CN112410870B - Growth control method and system for growing silicon carbide crystal based on liquid phase epitaxial method - Google Patents

Growth control method and system for growing silicon carbide crystal based on liquid phase epitaxial method Download PDF

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CN112410870B
CN112410870B CN202011314183.6A CN202011314183A CN112410870B CN 112410870 B CN112410870 B CN 112410870B CN 202011314183 A CN202011314183 A CN 202011314183A CN 112410870 B CN112410870 B CN 112410870B
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silicon carbide
crystal
carbide crystal
probe
current
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CN112410870A (en
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薛卫明
马远
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Clc Semiconductor Co ltd
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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
    • C30B19/00—Liquid-phase epitaxial-layer growth
    • C30B19/10—Controlling or regulating
    • C30B19/103—Current controlled or induced growth
    • 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
    • C30B29/36—Carbides

Abstract

The invention provides a growth control method and a system for growing silicon carbide crystals based on a liquid phase epitaxy method, wherein the method mainly comprises the following steps: arranging at least one group of probe sets above and below the directional seed crystal, and applying direct current; measuring the voltage or current between the probe sets to judge the morphology of the crystallization interface; the size and/or direction of the direct current applied to the probe group are changed, and the purpose of accurately controlling the morphology of the crystallization interface is realized, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated. The growth control method and the growth control system can realize the purpose of controlling the crystallization interface in real time so as to accurately control the crystal size; in addition, the control on the crystal size is more accurate, and the process is simpler and more convenient; finally, the introduction of the magnetic field during the whole crystal growth process further improves the overall quality of the crystal.

Description

Growth control method and system for growing silicon carbide crystal based on liquid phase epitaxial method
Technical Field
The invention belongs to the technical field of crystal growth, and particularly relates to a growth control method and a growth control system for growing a silicon carbide crystal based on a liquid phase epitaxy method.
Background
Silicon carbide as a third-generation semiconductor material has the advantages of large forbidden band width, large electron migration rate, high breakdown voltage, high thermal conductivity and the like compared with the traditional semiconductor. The advantages enable the high-power LED lamp to continuously work under severe conditions of high temperature, high pressure, high frequency and the like, and particularly have irreplaceable effects in the fields of aerospace, high-power electronic devices and the like.
At present, there are three main methods for preparing silicon carbide, namely a physical vapor transport method (abbreviated as PVT growth method), a chemical vapor deposition method and a liquid phase epitaxy method (abbreviated as LPE growth method). The silicon carbide crystal prepared by the liquid phase epitaxy method generally does not generate micropipe defects, is low in dislocation density, high in electron mobility and good in crystal quality, and has outstanding advantages in the preparation of P-type crystals, so that the silicon carbide crystal prepared by the method has great application prospects.
In the growth process of the silicon carbide crystal, the traditional PVT growth method or LPE growth method can not monitor and control the growth condition of the crystal, generally a preliminary temperature test is carried out before the beginning of the formal process to obtain preliminary growth information, the power of a heating power supply is adjusted according to the detection result, and the purpose of controlling the size of the grown crystal is achieved by changing the temperature distribution in a furnace body. The crystal interface in the crystal growth process of the method completely depends on the initial placement precision of a thermal field and the initial design, the appearance of the growth interface of the crystal in the growth process cannot be precisely controlled in real time, and the condition of the crystal interface cannot be known in real time, so that a common silicon carbide crystal has a facet, the formation reason of the facet is the autonomy of the crystal, the facet grows slowly under the same growth condition, a large amount of impurity elements exist around the facet, and the color of the region is obviously different from the colors of other regions when the facet is processed into a substrate; on the other hand, there are also many microscopic defects.
Therefore, a growth control method capable of accurately monitoring and controlling the shape of a crystal boundary surface in the process of growing the silicon carbide crystal based on a liquid phase epitaxy method is urgently needed in the field of growth of the silicon carbide crystal, so that the morphology of the crystal boundary in the process of growing the silicon carbide crystal is accurately monitored and controlled, and the growth quality of the silicon carbide crystal is improved.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a growth control method and system for growing a silicon carbide crystal based on a liquid phase epitaxy method, which are used to solve the problems in the prior art that the growth quality of the silicon carbide crystal is reduced, facets and impurity ion aggregation are easily generated, and the like, due to the fact that the crystal interface morphology of the silicon carbide crystal cannot be monitored and controlled in real time during the growth process.
To achieve the above and other related objects, the present invention provides a growth control method for growing a silicon carbide crystal based on liquid phase epitaxy, the growth control method comprising:
1) filling a metal flux and a silicon raw material into a graphite crucible for growing silicon carbide crystals by a liquid phase epitaxy method, and fixing the upper surface of the oriented seed crystal on a lifting mechanism;
2) vacuumizing the crystal growth furnace, and introducing protective gas;
3) heating the crystal growth furnace to a preset temperature by adopting a heater to melt the metal flux and the silicon raw material into a melt, and dissolving graphite in the melt by utilizing the solubility of the melt to the graphite crucible until carbon elements in the melt are saturated;
4) arranging at least one upper probe above the upper surface of the directional seed crystal, correspondingly arranging at least one lower probe below the lower surface of the directional seed crystal respectively, wherein two upper probes and lower probes which are correspondingly arranged up and down form a group of probe groups, and applying direct current or direct current voltage on each group of probe groups to enable the upper probes to be positioned in a low-temperature region above a crystallization interface and the lower probes to be positioned in a high-temperature region below the crystallization interface; determining the current crystal interface morphology of the silicon carbide crystal by moving the lower probe and measuring the current or voltage loaded between each set of probe sets, wherein a certain contact voltage and a certain contact current exist between the silicon carbide crystal and the melt at the crystal interface, and the applied direct current or direct voltage interacts with the contact voltage or contact current to form the measured current or voltage;
and changing the magnitude and/or direction of the direct current applied to each group of probe groups according to the measured current or voltage information, and changing the magnitude and/or direction of the current on the crystallization interface to enable the heat release or heat absorption to be generated above or below the crystallization interface, thereby realizing the purpose of accurately controlling the morphology of the crystallization interface, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated;
5) the silicon carbide crystal is grown by matching the lifting mechanism with the control system of each group of probe sets;
6) annealing the grown silicon carbide crystal;
7) and reducing the temperature in the crystal growth furnace to room temperature, and taking out the silicon carbide crystal.
Optionally, a constant-direction magnetic field device is arranged outside the crystal growth furnace, and the direction of the generated magnetic field is perpendicular to the growth direction of the silicon carbide crystal, so that impurities and metal in the melt are far away from a crystal interface, and the growth quality of the silicon carbide crystal is improved.
Optionally, the magnetic field has a magnetic field strength between 0.1T and 1T.
Optionally, more than two groups of probe sets are correspondingly arranged up and down, the directional seed crystal is divided into more than two sub-regions, and the current or voltage information measured between the probe sets positioned on each sub-region is coupled with each other, so that all the lower probes in the sub-region move towards one direction at the same time.
Optionally, the upper probe is located on the surface of the upper surface of the oriented seed crystal, and the lower probe is located to move downward as the silicon carbide crystal grows; and the probe group determines the current or voltage information measured initially according to the surface morphology of the oriented seed crystal, and the probe group continuously moves the position of the lower probe and adjusts the magnitude and/or direction of the direct current applied to the probe group along with the growth of the silicon carbide crystal, so that the process of adjusting the morphology of the silicon carbide crystal interface in real time is realized.
Optionally, the current crystal interface morphology of the silicon carbide crystal is determined by measuring the current decrease or increase of the probe set at a preset distance between the lower probe and the crystal interface.
Optionally, the metal flux comprises at least one of the group consisting of titanium and germanium; the temperature of the low-temperature region of the upper probe above the crystallization interface is between 1300 ℃ and 1500 ℃, and the temperature of the high-temperature region of the lower probe below the crystallization interface is between 1600 ℃ and 1800 ℃.
Optionally, in the step 2), the vacuum degree of the crystal growth furnace is pumped to 10-4Pa, introducing argon as protective gas; in the step 6), the annealing temperature is between 1000 ℃ and 1200 ℃; in the step 7), the temperature in the crystal growth furnace is reduced to room temperature at the speed of 10-40 ℃/h.
The invention also provides a growth control system for growing silicon carbide crystals based on the liquid phase epitaxy method, which comprises:
the two ends of the direct current power supply are respectively connected to the upper part and the lower part of the crystallization interface of the silicon carbide crystal through at least one group of probe sets;
the monitoring module is used for measuring the current or voltage loaded between each group of probe sets so as to judge the current crystallization interface morphology of the silicon carbide crystal;
the adjusting module is used for adjusting the magnitude and/or direction of direct current applied to each group of probe sets, changing the magnitude and/or direction of current on a crystallization interface, and enabling heat release or heat absorption to be generated above or below the crystallization interface, so that the purpose of accurately controlling the morphology of the crystallization interface is achieved, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated;
and the movement control module is used for acquiring the current crystallization interface morphology information through the monitoring module and controlling the movement of the probe set by matching with the adjusting module.
Optionally, when a difference occurs between a preset value stored in the adjusting module and an actual value measured by the monitoring module, the adjusting module automatically adjusts the magnitude and/or direction of the direct current applied to each group of probe sets, so as to achieve the purpose of accurately controlling the morphology of the crystallization interface.
As mentioned above, the method and system for controlling the growth of the silicon carbide crystal based on the liquid phase epitaxy method achieve the purpose of accurately controlling the size of the silicon carbide crystal by applying direct current or direct voltage to the crystallization interface of the silicon carbide and adjusting the magnitude and/or direction of the direct current in real time, and compared with the traditional method for controlling the size of the silicon carbide crystal, the method and system for controlling the growth of the silicon carbide crystal based on the liquid phase epitaxy method are more accurate in controlling the size of the crystal and simpler and more convenient in process; in addition, in the whole crystal growth process, the influence of impurities is further reduced by introducing the magnetic field, and the overall quality of the silicon carbide crystal is improved.
Drawings
FIG. 1 shows a growth system for growing a silicon carbide crystal by liquid phase epitaxy according to a first embodiment of the invention, schematically in a state where an orientation seed crystal is inserted into the melt without starting crystallization to form a silicon carbide crystal.
FIG. 2 shows a growth system for growing a silicon carbide crystal based on liquid phase epitaxy in accordance with example two of the present invention, schematically illustrating the state in which an oriented seed crystal is extended into the melt and has crystallized to form a silicon carbide crystal.
FIG. 3 shows a growth system for growing a silicon carbide crystal by liquid phase epitaxy according to a third embodiment of the invention, schematically illustrating a state in which a directional seed crystal is inserted into the melt without starting crystallization to form a silicon carbide crystal.
Description of the element reference numerals
1 graphite crucible
2 oriented seed crystal
3 lifting mechanism
4 Probe group
40 upper probe
41 lower probe
5 melting body
6 constant direction magnetic field device
7 silicon carbide crystal
Distance between L lower probe and crystal interface
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 3. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
Example one
As shown in fig. 1, the present embodiment provides a growth control method for growing a silicon carbide crystal based on a liquid phase epitaxy method, which determines the morphology of a crystal interface of the silicon carbide crystal by monitoring the magnitude of current or voltage at two ends of the crystal interface, and adjusts the magnitude and/or direction of a direct current applied to two ends of the crystal interface according to the monitoring result, so as to achieve the purpose of accurately controlling the morphology of the crystal interface.
The growth control method comprises the following steps:
step S1, loading a metal flux and a silicon raw material into a graphite crucible 1 for growing silicon carbide crystals by a liquid phase epitaxy method, and fixing the upper surface of the directional seed crystal 2 on a pulling mechanism 3;
step S2, vacuumizing the crystal growth furnace, and introducing protective gas;
step S3, heating the crystal growth furnace to a preset temperature by a heater, melting the metal flux and the silicon raw material into a melt 5, and dissolving graphite in the melt 5 by utilizing the solubility of the melt 5 to the graphite crucible 1 until carbon in the melt 5 is saturated;
step S4, arranging at least one upper probe 40 above the upper surface of the directional seed crystal 2, respectively arranging at least one lower probe 41 below the lower surface of the directional seed crystal 2, wherein two upper probes 40 and lower probes 41 arranged vertically and correspondingly form a group of probe sets 4 (as shown in fig. 3), and applying a direct current or a direct voltage to each group of probe sets 4 to enable the upper probe 40 to be located in a low-temperature region above a crystallization interface and the lower probe 41 to be located in a high-temperature region below the crystallization interface; determining the current crystal interface morphology of the silicon carbide crystal by moving the lower probe 41 and measuring the current or voltage loaded between each set of probe sets 4, wherein a certain contact voltage and a certain contact current exist between the silicon carbide crystal and the melt at the crystal interface, and the applied direct current or direct voltage interacts with the contact voltage or contact current to form the measured current or voltage;
and changing the magnitude and/or direction of the direct current applied to each group of probe groups according to the measured current or voltage information, and changing the magnitude and/or direction of the current on the crystallization interface to enable the heat release or heat absorption to be generated above or below the crystallization interface, thereby realizing the purpose of accurately controlling the morphology of the crystallization interface, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated;
step S5, finishing the growth of the silicon carbide crystal through the matching of the lifting mechanism and the control system of each group of the probe sets;
step S6, annealing the grown silicon carbide crystal;
and step S7, reducing the temperature in the crystal growing furnace to room temperature, and taking out the silicon carbide crystal.
As an example, in step S1, the silicon raw material is a high-purity silicon lump or silicon powder. The metal flux is selected to be at least one of the group consisting of titanium and germanium. The crystal direction of the oriented seed crystal 2 is selected to be c-direction off-a direction of 4-20 degrees. The lifting mechanism 3 can move up and down, left and right, thereby driving the directional seed crystal 2 to move.
By way of example, in step S2, the crystal growth furnace vacuum degree is pumped to 10-4And introducing argon protective gas in the Pa magnitude.
For example, in step S3, when the metal flux is a titanium and/or germanium material, the preset temperature is preferably between 1400 ℃ and 1700 ℃, and in this case, in step S4, the temperature of the low temperature region of the upper probe 40 above the crystal interface is between 1300 ℃ and 1500 ℃, and the temperature of the high temperature region of the lower probe 41 below the crystal interface is between 1600 ℃ and 1800 ℃.
As shown in fig. 1, as an example, in step S4, the upper probe 40 is located on the surface of the upper surface of the oriented seed crystal 2, the lower probe 41 is located below the lower surface of the oriented seed crystal 2, and the position of the lower probe 41 moves downward along with the growth of the silicon carbide crystal; the probe group 4 determines the current or voltage information measured initially according to the surface morphology of the oriented seed crystal 2, and the process of adjusting the morphology of the silicon carbide crystal interface in real time is realized by continuously moving the position of the lower probe 41 and adjusting the magnitude and/or direction of the direct current applied to the probe group 4 along with the growth of the silicon carbide crystal. In the crystallization process of the silicon carbide crystal, the distance L between the lower probe 41 and a crystallization interface is between 0.5 and 10 mm. Since the material of the melt and the crystal are known, i.e., the resistivity of the material is known, and the current or voltage between the probe sets can be monitored in real time, the resistance of the conductive path (since the silicon carbide crystal is a conductor in a high temperature environment) can be determined, and the crystal thickness of the silicon carbide crystal can be calculated from the resistance, for example: normally, in the process of crystallizing the silicon carbide crystal, keeping the distance L between the lower probe 41 and the crystallization interface unchanged, namely keeping the resistance values of the melts connected in series on the conductive path and the melts in the silicon carbide crystal unchanged, and then obtaining the resistance value of the silicon carbide crystal according to the calculated resistance value on the conductive path, so as to obtain the thickness of the silicon carbide crystal; when the thickness of the obtained silicon carbide crystal differs from the predetermined value (i.e., a difference that becomes larger or smaller), by continuously moving the position of the lower probe 41 and changing the magnitude and/or direction of the direct current applied to each of the probe sets 4, thereby changing the current magnitude and/or current direction on the crystallization interface and generating heat release or heat absorption effect above or below the crystallization interface, because the silicon carbide crystal grows at low temperature, when the direction of the direct current is made to flow from the melt 5 to the silicon carbide crystal (as shown in the current direction I in fig. 1), the crystallization interface has an endothermic effect, the crystallization speed of the silicon carbide crystal slows down or even re-melts, when the direction of the direct current flows from the silicon carbide crystal to the melt 5, the crystallization interface belongs to a heat release effect, and the crystallization speed of the silicon carbide crystal is increased, so that the aim of adjusting the appearance of the crystallization interface of the silicon carbide crystal in real time is fulfilled. Preferably, the current crystal interface morphology of the silicon carbide crystal is determined by measuring the decrease or increase of the current of the probe set 4 at a predetermined distance between the lower probe 41 and the crystal interface.
As an example, in step S6, the annealing temperature is between 1000 ℃ and 1200 ℃. In step S7, the temperature in the crystal growth furnace is reduced to room temperature at a speed of 10 ℃/h-40 ℃/h.
Based on the above growth control method for growing silicon carbide crystal based on the liquid phase epitaxy method, this embodiment further provides a growth control system for growing silicon carbide crystal based on the liquid phase epitaxy method, where the system mainly uses an automatic control circuit for automatically regulating and controlling a crystal interface of the silicon carbide crystal, and the growth control system includes:
the two ends of the direct current power supply are respectively connected to the upper part and the lower part of the crystallization interface of the silicon carbide crystal through at least one group of probe groups 4;
the monitoring module is used for measuring the current or voltage loaded between each group of probe sets 4 so as to judge the current crystallization interface morphology of the silicon carbide crystal;
the adjusting module is used for adjusting the magnitude and/or direction of direct current applied to each group of probe sets 4, changing the magnitude and/or direction of current on the crystallization interface, and enabling heat release or heat absorption to be generated above or below the crystallization interface, so as to achieve the purpose of accurately controlling the morphology of the crystallization interface, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated;
and the movement control module is used for acquiring the current crystallization interface morphology information through the monitoring module and controlling the movement of the probe group 4 by matching with the adjusting module.
As an example, when the preset value stored in the adjusting module is different from the actual value measured by the monitoring module, the adjusting module automatically adjusts the magnitude and/or direction of the direct current applied to each group of the probe sets 4, so as to achieve the purpose of accurately controlling the morphology of the crystal interface.
Example two
As shown in fig. 2, the present embodiment further provides a growth control method for growing a silicon carbide crystal based on liquid phase epitaxy, by which the silicon carbide crystal with a smooth downward convex crystal interface as shown in fig. 2 can be obtained, and the formation of "facets" of the silicon carbide crystal is effectively avoided, the growth control method for growing a silicon carbide crystal based on liquid phase epitaxy in the present embodiment is substantially the same as the growth control method for growing a silicon carbide crystal based on liquid phase epitaxy in the first embodiment, the difference between the two methods is that in step S4, two or more sets of probe sets 4 are disposed above and below the directional seed crystal 2, each set of probe sets 4 monitors and adjusts the crystal interface of silicon carbide crystal in different regions, the control principle is the same as that in the first embodiment, since a plurality of sets of probe sets 4 are disposed, and in order to obtain a downward convex crystal interface, the direction of direct current between the probe sets 4 needs to be controlled, and the lower probe 41 is moved to accelerate the crystal growth of the concave part on the surface of the directional seed crystal 2 and slow down the growth of the part on the surface of the directional seed crystal 2 which grows too fast, so as to obtain a smooth convex-down growth interface and avoid the formation of facets.
As an example, the directional seed crystal 2 is divided into more than two sub-regions, the current or voltage information measured between the probe sets 4 located on each sub-region is coupled with each other, so that all the lower probes in the sub-region move in one direction at the same time, and then the direction of the direct current applied by the probe sets 4 is adjusted, so that the local multilayer crystal interface on the surface of the directional seed crystal can move.
EXAMPLE III
As shown in fig. 3, the present embodiment further provides a growth control method for growing a silicon carbide crystal based on a liquid phase epitaxy method, by which impurities in a crystallization process of the silicon carbide crystal can be reduced, and the crystallization quality of the silicon carbide crystal can be further improved. The growth control method for growing the silicon carbide crystal based on the liquid phase epitaxy method in the embodiment is substantially the same as the growth control method for growing the silicon carbide crystal based on the liquid phase epitaxy method in the embodiment, and the difference between the two methods is that in step S4, a constant direction magnetic field device 6 is further arranged outside the crystal growth furnace, the direction of a magnetic field generated by the constant direction magnetic field device 6 is perpendicular to the growth direction of the silicon carbide crystal, the magnetic field acts on the inside of the crystallization furnace, so that the movement of impurities and metal elements in a melt of the silicon carbide crystal in the crystallization process can be effectively controlled, and the impurities and the metal elements in the melt are far away from a crystallization interface, so that the growth quality of the silicon carbide crystal is improved.
As an example, the magnetic field intensity of the magnetic field generated by the constant direction magnetic field device 6 is between 0.1T and 1T.
In summary, the present invention provides a growth control method and system for growing silicon carbide crystals based on a liquid phase epitaxy method, wherein the method and system achieve the purpose of accurately controlling the size of the silicon carbide crystals by applying a direct current or a direct voltage to the crystallization interface of the silicon carbide and adjusting the magnitude and/or direction of the direct current in real time, and compared with the conventional silicon carbide crystal size control method, the growth control method and system of the present invention have the advantages of more accurate control of the crystal size and simpler and more convenient process; in addition, in the whole crystal growth process, the influence of impurities is further reduced by introducing the magnetic field, and the overall quality of the silicon carbide crystal is improved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims (8)

1. A growth control method for growing a silicon carbide crystal based on a liquid phase epitaxy method is characterized by comprising the following steps:
1) filling a metal flux and a silicon raw material into a graphite crucible for growing silicon carbide crystals by a liquid phase epitaxy method, and fixing the upper surface of the oriented seed crystal on a lifting mechanism;
2) vacuumizing the crystal growth furnace, and introducing protective gas;
3) heating the crystal growth furnace to a preset temperature by adopting a heater to melt the metal flux and the silicon raw material into a melt, and dissolving graphite in the melt by utilizing the solubility of the melt to the graphite crucible until carbon elements in the melt are saturated;
4) arranging at least one upper probe above the upper surface of the directional seed crystal, correspondingly arranging at least one lower probe below the lower surface of the directional seed crystal respectively, wherein two upper probes and lower probes which are correspondingly arranged up and down form a group of probe groups, and applying direct current or direct current voltage on each group of probe groups to enable the upper probes to be positioned in a low-temperature region above a crystallization interface and the lower probes to be positioned in a high-temperature region below the crystallization interface; determining the current crystal interface morphology of the silicon carbide crystal by moving the lower probe and measuring the current or voltage loaded between each set of probe sets, wherein a certain contact voltage and a certain contact current exist between the silicon carbide crystal and the melt at the crystal interface, and the applied direct current or direct voltage interacts with the contact voltage or contact current to form the measured current or voltage;
and changing the magnitude and/or direction of the direct current applied to each group of probe groups according to the measured current or voltage information, and changing the magnitude and/or direction of the current on the crystallization interface to enable the heat release or heat absorption to be generated above or below the crystallization interface, thereby realizing the purpose of accurately controlling the morphology of the crystallization interface, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated; wherein the upper probe is positioned on the surface of the upper surface of the oriented seed crystal, and the lower probe is positioned to move downward as the silicon carbide crystal grows; the probe group determines the current or voltage information measured initially according to the surface morphology of the oriented seed crystal, the position of the lower probe is continuously moved along with the growth of the silicon carbide crystal, and the size and/or direction of the direct current applied to the probe group are adjusted, so that the process of adjusting the morphology of the silicon carbide crystal interface in real time is realized; the current crystallization interface morphology of the silicon carbide crystal is judged by measuring the current decrease or increase of the probe group under the preset distance between the lower probe and the crystallization interface;
5) the silicon carbide crystal is grown by matching the lifting mechanism with the control system of each group of probe sets;
6) annealing the grown silicon carbide crystal;
7) and reducing the temperature in the crystal growth furnace to room temperature, and taking out the silicon carbide crystal.
2. The growth control method according to claim 1, characterized in that: the outside of the crystal growth furnace is provided with a constant direction magnetic field device, and the direction of the generated magnetic field is vertical to the growth direction of the silicon carbide crystal, so that impurities and metal in the melt are far away from a crystal interface, and the growth quality of the silicon carbide crystal is improved.
3. The growth control method according to claim 2, characterized in that: the magnetic field intensity of the magnetic field is between 0.1T and 1T.
4. The growth control method according to claim 1, characterized in that: more than two groups of probe groups are correspondingly arranged up and down, the directional seed crystal is divided into more than two sub-regions, and the current or voltage information measured between the probe groups positioned on each sub-region is mutually coupled, so that all the lower probes in the sub-regions move towards one direction at the same time.
5. The growth control method according to claim 1, characterized in that: the metal flux comprises at least one of the group consisting of titanium and germanium; the temperature of the low-temperature region of the upper probe above the crystallization interface is 1300-1500 ℃, and the temperature of the high-temperature region of the lower probe below the crystallization interface is 1600-1800 ℃.
6. The growth control method according to claim 1, characterized in that: in the step 2), the vacuum degree of the crystal growth furnace is pumped to 10-4Pa, introducing argon as protective gas; in the step 6), the annealing temperature is between 1000 ℃ and 1200 ℃; and 7) reducing the temperature in the crystal growth furnace to room temperature at a speed of 10-40 ℃/h.
7. A growth control system for use in the method for controlling growth of a silicon carbide crystal according to any one of claims 1 to 6, wherein the growth control system comprises:
the two ends of the direct current power supply are respectively connected to the upper part and the lower part of the crystallization interface of the silicon carbide crystal through at least one group of probe sets;
the monitoring module is used for measuring the current or voltage loaded between each group of probe sets so as to judge the current crystallization interface morphology of the silicon carbide crystal;
the adjusting module is used for adjusting the magnitude and/or direction of direct current applied to each group of probe sets, changing the magnitude and/or direction of current on a crystallization interface, and enabling heat release or heat absorption to be generated above or below the crystallization interface, so that the purpose of accurately controlling the morphology of the crystallization interface is achieved, wherein: the current direction flows from the melt to the silicon carbide crystal, so that the crystallization speed of the silicon carbide crystal is reduced; the current direction flows from the silicon carbide crystal to the melt, so that the crystallization speed of the silicon carbide crystal is accelerated;
and the movement control module is used for acquiring the current crystallization interface morphology information through the monitoring module and controlling the movement of the probe set by matching with the adjusting module.
8. The growth control system of claim 7, wherein: when the preset value stored in the adjusting module is different from the actual value measured by the monitoring module, the adjusting module automatically adjusts the size and/or direction of the direct current applied to each group of probe sets, so as to realize the purpose of accurately controlling the morphology of the crystallization interface.
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