Single crystal furnace and crystal rod growth method

Abstract

The present application relates to a single crystal furnace and a crystal rod growth method, wherein the single crystal furnace includes a furnace body and a crucible assembly located inside the furnace body, a flow guide tube is provided above the crucible assembly, a crystal rod pulling region is provided inside the flow guide tube, a water cooling jacket is provided between the crystal rod pulling region and the flow guide tube, and a temperature control tube is provided between the water cooling jacket and the flow guide tube in the axial direction of the water cooling jacket.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the priority of Chinese Patent Application No. 202310572370.1, filed in China on May 19, 2023, and all of its content is incorporated herein by reference. This application relates to the technical field of manufacturing silicon products, and particularly relates to a single - crystal furnace and a method for growing a crystal bar.

Background Art

[0002] Oxygen is the most important unintentional doping impurity in silicon single crystals grown by the Czochralski method and is incorporated from a quartz crucible during the crystal growth process. Oxygen atoms form natural oxygen precipitates during the cooling process of the crystal, which ablate or further grow during the thermal processes of subsequent device wafer manufacturing processes. Oxygen precipitates are the most important micro - defects, i.e., Bulk Micro Defects (BMDs), in silicon single crystals grown by the Czochralski method, and have a significant impact on the properties of single - crystal silicon wafers and the yield of device wafers. Oxygen precipitates of appropriate dimensions help improve the mechanical performance of silicon wafers and suppress warping during high - temperature processes. Also, oxygen precipitates and their induced defects within the bulk of the silicon wafer can effectively adsorb metal contaminants on the surface of the silicon wafer as gettering sites, i.e., internal gettering is possible. The control and utilization of oxygen precipitates during the device manufacturing process are core issues in silicon wafer defect engineering. Usually, by forming a denuded zone near the surface of the silicon wafer without crystal defects or metal impurities and forming a high - density BMD within the bulk, the yield can be improved.

[0003] Under normal circumstances, a high cooling rate is required during the growth process of BMD crystal rods. The closer the water cooling jacket is to the flow guide tube, the greater the cooling rate in that region. However, for safety reasons, the water cooling jacket cannot be too close to the liquid surface or too close to the flow guide tube. If the water cooling jacket is too close to the flow guide tube, the thermal shielding effect of the flow guide tube weakens, causing the liquid surface temperature to dissipate. This causes fluctuations in the solid-liquid-gas three-phase point, affecting the stable growth of the crystal rod and influencing the reaction between vacancy defects and interstitial atoms within the crystal rod. Therefore, a certain distance must be maintained between the water cooling jacket and the flow guide tube, resulting in a decrease in the cooling rate and affecting the formation of BMDs. [Overview of the project] [Problems that the invention aims to solve]

[0004] To solve the above problem, this application provides a single crystal furnace and a crystal rod growth method that solve the problem of low cooling rate in the region of the crystal rod corresponding to the position between the water-cooled jacket and the flow guide tube. [Means for solving the problem]

[0005] To achieve the above objective, the technical embodiment adopted in the present invention is a single crystal furnace comprising a furnace body and a crucible assembly located within the furnace body, wherein a flow guide tube is provided above the crucible assembly, a crystal rod pulling region is provided inside the flow guide tube, and a water cooling jacket is provided between the crystal rod pulling region and the flow guide tube. In the axial direction of the water-cooling jacket, a temperature control cylinder is provided between the water-cooling jacket and the flow guide cylinder.

[0006] Selectively, in the axial direction of the water-cooling jacket, the temperature control cylinder has a first end far from the crucible assembly and a second end close to the crucible assembly. The first end is connected to the water-cooling jacket and a gap is provided between the second end and the flow guide tube, or a gap is provided between the first end and the water-cooling jacket and the second end is connected to the flow guide tube.

[0007] Selectively, a gap is provided between the first end and the water-cooling jacket, and the second end is connected to the flow guide tube, wherein the distance between the temperature control tube and the water-cooling jacket in the radial direction of the water-cooling jacket is 2 mm to 5 mm.

[0008] Selectively, the first end has a first region, and the orthographic projection of the first region on the water-cooling jacket is located within the water-cooling jacket.

[0009] Selectively, an uneven structure is provided on the surface in the first region that is close to the water-cooling jacket.

[0010] Selectively, the uneven structure includes a plurality of protrusions and recesses that extend along the circumferential direction of the temperature control cylinder, thereby giving the uneven structure a wavy shape.

[0011] Selectively, in the radial direction of the water-cooling jacket, the temperature control cylinder is circumferentially positioned between the water-cooling jacket and the flow guide cylinder.

[0012] Selectively, in the axial direction of the water-cooling jacket, the thickness of the side wall of the temperature-regulating cylinder gradually decreases along the direction away from the crucible assembly.

[0013] Selectively, the flow guide tube includes a body and an extension, the extension being formed by bending and extending such that the end of the flow guide tube closest to the crucible assembly approaches the crystal rod pulling region. The extending portion has a first surface far from the crucible assembly, and the first surface is provided with a groove for connecting to the temperature control cylinder, and in the radial direction of the water cooling jacket, the groove has a first side wall far from the crystal rod pulling region, and the first side wall is provided with a locking groove extending along the radial direction of the water cooling jacket. The second end of the temperature control cylinder has a stopper that engages with the locking groove.

[0014] Selectively, in the radial direction of the water-cooling jacket, the groove has a second sidewall close to the crystal rod pulling region, and in the axial direction of the water-cooling jacket, the second sidewall extends away from the crucible assembly to form a blocking wall.

[0015] Selectively, the flow guide tube is made of a carbon fiber composite material, the direction of extension of the carbon fiber composite material bundle in the main body is parallel to the axial direction of the flow guide tube, and the direction of extension of the carbon fiber composite material bundle in the extension portion is parallel to the radial direction of the flow guide tube.

[0016] Selectively, a sealing coating is provided on the outer surface of the flow guide tube.

[0017] Selectively, the sealing coating located on the outer surface of the main body is a tungsten carbide coating, the sealing coating located on the bottom surface of the extended portion near the crucible assembly is a tungsten carbide coating, and the sealing coating located on surfaces other than the bottom surface of the extended portion is a pyrolysis carbon coating.

[0018] Selectively, a heat-absorbing coating is provided on the inner surface of the water-cooling jacket.

[0019] Selectively, in the axial direction of the water-cooling jacket, the thickness of the heat-absorbing coating gradually decreases along the direction away from the crucible assembly.

[0020] An embodiment of the present application is a method for growing a crystal bar, comprising: Putting a nitrogen-doped polysilicon material into a quartz crucible; Sealing the furnace body of a single crystal furnace, evacuating it, and flowing an inert gas into it; Heating to melt the polysilicon material; Further providing a method for growing a crystal bar, comprising lowering a plurality of seed crystals into corresponding sub-accommodation chambers, and performing a growth process including fusion, shoulder formation, shoulder dislocation, and equal-diameter growth.

Advantages of the Invention

[0021] As a beneficial effect of the present application, by providing the temperature control cylinder, the temperature of the region corresponding to the temperature control cylinder can be conducted to the water-cooled jacket, so that the cooling rate of the region is improved, and it can further help in the formation of BMD.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a schematic diagram showing the structure of a single crystal furnace in an embodiment of the present application. [Figure 2] FIG. 2 is a schematic diagram showing the structure of a flow guide cylinder in an embodiment of the present application. [Figure 3] FIG. 3 is a schematic diagram showing the structure of a temperature control cylinder in an embodiment of the present application.

Modes for Carrying Out the Invention

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art without creative efforts based on the described embodiments of the present disclosure shall fall within the protection scope of the present disclosure.

[0024] Unless otherwise defined, technical or scientific terms used in this disclosure have the ordinary meanings that are understood by those skilled in the art. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but merely distinguish different components. Similarly, similar words such as “one” or “one” do not indicate a limit on quantity, but indicate that there is at least one. Similar terms such as “include” or “incorporate” mean that the element or component listed before the term includes, but does not exclude, the element or component and its equivalents listed after the term. Similar terms such as “connected” or “linked” may include, but are not limited to, physical or mechanical connections, electrical connections, whether directly or indirectly connected. “Up,” “down,” “left,” “right,” etc., only indicate relative positions, and such relative positions may change accordingly if the absolute position of the object being described changes.

[0025] Referring to Figures 1 to 3, this embodiment is a single crystal furnace, comprising a furnace body and a crucible assembly located within the furnace body, the crucible assembly comprising a nested quartz crucible 6 and a graphite crucible 7, the quartz crucible 6 for containing a silicon melt 5, a flow guide tube 3 provided above the crucible assembly, a crystal rod pulling region for pulling out crystal rods 2 provided inside the flow guide tube 3, and a water cooling jacket 1 provided between the crystal rod pulling region and the flow guide tube 3. The present invention provides a single crystal furnace in which a temperature control cylinder 4 is provided between the water cooling jacket 1 and the flow guide cylinder 3 in the axial direction of the water cooling jacket 1 (see the X direction in Figure 1).

[0026] For a crystal rod with high-density BMD to be extracted, the region between the water-cooling jacket 1 and the flow guide tube 3 in the axial direction of the crystal rod needs to have a high cooling rate. However, for safety reasons, the water-cooling jacket 1 cannot be too close to the liquid surface. Secondly, if the water-cooling jacket 1 is too close to the flow guide tube 3, the thermal shielding effect of the flow guide tube 3 weakens, causing the temperature of the liquid surface to dissipate. This causes fluctuations in the solid-liquid-gas three-phase point, affecting the stable growth of the crystal rod and influencing the reaction between vacancy-type defects and interstitial atoms within the crystal rod. Therefore, a certain distance must be maintained between the water-cooling jacket 1 and the flow guide tube 3. As a result, the cooling rate is low in the region between the water-cooling jacket 1 and the flow guide tube 3 in the axial direction of the crystal rod. To address this problem, this embodiment provides a single crystal furnace and, by providing a temperature control tube 4 between the water-cooled jacket 1 and the flow guide tube 3, the temperature of the region between the water-cooled jacket 1 and the flow guide tube 3 is conducted to the water-cooled jacket 1 in the axial direction of the crystal rod. This improves the cooling rate of the region and is useful for drawing crystal rods with a high concentration of BMD.

[0027] In an exemplary embodiment, in the axial direction of the water-cooled jacket 1, the temperature control cylinder 4 has a first end far from the crucible assembly and a second end close to the crucible assembly. The first end is connected to the water-cooling jacket 1 and a gap is provided between the second end and the flow guide tube 3, or a gap is provided between the first end and the water-cooling jacket 1 and the second end is connected to the flow guide tube 3.

[0028] What needs to be explained is that the temperature control cylinder 4 is provided between the water cooling jacket 1 and the flow guide cylinder 3 in order to improve the cooling rate of the region between the water cooling jacket 1 and the flow guide cylinder 3 in the axial direction of the crystal rod. There may be multiple types of connection methods and relative positional relationships between the temperature control cylinder 4, the water cooling jacket 1 and the flow guide cylinder 3. For example, the temperature control cylinder 4 may be in contact with one of the water cooling jacket 1 and the flow guide cylinder 3, and not in contact with the other of the water cooling jacket 1 and the flow guide cylinder 3. For example, contact connections may be adopted between the temperature control cylinder 4 and both the water cooling jacket 1 and the flow guide cylinder 3.

[0029] It should be explained that if contact connections are used between the temperature control cylinder 4 and either the water cooling jacket 1 or the flow guide cylinder 3, the temperature control cylinder 4 will connect the water cooling jacket 1 and the flow guide cylinder 3 to each other, which is disadvantageous for individual motion control of the water cooling jacket 1 and the flow guide cylinder 3. Therefore, in some embodiments, the temperature control cylinder 4 may be selectively connected in contact to one of the water cooling jacket 1 and the flow guide cylinder 3, and not connected in contact to the other of the water cooling jacket 1 and the flow guide cylinder 3.

[0030] What needs to be explained is that when the temperature control cylinder 4 is non-contact connected to the other of the water cooling jacket 1 and the flow guide cylinder 3, in order to ensure heat conduction, the distance between the water cooling jacket 1 or the flow guide cylinder 3 that is non-contact connected to the temperature control cylinder 4 and the temperature control cylinder 4 will be less than a predetermined value. The setting of this predetermined value can be set according to the actual demand, so that the water cooling jacket 1 or the flow guide cylinder 3 that is non-contact connected to the temperature control cylinder 4 is close to the temperature control cylinder 4 but not in contact with it, so that the heat transfer effect can be realized between the temperature control cylinder 4 and the water cooling jacket 1 or the flow guide cylinder 3, while contact between the temperature control cylinder 4 and the water cooling jacket 1 or the flow guide cylinder 3 is avoided.

[0031] It should be explained that, in some embodiments, the temperature control cylinder 4 is selectively connected in contact with the flow guide cylinder 3 and non-contact with the water cooling jacket 1. In this way, friction between the temperature control cylinder 4 and the flow guide cylinder 3 is avoided during the raising and lowering motion of the water cooling jacket 1, and further contamination caused by dust due to friction is avoided. Furthermore, this connection method helps to conduct the temperature of the connection area between the flow guide cylinder 3 and the temperature control cylinder 4 to the water cooling jacket 1 via the temperature control cylinder 4.

[0032] Referring to Figure 1, in an exemplary embodiment, a gap is provided between the first end and the water-cooled jacket 1, and the second end is connected to the flow guide tube 3. In the radial direction of the water-cooled jacket 1, the distance between the temperature control tube 4 and the water-cooled jacket 1 is 2 to 5 mm, but is not limited to this.

[0033] Referring to Figure 1, in an exemplary embodiment, the first end has a first region 21, and the orthographic projection of the first region 21 on the water-cooled jacket 1 is located within the water-cooled jacket 1.

[0034] In the axial direction of the water-cooled jacket 1, the temperature control cylinder 4 and the water-cooled jacket 1 partially overlap; that is, the orthographic projection of the first region 21 onto the water-cooled jacket 1 is located within the water-cooled jacket 1. This facilitates heat conduction between the temperature control cylinder 4 and the water-cooled jacket 1.

[0035] In an exemplary embodiment, the surface of the first region 21 closest to the water-cooling jacket 1 is provided with an uneven structure 211.

[0036] By providing the aforementioned uneven structure 211, the surface area of ​​the surface in the first region 21 closest to the water-cooled jacket 1 can be increased, and the heat transfer area between the temperature control cylinder 4 and the water-cooled jacket 1 can be increased, thereby enhancing the heat transfer effect.

[0037] It should be explained that there may be multiple specific structural forms of the uneven structure 211, as long as the surface area of ​​the surface close to the water-cooling jacket 1 in the first region 21 can be increased. Below, several specific installation forms of the uneven structure 211 in this embodiment will be introduced.

[0038] In an exemplary embodiment, the uneven structure 211 includes a plurality of protrusions and recesses that extend along the circumferential direction of the temperature control cylinder 4, thereby giving the uneven structure 211 a wavy shape.

[0039] In an exemplary embodiment, the uneven structure 211 includes a plurality of spaced-apart protrusions on the surface of the first region 21 closest to the water-cooling jacket 1.

[0040] Exemplary, the multiple protrusions are uniformly distributed in the first region 21.

[0041] As an example, the multiple protrusions and the temperature-regulating cylinder 4 are an integrated structure. In this way, the manufacturing process is simplified, and the connection stability between the multiple protrusions and the body of the temperature-regulating cylinder 4 is improved.

[0042] Exemplary, the multiple protrusions are formed by the corresponding positions in the first region 21 extending toward the water-cooling jacket 1.

[0043] For example, a recess is formed between two adjacent protrusions, meaning that the formation of multiple protrusions is such that the corresponding position in the first region 21 is recessed in a direction away from the water cooling jacket 1, thereby forming the protrusions at the positions corresponding to the protrusions.

[0044] Exemplary, the surface of the first region 21 closest to the water-cooling jacket 1 includes alternately provided first sub-regions and second sub-regions, and the uneven structure 211 is formed on the surface of the first region 21 closest to the water-cooling jacket 1 by the first sub-regions extending toward the water-cooling jacket 1 to form the protrusions, and / or the uneven structure 211 is formed on the surface of the first region 21 closest to the water-cooling jacket 1 by the second sub-regions recessing toward the water-cooling jacket 1.

[0045] For example, in order to avoid damage to the water cooling jacket 1 by the protrusion, the end of the protrusion closest to the water cooling jacket 1 is rounded.

[0046] For example, in order to avoid damage to the water cooling jacket 1 by the protrusion, the end face of the protrusion closest to the water cooling jacket 1 is a plane parallel to the axial direction of the water cooling jacket 1.

[0047] For example, in order to avoid damage to the water cooling jacket 1 by the protrusion, the end face of the protrusion closest to the water cooling jacket 1 is a plane parallel to the axial direction of the water cooling jacket 1, the protrusion has a side surface adjacent to the end face, and the connection point between the side surface and the end face is rounded to form a curved surface.

[0048] In an exemplary embodiment, the temperature control cylinder 4 is circumferentially arranged between the water cooling jacket 1 and the flow guide cylinder 3 in the radial direction of the water cooling jacket 1.

[0049] Specifically, in the radial direction of the water-cooling jacket 1, the first end is located between the flow guide tube 3 and the water-cooling jacket 1, that is, the first end is located between the water-cooling jacket 1 and the flow guide tube 3, and the first end is located on the side of the water-cooling jacket 1 that is far from the crystal rod pulling region.

[0050] The crystal rod is located in the crystal rod pulling region, and as is well known, the role of the water-cooled jacket 1 is to cool the crystal rod. The first region 21, where the temperature control cylinder 4 and the water-cooled jacket 1 are superimposed, is located on the side of the water-cooled jacket 1 furthest from the crystal rod, thereby preventing the installation of the temperature control cylinder 4 from affecting the cooling effect of the water-cooled jacket 1.

[0051] In the axial direction of the water-cooled jacket 1, the length of the first region 21 can be specifically set according to the actual demand. The longer the length of the first region 21 in the axial direction of the water-cooled jacket 1, the larger the overlapping area between the temperature control cylinder 4 and the water-cooled jacket 1, and the better the heat transfer effect between the temperature control cylinder 4 and the water-cooled jacket 1. For example, the length of the first region 21 in the axial direction of the water-cooled jacket 1 is 70 mm to 100 mm, but is not limited to this.

[0052] It should be explained that the setting of the length of the first region 21 in the axial direction of the water-cooled jacket 1 is related to the required heat transfer effect, the overall height of the temperature control cylinder 4 in the axial direction of the water-cooled jacket 1, and the overall height of the water-cooled jacket 1. For example, in one specific embodiment, the length of the first region 21 in the axial direction of the water-cooled jacket 1 is 1 / 4 of the overall length of the temperature control cylinder 4, but is not limited to this.

[0053] In an exemplary embodiment, in the axial direction of the water-cooling jacket 1, the thickness of the side wall of the temperature-regulating cylinder 4 gradually decreases along the direction away from the crucible assembly.

[0054] By adopting the above setting configuration for the thickness of the side wall of the temperature control cylinder 4, it is useful for adjusting the temperature gradient in the axial direction of the crystal rod.

[0055] For example, in the radial direction of the flow guide tube 3, the extension direction of the side wall of the temperature control tube 4 on the side farther from the crystal rod pulling region is parallel to the axial direction of the flow guide tube 3, and in the radial direction of the flow guide tube 3, the side wall of the temperature control tube 4 on the side closer to the crystal rod pulling region is an inclined surface with respect to the axial direction of the flow guide tube 3.

[0056] For example, the thickness of the side wall of the temperature control cylinder 4 in the radial direction of the water-cooling jacket 1 is 9 mm to 16 mm, but is not limited to this.

[0057] In an exemplary embodiment, the flow guide tube 3 includes a main body 31 and an extension 32 (distinguished by a dashed line in Figure 2), the extension 32 being formed by bending and extending such that the end of the flow guide tube 3 closest to the crucible assembly approaches the crystal rod pulling region. The extending portion 32 has a first surface far from the crucible assembly, and the first surface is provided with a groove 321 for connecting to the temperature control cylinder 4, and in the radial direction of the water cooling jacket 1, the groove 321 has a first side wall far from the crystal rod pulling region, and the first side wall is provided with a locking groove 322 extending along the radial direction of the water cooling jacket 1. The second end of the temperature control cylinder 4 has a stopper 22 that engages with the locking groove 322.

[0058] The temperature control cylinder 4 may be bonded to the bottom of the groove 321 via an adhesive layer, but is not limited to this. For example, the temperature control cylinder 4 and the groove 321 may be connected by a press-fit method.

[0059] By providing the locking groove 322 and the stopper 22, relative rotation between the temperature control cylinder 4 and the flow guide cylinder 3 is prevented.

[0060] Referring to Figures 1 to 3, the locking groove 322 is provided extending from the first surface toward the bottom of the recessed groove 321. In this way, the temperature control cylinder 4 can be inserted into the recessed groove 321 from top to bottom, and at the same time, the stopper 22 can be inserted into the locking groove 322.

[0061] In an exemplary embodiment, in the radial direction of the water-cooling jacket 1, the groove 321 has a second sidewall close to the crystal rod pulling region, and in the axial direction of the water-cooling jacket 1, the second sidewall extends away from the crucible assembly to form a blocking wall 323.

[0062] By providing the aforementioned blocking wall 323, the connection stability between the temperature control cylinder 4 and the flow guide cylinder 3 is improved.

[0063] For example, a sealing layer is applied to the side of the blocking wall 323 closest to the crystal rod pulling region.

[0064] For example, the sealing layer may be a tungsten carbide coating or the pyrolysis carbon coating.

[0065] Exemplary, along the axial direction of the flow guide tube 3, the blocking wall 323 includes a first portion 3201 and a second portion 3202, the first portion 3201 being located near the crucible assembly, the first portion 3201 being coated with a tungsten carbide coating, and the second portion 3202 being coated with a pyrolysis carbon coating.

[0066] Compared to the tungsten carbide coating, the pyrolysis carbon coating is less expensive, while the tungsten carbide coating has stronger thermal stability and higher resistance to high temperatures. If the first portion 3201 is located near the crucible assembly, that is, close to the solution contained within the crucible assembly, the temperature of the first portion 3201 will be higher than the temperature of the second portion 3202. Therefore, by adopting a coating method in which the tungsten carbide coating is applied to the first portion 3201 and the pyrolysis carbon coating is applied to the second portion 3202, it is possible to reduce costs while providing an excellent sealing and protective function.

[0067] To facilitate coating and simplify the process, the first portion 3201 and the second portion 3202 of the flow guide cylinder 3 have a stepped structure in the axial direction.

[0068] Exemplary, the stepped structure is formed by the second portion 3202 being recessed along the radial direction of the flow guide tube 3 in a direction away from the crystal rod pulling region.

[0069] In an exemplary embodiment, the flow guide tube 3 is made of a carbon fiber composite material, the direction of extension of the carbon fiber composite material bundles in the main body 31 is parallel to the axial direction of the flow guide tube 3 in order to enhance the heat insulation effect, and the direction of extension of the carbon fiber composite material bundles in the extension portion 32 is parallel to the radial direction of the flow guide tube 3 in order to enhance the heat conduction effect.

[0070] In an exemplary embodiment, the outer surface of the flow guide tube 3 is provided with a sealing coating.

[0071] By providing a sealing coating, a sealing and protective function is achieved, preventing contamination by dust falling from the surface of the flow guide tube 3.

[0072] In an exemplary embodiment, the sealing coating located on the outer surface of the main body 31 is a tungsten carbide coating, the sealing coating located on the bottom surface of the extension 32 near the crucible assembly is a tungsten carbide coating, and the sealing coating located on surfaces other than the bottom surface of the extension 32 is a pyrolysis carbon coating.

[0073] Compared to the tungsten carbide coating, the pyrolysis carbon coating is less expensive, while the tungsten carbide coating has stronger thermal stability and higher resistance to high temperatures. Therefore, the pyrolysis carbon coating is provided in the high-temperature region of the flow guide tube 3, and the tungsten carbide coating is provided in the low-temperature region of the flow guide tube 3.

[0074] In an exemplary embodiment, the inner surface of the water-cooling jacket 1 is provided with a heat-absorbing coating. This enhances the cooling effect.

[0075] In an exemplary embodiment, the thickness of the heat-absorbing coating gradually decreases along the axial direction of the water-cooling jacket 1, away from the crucible assembly. This helps to regulate the temperature gradient in the axial direction of the formed crystal rod.

[0076] There are two particularly important points during the growth process of a crystal rod. The first is the state of the three phases of solid, liquid, and gas. During the isodiametric growth stage of the crystal rod, the growth state at this point must be particularly stable. At the same time, the temperature difference along the axial direction at this point determines the initial vacancy concentration and initial interstitial atom concentration within the crystal rod, which greatly influences the initial defect type of the crystal rod. The second is the thermal history that the crystal rod undergoes after it is drawn. This thermal history is closely related to the hot zone structure and temperature field at the upper end. In particular, for the drawing of crystal rods with BMD concentration requirements, it is necessary to perform crystal pulling with nitrogen doping. Nitrogen doping offers two major advantages. First, nitrogen provides the nuclei necessary for heterogeneous nucleation of oxygen precipitates, reducing the nucleation energy required for oxygen precipitate formation and promoting BMD generation. Second, nitrogen alters the defect distribution in the axial direction of the crystal rod. If the nitrogen concentration is constant, it can increase the defect-free region (margin region) in the axial direction of the crystal rod. According to V / G theory, this helps to increase the adjustment threshold for the pulling rate. The crystal pulling apparatus according to this disclosure can significantly alter the temperature gradient distribution in the high-temperature region of the crystal rod (the region below water-cooled jacket 1).

[0077] In order to extract crystal rods having a high concentration of BMD, the embodiments of the present application are a method for growing crystal rods, The process involves placing nitrogen-doped polysilicon material into a quartz crucible, The process involves sealing the furnace body of the single-crystal furnace, evacuating it, and then flowing in an inert gas. Heating to melt the polysilicon material, The present invention further provides a method for growing crystal rods, which includes lowering multiple seed crystals into corresponding sub-containment chambers and carrying out growth processes including fusion, shoulder formation, shoulder dislocation, and isodiameter growth.

[0078] Doping polysilicon materials with nitrogen provides the nuclei necessary for heterogeneous nucleation of oxygen precipitates, reducing the nucleation energy required for oxygen precipitate formation and promoting BMD generation. Furthermore, nitrogen alters the defect distribution in the axial direction of the crystal rod. If nitrogen is present at a constant concentration, it can increase the defect-free region (margin region) in the axial direction of the crystal rod. According to V / G theory, this helps to increase the adjustment threshold for the pulling rate.

[0079] Understandably, the embodiments described above are merely exemplary embodiments adopted to illustrate the principles of the present application, and the application is not limited thereto. Various modifications and improvements are possible for those skilled in the art without departing from the spirit and intent of the present application, and these modifications and improvements are also covered within the scope of the present application.

Claims

1. A single crystal furnace comprising a furnace body and a crucible assembly located within the furnace body, wherein a flow guide tube is provided above the crucible assembly, a crystal rod pulling region is provided inside the flow guide tube, and a water cooling jacket is provided between the crystal rod pulling region and the flow guide tube. A single crystal furnace in which a temperature control cylinder is provided between the water-cooling jacket and the flow guide cylinder in the axial direction of the water-cooling jacket.

2. In the axial direction of the water-cooling jacket, the temperature control cylinder has a first end far from the crucible assembly and a second end close to the crucible assembly. The single crystal furnace according to claim 1, wherein the first end is connected to the water-cooling jacket and a gap is provided between the second end and the flow guide tube, or a gap is provided between the first end and the water-cooling jacket and the second end is connected to the flow guide tube.

3. A gap is provided between the first end and the water-cooling jacket, the second end is connected to the flow guide cylinder, and in the radial direction of the water-cooling jacket, the distance between the temperature control cylinder and the water-cooling jacket is 2 mm to 5 mm, as described in claim 2.

4. The single crystal furnace according to claim 2, wherein the first end has a first region, and the orthographic projection of the first region on the water-cooled jacket is located within the water-cooled jacket.

5. The single crystal furnace according to claim 4, wherein an uneven structure is provided on the surface in the first region that is close to the water-cooling jacket.

6. The uneven structure includes a plurality of protrusions and recesses that extend along the circumferential direction of the temperature control cylinder, thereby forming a wave-like structure, as described in claim 5.

7. The single crystal furnace according to claim 3, wherein the temperature control cylinder is circumferentially provided between the water cooling jacket and the flow guide cylinder in the radial direction of the water cooling jacket.

8. The single crystal furnace according to claim 3, wherein, in the axial direction of the water-cooling jacket, the thickness of the side wall of the temperature control cylinder gradually decreases along the direction away from the crucible assembly.

9. The flow guide tube includes a main body and an extended portion, the extended portion being formed by bending and extending the end of the flow guide tube closest to the crucible assembly so as to approach the crystal rod pulling region. The extending portion has a first surface far from the crucible assembly, and the first surface is provided with a groove for connecting to the temperature control cylinder, and in the radial direction of the water cooling jacket, the groove has a first side wall far from the crystal rod pulling region, and the first side wall is provided with a locking groove extending along the radial direction of the water cooling jacket. The single crystal furnace according to claim 3, wherein the second end of the temperature control cylinder has a stopper that engages with the locking groove.

10. The single crystal furnace according to claim 9, wherein in the radial direction of the water-cooled jacket, the groove has a second side wall close to the crystal rod pulling region, and in the axial direction of the water-cooled jacket, the second side wall extends away from the crucible assembly to form a blocking wall.

11. The single crystal furnace according to claim 9, wherein the flow guide tube is made of a carbon fiber composite material, the direction of extension of the bundle of carbon fiber composite material threads in the main body is parallel to the axial direction of the flow guide tube, and the direction of extension of the bundle of carbon fiber composite material threads in the extension portion is parallel to the radial direction of the flow guide tube.

12. The single crystal furnace according to claim 9, wherein a sealing coating is provided on the outer surface of the flow guide tube.

13. The single crystal furnace according to claim 12, wherein the sealing coating located on the outer surface of the main body is a tungsten carbide coating, the sealing coating located on the bottom surface of the extended portion near the crucible assembly is a tungsten carbide coating, and the sealing coating located on surfaces other than the bottom surface of the extended portion is a pyrolysis carbon coating.

14. The single crystal furnace according to claim 1, wherein a heat-absorbing coating is provided on the inner surface of the water-cooling jacket.

15. The single crystal furnace according to claim 14, wherein, in the axial direction of the water-cooling jacket, the thickness of the heat-absorbing coating gradually decreases along the direction away from the crucible assembly.

16. A method for growing crystal rods, which is implemented by employing a single crystal furnace according to any one of claims 1 to 15, the method being The process involves placing nitrogen-doped polysilicon material into a quartz crucible, The process involves sealing the furnace body of the single-crystal furnace, evacuating it, and then flowing in an inert gas. Heating to melt the polysilicon material, A method for growing crystal rods, comprising lowering multiple seed crystals into corresponding sub-containment chambers and performing a growth process including fusion, shoulder formation, shoulder dislocation, and isodiameter growth.

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