Sintered ceramic body with large dimensions and method for manufacturing same

Abstract

A method of manufacturing a sintered ceramic body, the method comprising the following process steps: disposing a ceramic powder (5) within an interior volume of a spark plasma sintering tool (1), wherein the tool comprises: a die (2) comprising a sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining the interior volume; upper and lower punches (4, 4') operably coupled with the die, wherein each of the punches has an outer wall defining a diameter that is smaller than the diameter of the inner wall of the die, whereby a gap (3) is created between the punches and the inner wall when at least one of the punches is moved within the interior volume and the gap is 10 pm to 70 pm wide; creating a vacuum condition within the interior volume; moving at least one of the punches to apply pressure to the ceramic powder while heating, and sintering; and reducing the temperature of the sintered ceramic body.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a sintered ceramic body, in particular to a large sintered ceramic body having a high purity and a high density. Furthermore, the present disclosure also relates to a specific process for the preparation of a sintered ceramic body and in particular to a process for the preparation of a large sintered ceramic body preparable according to the method of the present disclosure. BACKGROUND

[0002] Ceramics can be used in a variety of industries, such as automotive, aerospace, semiconductor, optics, and medicine, among others. Ceramics generally offer high compressive strength, low thermal expansion, high thermal conductivity, excellent chemical resistance, and favorable dielectric and optical properties. However, for a variety of reasons, manufacturing ceramic parts having dimensions of about 100 mm to 200 mm and larger has proven challenging.

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

[0004] Certain ceramic materials are inherently refractory and difficult to densify. Thus, these are typically prepared by pressureless vacuum sintering, in which the ceramic powder is loaded in a furnace and sintered at temperatures of 1600 °C and higher for extended periods of time, often exceeding several days. This technique generally produces sintered ceramics having an unacceptable quality with lower densities and correspondingly higher porosities, which reduce properties such as chemical etching and / or erosion resistance. These manufacturing conditions also result in large grain sizes of about 20 pm and larger, and lower densities of less than about 95% of, for example, the theoretical value, reducing mechanical strength and leading to breakage at large sizes, making them unusable for many applications.

[0005] To facilitate densification, sintering aids are generally used. In applications where high purity is required for large body sizes, the sintering aids present in the sintered ceramic are incompatible with the end use of the ceramic article, thus precluding their use in applications requiring high purity of about 99.99% and higher. Sintering aids can also pose the problem that their specific properties can change the electrical, magnetic, or other properties in the sintered ceramic in a manner that is not desired by the end user.

[0006] Other ceramic materials are known to have low sintering strength, making them particularly difficult to handle at large sizes without breaking. This hinders their development as structural materials for a variety of applications. Attempts to prepare ceramic materials of large (>100 mm) body sizes, particularly those known to have low sintering strength, often result in breakage during or after sintering, upon cooling, during post-sintering treatments such as annealing or machining, or upon processing required treatments.

[0007] For semiconductor processing applications, vacuum processing chambers are used to etch and chemically vapor deposit (CVD) materials on semiconductor substrates. These vacuum processing chambers include components such as disks, rings, liners, and cylinders that confine the plasma to the wafer or substrate being processed. These chamber components, typically formed of a variety of plasma-resistant ceramic materials, are constantly attacked by the plasma and thus erode, corrode, and accumulate or release contaminants. This plasma attack causes a number of problems, including shortened component life, increased cost of consumables, transition metal contamination on the wafer, process drift, and particle contamination, which result in loss of equipment throughput, leading to extended tool down time.

[0008] Due to the erosive and corrosive nature of the plasma environment and the need to minimize particle and / or metal contamination, it is desirable for ceramic components used in plasma processing chambers to have suitably high erosion and corrosion resistance. Such components have been formed from materials that provide erosion and corrosion resistance in the plasma environment and have been described, for example, in US 5,798,016 and US 5,911,852; US 6,123,791 and US 6,352,611. However, these examples do not provide guidance for making ceramic materials and components having large sizes of about at least 100 mm to 200 mm and larger, as currently required for semiconductor processing chambers.

[0009] Large sintered ceramic bodies made to date are subject to the risk of cracking, high porosity, low density, and insufficient mass / purity for their use in corrosion-resistant applications. In addition, there is a need for increasingly large sizes of plasma-etch resistant ceramic components for etching chambers of the prior art. Currently, these requirements prevent the use of large numbers of sintered ceramic components in many plasma processing chambers.

[0010] There can be no commercially viable method to manufacture large ceramic body components with high (>96% of theoretical) density and minimal (<4% variation) density variation while also providing the high purity necessary for specific applications.

[0011] Spark plasma sintering (SPS) technology has been proposed as a solution for manufacturing ceramic bodies having large dimensions. Two scientific publications addressed the challenge of manufacturing large ceramic bodies by the electric discharge plasma sintering process, Eugene A. Olevsky et al., "Fundamental Aspects of Spark Plasma Sintering: I. Experimental Analysis of Scalability" (J. Am. Ceram. Soc, 95 [8], 2406 to 2413 (2012)) and "Fundamental Aspects of Spark Plasma Sintering: II. Experimental Analysis of Scalability" (J. Am. Ceram. Soc, 95 [8], 2414 to 2422 (2012)), which describe the problems related to temperature gradients that arise with the scaling up of the SPS process.

[0012] Attempts to use spark plasma sintering (SPS) technology to manufacture parts having large dimensions (> 100 mm) have so far been unsuccessful. This lack of success is at least in part due to the inability to control the temperature of larger dimension parts during the sintering process, resulting in temperature gradients during processing. In addition, the use of spark plasma sintering technology to densify those powders or powder mixtures having minimal or no electrical conductivity (i.e., insulators) is particularly challenging due to the low electrical conductivity inherent to the powders, thus exacerbating the temperature gradients of the powders during sintering. This temperature gradient results in variations in material properties such as density and grain size, each of which can affect mechanical strength. The inability to control this temperature gradient currently precludes the preparation of ceramic bodies having large dimensions of approximately greater than 100 mm that can be easily handled without breaking.

[0013] Japanese publication JP 2004 / 068089 A discloses an SPS processing apparatus in which a uniform temperature distribution is provided by optimizing the mold structure. Specifically, the shape of the molded product to be sintered is axisymmetric with respect to the central axis of the sintering chamber, and the electrodes of the power supply are installed at positions symmetric with respect to the central axis of the sintering chamber. It is preferred that the mold structure does not have to be changed to manufacture large dimension sintered ceramic bodies.

[0014] US 2018 / 201545 A discloses a focus ring having high plasma resistance and also provides a method for manufacturing the focus ring. The focus ring is formed of a sintered body of silicon carbide. The sintered body is composed of a plurality of first grains having an a-SiC crystal structure and a plurality of second grains having a b-SiC crystal structure. The sintered body contains the first grains in an amount of 70 vol% or more relative to the total amount of the first grains and the second grains. The volume average crystallite diameter of the first grains is 10 pm or less. This prior art document again focuses on the preparation of a plasma resistant material having improved stability against fluorine-based gases and oxygen. There is no indication in this prior art reference regarding the manufacture of large and dense high purity ceramic bodies having improved resistance to cracking. Therefore, there is a need in the art for larger sintered ceramic bodies having improved mechanical properties over large dimensions and being resistant to corrosion under plasma etching conditions.

[0015] For these and other reasons, there is a need for further development of ceramic materials providing a combination of high and uniform density over the entire sintered body with high purity. There is a particular need for a process for the preparation of large sintered ceramic bodies having a reduced risk of cracking and having sufficient quality with respect to density and density variation, purity, etching resistance and reduced surface roughness. SUMMARY

[0016] Embodiments provide a method for the preparation of large sintered ceramic bodies having improved mechanical properties and processability.

[0017] Embodiment 1. A method of manufacturing a sintered ceramic body, the method comprising the following process steps: (a) disposing at least one ceramic powder within an interior volume of a spark plasma sintering tool, wherein the spark plasma sintering tool comprises: a die comprising a sidewall, the sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining the interior volume; an upper punch and a lower punch operably coupled with the die, wherein each of the upper punch and the lower punch has an outer wall defining a diameter that is smaller than the diameter of the inner wall of the die, whereby a gap is created between each of the upper punch and the lower punch and the inner wall of the die when at least one of the upper punch and the lower punch is moved within the interior volume of the die, wherein the sintering tool has a central axis and the gap is 10 pm to 100 pm wide; (b) creating a vacuum condition within the interior volume; (c) moving at least one of the upper punch and the lower punch to apply pressure to the ceramic powder while heating the ceramic powder to a sintering temperature and sintering the ceramic powder to form a sintered ceramic body; and (d) reducing the temperature of the sintered ceramic body, wherein the at least one ceramic powder has a specific surface area of 1 m2 / g to 18 m2 / g measured according to ASTM C1274. 2 2 / g to 18 m ​

[0018] Embodiment 2. The method of embodiment 1, wherein the inner walls of the mold comprise at least one electrically conductive foil.

[0019] Embodiment 3. The method of embodiment 2, wherein the at least one electrically conductive foil comprises graphite, niobium, nickel, molybdenum, or platinum.

[0020] Embodiment 4. The method of any one of embodiments 1-3, wherein the mold, upper punch, and lower punch comprise at least one graphite material.

[0021] Embodiment 5. The method of embodiment 4, wherein the at least one graphite material has a grain size of 5 pm to 30 pm.

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

[0023] Embodiment 7. The method of any one of embodiments 4-6, wherein a radial deviation from an average coefficient of thermal expansion of the at least one graphite material varies around the central axis by at least one amount selected from the group consisting of: 0.3 x 10 -6 / °C and less, 0.25 x 10 -6 / °C and less, 0.2 x 10 -6 / °C and less, 0.18 x 10 -6 / °C and less, 0.16 x 10 -6 / °C and less, 0.14 x 10 -6 / °C and less, 0.12 x 10 -6 / °C and less, 0.1 x 10 -6 / °C and less, 0.08 x 10 -6 / °C and less, and 0.06 x 10 -6 / °C and less.

[0024] Embodiment 8. The method of any one of embodiments 1-7, wherein the at least one ceramic powder has an electrical resistivity of about 1 x 10 -5 ohm-cm to about 1 x 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, and titanium boride or titanium diboride and titanium nitride, and combinations thereof.

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

[0026] Embodiment 10. The method of any one of embodiments 1 to 9, wherein the gap is 10 pm to 70 pm wide, and the at least one ceramic powder has an electrical resistivity of about 1 x 10 +10 ohm-cm and greater, and the at least one ceramic powder is selected from the group consisting of: 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 aluminate oxide (LAO), yttrium silicate oxide, titanium silicate oxide, tantalum silicate oxide, yttrium nitride, yttrium oxynitride, aluminum nitride, aluminum oxynitride, silicon nitride, silicon oxynitride, sialon ceramic material, boron nitride, beryllium nitride, titanium nitride, tungsten nitride, forsterite, talc, cordierite, mullite, barium titanate, lead titanate, lead zirconate, lead zirconium titanate, Mn-Zn ferrite, Ni-Zn ferrite, and sialon ceramic, and combinations thereof.

[0027] Embodiment 11. The method of 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 of any one of embodiments 1 to 11, wherein the gap is axisymmetric about the central axis.

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

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

[0031] Embodiment 15. The method of any one of embodiments 1 to 14, wherein the method further comprises the optional steps of: (e) annealing the sintered ceramic body by increasing the temperature of the sintered ceramic body to an annealing temperature by applying heat; (f) decreasing the temperature of the sintered and annealed ceramic body to ambient temperature; 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 showerhead, a gas distribution plate, a remote plasma adapter, an etch chamber liner, a plasma source adapter, a gas inlet adapter, a diffuser, an electrostatic wafer chuck, a chuck, a positioning disk, a mixing manifold, an ion suppressor element, a faceplate, an isolator, a spacer, and a guard ring.

[0032] Embodiment 16. The method of any one of embodiments 1 to 15, wherein the temperature difference per centimeter of the at least one ceramic powder disposed within the interior volume defined by the toolset of the sintering apparatus during step c. is from 0.15 °C / cm to 5 °C / cm.

[0033] Embodiment 17. The method of any one of embodiments 1 to 16, wherein the temperature difference of the at least one ceramic powder disposed within the interior volume defined by the toolset of the sintering apparatus during step c. is from 1 °C to 100 °C.

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

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

[0036] Embodiment 20. A sintered ceramic body having a maximum dimension selected from the group consisting of 100 mm to 622 mm, 200 mm to 622 mm, 250 mm to 622 mm, 300 mm to 622 mm, 350 mm to 622 mm, 400 mm to 622 mm, 550 mm to 622 mm, 500 mm to 622 mm, and 550 mm to 622 mm, wherein the density is 98% and greater 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, wherein the density is measured according to ASTM B962-17.

[0037] Embodiment 21. The sintered ceramic body of embodiment 20 having a volumetric porosity of 0.1% to 2% as calculated from density measurements conducted according to ASTM B962-17.

[0038] Embodiment 22. The sintered ceramic body of embodiment 20 having a density variation as measured along a 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] Embodiment 23. The sintered ceramic body according to any one of embodiments 20 to 22, wherein the sintered ceramic body comprises less than 100 ppm of total impurities.

[0040] Embodiment 24. The sintered ceramic body according to any one of embodiments 20 to 23, obtainable by the process according to any one of embodiments 1 to 19.

[0041] Embodiment 25. Use of the sintered ceramic body according to embodiment 24 in a plasma processing chamber, in particular as a focus ring, window, nozzle, gas injector, showerhead, gas distribution plate, remote plasma adapter, etch chamber liner, plasma source adapter, gas inlet adapter, diffuser, electrostatic wafer chuck, chuck, positioning disk, mixing manifold, ion suppressor element, faceplate, spacer, spacer piece, and / or guard ring.

[0042] By providing a gap distance between the die system and the punch system, large sintered ceramic bodies with excellent mechanical properties can be produced.

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

[0044] The application will be described below with reference to the drawings, in which like reference numerals indicate identical elements:

[0045] Figure 1 is a cross-sectional view of an SPS sintering apparatus with a tool set located in a vacuum chamber (not shown) with a simple arrangement for sintering ceramic materials;

[0046] Figure 2A shows an embodiment of Figure 1 , showing one foil layer;

[0047] Figure 2B shows an alternative embodiment of Figure 1 , showing two foil layers;

[0048] Figure 2C shows another alternative embodiment of Figure 1 , showing three foil layers;

[0049] Figure 3A and Figure 3B is a top view of an SPS sintering apparatus of Figure 1 ;

[0050] Figure 4 is a graph depicting the radial variation of the average coefficient of thermal expansion (CTE) of the graphite materials A and B at 1200 °C;

[0051] Figure 5 a) shows the standard deviation of the coefficient of thermal expansion in ppm of the graphite materials A and B, and b) the variation of the coefficient of thermal expansion of the graphite materials A and B measured at operating temperatures from 200 °C to 1200 °C.

[0052] Figure 6 is a graph showing the coefficient of thermal expansion of the graphite materials A and B in the range from 400 °C to 1200 °C;

[0053] Figure 7 is a diagram of a cross-sectional view of an SPS sintering apparatus, wherein a), b) and c) show sintering of exemplary ceramic powders with resistivity from low to medium to high, respectively;

[0054] Figure 8 is a schematic diagram showing the temperature variation during sintering in the SPS sintering apparatus of Figure 1 ;

[0055] Figure 9 shows the grain size measurements of sintered ceramic bodies of YAG and yttria manufactured according to the apparatuses, materials and methods disclosed herein;

[0056] Figure 10 is a schematic diagram depicting an example of a plasma etching processing system;

[0057] Figure 11 is a schematic diagram depicting an example of a deposition processing system;

[0058] Figure 12 is an EDS (Energy Dispersive X-ray Spectroscopy) spectrum obtained from a selected area on the grain boundary;

[0059] Figure 13 shows the results of the excess coverage of sample 107 of the example on several grain boundaries, in atoms / nm 2 ; and

[0060] Figure 14 shows the results of the excess coverage of sample 114 of the example on several grain boundaries, in atoms / nm 2 .

[0061] Figure 15 a) shows SEM micrographs at 5000x, and b) shows the % of YAG theoretical density of the sintered ceramic body of sample 506 according to the example and the density variation over the largest dimension. DETAILED DESCRIPTION

[0062] The following detailed description is provided solely for the purpose of providing preferred exemplary embodiments of the application and is not intended to limit the scope, applicability or configuration of the application. Rather, the following detailed description of preferred exemplary embodiments will provide those skilled in the art with an enabling description of the preferred exemplary embodiments of the application. Various changes can be made to the function and arrangement of elements without departing from the spirit and scope of the application as set forth in the appended claims.

[0063] In describing the present application, it will be understood that the specific examples provided are intended to be illustrative only and are not intended to limit the scope, applicability or configuration of the application. Rather, the following detailed description of preferred exemplary embodiments of the application will provide those skilled in the art with an enabling description of the preferred exemplary embodiments of the application. Various changes can be made to the function and arrangement of elements without departing from the spirit and scope of the application as set forth in the appended claims.

[0064] Embodiments are described including the best mode known to the inventors for practicing the application. Variations on those embodiments that will become apparent to those of ordinary skill in the art upon reading the foregoing description are intended to be within the scope of the application. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the application to be practiced with the claims as specifically described and with variations as appropriate. Accordingly, the application includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the application unless otherwise indicated herein or otherwise obvious to one of ordinary skill in the art to be not within the scope of the application. Additionally, all features disclosed in relation to the process / method are also applicable to the product, such as the sintered ceramic body as disclosed herein.

[0065] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0066] Definitions

[0067] As used herein, the terms “semiconductor wafer”, “wafer”, “substrate” and “wafer substrate” can be 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.

[0068] As used herein, the terms “tool”, “tool set” and “equipment” can be used interchangeably.

[0069] As used herein, the term “sintered ceramic body” is synonymous with “sinter”, “body” or “sintered body” or “sintered ceramic body” and refers to a ceramic article formed from a powder composition as disclosed after being subjected to a pressure and heat treatment process which results in a sintered ceramic from the powder as disclosed. In certain embodiments, the term “sintered ceramic body” can refer to the entire body. “Unitary” means a single piece or a single unitary piece that is complete in and of itself, without additional parts, i.e., the piece is an integral piece with another piece formed as one unit.

[0070] The sintered ceramic body as disclosed herein is preferably polycrystalline and thus the sintered ceramic body can comprise two or more crystals without limitation.

[0071] As used herein, the term “purity” refers to the absence of various contaminants that do not comprise the bulk powder. For example, having a purity of 100% indicates that the powder comprises only the ceramic material itself.

[0072] As used herein, ambient temperature refers to a temperature of about 22°C to 25°C.

[0073] As used herein, ceramic powder refers to one or more crystalline powders or a combination of crystalline powders forming a powder mixture which can be milled, mixed, blended, calcined, sieved, etc. according to methods known to those skilled in the art. The ceramic powder as disclosed herein is preferably crystalline.

[0074] As used herein, the term “impurities” refers to those compounds / contaminants which can be present in a) the starting materials or powder mixture from which it is formed, b) the powder mixture after processing 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. Lower ppm levels correspond to lower impurity content as measured. When reported in ppm herein, all values are relative to the total mass of the material to be measured, such as, for example, the powder disclosed herein and / or the sintered ceramic body.

[0075] As used herein, the term “nanopowder” is intended to encompass a specific surface area (SSA) of 20 m 2 / g and larger, as measured according to ASTM C1274.

[0076] The term "calcining" when used in reference to a heat treatment process is understood herein to mean a heat treatment step that can be performed on a powder in air to, for example, remove moisture and / or surface impurities, increase crystallinity, and in some cases, modify the surface area of the powder and / or powder mixture.

[0077] The term "annealing" when applied to the heat treatment of ceramics is understood herein to refer to a heat treatment of the disclosed sintered ceramic body in air to a temperature and slowly cooling it to relieve stresses and / or normalize stoichiometry.

[0078] The term "Sa" known in the art relates to the arithmetic average height of a surface and represents the absolute value of the arithmetic average of the entire surface. According to the definition of ISO 25178-2-2012 section 4.1.7 is the arithmetic average of the absolute values of the ordinate within the defined area (A).

[0079] The term "Sz" known in the art relates to the maximum (peak to valley) height of a surface and represents the absolute value of the maximum height of the entire surface. According to the definition of ISO 25178-2-2012 section 4.1.6 is the sum of the maximum peak height value and the maximum pit height value within the defined area (A). The maximum pit height value Sv is defined according to ISO 25178-2-2012 section 4.1.5 as the minimum pit height value within the defined area (A) is subtracted.

[0080] The term "Sdr" known in the art relates to the interface development area ratio of a surface and represents the absolute value of the maximum height of the entire surface. According to the definition of ISO 25178-2-2012 section 4.3.2 is the ratio of the incremental interface area of a proportionally limited surface within the defined area (A) to the defined area. Sdr is a proportional expression of the increase in actual surface area over the increase of a perfectly flat surface. The Sdr of a flat surface is assigned a value of zero and the value increases with increasing surface area. Greater Sdr values correspond to greater increases in surface area resulting from a corrosion or etching and / or erosion process.

[0081] As used herein, the terms "substantially," "about," and "approximately" in connection with a number means a variation of ±10%.

[0082] As used herein, the term "sintering aid" refers to an additive that enhances densification and promotes sintering and thereby reduces porosity during the sintering process.

[0083] As used herein, the term "dopant" is used to mean those elements or compounds that can be intentionally added in relatively small amounts (about less than 10 mole percent) to alter or achieve certain ceramic properties to achieve a desired result. These results can be electrical, mechanical, optical, or other properties. In contrast, sintering aids differ from dopants in that sintering aids can be added to lower the temperature at which a powder can be sintered to high density.

[0084] In the following description, a given range includes both the lower and upper threshold values. Thus, a definition of "in a range from X to Y" or "in a range from X to Y" in terms of a parameter A means that A can be any value from X, Y, and any value from X to Y. A definition of "up to Y" or "at least X" in terms of a parameter A means that A can be any value less than Y, respectively, or A can be any value greater than X, respectively.

[0085] Apparatus / Spark Plasma Sintering Tool

[0086] Disclosed herein is a spark plasma sintering (SPS) tool comprising: a die comprising a sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining an interior volume capable of receiving at least one ceramic powder; and an upper punch and a lower punch operably coupled with the die, wherein each of the upper punch and the lower punch has an outer wall defining a diameter that is less 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 interior volume of the die, a gap is created between each of the upper punch and the lower punch and the inner wall of the die, wherein the gap is 10 pm to 100 pm wide, and the at least one ceramic powder has a specific surface area (SSA) of 1 m / g to 18 m / g measured according to ASTM C1274.

[0087] Figure 1 An SPS tool 1 having a simplified die / punch arrangement for sintering ceramic powders is depicted. Generally, the die / punch arrangement is within a vacuum chamber (not shown), as will be appreciated by one of ordinary skill in the art. Referring to Figure 1 , the spark plasma sintering tool 1 includes a die system 2 comprising a sidewall comprising an inner wall 8 having a diameter defining an interior volume capable of receiving at least one ceramic powder 5.

[0088] Still referring to Figure 1The spark plasma sintering tool 1 includes an upper punch 4 and a lower punch 4' operably coupled with the die system 2, where each of the upper punch 4 and the lower punch 4' has an outer wall 11 defining a diameter that is less than a diameter of the inner wall 8 of the die system 2, whereby a gap 3 is created between each of the upper punch 4 and the lower punch 4' and the inner wall 8 of the die system 2 when at least one of the upper punch 4 and the lower punch 4' is moved within the interior volume of the die system 2.

[0089] The die system 2, as well as the upper punch 4 and the lower punch 4', can include at least one graphite material, typically a low strength graphite material. In certain embodiments, the graphite materials disclosed herein can include at least one isotropic graphite material. In other embodiments, the graphite materials disclosed herein can include at least one reinforced graphite material, such as a carbon-carbon composite material, as well as graphite materials including fibers, particles, or sheets or a web or a laminate of other electrically conductive materials such as carbon in a matrix of isotropic graphite material. In other embodiments, the die and the upper and lower punches can include a combination of these isotropic and reinforced graphite materials.

[0090] The graphite material for some or all of the components of the tool, such as the die 6 and the punches 4 and 4', can include a porous graphite material exhibiting a porosity of about 5% to about 20%, about 5% to about 17%, about 5% to about 13%, about 5% to about 10%, 5% to about 8%, about 8% to about 20%, about 12% to 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%.

[0091] Preferably, the average pore size (pore diameter) of the graphite material is 0.4 pm to 5.0 pm, preferably 1.0 pm to 4.0 pm, and includes pores having a surface pore diameter of up to 30 pm, preferably up to 20 pm, preferably up to 10 pm. More preferably, there can be pores having a surface pore diameter of 10 pm to 30 pm.

[0092] The average grain size of the graphite material for the tool as disclosed herein can be <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, and preferably <0.010 mm.

[0093] The average grain size of the graphite material for tools as disclosed herein can be > 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, and preferably > 0.030 mm.

[0094] The density of the graphite material for tools as disclosed herein can be > 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 , and preferably > 1.75 g / cm 3 .

[0095] The density of the graphite material for tools as disclosed herein can be < 2.00 g / cm 3 , preferably < 1.90 g / cm 3 , preferably < 1.85 g / cm 3 , and preferably < 1.80 g / cm 3 .

[0096] In embodiments, the graphite material has a coefficient of thermal expansion (CTE) in the temperature range from about 400 °C to about 1200 °C of > 3.3 x 10 -6 / °C, > 3.5 x 10 -6 / °C, > 3.7 x 10 -6 / °C, > 4.0 x 10 -6 / °C, > 4.2 x 10 -6 / °C, > 4.4 x 10 -6 / °C, > 4.6 x 10 -6 / °C, > 4.8 x 10 -6 / °C.

[0097] In embodiments, the graphite material has a coefficient of thermal expansion (CTE) in the temperature range from about 400 °C to 1200 °C of < 7.2 x 10 -6 / °C, preferably < 7.0 x 10 -6 / °C, preferably < 6.5 x 10 -6 / °C, preferably < 6.0 x 10 -6 / °C, preferably < 5.0 x 10 -6 / °C, preferably < 4.8 x 10 -6 / °C, preferably < 4.6 x 10 -6 / °C.

[0098] In embodiments, the at least one graphite material has a coefficient of thermal expansion (CTE) in the temperature range of 400 °C to 500 °C of about 3.8 x 10 -6 / °C to about 7 x 10 -6 / °C, preferably about 4.0 x 10 -6 / °C to about 7 x 10 -6 / °C, preferably about 4.4 x 10 -6 / °C to about 7 x 10 -6 / °C, preferably about 4.0 x 10 -6 / °C to about 6 x 10 -6 / °C.

[0099] Table 1 lists properties of exemplary graphite materials as disclosed herein.

[0100] Table 1

[0101]

[0102]

[0103] The mold system 2 includes a mold 6 and at least one electrically conductive foil 7, optionally but preferably located on the inner wall of the mold, as shown in embodiments of Figures 2A to 2C The number of electrically conductive foils on the inner wall of the mold is not limited and can be provided 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 electrically conductive foils as circumferential gaskets between the mold 6 and each of the upper punch 4 and the lower punch 4', whereby the inner wall 8 of the mold system 2, including the at least one electrically conductive foil, if present, and the outer wall 11 of each of the upper and lower punches define the gap 3. The at least one electrically conductive foil 7 can comprise graphite, niobium, nickel, molybdenum, platinum, and other ductile, electrically conductive materials, and combinations thereof, which are stable in the temperature range according to the method as disclosed herein.

[0104] In certain embodiments, the electrically conductive foil can comprise a flexible and compressible graphite foil as disclosed herein having one or more of the following properties:

[0105] • a carbon content 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.%, and more preferably greater than 99.999 wt.%;

[0106] • impurities 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, and more preferably less than 3 ppm, each relative to the total mass of the foil;

[0107] • the tensile strength of the graphite foil ranges from 4.0 MPa to 6.0 MPa, preferably 4.2 MPa to 5.8 MPa, more preferably 4.4 MPa or 5.6 MPa; and / or

[0108] • the bulk density of the graphite foil preferably ranges from 1.0 g / cc to 1.2 g / cc, preferably 1.02 g / cc to 1.18 g / cc, more preferably 1.04 g / cc to 1.16 g / cc, more preferably 1.06 g / cc to 1.16 g / cc.

[0109] In embodiments, the at least one foil generally comprises graphite. In certain embodiments, the at least one foil as part of the die system can include a circumferential gasket between the surface of the die and each of the upper punch and the lower punch.

[0110] The graphite foil can improve the temperature distribution of the powder during sintering. Table 2 lists exemplary graphite foils such as Neograf® Neograf® and Toyo Tanso Perma- properties.

[0111] Table 2

[0112] Thickness (mm) 0.030-0.260 Density (Mg / m3) 0.5-2 Tensile Strength (MPa) 4.9-6.3 Resistivity (μOhm-m; 25°C) (parallel to surface) 5-10 Resistivity (μOhm-m; 25°C) (perpendicular to surface) 900-1100 CTE (xlO -6 / °C; parallel to surface), 350°C to 500°C 5-5.5 CTE (perpendicular to surface), 350°C to 500°C 2x10 -4 ]]> Compressibility (%) 40-50 Recovery (%) 10-20 Thermal Conductivity (W / mK, 25°C; parallel to surface) 175-225 Thermal Conductivity (W / mK, 25°C; perpendicular to surface) ～5 Impurities / Ash (wt%) <0.5

[0113] Referring now to Figure 2A , Figure 2B and Figure 2C , an SPS tool set with graphite foil arrangement embodiments is shown. The ceramic powder 5 is disposed between at least one of the upper punch 4 and the lower punch 4' and the gap 3 is shown between the outer wall 11 of each of the upper punch and the lower punch and the inner wall 8 of the die system 2. Figure 2A , Figure 2B and Figure 2C depict 1 to 3 layers of conductive foil 7 and the die 6 as part of the die system 2, respectively. Thus, the gap extends from the inner wall 8 of the die system 2 to the outer wall 11 of each of the upper punch and the lower punch. The gap distance is arranged such that the powder can be degassed prior to and / or during heating and sintering while also maintaining Ohmic contact between the punch and the die to improve the temperature distribution on the ceramic powder during heating and sintering.

[0114] The thickness of the graphite foil 7 can be, for example, 0.025 mm to 0.260 mm, preferably 0.025 mm to 0.200 mm, preferably 0.025 mm to 0.175 mm, preferably 0.025 mm to 0.150 mm, preferably 0.025 mm to 0.125 mm, preferably 0.035 mm to 0.200 mm, preferably 0.045 mm to 0.200 mm, and preferably 0.055 mm to 0.200 mm.

[0115] The distance of the gap 3 is measured from the inwardly facing surface of the foil 7 closest to the upper punch 4 and the lower punch 4' to the outer wall 11 of each of the upper punch and the lower punch. The preferred range of the distance of the gap 3 is preferably 10 pm to 100 pm, preferably 10 pm to 80 pm, preferably 10 pm to 70 pm, preferably 10 pm to 60 pm, preferably 10 pm to 50 pm, preferably 20 pm to 70 pm, preferably 30 pm to 70 pm, preferably 40 pm to 70 pm, preferably 50 pm to 70 pm, preferably 20 pm to 60 pm, preferably 20 pm to 50 pm, preferably 30 pm to 60 pm, preferably 30 pm to 50 pm.

[0116] Furthermore, the width of the gap 3 between the inner wall 8 of the die system 2 and the outer wall 11 of each of the upper punch 4 and the lower punch 4' can be determined by the person skilled in the art, so as to on the one hand sufficiently facilitate the powder degassing during the preheating, heating and sintering process, and on the other hand to achieve sufficient electrical contact for the Joule or resistance heating, so as to achieve sintering. If the distance of the gap 3 is less than 10 pm, the force required to move at least one of the upper punch and the lower punch within the inner volume of the die system and thereby assemble the tool set can cause damage to the tool set. Furthermore, if the gap 3 is less than 10 pm, the gases, organics, moisture, etc. adsorbed within the ceramic powder 5 cannot escape, which will prolong the processing time during manufacturing and can lead to residual porosity in the sintered ceramic body, thereby reducing the density. If when sintering an insulating material as disclosed herein, such as a ceramic having a high electrical resistivity of about 1 x 1010Ohm cm at room temperature, the gap 3 is less than 10 pm, the electrical resistivity of the sintered ceramic body can be reduced due to the electrical contact between the ceramic powder and the die system. This is because the ceramic powder is in contact with the die system, which is electrically conductive, and the electrical current can flow through the die system and the ceramic powder, thereby reducing the electrical resistivity of the sintered ceramic body. +10ohm-cm and greater, oxide and / or nitride ceramics and non-conductive mixed metal oxides, a gap 3 of greater than 70 pm can cause localized overheating, resulting in thermal gradients within the tool set 1 during sintering. These thermal gradients can result in low overall green density and high density variation and sintered ceramic bodies that are brittle and prone to cracking. Therefore, to form large size sintered ceramic bodies from non-conductive ceramic powders having high electrical resistivity (and therefore low electrical conductivity), a gap of 10 pm to 70 pm is preferred. Thus, in some embodiments, when sintering ceramic powders 5 comprising insulating, oxide or nitride ceramics, the distance of the gap 3 between the inner wall 8 of the die system 2 and the outer wall 11 of each of the upper and lower punches is preferably 10 pm to 70 pm, preferably 10 pm to 60 pm, preferably 10 pm to 50 pm, preferably 10 pm to 40 pm, preferably 20 pm to 70 pm, preferably 30 pm to 70 pm, preferably 40 pm to 70 pm, preferably 50 pm to 70 pm, preferably 30 pm to 60 pm. The gap 3 reduces thermal gradients in the powder compact comprising the insulating ceramic powder.

[0117] Accordingly, when the ceramic powder comprises non-oxide ceramics selected from carbides and borides and certain nitrides such as titanium nitride, each of which can have a lower electrical resistivity and partial electrical conductivity relative to oxide and nitride ceramics as disclosed herein, for example, about 1 x 10 -5 ohm-cm to about 1 x 10 +10 ohm-cm, a greater gap can be acceptable, for example, about 10 pm to about 100 pm. This increased gap can be attributed to the partial electrical conductivity of the powder or powder compact, whereby the partial electrical conductivity conducts electricity and, thereby, heat through the powder compact, thus reducing thermal gradients in the powder or powder compact comprising the disclosed non-oxide ceramics. When sintering those ceramic powders 5 having a certain electrical conductivity and, therefore, lower electrical resistivity, such as non-oxide ceramics and / or conductive mixed metal oxides as disclosed herein, a gap 3 of greater than 100 pm can result in localized overheating and thermal gradients within the tool set during sintering. These thermal gradients can result in low overall or green density and high density variation and sintered ceramic bodies that are brittle and prone to cracking. Therefore, when sintering non-oxide ceramics and / or conductive mixed metal oxides as disclosed herein, the distance of the gap 3 between the inner wall 8 of the die system 2 and the outer wall 11 of each of the upper and lower punches is 10 pm to 100 pm, preferably 10 pm to 80 pm, preferably 10 pm to 60 pm, preferably 10 pm to 40 pm, preferably 20 pm to 100 pm, preferably 40 pm to 100 pm, preferably 60 pm to 100 pm, preferably 30 pm to 80 pm, preferably 40 pm to 70 pm.

[0118] Without being bound by a particular theory, it is believed that the gap distance between the inner wall 8 of the die system 2 and the outer wall 11 of each of the upper and lower punches during sintering is beneficial for powder degassing of organics, moisture, adsorbed molecules, etc. during the sintering process according to step c) of the disclosed method. This results in large size sintered ceramic bodies with high density and low bulk porosity, low density variation, and improved mechanical properties, such that the body can be easily handled without breaking and machined into a specific form for manufacturing the sintered ceramic components for plasma processing chambers disclosed herein. The sintered ceramic bodies prepared as disclosed herein can have a size of 100 mm to about 625 mm relative to the largest dimension of the sintered ceramic body.

[0119] In practice, the upper punch 4 and the lower punch 4’ are not always perfectly aligned around the central axis. Figure 3A and Figure 3B is a plan view of the tool set 1 showing the alignment of the upper punch 4 and the lower punch 4’, the gap 3, the arbitrary number of conductive foils 7, and the die system 2 around the central axis 9. In the embodiment as shown in Figure 3A The gap can be axially symmetric about the central axis 9 in the embodiment as shown in Figure 3B The gap can be axially asymmetric about the central axis 9 in the other embodiment as shown in

[0120] The gap asymmetry performance can be measured by performing an absolute radial CTE deviation analysis over a certain temperature range. For example, Figure 4 shows the radial deviation of the average CTE of two isotropic graphite materials (A and B) that can be used as punches and dies for the apparatus 1 at 1200 °C. Figure 4 shows the expansion radial deviation in ppm / °C relative to the average expansion in the x-y plane of the graphite (expansion in the z-direction is not important for the operation of the tool 1). Figure 4 shows that for a material to successfully maintain the required gap over a large temperature range, from e.g. room temperature to 2000 °C, the maximum variation of the radial deviation from the average CTE in the x-y plane cannot be > 0.3 x 10 -6 / °C. Therefore, to maintain the required gap 3 over the temperature range required for sintering the insulating ceramic powder as disclosed herein having a resistivity of 1 x 10 +10 and more, it can be preferable to minimize the radial deviation from the average CTE and, therefore, the radial deviation is preferably 0.3 x 10 -6 / °C and less, preferably 0.25 x 10 -6 / ℃ and smaller, preferably 0.2×10 -6 / ℃ and smaller, preferably 0.18×10 -6 / ℃ and less. In some embodiments, it may be preferred to maintain a radial deviation from the average CTE of 0.16 × 10⁻⁶. -6 / ℃ and smaller, preferably 0.14×10 -6 / ℃ and smaller, preferably 0.12×10 -6 / ℃ and smaller, preferably 0.1×10 -6 / ℃ and smaller, preferably 0.08×10 -6 / ℃ and smaller, preferably 0.06×10 -6 / ℃ and less, to provide the desired gap 3 in a temperature range from room temperature to up to the sintering temperature of the ceramic powder and including up to and about 2000℃ of the operating temperature of the equipment. The disclosed radial deviation range of the average CTE of at least one graphite material in the x / y plane needs to be maintained at 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, each relative to the rotational position of the die and the upper punch and / or lower punch.

[0121] When sintered as disclosed herein, having approximately 1×10 -5 Up to 1×10 +10 When using partially conductive ceramic powder with high resistivity, the radial deviation from the average CTE can be 0.5 × 10⁻⁶. -6 / ℃ and smaller, preferably 0.4×10 -6 / ℃ and smaller, preferably 0.3×10 -6 / ℃及 Smaller, preferably 0.25×10 -6 / ℃ and smaller, preferably 0.2×10 -6 / ℃ and smaller, preferably 0.18×10 -6 / ℃ and smaller, preferably 0.16×10 -6 / ℃ and smaller, preferably 0.14×10 -6 / ℃ and smaller, preferably 0.12×10 -6 / ℃ and smaller, preferably 0.1×10 -6 / ℃ and smaller, preferably 0.08×10 -6 / ℃ and smaller, preferably 0.06×10 -6 / ℃ and less. Material B exhibits unacceptable CTE expansion in the xy plane, while material A exhibits acceptable CTE expansion over the entire temperature range.

[0122] Figure 5A) shows the standard deviation in parts per million (ppm) of the CTE of the graphite materials in the x / y plane, and B) Figure 4 the absolute change (delta) in CTE (from lowest to highest) in the x-y plane over the entire temperature range of the two materials. Preferred are those graphite materials which have a lower standard deviation and absolute change in CTE in the x / y plane.

[0123] Figure 6 Depicts the change in thermal expansion coefficient of graphite materials A and B from 400 °C to 1400 °C.

[0124] The advantages of the specific tool set 1 design used according to one embodiment can result in an overall technical effect to provide very high purity large ceramic bodies with high and uniform density and low bulk porosity, and thereby reduce the tendency for cracking in the sintering process according to the present disclosure, in particular the SPS process. Thus, all features disclosed in relation to the tool set also apply to sintered ceramic body products having a size larger than 100 mm.

[0125] By using a tool set as disclosed herein, a more uniform temperature distribution can be achieved in the powder to be sintered and sintered ceramic bodies, in particular large size cordierite sintered bodies (with a maximum size of more than, for example, 100 mm and / or 200 mm) having a very high (>98% of the theoretical density of the given material) and uniform (<4% variation over the maximum size) density can be prepared, thereby reducing the tendency for cracking. The word “uniform” means that a material or system has essentially the same properties at every point; it is uniform, without irregularities. Thus, “uniform temperature distribution” means that the temperature distribution is uniform in space and does not have a considerable gradient, i.e., there is a substantially uniform temperature regardless of the position along the horizontal x-y plane of the ceramic powder 5. More specifically, “uniform temperature distribution” means that the temperature distribution over at least one ceramic powder 5 disposed within the interior volume defined by the tool set of the sintering apparatus during heating and sintering is at most 0.15 °C / cm to 5 °C / cm.

[0126] The disclosed tool set can also include spacer elements, gaskets, shims, and other tool set components. Typically, such components are made of at least one graphite material having properties as disclosed herein.

[0127] Process for producing large sintered ceramic bodies

[0128] The above SPS tool 1 is used in the following process. Thus, all features disclosed in relation to the tool set 1 also apply to this process, and thus all features disclosed in relation to this process also apply to products of sintered ceramic bodies having a maximum size of 100 mm and even up to and including about 625 mm.

[0129] In one embodiment, disclosed herein is a method of manufacturing a sintered ceramic body, the method comprising the following process steps: (a) disposing at least one ceramic powder within an interior volume of a spark plasma sintering tool, wherein the spark plasma sintering tool comprises: a die comprising a sidewall, the sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining the interior volume; an upper punch and a lower punch operably coupled with the die, wherein each of the upper punch and the lower punch has an outer diameter that is less 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 interior volume of the die, a gap is created between each of the upper punch and the lower punch and the inner wall of the die, wherein the gap is 10 pm to 100 pm wide; (b) creating a vacuum condition within the interior volume; (c) moving at least one of the upper punch and the lower punch to apply pressure to the ceramic powder while heating the ceramic powder to a sintering temperature and sintering the ceramic powder to form a sintered ceramic body; and (d) reducing the temperature of the sintered ceramic body.

[0130] The method is characterized in that the above-mentioned SPS tool set is located inside a vacuum chamber and comprises at least one die system and an upper punch and a lower punch which together define a volume, whereby the sintering process of the powder is performed by disposing the powder within the volume defined by the tool set of the sintering apparatus. The die system can have an inner wall and the at least one punch system can have an outer wall, wherein the inner wall of the die system and the outer wall of the punch system are separated by a gap.

[0131] 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 technologies employ direct current to heat a conductive die structure, whereby the material to be sintered is deposited in the die. This way of heating allows very high heating and cooling rates to be applied, thereby enhancing densification mechanisms over diffusion mechanisms that promote grain growth, and transferring the inherent properties of the original powder into a near or fully dense product. The SPS method as disclosed herein preferably uses non-pulsed continuous direct current.

[0132] The specific process steps (a) to (d) are now explained in detail:

[0133] Process step (a) - disposing at least one ceramic powder within a tool set of a sintering apparatus :

[0134] As mentioned above, at least one ceramic powder is disposed in the die system between the upper punch and the lower punch of the sintering apparatus. The spark plasma sintering apparatus used in the process according to the present technology typically comprises a cylindrical die system. The ceramic powder is disposed in the die system, and the die system filled with the powder is disposed between the upper punch and the lower punch.

[0135] The ceramic powder to be disposed in the tool for sintering as disclosed herein can be, for example, a ceramic powder formed of any metal oxide (oxide ceramic), any metal nitride (nitride ceramic), any combination or mixture of metal oxides (mixed metal oxide), or a ceramic material formed of a non-oxide (carbide, boride as defined herein).

[0136] The oxide ceramic can be any metal oxide without limitation. The metal element forming the oxide ceramic can be one or two or more selected from the group consisting of metalloid elements such as boron (B), silicon (Si), germanium (Ge), antimony (Sb), and bismuth (Bi); representative 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), and gold (Au); and lanthanoid elements such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Er), and lutetium (Lu). Among them, it is preferable that the metal element is one or more elements selected from the group consisting of Mg, Y, Ti, Zr, Cr, Mn, Fe, Zn, Al, and Er.

[0137] More specifically, examples of the oxide ceramic include yttria, alumina, yttrium aluminum monocline (YAM), yttrium aluminum garnet (YAG), yttrium aluminum perovskite (YAP), zirconia, chromia, titania, cobaltite, magnesia, silica, calcium oxide, 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, terbium 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, yttria oxide, titanium silicate oxide, tantalum silicate oxide, and mixtures thereof. The oxide ceramic as disclosed herein can have a very high resistivity, and thus is an electrically non-conductive insulator.

[0138] The metal nitride can be any metal nitride without limitation. The metal element forming the nitride ceramic can be one or two or more selected from among metalloid elements such as boron (B), silicon (Si), germanium (Ge); representative 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), and gold (Au); and lanthanide elements such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Er), and lutetium (Lu). Specific examples of nitride ceramics include boron nitride, titanium nitride, silicon nitride, and aluminum nitride. In addition to electrically conductive titanium nitride, the nitride ceramic as disclosed herein can have a high resistivity and thus be a non-conductive insulator.

[0139] The mixed metal oxide can include oxides such as forsterite, talc, cordierite, mullite, barium titanate, lead titanate, lead zirconium titanate, Mn-Zn ferrite, Ni-Zn ferrite, and Sialon ceramic (silicon nitride), and mixtures thereof. These mixed metal oxides can be inherently electrically conductive or insulating, depending on the composition.

[0140] Examples of non-oxide ceramics include carbides such as tungsten carbide, chromium carbide, vanadium carbide, niobium carbide, molybdenum carbide, tantalum carbide, titanium carbide, zirconium carbide, hafnium carbide, silicon carbide, and boron carbide. The non-oxide ceramic including carbides as disclosed herein can have a moderate resistivity and thus have an electrical conductivity less than that of metals and greater than that of oxides and / or nitrides and mixed metal oxide ceramics as disclosed herein.

[0141] Examples of non-oxide ceramics include borides such as molybdenum boride, chromium boride, hafnium boride, zirconium boride, tantalum boride, and titanium boride or titanium diboride, and titanium nitride. The non-oxide ceramic including borides as disclosed herein can have a moderate resistivity and thus have an electrical conductivity less than that of metals and greater than that of oxides, nitrides, and mixed metal oxide ceramics as disclosed herein.

[0142] Ceramic powders including non-oxides such as carbides and borides can have an electrical conductivity between that of oxides, nitrides, and mixed metal oxides, and powders including metallic materials have very low resistivity.

[0143] The ceramic powder starting material used to perform the sintering process as disclosed herein is at least one commercially available ceramic powder of high purity. However, other ceramic powders can also be used, for example those manufactured by chemical synthesis processes and related methods.

[0144] In one embodiment, the multilayer sintered body can be formed by arranging different powders or different powder mixtures in a layered manner, respectively. For example, an alumina and yttria powder mixture can be used as a first powder, and for example, a different ceramic powder mixture such as a mixture of alumina and zirconia can be used as a second powder mixture. In one example, the zirconia is present in an amount of 5 to 25 vol.-%, preferably 10 to 25 vol.-%, preferably 15 to 25 vol.-%, preferably 15 to 17 vol.-%, preferably 20 to 25 vol.-%, preferably 5 to 20 vol.-%, preferably 5 to 15 vol.-%, preferably 5 to 10 vol.-%, preferably 15 to 20 vol.-%, each of the sintered ceramic body. The mixture of alumina and zirconia can be prepared and calcined as detailed herein. In such embodiments, the powder mixture is preferably homogenously dispersed.

[0145] In such mixtures comprising zirconia, the zirconia powder can have a particle size distribution with d10 between 0.08 pm to 0.20 pm, d50 between 0.3 pm to 0.7 pm and d90 between 0.9 pm to 5 pm. The average particle size of the zirconia powder used as starting material for the mixture according to one embodiment of the present application can be 0.3 pm to 1 pm.

[0146] The zirconia powder preferably has a specific surface area of 1 m 2 / g to 16 m 2 / g, preferably between 2 m 2 / g to 12 m 2 / g, and more preferably between 5 m 2 / g to 9 m 2 / g, and the purity of the zirconia powder starting material is typically higher than 99.5 %, preferably higher than 99.8 %, preferably higher than 99.9 %, preferably higher than 99.99 %. This corresponds to a total impurity content of 5000 ppm and less, preferably 2000 ppm and less, preferably 1000 ppm and less, preferably 100 ppm and less.

[0147] In some multi-layer embodiments, wherein the process component comprises a substrate layer and a surface layer, the substrate layer preferably comprises at least one crystalline phase comprising alumina and zirconia, wherein the zirconia is each present in an amount of 5 vol.% to 25 vol.%, preferably 10 vol.% to 25 vol.%, preferably 15 vol.% to 25 vol.%, preferably 15 vol.% to 17 vol.%, preferably 20 vol.% to 25 vol.%, preferably 5 vol.% to 20 vol.%, preferably 5 vol.% to 15 vol.%, preferably 5 vol.% to 10 vol.%, preferably 15 vol.% to 20 vol.% of the sintered ceramic body; and the surface layer comprises at least one yttrium aluminum oxide crystalline phase, wherein the at least one yttrium aluminum oxide crystalline phase comprises pores having a pore diameter of no more than 5 pm and at least 95% of the pores have a maximum pore diameter of 1.5 pm.

[0148] In such multi-layer embodiments, although the composition can not be limited, the layer of powder or powder mixture preferably has a closely matched coefficient of thermal expansion (CTE) in the temperature range of about 200 °C to about 1700 °C. Preferably, the difference in CTE is 0.5 x 10-6 / °C and less, preferably 0.4 x 10-6 / °C and less, preferably 0.3 x 10-6 / °C and less, preferably 0.2 x 10-6 / °C and less, preferably 0.1 x 10-6 / °C and less, preferably 0.09 x 10-6 / °C, preferably 0.07 x 10-6 / °C, and preferably 0.05 x 10-6 / °C.

[0149] The purity of the ceramic powder starting material is preferably higher than 99.99%, preferably higher than 99.995%, preferably higher than 99.9975%, preferably higher than 99.999%, preferably higher than 99.9995%, and in some embodiments, the purity of the ceramic powder is higher than 99.9999%. In other words, the total impurity level of the ceramic powder can each be 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, and still more preferably 1 ppm and lower (including 0 ppm) relative to the total mass of the ceramic powder starting material. High purity starting ceramic powders are desirable to provide high chemical corrosion and erosion resistance to minimize particle generation during use as a component in a semiconductor processing chamber.

[0150] The ceramic powders employed in the process of the present disclosure do not require sintering aids in comparison to other sintering techniques in the prior art. Thus, disclosed herein are ceramic powders and / or powder mixtures that are free or substantially free of sintering aids. Furthermore, the formation of a green body is not necessary, thus the ceramic powders can not comprise organic binders or dispersants, but they can be used if desired. In embodiments, the ceramic powders according to the method as disclosed herein can have a 18 m 2 / g and less, preferably 1 m 2 / g to 18 m 2 / g, typically lower than the specific surface area of nano-powders, which can have 20 m 2 / g to greater than 200 m 2 / g. The use of nano-powders with a SSA of more than 20 m 2 / g, which can have greater moisture / humidity and adsorbed gas content, can result in reduced bulk density when forming the powder compacts as disclosed herein, which can result in sintered ceramic bodies with lower density / higher porosity. Powders with a SSA of less than 1 m 2 / g can not result in full densification of the sintered ceramic body, as the driving force for sintering is reduced due to the low powder specific surface area. All SSA measurements are made according to measurements as per ASTM C1274 “Standard Test Method for Advanced Ceramic Specific Surface Area by Physical Adsorption”. In embodiments, the ceramic powder according to the methods as disclosed herein is essentially free or free of nano-powders as defined herein.

[0151] Particle size of the powders is measured using a Horiba LA-960 laser scattering particle size distribution analyzer, which is capable of measuring 10 nm to 5 mm particle size. The specific surface area of the ceramic powders is measured using a Horiba BET surface area analyzer SA-9601, which is capable of measuring 0.01 m 2 / g to 2000 m 2 / g, with a precision of 10% and less for most samples.

[0152] Preferably, the d10 particle size of the ceramic powder used as starting material in the SPS process as disclosed herein can be from 0.05 pm to 7 pm, preferably from 0.05 pm to 6 pm, preferably from 0.05 pm to 5 pm, preferably from 0.05 pm to 4 pm, preferably from 0.05 pm to 3 pm, preferably from 0.05 pm to 1 pm, preferably from 0.1 pm to 7 pm, preferably from 0.1 pm to 6 pm, preferably from 0.1 pm to 5 pm, preferably from 0.1 pm to 4 pm, preferably from 0.1 pm to 3 pm, preferably from 0.2 pm to 6 pm, preferably from 0.3 pm to 6 pm, preferably from 0.4 pm to 6 pm, and more preferably from 0.3 pm to 4 pm.

[0153] Preferably, the ceramic powder used as a starting material in the SPS process disclosed herein can have a median (d50) particle size of 0.15 pm to 100 pm, preferably 0.15 pm to 75 pm, preferably 0.15 pm to 50 pm, preferably 0.15 pm to 25 pm, preferably 0.15 pm to 10 pm, preferably 0.15 pm to 5 pm, preferably 0.15 pm to 3 pm, preferably 0.8 pm to 80 pm, preferably 0.8 pm to 60 pm, preferably 0.8 pm to 40 pm, preferably 0.8 pm to 30 pm, preferably 0.8 pm to 20 pm, preferably 0.8 pm to 10 pm, preferably 0.8 pm to 5 pm, preferably 1 pm to 100 pm, preferably 1 pm to 75 pm, preferably 1 pm to 60 pm, preferably 1 pm to 45 pm, preferably 1 pm to 30 pm, preferably 1 pm to 20 pm, preferably 1 pm to 10 pm, preferably 1 pm to 5 pm, preferably 10 pm to 100 pm, preferably 20 pm to 100 pm, preferably 40 pm to 100 pm, preferably 10 pm to 40 pm, preferably 20 pm to 40 pm, preferably 30 pm to 40 pm, preferably 3 pm to 10 pm, and preferably 2 pm to 8 pm.

[0154] Preferably, the ceramic powder used as a starting material in the SPS process disclosed herein can have a d90 particle size of 0.4 pm to 250 pm, preferably 0.4 pm to 100 pm, preferably 0.4 pm to 50 pm, preferably 0.4 pm to 25 pm, preferably 0.4 pm to 10 pm, preferably 0.4 pm to 5 pm, preferably 0.4 pm to 3 pm, preferably 0.4 pm to 1 pm, preferably 6 pm to 250 pm, preferably 6 pm to 200 pm, preferably 6 pm to 160 pm, preferably 6 pm to 120 pm, preferably 6 pm to 80 pm, preferably 6 pm to 40 pm, preferably 10 pm to 250 pm, preferably 20 pm to 250 pm, preferably 30 pm to 250 pm, preferably 40 pm to 250 pm, preferably 10 pm to 250 pm, preferably 10 pm to 140 pm, preferably 10 pm to 80 pm, preferably 3 pm to 80 pm, and preferably 10 pm to 40 pm.

[0155] Preferably, the ceramic powder used as a starting material in the SPS process disclosed herein can have a specific surface area, as measured according to ASTM C1274, of 1 m 2 / g to 18 m 2 / g, 2 m 2 / g to 18 m 2 / g, preferably 3 m 2 / g to 18 m 2 / g, preferably 4 m 2 / g to 18 m 2 / g, preferably 5 m2 / g to 18 m 2 / g, preferably 6 m 2 / g to 18 m 2 / g, preferably 1 m 2 / g to 16 m 2 / g, preferably 2 m 2 / g to 16 m 2 / g, preferably 4 m 2 / g to 16 m 2 / g, preferably 6 m 2 / g to 16 m 2 / g, preferably 1 m 2 / g to 14 m 2 / g, preferably 1 m 2 / g to 12 m 2 / g, preferably 1 m 2 / g to 10 m 2 / g, preferably 1 m 2 / g to 8 m 2 / g, preferably 2 m 2 / g to 12 m 2 / g, preferably 2 m 2 / g to 10 m 2 / g, and preferably 3 m 2 / g to 8 m 2 / g.

[0156] Preferably, the ceramic powder used as a starting material in the SPS processes disclosed herein has a log-normal particle size distribution, including a continuous distribution of particle sizes. Monomodal and bimodal particle size distributions can result in reduced powder packing density prior to sintering, and thus reduced density and / or higher density variation across the sintered ceramic body.

[0157] Preferably, the ceramic powder used in the SPS processes disclosed herein has a low amount of adsorbed gases and / or surface organics, moisture content, entrained gases, etc. The powder can optionally be subjected to various processing steps, such as tumbling, blending, calcining, sieving, etc., as desired, to minimize the weight loss relative to the total weight of the powder, and thus minimize the porosity in the sintered ceramic body. Table 3 lists the total average weight loss upon heating relative to the total weight of the powder in two or more measurements of exemplary ceramic powders. In embodiments, the ceramic powder has a weight loss relative to the total weight of the powder 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 Linseis, Inc. STA PT1600 thermogravimetric analyzer.

[0158]

[0159]

[0160] In some embodiments, the ceramic powder can be processed in a manner to remove unwanted moisture, organics, or agglomerates. Such processing can include tumbling and / or sieving prior to and / or after step a) thereof for use in the processes disclosed herein.

[0161] In certain embodiments, the ceramic powder can comprise more than one of the above oxides, nitrides, and non-oxide ceramics and combinations thereof, which 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. Calcination, drying, sieving, screening, tumbling, blending, and similar powder processing techniques can be used according to methods known in the art. For example, ball milling or end-to-end tumbling mixing can be performed as known to those skilled in the art. When high purity sintered ceramic bodies are desired, high purity (>99.99%) media can be used in order to maintain the purity of the starting powders during mixing. Wet ball milling or tumbling mixing can be performed by suspending the starting powders in various solvents such as ethanol, methanol, and other alcohols and / or water to form a slurry. A slurry can be formed having a powder loading of about 5% to about 50% by weight of the powder and a media loading of, for example, 40% to 100% by weight of the powder during milling or mixing.

[0162] In particular embodiments, the ceramic powder can optionally be calcined prior to use in the processes of the present disclosure. Exemplary calcination temperatures include temperatures of 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, 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, and preferably 6 to 8 hours in an oxygen-containing environment. Prior to and / or after calcination, the ceramic powder can be sieved and / or tumbled according to known methods. The starting ceramic powder as disclosed herein is preferably crystalline, and thereby has long-range crystalline order and identifiable X-ray diffraction peaks. In certain embodiments, the calcination conditions as disclosed herein can result in agglomeration of the powder mixture and thus can result in greater variability in the particle size distribution. Accordingly, in some embodiments, the particle size referred to herein can include individual particles, and in other embodiments, the particle size referred to herein can include agglomerates comprising more than one particle or agglomerates of multiple particles, which can be measured as a single large particle using laser particle detection methods as disclosed herein.

[0163] In some embodiments, although high density sintered ceramic bodies are not required, sintering aids can optionally be used as desired and combined with the ceramic powder according to the methods and materials as disclosed herein. In particular embodiments, the sintered ceramic body can comprise a sintering aid selected from the group consisting of silicon dioxide, zirconium oxide, calcium oxide, magnesium oxide, and combinations thereof. In certain embodiments, the sintered ceramic body can comprise a sintering aid added optionally in an amount of > 0.002 wt.%, preferably > 0.0035 wt.%, preferably > 0.005 wt.%, preferably > 0.0075 wt.%. In embodiments, the sintering aid can be added optionally in an amount of < 0.05 wt.%, preferably < 0.03 wt.%, preferably < 0.02 wt.%, preferably < 0.01 wt.%.

[0164] In other embodiments, dopants can be used as desired and combined with the ceramic powder according to the methods and materials as disclosed herein. Dopants such as rare earth oxides selected from Sc, La, Er, Ce, Cr, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu, and oxides and combinations thereof can be optionally added to the starting ceramic powder of step a) in amounts of < 0.05 wt.%, preferably < 0.03 wt.%, preferably < 0.01 wt.%, preferably 0.002 to 0.02 wt.%. In other embodiments, the above-mentioned dopants can be optionally added to the at least one ceramic powder of step a) in amounts of > 0.002 wt.%, preferably > 0.0035 wt.%, preferably > 0.005 wt.%, preferably > 0.0075 wt.%.

[0165] In further embodiments, both a dopant and a sintering aid can be optionally combined with the ceramic powder according to the methods as disclosed.

[0166] In embodiments, sintering can be performed with isothermal times of 0.5 minutes to 180 minutes, preferably 0.5 minutes to 120 minutes, preferably 0.5 minutes to 100 minutes, preferably 0.5 minutes to 80 minutes, preferably 0.5 minutes to 60 minutes, preferably 0.5 minutes to 40 minutes, preferably 0.5 minutes to 20 minutes, preferably 0.5 minutes to 10 minutes, preferably 0.5 minutes to 5 minutes, preferably 5 minutes to 120 minutes, preferably 10 minutes to 120 minutes, preferably 20 minutes to 120 minutes, preferably 40 minutes to 120 minutes, preferably 60 minutes to 120 minutes, preferably 100 minutes to 120 minutes, preferably 30 minutes to 60 minutes, preferably 15 minutes to 45 minutes, in other embodiments, sintering with isothermal dwell times can apply for 0 to 30 minutes; preferably 0 minutes to 20 minutes; preferably 0 minutes to 10 minutes; preferably 0 minutes to 5 minutes. In certain embodiments, sintering can be performed with zero isothermal time, or no isothermal holding time, and upon reaching the sintering temperature, the cooling step as disclosed herein is initiated.

[0167] Process step (b) - creating vacuum conditions within the internal volume;

[0168] Once the ceramic powder is loaded into the die, a pressure of 5 MPa to 20 MPa, preferably 8 MPa to 20 MPa, preferably 10 MPa to 20 MPa, and preferably 5 MPa to 10 MPa, can be applied to the ceramic powder disposed within the interior volume of the spark plasma sintering tool, whereby after the pressure is applied the ceramic powder forms a powder compact that can have a fill density of 20 vol% to 60 vol%, 20 vol% to 50 vol%, preferably 30 vol% to 60 vol%, preferably 30 vol% to 55 vol%, preferably 40 vol% to 60 vol%, and preferably 40 vol% to 50 vol%. Higher fill densities are desirable to improve the thermal conductivity within the powder compact, thereby reducing the temperature differential in the powder compact during heating and sintering. The powder compact is formed from the ceramic powder disclosed herein without the use of organic additives such as dispersants, binders, anti-flocculants, and the like, and thus is free or substantially free of organics. Thereafter, vacuum conditions known to those skilled in the art are established within the chamber between the punches enclosed by the die. Typical vacuum conditions include 10 -2 tor to 10 -3 tor. The vacuum is applied primarily to remove air to prevent the graphite material from burning and to remove most of the air from the powder.

[0169] Process step (c) moving at least one of the upper punch and the lower punch to apply pressure to the ceramic powder, while simultaneously heating the ceramic powder to a sintering temperature and sintering the ceramic powder to form a sintered ceramic body; and process step (d) reducing the temperature of the sintered ceramic body Figure 7

[0170] After the at least one ceramic powder is disposed in the die and most of the air has been removed from the interior volume defined by the tool set and the powder 5, a pressure is applied to the ceramic powder disposed between the graphite punches by moving at least one of the upper punch and the lower punch toward the other in the axial direction. The pressure is applied to the at least one ceramic powder disposed within the interior volume defined by the tool set, the pressure ranging from 5 MPa to 60 MPa, preferably 5 MPa to 40 MPa, preferably 5 MPa to 20 MPa, preferably 5 MPa to 15 MPa, preferably 10 MPa to 60 MPa, preferably 10 MPa to 40 MPa, preferably 10 MPa to 30 MPa, preferably 10 MPa to 20 MPa, preferably 13 MPa to 18 MPa, preferably 15 MPa to 60 MPa, preferably 15 MPa to 40 MPa, preferably 15 MPa to 30 MPa, preferably 20 MPa to 40 MPa. The pressure is applied to the at least one ceramic powder in the axial direction.

[0171] In preferred embodiments, the ceramic powder is heated directly by the punches and die of the SPS apparatus. The die can be constructed of an electrically conductive material such as a variety of graphite materials as disclosed herein, which facilitates resistive / joule heating. SPS apparatus and procedures are disclosed, for example, in US 2010 / 0156008 Al, which is incorporated herein by reference.

[0172] Applying heat to the ceramic powder disposed in the die assists in a sintering temperature of 1000°C to 1700°C, preferably 1200°C to 1700°C, preferably 1400°C to 1700°C, preferably 1500°C to 1700°C, more preferably 1600°C to 1700°C, preferably 1400°C to 1650°C, preferably 1500°C to 1650°C, preferably 1400°C to 1600°C, preferably 1500°C to 1600°C.

[0173] Figure 7 A, Figure 7 B and Figure 7 C illustrates the effect of different kinds of ceramic powders on the current path and heating in the SPS apparatus comprising a gap as disclosed herein. In Figure 7 A), the ceramic powder 5 is a predominantly conductive powder (e.g., a metal powder). Here, the powder resistivity is less than graphite, and the current flows directly through the powder rather than extending into the die 6 or die system 2, thereby assisting in uniform sintering of the powder disposed between the punches 4 and 4'. Thus, for the metal ceramic powder 5, the size of the gap 3 is irrelevant to the current path and heating.

[0174] In Figure 7 B), the ceramic powder 5 is a partial conductor (e.g., non-oxide ceramics and / or those mixed metal oxides as disclosed herein having a resistivity from about 1 x 10 -5 to 1 x 10 +10 , and the resistivity of these partial conductors can be greater than, about, or less than the resistivity of graphite, and the current flows through both the powder and the graphite, depending on the resistivity of the powder. Thus, the size of the gap 3 between the graphite die 6 (or graphite die system 2) and the upper and lower punches 4 and 4' is preferably 10 pm to 100 pm to ensure sufficient current flow and heating of the ceramic powder 5. According to Figure 7 B, the gap can be maintained from ambient temperature to the specific sintering temperature of the partially conductive ceramic powder to be sintered, and up to and including a maximum apparatus temperature of about 2,000°C.

[0175] In Figure 7 C), the ceramic powder 5 is an insulator (e.g., oxide ceramics, nitride ceramics, and non-conductive mixed metal oxides as disclosed herein), and the current passes from the upper punch 4 only through the graphite die 6 (or graphite die system 2) and into the lower punch 4' to sinter the ceramic powder 5. In this embodiment, as Figure 7 C illustrates, there is no significant current flow through the ceramic powder 5. According to Figure 8 C), the at least one ceramic powder 5 has, for example, a resistivity greater than 1 x 10 +5The resistivity of the oxide ceramic powder. By a gap distance of 10 pm to 70 pm, it is made possible to achieve a uniform temperature distribution in the oxide ceramic powder during the sintering process and thereby a high and uniform density and a low porosity. According to Step (e) in an optional step, annealing the sintered ceramic body by increasing the temperature of the sintered ceramic body to an annealing temperature and performing annealing by applying heat; and process step (f) reducing the temperature of the sintered ceramic body to ambient temperature by removing the heat source applied to the sintering apparatus and removing the sintered ceramic body The gap of C is maintained from the ambient temperature to the specific sintering temperature of the insulating ceramic powder to be sintered and up to and including a maximum equipment temperature of about 2,000 °C.

[0176] With reference to Description of the resulting sintered ceramic body , the temperature difference within 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 can be less than 100 °C, 1 °C to 100 °C, preferably 1 °C to 80 °C, preferably 1 °C to 60 °C, preferably 1 °C to 40 °C, preferably 1 °C to 20 °C, preferably 1 °C to 10 °C, preferably 5 °C to 100 °C, preferably 10 °C to 100 °C, preferably 20 °C to 100 °C, preferably 5 °C to 75 °C, preferably 5 °C to 50 °C, and preferably 5 °C to 25 °C, thereby applying this temperature difference to the ceramic powder during heating and sintering to achieve a uniform temperature distribution in the ceramic powder during sintering. When the size of the punch and die increases, the uniformity of the temperature in the powder 5 during sintering poses a greater challenge. Thus, the uniformity of the temperature disclosed at larger sizes can be more easily achieved at smaller sizes of the punch and die, and thus a small (i.e., e.g., 25 °C and less) variation of the disclosed temperature when sintering larger ceramic bodies can be assumed to be at least equal to or less than the temperature variation disclosed for smaller ceramic bodies.

[0177] The temperature gradient within the largest dimension of the sintered ceramic body can also be expressed by the normalized change of temperature within the largest dimension. Thus, in certain embodiments, the temperature difference of the at least one ceramic powder 5 disposed within the interior volume defined by the tool set of the sintering apparatus during heating and sintering is from 0.15 °C / cm to 5 °C / cm, preferably from 0.15 °C / cm to 3 °C / cm, preferably from 0.15 °C / cm to 2 °C / cm, preferably from 0.15 °C / cm to 1 °C / cm, preferably from 0.15 °C / cm to 0.5 °C / cm, preferably from 0.4 °C / cm to 5 °C / cm, preferably from 0.4 °C / cm to 3 °C / cm, preferably from 0.4 °C / cm to 1 °C / cm, and preferably from 0.25 °C / cm to 0.80 °C / cm to achieve a uniform temperature distribution within the ceramic powder during sintering. The word “uniform” means that a material or system has essentially the same properties at every point; it is uniform, without irregularities. Thus, a “uniform temperature distribution” means that the temperature distribution is uniform in space and does not have a considerable gradient, i.e., there is a substantially uniform temperature regardless of the position along the ceramic powder 5 in the horizontal x-y plane. More specifically, a “uniform temperature distribution” means that the temperature distribution on the at least one ceramic powder 5 disposed within the interior volume defined by the tool set of the sintering apparatus during heating and sintering is at most 0.15 °C / cm to 5 °C / cm.

[0178] By using an SPS tool set having a gap size range as disclosed herein, whereby the gap is maintained throughout the method and in particular during the sintering step c) of the method as disclosed, resistive overheating is prevented and thus this temperature difference can be minimized, such that the density in the sintered ceramic body has a minimal variation within the distance between the inner surface 8 of the mold system and the center axis 9 defining the center. The uniform densification during sintering can result in a density variation over the largest dimension of the sintered ceramic body as disclosed herein, which is preferably less than 4%, less than 3%, preferably less than 2%, preferably less than 1%, more preferably less than 0.5%, preferably from 0.25% to 5%, preferably from 0.25% to 4%, preferably from 0.25% to 3%, preferably from 0.25% to 2%, preferably from 0.25% to 1%, preferably from 0.25% to 0.5%, preferably from 0.5% to 3.5%, and more preferably from 1% to 3% over the largest dimension of the sintered ceramic body.

[0179] Further contributing to the uniform densification during sintering is a high packing density of the powder compact comprising the ceramic powder as disclosed herein before sintering of from 30% to 60% by volume, which can be achieved using the ceramic powder and method as disclosed.

[0180] The temperature of the sintering apparatus according to the present disclosure is typically measured within a mold containing at least one graphite material of the sintering apparatus. Thus, it is preferred to measure the temperature as close as possible to the ceramic powder being sintered in order to indeed achieve the indicated temperature within the ceramic powder.

[0181] In one embodiment, the sequence of application of pressure and temperature can vary according to the present disclosure, meaning that the indicated pressure can be applied first, followed by the application of heat to reach the desired temperature. Furthermore, in other embodiments, the indicated heat can also be applied first to reach the desired temperature and thereafter the indicated pressure is applied. In a third embodiment according to the present disclosure, temperature and pressure can be applied simultaneously to the ceramic powder to be sintered and increased until the indicated values are reached.

[0182] Inductive or radiative heating methods can also be used to heat the sintering apparatus and the ceramic powder in the set of tools for indirect heating.

[0183] In contrast to other sintering techniques, there is no need to prepare the powder prior to sintering, i.e. by cold pressing or forming a green body using organic additives such as binders, dispersants, etc. prior to sintering, and the powder is directly filled into the inner volume of the spark plasma sintering tool to form a powder compact without using the above-mentioned organic additives. This reduced processing can provide a higher purity in the final sintered ceramic body.

[0184] According to aspects of process step c), the temperature and pressure are maintained for a period of time of 1 minute to 360 minutes, preferably 1 minute to 240 minutes, preferably 1 minute to 120 minutes, preferably 1 minute to 60 minutes, preferably 5 minutes to 360 minutes, preferably 10 minutes to 360 minutes, preferably 30 minutes to 360 minutes, preferably 45 minutes to 360 minutes, preferably 60 minutes to 360 minutes, preferably 60 minutes to 90 minutes for sintering. At the end of step c) of the sintering process, the ceramic powder sintered to form a sintered ceramic body is preferably cooled according to the natural convection of the process chamber (non-forced cooling) until a temperature is reached that can facilitate the optional annealing process of step e). In further embodiments, the now sintered ceramic body can be cooled under inert gas convection, for example under 1 bar of argon or nitrogen. Other gas pressures greater or lower than 1 bar can also be used. In order to initiate the cooling step, the electrical power applied to the SPS apparatus can be removed. The pressure applied to the sintered sample is removed at the end of the sintering process before (natural) cooling occurs.

[0185] Upon sintering of the powder to form a sintered ceramic body, a volume reduction of about 30% can occur, depending on the packing density of the ceramic powder 5 prior to the sintering step.

[0186] Table 4 Table 5 Figure 15 :

[0187] In optional step (e), the sintered ceramic body resulting from step d) is subjected to an annealing process. The annealing can 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, the sintered ceramic body can be removed from the sintering apparatus after cooling according to process step (d) and the annealing process step can be performed in a separate apparatus such as a furnace. In other embodiments, for annealing according to the present disclosure, the ceramic body in step (c) can subsequently be annealed within the sintering apparatus without removing from the sintering apparatus between sintering step (c) and optional annealing step (e).

[0188] Annealing results in refinement of the chemical and physical properties of the sintered ceramic body. The annealing step can be performed by conventional methods for annealing of glasses, ceramics and metals and the degree of refinement can be selected by choice of annealing temperature and duration of time allowed to continue annealing.

[0189] The optional annealing step (e) can be performed at a temperature of 1200 °C to 1800 °C, preferably 1250 °C to 1700 °C, more preferably 1300 °C to 1650 °C. At such temperatures, oxygen vacancies in the crystal structure can be corrected back to the stoichiometric ratio.

[0190] 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 to 12 hours, preferably 6 to 10 hours.

[0191] The optional annealing process step (e) is preferably performed in an oxidizing atmosphere in air.

[0192] After performing the optional process step (e) of annealing the sintered ceramic body, the temperature of the annealed sintered ceramic body is reduced to ambient temperature according to process step (f). The sintered and in certain embodiments annealed ceramic body thus produced is highly dense and typically has an average grain size of 0.25 μm to 18 μm, preferably 0.25 μm to 13 μm, preferably 0.25 μm to 10 μm, preferably 0.25 μm to 8 μm, preferably 0.25 μm to 5 μm, preferably 0.5 μm to 18 μm, preferably 0.75 μm to 18 μm, preferably 1 μm to 18 μm, preferably 2 μm to 18 μm, preferably 5 μm to 18 μm, preferably 0.5 μm to 10 μm, preferably 0.75 μm to 8 μm, preferably 0.75 μm to 5 μm.

[0193] In some embodiments, sintered (and in certain embodiments, annealed) ceramic bodies according to the present disclosure can comprise non-conductive metal oxides, nitrides, or mixed metal oxides formed from ceramic powders having properties as disclosed herein.

[0194] In alternative embodiments, sintered (and in certain embodiments, annealed) ceramic bodies according to the present disclosure can include sintered ceramic bodies formed from mixed metal oxides such as forsterite, talc, cordierite, mullite, barium titanate, lead titanate, lead zirconium titanate, Mn-Zn ferrite, Ni-Zn ferrite, and Sialon ceramics, and mixtures thereof, having properties as disclosed herein. Mixed metal oxides as disclosed herein can be conductive or insulating and are formed according to particular gap widths, apparatuses, and methods as disclosed.

[0195] According to one embodiment and as described above, the SPS process is suitable for making large sintered ceramic bodies having maximum dimensions of 100 mm and greater. The process as disclosed provides for rapid powder consolidation and densification, maintains small (about less than 15 pm) average grain size in the sintered body, in some embodiments transfers from the starting ceramic powder particle size, and achieves high densities exceeding 98% of the theoretical density of the particular material with <4% variation in density across the maximum dimension. This combination of fine grain size, uniformity, and high density provides large size, high strength sintered ceramic bodies suitable for machining, handling, and use as components in semiconductor processing chambers. Accordingly, sintered (and in certain embodiments, annealed) ceramic bodies according to the present disclosure can comprise metal oxides, metal nitrides, metal carbides, metal borides, or mixed metal oxides having diameters greater than 100 mm having properties as disclosed herein according to certain embodiments.

[0196] For example, in one embodiment, the sintered (and in certain embodiments annealed) ceramic body can be formed from the powders disclosed herein into a disc shape having a size of 40 mm to about 625 mm, a thickness ranging from about 3 mm to about 60 mm, preferably a thickness of 5 mm to 50 mm. In another embodiment, the sintered (and in certain embodiments annealed) ceramic body can be formed into a circular disc shape having a diameter of 100 mm to about 625 mm. In an alternative embodiment, 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 mm to about 625 mm, preferably 350 mm to about 625 mm, preferably 400 mm to about 625 mm, more preferably 450 mm to about 625 mm, more preferably 500 mm to about 625 mm, more preferably 550 mm to about 625 mm, each relative to the maximum dimension of the sintered ceramic body.

[0197] Finally, the sintered ceramic body can be machined to form a final sintered component, e.g., for a plasma processing chamber, such as a dielectric window or RF window, a focus ring, a nozzle or gas injector, a showerhead, a gas distribution plate, an etch chamber liner, a plasma source adapter, a gas inlet adapter, a diffuser, an electrostatic wafer chuck, a chuck, a positioning disk, a mixing manifold, an ion suppressor element, a faceplate, an isolator, a spacer, and a guard ring, for example. The sintered ceramic body (or sintered and annealed) can be machined to produce the sintered component according to methods known to those skilled in the art.

[0198] The methods as disclosed herein provide high density and related low porosity, minimal density variation, high purity, high mechanical strength, and thus handleability of the sintered ceramic body / component, particularly for those ceramic bodies having a maximum dimension greater than, for example, 100 to about 625 mm. All features disclosed with respect to the process / method are also applicable to the product of the sintered ceramic body as disclosed herein.

[0199] Figure 15

[0200] The particular ceramic bodies prepared according to the process disclosed above have improved resistance to cracking by high density and minimal density variation, high mechanical strength, and in addition, higher purity and improved etch resistance. In the following, separate embodiments of ceramic bodies having improved properties prepared according to the methods as disclosed herein are described. All features disclosed with respect to the product of the sintered ceramic body are also applicable to the process / method as disclosed herein.

[0201] ​Density measurements were made according to ASTM B962-17. The density values and standard deviations reported herein are the average of 5 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 volumetric porosity (Vp) is calculated from the density measurements as follows:

[0202]

[0203] where p sample is the (Archimedes) density measured according to ASTM B962-17, ptheoretical is the reported theoretical density, and RD is the relative fractional density. Using this calculation, volumetric porosity levels of 0.1% to 4% and less are calculated from the measured density values of the sintered ceramic bodies as disclosed herein. Along with high packing or bulk densities, variations in density can also improve handleability at large sizes. Table 4 discloses the theoretical density (as disclosed according to available literature), density, theoretical density %, volumetric porosity %, and size of a number of exemplary sintered ceramic bodies comprising oxide and nitride ceramics as disclosed herein. For reference, YAG as known to those skilled in the art comprises a yttrium aluminum garnet structure with a composition of Y3Al50i2, ZTA comprises zirconia toughened alumina, and spinel comprises magnesium aluminate spinel MgAl204. As shown in Tables 4 and 5, for all materials, a theoretical density of greater than 97% of the theoretical density of the respective material was achieved, which were manufactured with a sintering set of tools as disclosed herein having a gap of 10 pm to 70 pm for the insulator material. The very high theoretical density of zirconia can be affected by the presence of hafnium oxide, which is common for zirconia powders and can increase the overall density. 12

[0204] Figure 15

[0205]

[0206] Density variations were measured from samples taken from the maximum size, then the variation was calculated relative to the highest density measured.

[0207] Table 5 lists the size, average density, theoretical density percent (TD), volumetric porosity %, density variation %, and variation % / cm of exemplary sintered ceramic bodies according to embodiments as disclosed herein.

[0208] Figure 15

[0209]

[0210]

[0211] ​Sample 506 containing YAG is shown in Figure 15 A and Table 6 B in. Table 7 A) shows the high-density microstructure in a SEM micrograph at 5000x, and b) shows the percentage of the theoretical YAG density of the sintered ceramic body according to Example 506 disclosed herein, as well as the density variation at the maximum size. Analysis was performed using the Heyn line intercept method known to those skilled in the art. Table 8: Dielectric Results A 5000x SEM image of sample A was used for grain size measurement, and the average grain size was measured to be 6.2 μm with a standard deviation of 0.71 μm in 25 replicates. The maximum and minimum grain sizes of sample 506 were also measured to be 7.7 μm and 5.0 μm, respectively. Hardness was measured according to ASTM standard C1327, and the average hardness was measured to be approximately 14.8 GPa, using an applied load of 0.025 kgf. The average hardness was calculated through 8 measurements or replicates on the sample surface, with maximum and minimum hardness values ​​of 16 GPa and 12.7 GPa, respectively.

[0212] Density measurements were performed on samples cut along the sample radius according to ASTM B962-17, and the density results are shown in... Figure 8 In section B, five measurements were taken at six locations along the radius. The average density measured was 4.546 g / cc, corresponding to 99.783% of the theoretical YAG value, with a volumetric porosity of 0.217%. The density along the radius ranged from 99.7% to 99.9% of the theoretical YAG value. The density variation relative to the highest density measurement along the radius was measured as shown in Figure 25B, with a maximum density variation of 0.208%.

[0213] In contrast, according to Table 6, sintered ceramic bodies made from non-conductive oxide ceramics using sintering equipment with gap sizes greater than approximately 90 μm result in theoretical densities of non-conductive oxide ceramics ranging from 95% to less than 97%, with density variations of 4.5% and greater. Sintered ceramic bodies prepared according to Table 6 generally result in lower and non-uniform densities and lead to cracking, particularly at body sizes of, for example, 150 mm and greater.

[0214] Figure 9

[0215]

[0216]

[0217] The resistivity of sintered ceramic bodies with gap widths ranging from 10 μm to 70 μm formed using this method and apparatus was measured. Table 7 lists the resistivity measurements of exemplary sintered ceramic bodies. This process and material result in sintered ceramic bodies with high resistivity and correspondingly low electrical conductivity.

[0218] Table 9

[0219]

[0220] As the frequency increases, it becomes important to provide sintered ceramic bodies with low dielectric loss. The high total purity of sintered ceramic bodies as disclosed herein in Tables 6 and 7, and particularly those with low silica content, provide preferred results for dielectric constant and dielectric loss or dissipation factor as disclosed in Table 8 for sintered ceramic bodies comprising yttria. In addition, dielectric loss can be affected by grain size and grain size distribution. Fine grain size can also provide reduced dielectric loss and thereby reduced heating when used at higher frequencies. For sintered ceramic bodies comprising high purity yttria, dielectric loss of about 1 x 10 -4 to 5 x 10 -2 , preferably 1 x 10 -4 to 1 x 10 -2 , more preferably 1 x 10 -4 to 1 x 10 -3 may be achieved. As shown in Table 8, yttria sample 157 had an average dielectric constant of 11.3 and an average dielectric loss of 3.6 x 10 -2 over 4 measurements.

[0221] Table 10

[0222]

[0223] In preferred embodiments, high mechanical strength can be achieved by controlling the grain size in the sintered ceramic body, whereby finer grain size provides higher flexural strength. Applications of ceramic sintered bodies Exemplary grain size and grain size distribution for YAG (yttrium aluminum garnet) and yttria sintered ceramics as disclosed herein are shown. Table 9 lists the grain size characteristics of sintered ceramic bodies of Figure 10 .

[0224] Figure 10

[0225]

[0226] Correspondingly, Table 10 lists the 4-point flexural strength results for exemplary sintered ceramic bodies as disclosed. Measurements were made according to ASTM C1161-18, where n is the number of tests made. High strength was measured for those materials comprising sintered ceramic bodies as disclosed.

[0227] Figure 11

[0228]

[0229] The sintered ceramic bodies and related components as disclosed herein provide improved plasma resistance and enhanced ability to clean within a semiconductor processing chamber through certain material properties and features described below.

[0230] Examples :

[0231] The sintered ceramic bodies thus produced can be used in semiconductor plasma processing equipment for plasma etching, deposition, and similar processes.

[0232] Most integrated circuit (IC) fabrication processes generally include a plurality of fabrication steps that can sequentially form, shape, or otherwise modify various layers. One way of forming a layer can be to deposit and then etch the layer. Generally, etching can include forming an etch mask on an underlying layer. The etch mask can have a particular pattern that can mask certain portions of the underlying layer while exposing other portions. The portions of the underlying layer exposed by the etch mask can then be removed. In this way, the etch mask pattern can be transferred to the underlying layer.

[0233] Etching can include "wet" chemical etching and "dry" plasma etching. In many cases, plasma etching can provide greater controllability and greater directional control (e.g., anisotropy) if desired.

[0234] Accordingly, plasma etching is currently used to process semiconductor materials for the manufacture of electronic devices. Small features can be etched into the surface of a semiconductor material in order to be more efficient or enhance certain properties when used in an electronic device. For example, plasma etching can be used to create deep trenches on a silicon surface for use in microelectromechanical systems. This application suggests that plasma etching also has the potential to play a major role in microelectronics production. Similarly, there is currently research into how this process can be adapted to the nanoscale.

[0235] Plasma etching is generally performed in a so-called plasma etching chamber, which is generally 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.

[0236] During plasma etching, a plasma is formed above the surface of the substrate by supplying radio frequency (RF) electromagnetic radiation to a low-pressure gas (or mixture of gases). By adjusting the potential of the substrate, the charged species in the plasma can be directed to impact the surface of the substrate and thereby remove material (e.g., atoms) from the surface of the substrate.

[0237] By using a gas that chemically reacts with the material to be etched, plasma etching can be made more efficient. So-called "reactive ion etching" combines the high-energy impact effect of the plasma with the chemical etching effect of the reactive gas.

[0238] The sintered ceramic body according to the invention can be formed as a chamber component for semiconductor plasma processing chambers. Such components can have benefits including extended component life under corrosive etching conditions. Such ceramics can be made dense and pure, especially at large sizes, by sintering using the aforementioned SPS process. In the case of plasma processing, high-density ceramics can have many advantages. These include resistance to particle formation, improved resistance to plasma etching, and increased component life. Furthermore, cleaning high-density sintered ceramic components can be easier because they can be cleaned using corrosive cleaning methods such as highly corrosive or abrasive chemicals.

[0239] Examples of chamber components that may include sintered ceramic bodies according to this disclosure include substrate support assemblies, electrostatic chucks (ESCs), rings (e.g., process kit rings or single rings), chamber walls, bases, gas distribution plates, spray nozzles, gaskets, gasket kits, shielding components, plasma screens, flow equalizers, cooling substrates, chamber viewing ports, chamber covers, etc.

[0240] like Figure 4 As shown, embodiments of the technology disclosed herein can be used as components in a plasma processing system 9500, which can be configured for semiconductor etching processes and is also referred to as a "plasma etching processing system". The plasma etching processing system 9500 in the embodiments may include a remote plasma region. The remote plasma region may include a remote RF source / matching network 9502, which is also referred to as a remote plasma source ("RPS").

[0241] The plasma etching system 9500 may 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 cover ring or electrode cap 9514, a top shielding ring 9512, and a shielding ring 9513 surround the wafer 50 and the positioning disk 9509. In a physical vapor deposition (PVD) process, a substrate ring including the cover ring 9514 is provided around the periphery of the substrate. The cover ring 9514 shields the sidewall surfaces and peripheral edges of the positioning disk that would otherwise be exposed to the excited gases in the chamber, preventing the deposition of process residues. Therefore, the cover ring 9514 reduces the accumulation of process residues on the positioning disk 9509, which would eventually peel off and contaminate the substrate. The cover ring also reduces the erosion of the positioning disk 9509 by the excited gases. Providing a cover ring 9514 also reduces the frequency of cleaning required for the suction cup and / or positioning plate 9509, because the cover ring itself can be periodically removed from the chamber and cleaned, for example, with HF and HNO3, to remove process residues that accumulate on the ring during substrate process cycles. Comparative Example 1The arrangement of cover rings 9514 can be seen, where the cover rings cover portions of the support surface of the puck 9509. Other portions of the surface of the puck 9509 can be covered with top shield rings 9512 and / or shield rings 9513. The top plate / window / cover 9507 forms an upper wall of the vacuum chamber 9550. The showerhead 9517 forms an upper wall of the vacuum chamber 9650 or is mounted below an upper wall. The top plate / window / cover 9507, the gas distribution system 9506, the showerhead 9517, the cover rings or electrode covers 9514, the top shield rings 9512, the shield rings 9513, the chamber liner (not shown), and the chuck or ESC 9508 and the puck 9509 can all or in part be made of an embodiment of a sintered ceramic body as disclosed herein.

[0242] Portions of the surface of the showerhead 9517 can be covered with shield rings 9712. Some portions of the surface of the showerhead 9517, in particular the radial sides of the surface of the showerhead 9517, can be covered with top shield rings 9710. The shield rings 9712, the showerhead 9517, and the top shield rings 9710 can all or in part be made of an embodiment of a sintered ceramic body as disclosed herein.

[0243] A remote plasma source 9502 is provided outside the window 9507 of the chamber 9550 for accommodating a wafer 50 to be processed. The remote plasma region can be in fluid communication with the vacuum chamber 9550 through the gas delivery system 9506. In the chamber 9550, an active plasma can be generated by supplying a process gas to the chamber 9550 and supplying high frequency power to the plasma source 9502. By using the active plasma thus generated, a predetermined plasma process is performed on the wafer 50. Planar antennas with a predetermined pattern are widely used for high frequency antennas of the plasma etching process system 9500.

[0244] As Comparative Example 2: (Sample 363)As shown, embodiments of the technology as disclosed herein can be used as components in a plasma processing system 9600, which can be configured for a semiconductor deposition process, also referred to as a “deposition processing system.” The deposition processing system 9600 includes a vacuum chamber 9650, a vacuum source, and a chuck 9609 on which a wafer 50 (also denoted as a semiconductor substrate) is supported. The processing system can also include a nozzle or injector 9614 in fluid communication with a gas delivery system 9616 for supplying process gas to the interior of the vacuum chamber 9650. The top wall 9700 of the chamber 9650 can include a central opening configured to receive a center gas injector (also referred to as a nozzle) 9614. In certain embodiments, the top wall 9700 of the chamber can include an RF or dielectric window configured with a central opening to accommodate the injector 9614. An RF energy source energizes the process gas into a plasma state to process the substrate 50. Embodiments of the top wall including the RF or dielectric window 9700, the gas delivery system 9616, and the center gas injector 9614 can be made, in whole or in part, from embodiments of the sintered ceramic body as disclosed herein.

[0245] The deposition processing system 9600 can also include an electrostatic chuck 9608 designed to carry the wafer 50. The chuck 9608 can include a chuck 9609 for supporting the wafer 50. Portions of the support surface of the chuck 9609 can be covered with a deposition ring 9615. Other names for the deposition ring 9615 such as deposition shield or deposition ring assembly are considered synonymous and can be used interchangeably herein. The deposition ring 9615 can be made, in whole or in part, from embodiments of the sintered ceramic body as disclosed herein.

[0246] The chuck 9609 can be formed, in whole or in part, from embodiments of the sintered ceramic body as disclosed herein and can have a clamping electrode disposed within the chuck proximate to the support surface of the chuck 9609 to electrostatically hold a wafer 50 when disposed on the chuck 9609. The chuck 9608 can include a base 9611 having an annulus extending to support the chuck 9609 and a shaft 9610 disposed between the base and the chuck to support the chuck above the base such that a gap is formed between the chuck 9609 and the base 9610, with the shaft 9610 supporting the chuck proximate to a peripheral edge of the chuck 9609. The chuck 9608, the chuck 9609, and the deposition ring 9615 can be made, in whole or in part, from embodiments of the sintered ceramic body as disclosed herein.

[0247] The present disclosure is illustrated by the following examples section.

[0248] Example 1 : (Sample 353) High density, large size polycrystalline sintered ceramic body;

[0249] The following examples are included to more clearly demonstrate the overall nature of the disclosure. These examples are exemplary of the disclosure and are not intended as limiting.

[0250] All particle sizes were measured using a Horiba LA-960 laser scattering particle size distribution analyzer, which is capable of measuring particle sizes from 10 nm to 5 mm. All specific surface area (SSA) measurements of starting powders, powder mixtures, and calcined powder mixtures were performed using a Horiba BET surface area analyzer, model SA-9601, which is capable of measuring specific surface areas from 0.01 m 2 / g to 2000 m 2 / g, with a precision of 10% or less for most samples. Purity and impurities were measured using ICP-MS, Agilent 7900 ICP-MS model G8403.

[0251] The radial variation of the gap feature and average coefficient of thermal expansion (CTE) of at least one graphite material according to an embodiment was measured within a spark plasma sintering tool, wherein the tool comprises: a die comprising a sidewall, the sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining an interior volume; an upper punch and a lower punch operably coupled with the die, wherein each of the upper punch and the lower punch has an outer wall defining a diameter that is less than the diameter of the inner wall of the die, whereby a gap is created between each of the upper punch and the lower punch and the inner wall of the die when at least one of the upper punch and the lower punch is moved within the interior volume of the die. As shown in FIG. 1, the sintering tool has a central axis, wherein the radial deviation of the average coefficient of thermal expansion of the at least one graphite material varies by 0.3 x 10 Example 2: (Sample 506); polycrystalline YAG sintered ceramic body with large size; / °C or less, preferably 0.2 x 10 -6 / °C or less, preferably 0.18 x 10 -6 / °C or less, preferably 0.18 x 10 -6 / °C or less, preferably 0.1 x 10 -6 / °C or less, preferably 0.08 x 10 -6 / °C or less, and preferably 0.06 x 10 -6 / °C or less.

[0252] The terms “apparatus” and “tool” are used interchangeably with respect to a spark plasma sintering apparatus.

[0253] All density measurements were performed according to ASTM B962-17, based on the Archimedes method known to those skilled in the art. Embodiments of the oxide powders and ceramics formed therefrom are inherently insulating high resistance materials having a resistivity of about 1 x 10 +10 ohm-cm or more.

[0254] Figure 15

[0255] A polycrystalline ceramic sintered body having a maximum dimension of 406 mm was prepared from a yttria crystalline powder having a specific surface area of 4.5 m 2 / g to 6.5 m 2 / g, and a d10 particle size of 1.5 pm to 3.5 pm, a d50 particle size of 4 pm to 6 pm, and a d90 particle size of 6.5 pm to 8.5 pm. The powder had a total impurity of about 14 ppm relative to the total mass of the yttria powder as measured using ICPMS techniques. The die of the spark plasma sintering tool was lined with at least one graphite foil having properties as disclosed herein, and the die, as well as each of the upper punch and lower punch of the tool, included at least one graphite material as disclosed herein. The powder was disposed within an interior volume defined by the spark plasma sintering tool, and the tool had a gap of about 100 pm. The gap was configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper punch and lower punch of the spark plasma sintering apparatus. A vacuum condition of 10 -2 torr to 10 -3 torr was generated within the interior volume. The powder was sintered at 1400 °C under a pressure of 20 MPa for a duration of 30 minutes to form a disc-shaped sintered ceramic body having a maximum dimension or diameter of 406 mm. The total density of the sample was measured to be 4.78 g / cc, or 95.03% of the theoretical density of yttria (reported as 5.03 g / cc). The measured density variation was about 4.5% relative to the highest density measurement on the maximum dimension. The sintered ceramic body prepared as the method disclosed according to this example using the apparatus having a gap resulted in a low total density, high density variation, and subsequent fracture of the sintered body.

[0256] Figure 15

[0257] High purity (>99.99%) yttrium oxide and aluminum oxide powders are combined in a molar ratio to form a powder mixture to form a sintered ceramic body comprising a yttrium aluminum garnet (YAG) phase upon sintering. After wet tumbling mixing as known to those skilled in the art, the powders are calcined at 1,000 °C for 10 hours. The calcined powder mixture has a specific surface area (SSA) of about 3.5 m2 / g to 5.5 m2 / g, a d10 particle size of about 0.8 pm to 2 pm, a d50 particle size of about 90 pm to 110 pm, and a d90 particle size of about 240 pm to 250 pm. In certain embodiments, the calcination conditions as disclosed herein can result in agglomeration of the powder mixture and thus can result in greater variability in the particle size distribution. Accordingly, in some embodiments, the particle size referred to herein can include individual particles, and in other embodiments, the particle size referred to herein can include agglomerates comprising more than one particle or agglomerates of multiple particles, which can be measured as a single large particle using laser particle detection methods as disclosed herein.

[0258] A die of a spark plasma sintering tool is lined with at least one graphite foil having properties as disclosed herein, and the die, as well as each of the upper and lower punches of the tool, comprise at least one graphite material as disclosed herein. The calcined powder mixture is disposed within an interior volume defined by the tool of the spark plasma sintering tool, wherein the tool has a gap of about 50 pm to 70 pm at ambient temperature, wherein the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper and lower punches of the spark plasma sintering apparatus. A 10 -2 tor to 10 -3 tor vacuum condition, and a pressure of about 5 MPa is applied to form a powder compact from the calcined powder mixture having a fill density of about 50%. The powder compact within the interior volume is heated according to the method as disclosed herein. Upon heating, no consolidation of the powder compact is achieved by the sintering apparatus during the heating process. Accordingly, the radial variation in the average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper and lower punches exceeds 0.3 x 10 -6 / °C (from ambient temperature up to a maximum temperature of the apparatus sintering and / or operation of about 2,000 °C) over the temperature range according to the method as disclosed herein. Accordingly, the required gap distance of 10 pm to 70 pm cannot be maintained over the required temperature range from ambient temperature to sintering temperature, which in this case is set to a predetermined value of 1450 °C. The sintered ceramic body prepared according to this example fractured upon removal from the tool, indicating a low density, and thus a low strength.

[0259] Example 3: (Sample 152); polycrystalline yttria sintered ceramic body;

[0260] a specific surface area of 6 m2 / g to 8 m 2 / g, and a d10 particle size of 1 pm to 3 pm, a d50 particle size of 4 pm to 6 pm, and a d90 particle size of 7.5 pm to 9.5 pm. The powder has about 25 ppm total impurities relative to the total mass of the yttria powder. The die of the spark plasma sintering tool is lined with at least one graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprises at least one graphite material as disclosed herein. The yttria powder is disposed within an interior volume defined by the spark plasma sintering tool having a gap of about 50 pm to about 70 pm, wherein the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper and lower punches of the sintering apparatus. The yttria powder is subjected to a pre-application of pressure in a multi-step process, whereby a pressure of about 10 MPa is pre-applied under a vacuum of about 10"2Torr to 10"3Torr to form a powder compact having a packing density of about 35% to 45% by volume. The powder compact is sintered at a temperature of 1550 °C, a pressure of 20 MPa for a duration of 60 minutes. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper and lower punches is determined to be about 0.2 x 10 -6 / °C or less about the center axis of the sintering tool. The average density is obtained from 5 measurements, and the measured density is 5.020 g / cc or 99.80% of the theoretical density of yttria (5.03 g / cm3 according to D.R. Lide, CRC Handbook of Chemistry and Physics 84th Edition, 2012 (“CRC Handbook”)). Thus, using an apparatus having a specific gap distance and radial variation as disclosed herein, a high density, large size sintered ceramic can be formed.

[0261] Example 4 (Sample 329): polycrystalline spinel sintered ceramic body:

[0262] a specific surface area of 2 m 2 / g to 3 m 2 / g, a d10 particle size of 2.5 pm to 4.5 pm, a d50 particle size of 6 pm to 8 pm, and a d90 particle size of 11 pm to 13 pm. The powder has an average purity of 99.998% and an average impurity of about 21 ppm relative to the total mass of the yttria powder. The die of the spark plasma sintering tool is lined with at least one graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprises at least one graphite material as disclosed herein. The yttria powder is disposed within an interior volume defined by the spark plasma sintering tool having a gap of about 50 pm to about 70 pm, wherein the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper and lower punches of the sintering apparatus. The yttria powder is subjected to a pre-application of pressure in a multi-step process, whereby a pressure of about 10 MPa is pre-applied under a vacuum of about 10"2Torr to 10"3Torr to form a powder compact having a packing density of about 35% to 45% by volume. The powder compact is sintered at a temperature of 1550 °C, a pressure of 20 MPa for a duration of 60 minutes. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper and lower punches is determined to be about 0.2 x 10 2 / g to 8.5 m 2 / g, d10 particle size of 0.75 pm to 1.5 pm, d50 particle size of 2 pm to 5 pm, and d90 particle size of 18 pm to 24 pm, in a molar ratio to form a sintered ceramic body comprising a yttrium aluminum garnet (YAG) phase upon sintering. Ball milling known to those skilled in the art was performed, and after calcination at 1050 °C for 6 hours in air, the specific surface area of the calcined powder mixture was measured to be 3.5 m2 / g. The sintered ceramic body was measured to have a density of 99.5% of theoretical density (TD) or greater, a grain size of 0.5 pm to 1.5 pm, and a hardness of 15 GPa to 20 GPa. 2 / g to 5.5 m 2 / g, d10 particle size of 1 pm to 3.5 pm, d50 particle size of 5 pm to 8 pm, and d90 particle size / agglomerate size of 130 pm to 160 pm. In certain embodiments, the calcination conditions as disclosed herein can result in agglomeration of the powder mixture and thus can result in greater variability of the particle size distribution. Thus, in some embodiments, the particle size referred to herein can include individual particles, and in other embodiments, the particle size referred to herein can include agglomerates comprising more than one particle or agglomerates of multiple particles, which can be measured as a single large particle using the laser particle detection method as disclosed herein. The purity of the calcined powder mixture is about the same as the purity of the starting powders. The powders, powder mixtures, and / or calcined powder mixtures can be sieved, tumbled, mixed, and / or milled in various process steps according to known methods. The die of the spark plasma sintering apparatus is lined with at least one graphite foil having properties as disclosed herein, and the die, as well as each of the upper punch and lower punch of the apparatus, comprises at least one graphite material as disclosed herein. The calcined powder mixture is disposed within an interior volume defined by the tooling of the spark plasma sintering apparatus, wherein the tooling has a gap of about 30 pm to 50 pm. The gap is configured between the inward-facing surface of the at least one graphite foil and the outer wall of each of the upper punch and lower punch of the spark plasma sintering apparatus. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper punch and lower punch is determined to be about 0.1 x 10 -6 / °C and less about the center axis of the sintering tooling. The calcined powder mixture is disposed within an interior volume defined by the tooling set of the sintering apparatus as disclosed herein, and a pressure of 10 -2 kPa to 10 -3vacuum conditions. The calcined powder mixture within the internal volume was heated to 800 °C at 5 °C / minute, a pressure of 5 MPa was applied at this temperature to form a powder compact with a fill density of about 40% to 50% by volume, then heat was applied at a rate of about 2 °C / minute to about 3 °C / minute and pressure was applied at a rate of about 0.2 MPa / min to about 0.25 MPa / min to reach sintering conditions of 1650 °C and 15 MPa for 60 minutes to form a disc-shaped polycrystalline YAG sintered ceramic body with a maximum dimension of 622 mm. Density measurements were made on samples cut along the radius of the sample according to ASTM B962-17, and the density results are shown in Example 5: High density polycrystalline sintered ceramic body; B. Five measurements were made at 6 locations along the radius, and the average density measured was 4.55 g / cc, corresponding to 99.78% of the theoretical value for YAG. The density across the radius was 99.7% to 99.9% of the theoretical value for YAG (reported as 4.556 g / cc). Relative to the highest density measurement along the radius, the density variation was measured as shown in Example 6: High density polycrystalline sintered ceramic body B, and the maximum density variation measured was 0.21%. During sintering of the powders and powder mixtures using a spark plasma sintering apparatus as disclosed herein, pressure and temperature were applied in a radially symmetric configuration about the central axis 9. Thus, properties such as high density (>99% of the theoretical value for YAG) and minimal density variation (<0.21%) were maintained across the radius and also correspondingly across the diameter or maximum dimension of the sintered ceramic body. Thus, a sintered ceramic body is disclosed herein having an average density of 4.546 g / cc, a density range of 99.7% to 99.9% of the theoretical density for YAG (a commercially available YAG sample was measured, and an average density of 4.556 g / cc was obtained, and is used as the theoretical density for YAG herein), and a maximum density variation across the diameter of the sintered ceramic body of 0.21% and less.

[0263] Example 7: Large size polycrystalline sintered ceramic body

[0264] A 100 mm sintered yttria body was formed from a yttria powder having a specific surface area of 6.5 m 2 / g to 8.0 m 2 / g and a purity of 99.999% (corresponding to an average total impurity of 18 ppm relative to the total mass of the yttria powder). The d10 particle size was 1.5 pm to 3.5 pm, the median particle size (d50) was 4 pm to 6 pm, and the d90 particle size was 7.5 pm to 9.5 pm. The die of the spark plasma sintering apparatus was lined with at least one graphite foil having properties as disclosed herein, and each of the upper punch and lower punch of the die and apparatus included at least one graphite material as disclosed herein. The yttria powder was disposed within the internal volume defined by the sintering apparatus, and a pressure of 10 -2Tooling to 10 -3 The tooling has a gap of about 25 pm to about 50 pm, where the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper punch and lower punch of the sintering apparatus. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper punch and lower punch is determined to be about 0.25 x 10 -6 / °C and less about the radial variation of the central axis of the sintering tooling. Sintering is performed at 1400 °C, 30 MPa for 30 minutes. Thereafter, annealing is performed in air at 1400 °C for 8 hours. The average density is measured to be 5.02 g / cc, corresponding to 99.9% of the theoretical density of yttria (according to D.R. Lide, CRC Handbook of Chemistry and Physics 84 th Edition, 2012 (“CRC Handbook”), the theoretical density of yttria is 5.03 g / cm 3 ).

[0265] Example 8: Zirconia toughened alumina (ZTA) sintered body; A magnesium oxide powder having a total purity of 99.9994% (corresponding to 6 ppm of total impurities), a surface area of 4 m 2 / g to 6 2 / g, and an average particle size or d50 particle size of between 3 pm and 4 pm is combined with an aluminum oxide powder having a purity of 99.9995% (corresponding to 5 ppm of total impurities), a surface area of 6 m 2 / g to 8 m 2 / g, and an average particle size or d50 particle size of between 2.5 pm and 4.5 pm. The powders are weighed in relative amounts to produce a powder mixture in molar ratios to form spinel MgAl204 having a cubic crystal structure upon sintering. The powder mixture is subjected to wet tumbling milling according to methods known to those skilled in the art. The powder mixture is calcined in an oxygen-containing environment at 850 °C for 4 hours, and is measured to have a specific surface area of 5 m2 / g 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 is lined with at least one graphite foil having properties as disclosed herein, and the die and each of the upper punch and lower punch of the apparatus comprise at least one graphite material as disclosed herein. The calcined powder mixture is disposed within an interior volume defined by the sintering apparatus, and a pressure of 10 -2 Tooling to 10 -3under vacuum conditions. The tool has a gap of about 20 pm to about 40 pm, where the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper punch and the lower punch of the sintering apparatus. The average coefficient of thermal expansion (CTE) of at least one graphite material comprising the die and / or the upper punch and the lower punch varies radially about a central axis of the sintering tool by about 0.1 x 10 -6 / °C and less. The calcined powder mixture was then sintered according to the method as disclosed herein at a temperature of 1500 °C, a pressure of 20 MPa under vacuum for a duration of 30 minutes, thereby forming a ceramic sintered body having a maximum dimension of 100 mm. The density measured on the sintered ceramic body was 3.546 g / cc or 99.04% of the theoretical density. Hardness measurements were performed on the sintered ceramic body according to ASTM C1327 using an applied load of 0.025 kgf. The average hardness measured in 8 measurements was 15.06 GPa and the standard deviation was 0.75. Thereafter, annealing was performed at 1500 °C and allowed to cool passively under atmospheric environment. The density on the annealed sintered ceramic body was measured to be 3.553 g / cc or 99.24% of the theoretical density (the theoretical density of magnesium aluminate spinel is 3.579 g / cm 3 ) according to L. Ping et al., “Magnesium aluminate (MgAl2O4) spinel produced via self-heat-sustained (SHS) technique”, Materials Research Bulletin 36 (2001).

[0266] Example 9: (Sample 421) large size multilayer sintered ceramic body; from 2 m 2 / g to 3 m 2A sintered ceramic body having a maximum dimension of 406 mm was prepared from a crystalline yttria powder having a specific surface area of 4.5 m2 / g and a d10 particle size of 2.5 pm to 4 pm, a d50 particle size of 6 pm to 7.5 pm, and a d90 particle size of 11.5 pm to 13 pm. The powder had a total impurity of about 12 ppm relative to the total mass of the yttria powder. The mold was lined with a graphite foil having properties as disclosed herein, and each of the mold and upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 50 pm, whereby the gap was configured between the inward-facing surface of the at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Pre-application of pressure was performed in a multi-step process, whereby a pressure of about 10 MPa was pre-applied under vacuum to form a powder compact having a fill density of about 35 vol% to 45 vol%. The powder compact was sintered at a temperature of 1550 °C, a pressure of 20 MPa for a duration of 60 minutes. The average density was obtained from 5 measurements, and the measured density was 5.020 g / cc or 99.801% of the theoretical density of yttria (reported as 5.03 g / cc as disclosed herein).

[0267] Example 10: (Sample 477) large size multilayer sintered ceramic body;

[0268] A crystalline yttria powder having a specific surface area of 4.5 m 2 / g to 6 m 2 / g and a crystalline alumina powder having a specific surface area of 3.5 m 2 / g to 5 m 2 / g were combined in a molar ratio to form a yttrium aluminum garnet (YAG) phase upon sintering. High purity alumina media (>99.99% as measured by ICPMS) was added at a loading of 50% by weight of the powders, and ethanol was added to form a slurry of about 40 vol%. Ball milling was performed using a rolling action about a horizontal axis for a duration of 12 hours, and then ethanol was extracted from the powder mixture using a rotary evaporator. After calcination in air at 1000 °C for 10 hours, the specific surface area of the calcined powder mixture was measured to be 7 m 2 / g to 8 m 2 / g, the d10 particle size was measured to be 0.75 pm to 1.75 pm, the d50 particle size was measured to be 90 pm to 110 pm, and the d90 particle size was measured to be 240 pm to 280 pm. The powder mixture can be sieved, mixed, and / or milled according to known methods at various process steps. The mold is lined with a graphite foil having properties as disclosed herein, and each of the mold and the upper and lower punches comprise a graphite material as disclosed herein. The powder is disposed within the interior volume of a spark plasma sintering tool having a gap width of about 50 pm to about 70 pm, whereby the gap is configured between the at least one foil’s inward-facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. The calcined powder mixture is sintered under vacuum at 1550 °C, 20 MPa pressure for 60 minutes to form a sintered ceramic body having a maximum dimension of 406 mm. Density measurements are taken on the maximum dimension of the sintered body, and the average density measured over 135 measurements was 4.543 g / cc, corresponding to 99.709% of the theoretical density of YAG and a volume porosity of 0.291% calculated from the density measurements. The density was found to vary from 4.526 g / cc to 4.553 g / cc (or from 99.335% to 99.936% of the YAG theoretical value) on the maximum dimension of the polycrystalline sintered ceramic body, and the density variation on the maximum dimension was determined to be 0.601%.

[0269] Example 11 : 80 mole% yttria - 20 mole% zirconia ceramic sintered body;

[0270] A crystalline powder of yttrium oxide having a specific surface area of 2 m 2 / g to 4 m 2 / g to 8 m 2 / g to 8 m 2 / g to 8 m A crystalline powder of yttrium oxide having a specific surface area of 2 m 2 / g to 5 m 2The d10 particle size was measured to be 1 pm to 3 pm, the d50 particle size was measured to be 3.5 pm to 6 pm, and the d90 particle size was measured to be 6 pm to 12 pm. The calcined powder mixture can be sieved, blended, and / or milled in various process steps according to known methods. The purity of the calcined powder was measured using ICPMS methods known to those skilled in the art, and the total impurity content was about 7 ppm, corresponding to a purity of about 99.9993%. The mold was lined with a graphite foil having properties as disclosed herein, and each of the mold and the upper and lower punches comprised a graphite material as disclosed herein. The calcined powder mixture was disposed within an interior volume of a spark plasma sintering tool having a gap width of about 40 pm to about 60 pm, whereby the gap was configured between the inward-facing surface of the at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. The calcined powder mixture within the interior volume was subjected to a pre-sintering pressure of 10 MPa to form a powder compact having a fill density of about 45 vol.%. The calcined powder mixture was sintered under vacuum at 1600 °C, 15 MPa pressure for 60 minutes to form a sintered ceramic body having a maximum dimension of 616 mm. Density measurements were made according to ASTM B962-17 using the Archimedes principle, and the average density measured for the sintered ceramic body was 99.1% of the theoretical density of YAG (4.556 g / cc).

[0271] Single step, CF4etch volume procedure

[0272] A zirconia powder having a specific surface area of 6 m2 / g to 8 m2 / g, a d10 particle size of 0.5 pm to 0.2 pm, a d50 particle size of 0.2 pm to 0.5 pm, and a d90 particle size of 1.2 pm to 3 pm and an alumina powder having a specific surface area of 6 m2 / g to 8 m2 / g, a d10 particle size of 0.05 pm to 0.15 pm, a d50 particle size of 0.2 pm to 0.5 pm, and a d90 particle size of 0.4 pm to 1 pm are weighed and combined to produce a powder mixture in a molar ratio to form, upon sintering, a zirconia toughened aluminum phase in which the zirconia is present in an amount of about 16 vol.%. The zirconia powder contains about 2 mol.% to 4 mol.% of Hf02and is stabilized with yttria in an amount of about 3 mol.%. Hf02is present in many commercially available zirconia powders, and yttria is known to those skilled in the art to be used to stabilize zirconia. Thus, yttria and hafnia are not considered to be impurities in the zirconia as disclosed herein. The zirconia powder has a total impurity of about 20 ppm in addition to Hf and Y. The powders are combined in a ratio to form, upon sintering, a composite oxide layer comprising about 16 vol.% zirconia and a balance of alumina. The powder mixture comprising zirconia and yttria is transferred to a vessel for wet ball milling. The powder mixture comprises zirconia and yttria without the use of a sintering aid such as MgO or silica. Thus, disclosed herein is a sintered ceramic body comprising a zirconia alumina layer that is free or substantially free of sintering aids. A high purity (>99.99%) alumina media is used with a loading of about 75% to 80% relative to the weight of the powder, and ethanol is added to the vessel to form a slurry and to enhance mixing. In other cases, the ball milling can be done with water or under dry conditions using only alumina or zirconia media. The ball milling is done using a rolling action around a horizontal axis at 150 rpm for a duration of 20 hours, and then the ethanol is extracted from the powder mixture using a rotary evaporator. The powder mixture is calcined at 600 °C for 8 hours. As known to those skilled in the art, the calcined powder mixture can optionally be sieved, tumbled, blended, etc. after calcination. The die of the spark plasma sintering apparatus is lined with at least one graphite foil having the properties as disclosed herein, and the die, as well as each of the upper punch and lower punch of the apparatus, comprises at least one graphite material as disclosed herein. The calcined powder mixture is disposed within an interior volume defined by the spark plasma sintering tool, wherein the tool has a gap of about 25 pm to about 45 pm. The gap is configured between the inward facing surface of the at least one graphite foil and the outer wall of each of the upper punch and lower punch of the spark plasma sintering apparatus. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper punch and lower punch is determined to be about 0.1 x 10 -6 / ℃ and lower. The calcined powder mixture is placed within an internal volume defined by a tool assembly of a sintering apparatus as disclosed herein, and 10 ℃ is produced within that volume. -2 Up to 10 -3 The vacuum conditions of the Tönnies are applied. A pressure of about 5 MPa is applied to form a powder compact having a filling density of about 40 to 50 vol%. The calcined powder mixture within the internal volume is heated to 800°C at a rate of 5°C / min to 10°C / min, and then simultaneously heated at a rate of about 3°C / min to about 5°C / min and pressure is applied at a rate of about 0.2 MPa / min to about 0.25 MPa / min to achieve sintering conditions according to the method disclosed herein: 1450°C, 20 MPa pressure, for a duration of 30 minutes, to form a sintered body with a size of 150 mm. The densities of embodiments of the ZTA sintered ceramic bodies are recorded in the table below. The sintered ceramic bodies disclosed herein may comprise a particulate composite of crystalline phases of zirconium oxide and alumina in the disclosed volume amounts. The particulate composite may comprise zirconium oxide particles or regions dispersed in an alumina matrix, wherein the particulate composite comprises two independent crystalline phases, and preferably the sintered ceramic body does not form a solid solution. Since yttrium oxide and zirconium oxide exist as separate phases, the volume mixing rule can be applied to calculate the theoretical density, as reported below.

[0273]

[0274] In one set of embodiments, ZTA sample 365, comprising 20 vol% zirconium oxide and 80 vol% alumina, was prepared according to Example 8 and sintered at 1450°C and 20 MPa for 30 minutes. ZTA sample 562, comprising approximately 16 vol% zirconium oxide and approximately 84 vol% alumina, was prepared according to Example 8 and sintered at 1500°C and 15 MPa for 30 minutes, as shown below.

[0275]

[0276] Single step, CF4etch volume procedure

[0277] A multilayer sintered ceramic body is formed from a first and a second powder mixture. The first powder mixture comprises alumina and zirconium oxide to form a particulate composite of crystalline phases of zirconium oxide and alumina in volumetric amounts as disclosed in Example 8. The second powder comprises alumina and yttrium oxide to form a layer comprising a YAG phase. The first powder mixture comprises alumina powder having a specific surface area of ​​6 m². 2 / g to 8m 2The zirconia powder has a d10 particle size of 0.05 μm to 0.15 μm, a d50 particle size of 0.2 μm to 0.5 μm, a d90 particle size of 0.4 μm to 1 μm, and a surface area of ​​6 m² / g to 8 m² / g. The alumina powder has a total impurity content of about 2 ppm to 10 ppm. The zirconia powder contains about 2 mol% to 4 mol% Hf and is stabilized with about 3 mol% yttrium oxide. Hf and Y are not considered impurities in the zirconia as disclosed herein. In addition to Hf and Y, the zirconia powder has a total impurity content of about 20 ppm. The powders are combined in a certain ratio to form at least one particulate composite layer comprising about 16 vol% zirconia and the balance alumina upon sintering. Alumina and zirconium oxide powders were mixed using a conventional powder preparation technique involving wet ball milling to prepare a powder mixture, wherein a high-purity (>99.99%) alumina media was used at a loading of approximately 75% to 80% relative to the powder weight. An approximately 40% by volume slurry was formed by adding ethanol. The slurry was ball-milled at approximately 150 RPM for approximately 20 hours, followed by drying, tumbling, and sieving 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 specific surface area of ​​the first calcined powder mixture was 6 m². 2 / g to 8m 2 / g. The total impurities of the first calcined powder mixture are about 15 ppm, and it contains about 14 ppm or less of Si and about 5 ppm or less of Mg. As is known to those skilled in the art, the powder mixture can be sieved, tumbled, blended, etc.

[0278] The second powder mixture contains alumina powder, wherein the specific surface area of ​​the alumina powder is 6 m². 2 / g to 8m 2 / g, d10 particle size is 0.05μm to 0.15μm, d50 particle size is 0.2μm to 0.5μm, d90 particle size is 0.4μm to 1μm, and the specific surface area of ​​yttrium oxide powder is 2m². 2 / g to 3m 2 / g, d10 particle size of 2 pm to 4 pm, d50 particle size of 6 pm to 8 pm, and d90 particle size of 11 pm to 13 pm. The total impurity content of the alumina and yttria powders is about 2 ppm to 10 ppm. These powders are combined in proportion to form a corrosion resistant layer comprising YAG (yttrium aluminum oxide, garnet phase) upon sintering. The alumina and yttria powders are mixed using conventional powder preparation techniques of wet ball milling to produce a second powder mixture, wherein a high purity (>99.9%) media is used at about 60% loading relative to the weight of the powder. A slurry of about 40% by volume is formed by the addition of ethanol. The slurry is milled at 150 RPM for about 15 hours, after which drying, tumbling, and sieving are performed to form the first powder mixture according to methods known to those skilled in the art. The second powder mixture is calcined at 850 °C for 6 hours. The specific surface area of the second calcined powder mixture is 2 m 2 / g to 4 m 2 / g, and d50 particle size of 9 pm to 13 pm. The second calcined powder mixture has a total impurity of about 8 ppm, and can be sieved, tumbled, blended, etc. as known to those skilled in the art.

[0279] The die of the spark plasma sintering apparatus is lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprise a graphite material as disclosed herein. The average coefficient of thermal expansion (CTE) of at least one graphite material comprising the die and / or the upper and lower punches varies radially about the central axis of the sintering tool is determined to be about 0.08 x 10 -6 / °C and less. The first and second calcined powder mixtures are disposed to form at least two separate layers within the interior volume of the spark plasma sintering tool, which has a gap width of about 25 pm to about 45 pm, whereby the gap is configured between the inwardly facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus.

[0280] The first and second calcined powder mixtures are sintered at a temperature of 1600 °C for 60 minutes at 15 MPa to form a multilayer sintered ceramic body comprising at least two layers comprising YAG and ZTA having a maximum dimension of 572 mm. Density measurements cannot be accurately made on the multilayer body due to the different density regions comprising the multilayer structure.

[0281] A further multilayer sintered ceramic body comprising at least two layers comprising YAG and ZTA having a maximum dimension of 622 mm is prepared according to Example 9 and sintered at 1625 °C, 15 MPa for 60 minutes.

[0282] Single step, CF4etch rate procedure

[0283] A multi-layer sintered ceramic body is formed from a first and second powder mixture. The first powder mixture comprises alumina and zirconia to form a zirconia toughened alumina (ZTA) according to Example 8. The second powder mixture comprises about 20 mole percent zirconia and a balance yttria.

[0284] The first powder mixture comprises an alumina powder, wherein the alumina powder has a specific surface area of 6 m 2 / g to 8 m 2 / g, a d10 particle size of 0.05 pm to 0.15 pm, a d50 particle size of 0.2 pm to 0.5 pm, and a d90 particle size of 0.4 pm to 1 pm, and the zirconia powder has a surface area of 6 m 2 / g to 8 m 2 / g, a d10 particle size of 0.5 pm to 0.2 pm, a d50 particle size of 0.2 pm to 0.5 pm, and a d90 particle size of 1.2 pm to 3 pm. The total impurity content of the alumina powder is about 2 ppm to 10 ppm. The zirconia powder comprises about 2 mole percent to 4 mole percent Hf and is stabilized with yttria in an amount of about 3 mole percent. Hf02is present in many commercially available zirconia powders, and yttria is known to those skilled in the art to be used to stabilize zirconia. Thus, yttria and hafnium oxide are not considered to be impurities in the zirconia as disclosed herein. The zirconia powder has a total impurity of about 20 ppm in addition to Hf and Y. The first powder mixture comprises zirconia and alumina without the addition of sintering aids such as MgO or silica. Thus, disclosed herein is a multi-layer sintered ceramic body comprising zirconia alumina (ZTA) layers that is free or substantially free of sintering aids. The powders are combined in a ratio to form a layer comprising about 16 volume percent zirconia and a balance alumina upon sintering. The alumina and zirconia powders are mixed using conventional powder preparation techniques of wet ball milling, wherein a high purity (>99.99%) alumina media is used at a loading of about 75% to 80% relative to the weight of the powder. A slurry of about 40 volume percent is formed by the addition of ethanol. The slurry is ball milled at about 150 RPM for about 20 hours, after which drying, tumbling, and sieving are performed according to methods known to those skilled in the art to form the first powder mixture. The first powder mixture is calcined at 900 °C for 6 hours. The first calcined powder mixture has a specific surface area of 5 m 2 / g to 7 m 2 / g. The first calcined powder mixture has a total impurity of about 15 ppm, and comprises about 14 ppm or less Si and less than about 5 ppm Mg. The powder mixture can be sieved, tumbled, blended, etc. as known to those skilled in the art.

[0285] The second powder mixture comprises a zirconia powder having a surface area of 6 m 2 / g to 8 m 2 / g, a d10 particle size of 0.5 pm to 0.2 pm, a d50 particle size of 0.2 pm to 0.5 pm, and a d90 particle size of 1.2 pm to 3 pm, and a specific surface area of the yttria powder of 2 m 2 / g to 3 m 2 / g, a d10 particle size of 2 pm to 4 pm, a d50 particle size of 6 pm to 8 pm, and a d90 particle size of 11 pm to 13 pm. The total impurity content of the zirconia and yttria powders is about 2 ppm to 10 ppm. As known to those skilled in the art, Si and Mg were not detected in the yttria and zirconia powders using ICPMS, and thus, the yttria and zirconia powders contain about 14 ppm or less Si and about 5 ppm or less Ca, Li, and Mg, in the form of silica, calcium oxide, Li / lithium fluoride, and magnesium oxide, respectively. The powders are combined in a ratio to form, upon sintering, a layer comprising at least one crystalline phase comprising 20 mole percent zirconia and a balance yttria. The zirconia and yttria powders are mixed using conventional powder preparation techniques of wet ball milling to produce a second powder mixture, wherein a 3 mole percent yttria stabilized zirconia media is used with an approximate 90% loading relative to the weight of the powders. A slurry of about 40% by volume is formed by the addition of ethanol. The slurry is milled at 150 RPM for about 12 hours, after which drying, tumbling, and sieving are performed according to methods known to those skilled in the art to form the second powder mixture. The second calcined powder mixture has a specific surface area of 2 m 2 / g to 4 m 2 / g, and a d50 particle size of 6 pm to 10 pm. The second calcined powder mixture has a total impurity of about 8 ppm, and contains about 14 ppm or less Si and about 5 ppm or less Mg, in the form of silica and magnesium oxide, respectively. The second powder mixture can be sieved, tumbled, blended, etc., as known to those skilled in the art.

[0286] The die of the spark plasma sintering apparatus is lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprise a graphite material as disclosed herein. The average coefficient of thermal expansion (CTE) of at least one graphite material comprising the die and / or the upper and lower punches varies radially about a central axis of the sintering tool is determined to be about 0.08 x 10 -6 / °C and less. The first and second calcined powder mixtures are disposed to form at least two separate layers within an interior volume of a spark plasma sintering tool having a gap width of about 25 pm to about 45 pm, wherein the gap is configured between an interior-facing surface of at least one foil and an outer wall of each of the upper and lower punches of the sintering apparatus.

[0287] The first and second calcined powder mixtures are disposed within an interior volume defined by a tool set of a sintering apparatus as disclosed herein, respectively, to form a multi-layer sintered ceramic body comprising at least two separate layers.

[0288] The first and second calcined powder mixtures are sintered at a temperature of 1500 °C for 45 minutes at 15 MPa to form a multi-layer sintered ceramic body having a maximum dimension of 150 mm. Density measurements cannot be accurately performed due to the multi-layer structure comprising regions of different densities.

[0289] Single step CF4Sdr procedure (no etch, etch)

[0290] A yttria powder having a surface area of 6 m 2 / g to 8 m 2 / g and a zirconia powder having a surface area of 6 m 2 / g to 8 m 2 / g are weighed and combined to produce a powder mixture in a ratio of 80 mole percent yttria and 20 mole percent zirconia. The purity of the yttria powder is greater than about 99.998% relative to 100% pure yttria and the purity of the zirconia powder is greater than about 99.79% relative to 100% pure zirconia. An amount of ethanol is added to the powder mixture in an amount of 50% by weight of the powder and a zirconia medium is added to the powder mixture in an amount of 100% by weight of the powder to form a slurry. The slurry is placed in an axial rotating ball mill at 80 RPM to 90 RPM for 12 hours, after which the slurry is removed from the mill. The ethanol is extracted from the slurry using a rotary evaporator and the powder mixture is calcined in air at 1000 °C for 8 hours. The calcined powder mixture can optionally be sieved, tumbled, blended, etc. according to known methods before and / or after calcination.

[0291] The die of the spark plasma sintering apparatus is lined with at least one graphite foil having properties as disclosed herein and each of the upper punch and lower punch of the apparatus and the die comprise at least one graphite material as disclosed herein. The average coefficient of thermal expansion (CTE) of the at least one graphite material comprising the die and / or the upper punch and lower punch varies radially about the central axis of the sintering tool is determined to be about 0.08 x 10 -6 / °C and less. The calcined yttria-zirconia powder mixture is disposed within an interior volume defined by the sintering apparatus and a pressure of 10 -2 kiloPascals to 10 -3under vacuum conditions. The tool has a gap of about 25 pm to about 45 pm, where the gap is configured between an inward-facing surface of the at least one graphite foil and an outer wall of each of the upper punch and lower punch of the sintering apparatus. The average coefficient of thermal expansion (CTE) of at least one graphite material comprising the die and / or the upper punch and lower punch is determined to be about 0.2 x 10 -6 / °C and less around a central axis of the sintering tool. According to the method as disclosed herein, sintering is performed under vacuum at 1500 °C, 30 MPa for 30 minutes to form a 100 mm sintered ceramic body. Thereafter, annealing is performed in air at 1200 °C for 8 hours. The average density calculated over 5 measurements is 5.135 g / cc.

[0292] Another sintered ceramic body comprising 90 mole percent yttria and 10 mole percent zirconia is prepared according to the materials, apparatus, and methods of Example 11.

[0293] The following yttria samples H1 / 66 to H4 / 152 according to embodiments of the application are prepared according to the present disclosure.

[0294] H1 / 66:

[0295] A 80 mm sintered yttria body is formed from a powder having a surface area of 2.5 m 2 / g to 3.5 m 2 / g, a d50 particle size of 5.4 pm and a TREO (total rare earth oxide) < 10 ppm, and a total impurity of 48 ppm, a powder purity of 99.9952%. The die of the sintering apparatus is lined with a graphite foil having properties as disclosed herein, and the die as well as each of the upper punch and lower punch comprises a graphite material as disclosed herein. The powder is disposed within an interior volume of a spark plasma sintering tool having a gap width of about 50 pm to about 70 pm, whereby the gap is configured between an inward-facing surface of the at least one foil and an outer wall of each of the upper punch and lower punch of the sintering apparatus. The body is formed at a sintering temperature of 1500 °C under 30 MPa for 60 minutes. Annealing is performed in air at a temperature gradient of 5 °C / minute to 1450 °C for 1 hour, and then at a temperature gradient of 1400 °C for 8 hours. The density of the yttria sintered body is 4.948 g / cm 3 and the maximum pore size is 1.1 pm. The d10, d50, and d90 grain sizes are measured to be 0.5 pm, 0.8 pm, and 1.4 pm, respectively.

[0296] H2 / 65:

[0297] A 40 mm sintered yttria body is formed from a powder having a surface area of 6.5 m 2 / g to 7.5 m 2 / g. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 40 pm to about 60 pm, whereby the gap was configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering was performed at a sintering temperature of 1550 °C for 10 minutes at 30 MPa. Annealing was performed in air for 4 hours at a temperature of 1300 °C in a furnace. The starting yttria powder had a total purity of 99.999% corresponding to 10 ppm. The median particle size was measured to be 5.82 pm. The total impurity level of the sintered yttria body was 11 ppm. The purity of the starting powder was maintained in the sintered yttria body, indicating that very little or no contaminants were introduced during processing. The d10, d50, and d90 grain sizes were measured to be 4.0 pm, 13.0 pm, and 27.1 pm, respectively, and the average grain size was measured to be 14 pm.

[0298] H3 / 79:

[0299] A 40 mm sintered yttria body was formed from a powder having a surface area of 2.5 m 2 / g to 3.5 m 2 / g and a median (d50) particle size of 5.17 pm. The starting powder had a total impurity of 2 ppm to 4 ppm. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 40 pm to about 60 pm, whereby the gap was configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering of the yttria body was performed at a sintering temperature of 1500 °C, a pressure of 30 MPa, for a duration of 10 minutes. The temperature was ramped at 50 °C / min while the pressure was applied at 5 MPa / min. Annealing was performed by ramping to 1300 °C at 5 °C / min and holding in air for 4 hours. The total impurity content of the sintered yttria body was between 9 ppm to 10 ppm, indicating minimal contaminants introduced due to the process. The maximum pore size was measured to be 0.6 pm, and the density was measured to be 5.03 g / cc. The d10, d50, and d90 grain sizes were measured to be 0.8 pm, 1.4 pm, and 2.4 pm, respectively. The average grain size was also measured to be 1.47 pm.

[0300] H4 / 152:

[0301] A 100 mm sintered yttria body was formed from a powder having a surface area of 6 m 2 / g to 8 m 2 / g and the purity of TREO was 99.999% (<10 ppm) with an average total impurity of 18 ppm. The median particle size (d50) was 4.65 pm. The sintering apparatus had a die lined with a graphite foil having properties as disclosed herein, and each of the upper and lower punches comprised a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 50 pm, whereby the gap was configured between the at least one foil’s inward-facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering was performed at 1400 °C, 30 MPa for 30 minutes. Thereafter, annealing was performed at 1400 °C in air for 8 hours. The measured density was 5.024 g / cm 3 , the maximum pore size was 2 pm. After a 2-step CF4 / O2 etching process as disclosed herein, the average step height achieved was 0.98 pm, the average etch rate was 0.68 nm / min, and the etch volume was 340000 pm 3 . The measured arithmetic average height (Sa) before and after a two-step CF4 / O2 etching process as disclosed herein was 10 nm and 14 nm, respectively. After an oxygen etching process as disclosed herein, the average step height achieved was 0.1 pm, the average etch rate was 0.07 nm / min, and the etch volume was 30000 pm 3 . After an SF6 etching process as disclosed herein, the average step height achieved was 0.28 pm, the average etch rate was 0.19 nm / min, and the etch volume was 90000 pm 3 .

[0302] Single step CF4Sa (no etch, etch)

[0303] To evaluate etching performance, polished ceramic samples with dimensions of 6 mm x 6 mm x 2 mm were mounted onto a c-plane sapphire wafer using a silicone-based thermal dissipation compound. The area of each part was protected from the etching process by adhering a 5 mm x 5 mm square of sapphire ceramic to the sample surface.

[0304] The dry etching process was performed using an industry standard Plasma-Therm Versaline DESC PDC deep silicon etcher. The etching was done over a 4 hour etch segment with a total duration of 24 hours. The process was performed at a pressure of 10 mTorr, CF4 flow of 90 standard cubic centimeters per minute (seem), oxygen flow of 30 seem, and argon flow of 20 seem. The bias was 600 volts and 2000 watt ICP power. The silicon etch rate for this etch recipe was 512 nm / min. The etch recipe etched fused silica (quartz glass) at a rate of 72 nm / min. The etching conditions used herein to evaluate sample performance were selected to subject the disclosed materials to extreme etching conditions to differentiate performance.

[0305] After the etching procedure was completed, the surface roughness was measured.

[0306] Surface roughness measurement :

[0307] In one embodiment, the sintered yttria body is characterized by an etch volume of less than about 12000 pm 3 , preferably less than about 9000 pm 3 , more preferably less than about 7000 pm 3 . The etch volume is achieved in case of performing an etching process as reference process, wherein a sample having dimensions of 6 mm x 6 mm x 2 mm is subjected to etching conditions for 24 hours at a pressure of 10 mTorr, wherein the CF4 flow is 90 standard cubic centimeters per minute (seem), the oxygen flow is 30 standard cubic centimeters per minute (seem), and the argon flow is 20 standard cubic centimeters per minute (seem), the bias is 600 volts and the 2000 watt ICP power. The corresponding etching process is described in further more detail in the experimental section below. Thus, the etch volume correlates to the volume of the yttria body that is removed during the indicated etching process.

[0308] Step height measurement :

[0309] In some embodiments, the yttria body is characterized by exhibiting an etch 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 etch rate is achieved in case of a single step CF4as reference process, wherein a sample having dimensions of 6 mm x 6 mm x 2 mm is subjected to etching conditions for 24 hours at a pressure of 10 mTorr, with a CF4flow of 90 standard cubic centimeters per minute (seem), an oxygen flow of 30 standard cubic centimeters per minute (seem), and an argon flow of 20 standard cubic centimeters per minute (seem), a bias of 600 volts and a 2000 Watt ICP power. The etch rate is thus related to the thinning of the yttria body removed during the indicated etching process.

[0310] Etch rate calculation

[0311] In some embodiments, the sintered yttria body is characterized by having an interface development area ratio of less than 100 x 10 -5 , more preferably less than 75 x 10 -5 , most preferably less than 50 x 10 -5 in the unetched area according to ISO Standard 25178-2-2012 Section 4.3.2; and an interface development area ratio of less than 600 x 10 -5 , more preferably less than 500 x 10 -5 , more preferably less than 400 x 10 -5 , more preferably less than 300 x 10 -5 , most preferably less than 200 x 10 -5 in the etched area according to ISO Standard 25178-2-2012 Section 4.3.2. This latter interface development area ratio is achieved in case of a CF4etching time of 24 hours for a yttria body sample having dimensions of 6 mm x 6 mm x 2 mm subjected to etching conditions of a pressure of 10 mTorr, a CF4flow of 90 standard cubic centimeters per minute (seem), an oxygen flow of 30 standard cubic centimeters per minute (seem), and an argon flow of 20 standard cubic centimeters per minute (seem), a bias of 600 volts and a 2000 Watt ICP power. The corresponding etching process is described in further more detail below.

[0312] Volume measurement

[0313] In some embodiments, the sintered yttria body is further characterized by an arithmetic average height Sa of less than 30 nm, more preferably less than 28 nm, most preferably less than 25 nm according to ISO Standard 25178-2-2012 Section 4.1.7; and an arithmetic average height Sa of less than 40 nm, more preferably less than 35 nm, most preferably less than 30 nm according to ISO Standard 25178-2-2012 Section 4.1.7. This latter arithmetic average height Sa is achieved on a yttria body sample having dimensions of 6 mm x 6 mm x 2 mm subjected to the following etching conditions for 24 hours: a pressure of 10 mTorr, a CF4 flow rate of 90 standard cubic centimeters per minute (seem), an oxygen flow rate of 30 standard cubic centimeters per minute (seem), and an argon flow rate of 20 standard cubic centimeters per minute (seem), a bias voltage of 600 volts and an ICP power of 2000 Watts. The corresponding etching process is described in further more detail below.

[0314] ​

[0315] Surface roughness measurements were performed using a Keyence 3D Laser Scanning Confocal Digital Microscope Model VK-X250X under ambient conditions in a Class 1 cleanroom. The microscope was located on a TMC Desktop CSP Passive Table Isolator with a natural frequency of 2.8 Hz.

[0316] This non-contact system uses a laser beam of light and optical sensors to analyze the surface by reflected light intensity. The microscope collects 1,024 data points in the x direction and 786 in the y direction, for a total of 786,432 data points. After a given scan is completed, the objective lens is moved a set interval in the z direction and the intensity between scans is compared to determine the focal point. ISO 25178 Surface Texture (areal roughness measurement) is a collection of international standards related to surface roughness analysis compatible with this microscope.

[0317] A confocal microscope was used to laser scan the sample surface at 10x magnification to capture detailed images of the sample. Linear roughness was obtained over the profile of 7 sub-blocks. The lambda chi (l) representing the sampling length of the measurement was adjusted so that the line readings were limited to measurements from 5 of the 7 middle blocks in accordance with ISO Specification 4288: Geometrical Product Specifications (GPS) - Surface Texture: Profile Method - Rules and Procedures to Evaluate Surface Texture.

[0318] Regions within the etched and masked area of the sample were selected for measurement. The regions were selected that best represented the typical sample surface and were used to calculate Sa and Sdr.

[0319] The surface roughness Sa and Sdr are parameters known in the basic 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).

[0320] ​

[0321] The step height as a result of the etching process is measured directly using a Keyence 3D laser scanning confocal digital microscope model VK-X250X at a magnification of 20X. Selected areas in the etched and unetched regions of the sample are used to produce separate reference planes. The average height difference in three measurements between these reference planes can be taken as the step height.

[0322] ​

[0323] The average etch rate in nanometers per hour can be calculated from the average step height by dividing the step height by the total etch time to obtain the etch rate in nanometers per minute.

[0324] ​

[0325] The etched volume is calculated from the measurements of a Keyence 3D laser scanning confocal digital microscope model VK-X250X at 50X. A 7x7 image template is created from which a 7x1 region is selected for measurement. A reference plane is first established on a representative area of the sample that has been masked and thus not etched. To establish the reference plane, an area within the masked region is selected. A tilt correction is done on the entire area to account for variations in sample thickness and mounting that allows the software. Thereafter, a total area of 600pm x 200pm is selected in the etched region of the image at the maximum distance from the masked surface. The height of the etched surface is measured compared to the reference plane created on the masked surface and the volume of material removed by etching in the selected region relative to the reference plane is calculated.

[0326] Difference between Ra and Sa measurements :

[0327] Sa is the arithmetic average height of a surface and is described in ISO 25178: Geometric Product Specifications (GPS) - Surface texture: areal is an International Organization for Standardization standardization collection of international standards related to the analysis of 3D areal surface texture. This is based on a non-contact laser electronic microscope.

[0328] Ra is the arithmetical mean roughness of the 2D profile according to ISO 4287:1997 Geometrical Product Specifications (GPS) - Surface texture: Profile method for the determination of surface texture. This is based on a mechanical stylus in contact with the surface to create a linear profile.

[0329] Sa represents the height difference of the 3D measured surface, while Ra represents the height difference of the 2D linear profile scan.

[0330] Ra is limited by the stylus tip geometry, thus can lead to loss of fine feature details and distortion of peaks and valleys. This can be problematic when measuring fine sub-micron features and limits the use of Ra values for comparison with Sa values.

[0331] Further samples were prepared according to the process of the present invention and summarized in the following table. Where applicable, they were compared to a commercially available quartz (TSC 03) and to comparative yttria samples (107, 108 and 118).

[0332] As one example, sample 188-1 was prepared as follows: a yttria powder having a surface area of 2 m 2 / g to 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 yttria sintered body. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprised a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, 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. Pre-application of pressure was performed in a multi-step process, whereby a 20 MPa pressure was pre-applied under vacuum. Thereafter, a 5 MPa was applied while heating from room temperature to 600 °C at a rate of 10 °C / minute. The pressure was increased to 30 MPa at a rate of 10 °C / minute between 600 °C and the sintering temperature. Sintering was performed at a temperature of 1400 °C, a pressure of 30 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and allowed to cool naturally. Annealing was performed in an oxygen-containing environment at a temperature of 1400 °C for 8 hours. The density was 5.002 g / cm 3 .

[0333] In another example, sample 116 was prepared as follows: a yttria powder having a surface area of 6.5 m 2 / g to 7.5 m 2A 40 mm yttria sample was formed from a powder having a surface area of 5 m2 / g. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die, and the upper and lower punches, included a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 40 pm to about 60 pm, whereby the gap was configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. Sintering was performed at a sintering temperature of 1550 °C for 10 minutes at 30 MPa. Annealing was performed in air for 9 hours in a furnace at a temperature between 1400 °C and 1450 °C. The starting yttria powder had a total purity of 99.999% corresponding to 10 ppm. The median particle size was measured to be 5.82 pm. The total impurity level of the sintered yttria body was 11 ppm. The purity of the starting powder was maintained in the sintered yttria body, indicating that very little or no contaminants were introduced during processing. The d10, d50, and d90grain sizes were measured to be 0.7 pm, 6.7 pm, and 25.4 pm, respectively.

[0334] In another embodiment, sample 224 was prepared as follows: a yttria powder having a surface area of 5 m 2 / g to 6 m 2 A 100 mm yttria sintered body was formed from a yttria powder having a surface area of 5 m2 / g to 6 m2 / g and an average total impurity of 8 ppm (corresponding to a powder purity of 99.9992%). The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die, and the upper and lower punches, included a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, whereby the gap was configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pre- applied pressure was applied at 20 MPa for about 5 minutes and a vacuum of 50 mTorr was established. Thereafter, the pressure was reduced to 5 MPa, and heating to 600 °C was accomplished at a rate of 10 °C / minute. The application of heat and pressure was performed simultaneously to reach a pressure of 20 MPa, and the temperature was applied at a rate of 10 °C / minute to 1400 °C. Sintering was performed at a temperature of 1400 °C, a pressure of 20 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and allowed to cool naturally. The d10, d50, and d90grain sizes of the yttria sintered body were 0.4 pm, 0.7 pm, and 1.2 pm, respectively.

[0335] In another embodiment, sample 189-1 was prepared as follows: a yttria powder having a surface area of 4.2 m 2A 100 mm yttria sinter was formed from a yttria powder having a total impurity of 24.8 ppm (corresponding to a powder purity of 99.9975%) and a specific surface area of 9 m2 / g. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprised a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, whereby the gap was configured between the inward-facing surface of the at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Pre-application of pressure was performed in a multi-step process, whereby a 20 MPa pressure was pre-applied under vacuum. Thereafter, a 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 at a rate of 10 °C / min between 600 °C and the sintering temperature. Sintering was performed at a temperature of 1400 °C, a pressure of 30 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and allowed to cool naturally. Annealing was performed in an oxygen-containing environment at a temperature of 1400 °C for 8 hours. The impurity of the yttria sinter was 36 ppm, and the purity was 99.996%. The density of the annealed and sintered yttria body was 5.006 g / cm3. 3 and having a maximum pore diameter of 0.7 microns. After a 2-step CF4 / O2 etch process as disclosed herein, an average step height of 0.82 pm, an average etch rate of 0.57 nm / min, and an etch volume of 270,000 pm3were obtained. 3 .

[0336] In another embodiment, sample 045 was prepared as follows: a yttria powder having a total impurity of 24.8 ppm (corresponding to a powder purity of 99.9975%) and a specific surface area of 9 m 2 / g to 10 m 2A 100 mm yttria sinter was formed using yttria powder having a surface area of 4 m2 / g and a total impurity of 26 ppm (corresponding to a powder purity of 99.9974%). The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, whereby the gap was configured between the inwardly facing surface of at least one foil and the outer wall of each of the upper and lower punches of the sintering apparatus. Pre-application of pressure was performed in a multi-step process, whereby a 20 MPa pressure was pre-applied under vacuum as disclosed herein. Thereafter, a 5 MPa was applied while heating from room temperature to 600 °C at a rate of 10 °C / minute. The pressure was increased to 30 MPa at a rate of 10 °C / minute between 600 °C and the sintering temperature. Sintering was performed at a temperature of 1400 °C, a pressure of 30 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and allowed to cool naturally. The average density measured using the Archimedes method was 5.021 g / cm3. 3 . Annealing was performed in an oxygen-containing environment at a temperature of 1400 °C for 8 hours. The average density measured using the Archimedes method after annealing was 5.010 g / cm3 3 .

[0337] In another embodiment, sample 200-1 was prepared as follows: yttria powder having a surface area of 4 m 2 / g to 5 m 2 / g and a total impurity of 9.5 ppm (corresponding to a powder purity of 99.9991%) was used to form a 150 mm yttria sinter. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, whereby the gap was configured between the inwardly facing 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 20 MPa for about 5 minutes. Thereafter, the pressure was decreased to 5 MPa, and heating to 600 °C was completed at a rate of 25 °C / minute. Application of heat and pressure was performed simultaneously, heating to 1000 °C at a heating rate of 25 °C / min and pressurizing to 20 MPa at a pressure rate of 5 MPa / min. Heating was performed at 1000 °C to the sintering temperature at a rate of 10 °C / minute. Sintering was performed at a temperature of 1400 °C, a pressure of 20 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and allowed to cool naturally. Annealing was performed in an oxygen-containing environment at a temperature of 1400 °C for 8 hours. The density of the annealed and sintered yttria body was 4.945 g / cm3 3and having a maximum pore size of 1.4 microns. After a 2-step CF4 / O2 etch process as disclosed herein, an average step height of 0.2 pm, an average etch rate of 0.14 nm / min, and an etch volume of 60,000 pm3were obtained. After an oxygen etch process as disclosed herein, an average step height of 0.1 pm, an average etch rate of 0.07 nm / min, and an etch volume of 30,000 pm3were obtained. 3 After an SF6etch process as disclosed herein, an average step height of 0.27 pm, an average etch rate of 0.19 nm / min, and an etch volume of 80,000 pm3were obtained.

[0338] In another embodiment, sample 212-1 was prepared as follows: a yttrium oxide powder having a surface area of 5.6 m 2 / g and a total impurity of 8.1 ppm (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 properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, 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 pre-applied pressure was established at 20 MPa for about 5 minutes and a vacuum of 50 mTorr was established. Thereafter, the pressure was reduced to 5 MPa, and heating to 600 °C was accomplished at a rate of 50 °C / min. The application of heat and pressure was conducted simultaneously, pressurizing to 30 MPa at a pressure rate of 10 MPa / min and heating to 1450 °C at a rate of 25 °C / min. Sintering was conducted at a temperature of 1450 °C, a pressure of 30 MPa for 30 minutes to complete sintering. After sintering, the power to the sintering apparatus was turned off and the sintering apparatus was allowed to cool naturally. Annealing was conducted in an oxygen-containing environment at a temperature of 1400 °C for 8 hours. The density of the annealed and sintered yttrium oxide body was 5.022 g / cm 3 and having a maximum pore size of 1.0 microns. The total average impurity of the sintered yttrium oxide body was 6 ppm, corresponding to a purity of 99.9994%. After a 2-step CF4 / O2 etch process as disclosed herein, an average step height of 1.1 pm, an average etch rate of 0.77 nm / min, and an etch volume of 358,000 pm 3 .

[0339] In another embodiment, sample 314 was prepared as follows: a yttrium oxide powder having a surface area of 2 m 2 / g to 3 m 2A yttria powder having a surface area of 5 m2 / g to 6 m2 / g and a total impurity of 24.8 ppm (corresponding to a powder purity of 99.9975%) formed a yttria sintered body having a longest dimension of 406 mm. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 70 pm, whereby the gap was configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pressure of 5 MPa was pre-applied, and the temperature was ramped from room temperature to 800 °C at 10 °C / min. The application of heat and pressure was performed simultaneously, heating between 800 °C to 1000 °C at a heating rate of 10 °C / min, and the pressure was ramped to 20 MPa. The pressure was held at 20 MPa using a heating rate of 10 °C / min between 1000 °C and the sintering temperature. Sintering was performed at a temperature of 1450 °C, a pressure of 20 MPa, for a sintering duration of 60 minutes. The heat and pressure were terminated after the sintering duration and natural cooling occurred. Using a heating and cooling rate of 0.8 °C / min, the sintered yttria body was annealed at 1400 °C for 8 hours in an oxygen containing environment. The average density of the annealed and sintered yttria body was 4.935 g / cm 3 The density within the longest dimension ranged between 4.898 g / cm 3 and 4.970 g / cm 3 .

[0340] In another embodiment, sample 457 was prepared as follows: a yttria powder having a surface area of 5 m 2 / g to 6 m 2 / g and a total impurity of 17 ppm (corresponding to a powder purity of 99.9983%) was used to form a yttria sintered body having a longest dimension of 406 mm. Calcination of the powder was performed at 600 °C for 8 hours, and the surface area was 5 m 2 / g to 6 m 2 / g. The die of the sintering apparatus is lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches comprise a graphite material as disclosed herein. The powder is disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 70 pm, whereby the gap is configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pressure of 5 MPa is pre-applied, and the temperature is ramped from room temperature to 600 °C at 10 °C / min. The application of heat and pressure is performed simultaneously, heating between 600 °C to 1000 °C at a heating rate of 5 °C / min, and the pressure is ramped to 30 MPa. The pressure is held at 30 MPa using a heating rate of 5 °C / min between 1000 °C and the sintering temperature. Sintering is performed at a temperature of 1475 °C, a pressure of 30 MPa, for a sintering duration of 60 minutes. The pressure is removed after the sintering duration. Cooling is performed using forced convection at 50% blower power for about 4 hours. Cooling using different blower power levels from about 25% to 100% enables a forced convection cooling rate between 2.5 °C / min to 5 °C / min. Sintering is performed at a temperature of 1475 °C, a pressure of 30 MPa, for a duration of 60 minutes. The sintered yttria body is annealed in an oxygen-containing environment at 1400 °C for 4 hours 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 yttria body is 4.985 g / cm 3 The density range within the longest dimension is between 4.980 g / cm 3 and 4.989 g / cm 3 The maximum pore size measured is 1.4 pm, and the Sa value measured after the CF4 / O2 etching process as disclosed is 18 nm and the Sdr value is 1178 x 10 -5 The average grain size of this sample measured using line intercept technique is 0.65 pm.

[0341] In another embodiment, sample 353 is prepared as follows: a yttria powder having a surface area of 6.5 m 2 / g to 7.5 m 2 / g, and an average total impurity of 11 ppm (corresponding to a powder purity of 99.9989%) is used to form a yttria sintered body having a longest dimension of 406 mm. The powder can be blended, tumbled, sieved, etc. before and / or after calcination according to known methods. The powder is calcined at 1000 °C for 24 hours, and the surface area is 1.5 m 2 / g to 2.5 m 2 / g. The die of the sintering apparatus is lined with a graphite foil having properties as disclosed herein, and each of the upper and lower punches comprise a graphite material as disclosed herein. The powder is disposed within the interior volume of the spark plasma sintering tool having a gap width of about 30 pm to about 70 pm, whereby the gap is configured between the at least one foil's inward facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pressure of 5 MPa is pre-applied, and the temperature is ramped from room temperature to 800 °C at 10 °C / min. The application of heat and pressure is performed simultaneously, heating between 800 °C to 1000 °C at a heating rate of 10 °C / min, and the pressure is ramped to 30 MPa. The pressure is held at 30 MPa using a heating rate of 10 °C / min between 1000 °C and the sintering temperature. Sintering is performed at a temperature of 1475 °C, a pressure of 30 MPa, for a sintering duration of 60 minutes. The heat and pressure are terminated after the sintering duration and natural cooling occurs. The sintered yttria body is annealed in an oxygen containing environment at 1400 °C for 0 minutes (no isothermal annealing time) with 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 yttria body is 4.981 g / cm 3 .

[0342] In another embodiment, sample 414 is prepared as follows: yttria powder having a surface area of 6.5 m 2 / g to 7.5 m 2 / g, and an average total impurity of 11 ppm (corresponding to a powder purity of 99.9989%) is used to form a yttria sintered body having a longest dimension of 406 mm. The calcination of the powder is performed at 500 °C for 48 hours, and the surface area is 6.5 m 2 / g to 7.5 m 2 / g. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 70 pm, whereby the gap was configured between the at least one foil's inward-facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pressure of 5 MPa was pre-applied, and the temperature was ramped from room temperature to 800 °C at 10 °C / min. The application of heat and pressure was performed simultaneously, heating between 800 °C to 1000 °C at a heating rate of 10 °C / min, and the pressure was ramped to 30 MPa. The pressure was held at 30 MPa using a heating rate of 10 °C / min between 1000 °C and the sintering temperature. Sintering was performed at a temperature of 1400 °C, a pressure of 30 MPa, for a sintering duration of 60 minutes. The heat and pressure were terminated after the sintering duration and natural / passive cooling occurred. The average density of the annealed and sintered yttria body was 4.985 g / cm3. 3 .

[0343] In yet another embodiment, sample 476 was prepared as follows: yttria powder having a surface area of about 2 m 2 / g, and a total impurity of 5 ppm to 6 ppm (corresponding to a powder purity of 99.9995%) was used to form a yttria sintered body having a longest dimension of 406 mm. The powder was tumbled for 24 hours prior to sintering without the use of a milling media. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die and the upper and lower punches included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 70 pm, whereby the gap was configured between the at least one foil's inward-facing surface and the outer wall of each of the upper and lower punches of the sintering apparatus. A pressure of 5 MPa was pre-applied, and the temperature was ramped from room temperature to 600 °C at 10 °C / min. The application of heat and pressure was performed simultaneously, heating between 600 °C to 1000 °C at a heating rate of 5 °C / min, and the pressure was ramped to 30 MPa. The pressure was held at 30 MPa using a heating rate of 5 °C / min between 1000 °C and the sintering temperature. Sintering was performed at a temperature of 1475 °C, a pressure of 30 MPa, for a sintering duration of 60 minutes. The pressure was removed after the sintering duration. Cooling was performed using forced convection at 50% blower power. Cooling using different blower power levels enabled a forced convection cooling rate between 2.5 °C / min to 5 °C / min. The sintered yttria body was annealed in an oxygen-containing environment at 1400 °C for 4 hours using a heating rate of 1 °C / min and a cooling rate of 2 °C / min. The average density of the annealed and sintered yttria body was 4.953 g / cm3. 3The density range within the longest dimension is between 4.891 g / cm 3 and 5.014 g / cm 3 .

[0344] In one set of embodiments, samples 084 and 084-1, 085 and 085-1, 086 and 086-1, 087 and 087-1, 095 and 096 were prepared as follows: 100 mm yttria sinter bodies were prepared from a powder having a surface area of 6.5 m 2 / g to 7.5 m 2 / g, and an average total impurity of 11 ppm, given a powder purity of 99.9989%. The powder was calcined at 800 °C for 8 hours prior to sintering and had a surface area of 5 m 2 / g to 6.5 m 2 / g. The die of the sintering apparatus was lined with a graphite foil having properties as disclosed herein, and each of the die, and the upper and lower punches, included a graphite material as disclosed herein. The powder was disposed within the interior volume of a spark plasma sintering tool having a gap width of about 30 pm to about 60 pm, 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. Samples 084-1, 085-1, 086-1, 087-1, 095, and 096 were annealed at 1400 °C for 8 hours in an oxygen environment at a ramp rate of 5 °C / minute. The densities and process conditions are as disclosed in the corresponding density and sintering / annealing tables herein.

[0345] Tables 11-14 summarize the process conditions and resulting densities of samples prepared according to the processes of the present disclosure.

[0346] Table 11: Sintering and annealing conditions for sintered yttria bodies

[0347]

[0348]

[0349]

[0350]

[0351] Table 12: Density of 150 mm sintered yttria bodies

[0352]

[0353] Table 13: Density of 40 mm sintered yttria bodies

[0354]

[0355] Table 14: Density and density variation of 406 mm sintered yttria bodies

[0356]

[0357] Table 15 and Table 16 summarize the purity measured for the starting powder and sintered yttria samples prepared according to the processes disclosed herein.

[0358] Table 15: Purity characteristics of sintered yttria bodies

[0359]

[0360]

[0361] Table 16 shows the maintenance of purity during the processes disclosed herein from powder to sintered yttria bodies.

[0362] Table 16: Purity from powder to sintered yttria bodies

[0363]

[0364] Table 17 to Table 19 show the etching results of different process gases on a quartz (TSC 03) commercially available yttria component (107, 108, 118) and sintered yttria samples prepared according to the present disclosure, including processing conditions. CF4 / O2 etching was performed in a two-step process. Step 1 was performed for 1500 seconds at a pressure of 10 mtorr, CF4 flow of 90 seem, O2 flow of 30 seem, argon flow of 20 seem, and a bias voltage of 600 V, power of 2000 W. Step 2 was performed for 300 seconds at a pressure of 10 mtorr, CF4 flow of 0 seem, O2 flow of 100 seem, argon flow of 20 seem, and a bias voltage of 600 V, power of 2000 W. The first and second steps were repeated in order until the CF4 exposure time in the first step was 24 hours. The O2 etching conditions were: pressure 25 mtorr; CF4 / SF6 flow 0 seem; O2 flow 100 seem; Ar flow 20 seem; bias voltage 600 V; power 2000 W for a total of 6 hours, and the SF6 etching conditions were: pressure 25 mtorr; SF6 flow 100 seem; 02 flow 0 seem; Ar flow 50 seem; bias voltage 300 V; power 2000 W for a total of 24 hours. The results show that sintered yttria bodies prepared according to the present disclosure have excellent corrosion resistance.

[0365] Sintered yttria bodies prepared according to the present disclosure preferably exhibit a step height of 0.2 pm to 0.98 pm for a CF4 / O2 etching process as disclosed, 0.27 pm to 0.44 pm for a SF6 etching process as disclosed herein, and 0.1 pm to 0.13 pm for an O2 etching process as disclosed herein.

[0366] Sintered yttria bodies prepared according to the present disclosure preferably exhibit an etch volume of 0.6 x 10 5 to 3.4 x 10 5 μm 3 for a CF4 / O2 etching process as disclosed, an etch volume of 0.8 x 10 5 to 1.4 x 10 5 μm 3 for a SF6 etching process as disclosed herein, and an etch volume of 0.28 to 0.39 μm 3 for an O2 etching process as disclosed herein.

[0367] Sintered yttria bodies prepared according to the present disclosure preferably exhibit an etch rate of 0.14 nm / min to 0.68 nm / min for a CF4 / O2 etching process as disclosed, an etch rate of 0.19 nm / min to 0.310 nm / min for a SF6 etching process as disclosed herein, and an etch rate of 0.07 nm / min to 0.09 nm / min for an O2 etching process as disclosed herein.

[0368] Table 17: CF4 / O2 etching results

[0369]

[0370] Table 18: O2 etching results

[0371]

[0372] Table 19: SF6 etching results

[0373]

[0374] Table 20: Grain size results

[0375]

[0376] Grain boundaries

[0377] The composition and properties of the grain boundaries can be relevant for etching and erosion performance. As reported by M. Watanabe and D. B. Williams, (J. Microsc. 221 (2006) 89-109), the grain boundary properties can be calculated quantitatively by a > factor. As shown in Figure 12 spectra are obtained (EDS energy dispersive x-ray spectroscopy) from selected areas on the grain boundary and the two adjoining grains, and the difference in elemental composition between the grain boundary and the bulk grain is reported as atomic / nm 2Excess coverage (V.J. Keast, D.B. Williams, J. Microsc. 199 (2000) 45-55). Positive numbers for excess coverage indicate that the grain boundary has a higher concentration of a particular element relative to the bulk grain, and corresponding negative numbers indicate that the element is more concentrated in the bulk grain.

[0378] The grain boundary composition and excess coverage of comparative sample 107 (a commercially available yttria sample) was analyzed. Figure 13 The results of the excess coverage of sample 107 are shown in atomic / nm2over several grain boundaries. Silicon dioxide is present in the grain boundaries in an excess of about 8 atomic / nm2to 10 atomic / nm2relative to the adjoining grains.

[0379] The grain boundary composition and excess coverage of sample 114, formed from a common powder supplier as sample 152, was analyzed. Figure 14 The results of the excess coverage are shown in atomic / nm2. Silicon dioxide is present in the grain boundaries in an amount of about 2 atomic / nm2to about 4 atomic / nm2relative to the bulk grain composition. All other elements are present in an excess coverage amount less than silicon dioxide. These low levels of elements other than yttria oxide present in the grain boundaries of sample 114 corresponding to sample 152 can provide the preferred etch results across various process gases as reported in Tables 17, 18, and 19.

Claims

1. A method of making a sintered ceramic body, the method comprising the following process steps: a. disposing at least one ceramic powder within an interior volume of a spark plasma sintering tool, wherein the spark plasma sintering tool comprises: a. a mold comprising a sidewall, the sidewall comprising an inner wall and an outer wall, wherein the inner wall has a diameter defining an interior volume; an upper punch and a lower punch operably coupled with the mold, wherein each of the upper punch and the lower punch has an outer wall defining a diameter that is less than the diameter of the inner wall of the mold, whereby when at least one of the upper punch and the lower punch is moved within the interior volume of the mold, a gap is created between the outer wall of each of the upper punch and the lower punch and the inner wall of the mold, wherein the sintering tool has a central axis, and the gap is 10 pm to 100 pm wide, wherein the inner wall of the mold comprises at least one electrically conductive foil having a thickness of at least 25 pm to 260 pm, and wherein the gap is measured from an inward facing surface of the electrically conductive foil closest to the upper punch and the lower punch to the outer wall of each of the upper punch and the lower punch; b. creating a vacuum condition within the interior volume; c. moving at least one of the upper punch and the lower punch to apply pressure to the ceramic powder while heating the ceramic powder to a sintering temperature and sintering the ceramic powder to form the sintered ceramic body; and d. reducing the temperature of the sintered ceramic body, wherein the at least one ceramic powder has a specific surface area of 1 m 2 / g to 18 m 2 / g, measured according to ASTM C1274, and the inner diameter of the mold is greater than or equal to 100 mm.

2. The method of claim 1, wherein the at least one ceramic powder has a resistivity of 1 x 10 -5 ohm-cm to 1 x 10 10 ohm-cm, and the at least one ceramic powder is selected from 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, and titanium boride or titanium diboride and titanium nitride, and combinations thereof.

3. The method of claim 1 or 2, wherein the gap has a width of 10 pm to 70 pm.

4. The method of claim 1 or 2, wherein the gap is axisymmetric around the central axis or the gap is asymmetric around the central axis.

5. The method of claim 1 or 2, wherein the at least one ceramic powder has a specific surface area (SSA) of 1 m2 / g to 16 m2 / g. 2 2 / g to 16 m2 / g.​ 6. The method of claim 1 or 2, wherein the method further comprises the following steps: e. annealing the sintered ceramic body by increasing the temperature of the sintered ceramic body to an annealing temperature; f. reducing the temperature of the sintered and annealed ceramic body to an ambient temperature; 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 showerhead, a gas distribution plate, a remote plasma adapter, an etch chamber liner, a plasma source adapter, a gas inlet adapter, a diffuser, an electron wafer chuck, a chuck, a positioning disk, a mixing manifold, an ion suppressor element, a faceplate, an isolator, a spacer, and a guard ring.

7. The method of claim 1 or 2, wherein a temperature difference per centimeter of the at least one ceramic powder disposed within the interior volume defined by the spark plasma sintering tool during step c. is 0.15 °C / cm to 5 °C / cm.

8. The method of claim 1 or 2, wherein a temperature difference of the at least one ceramic powder disposed within the interior volume defined by the spark plasma sintering tool during step c. is 1 °C to 100 °C.

9. The method of claim 1 or 2, wherein the at least one ceramic powder has a d50 particle size of 0.8 pm to 100 pm.

10. The method of claim 1 or 2, wherein the at least one ceramic powder comprises a powder compact having a packing density of 20% to 60% by volume.

11. The method of claim 1 or 2, wherein the method uses non-pulsed continuous direct current.

12. A sintered ceramic body prepared according to the method of any one of claims 1 to 11, having a maximum dimension of 100 mm to 622 mm, wherein the sintered ceramic body has a density of 98% and greater of the reported theoretical density of the ceramic from which the sintered ceramic body is formed, and the density of the sintered ceramic body varies by 0.5% to 4% along the maximum dimension, wherein the density is measured according to ASTM B962-17.

13. The sintered ceramic body of claim 12, having a volumetric porosity of 0.1% to 2% as calculated from density measurements according to ASTM B962-17.

14. The sintered ceramic body of claim 12, having a maximum dimension measured density variation of less than 3%.

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