Silicon carbide single crystal growth device
By adopting a dynamic stretched crucible structure and partition heating technology in the silicon carbide single crystal growth device, the problem of limited growth quality and thickness of single crystals is solved, and the growth of high-quality single crystals and energy consumption is reduced.
Patent Information
- Application Number
- CN202420543364.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-19
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2034-03-19
AI Technical Summary
The single crystal grown in existing silicon carbide single crystal growth devices are not high in quality and limited in thickness, resulting in defects in crystals and unstable temperature gradient during growth, affecting device performance.
A silicon carbide single crystal growth device including a heating structure and a crucible structure is designed to control the balance of the axial temperature gradient through the sliding connection and dynamic stretching of the side walls of the upper and lower crucibles, and to pass the partitions of the main heating zone and the auxiliary heating zone. Heating reduces energy consumption and heat loss, while using porous graphite structures and metal coatings to improve the temperature uniformity of the powder and the mechanical stability of the crucible.
The thickness and quality of the single crystal are improved, defects such as dislocation are reduced, the stability of the growth interface and the dynamic balance of the temperature gradient are achieved, and energy consumption and production costs are reduced.
Smart Images
Figure CN222182546U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of silicon carbide, in particular to a silicon carbide single crystal growth device. Background Art
[0002] The development and progress of semiconductor materials are core key technologies. As one of the important representatives of the third generation of semiconductor materials, silicon carbide single crystal materials have become a hot semiconductor material in the future due to their large bandgap, high saturated electron mobility, strong breakdown field, and high thermal conductivity. Good silicon carbide single crystal growth equipment is the basis for obtaining high-quality silicon carbide crystals, and directly affects the effective thickness of single crystals, which determines the substrate cost; the single crystal growth thermal field is the key to obtaining high-quality silicon carbide wafers, which directly affects the performance of silicon carbide devices; the filling of silicon carbide powder is an important factor affecting crystal growth, and it runs through the entire crystal growth process. The structural design of silicon carbide single crystal growth equipment and growth thermal field will directly affect the growth quality of the ingot (such as defect density, grain boundaries and microtubes, etc.), so the growth equipment required for growing crystals and the structure of the silicon carbide growth thermal field become important links to ensure the quality of single crystals. Utility Model Content
[0003] The utility model aims to overcome the problems of low quality and limited thickness of single crystals grown by existing silicon carbide single crystal growing devices, and provides a silicon carbide single crystal growing device.
[0004] In order to achieve the above object, the utility model provides a silicon carbide single crystal growth device, comprising:
[0005] Heating structures;
[0006] a crucible structure located inside the heating structure;
[0007] The crucible structure comprises a lower crucible and an upper crucible with openings arranged opposite to each other, and the upper crucible and the lower crucible are connected by sliding side walls; the inner bottom surface of the lower crucible is used to place silicon carbide powder, and the inner top surface of the upper crucible is used to fix silicon carbide seed crystals.
[0008] As an implementation method, the heating structure includes a main heating zone and an auxiliary heating zone located above and / or below the main heating zone, the main heating zone and the auxiliary heating zone are heated by different heaters respectively, and the interior of the main heating zone is connected to the interior of the auxiliary heating zone; the junction of the main heating zone and the auxiliary heating zone has a first protrusion that is arranged around the inner surface of the side wall and extends toward the interior of the heating structure; the heating structure also includes an upper lifting seat and / or a lower lifting seat, the upper lifting seat is used to connect to the outer top surface of the upper crucible, and the lower lifting seat is used to connect to the outer bottom surface of the lower crucible; the outer side of the upper lifting seat and / or the lower lifting seat has a second protrusion that is arranged around and corresponds to the first protrusion;
[0009] When the upper crucible and / or the lower crucible are not stretched, the crucible structure is located inside the main heating zone, and the first protrusion is engaged with the corresponding second protrusion; when the upper crucible and / or the lower crucible are stretched so that the upper crucible and the lower crucible slide, the first protrusion is separated from the corresponding second protrusion, and the crucible structure moves from being located in the main heating zone to being located in both the main heating zone and the auxiliary heating zone.
[0010] As an implementation method, the inner surface of the side wall of the main heating zone has at least one layer of first heater arranged around it; the inner surface of the side wall of the auxiliary heating zone has at least one layer of second heater arranged around it.
[0011] As an implementation mode, the main heating zone further includes at least two first through holes arranged around the side wall at the position corresponding to each layer of the first heater, the at least two first through holes are evenly spaced, at least two first thermometers respectively pass through the corresponding first through holes, and there is a gap between the first thermometer and the first heater of the corresponding layer; the auxiliary heating zone further includes at least two second through holes arranged around the side wall at the position corresponding to each layer of the second heater, the at least two second through holes are evenly spaced, at least two second thermometers respectively pass through the corresponding second through holes, and there is a gap between the second thermometer and the second heater of the corresponding layer.
[0012] As an implementable embodiment, the heating structure further comprises a lower heating plate and an upper heating plate, the lower heating plate is located between the lower lifting seat and the lower crucible, and the upper heating plate is located between the upper lifting seat and the upper crucible.
[0013] As an implementation method, a third through hole is provided on the top of the heating structure, and the upper heating plate and the upper lifting seat are respectively provided with a first through hole and a second through hole on the same vertical line as the third through hole, and the third thermometer contacts the outer top surface of the upper crucible through the third through hole, the first through hole, the second through hole;
[0014] A fourth through hole is provided at the bottom of the heating structure, and the lower heating plate and the lower lifting seat are respectively provided with a third through hole and a fourth through hole which are in the same vertical line as the fourth through hole, and the fourth thermometer contacts the outer bottom surface of the lower crucible through the third through hole, the third through hole and the fourth through hole.
[0015] As an implementation method, a porous graphite structure is also provided on the inner bottom surface of the lower crucible, and the porous graphite structure includes at least one porous graphite annular plate, and when there are at least two porous graphite annular plates, at least two porous graphite annular plates are coaxially arranged and their diameters increase successively, and at least one of the porous graphite annular plates is used to separate the silicon carbide powder into multiple layers of silicon carbide powder, wherein the outermost layer of the silicon carbide powder is also evenly mixed with carbon powder.
[0016] As an implementation method, the porous graphite structure has a bottom plate, and the bottom plate is a convex plate protruding toward the porous graphite annular plate.
[0017] As an implementable embodiment, the porous graphite structure and the lower crucible are detachably connected or fixedly connected or formed in one piece.
[0018] As an implementable embodiment, the upper crucible and the lower crucible are connected by sliding through the side walls, which includes: the outer surface of the side wall of the lower crucible and the inner surface of the side wall of the upper crucible are connected by sliding.
[0019] As an implementation method, the inner surface of the side wall of the upper crucible and the outer surface of the side wall of the lower crucible are covered with a coating, and the material of the coating is at least one of metal tantalum, metal hafnium, metal niobium, metal zirconium, tantalum carbide, hafnium carbide, niobium carbide, and zirconium carbide coatings.
[0020] The beneficial effects of the utility model are as follows: the utility model provides a silicon carbide single crystal growth device, which comprises a lower crucible and an upper crucible with openings arranged opposite to each other, and the upper crucible and the lower crucible are connected by side wall sliding. On the one hand, the growth space between the upper crucible and the lower crucible can be fully utilized to further improve the crystal growth thickness, and the combination of the upper crucible and the lower crucible is also more conducive to the stability of the growth space. On the other hand, the upper crucible and the lower crucible are connected by side wall sliding, and the distance between the silicon carbide single crystal growth interface and the silicon carbide powder interface can be maintained by dynamic stretching to control the dynamic balance of the axial temperature gradient, thereby maintaining the stability of the growth interface during the growth process and reducing defects such as dislocations.
[0021] The utility model provides a silicon carbide single crystal growth device, which divides the heating structure into a main heating zone and an auxiliary heating zone. In the early stage of single crystal growth, the crucible structure is heated only by the main heating zone, thereby achieving energy saving. The first protrusion and the corresponding second protrusion are engaged with each other to reduce heat loss, thereby reducing energy consumption and stabilizing the ambient temperature of the main heating zone.
[0022] The utility model provides a silicon carbide single crystal growth device, which can freely adjust the growth space of the growing crystal by setting the number of first heaters and second heaters and the height of each heater layer.
[0023] The utility model provides a silicon carbide single crystal growth device, which is more conducive to the control of the radial temperature gradient of the upper seed crystal and the full sublimation of the lower powder material through the use of an upper heating plate and a lower heating plate.
[0024] The utility model provides a silicon carbide single crystal growth device, which is used to fill silicon carbide powder through a porous graphite structure, and uses a porous graphite annular plate to layer the silicon carbide powder, and adjusts the doping ratio of the outermost silicon carbide powder layer. At the same time, the lower position of the powder is emptied through the bottom protrusion of the porous graphite structure, which reduces the waste of the bottom powder due to low utilization rate on the one hand, and makes the temperature distribution of the powder more uniform through the porous graphite on the other hand.
[0025] The utility model provides a silicon carbide single crystal growth device, which reduces corrosion of the crucible by the growth atmosphere while reducing the resistance of the crucible during the stretching process by coating the inner surface of the side wall of the upper crucible and the outer surface of the side wall of the lower crucible with a coating, wherein the coating material is a metal tantalum, metal hafnium, metal niobium, metal zirconium, tantalum carbide, hafnium carbide, niobium carbide or zirconium carbide coating, thereby maintaining mechanical stability. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 and Figure 2 A schematic diagram of a silicon carbide single crystal growth device provided in some embodiments of the present utility model;
[0027] Figure 3 A schematic side cross-sectional view of a heating structure provided in some embodiments of the utility model;
[0028] Figure 4 A schematic side cross-sectional view of a porous graphite structure provided in some embodiments of the present utility model;
[0029] Figure 5 A schematic top view of a porous graphite structure provided in some embodiments of the present invention. DETAILED DESCRIPTION
[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0031] The terms "first", "second", and similar words used in the specification and claims of this application do not indicate any order, quantity or importance, but are only used to distinguish different components. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, the meaning of "multiple" is two or more. Positional terms such as "upper", "lower", "horizontal direction", "vertical direction", "same vertical line" are defined relative to the orientation schematically placed in the accompanying drawings, and it should be understood that these directional terms are relative concepts, which are used for description and clarification relative to, and may change accordingly according to changes in the orientation in which the device is placed.
[0032] In this application document, unless otherwise clearly specified and limited, the terms "connected", "connection", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two structures or the interaction relationship between two structures, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0033] According to research, the relatively fixed heater of silicon carbide single crystal growth equipment determines that the upper limit of the thickness of the crystal grown in a single furnace is relatively low, the thickness of a single crystal and the number of wafers that can be obtained are restricted, and the cost is difficult to reduce; at the same time, the temperature measurement scheme of silicon carbide single crystal growth equipment with only upper and lower temperature measurement holes cannot guarantee the temperature accuracy and stability of the growth chamber, which brings greater uncertainty to the growth of silicon carbide in the "black box" growth chamber. Moreover, the fixed thermal field growth structure cannot guarantee that the dynamic distance between the silicon carbide raw material and the single crystal growth interface remains stable. As the crystal thickness increases, the temperature gradient of the silicon carbide powder and the single crystal growth interface will decrease, which directly affects the axial temperature gradient in the growth chamber, further reduces the growth rate, and breaks the steady state of the crystal growth interface, which may cause defects such as micropipes, grain boundaries and dislocations during the crystal growth process.
[0034] Therefore, see Figure 1 Some embodiments of the present invention provide a silicon carbide single crystal growth device, comprising:
[0035] Heating structure 100;
[0036] A crucible structure 200 located inside the heating structure 100;
[0037] The crucible structure 200 includes a lower crucible 210 and an upper crucible 220 with openings arranged opposite to each other, the upper crucible 210 and the lower crucible 220 are connected by sliding through side walls, and an inner cavity 215 is provided between the upper crucible 210 and the lower crucible 220; the inner bottom surface 221 of the lower crucible is used to place the silicon carbide powder 300, and the inner top surface of the upper crucible 220 is used to fix the silicon carbide seed crystal 400; when the crucible structure 200 is heated by the heating structure 100, the upper crucible 210 and / or the lower crucible 220 are stretched outward to increase the height of the inner cavity 215 (such as Figure 2 2 is a schematic diagram showing the simultaneous stretching of the upper crucible 210 and the lower crucible 220 to a certain state). On the one hand, by using the inner cavity between the upper crucible 210 and the lower crucible 220 as a growth space, the thickness of the grown crystal can be further increased, and the combination of the upper crucible 210 and the lower crucible 220 is also more conducive to the stability of the growth space; on the other hand, the upper crucible 210 and the lower crucible 220 are connected by side wall sliding, and the distance between the silicon carbide single crystal growth interface and the silicon carbide powder interface can be maintained by dynamic stretching to control the dynamic balance of the axial temperature gradient, maintain the stability of the growth interface during the growth process, and reduce defects such as dislocations.
[0038] In some embodiments, see Figure 3 The heating structure 100 includes an outer frame structure 150, and the outer frame structure 150 includes side walls, a top and a bottom, and the outer frame structure 150 is made of heat-insulating materials. In some embodiments, the inner surface of the side wall of the heating structure 100 is provided with a plurality of heaters distributed in an array. In some embodiments, see Figure 3 The heating structure 100 includes a main heating zone 120 and an auxiliary heating zone 110 located above and / or below the main heating zone 120. Figure 3An exemplary diagram is provided in which an auxiliary heating zone 110 is provided above and below the main heating zone 120, the main heating zone 120 and the auxiliary heating zone 110 are heated by different heaters respectively, and the interior of the main heating zone 120 is connected to the interior of the auxiliary heating zone 110; a first protrusion 130 is arranged around the junction of the inner surface of the side wall of the main heating zone 120 and the auxiliary heating zone 110, and the heating structure 100 also includes a second protrusion 130 corresponding to the first protrusion 130. 40, the second protrusion is located in the auxiliary heating zone, and is used to engage with the first protrusion 130 when the crucible structure 200 is only located in the main heating zone 120. When the upper crucible 210 and / or the lower crucible 220 are stretched, the upper crucible 210 and / or the lower crucible 220 move toward the end of the crucible structure 200, and the first protrusion 130 and the corresponding second protrusion 140 are separated, so that the crucible structure 200 can be located in the auxiliary heating zone 110 at the same time. In one embodiment, the outer side of the end of the crucible structure 200 has a second protrusion that is arranged around and corresponds to the first protrusion 130, that is, the second protrusion can be directly arranged on the crucible structure 200 and formed integrally with the crucible structure. In one embodiment, see Figure 1 and Figure 2 The outer side of the lifting seat for connecting the end surface of the crucible structure 200 has a second protrusion 140 arranged around and corresponding to the first protrusion 130, and the lifting seat includes an upper lifting seat 241 and / or a lower lifting seat 242. In one embodiment, the first protrusion 130 and the second protrusion 140 are both thermal insulation materials, specifically graphite thermal insulation materials.
[0039] When the upper crucible 210 and / or the lower crucible 220 are not stretched, Figure 1 As shown, the crucible structure 200 is located inside the main heating zone 120, and the crucible structure 200 is heated only by the main heating zone 120, and the first protrusion 130 and the second protrusion 140 are engaged with each other, so as to reduce the loss of heat, thereby reducing energy consumption, and at the same time maintaining the stability of the ambient temperature and the stability of the crystal growth temperature in the main heating zone 120; when the upper crucible 210 and / or the lower crucible 220 are stretched, the crucible structure 200 is stretched from Figure 1 As shown, the main heating zone 120 moves to Figure 2As shown, the crucible structure 200 is located at the main heating zone 120 and the auxiliary heating zone 110 at the same time, so that the crucible structure 200 is heated by the main heating zone 120 and the auxiliary heating zone 110. It should be noted that the specific implementation method of stretching the upper crucible 210 and / or the lower crucible 220 can be determined according to the setting method of the auxiliary heating zone 110. For example, when there is an auxiliary heating zone 110 above the main heating zone 120, the upper crucible 210 can be stretched outwards, when there is an auxiliary heating zone 110 below the main heating zone 120, the lower crucible 220 can be stretched outwards, and when there are auxiliary heating zones 110 above and below the main heating zone 120, the upper crucible 210 and the lower crucible 220 can be stretched outwards at the same time.
[0040] In some embodiments, the inner surface of the side wall of the main heating zone 120 has at least one first heater 121 arranged around it, see Figure 3 The figure is an example of having two layers of first heaters, each layer of first heaters may include a plurality of heaters arranged at intervals; the inner surface of the side wall of the auxiliary heating zone 110 has at least one layer of second heaters 111 arranged around it, see Figure 3 For example, a layer of second heater 111 is provided. Each layer of second heater may include a plurality of heaters arranged at intervals. In one embodiment, the number of layers of first heater and second heater and the number of layers of first heater and second heater may be determined according to the desired thickness of the single crystal to be grown. Figure 3 In one embodiment, there is a third protrusion 123 between the first heaters 121 of different layers in the main heating zone 120, and the third protrusion 123 is also a heat-insulating material, specifically a graphite heat-insulating material. In one embodiment, both the first heater and the second heater are graphite resistive heaters.
[0041] Some embodiments of the utility model separate the heaters in adjacent layers by thermal insulation materials to ensure the stability of the temperature zones between the heaters in different layers. Meanwhile, the purpose of setting the axial temperature gradient can be achieved by setting the output power of different heaters.
[0042] In some embodiments of the utility model, a growth device with a multi-layer heater can stretch the growth crucible in both the upper and lower directions, so as to make full use of the growth space in the growth crucible and expand the growable thickness of the crystal. The number of heaters to be used can be determined according to actual production needs. While maintaining a larger stable temperature zone, the number of heaters used can be increased to extend the effective thickness of the crystal for a single growth, increase the output of a single crystal, and further reduce costs.
[0043] In some embodiments, the main heating zone 120 further includes at least two first through holes arranged around the side wall at the position corresponding to each layer of the first heater 111, the at least two first through holes are evenly spaced, at least two first thermometers 122 respectively pass through the corresponding first through holes, and there is a gap between the first thermometer 122 and the first heater 111 of the corresponding layer; the auxiliary heating zone 110 further includes at least two second through holes arranged around the side wall at the position corresponding to each layer of the second heater 111, the at least two second through holes are evenly spaced, at least two second thermometers 112 respectively pass through the corresponding second through holes, and there is a gap between the second thermometer 112 and the second heater 111 of the corresponding layer, for measuring the temperature of a fixed position in the heating structure 100. In one embodiment, both the first thermometer 122 and the second thermometer 112 are thermocouple thermometers. In one embodiment, the first thermometer 122 and the second thermometer 112 may correspond to the middle position of the first heater of the corresponding layer in the vertical direction.
[0044] In some embodiments, the heating structure 100 further includes an upper lifting seat 241 and a lower lifting seat 242, which are respectively located at the two end surfaces of the crucible structure 200, namely, the outer bottom surface 222 of the lower crucible and the outer top surface 212 of the upper crucible, and are respectively used to fix the upper crucible 210 and the lower crucible 220, and by moving the upper lifting seat 241 and the lower lifting seat 242, the upper crucible 210 and the lower crucible 220 can be moved. In some embodiments, when the heating structure 100 includes a main heating zone 120 and an auxiliary heating zone 110 located above or below the main heating zone 120, the heating structure 100 may also include only the upper lifting seat 241 or only the lower lifting seat 242. In one embodiment, the second protrusion 140 is arranged around the outer side of the upper lifting seat 241 and / or the lower lifting seat 242. It should be noted that the second protrusion 140 is arranged around the outer side of the upper lifting seat 241 and / or the lower lifting seat 242, including the following situations: the second protrusion 140 is arranged on the outer side of the upper lifting seat 241 or the outer side of the lower lifting seat 242, and the two second protrusions 140 are respectively on the outer sides of the upper lifting seat 241 and the lower lifting seat 242, which is determined according to the actual setting of the auxiliary heating zone 110.
[0045] In some embodiments, the heating structure 100 also includes an upper heating plate 231 and a lower heating plate 232, and the upper heating plate 231 and the lower heating plate 232 are used to heat the outer top surface 212 of the upper crucible and the outer bottom surface 222 of the lower crucible, respectively, to compensate for the insufficient and uneven heating of the lateral heater, and then control the axial and radial temperature gradients to reduce thermal stress and shear stress.
[0046] In some embodiments, the top of the heating structure 100 is provided with a third through hole, the upper heating plate 231 and the upper lifting seat 241 are respectively provided with a first through hole and a second through hole on the same vertical line as the third through hole, and the third thermometer 250 is in contact with the outer top surface 212 of the upper crucible through the third through hole, the first through hole, and the second through hole, and is used to detect the temperature of the outer top surface 212 of the upper crucible, and can be used to detect the temperature of the central area of the outer top surface 212 of the upper crucible. In some embodiments, the bottom of the heating structure 100 is provided with a fourth through hole, the lower heating plate 232 and the lower lifting seat 242 are respectively provided with a third through hole and a fourth through hole on the same vertical line as the fourth through hole, and the fourth thermometer 260 is in contact with the outer bottom surface 222 of the lower crucible through the third through hole, the third through hole, and the fourth through hole, and is used to detect the temperature of the outer bottom surface 222 of the lower crucible, and can be used to detect the temperature of the central area of the outer bottom surface 222 of the lower crucible. In one embodiment, the third thermometer 250 and the fourth thermometer 260 are both thermocouple thermometers.
[0047] Taking advantage of the high accuracy of thermocouple thermometers, the temperature of the equipment growth chamber is calculated and determined by measuring the temperature at a fixed position on the side of the insulation cylinder. At the same time, the temperatures of the upper and lower thermometers are corrected to more accurately grasp the temperature of the single crystal growth position (the inner top surface of the upper crucible is also the center of the back of the seed crystal) and the silicon carbide powder (the inner bottom surface of the lower crucible is also the center of the circle directly below the powder area).
[0048] In some embodiments, see Figure 1, the upper crucible 210 and the lower crucible 220 are connected by sliding through the side wall, including: the outer surface of the side wall of the lower crucible 210 and the inner surface of the side wall of the upper crucible 220 are connected by sliding. In some embodiments, in the early stage of single crystal growth, when the crucible structure 200 is located inside the heating structure 100, the upper crucible 210 is connected to the upper heating plate 231 by threading, the lower crucible 210 is fixed in the positioning groove of the lower heating plate 232 by gravity, and the upper crucible 210 and the lower crucible 220 are both located in the main heating zone 120, and the second protrusion 140 is located in the auxiliary heating zone 110 and is engaged with the first protrusion 130. The first heater 121 of the main heating zone 120 is used to perform initial heating and crystal growth. When the thickness of the crystal reaches several millimeters or the growth time is 10 hours or 15 hours, the distance between the silicon carbide raw powder and the single crystal growth interface needs to be maintained so as to maintain the temperature gradient between the powder and the growth interface. The upper crucible 210 and / or the lower crucible 220 are pulled outward so that the crucible structure 200 moves from being located in the main heating zone 120 to being located in both the main heating zone 120 and the auxiliary heating zone 110, so that the crucible structure 200 is heated by the main heating zone 120 and the auxiliary heating zone 110.
[0049] In some embodiments, the inner surface of the side wall of the upper crucible and the outer surface of the side wall of the lower crucible are coated with a coating, and the material of the coating is at least one of metal tantalum, metal hafnium, metal niobium, metal zirconium, tantalum carbide, hafnium carbide, niobium carbide, and zirconium carbide coating. This can effectively reduce the corrosion of the crucible by the silicon carbide atmosphere during the growth process, and can also reduce the sliding resistance of the crucible during the stretching process, and maintain a stable environment during the growth process.
[0050] Further research has shown that the filling and processing of silicon carbide powder during the growth process determines the partial pressure and proportion of each substance in the growth atmosphere. The early crystal growth nucleation and the later stable growth are determined by the growth atmosphere of the powder sublimation. In the early stage of crystal growth, excessive partial pressure of silicon atmosphere will affect the initial nucleation of silicon carbide on the seed crystal, causing more defects in subsequent growth; as the silicon carbide crystal continues to grow, the powder will gradually carbonize, and the carbonized particles will overcome their own gravity under the action of the temperature field and be transported to the growth zone to form defects such as carbon encapsulation, which reduces the effective thickness and utilization rate of the crystal ingot, causing waste of resources and increasing production costs.
[0051] Therefore, in some embodiments of the present invention, the inner bottom surface 221 of the lower crucible is further provided with the following Figure 4 and Figure 5The porous graphite structure shown in the figure comprises at least one porous graphite annular plate 10, and when there are at least two porous graphite annular plates 10, at least two porous graphite annular plates 10 are coaxially arranged and their diameters are successively larger, and at least one of the porous graphite annular plates 10 is used to separate the silicon carbide powder into multiple layers of silicon carbide powder, wherein the outermost layer of the silicon carbide powder layer 11 is also uniformly mixed with carbon powder, so that in the early stage of growth, the outermost layer of the silicon carbide powder layer will preferentially sublimate and crystallize, and the carbon powder in the powder will first react with the silicon atmosphere in the early stage of growth to generate Si2C and SiC2 , in order to reduce the problem of excessively high proportion of silicon atmosphere in the initial growth atmosphere, and reduce the generation of polycrystals and polymorphs in the nucleation and early growth stages; and in the later growth stages, since the outermost lower powder is the position where the temperature rises the highest and fastest, the powder will carbonize, and the carbonization starts from the bottom, but since the outermost lower powder is the position where the temperature rises the highest and fastest, the powder will sinter together at high temperature to form a whole similar to a porous material, and thus will filter the powder volatilized in the later stage, that is, during the upward sublimation of the atmosphere, the upper powder will filter the lower carbonized powder that may be carried by the atmosphere, further reducing carbon encapsulation. Moreover, the porous graphite material of the porous graphite annular plate plays a certain filtering role in this process, and the atmosphere will also diffuse toward the center through the porous graphite material, thereby reducing the amount of carbon encapsulation.
[0052] In some embodiments, the outermost porous graphite annular plate in the porous graphite structure may be in contact with the inner surface of the crucible side wall, so that the outermost silicon carbide powder layer 11 is located between two of the porous graphite annular plates. In some embodiments, the outermost porous graphite annular plate in the porous graphite structure may also be spaced from the inner surface of the crucible side wall, so that the outermost silicon carbide powder layer 11 is located between the outermost porous graphite annular plate and the inner surface of the crucible side wall.
[0053] Exemplarily, when the powder is filled, the outermost layer of silicon carbide powder is mixed with micron-sized carbon powder of a certain concentration (carbon-silicon ratio of 1.05:1 to 1.1:1), except that the middle layer of the outermost layer of silicon carbide powder is normally loaded according to the carbon-silicon ratio of 1:1. After assembly, the lower crucible 220 is placed above the lower heating plate 232, and the upper surface of the powder is within the second layer of the first heater 121 in the vertical direction of the main heating zone 120. The furnace is evacuated to a high vacuum state, and the growth chamber is heated. At the same time, argon gas and vacuum operations are repeatedly performed to ensure the purity and uniform distribution of argon protective gas in the growth chamber. The power is increased to raise the upper and lower temperatures to 2000°C, and the powder is sintered. Sintering the powder into a block can effectively reduce edge defects (microtubes and dislocations, etc.); the gas pressure in the furnace is slowly reduced to the growth pressure in stages, and the temperature is slowly increased to the growth temperature of 2300°C while the pressure is reduced. In this process, the seed crystal slowly completes nucleation.
[0054] During the growth process, in the initial growth stage, under the heating of the first heater, the temperature gradually decreases from the outside to the inside, and the high temperature zone is located in the outermost silicon carbide powder layer 11. Therefore, the outermost silicon carbide powder layer 11 will sublime and crystallize first, and the carbon powder in the powder will first react with the silicon atmosphere in the initial growth stage to generate Si2C and SiC2, so as to reduce the problem of excessively high proportion of silicon atmosphere in the initial growth atmosphere, and reduce the generation of polycrystalline and polymorphic in the initial nucleation and growth stages, thereby effectively inhibiting the formation and development of dislocations and ensuring high-quality growth in the initial stage. As the growth progresses, the crystal reaches a certain thickness, and the high temperature zone gradually moves toward the center, and the middle layer powder begins to sublime. Due to the sufficient raw materials of the gas phase components and the dislocation inhibition of the initial crystal, the crystal grows rapidly at this stage. At this time, since the growth of the crystal enters a stable period, the growth rate also tends to be stable. Therefore, the auxiliary heating zone 110 is used for heating at the same time, and the upper crucible 210 cooperates with the crystal growth speed and moves up slowly at a certain rate to keep the distance between the single crystal growth interface and the powder interface dynamically stable, and keep the axial temperature gradient relatively stable. By extending the growth time, the effective thickness of the crystal is increased at a relatively constant rate. After the crystal growth is completed, each powder area can be cleaned separately, and some graphite parts with severe corrosion can be replaced separately, avoiding the high cost of replacing all of them.
[0055] Furthermore, after research, it was found that in the traditional full-filling method of silicon carbide powder filling, the outer part of the powder is severely carbonized, while the powder in the lower center basically maintains its original state, and the powder utilization rate is low.
[0056] Therefore, see Figure 4The porous graphite structure has a bottom plate 20, and the bottom plate 20 protrudes toward the porous graphite annular plate 10. The bottom plate 20 replaces the silicon carbide powder to reduce the waste caused by insufficient use of the powder. In some embodiments, the bottom plate 20 can be a conical plate, and the conical plate can be a conical structure.
[0057] In some embodiments, the porous graphite structure and the lower crucible 220 are detachably connected. In some embodiments, the porous graphite structure and the lower crucible 220 may also be fixedly connected or formed as one piece.
[0058] Some embodiments of the utility model design a structure of layered filling of porous graphite, use porous graphite material to divide powder, adjust the doping ratio of different layered powders, and at the same time, the porous graphite in the lower position of the powder is suspended through the circular bottom plate. On the one hand, it reduces the waste of the bottom powder due to low utilization rate, and on the other hand, the temperature distribution of the powder is made more uniform through the porous graphite.
[0059] Some embodiments of the present invention change the growth atmosphere ratio by changing the filling method of silicon carbide powder: by adding appropriate amounts of carbon particles to the powder at different positions, the powder is changed from outside to inside, and the atmosphere ratio of the sublimation process is greatly different, which affects the initial nucleation and later growth and reduces silicon droplets and carbon inclusions.
[0060] Accordingly, some embodiments of the present invention further provide a method for preparing a silicon carbide single crystal, comprising:
[0061] A silicon carbide single crystal growth device is provided; the silicon carbide single crystal growth device comprises a heating structure 100 and a crucible structure 200 located inside the heating structure 100, the crucible structure comprises a lower crucible 210 and an upper crucible 220 with openings arranged opposite to each other, the upper crucible 210 and the lower crucible 220 are connected by sliding through side walls, silicon carbide powder is placed on the inner bottom surface of the lower crucible 220, and a silicon carbide seed crystal is fixed on the inner top surface of the upper crucible 210;
[0062] The crucible structure is heated by the heating structure to grow a single crystal; during the growth of the single crystal, the upper crucible 210 and / or the lower crucible 220 are stretched to maintain the distance between the silicon carbide single crystal growth interface and the silicon carbide powder interface to control the dynamic balance of the axial temperature gradient. In one embodiment, when only the upper crucible 210 is pulled up or only the lower crucible 220 is stretched, the stretching speed and the rate of single crystal growth can be kept consistent. In one embodiment, when the upper crucible 210 and the lower crucible 220 are stretched at the same time, the stretching speed can also be adjusted according to the single crystal growth speed, so that the crystal growth speed and the height growth speed of the cavity 215 are kept consistent, thereby maintaining the temperature dynamic balance. In some embodiments, the silicon carbide powder and the silicon carbide seed crystal can be placed in the crucible structure 200, and then the crucible structure 200 is placed in the heating structure 200. In some embodiments, please refer to the previous description for the specific introduction of some other silicon carbide single crystal growth devices.
[0063] In some embodiments, according to the distance between the silicon carbide seed crystal and the silicon carbide powder in the crucible structure, the upper crucible and / or the lower crucible may not be stretched at the initial stage of single crystal growth, so that the crucible structure 200 is only located inside the main heating zone 120, and the first heater 121 of the main heating zone 120 may be used for initial heating and crystal growth. In the middle and late stages of single crystal growth, in order to maintain a stable temperature gradient between the single crystal growth interface and the silicon carbide powder, for example, when the thickness of the crystal reaches several millimeters or the growth time reaches 5 hours, it is necessary to preheat the second heater 111 of the auxiliary heating zone 110 to reach the growth temperature. In the subsequent crucible stretching process, the temperature of the crucible environment (referring to the entire growth chamber) can be controlled at the crystal growth temperature, thereby reducing the growth rate changes caused by temperature fluctuations, thereby causing possible polymorphic problems, such as Figure 3 As shown, the upper crucible 210 and / or the lower crucible 220 are gradually raised and / or lowered after the crystal growth time of 10 hours or 15 hours, and the speed of raising or lowering the crucible matches the crystal growth speed. In some embodiments, the speed can be controlled within the range of 0.2 mm / h to 0.5 mm / h.
[0064] Although the utility model has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the utility model. Any technical personnel in this field can make possible changes and modifications to the technical solution of the utility model by using the methods and technical contents disclosed above without departing from the spirit and scope of the utility model. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the utility model without departing from the content of the technical solution of the utility model are within the protection scope of the technical solution of the utility model.
Claims
1. A silicon carbide single crystal growth device, characterized in that: include: Heating structures; a crucible structure located inside the heating structure; The crucible structure comprises a lower crucible and an upper crucible with openings arranged opposite to each other, and the upper crucible and the lower crucible are connected by sliding side walls; the inner bottom surface of the lower crucible is used to place silicon carbide powder, and the inner top surface of the upper crucible is used to fix silicon carbide seed crystals.
2. The silicon carbide single crystal growth device according to claim 1, characterized in that: The heating structure comprises a main heating zone and an auxiliary heating zone located above and / or below the main heating zone, the main heating zone and the auxiliary heating zone are heated by different heaters respectively, and the interior of the main heating zone is connected to the interior of the auxiliary heating zone; the junction of the main heating zone and the auxiliary heating zone has a first protrusion arranged around the inner surface of the side wall and extending toward the interior of the heating structure; the heating structure also comprises an upper lifting seat and / or a lower lifting seat, the upper lifting seat is used to connect to the outer top surface of the upper crucible, and the lower lifting seat is used to connect to the outer bottom surface of the lower crucible; the outer side of the upper lifting seat and / or the lower lifting seat has a second protrusion arranged around and corresponding to the first protrusion; When the upper crucible and / or the lower crucible are not stretched, the crucible structure is located inside the main heating zone, and the first protrusion is engaged with the corresponding second protrusion; when the upper crucible and / or the lower crucible are stretched so that the upper crucible and the lower crucible slide, the first protrusion is separated from the corresponding second protrusion, and the crucible structure moves from being located in the main heating zone to being located in both the main heating zone and the auxiliary heating zone.
3. The silicon carbide single crystal growth device according to claim 2, characterized in that: The inner surface of the side wall of the main heating zone has at least one layer of first heaters arranged around it; the inner surface of the side wall of the auxiliary heating zone has at least one layer of second heaters arranged around it.
4. The silicon carbide single crystal growth device according to claim 2, characterized in that: The main heating zone also includes at least two first through holes arranged around the side wall at the position corresponding to each layer of the first heater, the at least two first through holes are evenly spaced, at least two first thermometers respectively pass through the corresponding first through holes, and there is a gap between the first thermometer and the first heater of the corresponding layer; the auxiliary heating zone also includes at least two second through holes arranged around the side wall at the position corresponding to each layer of the second heater, the at least two second through holes are evenly spaced, at least two second thermometers respectively pass through the corresponding second through holes, and there is a gap between the second thermometer and the second heater of the corresponding layer.
5. The silicon carbide single crystal growth device according to claim 2, characterized in that: The heating structure further comprises a lower heating plate and an upper heating plate, wherein the lower heating plate is located between the lower lifting seat and the lower crucible, and the upper heating plate is located between the upper lifting seat and the upper crucible.
6. The silicon carbide single crystal growth device according to claim 5, characterized in that: The top of the heating structure is provided with a third through hole, the upper heating plate and the upper lifting seat are respectively provided with a first through hole and a second through hole on the same vertical line as the third through hole, and the third thermometer contacts the outer top surface of the upper crucible through the third through hole, the first through hole, the second through hole; A fourth through hole is provided at the bottom of the heating structure, and the lower heating plate and the lower lifting seat are respectively provided with a third through hole and a fourth through hole which are in the same vertical line as the fourth through hole, and the fourth thermometer contacts the outer bottom surface of the lower crucible through the third through hole, the third through hole and the fourth through hole.
7. The silicon carbide single crystal growth device according to claim 1, characterized in that: A porous graphite structure is also provided on the inner bottom surface of the lower crucible, and the porous graphite structure includes at least one porous graphite annular plate. When there are at least two porous graphite annular plates, at least two porous graphite annular plates are coaxially arranged and their diameters increase successively. At least one of the porous graphite annular plates is used to separate the silicon carbide powder into multiple layers of silicon carbide powder, wherein the outermost layer of the silicon carbide powder is also evenly mixed with carbon powder.
8. The silicon carbide single crystal growth device according to claim 7, characterized in that: The porous graphite structure has a bottom plate, and the bottom plate is a convex plate protruding toward the porous graphite annular plate.
9. The silicon carbide single crystal growth device according to claim 7, characterized in that: The porous graphite structure and the lower crucible are detachably connected or fixedly connected or integrally formed.
10. The silicon carbide single crystal growth device according to claim 1, characterized in that: The upper crucible and the lower crucible are connected by sliding through the side walls, which includes: an outer surface of the side wall of the lower crucible and an inner surface of the side wall of the upper crucible are connected by sliding.
11. The silicon carbide single crystal growth device according to claim 10, characterized in that: The inner surface of the side wall of the upper crucible and the outer surface of the side wall of the lower crucible are covered with a coating, and the material of the coating is one of metal tantalum, metal hafnium, metal niobium, metal zirconium, tantalum carbide, hafnium carbide, niobium carbide, and zirconium carbide coating.