Manufacturing method of large diameter quartz crucible for Czochralski single crystal

Abstract

The present invention relates to a method for manufacturing a quartz crucible for a large outer diameter Czochralski single crystal, specifically, a vacuum arc method in which a crucible blank is melted by emitting a high-temperature arc using an electrode bundle consisting of 2N+1 (N is an integer of 2 or more) electrodes, and finally quenched to form a quartz crucible initial product, the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes, the 2N auxiliary electrodes are distributed at equal intervals on a circumference with the central main electrode as the center, and the central main electrode is aligned with the axial center line of the crucible mold. The 2N auxiliary electrodes are connected to two phases of industrial three-phase power, and the two phases of power are alternately arranged on the auxiliary electrodes, and the central main electrode is connected to the remaining phase of the industrial three-phase power, and in the process of melting the crucible blank, discharge occurs between two adjacent auxiliary electrodes of the 2N auxiliary electrodes to generate a high-temperature arc, and discharge also occurs between the 2N auxiliary electrodes and the central main electrode to generate a high-temperature arc. The manufacturing method of the present invention is particularly suitable for producing large crucibles and improving the quality of the bottom of the crucible.

Description

[Technical field]

[0001] The present invention relates to the technical field of manufacturing a quartz crucible for a Czochralski single crystal, and in particular to a method for manufacturing a quartz crucible with a large outer diameter for a Czochralski single crystal. [Background technology]

[0002] Silicon single crystals are one of the most important raw materials for manufacturing silicon-based semiconductor materials and solar cells. Silicon single crystals are mainly produced by the CZ Czochralski method. In the CZ Czochralski method, polycrystalline silicon raw material is placed in a quartz crucible, heated and melted to form silicon melt, and a seed crystal is lowered by a pulling rod to contact the silicon melt, and then the seed crystal is gently pulled up to form a silicon single crystal rod. Quartz crucibles generally have a two-layer structure, with the inner wall being a transparent layer that does not contain bubbles and the outer wall being an opaque layer that contains many bubbles. Since the inner wall is in contact with the silicon melt, if bubbles are present on the inner wall at high temperatures, they will burst due to erosion of the silicon melt, and the fragments will dissolve in the silicon melt, affecting the yield and quality of the silicon single crystal. The outer wall needs to dissipate heat from the heater evenly, so a certain number and size of bubbles are required to heat the silicon melt evenly. The quality of the quartz crucible, which is the only material that comes into contact with the silicon liquid, greatly affects the quality of the silicon single crystal. For example, the bubble content of the inner wall of the quartz crucible, the purity of the quartz crucible, and the high-temperature deformation resistance of the quartz crucible.

[0003] The vacuum arc method is commonly used to make quartz crucibles. When using this method, high-purity quartz sand raw material is put into a graphite mold or metal die, and the quartz sand raw material is uniformly molded on the inner surface of the mold using a molding device. After that, the quartz sand is melted at a high temperature of over 3000°C using a high-temperature arc (usually three graphite electrodes of a three-phase arc furnace, or sometimes copper electrodes are used), and finally quenched to form a quartz (glass) crucible. In the process of making quartz crucibles using the vacuum arc method, the temperature of the arc has a great impact on the quality of the quartz crucible, and the main influences include the bubble content, purity (impurity content) of the inner wall of the crucible, high-temperature deformation resistance, and degree of vitrification, so how to optimize the control of the arc is very important.

[0004] With the development of the semiconductor and solar energy industries, the size of silicon single crystals has rapidly shifted from the traditional 4 inch, 6 inch, and 8 inch to the current 8 inch and 12 inch, and the size of the quartz crucibles used has also shifted from the traditional 16 inch, 18 inch, and 24 inch to the current 24 inch, 28 inch, 32 inch, and 36 inch (all referring to the outer diameter of the crucible). In the industry, crucibles larger than 28 inches are usually considered large crucibles, and the depth of large crucibles is generally between 500 and 750 mm. Compared with small quartz crucibles, large quartz crucibles have a large outer diameter and a thick wall. In the normal melting process, the three electrodes are energized to discharge the arch, which can meet the temperature required for producing a 22-inch to 24-inch crucible. However, when producing a large quartz crucible, the temperature generated by the three electrodes cannot fully melt the raw material inside the large mold, and the heat loss is large, which leads to a long melting time and large energy consumption, and the effect is not clear. As a result, it is difficult to form the outer dimensions of the quartz crucible, and the degree of vitrification of the inner surface is also reduced accordingly, which leads to a deterioration in the quality of the crucible. In the process of pulling single crystals, the quartz crucible is prone to many problems such as collapse and crystallization.

[0005] In order to meet the needs of large crucible production, researchers in the industry have proposed ways to increase the number of electrodes, for example, CN104926086A proposes to adopt six graphite electrodes, which are evenly spaced around the axis of the crucible mold, and the six electrodes are connected to form a regular hexagon. US6853673B2 and US7905112B2 also propose two-phase four electrodes or three-phase six or nine graphite electrodes, which are evenly spaced around the axis of the crucible mold to form a regular hexagon or regular nonagon. Increasing the number of electrodes can certainly increase the production temperature, but with the above electrode arrangements, although the arc range of the arc is expanded, the arc is discharged between adjacent electrodes, which reduces the arc center temperature and causes poor quality at the center bottom of the quartz crucible (such as pores and high impurity content). This is mainly because the depth of the large crucible is large, and when the number of electrodes is increased to six or nine, the crucible peripheral wall can be taken into consideration, but it is difficult to take the bottom of the crucible into consideration; the temperature at the bottom of the crucible is not sufficient; the degree of polishing is insufficient; some of the vaporized impurity dust falls to the bottom where the temperature is slightly lower and cannot be removed. In response to this, Japan JP2015147688A proposes six graphite electrodes, which are distributed on a concentric circumference with the axis line of the crucible mold as the center, forming two equilateral triangles inside and outside, and two three-phase powers inside and outside, thereby increasing the heating temperature at the bottom of the crucible blank. However, this method has the following problems remaining. (1) There is a gap in the center of the graphite electrode, and the central temperature is still not sufficient. (2) The device is extremely complicated, the manufacturing design is troublesome, and it is difficult to operate and difficult to control in a high-temperature arc environment. (3) When used, the system faces many problems, so it is not actually used. (4) There is also a possibility of discharge between the inner and outer circles, and the two three-phase power sources will have a significant impact on the production system and the power grid. Summary of the Invention [Problem to be solved by the invention]

[0006] In response to the above-mentioned defects and shortcomings of the prior art, the present invention provides a method for manufacturing a quartz crucible for a large outer diameter Czochralski single crystal by more rationally designing the number of electrodes and the distribution positions of the electrodes, thereby increasing the center temperature when the electrodes emit an arc, increasing the melting temperature of the bottom of the quartz crucible blank, improving the polishing degree of the bottom of the crucible, and improving the quality of the bottom of the crucible, thereby meeting the needs of manufacturing large quartz crucibles. [Means for solving the problem]

[0007] In order to achieve the above objectives, the main technical solutions used in the present invention are as follows:

[0008] The present invention is a vacuum arc method in which high-purity quartz sand raw material is charged into a crucible mold, the quartz sand raw material is uniformly molded on the inner surface of the mold by a molding device to form a crucible blank, a high-temperature arc is emitted using an electrode bundle consisting of 2N+1 (N is an integer of 2 or more) electrodes to melt the crucible blank, and finally, the crucible blank is quenched to form a quartz crucible initial product, the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes, the 2N auxiliary electrodes are distributed at equal intervals on a circumference centered on the central main electrode, and the central main electrode is aligned with the axial center line of the crucible mold, The 2N auxiliary electrodes are connected to two phases of industrial three-phase power, the two phases of power being arranged alternately on the auxiliary electrodes, and the central main electrode is connected to the remaining phase of the industrial three-phase power, and during the process of melting a crucible blank, discharge occurs between two adjacent ones of the 2N auxiliary electrodes to generate a high-temperature arc, and discharge also occurs between the 2N auxiliary electrodes and the central main electrode to generate a high-temperature arc.

[0009] According to a preferred embodiment of the present invention, N=2 to 4, ie the number of electrodes in the electrode bundle is 5, 7 or 9.

[0010] According to a preferred embodiment of the present invention, the cross-sectional area of ​​the central main electrode is larger than the cross-sectional area of ​​a single one of the auxiliary electrodes.

[0011] According to a preferred embodiment of the present invention, the cross-sectional area of ​​the central main electrode is S1, the cross-sectional area of ​​the single auxiliary electrode is S2, and S1 and S2 satisfy 1.5S2≦S1≦3.8S2. The central main electrode is slightly thicker than the single auxiliary electrode around it, but it is preferable to meet the above requirement, otherwise there may be a problem of imbalance between the three-phase power, which may shock the power supply system. Preferably, S1=2S2.

[0012] According to a preferred embodiment of the present invention, the diameter of the auxiliary electrode is 55-65 mm, and the diameter of the central main electrode is 68-125 mm.

[0013] According to a preferred embodiment of the present invention, when calculated from the center points of the lower end faces of the 2N auxiliary electrodes, the radius of the circumference on which the 2N auxiliary electrodes are located is 1 / 4 to 3 / 4 of the outer radius of the melting object crucible.

[0014] According to a preferred embodiment of the present invention, the lower end surfaces of the central main electrode and the 2N auxiliary electrodes are in the same plane, and the central main electrode and the 2N auxiliary electrodes are movable downward as the electrodes wear out.

[0015] According to a preferred embodiment of the present invention, the central main electrode remains radially fixed and the 2N auxiliary electrodes are adjustable to allow opening and closing movements relative to the central main electrode.

[0016] According to a preferred embodiment of the present invention, when calculated at the center point of the lower end surface of the 2N auxiliary electrodes, the range of opening and closing movement of the 2N auxiliary electrodes is such that the radius of the circumference on which the 2N auxiliary electrodes are located is 1 / 4 to 2 / 4 of the outer radius of the crucible to be melted.

[0017] According to a preferred embodiment of the present invention, the central main electrode and the 2N auxiliary electrodes are also connected to a copper rod, the copper rod to which the central main electrode is connected is fixed at the central position of a fixed bracket, the tops of the copper rods to which the 2N auxiliary electrodes are connected are fixed by clamping mechanisms, the number of clamping mechanisms is 2N corresponding to the number of auxiliary electrodes, each of the clamping mechanisms is rotatably connected to the fixed bracket at a pivot point at its central portion, one end of the clamping mechanism is connected to a nut via a link, the nut is fitted into a screw, a bottom end of the screw and the fixed bracket are combined, the screw is a rotating member, the nut moves up and down the screw by rotating the screw, the nut pulls up the 2N clamping mechanisms to open and close, and the 2N auxiliary electrodes are driven to open and close relative to the central main electrode.

[0018] According to a preferred embodiment of the present invention, the vacuum degree is controlled at -0.093Mpa~-0.1Mpa during the entire melting process, and when connected to a vacuum system, impurities such as gas caused by melting can be discharged in a timely manner to ensure the purity of the crucible product, and the power of the electrode is 1000~2000KW.

[0019] According to a preferred embodiment of the present invention, when melting a quartz crucible with an outer diameter of 28 inches, the electrode power is 1000-1100 KW, when melting a quartz crucible with an outer diameter of 32 inches, the electrode power is 1300-1400 KW, and when melting a quartz crucible with an outer diameter of 36 inches, the electrode power is 1500-1600 KW.

[0020] According to a preferred embodiment of the present invention, the manufactured quartz crucible initial product is cut, inspected, washed, dried, packaged and stored in order. Effect of the Invention

[0021] As can be easily seen from the prior art, industrial three-phase power is used to manufacture quartz crucibles, and currently, in the prior art, the number of electrodes is always a multiple of three, and it is difficult for manufacturers and designers in the industry to adopt 2N+1 electrodes and come up with an electrode arrangement scheme in which one central main electrode is placed at the center and connected to one-phase power, and the remaining 2N auxiliary electrodes are placed at equal intervals on the circumference and alternately connected to two-phase power. According to the above arrangement, high-temperature arcs are generated between two adjacent electrodes among the 2N auxiliary electrodes on the circumference, and high-temperature arcs are generated by discharge between all 2N auxiliary electrodes on the circumference and the main electrode at the center, so the temperature at the center of the arc is also very high. The auxiliary electrodes on the circumference are mainly used to melt the peripheral wall of the crucible blank and high-temperature polish it (to increase the degree of vitrification and gasify and volatilize impurities to improve purity), while the arc center is mainly used to high-temperature polish the bottom of the large crucible, thereby producing quartz crucible products with fewer pores, higher degree of vitrification, and lower impurity content, and improving the yield of crucible production. In addition, the central main electrode is slightly thicker than the auxiliary electrodes around it, and the burnout and oxidation speeds of the central main electrode and the auxiliary electrodes are almost the same, which further enhances the heating effect of the arc.

[0022] As described above, the manufacturing method of the present invention can relatively widely open 2N auxiliary electrodes around the central main electrode by arranging one central main electrode and connecting it to one-phase power, thus making it possible to increase the distance between adjacent auxiliary electrodes on the circumference and further widen the heating range, which not only takes into account the problem that the inner diameter of a large crucible is large and the peripheral wall is difficult to heat, but also simultaneously solves the problem that the temperature of the bottom of the crucible is insufficient and the polishing degree is insufficient. The manufacturing method of the present invention is particularly suitable for manufacturing a large crucible and improving the quality of the bottom of the crucible. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a schematic diagram showing the structure of a quartz crucible. [Diagram 2]FIG. 1 is a schematic diagram of the production of a quartz crucible by melting with electrodes. [Diagram 3] FIG. 1 is a schematic diagram of the production of a quartz crucible by melting with three three-phase graphite electrodes in the prior art. [Figure 4] FIG. 1 is a schematic diagram of producing a quartz crucible by melting with six three-phase graphite electrodes in the prior art. [Diagram 5] FIG. 2 is a schematic diagram of an arrangement of five three-phase electrodes according to the first embodiment of the present invention. [Figure 6] FIG. 11 is a schematic diagram of an arrangement of seven three-phase electrodes according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a schematic diagram of an arrangement of nine three-phase electrodes according to a third embodiment of the present invention. [Figure 8] In the present invention, this structure enables the opening and closing movement of the peripheral auxiliary electrodes relative to the central main electrode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In order to better explain and facilitate the understanding of the present invention, the present invention will be described in detail below by means of specific embodiments with reference to the drawings.

[0025] 1 shows a schematic diagram of a quartz crucible, which includes an inner transparent layer 1 and an outer opaque layer 2, in which the transparent layer 1 is in direct contact with the silicon melt. The transparent layer 1 includes a straight wall surface H, a curved transition surface L, and a bottom W.

[0026] 2-3 show schematic diagrams of the production of a quartz crucible by high-temperature arc melting using three three-phase graphite electrodes in the prior art. Here, the three three-phase graphite electrodes 3 are distributed at equal intervals on a circumference with the axial line of the crucible mold as the center, and can form an equilateral triangle. The three three-phase graphite electrodes 3 are connected to the U phase, W phase, and V phase, respectively. The arc is generated by discharging between the U phase and the W phase, the W phase and the V phase, and the V phase and the U phase, and the heat source area is small, which is not suitable for the production of a large quartz crucible.

[0027] FIG. 4 shows a schematic diagram of the production of a quartz crucible by high-temperature arc melting with six three-phase graphite electrodes in the prior art. Here, the six three-phase graphite electrodes 3 are distributed at equal intervals on a circumference with the axial line of the crucible mold as the center, and can form a regular hexagon. The six graphite electrodes 3 are connected to the U phase, W phase, V phase, U phase, W phase, and V phase, respectively, in sequence. The arc is generated by discharging between the U phase and the W phase, the W phase and the V phase, the V phase and the U phase, the U phase and the W phase, the W phase and the V phase, and the V phase and the U phase. Although the heat source area caused by this is larger than that of the three three-phase electrodes in FIG. 3, the temperature at the center position of the arc is low, and the melting degree at the bottom of the crucible is insufficient, which is particularly unsuitable for the production of large quartz crucibles.

[0028] Hereinafter, specific examples 1 to 3 of the present invention correspond to FIGS. EXAMPLES

[0029] FIG. 5 shows a preferred embodiment 1 of the present invention, which is for manufacturing a quartz crucible with an outer diameter of 28 inches. The manufacturing method includes: putting high-purity quartz sand raw material into a crucible mold 10, uniformly molding the quartz sand raw material on the inner surface of the crucible mold 10 by a molding device to form a crucible blank 20, releasing a high-temperature arc using an electrode bundle 30 consisting of five graphite electrodes to melt the crucible blank, and finally quenching to form a quartz crucible initial product. During the entire melting process, the vacuum degree is controlled to -0.093Mpa to -0.1Mpa (connected to a vacuum system to discharge impurities such as gas caused by melting), and the power of the electrodes is 1000KW. After the manufacturing is completed, the initial quartz crucible is cut, inspected, washed, dried, and packaged / stored in order.

[0030] The electrode bundle 30 includes one thick central main electrode 300 and four thin auxiliary electrodes 301, 302, 303, and 304. The diameter of the central main electrode 300 is 100 mm, and the diameters of the auxiliary electrodes 301, 302, 303, and 304 are about 60±0.5 mm, respectively. The central main electrode 300 is aligned with the axis of the crucible mold, and the four auxiliary electrodes 301, 302, 303, and 304 are equally spaced on a circumference centered on the central electrode, and can be connected as a square. When calculated at the center point of each auxiliary electrode, the radius of the circumference on which the four auxiliary electrodes 301, 302, 303, and 304 are located is 1 / 4 of the outer radius of the crucible to be melted. The central main electrode 300 is connected to the U-phase of an industrial three-phase AC power supply, while the four auxiliary electrodes 301, 302, 303, and 304 are successively connected to the W-phase, V-phase, W-phase, and V-phase of the industrial three-phase AC power supply. The lower end surfaces of the central main electrode 300 and the four auxiliary electrodes 301, 302, 303, and 304 are on the same plane, and the central main electrode 300 and the four auxiliary electrodes 301, 302, 303, and 304 can move downward as the electrodes wear out. In the process of melting the crucible blank, discharge occurs between two adjacent auxiliary electrodes among the four auxiliary electrodes 301, 302, 303, and 304 to generate a high-temperature arc, and discharge also occurs between each of the auxiliary electrodes 301, 302, 303, and 304 and the central main electrode 300 to generate a high-temperature arc. EXAMPLES

[0031] FIG. 6 shows a preferred embodiment 2 of the present invention, which is for manufacturing a quartz crucible with an outer diameter of 32 inches. The manufacturing method includes: putting high-purity quartz sand raw material (high-purity quartz sand ≧99.99%) into a crucible mold 10, uniformly molding the quartz sand raw material on the inner surface of the crucible mold 10 by a molding device to form a crucible blank 20, using an electrode bundle 40 consisting of seven graphite electrodes to emit a high-temperature arc to melt the crucible blank, and finally quenching to form a quartz crucible initial product. The electrodes are located at the lower end of the electrode bundle at a position 550 mm away from the bottom of the crucible, and the vacuum degree is controlled to -0.093Mpa to -0.1Mpa during the entire melting process, and the power of the electrodes is 1400KW. After manufacturing, the initial quartz crucible is cut, inspected, washed, dried, packaged, and stored in order.

[0032] The electrode bundle 40 includes one thick central main electrode 400 and six thin auxiliary electrodes 401, 402, 403, 404, 405, and 406. The diameter of the central main electrode 400 is 110 mm, and the diameters of the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 are each about 60±0.5 mm. The central main electrode 400 is aligned with the axis of the crucible mold, and the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 are equally spaced on a circumference centered on the central electrode, and can be connected as a regular hexagon. When calculated at the center point of each auxiliary electrode, the radius of the circumference on which the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 are located is 3 / 4 of the outer radius of the crucible to be melted. The central main electrode 400 is connected to the U phase of an industrial three-phase AC power, while the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 are successively connected to the W phase, V phase, W phase, V phase, W phase, and V phase of the industrial three-phase AC power. The lower end surfaces of the central main electrode 400 and the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 are on the same plane, and the central main electrode 400 and the six auxiliary electrodes 401, 402, 403, 404, 405, and 406 can move downward as the electrodes wear out. During the process of melting the crucible blank, discharge occurs between two adjacent ones of the six auxiliary electrodes 401, 402, 403, 404, 405, and 406, generating a high-temperature arc, and discharge also occurs between each of these auxiliary electrodes 401, 402, 403, 404, 405, and 406 and the central main electrode 400, generating a high-temperature arc. EXAMPLES

[0033] FIG. 7 shows a preferred embodiment 3 of the present invention, which is for manufacturing a quartz crucible with an outer diameter of 36 inches. The manufacturing method includes: putting high-purity quartz sand raw material (high-purity quartz sand ≧99.99%) into a crucible mold 10, uniformly molding the quartz sand raw material on the inner surface of the crucible mold 10 by a molding device to form a crucible blank 20, discharging a high-temperature arc using an electrode bundle 50 consisting of nine graphite electrodes to melt the crucible blank, and finally quenching to form a quartz crucible initial product. The electrodes are located at a position 550 mm away from the bottom of the crucible at the lower end of the electrode bundle, and the degree of vacuum is controlled to -0.093Mpa to -0.1Mpa throughout the entire melting process, and the power of the electrodes is 1600KW. After manufacturing, the initial quartz crucible is cut, inspected, washed, dried, packaged, and stored in order.

[0034] The electrode bundle 50 includes one thick central main electrode 500 and eight thin auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508. The diameter of the central main electrode 500 is 110 mm, and the diameters of the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 are each about 58 mm. The central main electrode 500 is aligned with the axis of the crucible mold, and the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 are equally spaced on a circumference centered on the central electrode, and can be connected to form a regular octagon. When calculated from the center point of each auxiliary electrode, the radius of the circumference on which the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 are located is 2 / 4 of the outer radius of the crucible to be melted. The central main electrode 500 is connected to the U phase of an industrial three-phase AC power, while the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 are sequentially connected to the W phase, V phase, W phase, V phase, W phase, V phase, W phase, and V phase of the industrial three-phase AC power. The lower end surfaces of the central main electrode 500 and the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 are on the same plane, and the central main electrode 500 and the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 can move downward as the electrodes wear out. In the process of melting the crucible blank, discharge occurs between two adjacent auxiliary electrodes among the eight auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 to generate a high-temperature arc, and discharge also occurs between each of the auxiliary electrodes 501, 502, 503, 504, 505, 506, 507, and 508 and the central main electrode 500 to generate a high-temperature arc.

[0035] In the above Examples 1 to 3, the central main electrode 300, 400 or 500 remains fixed in the radial direction, and the remaining auxiliary electrodes also remain fixed in the radial direction. Preferably, when calculated at the center point of the auxiliary electrodes, the radius of the circumference on which all the auxiliary electrodes are located is 1 / 4 to 3 / 4 of the outer radius of the melting target crucible.

[0036] In another embodiment, an electrode bundle may be provided in which the radius of the circumference where the auxiliary electrodes are located can be adjusted. For example, the central main electrode 300, 400, or 500 remains fixed in the radial direction, and the remaining auxiliary electrodes can be adjusted to be open and closed relative to the central main electrode 300, 400, or 500, that is, the radius of the circumference where the remaining auxiliary electrodes (calculated at the center point of the lower end surface of each auxiliary electrode) are located can be changed, and the changeable width is preferably 1 / 4 to 2 / 4 of the outer radius of the melting target crucible (if the adjustment range is too large, there may be a clear difference in height between the lower end surfaces of all the electrodes, which is disadvantageous to the generation of an arc). In this case, the lower end surfaces of the central main electrode and the remaining auxiliary electrodes are maintained on the same plane as much as possible, and the central main electrode and the auxiliary electrodes can move downward as the electrodes wear out.

[0037] The above embodiment can be realized by the structure shown in FIG. 8. The central main electrode 300 and the four auxiliary electrodes 301, 302, 303, and 304 are also connected to copper rods, respectively. The copper rod connected to the central main electrode 300 is fixed at the center position of the fixed bracket 60, and the tops of the copper rods connected to the remaining four auxiliary electrodes 301, 302, 303, and 304 are fixed by clamping mechanisms 601, and the number of clamping mechanisms 601 is also four. The clamping structure 601 is a seesaw structure, and its central part is rotatably connected to the fixed bracket. One end of the clamping mechanism 601 is connected to a nut 603 via a link 602, and the nut 603 is fitted into a screw 604. The bottom end of the screw 604 and the fixed bracket are combined, but can rotate with respect to the fixed bracket 60. By rotating the screw 604, since the screw 604 cannot move in the vertical direction, the nut 603 moves up and down along the screw 604, thereby driving the link 602, which drives one end of the clamping structure 601 to change the angle of the clamping structure 601, thereby driving the four auxiliary electrodes 301, 302, 303, and 304 to open and close relative to the central main electrode 300, thereby adjusting the area of ​​the heat source surface to accommodate the melting of quartz crucibles of various sizes.

[0038] Comparing the crucible manufactured in Example 1 with a 28-inch crucible produced using six electrodes as shown in Figure 3 (Prior Art 1) and Figure 4 (Prior Art 2), when the graphite electrode power is 1000KW, the vacuum degree is -0.093Mpa to -0.1Mpa, and the radius of the circumference where the (auxiliary) electrode is located is 1 / 4 of the outer radius of the crucible to be melted, the crucible is melted at the same electrode position (the lower end of the electrode is 380mm away from the bottom of the crucible). The raw material for the crucible is quartz raw material from the same lot, and the purity of the high-purity quartz sand is 99.99% or more.

[0039] The results of detecting the average impurity content of the peripheral wall and bottom of the crucibles produced in Example 1 and Prior Art 1-2 using atomic absorption spectrometry are shown in Table 1 below (two test values ​​were taken for each position and the average was taken, and the test depth was 20 μm from the inner surface) (unit: wt. ppb).

[0040] [Table 1]

[0041] As can be seen from the above table, the purity of the inner layer of the crucible manufactured by the conventional technology 2 is better than that of the conventional technology 1, but the purity of the inner layer of the crucible manufactured by the embodiment 1 of the present invention is better than that of the conventional technology 2. Although the contents of some elements are equal to or slightly higher than those of the conventional technology, overall, the average total content of various impurity elements in the inner layer peripheral wall and bottom of the quartz crucible manufactured by the embodiment 1 of the present invention is significantly lower than those of the conventional technology 1 and the conventional technology 2. This suggests that the present invention is indeed applicable to the manufacture of high-quality quartz crucibles.

[0042] Similarly, the results of detecting the average impurity content of the peripheral walls and bottoms of the 32-inch and 36-inch quartz crucibles produced in Examples 2 and 3 are shown in Table 2 below (two test values ​​were taken for each position and the average was taken, and the test depth was 20 μm from the inner surface) (unit: wt. ppb).

[0043] [Table 2]

[0044] From the above comparison, it was found that the quality of the manufactured 32-inch and 36-inch quartz crucibles was equivalent to that of the 28-inch quartz crucible of Example 1. This suggests that the manufacturing method of the present invention is very suitable for producing large crucibles of 32 inches or more, and that the purity of the crucible inner layer can be ensured.

[0045] As described above, the quartz crucibles manufactured in Examples 1 to 3 of the present invention have a lower impurity content on the inner layer surface and are cleaner, which can reduce the introduction of impurities in the silicon single crystal production process by crystal pulling and ensure the production quality of silicon single crystal. In addition, the quartz glass crucibles manufactured in Examples 1 to 3 were inspected and found to have no cracks or dents on the surface, and no bubbles or convex areas visible to the naked eye. The technical solution of the present invention has already been test-produced within the company, and the results show that the system runs stably and the product quality is reliable.

[0046] It should be noted that the above embodiments are only used to describe the technical solutions of the present invention, and are not intended to limit the present invention. The present invention has been described in detail with reference to the above embodiments. However, those skilled in the art should understand that the technical solutions described in the above embodiments can be modified or part or all of the technical features can be equally replaced, and such modifications or replacements do not cause the essence of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a large diameter quartz crucible for a Czochralski single crystal, comprising the steps of: A vacuum arc method in which high-purity quartz sand raw material is charged into a crucible mold, the quartz sand raw material is uniformly molded on the inner surface of the mold by a molding device to form a crucible blank, a high-temperature arc is emitted using an electrode bundle consisting of 2N+1 (N is an integer of 2 or more) electrodes to melt the crucible blank, and finally, the crucible blank is quenched to form a quartz crucible initial product, wherein the 2N+1 electrodes include one central main electrode and 2N auxiliary electrodes, the 2N auxiliary electrodes are distributed at equal intervals on a circumference centered on the central main electrode, and the central main electrode is aligned with the axial center line of the crucible mold, a central main electrode connected to the remaining phase of the industrial three-phase power; and, during a process of melting a crucible blank, discharge occurs between two adjacent ones of the 2N auxiliary electrodes to generate a high-temperature arc, and discharge also occurs between the 2N auxiliary electrodes and the central main electrode to generate a high-temperature arc.

2. 2. The method according to claim 1, wherein N=2 to 4, i.e., the number of electrodes in the electrode bundle is 5, 7 or 9.

3. The method of claim 1 , wherein the cross-sectional area of ​​the central main electrode is greater than the cross-sectional area of ​​a single one of the auxiliary electrodes.

4. 4. The method according to claim 1, 2 or 3, wherein a cross-sectional area of ​​the central main electrode is S1, a cross-sectional area of ​​the single auxiliary electrode is S2, and S1 and S2 satisfy 1.5S2≦S1≦3.8S2.

5. The method according to claim 4, characterized in that the diameter of the auxiliary electrode is 55 to 65 mm, and the diameter of the central main electrode is 68 mm to 125 mm.

6. 2. The method according to claim 1, wherein lower end surfaces of the central main electrode and the 2N auxiliary electrodes are flush with each other, and the central main electrode and the 2N auxiliary electrodes are movable downward as the electrodes wear.

7. The manufacturing method according to claim 1, characterized in that, when calculated at the center points of the lower end faces of the 2N auxiliary electrodes, the radius of a circumference on which the 2N auxiliary electrodes are located is 1 / 4 to 3 / 4 of the outer radius of the melting object crucible.

8. 2. The method of claim 1, wherein the central main electrode remains fixed radially, and the 2N auxiliary electrodes are adjustable to allow opening and closing movements relative to the central main electrode.

9. The manufacturing method described in claim 8, characterized in that, when calculated at the center points of the lower end faces of the 2N auxiliary electrodes, the range of opening and closing movements of the 2N auxiliary electrodes is such that the radius of a circumference on which the 2N auxiliary electrodes are located is 1 / 4 to 2 / 4 of the outer radius of the crucible to be melted.

10. 9. The manufacturing method according to claim 8, wherein the central main electrode and the 2N auxiliary electrodes are also connected to a copper rod, the copper rod to which the central main electrode is connected is fixed at a central position of a fixed bracket, and tops of the copper rods to which the 2N auxiliary electrodes are connected are fixed by clamping mechanisms, the number of clamping mechanisms being 2N corresponding to the number of auxiliary electrodes, the clamping mechanisms being rotatably connected to the fixed bracket at pivot points at their central positions, one end of the clamping mechanism being connected to a nut via a link, the nut being fitted into a screw, a bottom end of the screw being combined with the fixed bracket, the screw being a rotating member, the nut being moved up and down along the screw by rotating the screw, the nut being pulled up and down by the 2N clamping mechanisms to perform opening and closing movements, and the 2N auxiliary electrodes being driven to perform opening and closing movements relative to the central main electrode.

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