A graphite thermal field single crystal growth device for preparing silicon carbide crystals

Abstract

The invention discloses a graphite thermal field single crystal growth device for preparing silicon carbide crystals, relates to the technical field of preparation of silicon carbide single crystals and crystal growth, and comprises a sealed cavity, a heating structure, a heat preservation structure, a temperature regulating structure, a crucible and a temperature measuring mechanism; the heat preservation structure is arranged in the sealed cavity; the heating structure is arranged in the heat preservation structure, and the temperature measuring mechanism is arranged on the sealed cavity; the temperature regulating structure is arranged in the heat preservation structure, and the crucible and a seed crystal holder are arranged in the heat preservation structure; the heating structure heats the bottom and top of the crucible, and controls the temperature of the crucible in the axial and radial directions; the temperature measuring mechanism measures the temperature of the top and bottom of the crucible respectively; the heat preservation structure insulates the thermal field of the entire cavity, and can also reduce the heat loss of the crucible, so as to realize accurate temperature control of various parts of the crucible; the temperature regulating structure can reduce the radial temperature gradient of the crucible; thereby reducing the radial temperature gradient and stress gradient of the crystal during the growth of the silicon carbide single crystal, reducing the defects of crystal growth, and ensuring the quality of the crystal.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of silicon carbide single crystal and crystal growth, and in particular to a graphite thermal field single crystal growth device for preparing silicon carbide crystal. Background Art

[0002] Silicon carbide is a high-quality wide bandgap semiconductor material with the advantages of wide bandgap, high breakdown electric field, high thermal conductivity, and high saturated electron drift rate. It can meet the needs of high-temperature, high-power, low-loss, and large-diameter devices. Silicon carbide single crystals cannot be formed by melting, and the sublimation growth technology based on the improved Lely method - physical vapor transport is a common method for obtaining silicon carbide single crystals. The growth principle of silicon carbide single crystals prepared by the PVT method is: high-purity silicon carbide powder source decomposes at high temperature to form gaseous substances (mainly Si, SiC2, Si2C, etc.), which are driven by supersaturation and sublimate to the seed crystal at the cold end for growth. Supersaturation is caused by the temperature gradient between the seed crystal and the powder source.

[0003] In the prior art, medium frequency induction heating is mostly used. During the crystal growth process, the temperature gradient in the crystal is adjusted by adjusting the relative position of the thermal field and the coil so that the crystal can continue to grow. The flexibility of temperature regulation of induction coil heating is very limited. When the induction coil moves axially, the axial temperature can be adjusted on the one hand, and the radial temperature gradient will also change accordingly. The induction coil has a certain linkage when adjusting the temperature, and the temperature control during growth is not accurate enough, which will affect the growth quality and growth rate of the crystal and is not conducive to the growth of large-size high-quality crystals. The graphite heating method can solve this problem. In addition, the radial temperature gradient of medium frequency induction heating is not easy to adjust. If the gradient is too large, it will lead to excessive thermal stress, which is easy to produce micropipes, stacking fault grain boundaries, and other defects.

[0004] At present, the graphite crucible is also heated by resistance heating. In the prior art, the heating resistor is generally located at the bottom and around the crucible, so that the crucible has a relatively good temperature gradient in the axial direction. This heating method will also cause a large temperature gradient in the radial direction of the seed crystal. However, in the process of growing silicon carbide single crystals, it is necessary to control the radial temperature uniformity at the seed crystal in order to grow silicon carbide single crystals of better quality. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a graphite thermal field single crystal growth device for preparing silicon carbide crystals, which ensures that the crucible is more accurately controlled to achieve a suitable axial temperature gradient and effectively reduces the radial temperature gradient at the top of the crucible, thereby reducing the radial temperature gradient and stress gradient of the crystal during the growth of the silicon carbide single crystal, which can effectively reduce the defects of crystal growth and ensure the quality of the crystal.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a graphite thermal field single crystal growth device for preparing silicon carbide crystals, comprising a sealed cavity, a heating structure, a heat preservation structure, a temperature regulating structure, a crucible and a temperature measuring mechanism; the heat preservation structure is arranged in the sealed cavity; the temperature regulating structure is located in the heat preservation structure, the heating structure is arranged in the heat preservation structure, and the temperature measuring mechanism is arranged on the sealed cavity; the heat preservation structure is used to arrange a crucible, and a seed crystal holder is arranged in the crucible.

[0008] Optionally, the heating structure includes an upper auxiliary heating resistor and a lower main heating resistor; the upper auxiliary heating resistor and the lower main heating resistor operate independently; the upper auxiliary heating resistor is arranged in the upper part of the insulation structure; the lower main heating resistor is arranged around the crucible.

[0009] Optionally, the upper auxiliary heating resistor and the lower main heating resistor are respectively provided with a group of electrodes, namely an upper electrode and a lower electrode, the upper electrode is two-phase heating, and the lower electrode is three-phase heating, and the upper electrode and the lower electrode are sealed with the sealed cavity by a flange and an O-ring or a metal gasket.

[0010] Optionally, the thermal insulation structure includes a thermal insulation structure upper cover, a thermal insulation structure cylinder and a thermal insulation structure lower cover.

[0011] Optionally, the temperature regulating structure includes a first upper temperature regulating ring, a second upper temperature regulating ring and a lower temperature regulating ring; the first upper temperature regulating ring and the second upper temperature regulating ring are located at the upper part of the crucible, and the lower temperature regulating ring is located at the bottom of the crucible.

[0012] Optionally, the crucible includes a crucible cover, a seed crystal holder, a seed crystal, a crucible liner, a small crucible liner, a large crucible liner, a porous crucible material box or a porous graphite material box, a crucible body, a crucible lower cover, and a crucible support; the top of the crucible body is open, the crucible cover is arranged on the top of the crucible body, the seed crystal holder is arranged between the large crucible liner and the crucible cover, the seed crystal is located at the bottom of the seed crystal holder, and the crucible liner is located on the upper part of the large crucible liner. The large crucible lining is arranged at the upper inner part of the crucible body, the small crucible lining is arranged inside the large crucible lining, the porous crucible material box or the porous graphite material box is centrally placed at the bottom of the crucible lower cover, the crucible body is located at the upper part of the crucible lower cover, the crucible support is arranged at the bottom of the crucible lower cover, the crucible support height is adjustable, and the crucible lining cover is located at the upper part of the large crucible lining; the crucible upper cover is designed with a middle opening and a step structure as a stepped structure.

[0013] Optionally, the temperature measuring mechanism includes an upper temperature measuring device and a lower temperature measuring device, and the upper temperature measuring device and the lower temperature measuring device are respectively arranged at the top and the bottom of the sealed cavity.

[0014] Optionally, the upper temperature measuring device and the lower temperature measuring device are both infrared thermometers or thermocouples, or the upper temperature measuring device and the lower temperature measuring device are infrared thermometers and thermocouples used in combination.

[0015] Compared with the prior art, the present invention has achieved the following technical effects:

[0016] The graphite thermal field single crystal growth device for preparing silicon carbide crystals in the present invention mainly comprises a sealed chamber, a heating structure, a heat preservation structure, a temperature regulating structure, a crucible and a temperature measuring mechanism; the heating structure can realize heating of the four sides and the top of the crucible respectively, so that the temperature of the crucible can be controlled in the axial and radial directions respectively, and the temperature of the top and the bottom of the crucible can be measured respectively in combination with the temperature measuring mechanism; the heat preservation structure can heat the thermal field of the entire sealed chamber; the temperature regulating structure can adjust the local temperature of the crucible, reduce the radial temperature gradient of the crucible, realize multi-zone temperature regulation of the crucible, accurately control the temperature of each part of the crucible, make the axial temperature gradient of the crucible reach the most suitable temperature, and at the same time, effectively reduce the radial temperature gradient of the top and bottom of the crucible; thereby reducing the radial temperature gradient and stress gradient of the crystal during the growth of the silicon carbide single crystal, effectively reducing the defects of crystal growth, and ensuring the quality of the crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic structural diagram of a graphite thermal field single crystal growth device for preparing silicon carbide crystals according to the present invention;

[0019] Figure 2 It is a schematic diagram of the upper auxiliary heating resistor and electrode structure in the graphite thermal field single crystal growth device for preparing silicon carbide crystals of the present invention;

[0020] Figure 3 It is a schematic diagram of the lower main heating resistor and electrode structure in the graphite thermal field single crystal growth device for preparing silicon carbide crystals of the present invention;

[0021] Figure 4 A schematic diagram of the crucible structure of a graphite thermal field single crystal growth device for preparing silicon carbide crystals according to the present invention;

[0022] Figure 5 It is a structural schematic diagram of another embodiment of the graphite thermal field single crystal growth device for preparing silicon carbide crystals of the present invention;

[0023] Description of reference numerals:

[0024] 1. Upper temperature measuring device; 2. Upper auxiliary heating resistor; 4. Lower main heating resistor; 5. Upper electrode; 7. Lower electrode; 8. Lower temperature measuring device; 9. Sealed chamber; 10. Insulation structure; 101. Insulation structure upper cover; 102. Insulation structure cylinder; 103. Insulation structure lower cover; 11. Crucible; 111. Crucible upper cover; 112. Seed crystal holder; 113. Seed crystal; 114. Small lining of crucible; 115. Large lining of crucible; 116. Porous crucible material box; 117. Crucible body; 118. Crucible support; 119. Crucible lining cover; 120. Crucible lower cover; 12. Temperature control structure; 121. First upper temperature control ring; 122. Second upper temperature control ring; 123. Lower temperature control ring. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Embodiment 1:

[0027] like Figure 1 As shown, this embodiment provides a graphite thermal field single crystal growth device for preparing silicon carbide crystals, including a sealed chamber 9, a heating structure, a heat preservation structure 10, a temperature adjustment structure 12, a crucible 11 and a temperature measuring mechanism; the heat preservation structure 10 is arranged in the sealed chamber 9; the temperature adjustment structure 12 is arranged in the heat preservation structure 10, the heating structure is arranged in the heat preservation structure 10, and the temperature measuring mechanism is arranged on the sealed chamber 9; the crucible 11 is arranged in the heat preservation structure 10, and the seed crystal holder 112 is arranged in the crucible 11.

[0028] In this specific embodiment, the sealed cavity 9 includes a cavity, an upper flange and a lower flange. The upper flange is arranged at the top of the cavity, and the lower flange is arranged at the bottom of the cavity.

[0029] The heating structure includes an upper auxiliary heating resistor 2 and a lower main heating resistor 4; the upper auxiliary heating resistor 2 and the lower main heating resistor 4 operate independently, that is, the upper auxiliary heating resistor 2 and the lower main heating resistor 4 respectively use independent power supplies, and the upper auxiliary heating resistor 2 and the lower main heating resistor 4 can be controlled separately, and the axial and radial temperatures of the crucible 11 can be accurately controlled by adjusting the power of the upper auxiliary heating resistor 2 and the lower main heating resistor 4; the upper auxiliary heating resistor 2 is arranged in the upper part of the insulation structure 10; the lower main heating resistor 4 is arranged around the crucible 11.

[0030] The upper auxiliary heating resistor 2 and the lower main heating resistor 4 each have a set of electrodes, namely an upper electrode 5 and a lower electrode 7, which pass through the upper flange and the lower flange respectively, and are sealed and connected to the upper flange and the lower flange by flanges and O-rings; Figure 2 As shown, it is a schematic diagram of the structure of the upper auxiliary heating resistor 2 and the upper electrode. The heating resistor is made of graphite material, the electrode structure is made of graphite, molybdenum-lanthanum alloy and copper material, the inner part of the insulation structure 10 is graphite material, the outer part of the insulation structure is copper material, and the connecting part of the two materials is molybdenum-lanthanum alloy; Figure 3 As shown, it is a schematic structural diagram of the lower main heating resistor 4 and the lower electrode 7.

[0031] The insulation structure 10 includes an insulation structure upper cover 101, an insulation structure cylinder 102, and an insulation structure lower cover 103. The insulation structure cylinder 102 is formed by splicing two sections of insulation materials. The insulation structure 10 is made of graphite felt. The insulation structure 10 provides an appropriate temperature environment for the entire crucible 11 to reduce heat loss in the entire growth environment.

[0032] The temperature control structure 12 includes a first upper temperature control ring 121, a second upper temperature control ring 122 and a lower temperature control ring 123; the temperature control structure 12 is made of a material with low thermal conductivity, such as graphite felt, ceramics, etc. The first upper temperature control ring 121, the second upper temperature control ring 122 and the lower temperature control ring 123 are arranged around the crucible 11. The first upper temperature control ring 121 and the second upper temperature control ring 122 are mainly used to adjust the radial temperature gradient of the upper part of the crucible 11, and the lower temperature control ring 123 is mainly used to adjust the radial temperature gradient of the bottom of the crucible 11. Different degrees of temperature adjustment can be achieved by changing the thickness and position of the first upper temperature control ring 121, the second upper temperature control ring 122 and the lower temperature control ring 123. The temperature control structure 12 can effectively reduce the radial temperature gradient of the crucible 11 and improve the growth quality of the crystal.

[0033] like Figure 4As shown, the entire crucible 11 is a cylindrical structure, and the crucible 11 includes a crucible upper cover 111, a seed crystal holder 112, a seed crystal 113, a small crucible liner 114, a large crucible liner 115, a porous crucible material box 116, a crucible body 117, a crucible support 118, a crucible liner cover 119, and a crucible lower cover 120. The crucible upper cover 111 is arranged on the top of the crucible body 117, the seed crystal holder 112 is arranged between the large crucible lining 115 and the crucible upper cover 111, the seed crystal 113 is located at the bottom of the seed crystal holder 112, and the crucible lining cover 119 is located on the large and small liners for sealing the crucible 11; the large crucible lining 115 is arranged on the upper inner part of the crucible body 117, the small crucible lining 114 is arranged on the inner side of the large crucible lining 115, the porous crucible material box 116 is placed in the center of the bottom of the crucible lower cover 120, the crucible body 117 is located on the crucible lower cover 120, and the crucible support 118 is arranged at the bottom of the crucible lower cover 120.

[0034] The crucible cover 111 is designed as a central opening and a cylindrical step structure, and the step height is 30-50mm. The opening is for the upper temperature measuring device to directly measure the temperature of the seed crystal holder 112, so that the temperature measurement is more accurate, which is conducive to the crucible reaching the most suitable temperature range. A temperature regulating ring can be arranged at the step to properly adjust the temperature of the crucible 11; the step design of the crucible cover 111 is convenient for the installation of the temperature regulating ring. This structure can make up for the disadvantage of large central heat dissipation caused by the opening of the temperature measuring hole of the crucible cover 111, thereby reducing the radial temperature gradient of the crucible cover 111, that is, the seed crystal 113, that is, reducing the radial temperature gradient of the crystal growth; the crucible liner cover 119 is located on the large crucible liner 115, and is used for the crucible 1 1, in order to facilitate assembly, a certain gap is left between the lower end surface of the crucible liner cover 119 and the small crucible liner 114, preferably 0-1mm; the inner cylindrical surface of the crucible liner cover 119 is farther away from the seed crystal than the inner end surface of the small crucible liner 114, preferably 1-2mm, which is conducive to the assembly of the crucible; the small crucible liner 114 is located on the inner side of the large crucible liner 115, both of which are cylindrical in structure, and the diameter of the inner cylindrical surface of the small crucible liner 114 is 2-3mm smaller than the diameter of the outer cylindrical surface of the seed crystal 113. Since the seed crystal 113 is first installed on the crucible cover 111 and then assembled on the crucible body 117, the small crucible liner 114 can prevent the seed crystal 113 from falling off after the crucible cover 111 is assembled and falling into the material box The radial spacing between the small crucible liner 114 and the large crucible liner 115 is 1-10mm; the small crucible liner 114 and the large crucible liner 115 are used to guide the gas phase components of silicon carbide. The large and small linings can have a certain angle of inclination to ensure that the silicon carbide gas phase organization can flow smoothly and the gas phase components are evenly transmitted to the seed crystal 113 at a preset speed; the small crucible liner 114 and the crucible liner cover 119 are coated with TaC coating on the surface close to the crystal to prevent the small crucible liner 114 and the crucible liner cover 119 from volatilizing at high temperature and affecting the proportion of gas phase components; the porous crucible material box 116 is cylindrical, and the side wall is designed as a porous structure with a hole size of about 2 mm in diameter, which ensures the strength of the raw material box. On the basis of the crucible, as many holes as possible are opened. Such a design can make the gas phase components formed by the gasification of the silicon carbide source material more uniform inside the crucible, and at the same time can reduce the crystallization of the silicon carbide source material during the ascent; in addition, the source material box can also be made of porous graphite material, and the graphite material does not need to be perforated, and the gas phase components can also be made more uniform; the crucible body 117 is connected to the crucible upper cover 111 and the crucible lower cover 120 through threads, and the use of threads can play a good sealing role. The large crucible liner 115 and the crucible liner cover 119 are assembled on the crucible body 117; the middle part of the crucible lower cover 120 is raised, and this part is used to position the porous crucible material box 116 to ensure that the material box is in the middle of the crucible 11 and the uniformity of the growth of silicon carbide crystals;The crucible support 118 supports the crucible 11 and is designed to be height-adjustable. The crucible support 118 is divided into two parts, one part is located at the bottom of the crucible and is a circular ring structure, and the other part is located under the lower temperature regulating ring 123 and is a three-rod support. The crucible support 118 can make the crucible as a whole be located in the most appropriate axial position and in the optimal axial temperature gradient. ;

[0035] The temperature measuring mechanism includes an upper temperature measuring device 1 and a lower temperature measuring device 8, and the upper temperature measuring device 1 and the lower temperature measuring device 8 are respectively arranged at the top and the bottom of the sealed cavity. Specifically, a temperature measuring pipe is respectively arranged in the middle of the upper flange and the lower flange, and the upper temperature measuring device 1 and the lower temperature measuring device 8 are respectively arranged on the temperature measuring pipes on the upper flange and the lower flange.

[0036] The upper temperature measuring device 1 and the lower temperature measuring device 8 are both infrared thermometers or thermocouples.

[0037] Embodiment 2:

[0038] This embodiment is an improved embodiment based on the first embodiment. It mainly provides other solutions for the arrangement of electrodes, such as Figure 5 As shown, the arrangement of the electrodes can be adjusted on the matching lower electrode 7 of the lower main heating resistor 4. The lower electrode 7 can be arranged as follows: the electrode passes through the cavity and is parallel to the lower flange. The electrode and the cavity are sealed and connected by a flange and an O-ring.

[0039] In this embodiment, it should be noted that the growth device in the example is lifted by the upper flange cover of the chamber, so the upper electrode 5 cannot be arranged in parallel with the upper flange, and can only be carried out by passing through the upper flange, which is helpful for feeding and taking out the finished product and reduces the number of disassembly of the upper electrode 5. On the contrary, if the growth device is lifted by the lower flange cover of the chamber, the lower electrode 7 cannot be arranged in parallel with the lower flange.

[0040] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure mark in the claims should not be regarded as limiting the claims involved.

[0041] The present specification uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A graphite thermal field single crystal growth device for preparing silicon carbide crystals, characterized in that: It comprises a sealed cavity, a heating structure, a heat preservation structure, a temperature adjustment structure, a crucible and a temperature measuring mechanism; the heat preservation structure is arranged in the sealed cavity; the temperature adjustment structure is located in the heat preservation structure, the heating structure is arranged in the heat preservation structure, and the temperature measuring mechanism is arranged on the sealed cavity; the heat preservation structure is used to arrange a crucible, and a seed crystal holder is arranged in the crucible; The heating structure comprises an upper auxiliary heating resistor and a lower main heating resistor; the upper auxiliary heating resistor and the lower main heating resistor operate independently; the upper auxiliary heating resistor is arranged in the upper part of the thermal insulation structure; The lower main heating resistor is arranged around the crucible; The temperature regulating structure comprises a first upper temperature regulating ring, a second upper temperature regulating ring and a lower temperature regulating ring; the first upper temperature regulating ring and the second upper temperature regulating ring are located at the upper part of the crucible, and the lower temperature regulating ring is located at the bottom of the crucible; The temperature regulating structure is made of low thermal conductivity material.

2. The graphite thermal field single crystal growth device for preparing silicon carbide crystal according to claim 1, characterized in that: The upper auxiliary heating resistor and the lower main heating resistor are respectively provided with a group of electrodes, namely an upper electrode and a lower electrode, the upper electrode is two-phase heating, and the lower electrode is three-phase heating. The upper electrode and the lower electrode are sealed with the sealed cavity by flanges and O-rings or metal gaskets.

3. The graphite thermal field single crystal growth device for preparing silicon carbide crystal according to claim 1, characterized in that: The thermal insulation structure comprises a thermal insulation structure upper cover, a thermal insulation structure cylinder and a thermal insulation structure lower cover.

4. The graphite thermal field single crystal growth device for preparing silicon carbide crystal according to claim 1, characterized in that: The crucible comprises a crucible cover, a seed crystal holder, a seed crystal, a crucible liner, a small crucible liner, a large crucible liner, a porous crucible material box or a porous graphite material box, a crucible body, a crucible cover, and a crucible support; the crucible body is open at the top, the crucible cover is arranged on the top of the crucible body, the seed crystal holder is arranged between the large crucible liner and the crucible cover, the seed crystal is located at the bottom of the seed crystal holder, the crucible liner is located on the upper part of the large crucible liner, and the crucible The large crucible lining is arranged at the upper part of the crucible body, the small crucible lining is arranged inside the large crucible lining, the porous crucible material box or the porous graphite material box is centrally placed at the bottom of the lower cover of the crucible, the crucible body is located at the upper part of the lower cover of the crucible, the bottom of the lower cover of the crucible is provided with the crucible support, the height of the crucible support is adjustable, and the crucible lining cover is located at the upper part of the large crucible lining; the upper cover of the crucible is designed to have a middle opening and a step structure of a stepped structure; A certain gap is left between the lower end surface of the crucible liner and the small inner liner of the crucible to facilitate assembly; The inner cylindrical surface of the crucible lining cover is farther away from the seed crystal than the inner end surface of the small inner lining of the crucible, with a spacing of 1-2 mm, which is conducive to the assembly of the crucible; The small crucible liner is used to prevent the seed crystal from falling off and falling into the material box after the crucible cover is assembled; The radial spacing between the small crucible lining and the large crucible lining serves to guide the silicon carbide gas phase components, thereby ensuring that the silicon carbide gas phase structure can flow smoothly and uniformly transmit the gas phase components to the seed crystal at a preset speed.

5. The graphite thermal field single crystal growth device for preparing silicon carbide crystal according to claim 1, characterized in that: The temperature measuring mechanism comprises an upper temperature measuring device and a lower temperature measuring device, and the upper temperature measuring device and the lower temperature measuring device are respectively arranged at the top and the bottom of the sealed cavity.

6. The graphite thermal field single crystal growth device for preparing silicon carbide crystal according to claim 5, characterized in that: The upper temperature measuring device and the lower temperature measuring device are both infrared thermometers or thermocouples, or the upper temperature measuring device and the lower temperature measuring device are infrared thermometers and thermocouples used in combination.

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