CN117071051A - Balanced solidification method for preparing compound crystal by temperature gradient solidification - Google Patents
Balanced solidification method for preparing compound crystal by temperature gradient solidification Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 151
- 238000000034 method Methods 0.000 title claims abstract description 74
- 238000007711 solidification Methods 0.000 title claims abstract description 26
- 230000008023 solidification Effects 0.000 title claims abstract description 26
- 150000001875 compounds Chemical class 0.000 title claims abstract description 9
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 claims abstract description 78
- 229910052810 boron oxide Inorganic materials 0.000 claims abstract description 72
- GPXJNWSHGFTCBW-UHFFFAOYSA-N Indium phosphide Chemical compound [In]#P GPXJNWSHGFTCBW-UHFFFAOYSA-N 0.000 claims abstract description 69
- 239000000155 melt Substances 0.000 claims abstract description 61
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims abstract description 60
- 229910052738 indium Inorganic materials 0.000 claims abstract description 57
- 239000007788 liquid Substances 0.000 claims abstract description 47
- 238000001816 cooling Methods 0.000 claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 238000002360 preparation method Methods 0.000 claims abstract description 10
- 238000002347 injection Methods 0.000 claims description 24
- 239000007924 injection Substances 0.000 claims description 24
- 238000003860 storage Methods 0.000 claims description 21
- 239000000463 material Substances 0.000 claims description 16
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims description 9
- 239000011574 phosphorus Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 7
- 238000007599 discharging Methods 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 2
- 239000000758 substrate Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 description 7
- 230000035882 stress Effects 0.000 description 7
- 238000000137 annealing Methods 0.000 description 6
- 238000002425 crystallisation Methods 0.000 description 4
- 230000008025 crystallization Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910011255 B2O3 Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 206010011985 Decubitus ulcer Diseases 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/003—Heating or cooling of the melt or the crystallised material
-
- 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
-
- 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
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
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- Crystallography & Structural Chemistry (AREA)
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- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention provides a balanced solidification method for preparing compound crystals by temperature gradient solidification, which belongs to the technical field of crystal preparation, and comprises the steps of growing indium phosphide crystals in a melt of a crucible of a liquid seal pulling system by controlling a multi-section heating system, injecting indium into the melt after the crystal size is larger than a required size, and reducing the temperature of the melt to keep the melt and the indium phosphide crystals approximately balanced, wherein the crystals are kept slightly long in the process until the temperature is reduced; and in the cooling process, removing most of boron oxide when the system temperature is 700-900K. And finally, the melt in the crucible is pure indium, and the crystal is wrapped by the pure indium after the melt is solidified. The indium solidifies and can shrink, meanwhile, because the indium has good plasticity and is still in a liquid state at 200 ℃, the restriction of the crucible to the crystal is reduced, and the crystal can not be cracked by boron oxide and the crucible.
Description
Technical Field
The invention belongs to the technical field of crystal preparation, and particularly relates to a balanced solidification method for preparing compound crystals by temperature gradient solidification.
Background
InP (indium phosphide) material is an important compound semiconductor material, is one of the first choice materials for preparing high-frequency and high-speed devices, has great advantages in the frequency band above 100GHz, and has the characteristics of high frequency, low noise, high efficiency, radiation resistance and the like. The semi-insulating indium phosphide substrate is widely applied to the fields of 5G networks, terahertz communication, millimeter wave communication, detection and the like.
Crystal production can be largely classified into a horizontal Bridgman method (Horizontal Bridgman, HB), a liquid-sealed Czochralski method (Liquid Encapsulating Czochralski, LEC), a vapor pressure controlled Czochralski method (Vaporpressure Controlled Czochralski, VCZ), a vertical Bridgman method (Vertical Bridgman, VB), a vertical temperature gradient solidification technique (Vertical Gradient Freeze, VGF), or the like.
1. Horizontal Bridgman method (HorizontalBridgman, HB)
The growth of single crystals in the HB method can be realized by horizontally moving a charging ampere bottle or a heating furnace body, and the device and the operation are simpler, so that the advantages and the disadvantages are also clearer:
(1) The advantages are that: the HB single crystal furnace has simple manufacture, low cost and better control of the stoichiometric ratio of the melt; the crystal growth temperature gradient is small, the crystal dislocation is less, and the stress is small; seeding and crystal growth can be observed, which is beneficial to improving the crystal forming rate of the crystal;
(2) Disadvantages: the cross section of the crystal is D-shaped, and if the crystal is processed into a round shape, waste is caused; si contamination is present.
2. Liquid seal Czochralski method (LiquidEncapsulating Czochralski, LEC)
The LEC method employs a multi-heater growth furnace and a reusable PBN crucible to perform crystal growth under a specific atmosphere. The method has the main advantages and disadvantages that:
(1) The advantages are that: the reliability is high, and the method is suitable for mass production; the seeding and the growth of the crystal are visible, the crystallization condition is controllable, and the yield is high;
(2) Disadvantages: the temperature gradient of the crystal is large, the dislocation density of the grown crystal is high, and the residual stress is high; the control of crystal isodiametric and stoichiometric ratio is poor; the single crystal furnace has high manufacturing cost.
3. Vapor pressure controlled Czochralski method (VaporpressureControlled Czochralski, VCZ)
The VCZ single crystal growth process is a modified process of the LEC method. Compared with the LEC method, the VCZ method reduces the nonlinearity of the temperature field, reduces the probability of dislocation generation, and increases the uniformity of dislocation distribution in the axial direction and the radial direction of the crystal.
(1) The advantages are that: dislocation density and residual stress are lower than those of LEC method; the stoichiometric ratio of the crystal is controllable;
(2) Disadvantages: the single crystal furnace has complex structure and high manufacturing cost; the process operation difficulty is high and the running cost is high; the content of the crystal carbon is uncontrollable; the crystal length is short, and the method is not suitable for large-scale production.
4. Vertical Bridgman method (VerticalBridgman, VB) or vertical temperature gradient solidification technique (VerticalGradient Freeze, VGF)
The VGF/VB method is a growing method which has been developed and developed in the last 80 th century and which is capable of growing large-diameter, low dislocation, low thermal stress, high quality III-V semiconductor single crystals. The growth principle is that polycrystal, B2O3 and seed crystal are vacuum sealed in quartz tube, the furnace body and the quartz tube are vertically placed, and after the molten polycrystal contacts the seed crystal below, the crystal is slowly cooled to make monocrystal growth. The method has the main advantages and disadvantages that:
(1) The advantages are that: dislocation density and residual stress are lower than those of LEC method; the crystal has good isodiameter and high material utilization rate; the seed rod lifting and rotating device is reduced, and the manufacturing cost of the single crystal furnace is low; the monocrystalline material is easy to grow, and the semi-insulating monocrystalline material is easy to grow; the requirements on operators are low, and the method is suitable for mass production;
(2) Disadvantages: double crystals and flower crystals are easy to generate; crystal growth is not visible, and depends on the consistency and stability of the single crystal growth system; the tail of the crystal is easy to be stuck and cracked by liquid-sealed boron oxide; the yield is low.
Specifically to the growth of InP crystals, there are two common methods: one is vertical temperature gradient solidification (VGF), and the other is the liquid-sealed czochralski method (LEC), and the problems also exist: VGF crystal preparation techniques can grow low defect crystals, but yields are very low; the LEC crystal growth system has high yield of grown crystals but high defect density.
If the two methods of LEC and VGF can be combined, the advantages of both methods are obtained, and a high-yield, low-defect InP crystal can be produced.
However, conventionally, the VGF technique cannot be applied to the preparation of indium phosphide crystals in LEC crystal growth systems, because according to the existing process, indium phosphide itself is solidified and expanded to be restrained by a crucible, causing cracking, and boron oxide solidification also generates a great stress to the inside of the contacted crystals, causing direct breakage of the crystals.
Disclosure of Invention
The object of the present invention is to overcome the drawbacks of the prior art.
The invention adopts the following technical scheme to realize the aim of the invention: the equilibrium solidification method for preparing the compound crystal by temperature gradient solidification is realized based on a crystal preparation device, wherein the crystal preparation device comprises a furnace body, a crucible, a first heater, a second heater, a third heater, a lower heater, a seed crystal rod, a thermocouple group arranged on the periphery of the crucible, an observation rod, a pressure gauge and an inflation and deflation pipeline; the key point is that the device also comprises an indium injection system, wherein the indium injection system comprises a liquid suction upper pipe, a boron oxide temporary storage chamber, a liquid suction pipe valve, a driving device and an auxiliary heater.
The method comprises the following steps:
step 1: charging, namely placing indium phosphide polycrystal material and solid boron oxide in a crucible, mounting seed crystals on seed rods, mounting an observation rod on a furnace body, and placing the indium phosphide polycrystal in a boron oxide temporary storage chamber;
step 2: vacuumizing the furnace body to 10 through the inflation and deflation pipeline -5 Pa-10Pa, and then filling inert gas to 2.8-5MPa;
step 3: heating the indium phosphide polycrystal material and the boron oxide through a first heater, a second heater, a third heater and a lower heater to form melt and liquid boron oxide;
step 4: lowering the seed rod to make the seed crystal contact with the melt, and regulating the first heater, the second heater, the third heater and the lower heater to obtain a temperature gradient of 0.5K/cm-50K/cm from the bottom of the crucible to the surface of the melt;
gradually reducing the overall temperature of the melt until indium phosphide crystals grow on the seed crystal, and keeping the indium phosphide crystals from contacting the inner wall of the crucible;
step 5: when the indium phosphide crystal grows to meet the required size, the boron oxide temporary storage chamber is heated by the auxiliary heater, so that indium phosphide polycrystal is decomposed into phosphorus gas and indium melt, and the indium melt enters the melt;
step 6: cooling the melt by the first heater, the second heater, the third heater and the lower heater;
step 7: stopping cooling when the temperature of the melt is reduced to 700-900K, and observing the injection condition of indium until the injection is completed;
step 8: the liquid suction pipe moves to a position 1mm above the interface between the boron oxide and the melt, a valve of the liquid suction pipe is opened, and the boron oxide enters the boron oxide temporary storage chamber through the liquid suction pipe; closing a liquid suction pipe valve, lifting the indium injection system to enable the bottom of the liquid suction pipe to be separated from the residual boron oxide liquid level, and closing an auxiliary heater;
step 9: continuously adjusting the power of the first heater, the second heater, the third heater and the lower heater until the temperature inside the furnace body reaches the room temperature;
step 10: and (5) discharging, disassembling the furnace, and taking out the indium phosphide crystal.
Further, in the step 1, the amount of the indium phosphide polycrystal which is put into the boron oxide temporary storage chamber is 5-20% of the amount of the indium phosphide polycrystal material which is put into the crucible.
Further, in step 9, the pressure inside the furnace body is kept unchanged during the cooling process.
According to the invention, indium phosphide crystals are grown in a melt of a crucible of a liquid seal pulling system by controlling a multi-section heating system, after the crystal size is larger than a required size, indium is injected into the melt through an indium injection system, the crystallization point of the melt is reduced, the temperature of the melt is reduced, so that the melt and the indium phosphide crystals keep approximately balanced, the change of a growth interface is observed through an observation window during cooling, and the crystal is kept slightly long in the process until the temperature of the system reaches room temperature; and removing boron oxide when the system temperature is 700-900K in the cooling process. And finally, the melt in the crucible is pure indium, and the crystal is wrapped by the pure indium after the melt is solidified.
The beneficial effects are that: the method provided by the invention comprises the following steps: removing most of the boron oxide before the crystal is completely solidified; 2: and (3) in the cooling process, injecting indium into the melt to form a non-proportioning melt, wherein the melt finally contains only indium.
The indium phosphide can expand during solidification, and the indium can shrink during solidification, meanwhile, because the indium has good plasticity and is still in a liquid state at 200 ℃, the restraint of the crucible to the crystal is reduced, and the situation that the crystal is not cracked by boron oxide and the crucible can be realized.
Drawings
FIG. 1 is a schematic view of the structure of the device after loading;
FIG. 2 is a schematic view of crystal growth;
FIG. 3 is a schematic view of indium injection;
FIG. 4 is a schematic diagram of boron oxide absorption after crystal growth;
FIG. 5 is a schematic diagram after cooling;
FIG. 6 is a schematic view of a crystal decubitus.
Wherein, 1: a furnace body; 2: seed rods; 3: a liquid suction upper tube; 4: a boron oxide temporary storage chamber; 5: a first heater; 6: a second heater; 7: a third heater; 8: a lower heater; 9: a thermal insulation sleeve; 10: a crucible; 11: seed crystal; 12: boron oxide; 13: indium phosphide crystals; 13-1: post-grown indium phosphide crystals, 14: a melt; 15: a pipette; 16: a crucible rod; 17: a first thermocouple; 18: a second thermocouple; 19: a third thermocouple; 20: polycrystalline indium phosphide; 21: a pressure gauge; 22: an inflation and deflation pipeline; 23: an observation rod; 24: a driving device; 25: an auxiliary heater; 26: solid indium; 27: a cylindrical support; 28: a heating plate; 29: baking oven, 30: pipette valve, 31: indium.
Detailed Description
The invention provides a balanced solidification method for preparing compound crystals by temperature gradient solidification, which comprises the steps of growing indium phosphide crystals in a melt of a crucible of a liquid seal lifting system by controlling a multi-section heating system, injecting indium into the melt by an indium injection system after the crystal size is larger than a required size, reducing the crystallization point of the melt, simultaneously reducing the temperature of the melt to keep the melt and the indium phosphide crystals approximately balanced, observing the change of a growth interface by an observation window during cooling, and keeping the crystal slightly long in the process until the temperature of the system reaches room temperature; boron oxide is removed at a system temperature of 700-900K.
In order to implement the above method, the present invention proposes a preferred embodiment of the crystal preparation device.
Referring to fig. 1, the crystal preparation device comprises a closed furnace body 1, a crucible 10 arranged in the furnace body 1, a multi-section heating system consisting of a first heater 5, a second heater 6, a third heater 7 and a lower heater 8, a seed rod 2 capable of moving up and down, a thermocouple group, an observation rod 23, a pressure gauge 21 and an air charging and discharging pipeline 22 which penetrate through the furnace body 1 and are arranged on the periphery of the crucible 10.
The first heater 5, the second heater 6 and the third heater 7 are sequentially arranged on the periphery of the crucible 10 from top to bottom, and the lower heater 8 is arranged below the crucible 10.
The first heater 5, the second heater 6, the third heater 7 and the lower heater 8 provide a vertical temperature gradient during crystal growth.
Insulating sleeves are arranged outside the periphery of the crucible 10, the first heater 5, the second heater 6 and the third heater 7, and the temperature inside the crucible 10 is kept during crystal growth.
The observation rod 23 passes through the top of the furnace body 1, and the growth of the crystal in the crucible 10 can be seen through the observation rod 23.
In order to obtain the temperature of each position inside the furnace body 1, the thermocouple group in this embodiment includes a first thermocouple 17, a second thermocouple 18, and a third thermocouple 19, which are disposed at the bottom of the crucible 10, disposed at the side of the crucible 10.
A first thermocouple 17 is provided between the first heater 5 and the second heater 6, a second thermocouple 18 is provided between the second heater 6 and the third heater 7, and a third thermocouple 19 is provided at a bottom center position of the crucible 10 by a crucible rod 16. In setting the vertical temperature gradient inside the crucible 10, the values of the first thermocouple 17, the second thermocouple 18, and the third thermocouple 19 are read to determine and set the power of the heater.
The apparatus further comprises an indium injection system comprising a pipette up tube 3, a boron oxide temporary storage chamber 4, a pipette 15, a pipette valve 30, a driving means 24 and an auxiliary heater 25.
The equilibrium solidification method for preparing the compound crystal by realizing temperature gradient solidification based on the device comprises the following steps:
step 1: charging, namely placing indium phosphide polycrystal material and solid boron oxide into a crucible 10, mounting a seed crystal 11 on a seed rod 2, mounting an observation rod 23 on a furnace body 1, and placing indium phosphide polycrystal 20 into a boron oxide temporary storage chamber 4; fittings such as thermocouples, pressure gauges 21, etc. are assembled as shown in fig. 1.
The amount of the indium phosphide polycrystal 20 placed in the boron oxide temporary storage chamber 4 is 5-20% of the amount of the indium phosphide polycrystal material added into the crucible.
Step 2: through the air charging and discharging pipeline 22 vacuuming the furnace body 1 to 10 -5 Pa-10Pa, and then charging inert gas to 2.8-5MPa through a charging and discharging pipeline 22.
Step 3: the first heater 5, the second heater 6, the third heater 7 and the lower heater 8 in the multi-stage heating system are activated to heat the indium phosphide polycrystal material and the boron oxide in the crucible 10 until the melt 14 and the liquid boron oxide 12 are formed.
Step 4: the seed rod 2 is lowered so that the seed crystal 11 is brought into contact with the melt 14, and the first heater 5, the second heater 6, the third heater 7, and the lower heater 8 in the multi-stage heating system are adjusted so that the melt 14 attains a temperature gradient of 0.5K/cm to 50K/cm from the bottom of the crucible 10 to the surface of the melt 14.
The temperature gradient is regulated by the feedback of the display values of the first thermocouple 17, the first thermocouple 18 and the third thermocouple 19.
The bulk temperature of the melt 14 is gradually lowered while maintaining the temperature gradient constant until the indium phosphide crystal 13 grows on the seed crystal 11, as shown in fig. 2.
By adjusting the lower heater 8 while maintaining the temperature gradient unchanged, the indium phosphide crystal 13 was grown.
During the crystal growth process, the indium phosphide crystal 13 is controlled not to contact the inner wall of the crucible 10, leaving room in the crucible 10 for the subsequent process.
The above steps complete the crystal growth, and the grown crystal should be subsequently annealed according to the process flow.
If in-situ annealing is carried out, the solidification expansion of the indium phosphide itself can be restrained by a crucible to crack, and meanwhile, the solidification of the boron oxide can generate great stress on the contacted crystal, so that the crystal can be directly broken; if the crystal is pulled out of the melt for annealing, if the annealing space is in a low-temperature environment, the temperature of the crystal is quickly lost, the temperature gradient in the crystal is greatly increased, and great stress can be generated in the crystal to generate dislocation defects.
One way to solve the problem is to raise the temperature of the annealing environment, and to prevent the decomposition of the crystal by disposing a phosphorus vapor pressure of 0.1MPa or more in the annealing environment. However, as the annealing temperature increases, the required phosphorus vapor pressure increases.
The core of the invention is that when the crystal grows, the crystal is controlled not to grow to the edge of the crucible, after the crystal grows, indium is injected into the melt, and the temperature of the melt is reduced; after the injection is completed, the liquid boron oxide is removed, the periphery of the crystal is wrapped with a layer of indium when the temperature of the crystal is reduced, only a small amount of boron oxide is covered, and the crystal is not constrained by the crucible and is not affected by the boron oxide when the crystal expands.
Step 5: when the indium phosphide crystal 13 was grown to meet the desired size, the bottom of the liquid-suction pipe 15 was positioned above the boron oxide liquid surface. The boron oxide buffer chamber 4 is heated by the auxiliary heater 25 so that the indium phosphide polycrystal 20 is decomposed into phosphorus gas and indium 31, and the indium 31 is introduced into the melt 14 as shown in fig. 3.
The indium phosphide begins to decompose into phosphorus and indium when heated to more than 800 ℃, the phosphorus is gas and is collected in the upper space of the furnace body 1 and cannot enter the melt 14, the indium 31 is melt, the specific gravity of the indium is greater than that of the boron oxide, and the indium is introduced into the melt 14.
Indium is placed in the boron oxide buffer chamber 4, and indium can be directly injected into the melt 14 without generating phosphorus gas. However, the melting point of indium is very low, only 156 ℃, and since the temperature in the furnace body 1 is high, it is difficult to control the start time of indium injection, so in this embodiment, the indium phosphide polycrystal 20 is decomposed to realize indium injection.
Step 6: the temperature of the melt 14 is reduced by the first heater 5, the second heater 6, the third heater 7 and the lower heater 8.
Indium injection into the melt 14 will result in a decrease in the crystallization point of the melt, and to ensure that the crystal is not melted, the temperature of the melt 14 is reduced so that the melt remains approximately in equilibrium with the indium phosphide crystal.
Step 7: when the temperature of the melt 14 is reduced to 700-900K, stopping reducing the temperature, observing the injection condition of indium in the liquid suction pipe 15 through the observation rod 23 until the injection is completed, and closing the auxiliary heater 25.
The boron oxide is now still in the liquid state.
Step 8: the liquid suction pipe 15 moves to a position 1mm above the interface between the boron oxide 12 and the melt 14, the liquid suction pipe valve 30 is opened, and the boron oxide 12 enters the boron oxide temporary storage chamber 4 through the liquid suction pipe 15, as shown in fig. 4; the pipette valve 30 is closed and the indium injection system is raised so that the bottom of the pipette 15 breaks free from the residual boron oxide 12 level.
It should be noted that the residual boron oxide is not shown in the drawings.
The upper pipette 3 is communicated with the outside of the furnace body 1 through a pipette valve 30 or connected to a container with ambient pressure. The liquid boron oxide 12 enters the boron oxide temporary storage chamber 4 through the liquid suction pipe 15 by opening the liquid suction pipe valve 30 because the internal pressure of the furnace body 1 is larger than the external pressure of the liquid suction pipe valve 30. The liquid boron oxide 12 may be directly discharged to the outside of the pipette valve 30, or the liquid boron oxide 12 may be left in the boron oxide temporary storage chamber 4 by controlling the opening degree of the pipette valve 30.
In this embodiment, the opening of the pipette valve 30 is controlled to leave the liquid boron oxide 12 in the boron oxide temporary storage chamber 4.
When no liquid boron oxide enters the pipette 15, the pipette valve 30 is closed and the indium injection system is raised so that the bottom of the pipette 15 breaks away from the residual boron oxide 12 level.
During the entry of the boron oxide 12 into the boron oxide holding chamber 4 through the liquid suction pipe 15, the boron oxide entering the boron oxide holding chamber 4 needs to be heated, otherwise the boron oxide is solidified. When no liquid boric oxide enters the pipette 15, the auxiliary heater 25 is turned off.
Step 9: the power of the first heater 5, the second heater 6, the third heater 7 and the lower heater 8 is continuously adjusted until the inside of the furnace body 1 reaches the room temperature, and the crystal and indium in the crucible 10 are solidified, as shown in fig. 5.
In the cooling process of the step 9, the pressure inside the furnace body 1 is kept unchanged, the pressure inside and outside the boron oxide temporary storage chamber 4 is balanced, and liquid boron oxide cannot enter the crucible 10. As the auxiliary heater 25 has been turned off, the liquid boron oxide in the boron oxide temporary storage chamber 4 solidifies with further cooling.
The cooling process from step 6 is started, the periphery of the indium phosphide crystal 13 continues to grow, the formed indium phosphide crystal 13-1 which is grown after that, the part of the crystal does not meet the quality requirements, and the crystal needs to be polished in the subsequent use.
The amount of indium injection is controlled, and the amount of indium phosphide polycrystal 20 which is put into the boron oxide temporary storage chamber 4 is 5-20% of the amount of indium phosphide polycrystal material which is added into the crucible, so that the phosphorus in the melt 14 is fully absorbed in the cooling process, and after the cooling is finished, indium phosphide crystal 13, after-grown indium phosphide crystal 13-1 and indium 26 are respectively arranged in the crucible 10 from inside to outside.
The melting point of indium is very low, the indium can shrink during solidification, and the expansion of the indium phosphide crystal 13 during solidification is partially counteracted during the cooling process; the solid indium is soft in texture and when the indium phosphide crystal 13 swells, the indium forms a buffer protection between the crucible 10 and the indium phosphide crystal 13. In addition, the post-grown indium phosphide crystal 13-1 also formed a protective effect on the internal indium phosphide crystal 13.
The thickness of the post-grown indium phosphide crystal 13-1 outside the indium phosphide crystal 13 was related to the melt 14 remaining in the crucible 10 at the time of indium injection, and the post-grown indium phosphide crystal 13-1 was thicker in the drawing for clarity of illustration, but does not represent a true scale.
Step 10: and (5) discharging, disassembling the furnace, and taking out the indium phosphide crystal 13. The method specifically comprises the following steps:
step 10-1: the seed crystal 11 is separated from the seed rod 2, and the seed rod 2 is lifted;
step 10-2: the furnace body 1 is deflated to the ambient pressure through the inflation and deflation pipeline 22;
step 10-3: taking out the crucible 10, placing the cylindrical support 27 on the heating plate 28, and inverting the crucible 10 on the cylindrical support 27; the crucible 10 is taken out after the solid indium 26 is melted and separated from the crucible 10 by baking in a baking furnace 29, and the indium phosphide crystal 13 and the post-grown indium phosphide crystal 13-1 are cooled to room temperature.
The method provided by the invention solves the problems existing in the prior art.
Effect contrast:
for the 4 inch crystals prepared: LEC method, N-type dislocation density: 5000-10000cm -2 The crystal may be broken; VGF method, N-type dislocation density: 300-500cm -2 The method comprises the steps of carrying out a first treatment on the surface of the The invention relates to N-type dislocation density: 300-500cm -2 The yield is higher than that of the VGF method; the method provided by the invention can realize high yield and LEC method without breaking the crystalThe advantage of low dislocation defects with the VGF method.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same; while the invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that: modifications and equivalents of some of the technical features of the specific embodiments of the present invention may be made without departing from the spirit of the technical solutions of the present invention, and they are all included in the scope of the technical solutions claimed in the present invention.
Claims (7)
1. The equilibrium solidification method for preparing the compound crystal by temperature gradient solidification is realized based on a crystal preparation device, wherein the crystal preparation device comprises a furnace body (1), a crucible (10), a first heater (5), a second heater (6), a third heater (7) and a lower heater (8), a seed rod (2), a thermocouple group, an observation rod (23), a pressure gauge (21) and an inflation and deflation pipeline (22), wherein the thermocouple group, the observation rod (23), the pressure gauge (21) and the inflation and deflation pipeline (22) are arranged at the periphery of the crucible (10); the device is characterized by further comprising an indium injection system, wherein the indium injection system comprises a liquid suction upper pipe (3), a boron oxide temporary storage chamber (4), a liquid suction pipe (15), a liquid suction pipe valve (30), a driving device (24) and an auxiliary heater (25);
the method comprises the following steps:
step 1: charging, namely placing indium phosphide polycrystal material and solid boron oxide in a crucible (10), mounting a seed crystal (11) on a seed rod (2), mounting an observation rod (23) on a furnace body (1), and placing indium phosphide polycrystal (20) in a boron oxide temporary storage chamber (4);
step 2: vacuumizing the furnace body (1) to 10 through the inflation and deflation pipeline (22) -5 Pa-10Pa, and then filling inert gas to 2.8-5MPa;
step 3: heating the indium phosphide polycrystal material and the boron oxide through a first heater (5), a second heater (6), a third heater (7) and a lower heater (8) to form a melt (14) and liquid boron oxide (12);
step 4: lowering the seed rod (2) so that the seed crystal (11) is in contact with the melt (14), and adjusting the first heater (5), the second heater (6), the third heater (7) and the lower heater (8) so that the melt (14) obtains a temperature gradient of 0.5K/cm-50K/cm from the bottom of the crucible (10) to the surface of the melt (14);
gradually reducing the overall temperature of the melt (14) until an indium phosphide crystal (13) grows on the seed crystal (11), and keeping the indium phosphide crystal (13) from contacting the inner wall of the crucible (10);
step 5: when the indium phosphide crystal (13) grows to meet the required size, the boron oxide temporary storage chamber (4) is heated by the auxiliary heater (25) so that the indium phosphide polycrystal (20) is decomposed into phosphorus gas and indium, and the indium (31) enters the melt (14);
step 6: cooling the melt (14) by the first heater (5), the second heater (6), the third heater (7) and the lower heater (8);
step 7: stopping cooling when the temperature of the melt (14) is reduced to 700-900K, and observing the injection condition of indium until the injection is completed;
step 8: the liquid suction pipe (15) moves to a position 1mm above the interface between the boron oxide (12) and the melt (14), a liquid suction pipe valve (30) is opened, and the boron oxide (12) enters the boron oxide temporary storage chamber (4) through the liquid suction pipe (15); closing a liquid suction pipe valve (30), lifting the indium injection system to enable the bottom of the liquid suction pipe (15) to be separated from the residual boron oxide (12) liquid level, and closing an auxiliary heater (25);
step 9: continuously adjusting the power of the first heater (5), the second heater (6), the third heater (7) and the lower heater (8) until the inside of the furnace body (1) reaches the room temperature;
step 10: discharging, disassembling the furnace, and taking out the indium phosphide crystal (13).
2. The method according to claim 1, characterized in that in step 1, the amount of indium phosphide polycrystal (20) to be put into the boron oxide temporary storage chamber (4) is 5-20% of the amount of indium phosphide polycrystal material to be fed into the crucible.
3. The method of claim 1, wherein the step of determining the position of the substrate comprises,
the step 10 specifically comprises the following steps:
step 10-1: the seed crystal (11) is separated from the seed rod (2), and the seed rod (2) is lifted;
step 10-2: the furnace body (1) is deflated to the ambient pressure through an inflation and deflation pipeline (22);
step 10-3: taking out the crucible (10), placing the cylindrical support (27) on a heating plate (28), and inverting the crucible (10) on the cylindrical support (27); the crucible (10) is taken out after the solid indium (26) is melted and separated from the crucible (10) by baking in a baking furnace (29), and the indium phosphide crystal (13) is cooled to room temperature.
4. The method according to claim 1, wherein the first heater (5), the second heater (6) and the third heater (7) are arranged on the periphery of the crucible (10) from top to bottom, and the lower heater (8) is arranged below the crucible (10).
5. The method according to claim 4, characterized in that the thermocouple group comprises a first thermocouple (17), a second thermocouple (18) arranged at the side of the crucible (10), a third thermocouple (19) arranged at the bottom of the crucible (10).
6. The method according to claim 5, characterized in that in step 4, the temperature gradient is regulated by adjusting the first heater (5), the second heater (6), the third heater (7) and the lower heater (8) so that the melt (14) obtains a temperature gradient of 0.5K/cm-50K/cm from the bottom of the crucible (10) to the surface of the melt (14), and by feeding back the display values of the first thermocouple (17), the first thermocouple (18) and the third thermocouple (19).
7. The method according to claim 1, characterized in that in step 9, the pressure inside the furnace body (1) is kept unchanged during the cooling.
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