Magnetic ring water cooling screen and crystal pulling device

Abstract

The utility model discloses a magnetic ring water cooling screen and a crystal pulling device. The magnetic ring water cooling screen comprises a body, a water inlet pipeline, a water outlet pipeline, a water flow channel and a permanent magnet ring, wherein the water inlet pipeline is arranged at the top of one side of the body, and the water outlet pipeline is arranged at the top of the other side of the body; the water flow channel is arranged in the side wall of the body; the water inlet pipeline, the water outlet pipeline and the water flow channel are communicated; the permanent magnet ring is arranged to be of an annular structure defined by a plurality of magnets, and the permanent magnet ring is located in the water flow channel. A magnetic field generated by the magnetic ring water-cooling screen corresponds to the interior of a melt, so that heat convection of the melt can be effectively inhibited, and the quality of single crystals is improved.

Description

Technical Field

[0001] The utility model relates to a magnetic ring water cooling screen and a crystal pulling device. Background Art

[0002] In the Czochralski method of growing crystals, melt convection affects the oxygen content in the crystal and its distribution uniformity; therefore, suppressing melt convection is one of the important ways to improve the quality of single crystals. With the increasing demand for large-diameter and high-quality single crystal silicon in the semiconductor material field and the solar energy field, the crucible size and thermal field size have also increased accordingly. The amount of melt in the Czochralski single crystal silicon growth system has increased, and the thermal convection in the crucible has become more intense. In order to ensure the quality of the crystal, the thermal convection in the melt needs to be suppressed.

[0003] At present, a magnetic field generating device is set in the magnetron crystal pulling device. The magnetic field generated by the magnetic field generating device passes through the silicon liquid in the crucible, so that the silicon liquid and the magnetic field interact to generate Lorentz force, thereby inhibiting the thermal convection of the silicon liquid and the scouring of the crucible wall by the silicon liquid, thereby reducing the impact of uneven crystal pulling and reducing impurities in the silicon liquid. However, different magnetic field devices are different, the distribution of the magnetic field is also different, and thus the effect of crystal pulling is also different. Utility Model Content

[0004] In view of this, one object of the utility model is to provide a magnetic ring water cooling screen, the magnetic field generated by which corresponds to the inside of the melt can effectively suppress the heat convection of the melt and improve the quality of the single crystal. Another object is to provide a crystal pulling device.

[0005] The utility model provides a magnetic ring water cooling screen, comprising a body, a water inlet pipe, a water outlet pipe, a water flow channel and a permanent magnetic ring; wherein:

[0006] The water inlet pipe is arranged at the top of one side of the main body, and the water outlet pipe is arranged at the top of the other side of the main body; the water flow channel is arranged in the side wall of the main body; the water inlet pipe, the water outlet pipe and the water flow channel are connected; the permanent magnetic ring is arranged as a ring structure surrounded by multiple magnets, and the permanent magnetic ring is located in the water flow channel.

[0007] In the utility model, the magnetic ring water cooling screen mainly includes a main body, a water inlet pipe, a water outlet pipe, a water flow channel and a permanent magnetic ring. Among them, the permanent magnetic ring is arranged as a ring structure surrounded by a plurality of magnets, and the permanent magnetic ring is located in the water flow channel. The structure of the permanent magnetic ring has a relatively important influence on the effect of crystal pulling. The magnets in the prior art are mostly block-shaped, and different structures will form different magnetic field distributions, and finally the effect of crystal pulling is different. The permanent magnetic ring of the utility model is arranged as a ring structure, and only under a specific magnetic field strength, combined with the corresponding process method, can a qualified crystal be pulled.

[0008] The utility model arranges the permanent magnetic ring at the bottom of the water flow channel with a specific structure, which can effectively suppress the heat convection of the melt in the crucible and has basically no effect on the shape of the solid-liquid interface of the melt, which is conducive to the stable growth of single crystals and the acquisition of high-quality single crystals.

[0009] According to the magnetic ring water cooling screen of the utility model, preferably, the body is set as a ring structure, and its bottom is set as a flat bottom structure. In this way, the water flow channel of the water cooling screen can be used to keep the magnet at a certain temperature.

[0010] According to the magnetic ring water cooling screen of the utility model, preferably, the water inlet pipe includes a first water inlet vertical part, a first water inlet horizontal part and a second water inlet vertical part which are connected to each other; the second water inlet vertical part is vertically arranged, and one end thereof is connected to the top of one side of the water flow channel; the two ends of the first water inlet horizontal part are respectively vertically connected to the other end of the second water inlet vertical part and one end of the first water inlet vertical part; the top opening of the first water inlet vertical part is a water inlet.

[0011] According to the magnetic ring water cooling screen of the utility model, preferably, the water outlet pipe includes a first water outlet vertical portion, a first water outlet horizontal portion and a second water outlet vertical portion which are connected to each other; the second water outlet vertical portion is vertically arranged, and one end thereof is connected to the top of the other side of the water flow channel; the two ends of the first water outlet horizontal portion are respectively vertically connected to the other end of the second water outlet vertical portion and one end of the first water outlet vertical portion; the top opening of the first water outlet vertical portion is a water outlet; the first water inlet vertical portion and the first water outlet vertical portion are both arranged away from the central axis of the main body.

[0012] According to the magnetic ring water cooling screen of the utility model, preferably, the permanent magnetic ring is configured as a vertical bar-shaped ring structure surrounded by a plurality of magnets.

[0013] In the present invention, the permanent magnetic ring is configured as a vertical stripe ring structure surrounded by multiple magnets, preferably a vertical stripe ring structure surrounded by four magnets. The magnetic ring with such a structure can form a sufficient magnetic field strength and use a high gradient magnetic field to pull out qualified crystals.

[0014] According to the magnetic ring water cooling screen of the utility model, preferably, a plurality of the permanent magnetic rings are arranged along the circumference of the water flow channel and two adjacent permanent magnetic rings are abutted against each other.

[0015] According to the magnetic ring water cooling screen of the utility model, preferably, it also includes a circular ring support; the circular ring support is located in the water flow channel and is arranged at the lower end of the permanent magnetic ring.

[0016] According to the magnetic ring water cooling screen of the utility model, preferably, the material of the circular ring support is a heat-insulating material, so as to support the magnet and block the heat, and prevent the magnetic field from failing.

[0017] On the other hand, the utility model also provides a crystal pulling device, which includes the magnetic ring water cooling shield, the inner guide tube, the outer guide tube, the crucible and the inner guide support ring as described above; wherein,

[0018] Most of the body of the magnetic ring water cooling screen is arranged in the inner guide tube, and the positions of the water inlet pipe and the water outlet pipe close to the water flow channel are connected to the outer guide tube through fixing parts;

[0019] The inner guide tube is arranged on the inner side of the outer guide tube;

[0020] The crucible is used to contain silicon liquid and is arranged below the magnetic ring water cooling shield, the inner guide tube and the outer guide tube;

[0021] The inner guide support ring is arranged at the bottom of the body of the magnetic ring water cooling screen.

[0022] According to the crystal pulling device of the utility model, preferably, the lower end of the inner guide tube and the lower end of the outer guide tube are both configured as flat bottom structures; and the distance from the bottom of the outer guide tube to the silicon liquid is 30-40 mm.

[0023] In the utility model, the lower ends of the inner guide tube and the outer guide tube are both arranged as a flat bottom structure, which matches the structure of the magnetic ring water cooling screen. It can not only effectively suppress the thermal convection of the melt, but also lengthen the argon flow channel, increase the argon flow rate, reduce the oxygen content, and further improve the quality of the crystal rod.

[0024] The method of pulling a single crystal by using the crystal pulling device as described above comprises the steps of melting, temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter, and finishing in sequence; wherein,

[0025] In the steps of shoulder release, shoulder rotation and equal diameter, the furnace pressure is 9-13 Torr, the rotation speed of the seed crystal is 4-7 rpm, the rotation speed of the crucible is 2-4 rpm, and the flow rate of the inert gas is 80-90 slpm.

[0026] In the shoulder release step, the furnace pressure may be 9-13 Torr, preferably 10-12 Torr. The rotation speed of the seed crystal may be 4-7 rpm, preferably 5-6 rpm. The rotation speed of the crucible may be 2-4 rpm, preferably 2.5-3.5 rpm. The inert gas flow rate may be 80-90 slpm, preferably 80-85 slpm.

[0027] In the shoulder transfer step, the furnace pressure may be 9-13 Torr, preferably 10-12 Torr. The rotation speed of the seed crystal may be 4-7 rpm, preferably 5-6 rpm. The rotation speed of the crucible may be 2-4 rpm, preferably 2.5-3.5 rpm. The inert gas flow rate may be 80-90 slpm, preferably 80-85 slpm.

[0028] In the equal diameter step, the furnace pressure can be 9-13 Torr, preferably 10-12 Torr. The rotation speed of the seed crystal can be 4-7 rpm, preferably 5-6 rpm. The inert gas flow rate can be 80-90 slpm, preferably 80-85 slpm. The rotation speed of the crucible will change, and its starting speed can be 2-4 rpm, preferably 2.5-3.5 rpm; its intermediate speed can be 3-4 rpm, preferably 3.5-4 rpm; its final speed can be 2-4 rpm, preferably 2.5-3.5 rpm. It should be noted that the starting speed refers to the speed when the crucible just enters the equal diameter, which is the same as the speed when the shoulder is placed and the shoulder is turned; the intermediate speed refers to the speed after entering the equal diameter, at which time the speed of the crucible will increase rapidly; the final speed refers to the speed when the equal diameter process reaches a certain amount of residual material, at which time the speed of the crucible will be reduced until it ends and no longer changes.

[0029] The magnetic field strength of the permanent magnetic ring is 531.77-770.08 A / m, and the distance between the permanent magnetic ring and the central axis of the main body of the magnetic ring water cooling screen is 100-150 mm; the diameter of the single crystal rod obtained by straight-pull single crystal is 250-300 mm.

[0030] The diameter of the single crystal rod obtained by pulling a single crystal can be 250-300 mm, preferably 250-280 mm, and more preferably 250-260 mm. It should be noted that different sizes of crystal rods will correspond to different sizes of water-cooling screens, that is, the distance from the inner mouth of the water-cooling screen to the single crystal rod changes with the size of the pulled crystal rod, and can be adjusted according to actual needs. The magnetic field strength range can be 531.77-770.08 A / m, which can effectively suppress the thermal convection of the melt, and is conducive to the uniform distribution of impurities in the single crystal product, with little effect on the shape of the solid-liquid interface, which can be conducive to the stable growth of single crystals.

[0031] Compared with the prior art, the utility model has the following beneficial effects:

[0032] (1) The utility model arranges a permanent magnetic ring in a water flow channel with a specific structure of a magnetic ring water cooling screen, and arranges a main body with a flat bottom structure, and arranges a circular ring support under the permanent magnetic ring. The magnetic field generated in the corresponding melt can effectively suppress the thermal convection of the melt, and has basically no effect on the shape of the solid-liquid interface of the melt, which is conducive to the stable growth of single crystals and the acquisition of high-quality single crystals.

[0033] (2) The magnetic ring assembly of the utility model generates a Lorentz force in the opposite direction of the melt movement to play a stirring role, so that the impurities continuously segregated from the crystal-melt interface are dispersed more quickly and evenly by the entire silicon melt, and are not easily enriched below the crystal-melt interface, thereby improving the axial and radial uniformity of the impurity distribution of the growing crystal.

[0034] (3) The lower end of the outer guide tube of the utility model is a flat bottom structure, which matches the structure of the main body of the magnetic ring water cooling screen. This can lengthen the inert gas flow channel, increase the inert gas flow rate, take away more oxygen, and reduce the oxygen content in the obtained single crystal rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the magnetic ring water cooling screen of the utility model.

[0036] Figure 2 It is a structural schematic diagram of the crystal pulling device of the utility model.

[0037] Figure 3 It is a magnetic field vector diagram of the utility model.

[0038] Figure 4 This is a comparison chart of the average oxygen content in the head between Example 1 and Comparative Example 1.

[0039] Description of reference numerals:

[0040] 100-magnetic ring water cooling screen;

[0041] 1-main body, 2-water inlet pipe, 21-first water inlet vertical part, 22-first water inlet horizontal part, 23-second water inlet vertical part, 3-water outlet pipe, 31-first water outlet vertical part, 32-first water outlet horizontal part, 33-second water outlet vertical part, 4-water flow channel, 5-permanent magnetic ring, 6-circular ring support;

[0042] 200-inner guide tube, 300-outer guide tube, 400-crucible, 500-inner guide support ring, 600-silicon liquid. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific implementation methods, but the protection scope of the present invention is not limited thereto.

[0044] Example 1

[0045] Figure 1 It is a structural schematic diagram of the magnetic ring water cooling screen of the utility model.

[0046] like Figure 1 As shown, the magnetic ring water cooling shield 100 of the present invention includes a main body 1, a water inlet pipe 2, a water outlet pipe 3, a water flow channel 4, a permanent magnetic ring 5 and a circular ring support 6.

[0047] The body 1 is configured as an annular structure, and its bottom is configured as a flat bottom structure. The water flow channel 4 is configured in the side wall of the body 1, and its longitudinal section is close to two symmetrically arranged right triangles.

[0048] The water inlet pipe 2 is arranged on one side of the top of the body 1, and the water outlet pipe 3 is arranged on the other side of the top of the body 1. The water inlet pipe 2, the water outlet pipe 3 and the water flow channel 4 are connected. Specifically, the water inlet pipe 2 includes a first water inlet vertical portion 21, a first water inlet horizontal portion 22 and a second water inlet vertical portion 23 which are connected. The second water inlet vertical portion 23 is arranged vertically, and one end thereof is connected to the top of one side of the water flow channel 4. The two ends of the first water inlet horizontal portion 22 are vertically connected to the other end of the second water inlet vertical portion 23 and one end of the first water inlet vertical portion 21, respectively. The top opening of the first water inlet vertical portion 21 is a water inlet.

[0049] The water outlet pipe 3 includes a first water outlet vertical portion 31, a first water outlet horizontal portion 32 and a second water outlet vertical portion 33 connected to each other. The second water outlet vertical portion 33 is vertically arranged, and one end thereof is connected to the top of the other side of the water flow channel 4. The two ends of the first water outlet horizontal portion 32 are respectively vertically connected to the other end of the second water outlet vertical portion 33 and one end of the first water outlet vertical portion 31. The top opening of the first water outlet vertical portion 31 is a water outlet. The first water inlet vertical portion 21 and the first water outlet vertical portion 31 are both arranged away from the central axis of the body 1.

[0050] In this way, the cooling water introduced through the water inlet pipe 2 flows into the water flow channel 4, then passes through the water flow channel 4, and then enters the water outlet pipe 3, and the cooling water is discharged through the water outlet pipe 3.

[0051] The permanent magnetic ring 5 is located in the water flow channel 4. Specifically, the permanent magnetic ring 5 is set as a vertical strip ring structure surrounded by four magnets, and multiple permanent magnetic rings 5 ​​are arranged along the circumference of the water flow channel 4 and two adjacent permanent magnetic rings 5 ​​are abutted. The structure of the permanent magnetic ring 5 has a great influence on the magnetic field distribution. Different magnetic field distributions correspond to different crystal pulling effects. The corresponding magnetic field strength is 531.77 to 770.08 A / m.

[0052] The circular ring support 6 is installed at the lower end of the permanent magnetic ring 5 and is made of heat-insulating material to support the magnet and block heat to prevent the magnetic field from failing.

[0053] In this way, a specific magnetic field distribution is formed, ensuring sufficient magnetic field strength, which can effectively suppress melt thermal convection and facilitate the uniform distribution of impurities in the single crystal product. It is also beneficial to the stable growth of single crystals and improves the quality of single crystals.

[0054] Example 2

[0055] Figure 2 It is a structural schematic diagram of the crystal pulling device of the utility model.

[0056] like Figure 2As shown, the crystal pulling device of the present invention comprises the magnetic ring water cooling shield 100, the inner guide tube 200, the outer guide tube 300, the crucible 400 and the inner guide support ring 500 described in Example 1.

[0057] Most of the body 1 of the magnetic ring water cooling screen 100 is arranged in the inner guide tube 200, and its water inlet pipe 2 and water outlet pipe 3 are connected to the outer guide tube 300 through fixing parts near the water flow channel 4.

[0058] The inner guide tube 200 is arranged on the inner side of the outer guide tube 300 and is placed on the upper edge of the outer guide tube 300. The lower ends of the inner guide tube 200 and the outer guide tube 300 match the structure of the body 1 of the magnetic ring water cooling screen 100, that is, both are set to a flat bottom structure, which can lengthen the argon flow channel, increase the argon flow rate, and reduce the oxygen content.

[0059] The crucible 400 is used to contain the silicon liquid 600 and is disposed below the magnetic ring water cooling shield 100 , the inner guide tube 200 and the outer guide tube 300 ; the distance from the bottom of the outer guide tube 300 to the silicon liquid 600 is 30 mm.

[0060] The inner guide support ring 500 is arranged at the bottom of the body 1 of the magnetic ring water cooling shield 100 .

[0061] The following describes a method for pulling single crystals using the above crystal pulling device:

[0062] It mainly includes the steps of melting, temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter, and finishing. Specifically,

[0063] In the shoulder release step, the furnace pressure was 11 Torr, the rotation speed of the seed crystal was 6 rpm, the rotation speed of the crucible was 3 rpm, and the inert gas flow rate was 80 slpm.

[0064] In the shoulder rotation step, the furnace pressure was 11 Torr, the rotation speed of the seed crystal was 6 rpm, the rotation speed of the crucible was 3 rpm, and the inert gas flow rate was 80 slpm.

[0065] In the equal diameter step, the furnace pressure is 11 Torr, the rotation speed of the seed crystal is 6 rpm, and the rotation speed of the crucible is 3-4-3 rpm, that is, after entering the equal diameter, the crucible rotation speed instantly increases from 3 rpm to 4 rpm. In the later stage of the equal diameter, when the remaining material is 50-70 kg, the crucible rotation speed decreases from 4 rpm to 3 rpm, and does not change until the end; the inert gas flow rate is 80 slpm, and the liquid port distance (the distance from the bottom of the outer guide tube 300 to the silicon liquid 600) is 30 mm. The specific parameters are shown in Table 1.

[0066] The diameter of the single crystal rod for crystal pulling is in the range of 250 to 300 mm, the magnetic field strength range is 531.77 to 770.08 A / m, and the distance between the permanent magnetic ring 5 and the axis is 100 to 150 mm. The magnetic field vector diagram is shown in Figure 3 As shown, the arrows indicate the magnetic field direction distribution of the magnetic ring and the performance of the magnetic field strength characteristics.

[0067] Table 1

[0068]

[0069] Comparative Example 1

[0070] The existing method is adopted, that is, in the equal diameter step, the rotation speed of the seed crystal is 9 revolutions, the rotation speed of the crucible is 5-7 revolutions, and the rest is the same as in Example 1.

[0071] The comparison of the average oxygen content of the crystal rod head of Example 1 and Comparative Example 1 is shown in the figure Figure 4 As shown in FIG. 1 , R1 to R6 represent the first to sixth crystal rods.

[0072] Depend on Figure 4 It can be seen that the utility model improves the structure of the magnetic ring water cooling screen and the crystal pulling device, and cooperates with a specific process (at low seed crystal speed and low crucible speed) to obtain a single crystal rod with a head oxygen content of no more than 10ppma. Compared with the prior art, the oxygen content has been significantly reduced.

[0073] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement, and substitution that can be thought of by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A magnetic ring water cooling screen, characterized in that: It includes a body, a water inlet pipe, a water outlet pipe, a water flow channel and a permanent magnetic ring; wherein, The water inlet pipe is arranged at the top of one side of the main body, and the water outlet pipe is arranged at the top of the other side of the main body; the water flow channel is arranged in the side wall of the main body; the water inlet pipe, the water outlet pipe and the water flow channel are connected; the permanent magnetic ring is arranged as a ring structure surrounded by multiple magnets, and the permanent magnetic ring is located in the water flow channel.

2. The magnetic ring water cooling screen according to claim 1 is characterized in that: The body is configured as an annular structure, and the bottom thereof is configured as a flat bottom structure.

3. The magnetic ring water cooling screen according to claim 1 is characterized in that: The water inlet pipe includes a first water inlet vertical portion, a first water inlet horizontal portion and a second water inlet vertical portion which are connected to each other; the second water inlet vertical portion is vertically arranged, and one end thereof is connected to the top of one side of the water flow channel; the two ends of the first water inlet horizontal portion are respectively vertically connected to the other end of the second water inlet vertical portion and one end of the first water inlet vertical portion; the top opening of the first water inlet vertical portion is a water inlet.

4. The magnetic ring water cooling screen according to claim 3 is characterized in that: The water outlet pipe includes a first water outlet vertical portion, a first water outlet horizontal portion and a second water outlet vertical portion which are connected to each other; the second water outlet vertical portion is vertically arranged, and one end thereof is connected to the top of the other side of the water flow channel; the two ends of the first water outlet horizontal portion are respectively vertically connected to the other end of the second water outlet vertical portion and one end of the first water outlet vertical portion; the top opening of the first water outlet vertical portion is a water outlet; the first water inlet vertical portion and the first water outlet vertical portion are both arranged away from the central axis of the body.

5. The magnetic ring water cooling screen according to claim 2 is characterized in that: The permanent magnetic ring is configured as a vertical strip-shaped ring structure surrounded by a plurality of magnets.

6. The magnetic ring water cooling screen according to claim 5, characterized in that: A plurality of permanent magnetic rings are arranged along the circumference of the water flow channel and two adjacent permanent magnetic rings are in contact with each other.

7. The magnetic ring water cooling screen according to claim 1 is characterized in that: It also includes a circular ring support; the circular ring support is located in the water flow channel and is arranged at the lower end of the permanent magnetic ring.

8. The magnetic ring water cooling screen according to claim 7 is characterized in that: The material of the circular ring support is a heat-insulating material.

9. A crystal pulling device, characterized in that: It comprises the magnetic ring water-cooled shield, inner guide tube, outer guide tube, crucible and inner guide support ring as described in any one of claims 1 to 8; wherein, Most of the body of the magnetic ring water cooling screen is arranged in the inner guide tube, and the positions of the water inlet pipe and the water outlet pipe close to the water flow channel are connected to the outer guide tube through fixing parts; The inner guide tube is arranged on the inner side of the outer guide tube; The crucible is used to contain silicon liquid and is arranged below the magnetic ring water cooling shield, the inner guide tube and the outer guide tube; The inner guide support ring is arranged at the bottom of the body of the magnetic ring water cooling screen.

10. The crystal pulling device according to claim 9, characterized in that: The lower ends of the inner guide tube and the outer guide tube are both configured as flat bottom structures; the distance from the bottom of the outer guide tube to the silicon liquid is 30-40 mm.

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