阅读说明：本技术 籽晶的铺设方法 (Seed crystal laying method ) 是由 黎晓丰 陈伟 李林东 唐珊珊 王全志 于 2020-07-01 设计创作，主要内容包括：本发明公开了一种籽晶的铺设方法,所述籽晶的铺设方法包括：以阵列排布的方式铺设多个第一籽晶以构成籽晶阵列,并使相邻两个所述第一籽晶之间彼此间隔开以限定出第一间隙；在所述籽晶阵列的至少一个侧边处铺设形成为条状结构的至少一个第二籽晶,并使所述第二籽晶沿所述籽晶阵列的所述至少一个侧边延伸,且至少一个所述第二籽晶覆盖至少一个所述第一间隙的至少一部分。根据本发明的籽晶的铺设方法,一方面,可以避免多个第一籽晶相互挤压产生应力而在高温下生成位错,另一方面,可以避免籽晶阵列的上述至少一个侧边处产生多晶。另外,还可以防止外部的携带杂质的气体通过第一间隙进入籽晶阵列,从而可以减少缺陷的产生,提升晶体硅的质量。(The invention discloses a seed crystal laying method, which comprises the following steps: laying a plurality of first seed crystals in an array arrangement mode to form a seed crystal array, and enabling two adjacent first seed crystals to be spaced from each other to define a first gap; laying at least one second seed formed in a stripe configuration at least one side of the seed array and extending the second seed along the at least one side of the seed array with the at least one second seed covering at least a portion of at least one of the first gaps. According to the seed crystal laying method, on one hand, the situation that the plurality of first seed crystals are mutually extruded to generate stress to generate dislocation at high temperature can be avoided, and on the other hand, the situation that polycrystal is generated at the at least one side edge of the seed crystal array can be avoided. In addition, the gas carrying impurities outside can be prevented from entering the seed crystal array through the first gap, so that the generation of defects can be reduced, and the quality of the crystalline silicon is improved.)

1. A seed crystal laying method is characterized by comprising the following steps:

laying a plurality of first seed crystals in an array arrangement mode to form a seed crystal array, and enabling two adjacent first seed crystals to be spaced from each other to define a first gap;

laying at least one second seed formed in a stripe configuration at least one side of the seed array and extending the second seed along the at least one side of the seed array with the at least one second seed covering at least a portion of at least one of the first gaps.

2. The seed crystal laying method as set forth in claim 1, wherein the second seed crystal comprises a plurality of seed crystals arranged in sequence along the extending direction of the side of the seed crystal array.

3. The seed crystal placement method as set forth in claim 2, wherein a plurality of the seed crystals correspond one-to-one to a plurality of the first seed crystals located on the side of the seed crystal array.

4. A seed crystal placement method as set forth in claim 3, wherein each of the sub-seed crystals includes a first seed strip and at least one second seed strip sequentially disposed toward a center of the seed crystal array, adjacent two of the plurality of the sub-seed crystals being spaced apart from each other to define a second gap communicating with the corresponding first gap, adjacent two of the plurality of the sub-seed crystals being in contact with the first seed strip.

5. A seed crystal laying method as set forth in claim 4, wherein the width of the first gap is h₁The width of the second gap is h₂Wherein, the h₁、h₂Satisfies the following conditions: h is not less than 0.5mm₁≤5mm，0.5mm≤h₂≤5mm。

6. The seed crystal laying method as set forth in claim 4, wherein adjacent two of the seed bars in each of the seed crystals are in contact.

7. The seed crystal laying method as set forth in claim 2, wherein a plurality of the seed crystals are arranged to be staggered from a plurality of the first seed crystals located on the side of the seed crystal array in the extending direction of the side so that each of the seed crystals covers at least one of the first gaps.

8. The seed crystal laying method as set forth in claim 7, wherein each of the seed crystals has an end surface displaced from the corresponding end surface of the first seed crystal by a distance a, wherein a satisfies: a is more than or equal to 0.5mm and less than or equal to 5 mm.

9. A seed crystal laying method as set forth in claim 7 wherein a plurality of said sub-seed crystals are arranged at intervals, each of said sub-seed crystals comprising a plurality of third seed strips arranged in sequence toward a center away from said seed crystal array.

10. A seed crystal placement method as set forth in claim 9, wherein adjacent two of the third seed strips in each of the seed crystals are in contact.

11. The seed crystal laying method as set forth in any one of claims 1 to 10, wherein the second seed crystal is plural, and at least one of the second seed crystals is provided on each of four sides of the seed crystal array.

12. A seed crystal placement method as claimed in claim 11, wherein a seed block is provided at least one of four corners of said seed crystal array, said seed block being located between ends of two adjacent second seed crystals.

13. The seed crystal placement method according to any one of claims 1 to 10, wherein each of the first seed crystals is a square seed crystal, each of the first seed crystals has a side length of L, wherein L satisfies: l is more than or equal to 125mm and less than or equal to 210 mm.

14. The seed crystal laying method according to any one of claims 1-10, wherein the second seed crystal has a length b and a width c, wherein b and c satisfy: b is more than or equal to 125mm and less than or equal to 210mm, and c is more than or equal to 5mm and less than or equal to 40 mm.

15. A seed crystal placement method as set forth in any one of claims 1 to 10, wherein each of the first seed crystals has a thickness s₁The thickness of the second seed crystal is s₂Wherein said s₁、s₂Satisfies the following conditions: s is not less than 5mm₁≤30mm，5mm≤s₂≤30mm。

16. A seed crystal placement method as claimed in any one of claims 1 to 10, wherein a plurality of said first seed crystals are arranged in an X row and Y column array, wherein X, Y satisfies: x is more than or equal to 4 and less than or equal to 9, and Y is more than or equal to 4 and less than or equal to 9.

17. A seed crystal placement method as claimed in any one of claims 1 to 10, wherein said second seed crystal comprises N fourth seed strips arranged in sequence along a center facing away from said array of seed crystals, wherein said N satisfies: n is more than or equal to 1 and less than or equal to 5.

Technical Field

The invention relates to the technical field of crystalline silicon ingots, in particular to a seed crystal laying method.

Background

The ingot casting single crystal (cast-mono wafer) is a silicon wafer which is prepared by adding single crystal seed crystals into a polycrystalline ingot furnace on the basis of a conventional polycrystalline ingot casting process, forming a square silicon ingot after directional solidification, and finally preparing a single crystal through links such as squaring, slicing and the like. Among them, the single crystal seed crystal plays a decisive role in the crystal silicon quality of the cast single crystal.

In the related technology, polycrystal is easily generated around the whole seed crystal layer due to stress, so that more polycrystal exists around the cast single crystal, and dislocation is easily generated due to mutual extrusion among the seed crystals in the ingot casting process, so that the quality of the crystalline silicon is low.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, an object of the present invention is to provide a seed crystal laying method, which can prevent the seed crystals from being squeezed against each other to generate dislocation, and can prevent polycrystal from being generated, so that the quality of crystalline silicon can be improved.

The seed crystal laying method comprises the following steps: laying a plurality of first seed crystals in an array arrangement mode to form a seed crystal array, and enabling two adjacent first seed crystals to be spaced from each other to define a first gap; laying at least one second seed formed in a stripe configuration at least one side of the seed array and extending the second seed along the at least one side of the seed array with the at least one second seed covering at least a portion of at least one of the first gaps.

According to the seed crystal laying method provided by the embodiment of the invention, by spacing two adjacent first seed crystals from each other to define the first gap and laying the second seed crystal at least one side edge of the seed crystal array and covering at least one part of the at least one first gap by the at least one second seed crystal, on one hand, the situation that a plurality of first seed crystals are pressed against each other to generate stress and generate dislocation at high temperature can be avoided, and on the other hand, the situation that polycrystal is generated at the at least one side edge of the seed crystal array can be avoided. In addition, the gas carrying impurities outside can be prevented from entering the seed crystal array through the first gap, so that the generation of defects can be reduced, and the quality of the crystalline silicon is improved.

According to some embodiments of the present invention, the second seed crystal includes a plurality of sub-seed crystals arranged in sequence along an extending direction of the side of the seed crystal array.

According to some embodiments of the present invention, a plurality of the sub-seeds corresponds one-to-one to a plurality of the first seeds located on the side of the seed array.

According to some embodiments of the present invention, each of the sub-seeds includes a first seed strip and at least one second seed strip sequentially disposed toward a center of the seed array, adjacent two of the sub-seeds being spaced apart from each other to define a second gap communicating with the corresponding first gap, adjacent two of the sub-seeds being in contact with the first seed strip.

According to some embodiments of the invention, the first gap has a width h₁The width of the second gap is h₂Wherein, the h₁、h₂Satisfies the following conditions: h is not less than 0.5mm₁≤5mm，0.5mm≤h₂≤5mm。

According to some embodiments of the invention, adjacent two of the seed bars in each of the sub-seeds are in contact.

According to some embodiments of the present invention, the plurality of seed crystals are arranged to be offset from the plurality of first seed crystals located on the side of the seed crystal array in the extending direction of the side so that each of the seed crystals covers at least one of the first gaps.

According to some embodiments of the invention, the end surface of each of the seed crystals is offset from the end surface of the corresponding first seed crystal by a distance a, wherein a satisfies: a is more than or equal to 0.5mm and less than or equal to 5 mm.

According to some embodiments of the invention, a plurality of the sub-seed crystals are arranged at intervals, and each of the sub-seed crystals comprises a plurality of third seed strips arranged in sequence along a direction away from the center of the seed crystal array.

According to some embodiments of the invention, adjacent two of the third seed strips in each of the sub-seeds are in contact.

According to some embodiments of the invention, the second seed crystal is a plurality of second seed crystals, and at least one second seed crystal is respectively arranged on four sides of the seed crystal array.

According to some embodiments of the invention, a seed block is disposed at least one of four corners of the seed crystal array, and the seed block is located between ends of two adjacent second seed crystals.

According to some embodiments of the invention, each of the first seed crystals is a square seed crystal, each of the first seed crystals has a side length L, wherein L satisfies: l is more than or equal to 125mm and less than or equal to 210 mm.

According to some embodiments of the invention, the second seed crystal has a length b and a width c, wherein b and c satisfy: b is more than or equal to 125mm and less than or equal to 210mm, and c is more than or equal to 5mm and less than or equal to 40 mm.

According to some embodiments of the invention, each of the first seed crystals has a thickness s₁The thickness of the second seed crystal is s₂Wherein said s₁、s₂Satisfies the following conditions: s is not less than 5mm₁≤30mm，5mm≤s₂≤30mm。

According to some embodiments of the invention, the plurality of first seed crystals are arranged in an X row and Y column array, wherein X, Y respectively satisfy: x is more than or equal to 4 and less than or equal to 9, and Y is more than or equal to 4 and less than or equal to 9.

According to some embodiments of the invention, the second seed crystal comprises N fourth seed strips arranged in sequence along a direction away from a center of the seed crystal array, wherein N satisfies: n is more than or equal to 1 and less than or equal to 5.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1a is a schematic flow diagram of a seed crystal placement method according to an embodiment of the present invention;

FIG. 1b is a schematic diagram of the structure of an array of seed crystals and a second seed crystal according to an embodiment of the present invention;

FIG. 2 is a schematic view of a partial structure of an array of seed crystals and a second seed crystal according to one embodiment of the invention;

fig. 3 is a schematic view of a partial structure of a seed array and a second seed according to another embodiment of the present invention.

Reference numerals:

1: a seed crystal array; 11: a first seed crystal; 12: a first gap; 13: a seed crystal block;

2: a second seed crystal; 21: seed crystal; 211: a first seed bar;

212: a second seed bar; 213: a second gap; 214: and a third seed bar.

Detailed Description

Embodiments of the present invention will be described in detail below, the embodiments described with reference to the drawings being illustrative, and the embodiments of the present invention will be described in detail below.

A method of laying seed crystals according to an embodiment of the present invention will be described below with reference to fig. 1a to 3. The seed crystal laying method can be used for laying single crystal seed crystals. In the following description of the present application, a method of laying seed crystals is explained by taking as an example that a single crystal seed crystal is laid.

As shown in fig. 1a to 3, a seed crystal laying method according to an embodiment of the present invention includes:

the plurality of first seed crystals 11 are laid in an array arrangement to constitute the seed crystal array 1, and adjacent two first seed crystals 11 are spaced apart from each other to define a first gap 12. In the description of the present invention, "a plurality" means two or more. Therefore, the dislocation generated at high temperature due to the stress generated by mutual extrusion of the first seed crystals 11 in the ingot casting process can be avoided, so that the generation of defects is avoided, and the quality of the crystalline silicon can be improved.

For example, twenty-five first seed crystals 11 are shown in the example of fig. 1b, and the twenty-five first seed crystals 11 may be arranged in a rectangular array of five rows and five columns. It is understood that twenty-five first seed crystals 11 are shown in fig. 1b for illustrative purposes, but it is obvious to those skilled in the art after reading the technical solution of the present application that the solution can be applied to other number of first seed crystals 11, which also falls within the scope of the present invention.

At least one second seed crystal 2 formed in a stripe structure is laid at least one side edge of the seed crystal array 1, and the second seed crystal 2 is made to extend along the at least one side edge of the seed crystal array 1, and the at least one second seed crystal 2 covers at least a part of the at least one first gap 12.

For example, in the example of fig. 1b, the second seed crystal 2 is provided at each of four sides of the seed crystal array 1, and the second seed crystal 2 is located outside the seed crystal array 1. Here, it should be noted that the direction "outer" is understood as a side away from the center of the seed crystal array 1, and the opposite direction is defined as "inner", i.e., a side toward the center of the seed crystal array 1.

When the seed crystal array 1 is laid at the bottom of the crucible, four side edges of the seed crystal array 1 can correspond to four side walls of the crucible one by one. Because the second seed crystal 2 is arranged between the inner side wall of the crucible and the seed crystal array 1, the gap between the seed crystal array 1 and the inner side wall of the crucible can be reduced, and the generation of polycrystal can be avoided. Furthermore, since multiple grains may grow on the inner sidewall of the crucible, the second seed crystal 2 may block the multiple grains from growing into the seed crystal array 1. Therefore, by arranging the second seed crystal 2, polycrystal generation at the at least one side edge of the seed crystal array 1 can be avoided, and the quality of the crystalline silicon can be improved.

It should be noted that "at least one second seed crystal 2 covers at least a portion of at least one first gap 12" means that one or more second seed crystals 2 may cover a portion of one first gap 12; alternatively, one or more second seed crystals 2 cover a portion of each first gap 12; still alternatively, one or more second seed crystals 2 completely cover a first gap 12; still alternatively, one or more second seed crystals 2 completely cover all of the first gaps 12; of course, it is also possible that some of the first gaps 12 are completely covered by one or more second seed crystals 2, and each of the remaining first gaps 12 is partially covered by one or more second seed crystals 2. With the arrangement, the external gas carrying impurities can be prevented from entering the seed crystal array 1 through the first gap 12, so that the quality of the crystalline silicon can be further ensured, and the generation of defects is reduced.

According to the seed crystal laying method of the embodiment of the invention, by spacing two adjacent first seed crystals 11 from each other to define the first gap 12, laying the second seed crystal 2 at least one side edge of the seed crystal array 1 and covering at least one part of the at least one first gap 12 with the at least one second seed crystal 2, on one hand, the plurality of first seed crystals 11 can be prevented from pressing against each other to generate stress and generate dislocation at high temperature, and on the other hand, polycrystal can be prevented from being generated at the at least one side edge of the seed crystal array 1. In addition, the external gas carrying impurities can be prevented from entering the seed crystal array 1 through the first gap 12, so that the generation of defects can be reduced, and the quality of crystalline silicon can be improved.

In some embodiments of the present invention, referring to fig. 2 and 3, the second seed crystal 2 includes a plurality of sub-seed crystals 21 arranged in sequence along the extending direction of the above-mentioned side of the seed crystal array 1. So set up, can reduce the length of every seed crystal 21 to can reduce the processing degree of difficulty of second seed crystal 2, convenient processing.

In some alternative embodiments of the present invention, in conjunction with fig. 2, a plurality of sub-seeds 21 are in one-to-one correspondence with the plurality of first seeds 11 located on the above-mentioned side of the seed array 1.

For example, in the example of fig. 1b and 2, the seed array 1 has four sides, five first seeds 11 are provided on each side of the seed array 1, and accordingly, five sub-seeds 21 are provided at each side of the seed array 1, and five sub-seeds 21 are provided outside the five first seeds 11, respectively. Wherein the length of each sub-seed crystal 21 may be equal to the length of the first seed crystal 11. During processing, each of the sub-seeds 21 may be formed by cutting a seed having the same size as the first seed 11. So set up, every sub-seed crystal 21 can be better backstop in the outside of the first seed crystal 11 that corresponds, when avoiding producing polycrystal, makes whole seed crystal array 1's structure more stable, and convenient processing.

In some embodiments of the present invention, as shown in fig. 2, each of the sub-seeds 21 includes a first seed strip 211 and at least one second seed strip 212 sequentially disposed toward the center of the seed array 1, adjacent two of the second seed strips 212 in the plurality of sub-seeds 21 are spaced apart from each other to define a second gap 213, the second gap 213 communicates with the corresponding first gap 12, and adjacent two of the first seed strips 211 in the plurality of sub-seeds 21 are in contact.

For example, in the example of fig. 2, each sub-seed 21 includes a first seed strip 211 and two second seed strips 212, the first seed strip 211 is located on one side of the two second seed strips 212 away from the center of the seed array 1, the second seed strips 212 of adjacent two sub-seeds 21 are spaced apart from each other along the extension direction of the side edges, and the first seed strips 211 of adjacent two sub-seeds 21 are in contact with each other. Therefore, by defining the second gap 213 between two adjacent second seed rods 212 in the plurality of seed crystals 21, mutual extrusion due to volume expansion between two adjacent second seed rods 212 in the plurality of seed crystals 21 during the ingot casting process can be avoided, so that generation of dislocation at high temperature due to stress generation between two adjacent second seed rods 212 can be avoided, and generation of defects can be avoided. Moreover, by contacting two adjacent first seed strips 211 in the plurality of seed crystals 21, the gas carrying impurities can be blocked outside the seed crystal array 1, so that the impurities can be prevented from entering the inside of the seed crystal array 1, and the generation of defects can be further avoided.

Alternatively, referring to fig. 2, the first gap 12 has a width h₁A second gap 213 having a width h₂Wherein h is₁、h₂Satisfies the following conditions: h is not less than 0.5mm₁≤5mm，0.5mm≤h₂Less than or equal to 5 mm. For example, when h₁If the first gap 12 is too small < 0.5mm, the adjacent two first seed crystals 11 may be squeezed during the ingot casting process, thereby possibly generating dislocation conduction at high temperatureCausing the occurrence of defects; when h is generated₁When the thickness is more than 5mm, the first gap 12 is too large, and crystal growth can occur at the first gap 12, so that the quality of the crystal silicon is too poor; when h is generated₂If the second gap 213 is too small < 0.5mm, during the ingot casting process, the adjacent two second seed crystal strips 212 in the plurality of seed crystals 21 may be squeezed, so that dislocation may be generated at high temperature to cause defects; when h is generated₂At > 5mm, the second gap 213 is too large and crystal growth may occur at the second gap 213, resulting in too poor a quality of the crystalline silicon. Thereby, by making h₁、h₂Satisfies the following conditions: h is not less than 0.5mm₁≤5mm、0.5mm≤h₂Less than or equal to 5mm, dislocation can be avoided between two adjacent first seed crystals 11 and two adjacent second seed crystal strips 212, so that defects can be avoided, and the quality of crystalline silicon can be improved. Wherein h is₁And h₂May be equal.

Alternatively, in conjunction with fig. 2, two adjacent seed bars in each sub-seed 21 are in contact. Note that "seed bar" refers to the first seed bar 211 and the second seed bar 212 described above. For example, in the example of fig. 2, two adjacent seed bars in each seed bar are arranged in sequence in the width direction of the seed bar, and the first seed bar 211 in each seed crystal 21 is in contact with the adjacent second seed bar 212 and two adjacent second seed bars 212 are in contact. Since the widths of first and second seed bars 211 and 212 are much smaller than the lengths, first and second seed bars 211 and 212 hardly undergo volume expansion in the width direction, and thus dislocation is not generated. Therefore, the structure of the seed crystals 21 is more compact and the arrangement is convenient while the dislocation between two adjacent seed crystal strips in each seed crystal 21 is ensured.

In other embodiments of the present invention, as shown in fig. 3, a plurality of sub-seeds 21 are disposed to be offset from a plurality of first seeds 11 located on the side of the seed array 1 in the extending direction of the side so that each sub-seed 21 covers at least one first gap 12. That is, each of the sub-seeds 21 may cover one first gap 12, or may cover a plurality of first gaps 12. For example, in the example of fig. 3, five sub-seeds 21 may be provided at each side of the seed array 1, and the five sub-seeds 21 may correspond one-to-one to the five first seeds 11 located on each side of the seed array 1, with each sub-seed 21 covering one first gap 12. Therefore, through the arrangement, gas can be prevented from entering the seed crystal array 1 through the first gap 12, so that deposition of impurities can be avoided, and high quality of crystalline silicon is guaranteed.

Alternatively, as shown in fig. 3, the end face of each sub-seed crystal 21 is offset from the end face of the corresponding first seed crystal 11 by a distance a, where a satisfies: a is more than or equal to 0.5mm and less than or equal to 5 mm. For example, in the example of fig. 3, two adjacent seed crystals 21 are spaced apart from each other, and the gap between two adjacent seed crystals 21 is not communicated with the corresponding first gap 12, and the gap between two adjacent seed crystals 21 is staggered from the corresponding first gap 12 by a distance a. For example, when a is less than 0.5mm, the offset distance between the end surface of each seed crystal 21 and the corresponding end surface of the first seed crystal 11 is too small, which may cause gas impurities to enter the interior of the seed crystal array 1 through the first gap 12 during ingot casting; when a is larger than 5mm, the offset distance between the end face of each seed crystal 21 and the end face of the corresponding first seed crystal 11 is too large, and defects are likely to occur. Thus, by making a satisfy: a is more than or equal to 0.5mm and less than or equal to 5mm, so that defects can be avoided while gas is prevented from entering the interior of the seed crystal array 1, and the quality of the crystalline silicon can be further improved.

In some embodiments of the present invention, referring to fig. 3, a plurality of sub-seeds 21 are arranged at intervals, and each sub-seed 21 includes a plurality of third seed bars 214 arranged in sequence toward the center away from the seed array 1. Therefore, the plurality of seed crystals 21 are arranged at intervals, so that mutual extrusion caused by volume expansion between two adjacent seed crystals 21 in the ingot casting process can be avoided, dislocation generated between two adjacent seed crystals 21 due to stress generation at high temperature can be avoided, and defects can be avoided.

Alternatively, adjacent two third seed bars 214 in each sub-seed 21 are in contact. For example, in the example of fig. 3, two adjacent third seed bars 214 in each seed bar are sequentially arranged in the width direction, and since the width of the third seed bar 214 is much smaller than the length, the third seed bar 214 hardly undergoes volume expansion in the width direction, and thus dislocation is not generated. So set up, when guaranteeing that can not produce the dislocation between the adjacent two third seed crystal strips 214 in every sub-seed crystal 21, make the structure of sub-seed crystal 21 compacter, the convenient arrangement.

Alternatively, as shown in fig. 1 b-3, the number of the second seed crystals 2 may be multiple, and at least one second seed crystal 2 is respectively arranged on four sides of the seed crystal array 1. For example, in the example of fig. 1b, a plurality of second seed crystals 2 are wrapped around the outer periphery of the seed crystal array 1. From this, the second seed crystal 2 of four sides departments of seed crystal array 1 can reduce the distance between the inside wall of seed crystal array 1 and the crucible that corresponds, and can block that the polycrystal grows to seed crystal array 1 from the side of seed crystal array 1 to can avoid four sides departments of seed crystal array 1 to produce the polycrystal, thereby can further promote crystalline silicon's quality.

Further, referring to fig. 1b, a seed block 13 is disposed at least one of four corners of the seed crystal array 1, and the seed block 13 is located between ends of two adjacent second seed crystals 2. For example, four seed blocks 13 are shown in the example of fig. 1b, and the four seed blocks 13 are respectively disposed at four corners of the seed array 1. Thereby, the seed crystal piece 13 can fill the gap between the end portions of the adjacent two second seed crystals 2, so that the generation of polycrystals can be further avoided.

In some alternative embodiments of the present invention, in conjunction with fig. 1b, each first seed crystal 11 may be a square seed crystal, each first seed crystal 11 having a side length L, wherein L satisfies: l is more than or equal to 125mm and less than or equal to 210 mm. For example, when L < 125mm, the side length of each first seed crystal 11 is too small, so that the output power of the photovoltaic module may be reduced; when L > 210mm, the side length of each first seed crystal 11 is too large, which may increase the difficulty of the glass process and reduce the load capacity of the photovoltaic module. Thus, by making L satisfy: l is more than or equal to 125mm and less than or equal to 210mm, so that the photovoltaic module can have larger output power and can reduce the difficulty of glass manufacturing process.

Optionally, the length of the second seed crystal 2 is b, and the width of the second seed crystal 2 is c, where b and c satisfy: b is more than or equal to 125mm and less than or equal to 210mm, and c is more than or equal to 5mm and less than or equal to 40 mm. Specifically, for example, when c < 5mm, the width of the second seed crystal 2 is too small, so that the gap between the seed crystal array 1 and the inner wall of the crucible may be too large, resulting in the generation of polycrystal; when c > 40mm, the width of the second seed crystal 2 is too large, which may result in too small a gap between the second seed crystal 2 and the inner wall of the crucible, causing the crucible to crack due to too much force. Thus, by making the width c of the second seed crystal 2 satisfy: c is more than or equal to 5mm and less than or equal to 40mm, thereby avoiding the generation of polycrystal, ensuring the normal use of the crucible and prolonging the service life of the crucible.

Optionally, each first seed crystal 11 has a thickness s₁The second seed crystal 2 has a thickness s₂Wherein s is₁、s₂Satisfies the following conditions: s is not less than 5mm₁≤30mm，5mm≤s₂Less than or equal to 30 mm. Wherein the thickness of the second seed crystal 2 refers to the dimension of the second seed crystal 2 in the height direction of the crucible. For example, when s₂When the thickness of the second seed crystal 2 is less than 5mm, the second seed crystal 2 enters a crystal growth stage without being completely melted, so that polycrystal generation can be caused; when s is₂When the thickness is more than 30mm, the thickness of the second seed crystal 2 is too large, and in the charging process, the pressure of the second seed crystal 2 on the crucible is large due to the extrusion of the upper silicon material, so that the crucible is not favorable. Wherein s is₁And s₂May be equal. Thereby, by making the thickness s of the second seed crystal 2₂S is less than or equal to 5mm₂Less than or equal to 30mm, and can reduce the extrusion of the second seed crystal 2 to the crucible while avoiding generating polycrystal.

In some embodiments of the present invention, the plurality of first seed crystals 11 are arranged in an X row and Y column array, wherein X, Y respectively satisfy: x is more than or equal to 4 and less than or equal to 9, and Y is more than or equal to 4 and less than or equal to 9. Wherein X, Y may or may not be equal. When X and Y are equal, the plurality of first seed crystals 11 may be arranged in a square array, for example, the arrangement of the first seed crystals 11 is 5 × 5, 6 × 6, 7 × 7, or 8 × 8.

In some embodiments of the invention, referring to fig. 1 b-3, the second seed crystal 2 comprises N fourth seed strips arranged in sequence along a center facing away from the seed crystal array 1, wherein N satisfies: n is more than or equal to 1 and less than or equal to 5. For example, three fourth seed stripes are shown in the example of fig. 1 b-3, which are sequentially arranged in a direction away from the center of the seed crystal array 1. When N > 5, the structure of the second seed crystal 2 is excessively complicated. Thus, by making N satisfy: n is more than or equal to 1 and less than or equal to 5, so that the second seed crystal 2 has a simple structure and is convenient to arrange while polycrystalline generation is avoided.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", and the like, indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

In the description of the present invention, "the first feature", "the second feature", "the third feature", and "the fourth feature" may include one or more of the features.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.