High-purity silicon particulate material and methods of making

Abstract

To provide a product and a production method according to the present invention concerning a high-purity silicon particulate material.SOLUTION: A high-purity silicon particulate material has a relatively small size, a small surface area, and a relatively smooth and rounded shape and is attractive as a high-purity and high-performance supply raw material for production of a silicon crystal and a silicon wafer produced from the silicon crystal. The present invention also relates to a method for producing the high-purity silicon particulate material.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a high-purity silicon particulate material having a relatively small size, a small surface area, and a relatively smooth and rounded shape, which is attractive as a high-purity, high-performance feedstock for use in the manufacture of silicon crystals and silicon wafers. The present invention also relates to a method for manufacturing a high-purity silicon particulate material.

Background Art

[0002] The present invention relates to the production of silicon crystals, typically the production of silicon particulate materials used in the low-cost and high-volume production of silicon crystals.

[0003] Silicon crystals and wafers manufactured from silicon crystals are a major feedstock for the manufacture of integrated circuits, power devices (MOSFETs, IGBTs), microelectronic devices, and solar cells. Silicon crystals are machined, sliced, and polished to produce crystalline silicon wafers, which are used in the manufacturing processes to produce integrated circuits, power devices, and solar cells. Silicon crystals need to contain few crystal defects and few metallic impurities such as nickel, iron, copper, chromium, etc. and carbon (in the range of parts per million (ppm) to parts per trillion (ppt)). Impurities, specifically metallic impurities, are a problem in producing integrated circuits because they reduce their electrical efficacy. Metal contaminants such as chromium, cobalt, iron, nickel, and copper reduce the efficiency of solar cells. Contaminants can be introduced into the silicon particulate material at any point in the manufacturing process, and thus steps to prevent contamination as well as steps to remove contaminants need to be taken.

[0004] Polycrystalline silicon is a feedstock for producing single-crystalline or multicrystalline silicon ingots required for the manufacture of silicon wafers. High-quality polycrystalline silicon (also called polysilicon) is required to prepare wafers for efficient solar cells for photovoltaic panels and high-performance silicon wafers for semiconductor devices. Further, highly pure silicon particulate feedstock provides a higher yield in the crystallization process, for example, by enabling the production of larger ingots, which reduces production costs and ultimately the cost per wafer.

[0005] Manufacturing silicon crystals and wafers is a costly process, and there is continuous pressure from users of silicon wafers to reduce manufacturing costs and improve the performance quality of the wafers. Important elements of the performance quality of wafers include metal contamination and surface defects. Metallic impurities such as iron can affect the electrical properties of crystalline silicon wafers, while metallic impurities such as nickel can result in surface defects (defects that can lead to failure of semiconductor devices). Manufacturers of silicon crystals and silicon wafers must continuously research to reduce costs and improve the performance of these products by reducing impurities in crystal growth and wafer manufacturing while reducing manufacturing costs. Metallic impurities in silicon wafers originate from the silicon metal used as a feedstock for manufacturing silicon crystals. Since metallic impurities are detrimental to the performance of semiconductor devices, there is continuous pressure from manufacturers of semiconductor devices to reduce metallic impurities in silicon wafers, and thus, next-generation advanced device designs require silicon particles / particulate materials containing even lower levels of metallic impurities.

[0006] Manufacturers of silicon crystals and silicon wafers standardize specifications for producing high-purity silicon particulate materials in order to maximize the uniformity of the silicon crystal growth process. The silicon particulate materials must meet requirements for purity, size, and packaging. Methods for producing silicon crystals using high-purity silicon particulate materials at low manufacturing costs include producing crystals with diameters of 300 - 450 mm, producing large-mass crystals (> 350 kg), and using a method of replenishing (known as refilling) the silicon particulate material into the contents of a container, typically a crucible, while the crucible still contains the molten material.

[0007] There are multiple methods for producing highly pure polycrystalline silicon, including fluidized bed reduction and the Siemens process. The polycrystalline silicon produced by the Siemens process has sufficient purity to be suitable for both integrated circuit applications and solar cell applications. The Siemens process is a chemical vapor deposition (CVD) process in which several parallel, long (meters), and thin (mm diameter or cross-section) silicon filaments acting as substrates are attached to a process vessel, and two or more of the silicon filaments are connected at the top by silicon bridges to form a substantially U-shape (U-rods). The process vessel is closed, purged with an inert gas, and then a mixture of hydrogen and chlorosilane gas (typically trichlorosilane (HSiCl3) or silicon tetrachloride (SiCl4)) is fed into the process vessel. "Chlorosilane" can refer to any species of silane characterized by one or more chlorine atoms bonded to silicon, including monochlorosilane (H3SiCl), dichlorosilane (H2SiCl2), trichlorosilane (HSiCl3), silicon tetrachloride (SiCl4), and various chlorinated disilanes such as hexachlorodisilane ((SiCl3)2) and pentachlorodisilane (HCl5Si2), but is not limited to these. Since the impurities in the silicon crystal are required to be extremely low, the chlorosilane gas typically has a metallic impurity concentration in the range of ppb to ppt. Then, an electric current is applied to the filaments to heat them to a target temperature in the range of 800 - 1200 °C, which is high enough to decompose the supply flow of chlorosilane gas, resulting in the deposition of silicon onto the filaments and the growth of the diameter of the coated filaments. After a sufficient time, the process ends and the coated filaments, referred to here as "rods", are removed. The weight of each silicon rod is typically in the range of 100 - 250 kg, and the diameter is typically in the range of 100 - 200 mm.

[0008] Since the impurity levels in the feedstock chlorosilane gas are very low, the silicon produced has metallic impurity levels below those of the chlorosilane gas. The polysilicon produced by this method is often referred to as the purest man-made material in the world. The total concentration of iron, nickel, and copper impurities in this silicon rod material, referred to as bulk impurities, needs to be 40 pptw, 30 pptw, 20 pptw, or 10 pptw or less, measured in parts per trillion by weight (pptw). The concentration of carbon impurities is less than 10 ppbw (parts per trillion by weight).

[0009] Verification of the bulk donor and acceptor impurity levels (e.g., phosphorus, arsenic, boron, and aluminum) and metallic impurities in the silicon rod is performed by methods known in the art, including the method defined in SEMI MF1723, which is incorporated herein by reference. Verification of the metal impurity levels is performed by removing the freeze-out section of the crystal (the solidified impurities melted and swept from one end of the surface of the crystalline material to the other by the induction coil during the float zone process) from the method of SEMI MF1723, dissolving it using HF / HNO3, and creating a sample suitable for testing by ICP-MS. Due to the very low impurity levels, the ICP-MS test must operate at a minimum elemental concentration detection limit of <10 ppta or <1 ppta of metal contaminants. Verification of the bulk carbon in silicon can be measured by secondary ion mass spectrometry or by Fourier transform infrared spectroscopy using the sample preparation found in M. Porrini et al., Solid State Phenomena Vols. 108-109 (2005) pp. 591-596, which is incorporated herein by reference in its entirety.

[0010] Moreover, highly pure single-crystalline silicon can be prepared by various methods, such as the Czochralski method (CZ method), using highly pure polycrystalline silicon produced by the Siemens process. In fact, most of the silicon particulate materials used in the CZ method are produced using the Siemens process. In the CZ method, a particulate material of silicon, generally referred to as polysilicon (the polycrystalline form of silicon), is melted in a quartz crucible placed in a furnace. Next, a small crystal of silicon in the form of a small-diameter cylinder, called a seed crystal, is immersed in the crucible of molten silicon and then slowly withdrawn into a long, cylindrical, vertical chamber maintained in an inert ambient environment. The crucible rotates continuously about a vertical axis while simultaneously rotating the seed crystal in the opposite direction and slowly withdrawing (pulling) the seed crystal from the crucible. The molten silicon in the crucible solidifies on the pulled seed crystal, forming a single-crystalline ingot having a diameter much larger than that of the seed. During this process, the ingot is withdrawn from the melt at a controlled rate to form an ingot having a desired diameter as the volume of the molten silicon is consumed. Since such crystals are highly pure, most of the semiconductor chips used in electronic devices and solar panels are made from single-crystalline silicon produced by the Czochralski method.

[0011] As described above, producing larger, high-purity single-crystalline silicon crystal materials at low cost is an ongoing manufacturing effort. Methods of reducing cost include implementing steps to maximize equipment efficiency and process time. For the highest levels of efficiency and purity, the feedstock of polysilicon used in the CZ method must be in the form of small particulate matter. The ideal shape of these particulate materials is spherical and small in size to minimize the space between the particulate materials loaded into the crucible. When the feedstock is completely melted, the volume of molten silicon is smaller than the volume of the particulate material it occupies, but larger and / or irregularly shaped chips or chunks of silicon feedstock require more time to melt due to the size and larger interstitial spaces between the particulate materials in the crucible. If this filled volume of molten silicon is not maximized, it reduces the efficiency of the crystal growth process. Small particulate materials are used to ensure a high-density packing of the particulate materials in the crucible to melt the silicon in a reasonable time. The quartz crucible that holds the polycrystalline material in the CZ reactor is exposed to extreme temperatures when melting the silicon and during cooling of the reactor after the ingot has been pulled. One way to extend the life of the crucible, enable longer crystal pulls, shorten the process time between ingot pulls, and thereby improve the efficiency and cost-effectiveness of the crystal growth process is to replenish (known as refilling) the crucible with polycrystalline silicon material particulate matter while the crucible still contains a residual volume of molten material.

[0012] There are two methods for refilling. In the intermittent (batch) method, after the crystal is taken out from the CZ furnace (the furnace used in the Czochralski method), a quartz container filled with silicon material particulate matter is inserted into the cylindrical vertical chamber of the CZ furnace above the crucible, and then the bottom is opened to let the silicon particulate matter fall into the crucible; in the continuous method, the silicon particulate matter is added to the crucible throughout the crystal growth process. Typical requirements for the silicon particulate matter used for crucible refilling for the production of high-performance silicon crystals and silicon wafers include silicon particle size, minimum metal impurities, and minimum and maximum limits for high-purity packaging. The silicon particulate matter used for refilling is selected such that the particulate matter has a typical size range of approximately ≧3 mm to ≦75 mm. The target range can be in the range of 5 mm to 50 mm or 20 mm to 70 mm. The particulate matter is packaged in high-purity polymer bags in a cleanroom environment operating at least under ISO5 particle control (for example, the packaging may be carried out under ISO4 particle control). Since the silicon particulate matter is necessary to keep the impurities of the produced crystal low, it is highly desirable that the surface and bulk impurities are low. For example, the total concentration of metal impurities such as iron, nickel, copper, and chromium (the sum of surface and bulk impurities) is in the range of 1 to 50 pptw, and carbon should be less than 100 ppbw.

[0013] The polycrystalline silicon rods produced by CVD are not in a useful state for the application of producing single-crystalline silicon crystals. The polycrystalline silicon rods have to be crushed into small pieces. When the silicon rods are taken out from the Siemens CVD process, the silicon rods are in their purest state. The main challenge for the manufacturers of silicon particulate matter is the method of converting the silicon rods into small particulate matter (a process called crushing). The most common methods of crushing include using a jaw crusher, a roll crusher, and manual breaking of the rods by humans using hammers. Crushing of the silicon rods can potentially add significant contamination to the surface of the silicon particulate matter.

[0014] To produce high-purity silicon particulate matter, the technique of grinding silicon rods into particulate matter must result in particulate matter with minimal additional contamination on the surface of the particulate matter. Originally, grinding was performed in a cleanroom where an operator used a hammer to break the silicon rods into large pieces and then further used the hammer to reduce the large pieces into smaller pieces. The pieces were then hand-sorted on a table into the target particle size range. The particulate matter was then manually transferred into bags, typically having a weight of 5 kg ± 50 g of particulate matter per bag. Figure 1 presents this process flow.

[0015] The process flow of Figure 1 is known in the art. This is labor-intensive, slow, adds undesirable contamination, and results in undesirable particle size and contamination variations as well as product waste due to the manual nature of the method. An improvement to the process shown in Figure 1 is shown in Figure 2. To provide particulate matter in the desired size range, mechanical crushing of large pieces of silicon rods using a jaw crusher or a roll crusher was developed to improve control of the grinding. Sieving was used to sort the particulate matter to achieve a higher uniformity of the particle size range. Chemical cleaning using acids such as a mixture of H2O2 + HCl, or H2O2 + HF, or HNO3 + HF was used to remove surface contamination added during the grinding process.

[0016] A new method of comminution is high voltage pulse crushing (HVPC). In this method, silicon rods are partially or fully immersed in a vessel filled with deionized water. Two or more metal electrodes are placed across the rod, and the high voltage generated between the electrodes creates an electrical arc discharge. This discharge creates a high-pressure shock wave within the vessel, breaking the silicon rod into pieces. The high voltage pulse crusher can be calibrated to provide a specific size range of particles. Further, silicon pieces / particles can be crushed with a high voltage pulse crusher, regardless of the presence or absence of silicon rods. Further, both polycrystalline and single-crystalline forms of silicon can be crushed by HVPC. The commercial use of HVPC in silicon has been limited to the production of silicon for solar cell applications. To date, the HVPC method has not penetrated the silicon semiconductor process because it tends to contaminate the crushed silicon particulate material with high concentrations of metal impurities. These impurities are derived from the electrodes of the HVPC apparatus. The added impurities make it difficult to clean the silicon particulate material to levels acceptable for use in the manufacture of silicon crystals and wafers.

[0017] Modifications of these comminution methods are practiced today to produce commercially available large quantities of high-purity silicon particulate material. However, both manual and mechanical comminution result in undesirable variations in particle size and shape, particle surface area, impurities, and operating costs, which are each not favorable for meeting the future needs of silicon crystal growth manufacturing for low-cost, higher uniformity, high-purity silicon particulate material.

[0018] As described above, high voltage pulse crushing has been very successful in crushing silicon rods or scrap crystals used in the silicon solar industry, but the HVPC method has failed when applied to the silicon semiconductor industry due to the contamination added by the HVPC process. Thus, the use of HVPC to produce semiconductor grade particulate material has not been successful to date. However, Applicant has unexpectedly discovered a novel method for successfully preparing silicon particulate materials, including high voltage pulse crushing, that meet the high purity requirements of the semiconductor industry.

[0019] Once the silicon particulate materials are formed, they are typically conveyed by a conveyor made of or coated with a plastic / polymer material, which feeds them to a sorting system that separates the particulate materials into a target size range by separating particulate materials that are too small and too large to fit into the target size range. Sorting is typically accomplished by passing the silicon particulate material over sieves of different aperture sizes to separate the particulate material in a range of particle sizes that fit the minimum and maximum particle sizes. The separated pieces are often tested by passing the silicon pieces through a camera (e.g., CANTY Tiltsizer, JM Canty, Inc., Buffalo, NY) to image the particulate material and then using a machine that determines particle size measurement criteria such as distribution by length dimensions (minimum length, maximum length), volume, and aspect ratio.

[0020] The conveyor wears down the moving silicon particulate material, generating very small silicon particulate material (often referred to as "fine particles") and silicon dust. These small particulate materials and dust are waste that do not produce silicon particulate material in the required size range and thus add cost to the process. Furthermore, since these silicon fine particles and dust are from the surface of the ground silicon particulate material, they often have a high level of contamination. The fine particles and dust wear down the polymeric plastic conveyor, creating carbon particles. The silicon fine particles, dust, and carbon particles continuously accumulate on the conveyor, transfer to subsequent silicon particulate material moving on the conveyor, and add further contamination to the silicon particulate material. This contamination of the silicon particulate material has a metallic surface impurity level as high as 1000 ppbw and a carbon impurity as high as 300 ppbw. To control these sources of contamination, the manufacturing process has to be stopped periodically to clean and / or replace the conveyor, thus increasing the manufacturing cost of the silicon particulate material.

[0021] Another strategy for reducing surface contamination is to use acid chemistry to dissolve the top surface of the contaminants and / or silicon to reduce the level of impurities on the surface to the range of 1 to 100 ppta. Metallic and non-metallic contaminants, as well as when producing high-purity silicon and affecting the quality of the product, it is also beneficial to attempt to remove contaminants when they occur (i.e., during grinding). A common method for cleaning silicon pieces is to clean with an acidic chemical mixture containing HF / H2O2 / HCl / HNO3, such as HF / HNO3 and / or HF / H2O2 and / or H2O2 / HCl, to dissolve the top surface and impurities of silicon, as well as silicon particles and dust. Carbon contaminants that cannot be dissolved by the silicon etchant can be washed away from the silicon particulate matter. After cleaning with the acidic chemical mixture, the silicon particulate matter is rinsed with high-purity deionized water, dried, and packaged. The various grinding methods (hammer, jaw crusher, high-voltage pulse crushing) mentioned above require unique cleaning strategies to bring the silicon surface free of metal and carbon impurities to the level of 1 to 100 ppta.

[0022] The impurities accumulated on the surface of the silicon particulate matter are an important concern in the use of silicon in the CZ crystal growth method, and silicon manufacturers are seeking new and better methods to minimize surface contamination. Another strategy is to use automation to control the handling of silicon, that is, after the silicon is loaded into the grinding process, humans do not touch the silicon. Another strategy is to optimize the grinding process to minimize the surface area of the particulate matter by controlling its size and shape for the purpose of producing particulate matter with an aspect ratio as close to 1 as possible.

[0023] Therefore, there remains a significant need for high-purity silicon that meets the continuously increasing requirements of the semiconductor industry, as well as new and improved methods for producing high-purity silicon particulate materials.

[0024] These limitations gave rise to the driving force for inventing improved techniques for manufacturing high-purity silicon particulate matter, resulting in higher-purity silicon particulate matter.

Summary of the Invention

[0025] An object of the present invention is to provide a high-purity silicon particulate material having a very low impurity level.

[0026] A further object of the present invention is to provide a method for preparing a high-purity silicon particulate material that enables the low-cost production of silicon crystals having a very low impurity level.

[0027] In one aspect, the present invention provides a grinding method capable of generating small particulate matter having a small surface area and a rounded shape, as well as a cleaning method for providing a high-purity silicon particulate material. The inventors placed silicon, typically a high-purity (ppta) silicon rod, typically a high-purity polycrystalline silicon rod, typically a high-purity polycrystalline silicon rod produced by the Siemens process, into a process vessel filled with water, typically high-purity deionized (DI) water, at least within an ISO 7 cleanroom, placed the process vessel into a high-voltage pulse crushing (HVPC) system, and discovered a grinding method including grinding the rod into small silicon particulate matter. The process vessel is mechanically drained, rinsed with deionized water, the particulate matter is mechanically transferred to a vibrating sieve conveyor, and the pieces are sorted and separated on the vibrating sieve conveyor in the presence of a high-purity deionized water shower. When the silicon particulate matter is washed / rinsed with water, dust is removed from the surface and wear of the conveyor is minimized. The sorted particulate matter is separated into three groups. The sorted particulate matter exceeding the maximum target size is transferred to a reprocessing step where the silicon particulate material exceeding the maximum target size is accumulated in a holding vessel and then returned to the process vessel for further grinding in a high-voltage pulse crusher. The sorted particulate matter below the minimum target size is discarded as waste. The sorted particulate matter within the target size window is mechanically collected in a perforated polymer basket and transferred to an automated cleaning / etching system.

[0028] The inventors discovered a method for cleaning particulate materials. Here, the cleaning is performed within a cleanroom area of ISO 6 or less, and the vessel containing the particulate matter passes through a bath containing: Optionally, cleaning in one or more optionally heated baths containing a caustic detergent and high-purity (typically 18 Mohm-cm) deionized water with a pH of ≧ 10, Rinsing in one or more baths of high-purity (typically 18 Mohm-cm) deionized water, To dissolve contaminants added during the top surface of the silicon particulate material and the grinding process, etching in one or more acid baths containing one or more acids, such as a mixture of HF (e.g., 49% w / w) / HNO3 (e.g., 68 - 77% w / w), Rinsing in one or more baths of high purity (typically 18 Mohm-cm) deionized water, Optionally, immersion in a mixture of ozone (e.g., 1 - 5% ozone) and high purity (typically 18 Mohm-cm) deionized water, and Rinsing in a bath of high purity (typically 18 Mohm-cm) deionized water at high temperature (e.g., ≥20 °C). The polymer basket containing the particles / particulate material is dried in a drying chamber to which a vacuum is applied to create a low atmospheric pressure and then in a second drying chamber with heated (e.g., ≥30 °C) high air flow at a relative humidity (e.g., ≤34%) to accelerate the drying process. The packaging step, which is carried out in a cleanroom operated at ISO5 or in a cleanroom of ISO4 standard, includes transferring pieces of high purity silicon particulate material to a polyethylene / polymer bag, heat-sealing the bag, labeling the heat-sealed bag, and placing the heat-sealed bag in a box. Once packaged, the highly pure silicon particulate material within the bag can be sampled and optionally tested for surface impurities.

[0029] The method developed according to the present invention unexpectedly reveals that the method can be used to produce particulate materials of high purity silicon materials having a controlled size range, a very low aspect ratio, and very low levels of surface and bulk contamination of iron, nickel, copper, and carbon. Here, the particulate material has high uniformity and low variability.

[0030] The high-purity silicon particulate material includes silicon particulate material having a polycrystalline structure, the silicon particulate material has a particle size distribution in the range of 3 mm or more and 75 mm or less, the silicon particulate material has an average aspect ratio of 1.55 or less, and the silicon particulate material includes a combination of surface impurities and bulk impurities with a total iron impurity of 20 pptw or less, a total nickel impurity of 4 pptw or less, and a total copper impurity of 4 pptw or less.

[0031] Verification of the surface metal impurity level is performed by procedures as documented in WO 2016 / 051761 A1, which is incorporated herein by reference in its entirety, which describes dissolving the surface of silicon pieces using HF / HNO3 to create a sample suitable for testing by graphite furnace ICP-MS method. Due to the very low impurity levels, the ICP-MS test must have a minimum detection limit of 10 pptw or less and 1 pptw or less. The surface impurity test is performed in an ISO 4 cleanroom environment. Verification of surface carbon is measured using a LECO RC612 system in a cleanroom environment of ISO 5 or less. The total elemental impurity in the high-purity silicon particulate material is derived by adding the bulk and surface values of a given element.

[0032] When using high-purity polycrystalline silicon particulate material and using the CZ method and a refill approach to grow silicon crystals, many successive large silicon crystals (diameter > 200 mm and mass > 350 kg) can be produced with very low impurities, lower than the impurities of the feedstock high-purity silicon particulate material. The silicon crystals produced are useful for manufacturing silicon wafers having very low metal impurities, lower than the metal impurities of the high-purity silicon particulate material.

[0033] Other features and advantages of the present invention will become apparent from the following detailed description, examples, and drawings. However, while the detailed description and specific examples illustrate embodiments of the invention, it should be understood that they are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

[0034] The following drawings form a part of this specification and are included to further illustrate certain aspects of the present disclosure, and the invention can be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.

Brief Description of the Drawings

[0035]

Figure 1

[0036]

Figure 2

[0037]

Figure 3

Best Mode for Carrying Out the Invention

[0038] The subject matter can be more readily understood by reference to the following detailed description, which forms a part of this disclosure. The present invention is not limited to the specific products, methods, conditions, or parameters described or shown herein, and it should be understood that the terms used herein are for the purpose of describing specific embodiments by way of example only and are not intended to limit the claimed invention.

[0039] The object of the present invention is to provide a method and materials that meet the requirements of cost, uniformity, and purity related to the production of high-purity silicon particulate matter for manufacturing silicon crystals and silicon wafers, meeting current and future requirements. The process of the present invention attempts to eliminate the variations and costs associated with manual and mechanical grinding while minimizing the concentration of impurities in and on the silicon particulate matter.

[0040] Unless otherwise defined herein, scientific and technical terms used in connection with this application shall have the meanings commonly understood by those skilled in the art. Further, unless the context otherwise requires, singular terms shall include the plural, and plural terms shall include the singular.

[0041] As used above and throughout this disclosure, the following terms and abbreviations shall be understood to have the following meanings unless otherwise indicated.

[0042] PPMA is parts per million by atomic number, defined as the ratio of the count of impurity atoms to the total atoms in a material, and refers to the concentration of impurity atoms multiplied by 1E6 (i.e., 1,000,000 or 10 6 ).

[0043] PPBA is parts per billion by atomic number, defined as the ratio of the count of impurity atoms to the total atoms in a material, and refers to the concentration of impurity atoms multiplied by 1E9 (i.e., 1,000,000,000 or 10 9 ).

[0044] PPTA is parts per trillion by atomic number, defined as the ratio of the count of impurity atoms to the total atoms in a material, and refers to the concentration of impurity atoms multiplied by 1E12 (i.e., 1,000,000,000,000 or 10 12 ).

[0045] PPMW is parts per million by weight, defined as the ratio of the weight of impurity atoms to the total weight of the material, and refers to the concentration of impurity atoms multiplied by 1E6 (i.e., 1,000,000 or 10 6 ).

[0046] PPBW is parts per billion by weight, defined as the ratio of the weight of impurity atoms to the total weight of the material, and refers to the concentration of impurity atoms multiplied by 1E9 (i.e., 1,000,000,000 or 10 9 ).

[0047] PPTW is parts per trillion by weight, defined as the ratio of the weight of impurity atoms to the total weight of the material, and refers to the concentration of impurity atoms multiplied by 1E12 (i.e., 1,000,000,000,000 or 10 12 ).

[0048] Particle size is the longest straight line between two points on the particle (e.g., in the case of a sphere, the diameter is the particle size).

[0049] Silicon impurity concentrations, such as relative units like ppmw and ppbw, are often provided in various units of the SEMI standard, and the document SEMI AUX022-0611 Conversion of Units for Impurity Concentrations in Silicon is incorporated by reference in its entirety.

[0050] The term "aspect ratio" is defined as the ratio of the longest dimension to the shortest dimension measured for a particle. A sphere has an aspect ratio of 1. An ellipsoid can have an aspect ratio greater than 1, e.g., 1.55.

[0051] The ranges described herein include the endpoints and anything included therein. For example, the range 7 to 20 includes 7 and 20, and also 8, 15, 17, 19.6, etc. Further, the disclosure of a range, e.g., 7 to 20, also includes ranges within that range, e.g., 8 to 15, 9.9 to 17.4, etc.

[0052] When the phrase "at least ~ class" precedes the number of the ISO class, the number of that ISO class includes the highest level of contamination permitted. For example, "at least ISO 5 class" can be ISO 5, ISO 4, ISO 3, ISO 2, or ISO 1.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0054] In the present disclosure, the singular forms "a", "an", and "the" include plural referents, and references to a particular numerical value include at least that particular value unless the context clearly indicates otherwise. Thus, for example, a reference to "a material" is a reference to at least one or more such materials and their equivalents known to one of ordinary skill in the art. When a range of values is recited, another embodiment includes from one particular value and / or to the other particular value. Similarly, when values are expressed as approximations using the antecedent "about", it is understood that the particular value forms another embodiment. All ranges are inclusive and combinable.

[0055] As described herein, the present invention provides methods and materials that meet the cost, uniformity, and purity requirements associated with the production of high-purity silicon particulate materials that can be used to produce silicon crystals and silicon wafers.

[0056] The object of the present invention is achieved, in one embodiment, using a highly pure silicon particulate material comprising a silicon particulate material having a polycrystalline structure, the silicon particulate material comprising a particle size distribution in the range of 3 mm or more and 75 mm or less. The high-purity silicon particulate material has a particulate material with a low aspect ratio and a rounded or oval shape that results in a reduced surface area. The silicon particulate material with a smaller surface area reduces the uptake of particulate and dust contamination, and as a result, the amount of impurities added to the silicon particulate material during handling is reduced. The average aspect ratio of the aggregate of silicon particulate material is 1.55 or less, the total (total of surface impurities and bulk impurities) iron impurities are ≦20 pptw, the total nickel impurities are ≦4 pptw, and the total copper impurities are ≦4 pptw.

[0057] In various embodiments, the silicon particulate material may have bulk impurity levels of ≦10 pptw of iron, ≦4 pptw of nickel, and ≦4 pptw of copper, and the surface impurities of iron, nickel, and copper on the silicon particulate material are ≦4 pptw, for example, below the minimum detection limit of 1 pptw, and are evaluated using acid extraction and inductively coupled mass spectrometry (ICP-MS analysis). The silicon rod may be produced using the Siemens process.

[0058] In some embodiments, the silicon particulate material is the product of a silicon rod produced using the Siemens process.

[0059] In certain embodiments, the silicon particulate material has bulk impurity levels of ≦10 pptw of iron, ≦4 pptw of nickel, and ≦4 pptw of copper.

[0060] In another embodiment, the surface impurities of iron, nickel, and copper on the silicon particulate material are evaluated using acid extraction and inductively coupled mass spectrometry (ICP-MS analysis).

[0061] In various embodiments, the silicon particulate material is a product of a silicon rod made using the Siemens process having bulk impurity levels of ≤10 pptw iron, ≤4 pptw nickel, and ≤4 pptw copper.

[0062] In various embodiments, the silicon particulate material is a product of a silicon rod made using the Siemens process having bulk impurity levels of ≤10 pptw iron, ≤4 pptw nickel, and ≤4 pptw copper, and the surface impurities of iron, nickel, and copper on the silicon particulate material are evaluated using acid extraction and inductively coupled mass spectrometry (ICP-MS analysis).

[0063] In some embodiments, the silicon particulate material is a product of a silicon rod made using the Siemens process having bulk impurity levels of ≤10 pptw iron, ≤4 pptw nickel, and ≤4 pptw copper, and the surface impurities of iron, nickel, and copper on the silicon particulate material are evaluated using acid extraction and inductively coupled mass spectrometry (ICP-MS analysis) at a minimum detection limit of ≤4 pptw.

[0064] In certain embodiments, the present invention provides a product selected from integrated circuits and power devices including a silicon wafer comprising the silicon particulate material of any one or combination of the foregoing embodiments.

[0065] In additional embodiments, the present invention provides a product selected from integrated circuits and power devices generated from a wafer generated from the silicon particulate material of any one or combination of the foregoing embodiments.

[0066] In various embodiments, the present invention provides a single crystal silicon material comprising the silicon particulate material of any one or combination of the foregoing embodiments.

[0067] In certain embodiments, the present invention provides a single crystal silicon material generated from the silicon particulate material of any one or combination of the foregoing embodiments.

[0068] In some embodiments, the present invention provides a product selected from a silicon wafer, a solar cell, and a photovoltaic panel, which contains a single-crystalline silicon material of any one or combination of the foregoing embodiments.

[0069] In certain embodiments, the present invention provides a product selected from a silicon wafer, a solar cell, and a photovoltaic panel, which is produced from a single-crystalline silicon material of any one or combination of the foregoing embodiments.

[0070] In some embodiments, the present invention provides a silicon particulate material of any one or combination of the foregoing embodiments for use in an integrated circuit and / or a power device.

[0071] In various embodiments, the present invention provides a single-crystalline silicon material of any one or combination of the foregoing embodiments for use in a silicon wafer, a solar cell, and / or a photovoltaic panel.

[0072] In certain embodiments, the present invention provides a silicon material containing a silicon particulate material of any one or combination of the foregoing embodiments.

[0073] In some embodiments, the present invention provides a silicon particulate material for use in the manufacture of a silicon wafer, and the silicon wafer can be used to manufacture an integrated circuit and / or a power device.

[0074] In various embodiments, the present invention provides a single-crystalline silicon material for use in the manufacture of a silicon crystal, and the silicon crystal can be used to manufacture a silicon wafer for use in the manufacture of a solar cell and / or a photovoltaic panel.

[0075] The object of the present invention, in another aspect, is achieved by creating a fully automated touchless process for the grinding, sorting, rinsing, cleaning, and packaging of high-purity silicon particulate materials from silicon rods, where the silicon rods can be produced by the Siemens CVD process. The term touchless process refers to an automated process flow where no human has to handle any silicon during the normal execution of the process flow.

[0076] In one embodiment, the process flow of the method of the present invention is shown in FIG. 3.

[0077] The process flow of FIG. 3 is configured in a series of processing areas or rooms that can be connected by a vibrating conveyor. Silicon rods produced by a CVD process, such as the Siemens CVD process, are sent to a first room, which is a clean room operated under ISO7 particle control. The silicon rods are crushed into particulate matter using a particle crushing process such as high-voltage pulse crushing (HVPC). In this grinding method, the silicon rods are completely immersed in a process vessel filled with high-purity deionized water. Metal electrodes are placed near the top and bottom of the rod, and a high voltage is generated between the electrodes, creating an electrical arc discharge. This discharge creates a high-pressure shock wave within the vessel, decomposing the silicon rods into particulate matter. The CVD rods must start with a bulk impurity level low enough to meet the requirements of the semiconductor silicon crystal growth process and should thus have a bulk impurity level consistent with the requirements for the silicon particulate material. Typical concentration values for bulk impurities are iron ≤ 10 pptw, nickel ≤ 4 pptw, and copper ≤ 4 pptw.

[0078] After high voltage pulse crushing (HVPC), the particulate matter is mechanically transferred from the process vessel to the conveyor within a cleanroom that is at least ISO 7 particle controlled, introduced into no metallic material, and not contacted with any metallic material. While on the conveyor, the silicon particulate matter discharged from the process vessel is sprayed / rinsed with high purity (e.g., ≧10 - 18 Mohm-cm) deionized water during conveyance. The Applicant has unexpectedly found that by spraying / rinsing the particulate matter while conveying it, keeping the particulate matter wet from the process vessel removes fine particles and dust adhering to larger particulate matter and other contaminants added during crushing. Further, the Applicant has unexpectedly found that by spraying / rinsing the particulate matter to remove contaminants, the process becomes more efficient and effective by preventing the accumulation of contamination on the conveyor, which can wear the conveyor and add carbon contamination to the particulate matter. In the next step, the particulate matter is sorted into three groups to separate pieces that are too small and too large from pieces of the target range of sizes. The sorting is accomplished by conveying the silicon particulate matter over a vibrating solid polymer sieve while spraying high purity deionized water. The Applicant has unexpectedly found that by spraying the particulate matter during sieving, the water acts as a lubricant and the sieving is more effective because the particulate matter does not wear the sieve. Thus, the Applicant's novel process of spraying while conveying and sieving the particulate matter also minimizes the need to stop the process to clean and repair damage suffered from the accumulation of contaminants.

[0079] Following sieving, silicon particulate matter below the target size is removed from the process flow and silicon particulate matter above the target size is recovered into a solid polymer recovery vessel. Particulate matter that is too large is recovered into a solid polymer holding vessel and ultimately returned to the HVPC crushing step for size reduction.

[0080] The silicon particulate matter within the target size window is separated by methods known in the art. In this embodiment, the silicon particulate matter is conveyed by a conveyor to the step of being loaded into a perforated solid polymer basket. The basket containing the silicon particulate matter is sent to a wet cleaning system where it passes through a separate cleaning bath to remove surface contamination. The wet cleaning system is operated within a separate clean room maintained at least at ISO6 particle control.

[0081] The wet cleaning system includes the following steps.

[0082] A basket containing silicon particulate material is optionally immersed in one or more vessels containing a bath comprising a caustic detergent (i.e., any detergent formulation having a pH ≧ 10) and high purity deionized water, and the bath may optionally be heated to a temperature of ≧ 20 °C, such as 20 °C to 90 °C, or 20 °C to 40 °C. The heated water accelerates the cleaning action and enables faster cleaning of the silicon particulate material. During high voltage pulse crushing, arc discharge creates very fine silicon dust from the pulverization of the silicon rod, and iron dust is generated from the erosion of the electrodes, and then both are incorporated into the water in the process vessel. It is also known that arc discharge creates ozone and hydrogen peroxide in water. Ozone and hydrogen peroxide undergo hydrolysis reactions with iron and silicon particulate materials to form polymers. Iron-oxygen-silicon hydroxide polymers deposit as contaminants on the surface of larger silicon particulate materials within the process vessel. The polymer surrounds the silicon particulate material, and the presence of the polymer inhibits the etching of the silicon particulate material by acid. Thus, the Applicant has found unexpectedly that rinsing the particulate material in a caustic detergent is particularly useful in the HVPC process to break the bonding of the polymer material and to remove some of the iron from the particulate material before the particulate material enters the acid bath, enabling the reaction of the silicon particulate material with the acid. The level of iron contamination has long been known to be a factor that degrades the quality of silicon particulate material, but the conventional HVPC process for producing high purity silicon particulate material has not been successful in removing iron contaminants to obtain the low level of iron contamination in silicon particulate material achieved by the Applicant.

[0083] A basket containing silicon particulate material is immersed in one or more vessels containing a mixture comprising nitric acid (e.g., 70% w / w) and hydrofluoric acid (e.g., 49% w / w). This step etches the surface of the silicon particulate material and releases impurities from the surface of the silicon particulate material into the acid.

[0084] The basket containing silicon particulate matter is immersed in one or more vessels filled with high-purity deionized water, typically 18 Mohm-cm, to remove the acid carried over from the previous cleaning step.

[0085] The basket containing silicon particulate matter is optionally immersed in a vessel containing a mixture of high-purity deionized water, typically 18 Mohm-cm, and 1-5% ozone. The ozone coats the particulate matter, resulting in a silicon oxide film that makes the surface of the silicon particulate matter hydrophilic. This step inhibits the adsorption of new particulate matter onto the silicon particulate matter.

[0086] The basket containing silicon particulate matter is immersed in a vessel filled with high-purity deionized water, typically 18 Mohm-cm, heated to a temperature in the range of 20 °C or higher, for example 50-80 °C. The warm water heats the polysilicon and can make the drying step more efficient.

[0087] Following the cleaning step, the basket containing silicon particulate matter is transported to a drying chamber. The drying process consists of a first chamber where the pressure is reduced to a vacuum level sufficient to evaporate water from the surface of the particulate matter. The basket containing the particulate matter is then moved by a conveyor to a second chamber where the particulate matter is exposed to high-speed (forced) heated drying air to assist evaporation. The conditions in this chamber are an air temperature of ≥30 °C and a relative humidity of ≤34%, both of which assist the drying process for productivity purposes. The drying process is operated within a cleanroom maintained at least at ISO6 particle control to control the level of particulate matter and reduce contamination.

[0088] Following the cleaning procedure, the basket of high-purity silicon particulate matter is transferred to another cleanroom that is operated under at least ISO 5 particle control. The basket is transferred to a collection vessel. A bag, typically a polyethylene bag, is placed under the collection vessel. The bag is filled with the silicon particulate matter at the target weight (e.g., 5 kg ± 50 g) and sealed by a heat sealer. Using a touchless process, a label containing product information is attached to the bag. Optionally, the bag containing the silicon particulate matter is placed into a second bag, the bag is sealed, and then labeled as well. A robot removes the bag, places it on a conveyor, and then it is moved into a box by another robot.

[0089] In certain embodiments, the process for manufacturing a silicon particulate material includes grinding silicon to produce the silicon particulate material and cleaning the surface of the silicon particulate material, the cleaning optionally including immersing in one or more vessels containing a mixture including a caustic detergent and high-purity deionized water at a pH of 10 or greater; immersing in one or more vessels containing a mixture including one or more acids; immersing in one or more vessels containing high-purity deionized water; optionally, immersing in a vessel containing a mixture including ozone and high-purity deionized water; immersing in one or more vessels containing high-purity deionized water at a temperature above 20°C, and including immersing a perforated polymer basket containing the silicon particulate material in a separate bath.

[0090] In some embodiments, the process for manufacturing a silicon particulate material further includes transferring the silicon particulate material to a vibratory sieve conveyor.

[0091] In various embodiments, the process for manufacturing the silicon particulate material further includes rinsing the silicon particulate material with high-purity deionized water and simultaneously sorting the silicon particulate material via a vibrating sieve conveyor, and the silicon particulate material is sorted into materials that are 1) below the minimum target size, 2) within the target size window, and 3) above the maximum target size.

[0092] In some embodiments, the process for manufacturing the silicon particulate material further includes transferring the silicon particulate material below the minimum target size to a recovery vessel, transferring the silicon particulate material above the maximum target size to a holding vessel, and transferring the silicon particulate material within the target size window to a perforated polymer basket in a predetermined quantity batch.

[0093] In various embodiments, the cleaning step includes immersing the basket containing the silicon particulate material in one or more vessels containing a mixture containing one or more acids, one or more vessels filled with high-purity deionized water, and a vessel filled with high-purity deionized water optionally heated to a temperature of 20 °C or higher.

[0094] In some embodiments, the cleaning step includes immersing the basket containing the silicon particulate material in one or more optionally heated baths of caustic detergent, one or more vessels containing a mixture containing one or more acids, one or more vessels filled with high-purity deionized water, and a vessel filled with high-purity deionized water optionally heated to a temperature of 20 °C or higher.

[0095] In certain embodiments, the cleaning step includes immersing a basket containing silicon particulate material in one or more baths of caustic detergent, optionally heated; one or more vessels containing a mixture comprising one or more acids; one or more vessels filled with high purity deionized water; a vessel containing a mixture of high purity deionized water and 1 - 5% ozone; and a vessel filled with high purity deionized water optionally heated to a temperature of 20°C or greater.

[0096] In various embodiments, the cleaning step includes immersing a basket containing silicon particulate material in one or more vessels containing a mixture comprising one or more acids; one or more vessels filled with high purity deionized water; a vessel containing a mixture of high purity deionized water and 1 - 5% ozone; and a vessel filled with high purity deionized water optionally heated to a temperature of 20°C or greater.

[0097] In some embodiments, the process for manufacturing silicon particulate material further includes drying the silicon particulate material within a vacuum chamber.

[0098] In various embodiments, the process for manufacturing silicon particulate material further includes drying the silicon particulate material within a vacuum chamber at a low atmospheric pressure.

[0099] In certain embodiments, the process for manufacturing silicon particulate material further includes drying the silicon particulate material within a vacuum chamber at a level sufficient to evaporate water from the surface of the particulate material.

[0100] In various embodiments, the process for manufacturing silicon particulate material further includes drying the silicon particulate material within a chamber using forced air supplied at a controlled relative humidity and a controlled air temperature.

[0101] In some embodiments, the silicon is polycrystalline silicon.

[0102] In various embodiments, the polycrystalline silicon is a polycrystalline silicon rod.

[0103] In certain embodiments, the polycrystalline silicon rod is a polycrystalline silicon rod by the Siemens process.

[0104] In some embodiments, the silicon is single-crystalline silicon.

[0105] In various embodiments, the pulverization is performed using high-voltage pulse crushing (HVPC).

[0106] In certain embodiments, the pulverization is performed within a process vessel.

[0107] In various embodiments, the silicon rod is partially immersed in a process vessel filled with high-purity deionized water.

[0108] In some embodiments, the high-purity deionized water is high-purity deionized water of ≧16 Mohm-cm.

[0109] In some embodiments, the high-purity deionized water is high-purity deionized water of ≧18 Mohm-cm.

[0110] In certain embodiments, the temperature of the high-purity deionized water is ≧20 °C.

[0111] In some embodiments, the temperature of the high-purity deionized water is in the range of ≧20 °C, for example, 50 to 80 °C.

[0112] In various embodiments, the mixture containing one or more acids contains one or more of nitric acid, hydrofluoric acid, hydrogen peroxide, and / or hydrochloric acid.

[0113] In certain embodiments, the mixture containing one or more acids contains nitric acid and hydrofluoric acid.

[0114] In some embodiments, the mixture containing one or more acids includes nitric acid (e.g., 68 - 77% w / w) and hydrofluoric acid (e.g., 49% w / w).

[0115] In certain embodiments, the mixture containing one or more acids includes nitric acid (e.g., 68 - 70% w / w) and hydrofluoric acid (e.g., 49% w / w).

[0116] In various embodiments, the process is carried out in a series of cleanrooms operating in the range of ISO7 - ISO1.

[0117] In some embodiments, the process is carried out in a series of cleanrooms operating in the range of ISO7 - ISO4.

[0118] In certain embodiments, the relative humidity in the drying chamber is ≤ 34%.

[0119] In various embodiments, the air temperature in the drying chamber is ≥ 30°C.

[0120] In some embodiments, the process further includes subjecting silicon particulate material that exceeds the maximum target size accumulated in the holding vessel to a reprocessing step, and the reprocessing step includes transferring the silicon particulate material that exceeds the maximum target size to a grinding station and grinding the silicon particulate material that exceeds the maximum target size.

[0121] In various embodiments, the grinding station can be a process vessel.

[0122] In certain embodiments, the process further includes transferring the dried silicon particulate material to a polymer material bag, heat - sealing the bag, labeling the heat - sealed bag, and placing the heat - sealed and labeled bag into a box.

[0123] In various embodiments, the process further includes manufacturing integrated circuits and / or power devices from wafers made from crystalline silicon ingots made from silicon particulate materials.

[0124] In some embodiments, the process further includes generating single-crystalline silicon material from silicon particulate materials.

[0125] In certain embodiments, the process further includes generating single-crystalline silicon material by the Czochralski (CZ) method of crystal growth.

[0126] In various embodiments, the process further includes manufacturing silicon wafers, solar cells, and / or photovoltaic panels from the single-crystalline silicon material.

[0127] In some embodiments, the silicon particulate material is generated by any of the processes of the above-described embodiments.

[0128] The accuracy of the process can be evaluated offline for quality checks. For example, a bag of silicon particulate material is removed from the box. The contents of the bag are tested for surface impurities and particle size distribution. Verification of the surface metal impurity level is performed by procedures as documented in ASTM1724-96, which describes dissolving the surface of the silicon particulate material using an HF / HNO3 mixture and creating a sample suitable for testing by graphite furnace (GFAAS) or alternatively by ICP-MS method. The surface impurity test is performed in a cleanroom environment with at least ISO4 particle control. Due to the very low impurity levels, the surface test must have a minimum detection limit of ≤4 pptw.

[0129] The surface impurity test can be repeatedly applied to the same sample, and after sufficient repetition of the surface etching, the measured impurities should no longer change, and the value represents the concentration of impurities in the bulk of the particulate material.

[0130] Verification of surface carbon is measured in an ISO 5 cleanroom environment by using a LECO RC612 system (LECO Corporation, 3000 Lakeview Ave., St. Joseph, MI 49085).

[0131] To confirm that the particulate matter conforms to the target size range, a sample of the particulate matter is passed through silicon particulate matter using a camera (e.g., Canty Tiltsizer, JM Canty, Inc., Buffalo, NY) to image the particulate matter, and then tested using a machine that determines particle size measurement criteria such as distribution by length dimensions (minimum length, maximum length), volume, and aspect ratio.

[0132] The distribution of the particulate matter can be evaluated using a camera imaging-based particle sorting system that can derive the maximum and minimum length dimensions of the particulate matter and use this data to calculate the aspect ratio as follows.

[0133] Aspect ratio = maximum length dimension / minimum length dimension

[0134] The HVPC milling method was unexpectedly found to produce silicon particulate matter with a lower aspect ratio compared to milling methods such as human hammers or mechanical crushing. To provide high-purity silicon particulate matter that meets the ever-increasing requirements of the semiconductor industry, a new and improved method for producing high-purity silicon particulate materials is needed.

[0135] Furthermore, the applicant unexpectedly discovered that the process of the present invention can be used to produce particulate matter of high-purity silicon materials having a controlled size range and a very low aspect ratio, having high uniformity and low variability, and having a very low level of surface contamination including iron, nickel, copper, and carbon.

[0136] The method of the present invention minimizes additional contamination of silicon by using an automated process that, when sent for feeding into the grinding process, prevents human contact with the silicon rods. It is preferable to use a grinding method in which silicon is ground in high-purity water and then maintained in a wet state until it is carried, sorted, and automatically loaded into a basket for etching. To ensure the highest control of contamination, the automated process is carried out in a more stringent controlled cleanroom environment, starting from at least ISO7 control during grinding and up to at least ISO5 control during bagging.

[0137] Furthermore, this method minimizes additional contamination of silicon by not using mechanical contact rods or particle crushing. During the grinding of silicon, the silicon material can come into contact with other materials, especially metallic materials, and may collect metallic impurities that contaminate the silicon material. Manual crushing using a hammer not only results in pieces with different size distributions but also may introduce additional impurities (iron, tungsten, cobalt) on the surface of the silicon material. Therefore, roll crushers and jaw crushers may also introduce undesirable metallic impurities on the surface of the silicon material. Grinding by high-voltage pulse crushing does not require mechanical contact with an impact surface or a crushing surface that may separate from or adhere to the silicon particulate material, so this method has a low potential to contaminate silicon with such materials.

Example

[0138] The following examples are presented to more fully illustrate certain embodiments of the present invention. However, they should in no way be construed as limiting the broad scope of the present invention.

[0139] Example 1: Preparation of Silicon Particulate Material Silicon (polysilicon) rods with a diameter in the range of 125 - 145 mm were prepared by first manually removing the carbon ends (each leg being 125 - 150 mm apart) containing graphite sockets, and then separating the bridge portion connecting both legs using a tungsten carbide hammer. The two legs were then broken approximately in half to a length of 750 - 900 mm. Each leg portion was placed in a rectangular polymer process vessel filled with deionized water and then individually processed in an HVPC unit using the following parameters: the voltage was set to 180 - 190 kV, the frequency was set to 3 - 5 Hz, the speed was set to 6 - 12 mm / s, and the water gap was set to 25 mm. After HVPC treatment, most of the process water was drained from the process vessel. The crushed silicon particulate matter was then manually removed and manually sorted using a hand-held sieve with round holes having an upper limit of 65 mm and a lower limit of 20 mm using a "bullseye" size chart. The sorted silicon particulate matter was then either dried in air or packaged in a wet state.

[0140] After selecting the material to recover particulate matter in the desired size range, the material was divided into 5 kg batches. Using the contents of the 5 kg bags, the perforated polymer baskets were filled. Next, the selected 5 kg samples were processed by the different cleaning methods shown in Table 1 below. The selected samples were chemically cleaned in a caustic detergent at pH = 12 and then transferred inside and outside several baths containing deionized water. The selected samples were etched in a solution of 6 parts 70% HNO3 to 1 part 49% HF. Following chemical cleaning, all samples were rinsed with 18 Mohm-cm deionized water and dried. To test for surface impurities, 10 mm chips were removed from the etched samples and tested using the general method of WO 2016 / 051761 A1, which is incorporated herein by reference in its entirety, and the surface metal concentration was determined using ICP-MS. Surface metal contamination was determined by etching 10 mm samples with a HNO3 / HF mixture for a period that resulted in 5 um removal from the polished crystalline silicon wafer. Bulk metal contamination was determined by etching 10 mm samples with a HNO3 / HF mixture for a period that resulted in 25 um removal from the polished crystalline silicon wafer. After etching, the samples were removed, the acid was evaporated, the residue was reconstituted, and then tested by ICP-MS. The detection limit for the impurity test was <4 pptw.

Table 1

[0141] Example 2: Comparative Example Instead of milling by HVPC, a sample of silicon particulate material was prepared in the same manner as Example 1, except that milling was performed by a) tungsten carbide manual hammer and b) tungsten carbide manual hammer followed by a tungsten carbide roll crusher, and then washed with a solution of deionized water containing 1% HF and H2O2. The resulting surface and bulk metal contamination were tested using the sample method of Example 1.

Table 2

[0142] Example 3: Preparation of Silicon Particle-Like Material Silicon rods with diameters in the range of 127 - 144 mm were prepared for HVPC grinding by first manually removing the carbon ends (each leg being 125 - 150 mm apart) containing graphite sockets using a tungsten carbide hammer. Subsequently, the bridge portion connecting both legs was broken approximately in half. Using a vacuum lift assist, one leg and half of the bridge were loaded into the process vessel. The length of the leg and half of the bridge was in the range of 1775 - 1900 mm. The maximum allowable length of the process vessel was 2,100 mm. Each leg and half of the bridge portion was individually processed in the HVPC process vessel using the following parameters: the voltage was set to 175 - 200 kV, the frequency was set to 3 - 5 Hz, the speed was set to 10 - 15 mm / s, and the water gap was set to 15 - 25 mm. The resistivity of the deionized process water was in the range of 17 - 18 Mohm-cm. After HVPC treatment, most of the process water was drained from the process vessel. The HVPC silicon particulate material was screened by a vibratory classifier using two sets of polyurethane perforated screens to create a particle size range of 8 - 65 mm (maximum length). Subsequently, the screened silicon particulate material was spread on a polyurethane sheet and air-dried with a fan.

[0143] After screening, the HVPC particulate material was divided into 5 kg batches. Five bags were characterized by measuring the aspect ratio of the silicon particulate material using a CANTY Tiltsizer. Five samples of commercially available silicon particle-like materials ground using a roll crusher or jaw crusher were also characterized by measuring the aspect ratio of the silicon particulate material using a CANTY Tiltsizer.

Table 3

[0144] Although certain features of the present invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will occur to those skilled in the art. Accordingly, it is to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit and scope of the present invention.

Claims

1. A method for manufacturing a silicon particulate material, comprising: a) pulverizing silicon to produce a silicon particulate material; b) rinsing the silicon particulate material with deionized water; c) cleaning the surface of the silicon particulate material, the cleaning comprising: i) optionally, immersing in one or more vessels containing a mixture comprising a caustic detergent and high-purity deionized water at a pH of 10 or higher; ii) immersing in one or more vessels containing a mixture comprising one or more acids; iii) immersing in one or more vessels containing high-purity deionized water; iv) optionally, immersing in a vessel containing a mixture comprising ozone and high-purity deionized water; v) immersing in one or more vessels containing high-purity deionized water at a temperature of 20 °C or higher, wherein the cleaning comprises immersing a perforated polymer basket containing the silicon particulate material in a separate bath; A method comprising the above steps.

2. The method according to claim 1, further comprising transferring the silicon particulate material to a vibrating sieve conveyor.

3. The method according to claim 2, further comprising sorting the silicon particulate material via the vibrating sieve conveyor, wherein the sieving separates the silicon particulate material into three groups: 1) below a minimum target size, 2) within a target size window, and 3) above a maximum target size.

4. The method according to claim 3, further comprising transferring the silicon particulate material below the minimum target size to a collection vessel, transferring the silicon particulate material above the maximum target size to a holding vessel, and transferring the silicon particulate material within the target size window to a perforated polymer basket in a predetermined batch quantity.

5. The method according to claim 1, further comprising drying the wet silicon particulate material in a chamber to which a vacuum is applied to create a low atmospheric pressure.

6. The method according to claim 1, further comprising drying the silicon particulate material in a chamber using forced air supplied at a controlled relative humidity and a controlled air temperature.

7. The method according to claim 1, wherein the silicon is polycrystalline silicon.

8. The method according to claim 7, wherein the polycrystalline silicon is a polycrystalline silicon rod.

9. The method according to claim 8, wherein the polycrystalline silicon rod is a polycrystalline silicon rod by the Siemens method.

10. The method according to claim 1, wherein the pulverization is performed using high voltage pulse crushing (HVPC).

11. The method according to claim 1, wherein the mixture contains nitric acid and hydrofluoric acid.

12. The method according to claim 1, which is performed in a clean room operated in the range of ISO7 to ISO1.

13. The method according to claim 1, which is performed in a clean room operated in the range of ISO7 to ISO4.

14. The method according to claim 6, wherein the relative humidity in the drying chamber is 34% or less.

15. The method according to claim 6, wherein the air temperature in the drying chamber is 30°C or higher.

16. Further comprising subjecting the silicon particulate material exceeding the maximum target size accumulated in the holding vessel to a reprocessing step, the reprocessing step comprising: i) transferring the silicon particulate material exceeding the maximum target size to a pulverization station; ii) pulverizing the silicon particulate material of step i; The method according to claim 4, comprising.

17. a) transferring the silicon particulate material to a polymer material bag; b) heat-sealing the bag; c) attaching a label to the heat-sealed bag; d) placing the heat-sealed and labeled bag in a box; The method according to claim 1, further comprising.

18. The method according to claim 1, further comprising manufacturing an integrated circuit and / or a power device from a wafer made from a crystalline silicon ingot made from the silicon particulate material.

19. A silicon material produced by the method according to claim 1.

20. a) a polycrystalline structure, and b) a particle size distribution in the range of 3 mm or more and 75 mm or less, and c) an average aspect ratio of 1.55 or less, and d) a total surface impurity and bulk impurity of a total iron impurity of 20 pptw or less, a total nickel impurity of 4 pptw or less, and a total copper impurity of 4 pptw or less; A silicon particulate material having.

21. The silicon particulate material according to claim 20, having an iron bulk impurity of 10 pptw or less, a total nickel impurity of 4 pptw or less, and a total copper impurity of 4 pptw or less.

22. The silicon particulate material according to claim 20, which is a product of a polycrystalline silicon rod in the Siemens process.

23. The silicon particulate material according to claim 20, wherein the surface impurities of iron, nickel, and copper in the silicon particulate material are evaluated using acid dissolution and ICP-MS.

24. A product selected from an integrated circuit and a power device including a silicon wafer including the silicon particulate material according to claim 20.

25. A product selected from an integrated circuit and a power device generated from a wafer generated from the silicon particulate material according to claim 20.

26. A silicon material including the silicon particulate material according to claim 20.

27. The silicon particulate material according to claim 20 for use in the manufacture of a silicon wafer, wherein the silicon wafer can be used for manufacturing an integrated circuit and / or a power device.

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