Device for introducing dominant forced convection for growing single crystal by resistance heating LPE method

Abstract

The utility model relates to the technical field of single crystal preparation by a liquid phase epitaxy method, in particular to a leading forced convection introducing device for single crystal growth by a resistance heating LPE method, which comprises a graphite crucible and a graphite heating component arranged on the outer side of the graphite crucible, one end of the graphite seed crystal rod extends into the graphite crucible and is connected with the graphite seed crystal support; the seed crystal is adhered to the bottom surface of the graphite seed crystal support; the graphite annular turbofan is arranged in the graphite crucible; the graphite annular turbofan is connected with the graphite seed rod through a jackscrew clamp; the other end of the graphite seed crystal rod is externally connected with a seed crystal lifting and rotating mechanism; and the graphite seed crystal rod drives the seed crystal and the graphite annular turbofan to do lifting and rotating motion. According to the device, the influence of adverse convection on the whole flow field is weakened, and the controllability of the whole flow field can be improved; and meanwhile, an ideal temperature field for growing high-quality silicon carbide crystals in the growth cavity is ensured.

Description

Technical Field

[0001] This invention relates to the field of liquid phase epitaxy (LPE) for single crystal preparation, and particularly to a device for introducing dominant forced convection for single crystal growth using resistance heating (LPE). Background Technology

[0002] Liquid phase epitaxy (LPE) is a method for growing single-crystal thin layers by precipitating solid-phase materials from a solution and depositing them onto a substrate. Electromagnetic induction heating is commonly used in LPE silicon carbide single-crystal growth. However, the varying magnetic induction intensity at different locations within the growth cavity leads to uneven temperature distribution and uncontrollable temperature field. The magnetic induction intensity near the center of the coil is high, resulting in significant heat generation, while the magnetic induction intensity near the axis and the upper and lower ends is low, generating less heat. Furthermore, the skin effect occurs, increasing the difficulty of thermal field design and temperature field control. Secondly, during the melting process, the seed crystal is heated and baked, and some solution vapor condenses on the seed crystal growth surface. Direct growth at this point can lead to defects such as polymorphism. Therefore, a remelting process is required after preheating the seed crystal. For growth cavities heated by electromagnetic induction, the seed crystal and crucible need to be moved simultaneously and at the same speed during the remelting process to ensure a higher temperature at the liquid surface and a lower temperature at the bottom of the solution. However, maintaining contact between the seed crystal and the liquid surface without relative movement is difficult during this process. Meanwhile, when a large crystal growth temperature gradient is required, the temperature at the bottom of the solution will be much higher than the surface temperature. In this case, it is difficult to achieve the desired temperature field—low at the bottom and high at the surface—during remelting by adjusting the relative positions of the crucible and coil. Furthermore, the liquid-phase growth of silicon carbide single crystals involves four types of convection: buoyancy flow due to density differences caused by temperature differences, Marangoni convection due to surface tension differences caused by temperature differences, Lorentz convection due to electromagnetic induction heating, and forced convection due to the rotation of the seed crystal and crucible. These four types of convection interfere with and compete with each other, resulting in poor overall flow controllability and a decrease in overall flow field stability. Therefore, there is an urgent need to provide a device that enables controllable temperature field within the growth chamber and provides high overall flow field stability within the growth chamber.

[0003] This invention provides a device for introducing dominant forced convection for the growth of single crystals using the resistance heating LPE method, in order to solve the problems of uncontrollable temperature field in the growth cavity, high difficulty in thermal field design, and poor overall flow field stability in existing single crystal growth devices. Utility Model Content

[0004] The purpose of this invention is to provide a device for introducing dominant forced convection for the growth of single crystals using the resistance heating LPE method, so as to solve the problems of uncontrollable temperature field in the growth cavity, high difficulty in thermal field design, and poor overall flow field stability in existing single crystal growth devices.

[0005] The technical solution of this utility model is: a device for introducing dominant forced convection for growing single crystals by resistance heating LPE method, comprising a graphite crucible, a graphite heating component disposed outside the graphite crucible, a graphite seed crystal rod extending into the graphite crucible and connected to a graphite seed crystal holder, and a seed crystal bonded to the bottom surface of the graphite seed crystal holder; further comprising a graphite annular vortex fan disposed inside the graphite crucible; the graphite annular vortex fan being connected to the graphite seed crystal rod via a set screw clamp; the other end of the graphite seed crystal rod being externally connected to a seed crystal lifting and rotating mechanism; the graphite seed crystal rod driving the seed crystal and the graphite annular vortex fan to perform lifting and rotating movements.

[0006] Preferably, the graphite annular turbine fan includes an inner cylinder and an outer fixing ring arranged coaxially, and a plurality of fan blades fixedly arranged between the inner cylinder and the outer fixing ring; the plurality of fan blades are spaced apart and all have the same inclination angle; one end of the set screw clamp is fixedly connected to the inner cylinder and the other end is fixedly connected to the graphite seed crystal rod.

[0007] Preferably, the bottom of the inner side of the graphite crucible is spherical; a support rod is provided at the bottom end of the graphite crucible; and a flow guide cone is also provided inside the graphite crucible.

[0008] Preferably, the graphite heating assembly includes a top heating group, a side heating group, and a bottom heating group;

[0009] The top heating group and the bottom heating group are respectively disposed above and below the graphite crucible; the side heating group is disposed around the graphite crucible.

[0010] Preferably, the top heating group and the bottom heating group are both configured as annular, and the central axis of the top heating group and the bottom heating group coincides with the central axis of the graphite crucible; the side heating group is configured as vertically segmented.

[0011] Preferably, the graphite seed crystal holder has internal threads; the graphite seed crystal rod has external threads, and the graphite seed crystal holder is threadedly connected to the graphite seed crystal rod; the seed crystal is bonded to the graphite seed crystal holder by graphite adhesive through hot pressing.

[0012] Compared with the prior art, the advantages of this utility model are:

[0013] (1) This utility model provides a device for introducing dominant forced convection for single crystal growth using resistance heating LPE method. This device can drive the seed crystal and graphite annular vortex fan to move up and down and rotate via a graphite seed crystal rod. The bottom of the graphite crucible is spherical, and a flow guide cone is also provided inside the graphite crucible. During the rotation of the graphite annular vortex fan in the solution, eddies are formed in the solution. This causes the solution in the low-temperature zone to flow downwards and drives the high-carbon-concentration solution in the high-temperature zone to flow upwards, directly reaching the growth front of the seed crystal, promoting rapid crystal growth. Furthermore, the overall flow field is affected by the forced convection dominated by the annular vortex fan, thereby improving the controllability of the overall flow field. This device improves performance and suppresses non-ideal buoyancy flow, Marangoni convection, and avoids Lorentz convection caused by electromagnetic stirring, thus weakening the impact of unfavorable convection on the overall flow field. Simultaneously, the graphite heating assembly is divided into three parts, allowing for the regulation of heat generation by adjusting the power of each part, thereby controlling the temperature field in different regions of the growth chamber and ensuring an ideal temperature field for growing high-quality silicon carbide crystals. This solves the problems of uncontrollable temperature field within the growth chamber, difficult thermal field design, and poor overall flow field stability in existing single-crystal growth devices. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0015] Figure 1 This is a cross-sectional view of the apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to the present invention.

[0016] Figure 2 This is a schematic diagram of the graphite annular vortex fan described in this utility model;

[0017] Figure 3 This is a top view of the graphite annular turbine fan described in this utility model;

[0018] The components include: 1. Graphite crucible; 2. Graphite heating assembly; 21. Top heating assembly; 22. Side heating assembly; 23. Bottom heating assembly; 3. Graphite seed crystal rod; 4. Graphite seed crystal holder; 5. Seed crystal; 6. Graphite annular turbine fan; 61. Inner cylinder; 62. Outer fixing ring; 63. Fan blade; 7. Top screw clamp; 8. Flow guide cone; 9. Support rod. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments:

[0020] In the description of this utility model, it should be noted that the terms "upper", "lower", "side", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] A device for introducing dominant forced convection in the resistance-heated LPE method for growing single crystals, such as... Figure 1 As shown, the device includes a graphite crucible 1, a graphite heating assembly 2, a graphite seed crystal rod 3, a graphite seed crystal holder 4, and a seed crystal 5. The graphite assembly 2 is disposed outside the graphite crucible 1, and the graphite seed crystal holder 4 is disposed inside. A silicon block for crystal growth is placed in the growth chamber inside the graphite crucible 1. The graphite heating assembly 2 heats the graphite crucible 1, melting the silicon block into a solution. One end of the graphite seed crystal rod 3 extends into the graphite crucible 1 and connects with the graphite seed crystal holder 4. The seed crystal 5 is fixedly bonded to the bottom surface of the graphite seed crystal holder 4; the device also includes a graphite annular vortex fan 6 disposed in the graphite crucible 1; and the graphite annular vortex fan 6 is connected to the graphite seed crystal rod 3 through a set screw clamp 7; the other end of the graphite seed crystal rod 3 is externally connected to a seed crystal lifting and rotating mechanism, which can drive the graphite seed crystal rod 3 to perform lifting and rotating movements, so that the graphite seed crystal rod 3 can drive the seed crystal 5 and the graphite annular vortex fan 6 to perform lifting and rotating movements.

[0022] The graphite annular turbofan 6 is coated with a tantalum carbide coating; and, as Figure 2 As shown, the graphite annular turbine fan 6 includes an inner cylinder 61 and an outer fixing ring 62 arranged coaxially, and several fan blades 63 fixedly arranged between the inner cylinder 61 and the outer fixing ring 62; the fan blades 63 are spaced apart, and the inclination angles of the fan blades 63 are the same; one end of the set screw clamp 7 is fixedly connected to the inner cylinder 61, and the other end is fixedly connected to the graphite seed crystal rod 3. The bottom of the inner side of the graphite crucible 1 is spherical for guiding the flow and providing a flow channel for the flow of the solution in the growth chamber; a guide cone 8 is also provided in the graphite crucible 1, and the guide cone 8 is located at the center of the bottom of the graphite crucible 1; the fluid is further combed through the flow channels of the guide cone 8 and the spherical guide cone, guiding the originally horizontally inward flow of the fluid to flow upward to the crystal growth interface, forming an annular convection with upward convection in the center and downward convection around the perimeter, suppressing the downward convection in the center and the upward annular convection around the perimeter caused by the unfavorable buoyancy flow and Marangoni convection. A support rod 9 is provided on the outer side of the bottom of the graphite crucible 1 to support and fix the graphite crucible 1.

[0023] The graphite heating assembly 2 includes a top heating group 21, a side heating group 22, and a bottom heating group 23. The top heating group 21 is positioned above the graphite crucible 1, and the bottom heating group 23 is positioned below the graphite crucible 1. Both the top heating group 21 and the bottom heating group 23 are circular in shape, and their central axes coincide with the central axis of the graphite crucible 1. The side heating group 22 is positioned around the graphite crucible 1 and is vertically segmented. In this application, resistance heating is used instead of traditional electromagnetic induction heating. Therefore, no Lorentz force convection interference is generated during heating and crystal growth. Furthermore, by dividing the graphite heating assembly 2 into three parts, the heat output can be controlled by adjusting the power of the graphite heating groups in different parts, thereby achieving temperature control in different regions within the growth chamber. Meanwhile, to more uniformly heat the internal growth cavity of the graphite crucible 1, the outer diameters of the top heating group 21 and the bottom heating group 23 are not less than the inner diameter of the graphite crucible 1, and the outer diameters of the top heating group 21 and the bottom heating group 23 are not less than the diameter of the upper opening of the graphite crucible 1; the height of the side heating group 22 is not less than the height of the graphite crucible 1. Furthermore, an insulation layer is provided on the outside of the graphite heating assembly 2, and outside the insulation layer is a stainless steel outer cavity with built-in water-cooling pipes. The seed crystal lifting and rotating mechanism is located inside the stainless steel outer cavity; the seed crystal lifting and rotating mechanism includes a lifting module and a rotating module located at the output end of the lifting module; wherein, the output end of the rotating module is connected to the graphite seed crystal rod 3 and is used to drive the graphite seed crystal rod 3 to rotate; the lifting module is used to drive the rotating module and the graphite seed crystal rod 3 connected to the output end of the rotating module to perform lifting and lowering movements; thereby enabling the graphite seed crystal rod 3 to drive the seed crystal 5 and the graphite annular turbine fan 6 to perform lifting and rotating movements. The rotation of the seed crystal 5 at the crystal growth liquid surface and the graphite annular turbine 6 in the solution creates eddies, causing the solution in the low-temperature zone at the edge of the graphite crucible 1 to flow downwards. Upon reaching the bottom of the spherical crucible, the solution in the high-temperature zone at the bottom carries the high-carbon-concentration solution upwards, reaching the growth front of the seed crystal. Furthermore, the overall flow field is influenced by forced convection dominated by the annular turbine during the rotation of the seed crystal 5 and the graphite annular turbine 6, thus improving the overall flow field controllability. It also suppresses non-ideal buoyancy flow, Marangoni convection, and avoids Lorentz convection generated by electromagnetic stirring. In this embodiment, the lifting module uses a combination of a servo motor and a lead screw, while the rotating module uses a combination of a rotary motor, a worm gear reducer assembly, and transmission gears.

[0024] In addition, in this embodiment, the graphite seed crystal holder 4 has internal threads; the graphite seed crystal rod 3 has external threads; the seed crystal 5 is first bonded to the bottom surface of the graphite seed crystal holder 4 by hot pressing using graphite adhesive, and then the graphite seed crystal holder 4 and the graphite seed crystal rod 3 are connected by threaded connection; in other embodiments, the graphite seed crystal holder 4 and the graphite seed crystal rod 3 can adopt other connection methods.

[0025] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. It is obvious to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that it can be implemented in other specific forms without departing from the spirit or basic characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this utility model is defined by the appended claims rather than the foregoing description, and therefore, all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within this utility model.

Claims

1. An apparatus for introducing dominant forced convection for single crystal growth by resistance heating LPE method, comprising a graphite crucible (1), a graphite heating component (2) disposed outside the graphite crucible (1), a graphite seed rod (3) extending one end into the graphite crucible (1) and connected to a graphite seed crystal holder (4), and a seed crystal (5) bonded to the bottom surface of the graphite seed crystal holder (4); characterized in that, It also includes a graphite annular vortex fan (6) set inside the graphite crucible (1); the graphite annular vortex fan (6) is connected to the graphite seed crystal rod (3) through a set screw clamp (7); the other end of the graphite seed crystal rod (3) is externally connected to a seed crystal lifting and rotating mechanism; the graphite seed crystal rod (3) drives the seed crystal (5) and the graphite annular vortex fan (6) to perform lifting and rotating movements.

2. The apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to claim 1, characterized in that: The graphite annular turbine fan (6) includes an inner cylinder (61) and an outer fixing ring (62) arranged coaxially, and a number of fan blades (63) fixedly arranged between the inner cylinder (61) and the outer fixing ring (62); the number of fan blades (63) are spaced apart and have the same tilt angle; one end of the set screw clamp (7) is fixedly connected to the inner cylinder (61), and the other end is fixedly connected to the graphite seed crystal rod (3).

3. The apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to claim 1, characterized in that: The bottom of the graphite crucible (1) is spherical; a support rod (9) is provided at the bottom end of the graphite crucible (1); and a flow guide cone (8) is also provided inside the graphite crucible (1).

4. The apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to claim 2, characterized in that: The graphite heating assembly (2) includes a top heating group (21), a side heating group (22), and a bottom heating group (23); The top heating group (21) and the bottom heating group (23) are respectively disposed above and below the graphite crucible (1); the side heating group (22) is disposed on the periphery of the graphite crucible (1).

5. The apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to claim 4, characterized in that: The top heating group (21) and the bottom heating group (23) are both set in a circular shape, and the central axis of the top heating group (21) and the bottom heating group (23) coincides with the central axis of the graphite crucible (1); the side heating group (22) is set in a vertically segmented shape.

6. The apparatus for introducing dominant forced convection in the resistance heating LPE method for growing single crystals according to claim 5, characterized in that: The graphite seed crystal holder (4) has internal threads; the graphite seed crystal rod (3) has external threads, and the graphite seed crystal holder (4) is threadedly connected to the graphite seed crystal rod (3); the seed crystal (5) is bonded to the graphite seed crystal holder (4) by hot pressing with graphite adhesive.

Images