Monocrystalline silicon preparation method, crucible and device

Abstract

The invention provides a monocrystalline silicon preparation method, a crucible and a device, and relates to the technical field of monocrystalline silicon preparation.The monocrystalline silicon preparation method comprises the steps that raw materials are put into the crucible and converted into melt in a crystal pulling furnace, the melt is treated under the first preset condition, so that impurities in the melt move in the direction away from the crystal pulling position, and the impurities in the melt are separated from the crystal pulling position; the first preset condition is maintained until the conversion condition is met, the first preset condition is converted into a second preset condition, and the numerical value of the first preset condition is larger than that of the second preset condition. The problems that in the prior art, impurities in a single crystal silicon rod are reduced by increasing a magnetic field, and the cost is high are solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of single crystal silicon preparation, and in particular to a single crystal silicon preparation method, crucible and device. Background Art

[0002] With the development of the global economy and the growing demand for efficient and clean energy, photovoltaic power generation, as an important part of sustainable development, has received great attention and development worldwide. As the basic material of photovoltaic cells, the market demand for monocrystalline silicon wafers continues to expand.

[0003] Currently, silicon wafers on the market mainly use N-type materials, and their conductivity is controlled by doping with phosphorus. However, there is a problem of small segregation coefficient during phosphorus doping, and it is easily affected by other impurities, which leads to poor uniformity of silicon wafer resistivity.

[0004] In order to solve the problem of resistivity uniformity, the industry has tried to make improvements by increasing the magnetic field, but the high cost limits the application of this method. Summary of the invention

[0005] A technical problem to be solved by the present disclosure is that the prior art reduces impurities in single crystal silicon rods by increasing the magnetic field, which results in high costs.

[0006] In order to solve the above technical problems, the present disclosure provides a method for preparing single crystal silicon in the first aspect, and the steps are as follows:

[0007] The raw materials are loaded into a crucible and converted to a melt in a crystal pulling furnace. The melt is treated under a first preset condition so that impurities in the melt move away from the crystal pulling position. The first preset condition is maintained until a conversion condition is met. The first preset condition is converted to a second preset condition, and the first preset condition is numerically greater than the second preset condition.

[0008] In some embodiments, the first preset condition includes: the crucible has a rotation speed of 8-10 rpm;

[0009] The second preset condition includes: the rotation speed of the crucible is 4-5 rpm.

[0010] In some embodiments, the first preset condition includes: a furnace pressure of the crystal pulling furnace is 80-120 Torr;

[0011] The second preset condition includes: the furnace pressure of the crystal pulling furnace is 6-8 Torr.

[0012] In some embodiments, the first preset condition includes: the heating power is P1=P2(1.2-1.5);

[0013] The first preset condition includes: the heating power is P1=P2(0.9-1.1);

[0014] Among them, P1 is the heating power and P2 is the seeding power.

[0015] In some embodiments, the conversion conditions include: the temperature in the crystal pulling furnace reaches 1453-1455° C. and maintains the first preset condition for 30-40 minutes.

[0016] In some embodiments, charging the raw material into a crucible and converting it into a melt in a crystal pulling furnace comprises:

[0017] After the raw materials are placed in the crucible, when the raw materials are melted to the size of the lower tube hole of the guide tube, the raw materials are added to the crucible for the second time.

[0018] The second aspect of the present disclosure provides a crucible, which is based on the method for preparing single crystal silicon provided in the first aspect of the present disclosure, and comprises:

[0019] Crucible body;

[0020] The impurity collecting structure is arranged inside the crucible body and is located on the peripheral side of the bottom wall of the crucible body.

[0021] In some embodiments, the crucible comprises:

[0022] The protrusion structure is arranged inside the crucible body and located at the center of the bottom wall of the crucible body. The surrounding side of the protrusion structure constitutes an impurity collection structure.

[0023] In some embodiments, the protrusion height of the protrusion structure is 6%-10% of the height of the crucible body, and the outer circle radius of the protrusion structure is 15%-20% of the radius of the crucible body.

[0024] A third aspect of the present disclosure provides a single crystal silicon preparation device, which includes the crucible provided by the second aspect of the present disclosure.

[0025] The second aspect of the present disclosure provides a single crystal silicon preparation device that can directly use the crucible provided in the first aspect. The specific implementation structure can refer to the relevant content described in the first aspect, which will not be repeated here.

[0026] Through the above technical scheme, the method for preparing single crystal silicon provided by the present disclosure first loads the raw materials into a crucible, and melts the raw materials in the crucible in a crystal pulling furnace to convert the melt into a melt, then sets the internal environment of the crystal pulling furnace to a first preset condition to process the melt, maintains the first preset condition until the conversion condition is met, and converts the first preset condition in the crystal pulling furnace to a second preset condition. The first preset condition is numerically greater than the second preset condition. After the raw materials are converted into a melt in this way, the impurities in the melt at the first preset condition can move in a direction away from the crystal pulling position, so that the impurities at the crystal pulling position are reduced and evenly dispersed, effectively improving the resistivity of the generated single crystal silicon rod, without the need to set a magnetic field, while reducing impurities and expensive costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 It is a schematic flow chart of a method for preparing single crystal silicon disclosed in an embodiment of the present disclosure;

[0029] Figure 2 It is a schematic diagram of the structure of a single crystal silicon preparation device disclosed in an embodiment of the present disclosure;

[0030] Description of reference numerals:

[0031] 1. Water cooling screen; 2. Guide tube; 3. Crucible side; 4. Crucible; 5. Crucible support; 6. Support rod. 7. Raised structure. DETAILED DESCRIPTION

[0032] The following is a further detailed description of the embodiments of the present disclosure in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present disclosure, but cannot be used to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

[0033] The present disclosure provides these embodiments to make the present disclosure thorough and complete, and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the relative arrangement of the parts and steps, the composition of the materials, the numerical expressions and the numerical values ​​set forth in these embodiments should be interpreted as being merely exemplary, and not as limiting.

[0034] It should be noted that, in the description of the present disclosure, unless otherwise specified, the meaning of "multiple" is greater than or equal to two; the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present disclosure. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0035] In addition, the words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different parts. "Vertical" does not mean vertical in the strict sense, but is within the tolerance range. "Parallel" does not mean parallel in the strict sense, but is within the tolerance range. "Include" or "comprising" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements.

[0036] It should also be noted that in the description of the present disclosure, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances. When a specific device is described as being located between a first device and a second device, there may or may not be an intermediate device between the specific device and the first device or the second device.

[0037] All terms used in the present disclosure have the same meanings as those understood by those of ordinary skill in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries, for example, should be interpreted as having meanings consistent with their meanings in the context of the relevant technology, and should not be interpreted in an idealized or extremely formal sense, unless explicitly defined as such herein.

[0038] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0039] Embodiment 1

[0040] A first embodiment of the present disclosure provides a method for preparing single crystal silicon, the specific steps of which include:

[0041] S1. Load the raw materials into the crucible and convert them into melt in the crystal pulling furnace;

[0042] Specifically, the crucible and the crystal pulling furnace may be the crucible and the crystal pulling furnace used in the crystal pulling method in the prior art, and are not specifically limited thereto. After the raw material is placed in the crucible, it may be heated by a heating device inside the crystal pulling furnace until the raw material in the crucible is completely melted and converted into a molten material. The raw material placed in the crucible may be the raw material used in the traditional crystal pulling method, and generally may be high-purity polycrystalline silicon.

[0043] S2, treating the melt under a first preset condition so that impurities in the melt move in a direction away from the crystal pulling position;

[0044] Specifically, the first preset condition may be a condition of the internal environment of the crystal pulling furnace, such as the rotation speed of the crucible, the furnace pressure of the crystal pulling furnace, and / or the temperature in the crystal pulling furnace, which are not specifically limited. Generally speaking, in the conventional crystal pulling method, the seed crystal stage is at the center of the cross section of the crucible in the length direction, and is located at the liquid level of the melt in the crucible for crystal pulling. This position can be defined as the pulling position, so under the first preset condition, the impurities in the melt can move away from the center of the cross section of the seed crystal stage in the length direction of the crucible, and / or sink to the bottom of the crucible, so as to reduce the impurities at the crystal pulling position, thereby reducing the impurities in the generated single crystal silicon rod and improving the resistivity of the single crystal silicon rod.

[0045] S3, maintaining the first preset condition until a conversion condition is met, and converting from the first preset condition to the second preset condition;

[0046] Specifically, the second preset condition may be a condition suitable for processes such as temperature adjustment, seeding, shoulder release, shoulder rotation, and equal diameter. During the above process, if the second preset condition is set to the parameter value of the first preset condition, the parameter value is large, which will affect the melt by the internal environment, resulting in a decrease in the quality of the generated single crystal silicon rod. The conversion condition may be that the temperature in the furnace reaches a preset temperature, and the preset temperature may be a temperature suitable for processes such as temperature adjustment, seeding, shoulder release, shoulder rotation, and equal diameter. The conversion condition may also be the time to maintain the first preset condition, or a combination of the time to maintain the first preset condition and the preset temperature, without specific limitation.

[0047] Through the above technical scheme, the method for preparing single crystal silicon provided by the present disclosure first loads the raw material into a crucible, and melts the raw material in the crucible in a crystal pulling furnace to convert the melt into a melt, then sets the internal environment of the crystal pulling furnace to a first preset condition to process the melt, maintains the first preset condition until the conversion condition is met, and converts the first preset condition in the crystal pulling furnace to a second preset condition. The first preset condition is numerically greater than the second preset condition. After the raw material is converted into a melt in this way, the impurities in the melt in the first preset condition can move in a direction away from the crystal pulling position, so that the impurities at the crystal pulling position are reduced and dispersed more evenly, effectively improving the resistivity of the generated single crystal silicon rod.

[0048] In some embodiments, the first preset condition includes: the rotation speed of the crucible is 8-10 rpm; the second preset condition includes: the rotation speed of the crucible is 4-5 rpm.

[0049] Specifically, after the raw materials are conventionally loaded into the crucible, the crucible's rotation speed is generally set at 4-5rpm to promote the stability of crystal growth and control the temperature distribution of the melt, and during the processes of temperature adjustment, crystal seeding, shoulder release, shoulder rotation, equal diameter, and finishing, the crucible's rotation speed is always maintained at 4-5rpm to ensure that the surface and internal fluctuations of the melt are small, thereby reducing the formation of dislocations in the crystal and improving the quality of the crystal. In the present disclosure, when the raw materials inside the crucible are converted into a melt, by increasing the crucible's rotation speed to 8-10rpm, increasing the crucible's rotation speed can increase the centrifugal force on the impurities inside the melt, so that the impurities move away from the center of the crucible to the edge of the crucible due to the centrifugal force, effectively reducing the number of impurities at the crystal pulling position in the crucible. So as to improve the conductivity of the single crystal silicon rod.

[0050] Due to the acceleration of the crucible rotation speed, the fluctuation inside and on the surface of the melt becomes larger, which is not conducive to the growth conditions of single crystal silicon. Maintain the first preset condition until the conversion condition is met, adjust the first preset condition to the second preset condition, and convert the crucible rotation speed from 8-10rpm to 4-5rpm to reduce the fluctuation inside and on the surface of the melt. The specific rotation speed of the crucible under the first preset condition can be selected according to the concentration of impurities inside the raw material. A large number of raw materials can be sampled to test the concentration of impurities in the sampled samples, and the rotation speed of the crucible under the first preset condition can be adjusted according to the concentration. When the impurity concentration is high, the crucible rotation speed can be selected as 10rpm, and when the impurity concentration is low, the crucible rotation speed can be selected as 8rpm. It can also be selected according to the experience of the operator without specific limitation. For increasing the pressure in the furnace, the device for adjusting the air pressure in the crystal pulling furnace can be used, without adding other devices, and the cost is low.

[0051] In this embodiment, the rotation speed of the crucible under the first preset condition may be 9 rpm, and the rotation speed of the crucible under the second preset condition may be 5 rpm.

[0052] In some embodiments, the first preset condition includes: the furnace pressure of the crystal pulling furnace is 80-120 Torr; the second preset condition includes: the furnace pressure of the crystal pulling furnace is 6-8 Torr.

[0053] Specifically, in the process of preparing single crystal silicon rods by conventional crystal pulling method, the furnace pressure is usually 6-8Torr. The lower air pressure helps to control the stability of the melt surface and reduce the fluctuation of the melt surface. At the same time, under lower air pressure, the temperature distribution inside the melt is more uniform, which helps to improve the accuracy of temperature control. To increase the quality of the generated single crystal silicon rod. In the present disclosure, in the melting process of the raw materials in the crucible, the furnace pressure of 11Torr is adopted. When the raw materials inside the crucible are all melted into the melt, the furnace pressure is increased to 80-120Torr. Increasing the furnace pressure can effectively make the impurities with higher density inside the melt sink quickly to the bottom of the crucible, so that the impurities are away from the crystal pulling position, and the impurities are effectively reduced in the process of generating single crystal silicon rods. Entering the interior of the single crystal silicon rod. However, being at a high pressure for a long time is not conducive to controlling the stability of the melt surface, and will increase the defects inside the single crystal silicon rod, and will also increase the oxygen content inside the single crystal silicon rod. Therefore, when the preset temperature is reached, the impurities in the melt under the first preset condition flow to the bottom of the crucible, and the impurities in the melt near the opening of the crucible are reduced. At this time, the first preset condition is converted to the second preset condition, and the furnace pressure is changed to 6-8 Torr. This helps to ensure the smoothness of the melt surface, reduce the defects of the single crystal silicon rod, and improve the quality of the single crystal silicon rod. The specific value of the furnace pressure of the crystal pulling furnace can be determined according to the heating power and the heat loss in the furnace, and can also be adjusted according to the precipitation rate of the required impurities, without specific limitation. In this embodiment, the furnace pressure of the crystal pulling furnace can be 100 Torr. As for adjusting the rotation speed of the crucible, it can be achieved by adjusting the motor that drives the crucible to rotate inside the crystal pulling furnace, without the need to set up additional devices, and the cost is low.

[0054] In some embodiments, the first preset condition includes: the heating power is P1=P2(1.2-1.5); the first preset condition includes: the heating power is P1=P2(0.9-1.1); wherein P1 is the heating power and P2 is the seeding power.

[0055] Specifically, in the process of preparing single crystal silicon rods by conventional crystal pulling method, the heating power is usually set to 0.9 to 1.1 times of the seeding power. Such setting can help maintain the melt temperature at a stable level and ensure the uniformity of the temperature gradient during the crystal growth process. Because the furnace pressure inside the crystal pulling furnace increases when it is in the first preset state, the increase in furnace pressure will increase the heat loss of gas convection, which means that more heat may escape through the gas. Therefore, the corresponding setting of the heating power to 1.2-1.5 times the seeding power can effectively increase the temperature in the furnace and supplement the heat loss caused by the increase in furnace pressure. The specific selection of the heating power under the first preset condition can be selected according to the specific process memory and adjusted in conjunction with the furnace pressure in the crystal pulling furnace. If the high temperature in the first preset condition is maintained for a long time, the crystal quality will be reduced and the energy loss will be increased. Therefore, when the crystal pulling furnace is converted from the first preset condition to the second preset condition, the furnace pressure in the furnace will drop to 6-8Torr, and the heat loss will be reduced at this time, and no heat supplement is required, so when it is in the second preset condition, the heating power can be adjusted to 0.9 to 1.1 times the seeding power. Seeding power refers to the heating power used for initial crystal growth during the crystal pulling process, which is a pre-set parameter. The specific value of the seeding power can be preset by the method in the prior art, and it will not be repeated. In this embodiment, the heating power under the first preset condition can be set to 1.2 times the seeding power. The heating power under the second preset condition is set to 0.95 times the seeding power. For the adjustment of the heating power, the parameters of the heating device in the crystal pulling furnace can be adjusted without adding additional devices, and the price is low.

[0056] In some embodiments, the conversion conditions include: the temperature in the crystal pulling furnace reaches 1453-1455° C. and maintains the first preset condition for 30-40 minutes.

[0057] Specifically, the melting point of the raw material for preparing single crystal silicon is 1414°C under standard atmospheric pressure. Heating the temperature in the furnace to 1453-1455°C can completely melt the raw material that has not been completely converted into the melt, and at the same time can help ensure the stability and fluidity of the melt, avoid the drastic fluctuation of the melt surface or the influence of volatile impurities caused by excessive temperature, and help form a temperature gradient that is conducive to crystal growth. At the same time, the heating power of 1.2-1.5 times the seeding power can effectively maintain the temperature in the furnace between 1453-1455°C and fluctuate back and forth, so that the melt can have enough time to maintain the first preset condition, so that the impurities in the melt have enough time to move away from the crystal pulling position. Generally speaking, the time to maintain the first preset condition is between 30-40 minutes, and the resistivity of the single crystal silicon rod produced at the production site is the best. If it exceeds 40 minutes, the resistivity of the single crystal silicon rod will not be significantly improved or decreased. If it does not reach 30 minutes, the impurities in the melt will move away from the crystal pulling position. The effect is poor. The specific time can be selected according to the impurity concentration in the raw material, and is not specifically limited. In this embodiment, under the first preset condition, 1.2 times the seeding power can be used for 40 minutes, and when the temperature in the furnace reaches 1453°C, the first preset condition is switched to the second preset condition.

[0058] In some embodiments, loading the raw material into the crucible and converting it into a melt in the crystal pulling furnace includes: after placing the raw material into the crucible, when the raw material is melted to the size of the lower tube hole of the guide tube, adding the raw material into the crucible for the second time.

[0059] Specifically, the purpose of dividing the feeding step into two steps is that if there is too much silicon material in the latex at one time, the volume of the melt may be large, so that the temperature becomes difficult to control, and at the same time, it is prevented that too much fixed raw material is added to cause damage to the crucible. After the raw material is put into the crucible for the first time, it is necessary to wait for the size of the raw material put in the first time to be consistent with the size of the lower opening of the guide tube of the crystal pulling furnace before the second feeding. If the size of the raw material added for the first time is too large relative to the lower opening of the guide tube, it will cause crystallization when the raw material is added for the second time, causing damage to the crucible. If the size of the raw material added for the first time is too small for the lower opening of the guide tube, it will cause the crucible to bulge due to the high temperature of the melt.

[0060] The specific process of the single crystal silicon preparation method provided in the first embodiment of the present disclosure is summarized as follows:

[0061] Step 1: Load the raw materials into the crucible;

[0062] Step 2: Place the crucible into a crystal pulling furnace and perform vacuum treatment to maintain the pressure in the furnace below 40 mTorr;

[0063] Step 3: Turn on the heating device and set the heating power to melt the material;

[0064] Step 4: When the raw material is melted to the size of the lower tube hole of the guide tube, the raw material is added to the crucible for the second time;

[0065] Step 5: When the raw material in the crucible is converted into a melt, the furnace is adjusted to the first preset condition, that is, the furnace pressure is increased to 100 Torr, the crucible speed is adjusted to 9 rpm, and the heater power is adjusted to 1.2 times the seeding power;

[0066] Step 6: Maintain the first preset condition for 40 minutes, and when the temperature in the furnace reaches 1453°C, switch to the second preset condition, adjust the crucible speed to 5 rpm, the furnace pressure to 9 Torr, and the heating power to 0.95 times the seeding power for temperature control;

[0067] Step 7: Temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter and finishing processes are performed;

[0068] Among them, the argon gas consumption can be set to 100slpm, the furnace pressure can be set to 9Torr, the crucible rotation speed can be 5rpm, the crystal rotation speed can be 9rpm, the seeding pulling speed needs to be less than or equal to 500mm / h, the shoulder release pulling speed can be 30-100mm / h, the shoulder rotation pulling speed needs to be less than or equal to 120mm / h, and the equal diameter pulling speed needs to be greater than or equal to 110mm / h. The above parameters can be specifically selected by methods in the prior art, and will not be repeated here.

[0069] Embodiment 2

[0070] Embodiment 2 of the present disclosure provides a crucible, which is applied to the method for preparing single crystal silicon in the embodiment of the present disclosure, and includes: a crucible body 4 and an impurity collection structure; the impurity collection structure is arranged inside the crucible body 4 and is located on the peripheral side of the bottom wall of the crucible body 4.

[0071] Specifically, the crucible body 4 can be a standard crucible for preparing single crystal silicon rods by the crystal pulling method, and is not specifically limited. The impurity collection structure can be arranged in the crucible body 4, and can be a groove-shaped structure arranged on the circumferential side of the bottom wall of the crucible body 4, and the groove-shaped structure is close to the side wall of the crucible. When the single crystal silicon preparation method in the first embodiment of the present disclosure is adopted, when the crystal pulling furnace is in the first preset condition, the impurities in the melt move in the direction away from the crystal pulling position, that is, the impurities move from the center to the edge through the centrifugal force generated by the rotation, and due to the internal high furnace pressure environment, the impurities in the melt sink to the bottom of the crucible, so that the impurities enter the impurity collection structure, so as to reduce the number of impurities inside the single crystal silicon rod and increase the uniformity of impurities inside the single crystal silicon rod.

[0072] In some embodiments, the crucible includes: a protruding structure 7, which is disposed inside the crucible body 4 and located at the center of the bottom wall of the crucible body 4, and the surrounding side of the protruding structure 7 constitutes an impurity collecting structure.

[0073] Specifically, the protruding structure 7 can be a protruding block placed in the crucible body 4. In the present embodiment, the protruding structure 7 can be a bottom surface on the outside of the crucible body 4 that is recessed toward the inside of the crucible body 4 to form a protruding structure 7 located inside the crucible body 4. The space enclosed by the protruding structure 7 and the side wall of the crucible body 4 constitutes an impurity collection mechanism. In this arrangement, since the protruding structure 7 is located at the center of the bottom surface of the crucible body 4, its protruding direction extends along the center line of the length direction of the crucible body 4. Since the crystal pulling position is also at the center of the length direction of the crucible body 4, the protruding structure 7 can effectively suppress the downward heat convection of the growth interface of the single crystal silicon rod, thereby reducing the entry of impurities into the silicon rod and improving the uniformity of the longitudinal resistivity of the silicon rod.

[0074] In some embodiments, the protrusion height of the protrusion structure 7 is 6%-10% of the height of the crucible body 4 , and the outer circle radius of the protrusion structure 7 is 15%-20% of the radius of the crucible body 4 .

[0075] Specifically, the height of the crucible body 4 can be understood as the dimension in the length direction of the crucible body 4, the protrusion height of the protrusion structure 7 is 6%-10% of the height of the crucible body 4, and the outer circle radius of the protrusion structure 7 can be understood as the radius of the maximum outer circle of the protrusion structure 7 is 15%-20% of the radius of the crucible body 4. If the size is too large, the volume of the raw material and the melt contained in the crucible will be reduced, and if the size is too small, the impurity collection effect will not be obvious. Specifically, the size of the protrusion structure 7 can be selected according to the impurity concentration in the raw material.

[0076] The specific process of the method for preparing single crystal silicon in Example 1 using the crucible provided in Example 2 of the present disclosure is summarized as follows:

[0077] Step 1: Put the raw materials into the crucible, where the silicon material with a crucible bottom size of less than or equal to 30mm is 50kg, of which the 20-30mm raw material size must account for less than or equal to 10%, in order to prevent the raw materials from breaking the convex structure 7 at the bottom of the crucible. The remaining raw materials need to meet the requirements of less than or equal to 70mm, of which the 60-70mm raw materials account for less than or equal to 20%.

[0078] The specific process of step 2 to step 7 of the embodiment is consistent with the process described in embodiment 1 provided in the present disclosure. For details, please refer to the description in embodiment 1, and no further details will be given here.

[0079] Comparative Example

[0080] The comparative example provided in the present disclosure is a method for preparing single crystal silicon in the prior art, and the specific process is summarized as follows:

[0081] Step 1: Load the raw materials into the crucible;

[0082] Step 2: Load the crucible into a crystal pulling furnace and perform vacuum treatment;

[0083] Step 3: Turn on the heating device and set the heating power to melt the material;

[0084] Step 4: When the raw material in the crucible is converted into a melt, the furnace is adjusted to the second preset condition, the crucible speed is adjusted to 5 rpm, the furnace pressure is adjusted to 9 Torr, and the heating power is adjusted to 0.95 times the seeding power for temperature control;

[0085] Step 5: Temperature adjustment, seeding, shoulder release, shoulder rotation, equal diameter and finishing processes;

[0086] Among them, the argon gas consumption can be set to 100slpm, the furnace pressure can be set to 9Torr, the crucible rotation speed can be 5rpm, the crystal rotation speed can be 9rpm, the seeding pulling speed needs to be less than or equal to 500mm / h, the shoulder release pulling speed can be 30-100mm / h, the shoulder rotation pulling speed needs to be less than or equal to 120mm / h, and the equal diameter pulling speed needs to be greater than or equal to 110mm / h.

[0087] Table 1 Resistivity of single crystal silicon rods of different lengths prepared in Example 1, Example 2 and Comparative Example

[0088]

[0089] It can be seen from Table 1 that as the length of the single crystal silicon rod increases, the resistivity of the single crystal silicon rods prepared by the comparative example, Example 1 and Example 2 all decreases, but the resistivity of the single crystal silicon rod produced by Example 1 is higher than that of the comparative example at any length, from which it can be seen that the single crystal silicon preparation method adopted in Example 1 can improve the resistivity of the prepared single crystal silicon rod. At the same time, the resistivity of the single crystal silicon rods of various lengths prepared by Example 2 in Table 1 is generally higher than that of Example 1, from which it can be seen that the crucible provided in Example 2 in combination with the single crystal silicon preparation method provided in Example 1 can further reduce the impurity concentration of the prepared single crystal silicon rod and increase the uniformity of impurities in the prepared single crystal silicon rod, so as to improve the resistivity of the single crystal silicon rod.

[0090] Embodiment 3

[0091] A third embodiment of the present disclosure provides a single crystal silicon preparation device, which includes the crucible provided in the second embodiment of the present disclosure.

[0092] Specifically, the single crystal silicon preparation device can have a crystal pulling furnace in the prior art, which has components and devices in a conventional crystal pulling furnace such as a water-cooled screen 1, a guide tube 2, a crucible side 3, a crucible support 4 and a support rod 5, without specific limitation.

[0093] The crucible described in the third embodiment can directly use the crucible provided in the second embodiment. The specific implementation structure can refer to the relevant contents described in the second embodiment, which will not be described again here.

[0094] The single crystal silicon preparation device provided in the third embodiment of the present invention is internally provided with the crucible provided in the second embodiment of the present disclosure, and by implementing the single crystal silicon preparation method provided in the first embodiment of the present disclosure, the impurities at the crystal pulling position are reduced and evenly dispersed, thereby effectively improving the resistivity of the generated single crystal silicon rod.

[0095] So far, various embodiments of the present disclosure have been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Based on the above description, those skilled in the art can fully understand how to implement the technical solution disclosed here.

[0096] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present disclosure. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict.

Claims

1. A method for preparing single crystal silicon, characterized in that: The steps are as follows: The raw materials are loaded into a crucible and converted to a melt in a crystal pulling furnace. The melt is treated under a first preset condition so that impurities in the melt move away from a crystal pulling position. The first preset condition is maintained until a conversion condition is met. The first preset condition is converted to a second preset condition, and the first preset condition is numerically greater than the second preset condition.

2. The method for preparing single crystal silicon according to claim 1, characterized in that: The first preset condition includes: the rotation speed of the crucible is 8-10 rpm; The second preset condition includes: the rotation speed of the crucible is 4-5 rpm.

3. The method for preparing single crystal silicon according to claim 1 or 2, characterized in that: The first preset condition includes: the furnace pressure of the crystal pulling furnace is 80-120 Torr; The second preset condition includes: the furnace pressure of the crystal pulling furnace is 6-8 Torr.

4. The method for preparing single crystal silicon according to claim 3, characterized in that: The first preset condition includes: the heating power is P1=P2(1.2-1.5); The first preset condition includes: the heating power is P1=P2(0.9-1.1); Among them, P1 is the heating power and P2 is the seeding power.

5. The method for preparing single crystal silicon according to claim 4, characterized in that: The conversion conditions include: the temperature in the crystal pulling furnace reaches 1453-1455° C. and maintains the first preset condition for 30-40 minutes.

6. The method for preparing single crystal silicon according to claim 1, characterized in that: The raw materials are loaded into the crucible and converted into a melt in the crystal pulling furnace: After the raw materials are placed in the crucible, when the raw materials are melted to the size of the lower tube hole of the guide tube, the raw materials are added to the crucible for the second time.

7. A crucible, characterized in that: The crucible is based on the method for preparing single crystal silicon according to any one of claims 1 to 6, which comprises: Crucible body (4); An impurity collection structure is arranged inside the crucible body (4) and is located on the peripheral side of the bottom wall of the crucible body (4).

8. The crucible according to claim 7, characterized in that include: A protruding structure (7), wherein the protruding structure (7) is arranged inside the crucible body (4) and is located at the center of the bottom wall of the crucible body (4), and the peripheral side of the protruding structure (7) constitutes the impurity collecting structure.

9. The crucible according to claim 8, characterized in that The protrusion height of the protrusion structure is 6%-10% of the height of the crucible body (4), and the outer circle radius of the protrusion structure is 15%-20% of the radius of the crucible body (4).

10. A single crystal silicon preparation device, characterized in that: A crucible comprising the crucible according to claim 9.

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