CZ Crucible

Abstract

To provide a crucible for CZ capable of stably self-standing quartz glass crucible when a cylindrical quartz glass crucible with a bottom for growing a single crystal silicon ingot by a CZ method is arranged in a cylindrical graphite crucible with a bottom.SOLUTION: A crucible 1 for growing a single crystal silicon ingot by a CZ method includes a cylindrical graphite crucible 1B with a bottom and a cylindrical quartz glass crucible 1A with a bottom arranged within the graphite crucible 1B. Between an inner surface of a bottom of the graphite crucible 1B in a center axis 6 of the crucible 1 for CZ and an outer surface of the bottom of the quartz glass crucible 1A, there is a gap 7 in which the inner surface of the bottom of the graphite crucible 1B and the outer surface of the bottom of the quartz glass crucible 1A do not contact. The height of the gap 7 is 0.5 - 5.0 mm in the center axis 6 of the crucible 1 for CZ in a center axis direction. The size W of the gap 7 in a direction orthogonal to the center axis 6 of the crucible 1 for CZ is 60 mm or more in diameter.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a Czochralski method (hereinafter referred to as "CZ method") crucible for pulling single crystal silicon. [Background technology]

[0002] The CZ method is known as a method for producing single crystals. In particular, the CZ method is widely used industrially for the production of single crystal silicon, which is used as a material for semiconductor electronic components. In the CZ method, polycrystalline silicon or the like filled in a quartz glass crucible is melted with a heater, a seed crystal is immersed in the surface of the silicon melt, and the seed crystal is pulled upward while rotating the quartz glass crucible and the seed crystal immersed in the silicon melt, thereby growing a single crystal with the same crystal orientation as the seed crystal.

[0003] Fig. 7 is a schematic diagram showing a pulling apparatus used when pulling a single crystal by the above-mentioned CZ method. As shown in Fig. 7, the single crystal pulling apparatus 10 is configured to include a pulling chamber 12, a CZ crucible 13 provided in the pulling chamber 12, a heater 14 arranged around the CZ crucible 13, a crucible holding shaft 15 for rotating and elevating the CZ crucible 13 and its rotation and elevating mechanism (not shown), a seed chuck 17 for holding a silicon seed crystal 16, a wire 18 for pulling up the seed chuck 17, and a winding mechanism (not shown) for rotating or winding up the wire 18. In addition, a heat insulating material 19 is arranged around the outside of the heater 14. Single crystal silicon 20 is pulled up from the silicon melt 11 as a raw material by the wire 18.

[0004] The CZ crucible 13 placed in the single crystal pulling apparatus 10 is composed of a bottomed, cylindrical quartz glass crucible that contains the silicon melt 11, and a bottomed, cylindrical graphite crucible (sometimes called a "carbon susceptor") that contains the quartz glass crucible inside (for example, Patent Documents 1 and 2, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-17245 A [Patent Document 2] JP 2013-139356 A Summary of the Invention [Problem to be solved by the invention]

[0006] The quartz glass crucible is manufactured to a size that can be accommodated inside the graphite crucible, but it is difficult to manufacture the quartz glass crucible so that the outer surface of the quartz glass crucible and the inner surface of the graphite crucible are in complete contact due to manufacturing errors, etc. The inventors conducted extensive research and found that, although the outer surface of the quartz glass crucible is made to have a convex curved shape so as to conform to the shape of the inner surface of the graphite crucible, when the quartz glass crucible 13A is placed inside the graphite crucible 13B to form a CZ crucible 13, as shown in Fig. 8, due to individual differences such as manufacturing errors in the shapes of the outer surface of the quartz glass crucible and the inner surface of the graphite crucible, the bottom of the outer surface of the quartz glass crucible 13A and the inner surface of the graphite crucible 13B come into point contact at the central axis, making the quartz glass crucible 13A unstable. If the quartz glass crucible 13A shakes within the graphite crucible 13B, there is a risk that the quartz glass crucible 13A will break inside the graphite crucible 13B. Furthermore, during single crystal production, not only will the silicon melt shake, causing melt surface vibrations that make it difficult to pull up the single crystal silicon, but the quartz glass crucible 13A will become eccentric when pulling up the single crystal silicon, making it impossible to supply uniform heat to the silicon ingot, leading to deterioration in the quality of the silicon ingot.

[0007] To solve the above problems, it is conceivable to select and combine a quartz glass crucible 13A and a graphite crucible 13B that are compatible with each other to produce a stable CZ crucible. However, since there is no other way than to find a combination of a quartz glass crucible 13A and a graphite crucible 13B that are compatible with each other by trial and error, not only is this extremely inefficient, but it is not always possible to obtain a desirable combination.

[0008] The present invention has been made to solve the above problems, and has an object to provide a CZ crucible that enables a bottomed cylindrical quartz glass crucible for growing a single crystal silicon ingot by the CZ method to stably stand on its own when the bottomed cylindrical quartz glass crucible is placed inside a bottomed cylindrical graphite crucible. [Means for solving the problem]

[0009] The present invention has been made to achieve the above-mentioned object, and provides a CZ crucible for growing a single crystal silicon ingot by a CZ method, the CZ crucible including a bottomed, cylindrical graphite crucible and a bottomed, cylindrical quartz glass crucible disposed inside the graphite crucible, and a gap is provided between the inner surface of the bottom of the graphite crucible at the central axis of the CZ crucible and the outer surface of the bottom of the quartz glass crucible, such that the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible are not in contact with each other.

[0010] With such a CZ crucible, when the quartz glass crucible is placed inside the graphite crucible, there is no point contact and the quartz glass crucible can stably stand on its own.

[0011] In this case, the height of the gap in the central axis direction of the CZ crucible may be 0.5 mm to 5.0 mm.

[0012] This allows the quartz glass crucible to be more stable and self-supporting, and also makes it possible to effectively prevent deformation of the quartz glass crucible.

[0013] In this case, the size of the gap in the direction perpendicular to the central axis of the CZ crucible may be 60 mm or more in diameter.

[0014] This makes the quartz glass crucible more stable and self-supporting, making it easier to set up the quartz glass crucible.

[0015] At this time, the quartz glass crucible has a cylindrical straight body portion, a first curvature radius R1 continuous with the lower end of the straight body portion, a first curved portion having a second curvature radius R2 continuous with the first curved portion, and a bottom portion continuous with the second curved portion, and the first curvature radius R1 and the second curvature radius R2 are in the relationship of R1 < R2, and the outer surface of the bottom portion has a flat surface shape orthogonal to the central axis of the quartz glass crucible, and it can be a crucible for CZ.

[0016] Thus, even when the bottom of the quartz glass crucible is a flat surface, it hardly affects the shape of the inner surface of the quartz glass crucible, and the influence on the convection state of the silicon melt during the growth of the single crystal silicon ingot by the CZ method becomes smaller.

Effect of the Invention

[0017] As described above, according to the CZ crucible for pulling up single crystal silicon of the present invention, when the quartz glass crucible is disposed inside the graphite crucible, the quartz glass crucible can be stably self-supporting.

Brief Description of the Drawings

[0018] [Figure 1] An example of the CZ crucible according to the present invention is shown. [Diagram 2] An example of the shape (cross section) of the bottom of the quartz glass crucible used for the CZ crucible according to the present invention is shown. [Diagram 3] A preferred example of the quartz glass crucible used for the CZ crucible according to the present invention is shown. [Figure 4] Another preferred example of the quartz glass crucible used for the CZ crucible according to the present invention is shown. [Diagram 5] An example of a gap measuring jig for the gap between the quartz glass crucible and the graphite crucible is shown. [Figure 6] An example of a taper gauge is shown. [Figure 7] A conceptual diagram schematically showing a pulling device is shown. [Figure 8] An example of a conventional CZ crucible is shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described in detail below, but the present invention is not limited thereto.

[0020] As described above, there was a need for a CZ crucible that would enable a bottomed, cylindrical quartz glass crucible for growing a single crystal silicon ingot by the CZ method to stably stand on its own when placed inside a bottomed, cylindrical graphite crucible.

[0021] As a result of intensive research into the above-mentioned problems, the inventors have discovered that a CZ crucible for growing a single crystal silicon ingot by the CZ method includes a bottomed, cylindrical graphite crucible and a bottomed, cylindrical quartz glass crucible placed inside the graphite crucible, and a gap is formed between the inner surface of the bottom of the graphite crucible at the central axis of the CZ crucible and the outer surface of the bottom of the quartz glass crucible such that the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible are not in contact with each other, and thus the present invention has been completed.

[0022] The following description will be given with reference to the drawings.

[0023] First, in a CZ crucible for growing a single crystal silicon ingot by the CZ method, when a cylindrical quartz glass crucible with a bottom is placed inside a cylindrical graphite crucible with a bottom, the quartz glass crucible is ShakyWhen the inventors investigated the cause of the instability, they found that, as described above, the quartz glass crucible becomes unstable because the outer surface of the bottom of the quartz glass crucible and the inner surface of the bottom of the graphite crucible come into point contact at the central axis due to individual differences such as manufacturing errors in the outer surface shape of the bottom when the quartz glass crucible is manufactured. They then found that the above problem can be solved by providing a gap between the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible at the central axis of the CZ crucible, so that the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible do not come into contact with each other.

[0024] 1 shows an example of a CZ crucible according to the present invention. This CZ crucible 1 has a cylindrical graphite crucible 1B with a bottom and a cylindrical quartz glass crucible 1A with a bottom placed inside the graphite crucible. When the quartz glass crucible 1A is placed inside the graphite crucible 1B, as shown in the enlarged view of the bottom 5, there is a gap 7 between the inner surface of the bottom of the graphite crucible 1B at the central axis 6 of the CZ crucible 1 and the outer surface of the bottom of the quartz glass crucible 1A, so that the inner surface of the bottom of the graphite crucible 1B and the outer surface of the bottom of the quartz glass crucible 1A are not in contact with each other. Such a CZ crucible 1 avoids point contact (Figure 8) between the outer surface of the bottom of the quartz glass crucible 1A and the inner surface of the bottom of the graphite crucible 1B, and preferably has surface contact between the outer edge of the bottom of the quartz glass crucible 1A and the inner surface of the graphite crucible 1B, so that when the quartz glass crucible 1A is placed inside the graphite crucible 1B, it can stand on its own stably.

[0025] As long as such a CZ crucible 1 can be obtained, there is no particular limitation on the shape of the quartz glass crucible 1A or the graphite crucible 1B. Fig. 2 shows an example of the shape (cross section) of the bottom 5 of the quartz glass crucible 1A. As shown in Fig. 2, the cross section of the bottom 5 may be any of (A) convex, (B) flat, and (C) concave.

[0026] Fig. 3 shows a fused silica crucible 1A when the shape of the bottom is the flat cross-sectional shape shown in Fig. 2(B). By making the outer surface shape of the bottom 5 of the fused silica crucible 1A a flat surface (hereinafter simply referred to as "flat surface") 5A perpendicular to the central axis 6 of the fused silica crucible 1A, the crucible 1 for CZ can be surely and stably provided with a gap 7.

[0027] Fig. 4 shows a fused silica crucible 1A when the shape of the bottom is the concave cross-sectional shape shown in Fig. 2(C). By making the outer surface shape of the bottom 5 of the fused silica crucible 1A a concave surface (hereinafter simply referred to as "concave surface") 5B recessed from the above-mentioned flat surface 5A as shown in Fig. 4, the crucible for CZ having a gap 7 can also be obtained. In this case, a shape symmetric with respect to the central axis 6, in other words, a structure in which when the fused silica crucible 1A is viewed from the outer surface side of the bottom 5 in the direction of the central axis 6, the edge of the concave portion is circular with the central axis 6 as the center is most preferable in terms of stability.

[0028] Further, as the fused silica crucible 1A, a first curved portion 3 having a first curvature radius R1 continuous with the lower end of the cylindrical straight body portion 2 and a second curved portion 4 having a second curvature radius R2 continuous with the first curved portion 3 are provided, and it is more preferable that the relationship R1 < R2 is satisfied. The fused silica crucible 1A having such a shape hardly affects the shape of the inner surface of the fused silica crucible 1A even when forming the flat surface 5A or the concave surface 5B. Therefore, it hardly affects the convection state of the silicon melt during the growth of the single crystal silicon ingot by the CZ method.

[0029] Note that the first curvature radius R1 and the second curvature radius R2 are not particularly limited, but it is preferable that 100 mm ≤ R1 ≤ 200 mm and 800 mm ≤ R2 ≤ 900 mm. With such a configuration, it is possible to more stably suppress changes and disturbances in the convection state of the silicon melt.

[0030] The diameter of the quartz glass crucible 1A is not particularly limited, but in the present invention, it is preferable to use a crucible with a particularly large diameter, for example, a diameter of 32 inches (about 800 mm) or more.

[0031] In order to provide the gap 7 so that the inner surface of the bottom of the graphite crucible 1B and the outer surface of the bottom of the quartz glass crucible 1A are not in contact with each other, the method is not limited to adjusting the outer surface shape of the bottom of the quartz glass crucible 1A as described above, and it is of course also possible to adjust the inner surface shape of the graphite crucible 1B. It is preferable to provide a CZ crucible 1 having the gap 7 by setting the shape of the outer surface of the bottom of the quartz glass crucible 1A, in that it has little effect on the thermal conditions when growing a single crystal silicon ingot.

[0032] Regarding the size of the gap 7, the height of the gap 7 in the central axis direction at the central axis 6 of the CZ crucible 1 (H in FIG. 1) is preferably 0.5 mm to 5.0 mm. Considering the measurement error (lower limit of measurement) of the height H of the gap 7, a stable gap 7 can be ensured if it is 0.5 mm or more. Furthermore, during the growth of the single crystal silicon ingot, there is a risk that the gas trapped in the gap 7 will expand and the pressure in the gap 7 will increase. However, if H is in the range of 5.0 mm or less, the effect of the expansion of the gas trapped in the gap 7 can be reduced, resulting in a CZ crucible 1 that can effectively suppress deformation of the quartz glass crucible 1A.

[0033] Moreover, the size of the gap in the direction perpendicular to the central axis 6 (W in FIG. 1) is preferably 60 mm or more in diameter. By setting the size W in this way, the quartz glass crucible 1A can be more stably installed in the graphite crucible 1B, resulting in a CZ crucible 1 with less rattling. Also, the installation of the quartz glass crucible becomes easier.

[0034] Here, we will explain how to estimate the size (height H, width W) of the gap 7. For example, the outer surface shape of the quartz glass crucible 1A and the inner surface shape of the graphite crucible 1B to be actually combined are measured by a three-dimensional shape measuring device or the like, and the respective data are analyzed, thereby making it possible to estimate the size of the gap 7.

[0035] Furthermore, by using a gap measuring tool 30 as shown in FIG. 5 and a taper gauge as shown in FIG. 6 for the bottom of the quartz glass crucible 1A, the gap 7 between the inner surface of the bottom of the graphite crucible 1B at the central axis 6 of the CZ crucible 1 and the outer surface of the bottom of the quartz glass crucible 1A can be easily and reliably measured. Specifically, in FIG. 5, the part where the curved surface is formed (cross-sectional shape part 31; with gauge) has a shape that reflects the cross-sectional shape of the inner surface of the graphite crucible 1B. By applying this cross-sectional shape part 31 to the outer surface of the bottom 5 of the quartz glass crucible 1A, a gap is generated between the cross-sectional shape part 31 of the gap measuring tool 30 and the bottom of the quartz glass crucible 1A. By measuring the size of this gap, the values ​​of the height H and size W of the gap can be easily obtained. At this time, a conical taper gauge as shown in Fig. 6 is inserted into the gap, and the conical surface of the conical taper gauge is brought into contact with the cross-sectional shape portion 31 and the outer surface of the quartz glass crucible 1A, and the height H of the gap 7 can be measured from the contact position between the conical surface of the conical taper gauge and the cross-sectional shape portion and the outer surface of the quartz glass crucible 1A. By performing the measurement in this manner, the height and diameter of the gap 7 can be measured extremely simply and accurately without requiring skill. EXAMPLES

[0036] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

[0037] As comparative examples and examples, the CZ crucibles shown below were prepared, and an evaluation was made as to whether the quartz glass crucibles could stand on their own without rattling inside the graphite crucible. Next, single crystal silicon ingots were actually grown by the CZ method, and the degree of deformation of the quartz glass crucible and disturbance of crystallization (single crystallization rate) was evaluated. This single crystallization rate was calculated as the ratio of the weight of the single crystal product to the weight of the input raw material. The single crystallization rate of Comparative Example 1 was set to the standard of 1.0.

[0038] Comparative Example 1 The quartz glass crucible has a straight body with a diameter of 32 inches (approximately 800 mm), followed by a curvature radiusFirst curved section and curvature of R1=180mm radius A CZ crucible was prepared having a second curved portion with R2 = 815 mm, a convex bottom shape, and no gap between the bottom of the quartz glass crucible and the graphite crucible at the central axis (H = 0, W = 0).

[0039] Example 1 The quartz glass crucible has a straight body with a diameter of 32 inches (approximately 800 mm), followed by a curvature radius First curved section and curvature of R1=180mm radius A CZ crucible was prepared having a second curved portion with R2 = 815 mm, a flat bottom shape, and a gap between the bottom of the quartz glass crucible and the graphite crucible with dimensions of H = 10.0 mm and W = 255 mm.

[0040] Example 2 A CZ crucible was prepared under the same conditions as in Example 1, except that the size of the gap between the bottom of the quartz glass crucible and the graphite crucible was H=0.5 mm and W=60 mm.

[0041] Example 3 The quartz glass crucible has a straight body with a diameter of 32 inches (approximately 800 mm), followed by a curvature radius First curved section and curvature of R1=180mm radius A CZ crucible was prepared having a second curved portion with R2 = 815 mm, a bottom shape with a concave surface, and a gap between the bottom of the quartz glass crucible and the graphite crucible with dimensions of H = 3.0 mm and W = 70 mm.

[0042] Example 4 A CZ crucible was prepared under the same conditions as in Example 1, except that the size of the gap between the bottom of the quartz glass crucible and the graphite crucible was H=3.0 mm and W=140 mm.

[0043] Example 5 A CZ crucible was prepared under the same conditions as in Comparative Example 1, except that the size of the gap between the bottom of the quartz glass crucible and the graphite crucible was H=3.0 mm and W=440 mm.

[0044] Example 6 A CZ crucible was prepared under the same conditions as in Example 3, except that the size of the gap between the bottom of the quartz glass crucible and the graphite crucible was H=1.0 mm and W=30 mm.

[0045] Example 7 A CZ crucible was prepared under the same conditions as in Example 1, except that the size of the gap between the bottom of the quartz glass crucible and the graphite crucible was H=5.0 mm and W=180 mm.

[0046] As shown in Table 1, in the case of a CZ crucible having a gap between the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible, as in the examples, the quartz glass crucible can stably stand on its own when placed inside the graphite crucible.

[0047] [Table 1]

[0048] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0049] 1...CZ crucible (example of the present invention), 1A...quartz glass crucible, 1B...graphite crucible, 2...straight body portion; 3...first curved portion; 4...second curved portion; 5...bottom portion; 5A...Flat surface, 5B...Concave surface, 6...Central axis, 7...Gap, 10...single crystal pulling apparatus, 11...silicon melt, 12...pulling chamber, 13...CZ crucible (conventional example), 13A...quartz glass crucible, 13B...graphite crucible, 14... heater; 15... crucible holding shaft; 16... seed crystal; 17 ... seed chuck, 18 ... wire, 19 ... insulation material, 20 ... single crystal silicon, 30...gap measuring tool, 31...cross-sectional shape portion. H...height of the gap in the direction of the central axis, W...diameter of the gap in the direction perpendicular to the central axis.

Claims

1. A CZ crucible for growing a single crystal silicon ingot by the CZ method, The CZ crucible includes a cylindrical graphite crucible with a bottom and a cylindrical quartz glass crucible with a bottom disposed inside the graphite crucible, Between the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible at the central axis of the CZ crucible, there is a gap such that the inner surface of the bottom of the graphite crucible and the outer surface of the bottom of the quartz glass crucible are not in contact with each other; The quartz glass crucible has a cylindrical body portion, a first curved portion continuing from a lower end of the body portion and having a first radius of curvature R1, a second curved portion continuing from the first curved portion and having a second radius of curvature R2, and a bottom portion continuing from the second curved portion, the first radius of curvature R1 and the second radius of curvature R2 have a relationship of R1<R2, A CZ crucible, characterized in that the outer surface of the bottom has a flat surface shape perpendicular to the central axis of the quartz glass crucible.

2. 2. The CZ crucible according to claim 1, characterized in that the height of the gap in the central axis direction of the CZ crucible is 0.5 mm to 5.0 mm.

3. 3. The CZ crucible according to claim 1, wherein the size of the gap in the direction perpendicular to the central axis of the CZ crucible is 60 mm or more in diameter.

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