CN115198348A

CN115198348A - Method and device for preparing monocrystalline silicon

Info

Publication number: CN115198348A
Application number: CN202110396723.8A
Authority: CN
Inventors: 欧子杨; 白枭龙; 张昕宇
Original assignee: Zhejiang Jinko Solar Co Ltd; Jinko Solar Co Ltd
Current assignee: Zhejiang Jinko Solar Co Ltd; Jinko Solar Co Ltd
Priority date: 2021-04-13
Filing date: 2021-04-13
Publication date: 2022-10-18
Anticipated expiration: 2041-04-13
Also published as: CN115198348B

Abstract

The application provides a monocrystalline silicon preparation method and a monocrystalline silicon preparation device, wherein the monocrystalline silicon preparation device at least comprises a monocrystalline furnace, a crucible, a heater, a guide cylinder, a crystal pulling device and a hot cover plate; the crucible is used for containing silicon raw materials, and the silicon raw materials are melted under the action of the heater to form silicon melt; the thermal cover plate is detachably connected to the crystal pulling device and comprises a plurality of fan blades which are sequentially arranged at intervals along the circumferential direction, and the fan blades are obliquely arranged along the horizontal direction; the crystal lifting device is used for driving the hot cover plate to move towards the opening close to the lower end of the guide cylinder and driving the hot cover plate to rotate. The monocrystalline silicon preparation method and the monocrystalline silicon preparation device can inhibit heat loss and remarkably improve the melting efficiency; volatile matters in the silicon melt are effectively pressed to volatilize from the top, the crystal pulling environment of the monocrystalline silicon is improved, and the quality of the monocrystalline silicon is improved.

Description

Method and device for preparing monocrystalline silicon

Technical Field

The application relates to the technical field of photovoltaic cells, in particular to a monocrystalline silicon preparation method and device.

Background

At present, monocrystalline silicon for solar cells is mainly prepared by a czochralski method, silicon raw materials need to be changed from a solid state to a liquid state in a silicon material melting stage, a large amount of heat needs to be constantly absorbed in the process, part of the heat is originated from a side heater and a bottom heater of a crucible, the temperature loss of the upper part of a furnace cover in a thermal field is large, so that the side heater and the bottom heater need to provide higher power to maintain melting materials, and the melting efficiency is low.

Disclosure of Invention

In view of this, the present application provides a method and an apparatus for preparing monocrystalline silicon, which can suppress heat dissipation, improve melting efficiency, and improve quality of monocrystalline silicon.

In a first aspect, an embodiment of the present application provides a monocrystalline silicon preparation apparatus, which at least includes a monocrystalline furnace, a crucible, a heater, a guide cylinder, a crystal pulling apparatus, and a thermal cover plate;

the crucible is used for containing silicon raw materials, and the silicon raw materials are melted under the action of the heater to form a silicon melt;

the heat cover plate is detachably connected to the crystal pulling device and comprises a plurality of fan blades which are sequentially arranged at intervals along the circumferential direction, and the fan blades are obliquely arranged along the horizontal direction;

the crystal pulling device is used for driving the hot cover plate to move towards the opening close to the lower end of the guide cylinder and driving the hot cover plate to rotate.

With reference to the first aspect, in a possible implementation manner, the inclination angle between the fan blades on the thermal cover plate and the horizontal plane is 20 degrees to 45 degrees.

With reference to the first aspect, in a possible implementation manner, N layers of thermal cover plates are arranged on the crystal pulling device, N is greater than or equal to 1 and less than or equal to 10, the fan blade inclination directions of two adjacent layers of thermal cover plates are opposite, and the fan blade inclination angles on the same layer of thermal cover plate are consistent.

In a possible embodiment in combination with the first aspect, the thickness of the single layer of the thermal cover plate is 20mm to 50mm, and/or the thickness of the whole of the N layers of thermal cover plates is 20mm to 100mm.

With reference to the first aspect, in a possible embodiment, the outer edge of the thermal cover plate is circular, and the diameter of the thermal cover plate is 250mm to 300mm.

With reference to the first aspect, in a possible implementation manner, the shape of the outer edge of the hot cover plate matches the shape of the lower end opening of the guide cylinder, and the diameter of the hot cover plate is smaller than the inner diameter of the lower end opening of the guide cylinder.

With reference to the first aspect, in a possible implementation manner, the material of the fan blade includes at least one of carbon-carbon material, graphite, silicon, molybdenum, or tungsten.

With reference to the first aspect, in one possible embodiment, the crystal pulling apparatus is connected to the weight through a wire;

a clamping device is arranged in the auxiliary chamber at the top of the single crystal furnace, the clamping device comprises a driver and a telescopic fixture block connected with the driver, and the telescopic fixture block is used for locking the hot cover plate;

when the driver drives the telescopic clamping block to unlock the hot cover plate, the hot cover plate can be clamped and fixed on the heavy hammer.

In a second aspect, the present application provides a method of preparing single crystal silicon, the method comprising the steps of:

after silicon raw materials are put into a crucible in a single crystal furnace, a crystal lifting device drives a thermal cover plate to move to an opening at the lower end of a guide cylinder, wherein the thermal cover plate comprises a plurality of fan blades which are sequentially arranged at intervals along the circumferential direction, and the fan blades are obliquely arranged along the horizontal direction;

vacuumizing a single crystal furnace, introducing protective gas, driving the hot cover plate to rotate by the crystal pulling device, and melting a silicon raw material by a heater under the action of the protective gas to obtain silicon melt;

after the temperature of the silicon melt is stable, soaking a seed crystal into the silicon melt, and then sequentially carrying out seeding, shouldering and equal-diameter growth;

and after the isometric growth is finished, carrying out a final stage to ensure that the diameter of the crystal is gradually reduced until the crystal is separated from the silicon melt, and taking out the crystal after the crystal is cooled to the room temperature to obtain the monocrystalline silicon.

In combination with the second aspect, in one possible embodiment, the method further comprises the steps of:

after the monocrystalline silicon is taken out, the crystal pulling device drives the hot cover plate to move downwards and penetrate through the opening at the lower end of the guide cylinder, and the rotating speed of the hot cover plate is controlled to be 1-10 revolutions per minute.

With reference to the second aspect, in a possible implementation manner, after the hot cover plate passes through the lower end opening of the guide cylinder, the hot cover plate is lowered to a distance of 50mm to 400mm from the lower end opening of the guide cylinder.

In a possible embodiment, in combination with the second aspect, the rotation speed of the hot cover plate is 1 to 5 rpm during the pulling of the molten material and the monocrystalline silicon.

In combination with the second aspect, in one possible embodiment, the heater power of the bottom of the crucible is controlled to be 80kw to 90kw and the heater power of the side of the crucible is controlled to be 100kw to 120kw during melting.

In combination with the second aspect, in one possible embodiment, the method satisfies at least one of the following features a to d:

a. the inclination angle between the fan blades on the heat cover plate and the horizontal plane is 20-45 degrees;

b. the outer edge of the hot cover plate is circular, and the diameter of the hot cover plate is 250-300 mm;

c. the shape of the outer edge of the hot cover plate is matched with the shape of the opening at the lower end of the guide cylinder, and the diameter of the hot cover plate is smaller than the inner diameter of the opening at the lower end of the guide cylinder;

d. the fan blade is made of at least one of carbon-carbon material, graphite, silicon, molybdenum or tungsten.

With reference to the second aspect, in one possible embodiment, the crystal lifting device is connected to the weight through a metal wire;

the clamping device is arranged in the auxiliary chamber at the top of the single crystal furnace and comprises a driver and a telescopic clamping block connected with the driver, and the hot cover plate is locked in the auxiliary chamber through the telescopic clamping block.

In combination with the second aspect, in a possible embodiment, before the crystal pulling apparatus moves the hot cover plate to the opening at the lower end of the guide cylinder, the method further includes:

the crystal lifting device drives the heavy hammer to move upwards to the position below the hot cover plate;

and the driver is utilized to drive the telescopic clamping block to unlock the hot cover plate, and the hot cover plate moves downwards and is clamped and fixed on the heavy hammer.

The technical scheme of the application has at least the following beneficial effects:

in the process of melting, the hot cover plate is lowered to the opening at the lower end of the guide cylinder, so that the hot cover plate has a heat insulation effect, heat loss can be inhibited, and melting efficiency is obviously improved; and under the rotation of the hot cover plate, vortex-shaped polymer gas flow is formed, so that volatile matter deposition can be inhibited, in the whole single crystal silicon drawing process, oxide is taken away from the left two sides of the crucible and through the gas outlet at the bottom of the crucible by the polymer gas flow, volatile matters in silicon melt can be effectively pressed to volatilize from the top, the crystal pulling environment of the single crystal silicon is improved, and the quality of the single crystal silicon is improved.

Drawings

For a clearer explanation of the embodiments or technical solutions of the prior art of the present application, the drawings needed for the description of the embodiments or prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a single crystal silicon manufacturing apparatus provided in this embodiment;

FIG. 2 is a schematic view illustrating an installation state of a thermal cover plate and a weight according to the present embodiment;

fig. 3a and 3b are schematic diagrams of fan blade structures of the thermal cover plate according to the present embodiment, respectively;

FIG. 3c is a schematic structural diagram of a multi-layer thermal cover plate according to the present embodiment;

FIG. 4 is a schematic structural diagram of a clamping device in a single-crystal silicon preparation apparatus provided in an embodiment of the present application;

FIG. 5 is a thermodynamic diagram of an apparatus for producing single-crystal silicon provided in an embodiment of the present application;

fig. 6 is a schematic flow chart of a method for manufacturing single crystal silicon according to an embodiment of the present application.

Detailed Description

For better understanding of the technical solutions of the present application, the following detailed descriptions of the embodiments of the present application are provided with reference to the accompanying drawings.

It should be understood that the embodiments described are only a few embodiments of the present application, and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

In a first aspect, the present application provides a single crystal silicon manufacturing apparatus, and fig. 1 is a schematic view of an operating state of the single crystal silicon manufacturing apparatus provided herein; as shown in fig. 1, the single-crystal silicon production apparatus at least includes: the device comprises a single crystal furnace 1, a crucible 2, a crystal pulling device 3, a guide cylinder 4, a heater and a hot cover plate 6.

The crucible 2 is used for containing silicon raw material and dopant, and the silicon raw material in the crucible 2 is melted by the heater to form silicon melt.

The crystal pulling apparatus 3 is used for pulling a crystal rod. In some embodiments, crystal puller 3 is connected to weight 7 by a wire, such as a steel wire. As shown in fig. 2, the weight 7 is provided with a mounting assembly 72, and the mounting assembly 72 is used for mounting the thermal cover 6. Alternatively, the mounting assembly 72 may be connected to the thermal cover 6 by a snap-fit connection, a welded connection, or the like. Preferably, the connection is snap-fit for easy installation and removal of the thermal cover plate 6. The bottom of the weight 7 is also provided with a seed holder 71, and the seed holder 71 is used for holding a seed rod.

In the present embodiment, a guide cylinder 4 (only a partial structure is shown in fig. 1) is provided to collect a protective gas (argon and/or nitrogen) into a crucible 2, so that volatilization of SiO is accelerated, and the oxygen concentration in the melt can be greatly reduced. Meanwhile, the guide shell 4 can also play a role of heat shielding, the gathered protective gas can accelerate the cooling of the crystal, increase the axial temperature gradient of the crystal and improve the growth rate of the crystal.

The guide shell 4 is of a hollow structure, the lower end of the guide shell 4 is provided with an opening, and the hollow structure of the guide shell can be used as an airflow channel and a crystal bar growth channel, so that the volatilization of oxides in the crystal bar drawing process is facilitated. In this embodiment, the thermal cover plate 6 can pass through the lower opening of the guide shell 4.

The heater includes a bottom heater 52 disposed at the bottom of the crucible 2 and a side heater 51 disposed at the side of the crucible 2 for heating the silicon raw material and the dopant in the crucible 2 so that the silicon raw material is melted to form a silicon melt.

In the melting process, the power of a bottom heater 52 of the crucible is controlled to be 80-90 kw, and the power of a side heater 51 of the crucible is controlled to be 100-120 kw.

Further, the thermal cover plate 6 is detachably connected to the crystal pulling apparatus 3, specifically, to the mounting member 72 of the weight 7. The crystal pulling device 3 can drive the hot cover plate 6 to move towards the opening at the lower end of the guide cylinder 4 and drive the hot cover plate 6 to rotate.

As shown in fig. 3a, 3b and 3c, the heat cover plate 6 includes a plurality of blades 61 sequentially spaced in the circumferential direction, and the plurality of blades 61 are inclined in the horizontal direction. In the present embodiment, the inclination angle a between the fan blades 61 on the heat cover plate 6 and the horizontal plane is 20 degrees to 45 degrees, specifically 20 degrees, 25 degrees, 30 degrees, 32 degrees, 35 degrees, 38 degrees, 40 degrees, or 45 degrees, and may be other values within the above range, which is not limited herein. The fan blades 61 are obliquely arranged, so that vortex-shaped polymerization airflow is favorably formed, and the airflow is favorably flowed from top to bottom; during the pulling process of the monocrystalline silicon, the deposition of volatile matters can be inhibited, the oxide is taken away from the left two sides of the crucible 2 and the gas outlet at the bottom by the polymer gas flow, the volatile matters in the silicon melt can be effectively pressed to volatilize from the top, the crystal pulling environment of the monocrystalline silicon is improved, and the quality of the monocrystalline silicon is improved, for example, the oxygen content of the monocrystalline silicon is reduced. Preferably, the angle of inclination between the fan blades 61 on the thermal cover plate 6 and the horizontal plane is 30 degrees.

In some embodiments, the crystal pulling apparatus 3 is provided with N layers of hot cover plates, where N is 1 ≦ N ≦ 10, that is, the number of layers of the hot cover plate 6 may be 1 layer, 2 layers, 3 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, or 10 layers, etc., or may be other values within the above range, which is not limited herein.

As shown in fig. 3c, the inclination directions of the blades 61 of two adjacent layers of thermal cover plates 6 are opposite, and the inclination angles of the blades 61 on the same layer of thermal cover plate 6 are the same. For example, the inclination angle a may be 30 degrees.

Specifically, the thickness of the single layer of the thermal cover plate 6 is 20mm to 50mm, specifically, the thickness of the single layer of the thermal cover plate 6 may be 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm, or the like, or may be other values within the above range, which is not limited herein. The thickness is too thick, increases the load of weight, reduces the life of device. Preferably, the thermal cover plate 6 is a single-layer cover plate.

When the heat cover plate 6 has N layers, the overall thickness of the heat cover plate 6 with N layers is 20mm to 100mm, specifically, the single-layer thickness of the heat cover plate may be 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 100mm, or the like, or may be other values within the above range, which is not limited herein.

The heat cover plate 6 includes a plurality of blades 61, and the shape of the blades 61 may also be a sector, an arc, a square, a circle, etc., which is not limited herein.

The outer edge of the heat cover plate 6 is circular, and the diameter of the heat cover plate 6 is 250mm to 300mm, specifically 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, or the like, or may be other values within the above range, which is not limited herein. The shape of the outer edge of the hot cover plate 6 is matched with the shape of the lower end opening of the guide shell 4, and the diameter of the hot cover plate 6 is smaller than the inner diameter of the lower end opening of the guide shell 4, so that the hot cover plate 6 can conveniently penetrate through the lower end opening of the guide shell 4.

As an optional technical solution in the present application, the material of the fan blade 61 includes at least one of carbon-carbon material, graphite, silicon, molybdenum, or tungsten. Preferably, the lower surface of the fan blade 61 close to the silicon melt has a heat reflective layer to suppress heat dissipation, which is beneficial for increasing the melt velocity.

Further, as shown in fig. 4, a clamping device 8 is arranged on the auxiliary chamber 11 at the top of the single crystal furnace 1, the clamping device 8 includes a driver 81 and a retractable latch 82 connected to the driver 81, and the retractable latch 82 is used for locking the hot cover plate 6; when the driver 81 drives the retractable latch 82 to unlock the thermal cover 6, the thermal cover 6 can be fixed on the mounting assembly 72 of the weight 7.

Fig. 5 is a flowchart of a method for manufacturing single-crystal silicon according to an embodiment of the present application, which can be implemented by the single-crystal silicon manufacturing apparatus shown in fig. 1 to 4. As shown in fig. 5, the present application provides a method for preparing single crystal silicon, comprising the steps of:

step S10, after silicon raw materials are put into a crucible in a single crystal furnace, a crystal lifting device drives a hot cover plate to move to an opening at the lower end of a guide cylinder, wherein the hot cover plate comprises a plurality of fan blades which are sequentially arranged at intervals along the circumferential direction, and the fan blades are obliquely arranged along the horizontal direction;

step S20, vacuumizing a single crystal furnace, introducing protective gas, driving the hot cover plate to rotate by the crystal pulling device, and melting a silicon raw material by a heater under the action of the protective gas to obtain silicon melt;

step S30, after the temperature of the silicon melt is stable, soaking a seed crystal into the silicon melt, and then sequentially carrying out seeding, shouldering and equal-diameter growth;

and S40, after the equal-diameter growth is finished, performing a final stage to gradually reduce the diameter of the crystal until the crystal is separated from the silicon melt, and taking out the crystal after the crystal is cooled to room temperature to obtain the monocrystalline silicon.

In the scheme, in the process of melting, the hot cover plate 6 is lowered to the opening at the lower end of the guide cylinder 4, so that the hot cover plate 6 has a heat insulation effect, heat loss can be inhibited, and the melting efficiency is obviously improved; and under the rotation of the hot cover plate 6, vortex-shaped polymer airflow is formed, so that volatile matter deposition can be inhibited, in the whole single crystal silicon drawing process, oxide is taken away from the left two sides of the crucible and through the bottom air outlet by the polymer airflow, volatile matters in silicon melt can be effectively pressed to volatilize from the top, the crystal pulling environment of the single crystal silicon is improved, and the quality of the single crystal silicon is improved.

The present solution is described in detail below with reference to examples:

step S10, after the silicon raw material is put into the crucible 2 in the single crystal furnace 1, the crystal pulling device 3 drives the hot cover plate 6 to move to the opening at the lower end of the guide cylinder 4, wherein the hot cover plate 6 comprises a plurality of fan blades 61 which are sequentially arranged at intervals along the circumferential direction, and the fan blades 61 are obliquely arranged along the horizontal direction.

Before step S10, the method comprises:

the crystal pulling device 3 drives the weight 7 to move upwards to the lower part of the hot cover plate 6;

the driver 81 is utilized to drive the retractable latch 82 to unlock the thermal cover plate 6, and the thermal cover plate 6 moves downward and is fixed on the weight 7 in a snap-fit manner.

In this embodiment, the weight 7 is provided with a mounting component 72, and the thermal cover 6 can be mounted on the mounting component 72 so as to rotate with the weight 7 under the action of the crystal pulling device 3.

As can be understood, when the silicon raw material is charged, the weight 7 is raised into the sub-chamber 11 at the top of the single crystal furnace 1. At this time, the thermal cover 6 is locked by the retractable latch 82 of the engaging device 8 and is accommodated in the sub-chamber 11. When the silicon material is completely charged, the driver 81 drives the retractable latch 82 to unlock the thermal cover 6, so that the thermal cover 6 can descend and be fastened to the mounting component 72 of the weight 7. Illustratively, the driver 81 may be a pneumatic cylinder or a motor.

After silicon raw materials are put into the crucible 2 in the single crystal furnace 1, the crystal pulling device 3 drives the hot cover plate 6 to move to the opening at the lower end of the guide cylinder 4, and at the moment, the shape of the outer edge of the hot cover plate 6 is matched with the shape of the opening at the lower end of the guide cylinder 4, so that heat loss can be inhibited, and the melting efficiency is obviously improved.

As an optional technical solution of this application, the thermal cover plate 6 includes a plurality of flabellums 61 that set up along circumference interval in proper order, a plurality of flabellums 61 set up along the horizontal direction slope. In the present embodiment, the inclination angle a between the fan blades 61 on the heat cover plate 6 and the horizontal plane is 20 degrees to 45 degrees, specifically 20 degrees, 25 degrees, 30 degrees, 32 degrees, 35 degrees, 38 degrees, 40 degrees, or 45 degrees, and may be other values within the above range, which is not limited herein. Preferably, the inclination angle a between the fan blades 61 on the heat cover plate 6 and the horizontal plane is 30 degrees.

The crystal pulling device 3 is provided with N layers of hot cover plates 6, N is more than or equal to 1 and less than or equal to 10, that is, the number of the hot cover plates 6 can be 1 layer, 2 layers, 3 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers or 10 layers, and the like, and of course, other values within the above range can be also provided, and the limitation is not limited herein.

As shown in fig. 3c, the inclination directions of the blades 61 of two adjacent layers of thermal cover plates 6 are opposite, and the inclination angles of the blades 61 on the same layer of thermal cover plate 6 are the same.

When the thermal cover 6 has N layers, the overall thickness of the N layers of thermal cover 6 is 20mm to 100mm, specifically, the single-layer thickness of the thermal cover 6 may be 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 100mm, or the like, or may be other values within the above range, which is not limited herein.

The thermal cover plate 6 includes a plurality of blades 61, and the shape of the blades 61 may also be an arc, a square, a circle, and the like, which is not limited herein.

The outer edge of the heat cover plate 6 is circular, and the diameter of the heat cover plate 6 is 250mm to 300mm, specifically 250mm, 260mm, 270mm, 280mm, 290mm, or 300mm, or the like, or may be other values within the above range, which is not limited herein. The shape of the outer edge of the hot cover plate 6 is matched with the shape of the lower end opening of the guide shell 4, and the diameter of the hot cover plate 6 is smaller than the inner diameter of the lower end opening of the guide shell 4, so that the hot cover plate 6 can conveniently penetrate through the lower end opening of the guide shell 4.

And S20, vacuumizing the single crystal furnace 1, introducing protective gas, driving the hot cover plate 6 to rotate by the crystal pulling device 3, and melting a silicon raw material by a heater under the action of the protective gas to obtain silicon melt.

In the process of melting, the power of a bottom heater 52 of the crucible is controlled to be 80-90 kw, and the power of a side heater 51 of the crucible is controlled to be 100-120 kw. It will be appreciated that the bottom heater 52 and the side heater 51 cooperate to facilitate maintaining the silicon melt level of the silicon melt within crucible 2 at a temperature that will ensure the growth rate of the single crystal silicon throughout the silicon crystal pulling process.

In the process of pulling the molten material and the single crystal silicon, the rotation speed of the hot cover plate 6 is 1 r/min to 5 r/min, specifically, the rotation speed of the hot cover plate 6 may be 1 r/min, 2 r/min, 3 r/min, 4 r/min, or 5 r/min, or the like, or may be other values within the above range, which is not limited herein.

Understandably, as shown in fig. 6, under the rotation of the hot cover plate 6, a vortex-shaped polymer gas flow is formed in the single crystal furnace, which can inhibit volatile deposition, and during the whole single crystal silicon drawing process, the polymer gas flow takes away oxide from the left two sides of the crucible and through a bottom gas outlet, which can effectively suppress volatile in silicon melt to volatilize from the top, improve the pulling environment of the single crystal silicon and improve the quality of the single crystal silicon.

As an optional technical scheme of the application, the protective gas comprises any one of argon, krypton and nitrogen. The flow rate of the protective gas is 85 slpm-95 slpm. Specifically, the flow rate may be 85slpm, 86slpm, 87slpm, 88slpm, 89slpm, 90slpm, 91slpm, 92slpm, 93slpm, 94slpm or 95slpm, or the like, or may be other values within the above range, which is not limited herein, and preferably, the flow rate of the protective gas in the single crystal furnace 1 is adjusted to 88slpm to 92slpm. Through multiple experiments, the flow direction of the protective gas is from top to bottom by adjusting the flow of the protective gas, the protective gas is favorable for forming vortex-shaped polymerization gas flow, and the deposition of volatile matters can be inhibited.

And step S30, after the temperature of the silicon melt is stable, soaking a seed crystal into the silicon melt, and then sequentially carrying out seeding, shouldering and equal-diameter growth.

In the seeding process, the seeding speed is 200-290mm/h, the seeding length is 200-260 mm, and the crystal diameter is 5-8 mm.

Alternatively, the seeding speed may be 200mm/h, 210mm/h, 220mm/h, 240mm/h, 250mm/h, 260mm/h, 270mm/h, 280mm/h and 290mm/h, which is not limited herein. During seeding, the crystal diameter may be 5mm, 6mm, 7mm, 8mm, etc., and the crystal length may be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, etc., without limitation.

The temperature in the single crystal furnace 1 is 1250-1300 sp. Illustratively, the temperature in single crystal furnace 1 may be 1250sp, 1255sp, 1260sp, 1265sp, 1270sp, 1275sp, 1280sp, 1285sp, 1290sp, 1295sp, 1300sp, and preferably, the temperature in single crystal furnace 1 is 1300sp, and it is understood that the suitable seeding temperature may effectively improve the success rate of seeding, and of course, the temperature in single crystal furnace 1 may be other values, which is not limited herein.

During shouldering, the first pulling speed of the crystal is 50-80mm/h, so that the diameter of the crystal is gradually increased to 230-310mm.

Alternatively, the first pulling speed may be 50mm/h, 60mm/h, 70mm/h, 80mm/h, etc., and the diameter of the crystal is gradually increased to 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, etc., without limitation. Understandably, to ensure crystal pulling stability, the crystal growth rate is slower, as is the crystal pulling rate. In addition, the temperature in the single crystal furnace 1 can be gradually reduced in the whole shouldering process, and cannot be increased.

The diameter range of the crystal can be designed and controlled according to the size requirement of the cell piece on the silicon wafer, and is not limited herein.

In order to improve the uniformity of the distribution of the doping element in the silicon melt, the silicon melt needs to be sufficiently stirred, and the seed crystal may be rotated in the opposite direction to the crucible 2, or may be stirred.

Specifically, in the process of isodiametric growth, the second pulling speed of the crystal is 80-130mm/h, specifically 80mm/h, 90mm/h, 100mm/h, 110mm/h, 120mm/h, 130mm/h, and the like, which is not limited herein.

It can be understood that in the process of constant diameter growth, the impurity speed of impurity separated from each point in radial direction of crystal near the solid-liquid interface to silicon melt side near the interface is different, so that the doping concentration distribution in radial direction of crystal is not uniform, and the pulling speed in the stage of constant diameter growth is controlled to be lower than that in the seeding process. As the pulling speed is reduced, the doping elements at all positions of the crystal in the radial direction have enough time to diffuse into the melt, so that the distribution of the doping elements in the radial direction of the crystal is more uniform.

Similarly, in the process of the isometric growth, the rotating speed of the hot cover plate 6 is 1-5 r/min, and understandably, the hot cover plate 6 rotates to accelerate the heat conduction to the crystal bar through the protective gas flow, take away the heat on the crystal bar and form a temperature gradient more easily, so that the crystal growth rate is improved and the crystal bar drawing efficiency is accelerated.

In the final stage, the third pulling rate of the crystal is 20 to 80mm/h, and illustratively, the third pulling rate may be 20mm/h, 30mm/h, 40mm/h, 50mm/h, 60mm/h, 70mm/h, or 80mm/h.

In this embodiment, the oxygen content of the single crystal silicon is 12ppma or less, and specifically, it may be 12ppma, 10ppma, 9ppma, 8ppma, 7ppma, 6ppma, 5ppma, 4ppma, 3ppma, 2ppma, or the like. Understandably, in the whole single crystal silicon drawing process, because of the rotation action of the hot cover plate 6, vortex-shaped polymer gas flow is formed in the single crystal furnace 1, the deposition of volatile matters can be inhibited, in the whole single crystal silicon drawing process, the polymer gas flow takes away volatile oxides from the left two sides of the crucible 2 and through a bottom gas outlet, the volatile matters in silicon melt can be effectively pressed to volatilize from the top, the crystal pulling environment of the single crystal silicon is improved, oxygen impurities are difficult to enter a single crystal silicon rod, and the oxygen source of the single crystal silicon can be effectively reduced.

After step S40, the method further comprises the steps of:

after the monocrystalline silicon is taken out, the crystal pulling device 3 drives the hot cover plate 6 to move downwards and penetrate through the opening at the lower end of the guide cylinder, and the rotating speed of the hot cover plate 6 is controlled to be 1-10 revolutions per minute.

As an optional technical solution of the present application, the rotation speed of the hot cover plate 6 may be 1 r/min, 2 r/min, 3 r/min, 4 r/min, 5 r/min, 6 r/min, 7 r/min, 8 r/min, 9 r/min, or 10 r/min, and the like, which is not limited herein. Understandably, the hot cover plate 6 is descended to a position below the lower end opening of the guide shell 4, namely, the hot cover plate 6 extends into the crucible 2, and the hot cover plate 6 rotates to accelerate the dissipation of heat in the crucible 2, so that the single crystal furnace 1 can be rapidly cooled to the furnace opening temperature.

Optionally, the flow rate of the protective gas after the single crystal silicon is taken out is 85slpm to 95slpm. Specifically, the flow rate may be 85slpm, 86slpm, 87slpm, 88slpm, 89slpm, 90slpm, 91slpm, 92slpm, 93slpm, 94slpm or 95slpm, or the like, or may be other values within the above range, which is not limited herein. Preferably, the flow rate of the protective gas in the single crystal furnace 1 is adjusted to 88slpm to 92slpm. Through a plurality of tests, the protective gas is beneficial to accelerating the dissipation of heat in the crucible 2, so that the single crystal furnace 1 can be rapidly cooled to the blow-in temperature.

As an optional technical scheme of the application, after the hot cover plate 6 penetrates through the lower end opening of the guide shell 4, the distance between the hot cover plate 6 and the lower end opening of the guide shell 4 is 50-400 mm. Specifically, it may be 50mm, 100mm, 150mm, 200mm, 250mm, 300mm, 350mm, or 400mm, or the like, or may be other values within the above range, and is not limited herein.

The following are examples and test data for the examples:

example 1

Step (1), putting a silicon raw material and a dopant into a crucible 2;

step (2), the crystal lifting device 3 drives the hot cover plate 6 to move to an opening at the lower end of the guide cylinder 4;

step (3), vacuumizing the single crystal furnace 1, introducing protective gas, driving a hot cover plate 6 to rotate by the crystal pulling device 3, controlling the rotating speed of the hot cover plate 6 to be 5 revolutions per minute, and melting a silicon raw material by a heater under the action of the protective gas, wherein the power of a heater 51 at the bottom of the crucible 2 is 85kw, and the power of a heater 52 at the side of the crucible 2 is 110kw, so as to obtain silicon melt; the structure of the thermal cover plate 6 is shown in FIG. 3 a;

step (4), after the temperature of the silicon melt is stable, a crystal seed is immersed into the silicon melt by a crystal pulling device 3 to start seeding, the temperature in a single crystal furnace 1 is set to 1300sp during seeding, and the seeding speed is controlled to be 250mm/h;

step (5), after seeding is finished, shouldering is started, the pulling speed is reduced to 50mm/h, the diameter of the crystal is gradually increased to 250mm, then equal-diameter growth is started, the crystal lifting speed is controlled to be 100mm/h, and the rotating speed of the hot cover plate 6 is kept to be 5 revolutions/min;

step (6), entering a final stage after the equal-diameter growth is finished, controlling the lifting speed of the crystal to be 50mm/h, gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt, cooling the grown crystal in an upper furnace chamber to room temperature, and taking out the crystal, wherein the crystal is monocrystalline silicon;

and (7) after taking out the monocrystalline silicon, closing the heater 52 at the bottom of the crucible and the heater 51 at the side part, driving the hot cover plate 6 to move downwards by the crystal pulling device 3 and penetrate through the opening at the lower end of the guide shell 4, and controlling the rotating speed of the hot cover plate 6 to be 10 r/min.

Example 2

Step (1), putting a silicon raw material and a dopant into a crucible 2;

step (3), vacuumizing the single crystal furnace 1, introducing protective gas, driving the hot cover plate 6 to rotate by the crystal pulling device, controlling the rotating speed of the hot cover plate 6 to be 5 r/min, and melting silicon raw materials by a heater under the action of the protective gas, wherein the power of the heater 51 at the bottom of the crucible 2 is 85kw, and the power of the heater 51 at the side of the crucible 2 is 110kw, so as to obtain silicon melt; the thermal cover plate 6 in this embodiment is circular and is not provided with fan blades;

step (4), after the temperature of the silicon melt is stable, a crystal seed is immersed into the silicon melt by a crystal pulling device 3 to start seeding, the temperature in a single crystal furnace is set to 1300sp during seeding, and the seeding speed is controlled to be 250mm/h;

step (6), after the equal-diameter growth is finished, entering a final stage, controlling the lifting speed of the crystal to be 50mm/h, gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt, cooling the grown crystal in an upper furnace chamber to room temperature, and taking out the crystal, wherein the crystal is single crystal silicon;

and (7) after taking out the monocrystalline silicon, closing the heater 51 at the bottom of the crucible and the heater 52 at the side part, driving the hot cover plate 6 to move downwards by the crystal pulling device 3 and penetrate through the opening at the lower end of the guide cylinder 4, and controlling the rotating speed of the hot cover plate 6 to be 10 revolutions per minute.

Comparative example 1

Step (1), putting a silicon raw material and a dopant into a crucible 2;

step (2), vacuumizing the single crystal furnace 1, introducing protective gas, and melting silicon raw materials by using a heater under the action of the protective gas, wherein the power of a heater 51 at the bottom of the crucible 2 is 85kw, and the power of a heater 52 at the side of the crucible 2 is 110kw, so as to obtain silicon melt;

step (3), after the temperature of the silicon melt is stable, a crystal seed is immersed into the silicon melt by a crystal pulling device 3 to start seeding, the temperature in a single crystal furnace 1 is set to 1300sp during seeding, and the seeding speed is controlled to be 250mm/h;

step (4), after seeding is finished, shouldering is started, the pulling speed is reduced to 50mm/h, the diameter of the crystal is gradually increased to 250mm, then isodiametric growth is started, and the lifting speed of the crystal is controlled to be 100mm/h;

step (5), after the equal-diameter growth is finished, entering a final stage, controlling the lifting speed of the crystal to be 50mm/h, gradually reducing the diameter of the crystal until the crystal is separated from the silicon melt, cooling the grown crystal in an upper furnace chamber to room temperature, and taking out the crystal, wherein the crystal is single crystal silicon;

step (6) of taking out the silicon single crystal, and then closing the crucible bottom heater 51 and the side heater 52.

The experimental data of the above examples 1 and 2 and comparative example 1 are shown in tables 1 and 2.

TABLE 1

Parameter(s)	Example 1	Example 2	Comparative example 1
				Melt Rate (kg/h)	80	70	60
Equal diameter stage crystal growth rate (mm/h)	95	90	90
				Single crystal silica content (ppma)	12	13	13
Furnace shutdown Cooling time (h)	8	9	10
				Whole rod Rate (%)	50	35	35

TABLE 2 parameters of isometric growth stage

According to the data in table 1, in the process of melting, the hot cover plate of the present application is lowered to the opening at the lower end of the guide cylinder, so that the hot cover plate has a heat insulation effect, and can inhibit heat dissipation, and in example 1, compared with comparative example 1, the melting rate is increased by 20kg/h, and the melting efficiency is significantly improved. Compared with the comparative example 1, the crystal growth rate in the equal-diameter stage is obviously improved in the example 1. Moreover, the oxygen content of the single crystal silicon prepared in the example 1 is lower than that of the single crystal silicon prepared in the comparative example 1, which shows that the rotation of the hot cover plate can effectively suppress the volatile matters in the silicon melt from volatilizing from the top in the whole single crystal silicon drawing process, improve the pulling environment of the single crystal silicon and improve the quality of the single crystal silicon. During the blowing-out treatment, the heat cover plate can accelerate the heat loss in the single crystal furnace, accelerate the temperature reduction in the furnace and shorten the blowing-out cooling time.

The ingot rate is a ratio of the ingot to the ingot which is not broken, and since the volatilization of the oxide from the top is suppressed, the ingot is less likely to be broken.

According to the data in table 2, in the equal-diameter growth stage of the single crystal silicon preparation, the vortex-shaped polymerization airflow is formed under the rotation of the hot cover plate, so that the convection heat dissipation effect can be effectively enhanced, the temperature gradient can be favorably formed, and the crystal growth speed can be effectively increased by about 5mm/h.

Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.

Claims

1. A monocrystalline silicon preparation device is characterized by at least comprising a monocrystalline furnace, a crucible, a heater, a guide cylinder, a crystal pulling device and a hot cover plate;

the crystal lifting device is used for driving the hot cover plate to move towards the opening close to the lower end of the guide cylinder and driving the hot cover plate to rotate.

2. The apparatus for manufacturing single-crystal silicon according to claim 1, wherein the angle of inclination between the fan blades on the thermal cover plate and the horizontal plane is 20 to 45 degrees.

3. The single-crystal silicon preparation device of claim 1, wherein the crystal pulling device is provided with N layers of thermal cover plates, N is greater than or equal to 1 and less than or equal to 10, the inclination directions of the fan blades of two adjacent layers of thermal cover plates are opposite, and the inclination angles of the fan blades on the same layer of thermal cover plate are consistent.

4. The apparatus for manufacturing single-crystal silicon according to claim 3, wherein the single-layer thickness of the thermal cover plate is 20mm to 50mm, and/or the entire thickness of the N-layer thermal cover plate is 20mm to 100mm.

5. The apparatus for manufacturing single-crystal silicon according to claim 1, wherein an outer edge of the thermal cover plate is circular, and a diameter of the thermal cover plate is 250mm to 300mm.

6. The apparatus for manufacturing a silicon single crystal as claimed in claim 1, wherein the shape of the outer edge of the thermal cover plate is matched with the shape of the lower end opening of the guide shell, and the diameter of the thermal cover plate is smaller than the inner diameter of the lower end opening of the guide shell.

7. The apparatus of any one of claims 2 to 6, wherein the material of the fan blade comprises at least one of carbon-carbon material, graphite, silicon, molybdenum, or tungsten.

8. The apparatus for manufacturing a silicon single crystal as claimed in claim 1, wherein the crystal pulling apparatus is connected to a weight through a wire;

9. A method for preparing single crystal silicon, comprising the steps of:

after silicon raw materials are put into a crucible in a single crystal furnace, a crystal lifting device drives a heat cover plate to move to an opening at the lower end of a guide cylinder, wherein the heat cover plate comprises a plurality of fan blades which are sequentially arranged at intervals along the circumferential direction, and the fan blades are obliquely arranged along the horizontal direction;

when the temperature of the silicon melt is stable, soaking a seed crystal into the silicon melt, and then sequentially carrying out seeding, shouldering and equal-diameter growth;

and after the equal-diameter growth is finished, performing a final stage to ensure that the diameter of the crystal is gradually reduced until the crystal is separated from the silicon melt, and taking out the crystal after the crystal is cooled to room temperature to obtain the single crystal silicon.

10. The method for producing single-crystal silicon according to claim 9, characterized by further comprising the steps of:

11. The method for preparing single crystal silicon according to claim 10, wherein after the hot cover plate passes through the lower end opening of the guide cylinder, the hot cover plate is lowered to a distance of 50mm to 400mm from the lower end opening of the guide cylinder.

12. The method of claim 9, wherein the rotation speed of the hot lid plate is 1 to 5 rpm during the pulling of the melt and the single crystal silicon.

13. The method for producing single-crystal silicon according to claim 9, wherein a heater power of a bottom of the crucible is controlled to 80kw to 90kw and a heater power of a side of the crucible is controlled to 100kw to 120kw during the melting.

14. The method for producing single-crystal silicon according to claim 9, wherein the method satisfies at least one of the following characteristics a to d:

15. The method for producing single-crystal silicon according to claim 8, wherein the crystal pulling apparatus is connected to a weight through a wire;

16. The method for preparing monocrystalline silicon, as claimed in claim 15, wherein before the crystal pulling device moves the thermal cover plate to the opening at the lower end of the guide shell, the method further comprises: