阅读说明：本技术 用于铸造单晶硅的籽晶铺设方法、单晶硅锭及其铸造方法 (Seed crystal laying method for casting monocrystalline silicon, monocrystalline silicon ingot and casting method thereof ) 是由 雷琦 何亮 李建敏 程小娟 邹贵付 甘胜泉 陈仙辉 于 2020-04-29 设计创作，主要内容包括：本发明提供了一种铸造单晶硅的籽晶铺设方法,包括：提供坩埚,在所述坩埚底部间隔铺设上下表面平整的垫片,形成垫片层；在所述垫片层上铺设至少一个支撑片,以形成覆盖所述垫片及其之间空隙的支撑片层；依次交替设置所述垫片层和支撑片层,以形成(AB)-(n)排布形式的架空结构,其中,A为垫片层,B为支撑片层,n为大于或等于1的整数；在所述架空结构上铺设单晶硅籽晶,形成籽晶层。通过在籽晶层上设置价格便宜的架空结构,可以减少所用籽晶的数量、降低单晶硅的铸造成本,并降低所得单晶硅锭的尾部红区。本发明还提供了一种单晶硅锭及其铸造方法。(The invention provides a seed crystal laying method for casting monocrystalline silicon, which comprises the following steps: providing a crucible, and paving gaskets with flat upper and lower surfaces at intervals at the bottom of the crucible to form a gasket layer; laying at least one support sheet on the gasket layer to form a support sheet layer covering the gasket and the gap between the gaskets; alternately arranging the shim layer and the support sheet layer in sequence to form (AB) n The overhead structure is in an arrangement form, wherein A is a gasket layer, B is a support sheet layer, and n is an integer greater than or equal to 1; and laying monocrystalline silicon seed crystals on the overhead structure to form a seed crystal layer. By providing an inexpensive overhead structure on the seed layer, the number of seed crystals used can be reduced, and the number of seed crystals used can be reducedThe casting cost of the monocrystalline silicon is reduced, and the tail red area of the obtained monocrystalline silicon ingot is reduced. The invention also provides a monocrystalline silicon ingot and a casting method thereof.)

1. A seed crystal placement method for casting single crystal silicon, comprising:

providing a crucible, and paving gaskets with flat upper and lower surfaces at intervals at the bottom of the crucible to form a gasket layer;

laying at least one support sheet on the gasket layer to form a support sheet layer covering the gasket and a gap between the gaskets; wherein the shim and the support sheet are independently selected from high purity flakes having a melting point of 1400 ℃ or higher and a purity of 99.99% or higher;

alternately arranging the shim layer and the support sheet layer in sequence to form (AB)_nThe overhead structure is in an arrangement form, wherein A is a gasket layer, B is a support sheet layer, and n is an integer greater than or equal to 1;

and laying monocrystalline silicon seed crystals on the overhead structure to form a seed crystal layer.

2. A seed crystal placement method as defined in claim 1, wherein n is an integer of 1 to 4.

3. A seed crystal placement method as claimed in claim 1 or 2, wherein the height of said overhead structure is 10-120 mm.

4. A seed crystal placement method as set forth in claim 3, wherein the thickness of the spacer layer is 5-15 mm; the thickness of the support sheet layer is 5-15 mm.

5. A seed crystal placement method as set forth in claim 1, wherein a spacing between adjacent two of said spacers is smaller than a width of said support pieces.

6. A seed crystal laying method as set forth in claim 5, wherein the spacing between adjacent two of said spacers is 50mm to 150 mm; the width of the supporting piece is 100-200 mm.

7. The seed crystal placement method according to claim 1, wherein the spacer and the support sheet are independently selected from at least one of a silicon wafer having a purity of more than 99.9999%, a quartz wafer, a silicon carbide wafer, a silicon nitride wafer, an aluminum oxide wafer, a zirconium oxide wafer, an aluminum nitride wafer, and a boron nitride wafer.

8. A seed crystal laying method as claimed in claim 1, wherein when the number of the support pieces is two or more, a plurality of support pieces are spliced and laid.

9. A method for casting a single crystal silicon ingot, comprising the steps of:

providing a crucible, and paving gaskets with flat upper and lower surfaces at intervals at the bottom of the crucible to form a gasket layer;

laying at least one support sheet on the gasket layer to form a support sheet layer covering the gasket and a gap between the gaskets;

alternately arranging the shim layer and the support sheet layer in sequence to form (AB)_nAn overhead structure in an arrangement form, wherein A is a gasket layer, and B is a supportA strut layer, n is an integer greater than or equal to 1;

laying monocrystalline silicon seed crystals on the overhead structure to form a seed crystal layer;

filling silicon material on the seed crystal layer, heating to melt the silicon material in the crucible to form silicon melt, adjusting a thermal field in the crucible to form a supercooled state when the seed crystal layer is not completely melted, so that the silicon melt starts to grow crystals on the basis of the seed crystal layer, and annealing and cooling to obtain the single crystal silicon ingot after all the silicon melt is crystallized.

10. A single crystal silicon ingot produced by the casting method according to claim 9.

Technical Field

The invention relates to the field of semiconductor manufacturing, in particular to a seed crystal laying method for casting monocrystalline silicon, a monocrystalline silicon ingot and a casting method thereof.

Background

Since the century, the photovoltaic industry has become the fastest growing high-tech industry in the world. Among various solar cells, crystalline silicon (single crystal, polycrystal) solar cells play an extremely important role. Among them, as one of main raw materials for producing a solar cell, a method for manufacturing single crystal silicon includes a czochralski method and a casting method, wherein the casting method is a mainstream method for manufacturing single crystal silicon due to a large single charge amount and a low production cost.

The existing casting method of monocrystalline silicon is to lay monocrystalline seed crystals at the bottom of a quartz crucible, keep the seed crystals incompletely melted in the melting stage, and perform seeding growth on the monocrystalline seed crystals to obtain silicon ingots, which can be called monocrystalline silicon ingots or quasi-monocrystalline silicon ingots. But the thickness of the seed crystal used for casting the monocrystalline silicon at present is usually more than 30mm, which increases the cost of the casting the monocrystalline silicon to a certain extent; in addition, the monocrystalline silicon seed crystal is in direct contact with the quartz crucible, and impurities in the quartz crucible are easily diffused into the monocrystalline silicon seed crystal under high temperature conditions, so that the length of a bottom lifetime defective region (i.e., a tail red region) in the ingot casting monocrystalline silicon ingot is increased.

Disclosure of Invention

In view of this, the invention provides a method for casting a monocrystalline silicon ingot and a method for laying seed crystals for casting monocrystalline silicon, so as to reduce the number of seed crystals used in the conventional casting of monocrystalline silicon, reduce the casting cost, and reduce the tail red zone of the cast monocrystalline silicon.

In a first aspect, the present invention provides a seed crystal placement method for casting single crystal silicon, comprising:

providing a crucible, and paving gaskets with flat upper and lower surfaces at intervals at the bottom of the crucible to form a gasket layer;

laying at least one support sheet on the gasket layer to form a support sheet layer covering the gasket and a gap between the gaskets;

alternately arranging the shim layer and the support sheet layer in sequence to form (AB)_nThe overhead structure is in an arrangement form, wherein A is a gasket layer, B is a support sheet layer, and n is an integer greater than or equal to 1;

and laying monocrystalline silicon seed crystals on the overhead structure to form a seed crystal layer.

Optionally, the height of the overhead structure is not less than 10 mm. Preferably 10-120 mm. More preferably 10 to 30 mm.

Optionally, n is an integer from 1 to 4 (n ═ 1, 2, 3, or 4).

Optionally, the thickness of the shim layer is 5-15 mm. Further, the thickness deviation of the gasket in the gasket layer is less than 1 mm.

Optionally, the spacers in the spacer layer may be tiled in a single layer, or a plurality of spacers may be stacked to form a stacked structure, and then the stacked structure is disposed at an interval to form the spacer layer. At least one void is formed in each gasket layer.

Optionally, a spacing between two adjacent spacers (i.e., a width of a gap between the spacers) is smaller than a width of the support sheet. Further, the distance between two adjacent gaskets is 50mm-150 mm.

Optionally, the upper and lower surfaces of the gasket are square, rectangular, triangular or circular in shape. Preferably, the gasket is in the shape of a cuboid or a cube.

Optionally, the lateral ruler of the shimCun (i.e., length, width, or diameter in the horizontal direction, etc.) is 10-30 mm. Furthermore, the laying density of the gaskets at the bottom of the crucible is 20-40/m²。

Optionally, the support piece has a width of 100-200 mm.

Optionally, the support sheet layer has a thickness of 5-15 mm.

In the present invention, the spacer and the support sheet are independently selected from high-purity sheets having a melting point of 1400 ℃ or higher and a purity of 99.99% or higher. Optionally, the gasket and the support sheet are independently selected from at least one of a silicon wafer with purity of more than 99.9999%, a quartz sheet, a silicon carbide sheet, a silicon nitride sheet, an aluminum oxide sheet, a zirconium oxide sheet, an aluminum nitride sheet and a boron nitride sheet.

Preferably, the gasket is selected from at least one of a silicon wafer (polycrystalline silicon wafer, monocrystalline silicon wafer), a quartz wafer, a silicon carbide wafer and a silicon nitride wafer, and the purity is more than 99.9999%. Further preferably, the spacer is a silicon wafer.

Preferably, the support wafer is selected from a polycrystalline silicon wafer or a monocrystalline silicon wafer, and the purity is more than 99.9999%.

Optionally, when the number of the support sheets is more than two, the support sheets are spliced and laid. At the moment, when the support sheet layers are formed, the support sheets are ensured to be in close contact as much as possible, and the gap at the splicing position is minimized.

In the invention, during the process of arranging the overhead structure, the overhead structure may not be in close contact with the crucible side wall, and at the moment, a micro gap may exist between the overhead structure and the crucible side wall. Optionally, after the depositing and forming the seed layer, the method further includes: and filling a gap between the seed crystal layer and the side wall of the crucible with crushed polysilicon. Preferably, an upper plane of the polysilicon scraps is flush with an upper surface of the seed layer.

Optionally, the thickness of the seed layer is less than 30mm, preferably less than or equal to 20 mm. More preferably 10 to 20 mm.

Preferably, the crucible is a square crucible.

Optionally, the crucible is a ceramic crucible, a quartz crucible, a graphite crucible, a silicon nitride crucible, a silicon carbide crucible, a molybdenum crucible, or a tungsten crucible. Preferably, the crucible is a quartz crucible.

Optionally, the bottom and the side walls of the crucible are provided with a silicon nitride coating. The silicon nitride coating is provided by a conventional technique, and the manner, thickness, and the like of the silicon nitride coating are not particularly limited.

According to the seed crystal laying method for casting monocrystalline silicon, before monocrystalline silicon seed crystals are laid, the gasket layers and the support sheet layers are sequentially and alternately arranged at the bottom of the crucible, so that an overhead structure comprising at least one gasket layer and at least one support sheet layer is formed, the overhead structure is low in price, the seed crystal consumption required for casting monocrystalline silicon ingots can be remarkably reduced, the casting cost of the monocrystalline silicon is reduced, meanwhile, the pollution of impurities in the crucible to the formed silicon ingots can be reduced, and further, the tail red zone of ingot casting monocrystalline is reduced.

In a second aspect, the present invention provides a method of casting a single crystal silicon ingot, comprising:

providing a crucible, and paving gaskets with flat upper and lower surfaces at intervals at the bottom of the crucible to form a gasket layer;

laying at least one support sheet on the gasket layer to form a support sheet layer covering the gasket and a gap between the gaskets;

alternately arranging the shim layer and the support sheet layer in sequence to form (AB)_nThe overhead structure is in an arrangement form, wherein A is a gasket layer, B is a support sheet layer, and n is an integer greater than or equal to 1;

laying monocrystalline silicon seed crystals on the overhead structure to form a seed crystal layer;

filling silicon material on the seed crystal layer, heating to melt the silicon material in the crucible to form silicon melt, adjusting a thermal field in the crucible to form a supercooled state when the seed crystal layer is not completely melted, so that the silicon melt starts to grow crystals on the basis of the seed crystal layer, and annealing and cooling to obtain the single crystal-like silicon ingot after all the silicon melt is crystallized.

The steps of forming the overhead structure and forming the seed layer are as described in the first aspect of the present invention and will not be described herein.

In the process of heating the silicon material in the crucible, the gasket layer and the support sheet layer in the overhead structure are not melted, so that the seed crystal layer can be well supported, and impurities in the crucible can be prevented from diffusing into the molten silicon melt.

Optionally, during the heating to melt the silicon material to form the silicon melt, the temperature at the top of the crucible is 1510 ℃ to 1530 ℃ and the temperature at the bottom of the crucible is 1300 ℃ to 1360 ℃.

According to the casting method of the monocrystalline silicon ingot, provided by the second aspect of the invention, the overhead structure formed by the gasket layer and the support sheet layer alternately arranged between the bottom of the crucible and the seed crystal layer is adopted, so that the number of seed crystals used in the casting of the monocrystalline silicon at present is reduced, the casting cost is reduced, and the tail red area of the monocrystalline silicon ingot obtained by casting is reduced; the obtained single crystal silicon ingot has less red zone at the tail part, less impurities and higher quality.

In a third aspect, the invention provides a single crystal silicon ingot prepared by the casting method of the second aspect of the invention.

The single crystal silicon ingot obtained in the third aspect of the present invention has fewer impurities, fewer red regions (regions having a lifetime of less than 3 μ s) at the tail, a long minority carrier lifetime, and good quality.

Drawings

FIG. 1 is a schematic view of a crucible before charging in the production of a single crystal silicon ingot in example 1 of the present invention;

FIG. 2 is a minority carrier lifetime distribution diagram of a single crystal silicon provided in example 2 of the present application;

FIG. 3 is a schematic view showing the arrangement of seed crystals of single crystal silicon in example 3 of the present invention.

Detailed Description

The examples of the present application are further illustrated below in various examples. The present embodiments are not limited to the following specific examples.

Example 1

Referring to fig. 1, a seed crystal placement method for casting single crystal silicon includes:

providing a quartz crucible with the bottom area of 890mm by 890mm, spraying silicon nitride coatings on the bottom and the side walls of the crucible, and paving a plurality of polycrystalline silicon gaskets with the length and width of 20mm by 20mm, the thickness of 5mm and the purity of 99.9999% at intervals on the bottom 1 of the crucible to obtain gasket layers 21 which are paved on the bottom of the crucible, wherein the interval between the gaskets is 120 mm;

tightly splicing and laying a plurality of polysilicon support sheets with the length and width of 140mm by 140mm and the thickness of 10mm on the gasket layer 21 to form a support sheet layer 22 which covers each gasket and gaps among the gaskets; wherein, the gasket layer 21 and the support sheet layer 22 form an overhead structure 2;

monocrystalline silicon seed crystals with the length and width of 140mm x 140mm and the thickness of 15mm are spliced and laid on the polycrystalline silicon support sheet layer 22 of the overhead structure 2 according to a 6 x 6 mode, and the adjacent monocrystalline silicon seed crystals are closely contacted until the bottom of the crucible is fully paved to form the seed crystal layer 3.

Example 2

A method of casting a single crystal silicon ingot, comprising the steps of:

(1) an overhead structure 2 and a seed crystal layer 3 are sequentially formed at the bottom 1 of a crucible in the manner of example 1, and fig. 1 is a schematic diagram of the crucible before charging;

(2) filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

Effects of the embodiment

In order to verify the effect of the embodiment of the invention, the invention is also provided with comparative examples 1 and 2.

Comparative example 1

Comparative example 1 is a method of regrowing single crystal silicon by directly laying a seed layer on the bottom of a crucible, specifically comprising:

paving monocrystalline silicon seed crystals with the length and width of 140mm x 140mm and the thickness of 30mm on the surface of the silicon nitride coating at the bottom of the quartz crucible with the bottom area of 890mm x 890mm according to a 6 x 6 mode, and closely splicing adjacent monocrystalline silicon seed crystals until the bottom of the crucible is fully paved to form a seed crystal layer;

filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

Comparative example 2

A method of casting a single crystal silicon ingot, comprising the steps of:

tightly splicing and laying a plurality of polycrystalline silicon supporting sheets with the length and width of 140mm × 140mm and the thickness of 10mm on the surface of the silicon nitride coating at the bottom of the quartz crucible with the bottom area of 890mm × 890mm to form a supporting sheet layer with the thickness of 10 mm;

laying monocrystalline silicon seed crystals with the length and width of 140mm by 140mm and the thickness of 20mm according to a 6 x 6 mode, and closely splicing adjacent monocrystalline silicon seed crystals until the bottom of the crucible is fully paved to form a seed crystal layer;

filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

The silicon ingot prepared in example 1 was cut to obtain a silicon block and tested for minority carrier lifetime, and the structure is shown in fig. 2. As is apparent from fig. 2, the silicon single crystal ingot prepared by the method of example 1 of the present application has good uniformity of minority carrier lifetime, an average minority carrier lifetime of not less than 7 μ s, a small area of a region with low minority carrier lifetime (about 5%), a tail red region (region with lifetime of less than 3 μ s) of 42mm, a length of the tail red region of 5mm less than that of the silicon single crystal ingot of comparative example 1, and a length of the tail red region of 10mm less than that of the silicon single crystal ingot of comparative example 2.

In addition, the area ratio of the whole single crystal in the single crystal silicon ingot reaches more than 90%, and dislocation and impurities are less. The silicon block is cut into silicon wafers to prepare the solar cell, the average cell conversion efficiency of the solar cell reaches more than 21.5%, and the cell efficiency is respectively improved by more than 0.5% and 0.7% compared with the cell efficiency prepared by the monocrystalline silicon wafer of the comparison ratio 1-2.

Example 3

Referring to fig. 3, a seed crystal placement method for casting single crystal silicon includes:

(1) providing a quartz crucible with the bottom area of 890mm by 890mm, spraying silicon nitride coatings on the bottom and the side walls of the crucible, paving a plurality of polycrystalline silicon gaskets with the length and width of 20mm by 20mm, the thickness of 5mm and the purity of 99.9999% at intervals on the bottom 1 of the crucible to obtain a first gasket layer 21 which is paved on the bottom of the crucible, wherein the interval between every two gaskets is 120 mm;

(2) tightly splicing and laying a plurality of polysilicon support sheets with the length and width of 140mm by 140mm and the thickness of 10mm on the gasket layers to form a first support sheet layer 22 which covers each gasket and gaps among the gaskets;

(3) sequentially repeating the steps (1) to (2) for 1 time respectively to form the overhead structure 2, wherein the overhead structure comprises a first gasket layer 21, a first support sheet layer 22, a second gasket layer 23 and a second support sheet layer 24;

monocrystalline silicon seed crystals with the length and width of 140mm x 140mm and the thickness of 20mm are laid on the polycrystalline silicon support sheet layer 24 of the overhead structure 2 in a 6 x 6 mode, and the adjacent monocrystalline silicon seed crystals are closely spliced until the bottom of the crucible is fully paved to form the seed crystal layer 3.

Example 4

A method of casting a single crystal silicon ingot, comprising the steps of:

(1) forming an overhead structure 2 with the thickness of 30mm and a seed crystal layer 3 with the thickness of 20mm on the bottom 1 of the crucible in sequence according to the mode of the embodiment 3, and filling gaps between the seed crystal layer 3 and the side walls of the crucible 1 with polysilicon crushed aggregates 4 after the seed crystal layer 3 is formed, and referring to fig. 3;

(2) filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

The monocrystalline silicon ingot obtained by casting in the example 4 is cut to obtain a silicon block, the minority carrier lifetime is tested, the minority carrier lifetime is good in uniformity, and the length of a red area at the tail of the silicon ingot is reduced by 10mm compared with that of the comparative example 1.

Example 5

Referring to fig. 1, a seed crystal placement method for casting single crystal silicon includes:

providing a quartz crucible with the bottom area of 990mm, spraying silicon nitride coatings on the bottom and the side wall of the crucible, paving a plurality of polycrystalline silicon gaskets with the length and width of 30mm, the thickness of 10mm and the purity of 99.9999% on the bottom 1 of the crucible at intervals to obtain gasket layers 21 which are paved on the bottom of the crucible, wherein the interval between every two gaskets is 140 mm;

tightly splicing and laying a plurality of polysilicon support sheets with the length and width of 160mm by 160mm and the thickness of 10mm on the gasket layer 21 to form a support sheet layer 22 which covers each gasket and gaps among the gaskets; wherein, the gasket layer 21 and the support sheet layer 22 form an overhead structure 2;

monocrystalline silicon seed crystals with the length and width of 160mm x 160mm and the thickness of 20mm are spliced and laid on the polycrystalline silicon support sheet layer 22 of the overhead structure 2 according to a 6 x 6 mode, and the adjacent monocrystalline silicon seed crystals are closely contacted until the bottom of the crucible is fully paved to form the seed crystal layer 3.

Example 6

A method of casting a single crystal silicon ingot, comprising the steps of:

(1) forming an overhead structure and a seed crystal layer at the bottom of the crucible in sequence according to the mode of the embodiment 5; filling a gap between the seed crystal layer and the side wall of the crucible with a silicon chip material;

(2) filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

The monocrystalline silicon ingot obtained by casting in the example 6 is cut to obtain a silicon block, the minority carrier lifetime is tested, the minority carrier lifetime is good in uniformity, and the length of a red area at the tail of the silicon ingot is reduced by 4mm compared with that of the comparative example 1.

Example 7

Referring to fig. 1, a seed crystal placement method for casting single crystal silicon includes:

providing a quartz crucible with the bottom area of 990mm, spraying silicon nitride coatings on the bottom and the side wall of the crucible, paving a plurality of polycrystalline silicon gaskets with the length and width of 20mm, the thickness of 5mm and the purity of 99.9999% on the bottom 1 of the crucible at intervals to obtain gasket layers 21 which are paved on the bottom of the crucible, wherein the interval between every two gaskets is 140 mm;

tightly splicing and laying a plurality of polysilicon support sheets with the length and width of 160mm by 160mm and the thickness of 10mm on the gasket 21 layer to form a support sheet layer 22 which covers each gasket and gaps among the gaskets; wherein, the gasket layer 21 and the support sheet layer 22 form an overhead structure 2;

monocrystalline silicon seed crystals with the length and width of 160mm x 160mm and the thickness of 15mm are laid on the polycrystalline silicon support sheet layer 22 of the overhead structure 2 according to a 6 x 6 mode, and the adjacent monocrystalline silicon seed crystals are closely spliced until the bottom of the crucible is fully paved to form the seed crystal layer 3.

Example 8

A method of casting a single crystal silicon ingot, comprising the steps of:

(1) forming an overhead structure and a seed crystal layer at the bottom of the crucible in sequence according to the mode of the embodiment 7; filling a gap between the seed crystal layer and the side wall of the crucible with a silicon chip material;

(2) filling a silicon material on the seed crystal layer, and heating to melt the silicon material in the crucible into a silicon melt; detecting seed crystals through a quartz rod during ingot casting, adjusting a thermal field in a crucible to form a supercooled state when the seed crystals in a seed crystal layer are not completely melted so as to enable the silicon melt to start crystal growth on the basis of the seed crystal layer, and annealing and cooling after all the silicon melt is crystallized to obtain the single crystal silicon ingot.

The monocrystalline silicon ingot obtained by casting in the example 8 is cut to obtain a silicon block, the minority carrier lifetime is tested, the minority carrier lifetime is good in uniformity, and the length of a red area at the tail of the silicon ingot is reduced by 7mm compared with that of the comparative example 1.

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. Therefore, the protection scope of the present patent shall be subject to the appended claims.