Bottom heater and single crystal furnace
The innovative design of the bottom heater with symmetrically arranged heating strips outside electrode holes addresses the issue of local stress and deformation, extending service life and reducing production costs by optimizing layout and material usage.
Patent Information
- Application Number
- CN202421112096.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-21
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2034-05-21
AI Technical Summary
The existing bottom heaters in single crystal furnaces suffer from a limited service life due to long-term exposure to harsh conditions, leading to high production costs, as they are prone to deformation and damage from large local stresses under gravity, especially with the current design constraints.
A bottom heater design featuring two heating parts and two transition parts, with heating strips positioned outside the electrode holes and arranged symmetrically to reduce local stress, allowing for a more compact layout and reduced length, thereby extending the service life and optimizing material usage.
The new design reduces deformation, extends the service life of the bottom heater, saves raw materials, and lowers production costs by minimizing local stress and optimizing the layout of heating strips, enhancing the heating efficiency and uniformity.
Smart Images
Figure CN222251117U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of single crystal furnace heating, and in particular to a bottom heater and a single crystal furnace. Background Art
[0002] In the semiconductor, photovoltaic and other industries, single crystal furnaces are commonly used to produce non-dislocated single crystal silicon by the Czochralski method. In the single crystal furnace, a heater is used to heat the polysilicon placed in the crucible to melt it. There are usually two heaters, one of which surrounds the side of the crucible in a circle and is called the main heater. The other heater is placed at the bottom of the crucible and is called the bottom heater. The heater has a limited service life due to long-term exposure to harsh working conditions such as high current, high temperature and high-flow argon gas erosion, which will increase the production cost of the single crystal furnace. Among them, the bottom heater is used in large quantities and uses isostatic graphite as the raw material. The production cycle of isostatic graphite is long and the production cost is high. Optimizing the structure of the bottom heater to increase its service life can relatively reduce the production cost of the single crystal furnace.
[0003] Please refer to Figure 1 , Figure 1 It is a schematic diagram of the structure of the bottom heater in the related art. The bottom heater includes two serpentine strip-shaped heating bodies 01, and the heating bodies 01 include a plurality of heating ribs 011. The two ends of the two heating bodies 01 are connected by two transition areas 02, respectively. The transition area 02 is provided with an electrode connection hole 03, and the two electrode connection holes 03 are respectively used to connect the positive and negative electrodes of the power supply, so that the two heating bodies 01 are electrically connected in parallel to heat the crucible. Among them, the two transition areas 02 are extended to the outside of the heating body 01 and are relatively long, resulting in the design space for the heating body 01 between the two being limited. When the resistance design target value of the bottom heater is constant, the total length of the heating ribs is constant. Therefore, in order to design a heating body 01 that meets the resistance design target value in this relatively small design space, the heating ribs 01 will be relatively long, which is easy to generate large local stress under the action of gravity, resulting in large deformation, easy damage, and shortening the service life of the bottom heater.
[0004] Therefore, how to provide a solution to overcome or alleviate the above-mentioned defects is still a technical problem that needs to be solved urgently by those skilled in the art. Utility Model Content
[0005] The purpose of the present application is to provide a bottom heater to extend the service life of the bottom heater. Another purpose of the present application is to provide a single crystal furnace.
[0006] In order to solve the above technical problems, the present application provides a bottom heater, comprising two heating parts and two transition parts;
[0007] The heating part comprises a plurality of heating strips, each of which is connected end to end in sequence; the heating part has a first end and a second end, the first ends of two heating parts are connected through one transition part, and the second ends of two heating parts are connected through another transition part; the transition part is provided with an electrode hole;
[0008] The side of the center of the electrode hole away from the other electrode hole is defined as the outer side; in each of the heating parts, the heating strip at the first end and / or the second end is at least partially located on the outer side of the electrode hole at the corresponding end.
[0009] Optionally, in each of the heating parts, the center of gravity of the heating strip at the first end and / or the second end is located outside the electrode hole at the corresponding end.
[0010] Optionally, the transition part includes a first transition section and a second transition section, the first transition section protrudes toward one side of the other transition part to form the second transition section, a portion of the electrode hole is located in the first transition section, and the other portion is located in the second transition section, and in each of the heating parts, the first end and / or the second end is connected to the first transition section of the corresponding transition part.
[0011] Optionally, the two heating parts are symmetrically arranged about a first symmetry axis, and a center line connecting the two electrode holes coincides with the first symmetry axis.
[0012] Optionally, each of the heating parts is symmetrically arranged about a second symmetry axis, and the first symmetry axis and the second symmetry axis are perpendicular to each other.
[0013] Optionally, an end of the heating strip away from the first symmetry axis is defined as a third end, and a distance from the third end to the first symmetry axis is defined as a maximum height of the heating strip; each of the heating strips is at least partially parallel to the second symmetry axis;
[0014] In each of the heating parts, the difference in maximum heights of the heating strips in the middle is less than a first threshold, and / or the difference in maximum heights of the heating strips on both sides is less than a second threshold.
[0015] Optionally, in each of the heating parts, the maximum height of each heating strip in the middle is greater than the maximum height of each heating strip on both sides, and / or the difference in length between at least part of the heating strips in the middle and at least part of the heating strips on both sides is less than a third threshold.
[0016] Optionally, adjacent heating strips are connected via arc segments.
[0017] Optionally, the two heating parts and the two transition parts are integrally formed.
[0018] The present application also provides a single crystal furnace, comprising the bottom heater.
[0019] The bottom heater provided by the present application is provided with two heating parts and two transition parts. The heating part includes a plurality of heating strips, each of which is connected end to end in sequence. The first end and the second end of the two heating parts are respectively connected through a transition part, and the transition part is provided with an electrode hole. In each heating part, the heating strips at the first end and / or the second end are at least partially located outside the electrode hole at the corresponding end. In this way, the space on both sides of at least one transition part can be used to arrange the heating strips, increasing the layout space of the heating strips, and the length of the heating strips can be relatively shortened, so that the heating strips are not likely to generate large local stresses under the action of gravity, so as to reduce deformation and be not easily damaged, thereby extending the service life of the bottom heater. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a structural schematic diagram of a bottom heater in the related art;
[0021] Figure 2 A schematic diagram of the structure of a bottom heater provided in an embodiment of the present application;
[0022] Figure 3 This is a schematic structural diagram of a bottom heater according to another embodiment of the present application.
[0023] The reference numerals in the above drawings are described as follows:
[0024] 01-heating body, 011-heating ribs, 02-transition area, 03-electrode connection hole;
[0025] 1-heating part, 1a-heating strip, 1b-arc segment, 11-sub-heating part, 111-first heating unit, 112-second heating unit, 113-third heating unit, 114-fourth heating unit, 115-fifth heating unit;
[0026] 2-transition part, 2a-electrode hole, 21-first transition section, 22-second transition section;
[0027] a- first symmetry axis, b- second symmetry axis. DETAILED DESCRIPTION
[0028] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0029] It is important to note that: Figure 2-3 The dotted line in FIG. 1 is only used to divide the heating portion 1 and the transition portion 2 , and does not mean that the contour line exists between the two.
[0030] The terms "first", "second", etc. mentioned in this application are only used to facilitate the description of two or more structures or components with the same or similar structures and / or functions, and do not imply any special limitation on the order and / or importance.
[0031] In this application, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0032] Please refer to Figure 2 , Figure 2 A schematic structural diagram of a bottom heater according to an embodiment of the present application.
[0033] In the embodiment provided in the present application, the bottom heater includes two heating parts 1 and two transition parts 2. The heating part 1 includes a plurality of heating strips 1a, and each heating strip 1a is connected end to end in sequence. The heating part 1 has a first end and a second end, the first ends of the two heating parts 1 are connected by a transition part 2, and the second ends of the two heating parts 1 are connected by another transition part 2. The transition part 2 is provided with an electrode hole 2a; the side of the center of the electrode hole 2a away from the other electrode hole 2a is defined as the outer side, and the side of the center of the electrode hole 2a close to the other electrode hole 2a is defined as the inner side; in each heating part 1, the heating strips 1a at the first end and the second end are at least partially located on the outer side of the electrode hole 2a at the corresponding end.
[0034] In this way, the space on both sides of the two transition parts 2 can be utilized. Figure 2 The space in the upper and lower directions of the heating strips 1a can be used to increase the layout space of the heating strips 1a, which is beneficial to shortening the length of each heating strip 1a, making it difficult for them to generate large local stress under the action of gravity, thereby reducing deformation, preventing damage and extending the service life of the bottom heater.
[0035] In fact, in each heating part 1, only the heating strip 1a at the first end or the heating strip 1a at the second end may be at least partially located outside the electrode hole 2a at the corresponding end, without specific limitation. Obviously, when both the heating strips 1a at the first end and the second end meet the above-mentioned position relationship conditions with the electrode hole 2a, the effect is better. In addition, it is not difficult to understand that a straight line perpendicular to the line connecting the centers of the two electrode holes 2a is drawn through the center of the electrode hole 2a, and the side of the straight line away from the other electrode hole 2a is the outside of the electrode hole 2a.
[0036] During specific use, the material of the heating strip 1a can be isostatic graphite, and the two electrode holes 2a can be connected to the positive and negative electrodes of an external power source respectively so that the two heating parts 1 are connected in parallel. After power is turned on, the heating strip 1a generates heat by relying on its own resistance, and the heat is radiated to the bottom of the crucible to heat the raw materials in the crucible to melt the raw materials.
[0037] In the embodiment provided in the present application, in each heating portion 1, the center of gravity of the heating strip 1a at the first end and the second end can be located outside the electrode hole 2a at the corresponding end. In this way, the space on both sides of the two transition portions 2 can be further utilized for the layout of the heating strip 1a, thereby further shortening the length of the heating strip 1a, improving the situation of large local stress in the related art, and extending the service life of the bottom heater.
[0038] In actual configuration, the two heating parts 1 and the two transition parts 2 can be formed separately or integrally, and this application does not impose any limitation on this.
[0039] As an alternative, Figure 2 As shown, the two heating parts 1 and the two transition parts 2 are integrally formed, that is, the entire bottom heater can be manufactured using the same isostatically pressed graphite blank, which is beneficial to improving the uniformity of heating and extending the service life of the bottom heater.
[0040] Moreover, when the two heating parts 1 and the two transition parts 2 are integrally formed by using the same graphite blank, Figure 1 The transition area 02 of the related art extends to the outside of the heating body 01 and is relatively long, resulting in a large area of the graphite embryo plate on the upper and lower sides being cut and discarded. The bottom heater provided in the embodiment of the present application can utilize the space on the upper and lower sides of the transition part 2 to arrange the heating strip 1a, and can make full use of the graphite embryo plates on the upper and lower sides of the transition part 2, reducing the area of the graphite embryo plates that are cut and discarded here, thereby reducing the waste of raw materials. At the same time, the heating strip 1a can be relatively shortened. Figure 1 The length in the vertical direction is relatively reduced to reduce the length of the whole graphite blank for cutting. Figure 1 The size in the vertical direction makes the structure of the entire bottom heater more compact and occupies less space, thereby reducing the amount of graphite raw materials used. It can be seen that the bottom heater provided in the embodiment of the present application is conducive to saving the raw materials used in the manufacture of the bottom heater, which can directly reduce the manufacturing cost of the bottom heater, thereby reducing the production cost of the single crystal furnace.
[0041] In the embodiment provided in the present application, the transition part 2 includes a first transition section 21 and a second transition section 22. The first transition section 21 protrudes toward one side of the other transition part 2 to form the second transition section 22. A portion of the electrode hole 2a is located in the first transition section 21, and the other portion is located in the second transition section 22. The first end and the second end of the two heating parts 1 are both connected to the first transition section 21 of the corresponding transition part 2. In this way, the space of the transition part 2 can be fully utilized to open the electrode hole 2a, and the space occupied by the transition part 2 can be reduced, which is conducive to increasing the layout space of the heating strips. Specifically, the heating strips 1a at both ends of the heating part 1 can be arranged on the upper and lower sides of the first transition section 21, and the space on the upper and lower sides of the second transition section 22 can be used to layout other shorter heating strips 1a, so that the length of other heating strips 1a can be shortened accordingly, the service life of the bottom heater can be extended, and the structure of the entire bottom heater can be made more compact, graphite raw materials can be saved more, and the manufacturing cost of the bottom heater can be reduced.
[0042] In the specific setting, the connection between the first transition section 21 and the corresponding heating strip 1a can adopt an arc transition, and the second transition section 22 can be fan-shaped, which can not only provide sufficient space for the opening of the electrode hole 2a, but also further reduce the space occupied by the second transition section 22, and save the space on its upper and lower sides for the layout of the heating strip 1a.
[0043] In order to arrange the heating strips 1a more evenly, in the embodiment provided in the present application, the bottom heater is arranged axially symmetrically.
[0044] Specifically, Figure 2 As shown, the two heating parts 1 are symmetrically arranged about the first symmetry axis a, and the center line of the two electrode holes 2a coincides with the first symmetry axis a. In this way, the heating strips 1a can be evenly distributed on both sides of the first symmetry axis a, which is conducive to improving the situation of excessive local stress in the related art, thereby extending the service life of the bottom heater.
[0045] In the examples provided in this application, please refer to Figure 2 Each heating part 1 can be symmetrically arranged about the second symmetry axis b, and the first symmetry axis a and the second symmetry axis b can be perpendicular to each other. Figure 1 In the related art, the two heating bodies 01 are arranged symmetrically along the center, but not axially symmetrically. The heating ribs 011 cannot be evenly distributed. Some heating ribs 011 are even too long, which can easily generate large local stress at the root under the action of gravity, thus easily deforming and causing damage. Figure 1 and Figure 2It can be seen that the embodiment of the present application, by symmetrically arranging the bottom heater along the first symmetry axis a and the second symmetry axis b, can evenly distribute the heating strips 1a on both sides of the second symmetry axis b on the basis of evenly distributing the heating strips 1a on both sides of the first symmetry axis a. This is beneficial to further shortening the length of each heating strip 1a, making it less likely to generate large local stress, thereby further extending the service life of the bottom heater. At the same time, it is more beneficial to further save the graphite raw material used in the integral molding of the bottom heater, thereby further reducing the manufacturing cost of the bottom heater.
[0046] In actual configuration, the layout of the heating strips 1a in the heating portion 1 is not limited.
[0047] In the embodiment provided in the present application, the end of the heating bar 1a away from the first symmetry axis a is defined as the third end, the end close to the first symmetry axis a is defined as the fourth end, the distance from the third end to the first symmetry axis a is defined as the maximum height of the heating bar 1a, and the distance from the fourth end to the first symmetry axis a is defined as the minimum height of the heating bar 1a; each heating bar 1a is at least partially parallel to the second symmetry axis b;
[0048] In each heating part 1, the maximum height of each heating strip 1a satisfies the following two maximum height conditions:
[0049] The difference in maximum heights of the heating strips 1a in the middle is less than a first threshold;
[0050] The difference between the maximum heights of the heating strips 1a on both sides is smaller than the second threshold.
[0051] With such arrangement, by controlling the size of the first threshold and the second threshold, the maximum heights of the heating strips 1a in the middle can be controlled to be basically consistent, and the maximum heights of the heating strips 1a on both sides can be controlled to be basically consistent, thereby making the structure of the bottom heater more compact, more conducive to shortening the length of each heating strip 1a, and less prone to generating large local stress, thereby extending the service life. At the same time, it is more conducive to saving graphite materials used in manufacturing, reducing manufacturing costs, and also conducive to improving the uniformity of the heating effect.
[0052] In fact, the maximum height of each heating strip 1a may only meet one of the above two maximum height conditions, which will not be described in detail. Obviously, the effect is better when both of the above two maximum height conditions are met.
[0053] It is worth noting that each heating strip 1a is at least partially parallel to the second symmetry axis b. The left and right sides of each heating strip 1a may be parallel to the second symmetry axis b. Alternatively, one side of the left and right sides of some heating strips 1a may be inclined and the other side may be parallel to the second symmetry axis b, while the left and right sides of another part of the heating strips 1a may be parallel to the second symmetry axis b. There is no specific limitation. As an optional solution, Figure 2As shown, in each heating portion 1, one side of the left and right sides of the heating strip 1a at the first end and the second end can be parallel to the second symmetry axis b, and the other side is inclined outward and extends to the first transition section 21 of the transition portion 2, and the left and right sides of all the heating strips 1a between the first end and the second end are parallel to the second symmetry axis b. In this way, a straight heating strip 1a can be formed, which is not only easy to process and clean, but also can generate heat evenly during operation and extend the service life.
[0054] In the embodiment provided in the present application, in each heating portion 1, the heating strips 1a in the middle and the heating strips 1a on both sides meet the following two relative position conditions:
[0055] The maximum height of each heating strip 1a in the middle is greater than the maximum height of each heating strip 1a on both sides;
[0056] The difference between the length of at least part of the heating strip 1a in the middle and at least part of the heating strip 1a on both sides is smaller than the third threshold.
[0057] With such arrangement, on the one hand, by controlling the third threshold value, the lengths of the partial heating strips 1a in the middle and the partial heating strips 1a on both sides can be made basically the same, and the axially symmetrical structural design of the bottom heater makes the length distribution of the heating strips 1a more uniform, thereby reducing possible local stress, extending the service life, and making the heat generation more uniform, thereby improving the heating effect; on the other hand, the minimum height of the partial heating strips 1a in the middle can be made greater than the minimum height of the partial heating strips 1a on both sides. In other words, in the two heating parts 1, the spacing between the partial heating strips 1a in the middle that are symmetrical about the first symmetry axis a can be made greater than the spacing between the partial heating strips 1a on both sides that are symmetrical about the first symmetry axis a, thereby making it difficult for heat to be concentrated in the middle of the bottom heater during heating, thereby improving the heating effect.
[0058] Of course, the heating strips 1a in the middle and the heating strips 1a on both sides may only meet one of the above two relative position conditions, which will not be described in detail. Obviously, the effect is better when both of the above two relative position conditions are met.
[0059] It is not difficult to understand that each heating part 1 may include two sub-heating parts 11, and the two sub-heating parts 11 may be symmetrically arranged about the second symmetry axis b. In actual arrangement, the specific structure of each sub-heating part 11 is not limited, and for example, please refer to Figure 2The sub-heating part 11 may include a first heating unit 111, a second heating unit 112, a third heating unit 113, a fourth heating unit 114 and a fifth heating unit 115 connected in sequence, the first heating unit 111 is composed of a heating strip 1a at the corresponding end of the heating part 1, and all other heating units include at least one heating strip 1a. Among them, in each heating part 1, the heating strips 1a of the two fourth heating units 114 and the two fifth heating units 115 are the heating strips 1a in the middle, the heating strips 1a of the two first heating units 111, the two second heating units 112 and the two third heating units 113 are the heating strips 1a on both sides, the two first heating units 111 are transition units connecting the transition part 2 and other heating units, the second heating unit 112 is used to connect the corresponding first heating unit 111 and the third heating unit 113, and the fourth heating unit 114 is used to connect the corresponding third heating unit 113 and the fifth heating unit 115.
[0060] During specific settings, the difference in minimum heights of the heating strips 1a in the third heating unit 113 and the fourth heating unit 114 may be less than a fourth threshold value. By controlling the fourth threshold value, the minimum heights of the third heating unit 113 and the fourth heating unit 114 can be made substantially consistent, thereby making the structure of the bottom heater more compact and further improving the service life of the bottom heater and the uniformity of the heating effect.
[0061] In specific configuration, when a heating unit has more than two heating strips 1a, the difference in lengths of the heating strips 1a inside the heating unit can be controlled to be less than the fifth threshold, so that the distribution of the heating strips 1a is more uniform.
[0062] In the embodiments provided in this application, Figure 2 As shown, in each heating part 1, the length of each heating bar 1a in the first heating unit 111 and the third heating unit 113 may be greater than the length of each heating bar 1a in the second heating unit 112, and may be smaller than the length of each heating bar 1a in the fourth heating unit 114, and the difference between the length of each heating bar 1a in the fifth heating unit 115 located in the middle and the length of each heating bar 1a in the third heating unit 113 located on both sides is smaller than the above-mentioned third threshold value.
[0063] The above-mentioned first threshold, second threshold, third threshold, fourth threshold and fifth threshold are not specifically limited. When actually setting, they can be determined according to the specifications of the single crystal furnace used. For example, the bottom heater provided in the embodiment of the present application is used for heating the crucible in a single crystal furnace, and the above-mentioned thresholds can be controlled within 15mm.
[0064] In the embodiment of the present application, the shortest part of the second heating unit 112 can be arranged on the upper and lower sides of the second transition section 22 in the transition portion 2, and the space on both sides of the second transition section 22 can be fully utilized for short-segment layout, which is beneficial to further shorten the length of the longer heating strip 1a, further reduce possible local stress, and make the layout between the heating strips 1a more compact, which can reduce the area of the required graphite raw material, increase the utilization rate of the raw material, and directly reduce the manufacturing cost.
[0065] In specific configuration, the number of heating strips 1a in other heating units except the first heating unit 111 is not limited.
[0066] In one embodiment provided in this application, please refer to Figure 2 The first heating unit 111 includes one heating bar 1a, the second heating unit 112 includes two heating bars 1a and has the shortest length, the third heating unit 113 includes three heating bars 1a, the fourth heating unit 114 includes one heating bar 1a and has the longest length, and the fifth heating unit 115 includes three heating bars 1a. In this way, each heating part 1 includes 20 heating bars 1a.
[0067] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of the bottom heater of another embodiment provided by the present application. In another embodiment provided by the present application, the main difference from the previous embodiment is that the fifth heating unit 115 includes two heating strips 1a, and each heating part 1 includes 18 heating strips 1a. In this way, since the total length of the heating strips is determined according to the design target resistance value, the length of some heating strips 1a in this embodiment is slightly longer.
[0068] It is not difficult to understand that the quantity distribution of the heating strips 1a in each heating unit affects the length layout of the heating strips 1a, and can be flexibly designed according to the total design length of the heating strips.
[0069] In actual configuration, the connection structure between adjacent heating strips 1a is not limited, for example, Figure 2 As shown, adjacent heating strips 1a can be transitionally connected via arc segments 1b, which is beneficial to increase the strength of each heating strip 1a, making it less likely to deform, thereby extending the service life of the bottom heater.
[0070] In actual configuration, the shapes of the two electrode holes 2a are not limited. For example, they can be strip-shaped holes, that is, holes with a length greater than a width. Specifically, they can be Figure 2 The waist-shaped hole in the bottom heater can also be an elliptical hole or a rectangular hole. In this way, space can be provided for possible deformation during the heating process, thereby extending the service life of the bottom heater.
[0071] In the embodiments provided in the present application, a single crystal furnace is also provided, which includes the bottom heater in all the above embodiments.
[0072] The bottom heater in the above embodiment of the present application can make full use of the space on both sides of the two transition parts 2, and adopt an axisymmetric structure, so that the length of each heating strip 1a can be evenly distributed, and the length of the longer heating strip 1a can be reduced, thereby reducing the local stress of the bottom heater and extending the service life of the bottom heater. At the same time, the area of the graphite embryo plate used for processing and manufacturing can be reduced, the utilization rate of raw materials can be improved, and the manufacturing cost of the bottom heater can be reduced. The single crystal furnace provided in the embodiment of the present application can relatively reduce the production cost because it uses the bottom heater in the above embodiment to heat the crucible.
[0073] The principles and implementation methods of the present application are described in this article using specific examples. The description of the above embodiments is only used to help understand the device and its core idea of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.
Claims
1. A bottom heater, characterized in that: include: Two heating parts (1) and two transition parts (2); The heating portion (1) comprises a plurality of heating strips (1a), each of the heating strips (1a) being connected end to end in sequence; the heating portion (1) has a first end and a second end, the first ends of two heating portions (1) being connected via one transition portion (2), and the second ends of two heating portions (1) being connected via another transition portion (2); the transition portion (2) is provided with an electrode hole (2a); The side of the center of the electrode hole (2a) away from the other electrode hole (2a) is defined as the outer side; in each of the heating parts (1), the heating strip (1a) at the first end and / or the second end is at least partially located outside the electrode hole (2a) at the corresponding end.
2. The bottom heater according to claim 1, characterized in that: In each of the heating parts (1), the center of gravity of the heating strip (1a) at the first end and / or the second end is located outside the electrode hole (2a) at the corresponding end.
3. The bottom heater according to claim 1 or 2, characterized in that: The transition portion (2) comprises a first transition section (21) and a second transition section (22); the first transition section (21) protrudes toward one side of the other transition portion (2) to form the second transition section (22); a portion of the electrode hole (2a) is located in the first transition section (21) and another portion is located in the second transition section (22); in each of the heat generating portions (1), the first end and / or the second end is connected to the first transition section (21) of the corresponding transition portion (2).
4. The bottom heater according to claim 1 or 2, characterized in that: The two heating parts (1) are symmetrically arranged about the first symmetry axis (a), and a center line connecting the two electrode holes (2a) coincides with the first symmetry axis (a).
5. The bottom heater according to claim 4, characterized in that: Each of the heat generating parts (1) is symmetrically arranged about the second symmetry axis (b), and the first symmetry axis (a) and the second symmetry axis (b) are perpendicular to each other.
6. The bottom heater according to claim 5, characterized in that: The end of the heating strip (1a) away from the first symmetry axis (a) is defined as the third end, and the distance from the third end to the first symmetry axis (a) is defined as the maximum height of the heating strip (1a); each heating strip (1a) is at least partially parallel to the second symmetry axis (b); In each of the heating parts (1), the difference in maximum heights of the heating strips (1a) in the middle is less than a first threshold, and / or the difference in maximum heights of the heating strips (1a) on both sides is less than a second threshold.
7. The bottom heater according to claim 6, characterized in that: In each of the heating parts (1), the maximum height of each heating strip (1a) in the middle is greater than the maximum height of each heating strip (1a) on both sides, and / or the difference between the length of at least part of the heating strip (1a) in the middle and at least part of the heating strip (1a) on both sides is less than a third threshold.
8. The bottom heater according to claim 1 or 2, characterized in that: Adjacent heating strips (1a) are transitionally connected via arc segments (1b).
9. The bottom heater according to claim 1 or 2, characterized in that: The two heating parts (1) and the two transition parts (2) are integrally formed.
10. A single crystal furnace, characterized in that: The invention comprises the bottom heater according to any one of claims 1 to 9.