A high-strength seed crystal for large-diameter single-crystalline silicon and its preparation method

Abstract

The present invention belongs to the technical field of seed crystal manufacturing, and specifically refers to a high-strength seed crystal for large-diameter single-crystalline silicon and a preparation method thereof. The high-strength seed crystal for large-diameter single-crystalline 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. The present invention adopts a unique zoning design to improve the performance of the high-strength seed crystal for large-diameter single-crystalline silicon. In the first seed crystal region, silicon carbide reacts with silicon at high temperature to introduce elemental carbon, which hinders dislocations, strengthens grain boundaries, and improves strength and toughness; the quality of the seed crystal is improved by virtue of the high thermal conductivity; at the same time, silicon nitride is introduced to generate Si2N2O under low-oxygen conditions, which forms covalent bonds with elemental carbon. In the second heavily doped region, heavily doped atoms are introduced to form defects, strengthen the combination with carbon in the first seed crystal region, provide sites for light doping in the third lightly doped region, combine heavy doping and light doping, and avoid the negative impact of heavy doping on the quality of single-crystalline silicon.

Description

Technical Field

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

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

[0003] During the growth process of single-crystalline silicon, due to the influence of factors such as thermal stress and mechanical stress, dislocations, grain boundary defects and other problems are likely 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 single-crystalline silicon growth process, seriously affecting the crystal structure integrity of single-crystalline silicon, and thus reducing its electrical and mechanical properties; in addition, during the single-crystalline silicon growth process, the temperature changes greatly. If the thermal conductivity of the seed crystal is insufficient, it will lead to uneven heat distribution and thermal stress concentration, thereby increasing the formation probability of crystal defects.

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

[0005] Aiming at the defects of the existing technology, the high-strength seed crystal for large-diameter single-crystalline silicon prepared by the present invention improves the performance through a unique zoning design; in the first seed crystal zone, elemental carbon is introduced by the reaction of silicon carbide and silicon at high temperature. Elemental carbon not only hinders the movement of dislocations. When the crystal is deformed under force, dislocations need to bypass or cut through carbon particles, increasing the movement resistance and thus improving the strength of the seed crystal; it can also segregate at grain boundaries, filling defects and voids, enhancing the bonding force between grain boundary atoms, reducing the generation and expansion of grain boundary cracks, and improving the overall strength and toughness; in addition, elemental carbon forms a heat conduction channel with high thermal conductivity to uniformly transfer heat, reducing thermal stress concentration and crystal defects, and improving 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 Si 2 N 2 O under low-oxygen conditions. At high temperature, Si 2 N 2O forms covalent bonds of C-N, C-O, and C-Si with elemental carbon, enhancing the stability of the internal crystal structure, increasing the difficulty of dislocation movement, and improving the strength of the seed crystal; in the second heavily doped region, heavy-doped atoms are introduced to form defects on the surface of the seed crystal, improving the bonding of carbon at the interface with the first seed crystal region and providing sites for light doping in the third lightly doped region, achieving a tight combination of heavy doping and light doping and avoiding the impact of heavy doping on the quality of single-crystalline silicon.

[0006] To achieve the above object, the technical solution adopted by the present invention is a high-strength seed crystal for large-diameter single-crystalline silicon, which 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.

[0007] Further, the preparation method of the first seed crystal region comprises the following steps:

[0008] (a) Weigh 2 parts of silane coupling agent and add it to 15 - 20 parts of ethanol aqueous solution. The volume ratio of absolute ethanol to deionized water in the ethanol aqueous solution is 1:1. Add acid solution to adjust the pH range to 4 - 6, and stir at a rotation speed of 500 r / min for 30 min to obtain a hydrolysis solution;

[0009] (b) Weigh 1 - 3 parts of SiC and 1.5 - 2.5 parts of Si 3 N 4 and add them to the hydrolysis solution obtained in step (a). Ultrasonic for 20 min under the condition of a power of 1 KW, and then stir at a rotation speed of 500 r / min for 30 min to obtain an activator. Centrifuge the activator at a rotation speed of 7000 r / min and dry it at a temperature of 70 °C for 24 h to obtain SiC-Si 3 N 4 modified product;

[0010] (c) Weigh 400 - 600 parts of polysilicon and put it into argon atmosphere furnace I to melt the material for 3 h at a temperature of 1420 °C. The argon flow rate is 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid I;

[0011] (d) Add the SiC-Si 3 N 4 modified product obtained in step (b) to the pure silicon liquid I obtained in step (c), and keep the temperature at 1420 °C to obtain the silicon liquid in the first seed crystal region.

[0012] Further, the preparation method of the silicon liquid in the second heavily doped region comprises the following steps:

[0013] (i)Weigh 150 - 200 parts of polysilicon and put it into furnace II under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid II;

[0014] (ii)Weigh 0.2 - 0.4 parts of SbCl 3 and add it to the pure silicon liquid II obtained in step (i) to obtain mixed silicon liquid I;

[0015] (iii)Weigh 0.1 part of In 2 O 3 Put it into a tubular furnace with a hydrogen flow rate of 500 ml / min and carry out reduction treatment at a high temperature of 900 - 1100 °C for 2 h. Naturally cool it to room temperature to obtain elemental In;

[0016] (vi)Add the elemental In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii), and maintain the temperature at 1420 °C to obtain the second heavily doped region silicon liquid.

[0017] Furthermore, the preparation method of the third lightly doped region silicon liquid includes the following steps:

[0018] (α)Weigh 140 - 180 parts of polysilicon and put it into furnace III under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid III;

[0019] (β)Weigh 0.01 part of PCl 5 Put it into a tubular furnace with an argon flow rate of 500 ml / min and carry out reduction treatment at a high temperature of 400 - 600 °C for 4 h. Naturally cool it to room temperature to obtain elemental P;

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

[0021] (δ)Weigh 0.05 - 0.1 part of Al 2 O 3 Add it to the mixed silicon liquid II obtained in step (γ), and maintain the temperature at 1420 °C to obtain the third lightly doped region silicon liquid.

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

[0023] Step 1: Retain 100 parts of silicon liquid in the first seed crystal area in furnace I. Take fine crystals and place them 15 cm above the surface of the silicon liquid in the first seed crystal area. Preheat the fine crystals for 30 min, then slowly insert the preheated fine crystals 10 mm into the silicon liquid in the first seed crystal area. Keep the pulling speed of the fine crystals at 220 mm / h for 8 min, increase the speed at a rate of 1.25 mm / min to 245 mm / h, and then increase the speed at a rate of 2.5 mm / min to 270 mm / h. Draw out 30 parts of the silicon liquid from the first seed crystal area on the fine crystals to obtain the fine crystal - first seed crystal area;

[0024] Step 2: Retain 100 parts of silicon liquid in the second heavily doped area in furnace II. Place the fine crystal - first seed crystal area obtained in Step 1 15 cm above the surface of the silicon liquid in the second heavily doped area. Preheat the fine crystal - first seed crystal area for 30 min, then slowly insert the preheated fine crystal - first seed crystal area 10 mm into the silicon liquid in the second heavily doped area. Slowly adjust the pulling speed of the fine crystal from 270 mm / h to increase at a rate of 2 mm / min to 300 mm / h, and then increase the speed at a rate of 3 mm / min to 330 mm / h. Draw out 20 parts of the silicon liquid from the second heavily doped area on the fine crystal - first seed crystal area to obtain the fine crystal - first seed crystal area - second heavily doped area;

[0025] Step 3: Retain 100 parts of silicon liquid in the third lightly doped area in furnace III. Place the fine crystal - first seed crystal area - second heavily doped area obtained in Step 2 15 cm above the surface of the silicon liquid in the second heavily doped area. Preheat the fine crystal - first seed crystal area - second heavily doped area for 30 min, then slowly insert the preheated fine crystal - first seed crystal area - second heavily doped area 10 mm into the silicon liquid in the second heavily doped area. Slowly adjust the pulling speed of the fine crystal from 330 mm / h to increase at a rate of 3 mm / min to 380 mm / h. Draw out 10 parts of the silicon liquid from the third lightly doped area on the fine crystal - first seed crystal area - second heavily doped area to obtain the fine crystal - first seed crystal area - second heavily doped area - third lightly doped area. Remove the fine crystal to obtain the high - strength seed crystal body;

[0026] Step 4: Grind and polish the high - strength seed crystal 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 - crystal silicon obtained in Step 4 into absolute ethanol and ultrasonicate for 30 min under the condition of an ultrasonic frequency of 60 kHz. Then place the high - strength seed crystal precursor for large - diameter single - crystal silicon into a mixed acid for cleaning, and then alternately clean it 3 times with absolute ethanol and deionized water. Then heat it to 1300 °C under the condition of an argon flow rate of 25 L / min for annealing treatment for 24 h, and naturally cool it to room temperature to obtain a high - strength seed crystal for large - diameter single - crystal silicon.

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

[0029] The high-strength seed crystal for large-diameter single-crystalline silicon prepared by the present invention adopts a zoning design. In the first seed crystal zone, high temperature promotes the reaction between silicon carbide and silicon, and the generated elemental carbon plays multiple roles. On the one hand, when the crystal is stressed and deformed, the elemental carbon hinders the movement of dislocations. The dislocations need to bypass or cut through the carbon particles, increasing the resistance to dislocation movement and enhancing the strength of the seed crystal. On the other hand, the elemental carbon segregates at the grain boundaries, filling the grain boundary defects and voids, enhancing the binding force between grain boundary atoms. As the grain boundary is a relatively weak area of the crystal, this improves the overall strength and toughness of the seed crystal, reduces the generation and propagation of grain boundary cracks, and enhances the fracture resistance. Moreover, silicon nitride is introduced into this seed crystal zone, and Si 2 N 2 O is generated under low-oxygen conditions. At high temperatures, Si 2 N 2 O forms C-N, C-O, and C-Si covalent bonds with the elemental carbon. These covalent bonds make the atoms bind more closely, enhancing the stability of the internal structure of the seed crystal. Due to their high bond strength, dislocations need more energy to overcome obstacles or change directions to bypass, increasing the difficulty of dislocation movement and making the seed crystal less likely to undergo plastic deformation when stressed, further enhancing the strength of the seed crystal.

[0030] For the high-strength seed crystal for large-diameter single-crystalline silicon prepared by the present invention, in the second heavy doping zone, heavy doping atoms are introduced to form defects on the surface of the seed crystal, improving the binding of carbon at the interface with the first seed crystal zone. At the same time, the formed defects provide defect sites for the light doping in the third light doping zone, enabling the tight combination of heavy doping and light doping. Meanwhile, the existence of the light doping seed crystal zone avoids the influence of heavy doping on the quality of single-crystalline silicon.

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

[0032] Figure 1 It is a diagram of the preparation method of the high-strength seed crystal for large-diameter single-crystalline silicon proposed by the present invention;

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

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

[0035] Figure 4 It is the first furnace single-crystal whole bar rate of the high-strength seed crystal for large-diameter single-crystalline silicon prepared in the embodiment of the present invention;

[0036] Figure 5The single crystal whole bar rate of the high-strength seed crystal for large-diameter single-crystalline silicon prepared in the embodiment of the present invention;

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

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

[0039] Figure 8 The impurity introduction amount of the high-strength seed crystal for large-diameter single-crystalline silicon prepared in the embodiment of the present invention during single crystal preparation.

[0040] The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. Detailed Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a 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 those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

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

[0043] The preparation method of the high-strength seed crystal for large-diameter single-crystalline silicon in the following embodiments refers to Figure 1 The three-dimensional diagram of the high-strength seed crystal for large-diameter single-crystalline silicon refers to Figure 2 The zoning of the high-strength seed crystal for large-diameter single-crystalline silicon refers to Figure 3 Unless otherwise specified, they are all conventional methods; the materials used in the following embodiments, unless otherwise specified, are all high-purity industrial grades, with a purity of 99.999% or more. The volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution used is 1:1, and the mixed acid used is hydrofluoric acid:nitric acid with a mass ratio of 1:4, 40% concentration of hydrofluoric acid, and 70% concentration of nitric acid.

[0044] Embodiment 1: A high-strength seed crystal for large-diameter single-crystalline silicon, comprising the following raw materials in parts by weight: 30 parts of silicon liquid in the first seed crystal area, 20 parts of silicon liquid in the second heavily doped area, and 10 parts of silicon liquid in the third lightly doped area.

[0045] Preparation method of silicon liquid in the first seed crystal region, comprising the following steps:

[0046] (a) Weigh 2 parts of γ-aminopropyltriethoxysilane and add it to 15 parts of an ethanol aqueous solution. Add glacial acetic acid to adjust the pH range to 4, and stir for 30 min under the condition of a rotation speed of 500 r / min to obtain a hydrolysis solution;

[0047] (b) Weigh 1 part of SiC and 1.5 parts of Si 3 N 4 Add them to the hydrolysis solution obtained in step (a), ultrasonicate for 20 min under the condition of a power of 1 KW, and then stir for 30 min under the condition of a rotation speed of 500 r / min to obtain an activator. Centrifuge the activator under the condition of a rotation speed of 7000 r / min, and place it in a drying condition at a temperature of 70 °C for 24 h to obtain a SiC-Si 3 N 4 modified product;

[0048] (c) Weigh 400 parts of polysilicon and place it in argon atmosphere furnace I for melting the material for 3 h at a temperature of 1420 °C, with an argon flow rate of 25 L / min. Remove slag from the melted silicon liquid to obtain pure silicon liquid I;

[0049] (d) Add the SiC-Si 3 N 4 modified product obtained in step (b) to the pure silicon liquid I obtained in step (c), and maintain the temperature at 1420 °C to obtain the silicon liquid in the first seed crystal region.

[0050] Preparation method of silicon liquid in the second double-doped region, comprising the following steps:

[0051] (i) Weigh 150 parts of polysilicon and place it in argon atmosphere furnace II for melting the material for 3 h at a temperature of 1420 °C, with an argon flow rate of 25 L / min. Remove slag from the melted silicon liquid to obtain pure silicon liquid II;

[0052] (ii) Weigh 0.2 part of SbCl 3 and add it to the pure silicon liquid II obtained in step (i) to obtain a mixed silicon liquid I;

[0053] (iii) Weigh 0.1 part of In 2 O 3 Place it in a tube furnace with a hydrogen flow rate of 500 ml / min, and perform reduction treatment at a high temperature of 900 °C for 2 h, and naturally cool to room temperature to obtain elemental In;

[0054] (vi) Add the elemental In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii), and maintain the temperature at 1420 °C to obtain the silicon liquid in the second double-doped region.

[0055] Method for preparing silicon liquid in the third lightly doped region, comprising the following steps:

[0056] (α) Weigh 140 parts of polysilicon and place it in furnace III under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid III;

[0057] (β) Weigh 0.01 part of PCl 5 Place it in a tubular furnace with an argon flow rate of 500 ml / min, and perform reduction treatment at a high temperature of 400 °C for 4 h. Naturally cool it to room temperature to obtain elemental P;

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

[0059] (δ) Weigh 0.05 part of Al 2 O 3 Add it to the mixed silicon liquid II obtained in step (γ), and maintain the temperature at 1420 °C to obtain the silicon liquid in the third lightly doped region.

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

[0061] Step 1: Retain 100 parts of the silicon liquid in the first seed crystal region in furnace I, take fine crystals, place the fine crystals 15 cm above the surface of the silicon liquid in the first seed crystal region, preheat the fine crystals for 30 min, slowly insert the preheated fine crystals 10 mm into the silicon liquid in the first seed crystal region, maintain the pulling speed of the fine crystals at 220 mm / h for 8 min, increase the speed at a rate of 1.25 mm / min to 245 mm / h, and then increase the speed at a rate of 2.5 mm / min to 270 mm / h. Draw out 30 parts of the silicon liquid in the first seed crystal region from the fine crystals to obtain fine crystal - first seed crystal region;

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

[0063] Step 3: Retain 100 parts of silicon liquid in the third lightly doped region in Furnace III. Place the fine crystal - first seed crystal region - second heavily doped region obtained in Step 2 at a position 15 cm from the surface of the silicon liquid in the second heavily doped region, preheat the fine crystal - first seed crystal region - second heavily doped region for 30 min, slowly insert the preheated fine crystal - first seed crystal region - second heavily doped region 10 mm into the silicon liquid in the second heavily doped region, slowly adjust the pulling speed of the fine crystal from 330 mm / h to 380 mm / h at a growth rate of 3 mm / min, draw out 10 parts of the silicon liquid in the third lightly doped region from the fine crystal - first seed crystal region - second heavily doped region to obtain the fine crystal - first seed crystal region - second heavily doped region - third lightly doped region, and remove the fine crystal to obtain a high-strength seed crystal body;

[0064] Step 4: Grind and polish the high-strength seed crystal body obtained in Step 3 to obtain a high-strength seed crystal precursor for large-diameter single-crystalline silicon;

[0065] Step 5: Place the high-strength seed crystal precursor for large-diameter single-crystalline silicon obtained in Step 4 into absolute ethanol, ultrasonically treat it for 30 min under the condition that the ultrasonic frequency is 60 kHz, then place the high-strength seed crystal precursor for large-diameter single-crystalline silicon into a mixed acid for cleaning, then alternately clean it 3 times with absolute ethanol and deionized water, and then heat it to 1300 °C under the condition that the argon flow rate is 25 L / min for annealing treatment for 24 h, 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-crystalline silicon, comprising 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 preparation method of the silicon liquid in the first seed crystal region comprises the following steps:

[0068] (a) Weigh 2 parts of γ-aminopropyltriethoxysilane and add it to 18 parts of an ethanol aqueous solution, add glacial acetic acid to adjust the pH range to 5, and stir for 30 min under the condition of a rotation speed of 500 r / min to obtain a hydrolysis solution;

[0069] (b) Weigh 2 parts of SiC and 2 parts of Si 3 N 4 and add them to the hydrolysis solution obtained in step (a), ultrasonically treat it for 20 min under the condition of a power of 1 KW, then stir for 30 min under the condition of a rotation speed of 500 r / min to obtain an activator, centrifuge the activator under the condition of a rotation speed of 7000 r / min, and place it in a drying condition at 70 °C for 24 h to obtain a SiC - Si 3 N 4 modified product;

[0070] (c) Weigh 500 parts of polysilicon and put it into furnace I under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid I;

[0071] (d) Add the SiC - Si 3 N 4 modifier obtained in step (b) to the pure silicon liquid I obtained in step (c), and maintain at 1420 °C to obtain the silicon liquid in the first seed crystal region.

[0072] The preparation method of the silicon liquid in the second heavy doping region includes the following steps:

[0073] (i) Weigh 180 parts of polysilicon and put it into furnace II under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid II;

[0074] (ii) Weigh 0.3 parts of SbCl 3 and add it to the pure silicon liquid II obtained in step (i) to obtain the mixed silicon liquid I;

[0075] (iii) Weigh 0.1 part of In 2 O 3 Put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and carry out reduction treatment at a high temperature of 1000 °C for 2 h, and naturally cool to room temperature to obtain elemental In;

[0076] (vi) Add the elemental In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii), and maintain the temperature at 1420 °C to obtain the silicon liquid in the second heavy doping region.

[0077] The preparation method of the silicon liquid in the third light doping region includes the following steps:

[0078] (α) Weigh 160 parts of polysilicon and put it into furnace III under an argon atmosphere. Melt the material at a temperature of 1420 °C for 3 h, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid III;

[0079] (β) Weigh 0.01 part of PCl 5 Put it into a tubular furnace with an argon flow rate of 500 ml / min, and carry out reduction treatment at a high temperature of 500 °C for 4 h, and naturally cool to room temperature to obtain elemental P;

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

[0081] (δ) Weigh 0.08 part of Al 2 O3 Into the mixed silicon liquid II obtained in step (γ), while maintaining the temperature at 1420 °C, the third lightly doped region silicon liquid is obtained.

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

[0083] Embodiment 3: A high-strength seed crystal for large-diameter single-crystalline silicon, comprising the following raw materials in parts by weight: 30 parts of the first seed crystal region silicon liquid, 20 parts of the second heavily doped region silicon liquid, and 10 parts of the third lightly doped region silicon liquid.

[0084] The preparation method of the first seed crystal region silicon liquid includes the following steps:

[0085] (a) Weigh 2 parts of γ-aminopropyltriethoxysilane and add it to 20 parts of an ethanol aqueous solution. Add glacial acetic acid to adjust the pH range to 6, and stir for 30 min under the condition of a rotation speed of 500 r / min to obtain a hydrolysis solution;

[0086] (b) Weigh 3 parts of SiC and 2.5 parts of Si 3 N 4 Add them to the hydrolysis solution obtained in step (a), ultrasonicate for 20 min under the condition of a power of 1 KW, and then stir for 30 min under the condition of a rotation speed of 500 r / min to obtain an activator. Centrifuge the activator under the condition of a rotation speed of 7000 r / min and place it in a drying condition at 70 °C for 24 h to obtain the SiC-Si 3 N 4 modifier;

[0087] (c) Weigh 600 parts of polysilicon and place it in argon atmosphere furnace I to melt the material for 3 h at a temperature of 1420 °C, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid I;

[0088] (d) Add the SiC-Si 3 N 4 modifier obtained in step (b) to the pure silicon liquid I obtained in step (c), and maintain the temperature at 1420 °C to obtain the first seed crystal region silicon liquid.

[0089] The preparation method of the second heavily doped region silicon liquid includes the following steps:

[0090] (i) Weigh 200 parts of polysilicon and place it in argon atmosphere furnace II to melt the material for 3 h at a temperature of 1420 °C, with an argon flow rate of 25 L / min. Remove the slag from the melted silicon liquid to obtain pure silicon liquid II;

[0091] (ii) Weigh 0.4 part of SbCl 3Add it to the pure silicon liquid II obtained in step (i) to obtain the mixed silicon liquid I;

[0092] (iii) Weigh 0.1 part of In 2 O 3 Put it into a tubular furnace with a hydrogen flow rate of 500 ml / min, and carry out reduction treatment at a high temperature of 1100 °C for 2 h, and naturally cool to room temperature to obtain elemental In;

[0093] (vi) Add the elemental In obtained in step (iii) to the mixed silicon liquid I obtained in step (ii), and keep the temperature at 1420 °C to obtain the second heavily doped region silicon liquid.

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

[0095] (α) Weigh 180 parts of polysilicon and put it into furnace III under an argon atmosphere, carry out melting for 3 h at a temperature of 1420 °C, with an argon flow rate of 25 L / min, and remove slag from the melted silicon liquid to obtain pure silicon liquid III;

[0096] (β) Weigh 0.01 part of PCl 5 Put it into a tubular furnace with an argon flow rate of 500 ml / min, and carry out reduction treatment at a high temperature of 600 °C for 4 h, and naturally cool to room temperature to obtain elemental P;

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

[0098] (δ) Weigh 0.1 part of Al 2 O 3 Add it to the mixed silicon liquid II obtained in step (γ), and keep the temperature at 1420 °C to obtain the third lightly doped region silicon liquid.

[0099] This embodiment also provides a preparation method of a high-strength seed crystal for large-diameter single crystal silicon, and this embodiment is the same as the preparation method of a high-strength seed crystal for large-diameter single crystal silicon in Embodiment 1.

[0100] Comparative example:

[0101] The difference between Comparative Example 1 and Embodiment 2 is that the first seed crystal region silicon liquid only melts polysilicon and does not add other materials to obtain the first seed crystal region silicon liquid, and the rest is the same as Embodiment 2;

[0102] The difference between Comparative Example 2 and Embodiment 2 is that the second heavily doped region silicon liquid only melts polysilicon and does not add other materials to obtain the first seed crystal region silicon liquid, and the rest is the same as Embodiment 2;

[0103] Comparative Example 3 is an ordinary seed crystal, and the manufacturing standard is the same as that of the high-strength seed crystal for large-diameter single-crystalline silicon.

[0104] To verify the performance of the prepared high-strength seed crystal for large-diameter single-crystalline silicon, all the prepared products were used in the preparation of 12-inch single-crystalline silicon. The running time was calculated as one furnace per 550 h, the maximum feeding amount per furnace was 1200 kg, and the whole-bar rate was calculated as qualified products when the drawn length ≥ 1200 mm. Figure 4 For the whole-bar rate data of the first furnace of the prepared high-strength seed crystal for large-diameter single-crystalline silicon, it can be seen that the whole-bar rate of the high-strength seed crystal for large-diameter single-crystalline silicon obtained in the example is higher than that of the comparative example and the ordinary seed crystal corresponding to Comparative Example 3. Figure 5 For the whole-bar rate data of the second furnace of the prepared high-strength seed crystal for large-diameter single-crystalline silicon, although it slightly decreases compared with the whole-bar rate of the first furnace, the whole-bar rate of the example is still better than that of the comparative example. Figure 6 For the whole-bar rate of the third furnace of the prepared high-strength seed crystal for large-diameter single-crystalline silicon, the whole-bar rate of the example is the same as that of the previous two furnaces. Figure 7 For the hidden crack situation of the seed crystal after three furnaces of use of the prepared high-strength seed crystal for large-diameter single-crystalline silicon, it can be seen that the overall hidden crack of the example is relatively low, indicating that the prepared high-strength seed crystal for large-diameter single-crystalline silicon is superior to the comparative example and the ordinary seed crystal corresponding to Comparative Example 3 in terms of overall heat transfer. During the use process, due to uneven heat and strength problems, a relatively large hidden crack rate occurs. Figure 8 For the measurement of the impurities in the prepared single-crystalline silicon, the measurement standard is to take a silicon rod with a length ≥ 3000 mm, cut off 1000 mm of single-crystalline silicon material from both the head and the tail, and measure the impurity introduction amount of the middle single-crystalline silicon slice. Taking the impurity amount of qualified silicon wafer products as the detection standard, it can be seen that the impurity content in the silicon wafers prepared corresponding to the example is lower than that in the comparative example, indicating that the prepared high-strength seed crystal for large-diameter single-crystalline silicon has high stability.

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

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

[0107] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0108] The above description of the present invention and its implementation manners is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the purpose of the present invention, design similar manners and embodiments to this technical solution without creative efforts, they shall 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 polysilicon, wherein the mass fraction ratio of Al2O3, PCl5 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 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 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 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) Weighing In2O3, treating it at high temperature, and cooling 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 temperature, 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).

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