WO2020087718A1 - 一种制备碳化硅单晶的坩埚及其应用 - Google Patents

一种制备碳化硅单晶的坩埚及其应用 Download PDF

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Publication number
WO2020087718A1
WO2020087718A1 PCT/CN2018/123711 CN2018123711W WO2020087718A1 WO 2020087718 A1 WO2020087718 A1 WO 2020087718A1 CN 2018123711 W CN2018123711 W CN 2018123711W WO 2020087718 A1 WO2020087718 A1 WO 2020087718A1
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Prior art keywords
crucible
silicon carbide
collar
single crystal
carbide single
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PCT/CN2018/123711
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English (en)
French (fr)
Inventor
高超
刘家朋
李加林
宁秀秀
李长进
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山东天岳先进材料科技有限公司
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Priority claimed from CN201811303469.7A external-priority patent/CN109234801B/zh
Priority claimed from CN201821803138.5U external-priority patent/CN209481848U/zh
Priority claimed from CN201811303468.2A external-priority patent/CN109234800B/zh
Application filed by 山东天岳先进材料科技有限公司 filed Critical 山东天岳先进材料科技有限公司
Publication of WO2020087718A1 publication Critical patent/WO2020087718A1/zh

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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
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed 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
    • C30B29/36—Carbides

Definitions

  • the present application relates to a crucible for preparing silicon carbide single crystal and its application, which belongs to the field of preparation of silicon carbide single crystal.
  • the semiconductor silicon carbide single crystal material is a new generation of semiconductor single crystal material following the first generation semiconductor material represented by silicon material, and the second generation semiconductor material represented by gallium arsenide and indium phosphide. Its excellent physical properties include large forbidden band width, high thermal conductivity, high critical breakdown field strength and high saturation electron mobility, etc. It is the preferred substrate material for power electronic devices and microwave radio frequency devices.
  • silicon carbide single crystal materials have been revealed by scientists as early as the 1950s, but the preparation of electronic grade semiconductor silicon carbide single crystals gradually matured only after the invention of the improved Lely method in 1978. Especially under the technical leadership of CREE in the United States, the size of silicon carbide semiconductor materials has gradually developed from the original 2 inches to 6 inches and 8 inches, and the quality of materials has also continued to improve. However, compared with the excellent physical properties of the material itself and the urgent needs of the downstream application market, the quality improvement and cost reduction of silicon carbide single crystal substrates are still insufficient. This is mainly due to the limitations of physical methods and techniques for preparing silicon carbide single crystal semiconductor materials.
  • the physical vapor transport method is the main preparation method of silicon carbide semiconductor single crystal.
  • PVT physical vapor transport method
  • an intermediate frequency induction coil is used to form a magnetic field
  • a graphite crucible placed in the magnetic field is heated by induction heating to form a thermal field for silicon carbide single crystal growth.
  • the powder required for growing silicon carbide single crystal placed inside the graphite crucible is sublimated at high temperature to release gas phase components such as Si, Si 2 C, and SiC 2 and transported to the seed crystal for crystallization.
  • the existing technology includes: 1. The crucible is replaced after each growth cycle, which depends on the consistency of the crucible and the high cost of the graphite crucible, which does not help to reduce the manufacturing cost of silicon carbide single crystal. 2. Usually the thermal field and growth parameters will be fine-tuned during the growth period of silicon carbide single crystal to offset the thermal field change caused by the loss of graphite crucible. In the prior art, the thermal field is partially adjusted by moving the crucible position, and the patent CN107604439A passes Move the induction coil to adjust the thermal field of different growth cycles.
  • the above technologies all require complex equipment transformation and equipment control, which is not conducive to the reduction of the production cost of silicon carbide single crystals.
  • the present application provides a crucible for preparing silicon carbide single crystals.
  • a screw thread and a matching collar are added to the outside of the crucible body to realize rapid conversion of the crucible heating area, thereby improving the repeatability and stability of the thermal field.
  • the crucible structure of the present application is simple and easy to adjust, which can quickly and conveniently adjust the thermal field, and at the same time greatly reduce the manufacturing cost of silicon carbide single crystal and silicon carbide single crystal and single crystal substrate.
  • the crucible for preparing silicon carbide single crystal is characterized in that the crucible includes: a crucible body and at least one collar, the collar is disposed outside the crucible body, and the collar can move axially along the crucible body Collar.
  • At least one collar there is at least one collar, and multiple collars can also be used in combination.
  • the outer surface of the side wall of the crucible body and the inner surface of the collar are connected by threads.
  • an external thread is made on the outer surface of the side wall of the crucible body, so that the whole body of the crucible body has a screw structure; a collar structure is prepared, and the inner diameter of the collar is equal to the outer diameter of the crucible body and the internal thread structure is also prepared on the inside of the collar
  • the overall structure of the collar is a nut structure matched with the main body of the crucible.
  • the pitch of the thread is 0.2-2 mm.
  • the lower limit of the pitch value of the thread is selected from 0.5mm, 0.7mm, 1.0mm, 1.3mm or 1.5mmm
  • the upper limit is selected from 0.5mm, 0.7mm, 1.0mm, 1.3mm, 1.5mmm or 1.7mm.
  • the setting of the thread pitch of the present application makes the movement of the collar sufficiently accurate.
  • the pitch of the thread is 0.3-1.5 mm.
  • the projection height of the collar onto the crucible body is 5-15 mm.
  • the lower limit of the projection height of the collar to the crucible body is selected from 7 mm, 10 mm, 12 mm or 14 mm, and the upper limit is selected from 7 mm, 10 mm, 12 mm or 14 mm.
  • the projection height of the collar onto the crucible body is 7-13 mm.
  • the ratio of the projection height of the collar to the crucible body and the height of the crucible body is 1: 5-20.
  • the lower limit of the ratio of the projection height of the collar to the crucible body and the height of the crucible body is selected from 1: 7, 1:10, 1:12, 1:14 or 1:18, and the upper limit is selected from 1: 7, 1:10, 1:12, 1:14 or 1:18.
  • the ratio of the projection height of the collar to the crucible body and the height of the crucible body is 1: 7-18.
  • the projection height of the collar of the present application onto the crucible body allows the collar to cover enough thermal field area when moving to meet the thermal field adjustment requirements.
  • the thickness of the collar is 5-25 mm.
  • the lower limit of the thickness of the collar is selected from 7mm, 10mm, 15mm, 20mm or 23mm
  • the upper limit is selected from 7mm, 10mm, 15mm, 20mm or 23mm.
  • the thickness of the collar is 7-20 mm. The thickness of the collar of the present application balances the efficiency of heat blocking and heat conduction into the crucible body after the collar itself generates heat due to the skin effect.
  • the outer wall of the crucible body has a logo, and the logo may mark the position of the collar.
  • the mark is a scale mark.
  • the crucible is heated by induction heating; preferably, the heating device includes an intermediate frequency induction coil.
  • the heating device includes an intermediate frequency induction coil.
  • a single crystal of silicon carbide is prepared using the PVT method, and an intermediate frequency induction coil is used to inductively heat the crucible.
  • the crucible body is a graphite crucible
  • the collar is a graphite collar
  • the apparatus for preparing a silicon carbide single crystal including a crucible includes a seed crystal unit, and the seed crystal unit is disposed above the opening of the graphite crucible.
  • the seed crystal unit includes a carbonized single crystal seed crystal.
  • the PVT method refers to the physical vapor transport method.
  • a crystal growth apparatus characterized by comprising the crucible described in any one of the above.
  • the uneven current distribution inside the conductor causes the current to concentrate on the surface of the crucible.
  • the heating of the crucible is mainly concentrated on the surface and is conducted to the inside of the crucible by heat conduction.
  • the inside of the crucible changes due to the erosion of the silicon atmosphere, which affects the heat generation and conduction of the crucible, which in turn leads to changes in the thermal field.
  • the form of the change is usually manifested as the axial movement of the high temperature zone inside the crucible.
  • the crucible of this application can adjust and correct the thermal field by adjusting the position of the collar nested outside the crucible body without changing the position of the coil and the crucible.
  • the principle is based on the skin effect, the magnetic field of the intermediate frequency coil Acting on the outermost collar, the collar heats up and conducts heat to the inside of the crucible body. Because the collar is nested outside the crucible body, its heat transfer requires a longer transmission distance than the direct heating of the crucible body wall and conduction to the interior of the crucible body, so that the local thermal field in the crucible body is affected by the collar Changes, in turn, play a role in regulating the thermal field.
  • the crucible when used for a specific period, it is adjusted by rotating the collar to a specific position of the crucible body, and after the crystal growth is completed, the direction of the thermal field change is determined according to the loss of the crucible. If the high temperature zone moves upward in the axial direction and needs to be corrected in the next growth cycle, by rotating the graphite collar axially to the corresponding high temperature zone to the desired temperature zone position, the temperature in the high temperature zone caused by the previous cycle will be The temperature drops to restore the thermal field to the thermal field conditions close to the previous cycle.
  • this application can also design specific thermal fields in a targeted manner.
  • the design method of the thermal field is as follows: if the temperature where the seed crystal is placed needs to be designed to be low, the graphite collar is rotated to the place where the seed crystal is placed, thereby reducing the temperature where the seed crystal is placed; if the temperature between the seed crystal and the raw material is required If it is lowered, the graphite collar will be rotated to the position between the seed crystal and the raw material, and the temperature in this area will be reduced accordingly.
  • a specific thermal field area can be formed in a targeted manner, and the gas phase transmission path inside the crucible can be changed, thereby achieving fast and effective thermal field and fluid control.
  • the high temperature area refers to the area with the highest relative temperature in the crystal growth chamber. In this area, the heat is concentrated and the silicon carbide powder is sublimated the most.
  • the powder placed in the area is the main supply source of the atmosphere required for silicon carbide crystal growth.
  • the corresponding low temperature area in the chamber is the crystallization area of silicon carbide powder and the growth area of silicon carbide single crystal.
  • the position of the high-temperature region in the growth chamber can be identified according to the degree of sublimation of the silicon carbide powder after the first cycle of crystal growth.
  • the graphite insulation felt and graphite crucible used to form the thermal field of crystal growth will have a certain loss, and their physical and chemical properties will also drift. Therefore, in order to repeat the growth of the second cycle of crystals, it is necessary to perform simple and rapid adjustment of the high temperature region under the condition of repeated use of the previous thermal field.
  • the specific method is: after the first cycle of growth is completed, determine whether the high temperature region is located The preset position of the chamber; if it is, according to the crystal growth law, the high temperature region of the thermal field will drift towards the seed end after a round of crystal growth. In order to hedge the thermal field drift, the collar will be moved in the direction of the thermal field drift accordingly .
  • the adjustment amount is determined according to the crystal surface convexity. If the convexity change is large, the position of the adjustment collar is relatively large. If the convexity exceeds 1 times, the adjustment collar is moved up by 20mm; if the convexity is within the range of the crystal design, the adjustment amount can be smaller Not even adjusted.
  • the crucible body is a graphite crucible
  • the collar is a graphite collar
  • the present application provides an adjustable thermal field structure for preparing a silicon carbide single crystal.
  • the thermal field structure is provided with a screw thread and a matching collar device on the outside of the crucible body to achieve the crucible heating area. Fast conversion, thereby improving the repeatability and stability of the thermal field.
  • the thermal field structure is simple and easy to adjust, which can quickly and conveniently realize the thermal field adjustment, and at the same time greatly reduce the manufacturing cost of silicon carbide single crystal and single crystal substrate.
  • At least one sleeve ring movable along the axial direction of the crucible body is sleeved on the outside of the crucible body.
  • the heating device uses an induction method to heat the crucible.
  • the heating device includes an intermediate frequency induction coil.
  • a silicon carbide single crystal is prepared using the PVT method, and an intermediate frequency induction coil is used to inductively heat the graphite crucible.
  • a seed crystal unit is provided in the thermal field structure, and the seed crystal unit is provided above the opening of the graphite crucible.
  • the seed crystal unit includes a carbonized single crystal seed crystal.
  • the PVT method refers to the physical vapor transport method.
  • a method for preparing a silicon carbide single crystal characterized in that the crucible or the thermal field structure described in any one of the above is used for the preparation.
  • a method for improving the quality of continuously growing silicon carbide single crystals uses the outside of the crucible body to add threads and a matching collar device to achieve rapid conversion of the crucible heating area, thereby increasing heat Field repeatability and stability.
  • a simple and easy-to-adjust thermal field structure is formed, which can quickly and conveniently realize the thermal field adjustment, and at the same time greatly reduce the manufacturing cost of silicon carbide single crystal and silicon carbide single crystal and single crystal substrate.
  • the method for improving the quality of silicon carbide single crystal prepared by continuous growth includes at least a first growth cycle and a second growth cycle of silicon carbide single crystal growth.
  • the method is characterized in that the method includes the following steps:
  • the first growth cycle place the long crystal raw material in the crucible, and nest at least one collar on the first position of the crucible body wall, the high temperature area inside the crucible is at the first height during the long crystal growth, the first Silicon carbide single crystal;
  • Second growth cycle Place the long crystal raw material in the crucible, adjust the position of the collar nested on the wall of the crucible body, so that the high temperature area inside the crucible during the second growth cycle of the long crystal is roughly at the first height
  • the second silicon carbide single crystal
  • the distance between the collar and the seed crystal in the first growth cycle is greater than or equal to the distance between the collar and the seed crystal in the second growth cycle.
  • the position of the high-temperature region in the growth chamber can be identified according to the degree of sublimation of the silicon carbide powder after the first cycle of crystal growth.
  • the first growth cycle includes: placing a long crystal raw material in a crucible, and nesting at least one collar on a first position of the crucible body wall to prepare a first silicon carbide having a first convexity Single crystal
  • the second growth cycle includes: adjusting the position where the collar is nested on the wall of the crucible body according to the first convexity of the first growth cycle, and placing the long crystal raw material in the crucible to obtain a second convexity Silicon carbide single crystal.
  • the first silicon carbide single crystal has a first convexity, the first convexity is not greater than 8 mm; the second silicon carbide single crystal has a second convexity, the second convexity is not greater than 8mm.
  • the time for adjusting the position of the nesting ring on the wall of the crucible body is the weight or density change of the crucible in the first growth cycle;
  • the graphite insulation felt and graphite crucible used to form the thermal field of crystal growth will have a certain loss, and their physical and chemical properties will also drift. Therefore, in order to repeat the growth of the second cycle of crystals, it is necessary to perform simple and rapid adjustment of the high temperature region under the condition of repeated use of the previous thermal field.
  • the specific method is: after the first cycle of growth is completed, determine whether the high temperature region is located The preset position of the chamber; if it is, according to the crystal growth law, the high temperature region of the thermal field will drift towards the seed end after a round of crystal growth. In order to hedge the thermal field drift, the collar will be moved in the direction of the thermal field drift accordingly .
  • the adjustment amount is determined according to the crystal surface convexity. If the convexity change is large, the position of the adjustment collar is relatively large. If the convexity exceeds 1 times, the adjustment collar is moved up by 20mm; if the convexity is within the range of the crystal design, the adjustment amount can be smaller Not even adjusted.
  • the method for preparing the first silicon carbide single crystal and / or the second silicon carbide single crystal includes the following steps:
  • the 4-inch single crystal substrate prepared from the first silicon carbide single crystal and the second silicon carbide single crystal has a curvature of 6-13 ⁇ m.
  • the outer surface of the side wall of the crucible body and the inner surface of the collar are connected by threads.
  • an external thread is made on the outer surface of the crucible body, so that the whole body of the crucible body has a screw structure; a collar structure is prepared, and the inner diameter of the collar is equal to the outer diameter of the crucible body and the internal thread structure is also prepared on the inside of the collar
  • the whole ring has a nut structure matched with the main body of the crucible.
  • the pitch of the thread is 0.2-2 mm.
  • the lower limit of the range of the change value of the first distance is selected from 0.5mm, 0.7mm, 1.0mm, 1.3mm or 1.5mmm
  • the upper limit is selected from 0.5mm, 0.7mm, 1.0mm, 1.3mm, 1.5mmm or 1.7mm.
  • the setting of the thread pitch of the present application makes the movement of the collar sufficiently accurate.
  • the pitch of the thread is 0.3-1.5 mm.
  • the projection height of the collar onto the crucible body is 5-15 mm.
  • the lower limit of the height of the collar is selected from 7mm, 10mm, 12mm or 14mm, and the upper limit is selected from 7mm, 10mm, 12mm or 14mm.
  • the height of the collar is 7-13 mm.
  • the ratio of the projection height of the collar to the crucible body and the height of the crucible body is 1: 5-20.
  • the lower limit of the ratio of the height of the collar to the height of the crucible body is selected from 1: 7, 1:10, 1:12, 1:14 or 1:18, and the upper limit is selected from 1: 7 and 1: 10. 1:12, 1:14 or 1:18.
  • the ratio of the height of the collar to the height of the crucible body is 1: 7-18.
  • the height of the collar of the present application allows the collar to cover enough thermal field area when moving to meet the thermal field adjustment requirements.
  • the thickness of the collar is 5-25 mm.
  • the lower limit of the thickness of the collar is selected from 7mm, 10mm, 15mm, 20mm or 23mm
  • the upper limit is selected from 7mm, 10mm, 15mm, 20mm or 23mm.
  • the thickness of the collar is 7-20 mm. The thickness of the collar of the present application balances the efficiency of heat blocking and heat conduction into the crucible after the collar itself generates heat due to the skin effect.
  • the crucible body is a graphite crucible
  • the collar is a graphite collar
  • the outer wall of the crucible body has a logo, and the logo may mark the position of the collar.
  • the mark is a scale mark.
  • a scale mark can be made on the outside of the graphite crucible to accurately record the position of the collar along the axis of the graphite crucible
  • At least one sleeve ring movable along the axial direction of the crucible body is sleeved on the outside of the crucible body.
  • the heating device used in the crucible is an induction heating method; preferably, the heating device includes an intermediate frequency induction coil.
  • the heating device includes an intermediate frequency induction coil.
  • a silicon carbide single crystal is prepared using the PVT method, and an intermediate frequency induction coil is used to inductively heat the graphite crucible.
  • the crucible body is a graphite crucible
  • the collar is a graphite collar
  • the method for continuously preparing silicon carbide single crystals includes the following steps:
  • the graphite collar After placing the silicon carbide powder and the seed crystal for crystal growth in the graphite crucible and closing the graphite crucible, the graphite collar is nested in the topmost area of the graphite crucible body. Accurately record the position of the graphite collar along the axis of the graphite crucible body;
  • the silicon carbide single crystal is taken out to obtain the corrected silicon carbide single crystal, and the first convexity is controlled within 8 mm;
  • the carbonized single crystal seed crystal is above the opening of the graphite crucible.
  • the PVT method refers to the physical vapor transport method.
  • a screw thread and a matching graphite collar device are added on the outside of the crucible body to realize the rapid conversion of the crucible heating area, which can quickly and conveniently adjust the thermal field, and greatly reduce the silicon carbide The manufacturing cost of single crystal.
  • the crucible and method of the present application can adjust and correct the thermal field by adjusting the position of the collar nested outside the crucible body without changing the position of the induction heating coil and the crucible.
  • the thermal field is determined according to the loss of the crucible Change direction.
  • This application can also design a specific thermal field in a targeted manner, can form a specific thermal field area in a targeted manner, and change the gas phase transmission path inside the crucible, so as to achieve fast and effective thermal field and fluid control.
  • the continuous preparation method of silicon carbide single crystal of the present application has lower requirements on equipment, which is beneficial to reduce the manufacturing cost of silicon carbide single crystal.
  • the method for improving the quality of the continuous growth silicon carbide single crystal of the present application can realize the thermal field adjustment by simply adjusting the position of the graphite sleeve, which is convenient and fast, improves the thermal field repeatability, and is beneficial to the preparation of high quality stability and consistency of carbonization Silicon single crystal.
  • FIG. 1 is a schematic diagram of a thermal field structure including a crucible according to an embodiment of the present application.
  • FIG. 2 is a graph showing the change in the convexity of a silicon carbide single crystal that has been continuously grown 6 times in an example and a comparative example according to this application.
  • the terms “installation”, “connected”, “connected”, “fixed” and other terms should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection, electrical connection, or communication; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components .
  • installation can be a fixed connection or a detachable connection , Or integrated; it can be mechanical connection, electrical connection, or communication; it can be directly connected or indirectly connected through an intermediary, it can be the connection between two components or the interaction between two components .
  • the first feature is “on” or “under” the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly through an intermediary contact.
  • the description referring to the terms “one embodiment”, “some embodiments”, “examples”, “specific examples”, or “some examples” means specific features described in conjunction with the embodiment or examples , Structure, material or characteristic is included in at least one embodiment or example of the present application.
  • the schematic expressions of the above terms are not necessarily directed to the same embodiment or example.
  • the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
  • an embodiment of the present application discloses an adjustable thermal field structure for continuously preparing silicon carbide single crystals.
  • the thermal field structure includes a crucible and a heating device.
  • the crucible includes a crucible body 4 and a collar 3, and the exterior of the crucible body 4 Set an adjustable collar 3.
  • the collar 3 and the crucible body 4 are connected by a screw thread 5, and the entire outer wall of the crucible body 4 has a screw thread 5.
  • the collar 3 may be a graphite collar.
  • the pitch is set to 0.2-2 mm
  • the height of the graphite collar is set to 5-15 mm
  • the thickness of the graphite collar is 5-25 mm.
  • the pitch is set to 0.5 mm
  • the height of the graphite collar is set to 10 mm
  • the thickness of the graphite collar is 15 mm.
  • the crucible body 4 may be a graphite crucible, but is not limited to a graphite crucible, and may be any material used for preparing silicon carbide single crystals.
  • the thermal insulation structure 1 is made of a material with thermal insulation, such as graphite thermal insulation felt.
  • the heating device heats the crucible by medium induction heating, the heat preservation structure 1 is arranged outside the crucible, and the heating device is arranged outside the heat preservation structure 1.
  • the silicon carbide single crystal powder 6 is placed in the crucible.
  • the thermal field structure has a seed crystal unit disposed at the opening of the graphite crucible.
  • the seed crystal unit includes a carbonized single crystal seed crystal 2.
  • the thermal field is adjusted and corrected by adjusting the position of the graphite collar nested outside the graphite crucible body, and the magnetic field of the intermediate frequency coil acts on the outermost On the graphite collar, the graphite collar heats up and conducts heat to the interior of the graphite crucible.
  • the graphite collar is nested outside the body of the crucible, its heat transmission requires a longer transmission distance than the direct heating of the graphite crucible body wall and conduction to the interior of the graphite crucible, so that the local thermal field in the graphite crucible is affected by the graphite collar Influence and change, and then play a role in regulating the thermal field.
  • the graphite crucible when used for a specific period, it is adjusted by rotating the graphite collar to a specific position of the graphite crucible, and after the silicon carbide single crystal growth is completed, the direction of thermal field change is determined according to the graphite crucible loss . If the high temperature zone moves upward in the axial direction and needs to be corrected in the next growth cycle, by rotating the graphite collar axially to the corresponding high temperature zone to the desired temperature zone position, the temperature in the high temperature zone caused by the previous cycle will be The temperature drops to restore the thermal field to the thermal field conditions close to the previous cycle.
  • the adjustment amount is determined according to the crystal surface convexity. If the convexity change is large, the position of the adjustment collar is relatively large. If the convexity exceeds 1 times, the adjustment collar is moved up by 20mm; if the convexity is within the range of the crystal design, the adjustment amount can be smaller Not even adjusted.
  • a specific thermal field can also be designed in a targeted manner.
  • the design method of the thermal field is as follows: If the temperature at which the seed crystal is placed needs to be designed to be low, rotate the graphite collar to the seed crystal placement, so that the temperature at the seed crystal placement can be reduced; if the temperature between the seed crystal and the raw material is required If it is lowered, the graphite collar will be rotated to the position between the seed crystal and the raw material, and the temperature in this area will be reduced accordingly.
  • a specific thermal field area can be formed in a targeted manner, and the gas phase transmission path inside the crucible can be changed, thereby achieving fast and effective thermal field and fluid control.
  • a plurality of graphite collars can be designed and used in combination according to the thermal field.
  • the edge thickness of the silicon carbide single crystal is less than the center thickness, and the difference (convexity) between the center and edge thickness of the silicon carbide single crystal is 2 ⁇ 20mm.
  • the greater the convexity the worse the uniformity of the thermal field in the radial direction, and the worse the stress of the corresponding silicon carbide single crystal.
  • the resulting silicon carbide single crystal substrate often has quality problems such as greater curvature and warpage; The unevenness of the field leads to uneven distribution of impurities in the silicon carbide single crystal in the radial direction, which causes the unevenness of the resistivity within the surface of the silicon carbide single crystal substrate to become larger.
  • the reasonable silicon carbide single crystal convexity should be controlled within 8mm, and it will remain unchanged with the loss after repeated use of the graphite crucible and graphite insulation blanket to ensure the consistency and stability of the quality of the silicon carbide single crystal and the substrate Sex. Further, the silicon carbide single crystal convexity should be controlled within 5 mm.
  • the silicon carbide single crystal is prepared by using the thermal field structure prepared in the above embodiment, and the specific application method is as follows:
  • the graphite collar After placing the silicon carbide powder and the seed crystal for crystal growth in the graphite crucible and closing the graphite crucible, the graphite collar is nested in the topmost area of the graphite crucible body. Accurately record the position of the graphite collar along the axis of the graphite crucible body;
  • the silicon carbide single crystal is taken out to obtain the corrected silicon carbide single crystal, and the second convexity is controlled within 5 mm;
  • FIG. 2 is a graph showing the change in the convexity of a silicon carbide single crystal grown continuously six times in an example and a comparative example (conventional method).
  • the conventional method is: after using the same set of materials in the same equipment for 6 rounds of continuous growth of 4 inches of silicon carbide single crystal, the thermal field will gradually change with the loss of graphite insulation felt and graphite crucible, resulting in the convexity of silicon carbide single crystal Gradually increasing, the consistency and stability of the silicon carbide single crystal become worse, as shown in line A in Figure 2; while using the thermal field structure and thermal field adjustment method described in this application for thermal field correction adjustment, the continuous growth of The convexity of the 6-round crystal can be kept consistent, so that the silicon carbide crystal and the substrate with excellent consistency and stability can be obtained, as shown in line B in FIG. 2.
  • the curvature value of the silicon carbide single crystal substrate prepared by the conventional method is distributed between 15-39 ⁇ m, and the value is large and discrete; use
  • the substrate curvature value prepared by the thermal field structure and method of the present application is distributed between 6-13 ⁇ m, and the silicon carbide single crystal substrate has better surface quality and higher consistency.

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Abstract

本申请公开了一种制备碳化硅单晶的坩埚及其应用，属于碳化硅单晶的制备领域。该制备碳化硅单晶的坩埚包括坩埚主体和至少一个套环，所述套环设置在坩埚主体的外部，所述套环可沿坩埚主体轴向移动。本申请的坩埚在坩埚主体外侧增加螺纹及配套的套环，实现坩埚发热区的快速转换，能够快速便捷的实现热场的调整，同时大大降低碳化硅单晶、单晶衬底的制造成本。该提高连续生长碳化硅单晶品质的方法可通过简单的调节坩埚主体与套环的相对位置，不需要更换坩埚即可连续制备凸率均匀的碳化硅单晶；并且可针对性的设计特定热场，改变坩埚内部的气相传输路径，从而实现快捷有效的热场和流体控制。

Description

一种制备碳化硅单晶的坩埚及其应用 技术领域
本申请涉及一种制备碳化硅单晶的坩埚及其应用，属于碳化硅单晶的制备领域。
背景技术
半导体碳化硅单晶材料是继以硅材料为代表的第一代半导体材料、砷化镓和磷化铟等为代表的第二代半导体材料之后的新一代半导体单晶材料。其优异的物理性能包括较大的禁带宽度、高导热系数、高临界击穿场强和高饱和电子迁移率等，是功率电子器件、微波射频器件的优选衬底材料。
碳化硅单晶材料的优异性能早在20世纪50年代就已被科学家揭晓，但直至1978年改良Lely法发明之后，电子级半导体碳化硅单晶的制备才逐渐成熟。特别是在美国CREE公司的技术引领下，碳化硅半导体材料的尺寸从最初的2英寸逐渐发展至6英寸和8英寸，材料质量也不断提高。然而，相较于材料本身的优异的物理性能和下游应用市场的迫切需求，碳化硅单晶衬底的质量提升和成本降低仍显不足。这主要是由于制备碳化硅单晶半导体材料的物理方法和技术所限。
目前，物理气相输运法(PVT)是碳化硅半导体单晶主流的制备方法。在PVT法中，使用中频感应线圈形成磁场，放置在磁场内的石墨坩埚通过感应加热形成碳化硅单晶生长的热场。石墨坩埚内部放置的生长碳化硅单晶所需的粉料在高温下升华释放出Si、Si 2C、SiC 2等气相组分并传输至籽晶处结晶。由于石墨坩埚内部的硅组分会对石墨坩埚内壁造成侵蚀，因此石墨坩埚在重复使用的过程中其所形成的热场必然会发生变化，从而影响到碳化硅晶体生长的可重复性和衬底质量的一致性。
为了解决这一问题，现有的技术包括：1、每个生长周期后进行坩埚更换，这取决于坩埚质量是否一致，且石墨坩埚成本高昂，无助于碳化硅单晶制造成本的降低。2、通常在碳化硅单晶生长周期内会进行热场和生长参数的微调，以抵消石墨坩埚损耗引起的热场变化，现有技术中部分通过移动坩埚位置来调节热场，和专利CN107604439A通过移动感应线圈进行不同生长周期的热场调节。然而，以上述技术都需要复杂的设备改造和设备控制，不利于碳化硅单晶制备成本的降低。
发明内容
为了解决上述问题，本申请提供了一种制备碳化硅单晶的坩埚，在坩埚主体外侧增加螺纹及配套的套环，实现坩埚发热区的快速转换，从而提高热场重复性和稳定性。本申请的坩埚结构简单、易调整，能够快速便捷的实现热场的调整，同时大大降低碳化硅单晶及碳化硅单晶、单晶衬底的制造成本。
所述的制备碳化硅单晶的坩埚，其特征在于，所述坩埚包括：坩埚主体和至少一个套环，所述套环设置在坩埚主体的外部，所述套环可沿坩埚主体轴向移动套环。
可选地，所述套环至少为1个，也可以多个套环组合使用。
可选地，所述坩埚主体的侧壁外表面与所述套环的内表面通过螺纹连接。作为一种实施方式，在坩埚主体侧壁外表面制作外螺纹，使坩埚主体圆柱整体呈螺杆结构；制备套环结构，套环内径与坩埚主体外径相等且套环内侧同样制备内螺纹结构，使套环整体呈与坩埚主体相匹配的螺母结构。
可选地，所述螺纹的螺距为0.2‐2mm。进一步地，所述螺纹的螺距值下限选自0.5mm、0.7mm、1.0mm、1.3mm或1.5mmm，上限选自0.5mm、 0.7mm、1.0mm、1.3mm、1.5mmm或1.7mm。本申请的螺纹螺距的设置使得套环的移动足够精准。进一步地，所述螺纹的螺距为0.3‐1.5mm。
可选地，所述套环到所述坩埚主体的投影高度为5‐15mm。进一步地，所述套环到所述坩埚主体的投影高度的下限选自7mm、10mm、12mm或14mm，上限选自7mm、10mm、12mm或14mm。可选地，所述套环到所述坩埚主体的投影高度为7‐13mm。
可选地，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值为1：5‐20。进一步地，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值的下限选自1：7、1：10、1：12、1：14或1:18，上限选自1：7、1：10、1：12、1：14或1:18。更进一步地，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值为1：7‐18。本申请的套环到所述坩埚主体的投影高度使得套环在移动时可以覆盖足够的热场区域满足热场调整需求。
可选地，所述套环的厚度为5‐25mm。进一步地，所述套环的厚度的下限选自7mm、10mm、15mm、20mm或23mm，上限选自7mm、10mm、15mm、20mm或23mm。更进一步地，所述套环的厚度为7‐20mm。本申请的套环的厚度平衡了套环本身因集肤效应发热后热阻断与热传导至坩埚主体内的效率。
可选地，所述坩埚主体的外壁具有标识，所述标识可标记套环的位置。优选地，所述标识为刻度标记。
可选地，所述对所述坩埚使用加热装置进行感应加热；优选地，所述加热装置包括中频感应线圈。作为一种实施方式，使用PVT法制备碳化硅单晶，使用中频感应线圈感应加热坩埚。
可选地，所述的坩埚主体为石墨坩埚，所述的套环为石墨套环。
可选地，包括坩埚制备碳化硅单晶的装置包括籽晶单元，所述籽晶 单元设置在所述石墨坩埚开口上方。所述籽晶单元包括碳化单晶籽晶。
本申请中，PVT法，是指物理气相输运法。
根据本申请的另一方面，提供了一种晶体生长装置，其特征在于，包括上述任一项所述的坩埚。
根据集肤效应，导体中存在交变电磁场时，其内部的电流分布不均匀导致电流集中在坩埚表面，坩埚加热主要集中在表面并通过热传导至坩埚内部。随着晶体生长周期的加长，坩埚内部受硅气氛侵蚀而发生变化，影响坩埚热量的产生和传导，进而导致热场的变化，其变化的形式通常表现为坩埚内部高温区的轴向移动。通常为了对这种变化的热场进行校正，需要改进设备对坩埚和中频线圈的轴向相对位置进行调整，以改变坩埚在磁场中的轴向位置和发热中心，从而实现对温区位置的固化。
本申请的坩埚可以在不改变线圈和坩埚位置的情况下，通过调整嵌套于坩埚主体外侧的套环的位置进行热场的调整和校正，其原理即是基于集肤效应，中频线圈的磁场作用于最外侧的套环上，套环发热后将热量传导至坩埚主体内部。由于套环嵌套于坩埚主体外侧，其热量传输相较于坩埚主体壁直接发热并传导至坩埚主体内部需要更长的传输距离，从而使得坩埚主体内部局部区域的热场受套环影响而发生变化，进而起到调节热场的作用。
本申请中当坩埚使用特定周期后，通过以下方式调节：将套环旋转至坩埚主体特定位置，晶体生长结束后，根据坩埚的损耗情况确定热场变化方向。如高温区沿轴向向上移动，需要在下一生长周期进行校正，则通过向相应的高温区方向沿轴向旋转石墨套环至所需温区位置，则上一周期造成的高温区区域温度会下降，从而使热场恢复至接近上一周期的热场条件下。
除以上进行不同生长周期的热场调整外，本申请还可以针对性的设 计特定热场。热场设计方式如下：如果需要设计籽晶放置处的温度较低，则将石墨套环旋转至籽晶放置处，从而可以降低籽晶放置处的温度；如果需要籽晶和原料之间的温度降低，则将石墨套环旋转至籽晶与原料之间的位置，则该区域的温度相应的降低。通过这些调整，可以针对性的形成特定的热场区域，改变坩埚内部的气相传输路径，从而实现快捷有效的热场和流体控制。
所述高温区是指晶体生长腔室内相对温度最高的区域，在此区域内热量最集中、碳化硅粉料升华最充分，区域内所置粉料是碳化硅晶体生长所需气氛的主要供应源；其对应的腔室内低温区域为碳化硅粉料的结晶区及碳化硅单晶生长区。
本申请中根据第一周期晶体生长结束后的碳化硅粉料升华程度，可以识别出生长腔室内的高温区位置。
经过一轮晶体生长周期后，用于形成晶体生长热场的石墨保温毡和石墨坩埚都会有一定损耗，同时其理化性质也会发生漂移。因此，为重复生长第二个周期的晶体，需要在重复使用上一热场的条件下，进行简单快速的高温区调整，具体方法为:当第一周期生长结束后，判断高温区位置是否在腔室预设位置；如果是，根据晶体生长规律，热场高温区在经过一轮晶体生长后会向籽晶端漂移，为了对冲热场漂移，将套环相应的向热场漂移方向进行移动。
作为一种调整套环的方法，如果晶体生长后坩埚及保温毡密度或重量发生变化，则可以判定热场会发生变化，需要在下一周期进行热场调整。调整量根据晶体表面凸率确定。若凸率变化较大，则相应调整套环的位置较大，如凸率超过预设的1倍，则调整套环上移20mm；凸率在晶体设计的范围内，则调整量可以较小甚至不调整。
优选地，所述的坩埚主体为石墨坩埚，所述的套环为石墨套环。
根据本申请的另一方面，本申请提供了一种用于制备碳化硅单晶的可调节热场结构，该热场结构在坩埚主体外侧增加螺纹及配套的套环装置，实现坩埚发热区的快速转换，从而提高热场重复性和稳定性。该热场结构简单、易调整，能够快速便捷的实现热场的调整，同时大大降低碳化硅单晶和单晶衬底的制造成本。
所述的用于制备碳化硅单晶的可调节热场结构，其特征在于，所述热场结构包括：
坩埚，放置用于生长碳化硅单晶的原料；
加热装置，加热所述坩埚；
所述坩埚主体外部至少套设一个可沿坩埚主体轴向移动的套环。
可选地，所述加热装置对所述坩埚使用感应方式进行加热。优选地，所述加热装置包括中频感应线圈。作为一种实施方式，使用PVT法制备碳化硅单晶，使用中频感应线圈感应加热石墨坩埚。
可选地，该热场结构中设置籽晶单元，该籽晶单元设置在该石墨坩埚开口上方。该籽晶单元包括碳化单晶籽晶。
本申请中，PVT法，是指物理气相输运法。
根据本申请的另一方面，提供了一种碳化硅单晶的制备方法，其特征在于，使用上述任一项所述的坩埚或热场结构进行制备。
根据本申请的又一方面，提供了一种提高连续生长碳化硅单晶品质的方法，该方法使用坩埚主体的外侧增加螺纹及配套的套环装置，实现坩埚发热区的快速转换，从而提高热场重复性和稳定性。相比于之前的技术形成简单易调整的热场结构，能够快速便捷的实现热场的调整，同时大大降低碳化硅单晶及碳化硅单晶及单晶衬底的制造成本。
所述的提高连续生长制备碳化硅单晶的品质的方法，所述方法至少包括碳化硅单晶生长的第一生长周期和第二生长周期，其特征在于，所 述方法包括以下步骤：
第一生长周期：将长晶原料置于坩埚中，并将至少一个套环嵌套在坩埚主体壁的第一位置上，长晶时坩埚内部的高温区在第一高度上，制得第一碳化硅单晶；
第二生长周期：将长晶原料置于坩埚中，调整套环嵌套在坩埚主体壁上的位置，使得第二生长周期的长晶时坩埚内部的高温区大致在第一高度上，制得第二碳化硅单晶。
优选地，所述第一生长周期中套环与籽晶的距离大于或等于第二生长周期中套环与籽晶的距离。
本申请中根据第一周期晶体生长结束后的碳化硅粉料升华程度，可以识别出生长腔室内的高温区位置。
可选地，所述第一生长周期包括：将长晶原料置于坩埚中，并将至少一个套环嵌套在坩埚主体壁的第一位置上，制备具有第一凸率的第一碳化硅单晶；
所述第二生长周期包括：根据第一生长周期的第一凸率，调整套环嵌套在坩埚主体壁上的位置，将长晶原料置于坩埚中，制得具有第二凸率的第二碳化硅单晶。
可选地，所述第一碳化硅单晶具有第一凸率，所述第一凸率不大于8mm；所述第二碳化硅单晶具有第二凸率，所述第二凸率不大于8mm。
可选地，所述调整套环嵌套在坩埚主体壁上的位置的时间为第一生长周期的坩埚重量或密度变化；所述调整套环嵌套在坩埚主体壁上的位置移动距离根据所述第一碳化硅单晶的第一凸率的变化值。
经过一轮晶体生长周期后，用于形成晶体生长热场的石墨保温毡和石墨坩埚都会有一定损耗，同时其理化性质也会发生漂移。因此，为重复生长第二个周期的晶体，需要在重复使用上一热场的条件下，进行简 单快速的高温区调整，具体方法为:当第一周期生长结束后，判断高温区位置是否在腔室预设位置；如果是，根据晶体生长规律，热场高温区在经过一轮晶体生长后会向籽晶端漂移，为了对冲热场漂移，将套环相应的向热场漂移方向进行移动。
作为一种调整套环的方法，如果晶体生长后坩埚及保温毡密度或重量发生变化，则可以判定热场会发生变化，需要在下一周期进行热场调整。调整量根据晶体表面凸率确定。若凸率变化较大，则相应调整套环的位置较大，如凸率超过预设的1倍，则调整套环上移20mm；凸率在晶体设计的范围内，则调整量可以较小甚至不调整。
可选地，所述第一碳化硅单晶和/或第二碳化硅单晶的制备方法包括下述步骤：
1)将碳化硅粉料和用于晶体生长的籽晶放置于石墨坩埚内部并封闭石墨坩埚后，将套环嵌套于石墨坩埚最顶部区域；
2)将石墨坩埚和石墨保温毡放置于晶体生长炉腔内并密封后，设置碳化硅单晶生长温度为2100‐2200℃压力为5‐50mbar后进行为期100‐200h的晶体生长；
3)晶体生长结束后，打开炉膛，取出石墨坩埚后，可获得所述的碳化硅单晶。
可选地，由所述第一碳化硅单晶与所述第二碳化硅单晶制备的4英寸的单晶衬底弯曲度为6‐13μm。
可选地，所述坩埚主体的侧壁外表面与所述套环的内表面通过螺纹连接。作为一种实施方式，在坩埚主体外表面制作外螺纹，使坩埚主体圆柱整体呈螺杆结构；制备套环结构，套环内径与坩埚主体外径相等且套环内侧同样制备内螺纹结构，使套环整体呈与坩埚主体相匹配的螺母结构。
可选地，所述螺纹的螺距为0.2‐2mm。进一步地，所述第一距离的变化值的范围的下限选自0.5mm、0.7mm、1.0mm、1.3mm或1.5mmm，上限选自0.5mm、0.7mm、1.0mm、1.3mm、1.5mmm或1.7mm。本申请的螺纹螺距的设置使得套环的移动足够精准。进一步地，所述螺纹的螺距为0.3‐1.5mm。
可选地，所述套环到所述坩埚主体的投影高度为5‐15mm。进一步地，所述套环的高度的下限选自7mm、10mm、12mm或14mm，上限选自7mm、10mm、12mm或14mm。可选地，所述套环的高度为7‐13mm。
可选地，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值为1：5‐20。进一步地，所述套环的高度与所述坩埚主体的高度比值的下限选自1：7、1：10、1：12、1：14或1:18，上限选自1：7、1：10、1：12、1：14或1:18。更进一步地，所述套环的高度与所述坩埚主体的高度比值为1：7‐18。本申请的套环的高度使得套环在移动时可以覆盖足够的热场区域满足热场调整需求。
可选地，所述套环的厚度为5‐25mm。进一步地，所述套环的厚度的下限选自7mm、10mm、15mm、20mm或23mm，上限选自7mm、10mm、15mm、20mm或23mm。更进一步地，所述套环的厚度为7‐20mm。本申请的套环的厚度平衡了套环本身因集肤效应发热后热阻断与热传导至坩埚内的效率。
可选地，所述的坩埚主体为石墨坩埚，所述的套环为石墨套环。
可选地，所述坩埚主体的外壁具有标识，所述标识可标记套环的位置。优选地，所述标识为刻度标记。
作为一种实施方式，石墨坩埚外侧可进行刻度标记，以精准的记录套环沿石墨坩埚轴向所处的位置
可选地，所述坩埚主体外部至少套设一个可沿坩埚主体轴向移动的 套环。
本申请的套环至少为1个，也可以多个当套环组合使用。
可选地，所述坩埚使用的加热装置为感应加热方式；优选地，所述加热装置包括中频感应线圈。作为一种实施方式，使用PVT法制备碳化硅单晶，使用中频感应线圈感应加热石墨坩埚。
可选地，所述的坩埚主体为石墨坩埚，所述的套环为石墨套环。
可选地，所述连续制备碳化硅单晶的方法包括下述步骤：
1)将碳化硅粉料和用于晶体生长的籽晶放置于石墨坩埚内部并封闭石墨坩埚后，将石墨套环嵌套于石墨坩埚主体最顶部区域，石墨坩埚主体外侧可进行刻度标记，以精准的记录石墨套环沿石墨坩埚主体轴向所处的位置；
2)将石墨坩埚和石墨保温毡放置于晶体生长炉腔内并密封后，设置碳化硅单晶生长温度为2100‐2200℃压力为5‐50mbar后进行为期100‐200h的晶体生长；
3)晶体生长结束后，打开炉膛，取出石墨坩埚后可获得碳化硅单晶晶锭；
4)根据得到碳化硅单晶的凸率，沿石墨坩埚主体轴向旋转石墨套环一定距离，使石墨套环置于石墨坩埚主体特定位置后，重新在石墨坩埚内装入粉料和籽晶并封装于炉膛后进行晶体生长，重复碳化硅单晶步骤2)，无需改变其生长参数；
5)碳化硅单晶生长结束后，取出碳化硅单晶，得到校正后的碳化硅单晶，第一凸率控制在8mm以内；
6)重复使用该套石墨坩埚与石墨保温毡进行下一炉次碳化硅单晶生长，生长前根据上炉碳化硅单晶凸率数据和热场变化情况，向下移动石墨套环一定位置后，将石墨坩埚封装入炉膛并按上述步骤2)生长参数进 行晶体生长，可以得到碳化硅单晶第二凸率，第二凸率与第一凸率接近一致的碳化硅单晶。
可选地，所述碳化单晶籽晶所述石墨坩埚开口上方。
本申请中，PVT法，是指物理气相输运法。
本申请的有益效果包括但不限于：
本申请的制备碳化硅单晶的坩埚和方法，在坩埚主体外侧增加螺纹及配套的石墨套环装置，实现坩埚发热区的快速转换，能够快速便捷的实现热场的调整，同时大大降低碳化硅单晶的制造成本。
本申请的坩埚和方法，可以在不改变感应加热线圈和坩埚位置的情况下，通过调整嵌套于坩埚主体外侧的套环的位置进行热场的调整和校正。
本申请的提高连续生长碳化硅单晶的品质的方法中的坩埚使用特定周期后，通过以下方式调节：将套环旋转至坩埚主体特定位置，晶体生长结束后，根据坩埚的损耗情况确定热场变化方向。
本申请还可以针对性的设计特定热场，可以针对性的形成特定的热场区域，改变坩埚内部的气相传输路径，从而实现快捷有效的热场和流体控制。
本申请的连续制备碳化硅单晶的方法对设备要求较低，有利于降低碳化硅单晶制造成本。
本申请的提高连续生长碳化硅单晶的品质的方法通过简单调节石墨套筒位置即可实现热场调节，方便快捷，提高了热场重复性，有利于制备质量稳定性和一致性高的碳化硅单晶。
附图说明
此处所说明的附图用来提供对本申请的进一步理解，构成本申请的一部分，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1为本申请实施例涉及的包含坩埚的热场结构示意图。
图2为本申请涉及的实施例与对比例的连续生长6次碳化硅单晶的凸率变化图。
具体实施方式
为了更清楚的阐释本申请的整体构思，下面结合说明书附图以示例的方式进行详细说明。
了能够更清楚地理解本申请的上述目的、特征和优点，下面结合附图和具体实施方式对本申请进行进一步的详细描述。需要说明的是，在不冲突的情况下，本申请的实施例及实施例中的特征可以相互组合。
在下面的描述中阐述了很多具体细节以便于充分理解本申请，但是，本申请还可以采用其他不同于在此描述的其他方式来实施，因此，本申请的保护范围并不受下面公开的具体实施例的限制。
另外，在本申请的描述中，需要理解的是，术语“上”、“下”、“前”、“后”、“左”、“右”、“内”、“外”、“轴向”、“径向”、“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。
在本申请的描述中，“多个”的含义是两个或两个以上，除非另有明确具体的限定。
在本申请中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可 以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接，还可以是通信；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
在本申请中，除非另有明确的规定和限定，第一特征在第二特征“上”或“下”可以是第一和第二特征直接接触，或第一和第二特征通过中间媒介间接接触。在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本申请的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不是必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。
参考图1，本申请的实施例公开了一种连续制备碳化硅单晶的可调节热场结构，该热场结构包括坩埚和加热装置，坩埚包括坩埚主体4和套环3，坩埚主体4外部套设一个可调节的套环3。
作为一种实施方式，套环3与坩埚主体4通过螺纹连接5，坩埚主体4的外壁全部区域具有螺纹5。套环3可以为石墨套环。实施方式中，螺距设定为0.2‐2mm，石墨套环高度设定为5‐15mm，石墨套环的厚度为5‐25mm。进一步地，实施方式中，螺距设定为0.5mm，石墨套环高度设定为10mm，石墨套环的厚度为15mm。
本实施方式中，坩埚主体4可为石墨坩埚，但不限于石墨坩埚，可以为用于制备碳化硅单晶的任意材料。
作为一种实施方式，保温结构1由具有保温隔热的材料制成，如使用石墨保温毡制成。
进一步地，加热装置通过中感应加热方式加热坩埚，保温结构1设 置在坩埚的外部，加热装置设置在保温结构1的***。坩埚内放置生长碳化硅单晶粉料6。
进一步地，该热场结构中具有籽晶单元，该籽晶单元设置在石墨坩埚开口处，该籽晶单元包括碳化单晶籽晶2。
本申请的实施方式，在不改变线圈和石墨坩埚位置的情况下，通过调整嵌套于石墨坩埚主体外侧的石墨套环的位置进行热场的调整和校正，中频线圈的磁场作用于最外侧的石墨套环上，石墨套环发热后将热量传导至石墨坩埚内部。由于石墨套环嵌套于坩埚主体外侧，其热量传输相较于石墨坩埚主体壁直接发热并传导至石墨坩埚内部需要更长的传输距离，从而使得石墨坩埚内部局部区域的热场受石墨套环影响而发生变化，进而起到调节热场的作用。
作为本申请的实施方式，当石墨坩埚使用特定周期后，通过以下方式调节：将石墨套环旋转至石墨坩埚特定位置，碳化硅单晶生长结束后，根据石墨坩埚的损耗情况确定热场变化方向。如高温区沿轴向向上移动，需要在下一生长周期进行校正，则通过向相应的高温区方向沿轴向旋转石墨套环至所需温区位置，则上一周期造成的高温区区域温度会下降，从而使热场恢复至接近上一周期的热场条件下。
作为一种调整套环的方法，如果晶体生长后坩埚及保温毡密度或重量发生变化，则可以判定热场会发生变化，需要在下一周期进行热场调整。调整量根据晶体表面凸率确定。若凸率变化较大，则相应调整套环的位置较大，如凸率超过预设的1倍，则调整套环上移20mm；凸率在晶体设计的范围内，则调整量可以较小甚至不调整。
作为本申请的实施方式，还可以针对性的设计特定热场。热场设计方式如下：如果需要设计籽晶放置处的温度较低，则将石墨套环旋转至籽晶放置处，从而可以降低籽晶放置处的温度；如果需要籽晶和原料之 间的温度降低，则将石墨套环旋转至籽晶与原料之间的位置，则该区域的温度相应的降低。通过这些调整，可以针对性的形成特定的热场区域，改变坩埚内部的气相传输路径，从而实现快捷有效的热场和流体控制。
作为另一些实施方式，相应的可以根据热场设计多个石墨套环组合使用。
由于碳化硅单晶生长热场沿径向呈中心温度低、边缘温度高的特点，因此碳化硅单晶的边缘厚度小于中心厚度，碳化硅单晶中心与边缘厚度之差(凸率)为2‐20mm。凸率越大，表明热场沿径向均匀性越差，相应的碳化硅单晶应力越差，得到的碳化硅单晶衬底往往存在弯曲度和翘曲度较大等质量问题；同时热场的不均匀导致碳化硅单晶内部杂质沿径向分布不均，造成碳化硅单晶衬底面内的电阻率不均匀性变大。因此，合理的碳化硅单晶凸率应控制在8mm以内，且随着石墨坩埚及石墨保温毡重复使用后的损耗而保持不变，以保证碳化硅单晶和衬底质量的一致性与稳定性。进一步地，所述碳化硅单晶凸率应控制在5mm以内。
利用上述实施例中制备的热场结构制备碳化硅单晶，具体的使用方法如下所示：
1)将碳化硅粉料和用于晶体生长的籽晶放置于石墨坩埚内部并封闭石墨坩埚后，将石墨套环嵌套于石墨坩埚主体最顶部区域，石墨坩埚主体外侧可进行刻度标记，以精准的记录石墨套环沿石墨坩埚主体轴向所处的位置；
2)将石墨坩埚和石墨保温毡放置于晶体生长炉腔内并密封后，设置碳化硅单晶生长温度为2100‐2200℃压力为5‐50mbar后进行为期100‐200h的晶体生长；
3)晶体生长结束后，打开炉膛，取出石墨坩埚后可获得碳化硅单晶晶锭；
4)根据得到碳化硅单晶的第一凸率，沿石墨坩埚主体轴向旋转石墨套环一定距离，使石墨套环置于石墨坩埚主体特定位置后，重新在石墨坩埚内装入粉料和籽晶并封装于炉膛后进行晶体生长，重复碳化硅单晶步骤2，无需改变其生长参数；
5)碳化硅单晶生长结束后，取出碳化硅单晶，得到校正后的碳化硅单晶，第二凸率控制在5mm以内；
6)重复使用该套石墨坩埚与石墨保温毡进行下一炉次碳化硅单晶生长，生长前根据上炉碳化硅单晶凸率数据和热场变化情况，向下移动石墨套环一定位置后，将石墨坩埚封装入炉膛并按上述步骤2生长参数进行晶体生长，可以得到碳化硅单晶凸率接近一致的碳化硅单晶。
图2为实施例与对比例(常规方法)的连续生长6次碳化硅单晶的凸率变化图。常规方法为：在同一设备内使用同一套物料连续生长6轮次的4英寸碳化硅单晶后，随着石墨保温毡和石墨坩埚的损耗热场将逐渐发生变化，导致碳化硅单晶凸率逐渐增大，碳化硅单晶的一致性和稳定性变差，如图2中的A线；而使用本申请所述热场结构和调节热场的方法进行热场校正调节后，连续生长的6轮次晶体的凸率可以保持一致，从而得到一致性和稳定性优异的碳化硅晶体和衬底，如图2中的B线。
将上述常规方法和本申请的方法制备的碳化硅单晶加工为衬底后，使用常规方法制备的碳化硅单晶衬底弯曲度值分布于15‐39μm之间，数值较大且离散；使用本申请的热场结构和方法制备的衬底弯曲度值分布于6‐13μm之间，碳化硅单晶衬底面型质量较好且一致性较高。
以上所述，仅为本申请的实施例而已，本申请的保护范围并不受这些具体实施例的限制，而是由本申请的权利要求书来确定。对于本领域技术人员来说，本申请可以有各种更改和变化。凡在本申请的技术思想 和原理之内所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。

Claims (23)

  1. 一种制备碳化硅单晶的坩埚，其特征在于，所述坩埚包括坩埚主体和至少一个套环，所述套环设置在坩埚主体的外部，所述套环可沿坩埚主体轴向移动套环。
  2. 根据权利要求1所述的坩埚，其特征在于，所述坩埚主体的侧壁外表面与所述套环的内表面通过螺纹连接。
  3. 根据权利要求2所述的坩埚，其特征在于，所述螺纹的螺距为0.2‐2mm。
  4. 根据权利要求1所述的坩埚，其特征在于，所述套环到所述坩埚主体的投影高度为5‐15mm。
  5. 根据权利要求1所述的坩埚，其特征在于，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值为1：5‐20。
  6. 根据权利要求1所述的坩埚，其特征在于，所述套环的厚度为5‐25mm。
  7. 根据权利要求1所述的坩埚，其特征在于，所述坩埚主体的侧壁外表面具有标识，标识可标记套环的位置。
  8. 根据权利要求8所述的坩埚，其特征在于，所述标识为刻度标记。
  9. 根据权利要求1‐8中任一项所述的坩埚，其特征在于，所述的坩埚为石墨坩埚，所述的套环为石墨套环。
  10. 一种碳化硅晶体生长装置，其特征在于，包含权利要求1‐9中任一项所述的坩埚。
  11. 由权利要求1‐10中任一项所述的坩埚制成的可调节热场结构，其特征在于，其包括：
    坩埚，放置用于生长碳化硅单晶的原料；
    加热装置，加热所述坩埚；
    所述坩埚包括坩埚主体和所述坩埚主体外部至少套设一个可沿坩埚主体轴向移动的套环。
  12. 根据权利要求11所述的热场结构，其特征在于，所述加热装置对所述坩埚使用感应方式进行加热；优选地，所述加热装置包括中频感应线圈。
  13. 一种碳化硅单晶的制备方法和/或晶体生长装置,其特征在于，包括使用权利要求1‐9中任一项所述的坩埚，或权利要求10所述的生长装置，或权利要求11或12所述的热场结构。
  14. 一种提高连续生长碳化硅单晶品质的方法，所述方法至少包括碳化硅单晶生长的第一生长周期和第二生长周期，其特征在于，所述方法包括以下步骤：
    第一生长周期：将长晶原料置于坩埚中，并将至少一个套环嵌套在坩埚主体壁的第一位置上，长晶时坩埚内部的高温区在第一高度上，制得第一碳化硅单晶；
    第二生长周期：将长晶原料置于坩埚中，调整套环嵌套在坩埚主体壁上的位置，使得第二生长周期的长晶时坩埚内部的高温区大致在第一高度上，制得第二碳化硅单晶。
  15. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，
    所述第一生长周期包括：将长晶原料置于坩埚中，并将至少一个套环嵌套在坩埚主体壁的第一位置上，制得具有第一凸率的第一碳化硅单晶；
    所述第二生长周期包括：根据第一生长周期的第一凸率，调整套环嵌套在坩埚主体壁上的位置，将长晶原料置于坩埚中，制得具有第二凸 率的第二碳化硅单晶；
    优选地，所述第一凸率不大于8mm，所述第二凸率不大于8mm。
  16. 根据权利要求14或15所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述调整套环嵌套在坩埚主体壁上的位置的时间为第一生长周期的坩埚重量或密度变化；所述调整套环嵌套在坩埚主体壁上的位置移动距离根据所述第一碳化硅单晶的第一凸率的变化值。
  17. 根据权利要求14‐16中任一项所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述第一碳化硅单晶和/或第二碳化硅单晶的制备方法包括下述步骤：
    1)将碳化硅粉料和用于晶体生长的籽晶放置于石墨坩埚内部并封闭石墨坩埚后，将套环嵌套于石墨坩埚主体最顶部区域；
    2)将石墨坩埚和石墨保温毡放置于晶体生长炉腔内并密封后，设置碳化硅单晶生长温度为2100‐2200℃压力为5‐50mbar后进行100‐200h的晶体生长；
    3)晶体生长结束后，打开炉膛，取出石墨坩埚后，可获得所述的碳化硅单晶。
  18. 根据权利要求14‐16中任一项所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，由所述第一碳化硅单晶与所述第二碳化硅单晶制备的4英寸的单晶衬底弯曲度为6‐13μm。
  19. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述坩埚主体的侧壁外表面与所述套环的内表面通过螺纹连接；优选地，所述螺纹的螺距为0.2‐2mm。
  20. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述套环到所述坩埚主体的投影高度为5‐15mm。
  21. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法， 其特征在于，所述套环到所述坩埚主体的投影高度与所述坩埚主体的高度比值为1：5‐20。
  22. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述套环的厚度为5‐25mm。
  23. 根据权利要求14所述的提高连续生长碳化硅单晶的品质的方法，其特征在于，所述套环为石墨套环；优选地，所述坩埚主体的外壁具有标记套环位置的标识。
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CN102925957A (zh) * 2011-08-12 2013-02-13 昆山中辰矽晶有限公司 长晶装置
JP2014101246A (ja) * 2012-11-19 2014-06-05 Toyota Central R&D Labs Inc 単結晶製造装置、および単結晶の製造方法
JP2014234331A (ja) * 2013-06-04 2014-12-15 新日鐵住金株式会社 炭化珪素単結晶インゴットの製造方法及び炭化珪素単結晶インゴット
JP2018158857A (ja) * 2017-03-22 2018-10-11 昭和電工株式会社 炭化珪素単結晶インゴットの製造装置及び製造方法

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CN102925957A (zh) * 2011-08-12 2013-02-13 昆山中辰矽晶有限公司 长晶装置
JP2014101246A (ja) * 2012-11-19 2014-06-05 Toyota Central R&D Labs Inc 単結晶製造装置、および単結晶の製造方法
JP2014234331A (ja) * 2013-06-04 2014-12-15 新日鐵住金株式会社 炭化珪素単結晶インゴットの製造方法及び炭化珪素単結晶インゴット
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