WO2024221935A1 - Single crystal furnace and preparation method for monocrystalline silicon - Google Patents

Abstract

A single crystal furnace and a preparation method for monocrystalline silicon, relating to the technical field of semiconductor manufacturing. The single crystal furnace comprises a furnace body; a crucible supporting assembly is arranged in the furnace body; a crucible is arranged at the upper part of the crucible supporting assembly; a flow guide tube is arranged directly above the crucible; a heater is arranged between the inner wall of the furnace body and the periphery of the crucible; a seed crystal pulling mechanism is arranged at the top of the furnace body. The single crystal furnace further comprises: a water cooling structure located on the side of the flow guide tube away from the crucible supporting assembly, the water cooling structure comprising a plurality of mutually independent water cooling areas that are sequentially arranged in the direction away from the flow guide tube; and a mass flow controller used for respectively controlling the flow and the temperature of cooling water in different water cooling areas.

Description

Single crystal furnace and method for preparing single crystal silicon

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims priority to Chinese Patent Application No. 202310473614.0 filed in China on April 27, 2023, the entire contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates to the field of semiconductor manufacturing technology, and in particular to a single crystal furnace and a method for preparing single crystal silicon.

Background Art

Polysilicon is the main raw material for producing solar photovoltaic products and semiconductor products. The Czochralski (Cz) method is one of the most commonly used methods for preparing single crystal silicon. High-purity solid polysilicon raw materials are melted in the crucible of the crystal growth furnace (i.e., single crystal furnace) to form a melt. The seed crystal is lowered by the seed crystal pulling mechanism to make it contact with the melt in the rotating crucible. Then, the seed crystal is pulled out according to a certain process method, and the melt solidifies around the seed crystal to form a single crystal silicon rod.

The defect properties of single crystal silicon rods are sensitively dependent on the growth and cooling conditions of the crystal. The single crystal furnace includes a water-cooling jacket, which can achieve the stability of the longitudinal temperature gradient of the thermal field. However, in the related art, in the melting stage, due to the low position of the crucible, the temperature of the water-cooling jacket is also relatively low, resulting in a large longitudinal temperature gradient of the thermal field, and volatiles are easily accumulated on the water-cooling jacket; and in the later stage of single crystal equal diameter, due to the high position of the crucible, the crystal is closer to the water-cooling jacket, resulting in an increase in the temperature of the water-cooling jacket, so the longitudinal temperature gradient of the thermal field is small. In other words, the change in the position of the single crystal silicon rod makes the temperature of the water-cooling jacket not constant, so the longitudinal temperature gradient of the thermal field is also unstable, and the stable growth of the single crystal silicon rod cannot be guaranteed, resulting in more defects in the prepared single crystal silicon.

Summary of the invention

In order to solve the above technical problems, the present disclosure provides a single crystal furnace and a method for preparing single crystal silicon, which can reduce the defects of the prepared single crystal silicon.

In order to achieve the above objectives, the technical solution adopted by the embodiment of the present disclosure is:

A single crystal furnace, comprising a furnace body, wherein a crucible support assembly is arranged in the furnace body. A crucible is arranged on the upper part of the crucible support assembly, a guide tube is arranged directly above the crucible, a heater is arranged between the inner wall of the furnace body and the outer periphery of the crucible, a seed crystal pulling mechanism is arranged on the top of the furnace body, and the single crystal furnace also includes:

A water cooling structure located at a side of the guide tube away from the crucible support assembly, the water cooling structure comprising a plurality of mutually independent water cooling zones, the plurality of water cooling zones being arranged in sequence in a direction away from the guide tube;

Mass flow controllers are used to control the flow and temperature of cooling water in different water cooling zones.

In some embodiments, the mass flow controller is specifically used to control the temperature of the cooling water in the multiple water cooling zones to gradually decrease and/or the flow rate of the cooling water in the multiple water cooling zones to gradually increase in a direction away from the guide tube before the growth of the single crystal silicon rod.

In some embodiments, the temperature difference between adjacent water cooling zones is 1.5°C-2.5°C.

In some embodiments, the mass flow controller is specifically used to control the temperature of the cooling water in the multiple water cooling zones to gradually decrease, and/or the flow rate of the cooling water in the multiple water cooling zones to gradually increase as the crucible moves in a direction close to the guide tube during the growth of the single crystal silicon rod.

In some embodiments, the mass flow controller is also used to obtain a defect evaluation result of the single crystal silicon rod after the growth of the single crystal silicon rod is completed, and adjust the flow rate and/or temperature of the cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod.

In some embodiments, the mass flow controller is specifically used to reduce the temperature of the cooling water in the water cooling zone and/or increase the flow rate of the cooling water in the water cooling zone when V-rich defects exist in the single crystal silicon rod; and to increase the temperature of the cooling water in the water cooling zone and/or reduce the flow rate of the cooling water in the water cooling zone when N-rich defects exist in the single crystal silicon rod.

In some embodiments, the water cooling structure includes three water cooling zones.

The present disclosure also provides a method for preparing single crystal silicon, which is applied to the single crystal furnace as described above, and the method comprises:

Before the growth of the single crystal silicon rod, the temperature of the cooling water in the multiple water cooling zones is gradually reduced and/or the flow rate of the cooling water in the multiple water cooling zones is gradually increased by controlling the mass flow controller in a direction away from the guide tube.

In some embodiments, the method further comprises:

When the single crystal silicon rod grows, as the crucible moves in the direction close to the guide tube, The mass flow controller controls the temperature of the cooling water in the multiple water-cooling zones to gradually decrease, and/or the flow rate of the cooling water in the multiple water-cooling zones to gradually increase.

In some embodiments, the method further comprises:

After the growth of the single crystal silicon rod is completed, obtaining a defect evaluation result of the single crystal silicon rod;

The flow rate and/or temperature of the cooling water in the water cooling zone is adjusted according to the defect evaluation result of the single crystal silicon rod.

In some embodiments, adjusting the flow rate and/or temperature of cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod includes:

When the single crystal silicon rod has a V-rich defect, lowering the temperature of the cooling water in the water cooling zone and/or increasing the flow rate of the cooling water in the water cooling zone;

When N-rich defects exist in the single crystal silicon rod, the temperature of cooling water in the water cooling zone is increased and/or the flow rate of cooling water in the water cooling zone is reduced.

The beneficial effects of the present disclosure are:

In this embodiment, the water cooling structure includes multiple independent water cooling zones, and the mass flow controller can respectively control the flow and temperature of the cooling water in different water cooling zones. In this way, during the growth of single crystal silicon rods, the temperature and flow in different water cooling zones can be zoned and managed, which can reduce the longitudinal temperature gradient change during crystal growth, achieve a smooth transition of temperature zones, and then achieve a stable longitudinal temperature gradient of the thermal field, thereby reducing the defects of the prepared single crystal silicon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of a single crystal furnace according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram showing a process flow of a method for preparing single crystal silicon according to an embodiment of the present disclosure.

Reference numerals
1 single crystal silicon rod; 2 water cooling structure; 3 guide tube; 4 heater; 5 graphite crucible; 6 quartz crucible;
7 silicon solution; 8 crucible support assembly; 9 mass flow controller; 10 cooling water supply unit.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the embodiment of the present disclosure more clear, the technical solution of the embodiment of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the present disclosure. The described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art are within the scope of protection of the present disclosure.

The defect properties of single crystals depend sensitively on the growth and cooling conditions of the crystals, so the types and distribution of defects formed during the growth process can be controlled by adjusting the thermal environment near the growth interface.

Growth defects are divided into several categories: vacancy-type defects and interstitial-type defects. They are caused by the accumulation of vacancy point defects or interstitial point defects starting from a concentration exceeding the equilibrium. The formation of growth defects is closely related to the V/G value, where V is the growth rate and G is the temperature gradient of the crystal near the crystal growth interface. Vacancy-type defects are formed when the value of V/G exceeds a critical value, while interstitial-type defects are formed when the value of V/G is below a critical value. Therefore, the type, size and density of defects present in the crystal when the crystal grows in a specific hot zone are affected by the pulling rate. The cooling rate of the crystal is controlled between the solidification temperature and a temperature of about 1000°C, within which range when molten silicon is solidified into single crystal silicon, the nuclei of defects are formed and grow during the thermal treatment. In this way, silicon interstices or vacancies diffuse to the side of the ingot or are accelerated to unite with each other, which can suppress the supersaturation of interstices or vacancies below the critical value at which accumulation occurs. The temperature difference of the region of the ingot grown by the Czochralski method is minimized within the temperature range of 1000°C to 1100°C. More specifically, the temperature difference of the single crystal silicon ingot in the region of the ingot at a temperature of 1000°C to 1100°C does not exceed 20°C/cm. Optionally, the temperature control difference occurs at the peripheral portion of the ingot in the vertical direction. At the same time, when the ingot is at a temperature of 1000°C to 1100°C, the temperature of the growing ingot is controlled so that the temperature gradient difference between the central portion and the peripheral portion of the ingot is not greater than 1.5°C/cm.

The key component in the single crystal furnace is the water-cooling jacket, which can achieve the stability of the longitudinal temperature gradient of the thermal field; however, the water-cooling jacket designed by the relevant technology has a single structure, and the cooling water flow and temperature cannot be adjusted, so the cooling effect cannot be maximized. In the melting stage, due to the low position of the crucible, the heat of the crucible has less impact on the water-cooling jacket, making the temperature of the water-cooling jacket lower, resulting in a large longitudinal temperature gradient of the thermal field, and volatiles are easy to accumulate on the water-cooling jacket; and in the later stage of single crystal equal diameter, due to the high position of the crucible, the crystal is closer to the water-cooling jacket, the heat of the crucible affects the water-cooling jacket, the temperature of the water-cooling jacket rises, and the longitudinal temperature gradient of the thermal field is small. In other words, the change in the position of the single crystal makes the temperature of the water-cooling jacket not constant, so the longitudinal temperature gradient of the thermal field is not stable, and the stable growth of the single crystal cannot be guaranteed. In addition, the water-cooling jacket is only a component through which the cooling water flows, and there are no control measures for the cooling water in the water-cooling jacket. The cooling water is not fully utilized and most of it is wasted. The temperature of the water cooling jacket cannot be controlled at a constant temperature, and the longitudinal temperature gradient of the thermal field required for single crystal growth cannot be controlled.

The present disclosure provides a single crystal furnace and a method for preparing single crystal silicon, which can reduce defects in the prepared single crystal silicon.

The present disclosure provides a single crystal furnace, as shown in FIG1 , the single crystal furnace comprises a furnace body, a crucible support assembly 8 is arranged in the furnace body, a crucible is arranged on the upper part of the crucible support assembly 8, the crucible comprises a graphite crucible 5 and a quartz crucible 6 located in the graphite crucible 5, a silicon solution 7 is contained in the quartz crucible 6, a guide tube 3 is arranged directly above the crucible, a heater 4 is arranged between the inner wall of the furnace body and the outer periphery of the crucible, a seed crystal pulling mechanism is arranged on the top of the furnace body, and the single crystal furnace further comprises:

A water cooling structure 2 located at a side of the guide tube 3 away from the crucible support assembly 8, the water cooling structure 2 comprising a plurality of mutually independent water cooling zones, the plurality of water cooling zones being arranged in sequence in a direction away from the guide tube 3;

The mass flow controller (MFC) 9 is used to control the flow rate and temperature of cooling water in different water cooling zones respectively.

In this embodiment, the water cooling structure 2 includes a plurality of independent water cooling zones, and the mass flow controller 9 can respectively control the flow and temperature of the cooling water in different water cooling zones. Thus, during the growth of the single crystal silicon rod 1, by performing zone management on the temperature and flow in different water cooling zones, the longitudinal temperature gradient change during crystal growth can be reduced, a smooth transition of the temperature zones can be achieved, and the longitudinal temperature gradient of the thermal field can be stabilized, thereby reducing the defects of the prepared single crystal silicon.

In this embodiment, the water cooling structure 2 may include two mutually independent water cooling zones, three mutually independent water cooling zones, or more mutually independent water cooling zones.

In this embodiment, the mass flow controller 9 is connected to the cooling water supply unit 10, and can control the flow rate and temperature of the cooling water in different water cooling zones; thus, before the growth of the single crystal silicon rod 1, the mass flow controller 9 can set the flow rate and temperature of the cooling water in different water cooling zones; during the growth of the single crystal silicon rod 1, as the position of the single crystal silicon rod 1 changes, the mass flow controller 9 can also adjust the flow rate and temperature of the cooling water in different water cooling zones, so as to achieve the stability of the longitudinal temperature gradient of the thermal field, thereby reducing the defects of the prepared single crystal silicon.

In this embodiment, the mass flow controller 9 can be placed away from the single crystal silicon rod 1 before it grows. The direction of the guide tube 3 controls the temperature of the cooling water in the multiple water-cooling zones to gradually decrease, and/or the flow rate of the cooling water in the multiple water-cooling zones to gradually increase, so that the longitudinal temperature gradient of the thermal field can be achieved. In this embodiment, only the temperature of the cooling water in the multiple water-cooling zones can be adjusted, or only the flow rate of the cooling water in the multiple water-cooling zones can be adjusted, or both the temperature and flow rate of the cooling water in the multiple water-cooling zones can be adjusted. Among them, the lowering of the temperature of the cooling water in the water-cooling zone will reduce the ambient temperature near the water-cooling zone, and the higher the temperature of the cooling water in the water-cooling zone will increase the ambient temperature near the water-cooling zone; the lowering of the flow rate of the cooling water in the water-cooling zone will increase the ambient temperature near the water-cooling zone, and the higher the flow rate of the cooling water in the water-cooling zone will reduce the ambient temperature near the water-cooling zone.

In some embodiments, as shown in FIG1 , the water cooling structure 2 includes three independent water cooling zones: zone A, zone B, and zone C. Before the growth of the single crystal silicon rod 1 begins, the mass flow controller 9 controls the temperatures of the cooling water introduced into zones A, B, and C to be different, the temperature of the cooling water in zone A is higher than the temperature of the cooling water in zone B, and the temperature of the cooling water in zone B is higher than the temperature of the cooling water in zone C, so that the longitudinal temperature gradient of the thermal field can be achieved.

The temperature difference between adjacent water cooling zones may be 1.5-2.5°C, such as 1.5°C, 1.6°C, 1.7°C, 1.8°C, 1.9°C, 2.0°C, 2.1°C, 2.2°C, 2.3°C, 2.4°C or 2.5°C. Optionally, the temperature difference between adjacent water cooling zones may be 2.0°C, which is beneficial to reducing the formation of defects in the single crystal silicon rod 1.

Of course, the cooling water flow rate in zone A can also be controlled to be lower than that in zone B, and the cooling water flow rate in zone B can be controlled to be lower than that in zone C, which also helps to achieve the longitudinal temperature gradient of the thermal field.

During the growth of the single crystal silicon rod 1, as the seed crystal pulling mechanism pulls the single crystal silicon rod 1, the position of the crucible gradually moves up and approaches the water cooling structure 2. The heat of the crucible will affect the heat of the water cooling structure 2. In order to ensure the stability of the longitudinal temperature gradient of the thermal field, it is necessary to adjust the temperature and flow rate of the cooling water in the multiple water cooling zones. Specifically, as the crucible moves in the direction close to the guide tube 3, the temperature of the cooling water in the multiple water cooling zones is controlled to gradually decrease, and/or the flow rate of the cooling water in the multiple water cooling zones is gradually increased. This can offset the influence of the heat of the crucible and is beneficial to the stability of the longitudinal temperature gradient of the thermal field.

The mass flow controller 9 can set in advance the flow and temperature of the A zone, B zone, and C zone corresponding to the single crystal silicon rod 1 at different positions during the growth process of the single crystal silicon rod 1. For example, position 1 corresponds to: The flow rate in zone A is L1 and the temperature is T1; the flow rate in zone B is L2 and the temperature is T2; the flow rate in zone C is L3 and the temperature is T3. Position 2 corresponds to: the flow rate in zone A is L4 and the temperature is T4; the flow rate in zone B is L5 and the temperature is T5; the flow rate in zone C is L6 and the temperature is T6. When the single crystal silicon rod 1 moves to position 1, the flow rate in zone A can be controlled to be L1 and the temperature to be T1; the flow rate in zone B can be controlled to be L2 and the temperature to be T2; the flow rate in zone C can be controlled to be L3 and the temperature to be T3. When the single crystal silicon rod 1 moves to position 2, the flow rate in zone A can be controlled to be L4 and the temperature to be T4; the flow rate in zone B can be controlled to be L5 and the temperature to be T5; the flow rate in zone C can be controlled to be L6 and the temperature to be T6.

In this embodiment, only the temperature of the cooling water in the multiple water cooling zones may be adjusted, only the flow rate of the cooling water in the multiple water cooling zones may be adjusted, or both the temperature and flow rate of the cooling water in the multiple water cooling zones may be adjusted.

In some embodiments, the mass flow controller 9 is also used to obtain a defect evaluation result of the single crystal silicon rod 1 after the growth of the single crystal silicon rod 1 is completed, and adjust the flow rate and/or temperature of the cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod 1.

The defect properties of the single crystal are related to the cooling conditions of the crystal. By adjusting the thermal environment near the growth interface, the types and distribution of defects formed during the growth process can be controlled. Therefore, after the growth of the single crystal silicon rod 1 is completed, the flow rate and/or temperature of the cooling water in the water cooling zone can be adjusted according to the defects of the single crystal silicon rod 1 to achieve control and optimization of the longitudinal temperature gradient of the thermal field. Only the temperature of the cooling water in multiple water cooling zones can be adjusted, only the flow rate of the cooling water in multiple water cooling zones can be adjusted, or both the temperature and flow rate of the cooling water in multiple water cooling zones can be adjusted.

In some embodiments, the mass flow controller 9 is specifically used to reduce the temperature of the cooling water in the water cooling zone and/or increase the flow rate of the cooling water in the water cooling zone when V-rich defects exist in the single crystal silicon rod 1; and to increase the temperature of the cooling water in the water cooling zone and/or reduce the flow rate of the cooling water in the water cooling zone when N-rich defects exist in the single crystal silicon rod 1.

When a V-rich defect exists in the single crystal silicon rod 1, it indicates that the ambient temperature of the growth interface of the single crystal silicon rod 1 is relatively high. Therefore, the ambient temperature of the growth interface of the single crystal silicon rod 1 can be reduced by lowering the temperature of the cooling water in the water cooling zone and/or increasing the flow rate of the cooling water in the water cooling zone, thereby improving the V-rich defect; when an N-rich defect exists in the single crystal silicon rod 1, it indicates that the ambient temperature of the growth interface of the single crystal silicon rod 1 is relatively low. Therefore, the ambient temperature of the growth interface of the single crystal silicon rod 1 can be increased by increasing the temperature of the cooling water in the water cooling zone and/or decreasing the flow rate of the cooling water in the water cooling zone, thereby improving the N-rich defect.

The present disclosure also provides a method for preparing single crystal silicon, which is applied to the single crystal furnace as described above, and the method comprises:

Before the growth of the single crystal silicon rod 1, the temperature of the cooling water in the multiple water cooling zones is gradually reduced and/or the flow rate of the cooling water in the multiple water cooling zones is gradually increased by controlling the mass flow controller 9 in a direction away from the guide tube 3.

In this embodiment, the water cooling structure 2 includes a plurality of independent water cooling zones, and the mass flow controller 9 can respectively control the flow and temperature of the cooling water in different water cooling zones. Thus, during the growth of the single crystal silicon rod 1, by performing zone management on the temperature and flow in different water cooling zones, the longitudinal temperature gradient change during crystal growth can be reduced, a smooth transition of the temperature zones can be achieved, and the longitudinal temperature gradient of the thermal field can be stabilized, thereby reducing the defects of the prepared single crystal silicon.

In this embodiment, the mass flow controller 9 is connected to the cooling water supply unit 10, and can control the flow rate and temperature of the cooling water in different water cooling zones; thus, before the growth of the single crystal silicon rod 1, the mass flow controller 9 can set the flow rate and temperature of the cooling water in different water cooling zones; during the growth of the single crystal silicon rod 1, as the position of the single crystal silicon rod 1 changes, the mass flow controller 9 can also adjust the flow rate and temperature of the cooling water in different water cooling zones, so as to achieve the stability of the longitudinal temperature gradient of the thermal field, thereby reducing the defects of the prepared single crystal silicon.

In this embodiment, the mass flow controller 9 can control the temperature of the cooling water in the multiple water cooling zones to gradually decrease and/or the flow rate of the cooling water in the multiple water cooling zones to gradually increase before the growth of the single crystal silicon rod 1 in the direction away from the guide tube 3, so that the longitudinal temperature gradient of the thermal field can be achieved. In this embodiment, only the temperature of the cooling water in the multiple water cooling zones can be adjusted, only the flow rate of the cooling water in the multiple water cooling zones can be adjusted, or both the temperature and flow rate of the cooling water in the multiple water cooling zones can be adjusted.

In some embodiments, the method further comprises:

When the single crystal silicon rod grows, as the crucible moves in a direction close to the guide tube, the temperature of the cooling water in the multiple water cooling zones is gradually reduced and/or the flow rate of the cooling water in the multiple water cooling zones is gradually increased by controlling the mass flow controller.

During the growth of the single crystal silicon rod 1, as the seed crystal pulling mechanism pulls the single crystal silicon rod 1, the position of the crucible gradually moves up and approaches the water cooling structure 2. The heat of the crucible will affect the heat of the water cooling structure 2. In order to ensure the stability of the longitudinal temperature gradient of the thermal field, it is necessary to adjust the temperature and Flow rate, specifically, as the crucible moves in a direction close to the guide tube 3, the temperature of the cooling water in the multiple water-cooling zones is controlled to gradually decrease, and/or the flow rate of the cooling water in the multiple water-cooling zones is gradually increased, which can offset the influence of the heat of the crucible and is conducive to the stability of the longitudinal temperature gradient of the thermal field.

In this embodiment, only the temperature of the cooling water in the multiple water cooling zones may be adjusted, only the flow rate of the cooling water in the multiple water cooling zones may be adjusted, or both the temperature and flow rate of the cooling water in the multiple water cooling zones may be adjusted.

In some embodiments, as shown in FIG2 , the method further includes:

Step 101: After the growth of the single crystal silicon rod is completed, obtaining a defect evaluation result of the single crystal silicon rod;

Step 102: adjusting the flow rate and/or temperature of cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod.

The defect properties of the single crystal are related to the cooling conditions of the crystal. By adjusting the thermal environment near the growth interface, the types and distribution of defects formed during the growth process can be controlled. Therefore, after the growth of the single crystal silicon rod 1 is completed, the flow rate and/or temperature of the cooling water in the water cooling zone can be adjusted according to the defects of the single crystal silicon rod 1 to achieve control and optimization of the longitudinal temperature gradient of the thermal field. Only the temperature of the cooling water in multiple water cooling zones can be adjusted, only the flow rate of the cooling water in multiple water cooling zones can be adjusted, or both the temperature and flow rate of the cooling water in multiple water cooling zones can be adjusted.

In some embodiments, adjusting the flow rate and/or temperature of cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod includes:

When the single crystal silicon rod has a V-rich defect, lowering the temperature of the cooling water in the water cooling zone and/or increasing the flow rate of the cooling water in the water cooling zone;

When N-rich defects exist in the single crystal silicon rod, the temperature of cooling water in the water cooling zone is increased and/or the flow rate of cooling water in the water cooling zone is reduced.

When the single crystal silicon rod 1 has a V-rich defect, it indicates that the ambient temperature of the growth interface of the single crystal silicon rod 1 is high, so the ambient temperature of the growth interface of the single crystal silicon rod 1 can be reduced by lowering the temperature of the cooling water in the water cooling zone and/or increasing the flow rate of the cooling water in the water cooling zone, thereby improving the V-rich defect; when the single crystal silicon rod 1 has an N-rich defect, it indicates that the ambient temperature of the growth interface of the single crystal silicon rod 1 is low, so the ambient temperature of the growth interface of the single crystal silicon rod 1 can be reduced by increasing the temperature of the cooling water in the water cooling zone and/or reducing the flow rate of the cooling water in the water cooling zone. The flow rate of water is used to increase the ambient temperature of the growth interface of the single crystal silicon rod 1, thereby improving the N-rich defects.

It should be noted that each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments, since they are basically similar to the product embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the product embodiments.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "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 components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” or “under” another element, it can be “directly on” or “under” the other element or intervening elements may be present.

In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims (11)

A single crystal furnace, comprising a furnace body, a crucible support assembly is arranged in the furnace body, a crucible is arranged on the upper part of the crucible support assembly, a guide tube is arranged directly above the crucible, a heater is arranged between the inner wall of the furnace body and the outer periphery of the crucible, a seed crystal pulling mechanism is arranged on the top of the furnace body, and the single crystal furnace also includes: A water cooling structure located at a side of the guide tube away from the crucible support assembly, the water cooling structure comprising a plurality of water cooling zones that are independent of each other, and the plurality of water cooling zones are sequentially arranged in a direction away from the guide tube; Mass flow controllers are used to control the flow and temperature of cooling water in different water cooling zones. The single crystal furnace according to claim 1, wherein the mass flow controller is specifically used to control the temperature of the cooling water in the multiple water cooling zones to gradually decrease and/or the flow rate of the cooling water in the multiple water cooling zones to gradually increase in a direction away from the guide tube before the single crystal silicon rod grows. The single crystal furnace according to claim 2, wherein the temperature difference between adjacent water cooling zones is 1.5°C-2.5°C. The single crystal furnace according to claim 1, wherein the mass flow controller is specifically used to control the temperature of the cooling water in the multiple water cooling zones to gradually decrease, and/or the flow rate of the cooling water in the multiple water cooling zones to gradually increase as the crucible moves in a direction close to the guide tube when the single crystal silicon rod is growing. The single crystal furnace according to claim 1, wherein the mass flow controller is also used to obtain a defect evaluation result of the single crystal silicon rod after the growth of the single crystal silicon rod is completed, and adjust the flow rate and/or temperature of the cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod. The single crystal furnace according to claim 5, wherein the mass flow controller is specifically used to reduce the temperature of the cooling water in the water cooling zone and/or increase the flow rate of the cooling water in the water cooling zone when V-rich defects exist in the single crystal silicon rod; when N-rich defects exist in the single crystal silicon rod, increase the temperature of the cooling water in the water cooling zone and/or reduce the flow rate of the cooling water in the water cooling zone. The single crystal furnace according to claim 1, wherein the water cooling structure comprises three water cooling zones. A method for preparing single crystal silicon, applied to a single crystal furnace as claimed in any one of claims 1 to 7, the method comprising: Before the growth of the single crystal silicon rod, the mass flow control The device controls the temperature of the cooling water in the multiple water-cooling zones to gradually decrease, and/or the flow rate of the cooling water in the multiple water-cooling zones to gradually increase. The method for preparing single crystal silicon according to claim 8, wherein the method further comprises: When the single crystal silicon rod grows, as the crucible moves in a direction close to the guide tube, the temperature of the cooling water in the multiple water cooling zones is gradually reduced and/or the flow rate of the cooling water in the multiple water cooling zones is gradually increased by controlling the mass flow controller. The method for preparing single crystal silicon according to claim 8, wherein the method further comprises: After the growth of the single crystal silicon rod is completed, obtaining a defect evaluation result of the single crystal silicon rod; The flow rate and/or temperature of the cooling water in the water cooling zone is adjusted according to the defect evaluation result of the single crystal silicon rod. The method for preparing single crystal silicon according to claim 10, wherein adjusting the flow rate and/or temperature of the cooling water in the water cooling zone according to the defect evaluation result of the single crystal silicon rod comprises: When the single crystal silicon rod has a V-rich defect, lowering the temperature of the cooling water in the water cooling zone and/or increasing the flow rate of the cooling water in the water cooling zone; When N-rich defects exist in the single crystal silicon rod, the temperature of cooling water in the water cooling zone is increased and/or the flow rate of cooling water in the water cooling zone is reduced.