Single crystal furnace, single crystal silicon rod drawing method and silicon wafer

Abstract

The invention relates to a single crystal furnace, a single crystal silicon rod drawing method and a silicon wafer. The single crystal furnace comprises a main furnace body; the crucible is arranged in the main furnace body; the heat exchange assembly comprises a heat exchange screen and a first airflow channel, the heat exchange screen and the inner wall of the main furnace body surround to form a main crystal pulling channel communicated with the crucible, a liquid cooling channel surrounding the main crystal pulling channel is formed in the heat exchange screen, and a liquid cooling medium circulates in the liquid cooling channel; the bottom of the heat exchange screen is provided with a material passing port for a silicon single crystal rod to pass through, the main crystal pulling channel is communicated with the crucible through the material passing port, the first gas flow channel extends to the bottom of the heat exchange screen from the top of the heat exchange screen and is communicated with the material passing port, and first inert gas flows in the first gas flow channel. According to the single crystal furnace, the equal-diameter pulling speed of the single crystal silicon rod can be increased, the yield of the single crystal silicon rod can be increased, meanwhile, the single crystal silicon rod can be efficiently purified and protected, and the quality of the single crystal silicon rod is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic processing, in particular to a single crystal furnace, a single crystal silicon rod drawing method and a silicon wafer. BACKGROUND

[0002] In recent years, photovoltaic power generation, as a kind of green energy and a major energy for human sustainable development, has been increasingly valued and developed by countries around the world. Single crystal silicon wafer, as a kind of basic material for photovoltaic power generation, has a wide market demand. Single crystal silicon wafer is usually obtained by slicing processing of a single crystal silicon rod, and the single crystal silicon rod can be grown and drawn from silicon material.

[0003] With the integration of the semiconductor industry, there is an increasing demand for large-diameter and high-quality Czochralski silicon, and therefore, the demand for improving the performance and quality of crystalline silicon is increasingly prominent.

[0004] In related technologies, during the drawing of a single crystal silicon rod, an inner container flow channel is usually arranged on a heat shield, cooling water flows in the inner container flow channel, and the heat released during the growth of the single crystal silicon rod is transferred to the cooling water in the inner container flow channel through convection and radiation heat exchange, so as to improve the constant diameter drawing speed and the quality of the single crystal silicon rod. However, the above-mentioned method of taking away the heat of the single crystal silicon rod by the cooling water in the inner container flow channel of the heat shield has low efficiency, and the effect of improving the constant diameter drawing speed and the quality of the single crystal silicon rod is limited. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a single crystal furnace, a single crystal silicon rod drawing method and a silicon wafer, which can improve the constant diameter drawing speed of the single crystal silicon rod, facilitate the improvement of the yield of the single crystal silicon rod, and efficiently purify and protect the single crystal silicon rod, thereby effectively improving the quality of the single crystal silicon rod.

[0006] In a first aspect, the present application provides a single crystal furnace, comprising:

[0007] a main furnace body;

[0008] a crucible arranged in the main furnace body;

[0009] a heat exchange assembly comprising a heat exchange shield and a first gas flow channel, the heat exchange shield and the inner wall of the main furnace body surround a main crystal pulling channel in communication with the crucible, and the heat exchange shield has a liquid cooling channel surrounding the main crystal pulling channel formed therein;

[0010] a material passing opening is arranged at the bottom of the heat exchange shield, the main crystal pulling channel is in communication with the crucible through the material passing opening, the first gas flow channel extends from the top of the heat exchange shield to the bottom of the heat exchange shield and is in communication with the material passing opening, and the first gas flow channel flows a first inert gas.

[0011] The single crystal furnace according to the first aspect of the present application has at least the following beneficial effects:

[0012] The single crystal furnace of the present application has the following beneficial effects:

[0013] In this way, the liquid cooling medium in the liquid cooling channel cooperates with the first inert gas in the first gas flow channel to conduct away the latent heat of crystallization of the single crystal silicon rod, so that a relatively stable longitudinal temperature gradient is formed in the liquid surface area of the crucible, the diameter drawing speed of the single crystal silicon rod is improved, the yield of the single crystal silicon rod is improved, and the first inert gas directly blows onto the liquid surface area of the crucible and the surface of the single crystal silicon rod, efficiently carrying out the impurities such as oxides out of the main furnace body, realizing purification and protection of the single crystal silicon rod, and improving the quality of the single crystal silicon rod.

[0014] In some embodiments, the outlet of the first gas flow channel is inclined towards the direction close to the crucible.

[0015] In some embodiments, the first gas flow channel has a plurality of first gas flow channels, and the plurality of first gas flow channels are distributed along the axial direction of the main crystal drawing channel, and the outlets of the plurality of first gas flow channels are distributed along the circumferential direction of the material outlet.

[0016] In some embodiments, the single crystal furnace further comprises a secondary furnace body connected to the main furnace body, and a secondary crystal drawing channel is formed in the secondary furnace body and communicates with the main crystal drawing channel, the inner diameter of the secondary crystal drawing channel is smaller than the inner diameter of the main crystal drawing channel, and the secondary crystal drawing channel, the main crystal drawing channel and the crucible are coaxially communicated.

[0017] The heat exchange assembly further comprises a second gas flow channel and a third gas flow channel, the second gas flow channel is connected to the communication between the main crystal drawing channel and the secondary crystal drawing channel, and is used for introducing a second inert gas into the main crystal drawing channel, the third gas flow channel is connected to one end of the secondary crystal drawing channel away from the main crystal drawing channel, and is used for introducing a third inert gas into the secondary crystal drawing channel, the second inert gas and the third inert gas are the same kind of gas, and the second inert gas and the first inert gas are different kinds of gas.

[0018] In some embodiments, the first inert gas is helium, the second inert gas and the third inert gas are both argon, and the liquid cooling medium is cooling water.

[0019] In some embodiments, an exhaust passage is formed in the main furnace body and communicates with the opening of the crucible, for exhausting the first inert gas, the second inert gas and the third inert gas in the crucible out of the main furnace body.

[0020] In a second aspect, the present application provides a single crystal silicon rod drawing method, comprising:

[0021] The single crystal silicon rod drawing method is implemented by using the single crystal furnace described above, and comprises a melt stage, a temperature adjusting stage, a seeding stage, a shoulder forming stage and a constant diameter stage performed in sequence.

[0022] In the melt stage, a first flow rate of argon is introduced into the secondary crystal pulling passage, in the temperature adjusting stage, the seeding stage and the shoulder forming stage, a second flow rate of argon is introduced into the secondary crystal pulling passage, and the first flow rate is greater than the second flow rate.

[0023] In the melt stage, the temperature adjusting stage, the seeding stage and the shoulder forming stage, a third flow rate of argon is introduced into the primary crystal pulling passage, and the liquid cooling medium is circulated in the liquid cooling passage.

[0024] In the temperature adjusting stage and the seeding stage, a fourth flow rate of helium is introduced into the first gas flow passage, and in the shoulder forming stage, a fifth flow rate of helium is introduced into the first gas flow passage, and the fifth flow rate is greater than the fourth flow rate.

[0025] In the constant diameter stage, a sixth flow rate of argon is introduced into the secondary crystal pulling passage, a seventh flow rate of argon is introduced into the primary crystal pulling passage, and an eighth flow rate of helium is introduced into the first gas flow passage, the sixth flow rate is less than or equal to the second flow rate, the seventh flow rate is less than or equal to the third flow rate, and the eighth flow rate is less than or equal to the fifth flow rate.

[0026] According to the single crystal silicon rod drawing method of the second aspect of the present application, at least the following beneficial effects are achieved:

[0027] The single crystal silicon rod drawing method of the application, the argon gas of the main crystal drawing channel and the auxiliary crystal drawing channel covers the upper region of the equal-diameter growth of the single crystal silicon rod, absorbs the latent heat of crystallization of the single crystal silicon rod, and at the same time, removes the impurities such as oxides on the surface of the single crystal silicon rod. The argon gas flowing out of the material outlet at the bottom of the heat exchange screen of the first gas flow channel mainly flows along the lower surface of the single crystal silicon rod and the surface region of the silicon liquid, covers the core heat zone of the single crystal silicon rod, enables the helium gas to quickly guide out the latent heat of crystallization generated in the core heat zone of the single crystal silicon rod, forms a relatively stable longitudinal temperature gradient in the liquid surface region of the crucible, improves the equal-diameter drawing speed of the single crystal silicon rod, is beneficial to improving the yield of the single crystal silicon rod, and at the same time, plays a role in removing the impurities such as oxides in the core heat zone of the single crystal silicon rod, realizes the purification and protection of the single crystal silicon rod, and improves the quality of the single crystal silicon rod.

[0028] In some embodiments, the equal-diameter stage includes a first segment and a second segment, the axial length of the single crystal silicon rod in the first segment and the second segment is 0-2000mm and 2000mm-5000mm respectively; from the first segment to the second segment, the sixth flow, the seventh flow and the eighth flow all have a decreasing trend.

[0029] In some embodiments, during the melt stage, the temperature adjusting stage, the seeding stage, the shoulder stage and the equal-diameter stage, the crucible rotates around its own axis and the rotation speed has an increasing trend; during the temperature adjusting stage, the seeding stage, the shoulder stage and the equal-diameter stage, the single crystal silicon rod rotates around its own axis and the rotation speed has a decreasing trend.

[0030] In some embodiments, during the melt stage, the temperature adjusting stage, the seeding stage, the shoulder stage and the equal-diameter stage, the pressure in the main furnace body has a decreasing trend.

[0031] In a third aspect, the application provides a silicon wafer, which is cut from the single crystal silicon rod prepared by the single crystal silicon rod drawing method described above.

[0032] The above description is only a summary of the technical solutions of the application. In order to enable the technical means of the application to be more clearly understood, and to be implemented according to the content of the description, and in order to enable the above and other purposes, characteristics and advantages of the application to be more apparent and easy to understand, the following specific embodiments of the application are described. BRIEF DESCRIPTION OF DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not meant to limit the present application. Moreover, the same reference numerals in all the drawings represent the same or similar elements. In the drawings:

[0034] Figure 1 Figure 1 is a structural schematic diagram of a single crystal furnace according to an embodiment of the present application.

[0035] Figure 2 Figure 2 is a partial structural schematic diagram of a single crystal furnace according to an embodiment of the present application.

[0036] Figure 3 Figure 3 is a flow schematic diagram of a single crystal silicon rod drawing method according to an embodiment of the present application.

[0037] Figure 1 is a structural schematic diagram of a single crystal furnace according to an embodiment of the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0039] If not specifically stated, all the embodiments and optional embodiments of the present application can be combined to form new technical solutions.

[0040] If not specifically stated, all the technical features and optional technical features of the present application can be combined to form new technical solutions.

[0041] If not specifically stated, all the steps of the present application can be performed in sequence or randomly, and the preferred is performed in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0042] If not specifically stated, the "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, the "comprise" and "include" can mean that other components not listed can also be included, or only the listed components can be included.

[0043] If not specifically stated otherwise, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following satisfy the condition "A or B": A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0044] In the description of the embodiments of the present application, the term "plurality" refers to two or more (including two), and similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0045] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and are not intended to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0046] In the description of the embodiments of the present application, unless otherwise specifically stated and limited, the technical terms "mounting", "connection", "connection", "fixing", and the like should be understood broadly, for example, can be fixed connection, or can be detachable connection, or can be integrated; can be mechanical connection, or can be electrical connection; can be directly connected, or can be indirectly connected through an intermediate medium; can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0047] In the related art, during the pulling of a single crystal silicon rod, an inner container flow channel is often arranged on a heat shield, cooling water flows in the inner container flow channel, and the heat released during the growth of the single crystal silicon rod is transferred to the cooling water in the inner container flow channel through convection heat exchange and radiation heat exchange, so as to improve the constant diameter pulling speed and the quality of the single crystal silicon rod. However, the above method of taking away the heat of the single crystal silicon rod by the cooling water in the heat shield inner container flow channel has low efficiency, and the effect of improving the constant diameter pulling speed and the quality of the single crystal silicon rod is limited.

[0048] Based on this, one or more embodiments of the present application provide a single crystal furnace, referring to Figure 1 and Figure 2 The single crystal furnace includes a main furnace body 100, a crucible 200, and a heat exchange assembly 300.

[0049] The crucible 200 is arranged in the main furnace body 100. The heat exchange assembly 300 comprises a heat exchange screen 310 and a first gas flow channel 320. The heat exchange screen 310 and the inner wall of the main furnace body 100 surround a main crystal pulling channel 10 which is in communication with the crucible 200. The heat exchange screen 310 has a liquid cooling channel 311 formed therein and surrounding the main crystal pulling channel 10. The liquid cooling channel 311 flows a liquid cooling medium.

[0050] The bottom of the heat exchange screen 310 is provided with a material passing opening 312 through which a single crystal silicon rod (not shown in the figure) passes. The main crystal pulling channel 10 is in communication with the crucible 200 through the material passing opening 312. The first gas flow channel 320 extends from the top of the heat exchange screen 310 to the bottom of the heat exchange screen 310 and is in communication with the material passing opening 312. The first gas flow channel 320 flows a first inert gas.

[0051] It should be noted that, in the present application, the main furnace body 100 refers to the core bearing and sealing framework structure of the single crystal furnace, which is used to provide accommodation space and stable support for the crucible 200, the heat exchange assembly 300 and other components. The main furnace body 100 can be a cylindrical body, a square column body, a multi-prism body or the like, and the specific structure is not limited.

[0052] In the present application, the crucible 200 refers to a component for bearing the silicon melting and the growth of a single crystal silicon rod (not shown in the figure). The crucible 200 is arranged in the lower space of the main furnace body 100. The top of the crucible 200 is open, which facilitates the addition of silicon material and provides a clearance for the upward growth of the single crystal silicon rod.

[0053] The crucible 200 can comprise an inner layer quartz crucible and an outer layer heat preservation assembly which are nested with each other. The inner layer quartz crucible is made of high-purity quartz material. The inner wall of the inner layer quartz crucible is polished to reduce impurity residues. The outer layer heat preservation layer can be a cooperating structure of a graphite heat preservation sleeve and a graphite support seat. The graphite heat preservation sleeve closely adheres to the outer wall of the inner layer quartz crucible and plays a heat preservation and impact protection role. The bottom of the crucible 200 is connected to a rotating mechanism through a corresponding connecting seat, so that the crucible 200 can be driven by the rotating mechanism to rotate around its own axis. Through the self-rotation of the crucible 200, the silicon liquid melted in the crucible 200 is driven to flow, thereby achieving sufficient stirring of the silicon liquid and promoting the growth of the single crystal silicon rod.

[0054] The single crystal furnace further comprises a heating assembly (not shown in the figure). The heating assembly is arranged in the main furnace body 100. The heating assembly is used to heat the silicon material in the crucible 200 into silicon liquid, so as to grow a single crystal silicon rod extending along the main crystal pulling channel 10 from the silicon liquid. The heating assembly comprises a heater arranged around or attached to the outer wall of the crucible 200. The heater can be a graphite heating body or the like.

[0055] In the present application, the heat exchange assembly 300 refers to a heat exchange component which is adapted to the internal space of the main furnace body 100 and adjusts the internal thermal field of the main furnace body 100.

[0056] In the heat exchange assembly 300, the heat exchange screen 310 is configured as a cylindrical or conical structure. Referring to Figure 1 In some embodiments, the heat exchange screen 310 is configured as an inverted conical structure, and the upper and lower ends of the heat exchange screen 310 are open. The lower end opening can be understood as a material passing opening 312 for the single crystal silicon rod to pass through, and the material passing opening 312 is close to the opening of the crucible 200, so that the material passing opening 312 is close to the surface of the silicon liquid of the crucible 200. It can be understood that the main crystal pulling channel 10, the material passing opening 312 and the crucible 200 are coaxially communicated, and the material passing opening 312 is kept a certain distance from the liquid surface of the crucible 200 to avoid direct contact between the silicon liquid and the heat exchange screen 310.

[0057] The heat exchange screen 310 can be fixed to the top or side wall of the main furnace body 100 through a flange, so that the inner wall of the heat exchange screen 310 and part of the inner wall of the main furnace body 100 form the main crystal pulling channel 10 around the heat exchange screen 310. The main crystal pulling channel 10 is communicated with the crucible 200 through the material passing opening 312 at the lower end of the heat exchange screen 310. A hollow cavity consistent with the extension track of the heat exchange screen 310 is formed in the heat exchange screen 310, and the hollow cavity forms a liquid cooling channel 311. The liquid inlet 101 and the liquid outlet 102 are formed on the outer wall of the main furnace body 100, and the opposite ends of the liquid cooling channel 311 are communicated with the liquid inlet 101 and the liquid outlet 102, respectively. The external liquid supply device introduces liquid cooling medium into the liquid inlet 101, so that the liquid cooling medium flows along the liquid cooling channel 311. The liquid cooling medium absorbs the heat radiated by the single crystal silicon rod during crystallization in the main crystal pulling channel 10 during the circulation of the liquid cooling medium. The liquid cooling medium that absorbs heat finally flows out of the liquid outlet 102, so as to transfer the absorbed heat to the outside of the main furnace body 100. The liquid cooling channel 311 can be configured as a spiral channel to improve the heat exchange efficiency. The liquid cooling medium can be cooling water, ethylene glycol solution, propylene glycol solution, etc.

[0058] In the present application, the first gas flow channel 320 can also be formed inside the heat exchange screen 310, such as a hollow channel formed inside the heat exchange screen 310, which extends from the top of the heat exchange screen 310 to the material passing opening 312 at the bottom of the heat exchange screen 310. The hollow channel constitutes the first gas flow channel 320, so that the first inert gas flowing out of the first gas flow channel 320 can flow to the liquid surface of the crucible 200 through the material passing opening 312. In this embodiment, the first gas flow channel 320 and the liquid cooling channel 311 are distributed in the outward direction of the radial direction of the heat exchange screen 310 in sequence, and are independent of each other and not communicated with each other.

[0059] Alternatively, in other embodiments, the first gas flow channel 320 is a pipe structure fixedly attached to the inner wall of the heat exchange screen 310, the first gas flow channel 320 extends from the top of the heat exchange screen 310 to the material outlet 312 at the bottom of the heat exchange screen 310, so that the first gas flow channel 320 is in communication with the material outlet 312, so that the first inert gas flowing out of the first gas flow channel 320 can flow to the crucible 200. The first gas flow channel 320 can have at least two, at least two first gas flow channels 320 are uniformly and spacedly distributed around the central axis of the heat exchange screen 310.

[0060] A plurality of gas inlets 103 are formed on the outer wall of the main furnace body 100, the gas inlets 103 are in communication with the inlets of the corresponding first gas flow channels 320, and the external gas supply device introduces the first inert gas into the gas inlets 103, so that the first inert gas flows along the first gas flow channels 320. The first inert gas can be one or more of helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), etc.

[0061] The single crystal furnace of the embodiment of the present application is provided with the liquid cooling channel 311 in the heat exchange screen 310 and the first gas flow channel 320 flowing the first inert gas, the liquid cooling medium circulating in the liquid cooling channel 311 quickly absorbs the latent heat of crystallization generated in the single crystal silicon rod growth process, and at the same time, the first inert gas flowing out of the material outlet 312 at the bottom of the heat exchange screen 310 in the first gas flow channel 320 can flow to the liquid surface of the crucible 200 in the single crystal silicon rod growth process, and flow close to the solid-liquid interface region of the necking-up and constant-diameter stages of the single crystal silicon rod growth. On the one hand, the first inert gas absorbs the latent heat of crystallization of the single crystal silicon rod by using the heat conductivity of the first inert gas, and on the other hand, the first inert gas can wrap the impurities such as oxides generated at the liquid surface, and the first inert gas carrying the impurities can be extracted out of the main furnace body 100 under the action of the negative pressure device (not shown in the figure) at the bottom of the main furnace body 100.

[0062] In this way, the liquid cooling medium in the liquid cooling channel 311 cooperates with the first inert gas of the first gas flow channel 320 to conduct the latent heat of crystallization of the single crystal silicon rod, so that a relatively stable longitudinal temperature gradient is formed in the liquid surface region of the crucible 200, the constant-diameter pulling speed of the single crystal silicon rod is improved, and the yield of the single crystal silicon rod is improved. At the same time, the first inert gas directly blows to the liquid surface region of the crucible 200 and the surface of the single crystal silicon rod, efficiently taking out the impurities such as oxides out of the main furnace body 100, realizing the purification and protection of the single crystal silicon rod, and improving the quality of the single crystal silicon rod.

[0063] In the present application, the following is an example of a single crystal furnace for drawing a single crystal silicon rod with a diameter of 285 mm, and the equal diameter drawing speed is recorded during the equal diameter stage of the single crystal silicon rod. The data related to Example 1 and Comparative Example 1 are shown in Table 1 below. In Example 1, during the equal diameter stage of the single crystal silicon rod, a liquid cooling medium is introduced into the liquid cooling channel 311, the liquid cooling medium is cooling water, the flow rate of the cooling water is 75-85 L / min, the water temperature is 25-35°C, a first inert gas is introduced into the first gas flow channel 320, the first inert gas is helium, and the flow rate of the helium is 20 lpm. In Comparative Example 1, during the equal diameter stage of the single crystal silicon rod, the only difference from Example 1 is that the first gas flow channel 320 is kept closed and no gas is introduced.

[0064] Table 1

[0065]

[0066] In Table 1, the equal diameter length refers to the axial drawing growth length of the single crystal silicon rod during the equal diameter stage, and the average drawing speed refers to the average equal diameter drawing speed during the growth of the single crystal silicon wafer from 0 mm to 5000 mm. As can be seen from Table 1 above, compared to only having a single water cooling on the inner wall of the heat exchange screen 310, by having water cooling on the inner wall of the heat exchange screen 310 and blowing a helium gas flow out of the material passage 312 at the bottom of the heat exchange screen 310, the equal diameter drawing speed of the single crystal silicon rod is increased by about 4 mm / h (millimeters per hour) (calculated based on the average equal diameter drawing speed), which is more than 6% and increases the yield by 4 kg / d (kilograms per day).

[0067] In some embodiments of the present application, the outlet of the first gas flow channel 320 is inclined towards the direction close to the crucible 200.

[0068] Specifically, the material passage 312 at the bottom of the heat exchange screen 310 is circular, square, etc., the outlet of the first gas flow channel 320 corresponds to a circular, square, etc., the axial direction of the outlet of the first gas flow channel 320 is inclined towards the direction close to the crucible 200, and the included angle between the axial direction of the outlet of the first gas flow channel 320 and the axial direction of the material passage 312 is 20-30°, which can be 20°, 25°, 28°, 30°, etc.

[0069] By setting the outlet of the first gas flow channel 320 to be inclined towards the direction close to the crucible 200, on the one hand, the direct vertical blowing of the first inert gas to the silicon liquid can be avoided to cause the solid-liquid interface to fluctuate, and on the other hand, when the first inert gas flows out of the outlet of the first gas flow channel 320, it can flow along the surface of the single crystal silicon rod at the overpass 312 to the direction close to the liquid surface of the crucible 200, to form a gas curtain close to the surface of the single crystal silicon rod and the silicon liquid, to more efficiently entrap the oxide and other impurities on the surface of the single crystal silicon rod and the liquid surface of the silicon liquid, to efficiently discharge the oxide and other impurities, to reduce the deposition of the oxide and other impurities on the liquid surface of the silicon liquid in the crucible 200 and other thermal fields, to reduce the pollution of the oxide and other impurities to the silicon liquid, to reduce the oxygen content to improve the quality of the single crystal silicon rod.

[0070] In some embodiments of the present application, referring to Figure 1 and Figure 2 , the first gas flow channel 320 has a plurality of first gas flow channels 320, which are distributed along the circumference of the overpass 312.

[0071] Specifically, the first gas flow channel 320 is configured as a pipe structure attached to the inner wall of the heat exchange screen 310, and the shape of the first gas flow channel 320 is matched with the shape of the inner wall of the heat exchange screen 310. For example, when the heat exchange screen 310 is in the shape of a cone, the first gas flow channel 320 is in the shape of an arc. The first gas flow channel 320 has a plurality of first gas flow channels 320, such as 3, 5, 6, etc., which are not limited in particular.

[0072] The plurality of first gas flow channels 320 are distributed along the circumference of the inner wall of the heat exchange screen 310, and adjacent two first gas flow channels 320 do not intersect or interfere with each other. The outlets of the plurality of first gas flow channels 320 are evenly distributed in the shape of a ring around the circumferential edge of the overpass 312.

[0073] The above structure can make the first inert gas in the plurality of first gas flow channels 320 spray out towards the overpass 312 to form a ring-shaped gas curtain wrapping the single crystal silicon rod growth area and the surface of the silicon liquid, to increase the contact area of the first inert gas with the surface of the single crystal silicon rod and the surface of the silicon liquid, to more comprehensively entrap the oxide and other impurities on the surface of the single crystal silicon rod and the liquid surface of the silicon liquid, to efficiently discharge the oxide and other impurities, to further reduce the deposition of the oxide and other impurities on the liquid surface of the silicon liquid in the crucible 200 and other thermal fields, to reduce the pollution of the oxide and other impurities to the silicon liquid, to reduce the oxygen content to improve the quality of the single crystal silicon rod.

[0074] In some embodiments of the present application, referring to Figure 1 and Figure 2The single crystal furnace further comprises a sub-furnace body 400 connected to the main furnace body 100, a sub-crystal pulling channel 20 is formed in the sub-furnace body 400 and communicates with the main crystal pulling channel 10, the inner diameter of the sub-crystal pulling channel 20 is smaller than that of the main crystal pulling channel 10, and the sub-crystal pulling channel 20, the main crystal pulling channel 10 and the crucible 200 coaxially communicate.

[0075] The heat exchange assembly 300 further comprises a second gas flow channel 330 and a third gas flow channel 340, the second gas flow channel 330 is connected to the communication position between the main crystal pulling channel 10 and the sub-crystal pulling channel 20, and is used for introducing the second inert gas into the main crystal pulling channel 10, the third gas flow channel 340 is connected to the end of the sub-crystal pulling channel 20 away from the main crystal pulling channel 10, and is used for introducing the third inert gas into the sub-crystal pulling channel 20, the second inert gas and the third inert gas are the same kind of gas, and the second inert gas and the first inert gas are different kinds of gas.

[0076] Specifically, the bottom of the sub-furnace body 400 is sealingly connected to the top of the main furnace body 100 through a flange, so that the sub-crystal pulling channel 20 in the sub-furnace body 400 communicates with the main crystal pulling channel 10 in the main furnace body 100. The sub-furnace body 400 can be understood as an extension position of the main furnace body 100 in the axial direction, which is used to extend the axial length of the single crystal furnace for growing a single crystal silicon rod.

[0077] The top of the sub-furnace body 400 can be provided with a pulling mechanism (not shown in the figure), and the driving end of the pulling mechanism is connected to the seed crystal in the crucible 200, so as to drive the seed crystal to move along the main crystal pulling channel 10 and the sub-crystal pulling channel 20 in turn to perform the crystal pulling operation. The pulling mechanism can be a cooperation structure of a pulling head and a pulling rope.

[0078] The communication position between the main crystal pulling channel 10 and the sub-crystal pulling channel 20 can also be understood as the joint end of the main furnace body 100 and the sub-furnace body 400. The second gas flow channel 330 can be arranged on the outer wall of the bottom of the sub-furnace body 400 or the top of the main furnace body 100, and the second gas flow channel 330 can be a pipeline welded or connected to the outer wall of the bottom of the sub-furnace body 400 or the top of the main furnace body 100. The second gas flow channel 330 is connected to an external gas source, so that the external gas source sends the second inert gas to the main crystal pulling channel 10 through the second gas flow channel 330.

[0079] The second gas flow channel 330 can be arranged in multiple, and the outlet ends of the multiple second gas flow channels 330 are uniformly distributed along a ring at the communication position between the main crystal pulling channel 10 and the sub-crystal pulling channel 20. Moreover, the outlet end of each second gas flow channel 330 can be arranged obliquely towards the main crystal pulling channel 10.

[0080] The end of the secondary crystal pulling channel 20 away from the main crystal pulling channel 10 can be understood as the top end of the secondary crystal pulling channel 20, that is, the non-docking end of the secondary furnace body 400. Similarly, the third gas flow channel 340 can be arranged on the top outer wall of the secondary furnace body 400. The third gas flow channel 340 can be a pipe welded or connected by a flange on the top outer wall of the secondary furnace body 400. The third gas flow channel 340 is connected to an external gas source, so that the external gas source supplies the third inert gas to the secondary crystal pulling channel 20 through the third gas flow channel 340. The third gas flow channel 340 can be arranged in multiple, and the outlet ends of the multiple third gas flow channels 340 are uniformly distributed along a ring at the top end of the secondary crystal pulling channel 20. The outlet end of each third gas flow channel 340 can be arranged obliquely towards the secondary crystal pulling channel 20.

[0081] The first inert gas in the first gas flow channel 320 is helium, and the second inert gas in the second gas flow channel 330 and the third inert gas in the third gas flow channel 340 are both argon. The liquid cooling medium flowing in the liquid cooling channel 311 is cooling water.

[0082] In the above structure, during the axial growth of the single crystal silicon rod, the argon gas flowing out of the outlet of the first gas flow channel 320 flows to the silicon liquid surface of the crucible 200 through the material passage 312 at the bottom of the heat exchange screen 310. It can flow closely to the lower part of the single crystal silicon rod and the surface of the silicon liquid under the traction of the negative pressure device at the bottom of the main furnace body 100, absorb the latent heat of crystallization of the single crystal silicon rod, and at the same time carry the impurities such as oxides out of the main furnace body 100 along the exhaust channel 110 at the bottom of the main furnace body 100.

[0083] The argon gas of the second gas flow channel 330 is introduced into the main crystal pulling channel 10 from the communication between the main crystal pulling channel 10 and the secondary crystal pulling channel 20. Under the traction of the negative pressure device at the bottom of the main furnace body 100, part of the argon gas will flow along the inner wall of the main crystal pulling channel 10 to the bottom of the main furnace body 100. The annular gas flow formed thereby covers the upper region of the single crystal silicon rod in the diameter growth, and can also reduce the diffusion of hot gas in the main crystal pulling channel 10 to the secondary crystal pulling channel 20, and inhibit the upward escape of helium gas from the communication area between the material passage 312 of the heat exchange screen 310 and the crucible 200.

[0084] The argon gas of the third gas flow channel 340 is introduced into the secondary crystal pulling channel 20 from the top end of the secondary crystal pulling channel 20, and the argon gas is formed into a ring-shaped gas flow by the flow guiding effect of the secondary crystal pulling channel 20 with a small inner diameter and the traction of the negative pressure device at the bottom of the main furnace body 100, and flows downward along the inner wall of the secondary crystal pulling channel 20, and is combined with the argon gas introduced by the second gas flow channel 330 at the communication position between the main crystal pulling channel 10 and the secondary crystal pulling channel 20, and the ring-shaped gas flow formed by the two covers the upper region of the isodiametric growth and the pulling section of the single crystal silicon rod, absorbs the latent heat of crystallization of the single crystal silicon rod, and simultaneously cleans the impurities such as oxides on the surface of the single crystal silicon rod, and the ring-shaped gas flow flows along the inner wall of the main crystal pulling channel 10 to the discharge port 312, is supplemented to the helium gas flow, and is finally discharged to the outside of the main furnace body 100 along the exhaust channel 110 at the bottom of the main furnace body 100 together with the helium gas flow.

[0085] It should be noted that in the gas flow system formed by the argon gas flow discharged from the outlet of the first gas flow channel 320, the argon gas flow discharged from the outlet of the second gas flow channel 330 and the argon gas flow discharged from the outlet of the third gas flow channel 340, the helium gas flow discharged from the outlet of the first gas flow channel 320 mainly flows along the lower surface of the single crystal silicon rod and the surface region of the silicon liquid, covers the core heat area of the single crystal silicon rod, and uses the fact that the thermal conductivity of helium is more than six times the thermal conductivity of argon to quickly guide the latent heat of crystallization generated by the core heat area of the single crystal silicon rod to the helium, so that a relatively stable longitudinal temperature gradient is formed in the liquid surface region of the crucible 200, the isodiametric pulling speed of the single crystal silicon rod is improved, the yield of the single crystal silicon rod is improved, and the helium has a smaller density than the argon, and the helium has a stronger diffusion capacity, so that the helium can deeply remove the oxides and other impurities on the growth interface of the single crystal silicon rod and the liquid surface of the silicon liquid, the oxygen content is reduced to improve the quality of the single crystal silicon rod; the argon gas flow discharged from the outlet of the second gas flow channel 330 and the argon gas flow discharged from the outlet of the third gas flow channel 340 are combined at the communication position between the main crystal pulling channel 10 and the secondary crystal pulling channel 20 to form a gas flow that mainly covers the upper region of the isodiametric growth and the pulling section of the single crystal silicon rod, which not only plays a role in cleaning the oxides and other impurities on the corresponding parts of the single crystal silicon rod, but also has a downward flow trend that can inhibit the upward diffusion of the argon gas flow and improve the utilization efficiency of the argon gas flow.

[0086] In addition, during the flow of the argon gas flow and the helium gas flow, the heat exchange effect of the liquid cooling medium circulating in the liquid cooling channel 311 can stabilize the temperature of the inner wall of the heat exchange screen 310 and the inner wall of the main crystal pulling channel 10, reduce the probability of flow disorder in the main crystal pulling channel 10 and the secondary crystal pulling channel 20 above, improve the isodiametric pulling speed of the single crystal silicon rod, and improve the yield of the single crystal silicon rod.

[0087] In some embodiments of the present application, referring to Figure 1The main furnace body 100 is provided with an exhaust passage 110 which is in communication with the opening of the crucible 200 and is used to exhaust the first inert gas, the second inert gas and the third inert gas in the crucible 200 to the outside of the main furnace body 100.

[0088] Specifically, the exhaust passage 110 is formed by the inner wall of the main furnace body 100 and the outer wall of the crucible 200, so that the exhaust passage 110 is an annular passage surrounding the periphery of the crucible 200. Alternatively, the exhaust passage 110 is a pipeline arranged in the main furnace body 100, and the opposite ends of the exhaust passage 110 are in communication with the opening of the crucible 200 and a negative pressure device at the bottom of the main furnace body 100, respectively. The first inert gas, the second inert gas and the third inert gas in the crucible 200 are exhausted along the exhaust passage 110 by the negative pressure device, and the negative pressure device can be a vacuum pump.

[0089] It can be understood that the argon gas flow from the outlet of the first gas flow passage 320, the argon gas flow from the outlet of the second gas flow passage 330 and the argon gas flow from the outlet of the third gas flow passage 340 can all flow downward under the suction of the negative pressure device at the bottom of the main furnace body 100, and carry the latent heat of crystallization of the single crystal silicon rod and impurities such as oxides out of the single crystal furnace, so as to realize the purification and protection of the single crystal silicon rod and improve the quality of the single crystal silicon rod.

[0090] The single crystal furnace provided by the embodiment of the present application also provides a single crystal silicon rod drawing method. The single crystal silicon rod drawing method is implemented by using the single crystal furnace, and the single crystal silicon rod drawing method comprises a melt stage, a temperature adjustment stage, a seeding stage, a shoulder separation stage and an equal diameter stage which are sequentially performed. Figure 3 The single crystal silicon rod drawing method comprises the following steps:

[0091] In the melt stage, the first flow rate of argon is introduced into the auxiliary crystal pulling passage 20, and in the temperature adjustment stage, the seeding stage and the shoulder separation stage, the second flow rate of argon is introduced into the auxiliary crystal pulling passage 20, and the first flow rate is greater than the second flow rate.

[0092] In the melt stage, the temperature adjustment stage, the seeding stage and the shoulder separation stage, the third flow rate of argon is introduced into the main crystal pulling passage 10, and the liquid cooling medium is circulated in the liquid cooling passage 311.

[0093] In the temperature adjustment stage and the seeding stage, the fourth flow rate of helium is introduced into the first gas flow passage 320, and in the shoulder separation stage, the fifth flow rate of helium is introduced into the first gas flow passage 320, and the fifth flow rate is greater than the fourth flow rate.

[0094] In step S400, the sixth flow of argon is introduced into the secondary pulling channel 20, the seventh flow of argon is introduced into the primary pulling channel 10, and the eighth flow of helium is introduced into the first gas flow channel 320. The sixth flow is less than or equal to the second flow, the seventh flow is less than or equal to the third flow, and the eighth flow is less than or equal to the fifth flow.

[0095] In a specific arrangement, the first flow is 60-170 lpm, such as any one of 60 lpm, 70 lpm, 150 lpm, and 170 lpm. The second flow is 40-55 lpm, such as any one of 40 lpm, 50 lpm, and 55 lpm. The third flow is 50-60 lpm, such as any one of 50 lpm, 55 lpm, and 60 lpm. The fourth flow, the fifth flow, and the eighth flow are all 10-20 lpm, such as any one of 10 lpm, 15 lpm, and 20 lpm. The sixth flow and the seventh flow are both 20-60 lpm, such as any one of 20 lpm, 30 lpm, 50 lpm, and 60 lpm.

[0096] It should be noted that the specific values of the first flow, the second flow, the third flow, the fourth flow, the fifth flow, the sixth flow, the seventh flow, and the eighth flow can be set according to the actual single crystal furnace and the specifications of the single crystal silicon rod to be pulled, as long as the first flow is greater than the second flow, the fifth flow is greater than the fourth flow, the sixth flow is less than or equal to the second flow, the seventh flow is less than or equal to the third flow, and the eighth flow is less than or equal to the fifth flow, and the specific values are not limited.

[0097] The single crystal silicon rod pulling method described above, the silicon material in the single crystal furnace sequentially passes through the melting stage, the temperature adjusting stage, the seeding stage, the shoulder releasing stage, and the equal-diameter growth stage to obtain a single crystal silicon rod.

[0098] The single crystal silicon rod pulling method described above, in the melting stage, the temperature adjusting stage, the seeding stage, the shoulder releasing stage, and the equal-diameter growth stage, the primary pulling channel 10 and the secondary pulling channel 20 both introduce argon, and in the temperature adjusting stage, the seeding stage, the shoulder releasing stage, and the equal-diameter growth stage, the first gas flow channel 320 introduces helium. It should be noted that in the melting stage, the temperature adjusting stage, the seeding stage, the shoulder releasing stage, and the equal-diameter growth stage, the negative pressure device at the bottom of the primary furnace body 100 continuously operates to drive the argon gas flow and the helium gas flow to flow downward in a directional manner, carry the crystallization latent heat of the single crystal silicon rod and the oxides and other impurities out of the single crystal furnace, realize the purification and protection of the single crystal silicon rod, and improve the quality of the single crystal silicon rod.

[0099] The argon gas of the main crystal pulling channel 10 and the secondary crystal pulling channel 20 covers the upper region of the equal-diameter growth of the single crystal silicon rod, the pulling section, absorbs the latent heat of crystallization of the single crystal silicon rod, and at the same time, cleans the impurities such as oxides on the surface of the single crystal silicon rod. The argon gas flowing out of the material passage 312 at the bottom of the heat exchange screen 310 mainly flows along the lower surface of the single crystal silicon rod and the surface region of the silicon liquid in the first gas flow channel 320, covers the core heat zone of the single crystal silicon rod, enables the helium gas to quickly guide out the latent heat of crystallization generated in the core heat zone of the single crystal silicon rod, forms a relatively stable longitudinal temperature gradient in the liquid surface region of the crucible 200, improves the equal-diameter pulling speed of the single crystal silicon rod, is beneficial to improving the yield of the single crystal silicon rod, and at the same time, plays a role in cleaning the oxides and other impurities in the core heat zone of the single crystal silicon rod, realizes the purification and protection of the single crystal silicon rod, and improves the quality of the single crystal silicon rod.

[0100] In each stage, the argon gas flow introduced into the main crystal pulling channel 10 can be less than the argon gas flow of the secondary crystal pulling channel 20. In this way, the difference in the inner diameters of the main crystal pulling channel 10 and the secondary crystal pulling channel 20 can be adapted, the argon gas flow rate of the main crystal pulling channel 10 and the argon gas flow rate of the secondary crystal pulling channel 20 are relatively uniform, and when the argon gas of the main crystal pulling channel 10 and the argon gas of the secondary crystal pulling channel 20 converge at the communication between the main crystal pulling channel 10 and the secondary crystal pulling channel 20, the annular gas flow formed by the convergence can stably flow to the material passage 312 of the heat exchange screen 310, the probability of flow turbulence in the main crystal pulling channel 10 is reduced, and in the melting stage, a large amount of silicon oxide is generated on the surface of the silicon liquid. The annular gas flow formed by the convergence has a large flow rate and a relatively stable flow rate, can more quickly carry the silicon oxide and other impurities to the outside of the single crystal furnace, and is helpful to improving the quality of the single crystal silicon rod.

[0101] The single crystal silicon rod pulling method described above, for step S100, after the single crystal silicon rod enters the temperature adjusting stage after the melting stage, the argon gas flow introduced into the secondary crystal pulling channel 20 is reduced, and compared with the melting stage, the oxides and other impurities generated in the temperature adjusting stage, the seeding stage and the shoulder releasing stage are relatively reduced. Correspondingly, the argon gas flow introduced into the secondary crystal pulling channel 20 is reduced, the amount of argon gas used is reduced, at the same time, the temperature stability of the silicon liquid is required to be higher in the temperature adjusting stage, the seeding stage and the shoulder releasing stage, the argon gas flow introduced into the secondary crystal pulling channel 20 is kept unchanged, and is the second flow. The influence of the change of the gas flow on the temperature of the silicon liquid can be reduced.

[0102] The single crystal silicon rod drawing method described above, for step S200, in the melting stage, the temperature adjusting stage, the seeding stage and the shoulder forming stage, the third flow rate of argon is introduced into the main crystal drawing channel 10, and the liquid cooling medium is circulated in the liquid cooling channel 311. The third flow rate can be less than the second flow rate, which can be adapted to the difference in the inner diameters of the main crystal drawing channel 10 and the auxiliary crystal drawing channel 20, so that the argon flow rates of the main crystal drawing channel 10 and the auxiliary crystal drawing channel 20 are relatively uniform, and in the melting stage, the temperature adjusting stage, the seeding stage and the shoulder forming stage, the argon flow rate introduced into the main crystal drawing channel 10 remains unchanged, which is the third flow rate, and the influence of the change in the gas flow rate on the temperature of the silicon liquid can also be reduced.

[0103] The single crystal silicon rod drawing method described above, for step S300, in the temperature adjusting stage and the seeding stage, the fourth flow rate of helium is introduced into the first gas flow channel 320, so that the helium flowing out of the outlet of the first gas flow channel 320 flows to the silicon liquid surface of the crucible 200 through the material outlet 312 at the bottom of the heat exchange screen 310, which can flow closely to the lower part of the single crystal silicon rod and the silicon liquid surface under the traction of the negative pressure device at the bottom of the main furnace body 100, absorb the latent heat of crystallization of the single crystal silicon rod, and carry the impurities such as oxides out of the main furnace body 100 along the exhaust channel 110 at the bottom of the main furnace body 100.

[0104] Since the single crystal silicon rod enters the early stage of the constant diameter stage in the late stage of the shoulder forming stage, the diameter of the single crystal silicon rod has grown close to the target diameter, and the lateral growth gradually slows down. In the early stage of the constant diameter stage, the single crystal silicon rod begins to enter the longitudinal stable growth, and in this process, the latent heat of crystallization of the silicon liquid phase changing to solid phase will greatly increase. Based on this, after the single crystal silicon rod enters the shoulder forming stage after the seeding stage, the flow rate of helium introduced into the first gas flow channel 320 is appropriately increased from the fourth flow rate to the fifth flow rate, and the heat conduction efficiency of helium is much higher than that of argon. By increasing the flow rate of helium, a large amount of latent heat of the single crystal silicon rod head (the head of the constant diameter stage) and the solid-liquid interface can be quickly carried away by the helium flow, the single crystal silicon rod head and the solid-liquid interface can be quickly cooled, which is beneficial to the constant diameter crystallization growth of the single crystal silicon rod.

[0105] In the single crystal silicon rod drawing method, after the single crystal silicon rod enters the constant diameter stage, the silicon material in the crucible 200 becomes less, the single crystal silicon rod crystallizes faster, and the temperature needs to be supplemented to the solid-liquid interface. Therefore, after the single crystal silicon rod enters the constant diameter stage, the argon flow rate introduced into the secondary crystal drawing channel 20 is appropriately reduced from the second flow rate to a sixth flow rate, the argon flow rate introduced into the main crystal drawing channel 10 is appropriately reduced from the third flow rate to a seventh flow rate, and the helium flow rate introduced into the first gas flow channel 320 is appropriately reduced from the fifth flow rate to an eighth flow rate. In this way, the temperature of the solid-liquid interface can be relatively increased by reducing the cooling of the solid-liquid interface by the argon gas flow and the helium gas flow, so as to avoid the temperature of the solid-liquid interface from decreasing too fast, to form a relatively stable longitudinal temperature gradient in the solid-liquid interface region, to increase the constant diameter drawing speed of the single crystal silicon rod, and to facilitate the increase of the yield of the single crystal silicon rod.

[0106] In some embodiments of the present application, the constant diameter stage includes a first segment and a second segment, and the axial length of the single crystal silicon rod in the first segment and the second segment is 0-2000 mm and 2000 mm-5000 mm, respectively. From the first segment to the second segment, the sixth flow rate, the seventh flow rate, and the eighth flow rate all have a decreasing trend.

[0107] It should be noted that the decreasing trend of the sixth flow rate from the first segment to the second segment can be understood as decreasing the sixth flow rate in different segments of the constant diameter stage, or keeping the sixth flow rate unchanged in different segments of the constant diameter stage and then reducing it, or reducing the sixth flow rate in different segments of the constant diameter stage and then keeping it unchanged, and the specific manner is not limited. The same applies to the seventh flow rate and the eighth flow rate, which will not be described again.

[0108] After the single crystal silicon rod enters the constant diameter stage, the silicon material in the crucible 200 becomes less, the single crystal silicon rod crystallizes faster, and the temperature needs to be supplemented to the solid-liquid interface. Therefore, after the single crystal silicon rod enters the constant diameter stage, by setting the argon flow rate introduced into the secondary crystal drawing channel 20 to have a decreasing trend in the sequentially performed constant diameter segments, setting the argon flow rate introduced into the main crystal drawing channel 10 to have a decreasing trend in the sequentially performed constant diameter segments, and setting the helium flow rate introduced into the first gas flow channel 320 to have a decreasing trend in the sequentially performed constant diameter segments, the temperature of the solid-liquid interface can be relatively increased by reducing the cooling of the solid-liquid interface by the argon gas flow and the helium gas flow, so as to avoid the temperature of the solid-liquid interface from decreasing too fast, to form a relatively stable longitudinal temperature gradient in the solid-liquid interface region, to increase the constant diameter drawing speed of the single crystal silicon rod, and to facilitate the increase of the yield of the single crystal silicon rod.

[0109] In some embodiments of the present application, during the melt stage, the temperature adjusting stage, the seeding stage, the shoulder separation stage, and the constant diameter stage, the crucible 200 rotates around its own axis and the rotation speed has an increasing trend; during the temperature adjusting stage, the seeding stage, the shoulder separation stage, and the constant diameter stage, the single crystal silicon rod rotates around its own axis and the rotation speed has a decreasing trend.

[0110] It should be noted that the rotation of the crucible 200 around its own axis and the increasing trend of the rotation speed can be understood as that the rotation speed of the crucible 200 is increased in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, or is kept unchanged first and then increased in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, or is increased first and then kept unchanged in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, and the specific implementation is not limited.

[0111] Similarly, the rotation of the single crystal silicon rod around its own axis and the decreasing trend of the rotation speed can be understood as that the rotation speed of the single crystal silicon rod is decreased in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, or is kept unchanged first and then decreased in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, or is decreased first and then kept unchanged in the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage in sequence, and the specific implementation is not limited.

[0112] During the melt stage, the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage of the single crystal silicon rod in sequence, the rotation speed of the crucible 200 is set to have an increasing trend, which can fully stir the silicon liquid formed by melting, make the impurities in the silicon liquid more uniform, and increase the rotation speed of the crucible 200, which can reduce the temperature gradient of the internal thermal field of the crucible 200, increase the survival rate of the crystal pulling, because the uniformity of the internal thermal field of the crucible 200 is better, the convection phenomenon of the silicon liquid in the crucible 200 is weakened, and the impurities such as silicon oxide are not easy to gather at the growth surface of the single crystal silicon rod, thereby reducing the oxygen content in the single crystal silicon rod and improving the quality of the single crystal silicon rod.

[0113] Specifically, the rotation speed of the crucible 200 is 1-7 rpm (revolutions per minute), and specifically can be any one of 1 rpm, 2 rpm, 3 rpm and 7 rpm, the rotation speed of the single crystal silicon rod is 1-9 rpm, and specifically can be any one of 1 rpm, 2 rpm, 3 rpm, 7 rpm and 9 rpm, and the specific values of the rotation speed of the crucible 200 and the rotation speed of the single crystal silicon rod can be set according to the actual single crystal furnace and the specification of the single crystal silicon rod to be drawn.

[0114] In some embodiments of the present application, the pressure in the main furnace body 100 has a decreasing trend during the melt stage, the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage and the equal diameter stage.

[0115] It should be noted that in the single crystal furnace, the auxiliary furnace body 400 is sealed and connected with the top of the main furnace body 100 through a flange, so that the auxiliary crystal pulling channel 20 in the auxiliary furnace body 400 is in communication with the main crystal pulling channel 10 in the main furnace body 100, and the pressure in the main furnace body 100 is close to the pressure in the auxiliary furnace body 400, and there is no large pressure difference between the two. The pressure in the main furnace body 100 can be approximately equal to the pressure of the single crystal furnace.

[0116] During the melt stage, the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage, the pressure in the main furnace body 100 shows a decreasing trend, which can be understood as: the pressure in the main furnace body 100 decreases during the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage in turn, or remains unchanged before decreasing during the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage in turn, or decreases before remaining unchanged during the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage in turn, or decreases, remains unchanged and then decreases during the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage in turn, and the specific conditions are not limited.

[0117] During the melt stage, the temperature adjustment stage, the seed crystal stage, the shoulder stage and the equal diameter stage, by setting the pressure in the main furnace body 100 to show a decreasing trend, the pulling effect of the negative pressure device at the bottom of the main furnace body 100 can be matched, so that more impurities such as oxides can be carried by the argon gas flow and the helium gas flow to be discharged to the outside of the main furnace body 100 through the exhaust channel 110 at the bottom of the main furnace body 100, reducing the deposition of impurities such as oxides at the silicon liquid surface of the crucible 200 and other thermal fields, reducing the pollution of impurities such as oxides to the silicon liquid, and reducing the oxygen content to improve the quality of the single crystal silicon rod.

[0118] Specifically, the pressure in the main furnace body 100 is 5 torr-16 torr (pressure per millimeter of mercury), and specifically can be any one of 5 rpm, 6 rpm, 9 rpm and 16 rpm. The specific value of the pressure in the main furnace body 100 can be set according to the actual single crystal furnace and the specification of the single crystal silicon rod to be drawn.

[0119] In this application, the following is an example of a single crystal furnace for drawing a single crystal silicon rod with a diameter of 285 mm. The helium flow rate, argon flow rate, crucible rotation speed, single crystal silicon rod rotation speed, and single crystal furnace internal pressure of the single crystal silicon rod during the melt stage, temperature adjustment stage, seed crystal stage, shoulder stage and equal diameter stage are recorded to obtain Table 2 below. In this embodiment, the single crystal silicon rod is connected to the liquid cooling channel 311 during each growth stage, and the liquid cooling medium is cooling water with a flow rate of 80 L / min and a water temperature of 25°C.

[0120] Table 2

[0121]

[0122] Using the above process parameters, the minority carrier lifetime of the single crystal silicon rods of Example 2 and Comparative Example 2 at different segments of the constant diameter stage (directly reflecting the quality of the single crystal silicon rods) are shown in Table 3 below, wherein the only difference between Comparative Example 2 and Example 2 is that no gas is introduced into the main pulling channel and the first gas flow channel in Comparative Example 2, and the same amount of argon gas as in Example 2 is introduced into the secondary pulling channel, and the rest is the same as in Example 2.

[0123] Table 3

[0124]

[0125] As can be seen from Tables 2 and 3, the minority carrier lifetime of the single crystal silicon rods prepared by the single crystal silicon rod pulling method of the above examples is improved at each constant diameter segment, with an improvement of more than 11%, effectively improving the minority carrier lifetime of the single crystal silicon rods at different segments of the constant diameter stage, and improving the quality of the single crystal silicon rods. In addition, the present application also provides a silicon wafer, which is cut from the single crystal silicon rod prepared by the above single crystal silicon rod pulling method.

[0126] The silicon wafer of the present application has high quality because it is cut from the single crystal silicon rod prepared by the above single crystal silicon rod pulling method.

[0127] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict, they should be considered within the scope of the present application.

[0128] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be construed as limiting the scope of the patent application. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A single crystal furnace, characterized in that, include: main furnace body; The crucible is located inside the main furnace body; The heat exchange assembly includes a heat exchange screen and a first airflow channel. The heat exchange screen and the inner wall of the main furnace body surround each other to form a main crystal pulling channel that communicates with the crucible. A liquid cooling channel surrounding the main crystal pulling channel is formed inside the heat exchange screen. The heat exchange screen has a material inlet at its bottom, and the main crystal pulling channel is connected to the crucible through the material inlet. The first gas flow channel extends from the top of the heat exchange screen to the bottom of the heat exchange screen and is connected to the material inlet. The first gas flow channel carries a first inert gas.

2. The single crystal furnace according to claim 1, characterized in that, The outlet of the first airflow channel is inclined toward the crucible.

3. The single crystal furnace according to claim 1, characterized in that, The first airflow channel has multiple channels, which are distributed axially around the main crystal pulling channel, and the outlets of the multiple first airflow channels are distributed circumferentially along the material passage.

4. The single crystal furnace according to any one of claims 1-3, characterized in that, The single crystal furnace also includes a secondary furnace body connected to the main furnace body. A secondary crystal pulling channel is formed in the secondary furnace body and communicates with the main crystal pulling channel. The inner diameter of the secondary crystal pulling channel is smaller than the inner diameter of the main crystal pulling channel, and the secondary crystal pulling channel, the main crystal pulling channel, and the crucible are coaxially connected. The heat exchange assembly further includes a second airflow channel and a third airflow channel. The second airflow channel is connected to the connection between the main crystal pulling channel and the secondary crystal pulling channel, and is used to introduce a second inert gas into the main crystal pulling channel. The third airflow channel is connected to the end of the secondary crystal pulling channel away from the main crystal pulling channel, and is used to introduce a third inert gas into the secondary crystal pulling channel. The second inert gas and the third inert gas are the same type of gas, and the second inert gas and the first inert gas are different types of gas.

5. The single crystal furnace according to claim 4, characterized in that, The first inert gas is helium, the second inert gas and the third inert gas are both argon, and the liquid cooling medium in the liquid cooling channel is cooling water.

6. The single crystal furnace according to claim 4, characterized in that, An exhaust channel is formed inside the main furnace body, and the exhaust channel is connected to the opening of the crucible for discharging the first inert gas, the second inert gas and the third inert gas inside the crucible to the outside of the main furnace body.

7. A method for pulling single-crystal silicon rods, characterized in that, The single-crystal silicon rod pulling method is implemented using a single-crystal furnace as described in any one of claims 4-6, and the single-crystal silicon rod pulling method includes a melting stage, a temperature adjustment stage, a crystal pulling stage, a shoulder forming stage, and a constant diameter stage performed sequentially. During the melting stage, argon gas at a first flow rate is introduced into the secondary crystal pulling channel. During the temperature adjustment stage, the crystal pulling stage, and the shoulder formation stage, argon gas at a second flow rate is introduced into the secondary crystal pulling channel, wherein the first flow rate is greater than the second flow rate. During the melting stage, the temperature adjustment stage, the crystal pulling stage, and the shoulder formation stage, argon gas with a third flow rate is introduced into the main crystal pulling channel, and the liquid cooling medium is circulated in the liquid cooling channel. During the temperature control stage and the crystal-leading stage, a fourth flow rate of helium is introduced into the first gas flow channel. During the shoulder formation stage, a fifth flow rate of helium is introduced into the first gas flow channel, and the fifth flow rate is greater than the fourth flow rate. During the equal diameter stage, argon gas at a sixth flow rate is introduced into the secondary crystal pulling channel, argon gas at a seventh flow rate is introduced into the main crystal pulling channel, and helium gas at an eighth flow rate is introduced into the first gas flow channel. The sixth flow rate is less than or equal to the second flow rate, the seventh flow rate is less than or equal to the third flow rate, and the eighth flow rate is less than or equal to the fifth flow rate.

8. The method for pulling single-crystal silicon rods according to claim 7, characterized in that, The constant diameter stage includes a first segment and a second segment. The axial length of the monocrystalline silicon rod is 0-2000mm in the first segment and 2000mm-5000mm in the second segment. From the first segment to the second segment, the sixth flow rate, the seventh flow rate, and the eighth flow rate all show a decreasing trend.

9. The method for pulling single-crystal silicon rods according to claim 7, characterized in that, During the melting stage, the temperature adjustment stage, the crystal pulling stage, the shoulder forming stage, and the equal diameter stage, the crucible rotates around its own axis with an increasing rotational speed. During the temperature adjustment stage, the crystal pulling stage, the shoulder formation stage, and the constant diameter stage, the single crystal silicon rod rotates around its own axis with a decreasing rotational speed.

10. A silicon wafer, characterized in that, The silicon wafer is formed by cutting a single-crystal silicon rod obtained by the single-crystal silicon rod pulling method according to any one of claims 7 to 9.

Images