CN114232079A - Crystal pulling method and monocrystalline silicon wafer - Google Patents
Crystal pulling method and monocrystalline silicon wafer Download PDFInfo
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- CN114232079A CN114232079A CN202111418337.0A CN202111418337A CN114232079A CN 114232079 A CN114232079 A CN 114232079A CN 202111418337 A CN202111418337 A CN 202111418337A CN 114232079 A CN114232079 A CN 114232079A
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/14—Heating of the melt or the crystallised materials
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
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Abstract
The invention provides a crystal pulling method and a monocrystalline silicon wafer, and relates to the technical field of crystal growth. The crystal pulling method comprises the following steps: shortening the distance between the main heater and the auxiliary heater in the single crystal furnace to a first preset distance; in the melting stage, the heating power of the primary heater is increased to a first preset value, and the heating power of the secondary heater is increased to a second preset value. The interval between main heater, the secondary heater shortens, and the heating power of main heater increases in the melt stage, and the heating power of secondary heater increases, and is more concentrated at melt stage heat, has promoted the melt speed, reduces the reaction of crucible, molten silicon and oxygen, has reduced the production of oxygen impurity, and has reduced the melt time, has promoted crystal pulling efficiency. The natural convection is reduced, so that the oxygen impurities generated by scouring the crucible by the natural convection are reduced, the oxygen impurities in the crystal bar are reduced, the stability of a crystal growth interface can be improved due to low longitudinal temperature gradient, and the crystal growth interface is not easy to break.
Description
Technical Field
The invention relates to the technical field of crystal growth, in particular to a crystal pulling method and a monocrystalline silicon wafer.
Background
The currently common production process for processing silicon materials into monocrystalline silicon is the czochralski method. During the Czochralski method, the high content of oxygen impurities in the crystal can reduce the minority carrier lifetime of the crystal, and the content of the oxygen impurities needs to be controlled.
At present, the crystal/crucible rotation is mainly adjusted to reduce the oxygen impurity content of the crystal in the crystal pulling process of the Czochralski method. The inventor discovers in the process of researching the prior art as follows: existing means of reducing oxygen impurities can result in poor crystal pull stability.
Disclosure of Invention
The invention provides a crystal pulling method and a monocrystalline silicon wafer, and aims to solve the problems of high oxygen impurity content and unstable crystal pulling of a crystal in a crystal pulling process of a Czochralski method.
In a first aspect of the invention, there is provided a crystal pulling method comprising:
shortening the distance between the main heater and the auxiliary heater in the single crystal furnace to a first preset distance;
in the melting stage, the heating power of the primary heater is increased to a first preset value, and the heating power of the secondary heater is increased to a second preset value.
In the embodiment of the invention, the distance between the main heater and the auxiliary heater is shortened to the first preset distance, the heating power of the main heater is increased to the first preset value in the melting stage, the heating power of the auxiliary heater is increased to the second preset value, the heat is concentrated in the melting stage, the melting speed is improved, the reaction of a crucible, molten silicon and oxygen can be reduced, the generation of oxygen impurities is reduced, the melting time is reduced, and the crystal pulling efficiency is improved. Meanwhile, the longitudinal temperature gradient of the upper and lower parts of the molten silicon is properly reduced, on one hand, the natural convection is reduced, so that the oxygen impurities generated by scouring the crucible by the natural convection are reduced, the oxygen impurities in the crystal bar are reduced, on the other hand, the stability of a crystal growth interface can be improved due to the low longitudinal temperature gradient, the broken line is less, and the crystal pulling stability is improved.
Optionally, the method further includes: and reducing the distance between the liquid ports to the first liquid port distance in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage.
Optionally, the method further includes:
adjusting the position of the heat exchanger to a first position in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage; after the equal-diameter stage begins, moving the heat exchanger towards the molten silicon liquid level direction, and after the movement is finished, keeping the heat exchanger at a second position; the moving process lasts for 3-5 hours; according to the moving speed, the moving process is divided into at least two sections, and the heat exchanger in each section moves at a constant speed; the speed of uniform movement in each segment is in direct proportion to the pulling speed in the corresponding time period;
or, before the temperature adjusting stage begins, the position of the heat exchanger is adjusted to a first position; moving the heat exchanger towards the molten silicon liquid level direction in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage, and after the movement is finished, enabling the heat exchanger to be at a second position; the heat exchangers move at constant speed in each stage, the moving speeds of the heat exchangers in the temperature adjusting stage and the seeding stage are first preset speeds, the moving speeds of the heat exchangers in the shouldering stage and the shoulder turning stage are second preset speeds, and the moving speed of the heat exchanger in the constant diameter stage is a third preset speed; the third preset speed is greater than or equal to the second preset speed, and the second preset speed is greater than or equal to the first preset speed;
the first position is higher than the second position with respect to the surface of the molten silicon.
Optionally, under the condition that the heat exchanger in each segment moves at a constant speed, the moving speed is 8-12mm/h under the condition that the diameter is equal until the length of the crystal is at least 100mm and the pulling speed is at least 80 mm/h.
Optionally, the step of shortening the distance between the main heater and the sub-heater in the single crystal furnace to a first preset distance includes:
in the single crystal furnace, the position of the main heater is kept still and the auxiliary heater is lifted towards the direction of the main heater, so that the distance between the main heater and the auxiliary heater is shortened to a first preset distance.
Optionally, the first preset distance is 15-25 mm; and/or the first preset value is 96-136 kw; and/or the second preset value is 96-136 kw.
Optionally, the distance of the first liquid port is 20-25 mm.
Optionally, the first position is: 75-85mm from the molten silicon liquid level, and the second position is as follows: is 45-55mm away from the liquid level of the molten silicon.
Optionally, the first preset speed is: 4-5mm/h, and the second preset speed is as follows: 5-6mm/h, and the third preset speed is as follows: 8-12 mm/h.
Optionally, the step of adjusting the position of the heat exchanger to the first position in the temperature adjusting stage, the seeding stage, the shouldering stage and the shouldering stage includes:
adjusting the position of the heat exchanger to be 85mm away from the molten silicon liquid level in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage;
after the equal diameter stage is started, the heat exchanger is moved towards the molten silicon liquid level direction, and after the movement is finished, the heat exchanger is located at a second position, and the method comprises the following steps:
after the start of the equal diameter stage, the heat exchanger was moved toward the surface of the molten silicon liquid, and after the movement was completed, the distance between the heat exchanger and the surface of the molten silicon liquid was 55 mm.
In a second aspect of the invention, the invention also provides a monocrystalline silicon piece which is prepared by adopting any one of the crystal pulling methods.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive labor.
FIG. 1 is a schematic view showing a structure of a single crystal furnace according to an embodiment of the present invention;
FIG. 2 is a schematic view showing a structure of a single crystal furnace in the prior art;
FIG. 3 is a flow chart illustrating the steps of a crystal pulling method in an embodiment of the present invention;
FIG. 4 is a flow chart illustrating steps of another crystal pulling method in an embodiment of the present invention;
FIG. 5 is a flow chart illustrating steps of yet another method of pulling in an embodiment of the present invention.
Description of the figure numbering:
101-main heater, 102-auxiliary heater, 103-crucible, 104-heat shield, 105-heat exchanger, 200-molten silicon liquid level.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
FIG. 1 shows a schematic structural diagram of a single crystal furnace in an embodiment of the present invention. FIG. 2 shows a schematic structural diagram of a single crystal furnace in the prior art. The single crystal furnace has a main heater 101 and a sub-heater 102. The main heater 101 is a main heater for supplying heat to the thermal field of the single crystal furnace, and the sub-heater 102 is an auxiliary heater for supplying heat to the thermal field of the single crystal furnace. FIG. 3 shows a flow chart of the steps of a crystal pulling method in an embodiment of the present invention. Referring to fig. 3, the crystal pulling method includes the steps of:
step S1, the distance between the main heater and the sub-heater in the single crystal furnace is shortened to a first preset distance.
The main heater 101 is located above the sub-heater 102 with respect to the molten silicon surface 200. The distance between the main heater 101 and the sub-heater 102 may be specifically: the distance between the lower end surface of the main heater 101 and the upper end surface of the sub-heater 102. In the prior art, referring to fig. 2, the distance d1 between the main heater 101 and the auxiliary heater 102 is about 210mm generally, the inventor finds that the distance between the main heater 101 and the auxiliary heater 102 affects the temperature gradient of the thermal field, especially the longitudinal temperature gradient of the thermal field, in the prior art, the distance d1 is about 210mm, so that the longitudinal temperature gradient is too large, crystal pulling is unstable, and natural convection among molten silicon washes the crucible 103 seriously, so that more oxygen impurities exist in the crystal. In this regard, the inventors tried to shorten the distance between the main heater 101 and the sub-heater 102, and in a specific embodiment, referring to fig. 1, in the embodiment of the present invention, the distance d1 between the main heater 101 and the sub-heater 102 was shortened to a first predetermined distance, which may be 15-25mm, for example, 15mm, 20mm, or 25mm, and by shortening the distance between the main heater 101 and the sub-heater 102, the longitudinal temperature gradient of the upper and lower portions of the silicon melt was properly reduced, on one hand, the natural convection between the silicon melt was reduced, so that the oxygen impurities generated by the natural convection flushing the crucible 103 were reduced, and the oxygen impurities in the ingot were reduced, and on the other hand, the low longitudinal temperature gradient increased the stability of the crystal growth interface, i.e., the crystal pulling stability.
In step S2, in the melting stage, the heating power of the primary heater is increased to a first preset value, and the heating power of the secondary heater is increased to a second preset value.
The crystal pulling process by the Czochralski method mainly comprises the following steps: charging, melting, adjusting temperature, seeding, shouldering, shoulder rotating, diameter equalizing and ending. In the melting stage, the heating power of the primary heater 101 is increased to a first preset value, the heating power of the secondary heater 102 is increased to a second preset value, and whether the heating power of the primary heater 101 is equal to the heating power of the secondary heater 102 is not limited in particular. The heating power of the main heater 101 and the heating power of the sub-heater 102 in the remaining stages are not particularly limited.
Specifically, the inventor finds that in the prior art, due to the fact that the power of the primary heater and the secondary heater is low, the material melting speed is slow, the reaction time of the crucible 103 and the silicon melting is long, oxygen impurities are more, the material melting speed is slow, the production efficiency is low, meanwhile, the longitudinal temperature gradient is too large, crystal pulling is unstable, natural convection among the silicon melting erodes the crucible 103 seriously, and the oxygen impurities in the crystal are more. In the prior art, the heating power of the primary heater 101 is set to 80-90kw (kilowatt), and the heating power of the secondary heater 102 is set to 80-90kw, but in the embodiment of the present invention, in the melting stage, the heating power of the primary heater 101 is increased to a first preset value, optionally, the first preset value is 96-136 kw; for example, 96kw, 100kw, 105kw, 110kw, 115kw, 120kw, 125kw, 130kw, 135kw, 136kw may be mentioned. The heating power of the sub-heater 102 is increased to a second preset value, which is optionally 96-136kw, and may be 96kw, 100kw, 105kw, 110kw, 115kw, 120kw, 125kw, 130kw, 135kw, and 136kw, for example. Therefore, the melting rate is accelerated, the reaction time of the crucible 103 and the molten silicon is short, oxygen impurities are less, the melting rate is high, and the production efficiency is high. Meanwhile, in the melting stage, the heating power of the main heater 101 is increased to a first preset value, the heating power of the auxiliary heater 102 is increased to a second preset value, the longitudinal temperature gradient of the upper and lower parts of the molten silicon is properly reduced, on one hand, the natural convection between the molten silicon is reduced, so that the oxygen impurities generated by flushing the crucible 103 by the natural convection are reduced, the oxygen impurities in the crystal bar are reduced, on the other hand, the stability of a crystal growth interface can be improved due to the low longitudinal temperature gradient, the crystal pulling stability is not easy to break, and the crystal pulling stability is improved.
Optionally, the first preset value is 96-136 kw; and/or the second preset value is 96-136kw, that is, the heating power of the main heater 101 and the heating power of the auxiliary heater 102 are respectively increased by 20-40% on the basis of the heating power of the existing main heater 101 and the heating power of the existing auxiliary heater 102, so that the method is easy to realize, the increasing amplitude is proper, the melting speed is high, and the longitudinal temperature gradient of the upper part and the lower part of the molten silicon is proper.
Alternatively, the position of the main heater and the sub heater may be shortened in step S1, in which the position of the main heater 101 is kept unchanged, and the sub heater 102 is lifted toward the main heater 101, so that the distance d1 between the main heater 101 and the sub heater 102 is shortened to the first preset distance. The sub-heater 102 is easier to change and is simple to operate, compared to the main heater 101.
Alternatively, in the single crystal furnace, the position of the main heater 101 is kept still, and the sub-heater 102 is raised toward the main heater 101, so that the distance d1 between the main heater 101 and the sub-heater 102 is shortened to a first preset distance. Optionally, the position of the sub-heater 102 can be raised by 185mm-195mm relative to the molten silicon level 200, which is equivalent to that the position of the sub-heater 102 is raised by 50% or more towards the main heater 101 on the basis of the position of the sub-heater 102 in the prior art, and the operation is simple.
Optionally, the step S1 may be: in the single crystal furnace, the distance between the main heater 101 and the auxiliary heater 102 is shortened to 20mm, the distance d1 between the main heater 101 and the auxiliary heater 102 is shortened to 20mm, the longitudinal temperature gradient of the upper and lower parts of the molten silicon is more suitable, on one hand, the natural convection between the molten silicon is reduced, so that the oxygen impurities generated by flushing the crucible 103 by the natural convection are reduced, the oxygen impurities in a crystal bar are reduced, on the other hand, the longitudinal temperature gradient of the upper and lower parts of the molten silicon is more suitable, the stability of a crystal growth interface can be improved, and the crystal pulling stability is further improved.
FIG. 4 shows a flow chart of steps of another crystal pulling method in an embodiment of the present invention. Referring to fig. 4, the crystal pulling method includes the steps of:
step S1, the distance between the main heater and the sub-heater in the single crystal furnace is shortened to a first preset distance.
In step S2, in the melting stage, the heating power of the primary heater is increased to a first preset value, and the heating power of the secondary heater is increased to a second preset value.
Step S1 and step S2 can refer to the related descriptions, and are not repeated herein to avoid redundancy.
And step S3, reducing the distance between the liquid ports to the first liquid port distance in the temperature adjusting stage, the seeding stage, the shouldering stage, the shoulder rotating stage and the equal diameter stage.
The distance d2 between the liquid opening and the bottom of the heat shield 104 and the surface 200 of the molten silicon. Referring to fig. 2, in the prior art, the liquid opening distance d2 is 50mm in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder turning stage, and the liquid opening distance is reduced in the equal diameter stage. The inventor finds that one reason why the oxygen impurity in the crystal bar is more is that: in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage, the liquid mouth distance is larger, the space between the heat shield 104 and the molten silicon liquid level 200 is larger, and under the condition that the inert gas with the same flux circulates in the space between the heat shield 104 and the molten silicon liquid level 200, the flow velocity is smaller, oxygen is taken away, and if silicon oxide is less, oxygen impurities in the crystal bar are more. In the embodiment of the invention, referring to fig. 1, in the temperature adjusting stage, the seeding stage, the shouldering stage, the shoulder rotating stage and the isometric stage, the distance d2 between the liquid ports is reduced to the distance of the first liquid port, in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage, the space between the heat shield 104 and the molten silicon liquid level 200 is also reduced, and under the condition that the inert gas with the same flux circulates in the space between the heat shield 104 and the molten silicon liquid level 200, the flow rate is higher, more oxygen can be taken away, and further, the oxygen impurities in the crystal bar are reduced.
Optionally, the distance of the first liquid port is 20-25mm, which is equivalent to that on the basis of the prior art, the distance between the liquid ports is halved or even reduced more in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage, the space between the heat shield 104 and the molten silicon liquid level 200 is halved or even reduced more, the flow rate of inert gas with the same flux is approximately doubled or even more under the condition that the inert gas circulates in the space between the heat shield 104 and the molten silicon liquid level 200, more oxygen can be taken away, and further oxygen impurities in the ingot are reduced.
FIG. 5 is a flow chart illustrating steps of yet another method of pulling in an embodiment of the present invention. Referring further to FIG. 5, a flow chart of steps of another crystal pulling method in an embodiment of the present invention is shown. The crystal pulling method comprises the following steps:
step S1, the distance between the main heater and the sub-heater in the single crystal furnace is shortened to a first preset distance.
In step S2, in the melting stage, the heating power of the primary heater is increased to a first preset value, and the heating power of the secondary heater is increased to a second preset value.
And step S3, reducing the distance between the liquid ports to the first liquid port distance in the temperature adjusting stage, the seeding stage, the shouldering stage, the shoulder rotating stage and the equal diameter stage.
Step S1, step S2, and step S3 may refer to the related descriptions mentioned above, and are not described herein again to avoid redundancy. And step S4, adjusting the position of the heat exchanger to be a first position in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage.
The heat exchanger plays a role in heat exchange in the single crystal furnace. Referring to fig. 1, the heat exchanger 105 is adjusted to or raised to the first position in the temperature adjusting stage, the seeding stage, the shouldering stage, and the shouldering stage, the step S3 may cause a large temperature variation of the thermal field, which may cause unstable crystal pulling, and the step S4 adjusts the heat exchanger 105 to the first position in the temperature adjusting stage, the seeding stage, the shouldering stage, and the shouldering stage, which increases the heat exchanger 105, which is equivalent to a buffer for heat, so that the temperature variation of the thermal field is relatively stable, thereby avoiding unstable crystal pulling caused by the step S3.
Referring to fig. 1, alternatively, the first position may be: the distance d3 between the heat exchanger 105 and the molten silicon liquid level 200 is 75-85mm, and the heat exchanger is positioned at the position, so that the heat buffering effect is more matched with the temperature change of the thermal field, and the temperature change of the thermal field is more stable.
Optionally, the step S4 may be: the position of the heat exchanger 105 is adjusted to be 75-85mm away from the molten silicon liquid level in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage, so that the heat buffering is more reasonable, the temperature change of a thermal field is more stable, and the crystal pulling is more stable.
Step S5, after the equal diameter stage begins, moving the heat exchanger towards the liquid level direction of the molten silicon, and after the movement is finished, the heat exchanger is at the second position; the moving process lasts for 3-5 hours; according to the moving speed, the moving process is divided into at least two sections, and the heat exchanger in each section moves at a constant speed; the speed of uniform movement in each segment is in direct proportion to the pulling speed in the corresponding time period; the first position is higher than the second position with respect to the surface of the molten silicon.
After the isometric period begins, the heat exchanger 105 is moved towards the molten silicon level 200, and after the movement is finished, the heat exchanger 105 is at the second position, namely, the heat exchanger 105 is descended, and the moving process lasts for 3-5 hours. According to the moving speed, the moving process is divided into at least two sections, the heat exchanger in each section moves at a constant speed, the speed of the constant speed movement in each section is in direct proportion to the pulling speed in a corresponding time period, the pulling speed can be quickly and stably improved, and the pulling stability is good and the wire breakage is not easy to occur. The moving process lasts for 3-5 hours, the equal diameter is not finished after the moving is finished, the crystal pulling speed can be quickly and stably improved, the crystal pulling stability is good, and the wire breakage is not easy to occur. It should be noted that the number of segments in the moving process is not particularly limited.
Referring to fig. 1, alternatively, the second position may be: the distance d3 between heat exchanger 105 and the surface 200 of the molten silicon is 45-55mm, and heat exchanger 105 is in this position to make the thermal field more uniform.
Optionally, in step S5, the speed of the uniform movement in each segment is proportional to the pulling speed in the corresponding time period, so that the pulling speed can be increased rapidly and stably, and the pulling stability is good and the wire is not easily broken.
Optionally, in step S5, when the diameter is equal to at least 100mm and the pulling rate is at least 80mm/h (mm/h), the moving speed of the heat exchanger 105 is 8-12mm/h, e.g., 9mm/h, so that the pulling rate is increased more rapidly and stably, and the pulling stability is better and the wire is less likely to break.
Alternatively, in step S5, after the constant diameter stage is started, the heat exchanger 105 is moved in the direction of the molten silicon surface, and after the movement is completed, the distance between the heat exchanger 105 and the molten silicon surface 200 is 45 to 55 mm.
Optionally, the step S4 may further include: before the temperature adjusting stage begins, the position of the heat exchanger 105 is adjusted to the first position, the step S3 may cause the temperature of the thermal field to change greatly, which may cause unstable crystal pulling, and before the temperature adjusting stage begins, the position of the heat exchanger 105 is adjusted to the first position, that is, the heat exchanger 105 is raised, which is equivalent to providing a buffer for heat, so that the temperature change of the thermal field is relatively smooth, and the unstable crystal pulling caused by the step S3 is avoided. The step S5 may be: and the heat exchanger 105 is moved towards the molten silicon liquid level direction in the temperature adjusting stage, the seeding stage, the shouldering stage, the shoulder rotating stage and the constant diameter stage, and after the movement is finished, the heat exchanger 105 is positioned at the second position, and the first position is higher than the second position relative to the molten silicon liquid level. The heat exchanger 105 moves at a uniform speed in each stage, the moving speeds of the heat exchanger 105 in the temperature adjusting stage and the seeding stage are first preset speeds, the temperature adjustment and seeding are more stable, and the disconnection is not easy to occur. The moving speeds of the heat exchanger 105 in the shouldering stage and the shouldering stage are the second preset speeds, so that the shouldering and shouldering are more stable and are not easy to break. The moving speed of the heat exchanger 105 in the equal-diameter stage is a third preset speed, so that the crystal pulling speed is increased more quickly and stably, the crystal pulling stability is better, and the wire breakage is less prone to happening. The third preset speed is larger than or equal to the second preset speed, the second preset speed is larger than or equal to the first preset speed, the speed magnitude relation is more matched with the pulling speed in the corresponding stage, and if the speed magnitude relation is in a certain proportional relation, the operation of each stage is more stable and the wire breakage is not easy to occur.
Optionally, the first preset speed is: 4-5mm/h, so that the temperature adjustment and seeding are more stable and the wire breakage is not easy to occur. The second preset speed is: 5-6mm/h, so that the shoulder-laying and shoulder-turning are more stable. The third preset speed is: 8-12mm/h, so that the crystal pulling speed is increased more quickly and stably, and the crystal pulling stability is better.
The present application is further explained below with reference to specific examples:
example 1
In the first step, when the thermal field is installed, the distance between the main heater and the auxiliary heater is shortened from 210mm to 20 mm.
In the second step, in the melting stage, the heating power of the main heater is increased from 80KW to 100KW, and the heating power of the auxiliary heater is increased from 80KW to 120 KW.
Compared with the prior art, the crystal pulling mode corresponding to the embodiment 1 (1) saves the melting time by about 8 h; the melting time is shortened, so that the crystal pulling efficiency is improved by 20 percent, and the cost is effectively reduced. (2) The head oxygen content was reduced by 0.5 ppma; the reduction of the oxygen content effectively improves the quality of the crystal. (3) The wire breakage rate is reduced by 2%. The definition of broken wire is: the phenomenon that the ridge line of the crystal disappears from the beginning of seeding to the end of seeding, and if the crystal is broken before the equal diameter, the former crystal needs to be melted again for seeding again. The calculation mode of the wire breakage rate is as follows: total number of broken wires/total number of seeding from seeding start to ending. The reduction of the wire breakage rate can effectively improve the quality of the crystal, effectively reduce the production time and reduce the production cost. The saved melting time, the oxygen content of the crystal head and the wire breakage rate are all the results of counting the crystal pulling process of the 8 furnaces.
Example 2
In the first step, the distance between the main heater and the auxiliary heater in the single crystal furnace is shortened to 20 mm.
In the second step, in the melting stage, the heating power of the main heater is increased to 100kw, and the heating power of the auxiliary heater is increased to 120 kw.
And thirdly, reducing the distance between liquid ports to 25mm in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage.
Compared with the prior art, the crystal pulling mode corresponding to the example 2 (1) saves about 8h of melting time, (2) reduces the oxygen content of the head by 1ppma, and (3) reduces the wire breakage rate by 3%. In the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder turning stage in the embodiment 1, the liquid port distance is 50mm, and the liquid port distance is reduced to 25mm in the equal diameter stage. Different from the embodiment 1, in the embodiment 2, the liquid gap is reduced in the third step in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage, the space between the heat shield and the liquid level of the molten silicon is reduced in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage, and the flow rate is larger under the condition that the inert gas with the same flux flows in the space between the heat shield and the liquid level of the molten silicon, so that more oxygen can be taken away, and further, the oxygen impurities in the crystal bar are reduced. Thus, the oxygen content in the crystal head is lower in example 2 than in example 1. Here, the wire breakage rate was also defined as in example 1, as a result of counting the pulling process of 8 furnaces.
Example 3
In the first step, the distance between the main heater and the auxiliary heater in the single crystal furnace is shortened to 20 mm.
In the second step, in the melting stage, the heating power of the main heater is increased to 100kw, and the heating power of the auxiliary heater is increased to 120 kw.
And thirdly, reducing the distance between liquid ports to 25mm in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage.
And fourthly, adjusting the position of the heat exchanger to be 80mm away from the molten silicon liquid level in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage.
Fifthly, after the equal-diameter stage begins, moving the heat exchanger towards the molten silicon liquid level direction, and after the movement is finished, keeping the distance between the heat exchanger and the molten silicon liquid level to be 50 mm; the moving process lasts for 3 hours, after the equal-diameter stage begins, the pull speed in the first hour is 80mm/h, the drop speed of the heat exchanger in the first hour is 8.88mm/h, the pull speed in the second hour is 90mm/h, the drop speed of the heat exchanger in the second hour is 10mm/h, the pull speed in the third hour is 100mm/h, and the drop speed of the heat exchanger in the third hour is 11.12 mm/h.
Compared with the prior art, the crystal pulling mode corresponding to the example 3 (1) saves about 8h of melting time, (2) reduces the oxygen content of the head by 1ppma, and (3) reduces the wire breakage rate by 5 percent. The third step of example 2 or example 3 may result in large temperature variations in the thermal field, causing crystal pulling instability. Different from the embodiment 2, in the embodiment 3, in the fourth step, in the temperature adjusting stage, the seeding stage, the shouldering stage and the shouldering stage, the position of the heat exchanger is raised, and the raising of the heat exchanger is equivalent to providing a buffer for heat, so that the temperature change of the thermal field is relatively stable, and the instability of crystal pulling possibly caused by the third step is avoided. Meanwhile, in the fifth step, in the process of reducing the heat exchanger, each subsection moves at a constant speed, and the moving speed in each subsection is in direct proportion to the pulling speed in the corresponding time interval, so that the pulling speed can be stably improved, the pulling stability is good, and the wire breakage is not easy to occur. Therefore, the disconnection rate is lower in example 3 than in example 2. Here, the wire breakage rate was also defined as in example 1, as a result of counting the pulling process of 8 furnaces.
It should be noted that, for simplicity of description, the method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the embodiments are not limited by the order of acts described, as some steps may occur in other orders or concurrently depending on the embodiments. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred and that no particular act is required to implement the embodiments of the application.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal (such as a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present invention.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A crystal pulling method, comprising:
shortening the distance between the main heater and the auxiliary heater in the single crystal furnace to a first preset distance;
in the melting stage, the heating power of the main heater is increased to a first preset value; the heating power of the sub-heater is increased to a second preset value.
2. A crystal pulling method as set forth in claim 1 further comprising:
and reducing the distance between the liquid ports to the first liquid port distance in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage.
3. A crystal pulling method as set forth in claim 2 further comprising:
adjusting the position of the heat exchanger to a first position in the temperature adjusting stage, the seeding stage, the shouldering stage and the shoulder rotating stage; after the equal-diameter stage begins, moving the heat exchanger towards the molten silicon liquid level direction, and after the movement is finished, keeping the heat exchanger at a second position; the moving process lasts for 3-5 hours; according to the moving speed, the moving process is divided into at least two sections, and the heat exchanger in each section moves at a constant speed; the speed of uniform movement in each segment is in direct proportion to the pulling speed in the corresponding time period;
or, before the temperature adjusting stage begins, the position of the heat exchanger is adjusted to a first position; moving the heat exchanger towards the molten silicon liquid level direction in a temperature adjusting stage, a seeding stage, a shouldering stage, a shoulder rotating stage and an equal diameter stage, and after the movement is finished, enabling the heat exchanger to be at a second position; the heat exchangers move at constant speed in each stage, the moving speeds of the heat exchangers in the temperature adjusting stage and the seeding stage are first preset speeds, the moving speeds of the heat exchangers in the shouldering stage and the shoulder turning stage are second preset speeds, and the moving speed of the heat exchanger in the constant diameter stage is a third preset speed; the third preset speed is greater than or equal to the second preset speed, and the second preset speed is greater than or equal to the first preset speed;
the first position is higher than the second position with respect to the surface of the molten silicon.
4. A crystal pulling process as claimed in claim 3 wherein the rate of movement is 8 to 12mm/h with constant movement of the heat exchangers within each segment to a diameter of at least 100mm crystal length and at a pull rate of at least 80 mm/h.
5. A crystal pulling method as set forth in any one of claims 1 to 4 wherein the step of shortening the interval between the main heater and the sub-heater in the single crystal furnace to a first predetermined distance comprises:
in the single crystal furnace, the position of the main heater is kept still and the auxiliary heater is lifted towards the direction of the main heater, so that the distance between the main heater and the auxiliary heater is shortened to a first preset distance.
6. A crystal pulling method as set forth in any one of claims 1 to 4 wherein the melt is cooled,
the first preset distance is 15-25 mm; and/or the first preset value is 96-136 kw; and/or the second preset value is 96-136 kw.
7. A crystal pulling method as set forth in claim 2 wherein the first port distance is from 20 to 25 mm.
8. A crystal pulling method as set forth in claim 3 wherein the first position is: 75-85mm from the molten silicon liquid level, and the second position is as follows: is 45-55mm away from the liquid level of the molten silicon.
9. A crystal pulling method as set forth in claim 3 wherein the first predetermined rate is: 4-5mm/h, and the second preset speed is as follows: 5-6mm/h, and the third preset speed is as follows: 8-12 mm/h.
10. A monocrystalline silicon wafer produced by the crystal pulling method as claimed in any one of claims 1 to 9.
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