CN113564689A - Method for recycling seed crystals for casting monocrystals - Google Patents
Method for recycling seed crystals for casting monocrystals Download PDFInfo
- Publication number
- CN113564689A CN113564689A CN202010357713.9A CN202010357713A CN113564689A CN 113564689 A CN113564689 A CN 113564689A CN 202010357713 A CN202010357713 A CN 202010357713A CN 113564689 A CN113564689 A CN 113564689A
- Authority
- CN
- China
- Prior art keywords
- silicon
- crystal
- seed
- seed crystal
- crystals
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
-
- 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
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/14—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method characterised by the seed, e.g. its crystallographic orientation
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention provides a method for recycling seed crystals for casting monocrystals, which comprises the following steps: (1) splicing and laying monocrystalline silicon seed crystals with the same square opening size of a monocrystalline silicon-like ingot at the bottom of a crucible to form a seed crystal layer; preparing a mono-like silicon ingot by using the seed crystal layer; (2) the bottom surface of the quasi-monocrystalline silicon ingot faces upwards, the splicing seams of the seed crystals on the bottom surface are marked out by using seam marking lines, and the splicing seams extend to four side surfaces of the quasi-monocrystalline silicon ingot; squaring a mono-like silicon ingot to obtain a plurality of first silicon blocks, aligning a squaring steel wire with a seed crystal splicing seam before squaring, polishing and flattening two end faces of the first silicon blocks corresponding to the bottom of the crucible and an opening, then cutting off seed crystal regions on the first silicon blocks to obtain a plurality of recovered mono-crystalline silicon seed crystals, and marking the type of each single-crystalline silicon seed crystal; (3) and (3) reusing the seed crystal obtained in the step (2) according to the method in the step (1). The method can realize repeated high-quality reuse of the seed crystal for many times, and reduces the seed crystal cost of casting the single crystal.
Description
Technical Field
The invention relates to the field of quasi-monocrystalline silicon ingots, in particular to a method for recycling seed crystals for casting quasi-monocrystalline silicon.
Background
At present, a plurality of monocrystalline silicon seed crystals are paved at the bottom of a crucible to form a seed crystal layer, then a silicon material in a molten state is arranged above the seed crystal layer, and the temperature at the bottom of the crucible is controlled to be lower than the melting point of the seed crystals, so that the seed crystals are not completely melted; and cooling to enter a crystal growth stage, and growing a monocrystalline-like silicon ingot on the incompletely melted seed crystal layer by using the silicon material. Generally, in order to improve the quality of the obtained single crystal-like silicon ingot, the seed crystal layer is formed by splicing different types of seed crystals, so that a certain angle of crystal orientation difference is formed between side crystal orientations of the adjacent seed crystals, and a certain crystal boundary is formed at a splicing seam (see fig. 1), so that the generation of dislocation can be inhibited in the subsequent crystal growing process.
Although the battery efficiency of the mono-like silicon wafer produced by the method is higher than that of the common polycrystalline silicon wafer, the input cost of the seed crystal is also higher. In order to reduce the cost, the seed crystal is generally recycled, and the current seed crystal recycling method comprises the following steps: after preparing the mono-like silicon ingot, cutting the seed crystal position at the bottom of the silicon ingot to obtain a whole seed crystal large plate, and then laying the seed crystal large plate at the bottom of a crucible to cast a single crystal. However, the cutting of the seed crystal large plate is complex, a special large cutting machine is needed, the cutting cost is high, the cleaning of the cut seed crystal large plate is difficult, the seed crystal large plate is easy to crack at the splicing position of the seed crystal, and the repeated utilization degree is not high.
Disclosure of Invention
In view of the above, the invention provides a seed crystal recycling method for casting single-crystal-like silicon, so as to improve the seed crystal recycling effect and reduce the seed crystal cost of casting single-crystal-like silicon ingots.
The invention provides a method for recycling seed crystals for casting monocrystals, which comprises the following steps:
(1) providing a crucible, splicing and laying a plurality of monocrystalline silicon seed crystals with the crystal orientations of the growth surfaces belonging to the same crystal orientation group at the bottom of the crucible to form a seed crystal layer; arranging a silicon material in a molten state above the seed crystal layer, and controlling the temperature to enable the silicon material in the molten state to inherit the crystal orientation structure of the monocrystalline silicon seed crystal on the seed crystal layer to grow so as to prepare a monocrystalline-like silicon ingot;
the plurality of monocrystalline silicon seed crystals comprise at least two types, the side crystal directions of different types of seed crystals are different, and the types of two adjacent monocrystalline silicon seed crystals in the seed crystal layer are different;
(2) taking out the quasi-single crystal silicon ingot, enabling the bottom surface of the quasi-single crystal silicon ingot, which is in contact with the bottom of the crucible, to be upward, marking the splicing seams of the seed crystals on the bottom surface by using gap marking lines, and extending the splicing seams to four side surfaces of the quasi-single crystal silicon ingot;
squaring the mono-like silicon ingot to obtain a plurality of first silicon blocks, wherein a squaring steel wire is aligned with the splicing seams of the seed crystals before squaring, and the transverse size of the mono-crystalline silicon seed crystals in the step (1) is the same as the squaring size of the mono-like silicon ingot;
polishing and flattening two end faces of the first silicon block corresponding to the bottom of the crucible and the opening, cutting off a seed crystal area on the polished first silicon block to obtain a plurality of recovered monocrystalline silicon seed crystals, and marking the type of each monocrystalline silicon seed crystal;
(3) and (3) recycling the seed crystal obtained in the step (2) according to the method in the step (1).
And the angle deviation of the side crystal directions of two adjacent seed crystals in the seed crystal layers is in the range of 4-30 degrees.
In the step (1), the length and the width of the monocrystalline silicon seed crystal are both 50-210mm, and the height is 10-30 mm.
Wherein the length and the width of the bottom of the monocrystalline silicon-like ingot are both 200mm-1600 mm; the open size is 50-210 mm.
In the step (2), the first silicon block before polishing should satisfy the following conditions: the edge collapse depth of the first silicon block, which is vertical to the edge at the bottom of the crucible, is less than or equal to 0.5mm, and the edge collapse depths of other edges and the pit depths of all side surfaces are less than or equal to 2 mm; the deviation between the gap marking line on the first silicon block and the corresponding edge is less than or equal to 1.5 mm.
In the step (2), the roughness of the end face, corresponding to the bottom of the crucible, of the polished first silicon block is less than 0.5 mm.
Wherein, in the step (2), the height of the recovered monocrystalline silicon seed crystal is 10mm-30 mm.
Wherein the monocrystalline silicon seed crystal in the step (1) is derived from a monocrystalline rod, and the growth surface crystal orientation of the monocrystalline silicon seed crystal is selected from the <001>, <011> or <111> crystal orientation family.
Wherein, the control temperature in the step (1) is as follows: after a silicon material in a molten state is arranged above the seed crystal layer, controlling the bottom temperature of the crucible to be lower than the melting point of the seed crystal so that the seed crystal layer is not completely melted; and then controlling the temperature in the crucible to gradually rise along the direction vertical to the upward direction of the bottom of the crucible to form a temperature gradient, so that the silicon material in the molten state inherits the crystal orientation structure of the monocrystalline silicon seed crystal to grow on the monocrystalline silicon seed crystal, and obtaining the monocrystalline silicon-like ingot.
According to the method for recycling the seed crystals for casting the mono-like silicon ingot, the mono-crystalline silicon ingot is cast by selecting the mono-crystalline silicon seed crystals with the transverse size same as the opening size of the mono-like silicon ingot, and the obtained mono-crystalline silicon ingot is opened by aligning the splicing seams of the seed crystals after the bottom surface of the mono-like silicon ingot faces upwards, so that each first silicon block after being opened is ensured to be provided with one type of seed crystals, and the subsequent classification of the seed crystals is facilitated; the end face of the first silicon block corresponding to the bottom of the crucible is polished and then the seed crystal area at the tail part is cut off, so that the situation that a new splicing seam is added on the basis of the original seed crystal when the obtained seed crystal is subsequently recycled can be avoided, and the increase of dislocation of the obtained single crystal silicon ingot when the obtained seed crystal is recycled is further avoided. The quality of the quasi-monocrystalline silicon prepared by the seed crystal after being recycled is equivalent to that of the quasi-monocrystalline silicon prepared by the primary use of the monocrystalline silicon seed crystal cut from the monocrystalline rod. The invention can realize the repeated utilization of the seed crystal for many times by a simple method, and the prepared single crystal-like silicon ingot after repeated utilization for many times has higher quality and less dislocation, and can greatly reduce the seed crystal cost for casting the single crystal-like silicon (about 40 percent reduction).
Drawings
FIG. 1 is a top view of a plurality of monocrystalline silicon seed crystals after being laid on the bottom of a crucible;
FIG. 2 is a view showing a quasi-single crystal silicon ingot obtained after the first use of seed crystals and a gap marking line thereon;
FIG. 3 is a schematic structural diagram of a row of first silicon ingots obtained after slicing;
FIG. 4 is a schematic structural view of a first silicon block to be cut marked with a seed thickness mark line;
FIG. 5 is a graph showing Photoluminescence (PL) of a single-crystal-like silicon wafer (a) obtained by first using a seed crystal and a single-crystal-like silicon wafer (b) obtained by repeating the use of a seed crystal 1 time in example 1 of the present invention;
FIG. 6 is a top view of a plurality of monocrystalline silicon seed crystals after being deposited at the bottom of the crucible in another embodiment of the invention.
Detailed Description
While the following is a description of the preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
The first aspect of the embodiment of the invention provides a recycling method of seed crystals for casting single crystals, which comprises the following steps:
(1) providing a crucible, splicing and laying a plurality of monocrystalline silicon seed crystals with the crystal orientations of the growth surfaces belonging to the same crystal orientation group at the bottom of the crucible to form a seed crystal layer; arranging a silicon material in a molten state on the seed crystal layer, and controlling the temperature to enable the silicon material in the molten state to inherit the crystal orientation structure of the monocrystalline silicon seed crystal on the seed crystal layer to grow so as to prepare a monocrystalline-like silicon ingot;
the plurality of monocrystalline silicon seed crystals comprise at least two types, the side crystal directions of different types of seed crystals are different, and the types of two adjacent seed crystals in the seed crystal layer are different;
(2) taking out the quasi-single crystal silicon ingot, enabling the bottom surface of the quasi-single crystal silicon ingot, which is in contact with the bottom of the crucible, to be upward, marking the splicing seams of the seed crystals on the bottom surface by using gap marking lines, and extending the splicing seams to four side surfaces of the quasi-single crystal silicon ingot;
squaring the mono-like silicon ingot to obtain a plurality of first silicon blocks, wherein a squaring steel wire is aligned with the splicing seams of the seed crystals before squaring, and the transverse size of the mono-crystalline silicon seed crystals in the step (1) is the same as the squaring size of the mono-like silicon ingot;
polishing and flattening two end faces of the first silicon block corresponding to the bottom of the crucible and the opening, cutting off a seed crystal area on the polished first silicon block to obtain a plurality of recovered monocrystalline silicon seed crystals, and marking the type of each monocrystalline silicon seed crystal;
(3) and (3) recycling the seed crystal obtained in the step (2) according to the method in the step (1).
In the step (1), the seed crystals of the single crystal silicon may be laid in a manner according to the size of the crucible, and may be laid on the bottom of the crucible in a manner of, for example, 4 × 4, 5 × 5, 6 × 6, 7 × 7 …, or the like.
Preferably, the monocrystalline silicon seed crystal in step (1) is derived from a monocrystalline rod. In order to better recycle the seed crystal, the lateral dimensions (i.e., length, width) of the monocrystalline silicon seed crystal in step (1) are the same as the open square dimensions of the below-described monocrystalline-like silicon ingot.
Optionally, the monocrystalline silicon seed crystal in the step (1) has a length and a width of 50-210mm and a height of 10-30 mm.
In the step (1), the types of the monocrystalline silicon seed crystals are divided according to whether the side crystal directions of the monocrystalline silicon seed crystals are the same or not. The growth plane crystal orientation of the same type of seed crystal can be the same (e.g., as (001) or different, e.g., some as (001) and some as
). Optionally, the growth plane crystal orientation of the single crystal silicon seed crystal is selected from<001>、<011>Or<111>A family of crystal orientations.
Optionally, the angular deviation of the side crystal orientation of two adjacent seed crystals in the seed crystal layer is in the range of 4-30 °. The crystal directions of the side surfaces of two adjacent seed crystals in the seed crystal layer have angular deviation, so that dislocation of the seed crystal layer in the seeding process can be avoided. Preferably, the deviation of the angles of the side crystal directions of two adjacent seed crystals in the seed crystal layers is in the range of 5-20 degrees. This further contributes to the formation of a low grain boundary energy between adjacent seed crystals, and better suppresses dislocations generated during the casting of single crystal silicon.
In an embodiment of the invention, the plurality of monocrystalline silicon seed crystals to be spliced and laid comprise two types (namely a first type seed crystal and a second type seed crystal), the growth surfaces of the first type seed crystal and the second type seed crystal have the same crystal orientation, the side crystal orientations are different, and the first type seed crystal and the second type seed crystal are alternatively spliced and laid during laying.
Preferably, the temperature control in step (1) is: after a silicon material in a molten state is arranged above the seed crystal layer, controlling the bottom temperature of the crucible to be lower than the melting point of the seed crystal so that the seed crystal layer is not completely melted; and controlling the temperature in the crucible to gradually rise along the direction vertical to the upward direction of the bottom of the crucible to form a temperature gradient, so that the silicon material in a molten state grows on the seed crystal layer by inheriting the crystal orientation structure of the monocrystalline silicon seed crystal, and the monocrystalline silicon-like ingot is prepared.
In the step (1), the bottom size of the mono-like silicon ingot is basically the same as the size of the crucible. Optionally, the length and the width of the bottom of the single crystal-like silicon ingot are both 200-1600 mm. More preferably 1 to 1.4 m.
In the step (2), the gap mark lines extend to the four side faces of the single crystal-like silicon ingot, so that the squaring steel wire of the squaring machine is aligned with the splicing seams of the seed crystals, and thus, each first silicon block after squaring is ensured to be provided with only one type of seed crystals, and subsequent seed crystals are convenient to classify and recycle.
Optionally, in the step (2), the open size of the mono-like silicon ingot is 50-210mm, and the open size refers to the lateral dimension (i.e. length and width) of the first silicon block obtained after the mono-like silicon ingot is opened.
Further, the height of the first silicon block obtained after the opening in the step (2) is 200-480 mm. Preferably 280-360 mm.
Optionally, in the step (2), the polishing process of the first silicon block is specifically as follows: and adopting a surface grinder to carry out coarse grinding and fine grinding on the first silicon block in sequence.
Optionally, the roughness of the end face, corresponding to the bottom of the crucible, of the polished first silicon block is less than 0.5 mm. At the moment, the end face of the first silicon block corresponding to the bottom of the crucible is smooth, so that the monocrystalline silicon seed crystal cut from the polished first silicon block can be conveniently recycled, and new dislocation is prevented from being generated during recycling. The roughness refers to the height of the protrusions on the end face of the polished first silicon block corresponding to the bottom of the crucible.
In the step (2), the first silicon block before polishing should satisfy the following conditions: the edge collapse depth of the first silicon block, which is vertical to the edge at the bottom of the crucible, is less than or equal to 0.5mm, and the edge collapse depths of other edges and the pit depths of all side surfaces are less than or equal to 2 mm; the deviation between the gap marking line on the first silicon block and the corresponding edge is less than or equal to 1.5 mm.
Preferably, the edge collapse depth of each edge of the first silicon block before grinding is less than or equal to 0.5mm, and the pit depth of each side surface is less than or equal to 2 mm.
Optionally, the cutting the seed crystal region on the polished first silicon block specifically includes: and making a seed crystal thickness marking line on the polished first silicon block, and cutting at the seed crystal thickness marking line. The thickness mark line is made according to the height of the initial seed crystal.
Further, the distance between the seed crystal thickness mark line and the end face, corresponding to the bottom of the crucible, of the first silicon block is 10mm-30 mm. Namely, the height of the recovered monocrystalline silicon seed crystal is 10mm-30 mm.
In the step (2), after the seed crystal region on the polished first silicon block is cut off, a plurality of second silicon blocks are correspondingly obtained in addition to a plurality of recovered monocrystalline silicon seed crystals, and the second silicon blocks are sliced to obtain the monocrystalline silicon-like wafer for the solar cell.
Preferably, after a plurality of recovered monocrystalline silicon seed crystals are obtained, each seed crystal is cleaned by adopting a conventional method.
After the plurality of recovered seed crystals are obtained according to the step (2), the transverse size of each seed crystal is the same as the square opening size of the single crystal-like silicon ingot, so that the convenient reuse of each seed crystal is ensured, the recovered seed crystals are spliced and laid at the bottom of the crucible in the step (1), and the seed crystal layer is formed to perform seeding to prepare the single crystal-like silicon ingot, so that the 1 st reutilization of the seed crystals is realized. And (3) then, recovering the monocrystalline silicon-like ingot according to the mode of the step (2), and preparing the monocrystalline silicon-like ingot according to the method of the step (1), so that the 2 nd repeated use of the seed crystal is realized, and the like. The seed crystal obtained by the invention can be repeatedly used for 1-5 times, and the quality of the monocrystalline silicon-like ingot prepared after repeated use is equivalent to the quality of the monocrystalline silicon-like ingot obtained by using the monocrystalline silicon seed crystal in the step (1) for the first time. Optionally, the number of reuses of the seed crystal is 1-5.
Optionally, the dislocation density of the mono-like silicon ingot obtained by recycling the seed crystal is less than or equal to 104Per cm2And fewer dislocations.
The following describes embodiments of the present invention in terms of various specific embodiments.
Example 1
A method for recycling seed crystals for casting mono-like crystals comprises the following steps:
(1) a, B two types of seeds are provided: selecting two straight-pull single crystal round rods with the diameter of 9 inches (230mm) and the growth surface crystal direction of (100), taking a standard evolution pattern of the side surface crystal direction (100) as a reference, clockwise rotating one rod for 15 degrees, clockwise rotating the other rod for 40 degrees, and then evolving to obtain a first square rod and a second square rod with the end surface size of 158.7mm multiplied by 158.7mm, then placing the first square rod and the second square rod into a slicing machine for cutting to respectively form a plurality of A-type seed crystals and B-type seed crystals with the length of 158.7mm multiplied by 158.7mm, the width multiplied by 30 mm; the length and width of the seed crystal are the same as the square opening size of the following monocrystalline silicon-like ingot;
laying a seed crystal layer: providing a square crucible 1 with the inner diameter of 840mm and the width of 840mm, splicing and laying 25 monocrystalline silicon seed crystals with the length of 158.7mm, the width of 158.7mm and the width of 30mm at the bottom of the crucible 1 according to the 5 x 5 mode of fig. 1 to obtain a seed crystal layer 2, wherein the growing crystal directions of the 36 monocrystalline silicon seed crystals are the same and are (001), and the angle deviation of the side crystal directions of the A-type seed crystal and the B-type seed crystal is 25 degrees;
casting a quasi-single crystal: arranging a silicon material in a molten state on the seed crystal layer 1, and controlling the bottom temperature of the crucible to be lower than the melting point of the seed crystal so that the seed crystal layer is not completely melted; controlling the temperature in the crucible to gradually rise along the direction vertical to the upward direction of the bottom of the crucible to form a temperature gradient, so that the silicon material in a molten state is grown on the monocrystalline silicon seed crystal by inheriting the crystal orientation structure of the monocrystalline silicon seed crystal, and the similar monocrystalline silicon ingot with the length of 790mm, the width of 790mm and the height of 280 plus 360mm is prepared;
(2)2.1, taking out the mono-like silicon ingot obtained in the step (1), turning over the ingot to enable the bottom surface of the ingot, which is in contact with the bottom of the crucible, to be upward, and marking the growth direction of the silicon ingot by attention so as to facilitate subsequent cutting; then finding the splicing seams of the seed crystals on the silicon single crystal silicon ingot, marking the splicing seams by using seam marking lines, and paying attention to the fact that the seam marking lines extend to four side surfaces of the silicon single crystal silicon ingot (see figure 2, and figure 2 shows a plurality of transverse and longitudinal seam marking lines);
2.2, squaring the mono-like silicon ingot with the gap marking line, aligning a squaring steel wire of a squaring machine with a splicing seam (namely the gap marking line) of the seed crystal before squaring, and obtaining a plurality of first silicon blocks after squaring, wherein the transverse dimension of each first silicon block is 158.7mm long multiplied by 158.7mm wide;
2.3, selecting a first silicon block meeting the requirements according to the following standards: the edge collapse depth of the first silicon block corresponding to the edge vertical to the bottom of the crucible is less than or equal to 0.5mm, and the edge collapse depths of other edges and the pit depths of all side surfaces are less than or equal to 2 mm; the deviation between the gap marking line on the first silicon block and the corresponding edge is less than or equal to 1.5 mm; polishing and flattening the top surface and the bottom surface (namely, the two end surfaces corresponding to the bottom of the crucible and the opening, see fig. 3) of the selected first silicon block, wherein the roughness of the two end surfaces corresponding to the bottom of the crucible and the opening of the polished first silicon block is less than 0.5 mm;
2.4, making a seed crystal thickness marking line (see a dotted line on a figure 4) on the polished first silicon block according to the thickness of the seed crystal in the step (1), cutting at the seed crystal thickness marking line to separate a monocrystalline silicon seed crystal region on the first silicon block to obtain a plurality of second silicon blocks (the right side of the dotted line in the figure 4) and a plurality of recycled monocrystalline silicon seed crystals (the left side of the dotted line in the figure 4), and marking the type (the type A or the type B) of each monocrystalline silicon seed crystal;
(3) and (3) cleaning the seed crystal obtained in the step (2), laying the seed crystal at the bottom of the crucible 1 again according to the method in the step (1), and preparing the mono-like silicon ingot again to realize the 1 st reutilization of the seed crystal.
In this embodiment 1, the second silicon block obtained in step (2) is sliced and cleaned to obtain a quasi-monocrystalline silicon wafer, and then the quasi-monocrystalline silicon wafer can be used as a raw material to manufacture a solar cell by a screen printing process.
FIG. 5 is a graph showing Photoluminescence (PL) of a single-crystal-like silicon wafer (a) obtained by first using a seed crystal and a single-crystal-like silicon wafer (b) obtained by repeating the use of a seed crystal 1 time in example 1 of the present invention. As can be seen from FIG. 5, the quality of the cast single crystal obtained after the seed crystal is reused once according to the present invention is equivalent to the quality of the cast single crystal obtained after the seed crystal is used for the first time (see FIG. 5), and no new splicing seam is added, thereby illustrating that no new dislocation is added.
In addition, dislocation observation is carried out on the mono-like silicon ingot prepared after the seed crystal is repeatedly used once by adopting an optical microscope (magnified by 200 times)The average dislocation density of the silicon single crystal-like ingot is detected to be less than or equal to 104Per cm2。
Example 2
A method for recycling seed crystals for casting mono-like crystals comprises the following steps:
(1) a, B two types of seeds are provided: selecting two straight-pull single crystal round rods with the diameter of 9.5 inches (240mm) and the growth surface crystal direction of (100), taking a standard evolution pattern of a side surface crystal direction (110) as a reference, clockwise rotating one rod for 20 degrees, clockwise rotating the other rod for 30 degrees, and then evolving to obtain a first square rod and a second square rod with the end surface size of 166.75mm multiplied by 166.75mm, then placing the first square rod and the second square rod into a slicing machine for cutting to respectively form a plurality of A-type seed crystals and B-type seed crystals with the length of 166.75mm multiplied by 166.75mm, the width of the A-type seed crystals and the B-type seed crystals with the height of 25 mm; the length and width of the seed crystal are the same as the square opening size of the following monocrystalline silicon-like ingot;
laying a seed crystal layer: providing a square crucible (a crucible of G7) with the inner diameter of 1300mm and the width of 1300mm, splicing and laying 49 monocrystalline silicon seed crystals with the length of 166.75mm, the width of 166.75mm and the height of 25mm at the bottom of the crucible according to the mode of 7X 7 of figure 6 to obtain a seed crystal layer, wherein the angle deviation of the side crystal directions of the A-type seed crystal and the B-type seed crystal is 10 degrees, the growth surface crystal directions of the A-type seed crystal and the A-type seed crystal are opposite (the A-type seed crystal is equivalent to that the A-type seed crystal is turned over by 180 degrees up and down), and the growth surface crystal directions of the B-type seed crystal and the B-type seed crystal are opposite;
casting a quasi-single crystal: arranging a silicon material in a molten state on the seed crystal layer, and controlling the bottom temperature of the crucible to be lower than the melting point of the seed crystal so as to ensure that the seed crystal layer is not completely melted; controlling the temperature in the crucible to gradually rise along the direction vertical to the upward direction of the bottom of the crucible to form a temperature gradient, so that the silicon material in a molten state is grown on the monocrystalline silicon seed crystal by inheriting the crystal orientation structure of the monocrystalline silicon seed crystal, and the quasi-monocrystalline silicon ingot with the length of 1240mm, the width of 1240mm, the height of 250 and 360mm is prepared;
(2) taking out the quasi-monocrystalline silicon ingot obtained in the step (1), turning over the quasi-monocrystalline silicon ingot to enable the bottom surface of the quasi-monocrystalline silicon ingot, which is in contact with the bottom of the crucible, to be upward, and marking the growth direction of the silicon ingot by attention so as to facilitate subsequent cutting; then finding out the splicing seams of the seed crystals on the silicon single crystal ingot, marking the splicing seams by using seam marking lines, and paying attention to the fact that the seam marking lines extend to the four side surfaces of the silicon single crystal ingot;
then, cutting the mono-like silicon ingot with the gap marking lines, aligning a cutting steel wire of a cutting machine with the splicing seams of the seed crystals (namely the gap marking lines) before cutting, and obtaining a plurality of first silicon blocks after cutting, wherein the transverse dimension of each first silicon block is 166.75mm long multiplied by 166.75mm wide;
selecting first silicon blocks meeting the requirements, wherein the edge collapse depth of each edge of the selected first silicon blocks is less than or equal to 0.5mm, and the pit depth of each side surface is less than or equal to 2 mm; the method comprises the following steps of (1) polishing and flattening the top surface and the bottom surface (namely, the two end surfaces corresponding to the bottom of a crucible and an opening) of a selected first silicon block without a gap marking line on each edge of the selected first silicon block (namely, when squaring is carried out, a squaring steel wire and a seed crystal splicing seam are completely overlapped), wherein the roughness of the polished first silicon block corresponding to the bottom of the crucible and the two end surfaces of the opening is less than 0.5 mm;
making seed crystal thickness marking lines on the polished first silicon block according to the thickness of the seed crystals in the step (1), cutting at the seed crystal thickness marking lines to separate monocrystalline silicon seed crystal regions on the first silicon block to obtain a plurality of second silicon blocks and a plurality of recycled monocrystalline silicon seed crystals, and marking the specific type of each monocrystalline silicon seed crystal;
(3) and (3) after cleaning the seed crystal obtained in the step (2), repeating the step (1) once to realize the 1 st reutilization of the seed crystal, and repeating the steps (2) and (1) once in sequence to realize the 2 nd reutilization of the seed crystal.
As a result, it was found that the quality of the cast single crystal obtained after reusing the seed crystal 2 times was equivalent to that of the cast single crystal obtained by first utilizing the seed crystal, and that new dislocations were not substantially added.
Example 3
A method for recycling seed crystals for casting mono-like crystals comprises the following steps:
(1) a, B types of monocrystalline silicon seed crystals with the same growth surface crystal direction and 5-degree angle deviation of side surface crystal direction are spliced and paved at the bottom of a square crucible (G6 crucible, 6 multiplied by 6 which is 36 silicon blocks) with the inner diameter of 1100mm long and 1100mm wide according to the mode of figure 1 to form the seed crystal layer; wherein, the sizes of the A, B two types of seed crystals are as follows: 167.7mm long × 167.7mm wide × 30mm high;
arranging a silicon material in a molten state on the formed seed crystal layer, and controlling the temperature to ensure that the silicon material in the molten state inherits the crystal orientation structure of the monocrystalline silicon seed crystal on the seed crystal layer to grow so as to prepare a monocrystalline silicon-like ingot;
(2) turning over the quasi-monocrystalline silicon ingot prepared in the step (1) in the mode of the embodiment 1, and then squaring, and recovering various types of monocrystalline silicon seed crystals from the obtained first silicon blocks;
(3) and (3) cleaning the seed crystal obtained in the step (2), repeating the step (1) once to realize the 1 st reutilization of the seed crystal, repeating the steps (2) and (1) once again in sequence to realize the 2 nd reutilization of the seed crystal, and repeating the steps (2) and (1) once again in sequence to realize the 3 rd reutilization of the seed crystal.
As a result, it was found that the quality of the cast single crystal obtained after 3 times of reuse of the seed crystal was comparable to that of the cast single crystal obtained after the first use of the seed crystal, and that new dislocations were not substantially added.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (9)
1. A method for recycling seed crystals for casting monocrystals is characterized by comprising the following steps:
(1) providing a crucible, splicing and laying a plurality of monocrystalline silicon seed crystals with the crystal orientations of the growth surfaces belonging to the same crystal orientation group at the bottom of the crucible to form a seed crystal layer; arranging a silicon material in a molten state above the seed crystal layer, and controlling the temperature to enable the silicon material in the molten state to inherit the crystal orientation structure of the monocrystalline silicon seed crystal on the seed crystal layer to grow so as to prepare a monocrystalline-like silicon ingot;
the plurality of monocrystalline silicon seed crystals comprise at least two types, the side crystal directions of different types of seed crystals are different, and the types of two adjacent monocrystalline silicon seed crystals in the seed crystal layer are different;
(2) taking out the quasi-single crystal silicon ingot, enabling the bottom surface of the quasi-single crystal silicon ingot, which is in contact with the bottom of the crucible, to be upward, marking the splicing seams of the seed crystals on the bottom surface by using gap marking lines, and extending the splicing seams to four side surfaces of the quasi-single crystal silicon ingot;
squaring the mono-like silicon ingot to obtain a plurality of first silicon blocks, wherein a squaring steel wire is aligned with the splicing seams of the seed crystals before squaring, and the transverse size of the mono-crystalline silicon seed crystals in the step (1) is the same as the squaring size of the mono-like silicon ingot;
polishing and flattening two end faces of the first silicon block corresponding to the bottom of the crucible and the opening, cutting off a seed crystal area on the polished first silicon block to obtain a plurality of recovered monocrystalline silicon seed crystals, and marking the type of each monocrystalline silicon seed crystal;
(3) and (3) recycling the seed crystal obtained in the step (2) according to the method in the step (1).
2. A recycling method of seed crystals for casting mono-like crystals as set forth in claim 1, wherein in the step (1), the deviation of the angles of the side crystal directions of two adjacent seed crystals among the seed layers is in the range of 4 to 30 °.
3. A recycling method of seed crystals for casting mono-like crystal as claimed in claim 1, wherein in the step (1), the length and width of the single crystal silicon seed crystal are 50-210mm and the height is 10-30 mm.
4. A method of recycling a seed crystal for casting a mono-like crystal according to claim 1, wherein the length and width of the bottom of the mono-like silicon ingot are both 200mm to 1600 mm; the open size is 50-210 mm.
5. A recycling method of seed crystals for casting mono-like crystals as set forth in claim 1, wherein in the step (2), the first silicon block before polishing is performed satisfies the following condition: the edge collapse depth of the first silicon block, which is vertical to the edge at the bottom of the crucible, is less than or equal to 0.5mm, and the edge collapse depths of other edges and the pit depths of all side surfaces are less than or equal to 2 mm; the deviation between the gap marking line on the first silicon block and the corresponding edge is less than or equal to 1.5 mm.
6. A recycling method of a seed crystal for casting a single crystal as set forth in claim 1, wherein in the step (2), the roughness of the end surface of the ground first silicon ingot corresponding to the bottom of the crucible is less than 0.5 mm.
7. A recycling method of seed crystals for casting mono-like crystals as set forth in claim 1, wherein in the step (2), the height of the single-crystal silicon seed crystals after recovery is 10mm to 30 mm.
8. A method of recycling a seed crystal for casting a mono-like crystal according to claim 5, wherein in step (1) the single crystal silicon seed crystal is derived from a single crystal rod, and the growth plane crystal orientation of the single crystal silicon seed crystal is selected from the group of <001>, <011>, or <111> crystal orientations.
9. A method of recycling a seed crystal for casting a single-like crystal according to claim 1, wherein the temperature control in step (1) is: after a silicon material in a molten state is arranged above the seed crystal layer, controlling the bottom temperature of the crucible to be lower than the melting point of the seed crystal so that the seed crystal layer is not completely melted; and then controlling the temperature in the crucible to gradually rise along the direction vertical to the upward direction of the bottom of the crucible to form a temperature gradient, so that the silicon material in the molten state inherits the crystal orientation structure of the monocrystalline silicon seed crystal to grow on the monocrystalline silicon seed crystal, and obtaining the monocrystalline silicon-like ingot.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010357713.9A CN113564689A (en) | 2020-04-29 | 2020-04-29 | Method for recycling seed crystals for casting monocrystals |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010357713.9A CN113564689A (en) | 2020-04-29 | 2020-04-29 | Method for recycling seed crystals for casting monocrystals |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN113564689A true CN113564689A (en) | 2021-10-29 |
Family
ID=78157790
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010357713.9A Pending CN113564689A (en) | 2020-04-29 | 2020-04-29 | Method for recycling seed crystals for casting monocrystals |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113564689A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114211628A (en) * | 2021-12-16 | 2022-03-22 | 江苏协鑫硅材料科技发展有限公司 | Seed crystal recovery method |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102747417A (en) * | 2012-07-24 | 2012-10-24 | 江苏协鑫硅材料科技发展有限公司 | Method for ingotting monocrystalline silicon |
| KR101270071B1 (en) * | 2011-06-30 | 2013-06-04 | (주)세미머티리얼즈 | Silicon continuous casting apparatus and method |
| CN104152992A (en) * | 2014-08-06 | 2014-11-19 | 江西赛维Ldk太阳能高科技有限公司 | Seed crystal laying method, quasi-monocrystalline silicon piece preparation method and quasi-monocrystalline silicon piece |
| CN104790026A (en) * | 2015-04-30 | 2015-07-22 | 江西赛维Ldk太阳能高科技有限公司 | Reutilization method of seed crystals for casting monocrystals |
-
2020
- 2020-04-29 CN CN202010357713.9A patent/CN113564689A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101270071B1 (en) * | 2011-06-30 | 2013-06-04 | (주)세미머티리얼즈 | Silicon continuous casting apparatus and method |
| CN102747417A (en) * | 2012-07-24 | 2012-10-24 | 江苏协鑫硅材料科技发展有限公司 | Method for ingotting monocrystalline silicon |
| CN104152992A (en) * | 2014-08-06 | 2014-11-19 | 江西赛维Ldk太阳能高科技有限公司 | Seed crystal laying method, quasi-monocrystalline silicon piece preparation method and quasi-monocrystalline silicon piece |
| CN104790026A (en) * | 2015-04-30 | 2015-07-22 | 江西赛维Ldk太阳能高科技有限公司 | Reutilization method of seed crystals for casting monocrystals |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114211628A (en) * | 2021-12-16 | 2022-03-22 | 江苏协鑫硅材料科技发展有限公司 | Seed crystal recovery method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| TWI534307B (en) | Method of manufacturing crystalline silicon ingot | |
| CN104736746A (en) | Improved production of mono-crystalline silicon | |
| CN111745844A (en) | Border seed crystal and preparation method and application thereof | |
| EP2785898B1 (en) | Production of mono-crystalline silicon | |
| CN104790026A (en) | Reutilization method of seed crystals for casting monocrystals | |
| WO2014028831A1 (en) | System and method of growing silicon ingots from seeds in a crucible and manufacture of seeds used therein | |
| CN113564689A (en) | Method for recycling seed crystals for casting monocrystals | |
| CN107268069A (en) | Method for laying seed crystal and method for producing pseudo-single crystal ingot | |
| CN112519014B (en) | Seed crystal preparation method for ingot casting single crystal and laying method thereof | |
| WO2013112105A1 (en) | Method of preparing cast silicon by directional solidification | |
| CN112251803A (en) | Laying method for casting monocrystalline silicon seed crystal, crystalline silicon ingot and cutting and squaring method for crystalline silicon ingot | |
| CN111485287A (en) | Method for recycling monocrystalline silicon seed crystal, cast monocrystalline silicon piece and preparation method thereof | |
| US7361219B2 (en) | Method for producing silicon wafer and silicon wafer | |
| CN114540953A (en) | Cast crystalline silicon preparation method capable of reducing dislocation defects and polycrystalline proportion | |
| CN111349964B (en) | Preparation method of cast monocrystalline silicon with large area ratio and low dislocation density | |
| JP6798637B1 (en) | Gallium arsenide single crystal substrate | |
| TWI555887B (en) | Crucible for the production of crystalline semiconductor ingots and process for manufacturing the same | |
| JP5398775B2 (en) | Method for producing Si ingot crystal | |
| CN112226810A (en) | Method for recycling seed crystals for casting single crystals | |
| CN111876821B (en) | Cast monocrystalline silicon ingot and preparation method thereof, cast monocrystalline silicon piece and preparation method thereof | |
| CN214327963U (en) | Seed crystal crucible structure for ingot casting monocrystalline silicon | |
| CN113122913B (en) | Seed crystal laying method, monocrystalline silicon ingot casting method and monocrystalline silicon wafer | |
| JP4529712B2 (en) | Method for producing compound semiconductor single crystal | |
| TW202400861A (en) | Sic single crystal substrate | |
| CN112746321A (en) | Seed crystal laying method, preparation method of mono-like silicon ingot and mono-like silicon ingot |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20211029 |