Method for growing large-size semiconductor silicon single crystal rod by utilizing hook-shaped magnetic field

Abstract

The invention provides a method for growing a large-size semiconductor silicon single crystal rod by utilizing a hook-shaped magnetic field, which comprises the steps of charging, melting, temperature stabilization, seeding, shouldering, diameter equalization and ending, specifically, the hook-shaped magnetic field is applied to a melt, crystal rotation is opposite to crucible rotation in the seeding stage, and the diameter equalization is realized in the shouldering stage. And the specified crystal rotation is achieved by gradually reducing the crystal rotation to 0 and reversely increasing the crystal rotation, so that the crystal rotation in the equal-diameter stage and the crucible rotation are ensured to be in the same direction. The silicon single crystal rod obtained through pulling has low oxygen concentration and high oxygen content radial distribution uniformity, the ROG of the silicon single crystal rod can reach 10% or below, meanwhile, the V / G radial distribution uniformity of a solid-liquid interface can be improved, and the yield of the silicon single crystal rod is increased.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor silicon material growth, and more specifically to a method for growing large-size semiconductor single crystal silicon rods by utilizing a hook-shaped magnetic field. Background Art

[0002] Semiconductor-grade single crystal silicon is a key material for the production of semiconductor products such as integrated circuits, discrete devices, and sensors. The Czochralski method (Cz method) is the most common method for growing single crystal silicon. When growing silicon single crystals by the Czochralski method, the temperature of the silicon melt is above 1420°C. The uneven temperature distribution inside the melt causes very strong natural convection, which seriously damages the stability of crystal growth. In order to weaken the convection of the melt, on the one hand, crucible rotation can be applied, and the forced convection generated by the crucible rotation can be used to suppress natural convection; on the other hand, a magnetic field can be applied to the melt, and the Lorentz force generated by the magnetic field can be used to weaken the flow of the melt.

[0003] During the crystal growth process, SiO2 in the quartz crucible reacts with silicon melt at high temperature to generate SiO, thereby increasing the oxygen content in the melt, and part of the oxygen in the melt enters the crystal through segregation. Oxygen, as the impurity with the highest content and the most complex behavior in single crystal silicon, has a great impact on the quality of single crystal silicon, so it is necessary to strictly control the oxygen content and radial uniformity in single crystal silicon. In addition, the manufacture of defect-free near-perfect crystals requires strict control of the ratio of the crystal rod pulling speed V to the temperature gradient G in the growth direction (V / G). V / G needs to be strictly controlled within a certain range, and radial uniformity needs to be guaranteed.

[0004] At present, large-sized semiconductor single crystal silicon rods are mostly grown by the reverse crystal rotation / crucible rotation method, that is, the rotation direction of the crystal rod and the crucible is opposite, but the radial uniformity of the oxygen content of the single crystal silicon rod grown by this method is often poor. In addition, when growing crystals by the reverse crystal rotation / crucible rotation method, there is often a large difference in the temperature gradient G at the center and edge of the solid-liquid interface, which will cause V / G to be unevenly distributed in the radial direction, thereby introducing more defects and reducing the yield of the crystal rod. In order to improve the uniformity of V / G in radial distribution, patent CN101240444A adopts the crystal rotation / crucible rotation method to grow crystals in the same direction, and improves the uniformity of V / G radial distribution by controlling the position of the neutral plane (zero magnetic plane) of the CUSP magnetic field. However, in the actual crystal growth process, especially in the seeding stage, the crystal rotation and crucible rotation in the same direction will make the symmetry of the fine crystals at the necking position worse, and then twist, and there is a risk of fracture.

[0005] In order to improve the uniformity of the radial distribution of oxygen content while reducing the oxygen concentration, patent CN111615569A proposes a method for manufacturing single crystal silicon with low oxygen concentration and high uniformity of oriented distribution of oxygen concentration and resistivity using a hook-shaped magnetic field. The patent sets the crystal rotation in the range of 17 to 19 rpm, which is more effective in controlling the uniformity of oriented distribution of oxygen content when growing small-sized single crystal silicon rods with a diameter of 200 mm. However, when growing large-sized single crystal silicon rods with a diameter of 300 mm or more, such a high crystal rotation can easily cause the crystal rod to twist and deform. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for growing large-sized semiconductor single crystal silicon rods, which can improve the radial distribution uniformity of oxygen content and the radial distribution uniformity of V / G, thereby improving the yield of single crystal silicon rod products.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] A method for growing large-sized semiconductor single crystal silicon rods using a hook-shaped magnetic field comprises the following steps:

[0009] S1. Loading: Load polysilicon material into a quartz crucible, load the quartz crucible into a crystal growth furnace, evacuate the crystal growth furnace, introduce inert gas, and set the furnace pressure;

[0010] S2, melt: turn on the heater switch to heat up and melt the polysilicon material;

[0011] S3, temperature stabilization: after the polysilicon material is completely melted, adjust the crucible position and the gap between the melt surface and the bottom of the heat shield, adjust the magnetic field position, so that the deviation between the zero magnetic surface of the hook-shaped magnetic field and the melt surface position is within the allowable range, turn on the magnetic field power supply, set the maximum magnetic field strength of the hook-shaped magnetic field at the crucible wall to a specified value, and set the crucible speed to a specified value, and start temperature stabilization;

[0012] S4, seeding: Rotate in the opposite direction to the crucible and pull the seed crystal upward to produce fine crystals;

[0013] S5, shoulder release: reduce the seed crystal speed at a fixed rate within a certain period of time, and when the seed crystal speed drops to 0, increase the seed crystal speed in the opposite direction at a fixed rate until the seed crystal speed reaches the specified value;

[0014] S6, equal diameter: after the shoulder rotation, enter the equal diameter, during which the crystal rotation, crucible rotation and magnetic field strength are kept constant, and the crucible position is continuously raised to keep the gap between the melt surface and the bottom of the heat shield constant;

[0015] S7, ending: During the ending, the magnetic field strength is reduced at a fixed rate until the magnetic field strength drops to 0.

[0016] In a specific embodiment, the furnace pressure in step S1 is 10 to 30 torr; preferably, the furnace pressure is 15 to 20 torr.

[0017] In a specific embodiment, in step S3, the gap between the melt surface and the bottom of the heat shield is 20-60 mm; preferably, the gap is 40-50 mm.

[0018] In a specific embodiment, the deviation between the zero magnetic surface of the hook-shaped magnetic field and the melt surface in step S3 is ±100 mm; preferably, the zero magnetic surface of the hook-shaped magnetic field is 0 to 50 mm below the melt surface.

[0019] In a specific embodiment, the maximum magnetic field strength in step S3 is 500-3000 Gs; preferably, the maximum magnetic field strength is 1000-1500 Gs.

[0020] In a specific embodiment, the crucible rotation speed in step S3 is 0.5-6 rpm; preferably, the crucible rotation speed is 2-4 rpm.

[0021] In a specific embodiment, the rotation speed of the seed crystal in step S4 is 5 to 15 rpm; preferably, the rotation speed of the seed crystal is 8 to 12 rpm.

[0022] In a specific embodiment, the length of the fine crystals in step S4 is 200 to 500 mm; preferably, the length of the fine crystals is 250 to 350 mm.

[0023] In a specific embodiment, in step S5, the reduction rate of the seed crystal rotation speed is 1-5 rpm / min.

[0024] In a specific embodiment, in step S5, the reverse increase rate of the seed crystal rotation speed is 1-5 rpm / min.

[0025] In a specific embodiment, in step S5, the seed crystal rotation speed finally achieved is 5 to 15 rpm; preferably, the seed crystal rotation speed is 8 to 12 rpm.

[0026] In a specific embodiment, in step S7, the magnetic field intensity reduction rate is 1 to 50 Gs / min.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In the present invention, in the equal diameter stage, the crystal rotation and the crucible rotation have the same direction, which will greatly improve the convection of the melt below the solid-liquid interface, thereby improving the radial distribution uniformity of the oxygen content near the solid-liquid interface and the radial distribution uniformity of V / G. The change of the melt convection below the solid-liquid interface can also reduce the oxygen concentration at the interface. In addition, in the present invention, the directions of the crystal rotation and the crucible rotation are opposite in the seeding stage, and the crystal rotation is reduced to 0 during the shoulder release period and the crystal rotation is increased in the opposite direction to ensure that the crystal rotation and the crucible rotation in the equal diameter stage are in the same direction, which can increase the symmetry of the fine crystal during seeding. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of a crystal growth furnace based on an embodiment of the present invention.

[0030] Figure 2 , Figure 3 This is a schematic diagram of the convection at the solid-liquid interface and below it for different combinations of crystal rotation and crucible rotation directions.

[0031] Figure 4 This is a distribution diagram of oxygen content at different positions of single crystal silicon rods of equal diameter grown in Example 1 of the present invention.

[0032] Figure 5 This is a distribution diagram of oxygen content at different positions of single crystal silicon rods of equal diameter grown in Example 2 of the present invention.

[0033] Figure 6 This is a distribution diagram of oxygen content at different positions of single crystal silicon rods of equal diameter grown in Example 3 of the present invention.

[0034] Figure 7 This is a distribution diagram of oxygen content at different positions of single crystal silicon rods of equal diameter grown in comparative example 1 of the present invention.

[0035] Figure 8 This is a distribution diagram of oxygen content at different positions of single crystal silicon rods of equal diameter grown in comparative example 2 of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the present application, the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods. However, it should be understood that the following implementation methods are only used to illustrate the present invention rather than to limit the present invention.

[0037] The method of growing large-sized semiconductor single crystal silicon rods using a hook-shaped magnetic field of the present invention can be implemented by using a crystal growth furnace with a hook-shaped magnetic field in the prior art. The key to the present invention lies in the innovation of the crystal growth process. Specifically, see Figure 1, which exemplarily provides a crystal pulling furnace device that can realize the present invention. The crystal pulling furnace device mainly includes a main furnace chamber 1, an auxiliary furnace chamber 2, a quartz crucible 3 for holding polycrystalline silicon material 12, a graphite crucible 4, a heater 5, a heat preservation material 6, a seed crystal rotating and pulling mechanism 7 for rotating and pulling a crystal rod 10, a crucible rotating and lifting mechanism 8, a heat shield 9, and a hook-shaped magnetic field generating device 11.

[0038] In the present invention, in the seeding stage, the seed crystal rotating and pulling mechanism 7 and the crucible rotating and lifting mechanism 8 have opposite rotation directions, which ensures the symmetry of the temperature field around the fine crystal during seeding, thereby ensuring the uniformity of the fine crystal and improving the seeding quality. In the equal diameter stage, different from the commonly used crystal rotation / crucible rotation reverse crystal growth process, the seed crystal rotating and pulling mechanism 7 and the crucible rotating and lifting mechanism 8 have the same rotation direction, that is, the crystal rotation and the crucible rotation are in the same direction. Compared with the crystal rotation / crucible rotation reverse process, when the crystal is grown using the crystal rotation / crucible rotation unidirectional process, the convection conditions of the melt below the solid-liquid interface are completely different. Figure 2 It is a schematic diagram of the melt convection below the solid-liquid interface when the crystal rotation and crucible rotation are in the opposite directions. Figure 3 This is a schematic diagram of the melt convection below the solid-liquid interface when the crystal rotation and the crucible rotation are in the same direction. When the crystal rotation / crucible rotation are in the same direction, the convection direction of the melt below the solid-liquid interface is completely opposite to that when the crystal rotation / crucible rotation are in the opposite direction. Near the solid-liquid interface, due to the influence of the centrifugal force generated by the crystal rotation, the melt flow direction is from the center to the edge. When the crystal rotation / crucible rotation are in the same direction, this convection direction of the melt below the solid-liquid interface is conducive to avoiding the transmission of oxygen from the crucible wall to the solid-liquid interface, which is conducive to reducing the oxygen content introduced into the crystal rod and increasing the uniformity of the radial distribution of the oxygen content; in addition, this convection direction is also conducive to increasing the uniformity of the radial distribution of the temperature near the solid-liquid interface, thereby reducing the radial difference of V / G and improving the crystal rod yield.

[0039] In the present invention, since the crystal rotation and the crucible rotation are opposite in the seeding stage, in order to achieve the same direction of crystal rotation and crucible rotation when the diameter is equal, a transition method is adopted in the shoulder release stage. Specifically, at the beginning of shoulder release, the seed crystal rotation speed is first reduced at a fixed rate until the seed crystal rotation speed drops to 0, and then the seed crystal rotates in the opposite direction and the seed crystal rotation speed is increased at a fixed rate to a specified value. At this time, the seed crystal rotation direction is the same as the crucible rotation direction.

[0040] In a specific embodiment, the method for growing a large-sized semiconductor single crystal silicon rod of the present invention comprises the following steps:

[0041] Polysilicon material is placed in a quartz crucible in a single crystal furnace, and an inert gas, such as argon, is introduced into the furnace. The furnace pressure is set to a specified value, such as 10 to 30 torr, such as 10 torr, 15 torr, 20 torr, 25 torr, 30 torr, etc. Preferably, the furnace pressure is 15 to 20 Torr.

[0042] The temperature is raised to melt the polysilicon material. After the polysilicon material is completely melted, the crucible position is adjusted so that the gap between the melt surface and the bottom of the heat shield is within a certain range. The gap distance is 20 to 60 mm, for example, including but not limited to 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm; preferably, the gap distance is 40 to 50 mm.

[0043] Adjust the magnetic field position so that the deviation between the zero magnetic surface of the hook-shaped magnetic field and the position of the melt surface is within the allowable range. The deviation between the zero magnetic surface of the hook-shaped magnetic field and the position of the melt surface is ±100mm, such as ±90mm, ±80mm, ±70mm, ±60mm, ±50mm, ±40mm, ±30mm, ±20mm, ±10mm, ±5mm, 0mm, where 0mm represents zero deviation. The zero magnetic surface of the hook-shaped magnetic field can be above the melt surface or below the melt surface; preferably, the zero magnetic surface of the hook-shaped magnetic field is 0 to 50mm below the melt surface, such as 0mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, etc.

[0044] Turn on the magnetic field power supply, set the maximum magnetic field strength of the hook-shaped magnetic field at the crucible wall to a specified value, set the crucible speed to a specified value, and start temperature stabilization. The maximum magnetic field strength is 500-3000Gs, for example, including but not limited to 500Gs, 1000Gs, 1500Gs, 2000Gs, 2500Gs, 3000Gs; preferably, the maximum magnetic field strength is 1000-1500Gs. The crucible speed is 0.5-6rpm, for example, including but not limited to 0.5rpm, 1rpm, 1.5rpm, 2rpm, 2.5rpm, 3rpm, 3.5rpm, 4rpm, 4.5rpm, 5rpm, 5.5rpm, 6rpm; preferably, the crucible speed is 2-4rpm.

[0045] The seed crystal is rotated in the opposite direction to the crucible and pulled upward to draw out fine crystals with a diameter within a certain range and a specified length. The seed crystal rotation speed is 5 to 15 rpm, for example, including but not limited to 5 rpm, 6 rpm, 7 rpm, 8 rpm, 9 rpm, 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, 15 rpm; preferably, the seed crystal rotation speed is 8 to 12 rpm. The fine crystal length is 200 to 500 mm, for example, including but not limited to 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm; preferably, the fine crystal length is 250 to 350 mm.

[0046] The seed crystal speed is reduced at a fixed rate within a certain period of time, and when the seed crystal speed drops to 0, the seed crystal speed is increased in the opposite direction at a fixed rate until the seed crystal speed reaches a specified value. The reduction rate and reverse increase rate of the seed crystal speed are 1 to 5 rpm / min, for example, including but not limited to 1rpm / min, 2rpm / min, 3rpm / min, 4rpm / min, 5rpm / min. The final seed crystal speed is 5 to 15 rpm, for example, including but not limited to 5rpm, 6rpm, 7rpm, 8rpm, 9rpm, 10rpm, 11rpm, 12rpm, 13rpm, 14rpm, 15rpm; preferably, the final seed crystal speed is 8 to 12 rpm.

[0047] After shoulder release, the process of equalizing diameter is started after shoulder rotation. During the equalizing diameter process, the crystal rotation, crucible rotation and magnetic field strength are kept constant. During this period, the position of the crucible is continuously raised so that the gap between the melt surface and the bottom of the heat shield is always kept constant.

[0048] During the closing period, the magnetic field strength is reduced at a fixed rate until the magnetic field strength is reduced to 0. The magnetic field strength reduction rate is 1 to 50 Gs / min, for example, including but not limited to 1 Gs / min, 5 Gs / min, 10 Gs / min, 20 Gs / min, 30 Gs / min, 40 Gs / min, and 50 Gs / min.

[0049] Those skilled in the art will appreciate that, in the semiconductor single crystal silicon rod growth process of the present invention, unless otherwise specified, reference may be made to the prior art, such as conventional operations such as loading, melting, equalizing diameters, and finishing. Except for adjusting key process conditions, the present invention may refer to the prior art for other matters.

[0050] The present invention is further explained below by more specific examples, but the present invention is not limited thereto.

[0051] Example 1

[0052] Put 300kg of polysilicon material and dopant into the quartz crucible, then hang the quartz crucible into the single crystal furnace, close the furnace chamber, evacuate and introduce argon, set the furnace pressure to 20torr, and heat up to melt the polysilicon material. After the polysilicon material is completely melted, adjust the position of the crucible so that the gap between the melt surface and the bottom of the heat shield is 50mm. Adjust the magnetic field position so that the zero magnetic surface of the magnetic field is 30mm below the melt surface. Pass current through the upper and lower coils of the magnetic field, and set the maximum magnetic field strength to 1000Gs. Rotate the crucible clockwise at a speed of 3rpm to stabilize the temperature. When the liquid surface temperature reaches the required temperature for seeding and stabilizes, rotate and pull the seed crystal upward for seeding. During seeding, the seed crystal rotates counterclockwise at a speed of 10rpm. When the seeding length reaches 300mm, it is considered that the seeding is completed and the shoulder is released. At the beginning of shoulder release, the seed crystal rotation speed is reduced to 0 at a rate of 2rpm / min, and then the seed crystal rotation speed is increased clockwise at a rate of 2rpm / min until the seed crystal rotation speed rises to 10rpm. After shoulder rotation, enter the equal diameter stage. During the equal diameter stage, the crystal rotation is kept constant at 10rpm (clockwise), the crucible rotation is kept constant at 3rpm (clockwise), and the maximum magnetic field strength is kept constant at 1000Gs. During this period, the crucible position is continuously raised to keep the gap distance between the melt surface and the bottom of the heat shield constant. During the tailing period, the magnetic field strength is reduced at a rate of 10Gs / min until the magnetic field strength drops to 0. After the tailing is completed, the furnace is stopped for cooling to obtain a single crystal silicon rod with a diameter of 308mm.

[0053] The pulled crystal rod was cut into samples of equal diameters at different parts for processing to obtain samples with a diameter of 300 mm. The radial distribution of oxygen content in the samples was then tested according to the SEMI MF1188 standard. The test range of oxygen concentration was from the center of the sample to 10 mm from the edge of the sample. Subsequently, the ROG (radial oxygen concentration gradient) of the sample was calculated. The ROG calculation formula is as follows:

[0054] ROG(%)=(O max -O min ) / O min *100

[0055] Among them, O max is the highest oxygen content within the radial measurement range of the sample, O min The minimum oxygen content in the radial measurement range of the sample. The smaller the ROG value, the more uniform the radial distribution of oxygen content in the sample.

[0056] Figure 4 The radial distribution of oxygen content in samples of equal diameter at different locations is shown in Figure 2. The oxygen concentration at the head, middle, and tail of the ingot is below 11ppma, indicating that the oxygen content is effectively controlled; the ROG at the three locations is 2.8%, 4.2%, and 4.7%, respectively, and the radial oxygen content distribution is relatively uniform.

[0057] Example 2

[0058] Put 300kg of polysilicon material and dopants into the quartz crucible, then hang the quartz crucible into the single crystal furnace, close the furnace chamber, evacuate and introduce argon, set the furnace pressure to 20torr, and heat up to melt the polysilicon material. After the polysilicon material is completely melted, adjust the position of the crucible so that the gap between the melt surface and the bottom of the heat shield is 55mm. Adjust the position of the magnetic field so that the zero magnetic surface of the magnetic field coincides with the free liquid surface of the melt. Pass current through the upper and lower coils of the magnetic field, and set the maximum magnetic field strength to 500Gs. Rotate the crucible clockwise at a speed of 4rpm to stabilize the temperature. When the liquid surface temperature reaches the required temperature for seeding and stabilizes, rotate and pull the seed crystal upward for seeding. During seeding, the seed crystal rotates counterclockwise at a speed of 6rpm. When the seeding length reaches 300mm, it is considered that the seeding is completed and the shoulder is released. At the beginning of shoulder release, the seed crystal rotation speed is reduced to 0 at a rate of 2rpm / min, and then the seed crystal rotation speed is increased clockwise at a rate of 2rpm / min until the seed crystal rotation speed rises to 14rpm. After shoulder rotation, enter the equal diameter stage. During the equal diameter stage, the crystal rotation is kept constant at 14rpm (clockwise), the crucible rotation is kept constant at 4rpm (clockwise), and the maximum magnetic field strength is kept constant at 500Gs. During this period, the crucible position is continuously raised to keep the gap distance between the melt surface and the bottom of the heat shield constant. During the tailing period, the magnetic field strength is reduced at a rate of 10Gs / min until the magnetic field strength drops to 0. After the tailing is completed, the furnace is stopped for cooling to obtain a single crystal silicon rod with a diameter of 308mm.

[0059] Subsequently, under the same conditions as in Example 1, the oxygen concentration and ROG of samples with the same diameter and position were determined.

[0060] Figure 5 The radial distribution diagram of oxygen content of samples at different locations of equal diameter in Example 2. The oxygen concentrations at the head, middle, and tail of the crystal rod are all below 12 ppma, that is, the oxygen content is effectively controlled; the ROGs at the three locations are 3.4%, 3.9%, and 5.1%, respectively, and the radial oxygen content distribution is relatively uniform.

[0061] Example 3

[0062] Put 300kg of polysilicon material and dopant into the quartz crucible, then hang the quartz crucible into the single crystal furnace, close the furnace chamber, evacuate and introduce argon, set the furnace pressure to 20torr, and heat up to melt the polysilicon material. After the polysilicon material is completely melted, adjust the position of the crucible so that the gap between the melt surface and the bottom of the heat shield is 30mm. Adjust the magnetic field position so that the zero magnetic surface of the magnetic field is 60mm below the melt surface. Pass current through the upper and lower coils of the magnetic field, and set the maximum magnetic field strength to 1500Gs. Rotate the crucible clockwise at a speed of 2rpm to stabilize the temperature. When the liquid surface temperature reaches the required temperature for seeding and stabilizes, rotate and pull the seed crystal upward for seeding. During seeding, the seed crystal rotates counterclockwise at a speed of 10rpm. When the seeding length reaches 300mm, it is considered that the seeding is completed and the shoulder is released. At the beginning of shoulder release, the seed crystal rotation speed is reduced to 0 at a rate of 2rpm / min, and then the seed crystal rotation speed is increased clockwise at a rate of 2rpm / min until the seed crystal rotation speed rises to 8rpm. After shoulder rotation, enter the equal diameter stage. During the equal diameter stage, the crystal rotation speed is kept constant at 8rpm (clockwise), the crucible rotation speed is kept constant at 2rpm (clockwise), and the maximum magnetic field strength is kept constant at 1500Gs. During this period, the crucible position is continuously raised to keep the gap distance between the melt surface and the bottom of the heat shield constant. During the tailing period, the magnetic field strength is reduced at a rate of 10Gs / min until the magnetic field strength drops to 0. After the tailing is completed, the furnace is stopped for cooling to obtain a single crystal silicon rod with a diameter of 308mm.

[0063] Subsequently, under the same conditions as in Example 1, the oxygen concentration and ROG of samples with the same diameter and position were determined.

[0064] Figure 6 The radial distribution diagram of oxygen content of samples of different parts with equal diameter in Example 3 is shown. Its oxygen content is even lower, reaching below 10 ppma; the ROG of the three parts are 8.5%, 8.8% and 9.7% respectively, and the radial distribution uniformity of oxygen content is slightly poor, but the ROG can be controlled below 10%.

[0065] Comparative Example 1

[0066] Except that the crystal rotation was not reduced and increased in the opposite direction during the shoulder release stage, under the same conditions as in Example 1, a single crystal silicon rod with a diameter of 308 mm was obtained by pulling. That is, the difference between Comparative Example 1 and Example 1 is that in the equal diameter stage, the seed crystal rotates counterclockwise, which is opposite to the crucible rotation direction. Subsequently, under the same conditions as in Example 1, the oxygen concentration and ROG of the samples at the same position of the equal diameter were obtained.

[0067] Figure 7The radial distribution diagram of oxygen content of samples of equal diameter at different parts of comparative example 1. The oxygen content of the head is above 15 ppma, and the ROG of the head, middle and tail are 29.9%, 11.3% and 25.2% respectively, and the radial distribution uniformity of oxygen content is poor.

[0068] Comparative Example 2

[0069] Except that the final seed crystal speed reached when the seed crystal speed was increased clockwise after the seed crystal speed was reduced to 0 in the shoulder release stage was 3rpm, under the same other conditions as in Example 1, a single crystal silicon rod with a diameter of 308mm was pulled. That is, the main difference between the comparative example and Example 1 is that in the equal diameter stage, the crystal rotation is 3rpm (clockwise). Subsequently, under the same conditions as in Example 1, the oxygen concentration and ROG of the samples at the same position of the equal diameter were obtained.

[0070] Figure 8 The radial distribution diagram of oxygen content of samples at different positions of equal diameter in comparative example 2. The oxygen content at the head, middle and tail of the equal diameter is higher than that in the embodiment; the ROG at the three positions is 67.5%, 27.0% and 34.9% respectively, and the radial distribution uniformity of oxygen content is very poor.

[0071] From the above results, it can be seen that the method for growing large-sized single crystal silicon rods provided by the present invention has a lower oxygen content and a higher radial distribution uniformity of oxygen content, and its ROG can reach less than 10%.

[0072] It should be noted that the above embodiments are only for illustration and not for limiting the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any replacement, improvement, etc. made within the principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for growing large-sized semiconductor single crystal silicon rods using a hook-shaped magnetic field, characterized in that: The following steps are involved: S1. Loading: Load polysilicon material into a quartz crucible, load the quartz crucible into a crystal growth furnace, evacuate the crystal growth furnace, introduce inert gas, and set the furnace pressure; S2, melt: turn on the heater switch to heat up and melt the polysilicon material; S3, temperature stabilization: after the polysilicon material is completely melted, adjust the crucible position and the gap between the melt surface and the bottom of the heat shield, adjust the magnetic field position, so that the deviation between the zero magnetic surface of the hook-shaped magnetic field and the melt surface position is within the allowable range, turn on the magnetic field power supply, set the maximum magnetic field strength of the hook-shaped magnetic field at the crucible wall to a specified value, and set the crucible speed to a specified value, and start temperature stabilization; S4, seeding: Rotate in the opposite direction to the crucible and pull the seed crystal upward to produce fine crystals; S5, shoulder release: reduce the seed crystal speed at a fixed rate within a certain period of time, and then increase the seed crystal speed in the opposite direction at a fixed rate after the seed crystal speed drops to 0, until the seed crystal speed reaches the specified value; S6, equal diameter: after the shoulder rotation, enter the equal diameter, during which the crystal rotation, crucible rotation and magnetic field strength are kept constant, and the crucible position is continuously raised to keep the gap between the melt surface and the bottom of the heat shield constant; S7, ending: During the ending, the magnetic field strength is reduced at a fixed rate until the magnetic field strength drops to 0.

2. The method according to claim 1, characterized in that: The furnace pressure in step S1 is 10 to 30 torr; preferably, the furnace pressure is 15 to 20 torr.

3. The method according to claim 1, characterized in that: In the step S3, the gap between the melt surface and the bottom of the heat shield is 20-60 mm; preferably, the gap is 40-50 mm.

4. The method according to claim 1 or 3, characterized in that: In the step S3, the deviation between the zero magnetic surface of the hook-shaped magnetic field and the melt surface is ±100 mm; preferably, the zero magnetic surface of the hook-shaped magnetic field is 0 to 50 mm below the melt surface.

5. The method according to claim 4, characterized in that The maximum magnetic field strength in step S3 is 500-3000 Gs; preferably, the maximum magnetic field strength is 1000-1500 Gs.

6. The method according to claim 1, characterized in that The crucible rotation speed in step S3 is 0.5-6 rpm; preferably, the crucible rotation speed is 2-4 rpm.

7. The method according to claim 1, characterized in that The rotation speed of the seed crystal in step S4 is 5 to 15 rpm; preferably, the rotation speed of the seed crystal is 8 to 12 rpm.

8. The method according to claim 1 or 7, characterized in that: The length of the fine crystal in step S4 is 200-500 mm; preferably, the length of the fine crystal is 250-350 mm.

9. The method according to claim 1, characterized in that: In step S5, the decreasing rate of the rotation speed of the seed crystal is 1 to 5 rpm / min, and the reverse increasing rate of the rotation speed of the seed crystal is 1 to 5 rpm / min; Preferably, the seed crystal rotation speed finally achieved is 5 to 15 rpm, preferably 8 to 12 rpm.

10. The method according to claim 1, characterized in that In step S7, the magnetic field intensity reduction rate is 1 to 50 Gs / min.

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