CN119640390B

CN119640390B - A high-strength seed crystal for large-diameter single-crystal silicon and a preparation method thereof

Info

Publication number: CN119640390B
Application number: CN202510176871.7A
Authority: CN
Inventors: 陶莹
Original assignee: Beijing Maizhuji Technology Co ltd
Current assignee: Beijing Jiakeer Technology Co.,Ltd.
Priority date: 2025-02-18
Filing date: 2025-02-18
Publication date: 2025-05-27
Anticipated expiration: 2045-02-18
Also published as: CN119640390A

Abstract

The invention belongs to the technical field of seed crystal manufacture, and particularly relates to a high-strength seed crystal for large-diameter monocrystalline silicon and a preparation method thereof, wherein the high-strength seed crystal for large-diameter monocrystalline silicon comprises the following raw materials in parts by weight, 30 parts of silicon liquid in a first seed crystal region, 20 parts of silicon liquid in a second heavily doped region and 10 parts of silicon liquid in a third lightly doped region; the invention adopts a unique partition design to improve the high-strength seed crystal performance for large-diameter monocrystalline silicon, introduces simple substance carbon for reaction of silicon carbide and silicon at high temperature in a first seed crystal region to block dislocation, strengthen crystal boundary and improve strength and toughness, improves seed crystal quality by means of high heat conductivity, simultaneously introduces silicon nitride to generate Si ₂N₂ O under a low oxygen condition to form covalent bonds with simple substance carbon, introduces heavy doping atoms to form defects in a second heavy doping region to strengthen the combination with carbon in the first seed crystal region, and provides sites for light doping in a third light doping region to combine heavy doping with light doping, thereby avoiding the negative influence of heavy doping on the quality of monocrystalline silicon.

Description

High-strength seed crystal for large-diameter monocrystalline silicon and preparation method thereof

Technical Field

The invention belongs to the technical field of seed crystal manufacturing, and particularly relates to a high-strength seed crystal for large-diameter monocrystalline silicon and a preparation method thereof.

Background

At the current time of the rapid development of the semiconductor industry, the demand for large-diameter single crystal silicon is increasing. The large-diameter monocrystalline silicon is widely applied to various key fields such as integrated circuits, solar photovoltaics and the like, and the seed crystal is used as a base for the growth of the monocrystalline silicon, so that the performance quality of the seed crystal plays a decisive role in the quality of a final monocrystalline silicon product.

In the growth process of monocrystalline silicon, dislocation, crystal boundary defects and the like are easy to generate in the seed crystal due to the influences of factors such as thermal stress, mechanical stress and the like. In addition, in the growth process of the monocrystalline silicon, the temperature change is larger, if the heat conductivity of the seed crystal is insufficient, uneven heat distribution and concentrated thermal stress are caused, so that the formation probability of the crystal defects is increased.

In summary, in the existing seed crystal preparation technology, the strength, toughness, thermal performance and the relation between doping and monocrystalline silicon quality of the seed crystal are difficult to comprehensively consider, so that development of a preparation technology capable of comprehensively improving the performances of the seed crystal is of great significance in promoting the development of the large-diameter monocrystalline silicon industry.

Disclosure of Invention

Aiming at the defects in the prior art, the high-strength seed crystal for large-diameter monocrystalline silicon prepared by the method improves the performance through a unique partition design, elemental carbon is introduced by utilizing the reaction of silicon carbide and silicon at a high temperature in a first seed crystal region, the elemental carbon not only hinders dislocation movement, the dislocation needs to bypass or cut through carbon particles when the crystal is stressed and deformed to increase movement resistance so as to improve seed crystal strength, but also can be partially gathered to fill defects and gaps, strengthen bonding force between crystal boundary atoms, reduce the generation and expansion of crystal boundary cracks and improve the overall strength and toughness, in addition, the elemental carbon forms a heat conduction channel by virtue of high heat conductivity, heat stress concentration and crystal defects are reduced uniformly, seed crystal quality is improved, meanwhile, the content and distribution of the elemental carbon are reasonably controlled, the stability of a crystal structure is enhanced, on the other hand, silicon nitride is introduced to generate Si ₂N₂ O under a low oxygen condition, the Si ₂N₂ O and the elemental carbon form C-N, C-O, C-Si covalent bond at the high temperature, the stability of the internal structure of the crystal is enhanced, the difficulty of dislocation movement is increased, the strength is improved, the bonding of the heavily doped atoms at the surface of the crystal boundary atoms is improved, the interface of the crystal boundary is improved, the bonding with the first seed crystal region is improved, the light doping site is tightly bonded with the lightly doped silicon, and the lightly doped region is prevented from being tightly bonded with the lightly doped silicon.

In order to achieve the aim, the technical scheme adopted by the invention is that the high-strength seed crystal for large-diameter monocrystalline silicon comprises the following raw materials in parts by weight, namely 30 parts of silicon liquid in a first seed crystal region, 20 parts of silicon liquid in a second heavily doped region and 10 parts of silicon liquid in a third lightly doped region.

Further, the preparation method of the first seed crystal region comprises the following steps:

(a) Weighing 2 parts of silane coupling agent, adding the silane coupling agent into 15-20 parts of ethanol aqueous solution, wherein the volume ratio of the anhydrous ethanol to deionized water in the ethanol aqueous solution is 1:1, adding acid liquor to adjust the pH range to 4-6, and stirring for 30min at the rotating speed of 500r/min to obtain hydrolysate;

(b) 1-3 parts of SiC and 1.5-2.5 parts of Si ₃N₄ are weighed and added into the hydrolysate obtained in the step (a), ultrasonic treatment is carried out for 20min under the condition of power of 1KW, then stirring is carried out for 30min under the condition of rotating speed of 500r/min, an activated substance is obtained, centrifugal separation is carried out on the activated substance under the condition of rotating speed of 7000r/min, and drying is carried out for 24h under the condition of placing the activated substance at 70 ℃ to obtain the SiC-Si ₃N₄ modified substance;

(c) 400-600 parts of polysilicon are weighed and put into an argon atmosphere furnace I to be melted for 3 hours under the condition that the temperature is 1420 ℃, the flow rate of argon is 25L/min, and slag is removed from the melted silicon liquid to obtain pure silicon liquid I;

(d) Adding the SiC-Si ₃N₄ modified substance obtained in the step (b) into the pure silicon liquid I obtained in the step (C), and maintaining the temperature at 1420 ℃ to obtain the silicon liquid of the first seed crystal region.

Further, the preparation method of the second heavily doped region silicon liquid comprises the following steps:

(i) Weighing 150-200 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace II, melting for 3h at 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid II, wherein the flow rate of the argon is 25L/min;

(ii) Weighing 0.2-0.4 part of SbCl ₃ and adding the SbCl ₃ into the pure silicon liquid II obtained in the step (I) to obtain a mixed silicon liquid I;

(iii) Weighing 0.1 part of In ₂O₃, putting into a tubular furnace with hydrogen flow of 500ml/min, carrying out reduction treatment for 2h at a high temperature of 900-1100 ℃, and naturally cooling to room temperature to obtain elemental In;

(vi) Adding the simple substance In obtained In the step (iii) into the mixed silicon liquid I obtained In the step (ii), and maintaining the temperature at 1420 ℃ to obtain a second heavily doped region silicon liquid.

Further, the preparation method of the third lightly doped region silicon liquid comprises the following steps:

Weighing 140-180 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace III, melting the polysilicon for 3 hours at the temperature of 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid III, wherein the flow rate of the argon is 25L/min;

Weighing 0.01 part of PCl ₅, putting into a tubular furnace with argon flow of 500ml/min, reducing for 4 hours at the high temperature of 400-600 ℃, and naturally cooling to room temperature to obtain an elemental P;

(gamma) adding the simple substance P obtained in the step (beta) into the pure silicon liquid III obtained in the step (alpha), and maintaining the temperature at 1420 ℃ to obtain a mixed silicon liquid II;

And (delta) weighing 0.05-0.1 part of Al ₂O₃ to be added into the mixed silicon liquid II obtained in the step (gamma), and keeping the temperature at 1420 ℃ to obtain the third lightly doped region silicon liquid.

The invention also provides a preparation method of the high-strength seed crystal for the large-diameter monocrystalline silicon, which comprises the following steps:

Step one, reserving 100 parts of first seed crystal area silicon liquid in a furnace I, taking fine crystals, placing the fine crystals at a position 15cm away from the surface of the first seed crystal area silicon liquid, preheating the fine crystals for 30min, slowly inserting the preheated fine crystals into the first seed crystal area silicon liquid for 10mm, keeping the pulling speed of the fine crystals at 220mm/h for 8min, increasing the pulling speed of the fine crystals to 245mm/h at a speed of 1.25mm/min, increasing the pulling speed of the fine crystals at a speed of 2.5mm/min to 270mm/h, and extracting 30 parts of first seed crystal area silicon liquid from the fine crystals to obtain a fine crystal-first seed crystal area;

Step two, reserving 100 parts of second heavily doped region silicon liquid in a furnace II, placing the fine crystal-first seed crystal region obtained in the step one at a position 15cm away from the surface of the second heavily doped region silicon liquid, preheating the fine crystal-first seed crystal region for 30min, slowly inserting the preheated fine crystal-first seed crystal region into the second heavily doped region silicon liquid for 10mm, slowly adjusting the pulling speed of the fine crystal to 270mm/h to 300mm/h at a speed of 2mm/min, then extracting 20 parts of second heavily doped region silicon liquid from the fine crystal-first seed crystal region at a speed of 3mm/min to 330mm/h, and obtaining the fine crystal-first seed crystal region-second heavily doped region;

Step three, reserving 100 parts of third lightly doped region silicon liquid in a furnace III, placing the fine crystal-first seed crystal region-second heavily doped region obtained in the step two at a position 15cm away from the surface of the second heavily doped region silicon liquid, preheating the fine crystal-first seed crystal region-second heavily doped region for 30min, slowly inserting the preheated fine crystal-first seed crystal region-second heavily doped region into the second heavily doped region silicon liquid for 10mm, slowly adjusting the pulling rate of the fine crystal from 330mm/h to 380mm/h at a speed of 3mm/min, extracting 10 parts of third lightly doped region silicon liquid on the fine crystal-first seed crystal region-second heavily doped region, obtaining a fine crystal-first seed crystal region-second heavily doped region-third lightly doped region, and removing the fine crystal to obtain a high-strength seed crystal main body;

grinding and polishing the high-strength seed crystal main body obtained in the step three to obtain a high-strength seed crystal precursor for large-diameter monocrystalline silicon;

and fifthly, placing the high-strength seed crystal precursor for the large-diameter monocrystalline silicon obtained in the step four into absolute ethyl alcohol, carrying out ultrasonic treatment for 30min under the condition that the ultrasonic frequency is 60kHz, then placing the high-strength seed crystal precursor for the large-diameter monocrystalline silicon into mixed acid for cleaning, then using absolute ethyl alcohol and deionized water for cleaning for 3 times alternately, then heating to 1300 ℃ under the condition that the argon flow is 25L/min for annealing treatment for 24h, and naturally cooling to room temperature to obtain the high-strength seed crystal for the large-diameter monocrystalline silicon.

The beneficial effects obtained by the invention are as follows:

The high-strength seed crystal for large-diameter monocrystalline silicon prepared by the method adopts a partition design, silicon carbide is promoted to react with silicon at high temperature in a first seed crystal area, generated elemental carbon plays multiple roles, on one hand, when crystals are stressed and deformed, the elemental carbon blocks dislocation movement, dislocation needs to bypass or cut through carbon particles, dislocation movement resistance is increased, and seed crystal strength is improved, on the other hand, elemental carbon is biased at a crystal boundary, fills crystal boundary defects and gaps, enhances bonding force between crystal boundary atoms, the crystal boundary serves as a crystal relatively weak area, the integral strength and toughness of the seed crystal are improved, generation and expansion of crystal boundary cracks are reduced, fracture resistance is enhanced, silicon nitride is introduced in the seed crystal area, si ₂N₂ O is generated under the condition of less oxygen, and at high temperature, the covalent bonds enable the atomic bonding to be more compact, the stability of an internal structure of the seed crystal is enhanced, the bonding strength is high, the dislocation needs to overcome the blocking or changing direction, the dislocation movement difficulty is increased, the seed crystal is not easy to generate plastic deformation when being stressed, and the seed crystal strength is further improved.

The high-strength seed crystal for the large-diameter monocrystalline silicon, which is prepared by the invention, introduces heavy doping atoms into the second heavily doped region, forms defects on the surface of the seed crystal, improves the combination of carbon at the interface with the first seed crystal region, and simultaneously forms defects to provide defect sites for the light doping of the third lightly doped region, so that the heavy doping and the light doping are tightly combined, and meanwhile, the existence of the lightly doped seed crystal region avoids the influence of the heavy doping on the quality of the monocrystalline silicon.

The high-strength seed crystal for the large-diameter monocrystalline silicon, which is prepared by the invention, has the advantages that the simple substance carbon has higher heat conductivity, a heat conduction channel can be formed, the heat conductivity of the seed crystal is improved, the heat transfer is more uniform in the growth process of the seed crystal, the heat stress concentration is reduced, the crystal defect caused by the heat stress is reduced, and the quality and the performance of the seed crystal are improved.

Drawings

FIG. 1 is a diagram showing a method for preparing a high-strength seed crystal for large-diameter monocrystalline silicon according to the present invention;

FIG. 2 is a three-dimensional view of a high strength seed crystal for large diameter single crystal silicon according to the present invention;

FIG. 3 is a plan view showing a region of a high strength seed crystal for large diameter single crystal silicon according to the present invention;

FIG. 4 shows the first furnace single crystal rod setting rate of the high strength seed crystal for large diameter single crystal silicon prepared in the example of the present invention;

FIG. 5 shows the second furnace single crystal rod setting rate of the high strength seed crystal for large diameter single crystal silicon prepared in the example of the present invention;

FIG. 6 shows the rate of the whole third furnace single crystal rod of the high strength seed crystal for large diameter single crystal silicon prepared by the embodiment of the invention;

FIG. 7 shows the rate of hidden cracking of a high strength seed crystal for large diameter single crystal silicon prepared in accordance with an embodiment of the present invention;

FIG. 8 shows the impurity introduced amount of the high-strength seed crystal for large-diameter single crystal silicon prepared in the example of the present invention in single crystal preparation.

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and all other embodiments obtained by those skilled in the art without making any inventive effort based on the embodiments of the present invention are within the scope of protection of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the present application. The preferred methods and materials described herein are illustrative only and should not be construed as limiting the application.

The preparation method of the high-strength seed crystal for large-diameter monocrystalline silicon in the following examples refers to fig. 1, the three-dimensional diagram of the high-strength seed crystal for large-diameter monocrystalline silicon refers to fig. 2, the partition of the high-strength seed crystal for large-diameter monocrystalline silicon refers to fig. 3, and the materials used in the following examples are all high-purity industrial grade, the purity is 99.999% or more, the volume ratio of anhydrous ethanol and deionized water in the aqueous ethanol solution is 1:1, the mass ratio of hydrofluoric acid to nitric acid is 1:4,40% concentration hydrofluoric acid, and 70% concentration nitric acid.

Example 1A high strength seed crystal for large diameter single crystal silicon comprises the following raw materials, by weight, 30 parts of a first seed region silicon solution, 20 parts of a second heavily doped region silicon solution, and 10 parts of a third lightly doped region silicon solution.

The preparation method of the silicon liquid in the first seed crystal region comprises the following steps:

(a) 2 parts of gamma-aminopropyl triethoxysilane is weighed and added into 15 parts of ethanol water solution, glacial acetic acid is added to adjust the pH range to 4, and the mixture is stirred for 30min at the rotating speed of 500r/min to obtain hydrolysate;

(b) 1 part of SiC and 1.5 parts of Si ₃N₄ are weighed and added into the hydrolysate obtained in the step (a), ultrasonic treatment is carried out for 20min under the condition of power of 1KW, then stirring is carried out for 30min under the condition of rotating speed of 500r/min, an activated substance is obtained, centrifugal separation is carried out on the activated substance under the condition of rotating speed of 7000r/min, and drying is carried out for 24h under the condition of placing the activated substance at 70 ℃ to obtain a SiC-Si ₃N₄ modified substance;

(c) 400 parts of polysilicon are weighed and put into an argon atmosphere furnace I to be melted for 3 hours under the condition that the temperature is 1420 ℃, the flow rate of argon is 25L/min, and slag removal is carried out on melted silicon liquid to obtain pure silicon liquid I;

The preparation method of the second heavily doped region silicon liquid comprises the following steps:

(i) Weighing 150 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace II, melting the polysilicon for 3 hours under the condition that the temperature is 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid II, wherein the flow rate of the argon is 25L/min;

(ii) Weighing 0.2 part of SbCl ₃, and adding the SbCl ₃ into the pure silicon liquid II obtained in the step (I) to obtain a mixed silicon liquid I;

(iii) Weighing 0.1 part of In ₂O₃, putting into a tubular furnace with hydrogen flow of 500ml/min, carrying out reduction treatment for 2 hours at the high temperature of 900 ℃, and naturally cooling to room temperature to obtain elemental In;

The preparation method of the third lightly doped region silicon liquid comprises the following steps:

weighing 140 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace III, melting the polysilicon for 3 hours at the temperature of 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid III, wherein the flow rate of the argon is 25L/min;

Weighing 0.01 part of PCl ₅, putting into a tubular furnace with argon flow of 500ml/min, carrying out reduction treatment for 4 hours at a high temperature of 400 ℃, and naturally cooling to room temperature to obtain elemental P;

And (delta) weighing 0.05 part of Al ₂O₃ to the mixed silicon liquid II obtained in the step (gamma), and keeping the temperature at 1420 ℃ to obtain a third lightly doped region silicon liquid.

The embodiment also provides a preparation method of the high-strength seed crystal for the large-diameter monocrystalline silicon, which comprises the following steps:

Example 2A high strength seed crystal for large diameter single crystal silicon comprises the following raw materials, by weight, 30 parts of a first seed region silicon solution, 20 parts of a second heavily doped region silicon solution, and 10 parts of a third lightly doped region silicon solution.

(a) 2 parts of gamma-aminopropyl triethoxysilane is weighed and added into 18 parts of ethanol water solution, glacial acetic acid is added to adjust the pH range to 5, and the mixture is stirred for 30min at the rotating speed of 500r/min to obtain hydrolysate;

(b) Weighing 2 parts of SiC and 2 parts of Si ₃N₄, adding into the hydrolysate obtained in the step (a), carrying out ultrasonic treatment for 20min under the condition of power of 1KW, stirring for 30min under the condition of rotating speed of 500r/min to obtain an activated substance, carrying out centrifugal separation on the activated substance under the condition of rotating speed of 7000r/min, and drying for 24h under the condition of placing the activated substance into a temperature of 70 ℃ to obtain a SiC-Si ₃N₄ modified substance;

(c) Weighing 500 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace I, melting the polysilicon for 3 hours under the condition that the temperature is 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid I, wherein the flow rate of the argon is 25L/min;

(d) Adding the SiC-Si ₃N₄ modified substance obtained in the step (b) into the pure silicon liquid I obtained in the step (C), and keeping the temperature of 1420 ℃ to obtain the silicon liquid of the first seed crystal region.

(i) 180 parts of polysilicon is weighed and put into an argon atmosphere furnace II to be melted for 3 hours under the condition that the temperature is 1420 ℃, the flow rate of argon is 25L/min, and slag is removed from the melted silicon liquid to obtain pure silicon liquid II;

(ii) Weighing 0.3 part of SbCl ₃, and adding the SbCl ₃ into the pure silicon liquid II obtained in the step (I) to obtain a mixed silicon liquid I;

(iii) Weighing 0.1 part of In ₂O₃, putting into a tubular furnace with hydrogen flow of 500ml/min, carrying out reduction treatment for 2 hours at the high temperature of 1000 ℃, and naturally cooling to room temperature to obtain elemental In;

Weighing 160 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace III, melting the polysilicon for 3 hours at the temperature of 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid III, wherein the flow rate of the argon is 25L/min;

Weighing 0.01 part of PCl ₅, putting into a tubular furnace with argon flow of 500ml/min, carrying out reduction treatment for 4 hours at the high temperature of 500 ℃, and naturally cooling to room temperature to obtain elemental P;

and (delta) weighing 0.08 part of Al ₂O₃ to the mixed silicon liquid II obtained in the step (gamma), and keeping the temperature at 1420 ℃ to obtain a third lightly doped region silicon liquid.

This example also provides a method for producing a high-strength seed crystal for large-diameter single crystal silicon, which is the same as that of example 1.

Example 3A high strength seed crystal for large diameter single crystal silicon comprises the following raw materials, by weight, 30 parts of a first seed region silicon solution, 20 parts of a second heavily doped region silicon solution, and 10 parts of a third lightly doped region silicon solution.

(a) 2 parts of gamma-aminopropyl triethoxysilane is weighed and added into 20 parts of ethanol water solution, glacial acetic acid is added to adjust the pH range to 6, and the mixture is stirred for 30min at the rotating speed of 500r/min to obtain hydrolysate;

(b) Weighing 3 parts of SiC and 2.5 parts of Si ₃N₄, adding into the hydrolysate obtained in the step (a), carrying out ultrasonic treatment for 20min under the condition of power of 1KW, stirring for 30min under the condition of rotating speed of 500r/min to obtain an activated substance, carrying out centrifugal separation on the activated substance under the condition of rotating speed of 7000r/min, and drying for 24h under the condition of placing the activated substance at 70 ℃ to obtain a SiC-Si ₃N₄ modified substance;

(c) 600 parts of polysilicon is weighed and put into an argon atmosphere furnace I to be melted for 3 hours under the condition that the temperature is 1420 ℃, the flow rate of argon is 25L/min, and slag is removed from the melted silicon liquid to obtain pure silicon liquid I;

(i) 200 parts of polysilicon is weighed and put into an argon atmosphere furnace II to be melted for 3 hours under the condition that the temperature is 1420 ℃, the flow rate of argon is 25L/min, and slag is removed from the melted silicon liquid to obtain pure silicon liquid II;

(ii) Weighing 0.4 part of SbCl ₃, and adding the SbCl ₃ into the pure silicon liquid II obtained in the step (I) to obtain a mixed silicon liquid I;

(iii) Weighing 0.1 part of In ₂O₃, putting into a tubular furnace with hydrogen flow of 500ml/min, carrying out reduction treatment for 2 hours at the high temperature of 1100 ℃, and naturally cooling to room temperature to obtain elemental In;

(alpha) weighing 180 parts of polysilicon, putting the polysilicon into an argon atmosphere furnace III, melting the polysilicon for 3 hours at the temperature of 1420 ℃, and removing slag from the melted silicon liquid to obtain pure silicon liquid III, wherein the flow rate of the argon is 25L/min;

Weighing 0.01 part of PCl ₅, putting into a tubular furnace with argon flow of 500ml/min, carrying out reduction treatment for 4 hours at the high temperature of 600 ℃, and naturally cooling to room temperature to obtain elemental P;

And (delta) weighing 0.1 part of Al ₂O₃ to the mixed silicon liquid II obtained in the step (gamma), and keeping the temperature at 1420 ℃ to obtain a third lightly doped region silicon liquid.

Comparative example:

The difference between comparative example 1 and example 2 is that the first seed region silicon liquid only melts the polysilicon, and other materials are not added to obtain the first seed region silicon liquid, and the rest is the same as example 2;

The difference between comparative example 2 and example 2 is that the second heavily doped region silicon solution only melts the polysilicon, and no other material is added to obtain the first seed region silicon solution, and the rest is the same as example 2;

comparative example 3 is a common seed crystal, and the production standard is consistent with that of a high-strength seed crystal for large-diameter monocrystalline silicon.

In order to verify the performance of the prepared high-strength seed crystal for large-diameter monocrystalline silicon, all the prepared products are used for preparing 12-inch monocrystalline silicon, the operation time is calculated according to 550h in one furnace, the maximum feeding amount of each furnace is 1200kg, the whole bar rate is calculated to be a qualified product according to the drawing length of not less than 1200mm, and fig. 4 is the first furnace whole bar rate data of the prepared high-strength seed crystal for large-diameter monocrystalline silicon, and it can be seen that the whole bar rate of the high-strength seed crystal for large-diameter monocrystalline silicon obtained in the examples is higher than that of the comparative examples and the corresponding common seed crystal in comparative example 3; FIG. 5 is second furnace bar rate data of the prepared high-strength seed crystal for large-diameter single crystal silicon, which is slightly lower than the first furnace bar rate, but the bar rate of the example is still superior to that of the comparative example, FIG. 6 is a third furnace bar rate of the prepared high-strength seed crystal for large-diameter single crystal silicon, which is leveled with the first two furnaces, FIG. 7 is a case of hidden cracking of the seed crystal after the use of the prepared high-strength seed crystal for large-diameter single crystal silicon by three furnaces, it can be seen that the integral hidden cracking of the example is relatively low, which shows that the prepared high-strength seed crystal for large-diameter single crystal is superior to that of the comparative example in terms of integral heat transfer, the comparative example 3 is superior to the corresponding common seed crystal in terms of heat unevenness and strength in the use process, the measured standard is that silicon rods with lengths of more than 3000mm are taken, the single crystal silicon materials with lengths of 1000mm from the head to the tail are cut, the measured impurity introduction amount of the intermediate single crystal silicon is taken as a detection standard, it can be seen that the impurity slice of the silicon wafer of the comparative example is low in the impurity content of the prepared silicon wafer of the comparative example, the prepared high-strength seed crystal for large-diameter monocrystalline silicon has higher stability.

According to the test results, the prepared high-strength seed crystal for large-diameter monocrystalline silicon can be used for preparing 12-inch monocrystalline silicon, and the overall performance of the high-strength seed crystal is better than that of a common seed crystal.

It is apparent that the above comparative examples and examples are only a part of the comparative examples and examples of the present invention, which are all within the scope of the present invention as protected based on such reference to the comparative examples and examples.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

The invention and its embodiments have been described above with no limitation, and the invention is illustrated in the figures of the accompanying drawings as one of its embodiments, without limitation in practice. In summary, those skilled in the art, having benefit of this disclosure, will appreciate that the invention can be practiced without the specific details disclosed herein.

Claims

1. A high-strength seed crystal for large-diameter single-crystal silicon, characterized in that it comprises the following raw materials in parts by weight: 30 parts of silicon liquid in the first seed crystal region, 20 parts of silicon liquid in the second heavily doped region, and 10 parts of silicon liquid in the third lightly doped region;

The silicon liquid in the first seed crystal region includes the following raw materials: SiC, Si ₃ N ₄ , silane coupling agent and polysilicon, wherein the mass ratio of SiC, Si ₃ N ₄ , silane coupling agent and polysilicon is 1-3:1.5-2.5:2:400-600;

The second heavily doped silicon liquid comprises the following raw materials: SbCl ₃ , In ₂ O ₃ and polycrystalline silicon, wherein the mass fraction ratio of SbCl ₃ , In ₂ O ₃ and polycrystalline silicon is 0.2-0.4:0.1:150-200;

The third lightly doped silicon liquid comprises the following raw materials: Al ₂ O ₃ , PCl ₅ and polysilicon, wherein the mass fraction ratio of Al ₂ O ₃ , PCl ₅ and polysilicon is 0.05-0.1:0.01:140-180;

The method for preparing a high-strength seed crystal for large-diameter single-crystal silicon comprises the following steps:

Step 1: retain silicon liquid in the first seed crystal area in the furnace, take fine crystals, preheat the fine crystals, insert the preheated fine crystals into the silicon liquid in the first seed crystal area, and draw them out to obtain fine crystals - the first seed crystal area;

Step 2: retain the silicon liquid of the second heavily doped region in the furnace, preheat the fine crystal-first seed crystal region obtained in step 1, insert the preheated fine crystal-first seed crystal region into the silicon liquid of the second heavily doped region, and draw it out to obtain the fine crystal-first seed crystal region-second heavily doped region;

Step 3, retaining the silicon liquid of the third lightly doped area in the furnace, preheating the fine crystal-first seed crystal area-second heavily doped area obtained in step 2, inserting the preheated fine crystal-first seed crystal area-second heavily doped area into the silicon liquid of the third lightly doped area, leading out, obtaining fine crystal-first seed crystal area-second heavily doped area-third lightly doped area, removing the fine crystal, and obtaining a high-strength seed crystal body;

Step 4: grinding and polishing the high-strength seed crystal main body obtained in step 3 to obtain a high-strength seed crystal precursor for large-diameter single crystal silicon;

Step 5: Ultrasonicate the high-strength seed crystal precursor for large-diameter single-crystalline silicon obtained in step 4, shuffle, clean, anneal, and cool the high-strength seed crystal precursor for large-diameter single-crystalline silicon to obtain a high-strength seed crystal for large-diameter single-crystalline silicon.

2. The high-strength seed crystal for large-diameter single-crystal silicon according to claim 1, characterized in that the method for preparing the silicon liquid in the first seed crystal region comprises the following steps:

(a) weighing a silane coupling agent, adding it to an ethanol aqueous solution, adding an acid solution to adjust the pH, stirring, and obtaining a hydrolyzate;

(b) weighing SiC and Si ₃ N ₄ and adding them to the hydrolyzate obtained in step (a), ultrasonicating and stirring to obtain an activated product, separating and drying the activated product to obtain a SiC-Si ₃ N ₄ modified product;

(c) Weighing polycrystalline silicon to melt the material, removing slag, and obtaining pure silicon liquid I;

(d) adding the SiC-Si ₃ N ₄ modified product obtained in step (b) to the pure silicon liquid I obtained in step (c), and keeping the temperature, to obtain the first seed crystal region silicon liquid.

3. A high-strength seed crystal for large-diameter single crystal silicon according to claim 2, characterized in that the mass ratio of the silane coupling agent and the ethanol aqueous solution in step (a) is 2:15-20, the silane coupling agent is γ-aminopropyltriethoxysilane, the volume ratio of anhydrous ethanol and deionized water in the ethanol aqueous solution is 1:1, the acid solution is glacial acetic acid, the pH range is 4-6, and the melt temperature in step (c) is 1420°C.

4. The high-strength seed crystal for large-diameter single-crystal silicon according to claim 1, characterized in that the method for preparing the second heavily doped region silicon liquid comprises the following steps:

(i) Weighing polycrystalline silicon to melt, removing slag, and obtaining pure silicon liquid II;

(ii) weighing SbCl ₃ and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

(iii) Weigh In ₂ O ₃ , treat it at high temperature, and cool it to obtain elemental In;

(vi) adding the single substance In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii), and keeping the mixture warm to obtain a second heavily doped silicon liquid.

5. A high-strength seed crystal for large-diameter single-crystal silicon according to claim 4, characterized in that the melt temperature in step (i) is 1420°C, and hydrogen is used in the high-temperature treatment in step (iii).

6. The high-strength seed crystal for large-diameter single-crystal silicon according to claim 1, characterized in that the method for preparing the third lightly doped silicon liquid comprises the following steps:

(α) Weighing polycrystalline silicon to melt, removing slag, and obtaining pure silicon liquid III;

(β) Weigh PCl ₅ , treat it at high temperature, and cool it to obtain single substance P;

(γ) adding the elemental P obtained in step (β) to the pure silicon liquid III obtained in step (α) to obtain a mixed silicon liquid II;

(δ) Weigh Al ₂ O ₃ and add it to the mixed silicon liquid II obtained in step (γ) to obtain the third lightly doped silicon liquid.

7. A high-strength seed crystal for large-diameter single-crystal silicon according to claim 6, characterized in that the melt temperature in step (α) is 1420°C, and argon gas is used for high-temperature treatment in step (β).