CN116657242B - Preparation method of seed crystal for growing monocrystalline silicon by Czochralski method, seed crystal and growth method - Google Patents
Preparation method of seed crystal for growing monocrystalline silicon by Czochralski method, seed crystal and growth method Download PDFInfo
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- CN116657242B CN116657242B CN202310962205.7A CN202310962205A CN116657242B CN 116657242 B CN116657242 B CN 116657242B CN 202310962205 A CN202310962205 A CN 202310962205A CN 116657242 B CN116657242 B CN 116657242B
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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
- C30B15/36—Single-crystal growth by pulling from a melt, e.g. Czochralski method characterised by the seed, e.g. its crystallographic orientation
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
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Abstract
The invention belongs to the technical field of monocrystalline silicon production, and particularly relates to a preparation method of a seed crystal for growing monocrystalline silicon by a Czochralski method, the seed crystal and a growth method. The preparation method of the seed crystal comprises the steps of carrying out line drawing on a seed crystal mother rod to obtain a seed crystal mother rod for line drawing, wherein the seed crystal mother rod is a single crystal rod with an equal-diameter broken line, dislocation is arranged at the equal-diameter broken line end of the seed crystal mother rod, the line drawing is carried out at the boundary position of the dislocation, the seed crystal mother rod for line drawing is subjected to cutting-off treatment and grinding treatment, and the seed crystal for growing monocrystalline silicon by a Czochralski method is obtained, and the grinding treatment comprises the following steps: drawing a grinding mark at the position of the drawn line; one end of the seed crystal is provided with a dislocation part, the dislocation part is provided with the dislocation, and the length of the dislocation part accounts for 5% -10% based on the length of the seed crystal. The seed crystal prepared by the preparation method can increase the yield of single crystal silicon during growth, and meanwhile, the material cost can be saved because the single crystal rod with the equal diameter broken line is used as a seed crystal mother rod.
Description
Technical Field
The invention relates to the technical field of monocrystalline silicon production, in particular to a preparation method of a seed crystal for growing monocrystalline silicon by a Czochralski method, the seed crystal and a growth method.
Background
Monocrystalline silicon is an important material for preparing solar cells in the photovoltaic industry, and is usually prepared by adopting a Czochralski method, specifically, a massive silicon material is placed in a crucible, the silicon material is heated to a melting point to be melted, the temperature of a silicon solution is adjusted to be suitable for fusion, a seed crystal is slowly lowered from a monocrystalline furnace under the protection of inert gas, the seed crystal is inserted into the molten silicon solution through a preheating step, and the seed crystal is used as a seeding and drawing material to prepare a monocrystalline silicon rod.
The production process of the seed crystal generally adopts a solar-grade monocrystalline silicon rod as a seed crystal mother rod, the mother rod is put into a seed crystal drawing mill, the drawing mill processes the seed crystal meeting the technical requirement specification according to the set technological parameters, and the seed crystal with higher surface cleanliness is obtained by cleaning with a cleaning agent after the drawing mill is completed.
In the process of preparing monocrystalline silicon by the Czochralski method, the seed crystal is subjected to larger thermal shock due to higher temperature of the molten silicon in the process of inserting the seed crystal into the molten silicon. However, the seed crystal mother rod inevitably has some tiny defects, and the defects are introduced on the surface of the seed crystal when the seed crystal is extruded and sheared by mechanical stress in the process of drawing and grinding, when the seed crystal is subjected to thermal shock of a molten liquid level, the defects are easy to grow in a proliferation mode to cause surface defect body defects, and when single crystals are grown, the crystal orientation is easy to deflect, accidents such as shouldering and wire breakage of the equal diameter head (wire breakage with equal diameter length less than or equal to 500 mm) are caused, or the seed crystal is directly grown into polycrystal, and the yield of single crystal silicon is seriously influenced. If the thermal shock force is reduced by reducing the temperature of the silicon liquid, the silicon liquid may be crystallized due to the excessively low temperature, and the crystallized solid silicon may break the crucible to cause production or safety accidents.
Disclosure of Invention
The invention aims to overcome the defects that accidents such as shouldering broken line and broken line of the equal diameter head are caused by the increment growth of defects after the seed crystal receives thermal shock or the defects that the yield of the single crystal silicon is influenced due to the fact that the seed crystal grows into polycrystal when the single crystal silicon is prepared by the Czochralski method.
In order to achieve the above object, in a first aspect, the present invention provides a method for producing a seed crystal for growing single crystal silicon by the Czochralski method, the method comprising:
drawing lines on a seed crystal mother rod to obtain a seed crystal mother rod for drawing lines, wherein the seed crystal mother rod is a single crystal rod with equal-diameter broken lines, dislocation is arranged at the equal-diameter broken line end of the seed crystal mother rod, and the line drawing treatment is carried out at the boundary position of the dislocation;
cutting off the line-drawn seed crystal mother rod and carrying out sharpening treatment to obtain a seed crystal for growing monocrystalline silicon by a Czochralski method, wherein the sharpening treatment comprises: drawing a grinding mark at the position of the drawn line;
the single crystal rod with the equal-diameter broken line is a single crystal rod with the equal-diameter broken line subjected to end cutting treatment; or the cutting-off treatment comprises the step of cutting off the end of the isodiametric broken line of the drawn seed crystal mother rod;
one end of the seed crystal is provided with a dislocation part, the dislocation part is provided with the dislocation, and the length of the dislocation part accounts for 5% -10% based on the length of the seed crystal.
In some preferred embodiments, the dislocation portion has a length ranging from 10mm to 20mm.
In some preferred embodiments, the conditions for milling the marking include: the feed speed is 2700 r/min-3300 r/min, the feed multiplying power is 80% -100%, and the spindle rotating speed is 290 r/min-320 r/min.
In a second aspect, the present invention provides a seed crystal for growing single crystal silicon by the Czochralski method prepared by the preparation method of the first aspect, wherein one end of the seed crystal has a dislocation part, and the boundary position of the dislocation part has a mark.
In a third aspect, the present invention provides a method for growing single crystal silicon using the seed crystal of the second aspect, the method comprising: loading a polycrystalline silicon raw material into a crucible, placing the crucible into a main chamber of a single crystal growth furnace, installing a seed crystal into a secondary chamber of the single crystal growth furnace according to a dislocation part, heating and melting the polycrystalline silicon raw material to obtain molten silicon liquid, and descending the seed crystal from the secondary chamber to the main chamber, wherein the descending is that a mark is positioned below the liquid level of the molten silicon liquid;
and pulling the seed crystal upwards to crystallize the molten silicon liquid below the seed crystal, so as to obtain the monocrystalline silicon.
In some preferred embodiments, the lowering is such that the position of the mark is 3mm to 5mm below the position of the liquid surface of the molten silicon.
In some preferred embodiments, the method comprises: when the vertical distance between the bottom of the seed crystal and the crucible is 2500 mm-3500 mm, the descending speed is adjusted to 4500 mm/h-5500 mm/h, when the vertical distance between the bottom of the seed crystal and the crucible is 800 mm-1200 mm/h, the descending speed is adjusted to 2000 mm/h-3000 mm/h, when the bottom of the seed crystal descends to the upper end of the crucible, the descending speed is adjusted to 800 mm/h-1200 mm/h, when the vertical distance between the bottom of the seed crystal and the liquid level is 80 mm-120 mm, the descending speed is adjusted to 80 mm/h-120 mm/h, the crystal transition is adjusted to 2 r/min-4 r/min, when the bottom of the seed crystal contacts the liquid level, the descending speed is adjusted to 50 mm/h-70 mm/h, the crystal transition is adjusted to 5 r/min-9 r/min, and the argon flow is adjusted to 50 slpm-70 pm;
when the bottom of the seed crystal descends to the upper end of the crucible, the power of a heater in the single crystal growth furnace is adjusted, so that the temperature of the liquid level is kept at 1450-1470 ℃, and the adjusting speed of the power is below 0.4 kw/min.
Preferably, the conditions of the upward pulling seeding process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, the crystal pulling speed is 240 mm/h-350 mm/h, and the seeding length is 180mm-250mm.
More preferably, the conditions of the upward pulling shouldering process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-150 mm/h.
More preferably, the conditions of the upward pulling constant diameter growth process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-105 mm/h.
In the process of growing monocrystalline silicon by the Czochralski method, constant diameter wire breakage is easy to occur. In the prior art, dislocation of the single crystal silicon rod with the equal-diameter broken line needs to be completely cut, the silicon rod after cutting is degraded into a circulating material, and the single crystal rod with the equal-diameter broken line is used as a seed crystal mother rod for preparing seed crystals. The seed crystal is prepared by adopting the preparation method, and the single crystal rod with the equal diameter broken line is used as a seed crystal mother rod, so that on one hand, the material cost can be saved, and on the other hand, the yield of the single crystal silicon during growth can be increased.
The preparation method of the seed crystal comprises the steps that a single crystal bar with an equal-diameter broken line is provided with dislocation at an equal-diameter broken line end, line drawing is carried out on the boundary position of the dislocation, after line drawing, a seed crystal mother bar with the line drawn is obtained, cut-off treatment and grinding treatment are carried out, and then the seed crystal is obtained, wherein a mark is ground in the line drawing position in the grinding treatment process, a part of dislocation at the equal-diameter broken line end is reserved in the cut-off treatment and grinding treatment process, the dislocation part is formed at one end of the seed crystal, and the dislocation part accounts for 5% -10% based on the length of the seed crystal. When the seed crystal prepared by the preparation method grows monocrystalline silicon, after the seed crystal is contacted with the silicon liquid, the seed crystal is continuously lowered to a position above the mark position of the dislocation part, new defects caused by thermal shock are captured by the crystal boundary of the dislocation part due to the dislocation part, the growth of the new defects to the dislocation-free seed crystal position can be blocked, the growth of the new defects is blocked at the mark position of the seed crystal, the defect level of monocrystalline silicon at the welding position can be obviously reduced, the crystal cell arrangement of the silicon crystal is relatively orderly, the defect growth in the processes of seeding, shouldering and isodiametric after welding is obviously reduced, the seeding survival rate is effectively improved, the accidents such as shouldering and wire breakage of the isodiametric head are reduced, and the polycrystalline growth is restrained, so that the yield of monocrystalline silicon can be increased.
Specifically, after the cutting-off treatment and the grinding-out treatment, the ratio of the dislocation part is below 10% based on the length of the seed crystal, so that the new defect is more favorably absorbed and blocked through a dislocation grain boundary, when the seed crystal is inserted into molten silicon, the new defect caused by thermal shock is captured by the dislocation grain boundary, the defect is prevented from being greatly increased after being subjected to thermal shock, the crystallization is poor, the yield of monocrystalline silicon is improved, the ratio of the dislocation part is above 5%, the new defect is more favorably fully captured, the growth of the defect to the dislocation-free seed crystal position is blocked, and the accidents such as the shoulder-off line and the equal-diameter head line breakage of the seeding are reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram showing a whole flow of a method for preparing a seed crystal for growing single crystal silicon by a Czochralski method according to an embodiment of the present invention.
Description of the reference numerals
1-a seed crystal mother rod with an equal diameter broken line; 2-an equal-diameter broken wire end; 3-dislocation; 4-drawing a seed crystal mother rod; 5-cutting a seed crystal mother rod; 6-a first dislocation part; 7-the end of the seed; 8-a body portion of the seed crystal; 9-labelling; 10-second bit error.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The inventor of the invention researches and discovers that when the Czochralski method is used for producing monocrystalline silicon, the seed crystal is subjected to thermal shock of molten silicon liquid, the internal defects of the seed crystal and the mechanical defects generated in the processing process are increased in value, the wire breakage is easy in the processes of seeding, shouldering and isodiametric cutting, the production efficiency of the monocrystalline silicon is affected, and in addition, the isodiametric broken monocrystalline rod can only be used as a circulating material, and the material cost is increased.
In this regard, in a first aspect, the present invention provides a method for producing a seed crystal for growing single crystal silicon by the Czochralski method, the method comprising:
drawing lines on the seed crystal mother rod to obtain the seed crystal mother rod with the line drawn, wherein the seed crystal mother rod is a single crystal rod with the line broken in equal diameter, the line broken end of the seed crystal mother rod is provided with dislocation, the line drawing treatment is carried out at the boundary position of the dislocation,
cutting off the line-drawn seed crystal mother rod and carrying out sharpening treatment to obtain a seed crystal for growing monocrystalline silicon by a Czochralski method, wherein the sharpening treatment comprises: drawing a grinding mark at the position of the drawn line;
the single crystal rod with the equal-diameter broken line is a single crystal rod with the equal-diameter broken line subjected to end cutting treatment; or the cutting-off treatment comprises the step of cutting off the end of the isodiametric broken line of the drawn seed crystal mother rod;
one end of the seed crystal is provided with a dislocation part, the dislocation part is provided with the dislocation, and the length of the dislocation part accounts for 5% -10% based on the length of the seed crystal.
For the single crystal silicon rod with the broken line in the equal diameter, the common method for recycling is to cut off the dislocation cleanly, the silicon rod with the dislocation cut off is degraded into a circulating material, the single crystal rod with the broken line in the equal diameter is used as a seed crystal mother rod to prepare seed crystal for growing single crystal silicon, so that the material cost can be reduced, in addition, the dislocation at the broken line end in the equal diameter of the single crystal rod with the broken line in the equal diameter can be utilized, the occurrence of the accidents of crystal pulling, shouldering and broken line at the head of the equal diameter in the single crystal silicon growing process can be reduced, and the yield of the single crystal silicon can be increased.
The specific process of preparing seed crystal with the single crystal rod with equal diameter broken line includes drawing line in the dislocation boundary of the equal diameter broken line end of the single crystal rod with equal diameter broken line to distinguish dislocation and non-dislocation area, cutting and grinding the mother crystal rod with drawn line according to the seed crystal specification required for growing single crystal silicon, maintaining dislocation of partial equal diameter broken line end, forming dislocation part in one end of the seed crystal, and grinding mark in the drawing line position. According to the preparation method, one end of the prepared seed crystal is provided with the dislocation part, the boundary position of the dislocation part is provided with the mark, when the seed crystal is used for growing single crystals, the seed crystal is lowered to the position, above the position marked by the dislocation part, of the liquid level of molten silicon liquid, new defects caused by thermal shock are captured by the crystal boundary of the dislocation part due to the dislocation part, the growth of the new defects to the dislocation-free seed crystal position can be blocked, the growth of the new defects is blocked at the position marked by the seed crystal, the defect level of single crystal silicon at the welding position can be obviously reduced, the arrangement of crystal cells of the silicon is relatively orderly, the defect growth in the processes of seeding, shouldering and isodiametric is obviously reduced, the seeding survival rate is effectively improved, the accidents such as seeding shouldering and wire breakage and the isodiametric head wire breakage are reduced, and the polycrystalline growth is restrained, and the yield of single crystal silicon can be increased.
The length of the dislocation part is 5% -10% and the ratio of the dislocation part is below 10% based on the length of the seed crystal through the cutting-off treatment and the grinding treatment, new defects caused by thermal shock can be absorbed and blocked through dislocation crystal boundaries when the seed crystal is inserted into molten silicon, the new defects caused by thermal shock are captured by the dislocation crystal boundaries, the defects are prevented from being greatly increased after thermal shock, the crystallization is poor, the yield of monocrystalline silicon is improved, the ratio of the dislocation part is above 5%, the new defects can be fully captured, the growth of the defects to dislocation-free seed crystal positions is blocked, and accidents such as shoulder-drop wire breakage, equal-diameter head wire breakage and the like are reduced. The dislocation portion may have a specific ratio of, for example, 5%, 6%, 7%, 8%, 9% and 10%.
It will be appreciated that the seed crystal obtained after the chopping and milling processes has an end portion and a body portion, the body portion having a diameter smaller than the diameter of the end portion, the dislocation being located at an end of the body portion facing away from the end portion.
It will be appreciated that the boundary position of the dislocation at the end of the isodiametric broken line of the single crystal rod of the isodiametric broken line is first determined by visual inspection or the like before the line drawing process is performed. The choice of the way of scribing is wide, as long as dislocation and non-dislocation regions can be distinguished. The cutting-off mode has a wide optional range, so long as the seed crystal mother rod can be cut off smoothly, and specifically, for example, diamond wire cutting-off and tungsten wire cutting-off can be performed.
The single crystal rod with the equal-diameter broken line is a single crystal rod with the equal-diameter broken line subjected to end cutting treatment after the equal-diameter broken line is broken; or the cutting-off treatment comprises the step of cutting off the end of the isodiametric broken line of the drawn seed crystal mother rod. After the equal-diameter broken line, the equal-diameter broken line is not generally flush enough, the end cutting treatment is performed on the finger, and the equal-diameter broken line is cut flush for shaping.
The selectable range of conditions for milling the marks is wide, and in some preferred embodiments, the feed speed is 2700 r/min-3300 r/min, the feed rate is 80% -100%, and the spindle rotation speed is 290 r/min-320 r/min. Under the preferred scheme, the rotating speed of the main shaft is 290-320 r/min, the main shaft drives the tool bit to rotate at a high speed, so that the defects such as broken slag falling and the like in the process of taking out and grinding are prevented, the mechanical stress of dislocation areas is reduced, and the seed crystal is the basis of crystal growth, so that the thermal impact force of heat radiation in a furnace on the seed crystal is reduced, the mechanical stress received during the seed crystal machining is reduced as much as possible, the stress can squeeze crystal lattices, the arrangement of unit cells is uneven, the crystal growth is easy to generate defects, and even single crystal is changed into polycrystal. More preferably, the conditions of milling the mark further comprise that the mechanical coordinates are x-axis-500, y-axis-300 and z-axis-700, and the absolute coordinates are x-axis-80, y-axis-50 and z-axis-20. More preferably, the absolute coordinates of the marking position are X-axis-80, Y-axis-60 and Z-axis-15, and the current marking position is more easily distinguished by grinding the current position by 5mm through the Y-axis and the Z-axis.
The invention does not limit the specific form and size of the mark, and the ground boundary line can be melted into silicon liquid during welding, so that the subsequent seeding process is not influenced.
The length of the dislocation part of the seed crystal after the cutting-off treatment and the grinding treatment can be selected in a wider range, and in some preferred embodiments, the length of the dislocation part is 10 mm-20 mm. The length of the dislocation part is not less than 10mm, the absorption of dislocation crystal boundary is more favorable for blocking new defects when the monocrystalline silicon grows on the seed crystal, the new defects caused by thermal shock are captured by the dislocation crystal boundary when the seed crystal is inserted into molten silicon, the length of the dislocation part is not more than 20mm, and the prevention of dislocation and great increment of defects after the thermal shock is received is more favorable when the monocrystalline silicon grows on the seed crystal, so that the crystallization is poor. The dislocation portion may have a length of, for example, 10mm, 12mm, 14mm, 16mm, 18mm, and 20mm.
In some preferred embodiments, the polishing process further comprises a cleaning process, wherein the cleaning process is cleaning by a cleaning agent, the outer surface of the seed crystal is polished on the premise of avoiding excessive corrosion and occurrence of pits, non-silicon matters and dirt are removed, and the crystallinity of the surface of the seed crystal is improved.
In a second aspect, the present invention provides a seed crystal for growing single crystal silicon by the Czochralski method, the seed crystal being prepared by the preparation method of the first aspect, one end of the seed crystal having a dislocation portion, and a boundary position of the dislocation portion having a mark.
When the seed crystal Czochralski method is adopted to grow monocrystalline silicon, when the seed crystal is descended, the dislocation part completely enters molten silicon liquid according to the marks of the boundary positions of the dislocation part, new defects caused by thermal shock brought by the molten silicon liquid can be captured by the crystal boundary of the dislocation part, the growth of the defects to the dislocation-free position can be blocked, the growth of the defects is blocked at the position marked by the seed crystal, the defect magnitude of monocrystalline silicon at the welding position can be obviously reduced, the defect growth in the processes of seeding, shouldering, isodiametric, and the like after welding is obviously reduced, the seeding survival rate is improved, the accidents of seeding, shouldering, line breakage, isodiametric head line breakage and the like are reduced, the polycrystalline growth is restrained, and the yield of monocrystalline silicon is increased.
In a third aspect, the present invention provides a method for growing single crystal silicon using the seed crystal of the second aspect, the method comprising: loading a polycrystalline silicon raw material into a crucible, placing the crucible into a main chamber of a single crystal growth furnace, installing a seed crystal into a secondary chamber of the single crystal growth furnace according to a dislocation part, heating and melting the polycrystalline silicon raw material to obtain molten silicon liquid, and descending the seed crystal from the secondary chamber to the main chamber, wherein the descending is that a mark is positioned below the liquid level of the molten silicon liquid;
and pulling the seed crystal upwards to crystallize the molten silicon liquid below the seed crystal, so as to obtain the monocrystalline silicon.
In the process of descending the seed crystal, the mark of the boundary position of the dislocation part is positioned below the liquid level of the molten silicon, new defects caused by the high-temperature molten silicon on the seed crystal can be captured by the crystal boundary of the dislocation part, the growth of the defects to the dislocation-free position can be prevented, the defect level of monocrystalline silicon at the welding position can be reduced, the defect increment in the processes of crystal seeding, shouldering and isodiametric is reduced, the seeding survival rate is improved, the accidents of crystal seeding shouldering and line breakage, isodiametric head line breakage and the like are reduced, the polycrystalline growth is inhibited, and the yield of monocrystalline silicon is increased.
In some preferred embodiments, the descending is that the position of the mark is 3 mm-5 mm lower than the position of the liquid level of the molten silicon liquid, and in the preferred embodiment, the seed crystal at the welding position is more beneficial to ensuring no dislocation, reducing defect increment in the processes of seeding, shouldering and isodiametric after welding, improving the seeding survival rate, and reducing accidents such as seeding shouldering and isodiametric head wire breakage. The position of the mark below the level of the molten silicon liquid may be, for example, 3mm, 3.5mm, 4mm, 4.5mm, and 5mm.
In some preferred embodiments, the method comprises: when the vertical distance between the bottom of the seed crystal and the crucible is 2500 mm-3500 mm, the descending speed is adjusted to 4500 mm/h-5500 mm/h, when the vertical distance between the bottom of the seed crystal and the crucible is 800 mm-1200 mm/h, the descending speed is adjusted to 2000 mm/h-3000 mm/h, when the bottom of the seed crystal descends to the upper end of the crucible, the descending speed is adjusted to 800 mm/h-1200 mm/h, when the vertical distance between the bottom of the seed crystal and the liquid level is 80 mm-120 mm, the descending speed is adjusted to 80 mm/h-120 mm/h, the crystal transition is adjusted to 2 r/min-4 r/min, when the bottom of the seed crystal contacts the liquid level, the descending speed is adjusted to 50 mm/h-70 mm/h, the crystal transition is adjusted to 5 r/min-9 r/min, and the argon flow is adjusted to 50 slpm-70 pm;
when the bottom of the seed crystal descends to the upper end of the crucible, the power of a heater in the single crystal growth furnace is adjusted, so that the temperature of the liquid level is kept at 1450-1470 ℃, and the adjusting speed of the power is below 0.4 kw/min.
The inventor of the invention researches and discovers that the defect increment growth can be further blocked by adjusting the seed crystal descending process, and the accidents such as seeding, shouldering and wire breakage, equal-diameter head wire breakage and the like are reduced.
Specifically, the rate of descent of the seed crystal is controlled during the descent of the seed crystal from the sub-chamber to the point where the seed crystal contacts the molten silicon level. When the vertical distance between the bottom of the seed crystal and the crucible is 2500 mm-480 mm, when the vertical distance between the bottom of the seed crystal and the crucible is 800 mm-1200 mm, when the bottom of the seed crystal is flush with the upper end of the crucible, when the vertical distance between the bottom of the seed crystal and the molten silicon liquid level is 80 mm-120 mm, the descending rate of the seed crystal is gradually reduced when the bottom of the seed crystal contacts the molten silicon liquid level, the heat impact of high Wen Yemian on the seed crystal is reduced, the increment of defect increment is reduced, and the seeding breakage rate, the shouldering breakage rate and the equal-diameter head breakage rate are reduced.
Specifically, when the bottom of the seed crystal descends to the upper end of the crucible, namely when the bottom of the seed crystal is level with the upper end of the crucible, the power of a heater in the single crystal growth furnace is adjusted, so that the temperature of the liquid level is kept at 1450-1470 ℃, the thermal shock of high Wen Yemian on the seed crystal is reduced, and the increment of defects is reduced; the adjustment speed of the power is below 0.4kw/min, which is more beneficial to reducing the stress of the thermal shock of the molten silicon liquid on the seed crystal, thereby reducing the increment of dislocation; when the vertical distance between the bottom of the seed crystal and the liquid level is 80-120 mm, the crystal rotation is adjusted to 2-4 r/min, so that the thermal shock of the height Wen Yemian to the seed crystal is reduced, and the increment growth of defects is reduced; when the bottom of the seed crystal is contacted with the liquid level, the crystal transformation is adjusted to 5 r/min-9 r/min, the argon flow is adjusted to 50 slpm-70 slpm, the thermal shock of the high Wen Yemian to the seed crystal is reduced, and the defect increment growth is reduced.
The inventor of the invention researches and discovers that the defect increment growth can be further blocked by adjusting the crystal pulling process, and accidents such as crystal pulling, shouldering and wire breakage, equal-diameter head wire breakage and the like are reduced.
More preferably, the conditions of the upward pulling seeding process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, the crystal pulling speed is 240 mm/h-350 mm/h, and the seeding length is 180mm-250mm. Under the preferred scheme, in the seeding process, the crystal pulling speed and the seeding length are matched through the cooperation of the crystal rotation and the crucible rotation, so that the thermal impact force of the seed crystal is reduced, the great increment of dislocation caused by the thermal impact force is avoided, and the seeding survival rate is improved.
More preferably, the conditions of the upward pulling shouldering process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-150 mm/h. Under the preferred scheme, in the shouldering process, the crystal pulling speed is matched through the cooperation of crystal rotation and crucible rotation, so that the thermal impact force of the crystal is reduced, the dislocation increment caused by the thermal impact force is avoided, and the seeding survival rate is improved.
More preferably, the conditions of the upward pulling constant diameter growth process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-105 mm/h. Under the preferred scheme, in the equal-diameter growth process, the crystal pulling speed is matched through the cooperation of crystal rotation and crucible rotation, so that the thermal impact force of the crystal is reduced, the dislocation increment caused by the thermal impact force is avoided, and the seeding survival rate is improved.
The invention will be further described in detail with reference to specific examples.
Example 1
A method for preparing seed crystal for growing monocrystalline silicon by Czochralski method, referring to fig. 1, comprising the following steps:
step one: preparing a seed crystal mother rod 1 with an equal-diameter broken line, wherein an equal-diameter broken line end 2 of the seed crystal mother rod is provided with dislocation 3, and carrying out line drawing treatment on boundary positions of a dislocation region and a non-dislocation region so as to distinguish the dislocation region and the non-dislocation region;
step two: cutting off the line-drawn seed mother rod 4 obtained in the step one to obtain a cut-off seed mother rod 5, wherein the cutting off process is that the length of a first dislocation part 6 formed by dislocation areas is 8.5 percent based on the length of the cut-off seed mother rod 5, and the length of the first dislocation part 6 is 15mm;
step three: according to the seed crystal specification required by the growth of monocrystalline silicon, the truncated seed crystal mother rod 5 is subjected to drawing and grinding treatment, one end far away from the first dislocation part 6 is drawn and ground into an end part 7 of the seed crystal, one end where the first dislocation part 6 is located is drawn and ground into a body part 8 of the seed crystal, a mark 9 is drawn and ground at the line drawing position, when the mark 9 is drawn and ground, the mechanical coordinates of x-axis to 500, y-axis to 300 and z-axis to 700 are adjusted, the absolute coordinates of x-axis to 80, y-axis to 50 and z-axis to 20 are adjusted, the feeding speed is 3000r/min, the feeding multiplying power is 100%, and the main shaft rotating speed is 300r/min.
A seed crystal for growing single crystal silicon by Czochralski method, wherein one end of a body part 8 of the seed crystal is provided with a second dislocation part 10, the length of the second dislocation part 10 is 8.5% based on the length of the seed crystal, the length of the second dislocation part 10 is 15mm, and the boundary position of the second dislocation part 10 is provided with a mark 9.
A method for growing monocrystalline silicon from seed crystals, comprising the steps of:
step one: filling a polycrystalline silicon raw material into a crucible, placing the crucible into a main chamber of a single crystal growth furnace, installing a seed crystal into a secondary chamber of the single crystal growth furnace according to the second dislocation part 10 of the seed crystal, and heating and melting the polycrystalline silicon raw material to obtain molten silicon liquid;
step two: descending seed crystal from a main chamber of a growth furnace to a sub-chamber of the growth furnace until a mark is positioned below the liquid level of the molten silicon liquid, wherein the position of the mark is 4mm lower than the position of the liquid level of the molten silicon liquid, in the descending process, when the vertical distance between the bottom of the seed crystal and a crucible is 3000mm, the descending speed is adjusted to be 5000mm/h, when the vertical distance between the bottom of the seed crystal and the crucible is 1000mm, the descending speed is adjusted to be 1000mm/h, when the bottom of the seed crystal is flush with the upper end of the crucible, the power of a heater in the single crystal growth furnace is adjusted at a speed of 0.4kw/min, the temperature of the liquid level of the molten silicon is kept at 1450-1470 ℃, when the vertical distance between the bottom of the seed crystal and the liquid level of the molten silicon is 100mm, the descending speed is adjusted to be 100mm/h, the descending speed is adjusted to be 3r/min, when the bottom of the seed crystal contacts the liquid level of the molten silicon is adjusted to be 60mm/h, the crystal conversion is adjusted to be 7r/min, and the argon flow is adjusted to be 60 pm;
step three: and (3) pulling the seed crystal upwards to enable the molten silicon to crystallize below the seed crystal to obtain a single crystal silicon rod, wherein in the crystal pulling process of the upward pulling, the crystal is kept to be 7r/min, the crucible is changed to be 6.5r/min, the crystal pulling speed is 300mm/h, the crystal pulling length is 210mm, in the shoulder placing process of the upward pulling, the crystal is kept to be 8r/min, the crucible is changed to be 6r/min, the crystal pulling speed is 120mm/h, in the equal-diameter growth process of the upward pulling, the crystal is kept to be 8r/min, the crucible is changed to be 7r/min, and the crystal pulling speed is 90mm/h.
The method for growing monocrystalline silicon in the embodiment has the advantages that the seeding breakage rate is 10%, the shouldering breakage rate is 12%, the constant diameter head breakage rate is 8%, and the measuring methods of the seeding breakage rate, the shouldering breakage rate and the constant diameter head breakage rate are calculated according to the running data statistics of the monocrystalline furnace, so that polycrystal is basically not formed.
Example 2
The process was carried out in accordance with example 1, except that in the second step, the length of the first dislocation part 6 was 25mm and the length of the second dislocation part 10 was 25mm. The method for growing monocrystalline silicon in the embodiment has the advantages that the seeding breakage rate is 15%, the shoulder breakage rate is 18%, the constant diameter head breakage rate is 20%, and fewer polycrystal is formed.
Example 3
The process was carried out in accordance with example 1, except that in the second step, the length of the first dislocation part 6 was 8mm and the length of the second dislocation part 10 of the seed crystal was 8mm. The method for growing monocrystalline silicon in the embodiment has the advantages of 17 percent of seeding breakage rate, 25 percent of shoulder breakage rate, 18 percent of constant diameter head breakage rate and less polycrystal formation.
Example 4
Reference example 1 was made, except that in the seed crystal production method, in the third step, the spindle rotation speed was 250r/min when the mark was scraped. The method for growing monocrystalline silicon in the embodiment has the advantages that the seeding breakage rate is 14%, the shoulder breakage rate is 22%, the constant diameter head breakage rate is 27%, and fewer polycrystal is formed.
Example 5
The process is carried out in accordance with example 1, except that in the process of growing monocrystalline silicon with seed crystal, in step three, during the constant diameter growth process of pulling up, the crystal is maintained at 4r/min, the crucible is changed to 6r/min, and the pulling rate is 180mm/h. The method for growing monocrystalline silicon in the embodiment has the advantages of 13 percent of seeding breakage rate, 17 percent of shoulder breakage rate, 32 percent of constant diameter head breakage rate and less polycrystal formation.
Example 6
With reference to example 5, the difference is that in the method for growing single crystal silicon by seed crystal, in step three, during the shoulder process of upward pulling, the crystal is kept to be turned to 4r/min, the crucible is turned to 6r/min, and the pulling speed is 160mm/h. The method for growing monocrystalline silicon in the embodiment has the advantages that the seeding breakage rate is 15%, the shoulder breakage rate is 25%, the constant diameter head breakage rate is 38%, and fewer polycrystal is formed.
Example 7
With reference to example 6, a difference is that in the method for growing single crystal silicon by seed crystal, in the step three, in the seeding process of upward pulling, the crystal is turned to 4r/min, the crucible is turned to 6r/min, the pulling speed is 110mm/h, and the seeding length is 150mm. In the method for growing monocrystalline silicon in the embodiment, the seeding breakage rate is 24%, the shoulder breakage rate is 28%, the constant diameter head breakage rate is 43%, and a small amount of polycrystal is formed.
Example 8
The process of example 7 was conducted with the difference that in the second step, the crystal rotation was adjusted to 6r/min when the vertical distance between the bottom of the seed crystal and the molten silicon level was 100 mm. In the method for growing monocrystalline silicon in this example, the seeding breakage rate is 27%, the shoulder breakage rate is 33%, the constant diameter head breakage rate is 45%, and a small amount of polycrystal is formed.
Example 9
The process of example 7 was conducted with the difference that in the second step, the crystal rotation was adjusted to 12r/min when the bottom of the seed crystal was in contact with the surface of the molten silicon. In the method for growing monocrystalline silicon in this example, the seeding breakage rate is 29%, the shoulder breakage rate is 35%, the constant diameter head breakage rate is 44%, and a small amount of polycrystal is formed.
Example 10
Reference example 7 was made, except that the power of the heater in the single crystal growth furnace was adjusted at a rate of 0.4kw/min while the bottom of the seed crystal was flush with the upper end of the crucible, so that the temperature of the molten silicon level was maintained at 1560 ℃. In the method for growing monocrystalline silicon in the embodiment, the seeding breakage rate is 31%, the shoulder breakage rate is 32%, the constant diameter head breakage rate is 42%, and a small amount of polycrystal is formed.
Comparative example 1
The process is carried out in accordance with example 1, except that in the second step, the length of the first dislocation portion 6 constituted by the dislocation region is 12% and the length of the second dislocation portion 10 of the seed crystal is 12%. The method for growing monocrystalline silicon in the comparative example has a seeding breakage rate of 62%, a shoulder breakage rate of 71%, a constant diameter head breakage rate of 69%, and more polycrystal formation.
Comparative example 2
The process was carried out in accordance with example 1, except that in the second step, the length of the first dislocation portion 6 constituted by the dislocation region was 3.5% and the length of the second dislocation portion 10 of the seed crystal was 3.5%. In the method for growing monocrystalline silicon in the comparative example, the seeding breakage rate is 70%, the shoulder breakage rate is 73%, the breakage rate of the constant diameter head is 77%, and more polycrystal is formed.
Comparative example 3
Reference example 1 was made, except that a solar grade single crystal silicon rod was used as a seed rod for preparing a seed crystal. The method for growing monocrystalline silicon in the comparative example has a seeding breakage rate of 75%, a shoulder breakage rate of 78%, a constant diameter head breakage rate of 82%, and more polycrystal formation.
In comparative examples 1 and 3, the seed crystal containing dislocation part is adopted, the mark of the dislocation part is positioned below the liquid level of molten silicon in the process of growing monocrystalline silicon, and compared with the preparation of the seed crystal by adopting a solar grade monocrystalline silicon rod as a seed crystal mother rod, the seeding survival rate can be improved, and the seeding breakage rate, the shouldering breakage rate and the constant diameter head breakage rate can be reduced. In comparative example 1 and comparative examples 2 and 3, the dislocation portion was made to have a ratio of 5% to 10% based on the length of the seed crystal, and the seeding breakage rate, the shoulder breakage rate, and the constant diameter head breakage rate could be reduced.
Comparative examples 1-3, which make the dislocation length 10-20 mm, are more advantageous for reducing the seeding breakage rate, the shouldering breakage rate and the constant diameter head breakage rate. In comparative examples 1 and 4, during the marking process, the spindle rotation speed is 290r/min to 320r/min, which is more beneficial to reducing mechanical stress, reducing the seeding breakage rate, the shouldering breakage rate and the constant diameter head breakage rate, and reducing the formation of polycrystal. In comparative examples 1 and 5-10, the seeding survival rate is improved by controlling the seeding process, the shouldering process and the crystal rotation, the crucible rotation, the crystal pulling speed and the seeding length in the equal-diameter growth process, the seeding breakage rate, the shouldering breakage rate and the equal-diameter head breakage rate are reduced, when the vertical distance between the bottom of the seed crystal and the molten silicon liquid level is 80-120 mm, the crystal rotation is 2 r/min-4 r/min, when the bottom of the seed crystal contacts the molten silicon liquid level, the crystal rotation is 5 r/min-9 r/min, when the bottom of the seed crystal is lowered to the upper end of the crucible, namely, when the bottom of the seed crystal is leveled with the upper end of the crucible, the temperature of the molten silicon liquid level is regulated to 1450-1470 ℃, and the seeding breakage rate, the shouldering breakage rate and the equal-diameter head breakage rate are reduced.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (7)
1. A method for preparing a seed crystal for growing monocrystalline silicon by a Czochralski method, the method comprising:
drawing lines on a seed crystal mother rod to obtain a seed crystal mother rod for drawing lines, wherein the seed crystal mother rod is a single crystal rod with equal-diameter broken lines, dislocation is arranged at the equal-diameter broken line end of the seed crystal mother rod, and the line drawing treatment is carried out at the boundary position of the dislocation;
cutting off the line-drawn seed crystal mother rod and carrying out sharpening treatment to obtain a seed crystal for growing monocrystalline silicon by a Czochralski method, wherein the sharpening treatment comprises: drawing a grinding mark at the position of the drawn line;
the single crystal rod with the equal-diameter broken line is a single crystal rod with the equal-diameter broken line subjected to end cutting treatment; or the cutting-off treatment comprises the step of cutting off the end of the isodiametric broken line of the drawn seed crystal mother rod;
one end of the seed crystal is provided with a dislocation part, the dislocation part is provided with the dislocation, and the length of the dislocation part accounts for 5% -10% based on the length of the seed crystal;
the length of the dislocation part is 10 mm-20 mm.
2. The method of claim 1, wherein the conditions for milling the marks comprise: the feed speed is 2700 r/min-3300 r/min, the feed multiplying power is 80% -100%, and the spindle rotating speed is 290 r/min-320 r/min.
3. A method for growing single crystal silicon using the seed crystal prepared by the preparation method according to any one of claims 1 to 2, characterized in that the method comprises: loading a polycrystalline silicon raw material into a crucible, placing the crucible into a main chamber of a single crystal growth furnace, installing a seed crystal into a secondary chamber of the single crystal growth furnace according to a dislocation part, heating and melting the polycrystalline silicon raw material to obtain molten silicon liquid, and descending the seed crystal from the secondary chamber to the main chamber, wherein the descending is that a mark is positioned below the liquid level of the molten silicon liquid;
pulling the seed crystal upwards to crystallize the molten silicon liquid below the seed crystal, thereby obtaining the monocrystalline silicon; the lowering is performed so that the position of the mark is 3mm to 5mm lower than the position of the liquid surface of the molten silicon.
4. A method according to claim 3, characterized in that the method comprises: when the vertical distance between the bottom of the seed crystal and the crucible is 2500 mm-3500 mm, the descending speed is adjusted to 4500 mm/h-5500 mm/h, when the vertical distance between the bottom of the seed crystal and the crucible is 800 mm-1200 mm/h, the descending speed is adjusted to 2000 mm/h-3000 mm/h, when the bottom of the seed crystal descends to the upper end of the crucible, the descending speed is adjusted to 800 mm/h-1200 mm/h, when the vertical distance between the bottom of the seed crystal and the liquid level is 80 mm-120 mm, the descending speed is adjusted to 80 mm/h-120 mm/h, the crystal transition is adjusted to 2 r/min-4 r/min, when the bottom of the seed crystal contacts the liquid level, the descending speed is adjusted to 50 mm/h-70 mm/h, the crystal transition is adjusted to 5 r/min-9 r/min, and the argon flow is adjusted to 50 slpm-70 pm;
when the bottom of the seed crystal descends to the upper end of the crucible, the power of a heater in the single crystal growth furnace is adjusted, so that the temperature of the liquid level is kept at 1450-1470 ℃, and the adjusting speed of the power is below 0.4 kw/min.
5. The method of claim 4, wherein the conditions of the upward pull seeding process comprise: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, the crystal pulling speed is 240 mm/h-350 mm/h, and the seeding length is 180mm-250mm.
6. The method of claim 5, wherein the conditions of the upward pulling shouldering process include: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-150 mm/h.
7. The method of claim 6, wherein the conditions of the upward pulling constant diameter growth process comprise: the crystal transformation is 5 r/min-9 r/min, the crucible transformation is 5 r/min-8 r/min, and the crystal pulling speed is 80 mm/h-105 mm/h.
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| CN103436954A (en) * | 2013-09-11 | 2013-12-11 | 英利能源（中国）有限公司 | Seed crystal for seeding during manufacturing of silicon single crystal rod and manufacturing method of silicon single crystal rod |
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| JP2005281068A (en) * | 2004-03-30 | 2005-10-13 | Toshiba Ceramics Co Ltd | Silicon seed crystal and growth method of silicon single crystal |
| CN103436954A (en) * | 2013-09-11 | 2013-12-11 | 英利能源（中国）有限公司 | Seed crystal for seeding during manufacturing of silicon single crystal rod and manufacturing method of silicon single crystal rod |
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