Monocrystalline silicon ingot and its seed structure and seed method

Abstract

A single crystal silicon rod and a seed crystal structure and a seed crystal method thereof, the seed crystal structure comprising a seed crystal and a neck section connected with the seed crystal along a single crystal growth direction; the neck section comprises expansion sections and contraction sections arranged in sequence and alternately along the single crystal growth direction; wherein the diameter of the expansion section gradually increases along the single crystal growth direction, and the diameter of the contraction section gradually decreases along the single crystal growth direction; for any adjacent one of the expansion section and the contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction. The application discharges screw dislocations through an asymmetric fluctuation shape, overcomes the defect that screw dislocations are difficult to discharge in a medium-diameter neck section or a symmetric sinusoidal wave neck section in the related art, avoids that the residual screw dislocations penetrate the whole crystal rod in the form of point dislocations in the subsequent grown single crystal silicon rod, and significantly improves the crystal growth quality.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically to a single-crystal silicon rod and its seeding structure and seeding method. Background Technology

[0002] In the seeding stage of Czochralski-grown single-crystal silicon rods, those with a specific crystal orientation (generally...) will be grown. <100> or <111> When a seed crystal is immersed in a high-temperature silicon melt, it will inevitably generate dislocations due to thermal stress, such as edge dislocations, screw dislocations, and mixed dislocations. If these dislocation defects are not controlled, they will continue into the subsequently grown single-crystal silicon rod.

[0003] To address this issue, a dash neck is typically grown to allow dislocations to slide to the crystal surface and be expelled, resulting in a dislocation-free single crystal. Generally, the longer and smaller the diameter of the dash neck, the better the dislocation expulsion effect.

[0004] However, a characteristic of screw dislocations is that their dislocation lines are parallel to the slip vector. During crystal growth, the dislocation line extension paths of some screw dislocations will be parallel to the single crystal growth direction. Because the thermal stress field distribution inside the constant-diameter or symmetrical sinusoidal neck segments formed in related technologies is relatively symmetrical, it is difficult to generate sufficient radial asymmetric driving force to deflect these vertically downward-growing screw dislocations, making it difficult for them to slip out. The residual screw dislocations will form linear defects running through the entire single-crystal silicon rod in the subsequent growth, severely affecting the crystal formation quality of the single-crystal silicon rod. Summary of the Invention

[0005] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. This summary section is not intended to limit the key and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0006] To address the existing problems, this application provides a seed structure for a single-crystal silicon rod. The seed structure is used for the growth of integrated circuit-grade semiconductor single-crystal silicon rods. The resistivity of the single-crystal silicon rod is 1~20 mΩ·cm. The seed structure includes a seed crystal and a thin neck section connected to the seed crystal along the single-crystal growth direction. The narrow neck section includes expanding and contracting portions arranged sequentially and alternately along the single crystal growth direction; wherein the diameter of the expanding portion gradually increases along the single crystal growth direction, and the diameter of the contracting portion gradually decreases along the single crystal growth direction; The angle between the line connecting the outer contours of the smallest and largest diameters of the expanded portion and the central axis of the narrow neck section is the expansion angle, and the angle between the line connecting the outer contours of the largest and smallest diameters of the contracted portion and the central axis is the contraction angle. For any adjacent expansion portion and contraction portion, the expansion angle is less than the contraction angle, wherein the expansion angle is less than or equal to 35.26° and the contraction angle is greater than or equal to 54.74°; For any adjacent expansion section and contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction, so that the entire narrow neck section presents an asymmetric wave shape, so that screw dislocations are driven to the crystal surface and discharged.

[0007] In some embodiments of this application, the expansion angle is smaller than the angle between the sliding surface of the narrow neck segment and the central axis of the narrow neck segment, and the contraction angle is larger than the angle between the normal of the sliding surface of the narrow neck segment and the central axis of the narrow neck segment.

[0008] In some embodiments of this application, the maximum diameter of the narrow neck segment is 1.5 to 2.5 times the minimum diameter of the narrow neck segment; The minimum diameter of the narrow neck section is the diameter at the junction of the end of the constricted portion and the beginning of the adjacent expanded portion, and the maximum diameter of the narrow neck section is the diameter at the junction of the end of the expanded portion and the beginning of the adjacent constricted portion.

[0009] In some embodiments of this application, the minimum diameter of the thin neck segment is 3mm to 6mm.

[0010] In some embodiments of this application, the length of the thin neck segment is 200mm~300mm.

[0011] In some embodiments of this application, for any adjacent expansion portion and contraction portion, the ratio of the length of the expansion portion along the single crystal growth direction to the length of the contraction portion along the single crystal growth direction is greater than or equal to 2.

[0012] According to another aspect of this application, a method for seeding a single-crystal silicon rod is provided. This method is used for growing an integrated circuit-grade semiconductor single-crystal silicon rod, wherein the resistivity of the single-crystal silicon rod is 1~20 mΩ·cm. The method includes: Provides silicon melt and seed crystals; The seed crystal is immersed in the silicon melt, and the seed crystal is pulled up to form a thin neck segment connected to the seed crystal; In the process of forming the thin neck segment, the seed crystal is pulled alternately using a first pulling speed and a second pulling speed. A step-switching mode is used to switch between the first pulling speed and the second pulling speed. The second pulling speed is greater than the first pulling speed. Based on the first pulling speed, an expansion section with a diameter that gradually increases along the single crystal growth direction is formed, and based on the second pulling speed, a contraction section with a diameter that gradually decreases along the single crystal growth direction is formed. This results in the formed thin neck segment including the expansion section and the contraction section arranged sequentially and alternately along the single crystal growth direction. For any adjacent expansion section and contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction. This makes the thin neck segment as a whole present an asymmetric wave shape, so that screw dislocations are driven to the crystal surface and discharged. Wherein, the angle between the line connecting the outer contours of the smallest and largest diameters of the expanded portion and the central axis of the narrow neck segment is the expansion angle, and the angle between the line connecting the outer contours of the largest and smallest diameters of the contracted portion and the central axis is the contraction angle; For any adjacent expansion portion and contraction portion, the expansion angle is less than the contraction angle, wherein the expansion angle is less than or equal to 35.26° and the contraction angle is greater than or equal to 54.74°.

[0013] In some embodiments of this application, the first lifting speed is 0.5 mm / min to 3 mm / min, and the second lifting speed is 5 mm / min to 8 mm / min.

[0014] According to another aspect of this application, a single-crystal silicon rod is provided, comprising the seed structure of the single-crystal silicon rod described in any one of the above-mentioned methods.

[0015] According to another aspect of this application, a single-crystal silicon rod is provided, which is prepared by the above-described crystal-leading method, and the resistivity of the single-crystal silicon rod is 1~20 mΩ·cm.

[0016] The single-crystal silicon rod, its seeding structure, and its seeding method of this application can forcibly drive screw dislocations to the crystal surface and remove them. This overcomes the defect in related technologies where it is difficult to remove screw dislocations parallel to the single crystal growth direction in medium-diameter narrow neck sections or symmetrical sinusoidal narrow neck sections. It also avoids residual screw dislocations forming linear defects that run through the entire crystal rod in the subsequently grown single-crystal silicon rod, thus significantly improving the crystallization quality of the single-crystal silicon rod.

[0017] Meanwhile, the asymmetric wave shape significantly improves dislocation removal efficiency per unit length, enabling excellent dislocation removal with a shorter neck length. This shortens the overall length of the neck, reduces crystal pulling time, and increases equipment productivity. Furthermore, it avoids the risk of the neck breaking due to excessive stress caused by excessively increasing the neck length or excessively reducing the neck diameter in pursuit of complete dislocation removal, thus reducing the crystal pulling failure rate and minimizing production time wasted due to re-crystallization. Attached Figure Description

[0018] The following drawings, which are incorporated herein by reference and are used to understand this application, illustrate embodiments of the invention and their descriptions to explain the principles of the invention.

[0019] In the attached image: Figure 1 A schematic diagram of the crystal-leading structure of a single-crystal silicon rod according to a specific embodiment of this application is shown.

[0020] Figure 2 It shows Figure 1 An enlarged schematic diagram of region A in the middle.

[0021] Figure 3 A schematic diagram of the thin neck segment according to a specific embodiment of this application is shown.

[0022] Figure 4 A schematic diagram of the thin neck segment according to a specific embodiment of this application is shown. Detailed Implementation

[0023] The following description provides numerous specific details to offer a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with this application.

[0024] It should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this application to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0025] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0026] Spatial relation terms such as “below,” “under,” “below,” “below,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, then the element or feature described as “below” or “below” other elements or features will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. The device may be otherwise oriented (rotated 90 degrees or otherwise) and the spatial descriptive terms used herein will be interpreted accordingly.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0028] The characteristic of screw dislocations is that their dislocation lines are parallel to the slip vector. During crystal growth, the dislocation line extension paths of some screw dislocations will be parallel to the single crystal growth direction. Because the thermal stress field distribution inside the constant-diameter or symmetrical sinusoidal neck segments formed in related technologies is relatively symmetrical, it is difficult to generate sufficient radial asymmetric driving force to deflect these vertically downward-growing screw dislocations, making it difficult for them to slip out. The residual screw dislocations will form linear defects running through the entire single-crystal silicon rod in subsequent growth, severely affecting the crystal formation quality of the single-crystal silicon rod.

[0029] Furthermore, excessively increasing the neck length to ensure complete dislocation removal not only prolongs the crystal pulling time and reduces equipment capacity, but also poses a risk of breakage due to excessive stress when bearing the total weight of the crystal rod because the neck diameter is too small. If crystal pulling fails, it must be restarted, resulting in wasted production time.

[0030] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solutions proposed in this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0031] Example 1 This application provides a method for seeding a single-crystal silicon rod. The method is used for growing an integrated circuit-grade semiconductor single-crystal silicon rod with a resistivity of 1~20 mΩ·cm. The method includes: providing a silicon melt and a seed crystal 110; immersing the seed crystal 110 in the silicon melt; and pulling the seed crystal 110 to form a thin neck segment 130 connected to the seed crystal 110. Figure 1 As shown.

[0032] During the formation of the narrow neck section 130, the seed crystal 110 is pulled at alternating first and second pulling speeds, with the second pulling speed being greater than the first pulling speed. Specifically, when the diameter is expanded using the first pulling speed, the solid-liquid interface at the junction of the seed crystal 110 and the silicon melt has sufficient time to expand radially, causing the diameter of the solidified interface to gradually increase along the single crystal growth direction, thus forming the expansion section 131. When the diameter is reduced using the second pulling speed, which is greater than the first pulling speed, the upward movement rate of the solid-liquid interface is accelerated due to the increased second pulling speed. The radial thermal field does not have enough time to expand outward before being quickly pulled away from the high-temperature region, and the diameter of the solidified interface gradually decreases along the single crystal growth direction, thus forming the contraction section 132. By alternating the first and second pulling speeds when pulling the seed crystal 110, expansion sections 131 and contraction sections 132 arranged sequentially and alternately along the single crystal growth direction can be formed on the narrow neck section 130.

[0033] Since the expanding portion 131 and the contracting portion 132 are arranged alternately and continuously along the single crystal growth direction, the end diameter of the expanding portion 131 is the same as the beginning diameter of the adjacent contracting portion 132, and the end diameter of the contracting portion 132 is the same as the beginning diameter of the adjacent expanding portion 131. Therefore, the expanding portion 131 and the contracting portion 132 have the same diameter variation range. Since the first pulling speed is less than the second pulling speed, under the condition of the same diameter variation range, the time required to form the expanding portion 131 at the lower first pulling speed is significantly longer than the time required to form the contracting portion 132 at the higher second pulling speed. The length of each part of the necking segment 130 along the single crystal growth direction is equal to the product of the pulling speed and the duration of the corresponding stage. Since the increase in the duration of the expansion stage is greater than the decrease in the pulling speed, the product of the first pulling speed and the expansion duration is greater than the product of the second pulling speed and the contraction duration. Therefore, the length of the expanding portion 131 along the single crystal growth direction is greater than the length of the contracting portion 132 along the single crystal growth direction. In other words, the diameter change of the narrow neck 130 exhibits an asymmetrical undulating shape of "slow expansion and rapid contraction", that is, the axial extension of the expansion portion 131 is longer and the diameter change is relatively gentle, while the axial extension of the contraction portion 132 is shorter and the diameter change is relatively steep.

[0034] This asymmetric wave-like shape differs from the uniform-diameter thin neck segment 130 or the symmetrical sinusoidal thin neck segment 130 formed by constant-rate pulling. Under the synergistic effect of microdynamics and macroscopic geometry, on the one hand, the violent alternation of slow expansion and rapid contraction generates a dynamic asymmetric thermal stress gradient at the solid-liquid interface. This asymmetric radial driving force breaks the force balance of the screw dislocation maintaining vertical downward growth and actively drives it to deflect. On the other hand, the violent contraction causes the thin neck boundary to shrink sharply inward, directly and forcibly truncates the vertical downward extension path of the screw dislocation in geometric space, forcing the deflected dislocation line to intersect with the inwardly converging crystal surface. Through the synergy of asymmetric stress driving and boundary truncation, screw dislocations are forcibly driven to the crystal surface and discharged, overcoming the defect in related technologies where it is difficult to discharge screw dislocations parallel to the single crystal growth direction in medium-diameter narrow neck sections 130 or symmetrical sinusoidal narrow neck sections 130. This avoids residual screw dislocations forming linear defects that run through the entire crystal rod in the subsequently grown single crystal silicon rod, significantly improving the crystallization quality of the single crystal silicon rod.

[0035] Meanwhile, the asymmetric wave shape significantly improves dislocation removal efficiency per unit length, enabling excellent dislocation removal with a shorter neck length. This reduces the total length of the 130mm neck section, decreases crystal pulling time, and increases equipment productivity. Furthermore, it avoids the risk of the neck breaking due to excessive stress caused by excessively increasing the neck length or excessively reducing the neck diameter in pursuit of complete dislocation removal, thus lowering the crystal pulling failure rate and reducing production time wasted due to re-crystallization.

[0036] In some embodiments, the crystal orientation of the seed crystal 110 can be... <100> or <111> Silicon has a diamond structure, and its slip system is {111}. <110> That is, the slip surface is the {111} surface, and the slip direction is <110> Orientation. Different crystal orientations correspond to different angles between the slip plane and the central axis of the narrow neck 130. The asymmetric wave shape of the resulting narrow neck 130 must match the slip system of the corresponding crystal orientation to effectively drive the screw dislocation to slide along the slip plane to the crystal surface. For example, when the crystal orientation of the seed crystal 110 is... <100> In the direction, the slip surface is the {111} surface, and the {111} slip surface is... <100> The angle between the central axis of the narrow neck segment 130 of the crystal orientation and the angle between the two axes is 35.26°. The normal of the {111} slip plane is perpendicular to the angle between the central axis and the central axis of the narrow neck segment 130. <100> The included angle between the central axes of the narrow neck section 130 of the crystal orientation is 54.74°, which allows the "screw dislocation" parallel to the dislocation line of the Burgers vector to terminate at the dislocation slip plane {111} and extend to the surface of the narrow neck with the growth interface. This eliminates the screw dislocation defect that is parallel to the single crystal growth direction, avoids the residual screw dislocation from forming a line defect that runs through the entire single crystal rod in the subsequent growth of the single crystal silicon rod, and significantly improves the crystallization quality of the single crystal silicon rod.

[0037] In some embodiments, expansion and contraction angles are used to further define the geometric features of the asymmetric wave shape. For example, Figure 2 As shown, the expansion angle is the angle between the line connecting the outer contours of the expansion portion 131 at its minimum and maximum diameters and the central axis of the narrow neck section 130; the contraction angle is the angle between the line connecting the outer contours of the contraction portion 132 at its maximum and minimum diameters and the central axis. For any adjacent expansion portion 131 and contraction portion 132, since expansion portions 131 and contraction portions 132 are arranged sequentially and alternately along the single crystal growth direction, the end diameter of expansion portion 131 is the same as the beginning diameter of adjacent contraction portion 132, and the end diameter of contraction portion 132 is the same as the beginning diameter of adjacent expansion portion 131. Therefore, expansion portions 131 and contraction portions 132 have the same diameter variation range. Furthermore, since the length of expansion portion 131 along the single crystal growth direction is greater than the length of contraction portion 132 along the single crystal growth direction, according to trigonometric function relationships, under the premise of the same diameter variation range, the longer the axial length, the smaller the angle formed by the outer contour line and the central axis. Therefore, for any adjacent expansion portion 131 and contraction portion 132, the expansion angle of expansion portion 131 must be smaller than the contraction angle of contraction portion 132.

[0038] In addition, in order to ensure that the screw dislocation can slide smoothly along the slip surface to the crystal surface and be effectively discharged, the expansion angle is set to be less than the angle between the slip surface of the neck 130 and the central axis of the neck 130, and the contraction angle is set to be greater than the angle between the normal of the slip surface of the neck 130 and the central axis of the neck 130.

[0039] For example, the expansion angle is less than or equal to 35.26°, preferably in the range of 10° to 30°; the contraction angle is greater than or equal to 54.74°, preferably in the range of 55° to 65°.

[0040] In some embodiments, such as Figure 3 As shown, the minimum diameter of the narrow neck section 130 is R1, and the maximum diameter is R2, with R2 being 1.5 to 2.5 times R1. The minimum diameter R1 of the narrow neck section 130 is the diameter at the junction of the end of the constricted portion 132 and the beginning of the adjacent expanded portion 131, and the maximum diameter R2 of the narrow neck section 130 is the diameter at the junction of the end of the expanded portion 131 and the beginning of the adjacent constricted portion 132. For example, the minimum diameter R1 of the narrow neck section 130 can be 3 mm to 6 mm, and according to the above multiple relationship, the corresponding maximum diameter R2 is 4.5 mm to 15 mm. For instance, when the minimum diameter is 4 mm, the maximum diameter can be 8 mm.

[0041] In some embodiments, the length of the narrow neck segment is 200mm to 300mm. For example, the length of the narrow neck segment is 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, etc., and there is no limitation thereto.

[0042] In some embodiments, such as Figure 4 As shown, for any adjacent expansion portion 131 and contraction portion 132, the length of expansion portion 131 along the single crystal growth direction is Ln1, and the length of contraction portion 132 along the single crystal growth direction is Ln2. Ln1 / Ln2 is greater than or equal to 2, preferably 2.5 to 8.

[0043] With growth crystal orientation as <100> Taking monocrystalline silicon as an example, when the minimum diameter R1 of the neck section 130 is set to 5 mm and the maximum diameter R2 to 10 mm, and the expansion angle of the expansion portion 131 is taken as the theoretical maximum value of 35.26° and the contraction angle of the contraction portion 132 is taken as the theoretical minimum value of 54.74°, since the radial change on one side of both the expansion portion 131 and the contraction portion 132 is 2.5 mm, according to trigonometric function calculations, the axial length Ln1 of the expansion portion 131 along the single crystal growth direction is greater than 3.536 mm, and the axial length Ln2 of the contraction portion 132 along the single crystal growth direction is less than 1.767 mm. Therefore, it can be deduced that the ratio of Ln1 to Ln2 is greater than or equal to 2. Further geometric calculations show that regardless of how the specific ratio of the maximum diameter R2 to the minimum diameter R1 changes, the theoretical lower limit of the length ratio of the expansion portion 131 to the contraction portion 132 within a unit neck variation cycle is always 2. This provides mathematical support for the asymmetric wave-like shape of the neck section 130 exhibiting "slow expansion and rapid contraction".

[0044] In some specific examples, when the minimum diameter of the neck section 130 is controlled to be 3.5 mm and the maximum diameter to be 7 mm, and the expansion angle of the expansion portion 131 is 15° and the contraction angle of the contraction portion 132 is 60°, since the radial change on one side is 1.75 mm, according to trigonometric calculations, the axial length of the expansion portion 131 is approximately 6.53 mm, the axial length of the contraction portion 132 is approximately 1.01 mm, and the axial length of a complete neck fluctuation cycle formed by a single expansion portion 131 and contraction portion 132 is approximately 7.5 mm; if the crystal pulling operation reaches a total neck length of 300 mm, then the entire neck section 130 contains approximately 40 consecutive alternating expansion and contraction cycles.

[0045] In some embodiments, the transition process from the first pulling speed to the second pulling speed, and from the second pulling speed to the first pulling speed, can be a step-like switching or a gradual switching. A step-like switching refers to instantaneously switching the pulling speed between two speed values; a step-like switching of the pulling speed takes into account both high and low pulling speeds, forming a solid-liquid interface convex to the melt, causing the growth direction to deviate towards the fine grain surface, and promoting the synchronous outward discharge of screw dislocations; a gradual switching refers to smoothly transitioning the pulling speed from the current value to the target value with a preset acceleration, so as to reduce the thermal stress fluctuation caused by the sudden change in speed during the switching process.

[0046] In some embodiments, the first pulling speed can range from 0.5 mm / min to 3 mm / min, and the second pulling speed can range from 5 mm / min to 8 mm / min. For example, the first pulling speed can be set to 1.5 mm / min, and the second pulling speed to 6 mm / min. Within this speed range, the neck segment 130 can form an asymmetric wave shape with an expansion angle less than or equal to 35.26° and a contraction angle greater than or equal to 54.74°, which is beneficial for screw dislocations to slide along the slip plane to the crystal surface.

[0047] In some embodiments, after immersing the seed crystal 110 into the silicon melt, a necking transition segment 120 with a diameter gradually shrinking from the initial diameter of the seed crystal 110 to the target range is first grown by adjusting the pulling speed, such as... Figure 1 As shown; subsequently, the seed crystal 110 is pulled up alternately using the first pulling speed and the second pulling speed to continuously grow and form a thin neck segment 130 with an asymmetric undulating shape.

[0048] In some embodiments, the general basic conditions of the crystal-driving method of this application may include at least one of the following parameters: The crystal rotation speed is 8~10 RPM, and the crucible rotation speed is 0.3~1 RPM; Argon flow rate: 90~200 SLP; pressure: 20~100 torr. The distance between the liquid outlet and the liquid surface (i.e., the distance from the lower edge of the guide tube to the surface of the molten silicon) is 20~60mm; The magnetic field strength is 100~3000 Gauss.

[0049] This concludes the description of the key steps in the single-crystal silicon rod seeding method of this application. Other steps may also be included in the complete single-crystal silicon rod seeding method, which will not be elaborated here.

[0050] In summary, the seed crystal pulling method for single-crystal silicon rods of this application, by alternately using a first pulling speed and a second pulling speed greater than the first pulling speed during the formation of the thin neck segment, results in the formation of expansion and contraction sections that are continuously and alternately arranged along the single crystal growth direction in the thin neck segment. For any adjacent expansion and contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction, thereby giving the thin neck segment an overall asymmetric wave shape. Under the synergistic effect of micro-dynamics and macro-geometry, this asymmetric wave shape forces screw dislocations to be driven to the crystal surface and discharged, overcoming the defect in related technologies where medium-diameter thin neck segments or symmetrical sinusoidal waveform thin neck segments are difficult to discharge screw dislocations parallel to the single crystal growth direction. This avoids residual screw dislocations forming linear defects that run through the entire single crystal rod in the subsequently grown single-crystal silicon rod, significantly improving the crystallization quality of the single-crystal silicon rod.

[0051] Meanwhile, the asymmetric wave shape significantly improves dislocation removal efficiency per unit length, enabling excellent dislocation removal with a shorter neck length. This shortens the overall length of the neck, reduces crystal pulling time, and increases equipment productivity. Furthermore, it avoids the risk of the neck breaking due to excessive stress caused by excessively increasing the neck length or excessively reducing the neck diameter in pursuit of complete dislocation removal, thus reducing the crystal pulling failure rate and minimizing production time wasted due to re-crystallization.

[0052] Example 2 This application also provides a seeding structure for a single-crystal silicon rod, which is used for the growth of integrated circuit-grade semiconductor single-crystal silicon rods with a resistivity of 1~20 mΩ·cm. Figure 1 As shown, the crystal-leading structure includes a seed crystal 110 and a thin neck section 130 connected to the seed crystal 110 along the single crystal growth direction; the thin neck section 130 includes an expansion portion 131 and a contraction portion 132 arranged sequentially and alternately along the single crystal growth direction; wherein, the diameter of the expansion portion 131 gradually increases along the single crystal growth direction, and the diameter of the contraction portion 132 gradually decreases along the single crystal growth direction; for any adjacent expansion portion 131 and contraction portion 132, the length of the expansion portion 131 along the single crystal growth direction is greater than the length of the contraction portion 132 along the single crystal growth direction.

[0053] The crystal-leading structure of the single-crystal silicon rod in this embodiment exhibits an asymmetric wave-like shape with "slow expansion and rapid contraction" in diameter variation. That is, the axial extension of the expansion portion 131 is relatively long and the diameter change is relatively gentle, while the axial extension of the contraction portion 132 is relatively short and the diameter change is relatively steep.

[0054] This asymmetric wave-like shape differs from the uniform-diameter thin neck segment 130 or the symmetrical sinusoidal thin neck segment 130 formed by constant-rate pulling. Under the synergistic effect of microdynamics and macroscopic geometry, on the one hand, the violent alternation of slow expansion and rapid contraction generates a dynamic asymmetric thermal stress gradient at the solid-liquid interface. This asymmetric radial driving force breaks the force balance of the screw dislocation maintaining vertical downward growth and actively drives it to deflect. On the other hand, the violent contraction causes the thin neck boundary to shrink sharply inward, directly and forcibly truncates the vertical downward extension path of the screw dislocation in geometric space, forcing the deflected dislocation line to intersect with the inwardly converging crystal surface. Through the synergy of asymmetric stress driving and boundary truncation, screw dislocations are forcibly driven to the crystal surface and discharged, overcoming the defect in related technologies where it is difficult to discharge screw dislocations parallel to the single crystal growth direction in medium-diameter narrow neck sections 130 or symmetrical sinusoidal narrow neck sections 130. This avoids residual screw dislocations forming linear defects that run through the entire crystal rod in the subsequently grown single crystal silicon rod, significantly improving the crystallization quality of the single crystal silicon rod.

[0055] Meanwhile, the asymmetric wave shape significantly improves dislocation removal efficiency per unit length, enabling excellent dislocation removal with a shorter neck length. This reduces the total length of the 130mm neck section, decreases crystal pulling time, and increases equipment productivity. Furthermore, it avoids the risk of the neck breaking due to excessive stress caused by excessively increasing the neck length or excessively reducing the neck diameter in pursuit of complete dislocation removal, thus lowering the crystal pulling failure rate and reducing production time wasted due to re-crystallization.

[0056] In some embodiments, the crystal orientation of the seed crystal 110 can be... <100> or <111> .

[0057] In some embodiments, such as Figure 1 As shown, the seed crystal structure may also include a necking transition section 120, which connects the seed crystal 110 and the narrow neck section 130. The diameter of the necking transition section 120 gradually shrinks from the diameter of the seed crystal 110 to the target range along the single crystal growth direction.

[0058] In some embodiments, such as Figure 2 As shown, the angle between the line connecting the outer contours of the smallest and largest diameters of the expansion portion 131 and the central axis of the narrow neck section 130 is the expansion angle, and the angle between the line connecting the outer contours of the largest and smallest diameters of the contraction portion 132 and the central axis is the contraction angle; for any adjacent expansion portion 131 and contraction portion 132, the expansion angle is smaller than the contraction angle.

[0059] In some embodiments, the expansion angle is less than the angle between the sliding surface of the narrow neck 130 and the central axis of the narrow neck 130, and the contraction angle is greater than the angle between the normal of the sliding surface of the narrow neck 130 and the central axis of the narrow neck 130.

[0060] In some embodiments, the expansion angle is less than or equal to 35.26° and the contraction angle is greater than or equal to 54.74°, so that the "screw dislocation" with the Burgers vector parallel to the dislocation line can terminate at the dislocation slip plane {111} and extend to the neck surface with the growth interface, thereby eliminating the screw dislocation defect parallel to the single crystal growth direction, avoiding the formation of linear defects through the entire crystal rod by the residual screw dislocation in the subsequently grown single crystal silicon rod, and significantly improving the crystallization quality of the single crystal silicon rod.

[0061] In some embodiments, such as Figure 3As shown, the maximum diameter R2 of the narrow neck section 130 is 1.5 to 2.5 times the minimum diameter R1 of the narrow neck section 130; wherein, the minimum diameter R1 of the narrow neck section 130 is the diameter at the junction of the end of the constricted portion 132 and the beginning of the adjacent expansion portion 131, and the maximum diameter R2 of the narrow neck section 130 is the diameter at the junction of the end of the expansion portion 131 and the beginning of the adjacent constricted portion 132.

[0062] In some embodiments, the minimum diameter R1 of the narrow neck 130 is 3 mm to 6 mm, and the maximum diameter R2 is 4.5 mm to 15 mm.

[0063] In some embodiments, the length of the narrow neck segment is 200mm to 300mm. For example, the length of the narrow neck segment is 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, etc., and there is no limitation thereto.

[0064] In some embodiments, such as Figure 4 As shown, for any adjacent expansion portion 131 and contraction portion 132, the length of expansion portion 131 along the single crystal growth direction is Ln1, and the length of contraction portion 132 along the single crystal growth direction is Ln2. Ln1 / Ln2 is greater than or equal to 2, preferably 2.5 to 8.

[0065] For a detailed description of the crystal-leading structure of the single-crystal silicon rod, please refer to the description of the crystal-leading method of the single-crystal silicon rod in Example 1, which will not be repeated here.

[0066] Example 3 This application also provides a single-crystal silicon rod. The single-crystal silicon rod is prepared by the crystal-leading method described in Example 1, and the resistivity of the single-crystal silicon rod is 1~20 mΩ·cm.

[0067] This single-crystal silicon rod is a heavily doped crystal product. In conventional single-crystal growth processes, high doping concentrations can cause severe lattice distortion, making it extremely difficult to effectively remove screw dislocations from such heavily doped silicon rods. However, this embodiment benefits from the asymmetric wave shape formed by the aforementioned crystal pulling method, which allows for the forced removal of screw dislocations even under heavy doping conditions. Testing revealed no through-hole screw dislocations inside the single-crystal silicon rod.

[0068] Example 4 This application also provides a single-crystal silicon rod. The single-crystal silicon rod includes a seed crystal structure for the single-crystal silicon rod.

[0069] The crystal-leading structure of the single-crystal silicon rod can be the same as that in Example 2, as described above. It will not be repeated here.

[0070] Example 5 This embodiment verifies the beneficial effect of the single-crystal silicon rod seeding method of this application in eliminating screw dislocations through specific production experiments.

[0071] This experiment used a growth diameter of 300 mm and a crystal orientation of [missing information]. <100> Taking a single-crystal silicon rod as an example, the test results are shown in the table below: It can be seen that in the conventional control group, the ordinary crystal pulling process was used without special control. The diameter of the neck segment was controlled at 5±1mm, and the expansion and contraction angles of the neck segment were not specifically controlled. The length ratio of the expansion to contraction section only fluctuated randomly between 1 and 1.5, and the pulling speed was conventionally adjusted between 0.5mm / min and 6mm / min. In order to achieve the purpose of dislocation removal, the length of the neck segment must be stretched to 450mm. The crystal rods after crystal pulling were sliced, and crystal defects were detected by SIRD (Infrared Depolarized Scattering Morphology). Among the 300 conventional crystal rods tested, 7 were found to have abnormal signals of through-hole screw dislocations, and the defect rate reached 2.3%.

[0072] Three experimental groups were set up to verify the single-crystal silicon rod seeding method provided in this application. During the seeding stage, a step-by-step switching of the pulling speed was used between a low speed range of 0.5 mm / min to 3 mm / min and a high speed range of 4 mm / min to 8 mm / min. In the first experimental group, the minimum diameter R1 of the neck section was controlled to be 3.5 ± 0.5 mm, the maximum diameter R2 was 7 ± 1 mm, the resulting expansion angle was 30° ± 5°, and the contraction angle was 60° ± 5°. At this time, the length ratio of the expansion section to the contraction section was distributed between 2.0 and 4.6, and the length of the neck section was 200 mm. In the second experimental group, the minimum diameter R1 was controlled to be 4.0 ± 0.5 mm, the maximum diameter R2 was 8 ± 1 mm, the resulting expansion angle was 20° ± 5°, the contraction angle was 60° ± 5°, the length ratio was distributed between 3.0 and 8.0, and the length of the neck section was 250 mm. The third experimental group controlled the minimum diameter R1 to be 4.5±0.5mm and the maximum diameter R2 to be 9±1mm, resulting in an expansion angle of 15°±5°, a contraction angle of 60°±5°, and a length ratio distribution between 3.9 and 10.7, with a neck length of 300mm. In the actual geometric data statistics of the pulling process, typical parameter distributions, such as a length ratio of 2.5 when the expansion angle is 30° and the contraction angle is 55°, or a length ratio of 9.8 when the expansion angle is 10° and the contraction angle is 60°, perfectly conform to the theoretical data range derived from the crystal orientation slip plane in the aforementioned embodiments.

[0073] SIRD tests were also performed on over 200 single-crystal silicon rods with a doping concentration of P grown using the process described in this application. Even with the neck length significantly shortened to 200mm to 300mm, no through-hole screw dislocation signals were detected in the crystals in any of the experimental groups, and the line defect rate was 0%. This experimental data fully demonstrates that the crystal pulling method for single-crystal silicon rods described in this application not only significantly shortens the growth length of the neck and reduces crystal pulling time, thereby increasing equipment productivity, but also ensures that screw dislocations are completely eliminated, bringing the risk of dislocation defects remaining in subsequent crystal rods close to zero, achieving a dual breakthrough in crystallization quality and production efficiency.

[0074] Example 6 This embodiment verifies the effectiveness of the single-crystal silicon rod seeding method of this application in the growth process through specific production experiments. <110> The beneficial effects of crystal orientation in monocrystalline silicon.

[0075] In the field of monocrystalline silicon growth <110> The growth of crystal orientations is significantly more difficult than that of common orientations. <100> Crystal orientation. Due to <110> The growth direction of a single crystal is consistent with the direction of dislocation slip. When using ordinary crystal pulling technology, it is extremely difficult to remove dislocations from the seed crystal, resulting in a very low survival rate of shoulder formation after crystal pulling.

[0076] This experiment used a growth diameter of 300 mm and a crystal orientation of [missing information]. <100> Taking a single-crystal silicon rod as an example, the test results are shown in the table below: It can be seen that in the control group using conventional ordinary crystal pulling technology, the diameter of the neck segment is controlled at 5±1mm, the expansion angle and contraction angle of the neck segment are not specifically controlled, the length ratio of the expansion portion to the contraction portion fluctuates only between 1 and 1.5, and the pulling speed is conventionally adjusted between 0.5mm / min and 6mm / min; in order to cope with <110> The bottleneck of dislocation alignment is extremely difficult, and conventional processes have to extend the length of the narrow neck to 450 mm. However, even with such a long neck growth time, the crystal survival rate is still only about 30%. A large number of dislocations remain, causing frequent polycrystallineization or breakage of the crystal during the shoulder formation stage, resulting in an extremely low survival rate.

[0077] Three experimental groups were set up to verify the single-crystal silicon rod seeding method provided in this application. During the seeding stage, each experimental group alternated between a low-speed range of 0.5 mm / min to 3 mm / min and a high-speed range of 4 mm / min to 8 mm / min in a step-by-step speed switching. In the first experimental group, the minimum diameter R1 of the neck section was controlled to be 3.5 ± 0.5 mm, the maximum diameter R2 to be 7 ± 1 mm, the resulting expansion angle to be 30° ± 5°, the contraction angle to be 60° ± 5°, and the length ratio of the expansion to contraction section to be in the range of 2.0 to 4.6. The length of the neck section was significantly shortened to 200 mm, and the seeding survival rate of this group jumped to about 70%. In the second experimental group, the minimum diameter R1 was controlled to be 4.0 ± 0.5 mm, the maximum diameter R2 to be 8 ± 1 mm, the resulting expansion angle to be 20° ± 5°, the contraction angle to be 60° ± 5°, the length ratio to be in the range of 3.0 to 8.0, the length of the neck section to be 250 mm, and the seeding survival rate reached about 80%. The third experimental group controlled the minimum diameter R1 to be 4.5±0.5mm, the maximum diameter R2 to be 9±1mm, the expansion angle to be 15°±5°, the contraction angle to be 60°±5°, the length ratio to be in the range of 3.9 to 10.7, the length of the thin neck segment to be 300mm, and the crystal survival rate to be about 75%.

[0078] The comparative experimental data above demonstrate that even when facing dislocations with slip directions highly aligned with growth directions... <110> Even with crystal-oriented monocrystalline silicon, this application still demonstrates an extremely powerful error-correcting function, breaking through the limitations of conventional processes. <110> The limitation of difficult crystal orientation correction. This application not only significantly shortens the length of the narrow neck to 200mm to 300mm, greatly saving crystal pulling time, but also achieves a leap in the single crystal pull survival rate from 30% to 70% to 80%, providing a highly valuable solution for the efficient production of large-size single crystal silicon with special crystal orientation.

[0079] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of this application. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of this application. All such changes and modifications are intended to be included within the scope of this application as claimed in the appended claims.

[0080] Similarly, it should be understood that, in order to simplify this application and aid in understanding one or more aspects of the application, various features of this application may sometimes be grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of this application. However, this approach should not be construed as reflecting an intention that the claimed application requires more features than are expressly recited in each claim. Rather, as reflected in the corresponding claims, the point of application is that the corresponding technical problem can be solved with fewer features than all of a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of this application.

[0081] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the claims, any one of the claimed embodiments can be used in any combination.

[0082] It should be noted that the above embodiments are illustrative of this application and not limiting of it, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A seeding structure for a single-crystal silicon rod, characterized in that, The seed structure is used for the growth of integrated circuit-grade semiconductor single-crystal silicon rods. The resistivity of the single-crystal silicon rod is 1~20mΩ·cm. The seed structure includes a seed crystal and a thin neck section connected to the seed crystal along the single-crystal growth direction. The narrow neck section includes expanding and contracting portions arranged sequentially and alternately along the single crystal growth direction; wherein the diameter of the expanding portion gradually increases along the single crystal growth direction, and the diameter of the contracting portion gradually decreases along the single crystal growth direction; The angle between the line connecting the outer contours of the smallest and largest diameters of the expanded portion and the central axis of the narrow neck section is the expansion angle, and the angle between the line connecting the outer contours of the largest and smallest diameters of the contracted portion and the central axis is the contraction angle. For any adjacent expansion portion and contraction portion, the expansion angle is less than the contraction angle, wherein the expansion angle is less than or equal to 35.26° and the contraction angle is greater than or equal to 54.74°; For any adjacent expansion section and contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction, so that the entire narrow neck section presents an asymmetric wave shape, so that screw dislocations are driven to the crystal surface and discharged.

2. The seed crystal structure as described in claim 1, characterized in that, The expansion angle is less than the angle between the sliding surface of the narrow neck segment and the central axis of the narrow neck segment, and the contraction angle is greater than the angle between the normal of the sliding surface of the narrow neck segment and the central axis of the narrow neck segment.

3. The seed crystal structure as described in claim 1, characterized in that, The maximum diameter of the narrow neck segment is 1.5 to 2.5 times the minimum diameter of the narrow neck segment; The minimum diameter of the narrow neck section is the diameter at the junction of the end of the constricted portion and the beginning of the adjacent expanded portion, and the maximum diameter of the narrow neck section is the diameter at the junction of the end of the expanded portion and the beginning of the adjacent constricted portion.

4. The seed crystal structure as described in claim 3, characterized in that, The minimum diameter of the narrow neck section is 3mm to 6mm.

5. The seed crystal structure as described in claim 1, characterized in that, The length of the narrow neck section is 200mm~300mm.

6. The seed crystal structure as described in claim 1, characterized in that, For any adjacent expansion portion and contraction portion, the ratio of the length of the expansion portion along the single crystal growth direction to the length of the contraction portion along the single crystal growth direction is greater than or equal to 2.

7. A method for seeding a single-crystal silicon rod, characterized in that, The crystal pulling method is used for the growth of integrated circuit-grade semiconductor single-crystal silicon rods, wherein the resistivity of the single-crystal silicon rod is 1~20 mΩ·cm, and the crystal pulling method includes: Provides silicon melt and seed crystals; The seed crystal is immersed in the silicon melt, and the seed crystal is pulled up to form a thin neck segment connected to the seed crystal; In the process of forming the thin neck segment, the seed crystal is pulled alternately using a first pulling speed and a second pulling speed. A step-switching mode is used to switch between the first pulling speed and the second pulling speed. The second pulling speed is greater than the first pulling speed. Based on the first pulling speed, an expansion section with a diameter that gradually increases along the single crystal growth direction is formed, and based on the second pulling speed, a contraction section with a diameter that gradually decreases along the single crystal growth direction is formed. This results in the formed thin neck segment including the expansion section and the contraction section arranged sequentially and alternately along the single crystal growth direction. For any adjacent expansion section and contraction section, the length of the expansion section along the single crystal growth direction is greater than the length of the contraction section along the single crystal growth direction. This makes the thin neck segment as a whole present an asymmetric wave shape, so that screw dislocations are driven to the crystal surface and discharged. Wherein, the angle between the line connecting the outer contours of the smallest and largest diameters of the expanded portion and the central axis of the narrow neck segment is the expansion angle, and the angle between the line connecting the outer contours of the largest and smallest diameters of the contracted portion and the central axis is the contraction angle; For any adjacent expansion portion and contraction portion, the expansion angle is less than the contraction angle, wherein the expansion angle is less than or equal to 35.26° and the contraction angle is greater than or equal to 54.74°.

8. The crystal-driving method as described in claim 7, characterized in that, The first lifting speed is 0.5 mm / min to 3 mm / min, and the second lifting speed is 5 mm / min to 8 mm / min.

9. A single-crystal silicon rod, characterized in that, Including the seed structure of a single-crystal silicon rod as described in any one of claims 1 to 6.

10. A single-crystal silicon rod, characterized in that, The single-crystal silicon rod is prepared by the crystal-leading method as described in claim 7 or 8, and the resistivity of the single-crystal silicon rod is 1~20 mΩ·cm.

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