Silicon crystal foam material treatment method, silicon crystal foam material, silicon rod and silicon wafer

Abstract

The invention provides a silicon crystal foam material treatment method, a silicon crystal foam material, a silicon rod and a silicon wafer. The turbidity of the silicon crystal foam material is 5-200 NTU, preferably 5-60 NTU, and compared with the turbidity of the silicon crystal foam material in the prior art, the turbidity of the silicon crystal foam material is greatly reduced; due to the fact that the turbidity is low, the crystal forming rate and the whole rod rate of the drawn single crystal meet the standard, a large number of the crystals can be used for single crystal drawing, and the cost is reduced under the condition that the standard single crystal can be prepared.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, and in particular relates to a method for processing silicon crystal foam and silicon crystal foam, silicon rods, and silicon wafers. Background Technology

[0002] In the photovoltaic industry, polycrystalline silicon flakes are generated during the production of primary polycrystalline silicon, while monocrystalline silicon flakes are found in the recycled materials from monocrystalline silicon plants. Both polycrystalline and monocrystalline silicon flakes are collectively referred to as silicon crystal flakes. The particle size of silicon crystal flakes is typically 1–5 mm. Due to their small size, their surface area is much larger than that of silicon crystal blocks of the same weight. Therefore, the degree of silicon powder adhering to the surface of silicon particles in silicon crystal flakes is much higher than in blocks, resulting in higher turbidity, averaging 200–1000 NTU. Because of this high turbidity, the crystallization rate and ingot yield of silicon crystal flakes used for pulling monocrystalline silicon are low. Therefore, silicon crystal flakes are usually only used for ingot purification, Czochralski purification, or in small proportions for crystal pulling and grounding. They cannot be used in large quantities for crystal pulling, which is detrimental to the effective utilization of raw materials.

[0003] A device for removing light impurities from silicon crystal foam (patent number CN202321695672.X) describes a device for removing light impurities from silicon crystal foam, including a vibrating feeding device and an overflow cleaning device. The vibrating feeding device places the silicon crystal foam into the overflow cleaning device, which removes light impurities from the foam. This patent can remove light impurities from the foam, and with the help of pure water, it can also remove some silicon powder. However, in practical applications, drying is required after overflow cleaning, and silicon powder will be generated again during the drying stage, leading to an increase in turbidity. Summary of the Invention

[0004] This invention provides a method for processing silicon crystal foam, which yields silicon crystal foam with low turbidity. This effectively solves the technical problem that the high turbidity of silicon crystal foam results in low single crystal formation rate and ingot yield or even the inability to pull crystals.

[0005] According to one aspect of the present invention, a silicon crystal foam material is provided, wherein the turbidity of the silicon crystal foam material is 5 to 200 NTU, preferably, the turbidity of the silicon crystal foam material is 5 to 60 NTU.

[0006] Preferably, the silicon crystal flake material of the present invention is obtained by the following processing method:

[0007] The silicon crystal powder before treatment is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal powder before treatment melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

[0008] Preferably, the constant temperature heating temperature is 1300-1400℃ and the time is 1-4h. More preferably, the constant temperature heating temperature is 1350-1400℃ and the time is 3-4h.

[0009] Preferably, the silicon crystal foam is monocrystalline silicon foam or polycrystalline silicon foam;

[0010] Preferably, when the temperature is fixed, changing the heating time results in a difference between the turbidity reduction of the silicon crystal flake material before treatment and the time.

[0011] Monocrystalline silicon foam satisfies the following equation: y = K1t + b1;

[0012] Polycrystalline silicon foam satisfies the following formula: y = K2t + b2;

[0013] Where t is the heating time and y is the turbidity reduction rate;

[0014] 0.07 <K1<0.08,0.6<b1<0.7;

[0015] 0.1 <K2<0.2,0.5<b2<0.6。

[0016] With a fixed time, changing the heating temperature resulted in a variation in the turbidity reduction of the silicon crystal flake material before treatment, which was related to the temperature.

[0017] Monocrystalline silicon foam satisfies the following formula: y = K3T - b3;

[0018] Polycrystalline silicon foam material satisfies the following formula: y = K4T - b4;

[0019] Where T is the heating temperature and y is the turbidity reduction rate;

[0020] 0.001 <K3<0.002,1.3<b3<1.4;

[0021] 0.003 <K4<0.004,3.2<b4<3.3。

[0022] According to another aspect of the present invention, a silicon rod is also provided, which is made using the silicon crystal flake material of the present invention.

[0023] According to another aspect of the present invention, a silicon wafer is also provided, which is made using the silicon rod of the present invention.

[0024] According to another aspect of the present invention, a method for processing silicon crystal foam is also provided, wherein the silicon crystal foam before processing is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal foam melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

[0025] Preferably, the constant temperature heating temperature is 1300-1400℃ and the time is 1-4h. More preferably, the constant temperature heating temperature is 1350-1400℃ and the time is 3-4h.

[0026] Preferably, the silicon crystal foam is monocrystalline silicon foam or polycrystalline silicon foam;

[0027] Preferably, when the temperature is fixed, changing the heating time results in a difference between the turbidity reduction of the silicon crystal flake material before treatment and the time.

[0028] Monocrystalline silicon foam satisfies the following equation: y = K1t + b1;

[0029] Polycrystalline silicon foam satisfies the following formula: y = K2t + b2;

[0030] Where t is the heating time and y is the turbidity reduction rate;

[0031] 0.07 <K1<0.08,0.6<b1<0.7;

[0032] 0.1 <K2<0.2,0.5<b2<0.6。

[0033] With a fixed time, changing the heating temperature resulted in a variation in the turbidity reduction of the silicon crystal flake material before treatment, which was related to the temperature.

[0034] Monocrystalline silicon foam satisfies the following formula: y = K3T - b3;

[0035] Polycrystalline silicon foam material satisfies the following formula: y = K4T - b4;

[0036] Where T is the heating temperature and y is the turbidity reduction rate;

[0037] 0.001 <K3<0.002,1.3<b3<1.4;

[0038] 0.003 <K4<0.004,3.2<b4<3.3。

[0039] The beneficial effects of this invention are:

[0040] According to one aspect of the present invention, a silicon crystal foam material is provided, the turbidity of which is 5 to 200 NTU, preferably 5 to 60 NTU, which is significantly lower than the turbidity of silicon crystal foam materials in the prior art. Precisely because of its low turbidity, the crystallization rate and ingot yield of single crystals obtained by using it as a raw material meet the standards, and it can be used in large quantities for single crystal pulling. Therefore, while it is possible to prepare single crystals that meet the standards, the cost is reduced.

[0041] According to another aspect of the present invention, a method for preparing silicon crystal foam is provided. In this method, high-turbidity silicon crystal foam is heated at a constant temperature for a certain period of time, causing the silicon powder in the high-turbidity silicon crystal foam to melt while the silicon particles remain unmelted, thereby obtaining low-turbidity silicon crystal foam. The turbidity reduction of the foam is very high. Compared with silicon crystal foam obtained by existing processing methods, silicon crystal foam with low turbidity and high turbidity reduction can be prepared. Furthermore, precisely because the silicon crystal foam has low turbidity, the crystallization rate and rod yield of single crystals pulled using it as raw material meet the standard requirements. Attached Figure Description

[0042] The above and other objects, features, and advantages of the present invention will become more apparent from the more detailed description of the embodiments of the invention in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same parts or steps.

[0043] Figure 1 This is a schematic flowchart of the silicon crystal flake material processing method of the present invention.

[0044] Figure 2 This is a photograph of the silicon crystal foam obtained after processing in Example 1 of the present invention.

[0045] Figure 3 This is a photograph of the silicon crystal foam obtained after processing in Example 2 of the present invention.

[0046] Figure 4 This is a photograph of the silicon crystal foam obtained after processing in Example 3 of the present invention.

[0047] Figure 5 This is a photograph of the silicon crystal flake material obtained after processing in Comparative Example 3 of this invention.

[0048] Figure 6 This is a photograph of the silicon crystal flake material obtained after processing in Comparative Example 4 of this invention. Detailed Implementation

[0049] This invention provides a method for processing silicon crystal foam, as well as silicon crystal foam, silicon rods, and silicon wafers. The embodiments of this invention are described below with reference to the accompanying drawings.

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0052] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0053] When using expressions such as "at least one of A, B, and C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C. Similarly, when using expressions such as "at least one of A, B, or C," the meaning should generally be interpreted according to the understanding of someone skilled in the art. For example, "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C.

[0054] According to one aspect of the present invention, a silicon crystal foam material is provided, the turbidity of which is 5-200 NTU. The turbidity of the silicon crystal foam material affects the crystallization rate and ingot yield of single crystals. When the turbidity of the silicon crystal foam material is high, exceeding 200 NTU, the crystallization rate and ingot yield cannot meet the production process requirements. When the turbidity of the silicon crystal foam material is less than 200 NTU, such as 80 NTU, 100 NTU, 120 NTU, 140 NTU, 160 NTU, 180 NTU, and 200 NTU, the crystallization rate and ingot yield of the silicon crystal foam material are improved.

[0055] Preferably, the turbidity of the silicon crystal foam is 5-60 NTU, and the crystallization rate and ingot yield of the silicon crystal foam meet the production process requirements.

[0056] Preferably, the turbidity of the silicon crystal foam is 5 NTU, 8 NTU, 10 NTU, 15 NTU, 20 NTU, 25 NTU, 30 NTU, 35 NTU, 40 NTU, 45 NTU, 50 NTU, 55 NTU and 60 NTU.

[0057] The silicon crystal foam is monocrystalline silicon foam and / or polycrystalline silicon foam, preferably monocrystalline silicon foam or polycrystalline silicon foam.

[0058] The turbidity of the monocrystalline silicon foam according to the present invention is 50-200 NTU, preferably 50-60 NTU, and further preferably 50 NTU, 52 NTU, 54 NTU, 56 NTU, 58 NTU and 60 NTU.

[0059] The turbidity of the monocrystalline silicon foam material according to the present invention is 50-200 NTU, which is greatly reduced compared with the turbidity of 700-1000 NTU of the monocrystalline silicon foam material in the prior art. As a result, the crystallization rate of silicon rods prepared using the monocrystalline silicon foam material of the present invention is 70%-82%, and the whole rod rate is 40%-55%.

[0060] It should be noted that the crystallization rate and ingot yield mentioned in the technical solution of this invention are calculated by using 50% to 100% of the silicon crystal flakes of this invention and the balance of polycrystalline ingots as crystal pulling raw materials, and drawing silicon rods using conventional Czochralski technology, and then calculating them according to the formula.

[0061] When the turbidity of monocrystalline silicon foam is 60-200 NTU, the crystallization rate of the silicon rods obtained is 70%-80%, and the whole rod rate is 40%-48%.

[0062] Preferably, when the turbidity of the monocrystalline silicon foam is 50-60 NTU, the crystallization rate of the obtained silicon rod is 80%-82% and the whole rod rate is 48%-55%, which improves the crystallization rate and whole rod rate compared with the silicon rods prepared by monocrystalline silicon foam using the prior art.

[0063] The turbidity of the polycrystalline silicon foam material according to the present invention is 5 to 80 NTU, preferably 5 to 20 NTU, and further preferably 5 NTU, 8 NTU, 10 NTU, 12 NTU, 14 NTU, 16 NTU, 18 NTU, or 20 NTU.

[0064] The turbidity of the polycrystalline silicon foam of the present invention is 5-80 NTU, which is greatly reduced compared with the turbidity of 200-400 NTU of the polycrystalline silicon foam in the prior art. As a result, the crystallization rate of silicon rods prepared using the polycrystalline silicon foam of the present invention is 70%-85%, and the whole rod rate is 40%-60%.

[0065] When the turbidity of polycrystalline silicon foam is 20-80 NTU, the crystallization rate of the silicon rods obtained is 70%-80%, and the whole rod rate is 40%-50%.

[0066] Preferably, when the turbidity of the polycrystalline silicon foam is 5-20 NTU, the crystallization rate of the silicon rod obtained is 80%-85%, and the whole rod rate is 50%-60%, which improves the crystallization rate and whole rod rate compared with the silicon rods prepared by polycrystalline silicon foam using the prior art.

[0067] The silicon crystal foam material according to the present invention has a turbidity of 5 to 200 NTU, more preferably 5 to 60 NTU, which is significantly lower than the turbidity of silicon crystal foam material in the prior art. Precisely because of its low turbidity, the crystallization rate and ingot yield of the single crystal obtained by pulling meet the standards, and it can be used in large quantities for single crystal pulling. Therefore, the cost is reduced when it is possible to prepare single crystals that meet the standards.

[0068] The crystallization rate of the silicon crystal foam according to the present invention is 70% to 85%, further, the crystallization rate is 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, and 79%, preferably, the crystallization rate of the silicon crystal foam is 80% to 85%, and more preferably 80%, 81%, 82%, 83%, 84%, and 85%.

[0069] The crystallization rate of the monocrystalline silicon foam according to the present invention is 80% to 82%, and more preferably 80%, 80.5%, 81%, 81.5%, or 82%.

[0070] The crystallization rate of the polycrystalline silicon foam according to the present invention is 80% to 85%, and more preferably 80%, 81%, 82%, 83%, 84%, or 85%.

[0071] The silicon crystal shavings according to the present invention have a total ingot ratio of 40% to 60%, more preferably 40%, 41%, 42%, 43%, 44%, 45%, 46%, and 47%. Preferably, the total ingot ratio of the silicon crystal shavings is 48% to 60%, more preferably 48%, 50%, 52%, 53%, 55%, 57%, 59%, and 60%.

[0072] The integral rate of the monocrystalline silicon foam according to the present invention is 48% to 55%, and more preferably 48%, 50%, 52%, 54%, or 55%.

[0073] According to the present invention, the integral rate of polycrystalline silicon foam is 50% to 60%, and further, the integral rate of polycrystalline silicon foam is 50%, 52%, 54%, 56%, 58%, or 60%.

[0074] The silicon crystal flakes of the present invention can be used to prepare silicon rods with high crystallization rate and rod yield. Therefore, its application in single crystal pulling can not only produce silicon rods with good crystallization rate and rod yield, but also reduce costs.

[0075] The silicon crystal powder according to the present invention is obtained by the following processing method:

[0076] The silicon crystal powder before treatment is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal powder before treatment melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

[0077] According to the present invention, the silicon crystal foam is heated at a constant temperature of 1300-1400°C for a certain time of 1-4 hours. Preferably, the constant temperature is heated at 1350-1400°C for a certain time of 3-4 hours.

[0078] At a constant temperature, varying the heating time resulted in a decrease in turbidity of the untreated silicon crystal flakes relative to the time elapsed.

[0079] Monocrystalline silicon foam satisfies the following equation: y = K1t + b1;

[0080] Polycrystalline silicon foam satisfies the following formula: y = K2t + b2;

[0081] Where t is the heating time and y is the turbidity reduction rate;

[0082] 0.07 <K1<0.08,0.6<b1<0.7;

[0083] 0.1 <K2<0.2,0.5<b2<0.6。

[0084] With a fixed time, changing the heating temperature resulted in a variation in the turbidity reduction of the silicon crystal flake material before treatment, which was related to the temperature.

[0085] Monocrystalline silicon foam satisfies the following formula: y = K3T - b3;

[0086] Polycrystalline silicon foam material satisfies the following formula: y = K4T - b4;

[0087] Where T is the heating temperature and y is the turbidity reduction rate;

[0088] 0.001 <K3<0.002,1.3<b3<1.4;

[0089] 0.003 <K4<0.004,3.2<b4<3.3。

[0090] More specifically, for example, with the silicon crystal powder according to the present invention, when the temperature is fixed at 1350°C, changing the heating time results in a turbidity reduction in the silicon crystal powder before treatment relative to the time.

[0091] The single-crystal silicon foam material satisfies the following formula: y = 0.073t + 0.6682;

[0092] The polycrystalline silicon foam material satisfies the following formula: y = 0.112t + 0.5342;

[0093] Where t is the heating time and y is the turbidity reduction rate.

[0094] More specifically, for example, with the silicon crystal powder according to the present invention, when the heating temperature is changed while the time is fixed at 3.5 hours, the turbidity reduction of the silicon crystal powder before treatment is related to the temperature.

[0095] The single-crystal silicon foam material satisfies the following formula: y = 0.0017T - 1.398;

[0096] The polycrystalline silicon foam material satisfies the following formula: y = 0.0031T - 3.286;

[0097] Where T is the heating temperature and y is the turbidity reduction rate.

[0098] A silicon rod made from the aforementioned silicon crystal flake material.

[0099] Silicon rods made using the silicon crystal flakes of the present invention can achieve good crystallization rate and overall rod yield, and can also reduce costs.

[0100] A silicon wafer made from the aforementioned silicon rod.

[0101] Silicon wafers made using the silicon rods of this invention can meet product performance requirements while reducing costs.

[0102] According to another aspect of the present invention, a method for processing silicon crystal foam is also provided, wherein the silicon crystal foam before processing is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal foam before processing melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

[0103] The silicon crystal flake material before processing includes silicon particles and silicon powder. The silicon particles have a relatively large particle size of 1-5 mm, while the silicon powder has a relatively small particle size of micron or nanometer.

[0104] The melting point of solid crystalline silicon is the temperature at which pure monocrystalline or polycrystalline silicon completely transforms from a solid to a liquid state under standard atmospheric pressure, which is approximately 1414°C.

[0105] However, silicon powder does not have a fixed, uniform melting point. Its melting behavior is closely related to its particle size (especially nanoscale powders). In nanoscale silicon powder, the proportion of surface atoms increases dramatically. These surface atoms have higher energy (Gibbs free energy) than internal atoms. According to thermodynamic principles (Gibbs-Thomson effect), smaller particles and higher radii of curvature lead to a lower melting point. Therefore, very fine nanoscale silicon powder has a lower melting point than larger silicon particles, with the degree of reduction depending on the particle size, ranging from a few degrees to several hundred degrees Celsius (especially for extremely fine nanoscale silicon powder).

[0106] Micron-sized or larger silicon powders readily oxidize during heating, forming a silicon dioxide layer on their surface. At temperatures far below the melting point of silicon particles, sintering can begin at the contact points between the silicon powder particles. Sintering is a solid-state diffusion process in which the silicon powder particles agglomerate, grow necks, and densify.

[0107] Therefore, when silicon powder and silicon particles are heated simultaneously, at a temperature lower than the melting point of silicon particles, the nanoscale silicon powder melts because its melting point is lower than that of silicon particles. At the contact points of the micron-scale silicon powder, a local eutectic reaction occurs. The strong sintering effect densifies the micron-scale silicon powder, and the silicon oxide or other impurities formed on the surface further lower the local melting point, thus presenting a molten state.

[0108] In summary, during the constant temperature heating process of this invention, the silicon powder on the surface reaches a molten state before the internal silicon particles have time to melt, and adheres to the surface of the unmelted silicon particles, thereby reducing the turbidity of the silicon crystal foam.

[0109] According to the method of the present invention, the constant temperature heating temperature is 1300-1400℃, further, the constant temperature heating temperature is 1300℃, 1310℃, 1320℃, 1330℃, 1340℃, preferably, the constant temperature heating temperature is 1350-1400℃, further preferably, the constant temperature heating temperature is 1350℃, 1360℃, 1370℃, 1380℃, 1390℃, and 1400℃.

[0110] According to the method of the present invention, the constant temperature heating time is 1 to 4 hours, for example, 1 hour, 1.5 hours, 2 hours, and 2.5 hours, preferably 3 to 4 hours, and further preferably 3 hours, 3.5 hours, and 4 hours.

[0111] It should be noted that when the heating temperature is below 1300℃ and the heating time is less than 1 hour, the melting effect of silicon powder on the surface is not good, the surface is loose or partially loose, the silicon powder cannot completely adhere to the silicon particles, and the turbidity cannot be significantly reduced.

[0112] When the heating temperature exceeds 1400℃ and the heating time exceeds 4 hours, the silicon crystal foam will be completely melted, which will easily react with the container containing the foam, introducing new impurities, or even melting the container, making the silicon crystal foam unusable.

[0113] If the temperature is 1300℃, the reaction time should be greater than 1 hour, and the longer the reaction time, the greater the reduction in turbidity. If the temperature is 1400℃, the reaction time should be less than 4 hours, and the longer the reaction time within the 4-hour range, the greater the reduction in turbidity. However, when the temperature is 1300℃ to 1400℃ and the reaction time is 1 hour to 4 hours, the combined reaction conditions can significantly reduce the turbidity of the silicon crystal powder, which is the preferred parameter range. More preferably, the temperature is 1350℃ to 1400℃ and the reaction time is 3 to 4 hours.

[0114] Regarding the selection of temperature and time, within the scope of this invention, they can be selected interchangeably. For example, if the temperature is lower, the time can be longer, and if the time is longer, the temperature can be lower. Both can result in silicon crystal foam with turbidity within the scope of this invention. In other words, when both the temperature and time are within the scope of this invention, the turbidity of the silicon crystal foam can be reduced to the scope of this invention.

[0115] At a constant temperature, varying the heating time resulted in a decrease in turbidity of the untreated silicon crystal flakes relative to the time elapsed.

[0116] Monocrystalline silicon foam satisfies the following equation: y = K1t + b1;

[0117] Polycrystalline silicon foam satisfies the following formula: y = K2t + b2;

[0118] Where t is the heating time and y is the turbidity reduction rate;

[0119] 0.07 <K1<0.08,0.6<b1<0.7;0.1<K2<0.2,0.5<b2<0.6。

[0120] The above formula is a pattern obtained by the applicant through extensive experimental data fitting. Based on this formula, the turbidity reduction corresponding to different heating times can be predicted and evaluated during the actual processing of silicon crystal flakes.

[0121] To illustrate the above formula, we will use the first set of data; more data will not be provided.

[0122] The first set of data, with the heating temperature set to 1350℃ and the heating time varied, shows the turbidity comparison before and after the silicon crystal foam material treatment, as shown in Table 1.

[0123] In Table 1, the other processing conditions for the monocrystalline silicon foam are the same as those in Example 3, except that monocrystalline silicon foam with a turbidity of 803 NTU before processing is used, the heating temperature is fixed at 1350℃, and the duration is adjusted as shown in Table 1.

[0124] The other processing conditions for the polycrystalline silicon foam in Table 1 are the same as those in Example 6, except that the polycrystalline silicon foam with a turbidity of 213 NTU before processing is used, the heating temperature is fixed at 1350°C, and the duration is adjusted as shown in Table 1.

[0125] Table 1

[0126]

[0127] According to the test results in Table 1, when the temperature is fixed at 1350℃, changing the heating time affects the turbidity reduction of the silicon crystal foam.

[0128] The monocrystalline silicon foam material satisfies the following formula: y = 0.073t + 0.6682.

[0129] The polycrystalline silicon foam material satisfies the following formula: y = 0.112t + 0.5342;

[0130] Where t is the heating time and y is the turbidity reduction rate. With the heating temperature constant, the turbidity reduction rate gradually increases with the increase of heating time.

[0131] With a fixed time, changing the heating temperature resulted in a variation in the turbidity reduction of the silicon crystal flake material before treatment, which was related to the temperature.

[0132] Monocrystalline silicon foam satisfies the following formula: y = K3T - b3;

[0133] Polycrystalline silicon foam material satisfies the following formula: y = K4T - b4;

[0134] Where T is the heating temperature and y is the turbidity reduction rate;

[0135] 0.001 <K3<0.002,1.3<b3<1.4;

[0136] 0.003 <K4<0.004,3.2<b4<3.3。

[0137] The above formula is a pattern obtained by the applicant through extensive experimental data fitting. Based on this formula, the turbidity reduction corresponding to different heating times can be predicted and evaluated during the actual processing of silicon crystal flakes.

[0138] To illustrate the above formula, the second set of data will be used as an example; more data will not be provided.

[0139] The second set of data, with the heating time set to 3.5h, shows the comparison of turbidity before and after silicon crystal foam material treatment by changing the heating temperature.

[0140] In Table 2, the other processing conditions for the monocrystalline silicon foam are the same as those in Example 3, except that monocrystalline silicon foam with a turbidity of 803 NTU before processing is used, the heating time is fixed at 3.5 h, and the temperature is adjusted as in Table 1.

[0141] The other processing conditions for the polycrystalline silicon foam in Table 2 are the same as those in Example 6, except that the polycrystalline silicon foam with a turbidity of 213 NTU before processing is used, the heating time is fixed at 3.5 h, and the temperature is adjusted as shown in Table 2.

[0142] Table 2

[0143]

[0144]

[0145] According to the test results in Table 2, when the heating time is fixed at 3.5 hours, changing the heating temperature affects the turbidity reduction of the silicon crystal foam in relation to the temperature.

[0146] The single-crystal silicon foam material satisfies the following formula: y = 0.0017T - 1.398;

[0147] The polycrystalline silicon foam material satisfies the following formula: y = 0.0031T - 3.286;

[0148] Where T is the heating temperature and y is the turbidity reduction rate.

[0149] With the heating time remaining constant, the turbidity decrease gradually increases as the heating temperature rises.

[0150] An embodiment of the present invention provides a method for processing silicon crystal foam, wherein the silicon crystal foam is heated at a constant temperature for a certain period of time before processing, so that the silicon powder in the silicon crystal foam melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

[0151] The raw materials for silicon crystal foam include silicon particles and silicon powder. The silicon particles have a particle size of 1-5 mm, and the surface of the silicon particles is coated with silicon powder, which has a particle size of micron and nanometer. During the constant temperature heating process before treatment, the silicon powder on the surface of the silicon crystal foam melts under the external high temperature environment and adheres to the unmelted silicon particles, reducing the turbidity of the foam.

[0152] A specific processing method for silicon crystal flakes according to the present invention, such as... Figure 1As shown, the process includes the following steps: S1, dispensing silicon crystal powder into containers; S2, placing the containers in an ingot casting furnace, evacuating the furnace, and then introducing protective gas; S3, heating the silicon crystal powder at a constant temperature to melt the silicon powder on the surface of the silicon particles; S4, cooling the silicon crystal powder to allow the molten silicon powder to adhere to the silicon particles.

[0153] The steps described above will now be described in detail.

[0154] S1. Distribute the unprocessed silicon crystal powder into containers, as follows:

[0155] The unprocessed silicon crystal powder is packaged into multiple containers with a certain volume. The containers need to be heat-resistant and will not react with the silicon material in a high-temperature environment, thus not affecting the performance of the silicon material.

[0156] The container is preferably made of quartz, silicon, or silicon nitride. There is no specific limit to the volume of the container, but it should not be too large to facilitate melt molding.

[0157] Preferably, the container is made of a quartz tube with a diameter of 200-300 mm. More preferably, the diameter of the quartz tube is 200 mm, 220 mm, 240 mm, 250 mm, 260 mm, 280 mm, or 300 mm.

[0158] S2. Place the container in the ingot casting furnace, evacuate the furnace, and then introduce protective gas. The specific operation is as follows:

[0159] After placing the container in the ingot casting furnace, the furnace is first evacuated, and then a protective gas is introduced into the furnace. The container holding the silicon crystal powder is then heated using the ingot casting furnace.

[0160] Multiple containers are arranged in an array inside the ingot furnace to simultaneously heat multiple containers loaded with silicon crystal powder before processing, thereby improving the processing efficiency of silicon crystal powder.

[0161] After evacuating the ingot casting furnace, a protective gas is introduced into the furnace, and the furnace leakage rate is tested. The leakage rate should be ≤0.015mBar / 5min, and the furnace pressure should be maintained at 24-26mBar to prevent impurities from entering during the heating process.

[0162] Furthermore, the leakage rate is preferably 0.015 mBar / 5min, 0.010 mBar / 5min, 0.005 mBar / 5min, or 0.002 mBar / 5min; the furnace pressure is preferably 24 mBar, 25 mBar, or 26 mBar.

[0163] S3. The silicon crystal powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0164] Specifically, during the constant-temperature heating process of silicon crystal powder, a temperature sensor is used to monitor the temperature inside the furnace, and the preferred heating temperature is 1350-1400℃.

[0165] Furthermore, the preferred heating temperature is 1350℃, 1360℃, 1370℃, 1380℃, 1390℃, or 1400℃.

[0166] The preferred heating time is 3 to 4 hours, and more preferably 3 hours, 3.2 hours, 3.4 hours, 3.5 hours, 3.6 hours, 3.8 hours, or 4 hours.

[0167] The heating temperature is kept constant by adjusting the heating power at the bottom and sides of the ingot furnace, which is set to 60-80 kW. During the constant temperature heating process, the silicon powder on the surface of the silicon particles can be molten before the temperature reaches the melting point of the internal silicon particles, so that the silicon powder adheres to the surface of the unmelted silicon particles, and the silicon crystal flakes in the container are in a slightly molten state.

[0168] S4. Cool the silicon crystal powder to allow the molten silicon powder to adhere to the silicon particles.

[0169] During the cooling process, the ingot casting furnace stops heating. A protective gas is introduced into the ingot casting furnace to lower the furnace temperature to 280-320°C. More preferably, the furnace temperature can be lowered to 280°C, 290°C, 300°C, 310°C, or 320°C.

[0170] Using gas flow to cool silicon crystal flakes can accelerate the cooling process without introducing impurities.

[0171] The flow rate of the protective gas is set to 80–100 slpm, and the purging time is set to 8–10 h. More preferably, the flow rate of the protective gas is 80 slpm, 85 slpm, 90 slpm, 95 slpm, or 100 slpm, and the purging time can be set to 8 h, 9 h, or 10 h. The protective gas is preferably argon or nitrogen.

[0172] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, it is hereby declared that the following embodiments are only used to describe and illustrate the present invention in detail, and are not intended to limit the scope of protection of the present invention.

[0173] Example 1

[0174] A method for processing silicon crystal foam, wherein the silicon crystal foam is monocrystalline silicon foam with a turbidity of 780 NTU before processing, includes the following steps:

[0175] S1. Dispense the silicon crystal powder into containers;

[0176] 400 kg of monocrystalline silicon powder was packaged into quartz tubes with a diameter of 250 mm.

[0177] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0178] Multiple quartz tube arrays loaded with monocrystalline silicon flakes were placed into the ingot casting furnace. After evacuating the ingot casting furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015 mBar / 5min, while maintaining the furnace pressure at 25 mBar.

[0179] S3. The monocrystalline silicon powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0180] Temperature sensors are used to monitor the temperature inside the furnace, keeping the heating temperature at 1350℃, and the constant temperature heating time is set to 3 hours.

[0181] S4. Cool the silicon crystal powder to allow the molten silicon powder to adhere to the silicon particles.

[0182] Stop heating, introduce argon gas into the ingot furnace to lower the furnace temperature to 280°C, set the argon gas flow rate to 80 slpm, and set the argon gas introduction time to 8h. Then remove the monocrystalline silicon foam from the container.

[0183] Example 2

[0184] A method for processing silicon crystal foam, wherein the silicon crystal foam is monocrystalline silicon foam with a turbidity of 997 NTU before processing, includes the following steps:

[0185] S1. Dispense the monocrystalline silicon powder into containers.

[0186] 400 kg of monocrystalline silicon powder was packaged into quartz tubes with a diameter of 250 mm.

[0187] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0188] Multiple quartz tube arrays loaded with monocrystalline silicon flakes were placed into the ingot casting furnace. After evacuating the ingot casting furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015 mBar / 5min, while maintaining the furnace pressure at 25 mBar.

[0189] S3. The monocrystalline silicon powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0190] Temperature sensors are used to monitor the temperature inside the furnace, maintaining the heating temperature at 1400℃, and the constant temperature heating time is set to 4 hours.

[0191] S4. Cool down the monocrystalline silicon powder to allow the molten silicon powder to adhere to the silicon particles.

[0192] Stop heating, introduce argon gas into the ingot furnace to reduce the furnace temperature to 320°C, set the argon gas flow rate to 100 slpm, and set the argon gas introduction time to 10h. Then remove the single crystal silicon foam from the container.

[0193] Example 3

[0194] A method for processing silicon crystal foam, wherein the silicon crystal foam is monocrystalline silicon foam with a turbidity of 819 NTU before processing, includes the following steps:

[0195] S1. Dispense the silicon crystal powder into containers;

[0196] 400 kg of foam material was divided into quartz tubes with a diameter of 250 mm.

[0197] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0198] Multiple arrays of quartz tubes loaded with foam material were discharged into the ingot casting furnace. After evacuating the ingot casting furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015mBar / 5min, while maintaining the furnace pressure at 25mBar.

[0199] S3. The silicon crystal powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0200] Temperature sensors are used to monitor the temperature inside the furnace, keeping the heating temperature at 1370℃, and the constant temperature heating time is set to 3.5h.

[0201] S4. Cool the silicon crystal powder to allow the molten silicon powder to adhere to the silicon particles.

[0202] Stop heating, introduce argon gas into the ingot furnace to reduce the furnace temperature to 300°C, set the argon gas flow rate to 90 slpm, and set the argon gas introduction time to 9 hours. Then remove the monocrystalline silicon foam from the container.

[0203] Example 4

[0204] A method for processing silicon crystal foam, wherein the silicon crystal foam is polycrystalline silicon foam with a turbidity of 205 NTU before processing, includes the following steps:

[0205] S1. Dispense the polycrystalline silicon powder into containers;

[0206] 400 kg of polycrystalline silicon foam was packaged into quartz tubes with a diameter of 250 mm.

[0207] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0208] Multiple arrays of quartz tubes loaded with polycrystalline silicon flakes were placed into the ingot casting furnace. After evacuating the furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015 mBar / 5min, while maintaining the furnace pressure at 25 mBar.

[0209] S3. The polycrystalline silicon powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0210] Temperature sensors are used to monitor the temperature inside the furnace, keeping the heating temperature at 1350℃, and the constant temperature heating time is set to 3 hours.

[0211] S4. Cool down the polycrystalline silicon powder to allow the molten silicon powder to adhere to the silicon particles.

[0212] Stop heating, introduce argon gas into the ingot furnace to lower the temperature of the polycrystalline silicon foam to 280°C, set the argon gas flow rate to 80 slpm and the argon gas introduction time to 8h, and then remove the polycrystalline silicon foam from the container.

[0213] Example 5

[0214] A method for processing silicon crystal foam, wherein the silicon crystal foam is polycrystalline silicon foam with a turbidity of 390 NTU before processing, includes the following steps:

[0215] S1. Dispense the polycrystalline silicon powder into containers;

[0216] 400 kg of polycrystalline silicon foam was packaged into quartz tubes with a diameter of 250 mm.

[0217] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0218] Multiple arrays of quartz tubes loaded with polycrystalline silicon flakes were placed into the ingot casting furnace. After evacuating the furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015 mBar / 5min, while maintaining the furnace pressure at 25 mBar.

[0219] S3. The polycrystalline silicon powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0220] Temperature sensors are used to monitor the temperature inside the furnace, maintaining the heating temperature at 1400℃, and the constant temperature heating time is set to 4 hours.

[0221] S4. Cool down the polycrystalline silicon powder to allow the molten silicon powder to adhere to the silicon particles.

[0222] Stop heating, introduce argon gas into the ingot furnace to reduce the furnace temperature to 320°C, set the argon gas flow rate to 100 slpm, and set the argon gas introduction time to 10h. Then remove the polycrystalline silicon foam from the container.

[0223] Example 6

[0224] A method for processing silicon crystal foam, wherein the silicon crystal foam is polycrystalline silicon foam with a turbidity of 276 NTU before processing, includes the following steps:

[0225] S1. Dispense the polycrystalline silicon powder into containers;

[0226] 400 kg of polycrystalline silicon foam was packaged into quartz tubes with a diameter of 250 mm.

[0227] S2. Place the container in the casting furnace, evacuate the casting furnace, and then introduce protective gas.

[0228] Multiple arrays of quartz tubes loaded with polycrystalline silicon flakes were placed into the ingot casting furnace. After evacuating the furnace, argon gas was introduced into the furnace, and the furnace leakage rate was tested to ensure that the leakage rate was ≤0.015 mBar / 5min, while maintaining the furnace pressure at 25 mBar.

[0229] S3. The polycrystalline silicon powder is heated at a constant temperature to melt the silicon powder on the surface of the silicon particles.

[0230] Temperature sensors are used to monitor the temperature inside the furnace, keeping the heating temperature at 1370℃, and the constant temperature heating time is set to 3.5h.

[0231] S4. Cool down the polycrystalline silicon powder to allow the molten silicon powder to adhere to the silicon particles.

[0232] Stop heating, introduce argon gas into the ingot furnace to reduce the furnace temperature to 300°C, set the argon gas flow rate to 90 slpm, and set the argon gas introduction time to 9 hours. Then remove the polycrystalline silicon foam from the container.

[0233] Comparative Example 1

[0234] Compared with Example 3, Comparative Example 1 was processed with the same single crystal foam (same turbidity, same weight), but with a silicon crystal foam light impurity removal device (patent number CN202321695672.X) from the prior art.

[0235] The aforementioned device includes a vibrating feeding device and an overflow cleaning device. The vibrating feeding device places the monocrystalline silicon foam material into the overflow cleaning device, which removes light impurities from the monocrystalline silicon foam material and then dries the washed monocrystalline silicon foam material.

[0236] Comparative Example 2

[0237] Compared with Example 6, Comparative Example 2 was processed with the same polycrystalline foam material (same turbidity, same weight), but with a silicon crystal foam material light impurity removal device (patent number CN202321695672.X) from the prior art.

[0238] The aforementioned device includes a vibrating feeding device and an overflow cleaning device. The vibrating feeding device places the polycrystalline silicon foam into the overflow cleaning device, which removes light impurities from the polycrystalline silicon foam and then dries the washed polycrystalline silicon foam.

[0239] Comparative Example 3

[0240] Compared with Example 3, the comparative example is identical in all other conditions except that a temperature sensor is used to monitor the temperature inside the furnace, keeping the heating temperature at 1320°C.

[0241] Comparative Example 4

[0242] Compared with Example 3, this comparative example is identical in all other conditions except that a temperature sensor is used to monitor the temperature inside the furnace, keeping the heating temperature at 1420°C.

[0243] Comparative Example 5

[0244] Compared with Example 3, the comparative example had the same conditions except that the constant temperature heating time was 2.8 hours.

[0245] Comparative Example 6

[0246] Compared with Example 3, the comparative example had the same conditions except that the constant temperature heating time was 4.2 hours.

[0247] Comparative Example 7

[0248] Compared with Example 6, this comparative example is identical in all other conditions except that a temperature sensor is used to monitor the temperature inside the furnace, keeping the heating temperature at 1320°C.

[0249] Comparative Example 8

[0250] Compared with Example 6, this comparative example is identical in all other conditions except that a temperature sensor is used to monitor the temperature inside the furnace, keeping the heating temperature at 1420°C.

[0251] Comparative Example 9

[0252] The only difference between this comparative example and Example 6 is that the isothermal heating time is 2.8 hours.

[0253] Comparative Example 10

[0254] This comparative example is compared with Example 6, with all other conditions being the same, except that the constant temperature heating time is 4.2 hours.

[0255] Table 1 shows the test results of turbidity, turbidity reduction value, turbidity reduction rate, crystallization rate, and whole rod rate of silicon crystal powder before and after treatment in Examples 1-6 and Comparative Examples 1-10.

[0256] Turbidity was measured according to YS / T 1754-2024 "Determination of Dust on the Surface of Particulate Silicon - Turbidity Method". A certain mass of particulate silicon was weighed and placed in pure water. After ultrasonic cleaning, the dust on the surface of the particulate silicon was immersed in the pure water. The suspended particles in the pure water would scatter the light passing through the sample. This characteristic was used to characterize the amount of dust on the surface of the particulate silicon.

[0257] The silicon crystal flakes obtained in Examples 1-6 and Comparative Examples 1-10 of the present invention were subjected to crystal pulling to measure the crystal yield and the whole rod yield.

[0258] The raw materials used are 50% polycrystalline ingots and 50% silicon crystal flakes obtained from the examples or comparative examples by weight percentage. Other process parameters are conventional settings of the prior art, including a temperature stabilization time of 3 hours, a crystal pulling time of 1 hour, a crystal pulling speed of ≤300 mm / h, a shoulder expansion time of 3.5 hours, a shoulder diameter of ≤300 mm, and a constant diameter pulling speed of ≤100 mm / h, finally obtaining a crystal rod.

[0259] Crystallization rate = Number of crystals formed in one run / Total number of single crystals produced * 100%;

[0260] One-step crystal formation means: no expansion, break-up, or break-back, and the crystal pulling length is maintained at more than 700mm.

[0261] Ingot yield = Number of ingots / Total number of single crystals produced * 100%;

[0262] Among them, "whole rod" refers to: a single crystal produced after one crystal pulling process that maintains a length of 80% of the required segment length (4500mm), or a single crystal produced after expansion and maintaining a break within 300mm that meets the required segment length.

[0263] Table 1

[0264]

[0265]

[0266] Comparing Example 3 and Comparative Example 1, it can be seen that Example 3, using the processing method of this application, significantly reduced the turbidity of the monocrystalline silicon foam, and the processed monocrystalline silicon foam had good crystallization rate and rod yield; while Comparative Example 1, due to the generation of secondary silicon powder in the drying step, actually increased the turbidity; Example 3 achieved better technical results than Comparative Example 1.

[0267] Comparing Example 6 and Comparative Example 2, it can be seen that Example 6, using the processing method of this application, significantly reduced the turbidity of the polycrystalline silicon foam, and the processed polycrystalline silicon foam had good crystallization rate and rod yield; while Comparative Example 2, due to the generation of secondary silicon powder in the drying step, actually increased the turbidity; Example 6 achieved better technical results than Comparative Example 2.

[0268] In Comparative Examples 1 and 2, some silicon powder can be removed during the overflow cleaning process. However, in actual applications, the silicon crystal foam material after water washing needs to be dried. During the drying stage, silicon powder will be generated again. The amount of silicon powder generated again is more than the silicon powder removed by water washing, which leads to an increase in the turbidity of the silicon crystal foam material.

[0269] Compared with Example 3, Comparative Example 3 had other conditions unchanged, but the heating temperature was reduced to 1320°C, which is lower than 1350°C. This resulted in poor silicon powder melting effect on the surface of the monocrystalline silicon foam, a loose surface, a turbidity reduction of less than 90%, and a low crystallization rate and whole rod rate.

[0270] Compared with Example 3, Comparative Example 4 had other conditions unchanged, but the heating temperature was increased to 1420°C. Temperatures above 1400°C would cause the silicon crystal foam to be completely melted, making it easy to react with the container holding the foam and introduce new impurities, or even melt the container, rendering the foam unusable.

[0271] Compared with Example 6, Comparative Example 7 had other conditions unchanged, but the heating temperature was reduced to 1320°C, which is lower than 1350°C. This resulted in poor silicon powder melting effect on the surface of polycrystalline silicon foam, loose surface, turbidity reduction of less than 90%, and low crystallization rate and whole rod rate.

[0272] Compared with Example 6, Comparative Example 8 had other conditions unchanged, but the heating temperature was increased to 1420°C. Temperatures above 1400°C would cause the polycrystalline silicon foam to be completely melted, making it easy to react with the container holding the foam and introduce new impurities, or even melt the container, rendering the foam unusable.

[0273] Based on the data from Examples 1 to 6, Comparative Examples 3 and 4, Comparative Examples 7 and 8, and the above analysis, it can be seen that heating at 1300℃ to 1350℃ can reduce the turbidity of silicon crystal foam, but the effect is not good. Heating at 1350℃ to 1400℃ can effectively reduce the turbidity of silicon crystal foam without causing it to melt completely.

[0274] Compared with Example 3, Comparative Example 5, with other conditions unchanged, only shortened the heating time to 2.8h, less than 3h, which resulted in poor silicon powder melting effect on the surface of the monocrystalline silicon foam, loose surface, poor forming, turbidity reduction of less than 90%, and low crystallization rate and whole rod rate.

[0275] Compared with Example 6, Comparative Example 9, with other conditions unchanged, only shortened the heating time to 2.8h, less than 3h, which resulted in poor silicon powder melting effect on the surface of polycrystalline silicon foam, loose surface, poor forming, turbidity reduction of less than 90%, and low crystallization rate and whole rod rate.

[0276] Compared with Example 3, Comparative Example 6 had other conditions unchanged, but the heating time was extended to 4.2h. More than 4h would cause the monocrystalline silicon foam to be completely melted, which would easily react with the container holding the foam and introduce new impurities, or even melt the container, making the foam unusable.

[0277] Compared with Example 6, Comparative Example 10 had other conditions unchanged, but the heating time was extended to 4.2h. More than 4h would cause the polycrystalline silicon foam to be completely melted, which would easily react with the container holding the foam and introduce new impurities, or even melt the container, making the foam unusable.

[0278] Based on the data from Examples 1 to 6, Comparative Examples 5 and 6, Comparative Examples 9 and 10, and the above analysis, it can be seen that heating time of 1 to 3 hours can reduce the turbidity of silicon crystal foam, but the effect is not good. Heating time of 3 to 4 hours can effectively reduce the turbidity of silicon crystal foam without causing it to melt completely.

[0279] Therefore, during the isothermal micro-melting process of silicon crystal foam, the heating temperature is set to 1350-1400℃ and the heating time is set to 3-4h. The silicon powder on the surface can melt and adhere to the internal silicon particles, resulting in good molding effect, good surface hardness, and effectively reducing the turbidity of the foam.

[0280] If the temperature is too low or the heating time is too short, the silicon powder on the surface cannot adhere to the silicon particles inside, resulting in a loose surface, poor molding, and an inability to effectively improve the turbidity of the foam material.

[0281] If the temperature is too high or the heating time is too long, the silicon crystal powder will completely melt and react with the container holding the powder, introducing new impurities or even melting the container, making the silicon crystal powder unusable.

[0282] In Example 1, the constant temperature heating was 1350℃, and the heating time was 3 hours. The silicon powder on the surface of the silicon crystal foam had a better melting effect, while the internal silicon particles did not melt. The surface hardness was improved, the molding was better, and the turbidity was reduced. Figure 2 As shown.

[0283] In Example 2, the constant temperature heating was 1400℃, and the heating time was 4 hours. The silicon powder on the surface of the silicon crystal foam exhibited good melting effect while the internal silicon particles remained unmelted. This resulted in good surface hardness, good shaping, and reduced turbidity. Figure 3 As shown.

[0284] In Example 3, the constant temperature heating was 1370℃, and the heating time was 3.5 hours. The silicon powder on the surface of the silicon crystal foam exhibited good melting effect while the internal silicon particles remained unmelted. This resulted in good surface hardness, good forming, and reduced turbidity. Figure 4 As shown.

[0285] In Comparative Example 3, all other conditions were the same as in Example 3, except that the heating temperature was reduced to 1320°C. This resulted in poor silicon powder melting on the surface of the monocrystalline silicon foam, a porous surface, poor forming, and a turbidity reduction of less than 90%. Figure 5 As shown.

[0286] In Comparative Example 4, all other conditions were the same as in Example 3, except that the heating temperature was increased to 1420°C. This caused the monocrystalline silicon foam to completely melt, making it prone to reacting with the container holding the foam and introducing new impurities. It could even melt the container, rendering the foam unusable. Figure 6 As shown.

[0287] The embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. Furthermore, the definitions of the various components described above are not limited to the specific structures, shapes, or methods mentioned in the embodiments, and those skilled in the art can easily modify or substitute them.

[0288] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A silicon crystal flake material, characterized in that, The turbidity of the silicon crystal foam is 5-200 NTU; preferably, the turbidity of the silicon crystal foam is 5-60 NTU.

2. The silicon crystal flake material according to claim 1, characterized in that, The silicon crystal powder is obtained by the following processing method: The silicon crystal powder before treatment is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal powder before treatment melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

3. The silicon crystal flake material according to claim 2, characterized in that, The constant temperature heating temperature is 1300-1400℃, and the certain time is 1-4 hours; Preferably, the constant temperature heating is 1350–1400°C, and the certain time is 3–4 hours.

4. The silicon crystal flake material according to claim 3, characterized in that, The silicon crystal foam material is either monocrystalline silicon foam material or polycrystalline silicon foam material; With a fixed temperature, varying the heating time resulted in a difference between the turbidity reduction of the untreated silicon crystal flake material and the time required. The monocrystalline silicon foam material satisfies the following formula: y=K1t+b1; The polycrystalline silicon foam material satisfies the following formula: y=K2t+b2; Where t is the heating time and y is the turbidity reduction rate; 0.07 <K1<0.08,0.6<b1<0.7; 0.1 <K2<0.2,0.5<b2<0.6。 5. The silicon crystal flake material according to claim 4, characterized in that, With a fixed time, changing the heating temperature resulted in a relationship between the turbidity reduction of the silicon crystal flake material before treatment and the temperature. The monocrystalline silicon foam material satisfies the following formula: y = K3T - b3; The polycrystalline silicon foam material satisfies the following formula: y = K4T - b4; Where T is the heating temperature and y is the turbidity reduction rate; 0.001 <K3<0.002,1.3<b3<1.4; 0.003 <K4<0.004,3.2<b4<3.3。 6. A silicon rod, characterized in that, It is made using the silicon crystal foam material described in any one of claims 1 to 5.

7. A silicon wafer, characterized in that, It is made using the silicon rod described in claim 6.

8. A method for processing silicon crystal flakes, characterized in that, The silicon crystal powder before treatment is heated at a constant temperature for a certain period of time, so that the silicon powder in the silicon crystal powder before treatment melts while the silicon particles do not melt, and the molten silicon powder adheres to the silicon particles.

9. The processing method according to claim 8, characterized in that, The constant temperature heating temperature is 1300-1400℃, and the certain time is 1-4 hours; Preferably, the constant temperature heating is 1350–1400°C, and the certain time is 3–4 hours.

10. The processing method according to claim 9, characterized in that, The silicon crystal foam material is either monocrystalline silicon foam material or polycrystalline silicon foam material; With a fixed temperature, varying the heating time resulted in a difference between the turbidity reduction of the untreated silicon crystal flake material and the time required. The monocrystalline silicon foam material satisfies the following formula: y=K1t+b1; The polycrystalline silicon foam material satisfies the following formula: y=K2t+b2; Where t is the heating time and y is the turbidity reduction rate; 0.07 <K1<0.08,0.6<b1<0.7; 0.1 <K2<0.2,0.5<b2<0.6。 11. The processing method according to claim 10, characterized in that, With a fixed time, changing the heating temperature resulted in a relationship between the turbidity reduction of the silicon crystal flake material before treatment and the temperature. The monocrystalline silicon foam material satisfies the following formula: y = K3T - b3; The polycrystalline silicon foam material satisfies the following formula: y = K4T - b4; Where T is the heating temperature and y is the turbidity reduction rate; 0.001 <K3<0.002,1.3<b3<1.4; 0.003 <K4<0.004,3.2<b4<3.3。

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