Thermal field for controlling temperature gradient by changing coil turn spacing and heating crystal growth equipment

Abstract

The invention discloses a thermal field for controlling a temperature gradient by changing coil turn spacing, a graphite heating cylinder can be heated up and down simultaneously in a mode that a plurality of upper annular coils are arranged above the graphite heating cylinder and a plurality of lower annular coils are arranged below the graphite heating cylinder, and the coil induction thermal magnetic field coupling efficiency in the mode is high; rapid temperature rise in the material area of the graphite heating cylinder can be realized; and the turn spacing of the plurality of upper annular coils and the turn spacing of the plurality of lower annular coils are adjusted, and the arrangement mode of equal turn spacing of all the upper annular coils and the lower annular coils is not adopted, so that eddy current loss generated by cutting the heating cylinder by an alternating magnetic field generated by alternating current on the coils can be homogenized; and the radial heating uniformity of the graphite heating cylinder is ensured, so that a material area is uniformly heated in the vertical direction.

Description

Technical Field

[0001] The invention relates to the technical field of crystal growth or epitaxial heating, and in particular to a thermal field and heating crystal growth equipment. Background Art

[0002] Compared with resistance heating, induction heating has the advantages of no need for direct contact with the heating material, higher heating efficiency, and faster speed. At present, most SiC crystal growth equipment uses double cylindrical coils that are externally placed and distributed up and down outside the quartz tube to ensure the growth temperature of the crystal and the axial temperature gradient control. However, there are currently two problems:

[0003] 1) Due to the fact that the coil is placed outside and far away from the heating body and the thermal magnetic field coupling efficiency decreases significantly as the coil diameter increases, it takes 1 hour or more for the process area to rise from room temperature to process temperature; after the crystal growth process is completed in the process area, the product cooling process is very slow due to the lack of cooling measures. The above seriously affects the process cycle and production efficiency;

[0004] 2) The traditional cylindrical double coils distributed up and down will cause serious electromagnetic coupling when working at the same time, which poses great challenges to process adjustment, has a great impact on thermal field temperature control and power consumption, and may even damage the heating equipment.

[0005] Compared with cylindrical coils, disc coils have better heating efficiency and heating speed, and have been used in the field of CVD wafer epitaxy. However, due to the influence of various factors such as the large outer diameter of the coil, the eddy current loss inside the graphite heating tube is not uniform, resulting in a poor temperature gradient on the disc surface; therefore, a new technical solution is needed to solve this problem. Summary of the invention

[0006] Purpose of the invention: The present invention provides a thermal field that controls the temperature gradient by changing the coil turn spacing, so as to solve the problem of uneven eddy current loss inside the graphite heating tube resulting in poor disk temperature gradient.

[0007] The invention also provides a heating crystal growth device comprising the thermal field.

[0008] Technical solution: To solve the above problems, the present invention provides a method for controlling the thermal field of the temperature gradient by changing the coil turn spacing, and the following technical solution can be adopted.

[0009] A thermal field for controlling a temperature gradient by changing the coil turn spacing, comprising a graphite heating tube, an upper coil group located above the graphite heating tube, and a lower coil group located below the graphite heating tube; the upper coil group comprises a plurality of upper annular coils arranged from the inside to the outside, and the centers of all the upper annular coils are located on the central axis of the graphite heating tube; the lower coil group comprises a plurality of lower annular coils arranged from the inside to the outside, and the centers of all the lower annular coils are located on the central axis of the graphite heating tube; the number of upper annular coils in the upper coil group and the size of the upper annular coils are the same as the number of lower annular coils in the lower coil group and the size of the lower annular coils; in the upper coil group, there is a turn spacing between two adjacent upper annular coils, and the turn spacing of the innermost upper annular coil in the upper coil group is the smallest, and the turn spacing of the outermost upper annular coil in the upper coil group is the largest; in the lower coil group, there is a turn spacing between two adjacent lower annular coils, and the turn spacing of the innermost lower annular coil in the lower coil group is the smallest, and the turn spacing of the outermost lower annular coil in the lower coil group is the largest.

[0010] Furthermore, each upper annular coil and each lower annular coil are in a projection corresponding relationship above and below the graphite heating tube.

[0011] Furthermore, the distance between two adjacent turn spacings is equal or unequal. When the distance between two adjacent turn spacings is equal, they are set as a turn spacing group; or when a specific turn spacing is not equal to the distance of any other turn spacing, the specific turn spacing is also set as a turn spacing group; the distance of the turn spacing group located on the inner side is smaller than the distance of the turn spacing group located on the outer side.

[0012] Furthermore, the difference between the distances of each two adjacent groups of turn spacings is the same.

[0013] Furthermore, the difference between the distances between each two adjacent groups of turn spacings is 3 mm to 12 mm.

[0014] Further, when the upper coil group has 5 turns of the upper annular coil, that is, there are 4 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, and 12mm respectively, wherein two turn spacings of 3mm and 3mm form a turn spacing group, the turn spacing of 6mm is a turn spacing group alone, and the turn spacing of 12mm is a turn spacing group alone; the turn spacing of the 5-turn lower annular coil in the lower coil group corresponds to the projection of the turn spacing in the upper coil group;

[0015] When the upper coil group has 6 turns of the upper annular coil, there are 5 turn spacings in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 9mm, and 12mm respectively;

[0016] When the upper coil group has 7 turns of the upper annular coil, that is, the turn spacing is 6 in total, and the turn spacing from the inside to the outside is 3mm, 3mm, 6mm, 6mm, 9mm, and 12mm respectively;

[0017] When the upper coil group has 8 turns of the upper annular coil, that is, there are 7 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, and 12mm respectively;

[0018] When the upper coil group has 9 turns of the upper annular coil, that is, there are 8 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively;

[0019] When the upper coil group has 10 turns of the upper annular coil, that is, the turn spacings are 9 in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively;

[0020] When the upper coil group has 11 turns of the upper annular coil, there are 10 turn spacings in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively.

[0021] Furthermore, an upper graphite baffle is installed above the graphite heating tube, and a lower graphite baffle is installed below the graphite heating tube; the upper graphite baffle and the upper surface of the graphite heating tube together form an upper receiving cavity, and the upper coil group is located in the upper receiving cavity; the lower graphite baffle and the lower surface of the graphite heating tube together form a lower receiving cavity, and the lower coil group is located in the lower receiving cavity.

[0022] Furthermore, a top insulation layer located above the upper graphite partition and a bottom insulation layer located below the lower graphite partition are provided. The top insulation layer and the bottom insulation layer are surrounded by side walls to form an insulation space. The graphite heating tube, the upper receiving cavity, the lower receiving cavity and the side surrounding screen are all located in the insulation space.

[0023] Furthermore, the upper surface and the lower surface of the graphite heating tube are both circular surfaces, the top insulation layer is connected to the upper surface of the graphite heating tube through an upper support shaft, the bottom insulation layer is connected to the lower surface of the graphite heating tube through a lower support shaft, the upper support shaft and the lower support shaft are coaxially arranged, and the upper support shaft is connected to the center of the upper surface, and the lower support shaft is connected to the center of the lower surface; each upper annular coil is arranged around the upper support shaft, and each lower annular coil is arranged around the lower support shaft.

[0024] Beneficial effect: Compared with the prior art, the present invention can heat the graphite heating tube at the top and bottom simultaneously by arranging a plurality of upper annular coils above the graphite heating tube and a plurality of lower annular coils below the graphite heating tube. The coil induction thermal magnetic field coupling efficiency in this manner is high, and rapid heating of the material area of ​​the graphite heating tube can be achieved; and, the turn spacing of the plurality of upper annular coils and the plurality of lower annular coils is adjusted, and the arrangement method of equal turn spacing of all the upper annular coils and the lower annular coils is not adopted, so that the alternating magnetic field generated by the alternating current on the coil can be uniformized to cut the eddy current loss generated by the heating tube, thereby ensuring the uniformity of radial heating of the graphite heating tube, thereby uniformly heating the material area in the vertical direction.

[0025] The heating crystal growth equipment provided by the present invention comprises the above-mentioned thermal field. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the longitudinal cross-sectional structure of the thermal field in the present invention.

[0027] Figure 2 It is a schematic diagram of the arrangement relationship of the variable turn spacing between the upper coil group and the lower coil group in the thermal field of the present invention, and displays the simulation data of the loss distribution of the graphite disk.

[0028] Figure 3 It is a schematic diagram of the arrangement relationship of the turn spacing of the upper coil group and the lower coil group in the thermal field in the prior art, and shows the simulation data of the loss distribution of the graphite disk.

[0029] Figure 4 The figure shows the comparison of graphite disk loss distribution under different turn spacing and the schematic diagram of the statistical range of loss uniformity of the two.

[0030] Figure 5 This is a cloud diagram of the induced current distribution in the graphite cylinder in the thermal field of the present invention. DETAILED DESCRIPTION

[0031] like Figure 1 As shown, it includes a graphite heating tube 1, an upper coil group located above the graphite heating tube 1, and a lower coil group located below the graphite heating tube 1. The upper coil group includes a plurality of upper annular coils 2 arranged from the inside to the outside, and the centers of all the upper annular coils 2 are located on the central axis of the graphite heating tube 1. The lower coil group includes a plurality of lower annular coils 3 arranged from the inside to the outside, and the centers of all the lower annular coils 3 are also located on the central axis of the graphite heating tube. The alternating current of the upper coil group and the lower coil group generates an alternating magnetic field to cut the graphite heating tube 1 to generate an induced current, and the induced current flows through the graphite heating tube 1 to form eddy current loss as the heat source of the equipment; the induction coil in this form has a high thermal magnetic field coupling efficiency, and the high power density per unit volume on the graphite heating tube 1 can achieve rapid heating in the material area. The axial temperature gradient in the material area is adjusted by adjusting the current and power of the upper coil group and the lower coil group.

[0032] The periphery of the graphite heating tube 1 is provided with an inwardly recessed annular groove, in which an annular side surrounding screen 4 is installed. An upper graphite baffle 5 is installed above the graphite heating tube 1, and a lower graphite baffle 6 is installed below the graphite heating tube 1; the upper graphite baffle 5 and the upper surface of the graphite heating tube 1 together form an upper receiving chamber, and the upper coil group is located in the upper receiving chamber. The lower graphite baffle 6 and the lower surface of the graphite heating tube 1 together form a lower receiving chamber, and the lower coil group is located in the lower receiving chamber. A top insulation layer 7 is also provided above the upper graphite baffle 5, and a bottom insulation layer 8 is also provided below the lower graphite baffle 6. The top insulation layer 7 and the bottom insulation layer 8 together form an insulation space through the side wall. The graphite heating tube 1, the upper receiving chamber, the lower receiving chamber, and the side surrounding screen 4 are all located in the insulation space.

[0033] The number of upper annular coils in the upper coil group and the size of the upper annular coils are the same as the number of lower annular coils in the lower coil group and the size of the lower annular coils; the cross-section of each upper annular coil or lower annular coil is rectangular, and a hollow coolant channel is provided inside the coil. The upper and lower surfaces of the graphite heating tube 1 are both circular surfaces. The top insulation layer 7 is connected to the upper surface of the graphite heating tube 1 through the upper support shaft 9; the bottom insulation layer 8 is connected to the lower surface of the graphite heating tube 1 through the lower support shaft 10. The upper support shaft 9 and the lower support shaft 10 are coaxially arranged, and the upper support shaft 9 is connected to the center of the upper surface, and the lower support shaft 10 is connected to the center of the lower surface. Each upper annular coil 2 is arranged around the upper support shaft 9, and each lower annular coil 3 is arranged around the lower support shaft 10.

[0034] Please combine Figure 2 As shown, in the upper coil group, there is a turn spacing between two adjacent upper annular coils 2, and the turn spacing at the innermost side of the upper coil group is the smallest, and the turn spacing at the outermost side of the upper coil group is the largest. In the lower coil group, there is a turn spacing between two adjacent lower annular coils 3, and the turn spacing at the innermost side of the lower coil group is the smallest, and the turn spacing at the outermost side of the lower coil group is the largest. The distance between two adjacent turn spacings is equal or unequal. When the distance between two adjacent turn spacings is equal, it is set as a turn spacing group; or if a specific turn spacing is not equal to the distance of any other turn spacing, the specific turn spacing is also set as a turn spacing group; the distance of the turn spacing group located on the inner side is smaller than the distance of the turn spacing group located on the outer side. For example: when the material area diameter is 300-500mm, the number of coil turns ranges from 5 to 7 turns, and the turn spacing ranges from 3 to 12mm. Taking a 5-turn coil as an example, the ratio of the coil turn spacing is 4:2:1:1; when the material area diameter is 500-1000mm, the number of coil turns ranges from 7 to 10 turns, and the turn spacing ranges from 3 to 12mm.

[0035] If 3mm is used as the turn spacing:

[0036] When the upper coil group has 5 turns of the upper annular coil, that is, there are 4 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, and 12mm respectively, among which two turn spacings of 3mm and 3mm form a turn spacing group, the turn spacing of 6mm is a turn spacing group alone, and the turn spacing of 12mm is a turn spacing group alone; the turn spacing of the 5 turns of the lower annular coil in the lower coil group corresponds to the projection of the turn spacing in the upper coil group;

[0037] When the upper coil group has 6 turns of the upper annular coil, there are 5 turn spacings in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 9mm, and 12mm respectively;

[0038] When the upper coil group has 7 turns of the upper annular coil, that is, the turn spacing is 6 in total, and the turn spacing from the inside to the outside is 3mm, 3mm, 6mm, 6mm, 9mm, and 12mm respectively;

[0039] When the upper coil group has 8 turns of the upper annular coil, that is, there are 7 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, and 12mm respectively;

[0040] When the upper coil group has 9 turns of the upper annular coil, that is, there are 8 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively;

[0041] When the upper coil group has 10 turns of the upper annular coil, that is, the turn spacings are 9 in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively;

[0042] When the upper coil group has 11 turns of the upper annular coil, that is, the turn spacings are 10 in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively;

[0043] And so on.

[0044] The above-mentioned coil structure design with variable turn spacing can even out the eddy current loss generated by the alternating magnetic field generated by the alternating current on the coil cutting the heating tube, ensuring the uniformity of radial heating of the graphite heating tube, thereby uniformly heating the material area in the vertical direction and realizing precise control of the radial temperature gradient in the material area; Figure 2 It is a schematic diagram of the arrangement relationship between the upper coil group and the lower coil group in the thermal field of the present invention. Figure 3 It is a schematic diagram of the arrangement relationship between the upper coil group and the lower coil group in the thermal field in the prior art. Figure 3 As a prior art comparative example, it can be seen that:

[0045] Under the action of the skin effect of induction heating, the loss is concentrated on the upper and lower outer surfaces of the graphite heating tube 1;

[0046] See also Figure 3 and Figure 4 As shown, due to the characteristic of the alternating magnetic field of the disc coil generating induced current in the graphite cylinder (the induced current in the upper and lower centers of the graphite plate is close to 0), when the coil is designed with equal turn spacing, the distribution of the outer surface of the graphite cylinder shows a trend of first increasing and then decreasing from the center along the radial direction, among which the loss is the highest in the middle, the lowest in the outermost part, and the lowest in the center of the graphite cylinder.

[0047] See also Figure 2 and Figure 4 After the variable turn spacing structure design was carried out on the upper and lower heating coils of the equipment, the loss distribution uniformity of the outer surface of the graphite cylinder was improved. The following table compares the data of the two coils in the present invention and the comparative example by selecting the upper and lower 5-turn coils as an embodiment, where:

[0048] The outer diameter of the coils in the two turn spacing forms is the same, and the inner diameter is variable;

[0049] The number of coil turns under the two turn spacings is 5;

[0050] The turn spacing under the structural form of equal turn spacing is 3mm;

[0051] The other simulation boundary conditions given in the two turn spacing forms remain consistent.

[0052]

[0053] From the results, it can be seen that when the coil adopts a variable turn spacing structure, the loss deviation of the graphite heating tube disk increases from 36.48% to 18.41%, and the loss distribution standard deviation increases from 5.73E+5 to 2.05E+5, and the uniformity is improved.

[0054] The alternating current of the upper and lower annular coils generates low losses at the center of the graphite heating tube, so the top and bottom insulation screens are set to reduce the heat dissipation of the graphite tube along the axial direction and improve the heating uniformity of the graphite tube.

[0055] As shown in the figure, the magnetic flux lines generated by the disc coil decay sharply along the axial direction. Under the influence of the distance between the upper and lower annular coils, the mutual inductance coupling effect of the two coils is weak, which reduces the power loss and equipment failure rate caused by mutual inductance when the upper and lower annular coils are working; the following are the self-inductance and mutual inductance coefficients of the upper and lower double coils calculated in the simulation calculation;

[0056]

[0057] The mutual inductance coefficient between the two is -421.2Ph, and the mutual inductance coupling efficiency between the upper and lower coils is extremely low, so the electromagnetic coupling effect between the upper and lower coils can be ignored.

Claims

1. A thermal field for controlling a temperature gradient by changing the coil turn spacing, characterized in that: It includes a graphite heating tube, an upper coil group located above the graphite heating tube, and a lower coil group located below the graphite heating tube; the upper coil group includes a plurality of upper annular coils arranged from the inside to the outside, and the centers of all the upper annular coils are located on the central axis of the graphite heating tube; the lower coil group includes a plurality of lower annular coils arranged from the inside to the outside, and the centers of all the lower annular coils are located on the central axis of the graphite heating tube; the number of upper annular coils in the upper coil group and the size of the upper annular coils are the same as the number of lower annular coils in the lower coil group and the size of the lower annular coils; In the upper coil group, there is a turn spacing between two adjacent upper annular coils, and the turn spacing of the innermost upper coil group is the smallest, and the turn spacing of the outermost upper coil group is the largest; In the lower coil group, there is a turn spacing between two adjacent lower annular coils, and the turn spacing of the innermost lower annular coils in the lower coil group is the smallest, and the turn spacing of the outermost lower annular coils in the lower coil group is the largest.

2. The thermal field according to claim 1, characterized in that Each upper annular coil and each lower annular coil are in a projection corresponding relationship above and below the graphite heating tube.

3. The thermal field according to claim 1 or 2, characterized in that: The distance between two adjacent turn spacings is equal or unequal. When the distance between two adjacent turn spacings is equal, they are set as a turn spacing group; Or if a specific turn spacing is not equal to the distance between any other turn spacing, the specific turn spacing is also regarded as a turn spacing group; The distance of the turn pitch groups located on the inner side is smaller than the distance of the turn pitch groups located on the outer side.

4. The thermal field according to claim 3, characterized in that The difference between the distances of each two adjacent groups of turn spacings is the same.

5. The thermal field according to claim 4, characterized in that The difference between the distances between each two adjacent groups of turn spacing is 3 mm to 12 mm.

6. The thermal field according to claim 3, characterized in that When the upper coil group has 5 turns of the upper annular coil, that is, there are 4 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, and 12mm respectively, among which two turn spacings of 3mm and 3mm form a turn spacing group, the turn spacing of 6mm is a turn spacing group alone, and the turn spacing of 12mm is a turn spacing group alone; the turn spacing of the 5 turns of the lower annular coil in the lower coil group corresponds to the projection of the turn spacing in the upper coil group; When the upper coil group has 6 turns of the upper annular coil, there are 5 turn spacings in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 9mm, and 12mm respectively; When the upper coil group has 7 turns of the upper annular coil, that is, the turn spacing is 6 in total, and the turn spacing from the inside to the outside is 3mm, 3mm, 6mm, 6mm, 9mm, and 12mm respectively; When the upper coil group has 8 turns of the upper annular coil, that is, there are 7 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, and 12mm respectively; When the upper coil group has 9 turns of the upper annular coil, that is, there are 8 turn spacings, and the turn spacings from the inside to the outside are 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively; When the upper coil group has 10 turns of the upper annular coil, that is, the turn spacings are 9 in total, and the turn spacings from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively; When the upper coil group has 11 turns of the upper annular coil, there are 10 turn intervals in total, and the turn intervals from the inside to the outside are 3mm, 3mm, 3mm, 6mm, 6mm, 6mm, 9mm, 9mm, 12mm, and 12mm respectively.

7. The thermal field according to claim 1, characterized in that An upper graphite partition is installed above the graphite heating tube, and a lower graphite partition is installed below the graphite heating tube; the upper graphite partition and the upper surface of the graphite heating tube together form an upper receiving cavity, and the upper coil group is located in the upper receiving cavity; The lower graphite partition plate and the lower surface of the graphite heating tube together form a lower receiving cavity, and the lower coil assembly is located in the lower receiving cavity.

8. The thermal field according to claim 7, characterized in that A top insulation layer located above the upper graphite partition and a bottom insulation layer located below the lower graphite partition are also provided. The top insulation layer and the bottom insulation layer are surrounded by side walls to form an insulation space. The graphite heating tube, the upper receiving cavity, the lower receiving cavity and the side surrounding screen are all located in the insulation space.

9. The thermal field according to claim 7, characterized in that The upper surface and the lower surface of the graphite heating tube are both circular surfaces, the top insulation layer is connected to the upper surface of the graphite heating tube through an upper support shaft, the bottom insulation layer is connected to the lower surface of the graphite heating tube through a lower support shaft, the upper support shaft and the lower support shaft are coaxially arranged, and the upper support shaft is connected to the center of the upper surface, and the lower support shaft is connected to the center of the lower surface; each upper annular coil is arranged around the upper support shaft, and each lower annular coil is arranged around the lower support shaft.

10. A heating crystal growth device, characterized in that: Comprising the thermal field as claimed in any one of claims 1 to 9.

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