Sintered ceramic body of large dimension and fabrication method thereof

Abstract

To provide a method for preparing large sintered ceramic bodies with improved mechanical properties and handling capabilities.SOLUTION: A method of making a sintered ceramic body according to the present invention comprises the steps of: placing ceramic powder within the internal volume of a spark plasma discharge tool, the tool comprising a die including side walls including an inner wall and an outer wall, the inner wall having a diameter defining the internal volume, and an upper punch and a lower punch operably connected to the die, each of the punches having an outer wall defining a diameter smaller than the diameter of the die inner wall, thereby creating a gap between the punch and the inner wall when at least one of the punches is moved within the inner volume, where the gap is between 10 μm and 70 μm wide; creating a vacuum in the inner volume; and moving at least one of the punches to sinter the ceramic powder by applying pressure to the ceramic powder while heating and decreasing the temperature of the sintered body.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a sintered ceramic body, and more particularly to a large-sized sintered ceramic body of high purity and high density. Further, the present disclosure also relates to a specific process for the preparation of a sintered ceramic body, and more particularly to a method for the preparation of a large sintered ceramic body that can be prepared according to the method of the present disclosure.

Background Art

[0002] Ceramics are useful, inter alia, across a variety of industries such as automotive, aerospace, semiconductor, optical, and medical. Ceramics generally provide high compressive strength, low thermal expansion, high thermal conductivity, excellent chemical resistance, and favorable dielectric and optical properties. However, it has been found that the manufacture of ceramic parts of dimensions greater than about 100 mm to 200 mm or more is difficult for various reasons.

[0003] Ceramic materials are generally known to be brittle compared to other materials such as metals, cermets, and polymers. Thus, variations in the physical properties and the presence of defects in ceramic materials make them more prone to fracture than other more ductile materials.

[0004] Certain ceramic materials are inherently refractory and difficult to densify. As a result, ceramic materials are typically prepared by pressureless vacuum sintering, in which ceramic powder is loaded into a furnace and sintered at a temperature of 1600° C. for a long period, often for several days. In this technique, sintered ceramics of unacceptable quality with low density and correspondingly high porosity are often obtained, reducing performance such as chemical etching resistance and / or erosion resistance. These conditions for manufacture also reduce mechanical strength by resulting in a large particle size greater than about 20 μm and a low density, for example less than about 95% of the theoretical value, resulting in breakage at large dimensions and rendering them unusable in many applications.

[0005] Sintering aids are often used to promote densification. In applications where high purity is required over a large body size, the sintering aids present in the sintered ceramic do not conform to the end use of the ceramic article, and thus their use in applications requiring a high purity of about 99.99% or more is precluded. Sintering aids can also pose a problem in that, due to their specific properties, the electrical, magnetic, or other properties in the sintered ceramic can change in a manner undesirable to the end user.

[0006] Other ceramic materials are known to have low sintering strength, making it particularly difficult to handle them in large dimensions without breakage. This hinders the development of ceramic materials as structural materials for various applications. Attempts to prepare ceramic materials with a large (>100 mm) body size and particularly known to have low sintering strength often result in breakage during sintering or after sintering, during cooling, during post-sintering processes such as annealing or machining, or during handling required for processing.

[0007] In semiconductor processing applications, vacuum processing chambers are used for etching and chemical vapor deposition (CVD) of materials on semiconductor substrates. These vacuum processing chambers include components such as disks, rings, liners, and cylinders that confine the plasma on the wafers or substrates being processed. These chamber components formed from plasma ceramic materials are continuously attacked by the plasma, resulting in erosion, corrosion, and the accumulation or release of contaminants. This plasma attack causes many problems such as short component lifetimes leading to extended tool downtime, increased consumable costs, transition metal contamination on the wafers, process drift, and particle contamination resulting in device yield loss.

[0008] Due to the erosive and corrosive nature of the plasma environment, as well as the need to minimize particle and / or metal contamination, the ceramic components used within a plasma processing chamber desirably have suitably high erosion and corrosion resistance. Such components are formed from materials that provide resistance to corrosion and erosion in a plasma environment and are described, for example, in U.S. Patent Nos. 5,798,016, 5,911,852, 6,123,791, and 6,352,611. However, these examples do not provide direction for the preparation of ceramic materials and components of sizes of at least about 100 mm to 200 mm or greater, as are required in current semiconductor processing chambers.

[0009] Large sintered ceramic bodies prepared heretofore have mainly suffered from a risk of breakage, high porosity, low density, and quality / purity insufficient for use in corrosion resistant applications. Further, there is a growing need for plasma etching resistant ceramic components of ever larger dimensions for use in state-of-the-art etching chambers. These requirements currently impede the application of a number of sintered ceramic components in many plasma processing chambers.

[0010] There may not exist a commercially viable method for manufacturing large ceramic body components that have a high density (>96% of theoretical) and a minimum density deviation (<4% deviation) and also provide the high purity as required by certain applications.

[0011] Spark plasma sintering (SPS) technology has been proposed as a solution for manufacturing large-sized ceramic bodies. The issues in manufacturing large ceramic bodies by the spark plasma sintering process are addressed in two scientific publications by Eugene A. Olevsky et al., "Fundamental Aspects of Spark Plasma Sintering: I. Experimental Analysis of Scalability" (J. Am. Ceram. Soc, 95[8], 2406-2413 (2012)) and "Fundamental Aspects of Spark Plasma Sintering: II. Experimental Analysis of Scalability" (J. Am. Ceram. Soc, 95[8], 2414-2422 (2012)), which describe the problems arising with the scaling of SPS tooling with respect to the temperature gradient.

[0012] Attempts to use spark plasma sintering (SPS) technology to manufacture parts with large (>100 mm) dimensions have not been successful to date. This lack of success is due, at least in part, to the inability to control the temperature across large-sized parts during the sintering process, resulting in a temperature gradient during processing. Furthermore, the use of spark plasma sintering technology to densify powders or powder mixtures with minimal or no conductivity (i.e., insulators) is particularly difficult due to the inherently low conductivity of the powders, thus worsening the temperature gradient across the entire powder during sintering. This temperature gradient leads to variations in material properties such as density and particle size, and each of these properties affects the mechanical strength. The inability to control this temperature gradient currently hinders the manufacture of ceramic bodies with dimensions exceeding approximately 100 mm that can be easily handled without breakage.

[0013] Japanese Patent Application Laid-Open No. 2004 / 068089 discloses an SPS tooling apparatus that provides a uniform temperature distribution by optimizing the mold structure. Specifically, the shape of the compact to be sintered is axisymmetric with respect to the central axis of the sintering chamber, and the electrodes of the power supply are attached at symmetric positions with respect to the central axis of the sintering chamber. It is preferable that it is not necessary to change the mold structure in order to manufacture a large-sized sintered ceramic body.

[0014] U.S. Patent Application Publication No. 2018 / 201545 discloses a focus ring having high plasma resistance and also provides a method for manufacturing the above focus ring. The focus ring is formed of a sintered body of silicon carbide. The sintered body is composed of a plurality of first crystal grains having a crystal structure of α-SiC and a plurality of second crystal grains having a crystal structure of β-SiC. The sintered body contains the first crystal grains in an amount of 70% by volume or more based on the total of the first crystal grains and the second crystal grains. The volume average crystallite diameter of the first crystal grains is 10 μm or less. Again, this prior art document focuses on the preparation of a plasma-resistant material with improved stability against fluorine-based gases and oxygen gas. This prior art document does not mention the manufacture of large and dense high-purity ceramic bodies with improved resistance to breakage. Therefore, in this technical field, there is a need for larger sintered ceramic bodies having improved mechanical properties over a large size and being resistant to disintegration under plasma etching conditions.

[0015] For these and other reasons, there is a need for further development of ceramic materials that provide high and uniform density throughout the sintered body in combination with high purity. In particular, there is a need for a method for manufacturing large-sized sintered ceramic bodies with a reduced risk of breakage, sufficient quality in terms of density and density deviation, purity, and etching resistance, and a reduced surface roughness.

[0016] SUMMARY OF THE INVENTION Embodiments provide a method for preparing a large sintered ceramic body with improved mechanical properties and handling ability.

[0017] Embodiment 1. A method for producing a sintered ceramic body, comprising the following process steps: (a) a step of placing at least one ceramic powder within the internal volume of a spark plasma sintering tool, the spark plasma sintering tool including a die including a side wall including an inner wall and an outer wall, the inner wall having a diameter defining the internal volume, the die, and an upper punch and a lower punch operably connected to the die, each of the upper punch and the lower punch having an outer wall defining a diameter smaller than the diameter of the inner wall of the die, whereby when at least one of the upper punch and the lower punch is moved within the internal volume of the die, a gap is generated between each of the upper punch and the lower punch and the inner wall of the die, the sintering tool having a central axis, the gap having a width of 10 μm to 100 μm, the upper punch and the lower punch; (b) a step of generating a vacuum state within the internal volume; (c) a step of heating the ceramic powder to a sintering temperature while applying pressure to the ceramic powder by moving at least one of the sintering temperature punches to sinter the ceramic powder to form a sintered ceramic body; (d) a step of lowering the temperature of the sintered ceramic body, wherein the at least one ceramic powder has a specific surface area of 1 to 18 m 2 / g as measured according to ASTM C1274.

[0018] Embodiment 2. The method according to Embodiment 1, wherein the inner wall of the die includes at least one conductive foil.

[0019] Embodiment 3. The method according to Embodiment 2, wherein the at least one conductive foil includes graphite, niobium, nickel, molybdenum, or platinum.

[0020] Embodiment 4. The method according to any one of Embodiments 1 to 3, wherein the die, the upper punch, and the lower punch include at least one graphite material.

[0021] Embodiment 5. The method according to Embodiment 4, wherein the at least one graphite material has a particle size of 5 to 30 μm.

[0022] Embodiment 6. The method according to Embodiment 4 or 5, wherein at least one graphite material has a density of 1.45 to 2.0 g / cc.

[0023] Embodiment 7. The radial deviation from the average coefficient of thermal expansion of at least one graphite material is 0.3×10 -6 / °C or less, 0.25×10 -6 / °C or less, 0.2×10 -6 / °C or less, 0.18×10 -6 / °C or less, 0.16×10 -6 / °C or less, 0.14×10 -6 / °C or less, 0.12×10 -6 / °C or less, 0.1×10 -6 / °C or less, 0.08×10 -6 / °C or less, 0.06×10 -6 / °C or less, and at least one quantity varying selected from the group consisting of, the method according to any one of Embodiments 4 to 6.

[0024] Embodiment 8. At least one ceramic powder has a resistivity of about 1×10 -5 ohm-cm to about 1×10 +10 ohm-cm, and at least one ceramic powder is selected from the group consisting of tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, silicon carbide, boron carbide, molybdenum boride, chromium boride, hafnium boride, zirconium boride, tantalum boride, titanium boride or titanium diboride, and titanium nitride and combinations thereof, the method according to any one of Embodiments 1 to 7.

[0025] Embodiment 9. The gap has a width selected from the group consisting of 10 μm to 70 μm, 20 μm to 70 μm, 30 μm to 70 μm, 40 μm to 70 μm, 50 μm to 70 μm, 60 μm to 70 μm, 10 to 60 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, 20 μm to 60 μm, 20 μm to 50 μm, 30 μm to 60 μm, and 30 μm to 50 μm, the method according to any one of Embodiments 1 to 8.

[0026] Embodiment 10. The gap has a width of 10 to 70 μm, and at least one kind of ceramic powder has a resistivity of about 1 × 10 +10 ohm-cm or more, and at least one kind of ceramic powder is yttrium oxide, aluminum oxide, sapphire, yttrium aluminum monoclinic (YAM), yttrium aluminum garnet (YAG), yttrium aluminum perovskite (YAP), zirconium oxide, titanium oxide, cordierite, mullite, cobaltite, magnesium aluminate spinel, silicon dioxide, quartz, calcium oxide, cerium oxide, ferrite, spinel, zircon, nickel oxide, copper oxide, strontium oxide, scandium oxide, samarium oxide, lanthanum oxide, lutetium oxide, erbium oxide, erbium aluminum garnet (EAG), hafnium oxide, vanadium oxide, niobium oxide, tungsten oxide, manganese oxide, tantalum oxide, terbium oxide, europium oxide, neodymium oxide, zirconium aluminate oxide, zirconium silicate oxide, hafnium aluminate oxide, hafnium silicate oxide, titanium silicate oxide, lanthanum silicate oxide, lanthanum aluminate oxide (LAO), yttrium silicate oxide, titanium silicate oxide tantalum silicate oxide, yttrium nitride, oxynitride of yttrium, aluminum nitride, oxynitride of aluminum, silicon nitride, oxynitride of silicon, sialon material, boron nitride, beryllium nitride, titanium nitride, tungsten nitride, forsterite, steatite, cordierite, mullite, barium titanate, lead titanate, lead zirconate, lead zirconate titanate, Mn-Zn ferrite, Ni-Zn ferrite, and sialon, and a combination thereof, and the method according to any one of Embodiments 1 to 9.

[0027] Embodiment 11. The method according to any one of Embodiments 1 to 10, wherein at least one of the upper punch and the lower punch is coupled to an electrode, and at least one of the upper punch and the lower punch is in ohmic contact with the die.

[0028] Embodiment 12. The method according to any one of Embodiments 1 to 11, wherein the gap is axisymmetric about the central axis.

[0029] Embodiment 13. The method according to any one of Embodiments 1 to 12, wherein the gap is asymmetric about the central axis.

[0030] Embodiment 14. The method according to any one of Embodiments 1 to 13, wherein at least one kind of ceramic powder has a specific surface area (SSA) selected from the group consisting of 1 to 16 m 2 / g, 1 to 14 m 2 / g, 1 to 10 m 2 / g, 1 to 8 m 2 / g, 1 to 6 m 2 / g, 2 to 18 m 2 / g, 4 to 18 m 2 / g, 6 to 18 m 2 / g, 8 to 18 m 2 / g, 10 to 18 m 2 / g, 4 to 12 m 2 / g, 4 to 10 m 2 / g, and 6 to 8 m 2 / g.

[0031] Embodiment 15. The following optional steps: (e) annealing the sintered ceramic body by applying heat to raise the temperature of the sintered ceramic body to reach the annealing temperature; (f) lowering the temperature of the sintered and annealed ceramic body; and (g) machining the annealed sintered ceramic body into one selected from the group consisting of a focus ring, a window, a nozzle, a gas injector, a shower head, a gas distribution plate, a remote plasma adapter, an etching chamber liner, a plasma source adapter, a gas inlet adapter, a diffuser, an electronic wafer chuck, a chuck, a pack, a mixing manifold, an ion suppressor element, a face plate, an isolator, a spacer, and a protective ring. The method according to any one of Embodiments 1 to 14, further comprising the above steps.

[0032] Embodiment 16. The method according to any one of Embodiments 1 to 15, wherein during step c, the temperature difference per centimeter across at least one kind of ceramic powder disposed within the internal volume defined by the tool set of the sintering apparatus is 0.15 to 5 °C / cm.

[0033] Embodiment 17. The method according to any one of Embodiments 1 to 16, wherein during step c, the temperature difference across at least one kind of ceramic powder disposed within the internal volume defined by the tool set of the sintering apparatus is 1 to 100 °C.

[0034] Embodiment 18. The method according to any one of Embodiments 1 to 17, wherein at least one kind of ceramic powder has a d50 particle size selected from the group consisting of 0.8 to 100 μm, 0.8 to 80 μm, 0.8 to 60 μm, 0.8 to 40 μm, 0.8 to 30 μm, 0.8 to 20 μm, 0.8 to 10 μm, 0.8 to 5 μm, 1 to 100 μm, 3 to 100 μm, 5 to 100 μm, 10 to 100 μm, 20 to 100 μm, 40 μm, and 5 to 30 μm.

[0035] Embodiment 19. The method according to any one of Embodiments 1 to 18, wherein at least one kind of ceramic powder includes a powder compact having a packing density selected from the group consisting of 20% to 60% by volume, 30% to 60% by volume, 40% to 60% by volume, 20% to 50% by volume, 20% to 40% by volume, 30% to 50% by volume, 40% to 55% by volume, and 45% to 55% by volume.

[0036] Embodiment 20. A sintered ceramic body having a maximum dimension selected from the group consisting of 100 to 622 mm, 200 to 622 mm, 250 to 622 mm, 300 to 622 mm, 350 to 622 mm, 400 to 622 mm, 550 to 622 mm, 500 to 622 mm, and 550 to 622 mm, wherein the density is 98% or more of the reported theoretical density of the ceramic forming the sintered ceramic body, the density of the sintered ceramic body varies by 0.5% to 4% along the maximum dimension, and the density is measured in accordance with ASTM B962-17.

[0037] The sintered ceramic body according to Embodiment 20, having a volume porosity of 0.1 to 2% calculated from density measurements carried out in accordance with ASTM B962-17.

[0038] The sintered ceramic body according to Embodiment 20, having a density deviation measured along the maximum dimension, selected from the group consisting of less than 3%, less than 2%, less than 1%, less than 0.5%, 0.25 to 4.5%, 0.25 to 4%, 0.25 to 3%, 0.25 to 2%, 0.25 to 1%, 0.25 to 0.5%, 0.5 to 3.5%, 1 to 3%, 0.5 to 2%, and 0.5 to 1%.

[0039] The sintered ceramic body according to any one of Embodiments 20 to 22, containing less than 100 ppm of total impurities.

[0040] The sintered ceramic body according to any one of Embodiments 20 to 23, obtainable by the method according to any one of Embodiments 1 to 19.

[0041] Use of the sintered ceramic body according to Embodiment 24 as, in particular, a focus ring, window, nozzle, gas injector, showerhead, gas distribution plate, remote plasma adapter, etching chamber liner, plasma source adapter, gas inlet adapter, diffuser, electronic wafer chuck, chuck, pack, mixing manifold, ion suppressor element, faceplate, isolator, spacer, and / or protective ring in a plasma processing chamber.

[0042] By providing a gap distance between the die system and the punch system, it becomes possible to prepare a large sintered ceramic body having excellent mechanical properties.

[0043] Embodiments of the present invention can be used alone or in combination with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be described below in connection with the accompanying drawings in which like numbers represent like elements.

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Mode for Carrying Out the Invention

[0045] The following detailed description provides only preferred exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present invention. Rather, the following detailed description of the preferred exemplary embodiments provides an explanation that enables those skilled in the art to implement the preferred exemplary embodiments of the present invention. Various changes can be made to the functions and configurations of the elements without departing from the spirit and scope of the present invention as described in the appended claims.

[0046] In the context of describing the present invention (particularly in the context of the appended claims), the use of the terms "a", "an", "the", and similar referents shall be construed to cover both the singular and plural forms, unless otherwise indicated herein or unless there is a clear contradiction in the context. The terms "comprising", "having", "including", and "containing" shall be construed as open-ended terms (i.e., meaning "including but not limited to") unless otherwise specified. The recitation of a range of values herein is merely intended to serve as a shorthand method for referring individually to each separate value within that range, and each separate value is incorporated into the specification as if it were individually recited. All methods described herein can be performed in any suitable order, unless otherwise indicated herein or unless there is an obvious contradiction in the context. The use of any and all examples or exemplary language (e.g., "such as") is merely intended to clarify the present invention better and does not limit the scope of the present invention unless otherwise claimed. No language in this specification should be construed as indicating any element not claimed as essential to the practice of the invention. The use of the term "comprising" in this specification and in the claims includes the more restrictive language "consisting essentially of" and "consisting of".

[0047] Embodiments are described that include the best mode known to the inventors of the present invention for carrying out the present invention. Variations of those embodiments will be apparent to those skilled in the art upon reading the following detailed description. The inventors envision that those skilled in the art will use such variations as appropriate, and the inventors also envision that the present invention will be practiced otherwise than as specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the appended claims of this specification as permitted by the applicable law. Further, any combination of elements in all possible variations described above is included in the present invention unless otherwise indicated herein or clearly inconsistent. Further, all features disclosed with respect to the process / method are also applicable to the product, the sintered ceramic body, disclosed herein.

[0048] All references, including publications, patent applications, and patents, cited herein are incorporated herein by reference as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0049] Definitions As used herein, the terms "semiconductor wafer," "wafer," "substrate," and "wafer substrate" are used interchangeably. Wafers or substrates used in the semiconductor device industry typically have a diameter of, for example, 200 mm, or 300 mm, or 450 mm.

[0050] As used herein, the terms "tool," "tool set," and "apparatus" are used interchangeably.

[0051] As used herein, the term "sintered ceramic body" is synonymous with "sintered product", "body", "sintered body", or "sintered ceramic body", and refers to a solid ceramic article formed from a powder mixture after being subjected to a pressing and heat treatment process to produce a sintered ceramic from the powder as disclosed. In certain embodiments, the term "sintered ceramic body" refers to a one-piece body. "One-piece" means a complete single piece or single member by itself without additional pieces, i.e., the member is one monolithic piece formed as a unit with another member.

[0052] A sintered ceramic body as disclosed herein is preferably polycrystalline and thus may contain two or more crystals without limitation.

[0053] As used herein, the term "purity" refers to the absence of various impurities excluding bulk powder. As an example, 100% purity indicates that the powder contains only the ceramic material itself.

[0054] As used herein, ambient temperature refers to a temperature of about 22 - 25 °C.

[0055] As used herein, ceramic powder refers to one or more crystalline powders, or combinations of crystalline powders, for forming a powder mixture that can be pulverized, mixed, blended, calcined, sieved, etc. according to methods known to those skilled in the art. The ceramic powders disclosed herein are preferably crystalline.

[0056] As used herein, the term "impurity" refers to compounds / contaminants that may be present in a) the starting material or a powder mixture formed therefrom, b) the processed powder mixture and / or the calcined powder mixture, or c) the sintered ceramic body, including impurities other than the starting material itself. Impurities do not include optional dopants and / or optional sintering aids. Low ppm levels correspond to low impurity contents measured. When reported in ppm herein, all values are relative to the total mass of the measured material, such as the powders and / or sintered ceramic bodies disclosed herein.

[0057] As used herein, the term "nanopowder" is intended to include powders having a specific surface area (SSA) of 20 m 2 / g or greater when measured in accordance with ASTM C1274.

[0058] When used in connection with a heat treatment process, the term "calcination" or "calcining" is understood to mean a heat treatment step performed on a powder or powder mixture in air, for example, to remove moisture and / or surface impurities, increase crystallinity, and in some instances, modify the surface area of the powder and / or powder mixture.

[0059] When applied to the heat treatment of ceramics, the term "annealing" is understood herein to mean a heat treatment in which the disclosed sintered ceramic body is brought to a certain temperature in air and gradually cooled to relieve stress and / or standardize stoichiometry.

[0060] The term "Sa" known in the art relates to the arithmetic mean height of a surface and represents the absolute value of the arithmetic mean over the entire surface. The definition according to ISO25178-2-2012, section 4.1.7, is the arithmetic mean of the absolute values of the ordinate values within the defined area (A).

[0061] The term "Sz", which is known in the art, relates to the maximum (peak to valley) height of a surface and represents the absolute value of the maximum height across the surface. The definition according to ISO 25178-2-2012, section 4.1.6, is the sum of the maximum peak height value and the maximum valley height value within the defined area (A). The maximum valley height value Sv is defined as the minimum valley height value within the defined area (A) subtracted according to ISO 25178-2-2012, section 4.1.5.

[0062] The term "Sdr", which is known in the art, relates to the developed interface area ratio of a surface and represents the absolute value of the maximum height across the surface. The definition according to ISO 25178-2-2012, section 4.3.2, is the incremental ratio of the interface area of the scaled-limited surface within the defined area (A) across the defined area with respect to the defined area. Sdr is a proportional representation of the increase in the actual surface area beyond that of a perfectly flat surface. A flat surface is assigned an Sdr of 0, and the value increases with the increase in surface area. A large value of Sdr corresponds to a large increase in surface area resulting from a corrosion or etching and / or erosion process.

[0063] As used herein, the terms "substantially", "nearly", and "about" are used in connection with a number and allow a variance of plus or minus 10%.

[0064] As used herein, the term "sintering aid" refers to an additive that improves densification during the sintering process, thereby reducing porosity.

[0065] As used herein, the term "dopant" is used to represent an element or compound that can be intentionally added in relatively small amounts (less than about 10 mol%) to modify or achieve certain ceramic properties to achieve a desired result. These results may be electrical, mechanical, optical, or other properties. In contrast, a sintering aid is different from a dopant in that a sintering aid can be added to lower the temperature at which the powder can sinter to a high density.

[0066] In the following description, a given range includes the lower and upper threshold values. Thus, the definition in the sense of "range from X to Y" or "range from X to Y" for parameter A means that A is any value of X, Y and any value from X to Y. The definition in the sense of "up to maximum Y" or "at least X" for parameter A thus means that A is any value less than Y and Y, or that A is X and any value greater than X, respectively.

[0067] Apparatus / Spark Discharge Plasma Sintering Tool This specification discloses a spark discharge plasma sintering (SPS) tool, which comprises a die having a side wall with an inner wall defining an internal volume capable of receiving at least one ceramic powder and an outer wall, and an upper punch and a lower punch operatively connected to the die, each of the upper punch and the lower punch having an outer wall defining a diameter smaller than the diameter of the inner wall of the die, whereby when at least one of the upper punch and the lower punch moves within the internal volume of the die, a gap is formed between each of the upper punch and the lower punch and the inner wall of the die, the gap having a width of 10 μm to 100 μm, and the at least one ceramic powder having a specific surface area (SSA) of 1 to 18 m / g as measured according to ASTM C1274.

[0068] FIG. 1 shows an SPS tool 1 having a simplified die / punch arrangement used for sintering ceramic powder. Typically, the die / punch arrangement is within a vacuum chamber (not shown) as recognized by those skilled in the art. Referring to FIG. 1, the spark discharge plasma sintering tool 1 comprises a die system 2 having a side wall including an inner wall defining an internal volume capable of receiving at least one ceramic powder 5.

[0069] Referring further to FIG. 1, the spark discharge plasma sintering tool 1 includes an upper punch 4 and a lower punch 4' operably connected to a die system 2. Each of the upper punch 4 and the lower punch 4' has an outer wall 11 defining a diameter smaller than the diameter of the inner wall 8 of the die system 2. Thereby, when at least one of the upper punch 4 and the lower punch 4' moves into the internal volume of the die system 2, a gap 3 is formed between each of the upper punch 4 and the lower punch 4' and the inner wall 8 of the die system 2.

[0070] The die system 2 and the upper punch 4 and the lower punch 4' may include at least one type of graphite material. In certain embodiments, the graphite materials disclosed herein may include at least one isotropic graphite material. In other embodiments, the graphite materials disclosed herein may include, for example, at least one reinforced graphite material such as a carbon-carbon composite, and fibers, particles, or sheets or meshes of other conductive materials such as carbon in a matrix of an isotropic graphite material, or graphite materials including laminates. In other embodiments, the die and the upper and lower punches include combinations of these isotropic and reinforced graphite materials.

[0071] For example, the graphite material used for some or all of the parts of the tool such as the die 6 and the punches 4 and 4' may include a porous graphite material, which exhibits a porosity of about 5% to about 20%, about 5% to about 17%, about 5% to about 13%, about 5% to about 10%, about 5% to about 8%, about 8% to about 20%, about 12% to about 20%, about 15% to about 20%, about 11% to about 20%, about 5% to 15%, 6% to about 13%, preferably about 7% to about 12%.

[0072] Preferably, the graphite material has an average pore diameter (pore size) of 0.4 to 5.0 μm, preferably 1.0 to 4.0 μm, and includes pores having a surface pore diameter of up to 30 μm, preferably up to 20 μm, preferably up to 10 μm. More preferably, pores having a surface pore diameter of 10 to 30 μm may be present.

[0073] The graphite material used in the tools disclosed in this specification may have an average particle size of <0.05 mm, preferably <0.04 mm, preferably <0.03 mm, preferably <0.028 mm, preferably <0.025 mm, preferably <0.02 mm, preferably <0.018 mm, preferably <0.015 mm, preferably <0.010 mm.

[0074] The graphite material used in the tools disclosed in this specification may have an average particle size of >0.001 mm, preferably >0.003 mm, preferably >0.006 mm, preferably >0.008 mm, preferably >0.010 mm, preferably >0.012 mm, preferably >0.014 mm, preferably >0.020 mm, preferably >0.025 mm, preferably >0.030 mm.

[0075] The graphite material used in the tools disclosed in this specification is 1.45 g / cm 3 , preferably 1.50 g / cm 3 , preferably 1.55 g / cm 3 , preferably 1.60 g / cm 3 , preferably 1.65 g / cm 3 , preferably 1.70 g / cm 3 , preferably 1.75 g / cm 3 and may have a density of.

[0076] The graphite material used in the tools disclosed in this specification may have a density of <2.00 g / cm 3 , preferably <1.90 g / cm 3 , preferably <1.85 g / cm 3 , and preferably <1.80 g / cm 3 and may have a density of.

[0077] In an embodiment, the graphite material is ≧3.3×10 -6 / °C, ≧3.5×10 -6 / °C, ≧3.7×10 -6 / °C, ≧4.0×10 -6 / °C, ≧4.2×10 -6 / °C, ≧4.4×10 -6 / °C, ≥ 4.6×10 -6 / °C, ≥ 4.8×10 -6 has a coefficient of thermal expansion (CTE) over a temperature range of about 400 to about 1200 °C at / °C.

[0078] In an embodiment, the graphite material is <7.2×10 -6 / °C, preferably <7.0×10 -6 / °C, preferably <6.5×10 -6 / °C, preferably <6.0×10 -6 / °C, preferably <5.0×10 -6 / °C, preferably <4.8×10 -6 / °C, preferably <4.6×10 -6 may have a coefficient of thermal expansion (CTE) over a temperature range of about 400 to 1200 °C at / °C.

[0079] In an embodiment, at least one graphite material is about 3.8×10 -6 / °C to about 7×10 -6 / °C, preferably about 4.0×10 -6 / °C to about 7×10 -6 / °C, preferably about 4.4×10 -6 / °C to about 7×10 -6 / °C, preferably about 4.0×10 -6 / °C to about 6×10 -6 may have a coefficient of thermal expansion (CTE) at a temperature of 400 °C to 500 °C or higher at / °C.

[0080] Table 1 lists the properties of exemplary graphite materials disclosed herein.

[0081]

Table 1

[0082] As illustrated in the embodiments of FIGS. 2A-2C, die system 2 includes die 6 and, optionally but preferably, at least one conductive foil 7 located on the inner wall of the die. There is no limit to the number of conductive foils on the inner wall of the die, and one, two, three, four, five, six, seven, eight, nine, or ten conductive foils may be provided as circumferential liners between die 6 and each of upper punch 4 and lower punch 4', whereby an inner wall 8 of die system 2 (including at least one conductive foil if present) and outer walls 11 of each of the upper and lower punches define a gap 3. At least one conductive foil 7 includes graphite, niobium, nickel, molybdenum, platinum, and other ductile, conductive materials and combinations thereof that are stable within the temperature range according to the methods disclosed herein.

[0083] In certain embodiments, the conductive foil may include the flexible and compressible graphite foil disclosed herein and have the following properties, namely, ● A carbon content of greater than 99 wt%, preferably greater than 99.2 wt%, more preferably greater than 99.4 wt%, more preferably greater than 99.6 wt%, more preferably greater than 99.8 wt%, more preferably greater than 99.9 wt%, more preferably greater than 99.99 wt%, more preferably greater than 99.999 wt%, ● Less than 500 ppm, preferably less than 400 ppm, more preferably less than 300 ppm, more preferably less than 200 ppm, more preferably less than 100 ppm, more preferably less than 50 ppm, more preferably less than 10 ppm, more preferably less than 5 ppm, more preferably less than 3 ppm impurities relative to the total mass of the foil, ● A tensile strength of the graphite foil in the range of 0.4 - 6.0 MPa, preferably 4.2 - 5.8 MPa, more preferably 4.4 or 5.6 MPa, and / or ● Having one or more of a bulk density of the graphite foil preferably in the range of preferably 1.0 - 1.2 g / cc, preferably 1.02 - 1.18 g / cc, more preferably 1.04 - 1.16 g / cc, more preferably 1.06 - 1.16 g / cc.

[0084] In an embodiment, at least one foil typically includes graphite. In certain embodiments, at least one foil as part of the die system may include a circumferential liner between the surface of the die and each of the upper and lower punches.

[0085] The graphite foil can improve the temperature distribution of the entire powder during sintering. Table 2 lists the characteristics of exemplary graphite foils according to the embodiments disclosed herein, such as Neograf Grafoil®, Sigraflex® graphite foil, and Toyo Tanso Perma-Foil®.

[0086]

Table 2

[0087] Now referring to FIGS. 2A, 2B, and 2C, an SPS tool set having an embodiment of a graphite foil arrangement is shown. Ceramic powder 5 is placed between at least one of upper punch 4 and lower punch 4', and gap 3 is shown between the outer walls 11 of each of the upper and lower punches and the inner wall 8 of die system 2. FIGS. 2A, 2B, and 2C show one to three layers of conductive foil 7, and die 6 as part of die system 2. Thus, the gap extends from the inner wall 8 of die system 2 to the outer walls 11 of each of the upper and lower punches. The spacing of the gap is arranged so that the powder can be degassed before and / or during heating and sintering, and at the same time maintain ohmic contact between the punch and the die to improve the temperature distribution of the entire ceramic powder during heating and sintering.

[0088] The graphite foil 7 can have a thickness of, for example, 0.025 - 0.260 mm, preferably 0.025 - 0.200 mm, preferably 0.025 - 0.175 mm, preferably 0.025 - 0.150 mm, preferably 0.025 - 0.125 mm, preferably 0.035 - 0.200 mm, preferably 0.045 - 0.200 mm, preferably 0.055 - 0.200 mm.

[0089] The distance of the gap 3 is measured from the inner face of the foil 7 closest to the upper punch 4 and the lower punch 4' to the outer wall of each outer wall 11 of the upper and lower punches. The preferred range of the distance of the gap 3 is preferably 10 to 100 μm, preferably 10 to 80 μm, preferably 10 to 70 μm, preferably 10 to 60 μm, preferably 10 to 50 μm, preferably 20 to 70 μm, preferably 30 to 70 μm, preferably 40 to 70 μm, preferably 50 to 70 μm, preferably 20 to 60 μm, preferably 20 to 50 μm, preferably 30 to 60 μm, preferably 30 to 50 μm.

[0090] Furthermore, the width of the gap 3 between the inner wall 8 of the die system 2 and each outer wall 11 of the upper punch 4 and the lower punch 4' can be determined by those skilled in the art so that, on the one hand, the degassing of the powder during the preheating, heating, and sintering processes becomes sufficiently easy, and on the other hand, sufficient electrical contact for Joule or resistance heating can be obtained to perform sintering. When the distance of the gap 3 is less than 10 μm, the force required to move at least one of the upper and lower punches within the internal volume of the die system, thereby assembling the tool set, may cause damage to the tool set. Furthermore, when the gap 3 is less than 10 μm, gases, organic substances, moisture, etc. adsorbed in the ceramic powder 5 cannot escape, thereby extending the process time during manufacturing and reducing the density of the sintered ceramic body by leaving porosity. High resistivity (e.g., about 1×10 at room temperature +10When sintering an insulating material such as an oxide and / or nitride ceramic as disclosed herein having a resistivity of 1 ohm centimeter or more and an oxide ceramic containing a non-conductive mixed metal oxide, if the width of gap 3 exceeds 70 μm, local overheating may occur and a thermal gradient may occur within tool set 1 during sintering. These thermal gradients can result in a low overall bulk density and high density deviation, as well as a sintered ceramic body that is brittle and prone to breakage. As a result, in order to form a sintered ceramic body of large dimensions from a non-conductive ceramic powder having a high resistivity (and thus a low conductivity), a gap of 10 to 70 μm is preferred. Thus, in some embodiments, the spacing of gap 3 between the inner wall 8 of die system 2 and the outer walls 11 of each of the upper and lower punches when sintering ceramic powder 5 containing an insulating oxide or nitride ceramic is preferably 10 to 70 μm, preferably 10 to 60 μm, preferably 10 to 50 μm, preferably 10 to 40 μm, preferably 20 to 70 μm, preferably 30 to 70 μm, preferably 40 to 70 μm, preferably 50 to 70 μm, preferably 30 to 60 μm. Gap 3 reduces the thermal gradient across the powder compact containing the insulating ceramic powder.

[0091] Correspondingly, the ceramic powder includes a non-oxide ceramic selected from specific nitrides such as carbides and borides and titanium nitride, each of which has, with respect to the oxides and nitride ceramics disclosed herein, for example, at room temperature of about 1×10 -5 ohm centimeter to about 1×10 +10If it is possible to have a lower resistivity and partial conductivity in ohm-centimeters, for example, larger gaps of about 10 to about 100 μm may be acceptable. This increased gap may be due to the partial conductivity of the powder or powder compact, whereby the partial conductivity transmits current and thereby heat through the powder compact, thus reducing the thermal gradient across the powder or powder compact containing non-oxide ceramics as disclosed. When sintering ceramic powder 5 having some conductivity, such as non-oxide ceramics and / or conductive mixed metal oxides as disclosed herein, and thereby having a lower resistivity, gaps 3 greater than 100 μm can cause local overheating and thermal gradients within the tool set during sintering. These thermal gradients can result in a low overall bulk density or high density deviation, as well as a sintered ceramic body that is brittle and prone to breakage. As a result, when sintering non-oxide ceramics and / or conductive mixed metal oxides as disclosed herein, the spacing of the gaps 3 between the inner wall 8 of the die system 2 and the outer walls 11 of each of the upper and lower punches is 10 to 100 μm, preferably 10 to 80 μm, preferably 10 to 60 μm, preferably 10 to 40 μm, preferably 20 to 100 μm, preferably 40 to 100 μm, preferably 60 to 100 μm, preferably 30 to 80 μm, preferably 40 to 70 μm.

[0092] While not intending to be bound by a particular theory, the spacing of the gaps between the inner wall 8 of the die system 2 and the outer walls 11 of each of the upper and lower punches during sintering is thought to function to promote the degassing of organic matter, moisture, adsorbed molecules, etc. of the powder during the sintering process according to step c) of the disclosed method. This results in a large-sized sintered ceramic body having high density and low volume porosity, low density deviation, and improved mechanical properties. As a result, the sintered ceramic body can be easily handled without breaking and can be machined into a specific form for the manufacture of the sintered ceramic components disclosed herein for use within a plasma processing chamber. The sintered ceramic body produced as disclosed herein can have dimensions of 100 mm to about 625 mm with respect to the maximum dimension of the sintered ceramic body.

[0093] In practice, the upper punch 4 and the lower punch 4' are not always perfectly aligned around the central axis. FIGS. 3A and 3B are plan views of the tool set 1, showing the arrangement of the upper punch 4 and the lower punch 4' centered on the central axis 9, the gap 3, any number of conductive foils 7, and the die system 2. In the embodiment shown in FIG. 3A, the gap may be axially symmetric about the central axis 9. In another embodiment shown in FIG. 3B, the gap may be asymmetric about the central axis 9. The gap 3 may extend between 10 μm and 70 μm when sintering oxides and / or nitride ceramics as disclosed herein, and may extend between 10 μm and 100 μm in both axially symmetric and asymmetric embodiments as shown when sintering non-oxide ceramics as disclosed herein.

[0094] The asymmetric performance of the gap can be measured by performing a radial absolute deviation analysis of the CTE over a range of temperatures. For example, FIG. 4 shows the radial deviation from the average CTE at 1200° C. of two isotropic graphite materials (A and B) used as the punch and die of the apparatus 1 disclosed herein. FIG. 4 shows the radial deviation of the expansion relative to the average expansion in the x-y plane of the graphite in ppm / ° C. (the expansion in the z direction is not as important for the operation of the tool 1). FIG. 4 shows that in materials that can successfully maintain the desired gap over a large temperature range, for example, from room temperature to 2000° C., the radial deviation cannot change at a maximum of >0.3×10 -6 ppm / ° C. in the x-y plane. Therefore, in order to maintain the desired gap 3 over the temperature range required to sinter insulating ceramic powder having a resistivity of 1×10 +10 or more as disclosed herein, the radial deviation from the average CTE may preferably be minimized, and thus the radial deviation is preferably 0.3×10 -6 / ° C. or less, preferably 0.25×10 -6 / ° C. or less, preferably 0.2×10 -6 / ° C. or less, preferably 0.18×10-6 is below / °C. In certain embodiments, 0.16×10 -6 / °C or less, preferably 0.14×10 -6 / °C or less, preferably 0.12×10 -6 / °C or less, preferably 0.1×10 -6 / °C or less, preferably 0.08×10 -6 / °C or less, preferably 0.06×10 -6 It is preferred that the radial deviation from the average CTE is maintained to provide a desired gap 3 over the temperature range from room temperature to the sintering temperature of the ceramic powder, and this temperature range includes up to about 2,000 °C which is the operating temperature of the apparatus. The disclosed range of the radial deviation from the average CTE of at least one graphite material in the x / y plane should be maintained over a rotational position about the central axis 9 of 0 to 360 degrees, preferably 0 to 270 degrees, preferably 0 to 180 degrees, preferably 0 to 90 degrees, preferably 0 to 45 degrees, preferably less than 10 degrees, preferably less than 5 degrees, preferably about 3 degrees, preferably about 1 degree, respectively, with respect to the rotational positions of the die and the upper punch and / or the lower punch.

[0095] As disclosed herein, when sintering a partially conductive ceramic powder having a resistivity of about 1×10 -5 ~1×10 +10 , the radial deviation from the average CTE is 0.5×10 -6 / °C or less, preferably 0.4×10 -6 / °C or less, preferably 0.3×10 -6 / °C or less, preferably 0.25×10 -6 / °C or less, preferably 0.2×10 -6 / °C, preferably 0.18×10 -6 / °C or less, preferably, 0.16×10 -6 / °C or less, preferably 0.14×10 -6 / °C or less, preferably 0.12×10 -6 / °C or less, preferably 0.1×10 -6 / °C or less, preferably 0.08×10 -6 / °C or less, preferably 0.06×10 -6It is below / ℃. Material B shows an unacceptable CTE spread in the x-y plane, while Material A shows an acceptable CTE spread throughout the temperature range.

[0096] Figure 5A) shows the standard deviation in parts per million (ppm) of the CTE of the graphite material in the x-y plane, and B) shows the absolute change (delta) in CTE over a certain temperature range across the x-y plane of both materials in Figure 4 (from lowest to highest). A graphite material with a lower standard deviation and absolute change in CTE in the x / y plane is preferred.

[0097] Figure 6 shows the dispersion of the thermal expansion coefficients of graphite materials A and B at 400 - 1400℃.

[0098] The advantages of the design of a specific tool set 1 used according to one embodiment can result in an overall technical effect for obtaining a very high purity large ceramic body with high and uniform density and low volume porosity, thereby reducing the tendency of fracture in the sintering process according to the present disclosure, particularly in the SPS process. Therefore, all features disclosed regarding the tool set are also applicable to products of sintered ceramic bodies with dimensions exceeding 100 mm.

[0099] By using the toolset disclosed herein, it becomes possible to achieve a more homogeneous temperature distribution in the powder to be sintered, and a sintered ceramic body having a very high density (> 98% of the theoretical density of a given material) and a uniform density (< 4% variation over the maximum dimension), thereby reducing the tendency to fracture, especially for large-sized ones with a maximum dimension exceeding, for example, 100 mm and / or 200 mm. The term "homogeneous" means that a material or system has substantially the same properties at every point, is uniform and without irregularities. Thus, a "uniform temperature distribution" means that the temperature distribution is spatially uniform and has no significant gradient, that is, there is a substantially uniform temperature regardless of the position in the horizontal x - y plane along the ceramic powder 5. More specifically, a "uniform temperature distribution" means that the temperature distribution across at least one type of ceramic powder 5 disposed within the internal volume defined by the toolset of the sintering apparatus during heating and sintering is at most 0.15 - 5 °C / cm.

[0100] The disclosed toolset may further include spacer elements, shims, liners, and other toolset components. Typically, such components are manufactured from at least one of the graphite materials having the properties disclosed herein.

[0101] Preparation process of large sintered ceramic body The SPS apparatus 1 described above is employed in the following steps. Therefore, all features disclosed with respect to the toolset 1 are also applicable to this method, and thus all features disclosed with respect to this method are also applicable to products of sintered ceramic bodies having a maximum dimension of 100 mm and a maximum of about 625 mm.

[0102] In one embodiment, a method for producing a sintered ceramic body is disclosed herein, the method comprising the following process steps: (a) a step of disposing at least one ceramic powder within an internal volume of a spark plasma sintering tool, the spark plasma sintering tool comprising a die including a side wall including an inner wall and an outer wall, the inner wall having a diameter defining the internal volume, a die, an upper punch and a lower punch operably connected to the die, each of the upper punch and the lower punch having an outer diameter smaller than the diameter of the inner wall of the die, whereby when at least one of the upper punch and the lower punch is moved within the internal volume of the die, a gap is generated between each of the upper punch and the lower punch and the inner wall of the die, and the gap is between 10 μm and 100 μm, the upper punch and the lower punch; (b) a step of generating a vacuum state within the internal volume; (c) a step of heating the ceramic powder to a sintering temperature while applying pressure to the ceramic powder by moving at least one of the upper punch and the lower punch, and sintering the ceramic powder to form a sintered ceramic body; (d) a step of lowering the temperature of the sintered ceramic body.

[0103] This method is characterized in that the above-described SPS tool set is disposed within a vacuum chamber and comprises at least a die system, an upper punch and a lower punch, which together define a volume, and the sintering process of the powder is carried out by disposing the powder within the volume defined by the tool set of the sintering apparatus. The die system may have an inner wall, at least one punch system may have an outer wall, and the inner wall of the die system and the outer wall of the punch system are separated by a gap.

[0104] Pressure-assisted sintering can be achieved by Spark Plasma Sintering (SPS), also known as Field Assisted Sintering Technology (FAST) or Direct Current Sintering (DCS). Direct current and these related techniques use direct current to heat a conductive die configuration, whereby the material to be sintered is deposited within the die. This heating mode allows for the application of very high heating and cooling rates, enhancing densification mechanisms that exceed diffusion mechanisms promoting grain growth, and transferring the inherent properties of the original powder to their nearly or fully dense products. In the SPS method disclosed herein, preferably, non-pulsed continuous direct current is used.

[0105] Next, the specific steps (a) to (d) will be described in detail.

[0106] Process step (a) - a step of placing at least one ceramic powder into a tool set of a sintering apparatus At least one ceramic powder is placed within the die system between the upper punch and the lower punch of the aforementioned sintering apparatus. The Spark Plasma Sintering apparatus used in the method according to the present invention typically includes a cylindrical die system. The ceramic powder is placed in the die system, and the die system filled with the powder is placed between the upper punch and the lower punch.

[0107] The ceramic powder placed within the tool disclosed herein for sintering may be, for example, a ceramic powder formed from any metal oxide (oxide ceramic), any metal nitride (nitride ceramic), any combination or mixture of metal oxides (mixed metal oxides), or a ceramic material formed from non-oxides such as carbides and borides as defined herein.

[0108] The oxide ceramic may be any metal oxide without limitation. The metal elements constituting the oxide ceramic are semi-metal elements such as boron (B), silicon (Si), germanium (Ge), antimony (Sb), bismuth (Bi); typical elements such as magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), aluminum (Al), indium (In), tin (Sn); transition metal elements such as scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au); one or more selected from lanthanoid elements such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Er), lutetium (Lu). Among them, the metal element is preferably one or more elements selected from Mg, Y, Ti, Zr, Cr, Mn, Fe, Zn, Al, and Er.

[0109] More specifically, examples of the oxide ceramic include yttrium oxide, aluminum oxide, yttrium aluminum monoclinic (YAM), yttrium aluminum garnet (YAG), yttrium aluminum perovskite (YAP), zirconia, chromia, titania, cobaltite, magnesia, silica, calcia, ceria, ferrite, spinel, magnesium aluminate spinel, zircon, nickel oxide, silver oxide, copper oxide, zinc oxide, strontium oxide, scandium oxide, samarium oxide, bismuth oxide, lanthanum oxide, lutetium oxide, hafnium oxide, vanadium oxide, niobium oxide, tungsten oxide, manganese oxide, tantalum oxide, terpium oxide, europium oxide, neodymium oxide, tin oxide, antimony oxide, antimony-containing tin oxide, indium oxide, tin-containing indium oxide, zirconium aluminate oxide, zirconium silicate oxide, hafnium aluminate oxide, hafnium silicate oxide, titanium silicate oxide, lanthanum silicate oxide, lanthanum aluminate oxide, yttrium silicate oxide, titanium silicate oxide, tantalum silicate oxide, and mixtures thereof. The oxide ceramic disclosed herein may have a very high electrical resistivity and thus may be a non-conductive insulator.

[0110] The metal nitride may be any metal nitride without limitation. The metal elements constituting the nitride ceramic are semi-metal elements such as boron (B), silicon (Si), germanium (Ge); typical elements such as aluminum (Al), indium (In), tin (Sn); transition metal elements such as scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au); and one or more selected from lanthanoid elements such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Er), lutetium (Lu). Specific examples of the nitride ceramic include boron nitride, titanium nitride, silicon nitride, aluminum nitride, etc. Except for conductive titanium nitride, the nitride ceramics disclosed in this specification may have a high electrical resistivity and thus may be non-conductive insulators.

[0111] The mixed metal oxide may include oxides such as forsterite, steatite, cordierite, mullite, barium titanate, lead titanate, lead zirconate titanate, Mn-Zn ferrite, Ni-Zn ferrite, and sialon (silicon nitride), and mixtures thereof. These mixed metal oxides may be essentially conductive or insulating depending on the composition.

[0112] Examples of the non-oxide ceramic include carbides such as tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, silicon carbide, boron carbide. The non-oxide ceramic containing the carbide disclosed in this specification can have an appropriate electrical resistivity, and thus has a conductivity lower than that of the metal and higher than that of the oxide and / or nitride and mixed metal oxide ceramic disclosed in this specification.

[0113] Examples of non-oxide ceramics include borides such as molybdenum boride, chromium boride, hafnium boride, zirconium boride, tantalum boride, titanium boride, etc., titanium diboride, titanium nitride, etc. The non-oxide ceramic containing the boride disclosed in this specification can have an appropriate electrical resistivity, and thus has a conductivity lower than that of a metal and higher than that of the oxides, nitrides, and mixed metal oxide ceramics disclosed in this specification.

[0114] Ceramic powders containing non-oxides such as carbides and borides can have a conductivity between that of oxides, nitrides, and mixed metal oxides and powders containing metal materials having a very low resistivity.

[0115] The ceramic powder starting material for performing the sintering process disclosed in this specification is at least one high-purity commercially available ceramic powder. However, other ceramic powders, such as those produced from chemical synthesis processes and related methods, can also be used.

[0116] In one embodiment, the multi-layer sintered body can be formed by separately arranging different powders or different powder mixtures in layers. For example, a powder mixture of alumina and yttria can be used as the first powder, and a different ceramic powder mixture, such as a mixture of alumina and zirconia, can be used as the second powder mixture. In one example, zirconia is present in an amount of 5 to 25% by volume, preferably 10 to 25% by volume, preferably 15 to 25% by volume, preferably 15 to 17% by volume, preferably 20 to 25% by volume, preferably 5 to 20% by volume, preferably 5 to 15% by volume, preferably 5 to 10% by volume, preferably 15 to 20% by volume of the sintered ceramic body. The mixture of alumina and zirconia can be prepared and calcined as detailed in this specification. In such an embodiment, the powder mixture is preferably uniformly dispersed.

[0117] In such mixtures containing zirconia, the zirconia powder can have a particle size distribution with a d10 of 0.08 - 0.20 μm, a d50 of 0.3 - 0.7 μm, and a d90 of 0.9 - 5 μm. The average particle size of the zirconia powder used as a starting material for the mixture according to one embodiment of the present invention may be 0.3 - 1 μm.

[0118] The zirconia powder preferably has a specific surface area of 1 - 16 m 2 / g, preferably 2 - 12 m 2 / g, more preferably 5 - 9 m 2 / g, and the purity of the zirconia powder starting material is typically greater than 99.5%, preferably greater than 99.8%, preferably greater than 99.9%, preferably greater than 99.99%. This corresponds to a total impurity content of 5000 ppm or less, preferably 2000 ppm or less, preferably 1000 ppm or less, preferably 100 ppm or less.

[0119] In some multilayer embodiments where the process component includes a substrate layer and a surface layer, the substrate layer preferably includes at least one crystal phase containing alumina and zirconia, and the zirconia is present in an amount of 5 - 25% by volume, preferably 10 - 25% by volume, preferably 15 - 25% by volume, preferably 15 - 17% by volume, preferably 20 - 25% by volume, preferably 5 - 20% by volume, preferably 5 - 15% by volume, preferably 5 - 10% by volume, preferably 15 - 20% by volume of the sintered ceramic body, respectively. The surface layer includes at least one crystal phase of yttrium aluminum oxide, and at least one crystal phase of yttrium aluminum oxide includes pores with a pore diameter not exceeding 5 μm and pores having a maximum pore diameter of 1.5 μm for at least 95% of the pores.

[0120] In such multi-layer embodiments, the composition may be unrestricted, but the layers of powder or powder mixture preferably have a coefficient of thermal expansion (CTE) that closely matches over a temperature range of about 200 °C to about 1700 °C. Preferably, the difference in CTE is 0.5×10-6 / °C or less, preferably 0.4×10-6 / °C or less, preferably 0.3×10-6 / °C or less, preferably 0.2×10-6 / °C or less, preferably 0.1×10-6 / °C or less, preferably 0.09×10-6 / °C or less, preferably 0.07×10-6 / °C or less, preferably 0.05×10-6 / °C or less.

[0121] The purity of the ceramic powder starting material is preferably greater than 99.99%, preferably greater than 99.995%, preferably greater than 99.9975%, preferably greater than 99.999%, preferably greater than 99.9995%, and in some embodiments, the purity of the ceramic powder is greater than 99.9999%. In other words, the total impurity level of the ceramic powder is less than 100 ppm, preferably less than 50 ppm, more preferably less than 250 ppm, more preferably less than 10 ppm, more preferably less than 5 ppm, more preferably about 3 ppm, even more preferably 1 ppm or less (including 0 ppm), respectively, based on the total mass of the ceramic powder starting material. High-purity starting ceramic powders are desirable for providing high chemical corrosion resistance and erosion resistance, thereby minimizing particle generation during use as components within a semiconductor processing chamber.

[0122] In contrast to other sintering techniques in the prior art, the ceramic powders used in the processes of the present disclosure do not require sintering aids. Accordingly, ceramic powders and / or powder mixtures that do not contain or substantially contain sintering aids are disclosed herein. Further, the formation of a green body is not necessary, and thus the ceramic powder may be used as needed but may not contain an organic binder or dispersant. In embodiments, the ceramic powders according to the methods disclosed herein may have a specific surface area (SSA) of 18 m 2 / g or less, preferably 1 - 18 m 2 / g, and typically 20 m 2 / g~200m 2 Lower than the specific surface area of the nanopowder that can have an SSA of / g or more. It can have a higher moisture / humidity and adsorbed gas content, 20m 2 The use of nanopowders having an SSA exceeding / g can result in a decrease in packing density when forming a powder compact as disclosed herein, and can produce a sintered ceramic body having a lower density / higher porosity. 1m 2 Powders having an SSA of less than / g may not result in complete densification of the sintered ceramic body because the driving force for sintering is reduced due to the low powder specific surface area. All measurements of SSA were performed as measured according to ASTM C1274, "Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption". In embodiments, the ceramic powder by the method disclosed herein substantially does not contain or does not contain the nanopowder as defined herein.

[0123] The particle size measurement was performed using a Horiba model LA-960 laser scattering type particle size distribution analyzer capable of measuring particle sizes from 10 nm to 5 mm. The measurement of the specific surface area of the ceramic powder was performed using a Horiba BET surface area analyzer model SA-9601 that can be measured with an accuracy of 10% or less over a specific surface area of 0.01 to 2000 m 2 / g.

[0124] Preferably, the d10 particle size of the ceramic powder used as the starting material for the SPS process disclosed herein is 0.05 to 7 μm, preferably 0.05 to 6 μm, preferably 0.05 to 5 μm, preferably 0.05 to 4 μm, preferably 0.05 to 3 μm, preferably 0.05 to 1 μm, preferably 0.1 to 7 μm, preferably 0.1 to 6 μm, preferably 0.1 to 5 μm, preferably 0.1 to 4 μm, preferably 0.1 to 3 μm, preferably 0.2 to 6 μm, preferably 0.3 to 6 μm, preferably 0.4 to 6 μm, more preferably 0.3 to 4 μm.

[0125] Preferably, the median (d50) particle size of the ceramic powder used as a starting material in the SPS process disclosed herein is 0.15 to 100 μm, preferably 0.15 to 75 μm, preferably 0.15 to 50 μm, preferably 0.15 to 25 μm, preferably 0.15 to 10 μm, preferably 0.15 to 5 μm, preferably 0.15 to 3 μm, preferably 0.8 to 80 μm, preferably 0.8 to 60 μm, preferably 0.8 to 40 μm, preferably 0.8 to 30 μm, preferably 0.8 to 20 μm, preferably 0.8 to 10 μm, preferably 0.8 to 5 μm, preferably 1 to 100 μm, preferably 1 to 75 μm, preferably 1 to 60 μm, preferably 1 to 45 μm, preferably 1 to 30 μm, preferably 1 to 20 μm, preferably 1 to 10 μm, preferably 1 to 5 μm, preferably 10 to 100 μm, preferably 20 to 100 μm, preferably 40 to 100 μm, preferably 10 to 40 μm, preferably 20 to 40 μm, preferably 30 to 40 μm, preferably 3 to 10 μm, and preferably 2 to 8 μm.

[0126] Preferably, the d90 particle size of the ceramic powder used as a starting material in the SPS process disclosed herein is 0.4 to 250 μm, preferably 0.4 to 100 μm, preferably 0.4 to 50 μm, preferably 0.4 to 25 μm, preferably 0.4 to 10 μm, preferably 0.4 to 5 μm, preferably 0.4 to 3 μm, preferably 0.4 to 1 μm, preferably 6 to 250 μm, preferably 6 to 200 μm, preferably 6 to 160 μm, preferably 6 to 120 μm, preferably 6 to 80 μm, preferably 6 to 40 μm, preferably 10 to 250 μm, preferably 20 to 250 μm, preferably 30 to 250 μm, preferably 40 to 250 μm, preferably 10 to 250 μm, preferably 10 to 140 μm, preferably 10 to 80 μm, preferably 3 to 80 μm, and preferably 10 to 40 μm.

[0127] Preferably, the ceramic powder used as a starting material in the SPS process disclosed herein is 1 to 18 m as measured according to ASTM C12742 / g, 2 to 18 m 2 / g, preferably 3 to 18 m 2 / g, preferably 4 to 18 m 2 / g, preferably 5 to 18 m 2 / g, preferably 6 to 18 m 2 / g, preferably 1 to 16 m 2 / g, preferably 2 to 16 m 2 / g, preferably 4 to 16 m 2 / g, preferably 6 to 16 m 2 / g, preferably 1 to 14 m 2 / g, preferably 1 to 12 m 2 / g, preferably 1 to 10 m 2 / g, preferably 1 to 8 m 2 / g, preferably 2 to 12 m 2 / g, preferably 2 to 10 m 2 / g, preferably 3 to 8 m 2 / g has a specific surface area.

[0128] Preferably, the ceramic powder used as a starting material in the SPS process disclosed herein has a log-normal particle size distribution including a continuous distribution of particle sizes. Unimodal and bimodal particle size distributions can lead to a decrease in the powder packing density before sintering, thereby resulting in a decrease in density across the sintered ceramic body and / or a higher density deviation.

[0129] Preferably, the ceramic powder used in the SPS process disclosed herein has a small amount of adsorbed gas and / or surface organic matter, moisture content, trapped gas, etc. The powder may optionally be subjected to various processing steps such as tumbling, blending, firing, sieving, etc. to minimize the weight loss relative to the total powder weight, thereby minimizing the porosity in the sintered ceramic body. Table 3 lists the total average weight loss upon heating relative to the total powder weight over two or more measurements of an exemplary ceramic powder. In embodiments, the ceramic powder has a weight loss relative to the total powder weight of 0.01 to 0.75%, preferably 0.01 to 0.6%, preferably 0.01 to 0.45%, preferably 0.05 to 0.75%, preferably 0.1 to 0.75%, preferably 0.2 to 0.75%, preferably 0.25 to 0.6% as measured using a thermogravimetric analyzer model number STAPT1600 manufactured by Linseis, Inc.

[0130]

Table 3

[0131] In some embodiments, the ceramic powder may be treated in a manner that removes undesirable moisture, organic matter, or agglomeration. Such treatment may include tumbling and / or sieving before and / or after use in step a) of the method disclosed herein.

[0132] The ceramic powder, in certain embodiments, can include two or more of the aforementioned oxides, nitrides, and non-oxide ceramics and combinations thereof, and can be mixed under wet or dry conditions according to methods such as ball milling, attrition milling, high-shear mixing, planetary milling, jet milling, and other procedures known to those skilled in the art. Powder processing techniques such as calcination, drying, sieving, screening, tumbling, blending, etc. can be used according to methods known in the art. For example, as known to those skilled in the art, ball milling or tumble mixing can be performed. If a high-purity sintered ceramic body is desired, a high-purity (>99.99%) medium may be used to maintain the purity of the starting powder during mixing. Wet ball milling or tumble mixing can be performed by suspending the starting powder in various solvents such as ethanol, methanol, and other alcohols, and / or water to form a slurry. The slurry may be formed with a powder loading of about 5 to about 50% by weight of the powder and a medium loading of, for example, 40 to 100% by weight of the powder during milling or mixing.

[0133] In certain embodiments, the ceramic powder may optionally be calcined prior to use in the processes of the present development. Exemplary calcination temperatures are from about 600 °C to about 1,500 °C, preferably from about 700 °C to about 1,500 °C, preferably from about 800 °C to about 1,500 °C, preferably from about 900 °C to about 1,500 °C, preferably from about 1,000 °C to about 1,500 °C, preferably from about 600 °C to about 1,300 °C, preferably from about 700 °C to about 1,300 °C, preferably from about 800 °C to about 1,300 °C, preferably from about 900 °C to about 1,300 °C, preferably from about 1,000 °C to about 1,300 °C, preferably from about 600 °C to about 1,100 °C, preferably from about 700 °C to about 1,100 °C, preferably from about 800 °C to about 1,100 °C, preferably from about 900 °C to about 1,100 °C, preferably from about 1,000 °C to about 1,100 °C in an oxygen-containing environment for 4 to 12 hours, preferably 4 to 8 hours, preferably 4 to 6 hours, preferably 6 to 12 hours, preferably 8 to 12 hours, preferably 6 to 8 hours. Before and / or after firing, the ceramic powder may be sieved and / or tumbled according to known methods. The starting ceramic powder(s) disclosed herein is preferably crystalline and thereby has long-range crystallographic order and peaks distinguishable in X-ray diffraction. In certain embodiments, the firing conditions disclosed herein result in agglomeration of the powder mixture and thus may result in greater variability in the particle size distribution. Thus, in embodiments, the particle size referred to herein can include a single particle, and in other embodiments, the particle size referred to herein can include an aggregate of two or more particles or an aggregate of a plurality of particles that can be measured as a single large particle using the laser particle size detection method disclosed herein.

[0134] In some embodiments, although not required to achieve a high-density sintered ceramic body, sintering aids may be optionally used as desired in accordance with the methods and materials disclosed herein and may be combined with the ceramic powder. In certain embodiments, the sintered ceramic body may include an optional sintering aid selected from the group consisting of silica, zirconia, calcia, magnesia, and combinations thereof. In certain embodiments, the sintered ceramic body may include a sintering aid optionally added in an amount of 0.002 wt% or more, preferably 0.0035 wt% or more, preferably 0.005 wt% or more, preferably 0.0075 wt% or more. In an embodiment, the sintering aid may be optionally added in an amount of ≦0.05 wt%, preferably ≦0.03 wt%, preferably ≦0.02 wt%, preferably ≦0.01 wt%.

[0135] In other embodiments, dopants may be used as needed and may be combined with the ceramic powder in accordance with the methods and materials disclosed herein. For example, rare earth oxides selected from the group consisting of Sc, La, Er, Ce, Cr, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu and dopants of their oxides and combinations may be optionally added to the starting ceramic powder in step a in an amount of ≦0.05 wt%, preferably ≦0.03 wt%, preferably ≦0.01 wt%, preferably 0.002 - 0.02 wt%. In other embodiments, the aforementioned dopants may be optionally added to at least one ceramic powder in step a) in an amount of ≧0.002 wt%, preferably >0.0035 wt%, preferably ≧0.005 wt%, preferably ≧0.0075 wt%.

[0136] In a further embodiment, both dopants and sintering aids may be optionally combined with the ceramic powder in accordance with the methods as disclosed.

[0137] In an embodiment, sintering is typically carried out for an isothermal time of 0.5 to 180 minutes, preferably 0.5 to 120 minutes, preferably 0.5 to 100 minutes, preferably 0.5 to 80 minutes, preferably 0.5 to 60 minutes, preferably 0.5 to 60 minutes, preferably 0.5 to 40 minutes, preferably 0.5 to 20 minutes, preferably 0.5 to 10 minutes, preferably 0.5 to 5 minutes, preferably 5 to 120 minutes, preferably 10 to 120 minutes, preferably 20 to 120 minutes, preferably 40 to 120 minutes, preferably 60 to 120 minutes, preferably 100 to 120 minutes, preferably 30 to 60 minutes, preferably 15 to 45 minutes. In other embodiments, sintering under isothermal residence time can preferably be applied for 0 to 30 minutes, preferably 0 to 20 minutes; preferably 0 to 10 minutes; preferably 0 to 5 minutes. In certain embodiments, sintering can be carried out without an isothermal time or isothermal holding time, and after reaching the sintering temperature, the cooling process is started at the rate disclosed herein.

[0138] (b) A process step of creating a vacuum state within the internal volume When the ceramic powder is loaded into the die, a pressure of 5 to 20 MPa, preferably 8 to 20 MPa, preferably 10 to 20 MPa, preferably 5 to 10 MPa may be applied to the ceramic powder disposed within the internal volume of the spark plasma sintering tool, whereby the ceramic powder after applying the pressure can form a powder compact having a packing density of 20% to 60% by volume, 20% to 50% by volume, preferably 30% to 60% by volume, preferably 30% to 55% by volume, preferably 40% to 60% by volume, preferably 40% to 50% by volume. A higher packing density is desirable to improve the thermal conductivity within the powder compact and thereby reduce the temperature difference across the powder compact during heating and sintering. The powder compact is formed from the ceramic powder disclosed herein without using organic additives such as dispersants, binders, deflocculants, etc., and thus contains no or substantially no organic matter. Thereafter, vacuum conditions known to those skilled in the art are established within the chamber between the punches surrounded by the die. Typical vacuum conditions are 10 -2 ~10 -3The pressure of the toll is mentioned. It is evacuated mainly to remove air and protect the graphite material from combustion, and also to remove most of the air from the powder.

[0139] (c) A process step of sintering a ceramic powder to form a sintered ceramic body by heating the ceramic powder to a sintering temperature while applying pressure to the ceramic powder by moving at least one of an upper punch and a lower punch, and (d) a process step of lowering the temperature of the sintered ceramic body At least one type of ceramic powder is disposed in the die, and after most of the air is removed from the internal volume defined by the tool set and the powder 5, pressure is applied to the ceramic powder disposed between the graphite punches by axially moving at least one of the upper punch and the lower punch toward the other. The pressure applied to at least one type of ceramic powder disposed within the volume defined by the tool set ranges from 5 MPa to 60 MPa, preferably from 5 MPa to 40 MPa, preferably from 5 MPa to 20 MPa, preferably from 5 MPa to 15 MPa, preferably from 10 MPa to 60 MPa, preferably from 10 MPa to 40 MPa, preferably from 10 MPa to 30 MPa, preferably from 10 MPa to 20 MPa, preferably from 13 MPa to 18 MPa, preferably from 15 MPa to 60 MPa, preferably from 15 MPa to 40 MPa, preferably from 15 MPa to 30 MPa, preferably from 20 to 40 MPa. The pressure is applied axially to at least one type of ceramic powder.

[0140] In a preferred embodiment, the ceramic powder is directly heated by the punches and the die of the SPS apparatus. The die can include a conductive material such as some graphite materials as disclosed herein that facilitate resistive heating / Joule heating. The SPS apparatus and procedure are disclosed, for example, in U.S. Patent Application Publication No. 2010 / 0156008A1, which is incorporated herein by reference.

[0141] The application of heat to the ceramic powder provided in the die promotes a sintering temperature of 1000 - 1700 °C, preferably 1200 - 1700 °C, preferably 1400 - 1700 °C, preferably 1500 - 1700 °C, more preferably 1600 - 1700 °C, preferably 1400 - 1650 °C, preferably 1500 - 1650 °C, preferably 1400 - 1600 °C, preferably 1500 - 1600 °C.

[0142] Figures 7A, 7B, and 7C show the effects of different types of ceramic powders on the current path and heating in the gap including the SPS device as disclosed herein. In Figure 7A, the ceramic powder 5 is mainly a conductive powder (e.g., metal powder). Here, the powder resistivity is smaller than that of graphite, and the current flows directly through the powder rather than extending into the die 6 or die system 2, facilitating uniform sintering across the powder disposed between the punches 4 and 4'. Thus, in the case of the metal ceramic powder 5, the dimension of the gap 3 is irrelevant to the current path and heating.

[0143] In Figure 7B, the ceramic powder 5 is a partial conductor (e.g., non-oxide ceramic and / or mixed metal oxide that is partially conductive as disclosed herein and has a resistivity of, for example, about 1×10 -5 ~1×10 +10 ), and the resistivity of these partial conductors may be greater than, equal to, or less than the resistivity of graphite. The current flows through both the powder and graphite according to the resistivity of the powder. Thus, to ensure proper current flow and heating of the ceramic powder 5, the size of the gap 3 between the graphite die 6 or graphite die system 2 and the upper punch 4 and lower punch 4' is preferably 10 - 100 μm. The gap according to Figure 7B can be maintained in some embodiments from ambient temperature to a specific sintering temperature of the partially conductive ceramic powder being sintered and up to about 2,000 °C, which is the maximum temperature of the device.

[0144] In FIG. 7C, the ceramic powder 5 is an insulator (e.g., oxide ceramics, nitride ceramics, and non-conductive mixed metal oxides disclosed herein), and the current moves from the upper punch 4 only through the graphite die 6 (or graphite die system 2) to the lower punch 4' to sinter the ceramic powder 5. In this embodiment, as shown in FIG. 7C, no large current flows through the ceramic powder 5. At least one kind of ceramic powder 5 according to FIG. 7C has a resistivity exceeding, for example, 1×10 +5 . The gap distance between 10 and 70 μm enables a uniform temperature distribution across the oxide ceramic powder during the sintering process, thus high and uniform density and low porosity. The gap according to FIG. 7C is maintained from the ambient temperature to the sintering temperature of the insulating ceramic powder to be sintered and up to the maximum temperature of the apparatus of about 2000 °C.

[0145] Referring to FIG. 8, the temperature difference across the distance between the inner wall 8 of the die system and the central axis 9 of the SPS tool 1 is shown. The temperature difference may be less than 100 °C, 1 to 100 °C, preferably 1 to 80 °C, preferably 1 to 60 °C, preferably 1 to 40 °C, preferably 1 to 20 °C, preferably 1 to 10 °C, preferably 5 to 100 °C, preferably 10 to 100 °C, preferably 20 to 100 °C, preferably 5 to 75 °C, preferably 5 to 50 °C, preferably 5 to 25 °C, whereby this temperature difference is applied to the ceramic powder during heating and sintering to achieve a uniform temperature distribution across the entire ceramic powder during sintering. The uniformity of the temperature across the powder 5 during sintering poses a greater challenge as the dimensions of the punch and die increase. Thus, the uniformity of the temperature disclosed for larger dimensions can be more easily achieved with smaller dimensions of the punch and die, and thus, the small variation in temperature (i.e., for example, 25 °C or less) disclosed when sintering a larger ceramic body can be assumed to vary at least to the same extent or less than that disclosed for a smaller ceramic body.

[0146] The temperature gradient across the maximum dimension of the sintered ceramic body can be represented by the normalized change in temperature across the maximum dimension. Thus, in certain embodiments, the temperature difference across at least one ceramic powder 5 disposed inside the internal volume defined by the tool set of the sintering apparatus during heating and sintering is 0.15 to 5 °C / cm, preferably 0.15 to 3 °C / cm, preferably 0.15 to 2 °C / cm, preferably 0.15 to 1 °C / cm, preferably 0.15 to 0.5 °C / cm, preferably 0.4 to 5 °C / cm, preferably 0.4 to 3 °C / cm, preferably 0.4 to 1 °C / cm, preferably 0.25 to 0.80 °C / cm in order to achieve a uniform temperature distribution across the ceramic powder during sintering. The term "homogeneous" means that a material or system has substantially the same properties at every point and is uniform without irregularities. Thus, a "uniform temperature distribution" means that the temperature distribution is spatially uniform and has no significant gradient, i.e., there is a substantially uniform temperature regardless of the position in the horizontal x-y plane along the ceramic powder 5. More specifically, a "uniform temperature distribution" means that the temperature distribution across at least one ceramic powder 5 disposed within the internal volume defined by the tool set of the sintering apparatus during heating and sintering is at most 0.15 to 5 °C / cm.

[0147] By using an SPS tool set having a gap dimension range as disclosed herein, the gap is maintained throughout the process, particularly during sintering step c) of the method as disclosed, resistance overheating is prevented, and as a result, this temperature difference can be minimized such that the density of the sintered ceramic body has a minimum variation across the distance from the inner surface 8 of the die system to the central axis 9 defining the center. Uniform high densification during sintering results in a density deviation that is preferably less than 4%, less than 3%, preferably less than 2%, preferably less than 1%, more preferably less than 0.5%, preferably 0.25 to 5%, preferably 0.25 to 4%, preferably 0.25 to 3%, preferably 0.25 to 2%, preferably 0.25 to 1%, preferably 0.25 to 0.5%, preferably 0.5 to 3.5%, and preferably 1 to 3% across the maximum dimension of the sintered ceramic body as disclosed herein.

[0148] Even more contributing to uniform high densification during sintering is the high packing density of 30-60% by volume of the powder compact containing the ceramic powder disclosed herein before sintering, which can be achieved using the disclosed ceramic powder and method.

[0149] The temperature of the sintering apparatus according to the present disclosure is typically measured within a die containing at least one graphite material of the sintering apparatus. Therefore, it is preferred that the temperature be measured as close as possible to the sintered ceramic powder so that the indicated temperature is actually achieved within the ceramic powder.

[0150] In one embodiment, the order of application of pressure and temperature can be varied according to the present disclosure, which means that it is possible to apply the initially indicated pressure and then heat to reach the desired temperature. Further, in other embodiments, it is also possible to first perform the indicated heating to reach the desired temperature and then apply the indicated pressure. In a third embodiment according to the present disclosure, temperature and pressure can be simultaneously applied to the ceramic powder to be sintered and raised to reach the indicated values.

[0151] Methods of induction heating or radiative heating can also be used to heat the sintering apparatus to indirectly heat the ceramic powder within the tool set.

[0152] In contrast to other sintering techniques, the preparation of the powder before sintering, i.e., the preparation of the powder by using organic additives such as binders and dispersants to form a cold press or a green body before sintering, is not necessary. The powder is directly filled into the internal volume of the spark plasma sintering tool to form a powder compact without using the aforementioned organic additives. By reducing this processing step, a higher purity of the final sintered ceramic body is obtained.

[0153] According to the embodiment of process step c), the temperature and pressure are maintained for a period of 1 minute to 360 minutes, preferably 1 to 240 minutes, preferably 1 to 120 minutes, preferably 1 to 60 minutes, preferably 5 to 360 minutes, preferably 10 to 360 minutes, preferably 30 to 360 minutes, preferably 45 to 360 minutes, preferably 60 to 360 minutes, preferably 60 to 90 minutes for sintering. At the end of process step c) of the sintering process, the ceramic powder sintered to form a sintered ceramic body is preferably cooled according to the natural convection (non-forced cooling) of the process chamber until it reaches a temperature that can facilitate the optional annealing process of step e) (process d). In a further embodiment according to process step e), the sintered ceramic body may be cooled under the convection of an inert gas, for example, argon or nitrogen at 1 bar. Other gas pressures above or below 1 bar can also be used. To initiate the cooling process, the power applied to the SPS device can be removed. The pressure applied to the sintered sample is removed at the end of the sintering process before (natural) cooling occurs.

[0154] When sintering the powder to form a sintered ceramic body, depending on the packing density of the ceramic powder 5 before the sintering process, a volume reduction of about 30% may occur.

[0155] (e) In an optional step, a step of performing annealing by applying heat to raise the temperature of the sintered ceramic body to reach the annealing temperature and annealing the sintered ceramic body, and (f) a process step of lowering the temperature of the sintered ceramic body to ambient temperature by removing the heat source applied to the sintered ceramic body of the sintering device and removing the sintered ceramic body In an optional step (e), the sintered ceramic body obtained in step (d) is subjected to an annealing process. The annealing may be performed in a furnace outside the sintering apparatus or within the sintering apparatus itself without removing the sintered ceramic body from the apparatus. For example, in one embodiment, after cooling by process step (d), the sintered ceramic body may be removed from the sintering apparatus and the annealing process step may be performed in a separate apparatus such as a furnace. In other embodiments, for the purpose of annealing according to the present disclosure, the sintered ceramic body formed in step (c) may be continuously annealed within the sintering apparatus without the need to remove it from the sintering apparatus between the sintering step (d) and the optional annealing step (e).

[0156] This annealing can improve the chemical and physical properties of the sintered ceramic body. The annealing step can be performed by conventional methods used for annealing glass, ceramics, and metals, and the degree of improvement can be selected by choosing the annealing temperature and the duration for which annealing is continued.

[0157] The optional annealing step (e) can be carried out at a temperature of 1200 - 1800 °C, preferably 1250 - 1700 °C, more preferably 1300 - 1650 °C). At such temperatures, the oxygen vacancies in the crystal structure can be corrected to return to the stoichiometric ratio.

[0158] The step of annealing the sintered ceramic body can be completed in 5 minutes to 24 hours, preferably 20 minutes to 20 hours, preferably 60 minutes to 16 hours, preferably 4 - 12 hours, preferably 6 - 10 hours.

[0159] The optional annealing process step (e) is preferably carried out in an oxidizing atmosphere in air.

[0160] After an optional process step (e) of annealing the sintered ceramic body is performed, the temperature of the annealed sintered ceramic body is reduced to ambient temperature according to a process step (f) of reducing the temperature of the sintered and annealed ceramic body to ambient temperature. The thus manufactured sintered, and in certain embodiments annealed, ceramic body is of high density and typically has an average particle size of 0.25 μm to 18 μm, preferably 0.25 to 13 μm, preferably 0.25 to 10 μm, preferably 0.25 to 8 μm, preferably 0.25 to 5 μm, preferably 0.5 to 18 μm, preferably 0.75 to 18 μm, preferably 1 to 18 μm, preferably 2 to 18 μm, preferably 5 to 18 μm, preferably 0.5 to 10 μm, preferably 0.75 to 8 μm, preferably 0.75 to 5 μm.

[0161] In an embodiment, the sintered (and in certain embodiments annealed) ceramic body according to the present disclosure may comprise a non-conductive metal oxide, nitride, or mixed metal oxide formed from a ceramic powder having the properties disclosed herein.

[0162] In an alternative embodiment, the sintered (and in certain embodiments annealed) ceramic body according to the present disclosure may comprise a sintered ceramic body formed from a mixed metal oxide such as forsterite, steatite, cordierite, mullite, barium titanate, lead titanate, lead zirconate titanate, Mn-Zn ferrite, Ni-Zn ferrite and sialon, and mixtures thereof, having the properties disclosed herein. The mixed metal oxides disclosed herein may be conductive or insulating and may be formed according to the specific gap widths, devices, and methods disclosed.

[0163] The above-described SPS process according to one embodiment is suitable for use in the preparation of large sintered ceramic bodies having a maximum dimension of 100 mm or more. The disclosed process provides rapid powder compaction and densification, and in some embodiments retains a small (on the order of less than 15 μm) average particle size in the sintered body that is shifted from the particle size of the starting ceramic powder, achieving a high density that exceeds 98% of the theoretical density of a particular material with a density deviation of <4% across the maximum dimension. This combination of fine particle size, uniformity, and high density provides large-dimension, high-strength sintered ceramic bodies suitable for machining, handling, and use as components within semiconductor processing chambers. Thus, according to certain embodiments, the sintered (and in certain embodiments annealed) ceramic bodies according to the present disclosure can include metal oxides, metal nitrides, metal carbides, metal borides, or mixed metal oxides having a diameter of greater than 100 mm and having the properties disclosed herein.

[0164] For example, in one embodiment, the sintered (and in certain embodiments annealed) ceramic body can be formed in a disk shape having dimensions in the range of 40 mm to about 625 mm in size and a thickness in the range of about 3 mm to about 60 mm, preferably 5 to 50 mm, from a powder as disclosed herein. In another embodiment, the sintered (and in certain embodiments annealed) ceramic body may be formed in a disk shape having a diameter in the range of 100 mm to about 625 mm. In alternative embodiments, the sintered (and in certain embodiments annealed) ceramic body can be formed to have a maximum dimension of 100 mm to 406 mm. In other embodiments, the sintered (and in certain embodiments annealed) ceramic body has a size of 200 mm to about 625 mm, preferably 300 to about 625 mm, preferably 350 to about 625 mm, preferably 400 to about 625 mm, more preferably 450 to about 625 mm, more preferably 500 to about 625 mm, more preferably 550 to about 625 mm, with respect to the maximum dimension of each sintered ceramic body.

[0165] Finally, the sintered ceramic body can be machined to form final sintered components for use in plasma processing chambers such as, for example, dielectric windows or RF windows, focus rings, nozzles or gas injectors, showerheads, gas distribution plates, etching chamber liners, plasma source adapters, gas inlet adapters, diffusers, electrostatic wafer chucks, chucks, packs, hybrid manifolds, ion suppressor elements, face plates, isolators, spacers, and protective rings. Machining of the sintered ceramic body (or sintering and annealing) to produce the sintered components can be carried out according to methods known to those skilled in the art.

[0166] The methods disclosed herein provide high density and associated low porosity, minimal density deviation, high purity, and high mechanical strength, thereby providing handleability of sintered ceramic bodies / components, particularly sintered ceramic bodies / components having dimensions of 100 to over about 625 mm over their maximum dimension. All features disclosed with respect to the process / method are also applicable to the products of the sintered ceramic bodies disclosed herein.

[0167] Description of the obtained sintered ceramic body: Certain ceramic bodies prepared according to the methods disclosed above have improved fracture resistance due to high density and minimal density deviation, high mechanical strength, in addition to higher purity and improved etch resistance. Separate embodiments of the improved ceramic bodies prepared according to the methods disclosed herein are described below. All features disclosed with respect to the products of the sintered ceramic bodies are also applicable to the processes / methods disclosed herein.

[0168] Density measurements were performed in accordance with ASTM B962-17. The density values and standard deviations reported herein are for the average over five measurements. The relative density (RD) of a given material is defined as the ratio of the measured density of the sample to the reported theoretical density of the same material, as shown in the following equation. The volume porosity (Vp) is calculated from the density measurement values as follows:

[0169]

Number

[0170]

Table 4

[0171] The density deviation was measured from samples taken across the maximum dimension, and then the variation with respect to the highest density measured was calculated.

[0172] Table 5 lists the dimensions, average density, % theoretical density (TD), % volume porosity, % density deviation, and % variation per cm of exemplary sintered ceramic bodies according to the embodiments disclosed herein.

[0173]

Table 5

[0174] Sample 506 containing YAG is shown in FIGS. 15A and 15B. FIG. 15A shows a high-density fine structure in a SEM micrograph at 5000× magnification, and b) shows the % of the theoretical density of YAG and the density deviation over the maximum dimension for the sintered ceramic body according to Example 506 disclosed herein. The 5000× SEM image of FIG. 15A was analyzed for particle size measurement using the Heyn Line Intercept method known to those skilled in the art, and an average particle size of 6.2 μm with a standard deviation of 0.71 μm was measured over 25 repetitions. For sample 506, the maximum and minimum particle sizes of 7.7 μm and 5.0 μm were also measured, respectively. Hardness measurements were performed according to ASTM standard C1327, and an average hardness of about 14.8 GPa was measured. The average hardness was calculated from 8 measurements or repetitions over the sample surface, and the maximum and minimum hardness values were 16 and 12.7 GPa, respectively, using an applied load of 0.025 kgf.

[0175] Density measurements were performed according to ASTM B962-17 from samples cut across the radius of the sample, and the density results are shown in FIG. 15B. Five measurements were made at each of six positions along the radius, and an average density of 4.546 g / cc was measured, which corresponds to 99.783% of the theoretical value of YAG, and the volume porosity was 0.217%. The density over the radius was 99.7 - 99.9% of the theoretical value of YAG. The density variation as shown in FIG. 25B was measured with respect to the highest density measurement value along the radius, and a maximum density deviation of 0.208% was measured.

[0176] In contrast, sintered ceramic bodies made from non-conductive oxide ceramics using a sintering apparatus having a gap size exceeding about 90 μm resulted in a theoretical density between 95% and less than 97% and a density deviation of 4.5% or more for the non-conductive oxide ceramics, according to Table 6. The sintered ceramic bodies prepared according to Table 6 resulted in lower and non-uniform densities, especially at large body sizes of, for example, 150 mm or more, often resulting in breakage.

[0177]

Table 6

[0178] The electrical resistivity was measured for sintered ceramic bodies formed from a method and apparatus having a gap width between 10 and 70 μm. Table 7 lists the electrical resistivity measurements for exemplary sintered ceramic bodies. This process and material resulted in sintered ceramic bodies having a high electrical resistivity and correspondingly low conductivity.

[0179]

Table 7

[0180] Providing sintered ceramic bodies with low dielectric loss becomes important as the frequency increases. The high overall purity of the sintered ceramic bodies disclosed in Tables 6 and 7 herein, especially those having a low silica content, provides favorable results for the dielectric constant and dielectric loss or dielectric tangent disclosed in Table 8 for sintered ceramic bodies containing yttrium oxide. Furthermore, the dielectric loss can be affected by the particle size and particle size distribution. Fine particle sizes can also provide reduced dielectric loss, thereby providing reduced heating during use at high frequencies. About 1×10 -4 ~5×10 -2 , preferably 1×10 -4 ~1×10 -2 , more preferably 1×10 -4 ~1×10 -3The dielectric loss can be achieved for a sintered ceramic body containing high-purity yttrium oxide. Yttrium oxide sample 157 had an average dielectric constant of 11.3 and an average dielectric loss of 3.6×10-2 over four measurements, as listed in Table 8. -2 had an average dielectric loss of

[0181]

Table 8

[0182] In a preferred embodiment, high mechanical strength can be achieved through control of the particle size in the sintered ceramic body, whereby finer particle sizes provide higher flexural strength. FIG. 8 shows exemplary particle sizes and particle size distributions of YAG (yttrium aluminum garnet) and yttrium oxide sintered ceramics disclosed herein. Table 9 lists the particle size characteristics of the sintered ceramic body of FIG. 9.

[0183]

Table 9

[0184] Correspondingly, Table 10 lists the four-point flexural strength results for the disclosed exemplary sintered ceramic bodies. The measurements were performed in accordance with ASTM C1161-18, where n is the number of tests performed. High strength was measured for the materials containing the disclosed sintered ceramic bodies.

[0185]

Table 10

[0186] The sintered ceramic bodies and related components disclosed herein provide improved plasma resistance and enhanced cleaning ability in a semiconductor processing chamber due to the specific material properties and characteristics described below.

[0187] Application of the sintered ceramic body: The sintered ceramic body thus produced can be used in semiconductor plasma processing apparatuses for plasma etching, deposition, and similar processes.

[0188] Most integrated circuit (IC) manufacturing processes typically include several manufacturing steps that can successively form, shape, or otherwise modify various layers. One way to form a layer can be to deposit the layer and then etch it. Usually, etching can include forming an etching mask on the underlying layer. The etching mask can have a specific pattern that can mask certain portions of the underlying layer while exposing other portions. Then, by etching, the portions of the underlying layer exposed by the etching mask can be removed. In this way, the etching mask pattern can be transferred to the underlying layer.

[0189] Etching can include "wet" chemical etching and "dry" plasma etching. In many cases, plasma etching can provide higher controllability and greater directional control (e.g., anisotropy) if desired.

[0190] Therefore, plasma etching is currently used to process semiconductor materials for use in the manufacture of electronic devices. When used in electronic devices, small features can be etched on the surface of semiconductor materials to be more efficient or to improve certain properties. For example, deep trenches can be formed on the surface of silicon for use in microelectromechanical systems using plasma etching. This application suggests that plasma etching also has the potential to play a major role in the manufacture of microelectronics. Similarly, research is currently being conducted on ways to scale the process to the nanometer scale.

[0191] Plasma etching is typically performed in a so-called plasma etching chamber commonly used to etch one or more layers formed on a semiconductor substrate. During etching, the substrate is supported on a substrate support within the chamber.

[0192] During plasma etching, a plasma is formed above the surface of the substrate by supplying high-frequency (RF) electromagnetic radiation to a low-pressure gas (or gas mixture). By adjusting the potential of the substrate, the charged species in the plasma are directed to impinge on the surface of the substrate, thereby being able to remove material (e.g., atoms) therefrom.

[0193] Plasma etching can be made more effective by using a gas that chemically reacts with the material to be etched. So-called "reactive ion etching" combines the energy collision effect of the plasma and the chemical etching effect of the reactive gas.

[0194] The sintered ceramic body according to the present disclosure may be formed on a chamber component for use in a semiconductor plasma processing chamber. Such components may have advantages including an extension of the component life under aggressive etching conditions. Such a ceramic can be made dense and pure, especially in large dimensions, by sintering using the SPS process described above. The high-density ceramic can have many advantages associated with plasma processing. These advantages include resistance to particle generation, improvement of plasma etching resistance, and extension of the life of the component. In addition, the cleaning of high-density sintered ceramic parts may be made easier because it may be possible to use aggressive cleaning methods such as highly corrosive or aggressive chemicals.

[0195] Examples of chamber components that may include the sintered ceramic body according to the present disclosure include a substrate support assembly, an electrostatic chuck (ESC), a ring (e.g., a process kit ring or a single ring), a chamber wall, a base, a gas distribution plate, a showerhead, a liner, a liner kit, a shield, a plasma screen, a flow equalizer, a cooling base, a chamber viewport, a chamber lid, and the like.

[0196] As shown in FIG. 10, embodiments of the technology disclosed herein can be useful as components within a plasma processing system 9500 configured to be used in a semiconductor etching process, also referred to as a “plasma etching process system.” The plasma etching process system 9500 can include a remote plasma region. The remote plasma region can include a remote RF source / matching network 9502, also referred to as a remote plasma source (“RPS”).

[0197] The plasma etching processing system 9500 can include a vacuum chamber 9550 having a corrosion-resistant chamber liner (not shown), a vacuum source, and a chuck or electrostatic chuck ("ESC") 9509 on which a wafer 50, also referred to as a substrate, is supported. A covering or electrode cover 9514, an upper shield ring 9512, and a shield ring 9513 surround the wafer 50 and the pack 9509. In a physical vapor deposition (PVD) process, a substrate ring including the covering 9514 is provided around the substrate. The covering 9514 protects the sidewall surfaces and peripheral edges of the pack that would otherwise be exposed to the energized gas in the chamber from the deposition of process residues. Thus, the covering 9514 reduces the accumulation of process residues on the pack 9509 that would ultimately flake off and contaminate the substrate. The covering can also reduce the erosion of the pack 9509 by the excited gas. Providing the covering 9514 also allows the covering itself to be periodically removed from the chamber and cleaned, for example, with HF and HNO3, to remove the process residues that accumulate on the ring during the substrate processing cycle, thereby reducing the frequency with which the chuck and / or the pack 9509 need to be cleaned. The arrangement of the covering 9514 can be seen in FIG. 10, where the covering covers a portion of the support surface of the pack 9509. A further portion of the surface of the pack 9509 may be covered by the upper shield ring 9512 and / or the shield ring 9513. The upper plate / window / cover 9507 forms the upper wall of the vacuum chamber 9550. The showerhead 9517 either forms the upper wall of the vacuum chamber 9650 or is attached below the upper wall. The upper plate / window / cover 9507, the gas distribution system 9506, the showerhead 9517, the covering or electrode cover 9514, the upper shield ring 9512, the shield ring 9513, the chamber liner (not shown), and the chuck or ESC 9508 and the pack 9509 can be made in whole or in part from embodiments of a sintered ceramic body as disclosed herein.

[0198] A part of the surface of the shower head 9517 may be covered by a shield ring 9712. A part of the surface of the shower head 9517, particularly the radial side surface of the surface of the shower head 9517, may be covered by an upper shield ring 9710. The shield ring 9712, the cover ring 9517, and the upper shield ring 9710 can be made from a sintered ceramic body as disclosed herein.

[0199] The remote plasma source 9502 is provided outside the window 9507 of the chamber 9550 that houses the wafer 50 to be processed. The remote plasma region can be in fluid communication with the vacuum chamber 9550 via the gas supply system 9506. Inside the chamber 9550, a reactive plasma can be generated by supplying a processing gas to the chamber 9550 and supplying a high-frequency output to the plasma source 9502. By using the reactive plasma thus generated, a predetermined plasma treatment is performed on the wafer 50. Planar antennas having a predetermined pattern are widely used for the high-frequency antenna of the plasma etching processing system 9500.

[0200] As shown in FIG. 11, embodiments of the technology disclosed herein can be useful as components for use in a plasma processing system 9600, also referred to as a "deposition processing system", configured for use in a semiconductor deposition process. The volume processing system 9600 includes a vacuum chamber 9650, a vacuum source, and a chuck 9609 on which a wafer 50, also shown as a semiconductor substrate, is supported. The processing system can further include a nozzle or injector 9614 in fluid communication with a gas delivery system 9616 for supplying a processing gas into the interior of the vacuum chamber 9650. The upper wall 9700 of the chamber 9650 can include a central opening configured to receive a central gas injector (also referred to as a nozzle) 9614. In certain embodiments, the upper wall 9700 of the chamber can include an RF window or a dielectric window configured to have a central opening for housing the injector 9614. An RF energy source energizes the process gas to a plasma state and processes the substrate 50. Embodiments of the upper wall including the RF or dielectric window 9700, the gas delivery system 9616, and the central gas injector 9614 can be made entirely or in part from embodiments of a sintered ceramic body as disclosed herein.

[0201] System 9600 can further include an electrostatic chuck 9608 designed to hold the wafer 50. The chuck 9608 can include a pack 9609 for supporting the wafer 50. A portion of the support surface of the pack 9609 may be covered by a deposition ring 9615. Other names for the deposition ring 9615, such as a deposition shield or a deposition ring assembly, are to be construed as synonymous and may be used interchangeably herein. The deposition ring 9615 can be made entirely or in part from embodiments of a sintered ceramic body as disclosed herein.

[0202] The chuck 9609 may be formed wholly or in part from an embodiment of a sintered ceramic body as disclosed herein, and may have a chucking electrode disposed within the chuck proximate to the support surface of the chuck 9609 for electrostatically holding the wafer 50 when disposed thereon. The chuck 9608 may include a base 9611 having a ring shape extending for supporting the chuck 9609, and a shaft 9610 disposed between the base and the chuck for supporting the chuck above the base such that a gap is formed between the chuck 9609 and the base 9610, and the shaft 9610 supports the chuck proximate to the peripheral portion of the chuck 9609. The chuck 9608, the chuck 9609, and the deposition ring 9615 may be made wholly or in part from an embodiment of a sintered ceramic body as disclosed herein.

[0203] The present disclosure is illustrated by the following Examples section.

Examples

[0204] The following examples more clearly demonstrate the overall nature of the present disclosure. These examples are illustrative of the present disclosure and not limiting.

[0205] All particle size measurements were performed using a Horiba model LA-960 laser scattering particle size distribution analyzer capable of measuring particle sizes from 10 nm to 5 mm. Measurements of the specific surface area (SSA) of all starting powders, powder mixtures, and fired powder mixtures were performed using a Horiba BET surface area analyzer model SA-9601 capable of measuring with an accuracy of 10% or less over a specific surface area range of 0.01 to 2000 m 2 / g. Purity and impurities were measured using an Agilent 7900 ICP-MS model G8403 ICP-MS.

[0206] The characteristics of the gap and the radial dispersion of the average coefficient of thermal expansion (CTE) of at least one graphite material according to the embodiment are measured in a spark plasma sintering tool, the tool being a die including side walls including an inner wall and an outer wall, the inner wall having a diameter defining an internal volume, a die, an upper punch and a lower punch operably connected to the die, each of the upper punch and the lower punch having an outer wall defining a diameter smaller than the diameter of the inner wall of the die, whereby when at least one of the upper punch and the lower punch is moved within the internal volume of the die, a gap is generated between each of the upper punch and the lower punch and the inner wall of the die, the upper punch and the lower punch, and the sintering tool having a central axis, and the radial deviation from the average coefficient of thermal expansion of at least one graphite material is, as shown in FIG. 4, centered on the central axis 0.3×10 -6 / °C or less, preferably 0.2×10 -6 / °C or less, preferably 0.18×10 -6 / °C or less, preferably 0.1×10 -6 / °C or less, preferably 0.08×10 -6 / °C or less, preferably 0.06×10 -6 / °C or less.

[0207] The terms "apparatus" and "tool" are used interchangeably with respect to a spark plasma sintering apparatus.

[0208] All density measurements were performed according to ASTM B962-17 based on the Archimedes method known to those skilled in the art. Embodiments of oxide powders and the ceramics formed therefrom have been found to be essentially insulating high-resistance materials having a resistivity of about 1×10 +10 ohm-centimeters or more.

[0209] Comparative Example 1 4.5 to 6.5 m 2A polycrystalline ceramic sintered body with a maximum dimension of 406 mm was prepared from a crystalline powder of yttrium oxide having a specific surface area of / g, a d10 particle size of 1.5 to 3.5 μm, a d50 particle size of 4 to 6 μm, and a d90 particle size of 6.5 to 8.5 μm. This powder had a total impurity of about 14 ppm with respect to the total mass of the yttrium oxide powder when measured using ICPMS technology. The die of the spark plasma sintering tool was lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the tool and the upper and lower punches contained at least one graphite material disclosed herein. The powder was placed within the internal volume defined by the spark plasma sintering tool, and the tool had a gap of about 100 μm. The gap was configured between the inward-facing surface of at least one graphite foil and the outer walls of each of the upper and lower punches of the spark plasma sintering apparatus. 10 -2 ~10 -3 A vacuum condition of torr was generated inside the internal volume. The powder was sintered at 1400 °C for 30 minutes at a pressure of 20 MPa to form a disk-shaped sintered ceramic body having a maximum dimension or diameter of 406 mm. The overall density of the sample was measured to be 4.78 g / cc, or 95.03% of the theoretical density of yttrium oxide (reported as 5.03 g / cc). The density deviation was measured to be about 4.5% with respect to the highest density measurement value across the maximum dimension. The sintered ceramic body prepared according to the method of using an apparatus having a gap as disclosed in this example resulted in a low overall density, a high density deviation, and subsequent destruction of the sintered body.

[0210] Comparative Example 2: (Sample 363) High-purity (>99.99%) yttrium oxide and aluminum oxide powders were combined to form a powder mixture in a molar ratio that forms a sintered ceramic body containing a yttrium aluminum garnet (YAG) phase upon sintering. After performing wet tumble mixing as known to those skilled in the art, the powder was calcined at 1,000 °C for 10 hours. The calcined powder mixture had a specific surface area (SSA) of about 3.5 - 5.5 m2 / g, a d10 particle size of about 0.8 - 2 μm, a d50 particle size of about 90 - 110 μm, and a d90 particle size of about 240 - 250 μm. In certain embodiments, the firing conditions disclosed herein can result in aggregation of the powder mixture and thus may result in greater variability in the particle size distribution. Accordingly, in embodiments, the particle sizes referred to herein can include single particles, and in other embodiments, the particle sizes referred to herein can include aggregates of two or more particles or aggregates of multiple particles that can be measured as a single large particle using the laser particle size detection method disclosed herein.

[0211] The die of the spark discharge plasma sintering tool was lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the tool and the upper and lower punches included at least one graphite material disclosed herein. The calcined powder mixture was placed within the internal volume defined by the tool of the spark discharge plasma sintering tool, and the tool had a gap of about 50 - 70 μm at ambient temperature, the gap being configured between the inward-facing surface of at least one graphite foil and the respective outer walls of the upper and lower punches of the spark discharge plasma sintering apparatus. 10 within the internal volume -2 ~10 -3A vacuum condition of Torr was created, and a pressure of about 5 MPa was applied to form a powder compact having a packing density of about 50% from the calcined powder mixture. The powder compact within the internal volume was heated according to the method disclosed herein. During heating, the densification of the powder compact was not achieved by the sintering device during the heating process. Therefore, the radial variation of the average coefficient of thermal expansion (CTE) of at least one graphite material constituting the die and / or the upper punch and the lower punch was over the temperature range according to the method disclosed herein (from ambient temperature to the sintering temperature and / or up to the maximum operating temperature of the device of about 2000 °C) 0.3×10 -6 / °C exceeded. As a result, the required gap distance of 10 - 70 μm could not be maintained over the required temperature range from ambient temperature to the sintering temperature, which in this case was set to a predetermined value of 1450 °C. The sintered ceramic body produced according to this example cracked when removed from the tool and exhibited low density and thus low strength.

[0212] Example 1: (Sample 353) High-density and large-sized polycrystalline sintered ceramic body 6 - 8 m 2A sintered ceramic body with a maximum dimension of 406 mm was prepared from a crystalline powder of yttrium oxide having a specific surface area of / g, a d10 particle size of 1 - 3 μm, a d50 particle size of 4 - 6 μm, and a d90 particle size of 7.5 - 9.5 μm. The powder had a total impurity of about 25 ppm based on the total mass of the yttrium oxide powder. The die of the spark plasma sintering tool was lined with at least one graphite foil having the characteristics disclosed herein, and each of the die, the upper punch, and the lower punch contained at least one graphite material disclosed herein. Yttria powder was placed within an internal volume defined by a spark plasma sintering tool having a gap of about 50 - about 70 μm, whereby the gap was formed between the inward-facing surface of at least one graphite foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Pressure was applied to the yttrium oxide powder in advance in a multi-step process, with a pressure of about 10 MPa applied in advance under a vacuum of about 10-2 to 10-3 Torr to form a powder compact having a packing density of about 35 - 45 vol%. The powder compact was sintered at a temperature of 1550 °C for 60 minutes at a pressure of 20 MPa. The radial variation from the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper and lower punches was determined to be about 0.2×10 -6 / °C or less. When the average density was measured over five measurements, a density of 5.020 g / cc, i.e., 99.80% of the theoretical density of yttrium oxide (according to D.R. Lide, CRC Handbook of Chemistry and Physics 84th Edition, 2012 (「the CRC Handbook」), the theoretical density of yttrium oxide is 5.03 g / cm3) was measured. Therefore, a large-sized high-density sintered ceramic can be formed using an apparatus having a specific gap distance and radial variation as disclosed herein.

[0213] Example 2: (Sample 506) A large-sized polycrystalline YAG sintered ceramic body; with a specific surface area of 2 - 3 m 2 / g, yttria powder with a d10 particle size of 2.5 - 4.5 μm, a d50 particle size of 6 - 8 μm, and a d90 particle size of 11 - 13 μm (average purity 99.998%, average impurities being approximately 21 ppm relative to the total mass of the yttrium oxide powder), and a specific surface area of 6.5 - 8.5 m 2 / g, alumina powder with a d10 particle size of 0.75 - 1.5 μm, a d50 particle size of 2 - 5 μm, and a d90 particle size of 18 - 24 μm (purity 99.9994%, impurities being approximately 6 ppm relative to the total mass of the aluminum oxide powder) were blended in a molar ratio such that a sintered ceramic body containing a yttrium aluminum garnet (YAG) phase was formed. Ball milling known to those skilled in the art was carried out, and when fired at 1050 °C for 6 hours in air, the fired powder mixture had a specific surface area of 3.5 - 5.5 m 2It was measured to have a specific surface area of / g, a d10 particle size of 1 - 3.5 μm, a d50 particle size of 5 - 8 μm, and a d90 particle / aggregate size of 130 - 160 μm. In certain embodiments, the firing conditions disclosed herein may result in agglomeration of the powder mixture, and thus may result in greater variability in the particle size distribution. Thus, in embodiments, the particle sizes referred to herein can include single particles, and in other embodiments, the particle sizes referred to herein can include aggregates of two or more particles or aggregates of multiple particles that can be measured as a single large particle using the laser particle size detection method disclosed herein. The purity of the fired powder mixture was approximately the same as that of the raw material powder. The powder, powder mixture, and / or fired powder mixture may be sieved, tumbled, blended, and / or milled in various process steps according to known methods. The die of the spark plasma sintering apparatus was lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the apparatus and the upper and lower punches included at least one graphite material disclosed herein. The fired powder mixture was placed within an internal volume defined by a spark plasma sintering tool having a gap of about 30 - 50 μm. The gap is configured between the inward-facing surface of at least one graphite foil and the outer wall of each of the upper and lower punches of the sintering apparatus. The radial variation from the average coefficient of thermal expansion (CTE) centered on the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper and lower punches is about 0.1×10 -6 / °C or less was determined. The fired powder mixture was placed within an internal volume defined by the tool set of the sintering apparatus disclosed herein, and 10 -2 ~10 -3A Torr vacuum condition was created inside the volume. The calcined powder mixture inside the internal volume was heated to 800 °C at 5 °C / min, and a pressure of 5 MPa was applied at this temperature to form a powder compact having a packing density of about 40 - 50% by volume. Then, it was heated simultaneously at a heating rate of about 2 - about 3 °C / min, and the pressure was applied at a rate of about 0.2 - about 0.25 MPa / min to reach the sintering conditions of 1650 °C and 15 MPa for 60 minutes, forming a disk-shaped polycrystalline YAG sintered ceramic body with a maximum dimension of 622 mm. Density measurements were performed according to ASTM B962 - 17 from samples cut across the radius of the sample, and the density results are shown in Figure 15B. Five measurements were made at six positions along the radius, and an average density of 4.55 g / cc was measured, which corresponded to 99.78% of the theoretical value of YAG. The density across the radius was 99.7 - 99.9% of the theoretical value (reported as 4.556 g / cc for YAG). The density variation as shown in Figure 15B was measured with respect to the highest density measurement value along the radius, and a maximum density deviation of 0.21% was measured. During sintering of powders and powder mixtures using a spark plasma sintering apparatus as disclosed herein, the pressure and temperature are applied in a radially symmetric configuration about the central axis 9. Thus, properties such as high density (above 99% of the theoretical value of YAG) and minimum density deviation (less than 0.21%) are maintained across the radius and correspondingly across the diameter or maximum dimension of the sintered ceramic body. Thus, disclosed herein is a sintered ceramic body having an average density of 4.546 g / cc, with a density in the range of 99.7 - 99.9% of the theoretical density of YAG (a commercially available YAG sample was measured to obtain an average density of 4.556 g / cc, which was used as the theoretical density of YAG herein), and having a maximum density deviation of 0.21% or less across the diameter of the sintered ceramic body.

[0214] Example 3: (Sample 152) Polycrystalline yttrium oxide sintered ceramic body; A 100 mm sintered yttrium oxide body was formed at 6.5 - 8.0 m 2It was formed from yttrium oxide powder having a surface area of / g and a purity of 99.999% corresponding to an average total impurity of 18 ppm with respect to the total mass of the yttrium oxide powder. The d10 particle size was 1.5 - 3.5 μm, the median particle size (d50) was 4 - 6 μm, and the d90 particle size was 7.5 - 9.5 μm. The die of the spark plasma sintering apparatus was lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the apparatus and the upper punch and the lower punch included at least one graphite material disclosed herein. The yttrium powder was placed into the internal volume defined by the tool set of the sintering apparatus, and a vacuum condition of 10 -2 ~10 -3 Torr was created within the internal volume. The tool had a gap of about 25 - about 50 μm, and the gap was configured between the inward-facing surface of at least one graphite foil and the respective outer walls of the upper punch and the lower punch of the sintering apparatus. The radial variation of the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper punch and the lower punch was about 0.25×10 -6 / °C or less. Sintering was performed at 30 MPa at 1400°C for 30 minutes. Thereafter, annealing was performed at 1400°C in air for 8 hours. An average density of 5.02 g / cc was measured, which corresponded to 99.9% of the theoretical density of yttrium oxide (According to D.R.Lide, CRC Handbook of Chemistry and Physics 84 th Edition, 2012 (「the CRC Handbook」), the theoretical density of yttrium oxide is 5.03 g / cm 3 ).

[0215] Example 4 (Sample 329): Polycrystalline spinel sintered ceramic body: 99.9994% total purity corresponding to a total impurity of 6 ppm, 4 - 6 m 2 / g surface area, and magnesia powder having an average or d50 particle size of 3 - 4 μm, with a total purity of 99.9995% corresponding to a total impurity of 5 ppm, 6 - 8 m 2The surface area of / g and alumina powder having an average or d50 particle size of 2.5 to 4.5 μm were combined. The powders were weighed in relative amounts such that upon sintering, a powder mixture was produced in a molar ratio that forms spinel, MgAl2O4, having a cubic crystal structure. The powder mixture was wet tumble milled according to methods known to those skilled in the art. The powder mixture was calcined at 850 °C for 4 hours in an oxygen-containing environment and was measured to have a specific surface area of 5 to 6 m2 / g. The calcined powder mixture can optionally be sieved after calcination using methods known in the art. The die of the spark plasma sintering apparatus was lined with at least one graphite foil having the properties disclosed herein, and each of the die of the apparatus and the upper and lower punches included at least one graphite material disclosed herein. The calcined powder mixture was placed into the internal volume defined by the tool set of the sintering apparatus, and a vacuum condition of 10 -2 ~10 -3 Torr was created within the internal volume. The tool had a gap of about 20 to about 40 μm, which was configured between the inward-facing surface of at least one graphite foil and the respective outer walls of the upper and lower punches of the sintering apparatus. The radial variation from the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper and lower punches was about 0.1×10 -6It was determined that it was below / °C. Next, the calcined powder mixture was sintered under vacuum at a temperature of 1500 °C, a pressure of 20 MPa for 30 minutes according to the method disclosed in this specification to form a sintered ceramic body having a maximum dimension of 100 mm. The density of the sintered ceramic body was measured to be 3.546 g / cc or 99.04% of the theoretical density. Hardness measurement was performed on the sintered ceramic body using an applied load of 0.025 kgf according to ASTM C1327. Over 8 measurements, an average hardness of 15.06 GPa was measured with a standard deviation of 0.75. Thereafter, annealing was performed at 1500 °C and cooled passively in an air environment. The density of the annealed sintered ceramic body was measured to be 3.553 g / cc or 99.24% of the theoretical density (According to L. Ping et al., "Magnesium aluminate (MgAl2O4) spinel produced via self-heat-sustained (SHS) technique", Materials Research Bulletin 36 (2001), the theoretical density of magnesium aluminate spinel is 3.579 g / cm 3 is).

[0216] Example 5: High-density polycrystalline sintered ceramic body 2 - 3 m 2A sintered ceramic body with a maximum dimension of 406 mm was prepared from crystalline powder of yttrium oxide having a specific surface area of / g, a d10 particle size of 2.5 - 4 μm, a d50 particle size of 6 - 7.5 μm, and a d90 particle size of 11.5 - 13 μm. The powder had a total impurity of about 12 ppm with respect to the total mass of yttria powder. The die was lined with a graphite foil having the characteristics as disclosed in this specification, and each of the die and the upper and lower punches contained a graphite material as disclosed in this specification. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width of about 30 - about 50 μm, whereby the gap was formed between the inward surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. The pre-pressurization was performed in a multi-step process of pre-pressurizing at a pressure of about 10 MPa under vacuum to form a powder compact having a packing density of about 35 - 45 vol%. The powder compact was sintered at a temperature of 1550 °C for 60 minutes at a pressure of 20 MPa. The average density over 5 measurements was carried out, and a density of 5.020 g / cc, or 99.801% of the theoretical density of yttrium oxide (reported as 5.03 g / cc as disclosed in this specification) was measured.

[0217] Example 6: High-density polycrystalline sintered ceramic body 4.5 - 6 m 2 Crystalline powder of yttria having a specific surface area of / g and crystalline powder of alumina having a specific surface area of 3.5 - 5 m 2 / g were combined in a molar ratio that forms a yttrium aluminum garnet (YAG) phase during sintering. High-purity alumina media (>99.99% measured by ICPMS) was added at 50% by powder weight, and ethanol was added to form a slurry of about 40 vol%. Ball mill grinding using a rotational action centered on the horizontal axis was carried out for 12 hours, and then ethanol was extracted from the powder mixture using a rotary evaporator. After calcination at 1000 °C for 10 hours in air, the calcined powder mixture had a BET surface area of 7 - 8 m 2It was measured to have a specific surface area of / g, a d10 particle size of 0.75 - 1.75 μm, a d50 particle size of 90 - 110 μm, and a d90 particle size of 240 - 280 μm. The powder mixture can be sieved, blended, and / or milled in various process steps according to known methods. The die is lined with a graphite foil having the properties as disclosed herein, and each of the die and the upper and lower punches contains a graphite material as disclosed herein. The powder is placed within the internal volume of a spark plasma sintering tool having a gap width of about 50 - about 70 μm, whereby the gap is formed between the inward surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering device. The calcined powder mixture was sintered at 1550 °C for 60 minutes under a pressure of 20 MPa in a vacuum to form a sintered ceramic body with a maximum dimension of 406 mm. Density measurements were taken across the maximum dimension of the sintered body, and an average density of 4.543 g / cc was measured over 135 measurements, which corresponds to 99.709% of the theoretical density for YAG and a volume porosity of 0.291% calculated from the density measurements. The density was found to vary from 4.526 - 4.553 g / cc (or 99.335 - 99.936% of the theoretical value for YAG) across the maximum dimension of the polycrystalline sintered ceramic body, and the density deviation across the maximum dimension was determined to be 0.601%.

[0218] Example 7: Polycrystalline Sintered Ceramic Body of Large Dimensions 2 - 4 m 2 Crystalline powder of yttria having a specific surface area of / g (purity 99.9997% measured by ICPMS, reported above the reporting limit) and 6 - 8 m 2The crystalline powder of alumina having a specific surface area of / g (purity 99.9998% measured by ICPMS) was combined in a molar ratio that forms a yttrium aluminum garnet (YAG) phase during sintering. A high-purity alumina medium (>99.99% measured by ICPMS) was added at a loading of about 50% by powder weight, and ethanol was added to form a slurry of about 40% by volume. Ball milling was performed, and then ethanol was extracted from the powder mixture using a rotary evaporator. After calcination at 1050 °C for 6 hours in air, the calcined powder mixture had a specific surface area of about 3 - 5 m 2 / g, a d10 particle size of 1 - 3 μm, a d50 particle size of 3.5 - 6 μm, and a d90 particle size of 6 - 12 μm. It was measured to have. The calcined powder mixture can be sieved, blended, and / or ground in various process steps according to known methods. The purity of the calcined powder was measured using the ICPMS method known to those skilled in the art and had a total impurity content of about 7 ppm corresponding to a purity of about 99.9993%. The die was lined with a graphite foil having the properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The calcined powder mixture was placed within the internal volume of a spark plasma sintering tool having a gap width between about 40 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. A preliminary sintering pressure of 10 MPa was applied to the calcined powder mixture within the internal volume to form a powder compact having a packing density of about 45% by volume. The calcined powder mixture was sintered at 1600 °C for 60 minutes under a pressure of 15 MPa in a vacuum to form a sintered ceramic body with a maximum dimension of 616 mm. Density measurement was performed according to ASTM B962 - 17 using Archimedes' principle, and for the sintered ceramic body, an average density of 99.1% of the theoretical density of YAG (4.556 g / cc) was measured.

[0219] Example 8: Zirconia Toughened Alumina (ZTA) Sintered Body Weigh zirconia powder having a specific surface area of 6 - 8 m2 / g, a d10 particle size of 0.5 - 0.2 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 1.2 - 3 μm, and alumina powder having a specific surface area of 6 - 8 m2 / g, a d10 particle size of 0.05 - 0.15 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 0.4 - 1 μm, and combine them to produce a powder mixture in a molar ratio that forms a zirconia-reinforced aluminum phase during sintering. The zirconia was present in an amount of about 16% by volume. The zirconia powder contained about 2 - 4 mol% of HfO2 and was stabilized with yttria in an amount of about 3 mol%. HfO2 is present in many commercially available zirconia powders, and it is known to those skilled in the art that yttria stabilizes zirconia. Therefore, yttria and hafnia are not considered impurities in the zirconia disclosed herein. Except for Hf and Y, the zirconia powder had a total impurity of about 20 ppm. These powders were combined in a ratio that forms a composite oxide layer containing about 16% by volume of zirconia and the balance of alumina during sintering. The powder mixture containing zirconia and yttria was transferred to a container for wet ball milling. The powder mixture contained zirconia and yttria without using a sintering aid such as MgO or silica. Therefore, disclosed herein is a sintered ceramic body containing a zirconia-alumina layer that does not contain or substantially does not contain a sintering aid. A high-purity (>99.99%) alumina medium was used at a loading of about 75 - 80% relative to the powder weight, and ethanol was added to the container to form a slurry and promote mixing. In other cases, ball milling may be carried out using water or under dry conditions using only alumina or zirconia media. Ball milling using a rotational action centered on the horizontal axis was carried out at 150 rpm for 20 hours, and then ethanol was extracted from the powder mixture using a rotary evaporator. The powder mixture was calcined at 600°C for 8 hours. The calcined powder mixture can be optionally sieved, tumbled, blended, etc. after calcination, as is known to those skilled in the art.The die of the spark plasma sintering apparatus is lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the apparatus and the upper punch and the lower punch contains at least one graphite material disclosed herein. The calcined powder mixture was placed in an internal volume defined by a spark plasma sintering tool having a gap of about 25 to about 45 μm. The gap is configured between the inward-facing surface of at least one graphite foil and the outer wall of each of the upper punch and the lower punch of the sintering apparatus. The radial variation from the average coefficient of thermal expansion (CTE) centered on the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper punch and the lower punch is about 0.1×10. -6 / °C or less was determined. The calcined powder mixture was placed in an internal volume defined by the tool set of the sintering apparatus disclosed herein, and a vacuum condition of 10 -2 ~10 -3 Torr was created inside the volume. A pressure of about 5 MPa was applied to form a powder compact having a packing density of about 40 to 50% by volume. The fired powder mixture in the internal volume was heated to 800°C at 5 to 10°C / min, and then simultaneously, heat was applied at a heating rate of about 3 to about 5°C / min and pressure was applied at a rate of about 0.2 to about 0.25 MPa / min to reach the sintering conditions of 1450°C, 20 MPa, and 30 minutes according to the method disclosed herein, forming a sintered body with a dimension of 150 mm. The densities for embodiments of the ZTA sintered ceramic body are reported in the following table. The sintered ceramic body disclosed herein may include a particulate composite of crystalline phases of zirconia and alumina in an amount by volume as disclosed. The particulate composite can include particles or regions of zirconia dispersed in a matrix of alumina, the particulate composite includes two distinct crystalline phases, and preferably the sintered ceramic body does not form a solid solution. Since yttria and zirconia exist as separate phases, the rule of mixture by volume can be applied to calculate the theoretical density as reported below.

[0220]

Table 11

[0221] In a series of examples, a ZTA sample 365 containing 20% by volume of zirconia and 80% by volume of alumina was prepared according to Example 8 and sintered at 1450 °C for 30 minutes under a pressure of 20 MPa. A ZTA sample 562 containing approximately 16% by volume of zirconia and approximately 84% by volume of alumina was prepared according to Example 8 and sintered at 1500 °C for 30 minutes under a pressure of 15 MPa as listed below.

[0222]

Table 12

[0223] Example 9: (Sample 421) Multilayer sintered ceramic body of large dimensions A multilayer sintered ceramic body was formed from the first and second powder mixtures. The first powder mixture contained alumina and zirconia and formed a particle composite of the crystal phases of zirconia and alumina in a volume amount as disclosed according to Example 8. The second powder contained alumina and yttria and formed a layer containing the YAG phase. The first powder mixture contained alumina powder, and the alumina powder had a specific surface area of 6 - 8 m2, 6 - 8 m 2has a surface area of 6 - 8 m² / g, a d10 particle size of 0.05 - 0.15 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 0.4 - 1 μm, and the zirconia powder has a surface area of 6 - 8 m² / g, a d10 particle size of 0.5 - 0.2 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 1.2 - 3 μm. The total impurity content of the alumina powder was about 2 - 10 ppm. The zirconia powder contained about 2 - 4 mol% of Hf and was stabilized with about 3 mol% of yttria. Hf and Y are not considered impurities in the zirconia disclosed herein. Except for Hf and Y, the zirconia powder had a total impurity of about 20 ppm. The powders were combined in a ratio such that at least one particle composite layer containing about 16% by volume of zirconia and the balance alumina was formed during sintering. Alumina powder and zirconia powder were mixed to produce a powder mixture using a conventional powder preparation technique of wet ball milling using a high-purity (>99.99%) alumina medium at a loading of about 75 - 80% based on the powder weight. Ethanol was added to form a slurry of about 40% by volume. The slurry was ball milled at about 150 RPM for about 20 hours and then dried, tumbled, and sieved according to methods known to those skilled in the art to form a first powder mixture. The first powder mixture was calcined at 600 °C for 8 hours. The first calcined powder mixture 2 had a specific surface area of 6 - 8 m² / g. The first calcined powder mixture had a total impurity of about 15 ppm and contained Si of about 14 ppm or less and Mg in an amount of about 5 ppm or less. The powder mixture may be sieved, tumbled, blended, etc., as known to those skilled in the art.

[0224] The second powder mixture is an alumina powder with a specific surface area of 6 - 8 m² / g, a d10 particle size of 0.05 - 0.15 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 0.4 - 1 μm, and a specific surface area of 2 - 3 m² / g 2 / g, a zirconia powder having a d10 particle size of 0.05 - 0.15 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 0.4 - 1 μm 2 / g, with a d10 particle size of 2 - 4 μm, a d50 particle size of 6 - 8 μm, and a d90 particle size of 11 - 13 μm. The total impurity content of the alumina and yttria powders was about 2 - 10 ppm. The powders were combined in a ratio such that a corrosion-resistant layer containing YAG (yttrium aluminum oxide, garnet phase) was formed during sintering. Using a conventional powder preparation technique of wet ball milling with a high-purity (>99.9%) medium used at a loading of about 60% by powder weight, alumina powder and yttria powder were combined to produce a second powder mixture. Ethanol was added to form a slurry of about 40% by volume. The slurry was milled at 150 RPM for about 15 hours and then dried, tumbled, or sieved according to methods known to those skilled in the art to form a first powder mixture. The second powder mixture was calcined at 850 °C for 6 hours. The second calcined powder mixture had a specific surface area of 2 - 4 m 2 / g and a d50 particle size of 9 - 13 μm. The second calcined powder mixture had a total impurity of about 8 ppm and can be sieved, tumbled, blended, etc., as known to those skilled in the art.

[0225] The die of the spark plasma sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The radial variation from the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper and lower punches was about 0.08×10 -6 / °C or less. The first and second calcined powder mixtures were placed separately to form at least two separate layers within the internal volume of a spark discharge plasma sintering tool having a gap width of about 25 - about 45 μm, whereby the gap was formed between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus.

[0226] The first and second calcined powder mixtures were sintered at 15 MPa and a temperature of 1600 °C for 60 minutes to form a multi-layer sintered ceramic body including at least two layers containing YAG and ZTA with a maximum dimension of 572 mm. Due to the multi-layer structure including regions of different densities, density measurement could not be accurately performed on the multi-layer body.

[0227] An additional multi-layer sintered ceramic body including at least two layers containing YAG and ZTA with a maximum dimension of 622 mm was prepared according to Example 9 and sintered at 15 MPa at 1625 °C for 60 minutes.

[0228] Example 10: (Sample 477) Multi-layer sintered ceramic body of large dimensions A multi-layer sintered ceramic body was formed from the first and second powder mixtures. The first powder mixture included alumina and zirconia and formed zirconia toughened alumina (ZTA) according to Example 8. The second powder mixture contained about 20 mol% zirconia and the balance yttria.

[0229] The first powder mixture was alumina powder having a specific surface area of 6 - 8 m 2 / g, a d10 particle size of 0.05 - 0.15 μm, a d50 particle size of 0.2 - 0.5 μm, and a d90 particle size of 0.4 - 1 μm, and 6 - 8 m 2It contained zirconia powder having a surface area of 0.5 to 0.2 μm for d10 particle size, 0.2 to 0.5 μm for d50 particle size, and 1.2 to 3 μm for d90 particle size. The total impurity content of the alumina powder was about 2 to 10 ppm. The zirconia powder contained about 2 to 4 mol% of Hf and was stabilized with about 3 mol% of yttria. HfO2 is present in many commercially available zirconia powders, and it is known to those skilled in the art that yttria stabilizes zirconia. Therefore, yttria and hafnia are not regarded as impurities in the zirconia disclosed herein. Excluding Hf and Y, the zirconia powder had a total impurity of about 20 ppm. The first powder mixture contained zirconia and alumina without adding a sintering aid such as MgO or silica. Therefore, disclosed herein is a multilayer sintered ceramic body including a zirconia alumina (zta) layer that does not contain or substantially does not contain a sintering aid. These powders were combined in a ratio such that a layer containing about 16% by volume of zirconia and the balance of alumina was formed during sintering. Using a conventional powder preparation technique of wet ball milling with a high-purity (>99.99%) alumina medium at a loading of about 75 to 80% based on the powder weight, alumina powder and zirconia powder were combined to produce a first powder mixture. Ethanol was added to form a slurry of about 40% by volume. The slurry was ball milled at about 150 RPM for about 20 hours and then dried, tumbled, and sieved according to methods known to those skilled in the art to form the first powder mixture. The first powder mixture was calcined at 900 °C for 6 hours. The specific surface area of the first calcined powder mixture was 5 to 7 m 2 / g. The first calcined powder mixture had a total impurity of about 15 ppm and contained Si of about 14 ppm or less and Mg of less than about 5 ppm. The powder mixture may be sieved, tumbled, blended, etc., as known to those skilled in the art.

[0230] The second powder mixture had a surface area of 6 to 8 m 2 / g, zirconia powder having a d10 particle size of 0.5 to 0.2 μm, a d50 particle size of 0.2 to 0.5 μm, and a d90 particle size of 1.2 to 3 μm, and 2 to 3 m 2It contained yttria powder having a specific surface area of / g, a d10 particle size of 2 - 4 μm, a d50 particle size of 6 - 8 μm, and a d90 particle size of 11 - 13 μm. The total impurity content of the zirconia and yttria powders was about 2 - 10 ppm. Si and Mg were not detected in the yttria and zirconia powders using ICPMS known to those skilled in the art. Thus, the yttria and zirconia powders contained Si in the form of silica, calcia, Li / lithium fluoride, and magnesia at about 14 ppm or less, and Ca, Li, and Mg at about 5 ppm or less, respectively. These powders were combined in a ratio such that a layer containing at least one crystal phase containing 20 mol% zirconia and the balance yttria was formed during sintering. Mixing the zirconia powder and the yttria powder to produce a second powder mixture was carried out using a conventional powder preparation technique of wet ball milling using a 3 mol% yttria-stabilized zirconia medium at an addition amount of about 90% based on the powder weight. Ethanol was added to form a slurry of about 40% by volume. The slurry was milled at 150 RPM for about 12 hours and then dried, tumbled, or sieved according to methods known to those skilled in the art to form a second powder mixture. The second powder mixture was calcined at 850 °C for 6 hours. The second calcined powder mixture had a specific surface area of 2 - 4 m 2 / g and a d50 particle size of 6 - 10 μm. The second calcined powder mixture had a total impurity of about 8 ppm and contained Si at about 14 ppm or less and Mg at about 5 ppm or less, in the form of silica and magnesia, respectively. The second powder mixture may be sieved, tumbled, blended, etc., as known to those skilled in the art.

[0231] The die of the spark plasma sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The radial variation from the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper and lower punches was about 0.08×10 -6It was determined to be below / ℃. The first and second calcined powder mixtures were separately placed to form at least two separate layers within the internal volume of a spark plasma sintering tool having a gap width of about 25 to about 45 μm, and the gap was configured between the inward surface of at least one foil and the outer walls of each of the upper punch and the lower punch of the sintering apparatus.

[0232] The first and second calcined powder mixtures were separately placed within the internal volume defined by the tool set of the sintering apparatus disclosed herein to form a multi-layer sintered ceramic body including at least two separate layers.

[0233] The first and second calcined powder mixtures were sintered at a temperature of 1500 °C at 15 MPa for 45 minutes to form a multi-layer sintered ceramic body having a maximum dimension of 150 mm. Due to the multi-layer structure including regions of different densities, accurate density measurement could not be performed.

[0234] Example 11: 80 mol% yttria - 20 mol% zirconia sintered ceramic body 6 - 8 m 2 Powder of yttria having a surface area of / g and powder of zirconia having a surface area of 6 - 8 m 2 / g were weighed and mixed to prepare a powder mixture in a ratio of 80 mol% yttria and 20 mol% zirconia. The purity of the yttria powder was more than about 99.998% with respect to 100% pure yttria, and the purity of the zirconia powder was more than about 99.79% with respect to 100% pure zirconia. Ethanol in an amount of 50% by powder weight was added, and a zirconia medium in an amount of 100% by powder weight was added to the powder mixture to form a slurry. The slurry was placed in a shaft rotation ball mill at 80 - 90 RPM for 12 hours, and then the slurry was taken out of the mill. Ethanol was extracted from the slurry using a rotary evaporator, leaving the powder mixture, which was calcined in air at 1000 °C for 8 hours. The powder mixture may optionally be sieved, tumbled, blended, etc. according to known methods after calcination.

[0235] The die of the spark discharge plasma sintering apparatus is lined with at least one graphite foil having the characteristics disclosed herein, and each of the die of the apparatus and the upper punch and the lower punch contains at least one graphite material disclosed herein. The radial variation from the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper punch and the lower punch is about 0.08×10 -6 / °C or less was determined. A powder mixture calcined with yttria and zirconia was placed into the internal volume defined by the tool set of the sintering apparatus, and a vacuum condition of 10 -2 ~10 -3 Torr was created within the internal volume. The tool has a gap of about 25 to about 45 μm, and the gap is configured between the inward-facing surface of at least one graphite foil and the outer wall of each of the upper punch and the lower punch of the sintering apparatus. The radial variation of the average coefficient of thermal expansion (CTE) about the central axis of the sintering tool of at least one graphite material constituting the die and / or the upper punch and the lower punch is about 0.2×10 -6 / °C or less was determined. To form a 100 mm sintered ceramic body, sintering was performed at 1500 °C for 30 minutes at 30 MPa under vacuum according to the method disclosed herein. Thereafter, annealing was performed at 1200 °C for 8 hours in air. Over five measurements, the average density was calculated to be 5.135 g / cc.

[0236] A further sintered ceramic body containing 90 mol% yttria and 10 mol% zirconia was prepared according to the materials, apparatus, and method of Example 11.

[0237] The following yttrium oxide samples H1 / 66 to H4 / 152 according to embodiments of the present invention were prepared according to the present disclosure.

[0238] H1 / 66: An 80 mm yttrium oxide sintered body was formed at 2.5 to 3.5 m 2It was formed with a powder purity of 99.9952% from a powder having a surface area of / g, a d50 particle size of 5.4 μm, and <10 ppm of TREO (total rare earth oxides) and 48 ppm of total impurities. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 50 and about 70 μm, whereby the gap was configured between the inward surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. The body was formed at a sintering temperature of 1500 °C for 60 minutes at 30 MPa. Annealing was performed in air at a temperature gradient of 5 °C / min to 1450 °C for 1 hour and then at 1400 °C for 8 hours. The density of the yttrium oxide sintered body was 4.948 g / cm 3 and the maximum pore diameter was 1.1 μm. The d10, d50, and d90 particle sizes were measured to be 0.5, 0.8, and 1.4 μm, respectively.

[0239] H2 / 65: A 40 mm yttrium oxide sintered body was subjected to 6.5 - 7.5 m 2It was formed from a powder having a surface area of / g. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 40 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering was performed at 30 MPa at a sintering temperature of 1550 °C for 10 minutes. Annealing was performed in a furnace at a temperature of 1300 °C in air for 4 hours. The starting yttrium oxide powder had a total purity of 99.999% corresponding to 10 ppm. The median particle size was measured to be 5.82 μm. The yttrium oxide sintered body had a total impurity level of 11 ppm. The purity of the starting powder was maintained in the sintered yttrium oxide body, indicating that there were very few or no contaminants introduced during the process. The d10, d50, and d90 particle sizes were measured to be 4.0, 13.0, and 27.1 μm, respectively, and the average particle size was measured to be 14 μm.

[0240] H3 / 79: A 40 mm yttrium oxide sintered body, 2.5 to 3.5 m 2It was formed from a powder having a surface area of / g and a median (d50) particle size of 5.17 μm. The starting powder had a total impurity of 2 - 4 ppm. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width of about 40 - about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. The sintering of the yttrium oxide body was carried out using a sintering temperature of 1500 °C for 10 minutes at a pressure of 30 MPa. The temperature was raised at 50 °C / min while the pressure was applied at 5 MPa / min. Annealing was carried out by raising the temperature to 1300 °C at 5 °C / min and holding for 4 hours in air. The sintered yttrium oxide body had a total impurity level of 9 - 10 ppm, indicating that the introduction of contaminants as a result of the process was minimal. The maximum pore diameter was measured to be 0.6 μm, and the density was measured to be 5.03 g / cc. The d10, d50, and d90 particle sizes were measured to be 0.8, 1.4, and 2.4 μm, respectively. The average particle size of 1.47 μm was also measured.

[0241] H4 / 152: A 100 mm yttrium oxide sintered body was 6 - 8 m 2 It was formed from a powder having a surface area of / g, a TREO purity of 99.999% (<10 ppm), and an average total impurity of 18 ppm. The median particle size (d50) was 4.65 μm. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width of about 30 - about 50 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering was carried out at 30 MPa and 1400 °C for 30 minutes. Thereafter, annealing was carried out in air at 1400 °C for 8 hours. 5.024 g / cm 3The density was measured and the maximum pore size was 2 μm. After the two-step CF4 / O2 etching process disclosed herein, an average step of 0.98 μm, an average etching rate of 0.68 nm / min, and an etching volume of 340,000 μm 3 were obtained. Before and after the two-step CF4 / O2 etching process as disclosed herein, arithmetic mean heights (Sa) of 10 and 14 nm were measured, respectively. After the oxygen etching process disclosed herein, an average step of 0.1 μm, an average etching rate of 0.07 nm / min, and an etching volume of 30,000 μm 3 were obtained. After the SF6 etching process as disclosed herein, an average step of 0.28 μm, an average etching rate of 0.19 nm / min, and an etching volume of 90,000 μm 3 were obtained.

[0242] Single-step, CF4 etching procedure To evaluate the etching performance, polished ceramic samples with dimensions of 6 mm × 6 mm × 2 mm were placed on a c-plane sapphire wafer using a silicone-based heat sink compound. The areas of each part were blocked from exposure to the etching process by bonding a 5 mm × 5 mm square of sapphire ceramic to the sample surface.

[0243] The dry etching process was performed using a Plasma-Therm Versaline DESC PDC Deep Silicon Etch, a standard device in the industry. The etching was completed with a total duration of 24 hours in 4-hour etching segments. This process was carried out at a pressure of 10 millitorr, a CF4 flow rate of 90 standard cubic centimeters per minute (sccm), an oxygen flow rate of 30 sccm, and an argon flow rate of 20 sccm. The bias was 600 volts and 2000 watts of ICP power. This etching recipe corresponds to a silicon etching rate of 512 nm / min. The etching recipe etches fused silica (quartz glass) at a rate of 72 nm / min. The etching conditions used here to evaluate sample performance were selected to subject the disclosed materials to extreme etching conditions in order to distinguish performance.

[0244] At the completion of the etching procedure, the surface roughness was measured.

[0245] Single-step, CF4 etching volume procedure: In one embodiment, the yttrium oxide sintered body has an etching volume of less than about 12000 μm 3 preferably less than about 9000 μm 3 more preferably less than about 7000 μm 3 This etching volume is characterized by an etching volume of less than. This etching volume is realized when a sample with dimensions of 6 mm × 6 mm × 2 mm is subjected to an etching process as a reference process under etching conditions of 24 hours at a pressure of 10 millitorr, a CF4 flow rate of 90 standard cubic centimeters per minute (sccm), an oxygen flow rate of 30 standard cubic centimeters per minute (sccm), an argon flow rate of 20 standard cubic centimeters per minute (sccm), a bias of 600 volts, and an ICP power of 2000 watts. Each etching process will be described in more detail in the following experimental section. Thus, the etching volume is related to the volume of the yttrium oxide body removed during the indicated etching process.

[0246] Single-step, CF4 etching rate procedure: In some embodiments, the yttrium oxide body is characterized by an etching rate of less than about 0.08 nm / min, preferably less than about 0.06 nm / min, more preferably less than about 0.05 nm / min. This etching rate is achieved when a sample with dimensions of 6 mm × 6 mm × 2 mm is subjected to a single-step CF4 etching process as a reference process under etching conditions with a pressure of 10 millitorr, a CF4 flow rate of 90 standard cubic centimeters per minute (sccm), an oxygen flow rate of 30 standard cubic centimeters per minute (sccm), an argon flow rate of 20 standard cubic centimeters per minute (sccm), a bias of 600 volts, and an ICP power of 2000 watts for a duration of 24 hours. Thus, the etching rate is related to the reduction in the thickness of the yttrium oxide body removed during the indicated etching process.

[0247] Single-step CF4 Sdr procedure (unetched, etched) In some embodiments, the yttrium oxide sintered body has a developed interface area ratio in the unetched region of less than 100×10 -5 less than, more preferably less than 75×10 -5 less than, most preferably less than 50×10 -5 compared to a developed interface area ratio in a region of less than 600×10 -5 less than, more preferably less than 500×10 -5 less than, more preferably less than 400×10 -5 less than, most preferably less than 300×10 -5 less than, most preferably less than 200×10 -5It is characterized by having a developed interface area ratio in the etching area less than [specific value]. This latter developed interface area ratio is realized when a yttrium oxide sample with dimensions of 6 mm × 6 mm × 2 mm is subjected to a CF4 etching process under etching conditions of a pressure of 10 mTorr, a CF4 flow rate of 90 standard cubic centimeters per minute (sccm), an oxygen flow rate of 30 standard cubic centimeters per minute (sccm), an argon flow rate of 20 standard cubic centimeters per minute (sccm), a bias of 600 volts, and an ICP power of 2000 watts for 24 hours. Each etching process will be described in more detail below.

[0248] Single-step CF4 Sa (not etched, etched) In some embodiments, the yttrium oxide sintered body has an arithmetic mean height Sa of less than 30 nm, more preferably less than 28 nm, and most preferably less than 25 nm in accordance with item 4.1.7 of ISO standard 25178-2-2012, and further characterized by having an arithmetic mean height Sa of less than 40 nm, more preferably less than 35 nm, and most preferably less than 30 nm in accordance with item 4.1.7 of ISO standard 25178-2-2012. This latter arithmetic mean height Sa is realized when an etching process is performed on a yttrium oxide sample with dimensions of 6 mm × 6 mm × 2 mm under etching conditions of a pressure of 10 mTorr, a CF4 flow rate of 90 standard cubic centimeters per minute (sccm), an oxygen flow rate of 30 standard cubic centimeters per minute (sccm), an argon flow rate of 20 standard cubic centimeters per minute (sccm), a bias of 600 volts, and an ICP power of 2000 watts for 24 hours. Each etching process will be described in more detail below.

[0249] Measurement of surface roughness The measurement of surface roughness was carried out using a Keyence 3D laser scanning confocal digital microscope model VK-X250X under the environmental conditions of a class 1 clean room. The microscope was placed on a TMC tableTop CSP desktop passive vibration isolation table having a natural vibration frequency of 2.8 Hz.

[0250] This non-contact system uses a laser beam of light and an optical sensor to analyze the surface via the intensity of the reflected light. The microscope acquires a total of 786,432 data points with 1,024 data points in the x direction and 786 data points in the y direction. When a given scan is completed, the objective lens is moved at a set pitch in the z direction, and the intensity is compared between scans to determine the focus. ISO 25178 Surface Texture (Areal Roughness Measurement) is an international standard set related to the analysis of surface roughness, and this microscope complies with it.

[0251] The surface of the sample was laser scanned at a magnification of 10 using a confocal microscope to take a detailed image of the sample. The line roughness was obtained from the profiles of seven segmented blocks. Lambda k (λ), which represents the measurement sampling length, was adjusted according to ISO specification 4288: Geometrical Product Specifications (GPS) - Surface Texture: Profile Method - Rules and Procedures for the Evaluation of Surface Texture so that the line readings were limited to measurements from five of the seven central blocks.

[0252] The area was selected within the etched and masked area of the sample for measurement. The area was selected to most represent a typical sample surface and was used to calculate Sa and Sdr.

[0253] Surface roughness Sa and Sdr are parameters well known in the underlying technical field and are described, for example, in ISO standard 25178-2-2012, Sections 4.1.7 (Surface roughness Sa) and 4.3.2 (Surface roughness Sdr).

[0254] Step measurement The steps resulting from the etching process were directly measured by using a Keyence 3D laser scanning confocal digital microscope model VK-X250X at a magnification of 20. Separate reference planes were created using the selected areas of the etched and unetched regions of the sample. The difference in the average height over three measurements between these reference planes can be regarded as the step.

[0255] Calculation of Etching Rate The average etching rate (unit: nanometer / hour) can be calculated from the average step by dividing the step by the total etching time to obtain the etching rate (unit: nanometer / minute).

[0256] Volume Measurement The etched volume was calculated from the measured values at 50 times magnification of the Keyence 3D laser scanning confocal digital microscope model VK-X250X. A 7×7 image template was created, and a 7×1 area was selected for measurement. First, a reference plane is established on a representative area of the masked and thus unetched sample. To establish the reference plane, an area within the masked area is selected. To account for variations in sample thickness and mounting, software-based tilt correction is completed across the area. Then, in the etched area of the image that is at the maximum distance from the masked surface, a total area of 600 μm × 200 μm is selected. The height of the etched surface compared to the reference plane created on the masked surface is measured, and the volume of material removed by etching relative to the reference plane is calculated across the selected area.

[0257] Difference between Ra Measurement Value and Sa Measurement Value Sa is the arithmetic mean height of the surface and is described in ISO 25178: Geometric Product Specifications (GPS) - Surface Texture: Areal, which is an international standard collection of the International Organization for Standardization regarding the analysis of 3D areal surface texture. This is based on the non-contact laser microscopy method.

[0258] Ra represents the arithmetic mean roughness of a 2D profile according to ISO 4287:1997 Geometric Product Specifications (GPS) - Surface Texture: Profile Method. This is based on a mechanical stylus that contacts the surface to create a linear profile.

[0259] Sa represents the height difference across a 3D measured surface, while Ra represents the height difference across a 2D linear profile scan.

[0260] Ra is limited by the geometry of the stylus tip, and thus the details of fine features may be lost and distortion may occur at peaks and valleys. This is a problem when measuring fine sub-micron features and a limitation in the use of the Ra value for comparison with the Sa value.

[0261] Additional samples were prepared according to the method of the present invention and summarized in the following table. Where applicable, they were compared with commercially available quartz (TSC03) and comparative yttrium oxide samples (107, 108, and 118).

[0262] In one example, Sample 188-1 was prepared as follows. Yttrium oxide powder having a surface area of 2 - 3 m 2 / g and a total impurity of 13 ppm corresponding to a powder purity of 99.9987% was used to form a 100 mm yttrium oxide sintered body. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width of between about 30 and about 60 μm, whereby the gap was configured between the inward surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Preloading of the pressure was performed in a multi-step process, and a pressure of 20 MPa was preloaded under vacuum. Thereafter, 5 MPa was applied while heating from room temperature to 600 °C at a rate of 10 °C / min. The pressure was increased to 30 MPa between 600 °C and the sintering temperature at a rate of 10 °C / min. Sintering was performed at a temperature of 1400 °C and a pressure of 30 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was shut off to allow natural cooling. Annealing was performed at a temperature of 1400 °C for 8 hours in an oxygen-containing environment. The density was 5.002 g / cm 3 and was.

[0263] In another example, Sample 116 was prepared as follows. 6.5 - 7.5 m 2A 40 mm yttrium oxide sample was formed from a powder having a surface area of / g. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 40 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Sintering was performed at 30 MPa at a sintering temperature of 1550 °C for 10 minutes. Annealing was performed for 9 hours in a furnace at a temperature of 1400 - 1450 °C in air. The starting yttrium oxide powder had a total purity of 99.999% corresponding to 10 ppm. The median particle size was measured to be 5.82 μm. The yttrium oxide sintered body had a total impurity level of 11 ppm. The purity of the starting powder was maintained in the sintered yttrium oxide body, indicating that very few or no contaminants were introduced during processing. The d10, d50, and d90 particle sizes were measured to be 0.7, 6.7, and 25.4 μm, respectively.

[0264] In another example, sample 224 was made as follows. 5 - 6 m 2Yttrium oxide powder with a surface area of / g and an average of 8 ppm total impurities corresponding to a powder purity of 99.9992% was used to form a 100 mm yttrium oxide sintered body. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. The pressure was pre-applied at 20 MPa for about 5 minutes to establish a 50 millitorr vacuum. Thereafter, the pressure was reduced to 5 MPa and heated to 600 °C at a rate of 10 °C / min. Heat and pressure were simultaneously applied to reach a pressure of 20 MPa, and the temperature was increased to 1400 °C at a rate of 10 °C / min. Sintering was carried out at a temperature of 1400 °C and a pressure of 20 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was shut off to allow natural cooling. The yttrium oxide sintered bodies had d10, d50 and d90 particle sizes of 0.4, 0.7, and 1.2 μm, respectively.

[0265] In another example, Sample 189-1 was made as follows. 4.2 m corresponding to a powder purity of 99.9975% 2Using yttrium oxide powder with a surface area of / g and total impurities of 24.8 ppm, a 100 mm yttrium oxide sintered body was formed. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width of between about 30 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Applying pressure in advance was performed in a multi-step process, and a pressure of 20 MPa was applied in advance under vacuum. Then, while applying 5 MPa, heat was applied from room temperature to 600 °C at a rate of 10 °C / min. The pressure was increased to 30 MPa between 600 °C and the sintering temperature at a rate of 10 °C / min. Sintering was performed at a temperature of 1400 °C and a pressure of 30 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was shut off to allow natural cooling. Annealing was performed at a temperature of 1400 °C for 8 hours in an oxygen-containing environment. The impurity concentration of the obtained yttrium oxide sintered body was 36 ppm and the purity was 99.996%. The density of the annealed and sintered yttrium oxide body was 5.006 g / cm 3 and had a maximum pore diameter of 0.7 microns. After the two-step CF4 / O2 etching process disclosed herein, an average step of 0.82 μm, an average etching rate of 0.57 nm / min, and an etching volume of 270,000 μm 3 were obtained.

[0266] In another example, sample 045 was prepared as follows. Corresponding to a powder purity of 99.9974%, 9 - 10 m 2Using yttrium oxide powder with a surface area of / g and a total impurity of 26 ppm, a 100 mm yttrium oxide sintered body was formed. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed in this specification, and each of the die and the upper and lower punches contained the graphite material disclosed in this specification. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 60 μm, whereby the gap was formed between the inward surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Applying pressure in advance was carried out in a multi-step process in which a pressure of 20 MPa was applied in advance under vacuum as disclosed in this specification. Then, while applying 5 MPa, it was heated from room temperature to 600 °C at a rate of 10 °C / min. The pressure was increased to 30 MPa between 600 °C and the sintering temperature at a rate of 10 °C / min. Sintering was carried out at a temperature of 1400 °C and a pressure of 30 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was cut off to allow natural cooling. When the average density was measured by the Archimedes method, it was 5.021 g / cm 3 It was. Annealing was carried out at a temperature of 1400 °C in an oxygen-containing environment for 8 hours. When the average density after annealing was measured by the Archimedes method, it was 5.010 g / cm 3 It was.

[0267] In another example, sample 200-1 was prepared as follows. 4 to 5 m 2Yttrium oxide powder with a surface area of / g and a total impurity of 9.5 ppm corresponding to a powder purity of 99.9991% was used to form a 150 mm yttrium oxide sintered body. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Pressure was pre-applied at 20 MPa for about 5 minutes. Thereafter, the pressure was reduced to 5 MPa and heated to 600 °C at a rate of 25 °C / min. Heat and pressure were applied simultaneously, up to 1000 °C and 20 MPa, at a heating rate of 25 °C / min and a pressure increase rate of 5 MPa / min. Heat from 1000 °C to the sintering temperature at a rate of 10 °C / min. Sintering was carried out at a temperature of 1400 °C and a pressure of 20 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was shut off to allow natural cooling. Annealing was carried out at a temperature of 1400 °C for 8 hours in an oxygen-containing environment. The density of the annealed and sintered yttrium oxide body was 4.945 g / cm 3 and had a maximum pore diameter of 1.4 microns. After the two-step CF4 / O2 etching process disclosed herein, an average step of 0.2 μm, an average etching rate of 0.14 nm / min, and an etching volume of 60,000 μm3 were obtained. After the oxygen etching process disclosed herein, an average step of 0.1 μm, an average etching rate of 0.07 nm / min, and an etching volume of 30,000 μm 3 were obtained. After the SF6 etching process disclosed herein, an average step of 0.27 μm, an average etching rate of 0.19 nm / min, and an etching volume of 80,000 μm3 were obtained.

[0268] In another example, sample 212-1 was prepared as follows. Corresponding to a powder purity of 99.9992%, 5.6 m 2Yttrium oxide powder with a surface area of / g and total impurities of 8.1 ppm was used to form a 100 mm yttrium oxide sintered body. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. The pressure was pre-applied at 20 MPa for about 5 minutes to establish a 50 millitorr vacuum. Thereafter, the pressure was reduced to 5 MPa and heated to 600 °C at a rate of 50 °C / min. Heat and pressure were simultaneously applied to 30 MPa and 1450 °C) at a pressurization rate of 10 MPa / min and a rate of 25 °C / min. Sintering was carried out at a temperature of 1450 °C and a pressure of 30 MPa for 30 minutes to complete the sintering. After sintering, the power to the sintering apparatus was shut off to allow natural cooling. Annealing was carried out at a temperature of 1400 °C for 8 hours in an oxygen-containing environment. The density of the annealed and sintered yttrium oxide body was 5.022 g / cm 3 and had a maximum pore diameter of 1.0 micron. The sintered yttrium oxide body had a total average impurity of 6 ppm corresponding to a purity of 99.9994%. After the two-step CF4 / O2 etching process disclosed herein, an average step of 1.1 μm, an average etching rate of 0.77 nm / min, and 358,000 μm 3 of etched volume were obtained.

[0269] In another example, sample 314 was prepared as follows. 2 - 3 m 2Yttrium oxide powder with a surface area of / g and total impurities of 24.8 ppm corresponding to a powder purity of 99.9975% was used to form a yttrium oxide sintered body having a longest dimension of 406 mm. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 70 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Pressure was pre-applied at 5 MPa and the temperature was raised from room temperature to 800 °C at 10 °C / min. Heat and pressure were applied simultaneously to raise the pressure to 20 MPa and the temperature was raised from 800 °C to 1000 °C at a heating rate of 10 °C / min. The pressure was maintained at 20 MPa from 1000 °C to the sintering temperature at a heating rate of 10 °C / min. Sintering was carried out at a temperature of 1450 °C and a pressure of 20 MPa for a sintering time of 60 minutes. Heating and pressurization were terminated after the sintering time and natural cooling was carried out. The sintered yttrium oxide body was annealed at 1400 °C for 8 hours in an oxygen-containing environment using a heating and cooling rate of 0.8 °C / min. The average density of the annealed and sintered yttrium oxide body was 4.935 g / cm 3 and the density range across the longest dimension was 4.898 - 4.970 g / cm 3 was.

[0270] In another example, Sample 457 was prepared as follows. 5 - 6 m 2 / g of yttrium oxide powder with a surface area and total impurities of 17 ppm corresponding to a powder purity of 99.9983% was used to form a yttrium oxide sintered body having a longest dimension of 406 mm. The calcination of the powder was 5 - 6 m 2It was carried out at 600 °C for 8 hours using the surface area of / g. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed in this specification, and each of the die and the upper and lower punches contained the graphite material disclosed in this specification. The powder was placed in the internal volume of a spark plasma sintering tool having a gap width of about 30 to about 70 μm, whereby the gap was formed between the inward surface of at least one foil and the outer walls of the upper and lower punches of the sintering apparatus. The pressure was pre-applied at 5 MPa, and the temperature was raised from room temperature to 600 °C at 10 °C / min. Heat and pressure were applied simultaneously, the pressure was raised to 30 MPa, and the temperature was raised from 600 °C to 1000 °C at a heating rate of 5 °C / min. The pressure was maintained at 30 MPa from 1000 °C to the sintering temperature at a heating rate of 5 °C / min. Sintering was carried out at a temperature of 1475 °C and a pressure of 30 MPa for a sintering time of 60 minutes. The pressure was removed after the sintering time. Cooling was carried out using forced convection for about 4 hours at 50% blower output. Cooling using various blower output levels from about 25% to 100% enables a forced convection cooling rate of 2.5 °C / min to 5 °C / min. Sintering was carried out at a temperature of 1475 °C and a pressure of 30 MPa for 60 minutes. The sintered yttrium oxide body was annealed at 1400 °C for 4 hours in an oxygen-containing environment using a heating rate of 0.8 °C / min and a cooling rate of 2 °C / min. The average density of the annealed and sintered yttrium oxide body is 4.985 g / cm 3 and the density range over the longest dimension is 4.980 to 4.989 g / cm 3 It was. The maximum pore diameter was measured to be 1.4 μm, and an Sa value of 18 nm and 1178×10 -5 The Sdr value of was measured. For this sample, an average particle size of 0.65 μm was measured using the line intercept method.

[0271] In another example, sample 353 was prepared as follows. 6.5 to 7.5 m 2Yttrium oxide powder with a surface area of / g and an average total impurity of 11 ppm corresponding to a powder purity of 99.9989% was used to form a yttrium oxide sintered body with a maximum dimension of 406 mm. The powder may be blended, tumbled, sieved, etc. before and / or after calcination according to known methods. The calcination of the powder was carried out at 1000 °C for 24 hours, and the surface area was 1.5 - 2.5 m 2 / g. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 70 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. A pressure was pre-applied at 5 MPa, and the temperature was raised from room temperature to 800 °C at 10 °C / min. Heat and pressure were applied simultaneously to raise the pressure to 30 MPa and raise the temperature from 800 °C to 1000 °C at a heating rate of 10 °C / min. The pressure was maintained at 30 MPa from 1000 °C to the sintering temperature at a heating rate of 10 °C / min. Sintering was carried out at a temperature of 1475 °C and a pressure of 30 MPa for a sintering time of 60 minutes. Heating and pressurization were terminated after the sintering time, and natural cooling was performed. The yttrium oxide sintered body was annealed at 1400 °C for 0 minutes (without an isothermal annealing period) in an oxygen-containing environment at a heating rate of 0.8 °C / min and a passive cooling rate of 0.8 °C / min. The average density of the annealed and sintered yttrium oxide body was 4.981 g / cm 3 was.

[0272] In another example, Sample 414 was prepared as follows. 6.5 - 7.5 m 2 Yttrium oxide powder with a surface area of / g and an average total impurity of 11 ppm corresponding to a powder purity of 99.9989% was used to form a yttrium oxide sintered body with a maximum dimension of 406 mm. The calcination of the powder was carried out at 500 °C for 48 hours, and the surface area was 6.5 - 7.5 m 2 / g. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches included the graphite material disclosed herein. Powder was placed within the internal volume of a spark discharge plasma sintering tool having a gap width between about 30 and about 70 μm, whereby the gap was formed between the inward surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Pressure was pre-applied at 5 MPa, and the temperature was raised from room temperature to 800 °C at 10 °C / min. Heat and pressure were applied simultaneously to raise the pressure to 30 MPa and to raise the temperature from 800 °C to 1000 °C at a heating rate of 10 °C / min. The pressure was maintained at 30 MPa from 1000 °C to the sintering temperature at a heating rate of 10 °C / min. Sintering was carried out at a temperature of 1400 °C and a pressure of 30 MPa for a sintering time of 60 minutes. Heating and pressurization were terminated after the sintering period, and natural / passive cooling was carried out. The average density of the annealed and sintered yttrium oxide body was 4.985 g / cm 3 It was.

[0273] In yet another example, sample 476 was made as follows. Approximately 2 m 2Yttrium oxide powder with a surface area of / g and a total impurity of 5 - 6 ppm corresponding to a powder purity of 99.9995% was used to form a yttrium oxide sintered body with a longest dimension of 406 mm. Before sintering without using a grinding medium, the powder was tumbled for 24 hours. The die of the sintering apparatus was lined with a graphite foil having the characteristics disclosed herein, and each of the die and the upper and lower punches contained the graphite material disclosed herein. The powder was placed within the internal volume of a spark plasma sintering tool having a gap width between about 30 and about 70 μm, whereby the gap was formed between the inward surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Pressure was pre-applied at 5 MPa, and the temperature was raised from room temperature to 600 °C at a rate of 10 °C / min. Heat and pressure were applied simultaneously, and the pressure was raised to 30 MPa, and the temperature was raised from 600 °C to 1000 °C at a heating rate of 5 °C / min. The pressure was maintained at 30 MPa from 1000 °C to the sintering temperature at a temperature increase rate of 5 °C / min. Sintering was carried out at a temperature of 1475 °C and a pressure of 30 MPa for a sintering time of 60 minutes. After the sintering time, the pressure was removed. Cooling was performed using forced convection at a blower output of 50%. Cooling using various blower output levels enables a forced convection cooling rate of 2.5 °C / min to 5 °C / min. The sintered yttrium oxide body was annealed at 1400 °C for 4 hours in an oxygen-containing environment using a heating rate of 1 °C / min and a cooling rate of 2 °C / min. The average density of the annealed and sintered yttrium oxide body was 4.953 g / cm 3 and the density range across the longest dimension was 4.891 - 5.014 g / cm 3 was.

[0274] In a series of examples, samples 084 and 084 - 1, 085 and 085 - 1, 086 and 086 - 1, 087 and 087 - 1, 095 and 096 were fabricated as follows: A 100 mm yttrium oxide sintered body was prepared from a powder having a surface area of 6.5 - 7.5 m 2 / g and a total impurity of on average 11 ppm, providing a powder purity of 99.9989%. The powder was calcined before sintering at 800 °C for 8 hours and had a surface area of 5 - 6.5 m 2had a surface area of / g. The dies of the sintering apparatus were lined with graphite foils having the characteristics disclosed in this specification, and each of the die and the upper and lower punches contained the graphite material disclosed in this specification. Powder was placed within the internal volume of a spark plasma sintering tool having a gap width of between about 30 and about 60 μm, whereby the gap was configured between the inward-facing surface of at least one foil and the outer walls of each of the upper and lower punches of the sintering apparatus. Samples 084-1, 085-1, 086-1, 087-1, 095, and 096 were annealed at 1400 °C for 8 hours at a heating rate of 5 °C / min in an oxygen environment. The densities and process conditions are as disclosed in the corresponding density and sintering / annealing tables of this specification.

[0275] Tables 11-14 summarize the process conditions and the densities obtained for samples prepared according to the process of the present disclosure.

[0276]

Table 13-1

[0277]

Table 13-2

[0278]

Table 14

[0279]

Table 15

[0280]

Table 16

[0281] Tables 15 and 16 summarize the purities measured for the starting powders and sintered yttrium oxide samples fabricated according to the processes disclosed herein.

[0282]

Table 17-1

[0283]

Table 17-2

[0284] Table 16 shows the maintenance of purity during the processes disclosed herein from the powder to the sintered yttrium oxide body.

[0285]

Table 18

[0286] Tables 17 to 19 show the etching results of different process gases for quartz (TSC03), commercially available yttrium oxide parts (107, 108, 118), and sintered yttrium oxide samples prepared according to the present disclosure, including the processing conditions. The CF4 / O2 etching was performed in a two-step process. Step 1 was carried out at a pressure of 10 millitorr, a CF4 flow rate of 90 sccm, an O2 flow rate of 30 sccm, an argon flow rate of 20 sccm, a bias voltage of 600 V, and a power of 2000 W for 1500 seconds. Step 2 was carried out at a pressure of 10 millitorr, a CF4 flow rate of 0 sccm, an O2 flow rate of 100 sccm, an argon flow rate of 20 sccm, a bias voltage of 600 V, and a power of 2000 W for 300 seconds. The first and second steps were sequentially repeated until the CF4 exposure time in the first step reached 24 hours. The O2 etching conditions were a pressure of 25 millitorr, a CF4 / SF6 flow rate of 0 sccm, an O2 flow rate of 100 sccm, an Ar flow rate of 20 sccm, a bias voltage of 600 V, a total of 6 hours, and a power of 2000 W. The SF6 etching conditions were a pressure of 25 millitorr, a SF6 flow rate of 100 sccm, an 02 flow rate of 0 sccm, an Ar flow rate of 50 sccm, a bias voltage of 300 V, a total of 24 hours, and a power of 2000 W. The results show the excellent corrosion resistance of the yttrium oxide sintered body prepared according to the present disclosure.

[0287] The yttrium oxide sintered body prepared according to the present development preferably shows a step of 0.2 to 0.98 μm for the disclosed CF4 / O2 etching process, 0.27 to 0.44 μm for the SF6 etching process disclosed herein, and 0.1 to 0.13 μm for the O2 etching process disclosed herein.

[0288] The yttrium oxide sintered body prepared according to the present development preferably has an etching volume of 0.6×10 5 ~3.4×10 5 μm 3 for the disclosed CF4 / O2 etching process, 0.8×10 5 ~1.4×10 5 μm 3The etching volume and for the O2 etching process disclosed herein, 0.28 to 0.39 μm 3 is shown.

[0289] The yttrium oxide sintered body prepared according to the present development preferably exhibits an etching rate of 0.14 to 0.68 nm / min for the disclosed CF4 / O2 etching process, 0.19 to 0.310 nm / min for the SF6 etching process disclosed herein, and 0.07 to 0.09 nm / min for the O2 etching process disclosed herein.

[0290] [Table 19]

[0291] [Table 20]

[0292] [Table 21]

[0293] [Table 22]

[0294] grain boundary The composition and properties of the grain boundaries can be related to etching and erosion performance. As reported by M. Watanabe and D. B. Williams (J. Microsc. 221 (2006) 89 - 109), the grain boundary properties are [Number] calculable by factor quantification. The EDS (energy dispersive X-ray spectroscopy) spectrum is obtained from selected regions on the grain boundary and both adjacent particles as shown in FIG. 12, and the difference in elemental composition between the grain boundary and the bulk particle is atoms / nm 2Reported as the excess coverage in (V.J. Keast, D.B. Williams, J. Microsc. 199(2000)45--55). A positive number for the excess coverage indicates that the grain boundary has a higher concentration of a particular element relative to the bulk particles, and correspondingly a negative number indicates that the element has a higher concentration in the bulk particles relative to the grain boundary.

[0295] A comparative sample 107, which is a commercially available yttrium oxide sample, was analyzed with respect to its grain boundary composition and excess coverage. Figure 13 shows the results of the excess coverage in atoms / nm² over several grain boundaries for sample 107. The silica was present in an excess of about 8 - 10 atoms / nm² with respect to the adjacent particles at the grain boundary.

[0296] A sample 114 formed from the same powder supplier as sample 152 was analyzed with respect to its grain boundary composition and excess coverage. Figure 14 shows the results of the excess coverage in atoms / nm². The silica was present at the grain boundary in an amount of about 2 to about 4 atoms / nm² with respect to the bulk particle composition. All other elements were present with an excess coverage less than the amount of silica coverage. These low levels of elements other than yttrium oxide present at the grain boundaries of sample 114 corresponding to sample 152 may provide favorable etching results as reported in Tables 17, 18, and 19 over various process gases.

Claims

**Claim 1** A method for producing a sintered ceramic body, comprising the following process steps: a. A step of disposing at least one ceramic powder within an internal volume of a spark plasma sintering tool, wherein the spark plasma sintering tool is a die including a side wall including an inner wall and an outer wall, the inner wall having a diameter defining the internal volume, the die, an upper punch and a lower punch operably connected to the die, each of the upper punch and the lower punch having an outer wall defining a diameter smaller than the diameter of the inner wall of the die, whereby when at least one of the upper punch and the lower punch is moved within the internal volume of the die, a gap is generated between each of the upper punch and the lower punch and the inner wall of the die, the sintering tool having a central axis, the gap having a width of 10 μm to 100 μm, the upper punch and the lower punch; a step comprising; b. A step of generating a vacuum state within the internal volume; c. A step of heating the ceramic powder to a sintering temperature, sintering the ceramic powder to form the sintered ceramic body, and applying pressure to the ceramic powder by moving at least one of the upper punch and the lower punch; d. A step of lowering the temperature of the sintered ceramic body, including The method, wherein the at least one ceramic powder has a specific surface area of 1 to 18 m ２ / g as measured according to ASTM C1274. **Claim 2** The method according to claim 1, wherein the inner wall of the die includes at least one conductive foil. **Claim 3** The method according to claim 2, wherein the at least one conductive foil includes graphite, niobium, nickel, molybdenum, or platinum. **Claim 4** The method according to any one of claims 1 to 3, wherein the die, the upper punch, and the lower punch include at least one graphite material. **Claim 5** The method according to claim 4, wherein the at least one graphite material has a particle size of 5 to 30 μm. **Claim 6** The method according to claim 4 or 5, wherein the at least one graphite material has a density of 1.45 to 2.0 g / cc. **Claim 7** The radial deviation from the average coefficient of thermal expansion of the at least one graphite material is 0.3×10 －６ / °C or less, 0.25×10 －６ / °C or less, 0.2×10 －６ / °C or less, 0.18×10 － 6 / °C or less, 0.16×10 －６ / °C or less, 0.14×10 －６ / °C or less, 0.12×10 －６ / °C or less, 0.1×10 －６ / °C or less, 0.08×10 －６ / °C or less, 0.06×10 －６ varying by at least one amount selected from the group consisting of / °C or less, the method according to any one of claims 4 to 6. **Claim 8** The at least one ceramic powder has a resistivity of about 1×10 －５ ohm-cm to about 1×10+ １０ ohm-cm, and the at least one ceramic powder is selected from the group consisting of tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, silicon carbide, boron carbide, molybdenum boride, chromium boride, hafnium boride, zirconium boride, tantalum boride, titanium boride or titanium diboride, and titanium nitride, and combinations thereof, the method according to any one of claims 1 to 7. **Claim 9** The method according to any one of claims 1 to 8, wherein the gap has a width selected from the group consisting of 10 μm to 70 μm, 20 μm to 70 μm, 30 μm to 70 μm, 40 μm to 70 μm, 50 μm to 70 μm, 60 μm to 70 μm, 10 to 60 μm, 10 to 50 μm, 10 to 40 μm, 10 to 30 μm, 20 μm to 60 μm, 20 μm to 50 μm, 30 μm to 60 μm, and 30 μm to 50 μm.

10. The gap has a width of 10 to 70 μm, and the at least one ceramic powder has a resistivity of about 1×10 ＋１０ ohm-centimeters or more, and the at least one ceramic powder is yttrium oxide, aluminum oxide, sapphire, yttrium aluminum monoclinic (YAM), yttrium aluminum garnet (YAG), yttrium aluminum perovskite (YAP), zirconium oxide, titanium oxide, cordierite, mullite, cobaltite, magnesium aluminate spinel, silicon dioxide, quartz, calcium oxide, cerium oxide, ferrite, spinel, zircon, nickel oxide, copper oxide, strontium oxide, scandium oxide, samarium oxide, lanthanum oxide, lutetium oxide, erbium oxide, erbium aluminum garnet (EAG), hafnium oxide, vanadium oxide, niobium oxide, tungsten oxide, manganese oxide, tantalum oxide, terbium oxide, europium oxide, neodymium oxide, zirconium aluminate oxide, zirconium silicate oxide, hafnium aluminate oxide, hafnium silicate oxide, titanium silicate oxide, lanthanum silicate oxide, lanthanum aluminate oxide (LAO), yttrium silicate oxide, titanium silicate oxide, tantalum silicate oxide, yttrium nitride, oxy-nitride of yttrium, aluminum nitride, oxy-nitride of aluminum, silicon nitride, oxy-nitride of silicon, sialon material, boron nitride, beryllium nitride, titanium nitride, tungsten nitride, forsterite, steatite, cordierite, mullite, barium titanate, lead titanate, lead zirconate, lead zirconate titanate, Mn-Zn ferrite, Ni-Zn ferrite, and sialon and combinations thereof, the method according to any one of claims 1 to 9.

11. The method according to any one of claims 1 to 10, wherein at least one of the upper punch and the lower punch is coupled to an electrode, and at least one of the upper punch and the lower punch is in ohmic contact with the die.

12. The method according to any one of claims 1 to 11, wherein the gap is axisymmetric about the central axis.

13. The method according to any one of claims 1 to 12, wherein the gap is asymmetric about the central axis.

14. The at least one ceramic powder has a specific surface area (SSA) selected from the group consisting of 1 to 16 m ２ / g, 1 to 14 m ２ / g, 1 to 10 m ２ / g, 1 to 8 m ２ / g, 1 to 6 m ２ / g, 2 to 18 m ２ / g, 4 to 18 m ２ / g, 6 to 18 m ２ / g, 8 to 18 m ２ / g, 10 to 18 m ２ / g, 4 to 12 m ２ / g, 4 to 10 m ２ / g, and 6 to 8 m ２ / g, and the method according to any one of claims 1 to 13.

15. The method comprises any of the following optional steps e. annealing the sintered ceramic body by applying heat to raise the temperature of the sintered ceramic body to reach an annealing temperature; f. lowering the temperature of the sintered and annealed ceramic body to ambient temperature; g. machining the annealed sintered ceramic body into one selected from the group consisting of a focus ring, a window, a nozzle, a gas injector, a showerhead, a gas distribution plate, a remote plasma adapter, an etching chamber liner, a plasma source adapter, a gas inlet adapter, a diffuser, an electronic wafer chuck, a chuck, a pack, a mixing manifold, an ion suppressor element, a faceplate, an isolator, a spacer, and a protective ring. The method according to any one of claims 1 to 14 further comprises this step.

16. The method according to any one of claims 1 to 15, wherein the temperature difference per centimeter across the at least one ceramic powder disposed within the internal volume defined by the tool set of the sintering apparatus during step c is 0.15 to 5 °C / cm.

17. The method according to any one of claims 1 to 16, wherein the temperature difference across the at least one ceramic powder disposed within the internal volume defined by the tool set of the sintering apparatus during step c is 1 to 100 °C.

18. The method according to any one of claims 1 to 17, wherein the at least one ceramic powder has a d50 particle size selected from the group consisting of 0.8 to 100 μm, 0.8 to 80 μm, 0.8 to 60 μm, 0.8 to 40 μm, 0.8 to 30 μm, 0.8 to 20 μm, 0.8 to 10 μm, 0.8 to 5 μm, 1 to 100 μm, 3 to 100 μm, 5 to 100 μm, 10 to 100 μm, 20 to 100 μm, 40 μm, and 5 to 30 μm.

19. The method according to any one of claims 1 to 18, comprising a powder compact having a packing density selected from the group consisting of 20% to 60% by volume, 30% to 60% by volume, 40% to 60% by volume, 20% to 50% by volume, 20% to 40% by volume, 30% to 50% by volume, 40% to 55% by volume, and 45% to 55% by volume, wherein the at least one ceramic powder is present.

20. A sintered ceramic body having a maximum dimension selected from the group consisting of 100 to 622 mm, 200 to 622 mm, 250 to 622 mm, 300 to 622 mm, 350 to 622 mm, 400 to 622 mm, 550 to 622 mm, 500 to 622 mm, and 550 to 622 mm, wherein the density is 98% or more of the reported theoretical density of the ceramic forming the sintered ceramic body, and the density of the sintered ceramic body varies by 0.5% to 4% along the maximum dimension, and the density is measured according to ASTM B962-17.

21. The sintered ceramic body according to claim 20, having a volume porosity of 0.1% to 2% calculated from a density measurement performed according to ASTM B962-17.

22. The sintered ceramic body according to claim 20, having a density deviation measured along the maximum dimension selected from the group consisting of less than 3%, less than 2%, less than 1%, less than 0.5%, 0.25 to 4.5%, 0.25 to 4%, 0.25 to 3%, 0.25 to 2%, 0.25 to 1%, 0.25 to 0.5%, 0.5 to 3.5%, 1 to 3%, 0.5 to 2%, and 0.5 to 1%.

23. The sintered ceramic body according to any one of claims 20 to 22, wherein the sintered ceramic body contains less than 100 ppm of total impurities.

24. The sintered ceramic body according to any one of claims 20 to 23, obtained by the method according to any one of claims 1 to 19.

25. Use of the sintered ceramic body according to claim 24 as, in particular, a focus ring, window, nozzle, gas injector, showerhead, gas distribution plate, remote plasma adapter, etching chamber liner, plasma source adapter, gas inlet adapter, diffuser, electrostatic wafer chuck, chuck, pack, hybrid manifold, ion suppressor element, faceplate, isolator, spacer, and / or protective ring in a plasma processing chamber.

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