Granular silicon crystal pulling process, crucible and device

Abstract

The invention provides a grain silicon crystal pulling process, a crucible and a device, and relates to the technical field of monocrystalline silicon growth. The crystal pulling process of the granular silicon comprises the following steps: vacuumizing the interior of a furnace, adjusting the temperature in the furnace to a first preset temperature, adjusting the revolution of a crucible body to keep a first preset rotation speed, and filling inert gas into the furnace; the feeder descends to the water cooling screen along the auxiliary furnace chamber, first-time material pouring is carried out, and the particle silicon is poured into the crucible body at the preset speed; after the materials are poured for the first time, the temperature in the furnace is kept at the first preset temperature for a period of time, the temperature in the furnace is adjusted to the second preset temperature for melting, and the second preset temperature is larger than the first preset temperature; the interval between the starting time of the second pouring and the ending time of the first pouring is a first preset duration. According to the process, the crystal pulling quality and efficiency can be effectively improved, and the hydrogen jump phenomenon is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of single crystal silicon growth, and in particular to a crystal pulling process, a crucible and a device for granular silicon. Background Art

[0002] As the global demand for sustainable energy grows, photovoltaic power generation, as an important form of green energy, has received great attention from all countries. Monocrystalline silicon wafers are one of the basic materials of the photovoltaic industry and have broad market prospects. However, due to the policy influence of the United States and Europe, domestic photovoltaic companies are facing severe challenges and are generally in a loss-making state. In this context, reducing costs and improving efficiency have become the key to the development of the photovoltaic industry.

[0003] Granular silicon is a raw material that can significantly reduce costs and is widely used in the photovoltaic industry. However, due to the existence of hydrogen jump problems, its use has been limited to between 10% and 20%. The hydrogen jump problem can cause silicon splashing on the water-cooled screen during the production process, which in turn affects the operating stability of the single crystal furnace and seriously affects production capacity.

[0004] Therefore, how to provide a granular silicon crystal pulling process, crucible and device that can reduce the hydrogen jump phenomenon is a problem that urgently needs to be solved. Summary of the invention

[0005] To solve the above technical problems, the embodiments of the present invention provide a crystal pulling process for granular silicon, comprising the following steps: evacuating the furnace, adjusting the temperature in the furnace to a first preset temperature, adjusting the number of revolutions of the crucible body to maintain the first preset speed, and filling the furnace with inert gas; lowering the feeder along the auxiliary furnace chamber to the water-cooled screen, performing the first pouring, and pouring the granular silicon into the crucible body at a preset speed; after the first pouring, maintaining the temperature in the furnace at the first preset temperature for a period of time, and then adjusting the temperature in the furnace to a second preset temperature for melting the material, the second preset temperature being greater than the first preset temperature; the time interval between the start of the second pouring and the end of the first pouring is the first preset duration.

[0006] In some embodiments, the furnace is evacuated, specifically: the auxiliary furnace chamber and the main furnace chamber are evacuated so that the furnace pressure of the main furnace chamber reaches a first preset pressure value, and the furnace pressure of the auxiliary furnace chamber reaches a second preset pressure value, and the first preset pressure value is greater than the second preset pressure value.

[0007] In some embodiments, before the first pouring is performed and the granular silicon is poured into the crucible body at a preset speed, the process also includes: pre-treating the granular silicon, which includes the following steps: placing the granular silicon to be dehydrogenated in a sealed reaction container; turning on an ultraviolet light source and an ozone generator to allow ultraviolet light to irradiate the surface of the granular silicon while ozone gas enters the container; after the irradiation is completed, turning off the light source and taking out the granular silicon.

[0008] In some embodiments, the temperature in the furnace is adjusted to a first preset temperature, specifically: adjusting the power of the main heater and the bottom heater to 50KW to maintain the temperature in the furnace at 1000°C-1200°C; the temperature in the furnace is adjusted to a second preset temperature for melting the material, specifically: adjusting the power of the main heater to 90KW, adjusting the power of the bottom heater to 100KW to maintain the temperature in the furnace to the melting temperature of the granular silicon.

[0009] In some embodiments, the temperature in the furnace is maintained at the first preset temperature for a period of time, specifically: the temperature in the furnace is maintained at the first preset temperature for a period of time of 10 minutes to 20 minutes.

[0010] In some embodiments, the first preset duration is less than or equal to 30 minutes.

[0011] In some embodiments, the weight of a single pour is 120±20 kg.

[0012] In some embodiments, the flow rate of the inert gas charged into the furnace during the charging process is 200 slpm; the flow rate of the inert gas charged into the furnace during the chemical process is 120 slpm.

[0013] A crucible is provided. The crucible is based on the above-mentioned granular silicon crystal pulling process, and comprises: a crucible body, the bottom of which is provided with a smooth inclined surface inclined from the edge to the center.

[0014] A crystal pulling device for granular silicon includes: the above-mentioned crucible.

[0015] Through the above technical scheme, the crystal pulling process, crucible and crystal pulling device of granular silicon provided by the present disclosure adjust the speed of pouring granular silicon, control the granular silicon to gather as much as possible to the center of the crucible body when pouring into the furnace, and reduce the time interval between each pouring, so that the granular silicon poured each time covers the granular silicon poured last time, thereby avoiding the hydrogen jump phenomenon caused by too long exposure time. In addition, the temperature during pouring and the temperature during melting are controlled, and before reaching the high temperature melting temperature, the critical temperature for hydrogen jump is maintained for a period of time, and the temperature rise rate is controlled to prevent the temperature from rising too quickly and hydrogen jumps from occurring frequently. This process can effectively improve the quality and efficiency of crystal pulling and reduce the hydrogen jump phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 is a flow chart of the steps of a crystal pulling process provided in an embodiment of the present application;

[0018] Figure 2 It is a schematic diagram of the structure of a granular silicon crystal pulling device provided in an embodiment of the present application.

[0019] Description of reference numerals:

[0020] 1. Main furnace chamber; 2. Auxiliary furnace chamber; 3. Water cooling screen; 4. Crucible body; 5. Silicon liquid; 6. Feeder. DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The disclosed embodiment provides a crystal pulling process for granular silicon, comprising the following steps: evacuating the furnace, adjusting the temperature in the furnace to a first preset temperature, adjusting the number of revolutions of the crucible body 4 to maintain a first preset speed, and filling the furnace with an inert gas; lowering the feeder 6 along the auxiliary furnace chamber 2 to the water-cooled screen 3, performing the first pouring, and pouring the granular silicon into the crucible body 4 at a preset speed; after the first pouring, maintaining the temperature in the furnace at the first preset temperature for a period of time, adjusting the temperature in the furnace to a second preset temperature for melting the material, the second preset temperature being greater than the first preset temperature; the time interval between the start of the second pouring and the end of the first pouring is a first preset duration.

[0029] S1, evacuate the furnace, adjust the temperature in the furnace to a first preset temperature, adjust the number of revolutions of the crucible body 4 to maintain a first preset speed, and fill the furnace with inert gas;

[0030] Specifically, Figure 1As shown, in order to remove the air and other impurity gases in the furnace and create a high-purity environment for the subsequent growth of single crystal silicon, the furnace is evacuated. The temperature in the furnace is adjusted to a first preset temperature, which is a temperature at which hydrogen jump can occur. The temperature is less than the melting point of granular silicon, such as: the first preset temperature is 1000°C-1200°C. Setting the rotation speed of the crucible body 4 can promote heat conduction inside the melt, making the melt temperature more uniform, which is conducive to the subsequent growth of single crystal silicon. The first preset speed here can be set according to actual needs, such as: 5 rpm, 6 rpm, 10 rpm, etc. In addition, an inert gas is filled into the furnace to maintain the pressure and protective atmosphere in the furnace, prevent oxidation and other impurities from entering the furnace body, and also help control the gas flow in the furnace and improve the heat transfer effect. The inert gas filled here can be argon.

[0031] S2, lowering the feeder 6 along the auxiliary furnace chamber 2 to the water cooling screen 3, performing the first pouring, and pouring the granular silicon into the crucible body 4 at a preset speed;

[0032] Specifically, Figure 1 As shown, the feeder 6 is lowered along the auxiliary furnace chamber 2 to the position of the water-cooled screen 3. The water-cooled screen 3 is a component used to cool the furnace wall, which helps to control the temperature distribution in the furnace. The first pouring is carried out at the position of the water-cooled screen, that is, the granular silicon is started to be poured into the crucible body 4. During the pouring process, the speed of pouring the granular silicon needs to be controlled to maintain a preset speed, which can be less than or equal to 180 kg / min. Keeping it within a preset speed range is to ensure that the granular silicon can be evenly distributed in the crucible body 4, and to help control the temperature gradient of the melt and prevent the occurrence of hydrogen jump.

[0033] S3, after the first pouring of materials, the temperature in the furnace is maintained at the first preset temperature for a period of time, and then the temperature in the furnace is adjusted to a second preset temperature to melt the materials, wherein the second preset temperature is greater than the first preset temperature;

[0034] Specifically, Figure 1 As shown, the second preset temperature is greater than or equal to the melting point of granular silicon, and the first preset temperature is the critical temperature at which granular silicon can undergo hydrogen jumps. Prolonging the holding time of the first preset temperature in the furnace can prevent the temperature from rising too quickly, thereby preventing frequent hydrogen jumps. The holding time for maintaining the first preset temperature in the furnace can be set according to actual needs, such as 10 minutes, 20 minutes, or 30 minutes. This temperature control method helps ensure that granular silicon is more stable during the melting process, reduces the number of hydrogen jumps, and thus improves the quality of single crystal silicon.

[0035] S4. The time interval between the start time of the second pouring and the end time of the first pouring is a first preset time length.

[0036] Specifically, Figure 1 As shown, the first preset time here can be set according to actual needs, such as 20 minutes, 30 minutes or 35 minutes, etc. Controlling the interval time of adding materials can ensure that the newly added granular silicon covers the granular silicon of the previous batch in time, which can reduce the risk of hydrogen jump. Controlling the interval time helps to maintain the continuity of the melt surface and prevent the granular silicon from hydrogen jumping due to temperature changes and splashing onto the water cooling screen 3.

[0037] The crystal pulling process of granular silicon provided by the present disclosure adjusts the speed of pouring granular silicon, controls the granular silicon to gather as much as possible towards the center of the crucible body 4 when pouring into the furnace, and reduces the time interval between each pouring, so that the granular silicon poured each time covers the granular silicon poured last time, thereby avoiding the hydrogen jump phenomenon caused by too long exposure time. In addition, the temperature during pouring and the temperature during melting are controlled, and before reaching the high temperature melting temperature, the critical temperature for hydrogen jump to occur is maintained for a period of time, and the temperature rise rate is controlled to prevent the temperature from rising too fast and hydrogen jumps from occurring frequently. This process can effectively improve the quality and efficiency of crystal pulling and reduce the hydrogen jump phenomenon.

[0038] In some embodiments, the furnace is evacuated, specifically: the auxiliary furnace chamber 2 and the main furnace chamber 1 are evacuated, so that the furnace pressure of the main furnace chamber 1 reaches a first preset pressure value, and the furnace pressure of the auxiliary furnace chamber 2 reaches a second preset pressure value, and the first preset pressure value is greater than the second preset pressure value.

[0039] Specifically, the first preset pressure value and the second preset pressure value are not specifically limited here, as long as the first preset pressure value is greater than the second preset pressure value. For example, the first preset pressure value is 15 Torr, and the second preset pressure value is 13 Torr. The first preset pressure value being greater than the second preset pressure value can help the granular silicon transfer more smoothly from the auxiliary furnace chamber 2 to the main furnace chamber 1, reducing the splashing and loss of granular silicon during the transfer process. Properly increasing the pressure of the main furnace chamber 1 can suppress the height of the granular silicon jumping and prevent it from splashing onto the water cooling screen 3.

[0040] In some embodiments, before the first pouring is performed and the granular silicon is poured into the crucible body 4 at a preset speed, the process also includes: pre-treating the granular silicon, which includes the following steps: placing the granular silicon to be dehydrogenated in a sealed reaction container; turning on an ultraviolet light source and an ozone generator to irradiate the surface of the granular silicon with ultraviolet light while ozone gas enters the container; after the irradiation is completed, turning off the light source and taking out the granular silicon.

[0041] Specifically, place the granular silicon to be dehydrogenated in a sealed reaction container, and ensure that the reaction container is well sealed to avoid interference from external gases. Turn on the ultraviolet light source to irradiate the surface of the granular silicon with ultraviolet rays. At the same time, turn on the ozone generator to allow ozone gas to enter the container, and control the irradiation time and the time for the ozone gas to be introduced. For example, the irradiation time can be set between 10 minutes and 30 minutes, and the specific time depends on the amount of granular silicon and the required degree of dehydrogenation. After the predetermined irradiation time is reached, turn off the ultraviolet light source. If necessary, a small amount of inert gas (such as argon) can continue to be introduced to help exhaust the ozone gas in the container. After waiting for the gas composition in the container to return to a safe level, close the container and take out the treated granular silicon. This pretreatment method can effectively reduce the hydrogen content in the granular silicon, thereby reducing the probability of hydrogen jump phenomenon in the subsequent melting process.

[0042] In some embodiments, the temperature in the furnace is adjusted to a first preset temperature, specifically: adjusting the power of the main heater and the bottom heater to 50KW to maintain the temperature in the furnace at 1000°C-1200°C; the temperature in the furnace is adjusted to a second preset temperature for melting the material, specifically: adjusting the power of the main heater to 90KW, adjusting the power of the bottom heater to 100KW to maintain the temperature in the furnace to the melting temperature of the granular silicon.

[0043] Specifically, the temperature in the furnace is adjusted to the first preset temperature, that is, the power of the main heater and the bottom heater is adjusted to 50KW to maintain the temperature in the furnace at 1000℃-1200℃. The temperature in the furnace is adjusted to the second preset temperature for melting, that is, the power of the main heater is adjusted to 90KW, and the power of the bottom heater is adjusted to 100KW to maintain the temperature in the furnace to the melting temperature of granular silicon. By accurately controlling the power of the main heater and the bottom heater, it can be ensured that the temperature gradually rises to the required target temperature, which helps to control the temperature gradient during the melting process, reduce the number of hydrogen jumps, and thus improve the quality of single crystal silicon growth.

[0044] In some embodiments, the temperature in the furnace is maintained at the first preset temperature for a period of time, specifically: the temperature in the furnace is maintained at the first preset temperature for a period of time of 10 minutes to 30 minutes.

[0045] Specifically, adjust the power of the main heater and the bottom heater to 50KW, and maintain the temperature in the furnace at 1000℃-1200℃, which is the critical temperature at which hydrogen jump may occur in granular silicon. Maintain the first preset temperature for 10 minutes to 30 minutes. During this period of time, it can ensure that the temperature change of granular silicon during the melting process is more gentle, reducing the occurrence of hydrogen jump.

[0046] In some embodiments, the first preset duration is less than or equal to 30 minutes.

[0047] Specifically, the first preset time here is less than or equal to 30 minutes. Controlling the interval time of adding materials can ensure that the newly added granular silicon can cover the granular silicon of the previous batch in time, which can reduce the risk of hydrogen jump. Controlling the interval time helps to maintain the continuity of the melt surface and prevent the granular silicon from hydrogen jumping due to temperature changes and splashing onto the water cooling screen 3.

[0048] In some embodiments, the weight of a single pour is 120±20 kg.

[0049] Specifically, the weight of the first pour is 120±20kg, and the weight of the second pour is 120±20kg. By controlling the weight of each pour, the granular silicon can be evenly distributed in the crucible body 4, which helps to control the temperature gradient of the melt, reduce the number of hydrogen jumps, and thus improve the quality of single crystal silicon growth.

[0050] In some embodiments, the flow rate of the inert gas charged into the furnace during the charging process is 200 slpm; the flow rate of the inert gas charged into the furnace during the chemical process is 120 slpm.

[0051] Specifically, during the first and second pouring, the flow rate of the inert gas is increased, and the airflow direction of the inert gas should be opposite to the direction in which the granular silicon jumps. The gas flow can push the jumped granular silicon back into the melt to prevent them from splashing onto the water-cooled screen 3, effectively offsetting the jumping power of the granular silicon and reducing the occurrence of hydrogen jump.

[0052] Table 1 Hydrogen jump ratio of comparative examples and experimental items

[0053]

[0054] It can be seen from Table 1 that the hydrogen jump ratio of the test item, that is, the solution of the present application, and the comparative example is 64%:27%. The hydrogen jump probability in the present solution is greatly reduced compared with the comparative example.

[0055] A crucible is provided. The crucible is based on the above-mentioned granular silicon crystal pulling process, and comprises: a crucible body 4, the bottom of which is provided with a smooth inclined surface inclined from the edge to the center.

[0056] Specifically, Figure 2 As shown, in order to make the granular silicon gather as much as possible in the center of the crucible body 4 when pouring, a smooth inclined surface inclined from the edge to the center is provided at the bottom of the crucible body 4, which helps to guide the granular silicon to move to the center of the crucible body 4 instead of accumulating at the edge. When the granular silicon is poured into the crucible body 4, due to the existence of the bottom inclined surface, the granular silicon will roll or slide along the inclined surface toward the center. This ensures that each batch of granular silicon poured can cover the granular silicon poured in the previous batch, reducing the occurrence of hydrogen jump phenomenon.

[0057] A crystal pulling device for granular silicon includes: the above-mentioned crucible.

[0058] The granular silicon crystal pulling device provided in the present disclosure has the same effect as the granular silicon crystal pulling process, which will not be elaborated in detail here.

[0059] 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.

[0060] 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 granular silicon crystal pulling process, characterized in that: The steps include: The furnace is evacuated, the temperature in the furnace is adjusted to a first preset temperature, the number of revolutions of the crucible body (4) is adjusted to maintain a first preset speed, and an inert gas is filled into the furnace; The feeder (6) is lowered along the auxiliary furnace chamber (2) to the water cooling screen (3), and the first material pouring is performed, and the granular silicon is poured into the crucible body (4) at a preset speed; After the first pouring of materials, the temperature in the furnace is maintained at the first preset temperature for a period of time, and then the temperature in the furnace is adjusted to a second preset temperature to melt the materials, wherein the second preset temperature is greater than the first preset temperature; The time interval between the start time of the second pouring and the end time of the first pouring is the first preset time length.

2. The granular silicon crystal pulling process according to claim 1, characterized in that: The vacuuming of the furnace is specifically as follows: The auxiliary furnace chamber (2) and the main furnace chamber (1) are evacuated so that the furnace pressure of the main furnace chamber (1) reaches a first preset pressure value, and the furnace pressure of the auxiliary furnace chamber (2) reaches a second preset pressure value, wherein the first preset pressure value is greater than the second preset pressure value.

3. The granular silicon crystal pulling process according to claim 1, characterized in that: Before the first pouring of materials is performed and the granular silicon is poured into the crucible body (4) at a preset speed, the method further comprises: The granular silicon is pretreated, which comprises the following steps: Placing granular silicon to be dehydrogenated in a sealed reaction vessel; Turn on the ultraviolet light source and the ozone generator so that ultraviolet light irradiates the surface of the granular silicon and ozone gas enters the container at the same time; After the irradiation is completed, the light source is turned off and the granular silicon is taken out.

4. The granular silicon crystal pulling process according to claim 1, characterized in that: The step of adjusting the temperature in the furnace to a first preset temperature is specifically as follows: Adjust the power of the main heater and the bottom heater to 50KW to maintain the temperature in the furnace at 1000°C-1200°C; The step of adjusting the temperature in the furnace to a second preset temperature to melt the material is specifically as follows: The power of the main heater was adjusted to 90 KW, and the power of the bottom heater was adjusted to 100 KW to maintain the temperature in the furnace to the melting temperature of the granular silicon.

5. The granular silicon crystal pulling process according to claim 1, characterized in that: After the temperature in the furnace is kept at the first preset temperature for a period of time, specifically: Maintain the temperature in the furnace at the first preset temperature for 10 minutes to 20 minutes.

6. The granular silicon crystal pulling process according to claim 1, characterized in that: The first preset duration is less than or equal to 30 minutes.

7. The granular silicon crystal pulling process according to claim 1, characterized in that: The single dumping weight is 120±20kg.

8. The granular silicon crystal pulling process according to claim 1, characterized in that: The flow rate of inert gas into the furnace during the charging process is 200slpm; The flow rate of inert gas introduced into the furnace during the material processing is 120slpm.

9. A crucible, characterized in that: The crucible is based on the granular silicon pulling process according to any one of claims 1 to 8, and comprises: The bottom of the crucible body (4) is provided with a smooth inclined surface which slopes from the edge to the center.

10. A granular silicon crystal pulling device, characterized in that: include: A crucible comprising the crucible according to claim 9.

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