Crystal growth equipment

Abstract

The utility model discloses a crystal growth equipment, crystal growth equipment includes furnace body, crucible, side heater, heat insulation structure, first drive mechanism and second drive mechanism, the crucible is liftable in the furnace chamber and is used for holding molten soup, side heater is arranged in the furnace chamber and is arranged around the peripheral side of crucible, the heat insulation structure is used for holding the molten soup, and the heat insulation structure is used for holding the molten soup. The heat insulation structure is arranged in the furnace chamber in a liftable mode, the heat insulation structure is arranged between the crucible and the side heater at intervals and surrounds the crucible, the first driving mechanism is connected with the crucible to drive the crucible to ascend and descend relative to the furnace body, and the second driving mechanism is connected with the heat insulation structure to drive the heat insulation structure to ascend and descend relative to the crucible and the furnace body. Therefore, the crystal growth equipment can reduce the difference between the center temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the solid-liquid interface position, and increase the proportion of the COP-free area of the whole crystal bar.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of crystal growth, especially to a crystal growth equipment. BACKGROUND

[0002] Insulated gate bipolar transistor (IGBT) is suitable for controlling the gate voltage driving type switch element of large power, and it is widely used in rail transit, smart grid, aerospace, electric vehicle, photovoltaic wind power, variable frequency household appliance and other fields. As the substrate material of IGBT chip, the quality of semiconductor grade single crystal silicon wafer plays a crucial role in the performance of IGBT chip.

[0003] In the CZ crystal growth method (direct pulling single crystal manufacturing method) of large size, the degree of heat convection in the melt becomes very large, and the strong heat convection even causes the occurrence of turbulence, so that the degree of temperature change in the melt is more intense, and the uniformity of temperature gradient distribution at the solid-liquid interface is poor, especially the difference between the center temperature gradient and the edge temperature gradient of the crystal bar is huge, and it is difficult to grow a COP-free (COP-free area in the field of semiconductor materials refers to the area where the silicon wafer does not exist crystal originated particle (COP)) crystal bar. SUMMARY

[0004] The utility model aims at at least solves one of the technical problems existing in the prior art. For this purpose, the utility model provides a crystal growth equipment, which can reduce the difference between the center temperature gradient Gc and the edge temperature gradient Gs of silicon single crystal at the solid-liquid interface position, and improve the proportion of COP-free area of the whole crystal bar.

[0005] The crystal growth equipment according to the utility model embodiment comprises a furnace body, a furnace chamber is formed in the furnace body; a crucible, the crucible is arranged in the furnace chamber in a lifting manner and is used for containing a melt; a side heater, the side heater is arranged in the furnace chamber and surrounds the outer peripheral side of the crucible; a heat insulation structure, the heat insulation structure is arranged in the furnace chamber in a lifting manner, the heat insulation structure is arranged between the crucible and the side heater in a spaced manner and surrounds the crucible; a first driving mechanism, the first driving mechanism is connected with the crucible to drive the crucible to lift relative to the furnace body; a second driving mechanism, the second driving mechanism is connected with the heat insulation structure to drive the heat insulation structure to lift relative to the crucible and the furnace body.

[0006] According to the crystal growth equipment, the movement of the heat insulation structure is independent of the movement of the crucible, the change trend of the center temperature gradient Gc and the edge temperature gradient Gs at the solid-liquid interface position is flexibly adapted, the center temperature gradient Gc and the edge temperature gradient Gs at the solid-liquid interface position are matched and compensated by the different relative positions of the heat insulation structure relative to the crucible and the side heater in the up-down direction, the difference between the center temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the solid-liquid interface position is reduced, the temperature gradient distribution uniformity at the solid-liquid interface is improved, and the proportion of the COP-free area of the whole crystal bar is improved.

[0007] In some embodiments, the heat insulation structure comprises a heat insulation layer and a heat-resistant protective layer, the heat-resistant protective layer is fully wrapped outside the heat insulation layer, the heat insulation layer is hard felt, and the heat-resistant protective layer is a graphite piece.

[0008] In some embodiments, the heat insulation layer has a thermal conductivity less than or equal to 0.25 W / (m·K), the heat insulation layer is hard felt, and the heat-resistant protective layer is a graphite piece.

[0009] In some embodiments, the second driving mechanism comprises a driver arranged outside and below the furnace body, a plurality of connecting rods arranged at intervals along the circumference of the heat insulation structure, each connecting rod being arranged in the furnace body in the up-down direction and having an upper end connected to the heat insulation structure, and a connecting piece arranged outside the furnace body and formed as an open ring or a closed ring, the connecting piece being connected to the lower end of each connecting rod, the driver driving the plurality of connecting rods to rise and fall synchronously through the connecting piece, and the connecting piece being arranged around the first driving mechanism.

[0010] In some embodiments, the heat insulation structure comprises a heat insulation layer and a heat-resistant protective layer, the heat-resistant protective layer is fully wrapped outside the heat insulation layer, the heat insulation layer is hard felt, the heat-resistant protective layer is a graphite piece, the connecting rod is a graphite piece, and the upper end of the connecting rod is connected to the heat-resistant protective layer.

[0011] In some embodiments, the furnace body is formed with a through hole for the connecting rod to pass through, and the crystal growth equipment further comprises a plurality of protective tubes, each protective tube being arranged around the part of the corresponding connecting rod that extends outside the furnace body, the length of the protective tube in the up-down direction being adjustable, the upper end of the protective tube being sealingly connected to the edge of the corresponding through hole, and the lower end of the protective tube being sealingly connected to the connecting piece, so that the interior space of the furnace body and the interior space of the protective tube are communicated through the through hole, and the connecting piece blocks the lower end of the protective tube.

[0012] In some embodiments, the protective tube is a stainless steel corrugated tube.

[0013] In some embodiments, the crystal growth equipment also includes: a magnetic field device, which is arranged outside the furnace body and is used to generate a magnetic field. In the up and down directions, the center plane of the magnetic field is located at a distance h below the solid-liquid interface of the melt in the crucible, 50mm≤h≤100mm, wherein the magnetic field intensity of the magnetic field on the center plane in the axial direction of the furnace body is 0.

[0014] In some embodiments, the thermal insulation structure has a first position and a second position, and the thermal insulation structure rises and falls at least between the first position and the second position. In the first position, the upper end of the thermal insulation structure is flush with the lower end of the crucible when it is in the lowest position. In the second position, the upper end of the thermal insulation structure extends upward beyond the R angle of the crucible when it is in the highest position.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0017] Figure 1 is a cross-sectional view of a crystal growth apparatus according to one embodiment of the present invention;

[0018] Figure 2 yes Figure 1 Another cross-sectional view of the crystal growth apparatus shown in ;

[0019] Figure 3 is a schematic diagram of a crystal growth apparatus according to one embodiment of the present invention;

[0020] Figure 4 yes Figure 1 Schematic diagram of the assembly of the thermal insulation structure and the connecting rod shown in ;

[0021] Figure 5 yes Figure 1 Schematic diagram of the assembly of the heat insulation structure, furnace body structure, connecting rods, connecting parts and protective tubes shown in FIG;

[0022] Figure 6 yes Figure 5 Another assembly diagram of the heat insulation structure, furnace body structure, connecting rods, connecting parts and protection tube shown in;

[0023] Figure 7 yes Figure 5 A cross-sectional view of the heat insulation structure, furnace body structure, connecting rods, connecting parts and protective tube shown in FIG;

[0024] Figure 8 Fig. 1 is a control method flowchart of a crystal growth device according to an embodiment of the present application;

[0025] Figure 9 Fig. 2 is a schematic diagram of V / I interface at the solid-liquid interface position under different conditions, Figure 9 Fig. 2(a) is a schematic diagram of V / I interface at the solid-liquid interface position under the condition of Gs> Gc, Figure 9 Fig. 2(b) is a schematic diagram of V / I interface at the solid-liquid interface position under the condition of Gs≈ Gc, Figure 9 Fig. 2(c) is a schematic diagram of V / I interface at the solid-liquid interface position under the condition of Gs< Gc;

[0026] Figure 10 Fig. 3 is a cross-sectional morphology diagram of a crystal bar under drawing under different V / I interfaces corresponding to Fig. 2, Figure 9 Fig. 3(a) corresponds to Fig. 2(a), Figure 10 Fig. 3(b) corresponds to Fig. 2(b), Figure 9 Fig. 3(c) corresponds to Fig. 2(c); Figure 10 Figure 9 Figure 10 Fig. 4 is an oxygen content comparison diagram of crystal bars drawn by the prior art and the embodiment 2. Figure 9 Reference signs:

[0027] Figure 11 Fig. 1 is a crystal growth device 100,

[0028] Fig. 1 is a crystal growth device 100,

[0029] Fig. 1 is a crystal growth device 100,

[0030] Fig. 1 is a crystal growth device 100, DETAILED DESCRIPTION

[0031] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0032] ​​The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but a person of ordinary skill in the art will appreciate the applicability of other processes and / or the use of other materials.

[0033] The term "perfect crystal" used in this article does not mean an absolutely perfect crystal or a crystal without any defects, but rather allows the presence of a very small amount of one or more defects, which are not sufficient to cause a large change in certain electrical or mechanical properties of the crystal or the resulting wafer, thereby causing the performance of the electronic device made therefrom to deteriorate.

[0034] Below, with reference to the accompanying drawings, a crystal growth apparatus 100 according to an embodiment of the present invention will be described. Crystal growth apparatus 100 may be, but is not limited to, a single crystal silicon growth furnace. In the following description of this application, the crystal growth apparatus 100 is described as a single crystal silicon growth furnace. After reading the following solutions, those skilled in the art will readily understand implementations of the crystal growth apparatus 100 as other growth furnaces.

[0035] like Figure 1 and Figure 2 As shown, the crystal growth apparatus 100 includes a furnace body 1, a crucible 2, and a side heater 3. The furnace body 1 has a furnace chamber 1a. The crucible 2 is disposed in a liftable manner within the furnace chamber 1a and is used to hold molten metal. The side heater 3 is disposed within the furnace chamber 1a and surrounds the outer periphery of the crucible 2. The side heater 3 is used to heat the crucible 2. For example, the side heater 3 may be generally annular in structure and may be spaced apart radially outward from the crucible 2.

[0036] It can be understood that the crystal growth equipment 100 also includes a first driving mechanism 5, which is connected to the crucible 2 to drive the crucible 2 to rise and fall relative to the furnace body 1; for example, in the process of pulling single crystal silicon, the first driving mechanism 5 drives the crucible 2 to rise relative to the furnace body 1 to keep the melt level stable.

[0037] like Figure 1 and Figure 2As shown, the crystal growth apparatus 100 further comprises a heat insulation structure 4, which is arranged in the furnace chamber 1a in a liftable manner, is arranged between the crucible 2 and the side heater 3, and surrounds the crucible 2. For example, the heat insulation structure 4 is formed in a ring shape, is located radially inward of the side heater 3, and is located at the outer circumferential side of the crucible 2.

[0038] As can be seen, since the heat insulation structure 4 is liftable relative to the furnace body 1, the heat insulation structure 4 can adjust the temperature distribution at the outer circumferential side of the crucible 2 by adjusting the position thereof in the up-down direction, and the heat insulation structure 4 has a good blocking effect on heat conduction, so that the lifting of the heat insulation structure 4 relative to the furnace body 1 can change the center temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the position of the solid-liquid interface 20, so as to reduce the difference between the center temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the position of the solid-liquid interface 20, improve the uniformity of the temperature gradient distribution at the solid-liquid interface, and thus improve the proportion of the COP-free region in the whole ingot, which is beneficial to improving the proportion of the COP-free region in the wafer when the ingot is cut into wafers.

[0039] The crystal growth apparatus 100 further comprises a second driving mechanism 6 connected to the heat insulation structure 4 to drive the heat insulation structure 4 to lift relative to the crucible 2 and the furnace body 1, so that the heat insulation structure 4 can lift relative to the furnace body 1 and the crucible 2 under the action of the second driving mechanism 6, and then the first driving mechanism 5 and the second driving mechanism 6 are independently arranged, or the lifting movement of the crucible 2 and the lifting movement of the heat insulation structure 4 are independent, and the lifting movement of the heat insulation structure 4 can be synchronized with or unsynchronized with the lifting movement of the crucible 2, so that the lifting movement of the heat insulation structure 4 is more flexible relative to the crucible 2.

[0040] Therefore, during the crystal growth process, the position of the heat insulation structure 4 in the up-down direction can be flexibly adjusted according to actual needs. Since the center temperature gradient Gc and the edge temperature gradient Gs at the position of the solid-liquid interface 20 will change with the reduction of the remaining material in the crucible 2 and the change of the position of the crucible 2 during the crystal growth process, the movement of the heat insulation structure 4 is independent of the movement of the crucible 2 in the present application, so as to flexibly adapt to the change trend of the center temperature gradient Gc and the edge temperature gradient Gs at the position of the solid-liquid interface 20, to match and compensate the center temperature gradient Gc and the edge temperature gradient Gs at the position of the solid-liquid interface 20 by using the different relative positions of the heat insulation structure 4 relative to the crucible 2 and the side heater 3 in the up-down direction, so as to reduce the difference between the center temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the position of the solid-liquid interface 20, improve the uniformity of the temperature gradient distribution at the solid-liquid interface, and thus improve the proportion of the COP-free region in the whole ingot.

[0041] In the embodiment of the present application, "ring" is to be understood in a broad sense, that is, it is not limited to a "circular ring", for example, it can also be a "polygonal ring" and so on; the specific structure of the first driving mechanism 5 is not specifically limited, as long as the first driving mechanism 5 can drive the crucible 2 to rise and fall.

[0042] In some embodiments, as Figure 1 and Figure 2 As shown, the thermal insulation structure 4 includes a thermal insulation layer 41 and a heat-resistant protective layer 42. The heat-resistant protective layer 42 completely wraps around the thermal insulation layer 41. The thermal conductivity of the heat-resistant protective layer 42 is greater than that of the thermal insulation layer 41, and the thermal conductivity of the heat-resistant protective layer 42 is superior to that of the thermal insulation layer 41. Therefore, in the thermal insulation structure 4, the thermal insulation layer 41 is primarily used to achieve the purpose of heat insulation and heat conduction retardation. The heat-resistant protective layer 42 itself has good heat resistance and can protect the thermal insulation layer 41. For example, the heat-resistant protective layer 42 can prevent the thermal insulation layer 41 from being easily oxidized.

[0043] Obviously, the thermal insulation structure 4 needs to achieve thermal insulation and have certain heat resistance at the same time. In the above scheme, the thermal insulation structure 4 can achieve good heat resistance while meeting its thermal insulation purpose, so as to better withstand the high temperature environment in the furnace chamber 1a. Moreover, the thermal insulation structure 4 has a simple structure and good reliability in use.

[0044] For example, in Figure 4-Figure 7 In the example, the thermal insulation layer 41 is formed into an annular structure, and the heat-resistant protective layer 42 is wrapped around the inner circumferential wall, outer circumferential wall, top wall and bottom wall of the thermal insulation layer 41. The thickness of the heat-resistant protective layer 42 can be smaller than the radial thickness of the thermal insulation layer 41.

[0045] In some embodiments, as Figure 1 As shown, the thermal conductivity of the heat insulating layer 41 is less than or equal to 0.25 W / (m·K), the heat insulating layer 41 is made of hard felt, and the heat resistant protective layer 42 is made of graphite. Thus, the heat insulating structure 4 can achieve its heat insulating and heat resistant properties at a low cost.

[0046] For example, the thermal conductivity of the heat insulating layer (41) may be 0.12 W / (m·K), 0.14 W / (m·K), 0.15 W / (m·K), 0.18 W / (m·K), 0.2 W / (m·K), 0.21 W / (m·K), 0.23 W / (m·K) or 0.25 W / (m·K), etc.

[0047] In some embodiments, as Figure 1 、 Figure 4-Figure 7As shown, the second driving mechanism 6 includes a driver (such as a motor) and a plurality of connecting rods 62. The driver is arranged outside the furnace body 1, and the driver is located below the furnace body 1, which is beneficial to reducing the requirements for the heat resistance of the driver, reducing costs, and facilitating the improvement of the driver's reliability, and is beneficial to saving the horizontal space occupied by the crystal growth equipment 100; a plurality of connecting rods 62 are arranged at intervals along the circumference of the insulation structure 4, each connecting rod 62 is passed through the furnace body 1 in the up and down directions, and the upper end of each connecting rod 62 is connected to the insulation structure 4, the driver is connected to the lower end of each connecting rod 62 to drive multiple connected synchronous lifting and lowering, so as to achieve stable lifting and lowering of the entire insulation structure 4, and the arrangement of multiple connecting rods 62 can eliminate the need to open a large opening area of ​​the through hole 10 on the furnace body 1, which is beneficial to reducing the weakening of the furnace body 1 caused by the passing of the connecting rods 62.

[0048] For example, in Figure 1 and Figure 4 In the example shown, there are two connecting rods 62, and the two connecting rods 62 can be arranged opposite each other along the radial direction of the thermal insulation structure 4. Of course, there can also be three, four, or more connecting rods 62. It is understood that in the embodiment of the present application, the driver and the connecting rods 62 can be directly connected or indirectly connected through other structures.

[0049] like Figure 5-Figure 7 As shown, the second drive mechanism 6 also includes a connector 63, which is disposed outside the furnace body 1 and is formed in an open ring or closed ring shape. The connector 63 is connected to the lower end of each connecting rod 62. The driver drives the multiple connecting rods 62 to rise and fall synchronously through the connector 63, which facilitates the connection between the driver and the multiple connecting rods 62 and helps simplify the structure of the driver. Among them, the connector 63 is disposed around the first drive mechanism 5. Therefore, the arrangement of the connector 63 and the lifting and lowering movement of the connector 63 are unlikely to interfere with the first drive mechanism 5, facilitating the reliable operation of the first drive mechanism 5 and the second drive mechanism 6. In addition, the shape of the connector 63 is consistent with that of the thermal insulation structure 4 to facilitate the driver to achieve stable lifting and lowering of the thermal insulation structure 4 through the connector 63.

[0050] In some embodiments, as Figure 4-Figure 7 As shown, the thermal insulation structure 4 includes a thermal insulation layer 41 and a heat-resistant protective layer 42. The heat-resistant protective layer 42 is completely wrapped around the thermal insulation layer 41. The thermal insulation layer 41 is made of hard felt, and the heat-resistant protective layer 42 is made of graphite. The connecting rod 62 is also made of graphite, and the upper end of the connecting rod 62 is connected to the heat-resistant protective layer 42. As can be seen, the material of the connecting rod 62 is the same as that of the heat-resistant protective layer 42, and the two have similar physical and chemical properties. This makes the connection between the connecting rod 62 and the heat-resistant protective layer 42 more controllable and stable, and does not impose too many restrictions on the connection method between the two.

[0051] In the embodiment of the present application, there is no specific limitation on the connection method between the connecting rod 62 and the heat-resistant protective layer 42. Figure 7 In the example, the upper end of the connecting rod 62 is threadedly connected to the heat-resistant protective layer 42.

[0052] In some embodiments, as Figure 1 、 Figure 5-Figure 7 As shown, a through hole 10 is formed on the furnace body 1 for the connecting rod 62 to pass through, and the crystal growth equipment 100 also includes a plurality of protective tubes 7, each protective tube 7 surrounds the portion of the corresponding connecting rod 62 extending outside the furnace body 1, and the length of the protective tube 7 in the up and down directions is adjustable, the upper end of the protective tube 7 is sealed and connected to the edge of the corresponding through hole 10, and the lower end of the protective tube 7 is sealed and connected to the connecting piece 63, so that the internal space of the furnace body 1 and the internal space of the protective tube 7 are connected through the through hole 10, and the connecting piece 63 blocks the lower end of the protective tube 7.

[0053] In some embodiments, as Figure 7 As shown, the protection tube 7 is a stainless steel corrugated tube, so that the protection tube 7 has good reliability and adjustable length.

[0054] In some embodiments, as Figure 3 As shown, the crystal growth equipment 100 also includes a magnetic field device 8, which is arranged outside the furnace body 1, and the magnetic field device 8 is used to generate a magnetic field, and the magnetic field can be used to apply to the melt in the crucible 2; in the up and down directions, the center plane 80 of the magnetic field is located at a distance h below the solid-liquid interface 20 of the melt in the crucible 2, 50mm≤h≤100mm, wherein the component of the magnetic field intensity of the magnetic field on the center plane 80 in the axial direction of the furnace body 1 is 0, then the component of the magnetic field intensity at any point on the center plane 80 in the up and down directions is 0, that is, the surface of the magnetic field whose magnetic field intensity in the axial direction of the furnace body 1 is 0 is the center plane 80 of the magnetic field. Thus, the magnetic field can suppress various melt convection currents within crucible 2 that affect crystal quality, thereby improving crystal quality and impurity uniformity, facilitating the reduction of oxygen content in the crystal, and enabling the crystal oxygen content to be reduced to below 5 ppma, thereby enhancing the controllability of the oxygen content. In other words, the magnetic field influences the convection pattern of the melt within crucible 2. When the melt is 50 mm to 100 mm below the liquid surface, the probability of oxygen in the melt volatilizing by convection to the free surface is highest. This results in a relatively small amount of oxygen entering the crystal ingot, reducing the oxygen content. Thus, the combination of magnetic field device 8 and thermal insulation structure 4 can produce a COP-free, low-oxygen crystal ingot. For example, h can be 50 mm, 55 mm, 60 mm, 64 mm, 70 mm, 77 mm, 80 mm, 85 mm, 86 mm, 90 mm, 93 mm, or 100 mm, etc.

[0055] It can be understood that the central plane 80 of the magnetic field can be formed roughly as a plane or as a curved surface.

[0056] For example, in Figure 3 In the example, the magnetic field device 8 includes a first energized coil 81 and a second energized coil 82. The first energized coil 81 is disposed around the furnace body 1, and the second energized coil 82 is disposed around the furnace body 1, with the second energized coil 82 spaced below the first energized coil 81. The currents in the first energized coil 81 and the second energized coil 82 are equal in magnitude and opposite in direction. The magnetic field generated by the magnetic field device 8 is a hook-shaped magnetic field. The radial components of the magnetic fields generated by the first energized coil 81 and the second energized coil 82 are in the same direction, while the axial components are in opposite directions. The total radial component of the magnetic field intensity is the sum of the two radial components, and the total axial component is the difference between the two axial components. This generates a magnetic field that is vertically symmetrical about the center plane 80. It will be appreciated that the crystal growth apparatus 100 also includes a third drive mechanism for driving the magnetic field device 8 to rise and fall relative to the furnace body 1, so as to adjust the position of the magnetic field device 8 according to the position of the crucible 2.

[0057] In some technologies, the CZ method can stably produce large silicon wafers with a diameter of 200 mm or more by applying a magnetic field. However, for 12-inch single crystal silicon grown by the CZ method, it is very difficult to simultaneously meet the requirements of COP-free and low oxygen (the oxygen content of the crystal rod is less than 5 ppma). The present application cooperates with the thermal insulation structure 4 and the magnetic field device 8 to facilitate the pulling of COP-free and low-oxygen crystal rods.

[0058] In some embodiments, as Figure 1 As shown, the thermal insulation structure 4 has a first position and a second position, and the thermal insulation structure 4 rises and falls at least between the first position and the second position. In the first position, the upper end of the thermal insulation structure 4 is flush with the lower end of the crucible 2 when it is in the lowest position. In the second position, the upper end of the thermal insulation structure 4 extends upward beyond the R angle 21 when the crucible 2 is in the highest position.

[0059] It can be seen that the crucible 2 has a lowest position and a highest position, and the crucible 2 rises and falls between the lowest position and the highest position. When the crucible 2 is in the lowest position and the thermal insulation structure 4 is in the first position, the upper end of the thermal insulation structure 4 is flush with the lower end of the crucible 2, for example Figure 1 The horizontal position of the middle reference line L1 corresponds to the lower end of the crucible 2, and the upper end of the thermal insulation structure 4 in the first position is flush with the horizontal position of the reference line L1 when the crucible 2 is in the lowest position; when the crucible 2 is in the highest position and the thermal insulation structure 4 is in the second position, the upper end of the thermal insulation structure 3 extends upward beyond the R angle 21 of the crucible 2, for example Figure 1 The horizontal position of the middle reference line L2 corresponds to the top of the R corner 21 of the crucible 2 , and the upper end of the thermal insulation structure 4 in the second position extends upward beyond the horizontal position of the reference line L2 when the crucible 2 is in the highest position.

[0060] Therefore, the lifting range of the insulation structure 4 includes the movement range between the first position and the second position, so that the insulation structure 4 has a sufficient and appropriate movement range to match different actual production requirements; moreover, the above-mentioned movement setting of the insulation structure 4 can reduce the R angle 21 of the crucible 2 and the temperature of the bottom of the crucible 2, so that the oxygen content of the crystal rod is further reduced, thereby allowing more parts of the crystal rod to meet the target specifications, thereby improving the overall yield.

[0061] In some embodiments, the crystal growth apparatus 100 further includes a bottom heater 9 , which is also used to heat the crucible 2 . The bottom heater 9 is spaced below the crucible 2 and is disposed around the first driving mechanism 5 .

[0062] According to the control method of the crystal growth equipment 100 of the embodiment of the present invention, the crystal growth equipment 100 is the crystal growth equipment 100 according to the above-mentioned embodiment of the present invention, and the control method includes: step S10, the equal-diameter growth stage, the crucible 2 rises relative to the furnace body 1, and the insulation structure 4 moves relative to the furnace body 1 following the rise of the crucible 2 to separate at least part of the lower part of the crucible 2 from the side heater 3, and the rising speed of the crucible 2 is not equal to the moving speed of the insulation structure 4.

[0063] It can be understood that in the embodiment of the present application, the speed can be a vector, and the speed of the crucible 2 and the speed of the insulation structure 3 are not equal, including: the moving speeds of the two are different and / or the moving directions of the two are opposite.

[0064] It can be seen that in the equal-diameter growth stage, the insulation structure 4 and the crucible 2 will not be completely staggered in the vertical direction, so that the insulation structure 4 can always separate at least part of the lower part of the crucible 2 from the side heater 3 in the radial direction; due to the reduction of the residual material in the crucible 2 and the change of the position of the crucible 2 during the crystal growth process, the central temperature gradient Gc and the edge temperature gradient Gs at the solid-liquid interface 20 will change accordingly. For this reason, the present application adapts to the changing trend of the central temperature gradient Gc and the edge temperature gradient Gs at the solid-liquid interface 20 by setting the movement speed of the insulation structure 4 to be different from the movement speed of the crucible 2, so as to utilize the different relative positions of the insulation structure 4 relative to the crucible 2 and the side heater 3 in the vertical direction to match the central temperature gradient Gc and the edge temperature gradient Gs at the solid-liquid interface 20 to compensate, so as to reduce the difference between the central temperature gradient Gc and the edge temperature gradient Gs of the silicon single crystal at the solid-liquid interface 20, improve the uniformity of the temperature gradient distribution at the solid-liquid interface 20, and thus increase the proportion of the COP-free area of ​​the entire crystal rod.

[0065] It can be understood that the lower part of the crucible 2 may refer to the part of the crucible 2 located below the center of the crucible 2. For example, the crucible 2 includes a first part and a second part, the first part is located below the center of the crucible 2, and the second part is located above the center of the crucible 2. The first part is the lower part of the crucible 2; at least part of the lower part of the crucible 2 may refer to a part of the lower part of the crucible 2, or the entire lower part of the crucible 2. The center of the crucible 2 may be understood as the center position of the crucible 2 in the up and down directions.

[0066] In addition, the heat insulation structure 4 is used to separate at least part of the lower portion of the crucible 2 from the side heater 3 in the radial direction. Compared with the crystal growth equipment without the heat insulation structure, the high-temperature areas of the crucibles of the two will be different. The above-mentioned arrangement of the present application makes the high-temperature area of ​​the crucible 2 higher and closer to the melt surface. This has two advantages: first, the temperature of the melt surface in the crucible 2 is higher, the temperature gradient Gs at the edge of the solid-liquid interface 20 is reduced, and the uniformity of the temperature gradient distribution at the solid-liquid interface 20 is improved, and a flatter V / I interface (such as Figure 9 As shown in (b), Figure 9 In (b), Gs≈Gc, that is, Gs and Gc are roughly equivalent, and Figure 9 (a) Gs>Gc, Figure 9 (c) Gs<Gc); Second, the bottom temperature of crucible 2 is lower, oxygen will be lower, and the oxygen content of the crystal rod will be reduced. Figure 10 is with Figure 9 The cross-sectional morphology of the crystal rod at the pulled position under different V / I interfaces corresponds to each other. Figure 10 (a) with Figure 9 (a) Corresponding, Figure 10 (b) with Figure 9 (b) corresponding to, Figure 10 (c) with Figure 9 (c) Corresponding to Figure 10 It can be clearly seen in Figure 10 (b) COP-free area (black area in the figure) Figure 10 (a) and Figure 10 (c) Both are large.

[0067] Compared to some technologies that set the movement speed of the thermal insulation structure to the same as the movement speed of the crucible so that the thermal insulation structure and the crucible rise and fall synchronously, the "thermal insulation structure 4" in this solution can be set to an independent movement speed relative to the movement speed of the crucible 2. That is, the movement speed of the thermal insulation structure 4 is not easily limited by the movement speed of the crucible 2, which facilitates flexible adjustment of Gs and Gc. In addition, based on the technical problem to be solved, the oxygen concentration can currently be reduced to below 5ppma under the action of the magnetic field of the magnetic field device 8. However, it is actually very difficult to obtain a perfect crystal at the same time. Therefore, the current price of IGBT products is very high. The present application can achieve the technical goal of simultaneously taking into account low oxygen content and crystal quality through the cooperation of the magnetic field device 8 and the thermal insulation structure 4.

[0068] In some embodiments, the moving speed Vi of the thermal insulation structure 4 and the rising speed Vc of the crucible 2 satisfy Vi = a*Vc+b, where a is a proportional coefficient and is not equal to 0, and b is a speed increase value. The units of Vi, Vc, and b are all mm / min. It should be noted that in the embodiments of the present application, the moving speed Vi of the thermal insulation structure 4 and the rising speed Vc of the crucible 2 are both relative to the furnace body 1. If the rising speed Vc of the crucible 2 is a positive value, then when the moving speed Vi of the thermal insulation structure 4 is a positive value, the thermal insulation structure 4 also rises relative to the furnace body 1. When the moving speed Vi of the thermal insulation structure 4 is a negative value, the thermal insulation structure 4 descends relative to the furnace body 1.

[0069] It can be understood that the heat insulation structure 4 rises relative to the furnace body 1, which makes it easier for the high temperature area of ​​the crucible 2 to move upward as a whole to be closer to the molten liquid surface, Gs decreases, Gc increases, and the defect distribution of the entire wafer moves toward Figure 9 (c) Change; The insulation structure 4 is lowered relative to the furnace body 1, so that the high temperature area of ​​the crucible 2 approaches the R corner 21 of the crucible 2, Gs increases, Gc decreases, and the defect distribution of the entire wafer is toward Figure 9 (a) Change.

[0070] In some embodiments, a decreases step-by-step as the crystal grows, b=0, then during the entire equal-diameter growth stage, the moving speed of the insulation structure 4 and the rising speed of the crucible 2 are not linearly related, and the equal-diameter growth stage can be divided into multiple sub-stages. For example, the equal-diameter growth stage can be divided into a first sub-stage (which can correspond to the initial equal-diameter stage), a second sub-stage (which can correspond to the middle equal-diameter stage) and a third sub-stage (which can correspond to the late equal-diameter stage), each sub-stage corresponds to an a value, and the a values ​​corresponding to multiple sub-stages are different. In each sub-stage, the moving speed of the insulation structure 4 and the rising speed of the crucible 2 are linearly related, so as to simplify the control logic of the crystal growth equipment 100 under the premise that the COP-free area can meet the requirements.

[0071] For example, the isodiameter growth stage is divided into the first sub-stage, the second sub-stage, the third sub-stage, ... and the p-th sub-stage, which are carried out in sequence. p is a positive integer and is greater than or equal to 2. In the first sub-stage, a=a1; in the second sub-stage, a=a2; in the third sub-stage, a=a3; ...; in the p-th sub-stage, a=a p , a1>a2>a3>…>a p .

[0072] Further optionally, p ≥ 3, in the (p-1)th sub-stage, a is a positive value, and in the pth sub-stage, a is a negative value; in other words, in the final stage of isodiametric growth, a changes from a positive value to a negative value to better adapt to the changes in the center temperature gradient Gc and the edge temperature gradient Gs in the later stage, and to achieve corresponding compensation. It can be understood that in some technologies, the edge temperature gradient Gs is usually gradually reduced during the crystal growth process, especially in the later stage of isodiametric growth; in the embodiment of the present application, the thermal insulation structure 4 can mainly reduce Gs in the early and middle stages of isodiametric growth, while the value of Gs in the later stage of isodiametric growth may be too small. At this time, the thermal insulation structure 4 can be moved downward to appropriately increase Gs.

[0073] In some embodiments, a decreases in a stepwise manner as the crystal grows, and b decreases in a stepwise manner as the crystal grows. Similarly, during the entire isodiameter growth stage, the moving speed of the thermal insulation structure 4 and the rising speed of the crucible 2 are not linearly related. It is understood that the stages of a stepwise decrease and b stepwise decrease can be consistent or inconsistent.

[0074] For example, the isodiameter growth stage is divided into the first sub-stage, the second sub-stage, the third sub-stage, ... and the p-th sub-stage in sequence, where p is a positive integer and is greater than or equal to 2, and the stage in which a decreases stepwise is consistent with the stage in which b decreases stepwise. In the first sub-stage, a=a1, b=b1; in the second sub-stage, a=a2, b=b2; in the third sub-stage, a=a3, b=b3, ...; in the p-th sub-stage, a=a p , b=b3, a1>a2>a3>…>a p , b1>b2>b3>…>b p .

[0075] For example, the following table shows the values ​​of a and b at different constant diameter lengths in Examples 1 to 3:

[0076]

[0077] After testing, the COP-free area of ​​the crystal rods in the above embodiments 1 to 3 is improved. Among them, the COP-free area of ​​the crystal rod pulled by embodiment 3 is larger than that of the other two embodiments. Figure 11 Comparing the result curve of the common thermal field in the Figure 11 The oxygen content of the crystal rods drawn in the two schemes is shown in the following table.

[0078] Further optionally, p>3, in the (p-1)th sub-stage, the heat insulation structure 4 is raised relative to the furnace body 1, and in the pth sub-stage, the heat insulation structure 4 is lowered relative to the furnace body 1; in other words, in the last stage of the constant diameter growth, the heat insulation structure 4 is changed from the raised state to the lowered state relative to the furnace body 1, so as to better adapt to the changes of the center temperature gradient Gc and the edge temperature gradient Gs in the later period, and realize the corresponding compensation.

[0079] In some embodiments, -0.5≤a≤0.5, -0.1≤b≤0.1.

[0080] For example, a can be -0.5, -0.45, -0.4, -0.3, -0.2, -0.15, -0.1, -0.05, 0.03, 0.08, 0.12, 0.15, 0.2, 0.26, 0.3, 0.46, 0.5, etc.; b can be -0.1, -0.08, -0.05, -0.04, -0.01, 0, 0.02, 0.03, 0.06, 0.08, 0.1, etc. Optionally, during the crystal growth debugging process, it is determined whether the heat insulation structure 4 needs to be raised or lowered relative to the furnace body 1 according to the defect copper decoration result of the last furnace, for example, the values of the coefficients a and b in the moving speed Vi=a*Vc+b of the heat insulation structure 4 of the next furnace are adjusted according to the defect structure of the last furnace, so as to correct a and b.

[0081] Other configurations and operations of the crystal growth equipment 100 according to the embodiments of the present application are known to those skilled in the art, and will not be described in detail here.

[0082] In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, various possible combination manners are not described again in the present application. In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, it should also be considered as disclosed in the present application.

[0083] In the description of the present invention, it should be understood that the terms "center", "length", "width", "thickness", "up", "down", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention. In addition, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0084] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0085] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative use of the above terms does not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0086] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A crystal growth device, characterized in that: include: A furnace body, wherein the furnace body has a furnace chamber; a crucible, the crucible being arranged in a liftable manner in the furnace chamber and being used to hold molten metal; a side heater disposed in the furnace chamber and surrounding the outer circumference of the crucible; a heat insulation structure, the heat insulation structure being movably disposed in the furnace chamber, the heat insulation structure being spaced between the crucible and the side heater and surrounding the crucible; a first driving mechanism connected to the crucible to drive the crucible to move up and down relative to the furnace body; A second driving mechanism is connected to the thermal insulation structure to drive the thermal insulation structure to move up and down relative to the crucible and the furnace body.

2. The crystal growth apparatus according to claim 1, wherein: The thermal insulation structure comprises: thermal insulation; A heat-resistant protective layer is completely wrapped around the heat-insulating layer, and the thermal conductivity of the heat-resistant protective layer is greater than the thermal conductivity of the heat-insulating layer.

3. The crystal growth apparatus according to claim 2, wherein: The thermal conductivity of the heat insulation layer is less than or equal to 0.25 W / (m·K), the heat insulation layer is hard felt, and the heat-resistant protective layer is a graphite piece.

4. The crystal growth apparatus according to claim 1, wherein: The second driving mechanism comprises: A driver, the driver being arranged outside the furnace body and below the furnace body; a plurality of connecting rods, the plurality of connecting rods being arranged at intervals along the circumference of the heat insulation structure, each connecting rod being passed through the furnace body in the vertical direction and the upper end of the connecting rod being connected to the heat insulation structure; A connecting member is provided outside the furnace body and is formed into an open ring or a closed ring. The connecting member is connected to the lower end of each connecting rod. The driver drives the multiple connecting rods to rise and fall synchronously through the connecting member. The connecting member is arranged around the first driving mechanism.

5. The crystal growth apparatus according to claim 4, wherein: The thermal insulation structure includes a thermal insulation layer and a heat-resistant protective layer. The heat-resistant protective layer is completely wrapped outside the thermal insulation layer. The thermal insulation layer is hard felt. The heat-resistant protective layer is a graphite part. The connecting rod is a graphite part. The upper end of the connecting rod is connected to the heat-resistant protective layer.

6. The crystal growth apparatus according to claim 4, wherein: The furnace body is formed with a through hole for the connecting rod to pass through, and the crystal growth equipment further includes: Multiple protective tubes, each of which surrounds the portion of the corresponding connecting rod extending out of the furnace body, the length of the protective tube in the upper and lower directions is adjustable, the upper end of the protective tube is sealed and connected to the edge of the corresponding perforation, and the lower end is sealed and connected to the connecting piece, so that the internal space of the furnace body and the internal space of the protective tube are connected through the perforation, and the connecting piece blocks the lower end of the protective tube.

7. The crystal growth apparatus according to claim 6, wherein: The protective tube is a stainless steel bellows.

8. The crystal growth apparatus according to claim 1, wherein: Also includes: A magnetic field device is provided outside the furnace body and is used to generate a magnetic field. In the vertical direction, the center plane of the magnetic field is located at a distance h below the solid-liquid interface of the melt in the crucible, 50mm≤h≤100mm, wherein the component of the magnetic field intensity of the magnetic field on the center plane in the axial direction of the furnace body is 0.

9. The crystal growth apparatus according to any one of claims 1 to 8, characterized in that: The thermal insulation structure has a first position and a second position, and the thermal insulation structure is movable up and down at least between the first position and the second position. In the first position, the upper end of the heat insulating structure is flush with the lower end of the crucible when it is in the lowest position. In the second position, the upper end of the heat insulating structure extends upward beyond the R angle of the crucible when it is in the highest position.

Images