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

Abstract

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.The high-strength seed crystal for the large-diameter monocrystalline silicon is prepared from, by weight, 30 parts of first seed crystal area silicon liquid, 20 parts of second heavily-doped area silicon liquid and 10 parts of third lightly-doped area silicon liquid; the unique partition design is adopted to improve the performance of the high-strength seed crystal for the large-diameter monocrystalline silicon; in the first seed crystal area, silicon carbide reacts with silicon at high temperature to introduce elemental carbon which hinders dislocation, enhances grain boundary and improves strength and toughness; the seed crystal quality is improved by means of high thermal conductivity; meanwhile, silicon nitride is introduced to generate Si2N2O under the oxygen-deficient condition, and the Si2N2O and elemental carbon form a covalent bond; in the second seed crystal region, heavy doping atoms are introduced to form defects, the combination with carbon in the first seed crystal region is strengthened, sites are provided for light doping in the third seed crystal region, heavy doping and light doping are combined, and the negative influence of heavy doping on the quality of monocrystalline silicon is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of seed crystal manufacturing, and specifically refers to a high-strength seed crystal for large-diameter single-crystal silicon and a preparation method thereof. Background Art

[0002] As the semiconductor industry is booming, the demand for large-diameter single-crystal silicon is increasing day by day. Large-diameter single-crystal silicon is widely used in many key fields such as integrated circuits and solar photovoltaics; the performance of seed crystals, as the basis for the growth of single-crystal silicon, plays a decisive role in the quality of the final single-crystal silicon products.

[0003] During the growth of single crystal silicon, due to the influence of factors such as thermal stress and mechanical stress, dislocations and grain boundary defects are prone to occur inside the seed crystal. These defects will not only reduce the strength and toughness of the seed crystal itself, but may also continue to expand during the subsequent growth of single crystal silicon, seriously affecting the integrity of the crystal structure of the single crystal silicon, thereby reducing its electrical and mechanical properties; in addition, during the growth of single crystal silicon, the temperature changes greatly. If the thermal conductivity of the seed crystal is insufficient, it will lead to uneven heat distribution and concentrated thermal stress, thereby increasing the probability of crystal defects.

[0004] In summary, it is difficult to fully take into account the strength, toughness, thermal properties of the seed crystal, and the relationship between doping and the quality of single crystal silicon in the existing seed crystal preparation technology; therefore, developing a preparation technology that can comprehensively improve all aspects of seed crystal performance is of great significance to promoting the development of the large-diameter single crystal silicon industry. Summary of the invention

[0005] In view of the defects of the prior art, the high-strength seed crystal for large-diameter single-crystal silicon prepared by the present invention improves performance through a unique zoning design; in the first seed crystal zone, elemental carbon is introduced by utilizing the reaction of silicon carbide and silicon at high temperature. The elemental carbon not only hinders the movement of dislocations, but also increases the movement resistance and improves the strength of the seed crystal. It can also be concentrated at the grain boundary, fill defects and gaps, enhance the bonding force between atoms at the grain boundary, reduce the generation and expansion of grain boundary cracks, and improve the overall strength and toughness; in addition, the elemental carbon forms a heat conduction channel with its high thermal conductivity, evenly transfers heat, and reduces thermal stress concentration and crystal defects to improve the quality of the seed crystal; at the same time, its content and distribution are reasonably controlled to enhance the stability of the crystal structure; on the other hand, silicon nitride is introduced to generate Si2N2O under low oxygen conditions, and Si2N2O forms CN, CO, and C-Si covalent bonds with elemental carbon at high temperatures to enhance the stability of the internal structure of the crystal, increase the difficulty of dislocation movement, and improve the strength of the seed crystal; in the second seed crystal region, heavily doped atoms are introduced to form defects on the seed crystal surface to improve the combination with carbon at the interface of the first seed crystal region, and provide sites for light doping in the third seed crystal region, so as to achieve a close combination of heavy doping and light doping and avoid the influence of heavy doping on the quality of single crystal silicon.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is a high-strength seed crystal for large-diameter single crystal silicon, comprising the following raw materials in parts by weight: 30 parts of silicon liquid in the first seed crystal zone, 20 parts of silicon liquid in the second heavily doped zone, and 10 parts of silicon liquid in the third lightly doped zone.

[0007] Furthermore, the method for preparing the first seed crystal region comprises the following steps:

[0008] (a) weighing 2 parts of a silane coupling agent and adding it to 15-20 parts of an ethanol aqueous solution, wherein the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 1:1, adding an acid solution to adjust the pH range to 4-6, and stirring at a speed of 500 r / min for 30 minutes to obtain a hydrolyzate;

[0009] (b) Weighing 1-3 parts of SiC and 1.5-2.5 parts of Si3N4, adding them to the hydrolyzate obtained in step (a), ultrasonicating at a power of 1 kW for 20 minutes, and then stirring at a speed of 500 r / min for 30 minutes to obtain an activated product, centrifuging the activated product at a speed of 7000 r / min, and drying it at a temperature of 70°C for 24 hours to obtain a SiC-Si3N4 modified product;

[0010] (c) Weighing 400-600 parts of polycrystalline silicon, placing them in an argon atmosphere furnace I and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid I;

[0011] (d) Adding the modified SiC-Si3N4 obtained in step (b) to the pure silicon liquid I obtained in step (c), maintaining the temperature at 1420° C., to obtain the first seed crystal region silicon liquid.

[0012] Furthermore, the method for preparing the second heavily doped silicon liquid comprises the following steps:

[0013] (i) Weigh 150-200 portions of polycrystalline silicon and place them in an argon atmosphere furnace II for melting at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and remove slag from the melted silicon liquid to obtain pure silicon liquid II;

[0014] (ii) weighing 0.2-0.4 parts of SbCl3 and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

[0015] (iii) Weigh 0.1 parts of In2O3 and put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and reduce it at a high temperature of 900-1100°C for 2 hours, and cool it naturally to room temperature to obtain elemental In;

[0016] (vi) adding the single substance In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii) and maintaining the temperature at 1420° C. to obtain a second heavily doped silicon liquid.

[0017] Furthermore, the method for preparing the third lightly doped silicon liquid comprises the following steps:

[0018] (α) Weigh 140-180 parts of polycrystalline silicon and place them in an argon atmosphere furnace III for melting at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min. Deslagging the melted silicon liquid to obtain pure silicon liquid III;

[0019] (β) Weigh 0.01 part of PCl5 and put it into a tube furnace with an argon flow rate of 500 ml / min, perform reduction treatment at a high temperature of 400-600°C for 4 hours, and cool it naturally to room temperature to obtain single substance P;

[0020] (γ) adding the elemental P obtained in step (β) to the pure silicon liquid III obtained in step (α), maintaining the temperature at 1420° C., to obtain a mixed silicon liquid II;

[0021] (δ) Weigh 0.05-0.1 parts of Al2O3 and add it to the mixed silicon liquid II obtained in step (γ), maintain the temperature at 1420°C, and obtain the third lightly doped silicon liquid.

[0022] The present invention also provides a method for preparing a high-strength seed crystal for large-diameter single-crystal silicon, comprising the following steps:

[0023] Step 1, retain 100 parts of the first seed crystal area silicon liquid in the furnace I, take a fine crystal, place the fine crystal 15 cm away from the surface of the first seed crystal area silicon liquid, preheat the fine crystal for 30 minutes, slowly insert the preheated fine crystal into the first seed crystal area silicon liquid 10 mm, keep the fine crystal pulling speed at 220 mm / h for 8 minutes, increase the speed to 245 mm / h at 1.25 mm / min, and then increase the speed to 270 mm / h at 2.5 mm / min, draw out 30 parts of the first seed crystal area silicon liquid on the fine crystal, and obtain a fine crystal-first seed crystal area;

[0024] Step 2, retain 100 portions of the second heavily doped silicon liquid in the furnace II, place the fine crystal-first seed crystal region obtained in step 1 15 cm away from the surface of the second heavily doped silicon liquid, preheat the fine crystal-first seed crystal region for 30 min, slowly insert the preheated fine crystal-first seed crystal region into the second heavily doped silicon liquid region by 10 mm, slowly adjust the fine crystal pulling speed from 270 mm / h to 300 mm / h at an increase rate of 2 mm / min, and then to 330 mm / h at an increase rate of 3 mm / min, draw out 20 portions of the second heavily doped silicon liquid on the fine crystal-first seed crystal region, and obtain the fine crystal-first seed crystal region-second heavily doped region;

[0025] Step 3, retain 100 portions of the third lightly doped zone silicon liquid in furnace III, place the fine crystal-first seed crystal zone-second heavily doped zone obtained in step 2 15 cm away from the surface of the second heavily doped zone silicon liquid, preheat the fine crystal-first seed crystal zone-second heavily doped zone for 30 min, slowly insert the preheated fine crystal-first seed crystal zone-second heavily doped zone into the second heavily doped zone silicon liquid by 10 mm, slowly adjust the fine crystal pulling speed from 330 mm / h to 380 mm / h at an increase rate of 3 mm / min, draw out 10 portions of the third lightly doped zone silicon liquid on the fine crystal-first seed crystal zone-second heavily doped zone, obtain the fine crystal-first seed crystal zone-second doped zone-third lightly doped zone, remove the fine crystal, and obtain the high-strength seed crystal body;

[0026] 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;

[0027] Step 5. Place the high-strength seed crystal precursor for large-diameter single-crystalline silicon obtained in step 4 into anhydrous ethanol, and ultrasonicate it at an ultrasonic frequency of 60 kHz for 30 minutes. Then, place the high-strength seed crystal precursor for large-diameter single-crystalline silicon into mixed acid for cleaning, and then use anhydrous ethanol and deionized water to clean it alternately for 3 times. Then, heat it to 1300°C for annealing for 24 hours at an argon flow rate of 25 L / min, and naturally cool it to room temperature to obtain a high-strength seed crystal for large-diameter single-crystalline silicon.

[0028] The beneficial effects achieved by the present invention are as follows:

[0029] The high-strength seed crystal for large-diameter single-crystal silicon prepared by the present invention adopts a zoning design. In the first seed crystal zone, high temperature promotes the reaction of silicon carbide and silicon, and the generated elemental carbon plays multiple roles. On the one hand, when the crystal is deformed under stress, the elemental carbon hinders the movement of dislocations, and the dislocations need to bypass or cut through carbon particles, thereby increasing the resistance to dislocation movement and improving the strength of the seed crystal; on the other hand, the elemental carbon is concentrated at the grain boundary, filling the defects and gaps in the grain boundary, and enhancing the bonding force between atoms in the grain boundary. The grain boundary is a relatively weak area of ​​the crystal, and this improves the overall strength and toughness of the seed crystal, reduces the generation and expansion of grain boundary cracks, and enhances the fracture resistance; in addition, silicon nitride is introduced into the seed crystal zone to generate Si2N2O under low-oxygen conditions. At high temperature, Si2N2O forms CN, CO, and C-Si covalent bonds with elemental carbon. These covalent bonds make the atoms more tightly bonded, thereby enhancing the stability of the internal structure of the seed crystal. Because of its high bond strength, dislocations need more energy to overcome obstacles or change direction to bypass, thereby increasing the difficulty of dislocation movement, making it difficult for the seed crystal to undergo plastic deformation when subjected to stress, thereby further improving the strength of the seed crystal.

[0030] The high-strength seed crystal for large-diameter single crystal silicon prepared by the present invention introduces heavily doped atoms in the second seed crystal region to form defects on the surface of the seed crystal, thereby improving the bonding with carbon at the interface with the first seed crystal region. At the same time, the defects formed provide defect sites for light doping in the third seed crystal region, thereby achieving a close bonding between heavy doping and light doping. At the same time, the existence of the lightly doped seed crystal region avoids the influence of heavy doping on the quality of single crystal silicon.

[0031] The high-strength seed crystal for large-diameter single crystal silicon prepared by the present invention has a high thermal conductivity of elemental carbon, which can form a heat conduction channel, improve the thermal conductivity of the seed crystal, help to transfer heat more evenly during the growth of the seed crystal, reduce thermal stress concentration, and reduce crystal defects caused by thermal stress, thereby improving the quality and performance of the seed crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A diagram showing a method for preparing a high-strength seed crystal for large-diameter single-crystal silicon proposed by the present invention;

[0033] Figure 2 A three-dimensional diagram of the high-strength seed crystal for large-diameter single-crystal silicon proposed by the present invention;

[0034] Figure 3 A zoning plan view of a high-strength seed crystal for large-diameter single-crystal silicon proposed by the present invention;

[0035] Figure 4 The first batch of single crystal ingot rate of high-strength seed crystals for large-diameter single crystal silicon prepared in accordance with the embodiment of the present invention;

[0036] Figure 5 The single crystal ingot rate of the second furnace of high-strength seed crystals for large-diameter single crystal silicon prepared in accordance with the embodiment of the present invention;

[0037] Figure 6 The third furnace single crystal ingot rate of the high-strength seed crystal for large-diameter single crystal silicon prepared in the embodiment of the present invention;

[0038] Figure 7 The hidden crack rate of the high-strength seed crystal for large-diameter single-crystal silicon prepared in the embodiment of the present invention;

[0039] Figure 8 The amount of impurities introduced into the high-strength seed crystal for preparing large-diameter silicon single crystals according to the embodiment of the present invention during the preparation of the single crystal.

[0040] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0042] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0043] The preparation method of high-strength seed crystal for large-diameter single crystal silicon in the following embodiments is as follows: Figure 1 , 3D diagram reference for high strength seed crystal for large diameter single crystal silicon Figure 2 , reference for partitioning of high-strength seed crystals for large-diameter single crystal silicon Figure 3 , unless otherwise specified, are conventional methods; the materials used in the following embodiments, unless otherwise specified, are all high-purity industrial grade, with a purity of 99.999% or above, the volume ratio of anhydrous ethanol and deionized water in the ethanol aqueous solution used is 1:1, and the mixed acid used is hydrofluoric acid: nitric acid in a mass ratio of 1:4, 40% hydrofluoric acid, 70% nitric acid.

[0044] Embodiment 1: A high-strength seed crystal for large-diameter single-crystal silicon 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.

[0045] The method for preparing silicon liquid in the first seed crystal region comprises the following steps:

[0046] (a) Weighing 2 parts of γ-aminopropyltriethoxysilane, adding it to 15 parts of ethanol aqueous solution, adding glacial acetic acid to adjust the pH range to 4, stirring at a speed of 500 r / min for 30 minutes to obtain a hydrolyzate;

[0047] (b) Weighing 1 part of SiC and 1.5 parts of Si3N4, adding them to the hydrolyzate obtained in step (a), ultrasonicating for 20 min at a power of 1 kW, and then stirring for 30 min at a speed of 500 r / min to obtain an activated product, centrifuging the activated product at a speed of 7000 r / min, and drying it at a temperature of 70°C for 24 h to obtain a SiC-Si3N4 modified product;

[0048] (c) Weighing 400 parts of polycrystalline silicon, placing them in an argon atmosphere furnace I and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid I;

[0049] (d) Adding the modified SiC-Si3N4 obtained in step (b) to the pure silicon liquid I obtained in step (c), maintaining the temperature at 1420° C., to obtain the first seed crystal region silicon liquid.

[0050] The method for preparing the second heavily doped silicon liquid comprises the following steps:

[0051] (i) Weighing 150 parts of polycrystalline silicon, placing them into an argon atmosphere furnace II and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid II;

[0052] (ii) weighing 0.2 parts of SbCl3 and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

[0053] (iii) Weigh 0.1 parts of In2O3 and put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and reduce it at a high temperature of 900°C for 2 hours, and then cool it naturally to room temperature to obtain elemental In;

[0054] (vi) adding the single substance In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii) and maintaining the temperature at 1420° C. to obtain a second heavily doped silicon liquid.

[0055] The preparation method of the third lightly doped silicon liquid comprises the following steps:

[0056] (α) Weighing 140 parts of polycrystalline silicon, placing them in an argon atmosphere furnace III and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid III;

[0057] (β) Weigh 0.01 part of PCl5 and put it into a tube furnace with an argon flow rate of 500 ml / min. Perform reduction treatment at a high temperature of 400°C for 4 hours, and cool it naturally to room temperature to obtain single substance P;

[0058] (γ) adding the elemental P obtained in step (β) to the pure silicon liquid III obtained in step (α), maintaining the temperature at 1420° C., to obtain a mixed silicon liquid II;

[0059] (δ) Weigh 0.05 parts of Al2O3 and add it to the mixed silicon liquid II obtained in step (γ), maintain the temperature at 1420°C, and obtain the third lightly doped silicon liquid.

[0060] This embodiment also provides a method for preparing a high-strength seed crystal for large-diameter single-crystal silicon, comprising the following steps:

[0061] Step 1, retain 100 parts of the first seed crystal area silicon liquid in the furnace I, take a fine crystal, place the fine crystal 15 cm away from the surface of the first seed crystal area silicon liquid, preheat the fine crystal for 30 minutes, slowly insert the preheated fine crystal into the first seed crystal area silicon liquid 10 mm, keep the fine crystal pulling speed at 220 mm / h for 8 minutes, increase the speed to 245 mm / h at 1.25 mm / min, and then increase the speed to 270 mm / h at 2.5 mm / min, draw out 30 parts of the first seed crystal area silicon liquid on the fine crystal, and obtain a fine crystal-first seed crystal area;

[0062] Step 2, retain 100 portions of the second heavily doped silicon liquid in the furnace II, place the fine crystal-first seed crystal region obtained in step 1 15 cm away from the surface of the second heavily doped silicon liquid, preheat the fine crystal-first seed crystal region for 30 min, slowly insert the preheated fine crystal-first seed crystal region into the second heavily doped silicon liquid region by 10 mm, slowly adjust the fine crystal pulling speed from 270 mm / h to 300 mm / h at an increase rate of 2 mm / min, and then to 330 mm / h at an increase rate of 3 mm / min, draw out 20 portions of the second heavily doped silicon liquid on the fine crystal-first seed crystal region, and obtain the fine crystal-first seed crystal region-second heavily doped region;

[0063] Step 3, retain 100 portions of the third lightly doped zone silicon liquid in furnace III, place the fine crystal-first seed crystal zone-second heavily doped zone obtained in step 2 15 cm away from the surface of the second heavily doped zone silicon liquid, preheat the fine crystal-first seed crystal zone-second heavily doped zone for 30 min, slowly insert the preheated fine crystal-first seed crystal zone-second heavily doped zone into the second heavily doped zone silicon liquid by 10 mm, slowly adjust the fine crystal pulling speed from 330 mm / h to 380 mm / h at an increase rate of 3 mm / min, draw out 10 portions of the third lightly doped zone silicon liquid on the fine crystal-first seed crystal zone-second heavily doped zone, obtain the fine crystal-first seed crystal zone-second doped zone-third lightly doped zone, remove the fine crystal, and obtain the high-strength seed crystal body;

[0064] 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;

[0065] Step 5. Place the high-strength seed crystal precursor for large-diameter single-crystalline silicon obtained in step 4 into anhydrous ethanol, and ultrasonicate it at an ultrasonic frequency of 60 kHz for 30 minutes. Then, place the high-strength seed crystal precursor for large-diameter single-crystalline silicon into mixed acid for cleaning, and then use anhydrous ethanol and deionized water to clean it alternately for 3 times. Then, heat it to 1300°C for annealing for 24 hours at an argon flow rate of 25 L / min, and naturally cool it to room temperature to obtain a high-strength seed crystal for large-diameter single-crystalline silicon.

[0066] Example 2: A high-strength seed crystal for large-diameter single-crystal silicon 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.

[0067] The method for preparing silicon liquid in the first seed crystal region comprises the following steps:

[0068] (a) weighing 2 parts of γ-aminopropyltriethoxysilane and adding them to 18 parts of ethanol aqueous solution, adding glacial acetic acid to adjust the pH range to 5, stirring at a speed of 500 r / min for 30 minutes to obtain a hydrolyzate;

[0069] (b) Weighing 2 parts of SiC and 2 parts of Si3N4, adding them to the hydrolyzate obtained in step (a), ultrasonicating at a power of 1 kW for 20 min, and then stirring at a speed of 500 r / min for 30 min to obtain an activated product, centrifuging the activated product at a speed of 7000 r / min, and drying it at a temperature of 70°C for 24 h to obtain a SiC-Si3N4 modified product;

[0070] (c) Weighing 500 parts of polycrystalline silicon, placing them in an argon atmosphere furnace I and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid I;

[0071] (d) Adding the modified SiC-Si3N4 obtained in step (b) into the pure silicon liquid I obtained in step (c), maintaining the temperature at 1420° C., to obtain the first seed crystal region silicon liquid.

[0072] The method for preparing the second heavily doped silicon liquid comprises the following steps:

[0073] (i) Weighing 180 parts of polycrystalline silicon, placing them into an argon atmosphere furnace II and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid II;

[0074] (ii) weighing 0.3 parts of SbCl3 and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

[0075] (iii) Weigh 0.1 parts of In2O3 and put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and reduce it at a high temperature of 1000°C for 2 hours, and then cool it naturally to room temperature to obtain elemental In;

[0076] (vi) adding the single substance In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii) and maintaining the temperature at 1420° C. to obtain a second heavily doped silicon liquid.

[0077] The preparation method of the third lightly doped silicon liquid comprises the following steps:

[0078] (α) Weigh 160 parts of polycrystalline silicon and place them in an argon atmosphere furnace III to melt the materials at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min. Deslagging the melted silicon liquid to obtain pure silicon liquid III;

[0079] (β) Weigh 0.01 part of PCl5 and put it into a tube furnace with an argon flow rate of 500 ml / min. Perform reduction treatment at a high temperature of 500°C for 4 hours, and cool it naturally to room temperature to obtain single substance P;

[0080] (γ) adding the elemental P obtained in step (β) to the pure silicon liquid III obtained in step (α), maintaining the temperature at 1420° C., to obtain a mixed silicon liquid II;

[0081] (δ) Weigh 0.08 parts of Al2O3 and add it to the mixed silicon liquid II obtained in step (γ), maintain the temperature at 1420°C, and obtain the third lightly doped silicon liquid.

[0082] This embodiment also provides a method for preparing a high-strength seed crystal for large-diameter single-crystal silicon. This embodiment is the same as the method for preparing a high-strength seed crystal for large-diameter single-crystal silicon in Example 1.

[0083] Example 3: A high-strength seed crystal for large-diameter single-crystal silicon 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.

[0084] The method for preparing silicon liquid in the first seed crystal region comprises the following steps:

[0085] (a) Weighing 2 parts of γ-aminopropyltriethoxysilane, adding it to 20 parts of ethanol aqueous solution, adding glacial acetic acid to adjust the pH range to 6, stirring at a speed of 500 r / min for 30 minutes to obtain a hydrolyzate;

[0086] (b) 3 parts of SiC and 2.5 parts of Si3N4 were weighed and added to the hydrolyzate obtained in step (a), and ultrasonicated for 20 minutes at a power of 1 kW, and then stirred at a speed of 500 r / min for 30 minutes to obtain an activated product, and the activated product was centrifuged at a speed of 7000 r / min, and dried at a temperature of 70°C for 24 hours to obtain a SiC-Si3N4 modified product;

[0087] (c) Weighing 600 parts of polycrystalline silicon, placing them in an argon atmosphere furnace I and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid I;

[0088] (d) Adding the modified SiC-Si3N4 obtained in step (b) to the pure silicon liquid I obtained in step (c), maintaining the temperature at 1420° C., to obtain the first seed crystal region silicon liquid.

[0089] The method for preparing the second heavily doped silicon liquid comprises the following steps:

[0090] (i) Weighing 200 parts of polycrystalline silicon, placing them in an argon atmosphere furnace II and melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid II;

[0091] (ii) weighing 0.4 parts of SbCl3 and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

[0092] (iii) Weigh 0.1 parts of In2O3 and put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and reduce it at a high temperature of 1100°C for 2 hours, and then cool it naturally to room temperature to obtain elemental In;

[0093] (vi) adding the single substance In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii) and maintaining the temperature at 1420° C. to obtain a second heavily doped silicon liquid.

[0094] The preparation method of the third lightly doped silicon liquid comprises the following steps:

[0095] (α) Weighing 180 parts of polycrystalline silicon, placing them in an argon atmosphere furnace III, melting them at a temperature of 1420° C. for 3 hours with an argon flow rate of 25 L / min, and removing slag from the melted silicon liquid to obtain pure silicon liquid III;

[0096] (β) Weigh 0.01 part of PCl5 and put it into a tube furnace with an argon flow rate of 500 ml / min. Perform reduction treatment at a high temperature of 600°C for 4 hours, and cool it naturally to room temperature to obtain single substance P;

[0097] (γ) adding the elemental P obtained in step (β) to the pure silicon liquid III obtained in step (α), maintaining the temperature at 1420° C., to obtain a mixed silicon liquid II;

[0098] (δ) Weigh 0.1 parts of Al2O3 and add it to the mixed silicon liquid II obtained in step (γ), maintain the temperature at 1420°C, and obtain the third lightly doped silicon liquid.

[0099] This embodiment also provides a method for preparing a high-strength seed crystal for large-diameter single-crystal silicon. This embodiment is the same as the method for preparing a high-strength seed crystal for large-diameter single-crystal silicon in Example 1.

[0100] Comparative Example:

[0101] The difference between Comparative Example 1 and Example 2 is that the first seed crystal region silicon liquid is used to melt polysilicon only without adding other materials to obtain the first seed crystal region silicon liquid, and the rest is the same as Example 2;

[0102] The difference between Comparative Example 2 and Example 2 is that the second heavily doped silicon liquid only melts polysilicon without adding other materials to obtain the first seed crystal silicon liquid, and the rest is the same as Example 2;

[0103] Comparative Example 3 is a common seed crystal, and its manufacturing standard is consistent with the high-strength seed crystal for large-diameter single crystal silicon.

[0104] In order to verify the performance of the high-strength seed crystal for large-diameter single crystal silicon, all the products were used for the preparation of 12-inch single crystal silicon. The operation time was calculated based on 550h per furnace, the maximum feed amount per furnace was 1200kg, and the whole rod rate was calculated as qualified products according to the drawn length ≥1200mm. Figure 4 The first furnace full rod rate data of the prepared large diameter single crystal silicon high strength seed crystal, it can be seen that the full rod rate of the large diameter single crystal silicon high strength seed crystal obtained in the embodiment is higher than that of the comparative example and the ordinary seed crystal corresponding to the comparative example 3; Figure 5 The second furnace rod rate data for the prepared large-diameter high-strength seed crystal for single crystal silicon is slightly lower than that of the first furnace, but the rod rate of the embodiment is still better than that of the comparative example. Figure 6 The third furnace full rod rate of the prepared large-diameter single-crystal silicon high-strength seed crystals, wherein the embodiment has the same full rod rate as the first two furnaces; Figure 7 The following are the hidden cracks of the prepared large-diameter single-crystal silicon high-strength seed crystals after three furnaces of use. It can be seen that the overall hidden cracks of the embodiment are relatively low, indicating that the prepared large-diameter single-crystal silicon high-strength seed crystals are better than the comparative example in terms of overall heat transfer. The ordinary seed crystals corresponding to the comparative example 3 have uneven heat and strength problems during use, resulting in a large hidden crack rate. Figure 8 In order to measure the impurities in the prepared single crystal silicon, the measurement standard is to take a silicon rod with a length ≥ 3000mm, cut off 1000mm of single crystal silicon material at the head and tail, and measure the amount of impurities introduced into the single crystal silicon slice in the middle. The impurity content of qualified silicon wafer products is used as the detection standard. It can be seen that the impurity content in the silicon wafer prepared in the embodiment is lower than the impurity content in the comparison example, indicating that the prepared large-diameter single crystal silicon high-strength seed crystal has higher stability.

[0105] From the above test results, it can be seen that the high-strength seed crystal prepared for large-diameter single crystal silicon can meet the preparation of 12-inch single crystal silicon, and the overall performance is better than that of ordinary seed crystals.

[0106] Obviously, the above comparative examples and embodiments are only a part of comparative examples and embodiments of the present invention, and they and the comparative examples and embodiments based on such references are all within the scope of protection of the present invention.

[0107] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0108] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A high-strength seed crystal for large-diameter single-crystal silicon, characterized in that: The raw materials include the following 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 comprises the following raw materials: SiC, Si3N4, silane coupling agent and polycrystalline silicon, wherein the mass ratio of SiC, Si3N4, silane coupling agent and polycrystalline silicon is 1-3:1.5-2.5:2:400-600; The second heavily doped silicon liquid comprises the following raw materials: SbCl3, In2O3 and polycrystalline silicon, wherein the mass fraction ratio of SbCl3, In2O3 and polycrystalline silicon is 0.2-0.4:0.1:150-200; The third lightly doped silicon liquid comprises the following raw materials: Al2O3, PCl5 and polycrystalline silicon, and the mass fraction ratio of Al2O3, PCl5 and polycrystalline silicon is 0.05-0.1:0.01:140-180.

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 Si3N4 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-Si3N4 modified product; (c) Weighing polycrystalline silicon to melt the material, removing slag, and obtaining pure silicon liquid I; (d) adding the modified SiC-Si3N4 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. The 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 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 silicon liquid comprises the following steps: (i) Weighing polycrystalline silicon to melt and remove slag to obtain pure silicon liquid II; (ii) weighing SbCl3 and adding it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I; (iii) Weigh In2O3, 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. The 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 PCl5, treat it at high temperature, and cool it to obtain elemental 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 Al2O3 and add it to the mixed silicon liquid II obtained in step (γ) to obtain the third lightly doped silicon liquid.

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

8. A method for preparing a high-strength seed crystal for large-diameter single-crystal silicon according to any one of claims 1 to 7, characterized in that: The steps include: 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 third lightly doped area silicon liquid 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 third lightly doped area silicon liquid, leading out, obtaining fine crystal-first seed crystal area-second 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.

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