Polysilicon crushed material and method for producing same

Abstract

[Problem] To provide a polysilicon fracture object capable of suppressing resin contamination during filling into a resin bag, transportation after the filling, and removal from the resin bag, of the polysilicon fracture object, to a level unattainable by prior art means. [Solution] The polysilicon fracture object comprising a fragment having a ridge part generated by fracturing a polysilicon rod, in the fragment, the mean curvature radius (r) being 50 μm or greater for a ridge part forward end having an angle of 70° or narrower, and the polysilicon fracture object being obtained via a method comprising a fracturing step of fracturing a polysilicon rod to obtain a fragment, and an etching step of immersing the fragment obtained in the fracturing step into an etching solution to perform etching at an etching speed of 2.5 μm / hour or slower, so that the etching depth reaches 5 μm or deeper.

Description

[Technical Field]

[0001] The present invention relates to a novel crushed polysilicon material. Specifically, the present invention relates to crushed polysilicon material that can suppress resin contamination to an extremely low level when the crushed polysilicon material is packed into a resin bag, typically a polyethylene packaging bag, during transportation after packing, and when the crushed polysilicon material is removed from the resin bag. The present invention also relates to a method for producing the crushed polysilicon material. [Background technology]

[0002] When polysilicon is produced by the Siemens process, the product is obtained in the form of rods. These polysilicon rods have diameters of 80 to 150 mm and lengths of 1000 mm or more. Therefore, when used in other processes, such as single crystal production equipment using the CZ (Czochralski) process, they are generally crushed to an appropriate size and, if necessary, classified into products. Furthermore, the crushed polysilicon undergoes a purification process, such as an etching process, to remove surface impurities, and is then packed in clean resin bags and shipped.

[0003] However, when a resin bag filled with crushed polysilicon is opened and the crushed polysilicon is removed, resin powder generated from the resin bag may adhere to the bag, which has been a problem in the single crystal manufacturing process as a source of carbon contamination.

[0004] Conventionally, the problem of resin powder adhesion has been thought to be primarily caused by vibrations during transportation that cause the crushed polysilicon material to vibrate, resulting in the inner surface of the resin bag coming into contact with the crushed polysilicon material and being scraped off, and various countermeasures have been considered to address this problem.

[0005] For example, there has been proposed a method of filling a resin bag with crushed polysilicon material, removing the gas from the bag to tightly seal the crushed polysilicon material to the resin bag, thereby reducing the effects of vibration and preventing wear on the resin bag (Patent Document 1), and a method of minimizing contamination of the crushed polysilicon material by setting the filling rate of the crushed polysilicon material relative to the capacity of the resin bag within a specific range (Patent Document 2).These measures have made it possible to prevent resin powder from being generated in the resin bag.

[0006] However, while these techniques effectively prevent carbon contamination by resin, the inventors have found that there is room for further improvement. That is, the generation of resin powder due to wear of the resin bag can be prevented to some extent by reducing the number of contact points between the inner surface of the resin bag and the crushed polysilicon material, and it is also possible to remove the resin powder after transportation by means of winnowing or the like. However, the inventors' investigations have revealed that even in the crushed polysilicon material from which the resin powder has been reduced or removed in this manner, resin is still detected on the order of several ppm. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3496021 [Patent Document 2] Patent No. 5726984 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide crushed polysilicon material that can suppress resin contamination to an extremely low level when the crushed polysilicon material is filled into a resin bag, during transportation after filling, and when removed from the resin bag. [Means for solving the problem]

[0009] The inventors of the present invention have conducted extensive research to achieve the above-mentioned object. After crushed polysilicon material is packed into a resin bag and transported, the crushed polysilicon pieces (hereinafter, simply referred to as crushed pieces) that make up the crushed polysilicon material are removed from the resin bag. The resin components on the surface of the crushed polysilicon material are analyzed, and the resin components are identified. Further detailed examination of the surface of the crushed polysilicon material reveals that the resin in the resin bag is firmly attached to the surface of the crushed polysilicon material. Further detailed examination reveals that the resin adheres to the ridges, particularly sharp ridges, formed by crushing the crushed polysilicon material.

[0010] Based on the above findings, further investigations were conducted and it was found that by processing the edge portion so that the radius of curvature is equal to or greater than a specific value, the amount of resin adhering to the polysilicon fragments can be significantly reduced, leading to the completion of the present invention.

[0011] That is, according to the present invention, there is provided a polysilicon crushed material comprising crushed pieces having ridges generated by crushing a polysilicon rod, characterized in that the tip of the ridge (hereinafter also referred to as a specific ridge) in the crushed pieces has an angle of 70° or less, and the average radius of curvature (r) of the tip is 50 μm or more.

[0012] The above characteristic configuration is preferable because it is particularly effective for crushed polysilicon material having an average particle size of 20 to 100 mm.

[0013] The present invention also provides a polysilicon package in which the crushed polysilicon is packed in a resin bag.

[0014] Furthermore, the polysilicon fragments of the present invention can be suitably produced by a method including a crushing step of crushing polysilicon rods to form fragments, and an etching step of immersing the fragments obtained in the crushing step in an etching solution to etch them at an etching rate of 2.5 μm / min or less to an etching depth of 5 μm or more. [Effects of the Invention]

[0015] The crushed polysilicon material of the present invention is processed so that the radius of curvature at the tip of the specific edge portion is equal to or greater than a specific value, thereby extremely effectively preventing adhesion of resin to the crushed polysilicon material due to contact with the inner surface of a resin bag. Therefore, when the crushed polysilicon material is filled into the resin bag, during transportation, or during removal, the amount of resin from the inner surface of the resin bag that adheres to the surface of the crushed polysilicon material can be effectively reduced. Furthermore, by increasing the radius of curvature at the tip of the specific edge portion, it is possible to effectively prevent the generation of resin powder due to abrasion of the resin bag.

[0016] The present invention proposes a means for preventing resin contamination of crushed polysilicon material from a different perspective than the conventional resin contamination prevention means that devised a method for limiting the vibration of crushed polysilicon pieces inside a resin bag, and can be said to be extremely groundbreaking.

[0017] Of course, by combining the means of the present invention with conventional resin contamination prevention means that are devised from conventional packaging forms, a higher resin contamination prevention effect can be obtained. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing an example of fragments constituting the polysilicon fragments that are the subject of the present invention. FIG. [Figure 2] FIG. 10 is a schematic diagram showing a method for obtaining a cross section when determining the angle and radius of curvature (r) of the tip of a ridge. [Figure 3] 3 is a cross-sectional view taken along line AA' in FIG. 2, and is a schematic diagram showing how to determine the angle of the tip of the ridge portion. [Figure 4] FIG. 1 is a schematic diagram showing how to determine the radius of curvature (r) of the tip of a ridge. [Figure 5] 1 is a typical SEM photograph at 30 magnifications showing the state of the tip of the ridge of the crushed polysilicon obtained in Example 1. [Figure 6]1 is a typical SEM photograph at 30 magnifications showing the state of the ridge tip of the crushed polysilicon material obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Polysilicon crushed material) The crushed polysilicon material of the present invention is not particularly limited as long as it is made up of crushed pieces obtained by crushing polysilicon rods. For example, it is common for the crushed polysilicon material to be made up of crushed pieces obtained by crushing polysilicon rods obtained by the Siemens process using a known crushing method described below.

[0020] FIG. 1 is a schematic diagram showing a typical shape of the fragments constituting the polysilicon fragments of the present invention.

[0021] Referring to FIG. 1, the present invention will be described. The polysilicon fragments 1 obtained by crushing the silicon rod have ridges 2 formed by the crushing of the polysilicon rod, which are formed by the crushing of the polysilicon rod, i.e., ... The present invention is characterized in that, among these ridges present in the polysilicon fragments, the sharp specific ridges 2 having a ridge angle of 70° or less have an average tip radius of curvature (r) of 50 μm or more, preferably 60 μm or more. Furthermore, it is more preferable that, for all measurements taken using the measurement method described below, the proportion of ridges having a radius of curvature of 30 μm or less is 20% or less, and particularly 10% or less. By having such ridges, the polysilicon fragments of the present invention not only suppress the generation of resin powder due to scraping of the resin bag caused by contact with the inner surface of the resin bag, but also effectively prevent the adhesion of resin to the polysilicon fragments.

[0022] In the present invention, the specific ridge of a polysilicon fragment refers to a ridge that forms an angle of 70° or less with a cut plane perpendicular to the ridge. Here, the cut plane refers to a plane perpendicular to the ridge line of the ridge. In a straight ridge, as shown on the right side of FIG. 2, the cut plane is the plane perpendicular to the straight line (A-A'). In a curved ridge, as shown on the left side of FIG. 2, the cut plane is the plane perpendicular to the tangent to the curve at the measurement point (A-A'). Figure 3 shows a cross section of line A-A' in FIG. 2. The apex of FIG. 3 is the cut point of the ridge, and the curve (side) continuing from the ridge line indicates the cut portion of the surface of the fragment. The ridge angle θ is the intersection angle of two sides originating from the surface of the fragment. To measure the ridge angle θ, a photograph of the cut surface is taken at 1x magnification (1x), and the ridge angle θ is measured from this image. If the observation magnification of the cut surface is too high, the unevenness of the edges originating from the surface of the crushed material will be emphasized, making it difficult to draw a straight line. Therefore, the observation magnification is set to 1x, and an image is obtained in which the edges are approximately straight up to at least 5 mm from the apex. The ridge angle θ is then calculated from the intersection angle of the two edges. Furthermore, as will be described in detail in the Examples below, the measurement of the radius of curvature of the tip of a specific ridge is performed by randomly selecting multiple fragments having a specific ridge from the polysilicon fragments, obtaining 30x magnification images of the cut surface using a scanning electron microscope (SEM), and calculating the average value of the ridge radii from these images. The ridge angle θ and the radii of curvature are measured at three or more randomly selected cut surfaces of each polysilicon fragment, and a total of 20 or more fragments are measured. The average radius of curvature (r) is the average value of the radii of curvature at ridges with an ridge angle θ of 70° or less.

[0023] In this case, the radius of curvature (r) of the ridge tip was determined by drawing a circle with a radius that coincides with the arc of the ridge tip, as shown in Figure 4. If the observation magnification is too high, the crystal grains in the polysilicon are observed, causing noise when drawing the circle, but if the magnification is around 30x, such noise is not observed and a smooth circle can be drawn along the ridge tip.

[0024] In the present invention, it is necessary for the radius of curvature of the tip of the ridge portion to satisfy the above range in order to reduce the amount of resin adhering due to contact of the crushed polysilicon material with the resin bag, and further to reduce the amount of resin powder generated due to scraping of the resin body by the crushed polysilicon material.

[0025] In the past, polysilicon fragments were obtained by crushing polysilicon rods and then undergoing a cleaning process that included etching, but the radius of curvature of the ridge tip remains almost the same as immediately after crushing, and has a sharp angle. In contrast, the present invention has succeeded in giving ridges with the specific radius of curvature to the polysilicon fragments obtained by crushing polysilicon rods by performing a special etching process described below.

[0026] In the present invention, the size of the polysilicon fragments is not particularly limited. However, since the effects of the present invention are effective for fragments that have a certain mass and are prone to movement when packed into a resin bag, it is preferable that the average particle diameter calculated by measuring the major axis of the particles is 20 to 100 mm, particularly 30 to 80 mm.

[0027] As described above, the crushed polysilicon of the present invention has ridges that are less susceptible to resin adhesion due to contact with a resin bag. Therefore, the crushed polysilicon can be packed in a resin bag, transported, and then removed from the resin bag for use. The amount of resin adhesion can be reduced to 2 ppm by mass or less, and even 0.5 ppm by mass or less, making the crushed polysilicon suitable for use as a raw material for the CZ method, etc. Here, the amount of resin adhesion is calculated by converting the mass of the resin into the mass of carbon atoms.

[0028] In addition, in the crushed polysilicon material of the present invention, the surface concentration of metal impurities such as iron, chromium, nickel, copper, zinc, sodium, calcium, and tungsten is preferably 0.1 ppb (equivalent to elemental value) or less for each metal, and 2 ppb (equivalent to elemental value) or less in total.

[0029] The crushed polysilicon material of the present invention generates very little resin powder due to the scraping of the resin caused by contact with the resin bag. However, by providing a step of removing fine powder from the crushed polysilicon material removed from the resin bag, the amount of resin adhering to the material can be reliably reduced, and this makes it possible to keep the amount of resin entrained in the next step, for example, the step of putting the material into a crucible in the CZ method, very low.

[0030] In the present invention, the material for the resin bag may be any known resin that can be used to make bags, without any particular restrictions, but additive-free polyethylene resin is most commonly used. Furthermore, it is preferable that the surface of the resin bag that comes into contact with the crushed polysilicon material be as smooth as possible, since this reduces friction when the bag comes into contact with the edges of the crushed polysilicon material, thereby significantly enhancing the effects of the crushed polysilicon material of the present invention and further reducing the amount of resin adhering to the crushed polysilicon material.

[0031] The thickness of the film that constitutes the resin bag is not particularly limited, but is generally about 150 to 900 μm.

[0032] (Method of manufacturing crushed polysilicon) The method for obtaining the crushed polysilicon of the present invention is not particularly limited. For example, a method of sanding the edges of the crushed polysilicon having an angle of 70° or less can be adopted, but this is inefficient and may cause metal contamination. Therefore, a method of treating the edges in an etching process for cleaning the surface of the crushed polysilicon is preferably adopted.

[0033] That is, according to the present invention, the method is characterized by including a crushing step of crushing a polysilicon rod to obtain crushed pieces, and an etching step of immersing the crushed pieces obtained in the crushing step in an etching solution to etch the pieces at an etching rate of 2.5 μm / min or less to an etching depth of 5 μm or more.

[0034] In the above-described production method of the present invention, the crushing step may employ any method for crushing the polysilicon rods using a known crushing means, without any particular limitations. Specifically, the polysilicon rods to be crushed are preferably produced by the Siemens process. The polysilicon rods are obtained by cutting the joints of the U-shaped product, and generally have a deposition diameter of 80 to 150 mm and a length of approximately 1000 to 2000 mm. Of course, the U-shaped product may be crushed as is.

[0035] The method for crushing the polysilicon rods is not particularly limited, and any known crushing method may be used without any particular limitation, such as a method using a crushing device such as a jaw crusher or a roll crusher, or a method using a hammer.

[0036] After the crushing, the crushed material can be classified depending on the intended use, and in the present invention, as described above, crushed material classified to have an average particle size of 20 to 100 mm, particularly 30 to 80 mm, is preferably used. In such classification, it is particularly preferable to remove crushed pieces having a particle size of 10 mm or less.

[0037] In the production method of the present invention, it is important to immerse the crushed material obtained in the crushing step in an etching solution and etch it at an etching rate of 2.5 μm / min or less, preferably 1.1 to 2.5 μm / min, to an etching depth of 5 μm or more, preferably 8 to 15 μm, in order to obtain the desired crushed polysilicon material.

[0038] The etching depth is an average etching thickness calculated from the etching amount.

[0039] The inventors have found that, by adopting the above-mentioned specific conditions in the etching process, it is possible to preferentially dissolve the tip of the edge while minimizing dissolution of other portions of the polysilicon fragments. That is, if the etching rate is faster than the above-mentioned range or the etching depth is less than the above-mentioned range, it becomes difficult to achieve the desired radius of curvature at the specific edge.

[0040] The etching rate of the etching solution can be adjusted by adjusting the composition, temperature, and other conditions of the etching solution. Any known etching solution can be used without any particular limitations. However, it is preferable to use an etching solution containing hydrofluoric acid and nitric acid, with a hydrofluoric acid concentration of 0.5 to 10 mass % and a nitric acid concentration of 48 to 68 mass %. The etching temperature is preferably 15 to 30°C. The etching rate is calculated using the method described in WO2018 / 198947. Specifically, a polysilicon test piece with a controlled shape and size is placed in the etching bath, the etching amount is determined from the weight change of the polysilicon test piece, and the etching rate is calculated from the etching time and etching amount.

[0041] In the etching process of the present invention, the above-described etching conditions are employed, and the crushed polysilicon fragments are preferably oscillated in the etching solution to preferentially elute the ridge tips, resulting in more reproducible polysilicon fragments of the present invention. Preferentially eluting the ridge tips means that the etching depth at the ridge tips is deeper than at other portions. Specific etching conditions include a method in which etching is performed while oscillating at a frequency of 3 to 10 times per minute and an amplitude of 5 to 1,000 mm, particularly 10 to 500 mm. Increasing the oscillation frequency or amplitude of the crushed polysilicon fragments in the etching solution may result in the generation of new ridges due to friction or collision between the crushed polysilicon fragments or between the crushed polysilicon fragments and the cleaning basket. Furthermore, leaving the crushed polysilicon fragments in the etching solution tends to reduce the effect of preferentially etching the ridge tips.

[0042] Therefore, by subjecting the crushed material in the etching solution to the aforementioned moderate shaking and then etching, the tips of the ridges are etched more effectively, and it is possible to more reliably obtain crushed polysilicon material having the desired ridges.

[0043] In the above method, the vibration can be longitudinal vibration, lateral vibration, or longitudinal-lateral complex vibration, and the etching is generally performed by placing the polysilicon fragments to be treated in a known cleaning basket.

[0044] According to the method of the present invention, since the ridge tips are treated by etching, no fine powder is generated when the tips are removed, and furthermore, the amount of fine powder present in the obtained crushed polysilicon can be kept to an extremely small amount by cleaning the ridge tips during etching. Specifically, the content of fine powder in the crushed polysilicon can be kept to 200 ppmw or less, particularly 100 ppmw or less, for fine powder of 500 to 1000 μm, and 20 ppmw or less, particularly 10 ppmw or less, for fine powder of less than 500 μm.

[0045] In the manufacturing method of the present invention, the post-etching treatment in the etching step may be any known treatment without particular limitation. For example, the polysilicon is washed with ultrapure water, dried, and then shipped as crushed polysilicon.

[0046] Furthermore, known packaging and transportation methods can be adopted as shipping methods without any particular limitations. For example, the crushed polysilicon material is automatically or manually filled into a resin bag, the opening is sealed, and the bag is packed into a cardboard box as needed, and then shipped. [Example]

[0047] EXAMPLES Hereinafter, examples will be shown to explain the present invention more specifically, but the present invention is not limited to these examples.

[0048] In the examples, various measurements were carried out by the following methods.

[0049] (1) Radius of curvature (r) of the tip of a specific edge of the polysilicon fragment Twenty randomly selected fragments with a ridge angle (θ) of 70° or less (specific ridge) were extracted from 5 kg of crushed polysilicon. Each fragment was sealed in acrylic resin and cut at three locations to create a cross section perpendicular to the tangent to the ridge line of the specific ridge. SEM photographs of each cross section were taken at 30x magnification, and the ridge angle (θ) and the radius of curvature (r) at the tip of the ridge were measured in the resulting images. The radius of curvature (r) of the ridge tip was determined by drawing a circle that matched the arc shape of the ridge tip, as shown in Figure 4.

[0050] (2) Resin adhesion test Five kilograms of crushed polysilicon was placed in a 250 μm thick, 130 mm square gusset-shaped polyethylene resin bag, the opening of which was then fused. The bag was then placed in a 250 μm thick, 160 mm square gusset-shaped polyethylene resin outer bag, the opening of which was then fused. Six 175 mm square bottom, 240 mm high cardboard boxes were placed inside an outer cardboard box measuring 550 mm long, 370 mm wide, and 270 mm high. Each box contained the crushed polysilicon packed in the polyethylene resin bag. The boxes were then loaded onto a truck for a 200 km one-way transport test. The vibration intensity during transport was measured with a vibration meter, and the maximum resultant vibration acceleration was 5 Gal. After the transport test, the crushed polysilicon in the polyethylene resin bag was removed from the cardboard box, and the amount of resin attached was measured.

[0051] (3) Measurement of the amount of polyethylene resin attached to crushed polysilicon The crushed polysilicon material with the polyethylene resin adhering thereto was maintained at 250°C for 30 minutes or more in an inert gas atmosphere to remove organic volatile components, and then the temperature of the crushed polysilicon material was raised to 380°C in a flow of inert gas, and the resulting resin decomposition products were collected. The peak intensity of the resin decomposition products derived from linear unsaturated hydrocarbons, which are decomposition products specific to polyethylene resin, was measured, and the amount of resin adhering to the crushed polysilicon material was determined based on a calibration curve separately prepared by collecting and analyzing the gas evolved from heating a crushed polysilicon material sample with a known amount of polyethylene resin adhering thereto.

[0052] The amount of polyethylene resin attached was measured before and after the resin attachment test, and the value obtained by subtracting the measured value before from the measured value after was shown as the amount of attached resin.

[0053] (4) Amount of silicon fines in crushed polysilicon Approximately 1 kg of crushed polysilicon was placed in a 2 L beaker, and 1 L of ultrapure water was added so that the crushed polysilicon was completely submerged. The beaker was slowly rocked from side to side until the surface of the crushed polysilicon was completely in contact with the ultrapure water, causing the fine powder on the surface to be suspended in the ultrapure water. The resulting suspension of fine powder was passed through a 1000 μm mesh filter, then through a 500 μm mesh filter, and then the fine powder was collected on a 1 μm mesh filter paper. The collected 500 μm mesh filter and the 1 μm mesh filter paper were dried in a drying chamber at 110 ° C for 12 hours or more, and the mass of the 500 to 1000 μm fine powder recovered from the 500 μm mesh filter and the mass of the fine powder less than 500 μm were calculated from the difference in the mass of the filter paper before and after collection of the fine powder. The polysilicon fine powder content was calculated using the mass of the polysilicon used in this analysis. This operation was carried out again, and the newly calculated polysilicon fine powder contents were each added to the previously calculated values. This operation was further repeated until each increase due to this addition reached a fixed value that was smaller than the content before each addition by 5% or less, and this was used as the final value to determine the content of polysilicon fine powder.

[0054] Example 1 A polysilicon rod having a diameter of 150 mm and a length of 1000 mm was crushed with a hammer and then classified to obtain crushed polysilicon material having an average particle diameter of 64 mm and particle diameters ranging from 40 to 80 mm. The crushed polysilicon material was then etched under the following conditions, washed with ultrapure water, and dried to obtain crushed polysilicon material.

[0055] In a mixture of 50% electronics-grade nitric acid and 1.5% electronics-grade hydrofluoric acid, an etching basket containing crushed silicon was swung up and down at 25 times per minute with a swing width of 150 mm, and etching was performed while controlling the temperature of the mixture to maintain the liquid temperature at 20 to 28°C.

[0056] In the above etching process, the etching rate was calculated from the change in weight of the polysilicon test piece placed in the etching basket together with the crushed silicon material, and was found to be 2.1 μm / min. Etching was terminated when the etching depth reached 8 μm, and the polysilicon was washed with ultrapure water and then dried to obtain crushed polysilicon material.

[0057] The angle (θ) of the ridges of the crushed pieces and the radius of curvature (r) of the specific ridge tips were measured for the resulting crushed polysilicon. The average values ​​and the percentage of ridges with a radius of curvature of 30 μm or less were calculated. The results are shown in Table 1. Figure 5 shows a representative SEM photograph at 30x magnification of the ridge tips of the resulting crushed polysilicon. The amount of silicon fines in the crushed polysilicon is also shown in Table 1.

[0058] The crushed polysilicon was subjected to a resin adhesion test to measure the amount of resin adhered to the crushed polysilicon. The results are shown in Table 1.

[0059] Comparative Example 1 The same procedure as in Example 1 was carried out, except that the etching depth was set to 3 μm, to obtain crushed polysilicon.

[0060] The obtained crushed polysilicon pieces were evaluated in the same manner as in Example 1. The results are shown in Table 1. A representative SEM photograph of the ridge tips of the crushed polysilicon pieces obtained above at 30x magnification is shown in FIG.

[0061] Example 2 Crushed polysilicon was obtained in the same manner as in Example 1, except that crushed polysilicon having an average particle diameter of 92 mm in the particle diameter range of 70 to 110 mm was used.

[0062] The resulting crushed polysilicon was evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0063] Example 3 Crushed polysilicon was obtained by the same procedure as in Example 1, except that the etching depth of the crushed polysilicon was 11 μm.

[0064] The resulting crushed polysilicon was evaluated in the same manner as in Example 1. The results are also shown in Table 1.

[0065] [Table 1] [Explanation of symbols]

[0066] 1. Polysilicon fragments 2 Ridge 3. Fracture surface 4 Rod surface

Claims

1. A polysilicon crushed material is characterized in that it consists of crushed pieces having ridges generated by crushing a polysilicon rod, and the average radius of curvature (r) of the tips of the ridges having angles of 70° or less in the crushed pieces is 60 μm or more.

2. 2. The crushed polysilicon according to claim 1, wherein the average particle size is 20 to 150 mm.

3. A polysilicon package comprising a resin bag filled with the crushed polysilicon according to claim 1.

4. A polysilicon package in which the crushed polysilicon according to claim 2 is packed in a resin bag.

5. A method for producing crushed polysilicon material, comprising: a crushing step of crushing polysilicon rods to obtain crushed fragments; and an etching step of immersing the crushed fragments obtained in the crushing step in an etching solution that is a mixed acid aqueous solution of hydrofluoric acid and nitric acid, the mixed acid aqueous solution having a hydrofluoric acid concentration of 0.5 to 10 mass % and a nitric acid concentration of 48 to 68 mass %, and that does not contain a surfactant, and applying oscillation at a frequency of 3 to 10 times / min and an amplitude of 5 to 1000 mm to etch at an etching rate of 2.5 μm / min or less to an etching depth of 5 μm or more.

6. A method for producing crushed polysilicon material as described in claim 5, wherein the amplitude during the oscillation is 10 to 500 mm.

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