Method for producing single crystal silicon by the czochralski method

Abstract

The present application relates to a method for preparing single crystal silicon by using Czochralski method. The method comprises the following steps: driving the seed crystal to descend and contact with the silicon melt; forming a spindle-shaped necking crystal segment by using a segmented necking process, the spindle-shaped necking crystal segment comprises alternatingly arranged thin neck crystal segments and convex node crystal segments, and the diameter of the convex node crystal segment is larger than that of the thin neck crystal segment; forming an equal-diameter crystal segment by using an equal-diameter growth process to form a single crystal silicon crystal bar comprising the spindle-shaped necking crystal segment and the equal-diameter crystal segment, and the diameter of the equal-diameter crystal segment is larger than that of the convex node crystal segment. The present application solves the dislocation problem in the growth of single crystal silicon crystal by using Czochralski method, and ensures the quality of the grown single crystal silicon crystal bar.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a method for preparing single-crystal silicon using the Czochralski method. Background Technology

[0002] In the semiconductor field, single-crystal silicon plays a crucial role in the manufacture of solar cells, sensors, and high-performance electronic devices due to its excellent electrical and photoelectric properties. The Czochralski method, as the mainstream technology for growing large-size, high-quality single-crystal silicon, offers advantages such as large feed rate, large single-crystal diameter, high efficiency, and low cost. In the Czochralski method, the seeding stage is key to obtaining dislocation-free single crystals. A necking process (necking) is used to eliminate dislocations generated when the seed crystal contacts the melt, enabling subsequent growth of dislocation-free crystals.

[0003] However, the Czochralski method for growing single-crystal silicon, especially methods such as... <110> Single-crystal silicon with special crystal orientations faces technical challenges in dislocation removal during the necking stage. This challenge stems from the slip characteristics of silicon crystals as a diamond cubic structure: dislocation movement and multiplication mainly occur on the {111} atomic close-packed plane. <100> and <111> The crystal orientation, with its growth direction forming an angle of 36° and 19° with the {111} slip plane, neighs dislocations in the necking process need to move along the slip plane under the drive of thermal stress and efficiently slide out of the crystal side to be discharged. Traditional necking processes suffer from the problem of incomplete dislocation discharge under limited neck lengths, especially in… <110> In single-crystal silicon with special crystal orientations, the growth direction is exactly parallel to the {111} slip plane. This special crystallographic geometry makes dislocation removal during the necking process more difficult. Currently, some improved methods have been proposed to increase the success rate of crystal seeding and the quality of single crystals, such as using specially doped seed crystals. However, these methods often increase costs and offer limited improvement in performance.

[0004] Therefore, how to solve the dislocation problem in the Czochralski method of single-crystal silicon crystal growth, so as to ensure crystal quality while avoiding a significant increase in cost, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This invention provides a method for preparing single-crystal silicon using the Czochralski method, which solves the dislocation problem in the growth of single-crystal silicon crystals using the Czochralski method, thereby ensuring crystal quality while avoiding a significant increase in cost.

[0006] According to some embodiments, the present invention provides a method for preparing single-crystal silicon using the Czochralski method, comprising the following steps: The seed crystal is driven to descend and come into contact with the molten silicon. A segmented necking process is used to form a spindle-shaped necking segment, which includes alternating thin neck segments and raised node segments, and the diameter of the raised node segments is larger than the diameter of the thin neck segments. An equal-diameter growth process is used to form equal-diameter segments to form a single-crystal silicon rod including the spindle-shaped necked segment and the equal-diameter segment, wherein the diameter of the equal-diameter segment is larger than the diameter of the protruding node segment.

[0007] In some embodiments, a segmented necking process is used to form a spindle-shaped necked segment, wherein the spindle-shaped necked segment includes alternating thin neck segments and raised node segments, and the diameter of the raised node segments is larger than the diameter of the thin neck segments. The specific steps include: The seed crystal is pulled upward at a first speed to form a first narrow-necked crystal segment; The seed crystal is pulled upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin neck segment, and the diameter of the first protruding node segment is greater than the diameter of the first thin neck segment. The seed crystal is pulled upward at a third speed to form a second thin-necked crystal segment connected to the first protruding node crystal segment, and the third speed is greater than the second speed, and the diameter of the second thin-necked crystal segment is smaller than the diameter of the first protruding node crystal segment.

[0008] In some embodiments, the first velocity is equal to the third velocity, and the diameter of the first necked segment is equal to the diameter of the second necked segment.

[0009] In some embodiments, the specific steps of pulling the seed crystal upward at a first speed to form a first narrow crystal segment include: The pulling speed of the seed crystal is increased by a first preset acceleration, while simultaneously monitoring whether the diameter of the grown crystal reaches the target neck diameter. After determining that the diameter of the grown crystal has reached the target neck diameter, the current pulling speed of the seed crystal is used as the first speed, and the seed crystal is pulled upward at the first speed to form the first neck segment.

[0010] In some embodiments, the specific steps of pulling the seed crystal upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin-necked segment, and wherein the diameter of the first protruding node segment is greater than the diameter of the first thin-necked segment, include: The pulling speed of the seed crystal is reduced by a second preset acceleration, and the diameter of the grown crystal is monitored to see if it reaches the first thick neck diameter. After confirming that the diameter of the grown crystal has reached the first thick neck diameter, the pulling speed of the seed crystal is increased to form the first protruding node crystal segment.

[0011] In some embodiments, the first preset acceleration is greater than or equal to 0.5 mm / min. 2 And less than 2 mm / min 2 The second preset acceleration is greater than 0.2 mm / min. 2 And less than 2 mm / min 2 .

[0012] In some embodiments, the diameter of the first necked segment is 4mm to 6mm, and the diameter of the first protruding node segment is 8mm to 18mm.

[0013] In some embodiments, after the seed crystal is pulled upward at a third speed to form a second thin-necked segment connected to the first protruding node segment, the following steps are further included: The seed crystal is pulled upward at a fourth speed less than the third speed to form a second protruding node segment connected to the second thin neck segment. The diameter of the second protruding node segment is greater than the diameter of the second thin neck segment, and the maximum diameter of the second protruding node segment is less than the maximum diameter of the first protruding node segment. The seed crystal is pulled upward at a fifth speed to form a third thin-necked crystal segment connected to the second protruding node crystal segment, and the fifth speed is greater than the fourth speed, and the diameter of the third thin-necked crystal segment is smaller than the diameter of the second protruding node crystal segment.

[0014] In some embodiments, the difference between the maximum diameter of the second protruding node segment and the maximum diameter of the first protruding node segment is 1 mm to 5 mm.

[0015] In some embodiments, after the seed crystal is pulled upward at a fifth speed to form a third thin-necked segment connected to the second protruding node segment, the following steps are further included: The seed crystal is pulled upward at a sixth speed less than the fifth speed to form a third protruding node segment connected to the third thin neck segment. The diameter of the third protruding node segment is greater than the diameter of the third thin neck segment, and the maximum diameter of the third protruding node segment is less than the maximum diameter of the second protruding node segment. The seed crystal is pulled upward at a seventh speed to form a fourth thin-necked crystal segment connected to the third protruding node crystal segment, and the seventh speed is greater than the sixth speed, and the diameter of the fourth thin-necked crystal segment is smaller than the diameter of the third protruding node crystal segment.

[0016] The present invention provides a method for preparing single-crystal silicon using the Czochralski method. During the necking stage before constant-diameter growth, a segmented necking process is employed to form spindle-shaped necking segments. These spindle-shaped necking segments include alternating thin-necked segments and raised-node segments arranged vertically, with the diameter of the raised-node segments larger than that of the thin-necked segments. This scaling of the segment diameter creates an axial dimensional gradient-induced stress field distribution within the crystal. As the diameter increases, dislocations in the central region of the crystal move along the slip plane towards the crystal edge under the drive of thermal stress. During the diameter reduction process, these dislocations further move towards the surface and eventually slide off the crystal side and are eliminated. This method solves the dislocation problem in the Czochralski method for single-crystal silicon crystal growth, and particularly addresses... <110> This addresses the technical challenge of dislocation removal in monocrystalline silicon with special crystal orientations, where the slip plane is parallel to the growth direction, ensuring the quality and stability of the grown monocrystalline silicon ingots.

[0017] Meanwhile, the process of this invention is simple and easy to implement, requiring no large-scale modification of existing single crystal furnace equipment, and is low in cost, making it suitable for large-scale industrial production.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a method for preparing single-crystal silicon using the Czochralski method according to a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the structure inside the single crystal furnace during the growth of single crystal silicon rods in a specific embodiment of the present invention; Figure 3 This is a schematic diagram of a spindle-shaped necked crystal segment grown in a specific embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures 20. Quartz crucible 21. Graphite crucible 22. Silicon melt 23. Seed Crystal 24. Flow guide tube 25. Lifting structure 26. Thermal insulation shell 27. Support shaft 28. Heater Detailed Implementation The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This specific embodiment provides a method for preparing single-crystal silicon using the Czochralski method. Figure 1 This is a flowchart of a method for preparing single-crystal silicon using the Czochralski method, as described in a specific embodiment of the present invention. Figure 1 As shown, the method for preparing single-crystal silicon using the Czochralski method includes the following steps: Step S11: Drive the seed crystal to descend and contact the silicon melt; Step S12: A segmented necking process is used to form a spindle-shaped necking segment. The spindle-shaped necking segment includes alternating thin neck segments and protruding node segments, and the diameter of the protruding node segments is larger than the diameter of the thin neck segments. Step S13: An equal-diameter growth process is used to form an equal-diameter crystal segment to form a single-crystal silicon rod including the spindle-shaped necked crystal segment and the equal-diameter crystal segment, wherein the diameter of the equal-diameter crystal segment is larger than the diameter of the protruding node crystal segment.

[0023] Figure 2 This is a schematic diagram of the structure inside the single-crystal furnace during the growth of a single-crystal silicon ingot in a specific embodiment of the present invention. For example, such as... Figure 2As shown, the apparatus for growing single-crystal silicon rods using the Czochralski method includes a heat-insulating shell 26, which encloses a processing chamber to isolate the processing chamber from the external environment. The processing chamber contains a graphite crucible 21, a support shaft 27 located below and supporting the graphite crucible 21, a quartz crucible 20 nested within the graphite crucible 21, a heater 28 located outside the graphite crucible 21, and a flow guide tube 24 located above the quartz crucible 20. The quartz crucible 20 is used to contain the silicon melt 22, and the heater 28 is used to heat the silicon melt 22 within the quartz crucible 20. In one example, the heater 28 is a graphite heater. The flow guide tube 24 is used to introduce protective purging gases such as argon from top to bottom above the silicon melt within the quartz crucible 20 to purge impurities and provide an inert atmosphere protection for the grown single-crystal silicon rod. The protective purging gas is also used to cool the single-crystal silicon ingot grown in the quartz crucible 20, thereby increasing the axial temperature gradient of the single-crystal silicon ingot and promoting its rapid growth. In one example, the apparatus for growing a single-crystal silicon ingot using the Czochralski method further includes a pulling structure 25, which is used to pull the seed crystal 23 during the growth of the single-crystal silicon ingot. During the growth of the single-crystal silicon ingot, the seed crystal 23 is first slowly lowered to the surface of the silicon melt to initiate crystal growth. After crystal growth is completed, the seed crystal 23 is pulled upward by the pulling mechanism 25, thereby realizing the growth of the single-crystal silicon ingot.

[0024] Figure 3 This is a schematic diagram of a spindle-shaped necked segment grown in a specific embodiment of the present invention. In some embodiments, a segmented necking process is used to form the spindle-shaped necked segment, wherein the spindle-shaped necked segment includes alternating thin neck segments and raised node segments, and the diameter of the raised node segments is larger than the diameter of the thin neck segments. The specific steps include: The seed crystal is pulled upward at a first speed to form a first narrow-necked crystal segment; The seed crystal is pulled upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin neck segment, and the diameter of the first protruding node segment is greater than the diameter of the first thin neck segment. The seed crystal is pulled upward at a third speed to form a second thin-necked crystal segment connected to the first protruding node crystal segment, and the third speed is greater than the second speed, and the diameter of the second thin-necked crystal segment is smaller than the diameter of the first protruding node crystal segment.

[0025] In some embodiments, the first velocity is equal to the third velocity, and the diameter of the first necked segment is equal to the diameter of the second necked segment.

[0026] In some embodiments, the specific steps of pulling the seed crystal upward at a first speed to form a first narrow crystal segment include: The pulling speed of the seed crystal is increased by a first preset acceleration, while simultaneously monitoring whether the diameter of the grown crystal reaches the target neck diameter. After determining that the diameter of the grown crystal has reached the target neck diameter, the current pulling speed of the seed crystal is used as the first speed, and the seed crystal is pulled upward at the first speed to form the first neck segment.

[0027] In some embodiments, the specific steps of pulling the seed crystal upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin-necked segment, and wherein the diameter of the first protruding node segment is greater than the diameter of the first thin-necked segment, include: The pulling speed of the seed crystal is reduced by a second preset acceleration, and the diameter of the grown crystal is monitored to see if it reaches the first thick neck diameter. After confirming that the diameter of the grown crystal has reached the first thick neck diameter, the pulling speed of the seed crystal is increased to form the first protruding node crystal segment.

[0028] Specifically, during the growth of the single-crystal silicon ingot, protective purging gases such as argon are first introduced into the processing chamber, and the ingot is lowered vertically by the lifting structure 25 until it contacts the silicon melt 22 in the quartz crucible 20 for crystal introduction. Next, the seed crystal 23 is pulled upwards by the lifting structure 25, and the pulling speed of the seed crystal 23 is increased by a first preset acceleration to continuously shrink the diameter of the grown crystal. Simultaneously, an image acquisition device such as a CCD camera located inside the processing chamber continuously acquires images of the currently growing crystal, and the diameter of the currently growing crystal is calculated using an image processing algorithm to monitor the crystal diameter in real time. In one example, the image acquisition device can monitor the crystal diameter by acquiring 1 to 5 frames per second. Once the diameter of the grown crystal reaches the preset target neck diameter, the pulling speed of the seed crystal 23 is stopped, and the seed crystal 23 is pulled at the current pulling speed for a preset time. This allows for the growth of a first neck segment with a constant diameter at a stable pulling speed, and initially releases the thermal stress at the fusion interface. In one example, the length of the first neck segment is 5mm to 15mm.

[0029] After the first thin-necked segment of a predetermined length is grown, the pulling speed of the seed crystal is reduced by a second predetermined acceleration. During this stage, due to the reduction in the pulling speed, the crystal rises at a slower rate, the temperature distribution at the solid-liquid interface front changes, causing the diameter of the grown crystal to gradually increase, and the first protruding node segment begins to form. After confirming that the diameter of the grown crystal has reached the diameter of the first thick neck (i.e., the maximum diameter of the first protruding node segment), the pulling speed of the seed crystal is increased by the second predetermined acceleration, causing the diameter of the grown crystal to gradually decrease until the pulling speed of the seed crystal reaches the third speed, at which point the formation of the first protruding node segment is complete. Subsequently, the seed crystal is pulled upward at the third speed to form a second thin-necked segment connected to the first protruding node segment. The diameter of the second thin-necked segment remains constant, and the diameter of the second thin-necked segment is smaller than the diameter of the first protruding node segment, thereby forming a single spindle-shaped structure that is thin at both ends (i.e., the first thin-necked segment and the second thin-necked segment) and thick in the middle (i.e., the first protruding node). The second speed refers to the average pulling speed during the entire process of forming the first protruding node segment.

[0030] In this specific embodiment, during the formation of the first protruding node segment, because the diameter of the grown crystal is larger than the diameter of the previously grown first necked segment, an axial size gradient-induced stress field is generated inside the crystal, driving dislocations in the central region to move along the {111} sliding surface to the crystal edge. After the first protruding node is grown, during the subsequent necking growth of the second necked segment, the increased pulling speed accelerates the crystal growth rate, gradually reducing the crystal diameter. This causes dislocations that have already moved to the edge of the crystal to move further towards the surface under stress and slide out of the crystal side, thus achieving dislocation discharge.

[0031] In some embodiments, the first preset acceleration is greater than or equal to 0.5 mm / min. 2 And less than 2 mm / min 2 The second preset acceleration is greater than 0.2 mm / min. 2 And less than 2 mm / min 2 .

[0032] Specifically, in the initial stage of the segmented necking process, the first preset acceleration is set to be greater than or equal to 0.5 mm / min. 2 And less than 2 mm / min 2This allows for the rapid establishment of a temperature gradient and increased necking speed, thus quickly bypassing the region of rapid dislocation growth. Simultaneously, it avoids excessive acceleration leading to a sudden surge in pulling speed and a large abrupt change in crystal diameter, which could generate extremely high concentrated thermal stress and induce a large number of new dislocations. During the formation of the first protruding node segment, the second preset acceleration is set to be greater than 0.2 mm / min. 2 And less than 2 mm / min 2 This allows the grown crystal to expand slowly, gradually building a radial gradient stress field, avoiding the generation of new dislocations by instantaneous high stress, resulting in a smooth crystal diameter expansion curve without right-angle abrupt changes and a significant reduction in local peak thermal stress. At the same time, it avoids the sudden drop in pulling speed due to excessive acceleration, and the generation of ultra-high concentrated thermal stress due to excessive abrupt changes in crystal diameter, thus avoiding the induction of a large number of new dislocations.

[0033] In some embodiments, the diameter of the first necked segment is 4mm to 6mm, and the diameter of the first protruding node segment is 8mm to 18mm.

[0034] Specifically, by setting the diameter of the first narrow-necked segment to 4mm~6mm, it avoids both the significant decrease in mechanical strength caused by an excessively small diameter, thus preventing an increased risk of fracture during the pulling process, and the inability of thermal stress to effectively drive dislocations to the edge due to an excessively large diameter, thus preventing native dislocations from remaining in the crystal center. By setting the diameter of the first protruding node segment to 8mm~18mm, the radial stress difference of the crystal reaches its peak, generating the strongest dislocation migration driving force, pushing all the high-density native dislocations generated by the seed crystal fusion to the crystal edge and escaping.

[0035] In some embodiments, the first speed is 0.5 mm / min to 6 mm / min, and the maximum pulling speed during the growth of the first protruding node segment is 0.5 mm / min to 1 mm / min.

[0036] Specifically, by setting the pulling speed of the first thin-necked segment to 0.5 mm / min to 6 mm / min, the diameter of the first thin-necked segment can be kept stable within the range of 4 mm to 6 mm. By setting the maximum pulling speed during the growth of the first protruding node segment to 0.5 mm / min to 1 mm / min (i.e., the pulling speed when the grown crystal diameter reaches the diameter of the first thick neck), the diameter of the grown crystal can be gradually increased to facilitate the formation of the first protruding node segment with a diameter larger than that of the first thin-necked segment, while avoiding sudden changes in the pulling speed that could induce new dislocations.

[0037] In some embodiments, after the seed crystal is pulled upward at a third speed to form a second thin-necked segment connected to the first protruding node segment, the following steps are further included: The seed crystal is pulled upward at a fourth speed less than the third speed to form a second protruding node segment connected to the second thin neck segment. The diameter of the second protruding node segment is greater than the diameter of the second thin neck segment, and the maximum diameter of the second protruding node segment is less than the maximum diameter of the first protruding node segment. The seed crystal is pulled upward at a fifth speed to form a third thin-necked crystal segment connected to the second protruding node crystal segment, and the fifth speed is greater than the fourth speed, and the diameter of the third thin-necked crystal segment is smaller than the diameter of the second protruding node crystal segment.

[0038] In some embodiments, the difference between the maximum diameter of the second protruding node segment and the maximum diameter of the first protruding node segment is 1 mm to 5 mm.

[0039] In some embodiments, after the seed crystal is pulled upward at a fifth speed to form a third thin-necked segment connected to the second protruding node segment, the following steps are further included: The seed crystal is pulled upward at a sixth speed less than the fifth speed to form a third protruding node segment connected to the third thin neck segment. The diameter of the third protruding node segment is greater than the diameter of the third thin neck segment, and the maximum diameter of the third protruding node segment is less than the maximum diameter of the second protruding node segment. The seed crystal is pulled upward at a seventh speed to form a fourth thin-necked crystal segment connected to the third protruding node crystal segment, and the seventh speed is greater than the sixth speed, and the diameter of the fourth thin-necked crystal segment is smaller than the diameter of the third protruding node crystal segment.

[0040] For example, after forming the second thin-necked segment of a preset length (e.g., 5mm~15mm), the pulling speed of the seed crystal is reduced again by the second preset acceleration, causing the diameter of the grown crystal to gradually increase. The diameter of the grown crystal is monitored to ensure it reaches the second thick neck diameter (i.e., the maximum diameter of the second protruding node segment). Once it is confirmed that the diameter of the grown crystal has reached the second thick neck diameter, the pulling speed of the seed crystal is increased by the second preset acceleration, causing the diameter of the grown crystal to gradually decrease until the pulling speed of the seed crystal increases to the fifth speed, at which point the second protruding node segment is formed. Next, the seed crystal is pulled upwards at the fifth speed to form a third thin-necked segment with a constant diameter, thus forming a second spindle-shaped structure that is thin at both ends (i.e., the second thin-necked segment and the third thin-necked segment) and thick in the middle (i.e., the second protruding node segment). The maximum diameter of the second protruding node segment is smaller than the maximum diameter of the first protruding node segment. The fourth speed refers to the average pulling speed throughout the entire process of growing the second protruding node segment.

[0041] Then, the above steps are repeated: after forming the third thin-necked segment of a preset length (e.g., 5mm~15mm), the pulling speed of the seed crystal is reduced again by the second preset acceleration, so that the diameter of the grown crystal gradually increases, and the diameter of the grown crystal is monitored to see if it reaches the third thick-necked diameter (i.e., the maximum diameter of the third protruding node segment). After confirming that the diameter of the grown crystal has reached the third thick-necked diameter, the pulling speed of the seed crystal is increased by the second preset acceleration, so that the diameter of the grown crystal gradually decreases until the pulling speed of the seed crystal increases to the seventh speed, and the third protruding node segment is formed. Next, the seed crystal is pulled upward at the seventh speed to form a fourth thin-necked segment with a constant diameter, so as to form a third spindle-shaped structure that is thin at both ends (i.e., the third thin-necked segment and the fourth thin-necked segment) and thick in the middle (i.e., the third protruding node segment). The maximum diameter of the third protruding node segment is smaller than the maximum diameter of the second protruding node segment. Then, the above steps can be repeated again to form the next spindle-shaped structure. The sixth speed refers to the average pulling speed throughout the entire process of growing the third protruding node segment.

[0042] In one example, the diameters of the first, second, third, and fourth necked segments are all equal, for example, all being the target necked diameter (i.e., 4mm to 6mm). The difference between the maximum diameter of the second protruding node segment and the maximum diameter of the first protruding node segment is 1mm to 5mm (e.g., 3mm), and the difference between the maximum diameter of the third protruding node segment and the maximum diameter of the second protruding node segment is also 1mm to 5mm (e.g., 3mm).

[0043] This specific embodiment forms multiple spindle-shaped structures by repeatedly forming necked segments and raised node segments. Along the crystal growth direction, the maximum diameter of the multiple raised node segments decreases sequentially. That is, for any two adjacent raised node segments, the maximum diameter of the later-grown raised node segment is smaller than the diameter of the earlier-grown raised node segment. For example, the maximum diameter of the second raised node segment is smaller than the maximum diameter of the first raised node segment, and the maximum diameter of the third raised node segment is smaller than the maximum diameter of the second raised node segment. Since most of the primary dislocations in the central region of the growing crystal have been removed during the growth of the first raised node segment, the diameter difference between the subsequently grown raised node segments and their adjacent necked segments gradually decreases by sequentially decreasing the maximum diameter of the multiple raised node segments. This achieves the purpose of segmented necking and effectively avoids stress concentration problems caused by large diameter differences. While continuously removing residual dislocations, it effectively suppresses the generation of new dislocations, improving the stability of crystal growth.

[0044] The following example illustrates a method for preparing single-crystal silicon using the Czochralski method.

[0045] Example 1 The method for preparing single-crystal silicon using the Czochralski method includes the following steps: Step 1: The seed crystal descends and comes into contact with the silicon melt. Step 2: Crystal pulling and necking Step 201: Set the pulling speed for initial necking, at 0.5 mm / min. 2 The rate increases; Step 202: Monitor the diameter change of the lead neck in real time using a CCD camera; Step 203: When the diameter is monitored to be close to the target neck diameter of 6 mm, maintain an average pulling speed of 3.5 mm / min to keep the neck diameter growing at the target value of 10 mm.

[0046] Step 204, at 1 mm / min 2The acceleration is rapidly reduced to a pulling speed of 0.5 mm / min, allowing the diameter to grow to the target critical value of 15 mm.

[0047] Step 205, at 0.5 mm / min 2 The acceleration rapidly increases the pulling speed to 5 mm / min, causing the diameter to shrink again to the target neck diameter.

[0048] Step 206: Maintain the target neck diameter growth of 10 mm.

[0049] Step 207: Repeat steps 204-206 twice. The target critical value for the second diameter increase is 12 mm. The target critical value for the third diameter increase is 9 mm.

[0050] Step 3: After completing the neck reduction process, proceed with shoulder expansion and isometric growth.

[0051] Example 1 was repeated three times, and normal isodiameter growth was achieved in each case. Figure 3 This is a schematic diagram of a spindle-shaped necked crystal segment grown in a specific embodiment of the present invention. A schematic diagram of a spindle-shaped necked crystal segment grown in an embodiment is shown below. Figure 3 As shown. Among them, Figure 3 The solid arrows in the diagram indicate the direction of crystal growth. Testing revealed no dislocations at the end of the neck.

[0052] The method for preparing single-crystal silicon using the Czochralski method provided in this specific embodiment forms spindle-shaped necking segments during the necking stage before constant-diameter growth using a segmented necking process. These spindle-shaped necking segments include alternating thin-necked segments and raised-node segments arranged vertically, with the diameter of the raised-node segments larger than that of the thin-necked segments. This scaling process of the segment diameter creates a stress field distribution induced by an axial dimensional gradient within the crystal. During diameter increase, dislocations in the crystal's central region move along the slip plane towards the crystal edge under the drive of thermal stress; during diameter decrease, these dislocations further move towards the surface and eventually slide off the crystal's side surface and are eliminated. This solves the dislocation problem in the Czochralski method for single-crystal silicon crystal growth, particularly addressing... <110> This addresses the technical challenge of dislocation removal in monocrystalline silicon with special crystal orientations, where the slip plane is parallel to the growth direction, ensuring the quality and stability of the grown monocrystalline silicon ingots.

[0053] Meanwhile, this specific implementation method is simple and easy to implement, does not require large-scale modification of existing single crystal furnace equipment, has low cost, and is suitable for large-scale industrial production.

[0054] It should be noted that references to "an embodiment," "an embodiment," "an exemplary embodiment," "some embodiments," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. In addition, when a specific feature, structure, or characteristic is described in connection with an embodiment, whether explicitly described or not, implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art.

[0055] It should be noted that the terms "comprising" and "having," and their variations, used in this invention document are intended to cover non-exclusive inclusion. The terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence, unless explicitly indicated by the context. It should be understood that such data used interchangeably where appropriate. Furthermore, embodiments and features within embodiments of this invention can be combined with each other unless otherwise specified. In addition, descriptions of well-known components and technologies have been omitted in the above description to avoid unnecessarily obscuring the concepts of this invention. In the various embodiments described above, each embodiment focuses on its differences from other embodiments; similar or identical parts between embodiments can be referred to interchangeably.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing single-crystal silicon using the Czochralski method, characterized in that, Includes the following steps: The seed crystal is driven to descend and come into contact with the molten silicon. A segmented necking process is used to form a spindle-shaped necking segment, which includes alternating thin neck segments and raised node segments, and the diameter of the raised node segments is larger than the diameter of the thin neck segments. An equal-diameter growth process is used to form equal-diameter segments to form a single-crystal silicon rod including the spindle-shaped necked segment and the equal-diameter segment, wherein the diameter of the equal-diameter segment is larger than the diameter of the protruding node segment.

2. The method for preparing single-crystal silicon using the Czochralski method according to claim 1, characterized in that, The specific steps for forming spindle-shaped necked segments using a segmented necking process, wherein the spindle-shaped necked segments include alternating thin-necked segments and raised-node segments, and the diameter of the raised-node segments is larger than the diameter of the thin-necked segments, include: The seed crystal is pulled upward at a first speed to form a first narrow-necked crystal segment; The seed crystal is pulled upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin neck segment, and the diameter of the first protruding node segment is greater than the diameter of the first thin neck segment. The seed crystal is pulled upward at a third speed to form a second thin-necked crystal segment connected to the first protruding node crystal segment, and the third speed is greater than the second speed, and the diameter of the second thin-necked crystal segment is smaller than the diameter of the first protruding node crystal segment.

3. The method for preparing single-crystal silicon using the Czochralski method according to claim 2, characterized in that, The first velocity is equal to the third velocity, and the diameter of the first narrow-necked segment is equal to the diameter of the second narrow-necked segment.

4. The method for preparing single-crystal silicon using the Czochralski method according to claim 2, characterized in that, The specific steps for pulling the seed crystal upward at a first speed to form the first narrow-necked crystal segment include: The pulling speed of the seed crystal is increased by a first preset acceleration, while simultaneously monitoring whether the diameter of the grown crystal reaches the target neck diameter. After determining that the diameter of the grown crystal has reached the target neck diameter, the current pulling speed of the seed crystal is used as the first speed, and the seed crystal is pulled upward at the first speed to form the first neck segment.

5. The method for preparing single-crystal silicon using the Czochralski method according to claim 4, characterized in that, The specific steps of pulling the seed crystal upward at a second speed less than the first speed to form a first protruding node segment connected to the first thin-necked segment, wherein the diameter of the first protruding node segment is greater than the diameter of the first thin-necked segment, include: The pulling speed of the seed crystal is reduced by a second preset acceleration, and the diameter of the grown crystal is monitored to see if it reaches the first thick neck diameter. After confirming that the diameter of the grown crystal has reached the first thick neck diameter, the pulling speed of the seed crystal is increased to form the first protruding node crystal segment.

6. The method for preparing single-crystal silicon using the Czochralski method according to claim 5, characterized in that, The first preset acceleration is greater than or equal to 0.5 mm / min. 2 And less than 2 mm / min 2 The second preset acceleration is greater than 0.2 mm / min. 2 And less than 2 mm / min 2 .

7. The method for preparing single-crystal silicon using the Czochralski method according to claim 2, characterized in that, The diameter of the first narrow-necked segment is 4mm to 6mm, and the diameter of the first protruding node segment is 8mm to 18mm.

8. The method for preparing single-crystal silicon by the Czochralski method according to claim 7, characterized in that, After pulling the seed crystal upward at a third speed to form a second thin-necked crystal segment connected to the first protruding node crystal segment, the following steps are also included: The seed crystal is pulled upward at a fourth speed less than the third speed to form a second protruding node segment connected to the second thin neck segment. The diameter of the second protruding node segment is greater than the diameter of the second thin neck segment, and the maximum diameter of the second protruding node segment is less than the maximum diameter of the first protruding node segment. The seed crystal is pulled upward at a fifth speed to form a third thin-necked crystal segment connected to the second protruding node crystal segment, and the fifth speed is greater than the fourth speed, and the diameter of the third thin-necked crystal segment is smaller than the diameter of the second protruding node crystal segment.

9. The method for preparing single-crystal silicon using the Czochralski method according to claim 9, characterized in that, The difference between the maximum diameter of the second protruding node segment and the maximum diameter of the first protruding node segment is 1 mm to 5 mm.

10. The method for preparing single-crystal silicon by the Czochralski method according to claim 8, characterized in that, After pulling the seed crystal upwards at a fifth speed to form a third thin-necked crystal segment connected to the second protruding node crystal segment, the following steps are also included: The seed crystal is pulled upward at a sixth speed less than the fifth speed to form a third protruding node segment connected to the third thin neck segment. The diameter of the third protruding node segment is greater than the diameter of the third thin neck segment, and the maximum diameter of the third protruding node segment is less than the maximum diameter of the second protruding node segment. The seed crystal is pulled upward at a seventh speed to form a fourth thin-necked crystal segment connected to the third protruding node crystal segment, and the seventh speed is greater than the sixth speed, and the diameter of the fourth thin-necked crystal segment is smaller than the diameter of the third protruding node crystal segment.

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