Single crystal silicon rod and ending method thereof

Abstract

The invention provides a silicon single crystal rod and an ending method thereof. The silicon single crystal rod comprises an equal-diameter structure; the ending structure is connected to one end, far away from the growth starting end, of the equal-diameter structure, and the radial size of the ending structure is in a change trend of firstly decreasing, then increasing and then decreasing along the growth direction of the silicon single crystal rod; wherein, in the increasing phase, the radial dimension of the ending structure is at least partially increased to exceed the radial dimension of the isometric structure. According to the application, the ending structure with the change trend of decreasing, increasing and decreasing is formed at one end, far away from the growth starting end, of the equal-diameter structure, and the radial size of the ending structure at least partially exceeds the radial size of the equal-diameter structure in the increasing stage, so that an area with the local radial size increased is formed; the sliding line can be effectively prevented from climbing to the equal-diameter structure, internal defect expansion of the crystal is avoided, the yield of the single crystal silicon rod and the performance of the device are improved, and the process cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of single crystal silicon rod manufacturing, in particular to a single crystal silicon rod and a tailing method thereof. BACKGROUND

[0002] In the process of preparing a single crystal silicon rod by the Czochralski method (CZ method), the crystal is grown by slowly pulling and rotating from a molten silicon liquid, which is widely used in the semiconductor and photovoltaic industries to manufacture single crystal silicon rods with high purity and large size. After the isodiametric growth ends, the crystal needs to be separated from the molten surface, at which time thermal stress is concentrated at the interface, which is easy to produce dislocations in the crystal and climb along the slip plane to the isodiametric structure, polluting the isodiametric structure and affecting the yield of the single crystal silicon rod. Therefore, a tailing process is usually performed at the end of the growth of the single crystal silicon rod to achieve a smooth separation of the crystal and inhibit the regeneration and expansion of dislocations.

[0003] In related technologies, the tailing method of the single crystal silicon rod adopts continuous necking (necking process), that is, after the isodiametric growth ends, the crystal diameter is rapidly reduced and maintained for a certain length by rapid pulling and reducing the temperature of the heater, so as to form a tapered tailing structure. The tapered tailing structure limits the climbing length of dislocations in the tailing area and does not extend into the isodiametric structure. However, when the crystal is separated from the molten surface, new thermal stress will be generated due to the sharp temperature change, which will produce slip lines. This tailing structure cannot prevent the slip lines from climbing into the isodiametric structure, thereby causing the internal defects of the isodiametric structure to expand, reducing the yield of the single crystal silicon rod, affecting the performance of the device, and having a high process cost.

[0004] Therefore, improvements need to be made to at least partially solve the above problems. SUMMARY

[0005] A series of simplified concepts are introduced in the summary section, which will be further described in detail in the detailed description section. The summary section of the present application does not mean to attempt to limit the key features and necessary technical features of the claimed technical solutions, nor to attempt to determine the protection scope of the claimed technical solutions.

[0006] In view of the existing problems, the present application provides a single crystal silicon rod, which comprises: an isodiametric structure; and a tailing structure connected to one end of the isodiametric structure away from the growth starting end, wherein the radial dimension of the tailing structure along the growth direction of the single crystal silicon rod presents a change trend of first decreasing, then increasing, and then decreasing again, and in the increasing stage, the radial dimension of the tailing structure at least partially increases to exceed the radial dimension of the isodiametric structure.

[0007] Exemplarily, the tailing structure comprises a first reduced-diameter section, an expanded-diameter section and a second reduced-diameter section, one end of the first reduced-diameter section is connected to one end of the constant-diameter structure away from the growth starting end, the other end of the first reduced-diameter section is connected to the expanded-diameter section, the other end of the expanded-diameter section is connected to the second reduced-diameter section.

[0008] Exemplarily, the radial dimension of the first reduced-diameter section gradually decreases along the growth direction of the single crystal silicon rod, the maximum radial dimension of the first reduced-diameter section is the same as the radial dimension of the constant-diameter structure; the radial dimension of the expanded-diameter section gradually increases along the growth direction of the single crystal silicon rod, the minimum radial dimension of the expanded-diameter section is the same as the minimum radial dimension of the first reduced-diameter section; the radial dimension of the second reduced-diameter section gradually decreases along the growth direction of the single crystal silicon rod, the maximum radial dimension of the second reduced-diameter section is the same as the maximum radial dimension of the expanded-diameter section.

[0009] Exemplarily, the first angle between the profile line of the first reduced-diameter section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod is a first angle, the profile line of the first reduced-diameter section is a straight line connecting one end of the constant-diameter structure away from the growth starting end and the minimum radial dimension end point of the first reduced-diameter section; the second angle between the profile line of the expanded-diameter section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod is a second angle, the profile line of the expanded-diameter section is a straight line connecting the minimum radial dimension end point of the first reduced-diameter section and the maximum radial dimension end point of the expanded-diameter section; the third angle between the profile line of the second reduced-diameter section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod is a third angle, the profile line of the second reduced-diameter section is a straight line connecting the maximum radial dimension end point of the expanded-diameter section and the minimum radial dimension end point of the second reduced-diameter section, wherein the first angle, the second angle and the third angle are acute angles.

[0010] Exemplarily, the first angle is in the range of 15 degrees to 60 degrees, the second angle is in the range of 15 degrees to 60 degrees, and the third angle is in the range of 15 degrees to 60 degrees.

[0011] Exemplarily, the difference between the radial dimension of the constant-diameter structure and the minimum radial dimension of the first reduced-diameter section is a first distance, the difference between the maximum radial dimension of the expanded-diameter section and the minimum radial dimension of the first reduced-diameter section is a second distance, and the distance between the maximum radial dimension of the expanded-diameter section and the central axis of the single crystal silicon rod is a third distance.

[0012] Exemplarily, the first distance is in the range of 85% to 95% of the radius of the constant-diameter structure, the second distance is in the range of 90% to 110% of the radius of the constant-diameter structure, and the third distance is in the range of 100% to 110% of the radius of the constant-diameter structure.

[0013] For example, the first diameter reduction section, the diameter expansion section, and the second diameter reduction section are integrally formed structures.

[0014] Another aspect of this application provides a method for finishing a monocrystalline silicon rod, the method comprising: forming a constant-diameter structure after the monocrystalline silicon rod has completed a constant-diameter growth stage; controlling the radial dimension change of the monocrystalline silicon rod by adjusting the growth conditions of the monocrystalline silicon rod, and forming a finishing structure at one end of the constant-diameter structure away from its growth start end; the radial dimension of the finishing structure exhibits a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the monocrystalline silicon rod, wherein, in the increasing stage, the radial dimension of the finishing structure at least locally increases to exceed the radial dimension of the constant-diameter structure.

[0015] For example, the growth conditions of the single crystal silicon rod include at least one of the heater temperature, the pulling speed of the single crystal silicon rod, or the rotation speed of the crucible.

[0016] The single-crystal silicon rod and its finishing method provided in this application form a finishing structure with a "first decrease, then increase, then decrease" trend at the end of the constant-diameter structure away from the growth start end. During the growth phase, the radial dimension of the finishing structure at least locally exceeds the radial dimension of the constant-diameter structure, forming a region with locally expanded radial dimension. This effectively blocks the slip line from climbing towards the constant-diameter structure, avoids the propagation of internal crystal defects, improves the yield of single-crystal silicon rods and the performance of devices, and reduces process costs. Attached Figure Description

[0017] The following drawings, which are incorporated herein by reference as part of this invention, are provided for understanding the invention. The drawings illustrate embodiments of the invention and their descriptions, serving to explain the principles of the invention.

[0018] In the attached image: Figure 1 A schematic diagram of the single-crystal silicon rod tail structure related to the present application is shown; Figure 2 A schematic diagram of the tail structure of a single-crystal silicon rod according to a specific embodiment of this application is shown; Figure 3 A schematic diagram of the tailing structure of a single-crystal silicon rod according to another specific embodiment of this application is shown; Figure 4 A schematic diagram of the slip line of the tail structure of a single-crystal silicon rod is shown; Figure 5 A flowchart illustrating a finishing method for a single-crystal silicon rod according to an exemplary embodiment of this application is shown. Detailed Implementation

[0019] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that the invention may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0020] 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 the invention 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.

[0021] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms as defined in commonly used dictionaries shall be construed as having a meaning consistent with their meaning in the relevant field and / or the context of this specification, and not as interpreted in an ideal or overly formal sense, unless expressly defined herein.

[0022] 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.

[0023] After the constant-diameter growth of a single-crystal silicon rod is completed, the crystal needs to be removed from the melt surface. At this time, due to the concentration of thermal stress at the interface, dislocations are easily generated inside the crystal and climb along the slip plane to the constant-diameter structure, contaminating it. Therefore, a finishing process is usually performed at the end of the single-crystal silicon rod growth to achieve a smooth detachment of the crystal and suppress dislocation regeneration and propagation. If the crystal is lifted directly from the melt surface without finishing, a large number of dislocations will be generated instantaneously at the break point due to the drastic change in thermal stress at the interface, and they will rapidly climb upward along the main slip plane, resulting in dislocation contamination inside the constant-diameter structure. To ensure product quality, the contaminated constant-diameter structure must be removed subsequently, resulting in material waste and a decrease in the yield of single-crystal silicon rods. Therefore, the finishing process plays a crucial role in controlling dislocation propagation and improving the yield of single-crystal silicon rods.

[0024] In related technologies, such as Figure 1As shown, the single-crystal silicon rod is terminated using a continuous necking process (necking). After the constant-diameter structure 11 is grown, the crystal diameter is rapidly reduced and maintained at a certain length through methods such as rapid pulling and lowering the heater temperature to form a tapered termination structure 12, thus maintaining dislocation-free growth until completion. Due to the guiding effect of the tapered structure 12, the extension of dislocation climb is limited to the termination region and will not extend upwards into the constant-diameter structure 11, effectively protecting the integrity of the constant-diameter structure 11 crystal. However, when the crystal detaches from the melt surface, new thermal stress is generated due to the drastic temperature change, leading to slip lines. This termination structure cannot prevent slip lines from climbing into the constant-diameter structure, causing internal defects in the constant-diameter structure to expand, reducing the yield of the single-crystal silicon rod, affecting device performance, and increasing process costs.

[0025] Therefore, in view of the aforementioned technical problems, this application proposes a single-crystal silicon rod, comprising: Equal diameter structure; The tailing structure is connected to the end of the equal-diameter structure that is far from its growth start end. The radial dimension of the tailing structure changes with a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single crystal silicon rod. During the increasing phase, the radial dimension of the tail structure increases at least locally to exceed the radial dimension of the constant-diameter structure.

[0026] The single-crystal silicon rod of this application forms a tailing structure with a "first decrease, then increase, then decrease" trend at the end of the constant-diameter structure away from the growth start end. During the growth phase, the radial dimension of the tailing structure at least locally exceeds the radial dimension of the constant-diameter structure, forming a region with locally expanded radial dimension. This effectively blocks the slip line from climbing towards the constant-diameter structure, avoids the propagation of internal crystal defects, improves the yield of the single-crystal silicon rod and the performance of the device, and reduces the process cost.

[0027] Example 1 Below, for reference Figure 2 , Figure 3 and Figure 4 The single-crystal silicon rod in the embodiments of this application is described, wherein, Figure 2 A schematic diagram of the tail structure of a single-crystal silicon rod according to a specific embodiment of this application is shown. Figure 3 A schematic diagram of the tail structure of a single-crystal silicon rod according to another specific embodiment of this application is shown. Figure 4A schematic diagram of the slip line of the tailing structure of a single-crystal silicon rod is shown. The single-crystal silicon rod includes: a constant-diameter structure 21; and a tailing structure 22, which is connected to the end of the constant-diameter structure 21 away from its growth start end. The radial dimension of the tailing structure 22 changes with a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single-crystal silicon rod; wherein, in the increasing stage, the radial dimension of the tailing structure 22 increases at least locally to exceed the radial dimension of the constant-diameter structure 21.

[0028] In this embodiment, the single-crystal silicon rod includes a constant-diameter structure 21 and a tailing structure 22. The constant-diameter structure 21 is the main body of the single-crystal silicon rod whose diameter remains constant during growth. Its diameter is set according to the target product requirements, for example, it can be 150mm, 200mm, or 300mm, and is used for subsequent slicing to prepare semiconductor devices. The tailing structure 22 is formed at the end of the constant-diameter structure 21 away from its growth start end (i.e., the end away from the seed crystal). It is formed after the constant-diameter growth is completed by adjusting process parameters such as heater power, single-crystal silicon rod pulling speed, and crucible lifting. The radial dimension of the tailing structure 22 changes continuously along the growth direction of the single-crystal silicon rod, showing an overall trend of first gradually decreasing, then gradually increasing, and then gradually decreasing again. Specifically, in the initial stage, the radial dimension of the tailing structure 22 gradually decreases from a constant diameter. In the next stage, as the radial dimension increases, the radial dimension of the tailing structure 22 at least locally exceeds that of the constant diameter structure 21, forming a region with a relatively large diameter. Finally, the radial dimension of the tailing structure 22 decreases again, eventually narrowing to a point on the central axis of the single-crystal silicon rod, achieving a smooth separation from the molten surface. This final diameter reduction process ensures that the end of the single-crystal silicon rod's tailing structure gradually tapers, avoiding sudden breakage and reducing thermal disturbance and stress concentration. This diameter expansion region effectively blocks slip lines caused by thermal disturbance, preventing slip lines from climbing into the constant diameter structure, thereby avoiding dislocation contamination in the constant diameter structure, preventing the propagation of internal crystal defects, improving the yield of the single-crystal silicon rod and the performance of the device, and reducing process costs.

[0029] In some embodiments, such as Figure 2As shown, the single-crystal silicon rod includes a constant-diameter structure 21. This constant-diameter structure 21 is the main part formed during the stable growth stage of the crystal, and its diameter remains consistent along its entire axial length to meet the thickness uniformity requirements of subsequent slicing processes. The diameter of the constant-diameter structure is set according to product specifications, such as commonly used sizes like 150mm, 200mm, or 300mm, suitable for the semiconductor field. The length of the constant-diameter structure can be flexibly adjusted according to the growth cycle, for example, from 1500mm to 2000mm, constituting the effective usable area of ​​the single-crystal silicon rod for wafer processing. The constant-diameter structure 21 extends continuously above the growth start end. After the constant-diameter growth is completed, the system automatically enters the finishing stage, forming a finishing structure 22 at the end of the constant-diameter structure 21 furthest from its growth start end, achieving a smooth transition from a constant diameter to detachment from the melt. As the core functional area of ​​the single-crystal silicon rod, this constant-diameter structure meets high-quality standards in terms of crystal integrity, oxygen and carbon content, and dislocation density, which is the foundation for ensuring device performance.

[0030] In some embodiments, such as Figure 2 As shown, the single-crystal silicon rod includes a tailing structure 22, which is connected to the end of the constant-diameter structure 21 away from its growth start end. The radial dimension of the tailing structure 22 exhibits a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single-crystal silicon rod. Specifically, the tailing structure 22 is connected to the end of the constant-diameter structure 21 away from its growth start end, i.e., located in the end region of the crystal growth direction, and is formed by adjusting growth parameters after the constant-diameter stage is completed. The radial dimension of the tailing structure 22 (i.e., the diameter of the tailing structure) continuously evolves along the growth direction of the single-crystal silicon rod, showing an overall trend of first gradually decreasing, then gradually increasing, and finally decreasing again. In the initial stage, the radial dimension of the tailing structure 22 gradually decreases from the end of the constant-diameter structure 21 away from its starting point, achieving a smooth transition from the constant-diameter structure to the tailing structure. Subsequently, it enters a stage of radial dimension increase. By appropriately increasing the heater temperature and decreasing the pulling speed, replenishment growth occurs around the crystal periphery. In a certain section, the radial dimension of the tailing structure 22 at least locally exceeds that of the constant-diameter structure, forming a relatively enlarged region that helps alleviate thermal stress concentration. After the increase stage, the radial dimension of the tailing structure 22 again enters a decrease stage. This is achieved by gradually decreasing the heater temperature and increasing the pulling speed of the single-crystal silicon rod, causing the diameter to continuously shrink until it finally tapers to a point on the central axis of the single-crystal silicon rod, achieving complete detachment from the melt surface. This tailing structure maintains good geometric stability throughout the detachment process, avoiding severe thermal disturbances caused by sudden fracture. It effectively prevents slip lines caused by thermal disturbances from climbing towards the constant-diameter structure, thus ensuring the crystal integrity of the constant-diameter structure.

[0031] In some embodiments, the tailing structure 21 includes a first diameter reduction section 221, a diameter expansion section 222, and a second diameter reduction section 223. One end of the first diameter reduction section 221 is connected to the end of the equal diameter structure 21 away from its growth start end, the other end of the first diameter reduction section 221 is connected to the diameter expansion section 222, and the other end of the diameter expansion section 222 is connected to the second diameter reduction section 223. For example, the tailing structure 22 includes a first diameter-reducing segment 221, a diameter-expanding segment 222, and a second diameter-reducing segment 223 that are continuously connected. One end of the first diameter-reducing segment 221 is connected to the end of the constant-diameter structure 21 away from its growth starting end, that is, it begins to form immediately after the constant-diameter growth is completed. The radial dimension of the first diameter-reducing segment 221 gradually decreases along the growth direction of the single-crystal silicon rod, realizing a smooth transition from the tail end of the constant-diameter structure 21 to the subsequent structure. The other end of the first diameter-reducing segment 221 is connected to one end of the diameter-expanding segment 222. The two maintain a continuous shape at the connection point without steps or cracks. The radial dimension of the diameter-expanding segment 222 gradually increases along the growth direction of the single-crystal silicon rod, and its minimum radial dimension... The size is the same as the minimum radial dimension of the first diameter-reducing section 221, ensuring that the diameter at the connection is consistent and forming a seamless transition. The radial dimension of the diameter-expanding section 222 continues to increase during the extension process, at least locally exceeding the radial dimension of the equal-diameter structure 21, forming an intermediate region with a relatively large outer diameter. The other end of the diameter-expanding section 222 is connected to one end of the second diameter-reducing section 223, and the connection also maintains geometric continuity. The radial dimension of the second diameter-reducing section 223 gradually decreases along the growth direction, and its maximum radial dimension is the same as the maximum radial dimension of the diameter-expanding section 222. Then it continues to shrink, eventually narrowing to a point on the central axis of the single crystal silicon rod, completing the separation from the molten surface.

[0032] In some embodiments, such as Figure 3 As shown in (a), the angle between the outline of the first diameter-reducing segment 221 and the horizontal reference line perpendicular to the central axis of the single-crystal silicon rod (vertical dashed line in the figure) is the first angle A1. The outline of the first diameter-reducing segment 221 is a straight line connecting the end of the constant-diameter structure 21 away from its growth start end and the endpoint of the smallest radial dimension of the first diameter-reducing segment 221. Specifically, the end of the constant-diameter structure 21 away from its growth start end is the end position at the end of the constant-diameter growth stage, and the endpoint of the smallest radial dimension of the first diameter-reducing segment 221 is the position where the diameter of the first diameter-reducing segment 221 shrinks to the minimum during the extension of the first diameter-reducing segment 221 towards the tail direction. The straight line connecting these two feature points constitutes the outline of the first diameter-reducing segment 221, which is used to characterize the overall tilt trend of this segment. The horizontal reference line is a transverse reference line perpendicular to the central axis of the single-crystal silicon rod. The first angle A1 is the angle between the outline of the first diameter-reducing segment 221 and the horizontal reference line. Its size reflects the steepness of the diameter reduction of the first diameter-reducing segment 221, ensuring a smooth transition from the constant-diameter structure to the tail section and avoiding thermal stress concentration.

[0033] For example, such as Figure 3As shown in (b), the angle between the outline of the expanding section 222 and the horizontal reference line perpendicular to the central axis of the single-crystal silicon rod (vertical dashed line in the figure) is the second angle A2. The outline of the expanding section 222 is a straight line connecting the minimum radial dimension endpoint of the first narrowing section 221 and the maximum radial dimension endpoint of the expanding section 222. Specifically, the minimum radial dimension endpoint of the first narrowing section 221 is the point where the diameter of the first narrowing section 221 shrinks to its minimum during its extension towards the tail direction, and the maximum radial dimension endpoint of the expanding section 222 is the point where the diameter expands to its maximum during its extension along the growth direction. As its termination point, the straight line connecting these two key feature points constitutes the outline of the expanding section 222, which is used to characterize the overall outward expansion trend of the section. The horizontal reference line is a transverse reference line perpendicular to the central axis of the single-crystal silicon rod. The second angle A2 is the angle between the outline of the expansion section 222 and the horizontal baseline. Its size reflects the rate of increase in diameter and the degree of inclination of the expansion section 222. It avoids problems such as insufficient expansion due to too small an angle or melt backflow and increased thermal disturbance due to too large an angle.

[0034] For example, such as Figure 3 As shown in (c), the angle between the outline of the second diameter-reducing segment 223 and the horizontal reference line perpendicular to the central axis of the single-crystal silicon rod (vertical dashed line in the figure) is the third angle A3. The outline of the second diameter-reducing segment 223 is a straight line connecting the endpoint of the maximum radial dimension of the diameter-expanding segment 222 and the endpoint of the minimum radial dimension of the second diameter-reducing segment 223. The first angle, the second angle, and the third angle are acute angles. Specifically, the endpoint of the maximum radial dimension of the diameter-expanding segment 222 is the point where the diameter expands and reaches its maximum during the extension of the segment along the growth direction, serving as the starting point of the second diameter-reducing segment 223. The endpoint of the minimum radial dimension of the second diameter-reducing segment 223 is the point where the diameter continuously decreases and tapers to a point on the central axis during the continued extension of the segment along the growth direction, i.e., the end position where the crystal finally leaves the melt surface, also known as the "tapering point". The straight line connecting these two characteristic endpoints constitutes the outline of the second diameter-reducing segment 223, used to characterize its tendency to smoothly shrink from the maximum diameter towards the central axis. The horizontal reference line is a transverse reference line perpendicular to the central axis of the single-crystal silicon rod. The third angle A3 is the angle between the outline of the second diameter reduction segment 223 and the horizontal baseline. Its size reflects the steepness of the shrinkage process of the second diameter reduction segment 223, ensuring that the crystal can shrink smoothly and continuously in the final separation stage, avoiding excessively long tail length and increased growth cycle due to too small an angle, or excessively sharp ends and insufficient mechanical strength due to too large an angle, which may cause breakage.

[0035] The first, second, and third angles are all acute angles, ensuring that the outer surface of each segment is tilted appropriately. This avoids excessive angles that could lead to interface instability or excessively long tails that could result from excessively small angles. As a result, a good balance is achieved between structural stability, thermal field control, and dislocation suppression. The connections between each segment are smooth, without abrupt changes or inflection points, ensuring the continuity and integrity of crystal growth and improving the yield of single-crystal silicon rods.

[0036] In some embodiments, the first angle ranges from 15 degrees to 60 degrees, the second angle ranges from 15 degrees to 60 degrees, and the third angle ranges from 15 degrees to 60 degrees. Exemplarily, the first, second, and third angles may be equal or unequal, and there is no specific limitation thereto. For example, the first angle may be 20 degrees, the second angle may be 30 degrees, and the third angle may be 40 degrees, or the first, second, and third angles may all be 50 degrees.

[0037] In some embodiments, the difference between the radial dimension of the constant-diameter structure 21 and the minimum radial dimension of the first narrowing section 221 is the first distance D1; the difference between the maximum radial dimension of the expanding section 222 and the minimum radial dimension of the first narrowing section 221 is the second distance D2; and the distance between the maximum radial dimension of the expanding section 222 and the central axis of the single-crystal silicon rod is the third distance D3. Exemplarily, the first distance D1 reflects the degree of diameter reduction at the beginning of the taper stage, and its magnitude directly affects the shrinkage amplitude and transition smoothness of the first narrowing section, which is beneficial for releasing thermal stress and initially suppressing dislocation propagation. Exemplarily, the second distance D2 characterizes the increase in diameter of the expanding section relative to the narrowest point of the taper, reflecting the significance of the diameter expansion degree. A larger second distance D2 means that the expanding section is more prominent, effectively preventing the slip line from climbing upwards. Exemplarily, the third distance D3 is essentially equal to the radius value at the maximum position of the expanding section, directly reflecting the spatial range of outward expansion of this region. The magnitude of the third distance D3 determines the overall size of the expanding region, affecting the stability of the growth interface and the controllability of subsequent diameter reduction.

[0038] In some embodiments, the first distance D1 ranges from 85% to 95% of the radius of the equal-diameter structure 21, the second distance D2 ranges from 90% to 110% of the radius of the equal-diameter structure 21, and the third distance D3 ranges from 100% to 110% of the radius of the equal-diameter structure 21. For example, the first distance D1, ranging from 85% to 95% of the radius of the equal-diameter structure 21, means that the radial dimension of the first diameter-reducing segment 221 has a moderate reduction, achieving a smooth transition from the equal-diameter structure to the terminal region, avoiding thermal stress concentration, and preventing excessive diameter reduction from leading to low mechanical strength or interface instability, thus facilitating the smooth progress of the subsequent diameter-expanding stage. For example, the second distance D2, set to 90% to 110% of the radius of the equal-diameter structure 21, means that the diameter-expanding segment 222 has significant diameter recovery and expansion capabilities relative to the thinnest point of the terminal region, with its maximum size exceeding the diameter of the equal-diameter structure, effectively preventing the slip line from climbing upwards when the crystal finally detaches from the melt surface. For example, the third distance D3 is set to 100% to 110% of the radial dimension of the equal-diameter structure 21, ensuring that the expanded diameter region has sufficient spatial scale to fulfill its thermodynamic and structural functions, while also considering the feasibility and stability of process implementation. In summary, by controlling the first distance D2, the second distance D2, and the third distance D3 within the above ranges, a good balance can be achieved between structural strength, thermal field control, defect suppression, and process efficiency, thereby improving the yield of single-crystal silicon rods and reducing process costs.

[0039] In some embodiments, the first diameter-reducing section 221, the diameter-expanding section 222, and the second diameter-reducing section 223 are integrally formed structures. This finishing structure 22 is a naturally formed integral structure during the monocrystalline silicon growth process, achieved through orderly epitaxial growth by controlling process parameters such as heater temperature, the pulling speed of the monocrystalline silicon rod, crucible position, and rotation speed. Because it is integrally formed, the geometric contours at the joints of each section are smooth and continuous, without steps, depressions, or abrupt changes, avoiding stress concentration or dislocation sources caused by structural discontinuities. Furthermore, the integrally formed finishing structure 22 requires no additional processing steps, relying entirely on dynamic diameter control during the growth process. It has high compatibility with existing Czochralski equipment and is easy to promote and apply in industrial production. This structure not only ensures the reliability of the finishing process but also significantly improves the overall quality and yield of the monocrystalline silicon rod. In other examples, the first diameter-reducing section, the diameter-expanding section, and the second diameter-reducing section can also be other structures, which are not specifically limited.

[0040] like Figure 4 As shown, Figure 4 Figure (a) shows a schematic diagram of the slip line of the tail structure of a single-crystal silicon rod in the prior art. Figure 4Figure (b) illustrates a schematic diagram of the slip line in the tail structure of a single-crystal silicon rod in the prior art. At the moment the crystal detaches from the molten surface, a slip line (indicated by the arrow in the figure) is generated due to thermal stress. The slip line climbs upward at an angle of approximately 45°. The tail structure in the prior art is conical, with a small diameter and no geometric obstruction. The slip line can directly extend into the constant-diameter structure, leading to defects intruding into and contaminating the constant-diameter structure. In this application, the tail structure forms a "bulge" structure with a locally increased diameter in the diameter expansion section. Upon detachment from the molten surface, this generates thermal disturbance and a stress barrier, causing the slip line to deflect or terminate upon reaching the diameter expansion region, preventing further upward propagation. This effectively blocks the slip line from entering the constant-diameter structure, significantly improving crystal integrity. Compared to the prior art, this application changes the propagation path of the slip line, achieving a key breakthrough from "unobstructed propagation" to "controllable truncation."

[0041] In summary, the single-crystal silicon rod of this application forms a tailing structure with a "first decrease, then increase, then decrease" trend at the end of the constant-diameter structure away from the growth start end, and makes the radial dimension of the tailing structure at least locally exceed the radial dimension of the constant-diameter structure during the growth stage, forming a region with locally expanded radial dimension. This can effectively block the slip line from climbing towards the constant-diameter structure, avoid the expansion of internal crystal defects, improve the yield of single-crystal silicon rods and the performance of devices, and reduce process costs.

[0042] Example 2 This application also provides a method for finishing a single-crystal silicon rod, such as... Figure 5 As shown, the finishing method for a silicon rod according to an embodiment of this application may include the following steps: In step S1, the single-crystal silicon rod forms a constant-diameter structure after the constant-diameter growth stage; In step S2, by adjusting the growth conditions of the single crystal silicon rod, the radial dimension change of the single crystal silicon rod is controlled, and a tail structure is formed at the end of the constant diameter structure that is far from its growth start end. In step S3, the radial dimension of the tail structure changes with a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single crystal silicon rod. In the increasing stage, the radial dimension of the tail structure increases at least locally to exceed the radial dimension of the constant diameter structure.

[0043] The single-crystal silicon rod finishing method of this application forms a finishing structure with a "first decrease, then increase, then decrease" trend at the end of the constant diameter structure away from the growth start end. During the growth phase, the radial dimension of the finishing structure at least locally exceeds the radial dimension of the constant diameter structure, forming a region with locally expanded radial dimension. This effectively blocks the slip line from climbing towards the constant diameter structure, avoids the propagation of internal crystal defects, improves the yield of single-crystal silicon rods and the performance of devices, and reduces process costs.

[0044] Below, for referenceFigures 2 to 5 The finishing method of the single crystal silicon rod of this application is described in detail, wherein the structure that is the same as that of the aforementioned single crystal silicon rod will not be described in detail.

[0045] First, step S1 is performed, and the single-crystal silicon rod forms an equal-diameter structure after the equal-diameter growth stage.

[0046] In some embodiments, the fabrication process of the single-crystal silicon rod first undergoes a constant-diameter growth stage, after which a constant-diameter structure 21 with a constant radial dimension (i.e., diameter) is formed. Specifically, constant-diameter growth refers to controlling parameters such as heater power, single-crystal silicon rod pulling speed, and crucible rotation speed during the Czochralski process to match the crystal growth rate with the melt supply rate, thereby ensuring that the diameter of the grown single-crystal silicon rod remains constant. The diameter of the constant-diameter structure 21 is set according to product specifications, such as commonly used sizes like 150mm, 200mm, or 300mm, suitable for the semiconductor field. The length of the constant-diameter structure 21 can be flexibly adjusted according to the growth cycle, for example, from 1500mm to 2000mm. The constant-diameter structure 21 extends continuously above the growth start end. After the constant-diameter growth is completed, a finishing stage begins, where a finishing structure 22 is formed at the end of the constant-diameter structure 21 furthest from its growth start end, achieving a smooth transition from a constant diameter to detachment from the melt. The constant diameter structure 21 serves as the core functional area of ​​the single-crystal silicon rod. Its crystal integrity, oxygen and carbon content, and dislocation density all meet high-quality standards, which is the basis for ensuring device performance.

[0047] Next, step S2 is executed, in which the radial dimension change of the single crystal silicon rod is controlled by adjusting the growth conditions of the single crystal silicon rod, and a tail structure is formed at the end of the constant diameter structure that is far from its growth start end.

[0048] In some embodiments, a tailing structure 22 is formed at the end of the constant-diameter structure 21 away from its growth start end. Specifically, after the constant-diameter growth stage is completed, the growth conditions of the single-crystal silicon rod are controlled to regulate the radial dimension change of the single-crystal silicon rod, thereby forming a tailing structure 22 at the end of the constant-diameter structure 21 away from its growth start end. Exemplarily, the growth conditions of the single-crystal silicon rod may include at least one of the heater temperature, the pulling speed of the single-crystal silicon rod, or the rotation speed of the crucible, and are not specifically limited thereto.

[0049] In some embodiments, the tailing structure 22 includes a first diameter reduction section 221, a diameter expansion section 222, and a second diameter reduction section 223. One end of the first diameter reduction section 221 is connected to the end of the equal diameter structure 21 away from its growth start end, the other end of the first diameter reduction section 221 is connected to the diameter expansion section 222, and the other end of the diameter expansion section 222 is connected to the second diameter reduction section 223. For example, the tailing structure 22 includes a first diameter-reducing segment 221, a diameter-expanding segment 222, and a second diameter-reducing segment 222 that are continuously connected. One end of the first diameter-reducing segment 221 is connected to the end of the constant-diameter structure 21 away from its growth starting end, that is, it begins to form immediately after the constant-diameter growth is completed. The radial dimension of the first diameter-reducing segment 221 gradually decreases along the growth direction of the single-crystal silicon rod, realizing a smooth transition from the tail end of the constant-diameter structure 21 to the subsequent structure. The other end of the first diameter-reducing segment 221 is connected to one end of the diameter-expanding segment 222. The two maintain a continuous shape without steps or cracks at the connection point. The radial dimension of the diameter-expanding segment 222 gradually increases along the growth direction of the single-crystal silicon rod, and its minimum radial dimension... The size is the same as the minimum radial dimension of the first diameter-reducing section 221, ensuring that the diameter at the connection is consistent and forming a seamless transition. The radial dimension of the diameter-expanding section 222 continues to increase during the extension process, at least locally exceeding the radial dimension of the equal-diameter structure 21, forming an intermediate region with a relatively large outer diameter. The other end of the diameter-expanding section 222 is connected to one end of the second diameter-reducing section 223, and the connection also maintains geometric continuity. The radial dimension of the second diameter-reducing section 223 gradually decreases along the growth direction, and its maximum radial dimension is the same as the maximum radial dimension of the diameter-expanding section 222. Then it continues to shrink, eventually narrowing to a point on the central axis of the single crystal silicon rod, completing the separation from the molten surface.

[0050] Specifically, the steps for forming the tailing structure 22 include: First, the first diameter reduction stage: lowering the heater temperature and appropriately increasing the pulling speed of the single-crystal silicon rod, so that the growth rate of the crystal periphery is lower than the axial pulling speed, resulting in a gradual decrease in diameter, achieving a smooth transition from a constant diameter structure to the tailing initiation segment to form the first diameter reduction segment 221; Second, the diameter expansion stage: after the first diameter reduction stage, gradually increasing the heater temperature, decreasing the pulling speed, and coordinating with the crucible rotation speed, enhancing the melt's ability to replenish the crystal side, so that the radial dimension of the tailing structure 22 begins to expand. The radial dimension of the constant-diameter structure 21 is increased, at least locally exceeding it, forming an outwardly expanding region, thus forming the diameter-expanding segment 222. Finally, in the second diameter-reducing stage: after the diameter-expanding stage, the growth conditions are adjusted again, such as lowering the heater temperature and increasing the pulling speed, causing the crystal growth mode to switch back to diameter-reducing. The diameter continues to decrease, eventually narrowing to a point on the central axis, completing the separation from the melt surface, thus forming the second diameter-reducing segment 223. The first diameter-reducing segment 221, the diameter-expanding segment 222, and the second diameter-reducing segment 222 constitute the tailing structure 22. The entire tailing structure formation process relies on the coordinated adjustment of multiple parameters of the single-crystal silicon rod growth conditions to ensure that the radial dimension exhibits a continuous trend of first decreasing, then increasing, and then decreasing again along the growth direction, with smooth transitions between stages and no abrupt changes, avoiding interface instability or stress concentration. This allows for the construction of a complete tailing structure with blocking slip lines without introducing additional processing. It should be noted that adjusting the growth conditions also includes adjusting other parameters, such as the crucible position, crystal rotation speed, or gas type and flow rate, which are not specifically limited.

[0051] In summary, the single-crystal silicon rod finishing method of this application forms a finishing structure with a "first decrease, then increase, then decrease" trend at the end of the constant-diameter structure away from the growth start end, and makes the radial dimension of the finishing structure at least locally exceed the radial dimension of the constant-diameter structure during the growth stage, forming a region with locally expanded radial dimension. This can effectively block the slip line from climbing towards the constant-diameter structure, avoid the expansion of internal crystal defects, improve the yield of single-crystal silicon rods and the performance of devices, and reduce process costs.

[0052] It is worth mentioning that the above steps are only examples, and the order of the steps can be adjusted without conflict.

[0053] 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.

[0054] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of this application may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0055] Similarly, it should be understood that, in order to streamline this application and aid in understanding one or more of the various inventive aspects, 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, its inventive point lies in solving the corresponding technical problem with features fewer than all features 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.

[0056] Those skilled in the art will understand that, apart from the mutual exclusion of features, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or elements of any method or apparatus so disclosed may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0057] Furthermore, those skilled in the art will understand that although some embodiments 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.

[0058] The above description is merely a specific embodiment or illustration of the embodiments of this application. The scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A single-crystal silicon rod, characterized in that, include: Equal diameter structure; The tailing structure is connected to the end of the equal-diameter structure away from its growth start end. The radial dimension of the tailing structure changes with a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single crystal silicon rod. During the increasing phase, the radial dimension of the tail structure is at least locally increased to exceed the radial dimension of the constant diameter structure.

2. The single-crystal silicon rod as described in claim 1, characterized in that, The finishing structure includes a first diameter reduction section, a diameter expansion section, and a second diameter reduction section. One end of the first diameter reduction section is connected to the end of the equal diameter structure away from its growth starting end, the other end of the first diameter reduction section is connected to the diameter expansion section, and the other end of the diameter expansion section is connected to the second diameter reduction section.

3. The single-crystal silicon rod as described in claim 2, characterized in that, The radial dimension of the first diameter-reducing section gradually decreases along the growth direction of the single crystal silicon rod, and the maximum radial dimension of the first diameter-reducing section is the same as the radial dimension of the constant diameter structure. The radial dimension of the expanding section gradually increases along the growth direction of the single crystal silicon rod, and the minimum radial dimension of the expanding section is the same as the minimum radial dimension of the first shrinking section. The radial dimension of the second diameter-reducing section gradually decreases along the growth direction of the single crystal silicon rod, and the maximum radial dimension of the second diameter-reducing section is the same as the maximum radial dimension of the diameter-expanding section.

4. The single-crystal silicon rod as described in claim 2, characterized in that, The first angle is the angle between the outline of the first diameter reduction section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod. The outline of the first diameter reduction section is a straight line connecting the end of the equal diameter structure away from its growth start end and the endpoint of the smallest radial dimension of the first diameter reduction section. The angle between the outline of the expanded section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod is the second angle, and the outline of the expanded section is a straight line connecting the minimum radial dimension endpoint of the first reduced section and the maximum radial dimension endpoint of the expanded section. The angle between the outline of the second diameter reduction section and the horizontal reference line perpendicular to the central axis of the single crystal silicon rod is the third angle. The outline of the second diameter reduction section is a straight line connecting the endpoint of the maximum radial dimension of the diameter expansion section and the endpoint of the minimum radial dimension of the second diameter reduction section. The first angle, the second angle and the third angle are acute angles.

5. The single-crystal silicon rod as described in claim 4, characterized in that, The first angle ranges from 15 degrees to 60 degrees, the second angle ranges from 15 degrees to 60 degrees, and the third angle ranges from 15 degrees to 60 degrees.

6. The single-crystal silicon rod as described in claim 2, characterized in that, The difference between the radial dimension of the equal-diameter structure and the minimum radial dimension of the first narrowing section is the first distance; the difference between the maximum radial dimension of the expanding section and the minimum radial dimension of the first narrowing section is the second distance; and the distance between the maximum radial dimension of the expanding section and the central axis of the single-crystal silicon rod is the third distance.

7. The single-crystal silicon rod as described in claim 6, characterized in that, The first distance is 85% to 95% of the radius of the equal-diameter structure, the second distance is 90% to 110% of the radius of the equal-diameter structure, and the third distance is 100% to 110% of the radius of the equal-diameter structure.

8. The single-crystal silicon rod as described in claim 2, characterized in that, The first diameter reduction section, the diameter expansion section, and the second diameter reduction section are integrally formed structures.

9. A method for finishing a single-crystal silicon rod, characterized in that, The closing method includes: After the constant diameter growth stage, a single-crystal silicon rod forms a constant diameter structure. By adjusting the growth conditions of the single crystal silicon rod, the radial dimension change of the single crystal silicon rod is controlled, and a tail structure is formed at the end of the constant diameter structure away from its growth start end. The radial dimension of the tailing structure exhibits a trend of first decreasing, then increasing, and then decreasing again along the growth direction of the single crystal silicon rod. During the increasing phase, the radial dimension of the tailing structure at least locally increases to exceed the radial dimension of the constant diameter structure.

10. The termination method as described in claim 1, characterized in that, The growth conditions of the single-crystal silicon rod include at least one of the heater temperature, the pulling speed of the single-crystal silicon rod, or the rotation speed of the crucible.

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