CN111020691A

CN111020691A - System and control method for drawing crystal bar

Info

Publication number: CN111020691A
Application number: CN201911223375.3A
Authority: CN
Inventors: 薛抗美
Original assignee: Xuzhou Xinjing Semiconductor Technology Co Ltd
Current assignee: Zhonghuan Leading Xuzhou Semiconductor Materials Co ltd; Zhonghuan Advanced Semiconductor Materials Co Ltd
Priority date: 2019-12-03
Filing date: 2019-12-03
Publication date: 2020-04-17

Abstract

The application provides a system and a control method for drawing a crystal bar, wherein the system comprises: the first control unit is used for controlling the pulling speed of the pulled crystal bar to be constant; the acquisition unit is used for acquiring the distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is an interface between the crystal liquid and the current crystal bar; the crucible is used for containing crystal liquid; a heating device for heating the crucible; the second control unit is used for adjusting the crucible lifting ratio under the condition that the distance is different from the preset distance, so that the distance reaches the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate; and the third control unit is connected with the heating device and is used for controlling the heating power of the heating device so that the diameter of the crystal bar at each position is in a preset range. The system keeps the ratio of the pulling speed of the pulled crystal bar to the v/G of the temperature gradient of the solid-liquid interface unchanged, thereby reducing the defect concentration of the pulled crystal bar.

Description

System and control method for drawing crystal bar

Technical Field

The application relates to the field of semiconductors, in particular to a system and a control method for drawing a crystal bar.

Background

With the rapid progress of semiconductor chip technology, the minimum line width of devices is becoming smaller and smaller, and the requirements on the intrinsic defect size and concentration of polished silicon wafers are becoming stricter. The traditional low-density defect polished silicon wafer cannot meet the advanced semiconductor process with the minimum line width below 30 nm.

According to Voronkov's theory, the intrinsic defect species and concentration within the crystal are determined by v/G, where v is the growth rate and G is the average axial temperature gradient between the solidification temperature and about 1300 ℃ at the central axis. When v/G is larger than a certain critical value, the defects in the crystal are biased to void mode, and the density of the defects in the void mode is higher when the v/G value is larger, whereas when v/G is smaller than a certain critical value, the defects in the crystal are biased to insertion mode, and the density of the insertion mode defects is higher when the v/G value is smaller. Therefore, to reduce intrinsic crystal defects (COP and interstitial defects), control of the pulling rate and the temperature gradient is important.

In the prior art, as shown in fig. 1, a system for growing a single crystal includes a single crystal furnace 10, a heating device 20, a crucible 30, a conventional draft tube 40', a cold water ring 60, and a second image capturing device 80. Wherein, the heating device 20, the crucible 30, the conventional guide cylinder 40', the measured object 50 and the cold water ring 60 are all arranged in the single crystal furnace 10, and the second image acquisition device 80 is arranged outside the single crystal furnace 10. In the process of growing the single crystal, when the diameter of the crystal bar 02 exceeds the preset diameter range, the pulling speed can be correspondingly adjusted to control the diameter, so that the diameter is ensured to be in a reasonable range, the change of the pulling speed also causes the heating equipment 20 to be correspondingly changed, and the change of the pulling speed is adapted. The pulling rate is taken as a variable for adjusting the diameter, and generally has +/-20 percent of variation, and the variation of the pulling rate can influence the power and the heat flux of a solid-liquid interface, greatly influence the quality of crystals and influence the yield of defect-free crystal bars.

In order to maintain a stable temperature gradient, the distance between the solid-liquid interface 03 and the reference surface (the bottom of the conventional guide cylinder 40') is generally controlled to be constant. In the actual production process, the crucible lift ratio (the ratio of the crystal growth rate to the crucible lift rate) of each stage in the crystal bar 02 growth process is generally calculated according to the volume of the crucible, the density of the melt, the density of the crystal bar, the pulling speed of the crystal bar, the preset growth diameter of the crystal bar 02 and the preset distance between the reference surface and the solid-liquid interface 03, and the fixed crucible lift ratio of each stage is preset, so that the purpose of keeping the distance between the reference surface and the solid-liquid interface 03 unchanged is achieved. However, due to the change of the crystal growth diameter and the shape of the crucible, the distance between the conventional guide cylinder 40' and the solid-liquid interface 03 cannot be kept constant in the actual process, so that the temperature gradient of the solid-liquid interface 03 cannot be accurately controlled, and the growth of a defect-free wafer is influenced.

In addition, in order to control the nucleation, growth and annihilation of intrinsic defects, the control of different temperature intervals of the ingot is also an important factor affecting the yield of defect-free wafers. In the conventional crystal growth process, the cooling rate of the crystal bar in different temperature ranges is mainly controlled by the pulling speed, when the cooling rate is required to be high, the pulling speed is increased, and when the cooling rate is required to be reduced, the pulling speed is reduced. Too high a pulling rate may result in easy wire breakage, and too low a pulling rate may result in too high a production cost, which are not suitable methods for growing defect-free wafers.

Disclosure of Invention

The main purpose of the present application is to provide a system and a control method for pulling an ingot, which provide a device capable of achieving a constant pulling rate and a stable temperature gradient, and achieving growth of a defect-free wafer.

In order to achieve the above object, according to one aspect of the present application, there is provided a system for drawing an ingot, comprising: the first control unit is used for controlling the pulling speed of the pulled crystal bar to be constant; the acquisition unit is used for acquiring the distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is an interface between a crystal liquid and the current crystal bar; the crucible is used for containing crystal liquid; a heating device for heating the crucible; a second control unit for adjusting a crucible lift ratio, which is a ratio of a crystal growth rate to a crucible lift rate, so that the distance reaches a predetermined distance, in the case where the distance is different from the predetermined distance; and the third control unit is connected with the heating device and is used for controlling the heating power of the heating device so that the diameter of the crystal bar at each position is in a preset range.

Further, the third control unit includes: the second image acquisition equipment is arranged on one side, far away from the solid-liquid interface, of the crystal bar, and used for acquiring an image of one end, close to the solid-liquid interface, of the crystal bar and calculating the diameter of one end, close to the solid-liquid interface, of the crystal bar according to the image; and the PID diameter control module is used for predicting a curve of the diameter and the power, controlling the heating equipment to heat the crystal liquid according to the preset power under the condition that the diameter is within the preset range, and adjusting the power of the heating equipment under the condition that the diameter is not within the preset range.

Further, the acquisition unit includes: a measurement object located on a side of the solid-liquid interface away from the crystal liquid, the measurement object having a reflection on the solid-liquid interface; and the first image acquisition equipment is arranged on one side of the crystal bar, which is far away from the solid-liquid interface, and is used for acquiring an inverted image of the measured object on the solid-liquid interface and calculating the distance between the solid-liquid interface and the reference surface according to the inverted image.

Further, the second control unit further includes: the crucible lifting equipment is used for lifting the crucible; the PID crucible lifting ratio control module is used for presetting the lifting ratio of a crucible, and adjusting the crucible lifting ratio under the condition that the distance is different from the preset distance so that the distance reaches the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate, and the crucible is used for containing the crystal liquid; and the preset distance control module is used for judging the value of the distance and the preset distance.

Further, the system further comprises: the heating device, the crucible and the crystal bar are arranged in the single crystal furnace; the guide cylinder is positioned in the single crystal furnace and on one side of the solid-liquid interface, which is far away from the crystal liquid, the guide cylinder is provided with a plurality of cooling sections, the heat conductivity coefficients of the cooling sections are different along the direction far away from the solid-liquid interface, and the reference surface is the surface where one end of the guide cylinder, which is close to the solid-liquid interface, is positioned; and the cold water ring is positioned in the single crystal furnace and sleeved on part of the crystal bar, and the guide cylinder is surrounded on the outer sides of part of the crystal bar and part of the cold water ring.

Furthermore, the distance between one end of the cold water ring close to the solid-liquid interface and the solid-liquid interface is 300-600 mm.

Further, the draft tube includes: the first structure is positioned outside part of the crystal bar and part of the cold water ring, and a gap is formed between the first structure and the crystal bar; the second structure is connected with the first structure and is positioned on one side of the first structure, which is far away from the crystal bar, and the first structure and the second structure are surrounded to form a cavity; the blocking structures are arranged in the cavity at intervals to divide the cavity into a plurality of cooling cavities; an insulating material positioned within at least one of the cooling cavities such that a plurality of the cooling cavities form a plurality of the cooling sections.

Further, the heat insulation material is a heat insulation felt, and the heat conductivity coefficients of the heat insulation felts in different cooling cavities are different.

Further, the interval between part of the first structures and the crystal bar is increased along the direction far away from the solid-liquid interface, the width of at least part of the cavity in the reference direction is increased along the direction far away from the solid-liquid interface, and the reference direction is perpendicular to the length direction of the crystal bar.

Further, the first structure comprises a first structure layer and a rim part, the rim part is connected with the first structure layer, and the rim part protrudes in a direction away from the crystal bar.

Further, the draft tube still includes: a thermally reflective layer disposed at least on an outer surface of the first structure and/or an outer surface of the second structure.

Further, the heat reflection layer is a pyrolytic graphite layer.

Further, the material of the first structure and/or the material of the second structure is graphite.

Further, the guide shell is provided with a first opening and a second opening which are distributed along the direction far away from the solid-liquid interface, and the diameter of the first opening is smaller than or equal to 370 mm.

Further, the maximum thickness of one end of the guide shell close to the crucible is greater than or equal to 150 mm.

According to another aspect of the present application, there is provided a control method of drawing an ingot, including: controlling the pulling speed of the pulled crystal bar to be constant; obtaining the distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is the interface between crystal liquid and the current crystal bar, and the height of the reference surface is kept unchanged; and under the condition that the distance is different from the preset distance, adjusting a crucible lifting ratio to enable the distance to reach the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate, and the crucible is used for containing the crystal liquid.

Further, in the case where the distance is different from the predetermined distance, adjusting the crucible lift ratio so that the distance reaches the predetermined distance includes: and adjusting the crucible rising rate to ensure that the ratio of the adjusted rising rate to the initial rising rate is between 0.7 and 1.3.

Further, the method further comprises: and controlling the heating power of a heating device for heating the crystal liquid by using a PID control method so that the diameter of the crystal bar at each position is in a preset range.

Further, a measurement object is arranged on one side of the solid-liquid interface, which is far away from the crystal liquid, the measurement object has a reflection on the solid-liquid interface, and obtaining the distance between the solid-liquid interface and the reference surface includes: acquiring a reflection position of the measured object on the solid-liquid interface; and determining the distance between the solid-liquid interface and the reference surface according to the reflection position.

Further, the cooling rate of the crystal bar formed by drawing is controlled to be different in different areas far away from the solid-liquid interface.

Further, the method sequentially comprises a first area, a second area and a third area along the direction far away from the reference surface and the solid-liquid interface, and the method for controlling the cooling rate of the crystal bar formed by drawing to be different in different areas far away from the solid-liquid interface comprises the following steps: controlling the temperature of the first area to be 1200-1420 ℃; controlling the temperature of the second area to be 1100-1200 ℃; and controlling the temperature of the third area to be 850-1100 ℃.

Further, controlling the cooling rate of the crystal bar formed by drawing to be different in different areas far away from the solid-liquid interface, and the method also comprises the following steps: controlling the cooling rate of the first region to be greater than or equal to 2 ℃/min; controlling the cooling rate of the second area to be 0.5-1.5 ℃/min; controlling the cooling rate of the third zone to be greater than or equal to 1.5 ℃/min.

By applying the technical scheme of the application, the system for drawing the crystal bar is adopted to control the constant drawing speed of the drawn crystal bar, the drawing speed is no longer used as the variable of the diameter change, the power and the heat flux of the interface are kept stable, the distance between the solid-liquid interface and the reference surface is controlled by adjusting the crucible lifting ratio to realize the constant keeping of the preset distance and the actual distance, the temperature gradient of the solid-liquid interface is accurately controlled by forming a thermal field with proper temperature distribution in the crystal bar growth process, and the cooling rate is controlled in a segmented manner to reduce the nucleation concentration of initial crystal defects; the oxide precipitate which is not nucleated can be dissolved, and the concentration of future nucleation is reduced; the nucleation and growth of crystal intrinsic defects and the re-nucleation and growth of oxide precipitates are avoided, so that the sizes of the crystal intrinsic defects and the defects of the oxide precipitates are reduced, and the growth of defect-free wafers is realized.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. In the drawings:

FIG. 1 shows a schematic structural diagram of a prior art single crystal system;

FIG. 2 shows a schematic structural view of an embodiment of a system for drawing an ingot according to the present application;

FIG. 3 illustrates an exploded view of an embodiment of a draft tube according to the present application;

FIG. 4 illustrates a cross-sectional schematic view of an embodiment of a draft tube according to the present application;

FIG. 5 shows a flow chart of an embodiment of a control method for drawing an ingot according to the present application;

FIG. 6 shows a flow chart of an embodiment of a distance control method according to the present application;

FIG. 7 illustrates a predetermined distance control versus length of an ingot according to an embodiment of the present application;

FIG. 8 shows a flow chart of an embodiment of a diameter control method according to the present application; and

fig. 9 shows a plot of ingot length versus ingot diameter for an example according to the present application and a comparative example.

Wherein the figures include the following reference numerals:

01. crystal liquid; 02. crystal bar; 03. a solid-liquid interface; 10. a single crystal furnace; 20. a heating device; 30. a crucible; 40. a draft tube; 40', a conventional draft tube; 50. measuring the object; 60. a cold water ring; 70. a heat preservation structure; 80. a second image acquisition device; 90. a first image acquisition device; 100. a crucible lifting device; 41. a first structure; 42. a second structure; 43. a barrier structure; 44. a cooling chamber; 45. a thermal insulation material; 46. a first opening; 47. a second opening; 411. a first structural layer; 412. a rim portion; 421. a second structural layer; 422. a bottom portion.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. Also, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element or "connected" to the other element through a third element.

As described in the background of the invention, the prior art cannot draw defect-free crystals, and in order to solve the above problems, the present application proposes a control system for drawing an ingot. The system for drawing an ingot provided by the embodiment of the application is described below.

FIG. 2 is a schematic view of a partial structure of a system for drawing an ingot according to an embodiment of the present application. As shown in FIG. 2, the system for drawing an ingot comprises: the method comprises the following steps:

the first control unit is used for controlling the pulling speed of the pulling crystal rod 02 to be constant;

an obtaining unit, configured to obtain a distance between a solid-liquid interface 03 and a reference surface, where the solid-liquid interface 03 is an interface between a crystal liquid and the current crystal bar;

the crucible 30 is used for containing the crystal liquid 01;

a heating device 20 for heating the crucible 30;

a second control unit for adjusting a crucible lift ratio, which is a ratio of a crystal growth rate to a crucible lift rate, so that the distance reaches a predetermined distance, in a case where the distance is different from the predetermined distance;

and a third control unit connected to the heating apparatus 20, for controlling the heating power of the heating apparatus 20 so that the diameter of the ingot 02 at each position is within a predetermined range.

In the system for drawing the crystal bar, the first control unit controls the drawing speed of the drawn crystal bar to be constant, the drawing speed is not used as a variable of diameter change any more, the power and the heat flux of an interface are kept stable, the acquisition unit acquires the distance between the solid-liquid interface and the reference surface, and the second control unit controls the distance between the solid-liquid interface and the reference surface to reach the preset distance by adjusting the crucible lifting ratio under the condition that the distance is different from the preset distance, so that the temperature gradient of the solid-liquid interface is accurately controlled. The three units enable the ratio of the pulling speed of the pulled crystal bar to the v/G of the temperature gradient of the solid-liquid interface to be kept unchanged, thereby reducing the defect concentration of the pulled crystal bar.

In order to ensure that the diameter is still controlled within the predetermined range, in an embodiment of the present application, as shown in fig. 2, the third control unit further includes a second image capturing device 80 and a PID diameter control module, wherein the second image capturing device 80 is disposed on a side of the ingot 02 far away from the solid-liquid interface 03, the second image capturing device 80 captures an image of an end of the ingot 02 close to the solid-liquid interface 03, and calculates a diameter of the end of the ingot 02 close to the solid-liquid interface 03 according to the image; the PID diameter control module is used for predicting a diameter-power curve, controlling the heating device 20 to heat the crystal liquid 01 according to a preset power when the diameter is within the preset range, and adjusting the power of the heating device 20 when the diameter is not within the preset range.

Specifically, the third control unit controls the heating power of the heating device that heats the crystal liquid so that the thermal field and the environment can quickly reach thermal equilibrium so that the diameter of the above-described ingot at each position is within a predetermined range.

In one embodiment of the present application, according to curve data of the diameter and power of the ingot pulled by the previous single crystal furnace for multiple times, a polynomial regression analysis and modeling prediction control method is used to calculate predicted power curves of the ingot growing furnace at different stages, so as to obtain curve data of the diameter and power, and a PID diameter control module is used to preset a curve of the diameter and power of the ingot pulled by the next single crystal furnace. In the actual production process, as shown in fig. 8, a second image acquisition device is used for acquiring an image of one end of the crystal ingot close to the solid-liquid interface, and calculating the diameter of the end of the crystal ingot close to the solid-liquid interface according to the image, wherein the PID diameter control module controls the heating device to heat the crystal liquid according to a preset power under the condition that the diameter is within a preset range, and the PID controller adjusts the power of the heating device under the condition that the diameter is not within the preset range, so that the diameter of the crystal ingot at each position is within the preset range, a power compensation control loop is formed, the diameter deviation caused by the locking of the pulling speed is compensated, and the diameter is prevented from being out of control.

Specifically, the invention is adopted to add a control loop for compensating diameter deviation by power, and the diameter of the crystal bar can be controlled within +/-3mm of the preset diameter by matching PID parameter setting. Specifically, as shown in FIG. 9, the solid line represents the actual ingot diameter versus the crystal length obtained by the control method with the pull rate locked and without power compensation, and the fluctuation thereof exceeds +5/-7mm or more, and the dotted line represents the actual ingot diameter versus the ingot length obtained by the above-mentioned control method of the present application, and the fluctuation thereof is within +/-3 mm.

In order to control the temperature gradient and precisely obtain the distance between the solid-liquid interface 03 and the reference surface, in an embodiment of the present application, as shown in fig. 2, the obtaining unit includes a measurement object 50 and a first image capturing device 90, wherein the measurement object 50 is located on the side of the solid-liquid interface 03 away from the crystal 01, and the measurement object 50 has an inverted image on the solid-liquid interface 03; the first image capturing device 90 is disposed on a side of the ingot 02 remote from the solid-liquid interface 03, and the first image capturing device 90 is configured to capture an inverted image of the measurement object 50 on the solid-liquid interface 03 and calculate a distance between the solid-liquid interface 03 and the reference surface from the inverted image.

Specifically, the measuring object is a quartz rod, and the quartz rod is high temperature resistant and occupies a small space, so that the pulling of the crystal rod is not hindered. In addition, the method does not need a measuring device to contact the crystal liquid, so that the crystal liquid is prevented from being polluted.

In order to ensure that the distance is the same as the predetermined distance, in an embodiment of the present application, as shown in fig. 2, the second control unit further includes a crucible lifting device 100, a PID crucible lifting ratio control module, and a predetermined distance control module, wherein the crucible lifting device 100 is used for lifting the crucible 30; the PID crucible lifting ratio control module is used for presetting the lifting ratio of a crucible, and adjusting the crucible lifting ratio under the condition that the distance is different from the preset distance so that the distance reaches the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate, and the crucible is used for containing the crystal liquid; the preset distance control module is used for judging whether the distance is equal to the preset distance.

Specifically, according to curve data of the crucible lift ratio of the previous single crystal furnace and the distance between the solid-liquid interface and the reference surface, a polynomial regression analysis and modeling prediction control method is used for calculating predicted power curves of the long crystal furnace at different stages, curve data of the distance and the crucible lift ratio are obtained, and a PID controller is used as a preset curve of the distance and the crucible lift ratio of the next single crystal furnace. In the actual production process, as shown in fig. 6, a first image acquisition device acquires and measures a reflection image of an object on a solid-liquid interface, the distance between the solid-liquid interface and a reference surface is calculated according to the reflection image, a preset distance control module judges whether the distance is equal to the value of the preset distance, a PID crucible lift ratio control module does not adjust the crucible lift ratio under the condition that the distance is equal to the value of the preset distance, and the PID crucible lift ratio control module adjusts the crucible lift ratio according to a preset curve under the condition that the distance is not equal to the value of the preset distance, so that the distance reaches the preset distance, and the temperature gradient of the solid-liquid interface is accurately controlled.

In the crystal drawing process, besides the control of the drawing speed and the temperature gradient, the cooling rate of the crystal bar in different temperature intervals is controlled, the nucleation and the growth of intrinsic defects are avoided, and the method has important significance for the growth of defect-free wafers. In addition to intrinsic defects, defects of oxide precipitates generated during the crystal growth process also affect the chip yield. The nucleation temperature of the oxide precipitates is 900 to 600 ℃ and the growth temperature is 1050 to 900 ℃, and the nucleation and growth are also related to the cooling rate of the ingot in these temperature ranges. In this regard, the present application will further control the cooling rate of the crystal at different temperature intervals via the thermal field.

In an embodiment of the present application, as shown in fig. 2, the system further includes a single crystal furnace 10, a guide cylinder 40, and a cold water ring 60, wherein the heating device 20, the crucible 30, and the ingot 02 are disposed in the single crystal furnace 10; the draft tube 40 is positioned in the single crystal furnace 10 and is disposed on a side of the solid-liquid interface 03 away from the crystal liquid 01, the draft tube 40 has a plurality of cooling sections, the heat conductivity of the plurality of cooling sections is different in a direction away from the solid-liquid interface 03, and the reference surface is a surface on which one end of the draft tube close to the solid-liquid interface 03 is located; the cold water ring 60 is located in the single crystal furnace 10 and is sleeved on a part of the crystal bar 02, and the guide cylinder 40 is surrounded on the outer sides of a part of the crystal bar 02 and a part of the cold water ring 60. In the structure, the heating equipment heats the crystal liquid in the crucible, and the guide cylinder shields heat to form uniform temperature gradient. The lengthened cold water ring has a temperature gradient for increasing the solid-liquid interface 03, and in the system for drawing the crystal bar, the guide cylinder is provided with a plurality of cooling sections with different heat conductivity coefficients, so that the cooling rate of the crystal bar can be controlled in a segmented mode, a thermal field with proper temperature distribution is formed in the growth process of the crystal bar, and the defects of crystals are further reduced.

Specifically, the distance between the end of the cooling water ring 60 close to the solid-liquid interface 03 and the solid-liquid interface 03 is 300mm to 600mm, and the distance between the end of the cooling water ring 60 close to the solid-liquid interface 03 and the solid-liquid interface 03 is preferably 500mm to 600mm, so that the temperature can be rapidly lowered to 1050 to 900 ℃, and the formation of oxide precipitates can be reduced.

In an embodiment of the present application, as shown in fig. 3, the guide shell 40 includes a first structure 41, a second structure 42, a plurality of barrier structures 43, and a heat insulating material 45, wherein the first structure 41 is located outside a portion of the boule 02 and a portion of the cold water ring 60, and has a gap with the boule 02; a second structure 42 connected to the first structure 41 and located on a side of the first structure 41 away from the ingot 02, wherein the first structure 41 and the second structure 42 enclose a cavity; a plurality of baffle structures 43 are arranged in the cavity at intervals to divide the cavity into a plurality of cooling cavities 44; insulation 45 is positioned within at least one of the cooling cavities 44 such that a plurality of the cooling cavities 44 form a plurality of the cooling stages.

Specifically, due to the different cooling rates of the plurality of cooling sections, the nucleation and growth of intrinsic defects in different temperature sections can be controlled, so that the growth of defect-free wafers is realized.

In a specific embodiment of the present application, the heat insulating material is a heat insulating felt, and the heat conductivity coefficients of the heat insulating felt located in different cooling cavities are different. Specifically, the heat insulation felt comprises a hard felt and a soft felt, the heat insulation felt has multiple layers, and the heat conductivity coefficient of the heat insulation felt is changed by adjusting the combination of the hard felt and the soft felt, so that the cooling rate of the cooling section is adjusted.

In order to form a more stable and uniform temperature gradient and to realize growth of a defect-free wafer, in one embodiment of the present invention, as shown in fig. 2 and 4, a distance between a portion of the first structure 41 and the ingot 02 is increased in a direction away from the solid-liquid interface 03, and a width of at least a portion of the cavity in a reference direction, which is perpendicular to a longitudinal direction of the ingot 02, is increased in a direction away from the solid-liquid interface 03.

In a specific embodiment of the present invention, as shown in fig. 3, the first structure 41 includes a first structure layer 411 and a rim portion 412, the rim portion 412 is connected to the first structure layer 411, the rim portion 412 protrudes in a direction away from the ingot 02, the second structure 42 includes a second structure layer 421 and a bottom portion 422, the bottom portion 422 is connected to the second structure layer 421, and the bottom portion 422 protrudes in a direction close to the ingot 02. The first structural layer 411 and the second structural layer 421 are connected and enclosed to form a cavity, the edge 412 facilitates installation of the guide cylinder 40, and the bottom 422 facilitates placement of the guide cylinder 40, which is relatively stable.

In a specific embodiment of the present application, the guide shell further includes a heat reflective layer, and the heat reflective layer is disposed on at least an outer surface of the first structure 41 and/or an outer surface of the second structure 42. Specifically, the heat reflection layer can increase the heat reflection capability, so that the difference of the temperature gradient in the reference direction is reduced, the defect concentration of the center and the edge of the crystal bar is consistent, and the uniformity of the defect concentration of the crystal bar is further improved.

In an embodiment of the present application, the heat reflective layer is a pyrolytic graphite layer. Specifically, the pyrolytic graphite layer can increase the heat reflection capability by 50%, and a person skilled in the art can select a suitable heat reflection layer according to actual conditions.

In an embodiment of the present application, the material of the first structure 41 and/or the material of the second structure 42 is graphite. The graphite can enable the first structure or the second structure to reduce the difference of radial temperature gradients, thereby maintaining the cooling rate of each cooling section to be constant and further reducing the defect concentration of the crystal bar.

In an embodiment of the present application, as shown in fig. 4, the guide cylinder 40 has a first opening 46 and a second opening 47 distributed along a direction away from the solid-liquid interface 03, and a diameter of the first opening 46 is less than or equal to 370mm, so that a thermal insulation capability of an end of the guide cylinder close to the crucible is improved, thereby reducing a difference of a temperature gradient in a reference direction, making a defect concentration of a center and an edge of the ingot consistent, and further improving a defect concentration uniformity of the ingot.

In an embodiment of the present application, as shown in fig. 2, the maximum thickness of the end of the guide cylinder 40 close to the crucible is greater than or equal to 150mm, which improves the thermal insulation capability of the end of the guide cylinder close to the crucible, thereby reducing the difference of the temperature gradient in the reference direction, making the defect concentration of the center and the edge of the ingot consistent, and further improving the uniformity of the defect concentration of the ingot.

In a specific embodiment of the present application, the guide shell 40 has three cooling sections, which are a first cooling section, a second cooling section and a third cooling section along a direction away from the solid-liquid interface 03.

It should be noted that the cooling cavity of the guide shell forms three cooling sections by arranging a heat insulating material, and the cooling rates of the three cooling sections can be adjusted by adjusting the heat conductivity of the heat insulating material.

In a specific embodiment of the present application, as shown in fig. 2, the system further comprises a heat-insulating structure 70, wherein the heat-insulating structure 70 is disposed on an inner wall of the single crystal furnace 10. Specifically, the heat insulating structure is mainly formed of a heat insulating material, which reduces heat dissipation and saves energy, and those skilled in the art can select an appropriate heat insulating material according to actual conditions.

The embodiment of the application also provides a control method for pulling the crystal bar, and it should be noted that the system for pulling the crystal bar of the embodiment of the application can be used for executing the control method for pulling the crystal bar provided by the embodiment of the application. The method for drawing an ingot provided by the embodiment of the present application is described below.

FIG. 5 is a flow chart of a control method for drawing an ingot according to an embodiment of the present application. As shown in fig. 5, the method comprises the steps of:

s101, controlling the pulling speed of the pulled crystal bar to be constant, so that the actual pulling speed is equal to the set pulling speed;

step S102, obtaining a distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is an interface between a crystal liquid and the current crystal bar, and the height of the reference surface is kept unchanged;

step S103, under the condition that the distance is different from a preset distance, adjusting a crucible lifting ratio to enable the distance to reach the preset distance, wherein the crucible lifting ratio is the ratio of a crystal growth rate to a crucible lifting rate, and the crucible is used for containing the crystal liquid;

according to the control method for drawing the crystal bar, the drawing speed of the drawn crystal bar is controlled to be constant, the distance between the solid-liquid interface and the reference surface is controlled to be kept at the preset distance by adjusting the crucible lifting ratio, so that the temperature gradient of the solid-liquid interface is accurately controlled, the ratio of the drawing speed of the drawn crystal bar to the temperature gradient of the solid-liquid interface is kept unchanged, and the defect concentration of the drawn crystal bar is reduced.

In order to accurately control the temperature gradient of the solid-liquid interface and further reduce the defect concentration of a drawn crystal bar, in one embodiment of the application, the distance between the solid-liquid interface and the reference surface is directly obtained by using image acquisition equipment, and the crucible lift ratio is adjusted in real time according to the distance between the solid-liquid interface and the reference surface, so that the distance is kept constant. Specifically, the ratio of the adjusted rising rate to the initial rising rate is controlled within the range, so that the phenomenon that the crucible rising ratio is changed too fast is avoided, the distance between a solid-liquid interface and a reference surface is kept at a preset distance, the temperature gradient of the solid-liquid interface is accurately controlled, the ratio of the pulling speed of the pulled crystal bar to the temperature gradient of the solid-liquid interface is kept unchanged, and the defect concentration of the pulled crystal bar is further reduced.

Specifically, according to curve data of the crucible lift ratio of the multiple single crystal furnaces and the distance between the solid-liquid interface and the reference surface, a polynomial regression analysis and modeling prediction control method is used for calculating predicted power curves of the long crystal furnace at different stages to obtain curve data of the distance and the crucible lift ratio, and a PID (proportion integration differentiation) controller is used for presetting a curve of the distance and the crucible lift ratio of the next single crystal furnace. In the actual production process, as shown in fig. 6, a reflection image of a measured object on a solid-liquid interface is acquired, the distance between the solid-liquid interface and a reference surface is calculated according to the reflection image, whether the distance is equal to the value of the predetermined distance is judged, the crucible lift ratio is not adjusted when the distance is equal to the value of the predetermined distance, and the crucible lift ratio is adjusted according to a preset curve when the distance is not equal to the value of the predetermined distance, so that the distance reaches the predetermined distance, and the temperature gradient of the solid-liquid interface is accurately controlled.

In a specific embodiment of the application, the crucible lifting ratio is adjusted in real time, and the ratio of the adjusted lifting rate to the initial lifting rate is kept between 0.7 and 1.3. If the adjustment rate is too fast, the crystal may lose its crystal structure, and if the adjustment rate is too slow, the predetermined distance may not be maintained constant. It can be known through experiments that as shown in fig. 7, the solid line is a curve of the predetermined distance set value and the length of the ingot, and the dotted line is a curve of the predetermined distance actual value and the length of the ingot, the deviation between the predetermined distance actual value and the predetermined distance set value begins to occur at the beginning stage of the constant diameter, the predetermined distance actual value and the predetermined distance set value are quickly made to be equal through real-time adjustment, and the deviation is controlled within +/-1 mm. In the process of crystal growth, due to the change of actual conditions, the preset distance set value is changed according to the process requirements, and the ratio of the crucible heel ratio to the initial crucible heel ratio is adjusted in real time, so that the preset distance set value and the preset distance actual value are almost equal, and the yield of defect-free wafers is ensured.

In a specific embodiment of the present application, the method further includes: and step S104, PID controls the heating power of a heating device for heating the crystal liquid, so that the diameter of the crystal bar at each position is in a preset range.

In the control method for drawing the crystal bar, the PID controls the heating power of the heating equipment for heating the crystal liquid, so that the thermal field and the environment can quickly reach thermal balance, and the diameter of the crystal bar at each position is in a preset range.

In the application, the drawing speed is controlled to be constant (the actual drawing speed is equal to the set drawing speed), and the diameter is directly controlled by heating equipment. Preferably, a control loop for compensating the diameter deviation by power can be additionally arranged, the diameter deviation caused by constant pulling speed is compensated by means of short-time high-power temperature increase and decrease matched with proper PID parameter setting, and the cost loss caused by diameter runaway is avoided.

In the above method for controlling an ingot, in order to further ensure that the diameter of the ingot at each position is within a predetermined range when the pulling rate at which the ingot is pulled is constant, in an embodiment of the present application, as shown in fig. 8, the method for controlling an ingot comprises: according to curve data of the diameter and the power of the crystal bar pulled by the previous single crystal furnace for multiple times, calculating predicted power curves of the crystal growing furnace at different stages by using a polynomial regression analysis and modeling prediction control method to obtain curve data of the diameter and the power, and acquiring the diameter of one end, close to the solid-liquid interface, of the crystal bar by using a PID diameter controller as a preset curve of the diameter and the power of the next single crystal furnace; and in the case where the diameter is not within the predetermined range, adjusting the power of the heating device so that the diameter is within the predetermined range using a PID diameter controller.

Specifically, after acquiring the diameter of the end of the ingot near the solid-liquid interface, before controlling the heating power of the heating device, controlling the heating power of the heating device that heats the liquid crystal so that the diameter of the ingot at each position is within a predetermined range, further comprising: determining whether the diameter is within the predetermined range, the determining whether the diameter is within the predetermined range comprising: obtaining the difference between the diameter and a predetermined diameter; and judging whether the difference value is within a preset difference value range.

More specifically, in the case where the difference between the diameter and the predetermined diameter is not within the predetermined difference range, a PID parameter is set according to the difference between the diameter and the predetermined diameter, and a power PID controller controls the heating power of a heating device that heats the liquid crystal according to the PID parameter, so that the thermal field and the environment can rapidly reach thermal equilibrium, and the diameter of the ingot at each position is within the predetermined range. More specifically, the heating device may be a graphite heater, and the heating method of the heating device may be any suitable manner, and those skilled in the art may select a suitable heating device and a corresponding heating method according to actual situations.

In a specific embodiment of the present application, a control loop for compensating diameter deviation by power is added, and the diameter of the crystal bar can be controlled within +/-3mm of a predetermined diameter by matching with PID parameter setting. Specifically, as shown in FIG. 9, the curve is a graph of the relationship between the actual ingot diameter and the crystal length obtained by the control method with the pull rate locked and without power compensation, and the fluctuation of the curve exceeds more than +5/-7mm, and the straight line is a graph of the relationship between the actual ingot diameter and the ingot length obtained by the control method of the present application, and the fluctuation of the straight line is within +/-3 mm.

In a specific embodiment of the present application, the step of obtaining the distance between the solid-liquid interface and the reference surface includes: acquiring a reflection position of the object to be measured on the solid-liquid interface; and determining the distance between the solid-liquid interface and the reference surface according to the reflection position. The method is simple and easy to implement, and the measurement is carried out without the need of contacting the crystal liquid by a measuring device, so that the pollution of the crystal liquid is avoided.

Specifically, the measuring object is a quartz rod, and the quartz rod is high temperature resistant and occupies a small space, so that the pulling of the crystal rod is not hindered.

Specifically, a first image capturing device is used to capture a reflection image of the measurement object, an included angle is formed between a length direction of the measurement object and a direction of a target straight line, and the target straight line is a connection line between a center of a lens of the first image capturing device and a center of the measurement object. The first image acquisition equipment sends the acquired inverted image to image analysis software, the image analysis software analyzes the inverted image to obtain an inverted image position, and the distance between the solid-liquid interface and the reference surface is calculated according to the inverted image position.

In a specific embodiment of the present application, the method further includes:

and step S105, controlling the cooling rates of the crystal bar formed by drawing to be different in different areas far away from the solid-liquid interface.

In the control method for drawing the crystal bar, the cooling rate of the crystal bar is controlled in a segmented mode, and a thermal field with proper temperature distribution is formed in the growth process of the crystal bar, so that the defects of crystals are further reduced.

It should be noted that the steps illustrated in the flowcharts of the figures may be performed in a computer system such as a set of computer-executable instructions and that, although a logical order is illustrated in the flowcharts, in some cases, the steps illustrated or described may be performed in an order different than presented herein.

In order to improve the uniformity of the temperature gradient of the thermal field and further reduce the concentration of intrinsic defects and oxygen defects, in one embodiment of the present application, the ingot formed by drawing is controlled to have a first region, a second region and a third region in sequence along the direction away from the reference surface and the solid-liquid interface, and the cooling rates of the ingot formed by drawing are controlled to be different in different regions away from the solid-liquid interface, and the method comprises the following steps: controlling the temperature of the first area to be 1200-1420 ℃; controlling the temperature of the second area to be 1100-1200 ℃; and controlling the temperature of the third area to be 850-1100 ℃. Specifically, the temperature gradient of the thermal field is divided into the three temperature sections, and different cooling rates are adopted in different temperature sections, so that the temperature gradient of the thermal field is more uniform, and the defect concentration of the drawn crystal bar is further reduced. Of course, the temperature gradient of the thermal field may have four or more temperature sections, and those skilled in the art can select a suitable temperature gradient according to actual conditions.

In order to control the cooling rate of the ingot in stages and further reduce the concentration of intrinsic defects, in a specific embodiment of the present application, the method for controlling the cooling rate of the ingot formed by drawing to be different in different regions far away from the solid-liquid interface further comprises: controlling the first cooling rate to be greater than or equal to 2 ℃/min, specifically 2.5 ℃/min, 3 ℃/min, 3.5 ℃/min, 4 ℃/min, 4.5 ℃/min; controlling the cooling rate of the second area to be 0.5-1.5 ℃/min, specifically 1 ℃/min; the cooling rate of the third region is controlled to be greater than or equal to 1.5 ℃/min, specifically 2 ℃/min, 2.5 ℃/min, 3 ℃/min, 3.5 ℃/min, 4 ℃/min, 4.5 ℃/min. Specifically, the cooling rate in the first region is high at 1200-1420 ℃, and the nucleation concentration of initial crystal defects is reduced; the cooling rate of the second region is less than that of the first region, so that the crystal bar has long residence time in the temperature range of 1100-1200 ℃, oxide precipitates which are not nucleated can be dissolved, and the concentration of future nucleation is reduced; the cooling rate of the third region is greater than or equal to 1.5 ℃/min, the retention time of the crystal bar in the temperature range of 850-1100 ℃ is short, and the growth of crystal defects (COP and interstitial defects) and the re-nucleation and growth of oxide precipitates are avoided, so that the sizes of the crystal defects and the defects of the oxide precipitates are reduced.

The nucleation temperature of the oxide precipitates is 900-600 ℃, the growth temperature of the oxide precipitates is 1050-900 ℃, in the crystal growth process, the cooling rate in the growth temperature range can be reduced to increase the cooling time in the growth temperature range so as to dissolve small oxide precipitation nuclei, the cooling rate in the nucleation temperature range is increased to reduce the cooling time in the growth temperature range so as to avoid re-nucleation of the oxide precipitates, and therefore the concentration of defects of the oxide precipitates is reduced.

In order to make the technical solutions of the present application more clearly understood by those skilled in the art, the technical solutions of the present application will be described below with reference to specific embodiments.

Example 1

The system shown in fig. 2 is used, and includes a single crystal furnace 10, a heating device 20, a crucible 30, a guide cylinder 40, a measurement object 50, a cold water ring 60, a second image capturing device 80, and a first image capturing device 90. Wherein, the heating device 20, the crucible 30, the guide cylinder 40, the measuring object 50 and the cold water ring 60 are all arranged in the single crystal furnace 10. The heating device 20 is arranged to heat the crucible 30, the crucible 30 contains the crystal liquid 01, the second image acquisition device 80 acquires diameter data of the crystal bar, and the first image acquisition device 90 measures the distance between the solid-liquid interface 03 and the guide cylinder 40 according to the reflection of the measured object 50 on the solid-liquid interface 03. The draft tube 40 includes three cooling cavities 44, wherein the lowermost cooling cavity is filled with two layers of soft felt; the second intermediate cooling cavity is filled with five layers of heat-insulating hard felts; the third intermediate cooling chamber comprises three layers of soft felt, so that the guide cylinder forms three cooling sections. The diameter of the first opening of the guide shell is 370mm, and the reference surface is the surface of one end of the guide shell close to the solid-liquid interface 03. The maximum thickness of the guide cylinder 40 at the end close to the crucible is 150 mm. The outer surface of the guide shell comprises a heat reflection layer obtained by pyrolyzing the graphite layer coating. The cold water ring 60 is positioned in the single crystal furnace 10 and is sleeved on a part of the crystal bar 02, the guide cylinder 40 is arranged around the outer sides of the part of the crystal bar 02 and the part of the cold water ring 60, and the distance between one end of the cold water ring 60 close to the solid-liquid interface 03 and the solid-liquid interface 03 is 600 mm.

The system also comprises a first control unit, wherein the first control unit is used for controlling the pulling speed to be constant, the second control unit acquires and measures a reflection image of the object on the solid-liquid interface through the first image acquisition equipment, calculates the distance between the solid-liquid interface and the reference surface according to the reflection image, and judges whether the value of the distance is equal to the value of the preset distance through the preset distance control module, the PID crucible lifting ratio control module does not adjust the crucible lifting ratio under the condition that the distance is equal to the value of the preset distance, and the PID crucible lifting ratio control module adjusts the crucible lifting ratio according to the curve of the distance and the crucible lifting ratio under the condition that the distance is not equal to the value of the preset distance, so that the distance reaches the preset distance. And the third control unit acquires an image of one end, close to the solid-liquid interface, of the crystal ingot through the second image acquisition device, calculates the diameter of one end, close to the solid-liquid interface, of the crystal ingot according to the image, controls the heating device to heat the crystal liquid according to the preset power under the condition that the diameter is within a preset range, and adjusts the power of the heating device under the condition that the diameter is not within the preset range, so that the diameter of the crystal ingot at each position is within the preset range.

The system draws a 200mm crystal bar, and the drawing speed is 0.45 mm/min-0.55 mm/min in the whole crystal pulling process (a fixed value is used in a certain period, and the actual value is equal to the set value). The preset distance between the solid-liquid interface 03 and the bottom of the guide cylinder 40 is set to be 40-60 mm, the crucible heel ratio is preset in the whole drawing process, in the production process, the crucible ascending control module is adjusted according to the difference value between the reference distance and the actual distance, and the ratio of the adjusted ascending rate to the initial ascending rate is kept between 0.7-1.3.

Example 2

With the system shown in FIG. 2, the crucible-heel ratio was adjusted in real time without using the second control unit, and the remaining control method was the same as in example 1. The preset distance is set to be 40-60 mm, and the crucible heel ratio is preset.

Example 3

The system shown in FIG. 2 is adopted, the heating power of the heating device for heating the crystal liquid is not controlled by using the third control unit, the other control method is the same as that of the embodiment 1, and a 200mm crystal bar is drawn, wherein the crystal drawing speed is 0.45 mm/min-0.55 mm/minmm/min.

Comparative example 1

The diameter is controlled by adopting the pulling speed of the system shown in FIG. 1, and a 200mm crystal bar is pulled, wherein the pulling speed of the crystal is 0.45 mm/min-0.55 mm/min. The preset distance is set to be 40-60 mm.

The crystal ingots pulled in examples 1 to 3 and comparative example 1 were subjected to a defect test, and the test crystal ingots of any one of the examples or comparative examples were 3 crystal ingots continuously pulled from one crucible by a CCZ (continuous czochralski single crystal) process, and in terms of the pulling order, #1 was the first pulled crystal ingot, #2 was the second pulled crystal ingot, and #3 was the third pulled crystal ingot. Specific test results are shown in table 1 below.

TABLE 1

As can be seen from table 1, (1) the yield of the three ingots in example 1 exceeds 91%, the defect ratio loss is 8.7%, and the diameter smaller loss is 0-0.2%, that is, the yield of the ingot drawn by the system for drawing an ingot of the present application exceeds 91%, (2) the yield of the #1 ingot in example 2 exceeds 91%, the #2 and #3 ingots are gradually reduced, the yield loss is mainly the defect loss ratio, and the defect loss ratio of the #2 and #3 ingots is 15.3% -28.7%, because the second control unit is not used in example 2, the deformation amount of the crucible increases with the increase of the heating time, the difference between the predetermined distance and the reference distance is larger, the temperature gradient is less accurate, and the yield is gradually deteriorated after the #2 and # 3; (3) the yields #1, #2 and #3 of example 3 are all 88-90%, the defect loss ratio is equivalent to that of example 1, the main loss is the loss ratio caused by a smaller diameter, and the main reason is that in the case of example 3, the yield is slightly lower than that of example 1 because the diameter is not controlled by the third control unit under the condition of the pull-up speed locking. (4) Comparing example 1 with comparative example 1 of the system of fig. 1, it can be seen that the system of fig. 1 is not locked, the cooling rate is controlled without using the second third control unit and the segmented guide shell, and the system for drawing an ingot of the present application can improve the perfect pull yield by at least 22%. The system and the control method for drawing the crystal bar can effectively reduce the defect concentration of the drawn crystal bar and improve the crystal pulling yield of perfect crystals.

From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects:

1) in the system for drawing the crystal bar, the first control unit controls the drawing speed of the crystal bar to be constant. The acquisition unit acquires the distance between the solid-liquid interface and the reference surface, and the second control unit controls the distance between the solid-liquid interface and the reference surface to reach the preset distance by adjusting the crucible rise ratio under the condition that the distance is different from the preset distance, so that the temperature gradient of the solid-liquid interface is accurately controlled. The three units enable the ratio of the pulling speed of the pulled crystal bar to the temperature gradient of the solid-liquid interface to be kept unchanged, thereby reducing the defect concentration of the pulled crystal bar. The third control unit controls heating power of a heating device that heats the crystal liquid so that the thermal field and the environment can rapidly reach thermal equilibrium so that the diameter of the crystal ingot at each position is within a predetermined range. The guide shell is provided with a plurality of cooling sections with different heat conductivity coefficients, so that the cooling rate of the crystal bar can be controlled in a sectional manner, a thermal field with proper temperature distribution is formed in the growth process of the crystal bar, and the defects of the crystal are further reduced.

2) According to the control method for drawing the crystal bar, the drawing speed of the drawn crystal bar is controlled to be constant, the distance between the solid-liquid interface and the reference surface is controlled to be kept at the preset distance by adjusting the crucible lifting ratio, so that the temperature gradient of the solid-liquid interface is accurately controlled, the ratio of the drawing speed of the drawn crystal bar to the temperature gradient of the solid-liquid interface is kept unchanged, the defect concentration of the drawn crystal bar is reduced, the heating power of heating equipment for heating crystal liquid is controlled, the thermal field and the environment can quickly reach thermal balance, the diameter of the crystal bar at each position is in the preset range, the cooling rate of the crystal bar is controlled in a segmented mode, a thermal field with proper temperature distribution is formed in the crystal bar growing process, and the defects of crystals are further reduced.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A system for drawing an ingot, comprising:

the first control unit is used for controlling the pulling speed of the pulled crystal bar to be constant;

the acquisition unit is used for acquiring the distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is an interface between a crystal liquid and the current crystal bar;

the crucible is used for containing crystal liquid;

a heating device for heating the crucible;

a second control unit for adjusting a crucible lift ratio, which is a ratio of a crystal growth rate to a crucible lift rate, so that the distance reaches a predetermined distance, in the case where the distance is different from the predetermined distance;

and the third control unit is connected with the heating device and is used for controlling the heating power of the heating device so that the diameter of the crystal bar at each position is in a preset range.

2. The system of claim 1, wherein the third control unit comprises:

the second image acquisition equipment is arranged on one side, far away from the solid-liquid interface, of the crystal bar, and used for acquiring an image of one end, close to the solid-liquid interface, of the crystal bar and calculating the diameter of one end, close to the solid-liquid interface, of the crystal bar according to the image;

and the PID diameter control module is used for predicting a curve of the diameter and the power, controlling the heating equipment to heat the crystal liquid according to the preset power under the condition that the diameter is within the preset range, and adjusting the power of the heating equipment under the condition that the diameter is not within the preset range.

3. The system of claim 1, wherein the obtaining unit comprises:

a measurement object located on a side of the solid-liquid interface away from the crystal liquid, the measurement object having a reflection on the solid-liquid interface;

and the first image acquisition equipment is arranged on one side of the crystal bar, which is far away from the solid-liquid interface, and is used for acquiring an inverted image of the measured object on the solid-liquid interface and calculating the distance between the solid-liquid interface and the reference surface according to the inverted image.

4. The system of claim 1, wherein the second control unit further comprises:

the crucible lifting equipment is used for lifting the crucible;

the PID crucible lifting ratio control module is used for presetting the lifting ratio of a crucible, and adjusting the crucible lifting ratio under the condition that the distance is different from the preset distance so that the distance reaches the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate, and the crucible is used for containing the crystal liquid;

and the preset distance control module is used for judging the value of the distance and the preset distance.

5. The system of claim 1, further comprising:

the heating device, the crucible and the crystal bar are arranged in the single crystal furnace;

the guide cylinder is positioned in the single crystal furnace and on one side of the solid-liquid interface, which is far away from the crystal liquid, the guide cylinder is provided with a plurality of cooling sections, the heat conductivity coefficients of the cooling sections are different along the direction far away from the solid-liquid interface, and the reference surface is the surface where one end of the guide cylinder, which is close to the solid-liquid interface, is positioned;

and the cold water ring is positioned in the single crystal furnace and sleeved on part of the crystal bar, and the guide cylinder is surrounded on the outer sides of part of the crystal bar and part of the cold water ring.

6. The system of claim 5, wherein the distance between one end of the cold water ring close to the solid-liquid interface and the solid-liquid interface is 300-600 mm.

7. The system of claim 5, wherein the guide shell comprises:

the first structure is positioned outside part of the crystal bar and part of the cold water ring, and a gap is formed between the first structure and the crystal bar;

the second structure is connected with the first structure and is positioned on one side of the first structure, which is far away from the crystal bar, and the first structure and the second structure are surrounded to form a cavity;

the blocking structures are arranged in the cavity at intervals to divide the cavity into a plurality of cooling cavities;

an insulating material positioned within at least one of the cooling cavities such that a plurality of the cooling cavities form a plurality of the cooling sections.

8. The system of claim 7, wherein the insulation material is insulation blanket, and wherein the thermal conductivity of the insulation blanket is different in different cooling cavities.

9. The system of claim 7, wherein a spacing between a portion of the first structure and the ingot increases in a direction away from the solid-liquid interface, and wherein a width of at least a portion of the cavity in a reference direction perpendicular to a length direction of the ingot increases in the direction away from the solid-liquid interface.

10. The system of claim 7, wherein the first structure comprises a first structure layer and a rim portion, the rim portion being connected to the first structure layer and protruding away from the boule.

11. The system of claim 7, wherein the guide shell further comprises:

a thermally reflective layer disposed at least on an outer surface of the first structure and/or an outer surface of the second structure.

12. The system of claim 11, wherein the thermally reflective layer is a pyrolytic graphite layer.

13. The system of any one of claims 7 to 11, wherein the material of the first structure and/or the material of the second structure is graphite.

14. The system of any one of claims 7 to 11, wherein the draft tube has a first opening and a second opening distributed along the length away from the solid-liquid interface, the first opening having a diameter less than or equal to 370 mm.

15. The system of any one of claims 7 to 11, wherein a maximum thickness of an end of the draft tube proximate the crucible is greater than or equal to 150 mm.

16. A control method for drawing an ingot, comprising:

controlling the pulling speed of the pulled crystal bar to be constant;

obtaining the distance between a solid-liquid interface and a reference surface, wherein the solid-liquid interface is the interface between crystal liquid and the current crystal bar, and the height of the reference surface is kept unchanged;

and under the condition that the distance is different from the preset distance, adjusting a crucible lifting ratio to enable the distance to reach the preset distance, wherein the crucible lifting ratio is the ratio of the crystal growth rate to the crucible lifting rate, and the crucible is used for containing the crystal liquid.

17. The control method according to claim 16, wherein adjusting the crucible lift ratio so that the distance reaches the predetermined distance in the case where the distance is different from the predetermined distance comprises:

and adjusting the crucible rising rate to ensure that the ratio of the adjusted rising rate to the initial rising rate is between 0.7 and 1.3.

18. The control method according to claim 16, characterized in that the method further comprises: and controlling the heating power of a heating device for heating the crystal liquid by using a PID control method so that the diameter of the crystal bar at each position is in a preset range.

19. The control method according to claim 16, wherein a measurement object having an inverted image on the solid-liquid interface is provided on a side of the solid-liquid interface away from the crystal liquid, and the obtaining of the distance between the solid-liquid interface and the reference surface comprises:

acquiring a reflection position of the measured object on the solid-liquid interface;

and determining the distance between the solid-liquid interface and the reference surface according to the reflection position.

20. The method of claim 16, wherein the cooling rate of the ingot formed by drawing is controlled to be different in different regions away from the solid-liquid interface.

21. The method of claim 16, wherein the first zone, the second zone and the third zone are arranged in sequence along the direction away from the reference surface and the solid-liquid interface, and the controlling of the cooling rate of the ingot formed by drawing is different in different zones away from the solid-liquid interface comprises:

controlling the temperature of the first area to be 1200-1420 ℃;

controlling the temperature of the second area to be 1100-1200 ℃;

and controlling the temperature of the third area to be 850-1100 ℃.

22. The method of claim 21, wherein controlling the cooling rate of the ingot formed by drawing to be different in different regions away from the solid-liquid interface further comprises:

controlling the cooling rate of the first region to be greater than or equal to 2 ℃/min;

controlling the cooling rate of the second area to be 0.5-1.5 ℃/min;

controlling the cooling rate of the third zone to be greater than or equal to 1.5 ℃/min.