High purity silicon particulate material and methods of making

Abstract

A process for manufacturing a silicon particulate material comprising: comminuting silicon to produce silicon particulate material, rinsing the particulate material with deionized water, and cleaning a surface of the particulate material comprising submerging a perforated polymer basket containing the particulate material in separate baths comprising: optionally submerging in one or more vessels containing a mixture comprising caustic detergent and high purity deionized water at a pH ≥ 10, submerging in one or more vessels containing a mixture comprising one or more acids, submerging in one or more vessels containing high purity deionized water, optionally submerging in a vessel containing a mixture comprising ozone and high purity deionized water, and submerging in one or more vessels containing high purity deionized water at a temperature of ≥20°C. The process may further comprise transferring the silicon particulate material to a vibratory sieving conveyor. A silicon particulate material is defined, comprising; a polycrystalline structure, a particle size distribution of range ≥3 mm and ≤75 mm, an average aspect ratio of ≤1.55, and a combined surface impurity and bulk impurity of total iron impurity of ≤20 pptw, total nickel impurity of ≤4 pptw, and total copper impurity of ≤4 pptw.

Description

FIELD OF THE INVENTION

[001] The invention relates to a high purity silicon particulate material having relatively small size, low surface area, and a relatively smooth rounded shape making it attractive as a high purity, high performance feedstock for use in the manufacture of silicon crystals and silicon wafers. The invention also relates to methods of manufacturing the high purity silicon particulate material. BACKGROUND OF THE INVENTION

[002] This invention pertains to the creation of silicon particulate material that is used for manufacturing silicon crystals, typically low-cost, high-volume manufacturing of silicon crystals.

[003] Silicon crystals and wafers fabricated from the silicon crystals are a primary feedstock for the manufacture of integrated circuits, power devices (MOSFETS, IGBTs), microelectronic devices, and solar cells. The silicon crystals are machined, sliced, and polished to produce crystalline silicon wafers and the wafers are used in the manufacturing processes which produce integrated circuits, power devices, and solar cells. The silicon crystals must be nearly free of crystal defects and must contain very few metallic impurities such as nickel, iron, copper, chromium, and carbon (in the parts per million (ppm) to parts per trillion (ppt) range). Impurities, specifically metallic impurities, are problematic when producing integrated circuits as they lessen their electrical efficacy. Metal contaminants such as chromium, cobalt, iron, nickel, and copper reduce the efficiency of solar cells. Contaminants may be introduced to the silicon particulate material at any point in the manufacturing process and, therefore, steps to prevent contamination as well as steps to remove contaminants must be taken.

[004] Polycrystalline silicon is a feedstock to produce monocrystalline or multicrystalline silicon ingots needed for fabrication 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. Moreover, a highly pure silicon particulate feedstock provides higher yields in the crystallization processes, e.g., by enabling production of larger ingots, which reduces production costs and ultimately lowers the cost per wafer.

[005] Manufacturing silicon crystals and wafers is a costly process, and there is continuous pressure from the users of silicon wafers to reduce manufacturing costs and improve the wafer performance quality. Key elements of wafer performance quality include metallic contamination and surface defects. Metallic impurities such as iron can impact the electrical properties of the crystalline silicon wafer, while metallic impurities like nickel can lead to surface defects - defects that can result in failed semiconductor devices. Manufacturers of silicon crystals and silicon wafers must continually work to reduce costs and improve the performance of these products by reducing impurities in the crystal growth and wafer manufacturing while reducing the cost of manufacturing. Metallic impurities in the silicon wafers originate in the silicon metal used as a feedstock to manufacture silicon crystals. There is continual pressure to reduce metal impurities in silicon wafers from the manufacturers of semiconductor devices, as the metal impurities are detrimental to semiconductor device performance - as such future generations of advanced device designs require silicon particles / particulates with lower and lower levels of metal impurities.

[006] Manufacturers of silicon crystals and silicon wafers have standardized the specifications for making high purity silicon particulates to maximize the consistency of the silicon crystal growth process. The silicon particulates must conform to purity, size, and packaging requirements. Methods to produce silicon crystals using high purity silicon particulates at a low cost of manufacture include creating crystals with diameters 300-450 mm, creating large mass crystals (>350 kg), and by using methods to refill the contents of a container, typically a crucible, with silicon particulates while the crucible still contains molten material, known as recharging.

[007] There are multiple methods for producing highly pure polycrystalline silicon, including fluid bed reduction and the Siemens process. Polycrystalline silicon produced by the Siemens process is of sufficient purity that it is suitable for applications for both integrated circuit applications and solar cells. The Siemens process is a chemical vapor deposition (CVD) process wherein a process vessel is fitted with number of parallel, long (meters), and thin (mm diameter or cross section) silicon filaments which act as a substrate, wherein two or more of the silicon filaments are connected at the top with a silicon bridge to form roughly a U-shape (U-rod). The process vessel is closed, purged with inert gas, and then a mixture of hydrogen and a chlorosilane gas (typically trichlorosilane (HSiCh) or silicon tetrachloride (SiCh)) is delivered to the process vessel. ‘Chlorosilane’ may refer to any species of silane characterized by one or more chlorine atoms bonded to silicon and includes, but is not limited to, monochlorosilane (H<SiQ), dichlorosilane (HsSiCh), trichlorosilane (HSiCh), silicon tetrachloride (SiCLj), and various chlorinated disilanes such as hexachlorodisilane ((SiChh) and pentachlorodisilane (HChSis). Because of the requirement for extremely low impurities in a silicon crystal, the chlorosilane gas typically has metallic impurities concentration in the ppb-ppt range. Electrical current is then applied to the filaments to heat them to a target temperature in the range of 800-1200 °C, a temperature high enough to decompose the chlorosilane gas feed stream, which results in the deposition of silicon onto the filaments and the growth in diameter of the coated filaments. After sufficient time, the process is terminated, and the coated filaments, now referred to as “rods”, are removed. The weight of each silicon rod is typically in the range 100-250 kg and the diameter is typically in the range of 100-200 mm.

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

[009] Validation of the bulk donor and acceptor impurity levels (for example phosphorus, arsenic, boron and aluminum) and metallic impurities in silicon rods is performed by methods known in the art, including the method defined in SEMI MFI 723, incorporated herein by reference. Validation of the metal impurity levels is performed by taking the freeze out section (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) of the crystal from the method of SEMI MF 1723, dissolving it using HF / HNO3, and creating a suitable sample for testing by ICP-MS methods. Due to the very low impurity levels, the ICP-MS tests must operate with minimum elemental concentration detection limit for metal contaminants of <10 ppta or <1 ppta. Validation 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, incorporated by reference herein in its entirety.

[0010] The highly pure polycrystalline silicon produced by the Siemens process may then be used to prepare highly pure monocrystalline silicon by various methods, e.g., the Czochralski method (CZ method). Indeed, most silicon particulate material used in the CZ method are produced using the Siemens process. In the CZ method, particulates of silicon, commonly referred to as polysilicon (a poly crystalline form of silicon), are melted in a quartz crucible located inside a furnace. Then a small crystal of silicon in the form of a small diameter cylinder, referred to as a seed crystal, is dipped into the crucible of molten silicon and then is slowly withdrawn into a long cylindrical vertical chamber maintained in an inert ambient environment. The crucible continuously rotates on a vertical axis while the seed crystal is concurrently rotated in the opposite direction and the seed crystal is slowly withdrawn (pulled) from the crucible. The melted silicon in the crucible solidifies on the pulled seed crystal, forming a single crystal ingot with diameter much larger than the seed. During this process, the ingot is pulled from the melt at a controlled rate to form an ingot with the desired diameter, and the volume of molten silicon is consumed. Because of the high purity of such crystals, the majority' of semiconductor chips employed in electrical devices and solar panels are made from monocrystalline silicon produced by the Czochralski method.

[0011] As stated previously, it is a constant effort of manufacturing to produce larger, high purity monocrystalline silicon crystal material at a low cost. Methods to reduce cost include implementing steps to maximize the apparatus efficiency and process time. For the highest level of efficiency and purity, the feedstock of polysilicon used in the CZ method must be in the form of small particulates. The ideal shape of these particulates is spherical, and small in size to minimize the spaces between the particulates loaded in the crucible. Larger and / or irregular-shaped chips or chunks of silicon feedstock require longer time to melt due to size and larger interstitial spaces between the particulates in the crucible which, when the feedstock is fully melted, leave a volume of molten silicon that is smaller than the volume occupied by the partculates. This fill volume of molten silicon, if not maximized, reduces the efficiency of the crystal growth process. To melt the silicon in a reasonable time, small particulates are used to ensure dense packing of the particulates in the crucible. The quartz crucible that holds the polycrystalline material in a CZ reactor is exposed to extreme temperatures when melting the silicon and during the cool-down of the reactor once the ingot has been pulled. One method of extending the life of the crucible, enabling pulling of a longer crystal, and reducing the process time between the pulling of ingots, thereby improving the efficiency and cost-effectiveness of the crystal growth process, is to refill the crucible with polycrystalline silicon material particulates while the crucible still contains a residual volume molten material, known as recharging.

[0012] There are two methods of recharging - intermittent (batch-type), where after a crystal is removed from a CZ furnace (a furnace used in the Czochralski method), a quartz container filled with silicon material particulates is inserted into the CZ furnace cylindrical vertical chamber above the crucible and then the bottom is opened allowing the silicon particulates to fall into the crucible, and continuous, where the silicon particulates are added to the crucible throughout the crystal growth process. Typical requirements on silicon particulates used in crucible recharge for manufacture of high-performance silicon crystals and silicon wafers comprise minimum and maximum limits on silicon particle size, minimum metal impurities, and high purity packaging. The silicon particulates used in recharging are sorted so that the particulates have a typical size range of approximately > / = 3 mm to < / = 75 mm. Target ranges may be a range between 5 mm to 50 mm or 20 mm to 70 mm. The particulates are packaged into high purity polymer bags in clean room environments operating at least at ISO 5 particle control (e.g., packaging may also take place at ISO 4 particle control). It is very desirable that the silicon particulates have low surface and bulk impurities because this is needed to keep the crystals produced low in impurities. For example, the total concentration of metal impurities (sum of surface and bulk impurities) such as iron, nickel, copper, and chromium should be in the range of 1-50 pptw, and carbon less than 100 ppbw.

[0013] The polycrystalline silicon rods produced by CVD are not in a state which is useful for its application to produce monocrystalline silicon crystals. The poly crystal line silicon rods must be broken into small pieces. When a silicon rod is removed from the Siemens CVD process, it is in its purest state. A major challenge for manufacturers of silicon particulates is how to convert the silicon rods into small particulates, a process called comminution. The most common methods of comminution include jaw crushers, roll crushers, and manual breaking of the rods by people wielding hammers. The comminution of the silicon rods can add significant contamination to the surfaces of silicon particulates.

[0014] To produce high purity silicon particulates, technology to comminute silicon rods into particulates must be able to deliver particulates with minimum added contamination to the surface of the particulates. Originally, comminution was done in a clean room by operators wielding hammers to break the silicon rods into large pieces and further hammering to reduce the large pieces into smaller pieces. The pieces would then be sorted in the target particle size range by hand on a table. The particulates were then manually transferred into bags, typically with weight of 5 kg + / - 50 g particulates in each bag. Figure 1 presents this process flow.

[0015] The process flow of Figure 1 is known in the art. It is labor intensive, slow, adds undesired contamination, and results in undesired particle size and contamination variation as well as product waste due to the manual nature of the method. Improvement of the process shown in Figure 1 is shown in Figure 2. Mechanical crushing of the large pieces of silicon rods using jaw crushers or roll crushers was developed to improve the control of the comminution to provide particulates of the desired size range. The particulates were sorted using sieving to achieve higher consistency of the particle size range. Chemical cleaning with acid such as mixtures of H2O2+HCI, or H2O2+HF, or HNO3 + HF is used to remove surface contamination added during the comminution process.

[0016] An emerging method of comminution is high voltage pulse crushing (HVPC) In this method, a silicon rod is partially or fully submerged in a vessel filled with deionized water. Two or more metal electrodes are placed across the rod and a high voltage generated across the electrodes creates an electrical arc discharge. This discharge creates a high-pressure shock wave in the vessel which breaks apart the silicon rod into pieces. The high voltage pulse crusher may be calibrated to provide a specific size range of particles. Moreover, silicon pieces / particles may be comminuted in the high voltage pulse crusher, either with or without a silicon rod. Furthermore, silicon in both polycrystalline form and monocrystalline form may be comminuted by HVPC. Commercial applications of HVPC in silicon have been limited to manufacture of silicon for solar cell applications. To date, HVPC has not penetrated the silicon semiconductor process because the HVPC method tends to contaminate the comminuted silicon particulates with high concentrations of metal impurities. These impurities originate in the electrodes of the HVPC equipment. The impurities imparted make it difficult to clean the silicon particulates to a level acceptable for use in manufacturing silicon crystals and silicon wafers.

[0017] Variations of these comminution methods are practiced today to produce commercial high-volume quantities of high purity silicon particulates. However, both manual and machine comminution result in undesired variation of particle size and shape, particle surface area, impurities, and operating costs that are each unfavorable to meet the future needs of silicon crystal growth manufacturing for lower cost, higher consistency, high purity silicon particulates.

[0018] As mentioned, high voltage pulse crushing has been very successful for comminution of silicon rods or scrap crystals used in the silicon solar industry, however, the HVPC method has been unsuccessful when applied in the silicon semiconductor industry because of the contamination imparted by the HVPC process. Thus, the use of HVPC to produce semiconductor grade particulate matter has not previously been successful. However, Applicant has unexpectedly discovered a novel method to successfully prepare silicon particulate material comprising high voltage pulse crushing that meets the high-purity requirements of the semiconductor industry.

[0019] As the silicon particulates are formed, they are transported, typically by conveyors made from or coated with plastic / polymeric materials, which bring them to a sorting system which segregates the particulates into a target size range by separating out the particulates which are too small and too large for conformance to the target size range. Sorting is typically accomplished by conveying the silicon particulates over sieves of differing opening size to segregate a range of particulates conforming to a minimum and maximum particle size. The segregated pieces are often tested using a machine which passes the silicon pieces past a camera (for example, CANTY Tiltsizer, JM Canty, Inc., Buffalo, NY), images the particulates, and then determines particle size metrics such as the distributions by linear dimensions (minimum length, maximum length), volume, and aspect ratio.

[0020] The conveyors abrade the moving silicon particulates which produces very small silicon particulates (often referred to as “fines”) and silicon dust. These small particulates and dust do not produce silicon particulates in the required size range and as such are waste which adds cost to the process. Moreover, because these silicon fines and dust are from the surface of the comminuted silicon particulates, they often have high levels of contamination. The fines and dust abrade the polymer plastic conveyors creating carbon particles. The silicon fines, dust, and carbon particles continuously build up on the conveyors and transfer to subsequent silicon particulates moving on the conveyor adding additional contamination to the silicon particulates. This contamination to the silicon particulates has metallic surface impurity levels as high as 1000 ppbw and carbon impurities as high as 300 ppbw. To control these sources of contamination, the manufacturing process must be periodically stopped to clean and / or replace the conveyors, thus adding cost to manufacturing silicon particulates.

[0021] Another strategy to reduce surface contamination is to use acid chemistry to dissolve the contaminants and / or the top surface of the silicon to reduce the level of impurities on the surface to the range of 1-100 ppta. As metallic and non-metallic contaminants alike have deleterious effects when producing high purity silicon as well as on the quality of the product, it is also beneficial to attempt to remove contaminants when they occur (i.e., during comminution). The common method to clean the silicon pieces involves cleaning with acidic chemical mixtures comprising HF / H2O2 / HCI / HNO3, such as HF / HNO3 and / or HF / H2O2 and / or H2O2 / HCI, to dissolve the top surface of the silicon and the impurities, as well as silicon fines and dust. Carbon contaminants which cannot be dissolved by silicon etchants can be rinsed off of the silicon particulates. After cleaning with acidic chemical mixtures, the silicon particulates are rinsed with high purity deionized water, dried, and packaged. The various methods of comminution described above (hammering, jaw crusher, high voltage pulse crushing) require a unique cleaning strategy to render the silicon surface free of metal and carbon impurities to levels of 1-100 ppta.

[0022] The accumulated impurities on the surface of the silicon particulates are a key concern in the use of silicon in the CZ crystal growth method and the manufacturers of silicon seek new and better ways to minimize surface contamination. Another strategy is to control the handling of the silicon using automation - i.e., no humans touch the silicon after it is loaded into the comminution process. Another strategy is to optimize the comminution process to minimize the surface area of the particulate by controlling its size and shape, with the goal of producing a particulate with an aspect ratio as close to one as possible.

[0023] Accordingly, there remains a critical need for high purity silicon meeting the continuously increasing requirements of the semiconductor industry as well as new and improved methods to produce high purity silicon particulate materials.

[0024] These limitations provided the impetus to invent improved technology for the manufacture of high purity silicon particulates and have resulted in higher purity silicon particulates. SUMMARY OF THE INVENTION

[0025] An objective of the instant invention is to provide high purity silicon particulate materials with very low impurity levels.

[0026] A further objective of the instant invention is to provide a method of preparing high purity silicon particulate materials that enable lower cost manufacturing of silicon crystals with very low impurity levels.

[0027] In one aspect, the present invention provides a method of comminution which can produce small particulates with low surface area and rounded shape and a method of cleaning which provides high purity silicon particulate materials. The inventors have discovered a method of comminution comprising, in an at least ISO 7 clean room, placing 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, placing the process vessel into a high voltage pulse crushing (HVPC) system, and comminuting the rod into small silicon particulates. The process vessel is mechanically drained and rinsed with deionized water, the particulates are mechanically transferred to a vibratory sieving conveyor, and the pieces are sorted and separated on the vibratory sieving conveyor in the presence of a high purity deionized water shower. Showering / rinsing the silicon particulates with water removes dust from the surface and minimizes abrasion of the conveyor. The sorted particulates are separated into three groups. The sorted particulates above the maximum target size are transferred to a rework step wherein the silicon particulate material above the maximum target size is accumulated in a holding vessel and then is transferred back to the process vessel for further comminuting in the high voltage pulse crusher. The sorted particulates below the minimum target size are discarded as waste. The sorted particulates within a target size window are mechanically collected in a perforated polymer basket and transferred to an automated cleaning / etching system.

[0028] The inventors have discovered a method of cleaning the particulate material wherein the cleaning takes place in a clean room area, rated at ISO 6 or below, where the vessel containing the particulates passes through baths comprising optionally cleaning in one or more optionally heated baths comprising caustic detergent and high purity (typically, 18 Mohm-cm) deionized water at a pH of > / = 10; rinsing in one or more baths of high purity (typically, 18 Mohm-cm) deionized water; etching in one or more acid baths comprising a mixture of one or more acids, e.g., HF (e.g., 49% w / w) / HN03 (e.g., 68-77% w / w), to dissolve the top surface of the silicon particulates and the contamination imparted during the comminution process; rinsing in one or more baths of high purity (typically, 18 Mohm-cm) deionized water; optionally submerging 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 temperature (e.g., >1= 20 °C) high purity (typically, 18 Mohm-cm) deionized water. The polymer basket containing the particles / particulates undergoes drying in a drying chamber in which vacuum is applied to create subatmospheric pressure and, in a second drying chamber, undergoes drying comprising a heated (e.g., > / = 30 °C), high air flow, with relative humidity (e.g., < / = 34%) to accelerate the drying process. Packaging steps, which take place in a clean room operated at ISO 5 or in a clean room at ISO 4 standard, comprise transferring the pieces of high purity silicon particulate material into poly ethylene / polymeric bags, heat sealing the bags, labelling the heat-sealed bags, and placing the heat-sealed bags in a box. Once packaged, the highly-pure silicon particulate material in a bag is sampled and optionally can be tested for surface impurities.

[0029] The method developed by the instant invention unexpectedly revealed that the method can be used to manufacture particulates of high purity silicon material with a controlled size range, a very low aspect ratio, and very low levels of surface and bulk contamination of iron, nickel, copper, and carbon, wherein the particulates have high consistency and low variability.

[0030] The high purity silicon particulate material comprises silicon particulate material having a polycrystalline structure; wherein the silicon particulate material has a particle size distribution in a range greater than or equal to 3 mm and less than or equal to 75 mm; wherein the silicon particulate material has an average aspect ratio of less than or equal to 1.55; and wherein the silicon particulate material comprises combined surface impurity and bulk impurity tallying total iron impurity of less than or equal to 20 pptw, total nickel impurity of less than or equal to 4 pptw, and total copper impurity of less than or equal to 4 pptw.

[0031] Validation of the surface metal impurity levels is performed by procedures such as that documented in WO2016051761 Al, incorporated by reference herein in its entirety, which describes dissolving the surface of the silicon pieces using HF / HNOs and creating a suitable sample for testing by graphite furnace ICP-MS methods. Due to the very low impurity levels, the ICP-MS tests must have minimum detection limit less than or equal to 10 ppta, less than or equal to 1 ppta. Testing of surface impurities is performed in an ISO 4 clean room environment. Validation of the surface carbon is measured in an ISO 5 or lower clean room environment using a LECO RC612 system. The total elemental impurity in the high purity silicon particulate material is derived by adding the bulk and surface values for that given element.

[0032] When the high purity polycrystalline silicon particulate material is used to grow a crystal of silicon using the CZ method and recharge approach, many successive large crystals of silicon (diameter >200 mm and mass >350 kg) can be produced with very low impurities, lower than that of the feedstock high purity silicon particulate material. The silicon crystals produced are useful to fabricate silicon wafers with very low metal impurities, lower than that 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 figures. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the invention, 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 the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0035] Figure 1 depicts the historical process flow to convert silicon rods made by CVD into high purity silicon particulates.

[0036] Figure 2 depicts the currently practiced process flow to convert silicon rods made by CVD into high purity silicon particulates.

[0037] Figure 3 depicts the inventive process flow to convert silicon rods made by CVD into high purity silicon particulates. DETAILED DESCRIPTION OF THE INVENTION

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

[0039] The object of this invention is to provide a method and material that meets the cost, consistency, and purity requirements related to manufacture of high purity silicon particulates meeting present and future requirements to manufacture silicon crystals and silicon wafers. The inventive process strives to remove variations and costs associated with manual and mechanical comminution while minimizing the concentrations of impurities in and on the silicon particulates.

[0040] Unless otherwise defined herein, scientific and technical terms used in connection with the present application shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include pluralities and plural terms shall include the singular.

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

[0042] PPMA is part per million atomic and refers to a concentration of impurity atoms defined as the ratio of the count of impurity atoms to the total atoms in the material and multiplied by 1E6 (i.e., 1,000,000 or 106).

[0043] PPBA is part per billion atomic and refers to a concentration of impurity atoms defined as the ratio of the count of impurity atoms to the total atoms on the material and multiplied by 1E9 (i.e., 1,000,000,000 or 109).

[0044] PPTA is part per trillion atomic and refers to a concentration of impurity atoms defined as the ratio of the count of impurity atoms to the total atoms on the material and multiplied by IE 12 (i.e., 1,000,000,000,000 or 1012).

[0045] PPMW is part per million weight and refers to a concentration of impurity atoms defined as the ratio of the weight of impurity atoms to the total weight in the material and multiplied by 1E6 (i.e., 1,000,000 or 106).

[0046] PPBW is part per billion weight and refers to a concentration of impurity atoms defined as the ratio of the weight of impurity atoms to the total weight in the material and multiplied by 1E9 (i.e., 1,000,000,000 or 109).

[0047] PPTW is part per trillion weight and refers to a concentration of impurity atoms defined as the ratio of the weight of impurity atoms to the total weight in the material and multiplied by 1E12 (i.e., 1,000,000,000,000 or 1012).

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

[0049] Silicon impurity concentrations, such as the relative units of ppmw, ppbw, etc. are often provided in varying units of SEMI Standards and 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 on a particle. A sphere has an aspect ratio of 1. An ellipsoid may have an aspect ratio of greater than 1, e.g., 1.55.

[0051] Ranges described herein include the endpoints as well as anything encompassed therein. For example, the range 7-20 includes 7 and 20, as well as 8, 15, 17, 19.6, etc. Moreover, the disclosure of a range, e.g., 7-20, also includes ranges within said range, e.g., 8-15, 9.9-17.4, etc.

[0052] When the phrase “at least at” precedes an ISO room number, then that ISO room number contains the highest level of contamination allowed, e.g., “at least at ISO 5” may be ISO 5, ISO 4, ISO 3, ISO 2, or ISO 1.

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

[0054] In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. Thus, for example, a reference to “a material” is a reference to one or more of such materials and equivalents thereof known to those skilled in the art, and so forth. When a range of values is expressed, another embodiment incudes from the one particular and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it is understood that the particular value forms another embodiment. All ranges are inclusive and combinable.

[0055] As noted herein, the invention provides a method and material meeting the cost, consistency, and purity requirements related to the manufacture of high purity silicon particulates which may be used to manufacture silicon crystals and silicon wafers.

[0056] The object of this invention is achieved in one embodiment with the highly-pure silicon particulate material comprising silicon particulate material having a polycrystalline structure, wherein the silicon particulate material comprises a particle size distribution in a range greater than or equal to 3 mm and less than or equal to 75 mm. The high purity silicon particulate material has rounded or ellipsoid shape that leads to low aspect ratio particulates and reduction of surface area. Lower surface area silicon particulates reduce the incorporation of fines and dust contamination and, as a result, the amount of impurities imparted to the silicon particulates during conveyance is reduced. The average aspect ratio of a collection of silicon particulates is less than or equal to 1.55, and the total (combined surface impurity and bulk impurity) iron impurity is < / = 20 pptw, the total nickel impurity is < / = 4 pptw, and the total copper impurity is < / = 4 pptw.

[0057] In various embodiments, the silicon particulate material may have bulk impurity levels of iron < / = 10 pptw, of nickel < / = 4 pptw, and of copper < / = 4 pptw; and the iron, nickel, and copper surface impurities on the silicon particulate material are assessed using acid extraction and Inductively Coupled Mass Spectrometry Analysis (ICP-MS analysis) with minimum detection limits of < / = 4 pptw, e.g., less than 1 pptw. The silicon rod may be produced using the Siemens process.

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

[0059] In certain embodiments, the silicon particulate material has bulk impurity levels of iron <1= 10 pptw, of nickel < / = 4 pptw, and of copper < / = 4 pptw.

[0060] In another embodiment, the iron, nickel, and copper surface impurities on the silicon particulate material are assessed using acid extraction and Inductively Coupled Mass Spectrometry Analysis (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 iron < / = 10 pptw, of nickel < / = 4 pptw, and of copper < / = 4 pptw.

[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 iron < / = 10 pptw, of nickel < / = 4 pptw, and of copper < / = 4 pptw; and the iron, nickel, and copper surface impurities on the silicon particulate material are assessed using acid extraction and Inductively Coupled Mass Spectrometry Analysis (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 iron < / = 10 pptw, of nickel < / = 4 pptw, and of copper < / = 4 pptw; and the iron, nickel, and copper surface impurities on the silicon particulate material are assessed using acid extraction and Inductively Coupled Mass Spectrometry Analysis (ICP-MS analysis) with minimum detection limits of < / = 4 pptw.

[0064] In certain embodiments, the invention provides a product selected from an integrated circuit and a power device comprising a silicon wafer comprising silicon particulate material of any one or a combination of the preceding embodiments.

[0065] In additional embodiments, the invention provides a product selected from an integrated circuit and a power device produced from a wafer produced from the silicon particulate material of any one or a combination of the preceding embodiments.

[0066] In various embodiments, the invention provides a monocrystalline silicon material comprising the silicon particulate material of any one or a combination of the preceding embodiments.

[0067] In certain embodiments, the invention provides a monocrystalline silicon material produced from the silicon particulate material of any one or a combination of the preceding embodiments.

[0068] In some embodiments, the invention provides a product selected from a silicon wafer, a solar cell, and a photovoltaic panel comprising the monocrystalline silicon material of any one or a combination of the preceding embodiments.

[0069] In certain embodiments, the invention provides a product selected from a silicon wafer, a solar cell, and a photovoltaic panel produced from the monocrystalline silicon material of any one or a combination of the preceding embodiments.

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

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

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

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

[0074] In various embodiments, the invention provides a monocrystalline silicon material for use in manufacturing a silicon crystal, wherein the silicon crystal may be used to manufacture a silicon wafer used to fabricate a solar cell and / or a photovoltaic panel.

[0075] The object of this invention is achieved in another aspect by producing a fully automated and touchless process for the comminution, sorting, rinsing, cleaning, and packaging of high purity silicon particulate material from silicon rods wherein the silicon rods may be made by the Siemens CVD process. The term touchless process refers to an automated process flow which does not require a human to handle any silicon during the normal execution of the process flow.

[0076] In one embodiment, the process flow of the inventive method is shown in Figure 3.

[0077] The process flow of Figure 3 is configured into a series of processing areas or rooms which may be connected by vibratory conveyors. A rod of silicon, produced by a CVD process, such as the Siemens CVD process, is delivered to the first room which is a clean room operated at ISO 7 particle control. The silicon rod is broken into particulates using particle crushing processes such as high voltage pulse crushing (HVPC). In this comminution method, a silicon rod is fully submerged into a process vessel filled with high purity deionized water. Metal electrodes are placed near the top and near the bottom of the rod and a high voltage is generated across the electrodes creating an electrical arc discharge. This discharge creates a high-pressure shock wave in the vessel which breaks apart the silicon rod into particulates. The CVD rods must start with bulk impurity levels low enough to meet the requirements of the semiconductor silicon crystal growth process and, therefore, should have bulk impurity levels consistent with the requirements for the silicon particulates. Typical bulk impurity concentration values are: iron < / = 10 pptw, nickel <1= 4 pptw, and copper < / = 4 pptw.

[0078] After high voltage pulse crushing (HVPC) comminution, the particulates are machine-transferred from the process vessel to a conveyor in a clean room operated at least at ISO 7 particle control and are not introduced to or in contact with any metallic materials. While on a conveyor, the drained silicon particulates from the process vessel are sprayed / rinsed with high purity (e.g., > / = 10-18 Mohm-cm) deionized water during the transport. Applicant has unexpectedly found that keeping the particulates from the process vessel wet by spraying / rinsing the particulates while transporting them removes fines and dust stuck on larger particulates and other contaminants imparted during comminution. Further, Applicant has unexpectedly found that spraying / rinsing the particulates to remove the contaminants makes the process more efficient and effective by preventing contamination build-up on the conveyor, which can abrade the conveyor and add carbon contamination to the particulates. In the next step, the particulates are sorted into three groups to separate the pieces which are too small and the pieces which are too large from the pieces with size in the target range. Sorting is accomplished by conveying the silicon particulates over vibrating solid polymer sieves while spraying them with high purity deionized water. Applicant has unexpectedly found that spraying the particulates while sieving makes sieving more effective because the water acts as a lubricant so that the particulates do not abrade the sieves. Thus, Applicant’s novel process of spraying while transporting and sieving the particulates also minimizes the need to stop the process in order to clean and repair damage incurred by the accumulation of contaminants.

[0079] Following sieving, the silicon particulates that are below the target size are removed from the process flow, the silicon particulates that are above the target size are collected in a solid polymer collection vessel. The oversized particulates are collected in a solid polymer holding vessel and eventually returned to the HVPC comminution step for size reduction.

[0080] The silicon particulates within the target size window are separated by methods known in the art. In this embodiment, the silicon particulates are transported by conveyor to a step where they are loaded into perforated solid polymer baskets. The baskets with the silicon particulates are delivered to a wet cleaning system where they pass through separate cleaning baths to remove surface contamination. The wet cleaning system is operated in a separate clean room maintained at least at ISO 6 particle control.

[0081] The wet cleaning system comprises the following steps:

[0082] The basket containing the silicon particulate material is optionally submerged in one or more vessels containing baths comprising a caustic detergent (i.e., any detergent formulation with a pH > / = 10) and high purity deionized water, wherein the bath(s) may be optionally heated to a temperature >1= 20 °C, e.g., between 20 °C and 90 °C, or between 20 °C and 40 °C. The heated water accelerates the cleaning action, allowing for faster cleaning of the silicon particulate material. During high voltage pulse crushing, the arc discharge creates very fine silicon dust from the comminution of the silicon rod and iron dust is generated from erosion of the electrode, both of which then incorporate in the water in the process vessel. It is also known that the arc discharge creates ozone and hydrogen peroxide in the water. The ozone and hydrogen peroxide create hydrolysis reactions with the iron and silicon particulates to form a polymer. The iron-oxygen-silicon hydroxide polymers deposit as contamination on the surface of the larger silicon particulates in the process vessel. The polymer surrounds the silicon particulates, and the presence of the polymer inhibits etching of the silicon particulates by acids. Thus, Applicant has unexpectedly found that rinsing the particulates in caustic detergent is particularly useful in the HVPC process because it breaks down the polymeric material bonds, allowing for removal of a portion of the iron from the particulates prior to the particulates entering the acid bath and enabling the reaction of the silicon particulates with the acid. Although the level of iron contamination has long been a factor known to decrease the quality of the silicon particulates, prior HVPC processes for manufacturing of high purity silicon particulates have not successfully resulted in removing the iron contaminants to obtain the low levels of iron contamination m the silicon particulates that Applicant has achieved.

[0083] The basket containing the silicon particulates is submerged 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 particulates and releases the impurities from the silicon particulate surface into the acid.

[0084] The basket containing the silicon particulates is submerged in one or more vessels filled with high purity deionized water, typically 18 Mohm-cm, to remove any acid carried over from the prior cleaning steps.

[0085] The basket containing the silicon particulates is optionally submerged in a vessel containing a mixture comprising high purity deionized water, typically 18 Mohm-cm, and 1-5% ozone. The ozone coats the particulates to provide a silicon oxide film that renders the surface of the silicon particulates to be hydrophilic. This step inhibits the attraction of new particulates onto the silicon particulates.

[0086] The basket containing the silicon particulates is submerged in a vessel filled with high purity deionized water, typically 18 Mohm-cm, that is heated to a temperature greater than or equal to 20 °C, e.g., in the range of 50-80 °C. The hot water heats the polysilicon to enable the drying step to be more efficient.

[0087] Following the cleaning steps, the basket containing the silicon particulates 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 particulates. The basket containing the particulates then moves by conveyor to a second chamber where the particulates are exposed to high velocity (forced) heated dry air to aid in evaporation. The conditions in this chamber are < / = 34% relative humidity with an air temperature > / = 30 °C, both of which aid in the drying process for purposes of productivity. The drying process is operated in a clean room maintained at least at ISO 6 particle control to control the level of particulate matter and reduce contamination.

[0088] Following the cleaning procedure, the basket of high purity silicon particulates is transferred to another clean room operated at least at ISO 5 particle control. The basket is emptied into a collection vessel. A bag, typically a polyethylene bag, is placed under the collection vessel. The bag is filled with a target weight of silicon particulates (e.g., 5 kg + / - 50 g), and is sealed by a heat sealer. A label containing the product information is placed on the bag using a touchless process. Optionally, the bag containing the silicon particulates is put into a second bag, the bag is sealed and then is also labelled. A robot retrieves the bag and places it onto a conveyor where it is subsequently moved into a box by another robot.

[0089] In certain embodiments, a process for manufacturing a silicon particulate material comprises comminuting silicon to produce silicon particulate material and cleaning the surface of the silicon particulate material, the cleaning comprising submerging a perforated polymer basket containing the silicon particulate material in separate baths comprising: optionally submerging in one or more vessels containing a mixture comprising caustic detergent and high purity deionized water at a pH of greater than or equal to 10; submerging in one or more vessels containing a mixture comprising one or more acids; submerging in one or more vessels containing high purity deionized water; optionally submerging in a vessel containing a mixture comprising ozone and high purity deionized water; and submerging in one or more vessels containing high purity deionized water at a temperature of greater than 20 °C.

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

[0091] In various embodiments, the process for manufacturing a silicon particulate material further comprises rmsing the silicon particulate material with high purity deionized water and concurrently sorting the silicon particulate material via vibratory sieving conveyor, wherein the silicon particulate material is sieved into material 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 a silicon particulate material further comprises 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 in batches of predefined quantities into perforated polymer baskets.

[0093] In various embodiments, the cleaning steps comprise submerging the basket containing the silicon particulates in one or more vessels containing a mixture comprising one or more acids, in one or more vessels filled with high purity deionized water, and in a vessel filled with high purity deionized water that is optionally heated to a temperature greater than or equal to 20 °C.

[0094] In some embodiments, the cleaning steps comprise submerging the basket containing the silicon particulates in one or more optionally heated baths of caustic detergent, in one or more vessels containing a mixture comprising one or more acids, in one or more vessels filled with high purity deionized water, and in a vessel filled with high purity deionized water that is optionally heated to a temperature greater than or equal to 20 °C.

[0095] In certain embodiments, the cleaning steps comprise submerging the basket containing the silicon particulates in one or more optionally heated baths of caustic detergent, in one or more vessels containing a mixture comprising one or more acids, in one or more vessels filled with high purity deionized water, a vessel containing a mixture comprising high purity deionized water and 1 -5% ozone, and a vessel filled with high purity deionized water that is optionally heated to a temperature greater than or equal to 20 °C.

[0096] In various embodiments, the cleaning steps comprise submerging the basket containing the silicon particulates in one or more vessels containing a mixture comprising one or more acids, in one or more vessels filled with high purity deionized water, a vessel containing a mixture comprising high purity deionized water and 1-5% ozone, and a vessel filled with high purity deionized water that is optionally heated to a temperature greater than or equal to 20 °C.

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

[0098] In various embodiments, the process for manufacturing a silicon particulate material further comprises drying the silicon particulate material in a chamber with vacuum at subatmospheric pressure.

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

[00100] In various embodiments, the process for manufacturing a silicon particulate material further comprises drying the silicon particulate material in a chamber with forced air supplied with controlled relative humidity and controlled air temperature.

[00101] In some embodiments, the silicon is polycrystalline silicon.

[00102] In various embodiments, the polycrystalline silicon is a poly crystalline silicon rod.

[00103] In certain embodiments, the poly crystalline silicon rod is a Siemens process polycrystalline silicon rod.

[00104] In some embodiments, the silicon is monocrystalline silicon.

[00105] In various embodiments, comminuting is performed using high voltage pulse crushing (HVPC).

[00106] In certain embodiments, comminuting is performed in a process vessel.

[00107] In various embodiments, the silicon rod is partially submerged into a process vessel filled with high purity deionized water.

[00108] In some embodiments, the high purity deionized water is > / = 16 Mohm-cm high purity deionized water.

[00109] In some embodiments, the high purity deionized water is > / = 18 Mohm-cm high purity deionized water.

[00110] In certain embodiments, the temperature of the high purity deionized water is > / = 20 °C.

[00111] In some embodiments, the temperature of the high purity deionized water is > / = 20 °C, e.g., in the range of 50-80 °C.

[00112] In various embodiments, the mixture comprising one or more acids comprises one or more of nitric acid, hydrofluoric acid, hydrogen peroxide, and / or hydrochloric acid.

[00113] In certain embodiments, the mixture comprising one or more acids comprises nitric acid and hydrofluoric acid.

[00114] In some embodiments, the mixture comprising one or more acids comprises nitric acid (e.g., 68-77% w / w) and hydrofluoric acid (e.g., 49% w / w).

[00115] In certain embodiments, the mixture comprising one or more acids comprises nitric acid (e.g., 68-70% w / w) and hydrofluoric acid (e.g., 49% w / w).

[00116] In various embodiments, the process is performed in a successive series of clean rooms operated in the range of ISO 7 to ISO 1.

[00117] In some embodiments, the process is performed in a successive series of clean rooms operated in the range of ISO 7 to ISO 4.

[00118] In certain embodiments, the relative humidity in the drying chamber is < / = 34%.

[00119] In various embodiments, the air temperature in the drying chamber is >1= 30 °C.

[00120] In some embodiments, the process further comprises subjecting the silicon particulate material above the maximum target size accumulated in the holding vessel to rework steps, the rework steps comprising: transferring the silicon particulate material above the maximum target size to a comminution station; and comminuting the silicon particulate material above the maximum target size.

[00121] In various embodiments, the comminution station may be a process vessel.

[00122] In certain embodiments, the process further comprises transferring the dried silicon particulate material into a polymeric material bag; heat sealing the bag; labelling the heat sealed bag; and placing the heat sealed and labelled bag into a box.

[00123] In various embodiments, the process further comprises manufacturing an integrated circuit and / or a power device from a wafer made from a crystalline silicon ingot made from the silicon particulate material.

[00124] In some embodiments, the process further comprises producing a monocrystalline silicon material from the silicon particulate material.

[00125] In certain embodiments, the process further comprises producing a monocrystalline silicon material by the Czochralski (CZ) method of crystal growth.

[00126] In various embodiments, the process further comprises manufacturing a silicon wafer, a solar cell, and / or a photovoltaic panel from monocrystalline silicon material.

[00127] In some embodiments, a silicon particulate material is produced by the process of any of the above-mentioned embodiments.

[00128] The accuracy of the process can be evaluated offline for quality check. For example, a bag of silicon particulates is removed from a box. The contents of the bag are tested for surface impurities and particle size distribution. Validation of the surface metal impurity levels is performed by procedures such as that documented in ASTM 1724-96 which describes dissolving the surface of the silicon particulates using HF / HNO3 mixtures and creating a suitable sample for testing by graphite furnace (GFAAS) or, alternatively, by ICP-MS methods. Testing of surface impurities is performed in a clean room environment at least at ISO 4 particle control. Due to the very low impurity levels, the surface tests must have minimum detection limit of < / =4 pptw.

[00129] Repeated application of the surface impurities test on the same sample can be performed and, after sufficient repeats of surface etching, the measured impurities should not change and, as such, the values are representative of the concentration of impurities in the bulk of the particulate.

[00130] Validation of the surface carbon is measured in an ISO 5 clean room environment by using aLECORC612 system (LECO Corporation, 3000 Lakeview Ave., St. Joseph, MI 49085). [00131 ] To confirm that the particulates are conforming to the target size range, samples of the particulates are tested using a machine which passes the silicon particulates past a camera (for example, Canty Tiltsizer, JM Canty, Inc., Buffalo, NY), images the particulates, and then determines particle size metrics such as the distributions by linear dimensions (minimum length, maximum length), volume, and aspect ratio.

[00132] The distribution of the particulates can be evaluated using a camera imaging-based particle sorting system which can derive the largest and smallest linear dimensions of the particulates and use this data to calculate the aspect ratio as:

[00133] Aspect ratio = maximum linear dimension / minimum linear dimension.

[00134] It is unexpectedly found that the HVPC comminution method produces silicon particulates with lower aspect ratio compared to comminution methods such as human hammer or mechanical crushing. To deliver high purity silicon particulates meeting the continuously increasing requirements of the semiconductor industry, new and improved methods to produce high purity silicon particulate materials are required.

[00135] Further, Applicant has unexpectedly discovered that the inventive process can be used to manufacture particulates of high purity silicon material with a controlled size range and a very low aspect ratio, with high consistency and low variability, and having very low levels of surface contamination comprising iron, nickel, copper, and carbon.

[00136] This inventive method minimizes imparting additional contamination to the silicon by using an automated process wherein no humans touch the silicon rod once it is delivered to feed the comminution process. It is preferred to use comminution methods wherein the silicon is crushed in high purity water and then maintained wet during conveyance and sorting and until it is automatically loaded into baskets for etching. To ensure highest control of contamination, the automated process is executed in increasing controlled clean room environments, starting with at least ISO 7 control during comminution and up to at least ISO 5 control during bagging.

[00137] Moreover, this method minimizes imparting additional contamination to the silicon by using no mechanical-contact rod or particle crushing. During comminution of silicon, the silicon material may come into contact with other materials, specifically metallic materials, and collect metallic impurities, contaminating the silicon material. Manual crushing with hammers can not only lead to pieces of differing size distribution, but it also may impart additional impurities (iron, tungsten, cobalt) on the surface of the silicon material. So, too, can roll crushers and jaw crushers contribute unwanted metallic impurities on the surface of the silicon material. Because comminution by high voltage pulse crushing requires no mechanical contact with striking or crushing surfaces that may break off and adhere to the silicon particulate material, this method is less likely to contaminate the silicon with such materials. EXAMPLES

[00138] The following examples are presented in order to more fully illustrate certain embodiments of the invention. They should in no way be construed, however, as limiting the broad scope of the invention. Example 1: Preparation of Silicon Particulate Material

[00139] Silicon (polysilicon) rods of diameters ranging from 125-145 mm were prepared by first manually removing the carbon ends containing graphite sockets (125-150 mm off each leg) followed by separating the bridge section that connects 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 section was placed in a rectangular polymer process vessel filled with deionized water and then processed individually in an HVPC unit using the following parameters: voltage set to 180-190 kV, frequency set to 3-5 Hz, speed set to 6-12 mm / s, and water gap set to 25 mm. After HVPC processing, the bulk of the process water was drained from the process vessel. The crushed silicon particulates were then removed by hand and sorted manually using a “bullseye” sizing chart for the 65 mm upper limit and 20 mm round hole hand sieves for the lower limit. The sorted silicon particulates were then either allowed to dry in air or were packaged wet.

[00140] After sorting the material to collect the particulates in the desired size range, the material was divided into 5 kg batches. The contents of a 5 kg bag were used to fill a perforated polymer basket. Selected 5 kg samples were then processed through different cleaning methods shown in Table 1, below. Selected samples were chemically cleaned in a caustic detergent of pH = 12 and then moved in and out of several baths containing deionized water. Selected samples were etched in a solution of 6 parts 70% HNO3 to 1 part 49% HF. Following chemical cleaning, all samples were rinsed in 18 Mohm-cm deionized water and dried. To test surface impurities, a 10 mm chip was pulled from the etched sample and tested using the general method of WO2016051761A1 (herein incorporated by reference in its entirety) to determine surface metal concentrations with the use of ICP-MS. Surface metal contamination was determined by etching the 10 mm sample with a mixture of HNO3 / HF for a duration which results in 5 um removal on a polished crystalline silicon wafer. Bulk metal contamination was determined by etching the 10 mm sample with a mixture of HNO3 / HF for a duration which results in 25 um removal on a polished crystalline silicon wafer. After etching, the sample is removed, the acid is evaporated, the residue is reconstituted and then tested by ICP-MS. The limit of detection for the impurities testing was <4 pptw. TABLE 1 - Contamination Level of Silicon Particulate Material With and Without Acid Etching Cleaning Process Contamination Test - Etch Depth (um) Surface, Bulk, and Total Iron (PPtw) Copper Nickel (PPtw) No Clean 5 Surface 7900 n / a n / a Caustic Detergent Immersion, No Acid Etch 5 Surface 3800 <4 <4 Caustic Detergent Immersion, No Acid Etch 25 Bulk 6.6 <4 <4 Caustic Detergent Immersion, No Acid Etch Total 3806 <4 <4 Acid Etch Only 5 Surface 13 <4 <4 Acid Etch Only 25 Bulk <4 <4 <4 Acid Etch Only Total <17 <4 <4 Caustic Detergent Immersion, then Acid Etch 5 Surface 12 <4 <4 Caustic Detergent Immersion, then Acid Etch 25 Bulk <4 <4 <4 Caustic Detergent Immersion, then Acid Etch Total <16 <4 <4 Example 2: Comparative Example

[00141] Samples of silicon particulate material were prepared in similar fashion to Example 1 except, instead of comminution by HVPC, the comminution was done by a) tungsten carbide manual hammer and by b) tungsten carbide manual hammer, followed by tungsten carbide roll crusher, and then washed with a solution of deionized water with I % HF and H2O2. The resulting surface and bulk metal contamination were tested using the sample methods in Example 1. TABLE 2 - Contamination Level of Silicon Particulate Material re Comminution Process and Wash Used Process Contamination Test - Etch Depth (um) Surface, Bulk, and Total Iron (pptw) Copper (pptw) Nickel (pptw) Hammer 5 Surface 130 <4 <4 Hammer 15 Bulk <4 <4 <4 Hammer Total <134 <4 <4 Hammer, Crush, Acid Wash 5 Surface 18 <4 <4 Hammer, Crush, Acid Wash 15 Bulk 5 <4 <4 Hammer, Crush, Acid Wash Total 23 <4 <4 Example 3: Preparation of Silicon Particulate Material

[00142] Silicon rods of diameters ranging from 127-144 mm were prepared for HVPC comminution by first manually removing the carbon ends containing graphite sockets (125-150 mm off each leg) using a tungsten carbide hammer. The bridge section that connects both legs was then broken roughly in half. One leg and half the bridge were loaded into the process vessel using a vacuum lift assist. The length of the leg and the half bridge ranged from 1775-1900 mm. The maximum allowable length in process vessel was 2,100 mm. Each leg and half bridge section were processed individually in the HVPC process vessel using the following parameters: voltage set to 175-200 kV, frequency set to 3-5 Hz, speed set to 10-15 mm / s, and water gap set to 15-25 mm. Resistivity of the deionized process water ranged from 17-18 Mohm-cm. After HVPC processing, the bulk of the process water was drained from the process vessel. The HVPC silicon particulates were sorted by vibratory classifier using two sets of polyurethane perforated screens to create a particle size range of 8-65 mm (maximum length). The sorted silicon particulates were then spread out on polyurethane sheets and air dried with a fan.

[00143] After sorting, the HVPC particulates were divided into 5 kg batches. Five bags were characterized using a CANTY Tiltsizer to measure the aspect ratio of the silicon particulates. Five samples of commercially sold silicon particulate material which were comminuted using a roll crusher or a jaw crusher were also characterized using a CANTY Tiltsizer to measure the aspect ratio of the silicon particulates. TABLE 3 - Aspect Ratio Measurement of Silicon Particulate Material re HVPC or Mechanical Crushing Mean Value of Aspect Ratio Standard Deviation of Aspect Ratio of 5 Bags 90th Percentile Value of Aspect Ratio of 5 Bags HVPC 1 1.56 0.46 1.57 HVPC 2 1.55 0.42 HVPC 3 1.54 0.41 HVPC 4 1.57 0.48 HVPC 5 1.53 0.38 Average 1.55 Roll / Jaw Crusher 1 1.67 0.56 1.67 Roll / Jaw Crusher 2 1.57 0.46 Roll / Jaw Crusher 3 1.62 0.48 Roll / Jaw Crusher 4 1.55 0.43 Roll / Jaw Crusher 5 1.52 0.39 Average 1.59

[00144] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

1. A process for manufacturing a silicon particulate material comprising:a) commmuting silicon to produce silicon particulate material; andb) rinsing the silicon particulate material with deionized water;c) cleaning a surface of the silicon particulate material, the cleaning comprising submerging a perforated polymer basket containing the silicon particulate material in separate baths comprising:i) optionally submerging in one or more vessels containing a mixture comprising caustic detergent and high purity deionized water at a pH of greater than or equal to 10;ii) submerging in one or more vessels containing a mixture comprising one or more acids;iii) submerging in one or more vessels containing high purity deionized water;iv) optionally submerging in a vessel containing a mixture comprising ozone and high purity deionized water; andv) submerging in one or more vessels containing high purity deionized water at a temperature of greater than or equal to 20 °C.

2. The process of claim 1, further comprising transferring the silicon particulate material to a vibratory sieving conveyor.

3. The process of claim 2, further comprising sorting the silicon particulate material via the vibratory sieving conveyor, wherein the sieving is separating the silicon particulate material into three groups, wherein the three groups are 1) below the minimum target size, 2) within a target size window, and 3) above the maximum target size.

4. The process of claim 3, further comprising transferring the silicon particulate material below the minimum target size to a collection vessel, the silicon particulate material above the maximum target size to a holding vessel, and the silicon particulate material within the target size window in batches of predefined quantities into perforated polymer baskets.

5. The process of any of claims 1-4, further comprising drying the wet silicon particulate material in a chamber in which vacuum is applied to create subatmospheric pressure.

6. The process of any of claims 1 -5, further comprising drying the silicon particulate material in a chamber with forced air supplied with controlled relative humidity and controlled air temperature.

7. The process of any of claims 1-6, wherein the silicon is poly crystalline silicon.

8. The process of claim 7, wherein the polycrystalline silicon is a polycrystalline silicon rod, such as a Siemens process polycrystalline silicon rod.

9. The process of any of claims 1-8, wherein comminuting is performed using high voltage pulse crushing (HVPC).

10. The process of any of claims 1-9, wherein the mixture comprises nitric acid and hydrofluoric acid.

11. The process of any of claims 1-10, wherein the process is performed in clean rooms operated in the range of ISO 7 to ISO 1, for example in the range of ISO 7 to ISO 4.

12. The process of claim 6, wherein the relative humidity in the drying chamber is less than or equal to 34%.

13. The process of claim 6, wherein the air temperature in the drying chamber is greater than or equal to 30 °C.

14. The process of claim 4, further comprising subjecting the silicon particulate material above the maximum target size accumulated in the holding vessel to rework steps, the rework steps comprising:i) transferring the silicon particulate material above the maximum target size to a comminution station; andii) comminuting the silicon particulate material of step i).

15. The process of any of claims 1-14, further comprising:a) transferring the silicon particulate material into a polymeric material bag;b) heat sealing the bag;c) labelling the heat sealed bag; andd) placing the heat sealed and labelled bag into a box.

16. The process of any of claims 1-14, 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.

17. A silicon material produced by the process of any of claims 1-14.

18. Silicon particulate material comprising:a) a polycrystalline structure; andb) a particle size distribution in a range greater than or equal to 3 mm and less than or equal to 75 mm; andc) an average aspect ratio of less than or equal to 1.55; andd) combined surface impurity and bulk impurity of total iron impurity of less than or equal to 20 pptw, total nickel impurity of less than or equal to 4 pptw, and total copper impurity of less than or equal to 4 pptw.

19. The silicon particulate material of claim 18, wherein the silicon particulate material has bulk impurities of iron less than or equal to 10 pptw, total nickel impurity of less than or equal to 4 pptw, and of copper less than or equal to 4 pptw nickel.

20. The silicon particulate material of claim 18 or 19, wherein the silicon particulate material is a product of a Siemens process poly crystalline silicon rod.

21. The silicon particulate material of any of claims 18-20, wherein the iron, nickel, and copper surface impurity in the silicon particulate material are assessed using acid dissolution and ICP-MS.

22. An integrated circuit and / or a power device comprising a silicon wafer comprising the silicon particulate material of any of claims 18-21.

23. An integrated circuit and / or a power device produced from a wafer produced from the silicon particulate material of any of claims 18-21.

24. A silicon material comprising the silicon particulate material of any of claims 18-21.

25. The silicon particulate material of any of claims 18-21 for use in manufacturing a silicon wafer, wherein the silicon wafer may be used to manufacture an integrated circuit and / or a power device.Application No: GB2418819.5Claims searched: 1-17Examiner: Dr Danielle MerrikinDate of search: 19 June 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-17 EP 2695974 Al (WACKER CHEMIE AG) See whole document X 1-17 US 2011 / 0186087 Al (WOCHNER et al.) See whole document, in particular the Examples X 1-17 US 2018 / 0339908 Al (NETSU et al.) See whole document v A 1-17 EP 3760585 Al (TOKUYAMA CORP) See whole document, in particular the Examples X 1-17 JP 2015199619 A (TOKUYAMA CORP) See whole document, in particular the Examples and Table 1 v A 1-17 EP 4186859 Al (TOKUYAMA CORP) See whole documentCategories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From C01B 0033 / 037 01 / 01 / 2006

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