temperature, then the seed crystal is slowly pulled upwards, and a germanium single crystal rod is formed through the control of the pulling speed and the temperature. Due to the limitation of objective factors such as a thermal field, a thermal conductivity coefficient of the germanium single crystal rod and the like, the defects such as dislocation, bubbles and the like can be caused when the pulling speed is too high, and even the crystal pulling is out of control or the crystal rod is pulled off from the liquid level.
Disclosure of Invention
The invention aims to solve the technical problems that the defects and shortcomings in the background technology are overcome, the device and the method for preparing the high-purity single crystal germanium by the pulling method are provided, and the obtained crystal has good crystallization performance and no defects of cracking and the like.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a device for preparing high-purity single crystal germanium by a pulling method comprises a germanium single crystal growth furnace with a crucible arranged in a cavity, wherein a heating device is arranged around the crucible, the cross section of the heating device in the single crystal pulling direction is of a symmetrical structure in a shape of < >, the crucible is surrounded in the middle, the heating device is divided into an upper heater and a lower heater, the included angle between the upper heater and the lower heater is 110-160 degrees, and a plurality of high-frequency eddy current induction coils which are uniformly distributed from top to bottom are arranged in the upper heater and the lower heater so as to control the axial gradient and the radial gradient of a temperature field around the single crystal.
Furthermore, the upper heater and the lower heater are respectively formed by connecting at least three high-frequency eddy current induction coils in series.
Furthermore, the crucible is made of iridium metal.
Furthermore, the furnace wall of the germanium single crystal growth furnace is composed of a heat preservation cover, the heating device is arranged in the heat preservation cover, the heat preservation cover comprises a first heat preservation cover and a second heat preservation cover, the first heat preservation cover surrounds the heating device from the side face, the second heat preservation cover surrounds the crucible and the heating device from the bottom face and the top face, and the first heat preservation cover surrounds the first heat preservation cover from the side face.
Further, be provided with crucible mechanism that falls bottom the crucible, fall crucible mechanism and include the support column and fall crucible drive arrangement, the support column upper end is connected in the crucible bottom, and the lower extreme is connected in falling crucible drive arrangement, and the support column can oscilaltion and rotation under falling crucible drive arrangement drive.
Furthermore, the support column comprises a cooling device arranged at the center of the support column along the axial direction, and the upper end of the cooling device is in contact with the center of the crucible.
Furthermore, the support column further comprises an auxiliary heating device arranged on the periphery of the cooling device, the upper end of the auxiliary heating device is in contact with the bottom of the crucible, a first heat-preservation heat-insulation layer is arranged between the cooling device and the auxiliary heating device to separate the cooling device and the auxiliary heating device, and a second heat-preservation heat-insulation layer is arranged on the periphery of the auxiliary heating device to form the outermost layer of the support column.
The method for preparing the high-purity single crystal germanium by adopting the device comprises the steps of material melting, crystal growth, crystal seeding, shouldering, equal-diameter growth, cooling and ending.
In the material melting stage, the power of the high-frequency eddy current induction coil is gradually increased in the early stage to heat, meanwhile, the auxiliary heating device is started to heat the raw material to a first temperature, the stable power is kept in the middle stage, after heating is carried out for 30-60 min, the material melting power in the later stage is reduced by 5-20%, so that the raw material in the crucible is melted, and the raw material grows for 2-6 h in a heat preservation manner;
in the crystal growth stage, the auxiliary heating device is closed, the cooling device is started at the same time, the power of the high-frequency eddy current induction coil is adjusted to be reduced by 10% -30% compared with the later material melting power in the material melting stage, the temperature is reduced to a second temperature at a first rate, and crystal growth is carried out;
in the seeding stage, after the crystal growth is finished, adjusting the power of a high-frequency eddy current induction coil to be reduced by 30-50% compared with the post-stage material melting power in the material melting stage, cooling to the seeding temperature at a second rate, closing a cooling device, adjusting the axial and radial temperature field gradients by controlling the power of the high-frequency eddy current induction coils of an upper heater and a lower heater, wherein the temperature field gradient is 1-5 ℃/cm, adjusting the seed crystal to be in contact with the upper surface of the melt, starting single crystal pulling, controlling the crystal pulling speed to be 0.4-1 mm/min, the crucible lowering speed to be 0.01-0.1 mm/min, the crystal growth speed to be 50-80g/h, and the crystal diameter to be 20-40 mm;
the step of shouldering, wherein the coil power of the upper heater is adjusted to be 2-10% higher than that of the lower heater, the pulling speed is maintained at 0.6-1.6mm/min, and the growth speed of the crystal is controlled to be gradually increased from 50-80g/h to 500 g/h;
the equal-diameter growth is carried out, the pulling speed is maintained at 0.6-1.6mm/min, and the crystal growth speed is controlled at 500-2000 g/h;
and in the cooling stage, after the set length of the single crystal is reached, the cooling device is started, the power of the high-frequency eddy current induction coil is gradually reduced to 0KW, the pulling speed is reduced to 0, and the cooling is carried out at a third speed.
Further, the first temperature is 60-120 ℃ above the melting point of the grown crystal; the second temperature is 0-50 ℃ above the melting point of the grown crystal, and the third temperature is 20-50 ℃.
Further, the first rate is 1-10 ℃/h, the second rate is 20-50 ℃/h, and the third rate is 50-100 ℃/h.
The thermal field configuration is the most critical link for pulling low dislocation single crystals. During crystal growth, dislocations are produced in the crystal if the thermal stress in the crystal exceeds the critical shear stress at which the dislocations are produced. Once dislocations are generated in the crystal, according to the dislocation nucleation theory, the dislocations will proliferate in large quantities, and a low-dislocation single crystal cannot be obtained. The thermal stress and the thermal field temperature gradient in the crystal have a direct relation, and the conditions that the axial temperature gradient and the radial temperature gradient do not cause dislocation are respectively derived through theory:
where β is the coefficient of thermal expansion, b is the Burgs vector, G is the shear modulus, τ is the critical stress, R is the radius of the single crystal, and l is the length of the single crystal.
In addition, when the crystal is grown by the pulling method, the crystal needs to be pulled out of a heating area, the temperature gradient is large, the crystal is easy to crack in the cooling process, and the temperature gradient of the crystal also needs to be adjusted in order to reduce the cracking of the crystal.
The invention can accurately control the temperature field and the temperature gradient in the single crystal through the improvement of the device and the method, and the temperature gradient is set in a smaller range, thereby avoiding the defects of cracking and dislocation.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, the plurality of induction coils are arranged in the heating devices on two sides of the crucible, a special < > -shaped heating structure is adopted, the heating rate is high, the heat can be rapidly concentrated to melt the material in the stage of melting the material, and the temperature field can be accurately controlled by adjusting the power of the coils, so that the crystal grows directionally along the surface of the seed crystal, and the crystal cracking is avoided.
(2) The material melting rate can be further accelerated by arranging the auxiliary heating device in the supporting column, and the crucible is heated more uniformly.
(3) The cooling device is arranged at the center of the bottom of the crucible, so that the crystallization speed can be increased, the pulling speed of a crystal bar can be increased, the production efficiency can be improved, the single crystal pulling speed can be increased by 1.5-3 times, and the process time can be shortened by 20-40%.
(4) The whole device has good heat preservation and insulation effects, excellent air tightness and good process effect.
(5) The device can regulate and control the process of preparing the single crystal germanium according to production requirements, and has extremely high operation flexibility and automation potential.
(6) The crystal prepared by the invention has good crystallization performance, no defects of cracking, dislocation, bubbles, inclusion, scattering and the like, and high single crystal repetition rate, and achieves good crystal growth effect.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an apparatus for producing single crystal germanium by a Czochralski method according to an embodiment of the present invention;
wherein: 1. a germanium single crystal growth furnace; 2. a base; 3. a top cover; 4. a support frame; 5. a crucible; 6. melting the materials; 7. seed crystal; 8. lifting a pull rod; 9. a supporting seat; 10. a first heat-insulating cover; 11. a second heat-insulating cover; 12. a pulling and lifting drive device; 13. a crucible lowering drive device; 14. a cooling device; 15. a first heat preservation and insulation layer; 16. an auxiliary heating device; 17. a second heat insulation layer; 18. a heating device; 19. an upper heater; 20. a lower heater; 21. an air inlet pipe; 22. and an air outlet pipe.
Detailed Description
In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.
Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
As shown in fig. 1, the device for preparing high-purity single crystal germanium by the pulling method according to one embodiment of the present invention includes a germanium single crystal growth furnace 1, a base 2, a top cover 3, a support frame 4, a pulling mechanism, a crucible lowering mechanism, an air inlet pipe 21, and an air outlet pipe 22.
The base 2 and the top cover 3 are respectively arranged at the bottom and the top of the single crystal growth furnace and are fixed by a support frame 4.
The germanium single crystal growth furnace 1 comprises a crucible 5 arranged at the center of the furnace body, a heating device 18 arranged around the crucible 5, and a heat-insulating cover arranged around the heating device 18. Preferably, the crucible 5 is made of metal iridium, and can effectively absorb heat radiation so as to realize heat preservation and achieve the purpose of reducing the temperature gradient of the crystal.
The heating device 18 is of a symmetrical structure in a shape of < >, and is divided into an upper heater 19 and a lower heater 20, and the included angle between the upper heater 19 and the lower heater 20 is 110-160 degrees. The upper heater 19 and the lower heater 20 are each provided therein with a plurality of high-frequency eddy current induction coils and are equipped with a high-performance temperature detector. Preferably, the upper heater 19 and the lower heater 20 are each composed of at least three heating coils connected in series, so that the coils are uniformly distributed in the heater from top to bottom, and the power of the single heating coil is 10-30 KW. Preferably, the high-frequency eddy current induction coil is a double-layer coil with the width of 1-5 cm. The heating device 18 has high heating rate, can quickly concentrate heat to melt the material in the stage of melting the material, and can also accurately control the temperature field by adjusting the power of the coil to ensure that the crystal grows directionally along the surface of the seed crystal, thereby avoiding the crystal cracking. The growth of the single crystal is substantially at the central region of the "< >" shaped structure, and the axial temperature gradient and the radial temperature gradient within the single crystal can be controlled by controlling the power of the coils of the upper heater 19 and the lower heater 20, respectively.
The heat preservation cover comprises a first heat preservation cover 10 and a second heat preservation cover 11. The first heat-preserving cover 10 wraps the heating device 18 from the peripheral side face, the second heat-preserving cover 11 wraps the crucible 5 and the heating device 18 from the bottom face and the top face, and wraps the first heat-preserving cover 10 from the peripheral side face. Preferably, the first heat-preserving cover 10 is made of high-purity graphite material, and the second heat-preserving cover 11 is made of high-purity quartz material, so that internal heat preservation and external heat insulation are guaranteed.
The lifting and pulling mechanism comprises a lifting and pulling rod 8 and a lifting and pulling driving device 12. The upper end of the lifting rod 8 is connected with a lifting driving device 12, and the lower end is connected with the seed crystal 7. Preferably, the lifting rod 8 is a quartz rod. The lifting driving device 12 is fixedly arranged on the top cover 3, and the lifting driving device 12 comprises a driving motor. The lifting rod 8 is rotationally lifted under the driving of the driving motor, the control end of the driving motor is electrically connected with an electric cabinet, the electric cabinet is arranged on the top cover 3, and the electric cabinet can display the lifting speed, the rotating speed and the lifting length.
The crucible lowering mechanism comprises a supporting seat 9, a supporting column and a crucible lowering driving device 13. The supporting seat 9 is arranged at the bottom of the crucible 5, the upper end of the supporting column penetrates through the supporting seat 9 to be connected to the bottom of the crucible 5, and the lower end of the supporting column is connected to the crucible lowering driving device 13.
The crucible lowering driving device 13 is arranged on the base 2. In one embodiment, the crucible lowering driving device 13 comprises a driving motor, a control end of the driving motor is electrically connected with an electric cabinet, the electric cabinet is installed on the base 2, and the crucible lowering speed, the rotation speed and the lowering length can be displayed on the electric cabinet. The support column can be lifted up and down and rotated under the driving of the crucible lowering driving device 13, and provides support and rotation driving for the crucible 5. The crucible 5 rotates in the opposite direction to the rotation of the lifting rod 8.
In one embodiment, the support post is a multi-layered structure, and is distributed along a plurality of concentric rings of radial cross-section, including the auxiliary heating device 16, the temperature reducing device 14, and the thermal insulating layer.
The cooling device 14 is arranged at the center of the support column and at the center of the bottom of the crucible 5, the upper end of the cooling device is in contact with the bottom of the crucible 5, and heat exchange is carried out with the reverse convection at the center of the germanium melt so as to cool the solid-liquid interface, thereby accelerating crystallization and increasing the pulling speed. Preferably, the cooling device 14 is a cooling sleeve, a heat exchange medium is introduced into the cooling sleeve, the heat exchange medium is cooling water or cold air, and the cooling sleeve can synchronously ascend and descend along with the supporting column.
The upper end of the auxiliary heating device 16 is contacted with the bottom of the crucible 5. The material melting rate can be further accelerated, and the crucible is heated more uniformly. Preferably, the auxiliary heating device 16 is a resistance wire or a red copper heating tube. The auxiliary heating device 16 can be raised and lowered in synchronization with the support column.
The heat insulation layers are symmetrically distributed on two sides of the cooling device 14 to separate the cooling device 14 from the auxiliary heating device 16. The heat insulation layer comprises a first heat insulation layer 15 and a second heat insulation layer 17. The first heat insulation layer 15 is arranged at the periphery of the temperature reduction device 14. The auxiliary heating device 16 is arranged at the periphery of the first heat-insulation layer 15, and the second heat-insulation layer 17 is arranged at the periphery of the auxiliary heating device 16 to form the outermost layer of the support column. Preferably, the first heat-insulating layer 15 is made of graphite soft felt, and the second heat-insulating layer 17 is made of Al2O3A ceramic.
The method for preparing high-purity monocrystalline germanium, which is provided by the embodiment of the invention, takes 7N high-purity germanium as seed crystal and 5N germanium obtained by zone melting as raw material, and comprises the following steps:
s1: vacuumizing, namely firstly placing a 5N germanium raw material in a crucible 5, vacuumizing the crucible 5 for 1-2 times, filling nitrogen gas at a rate of 1-6L/min from an air inlet pipe 21, wherein the purity of the introduced nitrogen gas is more than 5N, and collecting and treating tail gas in an air outlet pipe 22;
s2: in the material melting stage, the power of a high-frequency eddy current induction coil of a heating device 18 is gradually increased to heat in the early stage, an auxiliary heating device 16 is started at the same time, the raw material is heated to a first temperature, the stable power is kept in the middle stage, after heating is carried out for 30-60 min, the material melting power in the later stage is reduced by 5-20%, the raw material in a crucible is melted, a fixed crucible is set to rotate, the crucible rotation is 1-4r/min, and the raw material grows for 2-6 h in a heat preservation manner;
s3: in the crystal growth stage, the auxiliary heating device 16 is closed, the cooling device 14 is simultaneously started, the power of the induction coil is reduced by 10% -30% compared with the material melting power in the later stage of the material melting stage, the temperature is reduced to a second temperature at a first rate, the crystal rotation, crucible rotation and thermal field temperature are adjusted, the crystal rotation is 5-15r/min, the crucible rotation is 2-6r/min, and the rotation directions of the crystal rotation and the crucible rotation are opposite to each other, so that the crystal grows;
s4: in the seeding stage, after the crystal growth is finished, the power of the induction coil is reduced by 30-50% compared with the later material melting power in the material melting stage, the temperature is reduced to the seeding temperature at a second speed, the cooling device 14 is closed after the seeding temperature is reached, the axial and radial temperature field gradients are adjusted by further controlling the power of the high-frequency eddy current induction coils of the upper heater 19 and the lower heater 20, and the temperature field gradient is 1-5 ℃/cm; adjusting seed crystals to be in contact with the upper surface of the melt 6, adjusting the crucible to rotate for 1-5 r/min and the crystal to rotate for 5-20 r/min, starting single crystal pulling, controlling the pulling speed of the crystals to be 0.4-1 mm/min, the crucible lowering speed to be 0.01-0.1 mm/min, the crystal growth speed to be 50-80g/h and the crystal diameter to be 20-40 mm;
s5: shouldering, namely adjusting the coil power of the upper heater 19 to be 2-10% higher than that of the lower heater 20, so that the shouldered part of the crystal obtains heat compensation, the uniformity of the head and tail temperature of the crystal is ensured, and the crystal is prevented from cracking; maintaining the pulling speed at 0.6-1.6mm/min, and gradually increasing the crystal growth speed from 50-80g/h to 500 g/h;
s6: growing in an equal diameter way, maintaining the pulling speed at 0.6-1.6mm/min, and controlling the crystal growth speed at 500-2000 g/h;
s7: a cooling stage, namely entering the cooling stage after the set length of the single crystal is reached, starting a cooling device 14, gradually reducing the power of an induction coil to 0KW, reducing the pulling speed, crystal rotation and crucible rotation to 0, and cooling at a third speed;
s8: in the ending stage, after the temperature is reduced to a third temperature, the cooling device 14 is closed, the crucible 5 is moved out, the materials are taken out integrally, the head part and the tail part are cut off by 20-30 mm, the rest materials are melted, and ingot casting is carried out to obtain 7N germanium; the cut head and tail materials are returned to the zone melting stage as production raw materials again to form a closed cycle of germanium, and no waste materials exist in the whole purification process.
Preferably, the first temperature is 60-120 ℃ above the melting point of the grown crystal; the second temperature is 0-50 ℃ above the melting point of the grown crystal, the third temperature is 20-50 ℃, and the first speed is 1-10 ℃/h; the second rate is 20-50 ℃/h, and the third rate is 50-100 ℃/h.
Example 1
With the arrangement of fig. 1, the upper heater 19 and the lower heater 20 are angled at 120 °. The upper heater 19 and the lower heater 20 are each composed of three heating coils connected in series, the power of the single heating coil being 10-30 KW.
The raw material used was 5N germanium after zone melting, and its product impurity content, ppm, is as follows:
| impurities | Mg | Al | Ca | Fe | Co | Ni | Cu | Zn | In | Pb |
| Content (wt.) | <0.05 | <0.05 | <0.1 | <0.05 | <0.02 | <0.02 | <0.01 | <0.05 | <0.01 | <0.02 |
(1) 5kg of 5N zone-melting germanium raw material is placed in a crucible 5 and a single crystal pulling furnace 1; vacuumizing the crucible 5 for 2 times by adopting vacuumizing equipment, then filling nitrogen at 4L/min, and keeping the low-pressure condition;
(2) and (3) material melting stage: the power of the high-frequency eddy current induction coil is gradually increased for heating at the early stage until the power is increased to 30KW of the maximum power, the auxiliary heating device 16 is started at the same time, the raw material is heated to about 1030 ℃, then the power of the 30KW is kept unchanged, the raw material is heated for 30min, the power of the coil is reduced to about 27KW, the raw material in the crucible 5 is melted, the crucible is adjusted to be 1.5r/min, and the raw material grows for 2h in a heat preservation way;
(3) crystal growth stage: closing the auxiliary heating device 16, simultaneously opening the cooling device 14, reducing the power of the induction coil to 24KW, reducing the power to about 980 ℃ at 8 ℃/h, adjusting the crystal to be 8r/min, the crucible to be 2r/min, and enabling the rotation directions of crystal rotation and crucible rotation to be opposite to each other, and growing crystals;
(4) and (3) seeding stage: after the crystal growth is finished, the power of the induction coil is reduced to 16KW, the temperature is reduced to 935 ℃ at 30 ℃/h, then the cooling device 14 is closed, further the power of the high-frequency eddy current induction coil of the upper heater 19 and the lower heater 20 is controlled to be 15KW, the axial and radial temperature field gradients are adjusted, the temperature field gradient is 4 ℃/cm, the seed crystal is adjusted to be in contact with the upper surface of the melt 6, the crucible is adjusted to be 2.9r/min and the crystal is adjusted to be 9.4r/min, the single crystal pulling is started, the crystal pulling speed is controlled to be 0.8mm/min, the crucible lowering speed is 0.08mm/min, the crystal growth speed is 65g/h, and the crystal diameter is 25 mm;
(5) shouldering: adjusting the coil power of the upper heater to be 16.5KW and the coil power of the lower heater to be 15KW, maintaining the pulling speed at 1.1mm/min, and controlling the growth speed of the crystal to be gradually increased from 65g/h to 500 g/h;
(6) and (3) isometric growth: maintaining the pulling speed at 1.2mm/min, and controlling the growth speed of the crystal at 1200 g/h;
(7) and (3) cooling: after the set length of the single crystal is reached, the cooling stage is started, the cooling device 14 is started, the power of the induction coil is gradually reduced to 0KW, the pulling speed, the crystal rotation and the crucible rotation are all reduced to 0, and the temperature is reduced at 70 ℃/h;
(8) and (3) ending: when the temperature is reduced to about 50 ℃, closing the cooling device 14, then moving the crucible 5 out, taking out the materials integrally, cutting off 20-30 mm of the head and the tail, melting the rest materials, and casting ingots to obtain 7N germanium; the cut head and tail materials are returned to the zone melting stage as production raw materials.
The prepared crystal has good crystallization performance and has no defects of cracking, dislocation, bubbles, inclusion, scattering and the like. The analysis and detection results of the 7N germanium product are shown in the following table.
7N germanium product analysis test results (ppb)
Example 2
With the arrangement of fig. 1, the upper heater 19 and the lower heater 20 are angled at 120 °. The upper heater 19 and the lower heater 20 are each composed of three heating coils connected in series, the power of the single heating coil being 10-30 KW.
The raw material used was 5N germanium after zone melting, and its product impurity content, ppm, is as follows:
| impurities | Mg | Al | Ca | Fe | Co | Ni | Cu | Zn | In | Pb |
| Content (wt.) | <0.03 | <0.05 | <0.1 | <0.03 | <0.02 | <0.02 | <0.02 | <0.05 | <0.01 | <0.02 |
(1) 5kg of 5N zone-melting germanium raw material is placed in a crucible 5 and a single crystal pulling furnace 1; vacuumizing the crucible 5 for 2 times by adopting vacuumizing equipment, then filling nitrogen at 5L/min, and keeping the low-pressure condition;
(2) and (3) material melting stage: the power of the high-frequency eddy current induction coil is gradually increased for heating at the early stage until the power is increased to 30KW of the maximum power, the auxiliary heating device 16 is started at the same time, the raw material is heated to about 1050 ℃, then the power of 30KW is kept unchanged, the raw material is heated for 30min, the power of the coil is reduced to about 27KW, the raw material in the crucible 5 is melted, the crucible is adjusted to be 1.8r/min, and the raw material grows for 2h in a heat preservation way;
(3) crystal growth stage: closing the auxiliary heating device 16, simultaneously opening the cooling device 14, reducing the power of the induction coil to 24KW, reducing the power to 970 ℃ at 8 ℃/h, adjusting the crystal to be 8.5r/min, adjusting the crucible to be 2.2r/min, and enabling the rotation directions of crystal rotation and crucible rotation to be opposite to each other to grow crystals;
(4) and (3) seeding stage: after the crystal growth is finished, the power of the induction coil is reduced to 17KW, the temperature is reduced to 930 ℃ at 35 ℃/h, then the cooling device 14 is closed, further, the power of the high-frequency eddy current induction coil of the upper heater 19 and the lower heater 20 is controlled to be 15KW, the axial temperature field gradient and the radial temperature field gradient are adjusted to be 4 ℃/cm, the seed crystal is adjusted to be in contact with the upper surface of the melt 6, the crucible rotation speed is adjusted to be 2.9r/min and the crystal rotation speed is adjusted to be 9.4r/min, the single crystal pulling is started, the crystal pulling speed is controlled to be 0.85mm/min, the crucible lowering speed is 0.084mm/min, the crystal growth speed is 70g/h, and the crystal diameter is 25 mm;
(5) shouldering: adjusting the coil power of the upper heater to be 16.5KW and the coil power of the lower heater to be 15KW, maintaining the pulling speed at 1.2mm/min, and controlling the growth speed of the crystal to be gradually increased from 70g/h to 500 g/h;
(6) and (3) isometric growth: maintaining the pulling speed at 1.25mm/min, and controlling the growth speed of the crystal at 1200 g/h;
(7) and (3) cooling: after the set length of the single crystal is reached, the cooling stage is started, the cooling device 14 is started, the power of the induction coil is gradually reduced to 0KW, the pulling speed, the crystal rotation and the crucible rotation are all reduced to 0, and the temperature is reduced at 65 ℃/h;
(8) and (3) ending: when the temperature is reduced to about 50 ℃, closing the cooling device 14, then moving the crucible 5 out, taking out the materials integrally, cutting off 20-30 mm of the head and the tail, melting the rest materials, and casting ingots to obtain 7N germanium; the cut head and tail materials are returned to the zone melting stage as production raw materials.
The prepared crystal has good crystallization performance and has no defects of cracking, dislocation, bubbles, inclusion, scattering and the like. The analysis and detection results of the 7N germanium product are shown in the following table.
7N germanium product analysis test results (ppb)
The foregoing is considered as illustrative of the preferred embodiments of the invention and is not to be construed as limiting the invention in any way. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should fall within the protection scope of the technical scheme of the present invention, unless the technical spirit of the present invention departs from the content of the technical scheme of the present invention.
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| CN113186599A (en) * | 2021-04-12 | 2021-07-30 | 武汉大学 | Preparation method of ultrathin two-dimensional germanium (110) single crystal with high crystallization quality |
| CN114045557A (en) * | 2021-10-25 | 2022-02-15 | 安徽光智科技有限公司 | Preparation method and equipment of ultra-high purity germanium single crystal |
| CN117305969A (en) * | 2023-08-22 | 2023-12-29 | 江苏宁达环保股份有限公司 | Large-diameter low-dislocation germanium single crystal thermal field system and configuration method |
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| CN108018601A (en) * | 2017-12-19 | 2018-05-11 | 清远先导材料有限公司 | Crystal growing apparatus, growing method and its application |
| CN211497865U (en) * | 2020-01-11 | 2020-09-15 | 中南大学 | Device for preparing high-purity single crystal germanium by pulling method |
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| US5476064A (en) * | 1993-03-29 | 1995-12-19 | Research Development Corporation Of Japan | Pull method for growth of single crystal using density detector and apparatus therefor |
| CN101063227A (en) * | 2007-05-24 | 2007-10-31 | 北京有色金属研究总院 | Process and device for growing low dislocation germanium single crystal by crucible lowering Czochralski method |
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| CN113186599A (en) * | 2021-04-12 | 2021-07-30 | 武汉大学 | Preparation method of ultrathin two-dimensional germanium (110) single crystal with high crystallization quality |
| CN113186599B (en) * | 2021-04-12 | 2022-08-05 | 武汉大学 | Preparation method of ultrathin two-dimensional germanium (110) single crystal with high crystallization quality |
| CN114045557A (en) * | 2021-10-25 | 2022-02-15 | 安徽光智科技有限公司 | Preparation method and equipment of ultra-high purity germanium single crystal |
| CN114045557B (en) * | 2021-10-25 | 2024-05-10 | 安徽光智科技有限公司 | Method and equipment for preparing ultra-high purity germanium monocrystal |
| CN117305969A (en) * | 2023-08-22 | 2023-12-29 | 江苏宁达环保股份有限公司 | Large-diameter low-dislocation germanium single crystal thermal field system and configuration method |
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