A crystal pulling method

Abstract

The present invention provides a crystal pulling method, which relates to the field of solar photovoltaic technology. The method comprises: heating the raw materials in the quartz crucible in the furnace body to form a melt; performing at least one impurity removal treatment on the melt; performing a low-pressure blowing treatment on the furnace body to discharge gas impurities from the furnace body; providing a pulling seed crystal, so that the pulling seed crystal pulls a single crystal from the melt. In the embodiment of the present invention, the melt is subjected to at least one impurity removal, and the furnace body is subjected to a low-pressure blowing treatment to discharge gas impurities from the furnace body, thereby greatly reducing the impurity content in the melt and the furnace body. Based on the pulling of the single crystal from the melt by the seed crystal, due to the low impurity content in the melt and the furnace body, it is easy to crystallize, the probability of broken edges is greatly reduced, etc., so that the yield of single crystal silicon is increased.

Description

Technical Field

[0001] The invention relates to the technical field of solar photovoltaic technology, and in particular to a crystal pulling method. Background Art

[0002] Single crystal silicon is the main raw material for making solar cells. The commonly used production process is the Czochralski method. The main process of the Czochralski method is: in a hot field, the raw material is melted to obtain a melt, the seed crystal is inserted into the melt, and the seed crystal is slowly lifted upward while rotating the seed crystal. After the processes of seeding, shoulder rotation, equal diameter, etc., a single crystal silicon rod is obtained.

[0003] At present, the demand for single crystal silicon is increasing, and the demand for raw materials is also increasing. However, the quality of the raw materials themselves, especially the purity, is also uneven. In this case, direct crystallization based on the melt makes crystallization difficult and the probability of edge breakage is high, resulting in a decrease in the yield of single crystal silicon rods. Summary of the invention

[0004] The present invention provides a crystal pulling method, which aims to improve the yield of single crystal silicon. The method comprises:

[0005] Heating the raw materials in the quartz crucible in the furnace body to form a melt;

[0006] Performing at least one impurity removal treatment on the melt;

[0007] Performing a low-pressure blowing treatment on the furnace body to discharge gas impurities from the furnace body;

[0008] A pulling seed crystal is provided, and the pulling seed crystal is used to pull a single crystal from the melt.

[0009] Optionally, the melt is subjected to at least one impurity removal treatment, comprising:

[0010] Providing a slag extraction seed crystal, so that the slag extraction seed crystal extracts a first unmelted material block from the melt; the first unmelted material block includes: a first impurity in the raw material;

[0011] A second unmelted material block is extracted from the melt; the second unmelted material block includes: a second impurity in the raw material.

[0012] Optionally, before providing the slag extraction seed crystal so that the slag extraction seed crystal extracts the first unmelted material block from the melt, the method further includes:

[0013] The size of the first unmelted material block is made to reach a first preset size range.

[0014] Optionally, providing a slag extraction seed crystal so that the slag extraction seed crystal extracts a first unmelted material block from the melt includes:

[0015] When the size of the first unmelted material block reaches a first preset size range, after providing the slag-lifting seed crystal, reducing the relative distance between the slag-lifting seed crystal and the quartz crucible, so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt;

[0016] Standing for a first preset time period to allow the first unmelted material block to adhere to the surface of the slag extraction seed crystal;

[0017] The relative distance between the slag-lifting seed crystal and the quartz crucible is increased so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt.

[0018] Optionally, after providing the slag-lifting seed crystal, reducing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt, comprising:

[0019] After providing the slag-extracting seed crystal, raising the quartz crucible;

[0020] Lowering the slag-lifting seed crystal so that the slag-lifting seed crystal contacts the first unmelted material block, and lowering the slag-lifting seed crystal at a preset speed so that the slag-lifting seed crystal is immersed in the melt; the preset speed is less than or equal to a set speed threshold;

[0021] The step of increasing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt comprises:

[0022] By raising the slag-lifting seed crystal, the relative distance between the slag-lifting seed crystal and the quartz crucible is increased.

[0023] Optionally, before extracting the second unmelted material block in the melt, the method further includes:

[0024] The melt is cooled to precipitate the second unmelted mass.

[0025] Optionally, before extracting the second unmelted material block in the melt, the method further includes:

[0026] Cleaning the first unmelted material block on the slag extraction seed crystal;

[0027] The step of extracting a second unmelted material block from the melt comprises:

[0028] Based on the cleaned slag extraction seed crystal, a second unmelted material block in the melt is extracted.

[0029] Optionally, cooling the melt to precipitate the second unmelted material block comprises:

[0030] The heating power of the furnace body is reduced to a first preset power range, and at least one of the following steps is performed to precipitate the second unmelted material block:

[0031] Adjusting the position of the quartz crucible to the low temperature area in the furnace body;

[0032] Increasing the flow rate of the inert gas to a first flow rate range, so that the inert gas takes away the heat;

[0033] Increasing the rotation speed of the quartz crucible to a first preset rotation speed range;

[0034] The throttle valve of the furnace body is opened to a preset opening.

[0035] Optionally, before extracting the second unmelted material block in the melt, the method further includes:

[0036] The size of the second unmelted material block is made to reach a second preset size range.

[0037] Optionally, the low-pressure blowing treatment is performed on the furnace body to discharge gas impurities from the furnace body, including:

[0038] reducing the gas pressure in the furnace to cause the melt to bubble, so that the gas impurities escape from the melt;

[0039] After the melt bubbling continues for a second preset time period, the heating power of the furnace body is reduced, and the flow rate of the inert gas in the furnace body is increased.

[0040] Optionally, reducing the gas pressure in the furnace body includes:

[0041] The flow rate of the inert gas in the furnace body is reduced.

[0042] Optionally, providing a pulling seed crystal so that the pulling seed crystal can be used to pull a single crystal from the melt includes:

[0043] Providing a pulling seed crystal, in the process of equalizing the diameter to the first preset length range, reducing the rotation speed of the pulling seed crystal and the quartz crucible to a second preset rotation speed range;

[0044] In the process of equalizing the diameter to the second preset length range, reducing the rotation speed of the grain-extracting seed crystal and the quartz crucible to a third preset rotation speed range;

[0045] The grain-extracting seed crystal is used to perform other crystal pulling operations; the other crystal pulling operations include: operations corresponding to the crystal pulling process except the process of equalizing the diameter to the first preset length range and the process of equalizing the diameter to the second preset length range.

[0046] Optionally, the first preset length range includes: 20%-50% of the total length of the single crystal;

[0047] The second preset length range includes: 50%-80% of the total length of the single crystal.

[0048] Optionally, the second preset speed range includes: 7-9r / min;

[0049] The third preset speed includes: 6-8r / min.

[0050] In an embodiment of the present invention, the raw materials in the quartz crucible in the furnace body are heated to form a melt; the melt is subjected to at least one impurity removal treatment; the furnace body is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body; and a pulling seed crystal is provided to pull a single crystal from the melt. In an embodiment of the present invention, the melt is subjected to at least one impurity removal treatment, the melt is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body, and thus the impurity content in the melt and the furnace body is greatly reduced. Based on the pulling of single crystals from the melt by pulling seed crystals, since the impurity content in the melt and the furnace body is low, crystallization is easy, the probability of broken edges is greatly reduced, etc., and the yield of single crystal silicon is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0052] Figure 1 A flow chart of a crystal pulling method in Embodiment 1 of the present invention is shown;

[0053] Figure 2 A flow chart of a crystal pulling method according to a second embodiment of the present invention is shown;

[0054] Figure 3 A flow chart of extracting a first unmelted material block according to a second embodiment of the present invention is shown. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Embodiment 1

[0057] Reference Figure 1, shows a flow chart of a crystal pulling method in Embodiment 1 of the present invention, which may specifically include the following steps:

[0058] Step 101, heating raw materials in a quartz crucible in a furnace body to form a melt.

[0059] In the embodiment of the present invention, the raw material may be native polycrystalline raw material, etc., and no specific limitation is made in the embodiment of the present invention.

[0060] In the embodiment of the present invention, the raw material may be loaded into a quartz crucible, and the quartz crucible loaded with the raw material is placed into a furnace body to melt the raw material to obtain a melt.

[0061] In the embodiment of the present invention, the furnace environment such as the furnace temperature during the raw material melting process is not specifically limited.

[0062] Step 102, performing at least one impurity removal treatment on the melt.

[0063] In the embodiment of the present invention, a slag extraction seed crystal may be provided in the furnace body, and the slag extraction seed crystal may be a new seed crystal or an unused seed crystal, or the slag extraction seed crystal may also be a waste seed crystal, etc. By using the waste seed crystal as the slag extraction seed crystal, the cost can be reduced to a great extent. In the embodiment of the present invention, this is not specifically limited.

[0064] In the embodiment of the present invention, the impurities in the raw material are usually insoluble or difficult to dissolve in the above melt. The impurities can be impurities in the raw material that are insoluble or difficult to dissolve in the above melt, and in the embodiment of the present invention, there is no specific limitation on this.

[0065] In the embodiment of the present invention, the melt may be subjected to at least one impurity removal treatment based on the slag extraction seed crystals in the furnace body.

[0066] Specifically, the relative distance between the slag extraction seed crystal and the quartz crucible can be changed so that the slag extraction seed crystal contacts the impurities in the melt, and the relative distance between the slag extraction seed crystal and the quartz crucible can be further reduced so that the slag extraction seed crystal drives the impurities to be immersed in the melt, and after standing for a preset time period, the impurities are adhered to the slag extraction seed crystal, and then the relative distance between the slag extraction seed crystal and the quartz crucible can be increased. For example, the quartz crucible can be kept stationary, the slag extraction seed crystal can be lifted, and the slag extraction seed crystal with impurities adhered can be separated from the melt, and then the impurities can be extracted from the melt. The preset time period can be set according to actual conditions, and is not specifically limited in the embodiments of the present invention.

[0067] In the embodiment of the present invention, the impurity removal treatment of the melt based on the slag extraction seed crystal in the furnace body can be performed once or multiple times, so as to extract impurities in the melt as much as possible, and the number of impurity removal times is not specifically limited.

[0068] Step 103, performing a low-pressure blowing treatment on the furnace body to discharge gas impurities from the furnace body.

[0069] In the embodiment of the present invention, the main component of the quartz crucible may be silicon dioxide. In order to prevent the silicon dioxide and other components in the quartz crucible from reacting with the melt and other components under high temperature to generate gas impurities, or if there are gas impurities in the furnace body, the melt may be subjected to low-pressure blowing to discharge the gas impurities from the furnace body.

[0070] In the embodiment of the present invention, the gas impurities may be silicon oxide gas, oxygen, etc. In the embodiment of the present invention, this is not specifically limited. Specifically, the gas pressure in the furnace body may be reduced, so that a certain gas pressure difference may be generated between the gas pressure in the melt and the gas pressure in the furnace body, thereby causing the melt to bubble and the gas impurities in the melt to escape, and then the gas impurities are discharged from the furnace body by performing ventilation treatment on the furnace body.

[0071] In the embodiment of the present invention, the furnace body is subjected to ventilation treatment, etc. Specifically, the flow rate of the inert gas in the furnace body can be increased, and the inert gas can be argon gas, etc. The gas impurities are discharged from the furnace body by the blowing effect of the inert gas, etc. In the embodiment of the present invention, this is not specifically limited.

[0072] In the embodiment of the present invention, during the heating process of molten silicon, there are usually more gas impurities, and the above-mentioned gas impurities usually have a greater interference with the pulling of single crystals. The furnace body is subjected to low-pressure blowing treatment to discharge the gas impurities from the furnace body, which can greatly discharge the above-mentioned gas impurities from the melt and the furnace body. In this way, the interference of the above-mentioned impurity gases on the crystal pulling process can be avoided, and the single crystal yield can be greatly improved.

[0073] Step 104, providing a pulling seed crystal, so that the pulling seed crystal pulls a single crystal from the melt.

[0074] In an embodiment of the present invention, the furnace body may be provided with a structure for replacing the seed crystal, or the seed crystal may be replaced manually. Since impurities are adhered to the slag seed crystal, in order to avoid the impurities on the slag seed crystal interfering with crystal pulling, the slag seed crystal may be replaced with a grain seed crystal, and the grain seed crystal may be an unused seed crystal.

[0075] In an embodiment of the present invention, the grain-extracted seed crystal may be an unused seed crystal, or may be a new seed crystal, and the subsequent crystal pulling may be performed using the grain-extracted seed crystal, thereby being able to avoid the above-mentioned impurities from interfering with or affecting the crystal pulling process, facilitating crystallization during the crystal pulling process, greatly reducing the probability of edge breakage, etc., thereby increasing the yield of single crystal silicon.

[0076] In an embodiment of the present invention, after the gas impurities are discharged from the furnace body, the slag extraction seed crystal is replaced with an unused seed crystal, which can avoid the interference or influence of the gas impurities on the grain extraction seed crystal, and is beneficial to improving the yield of single crystal silicon.

[0077] In the embodiment of the present invention, the crystal pulling environment may include: the temperature in the furnace body, the gas pressure in the furnace body, the rotation speed of the seed crystal, the rotation speed of the quartz crucible, etc. In the embodiment of the present invention, no specific limitation is made to this.

[0078] In the embodiment of the present invention, when the environment of the furnace body meets the crystal pulling environment, the single crystal can be pulled from the melt using the grain extraction seed crystal.

[0079] In an embodiment of the present invention, the raw materials in the quartz crucible in the furnace body are heated to form a melt; the melt is subjected to at least one impurity removal treatment; the furnace body is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body; and a pulling seed crystal is provided so that the pulling seed crystal pulls a single crystal from the melt. In an embodiment of the present invention, the melt is subjected to at least one impurity removal treatment, and the furnace body is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body, thereby greatly reducing the impurity content in the melt and the furnace body. Based on the pulling of single crystals from the melt by pulling seed crystals, since the impurity content in the melt and the furnace body is low, it is easy to crystallize, the probability of broken edges is greatly reduced, etc., so that the yield of single crystal silicon is increased.

[0080] Embodiment 2

[0081] Reference Figure 2 , Figure 2 A flow chart of a crystal pulling method according to the second embodiment of the present invention is shown, which may specifically include the following steps:

[0082] Step 201, heating the raw materials in the quartz crucible in the furnace body to form a melt.

[0083] In the embodiment of the present invention, step 201 may refer to the above step 101, and will not be described again here to avoid repetition.

[0084] Step 202, providing a slag extraction seed crystal, so that the slag extraction seed crystal extracts a first unmelted material block from the melt; the first unmelted material block includes: a first impurity in the raw material.

[0085] In the embodiment of the present invention, a slag extraction seed crystal is arranged in the furnace body. The slag extraction seed crystal can be a new seed crystal or an unused seed crystal, or a waste seed crystal, etc. In the embodiment of the present invention, there is no specific limitation on this.

[0086] In the embodiment of the present invention, the impurities in the raw material are usually insoluble or difficult to melt in the above-mentioned melt. The first impurity can be an impurity in the raw material that is insoluble or difficult to melt, and the first impurity can mainly be an impurity in the raw material that is insoluble at the temperature at which the silicon raw material melts. In the embodiment of the present invention, this is not specifically limited.

[0087] In an embodiment of the present invention, a first unmelted material block in the melt can be extracted based on the slag extraction seed crystal in the furnace body; the first unmelted material block can include: a first impurity in the raw material. The first impurity can exist in the melt in the form of a first unmelted material block.

[0088] Specifically, the relative distance between the slag-lifting seed crystal and the quartz crucible can be changed so that the slag-lifting seed crystal contacts the first unmelted material block in the quartz crucible, and the relative distance between the slag-lifting seed crystal and the quartz crucible is further reduced so that the slag-lifting seed crystal drives the first unmelted material block to be immersed in the melt, and after standing for a preset time period, the first unmelted material block is bonded to the slag-lifting seed crystal, and then the relative distance between the slag-lifting seed crystal and the quartz crucible can be increased. For example, the quartz crucible is kept stationary, the slag-lifting seed crystal is lifted, and the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt, and then the first unmelted material block is extracted from the melt. The preset time period can be set according to actual conditions, and is not specifically limited in the embodiments of the present invention.

[0089] In an embodiment of the present invention, the step of extracting the first unmelted material block in the melt based on the slag seed crystal in the furnace body can be performed once or multiple times to extract the first impurity in the raw material as much as possible.

[0090] In the embodiment of the present invention, optionally, providing a slag extraction seed crystal so that before the slag extraction seed crystal extracts a first unmelted material block from the melt, it may also include: making the size of the first unmelted material block reach a first preset size range.

[0091] In the embodiment of the present invention, the size of the first unmelted material block may be at least one of the length of the first unmelted material block, the width of the first unmelted material block, the thickness of the first unmelted material block, and the diameter of the first unmelted material block, etc. In the embodiment of the present invention, no specific limitation is made to this.

[0092] In the embodiment of the present invention, the first preset size range may be a size range in which the slag extraction seed crystal is convenient for extracting the first unmelted material block, or the first preset size range may be a size range in which the slag extraction seed crystal is convenient for extracting the first unmelted material block and the first unmelted material block is not easy to fall off the slag extraction seed crystal, etc. In the embodiment of the present invention, this is not specifically limited.

[0093] For example, the first preset size range may be: the diameter size of the first unmelted block is 200-250mm, that is, when the diameter size of the first unmelted block is 200-250mm, the first unmelted block in the melt is extracted based on the slag seed crystal in the furnace body. For example, when the diameter size of the first unmelted block is 200mm, the first unmelted block in the melt is extracted based on the slag seed crystal in the furnace body. For another example, when the diameter size of the first unmelted block is 250mm, the first unmelted block in the melt is extracted based on the slag seed crystal in the furnace body. For another example, when the diameter size of the first unmelted block is 225mm, the first unmelted block in the melt is extracted based on the slag seed crystal in the furnace body. After the size of the first unmelted block reaches the first preset size range, the first unmelted block in the melt is extracted based on the slag seed crystal in the furnace body; the first unmelted block includes: the first impurity in the raw material. This can prevent the first unmelted material block from easily falling off from the slag-lifting seed crystal, thereby preventing the first unmelted material block adhered to the slag-lifting seed crystal from falling into the molten silicon.

[0094] In the embodiment of the present invention, optionally, the first unmelted material block usually has a bright aperture or the like in the melt. In order to improve the recognition accuracy of the first unmelted material block, the first unmelted material block in the melt can be extracted based on the above-mentioned slag extraction seed crystal when a bright aperture or the like appears in the melt. In the embodiment of the present invention, this is not specifically limited.

[0095] In the embodiment of the present invention, refer to Figure 3 , Figure 3 A flow chart of extracting a first unmelted material block according to the second embodiment of the present invention is shown. Optionally, providing a slag extraction seed crystal so that the slag extraction seed crystal extracts the first unmelted material block from the melt may include:

[0096] Step 2021: After providing the slag-lifting seed crystal, reduce the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt.

[0097] Step 2022: Let the first unmelted material block adhere to the surface of the slag extraction seed crystal while standing for a first preset period of time.

[0098] Step 2023: increasing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt.

[0099] Specifically, after providing the slag-lifting seed crystal, the relative distance between the slag-lifting seed crystal and the upper quartz crucible can be reduced so that the slag-lifting seed crystal and the first unmelted material block in the quartz crucible are immersed in the melt. After providing the slag-lifting seed crystal, first, the quartz crucible is raised to a first preset height range, and the first preset height range can be set according to actual conditions. For example, the first preset height range can be 0-150mm. The quartz crucible can be initially in a position where the upper edge is parallel to the top layout position of the furnace body heater, and the quartz crucible is raised by 0-150mm based on this position. The first preset height can be set within this range according to actual conditions. Furthermore, in this embodiment, the quartz crucible rises 50-100mm relative to the reference position. Then, the slag-lifting seed crystal is lowered so that the slag-lifting seed crystal contacts the first unmelted material block in the quartz crucible and is immersed in the melt.

[0100] Specifically, after providing the slag-lifting seed crystal, the quartz crucible can be first raised, and then the slag-lifting seed crystal can be lowered to make it contact with the first unmelted material block in the above-mentioned quartz crucible. The relative distance between the slag-lifting seed crystal and the above-mentioned quartz crucible can be adjusted at a preset speed so that the above-mentioned slag-lifting seed crystal and the first unmelted material block in the above-mentioned quartz crucible are immersed in the above-mentioned melt. The above-mentioned preset speed is less than or equal to the set speed threshold. The set speed threshold can be set according to actual conditions, that is, when the above-mentioned slag-lifting seed crystal is in contact with the first unmelted material block in the above-mentioned quartz crucible, the relative distance between the above-mentioned slag-lifting seed crystal and the above-mentioned quartz crucible can be slowly adjusted to a second relative distance range so that the above-mentioned slag-lifting seed crystal and the first unmelted material block in the above-mentioned quartz crucible are immersed in the above-mentioned melt. In this way, on the one hand, it can be prevented that the melt in the above-mentioned quartz crucible spills out of the quartz crucible, causing unnecessary losses; on the other hand, it can be prevented that the first unmelted material block to which the slag-lifting seed crystal has been bonded is separated due to the impact of the melt. The second relative distance range can be set according to actual conditions, for example, the second relative distance range can be: 10-50mm. In the process of adjusting the slag seed crystal to be immersed in the quartz crucible, it is necessary to avoid the slag seed crystal from touching the bottom or side wall of the quartz crucible, so as not to damage the slag seed crystal, or cause the quartz crucible to tilt, so that the melt in the quartz crucible spills out of the quartz crucible, causing unnecessary losses. In the embodiments of the present invention, no specific limitation is made to this.

[0101] After the slag-lifting seed crystal and the first unmelted material block in the quartz crucible are immersed in the melt, they can be left to stand for a first preset time period so that the first unmelted material block is fully bonded to the surface of the slag-lifting seed crystal. The first preset time period can be the time required for the first unmelted material block to be fully bonded to the slag-lifting seed crystal and for the first unmelted material block to be difficult to fall off from the slag-lifting seed crystal. For example, the first preset time period can be 3-5 seconds, etc., and is not specifically limited in the embodiments of the present invention.

[0102] Increase the relative distance between the slag-lifting seed crystal and the quartz crucible to a third relative distance range, so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt in the quartz crucible. The third relative distance can be set according to actual conditions, and the third relative distance can be greater than the second relative distance range in which the slag-lifting seed crystal is immersed in the melt, so that the slag-lifting seed crystal can be separated from the melt in the quartz crucible. For example, if the second relative distance range is: 10-50mm, the third relative distance range can be: greater than 10-50mm. Specifically, the quartz crucible can be kept stationary, and the slag-lifting seed crystal can be raised to the third relative distance, so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt in the quartz crucible. Of course, the slag-lifting seed crystal can also be kept stationary, and the quartz crucible can be lowered, so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt in the quartz crucible.

[0103] It should be noted that before the slag extraction seed crystal bonded with the first unmelted material block is completely separated from the melt in the quartz crucible, the quartz crucible can be kept stationary, the slag extraction seed crystal can be lifted to a second preset height range, and the first unmelted material block at the liquid level can be extracted once or multiple times. The second preset height range can be less than or equal to the second relative distance range, so that the slag extraction seed crystal can continue to extract the first unmelted silicon under the liquid surface of the melt. The second preset height range can be set according to actual needs. For example, if the second relative distance range is: 10-50mm, the second preset height range can be: less than 10-50mm, etc.

[0104] In an embodiment of the present invention, optionally, after providing the slag-lifting seed crystal, reducing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt, may include: after providing the slag-lifting seed crystal, raising the quartz crucible; lowering the slag-lifting seed crystal so that the slag-lifting seed crystal contacts the first unmelted material block, and lowering the slag-lifting seed crystal at a preset speed so that the slag-lifting seed crystal is immersed in the melt; the preset speed is less than or equal to a set speed threshold; specifically, when the size of the first unmelted material block reaches a first preset size range, after providing the slag-lifting seed crystal, the quartz crucible may be raised first, and then the slag-lifting seed crystal may be lowered so that the slag-lifting seed crystal contacts the first unmelted material block in the quartz crucible, and the relative distance between the slag-lifting seed crystal and the quartz crucible may be adjusted at a preset speed so that the slag-lifting seed crystal and the first unmelted material block in the quartz crucible are immersed in the melt. The preset speed may be less than or equal to the set speed threshold. The set speed threshold can be set according to the actual situation. For example, the set speed threshold can be: 300-400mm / h. For example, if the set speed threshold is 400mm / h, the preset speed can be 350mm / h, that is, when the above-mentioned slag-lifting seed crystal is in contact with the first unmelted material block in the above-mentioned quartz crucible, the relative distance between the above-mentioned slag-lifting seed crystal and the above-mentioned quartz crucible can be slowly adjusted to the second relative distance range, so that the above-mentioned slag-lifting seed crystal and the first unmelted material block in the above-mentioned quartz crucible are immersed in the above-mentioned melt. In this way, on the one hand, it can be prevented that the melt in the above-mentioned quartz crucible spills out of the quartz crucible and causes unnecessary losses; on the other hand, it can be prevented that the first unmelted material block bonded to the slag-lifting seed crystal is detached due to the impact of the melt. The above-mentioned second relative distance range can be set according to the actual situation. For example, the second relative distance range can be: 10-50mm. In the process of adjusting the slag seed crystal to be immersed in the quartz crucible, it is necessary to prevent the slag seed crystal from touching the bottom or side wall of the quartz crucible, so as to avoid damaging the slag seed crystal, or causing the quartz crucible to tilt, so that the melt in the quartz crucible spills out of the quartz crucible, causing unnecessary losses. In the embodiments of the present invention, this is not specifically limited.

[0105] In the embodiment of the present invention, optionally, the increasing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt in the quartz crucible may include: increasing the relative distance between the slag-lifting seed crystal and the quartz crucible by raising the slag-lifting seed crystal. Specifically, the quartz crucible may be kept stationary, and the relative distance between the slag-lifting seed crystal and the quartz crucible may be increased by raising the third preset height range of the slag-lifting seed crystal so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt in the quartz crucible. The third preset height range may be set according to actual conditions, and the third preset height range may be greater than the second relative distance range, so that the slag-lifting seed crystal may be separated from the melt in the quartz crucible. For example, if the second relative distance range is 10-50 mm, the third preset height range may be greater than 10-50 mm. For example, if the second relative distance is 25 mm, the third preset height range may be 25.3 mm.

[0106] Step 203: Cool the melt to precipitate the second unmelted material block.

[0107] In the embodiment of the present invention, since impurities in the raw material are usually infusible or difficult to melt in the melt at the melting temperature of the silicon raw material, the melt can be cooled to precipitate a second unmelted material block, which can include: the second impurities in the raw material.

[0108] In the embodiment of the present invention, the second impurity may be an impurity that is infusible or difficult to melt in the melt, and the second impurity may mainly be an impurity that is difficult to melt in the melt at the melting temperature of the silicon raw material. In the embodiment of the present invention, this is not specifically limited.

[0109] In the embodiment of the present invention, the melt is cooled to precipitate the second unmelted material block. Specifically, for example, the temperature in the furnace body can be controlled, and then the temperature of the melt can be controlled to cool the melt, and at the same time, the second impurities in the melt are crystallized to obtain the second unmelted material block. In the embodiment of the present invention, this is not specifically limited.

[0110] In an embodiment of the present invention, optionally, cooling the melt to precipitate the second unmelted material block may include: reducing the heating power of the furnace body to a first preset power range, and performing at least one of the following steps to precipitate the second unmelted material block: adjusting the position of the quartz crucible to a low temperature area in the furnace body; increasing the flow rate of the inert gas to a first flow rate range, and allowing the inert gas to take away heat; increasing the rotation speed of the quartz crucible to a first preset rotation speed range; opening the throttle valve of the furnace body to a preset opening.

[0111] In an embodiment of the present invention, the melt can be cooled by reducing the heating power of the furnace body to a first preset power range; the first preset power range can be set according to actual conditions, etc. At the same time, the melt can be cooled to precipitate a second unmelted material block by adjusting the position of the quartz crucible to a low temperature area in the furnace body; the furnace body can be provided with a low temperature area, which is located in a preset position range of the furnace body, and the preset position range can be determined according to each furnace body. For example, in this embodiment, the position of the quartz crucible can be adjusted to a position where the upper edge of the quartz crucible is 0-100 mm higher than the top of the heater. Or, the flow rate of the inert gas can be increased to a first flow rate range, and the first flow rate range can be set according to actual conditions, etc. The heat is taken away by the inert gas, and the melt is cooled to precipitate a second unmelted material block; or, the rotation speed of the quartz crucible is increased to a first preset rotation speed range, and the first preset rotation speed range can be set according to actual conditions, etc. The melt is cooled to precipitate a second unmelted material block. Alternatively, the throttle valve of the furnace body may be opened to a preset opening, and the melt may be cooled to precipitate a second unmelted material block. The preset opening may be set according to actual conditions.

[0112] Specifically, the position of the quartz crucible is adjusted to the low temperature area in the furnace body, the flow rate of the inert gas is increased to the first flow rate range, the heat is taken away by the inert gas, the rotation speed of the quartz crucible is increased to the first preset rotation speed range, and the throttle valve of the furnace body is opened to the preset opening, etc., which can be selected or performed together. Selecting one of them can reduce the complexity of the operation, and performing them together can increase the speed of cooling and precipitating the second unmelted material block, etc. In the embodiment of the present invention, there is no specific limitation on this.

[0113] For example, the heating power of the furnace body can be reduced to a first preset power range, such as 40-60kw, and the position of the quartz crucible can be moved to a low temperature area in the furnace body, and the low temperature area can be located in a preset position range of the furnace body. After adjusting the position of the quartz crucible, the position of the quartz crucible can be: the upper edge of the quartz crucible is 0-100mm higher than the top of the heater. Further, the position of the quartz crucible can be adjusted to 0-50mm higher than the top of the heater. And the flow rate of the inert gas, such as argon, is increased to a first flow rate range, such as 80-100L / min, and the speed of the quartz crucible is increased to a first preset speed range, such as 6-9 rpm, etc., and the throttle valve of the furnace body is opened to a preset opening, such as 95% opening, so as to quickly cool the above-mentioned melt and crystallize to obtain a second unmelted material block, thereby improving the crystal pulling efficiency and reducing the crystal pulling time. In the embodiment of the present invention, no specific limitation is given to this.

[0114] In the embodiment of the present invention, it should be noted that in the process of cooling the melt to precipitate the second unmelted material block, the silicon raw material in the melt still needs to exist in the form of a molten liquid.

[0115] Step 204 , extracting a second unmelted material block from the melt; the second unmelted material block includes: a second impurity in the raw material.

[0116] In an embodiment of the present invention, the second unmelted block in the melt can be extracted based on the slag extraction seed crystal in the furnace body, or the slag extraction seed crystal can be cleaned to extract the second unmelted block in the melt, or a new seed crystal can be selected to extract the second unmelted block in the melt, etc. In the embodiment of the present invention, no specific limitation is made to this. The second unmelted block includes: a second impurity in the raw material. The second impurity can be an impurity that is infusible or refractory to the melt, and the second impurity can be mainly an impurity that is refractory to the melt at the melting temperature of the silicon raw material. In the embodiment of the present invention, no specific limitation is made to this.

[0117] Specifically, the relative distance between the slag-lifting seed crystal and the quartz crucible can be changed so that the slag-lifting seed crystal contacts the second unmelted material block in the quartz crucible, and the relative distance between the slag-lifting seed crystal and the quartz crucible is further reduced so that the slag-lifting seed crystal drives the second unmelted material block to be immersed in the melt together, and after standing for a third preset period of time, the second unmelted material block is bonded to the above-mentioned slag-lifting seed crystal, and then the relative distance between the slag-lifting seed crystal and the quartz crucible can be increased to separate the slag-lifting seed crystal bonded with the second unmelted material block from the above-mentioned melt, and then the second unmelted material block is extracted from the melt. The third preset period of time can be set according to actual conditions, for example, the third preset time period can be 3-5s, etc., and this is not specifically limited in the embodiments of the present invention.

[0118] In the embodiment of the present invention, this step can also be performed once or multiple times, so as to extract the second impurity in the raw material as much as possible.

[0119] In the embodiment of the present invention, optionally, before extracting the second unmelted block in the melt, the slag extraction seed crystal may be replaced with a third seed crystal, and the third seed crystal may be an unused seed crystal. The extraction of the second unmelted block in the melt based on the slag extraction seed crystal may include: extracting the second unmelted block in the melt based on the third seed crystal. In the process of extracting the second unmelted block in the melt, the first unmelted block on the slag extraction seed crystal may be prevented from falling into the melt. In the embodiment of the present invention, this is not specifically limited.

[0120] In an embodiment of the present invention, before extracting the second unmelted block in the melt, the process may further include: cleaning the first unmelted block on the slag extraction seed crystal; and extracting the second unmelted block in the melt may include: extracting the second unmelted block in the melt based on the cleaned slag extraction seed crystal. Specifically, the first unmelted block on the slag extraction seed crystal may be cleaned to reduce the first impurities on the slag extraction seed crystal, or the slag extraction seed crystal may not include the first impurities to avoid the first impurities on the slag extraction seed crystal from falling into the melt during the subsequent use of the slag extraction seed crystal to extract the second unmelted block in the melt.

[0121] In the embodiment of the present invention, the first unmelted material block on the slag extraction seed crystal is cleaned, and specifically, the first unmelted material block or the first impurity adhered to the slag extraction seed crystal is separated from the slag extraction seed crystal. This process can be performed outside the furnace body, thereby preventing the first unmelted material block or the first impurity adhered to the slag extraction seed crystal from falling into the furnace body and adversely affecting the subsequent crystal pulling process.

[0122] In an embodiment of the present invention, based on the cleaned slag seed crystal in the above-mentioned furnace body, the second unmelted material block in the above-mentioned melt is extracted, thereby preventing the first unmelted material block or the first impurity adhered to the slag seed crystal from falling into the melt, which can further reduce the impurity content in the melt.

[0123] In the embodiment of the present invention, since the melt is cooled in the aforementioned steps, in order to ensure the crystal pulling performance of the melt, etc., the heating power of the furnace body can be increased, the rotation speed of the quartz crucible can be reduced, the flow rate of the inert gas can be reduced, etc. For example, the heating power of the furnace body can be increased to 65-85kw, the rotation speed of the quartz crucible can be reduced to 1-3r / min (revolutions perminute), and the argon flow rate can be reduced to 40-80L / min. In the embodiment of the present invention, this is not specifically limited.

[0124] In the embodiment of the present invention, optionally, before extracting the second unmelted material block in the melt, the step may include: making the size of the second unmelted material block reach a second preset size range.

[0125] Specifically, the size of the second unmelted material block may be at least one of the length, width, thickness, and diameter of the second unmelted material block, etc. In the embodiment of the present invention, this is not specifically limited.

[0126] In the embodiment of the present invention, the second preset size range may be a size range in which the slag extraction seed crystal is convenient for extracting the second unmelted material block, or the second preset size range may be a size range in which the slag extraction seed crystal is convenient for extracting the second unmelted material block and the second unmelted material block is not easy to fall off the slag extraction seed crystal, etc. In the embodiment of the present invention, this is not specifically limited.

[0127] For example, the second preset size range can be: the diameter of the second unmelted material block is 200-300mm, that is, when the diameter of the second unmelted material block is 200-300mm, the second unmelted material block is firmly bonded to the above-mentioned slag extraction seed crystal, and the second unmelted material block in the melt is extracted.

[0128] For another example, the second preset size range can also be: the linear size of the second unmelted block is 100-150 mm, that is, when the linear size of the second unmelted block is 100-150 mm, the second unmelted block is firmly bonded to the above-mentioned slag extraction seed crystal, and the second unmelted block in the melt is extracted. The linear size of the second unmelted block can be: any one of the length size of the second unmelted block, the width size of the second unmelted block, the thickness size of the second unmelted block, and the diameter size of the second unmelted block.

[0129] When the size of the second unmelted material block reaches the second preset size range, the second unmelted material block in the melt is extracted; the second unmelted material block includes: the second impurity in the raw material. The second unmelted material block is not easy to fall off from the slag extraction seed crystal, and the second unmelted material block adhered to the slag extraction seed crystal can be prevented from falling into the molten silicon.

[0130] In the embodiment of the present invention, optionally, when the size of the second unmelted block reaches the second preset size range, the second unmelted block in the melt can be extracted based on the slag extraction seed crystal, or a new seed crystal can be replaced to extract the second unmelted block in the melt, or the slag extraction seed crystal can be cleaned, and the second unmelted block in the melt can be extracted based on the cleaned slag extraction seed crystal, etc. In the embodiment of the present invention, no specific limitation is made to this. By extracting the second unmelted block in the melt with a new seed crystal or based on the cleaned slag extraction seed crystal, etc., the first unmelted block can be prevented from falling into the melt again.

[0131] Step 205 , reducing the gas pressure in the furnace body to cause the melt to bubble, so that the gas impurities escape from the melt.

[0132] In an embodiment of the present invention, if the furnace body has a pressure closed-loop control, the pressure closed-loop of the furnace body may be a pressure control system for controlling normal crystal pulling of the furnace body, etc. In this step, the pressure closed-loop control of the above-mentioned furnace body may be exited. In the embodiment of the present invention, no specific limitation is made to this.

[0133] In the embodiment of the present invention, the gas pressure in the furnace body can be reduced to make the melt bubble so that gas impurities can escape from the melt. Specifically, the inert gas flow rate in the furnace body can be reduced. Since the gas pressure in the melt is the same as the gas pressure in the furnace body, the gas pressure in the furnace body can be reduced. Within a certain period of time, the gas pressure in the melt may be greater than the gas pressure in the furnace body, which will cause the melt to bubble and the gas impurities in the melt to escape from the melt.

[0134] In the embodiment of the present invention, optionally, reducing the gas pressure in the furnace body may include: reducing the flow rate of the inert gas in the furnace body. Specifically, the flow rate of the inert gas in the furnace body may be reduced to a second flow rate range to cause the melt to bubble, so that gas impurities in the melt escape from the melt.

[0135] For example, the argon flow rate can be reduced to a second flow rate range, and the second flow rate range can be set according to actual conditions, such as 10-50L / min. The gas pressure of the furnace body can be maintained in a first gas pressure range, and the first gas pressure range can be set according to actual conditions, such as 200-700Pa. The melt can be bubbled as quickly as possible or to the greatest extent possible to allow gas impurities in the melt to escape from the melt.

[0136] Step 206 : after the melt bubbling continues for a second preset time period, the heating power of the furnace body is reduced, and the flow rate of the inert gas in the furnace body is increased.

[0137] In an embodiment of the present invention, an inert gas may be introduced into the furnace body through the gas inlet of the furnace body. In order to allow the melt to bubble sufficiently and the gas impurities to escape sufficiently, after the melt bubbling continues for a second preset time period, the heating power of the furnace body may be reduced to a second preset power range, and the flow rate of the inert gas in the furnace body may be increased to a third flow rate range, so that the gas impurities are discharged from the vent of the furnace body under the blowing effect of the inert gas. The second preset time period range, the second preset power range, and the third flow rate range may be set according to actual conditions, and are not specifically limited in the embodiment of the present invention.

[0138] For example, the second preset time period range can be: 3-5min, the second preset power range can be 50-70kw, the inert gas can be argon, and the third flow range can be 40-80L / min. That is, when the melt bubbling continues for 3-5min, the heating power of the above-mentioned furnace body can be reduced to 50-70kw, and the flow rate of the inert gas in the above-mentioned furnace body can be increased to 40-80L / min, so that the above-mentioned gas impurities can be discharged from the vent of the furnace body under the blowing action of the above-mentioned argon gas.

[0139] In an embodiment of the present invention, optionally, after the gas impurities are discharged from the above-mentioned furnace body, the heating power of the furnace body can be increased to prepare for subsequent crystal pulling. For example, the heating power of the furnace body can be adjusted to 70-80kw to prepare for subsequent crystal pulling.

[0140] Step 207, providing a pulled seed crystal, and in the process of equalizing the diameter to the first preset length range, reducing the rotation speed of the pulled seed crystal and the quartz crucible to a second preset rotation speed range.

[0141] In the embodiment of the present invention, when the environment of the furnace body meets the crystal pulling environment, a pulling seed crystal can be provided. The pulling seed crystal can be a new seed crystal, an unused seed crystal, or a used seed crystal that will not introduce impurities, etc. The pulling seed crystal is performed using the pulling seed crystal. During the process of equalizing the diameter to the first preset length range, the rotation speed of the pulling seed crystal and the quartz crucible is reduced to a second preset rotation speed range. The first preset length range can be a length range where impurities have a greater impact on the broken edge during the equalizing process, etc., and in the embodiment of the present invention, this is not specifically limited.

[0142] In the embodiment of the present invention, the first preset length range may be: a certain length range before the length of the single crystal reaches half of the total length during the equal diameter process, or other ranges, etc. For example, if the total length of the single crystal is 3000 mm, the first preset length range may be: a certain length range before the length of the single crystal reaches 1500 mm during the equal diameter process, etc. In the embodiment of the present invention, no specific limitation is made to this.

[0143] In an embodiment of the present invention, optionally, the first preset length range includes: 20%-50% of the total length of the single crystal. Alternatively, the first preset length range may include: 10%-60% of the total length of the single crystal, etc. For example, if the total length of the single crystal is 3000mm, the first preset length range may be 600mm-1500mm. For example, the first preset length may be: 600mm, or, the first preset length may be: 1050mm, or, the first preset length may be: 1500mm, etc. Alternatively, if the total length of the single crystal is 3000mm, the first preset length range may be 300mm-1800mm. For example, the first preset length may be: 300mm, or, the first preset length may be: 1050mm, or, the first preset length may be: 1800mm, etc.

[0144] In the embodiment of the present invention, the first preset length range may be the length where impurities have a greater impact on the broken edge during the equal diameter process, and therefore, in order to weaken the convection of the quartz crucible and the grain seed crystal, so that the newly generated or remaining gas impurities in the melt interfere with the equal diameter process, the rotation speed of the grain seed crystal and the quartz crucible may be reduced to the second preset rotation speed range. The second preset rotation speed range may be set according to actual conditions or actual needs, and is not specifically limited in the embodiment of the present invention.

[0145] In an embodiment of the present invention, optionally, the second preset speed range may include: 7-9r / min, that is, the speed of the grain seed crystal in the first direction may be 7-9r / min, and the speed of the above-mentioned quartz crucible in the second direction may be 7-9r / min, and the first direction and the second direction may be opposite directions. For example, the first direction may be clockwise, and the second direction may be counterclockwise. In addition, the convection of the quartz crucible and the grain seed crystal may be weakened, so that the newly generated or remaining gas impurities in the melt interfere with the equal diameter process, thereby facilitating crystallization, greatly reducing the probability of broken edges, etc., so that the single crystal yield rate is increased. For example, the second preset speed may be 7r / min, or the second preset speed may be 8r / min, or the second preset speed may be 9r / min, etc.

[0146] Step 208, in the process of equalizing the diameter to the second preset length range, reducing the rotation speed of the grain-extracting seed crystal and the quartz crucible to a third preset rotation speed range.

[0147] In the embodiment of the present invention, when the environment of the furnace body meets the crystal pulling environment, the grain-extracting seed crystal is used for crystal pulling, and in the process of equalizing the diameter to the second preset length range, the rotation speed of the grain-extracting seed crystal and the quartz crucible is reduced to a third preset rotation speed range. The second preset length range can also be the length where impurities have a greater impact on the broken edge during the equalizing process, etc., and this is not specifically limited in the embodiment of the present invention.

[0148] In the embodiment of the present invention, the second preset length range may be: a certain length segment after the length of the single crystal reaches half of the total length during the equal diameter process, or other ranges, etc. For example, if the total length of the single crystal is 3000 mm, the second preset length range may be: a certain length segment after the length of the single crystal reaches 1500 mm during the equal diameter process, etc. In the embodiment of the present invention, no specific limitation is made to this.

[0149] In an embodiment of the present invention, optionally, the second preset length range includes: 50%-80% of the total length of the single crystal. Alternatively, the second preset length range includes: 40%-90% of the total length of the single crystal. For example, if the total length of the single crystal is 3000mm, the second preset length range can be: 1500-2400mm. Alternatively, if the total length of the single crystal is 3000mm, the second preset length range can be 1200mm-2700mm. For example, the second preset length can be: 1200mm, or, the second preset length can be: 1950mm, or, the first preset length can be: 2700mm, etc.

[0150] In the embodiment of the present invention, the second preset length range can be the length of the impurities that have a greater impact on the broken edge during the equal diameter process, so in order to weaken the convection between the seed crystal, the crystal rod, and the melt inside the quartz crucible, so that the newly generated or remaining gas impurities in the melt interfere with the equal diameter process, the rotation speed of the seed crystal or the crystal rod and the above-mentioned quartz crucible can be reduced to a third preset speed range. The third preset speed can be set according to actual conditions or actual needs, etc., and is not specifically limited in the embodiment of the present invention.

[0151] In an embodiment of the present invention, optionally, the third preset rotation speed may include: 6-8r / min. That is, the rotation speed of the seed crystal in the first direction may be 6-8r / min, and the rotation speed of the quartz crucible in the second direction may be 6-8r / min, and the first direction and the second direction may be opposite directions. For example, the first direction may be clockwise, and the second direction may be counterclockwise. In addition, the convection between the seed crystal, the crystal rod, and the melt inside the quartz crucible may be weakened, so that the newly generated or remaining gas impurities in the melt interfere with the equal diameter process, thereby facilitating crystallization, greatly reducing the probability of broken edges, etc., so that the yield of single crystal silicon is increased.

[0152] Step 209, using the grain-extracted seed crystal to perform other crystal pulling operations; the other crystal pulling operations include: operations corresponding to the crystal pulling process except the process of equalizing the diameter to the first preset length range and the process of equalizing the diameter to the second preset length range.

[0153] In the embodiment of the present invention, when the environment of the above-mentioned furnace body meets the crystal pulling environment, the above-mentioned seed crystal can be used to perform other crystal pulling operations. The above-mentioned crystal pulling operation can be an operation corresponding to the crystal pulling process except the above-mentioned process of equalizing the diameter to the first preset length range and the process of equalizing the diameter to the second preset length range in the entire crystal pulling process. For example, the operation of the equalizing process of other sizes except the above-mentioned first preset length range and second preset length range in the equalizing process, for example, the operation corresponding to the process of seeding, shoulder turning, etc. In the embodiment of the present invention, no specific limitation is made to this.

[0154] In the embodiment of the present invention, the furnace environment, the rotation speed of the seed crystal and the quartz crucible corresponding to the other crystal pulling operations can be set according to actual needs, and are not specifically limited in the embodiment of the present invention. For example, during the seeding process, the rotation speed of the seed crystal and the quartz crucible can be 7-10 r / min.

[0155] In the embodiment of the present invention, the single crystal obtained by the above method can have a success rate of about 10%-15%, a constant diameter breaking rate can be reduced by about 5%-10%, a life span of about 5%-8%, an oxygen impurity content of about 0.5-1.0 ppma, and an average increase of about 0.2-0.4 kg / h in unit yield. In the embodiment of the present invention, this is not specifically limited.

[0156] In an embodiment of the present invention, the raw materials in the quartz crucible in the furnace body are heated to form a melt; the melt is subjected to at least one impurity removal treatment; the furnace body is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body; and a pulling seed crystal is provided so that the pulling seed crystal pulls a single crystal from the melt. In an embodiment of the present invention, the melt is subjected to at least one impurity removal treatment, and the furnace body is subjected to a low-pressure blowing treatment to discharge gaseous impurities from the furnace body, thereby greatly reducing the impurity content in the melt and the furnace body. Based on the pulling of single crystals from the melt by pulling seed crystals, since the impurity content in the melt and the furnace body is low, it is easy to crystallize, the probability of broken edges is greatly reduced, etc., so that the yield of single crystal silicon is increased.

[0157] It should be noted that, for the method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0158] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0159] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0160] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A crystal pulling method, characterized in that: The method comprises: Heating the raw materials in the quartz crucible in the furnace body to form a melt; Performing at least one impurity removal treatment on the melt; Performing a low-pressure blowing treatment on the furnace body to discharge gas impurities from the furnace body; Providing a pulling seed crystal, so that the pulling seed crystal pulls a single crystal from the melt; The low-pressure blowing treatment is performed on the furnace body to discharge gas impurities from the furnace body, comprising: reducing the gas pressure in the furnace to cause the melt to bubble, so that the gas impurities escape from the melt; After the melt bubbling continues for a second preset time period, reducing the heating power of the furnace body and increasing the flow rate of the inert gas in the furnace body; Wherein, the melt is subjected to at least one impurity removal treatment, comprising: Providing a slag extraction seed crystal, so that the slag extraction seed crystal extracts a first unmelted material block from the melt; the first unmelted material block includes: a first impurity in the raw material; the first unmelted material block is an impurity in the raw material that is insoluble at the melting temperature of the raw material; Extracting a second unmelted material block from the melt; the second unmelted material block includes: a second impurity in the raw material; the second unmelted material block is an impurity in the raw material that is refractory at the melting temperature of the raw material; The providing of the slag extraction seed crystal so that the slag extraction seed crystal extracts a first unmelted material block from the melt comprises: After providing the slag-lifting seed crystal, reducing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt; Standing for a first preset time period to allow the first unmelted material block to adhere to the surface of the slag extraction seed crystal; The relative distance between the slag-lifting seed crystal and the quartz crucible is increased so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt.

2. The method according to claim 1, characterized in that Before providing the slag extraction seed crystal so that the slag extraction seed crystal extracts the first unmelted material block from the melt, the method further includes: The size of the first unmelted material block is made to reach a first preset size range.

3. The method according to claim 1, characterized in that After providing the slag-lifting seed crystal, reducing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal and the first unmelted material block are immersed in the melt, comprising: After providing the slag-extracting seed crystal, raising the quartz crucible; Lowering the slag-lifting seed crystal so that the slag-lifting seed crystal contacts the first unmelted material block, and lowering the slag-lifting seed crystal at a preset speed so that the slag-lifting seed crystal is immersed in the melt; the preset speed is less than or equal to a set speed threshold; The step of increasing the relative distance between the slag-lifting seed crystal and the quartz crucible so that the slag-lifting seed crystal bonded with the first unmelted material block is separated from the melt comprises: By raising the slag-lifting seed crystal, the relative distance between the slag-lifting seed crystal and the quartz crucible is increased.

4. The method according to claim 1, characterized in that: Before extracting the second unmelted material block in the melt, the method further comprises: The melt is cooled to precipitate the second unmelted mass.

5. The method according to claim 1, characterized in that Before extracting the second unmelted material block in the melt, the method further comprises: Cleaning the first unmelted material block on the slag extraction seed crystal; The step of extracting a second unmelted material block from the melt comprises: Based on the cleaned slag extraction seed crystal, a second unmelted material block in the melt is extracted.

6. The method according to claim 4, characterized in that The step of cooling the melt to precipitate the second unmelted material block comprises: The heating power of the furnace body is reduced to a first preset power range, and at least one of the following steps is performed to precipitate the second unmelted material block: Adjusting the position of the quartz crucible to the low temperature area in the furnace body; Increasing the flow rate of the inert gas to a first flow rate range, so that the inert gas takes away the heat; Increasing the rotation speed of the quartz crucible to a first preset rotation speed range; The throttle valve of the furnace body is opened to a preset opening.

7. The method according to claim 1, characterized in that Before extracting the second unmelted material block in the melt, the method further comprises: The size of the second unmelted material block is made to reach a second preset size range.

8. The method according to claim 1, characterized in that The step of reducing the gas pressure in the furnace body comprises: The flow rate of the inert gas in the furnace body is reduced.

9. The method according to claim 1, characterized in that: The step of providing a pulling seed crystal so that the pulling seed crystal pulls a single crystal from the melt comprises: Providing a pulling seed crystal, in the process of equalizing the diameter to the first preset length range, reducing the rotation speed of the pulling seed crystal and the quartz crucible to a second preset rotation speed range; In the process of equalizing the diameter to the second preset length range, reducing the rotation speed of the grain-extracting seed crystal and the quartz crucible to a third preset rotation speed range; The grain-extracting seed crystal is used to perform other crystal pulling operations; the other crystal pulling operations include: operations corresponding to the crystal pulling process except the process of equalizing the diameter to the first preset length range and the process of equalizing the diameter to the second preset length range.

10. The method according to claim 9, characterized in that The first preset length range includes: 20%-50% of the total length of the single crystal; The second preset length range includes: 50%-80% of the total length of the single crystal.

11. The method according to claim 9, characterized in that The second preset speed range includes: 7-9r / min; The third preset speed includes: 6-8r / min.

Images