Heater, single crystal manufacturing apparatus, single crystal manufacturing method

Abstract

To provide a heater with an improved output controllability, a manufacturing apparatus of a single crystal including the heater, and a manufacturing method of the single crystal using the heater.SOLUTION: A heater according to the invention is a cylindrical shaped heater used in a manufacturing apparatus of a single crystal and includes multiple slits that extend in a circumferential direction and penetrates in the circumferential direction. A manufacturing apparatus of a single crystal according to the invention includes the heater. A manufacturing method of the single crystal according to the invention uses the heater.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heater used in a single crystal manufacturing apparatus, a single crystal manufacturing apparatus equipped with the heater, and a single crystal manufacturing method using the heater. [Background technology]

[0002] FIG. 1 is a perspective view showing the schematic shape of a conventional heater. As shown in FIG. 1, a heater 90 used in a conventional single crystal manufacturing apparatus for pulling single crystals such as silicon single crystals has a generally cylindrical shape and is provided with a plurality of through slits 91, 92 extending in the axial (vertical) direction of the cylinder in the circumferential direction (equally spaced in the illustrated example). The through slit 91 extends axially from the upper end in the illustration and terminates at the lower end without opening at the lower end. On the other hand, the through slit 92 extends axially from the lower end in the illustration and terminates at the upper end without opening at the upper end. Because the through slits 91, 92 are alternately arranged in the circumferential direction, the heater 90 forms a long, serpentine current path. This configuration is suitable for the heater 90 to generate heat at a desired temperature by electrical resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 04-357191 Summary of the Invention [Problem to be solved by the invention]

[0004] During the production of single crystals, it is desirable to maintain a constant melt temperature and ensure stable crystal growth. To achieve this, stabilizing the heater output is essential. To stabilize the heater output, the temperature of the heater or the components heated by the heater and in the vicinity of the heater is measured, and the heater output is controlled. A radiation thermometer is sometimes used to measure the temperature of the heater or the components heated by the heater from outside the chamber of the single crystal production equipment housing the heater, and the heater output is controlled by feeding back the measured temperature results. In this case, it is not easy to change the position of the measurement point for measuring the temperature of the heater or the components heated by the heater and in the vicinity of the heater, and the temperature measurement point used to control the heater output is fixed. Therefore, it is desirable to reduce the influence of the fixed temperature measurement point used to control the heater output and to stably control the heater output.

[0005] However, even when measuring the temperature of a conventional heater, it was found that the heater output may not be controlled appropriately depending on the heater structure. For example, there are a one-piece heater and a two-part heater divided in two axially, and while the heater output can be controlled appropriately with the one-piece heater, it may not be controlled appropriately with the two-part heater. Conversely, there are cases where the heater output cannot be controlled appropriately with the one-piece heater, but can be controlled appropriately with the two-part heater.

[0006] Therefore, an object of the present invention is to provide a heater with improved output controllability, a single crystal manufacturing apparatus equipped with the heater, and a single crystal manufacturing method using the heater. [Means for solving the problem]

[0007] The gist and configuration of the present invention are as follows. (1) A cylindrical heater used in a single crystal manufacturing apparatus, A heater comprising a plurality of circumferential through slits extending in the circumferential direction.

[0008] (2) The heater described in (1) above, having a serpentine shape consisting of a circumferentially extending portion that extends in the circumferential direction and an axially extending portion that extends in the axial direction, both separated by the circumferential through slit.

[0009] (3) The heater according to (1) or (2) above, which has a structure that is plane-symmetrical with respect to a plane passing through the central axis of the cylinder.

[0010] (4) A single crystal manufacturing apparatus comprising the heater according to any one of (1) to (3) above.

[0011] (5) A method for producing a single crystal, using the heater according to any one of (1) to (3) above. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a heater with improved output controllability, a single crystal manufacturing apparatus equipped with the heater, and a single crystal manufacturing method using the heater. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing a schematic shape of a conventional heater. [Figure 2] 1 is a perspective view showing a schematic shape of a heater according to an embodiment of the present invention. [Figure 3] FIG. 3 is a perspective view showing a schematic shape of a heater according to a modified example of the embodiment of FIG. 2, in which the heater has four electrodes. [Figure 4] FIG. 1 is a cross-sectional view of a single crystal pulling furnace for explaining measurement of the temperature of a conventional integrated heater. [Figure 5] FIG. 1 is a cross-sectional view of a single crystal pulling furnace for explaining measurement of the temperature of a conventional two-split heater. [Figure 6] FIG. 10 is a schematic diagram for explaining measurement of the temperature of a conventional integrated heater. [Figure 7]FIG. 10 is a schematic diagram for explaining measurement of the temperature of a conventional two-split heater. [Figure 8] FIG. 2 is a cross-sectional view of a single crystal pulling furnace for explaining measurement of the temperature of the integrated heater of this embodiment. [Figure 9] FIG. 2 is a cross-sectional view of a single crystal pulling furnace for explaining measurement of the temperature of a two-split heater according to the present embodiment. [Figure 10] 5A and 5B are schematic diagrams for explaining measurement of the temperature of the integrated heater according to the embodiment. [Figure 11] 5 is a schematic diagram for explaining measurement of the temperature of a two-split heater according to the present embodiment. FIG. [Figure 12] FIG. 10 is a perspective view showing a schematic shape of a heater according to another embodiment of the present invention. [Figure 13] FIG. 13 is a perspective view showing a schematic shape of a heater according to a modification of the embodiment of FIG. 12, in which the heater has four electrodes. [Figure 14] FIG. 10 is a diagram showing test results of an example of the invention. [Figure 15] FIG. 10 is a diagram showing test results of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] <Heater> Fig. 2 is a perspective view showing a schematic shape of a heater according to one embodiment of the present invention. Heater 1 is used in an apparatus for producing single crystals such as silicon single crystals by the Czochralski method, and has a cylindrical shape as shown in Fig. 2. In the illustrated example, heater 1 has a structure that is plane-symmetrical with respect to a plane passing through the central axis of the cylinder, and a first axially penetrating (diametrically penetrating) slit 2 that passes through the plane and extends in the axial direction from the upper end in the illustration, dividing most of the axial direction into two, portion 1a and portion 1b, while portion 1a and portion 1b are connected at the lower end in the illustration.

[0016] The heater 1 also has a plurality of circumferential through slits 3 (slits that extend in the circumferential direction and penetrate in the radial direction) that extend in the circumferential direction. In the illustrated example, the heater 1 has a first circumferential through slit 3a that communicates with the first axial through slit 2 and extends to both sides in the circumferential direction from the communicating portion with the first axial through slit 2, and a second circumferential through slit 3b that does not communicate with the first axial through slit 2. In this example, the first circumferential through slits 3a and the second circumferential through slits 3b are arranged alternately at equal intervals in the axial direction. Each of the circumferential ends on one side of the plurality of second circumferential through slits 3b communicates with a second axial through slit 4 that extends in the axial direction.

[0017] The heater 1 has a serpentine shape consisting of a circumferentially extending portion 5a extending in the circumferential direction and an axially extending portion 5b extending in the axial direction, which are partitioned by a circumferentially through slit 3 (in the illustrated example, partitioned by a first axially through slit 2, a first circumferentially through slit 3a, a second circumferentially through slit 3b, and a second axially through slit 4).

[0018] In the illustrated example, the extension length of the circumferentially extending portion 5a is longer than the extension length of the axially extending portion 5b. Note that the circumferentially extending portion 5a at the illustrated lower end connects the portion 1a and the portion 1b without being divided by the first axial through-slit 2.

[0019] In the illustrated example, the two electrodes 6 extend in the axial direction and are connected to the circumferentially extending portion 5a at the upper end. This allows current to flow from the positive electrode to the negative electrode along the meandering shape. In the circumferentially extending portion 5a at the lower end, the current flows through a path that is approximately twice as long as the other circumferentially extending portions 5a.

[0020] FIG. 3 is a perspective view showing the schematic shape of a heater according to a modification of the embodiment shown in FIG. 2, in which four electrodes are provided. This modification differs from the example shown in FIG. 2 in that four electrodes are arranged at equal intervals in the circumferential direction at the lower end of the heater 1. As shown, the four electrodes 6 communicate with the circumferentially extending portion 5a at the lower end. One pair of opposing electrodes 6 are positive electrodes, and the other pair of opposing electrodes 6 are negative electrodes. In this configuration, current flows in two directions, from one positive electrode to two negative electrodes, in a serpentine shape.

[0021] The effects of the heater of this embodiment will be described below in comparison with conventional heaters. Fig. 4 is a cross-sectional view of a single crystal pulling furnace for explaining the measurement of the temperature of a conventional integrated heater. Fig. 5 is a cross-sectional view of a single crystal pulling furnace for explaining the measurement of the temperature of a conventional two-piece heater. Fig. 6 is a schematic view for explaining the measurement of the temperature of a conventional integrated heater. Fig. 7 is a schematic view for explaining the measurement of the temperature of a conventional two-piece heater.

[0022] Through investigations, the inventors have discovered that the reason for the difference in responsiveness to heater output between the one-piece structure and the two-split structure divided into two in the axial direction is due to the following phenomenon. As shown in Figure 1, a conventional heater has a through slit extending in the axial direction. Because current tends to travel the shortest path, current concentrates at the bends of the serpentine shape, resulting in the maximum amount of heat generated by Joule heat generated by the current. Therefore, as shown in Figures 4 and 6, in a cross-sectional view of an all-in-one heater, maximum heat-generating areas A appear alternately at the upper and lower ends of the heater in the horizontal direction. These maximum heat-generating areas A are the areas that most significantly reflect changes in heater power output. On the other hand, as shown in Figures 5 and 7, in a two-part heater, maximum heat-generating areas A appear alternately at the upper and lower ends of the upper half and the lower half of the two-part heater in the cross-sectional view. That is, in a conventional heater with a through slit extending in the axial direction, the maximum heat-generating areas A appear aligned horizontally when projected vertically. As a result, for the same temperature measurement point, depending on the position, one may measure the maximum heat generation area A and the other may measure another area (for example, the area between the two maximum heat generation areas A) with the one-piece and two-piece types.In such cases, the response will differ between the one-piece and two-piece types because the measured temperature in relation to the heater output will be different.

[0023] Fig. 8 is a cross-sectional view of a single crystal pulling furnace for explaining the measurement of the temperature of the integrated heater of this embodiment. Fig. 9 is a cross-sectional view of a single crystal pulling furnace for explaining the measurement of the temperature of the two-piece heater of this embodiment. Fig. 10 is a schematic view for explaining the measurement of the temperature of the integrated heater of this embodiment. Fig. 11 is a schematic view for explaining the measurement of the temperature of the two-piece heater of this embodiment.

[0024] The heater 1 of this embodiment has multiple circumferentially extending through-slits 3. Therefore, as shown in FIGS. 8 to 11 , whether the heater is an integrated heater or a two-piece heater, the meandering bends appear sequentially in the vertical direction, and the maximum heat generation portions A appear aligned vertically when projected horizontally. Therefore, when measuring the temperature from the horizontal direction, the maximum heat generation portion A can be the measurement target at any vertical position, whether the heater is an integrated heater or a two-piece heater. This prevents a difference in responsiveness to heater output between the integrated heater and the two-piece heater. Even if the maximum heat generation portion A cannot be the measurement target, the heater of the present invention allows a region near the maximum heat generation portion A to be the measurement target. Therefore, the difference in responsiveness to heater output between the integrated heater and the two-piece heater is smaller than that of conventional heaters. As described above, the heater 1 of this embodiment can improve the controllability of the heater output when controlling the heater output by measuring the heater temperature from the horizontal direction of the pulling furnace. It can also observe changes in the thermal environment (such as thinning or oxide deposition) that occur significantly in the maximum heat generation portion A. To ensure a good thermal environment, it is preferable to have a structure that is plane-symmetrical with respect to a plane passing through the central axis of the cylinder, as in this embodiment.

[0025] FIG. 12 is a perspective view showing a schematic shape of a heater according to another embodiment of the present invention. The heater 10 of the embodiment shown in FIG. 12 is used in a manufacturing apparatus for single crystals such as silicon single crystals, and is cylindrical as shown in FIG. 12. In the embodiment of FIG. 12, the first axial through slits 20 consist of a first axial through slit 20a extending axially from the upper end in the figure and a first axial through slit 20b extending axially from the lower end in the figure. The heater also has a first circumferential through slit 30a that communicates with the first axial through slit 20 (20a, 20b) and extends to both sides in the circumferential direction from the communicating portion with the first axial through slit 20, and a second circumferential through slit 30b that does not communicate with the first axial through slit 20. The first circumferential through slits 30a are arranged in a staggered pattern. In this example, the first circumferential through slits 30a and the second circumferential through slits 30b are arranged alternately at equal intervals in the axial direction. Each of the circumferential ends on one side of the plurality of second circumferential through slits 30b communicates with a second axial through slit 40 extending in the axial direction.

[0026] The heater 1 has a serpentine shape consisting of a circumferentially extending portion 50a extending in the circumferential direction and an axially extending portion 50b extending in the axial direction, which are partitioned by circumferential through slits 3 (30a, 30b) (in the illustrated example, partitioned by the first axial through slit 20, the first circumferential through slit 30a, the second circumferential through slit 30b, and the second axial through slit 40). Note that the circumferentially extending portion 50a at the lower end in the illustration extends in the circumferential direction without being divided by the first axial through slit 20.

[0027] In the illustrated example, the two electrodes 60 extend in the axial direction and communicate with the circumferentially extending portion 50a at the upper end as shown, so that the current flows from the positive electrode to the negative electrode along the meandering shape.

[0028] FIG. 13 is a perspective view showing the schematic shape of a heater according to a modification of the embodiment shown in FIG. 12, in which four electrodes are provided. This modification differs from the example shown in FIG. 12 in that four electrodes are arranged at equal intervals in the circumferential direction at the bottom end of the heater 1. As shown, the four electrodes 60 communicate with the circumferentially extending portion 50a at the bottom end. One pair of opposing electrodes 6 are positive electrodes, and the other pair of opposing electrodes 6 are negative electrodes. In this configuration, current flows in two directions, from one positive electrode to two negative electrodes, in a serpentine shape.

[0029] 12 and 13, the heater 10 is also provided with multiple circumferential through slits 30 extending in the circumferential direction, so that the maximum heat generation portions A appear aligned in the vertical direction when projected horizontally. Therefore, when measuring the temperature from the horizontal direction, the maximum heat generation portion A can be the measurement target at any vertical position, whether it is an integrated type or a two-piece type, and therefore it is possible to ensure that the responsiveness to heater output does not differ between the integrated type and the two-piece type. As described above, the heater 10 of the embodiment shown in Figures 12 and 13 can also improve the controllability of the output when controlling the heater output by measuring the heater temperature from the horizontal direction of the pulling furnace.

[0030] The heaters 1 and 10 shown in Figures 2, 3, 12, and 13 can be heaters made of high-purity carbon. These heaters 1 and 10 are preferably used to produce defect-free silicon single crystals. Here, "defect-free silicon single crystals" refer to crystals that do not contain, or are substantially free of, void defects caused by agglomeration of vacancies, called crystal originated particles (COPs), and dislocation cluster defects caused by agglomeration of interstitial silicon.

[0031] <Single crystal manufacturing equipment> An apparatus for producing a single crystal according to one embodiment of the present invention is used, for example, for producing silicon single crystals by the Czochralski method, and includes a single crystal pulling furnace equipped with the heaters 1 and 10 of the above-described embodiments around a crucible. In this example, the apparatus for producing a single crystal may further include a measurement unit (such as a radiation thermometer) that measures the temperature of the heater horizontally from outside the chamber in which the heater is housed. Other components of the single crystal pulling furnace may be similar to those of a conventional furnace, and therefore description thereof will be omitted. As an example, as shown in FIG. 4 and other figures, an apparatus for producing a single crystal 100 includes a crucible 102 for containing a silicon raw material such as polycrystalline silicon within a chamber 101. The crucible 102 is composed of a quartz crucible 102a and a carbon crucible 102b, with the quartz crucible 102a housed within the carbon crucible 102b. A heater 103 is disposed around the carbon crucible 102b, and a heat insulator 104 is disposed around the heater 103. The silicon raw material contained in the quartz crucible 102a is heated by the heater 103 to form a silicon melt M. A single crystal 106 is pulled up from the silicon melt M by a wire 105.

[0032] <Method of manufacturing single crystals> A method for producing a single crystal according to one embodiment of the present invention is a method for producing a silicon single crystal by, for example, the Czochralski method, and is carried out using a single crystal pulling furnace equipped with the heaters 1, 10 of the above-described embodiments around a crucible. Each step of the production method can be the same as in a normal method for producing a single crystal, and therefore a description thereof will be omitted. [Example]

[0033] Examples of the present invention will be described below, but the present invention is not limited to the following examples in any way.

[0034] To verify the effectiveness of the present invention, a comparison was made between the heater power controllability of a conventional heater (comparative example) with the structure shown in FIG. 1 and that of a heater (inventive example) with the structure shown in FIG. 2 using a pulling apparatus for producing 300 mm diameter single crystals by the Czochralski method. The effectiveness of the present invention was confirmed by evaluating whether applying the heater of the inventive example to a pulling apparatus with poor heater power controllability using the heater of the comparative example. This example was investigated by numerical simulation using a heat transfer analysis model. The heaters of the inventive example and comparative example were modeled based on the heat generation distribution of the heaters. Only the modeled heaters differed between the inventive example and comparative example; all other components of the pulling apparatus and process conditions were the same. After the seed crystal was immersed in the melt, the heater temperature was increased by 120 K when both the seed crystal position and the crucible position were raised by 55 mm in 55 minutes.

[0035] Fig. 14 shows the change in heater power and the change in heater temperature over time for an example of the invention, and Fig. 15 shows the change in heater power and the change in heater temperature over time for a comparative example. As shown in Figs. 14 and 15, the change in heater power over time was large in the heat generation distribution of the comparative example, while the change in heater power over time was small in the heat generation distribution of the example of the invention. This shows that the controllability of the heater power to increase the heater temperature by the same amount was more stable and better in the example of the invention than in the comparative example. [Explanation of symbols]

[0036] 1, 10: heater, 2, 20: first axial through slit; 3, 30: circumferential through slit, 4, 40: second axial through slit; 5a, 50a: circumferential extension part, 5b, 50b: Axial extension part, 6, 60: Electrode

Claims

1. A cylindrical heater used in a single crystal manufacturing apparatus, A plurality of circumferential through slits extending in the circumferential direction are provided, a first axial through slit consisting of a first upper end side axial through slit extending in the axial direction from the upper end of the heater and a first lower end side axial through slit extending in the axial direction from the lower end of the heater, A heater, characterized in that all of the circumferential through slits communicate with either the first upper end side axial through slit or the first lower end side axial through slit.

2. The heater according to claim 1 , having a serpentine shape composed of a circumferentially extending portion that extends in the circumferential direction and an axially extending portion that extends in the axial direction, the circumferentially extending portion being partitioned by the circumferential through slit.

3. 3. The heater according to claim 1, having a structure that is plane-symmetrical with respect to a plane passing through the central axis of the cylinder.

4. 3. A single crystal manufacturing apparatus comprising the heater according to claim 1 or 2.

5. A method for producing a single crystal, using the heater according to claim 1 or 2.

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