Process for sintering a large diameter YAG layer substantially free of unreacted yttrium oxide and yttrium-rich phases

Abstract

A method of producing a sintered ceramic body comprising at least one layer of polycrystalline yttrium aluminum garnet (YAG) of 99% by volume or more, substantially free of unreacted yttrium oxide and yttrium-rich phases, the method comprising sintering yttria and reacting the yttria in situ with alumina comprising fine particle sizes and coarse particle sizes, is disclosed herein.

Description

Technical Field

[0001] The present disclosure relates to a corrosion-resistant sintered ceramic body and components formed therefrom, a method for manufacturing a sintered ceramic body, and use in a semiconductor plasma processing chamber. The sintered ceramic body is essentially defect-free and is thus particularly resistant to etching and corrosion under plasma conditions.

Background Art

[0002] Semiconductor processing requires the use of halogen-based gases and oxygen and other gases in combination with high electric and magnetic fields to create a plasma etching environment. This plasma etching environment is created within a vacuum chamber for etching materials on a semiconductor substrate. The harsh plasma etching environment requires the use of highly corrosion-resistant materials for chamber components. These chambers include component parts such as disks or windows, liners, gas injectors, rings, and cylinders that confine the plasma over the wafers being processed. These components are formed from materials that provide resistance to corrosion and erosion in the plasma environment and are described, for example, in U.S. Patent Nos. 5,798,016, 5,911,852, 6,123,791, and 6,352,611. However, these parts used within a semiconductor processing chamber are continuously attacked by the plasma and, as a result, corrode, erode, and roughen on the surfaces of the chamber parts exposed to the plasma. This corrosion and erosion contribute to wafer-level contamination through the release of particles from the component surfaces into the chamber, resulting in yield loss of semiconductor devices.

[0003] Rare earth oxides, and in particular yttria alumina garnet YAG (yttria alumina garnet) (Y3Al5O 12, the cubic phase), as well as related families of yttrium aluminum oxides such as YAP (AlYO3) and YAM (Y4Al2O9), are known to have a wide range of technical and industrial applications. YAG with a cubic crystallographic phase has attracted much attention due to its uses such as a host material for solid-state lasers, transparent claddings, ballistic infrared window materials, and combinations of its mechanical, thermal, and optical characteristics. Particularly in laser applications, single-crystalline YAG is an ideal substrate due to its ability to host rare-earth dopants, and thus, much effort has been expended to fabricate single-crystalline YAG. In addition to optical applications, YAG is also known to be chemically very inert and exhibit high halogen-based plasma corrosion resistance and erosion resistance.

[0004] YAG-based ceramics are difficult to sinter to a high density required for advanced applications that require a minimum residual porosity in the final parts. In semiconductor applications involving plasma corrosion, porosity can accelerate chemical attack on the surface of chamber components and generate particles as the surface deteriorates with long-term use. In addition to the reduction in chemical resistance, excessive porosity can be detrimental to the mechanical and thermal properties of the ceramic, as is known to those skilled in the art. The densification of YAG ceramics typically requires vacuum sintering at a high temperature of about 1600 °C or higher for a long time such as 8 hours or more to achieve a theoretical density > 98%. To achieve a higher density closer to the theoretical value, pressure-assisted densification techniques such as hot isostatic pressing (HIP) are used after first vacuum sintering to a density of about 98% or directly from powder by uniaxial hot pressing (HP). In many cases, high temperature and long sintering times result in excessive grain growth and adversely affect the mechanical strength of the solid yttrium aluminum oxide body. To promote the densification of YAG ceramics, sintering aids such as silica (SiO2) are often used. However, the addition of sintering aids virtually deteriorates the corrosion resistance and erosion resistance of the yttrium aluminum oxide material and increases the possibility of impurity doping at the semiconductor device level during use in the chamber. Therefore, high-purity and high-density objects of yttrium aluminum oxide, especially objects having a cubic crystal phase (YAG, Y3Al5O 12 ) are desirable.

[0005] Films or coatings of yttrium aluminum oxide are known to be deposited on bases or substrates formed from different materials that are more readily available and have better mechanical and thermal properties. Such yttrium aluminum oxide films have been produced by several methods. However, these methods exhibit a limited film thickness that can be produced, insufficient adhesion between the film and the substrate, and a high level of volume porosity, resulting in particle dropout into the process chamber.

[0006] For high-density components fabricated from the YAG phase of yttrium aluminum garnet, a uniform fine structure is preferred to achieve uniform corrosion characteristics over a large area. Therefore, it is desirable to obtain a high phase purity where most of the body (>90% by volume) consists of YAG and the amount of residual phases of alumina, yttria, YAP or YAM is minimized. However, it is very difficult to fabricate a 100% polycrystalline YAG yttrium aluminum garnet ceramic body, and thus a minor amount (<1% by volume) of secondary oxide phases may be present. YAG according to the established yttria / alumina phase diagram exists only as a line compound following the stoichiometric composition, and thus YAG forms a phase-pure sintered body only over a very narrow composition range. For this reason, the resulting compositions are typically intended to fall on one side or the other of the line. Depending on the intended application, the starting composition is made either yttria-rich or alumina-rich so as to fall on the selected side of the line.

[0007] Fabricating a ceramic body for corrosion-resistant components of large dimensions made from YAG is difficult. Solid, phase-pure and high chemical purity components having a diameter of about 100 mm or more that can be handled and used as part of a chamber without breakage or cracking are difficult to manufacture beyond the laboratory scale. Primarily, the aforementioned problems can be attributed to the difficulty of sintering and the physical properties of YAG including high thermal expansion and low thermal conductivity. Currently, there is no economically feasible way to fabricate high-purity, crystalline phase-pure YAG sintered bodies or components with a diameter of 100 mm to about 625 mm or more for use in semiconductor etching and deposition applications. High-purity, crystalline phase-pure YAG sintered bodies or components larger than 100 mm are particularly difficult to fabricate.

[0008] One difficulty is that YAG is sintered from a mixture of yttrium oxide and alumina. In larger-sized sintered bodies and components, there tends to be regions where yttrium oxide and alumina do not fully react. Even when the starting stoichiometry is intentionally made yttria-rich or alumina-rich, the resulting YAG contains regions of both unreacted yttrium oxide and alumina, leading to YAG that is not optimal for its intended use.

[0009] Accordingly, there is a need for a commercially suitable manufacturing method that is particularly suitable for fabricating sintered ceramic bodies having uniform high density, low porosity, and high purity, large dimensions, and containing no regions of both unreacted yttrium oxide and alumina, and that provides enhanced plasma resistance to corrosion and corrosion under plasma etching and deposition conditions.

Summary of the Invention

[0010] To meet these and other needs, and in view of that object, the present disclosure provides embodiments of a multilayer sintered ceramic body, as well as a method for preparing a large multilayer sintered ceramic body having improved mechanical, electrical, and thermal properties and handling capabilities.

[0011] Embodiment 1. A method for preparing a sintered ceramic body, comprising: a) combining yttria powder and alumina powder to produce a mixture, wherein: i) the yttria powder is characterized by a particle size distribution in which at least 50% by volume of the particles have a size of less than 15 microns, and the remaining particles have a particle diameter (particle size) in the range of 1 micron to 23 microns; ii) the alumina powder is characterized by a multimodal particle size distribution including first and second maxima of particle size over the particle size distribution by percent amount of particle size, one of the first and second maxima being an absolute maximum within the particle size range of 0.75 micron to 1.35 microns, and the one of the first and second maxima having a particle size larger than the particle size of the other maximum; b) placing the mixture within a volume defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition within the volume; c) applying pressure to at least one layer of the mixture while heating to a sintering temperature, performing sintering to form a sintered ceramic body including at least one layer containing 90% to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG); d) cooling the temperature of the sintered ceramic body.

[0012] Embodiment 2. The method according to Embodiment 1, wherein 15% of the particles of the alumina powder have a size of less than 0.5 micron, 50% of the particles of the alumina powder have a size of less than 2 microns, and 100% of the particles of the alumina powder have a size of less than 15 microns.

[0013] Embodiment 3. The method according to Embodiment 2, wherein the first and second maxima are represented as percentages of the amount of particles, and the ratio of the first maximum to the second maximum is greater than 3.

[0014] Embodiment 4. The method according to Embodiment 2, wherein the first maximum is at a particle size of 3 to 5.5 microns.

[0015] Embodiment 5. The method according to Embodiment 2, wherein the second maximum is at a particle size of less than 0.0004 micron.

[0016] Embodiment 6. The method according to Embodiment 2, wherein the multimodal particle size distribution includes a third maximum value.

[0017] Embodiment 7. The method according to Embodiment 1, wherein the ratio of the first maximum value to the third maximum value is 2:3 to 9:1.

[0018] Embodiment 8. A method for producing the alumina-rich YAG layer of less than 1% in a sintered ceramic body, wherein the YAG layer substantially does not contain unreacted yttrium oxide, YAP or YAM phases, and the method comprises: a) providing an alumina powder containing alumina particles having a diameter of 23 microns or less, wherein 5% to 40% of the alumina particles have a diameter of less than 1 micron; c) providing yttrium oxide powder; c) combining the yttrium oxide powder and the alumina powder at a molar ratio of yttrium oxide to alumina of less than 3:5 to form a mixture of yttrium oxide and alumina; d) placing the mixture in a cylindrical volume having a diameter of more than 100 mm defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition in the volume; e) applying a uniaxial pressure to the fired mixture in the cylindrical volume while heating to a sintering temperature, performing sintering to form a sintered ceramic body including at least one layer in which yttrium oxide and alumina particles are combined with each other to form more than 99% by volume of polycrystalline yttrium aluminum garnet (YAG).

[0019] Embodiment 9. The method according to Embodiment 8, further comprising performing non-reactive firing of the mixture of yttrium oxide and the alumina by raising the temperature to the sintering temperature and maintaining the sintering temperature for a certain period of time before placing the mixture in the cylindrical volume.

[0020] Embodiment 10. The method according to Embodiment 8, wherein providing the alumina powder includes providing an alumina powder having a multimodal particle size distribution including at least two maximum values of particle size.

[0021] Embodiment 11. Providing the alumina powder comprises providing a first alumina powder having a particle diameter of less than 7 microns, wherein the first alumina powder particles include a first distribution of diameters, the distribution consisting of a single maximum represented as a percentage of the amount of the first alumina powder particles, and the single maximum being in the range of 0.2 to 0.4 microns, and providing a second alumina powder having a particle diameter of less than 11 microns, wherein the second alumina powder particles include a second distribution of diameters, the distribution including an absolute maximum represented as a percentage of the amount of the second alumina powder particles, and the absolute maximum being in the range of 3.4 to 4.4 microns, and mixing the first alumina powder and the second alumina powder together at a weight ratio of 4:1. The method according to Embodiment 8.

[0022] Embodiment 12. Providing the alumina powder includes providing an alumina powder having a multimodal particle size distribution including at least three maxima of particle diameters. The method according to Embodiment 8.

[0023] Embodiment 13. The method according to Embodiment 9, wherein the first maximum is a particle diameter of 3 to 5.5 microns.

[0024] Embodiment 14. The method according to Embodiment 13, wherein the first maximum is an absolute maximum represented as a percentage of the amount of particles.

[0025] Embodiment 15. The method according to Embodiment 9, wherein the second maximum is 0.7 to 1.5 microns.

[0026] Embodiment 16. The method according to Embodiment 9, wherein the ratio of the first maximum to the second maximum is in the range of 2:3 to 9:1.

[0027] A composition for sintering YAG (yttrium aluminum garnet), the composition comprising a mixture of yttria powder and alumina powder, wherein i) the yttria powder contains particles falling within a size range of 0 microns to 23 microns, and ii) the alumina powder contains particles falling within a size range of 0 microns to 12 microns, each of the alumina powder and the yttria powder having a particle size distribution including d50, d10, and d90, the ratio of the d50 of the yttria powder to the d50 of the alumina powder falling within a range of 2.64:1 to 6.89:1, the ratio of the d90 of the yttria powder to the d90 of the alumina powder falling within a range of 3.4:1 to 17:1, and the ratio of the d10 of the yttria powder to the d10 of the alumina powder falling within a range of 1.7:1 to 5:1.

[0028] Embodiment 18. The composition according to Embodiment 17, wherein the alumina powder further includes first and second maximum values of particle size across the alumina particle size distribution by percent amount of particle size.

[0029] Embodiment 19. The composition according to Embodiment 17, wherein the yttria powder and the alumina powder are present in a yttria-to-alumina molar ratio of less than 3:5.

[0030] Embodiment 20. The composition according to Embodiment 17, wherein the yttria powder and the alumina powder are present in a yttria-to-alumina molar ratio of 3:5 to 3:5.025.

[0031] Embodiments of the present invention can be used alone or in combination with each other.

Brief Description of the Drawings

[0032]

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Best Mode for Carrying Out the Invention

[0033] Here, specific embodiments will be referred to in detail. While the present disclosure is described in conjunction with these specific implementations, it will be understood that the present disclosure is not limited to such specific embodiments. On the contrary, the present disclosure is intended to encompass alternatives, modifications, and equivalents that may be included within the spirit and scope of the present invention as defined by the appended claims. In the following description, many specific details are set forth in order to provide a complete understanding of the disclosed embodiments. The present disclosure may be practiced without some or all of these specific details.

[0034] Semiconductor etching and deposition reactors require reactor components having surfaces with high resistance to corrosion and erosion by halogen-containing plasmas required for processing. The surfaces preferably minimize the release of particles from the component surfaces into the chamber. Further, the chamber components must have sufficient mechanical strength for handling and use, particularly at relatively large (greater than 100 mm in diameter, e.g., 100 - 625 mm) component dimensions. Sintered ceramic bodies may be machined into sintered components and thus must be handleable and machinable at large dimensions while providing corrosion resistance, low particle generation, and high mechanical strength. The sintered ceramic bodies disclosed herein include at least one layer comprising 90 - 99.8 volume % polycrystalline yttrium aluminum garnet (YAG), the at least one layer includes at least one surface, the at least one surface includes pores, and the pores have a pore diameter of 5 μm or less for at least 95% of the pores and a maximum pore diameter of 1.5 μm. These materials have excellent corrosion and erosion resistance. The use of these materials results in semiconductor plasma processing chamber components having surfaces that provide improved plasma resistance compared to other materials when subjected to halogen-based plasma etching and deposition conditions.

[0035] Definitions As used herein, the term "yttrium aluminum oxide" means at least one of the crystalline phases of yttrium aluminum oxide including Y3Al5O 12 (YAG; yttrium aluminum garnet / cubic phase), YAlO3 (YAP; yttrium aluminum perovskite phase), and Y4Al2O9 (YAM; yttrium aluminum monoclinic phase) and combinations thereof. The terms "YAG" and "YAG phase" are used interchangeably herein.

[0036] As used herein, the term "sintered ceramic body" refers to a single layer or a multi-layer body. In the case of a multi-layer body, this term refers to a single, integral sintered ceramic article formed by co-compressing one or more powder mixtures by applying pressure and heat, which forms a single high-density multi-layer sintered ceramic body. The single multi-layer sintered ceramic body can be machined into a single multi-layer sintered ceramic component useful as a chamber component in plasma processing applications. As used herein, the term "co-compacting" or "co-compaction" refers to a process in which at least two separate powder materials are placed in a die and subjected to pressure to form a powder compact. The powder compact does not contain a green body or formed body that is common in the art, or binders, dispersants, and other similar organic substances required for the formation of a tape.

[0037] "Single" or "integral" means a complete single piece or a single unit by itself without additional pieces, i.e., the component is one monolithic piece formed as one unit with another component.

[0038] As used herein, the term "substantially" is a descriptive term indicating approximation, meaning "to a significant degree" or "not the whole but most of what is specified", and is intended to avoid a strict numerical boundary for a specified parameter.

[0039] As used herein, the term "sintered ceramic component" or "multi-layer sintered ceramic component" refers to a single-layer sintered ceramic body, a multi-layer sintered ceramic body, or a corrosion-resistant ceramic after a machining process that forms the ceramic into a specific shape of a desired component for use in a semiconductor processing chamber disclosed herein.

[0040] As used herein, the term "powder mixture" means two or more starting powders that are mixed together prior to the sintering process and that are thereby formed into at least one layer of a multi-layer sintered ceramic body after the sintering step.

[0041] The term "annealing" as applied to the heat treatment of ceramics is understood herein to mean a heat treatment carried out in air to relieve stress and / or normalize the stoichiometry with respect to the disclosed multi-layer sintered ceramic body.

[0042] As used herein, the term "tool set" may include at least one die and at least two punches. When fully assembled, the tool set defines a volume for disposing the powder mixture, as disclosed.

[0043] The term "phase" as used herein is understood to mean a distinct crystalline region, portion or layer of a sintered ceramic body having a particular crystal structure.

[0044] "Solid solution" as used herein is defined as a mixture of different elements that share the same crystal lattice structure. The mixture within the lattice may be substitutional, where atoms of one starting crystal replace atoms of the other starting crystal, or interstitial, where atoms occupy normally vacant positions within the lattice.

[0045] As used herein, the term "nanopowder" is intended to encompass powders having a specific surface area greater than 20 m 2 / g.

[0046] The term "phase" as used herein is understood to mean a distinct crystalline region, portion or layer of a sintered ceramic body having a particular crystal structure.

[0047] As used herein, the term "layer" is understood to mean the thickness of a material, typically one of several. The material can be, for example, a ceramic powder, a powder mixture, a fired powder mixture, or a sintered region or sintered portion.

[0048] As used herein, "ambient temperature" refers to a temperature range of about 22°C to 25°C.

[0049] As used herein, the term "purity" refers to the absence of various contaminating substances in a) the starting materials from which a powder mixture can be formed, b) the processed powder mixture (or fired powder mixture), and c) the multi-layer sintered ceramic body or component disclosed herein. Higher purity (close to 100%) represents a material that is essentially free of, or contains very little, contaminating substances or impurities and substantially comprises the material composition present in the disclosed starting powder.

[0050] As used herein, the term "impurity" refers to a compound / contaminating substance present in a powder or sintered ceramic other than the intended compound itself. Impurities can be present in the starting powder, powder mixture, processed powder mixture, and sintered ceramic body. The impurity content of the powders, powder mixtures, and the first and second layers of the sintered body disclosed herein was determined using ICPMS.

[0051] The term "dopant" as used herein is a substance added to a bulk material to impart desired properties to a ceramic material (e.g., to change electrical properties). Typically, when used, a dopant is present at a low concentration, i.e., greater than 0.002 wt% and less than 1.0 wt%.

[0052] Impurities differ from dopants in that the dopants defined herein are compounds intentionally added to the starting powder or powder mixture to obtain certain electrical, mechanical, optical, or other properties, such as modification of the crystal grain size in a multi-layer sintered ceramic body.

[0053] As used herein, the term "sintering aid" refers to compounds such as silica (SiO2), lithia (Li2O), lithium fluoride (LiF), magnesia (MgO), and / or calcia (CaO) that enhance densification during the sintering process, thereby reducing porosity. Hf and Y present in the starting powder and remaining in the sintered ceramic are not included in any of the sintering aids, impurities, or dopants as defined herein.

[0054] As used herein, the terms "about" and "approximately" when used in connection with a number or feature disclosed herein allow for a variance of plus or minus 10%.

[0055] The following detailed description assumes that the present disclosure is implemented within an apparatus such as an etching chamber or a deposition chamber that is necessary as part of the fabrication of devices on a semiconductor wafer substrate. However, the present disclosure is not limited thereto. The workpiece can be of various shapes, sizes, and materials. In addition to semiconductor wafer processing, other workpieces for which the present invention can be utilized include various articles such as inorganic circuit boards with fine feature sizes, magnetic recording media, magnetic recording sensors, mirrors, optical elements, and microelectromechanical devices.

[0056] During the processing of semiconductor devices, corrosion-resistant parts or chamber components are used within the etching chamber and are exposed to a harsh corrosion environment that causes the release of particles into the etching chamber, resulting in yield losses due to wafer-level contamination. The sintered ceramic bodies and related components disclosed herein provide enhanced plasma etching resistance and an enhanced ability to be cleaned within a semiconductor processing chamber due to the specific material properties and characteristics described below.

[0057] A method of manufacturing a sintered ceramic body including at least one layer containing 90 vol% to 99.8 vol% of polycrystalline yttrium aluminum garnet (YAG), wherein the at least one layer includes at least one surface, the at least one surface includes pores, and the pores have a pore diameter of 5 μm or less for at least 95% of the pores and a maximum pore diameter of 1.5 μm, is disclosed herein. In a plurality of embodiments, the sintered ceramic body has a volume porosity of 0.1% to 4% calculated from density measurements performed in accordance with ASTM B962-17.

[0058] Preparation method The method disclosed herein for preparing a sintered ceramic body comprises: a) combining yttria powder and alumina powder to produce a mixture, wherein i) the yttria powder is characterized by a particle size distribution in which at least 50 vol% of the particles have a size of less than 15 microns and the remaining particles have a particle diameter in the range of 1 micron to 23 microns, and ii) the alumina powder is characterized by a particle size distribution in which 15% of the particles have a size of less than 0.5 microns, 50% of the particles have a size of less than 2 microns, and 100% of the particles have a size of less than 15 microns; b) placing the mixture within a volume defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition within the volume; c) applying pressure to at least one layer of the mixture while heating to a sintering temperature to perform sintering to form a sintered ceramic body including at least one layer containing 90 vol% to 99.8 vol% of polycrystalline yttrium aluminum garnet (YAG); and d) lowering the temperature of the sintered ceramic body. The residual phase consists essentially of unreacted aluminum oxide.

[0059] The following additional steps are optional: annealing the ceramic sintered body by heating to raise the temperature of the ceramic sintered body to the annealing temperature in an oxidizing atmosphere, an inert atmosphere, a vacuum atmosphere, or a reducing atmosphere according to the final desired oxidation state of the material, thereby forming an annealed ceramic sintered body; a step of lowering the temperature of the annealed ceramic sintered body; and machining the ceramic sintered body or the annealed ceramic sintered body to form ceramic sintered components such as a dielectric window or RF window, focus ring, nozzle or gas injector, shower head, gas distribution plate, etching chamber liner, plasma source adapter, gas inlet adapter, diffuser, electron wafer chuck, chuck, pack, mixing manifold, ion suppressor element, face plate, isolator, spacer, and / or protective ring in an etching chamber.

[0060] The preparation of the sintered ceramic body disclosed herein can be achieved, for example, by the use of pressure-assisted sintering such as Spark Plasma Sintering (SPS), also known as Field Assisted Sintering Technology (FAST) or Direct Current Sintering (DCS). These DC sintering techniques and related techniques use direct current to heat a conductive die configuration or tool set, thereby heating the material to be sintered. This heating mode allows for the application of very high heating and cooling rates, enhancing the densification mechanism beyond the diffusion mechanism that promotes grain growth, facilitating the preparation of a sintered ceramic body with a very fine crystal grain size, and transferring the inherent properties of the original powder to their nearly or fully dense product. The DC pressure-assisted method disclosed herein preferably utilizes a continuous direct current that is not pulsed to heat the disclosed tool set.

[0061] In multiple embodiments, the methods disclosed herein provide for the preparation of a ceramic sintered body comprising garnet cubic crystalline structure YAG in an amount of 90-99.5% by volume of cubic crystalline structure, preferably 90-99% by volume of cubic crystalline structure, preferably 95-99.5% by volume of cubic crystalline structure, preferably 95-99% by volume of cubic crystalline structure. In alternative embodiments, a phase of Al2O3 in an amount of 0.1-5% by volume, 0.1-3% by volume, 0.1-2% by volume, 0.1-1% by volume, preferably less than 1% by volume may be present in the ceramic sintered body comprising YAG.

[0062] In multiple embodiments, the disclosed processes provide for the preparation of highly phase-pure YAG of greater than 99% by volume of cubic crystalline structure having high (>98%) density, high purity, and low porosity. In alternative embodiments, the disclosed processes provide for the preparation of highly phase-pure YAG of 95% by volume or more of cubic crystalline structure having a second crystalline phase of 5% by volume or less of alumina, and the sintered body also has high density, high purity, and low porosity. In further embodiments, the disclosed processes provide for the preparation of a mixed phase and / or phase-pure ceramic sintered body of yttrium aluminum garnet, Y3Al5O 12 (YAG), yttrium aluminum perovskite YAlO3 (YAP) and / or yttrium aluminum monoclinic Y4Al2O9 (YAM) and combinations thereof. The disclosed ceramic sintered bodies are particularly suitable for use in plasma processing apparatuses such as semiconductor manufacturing apparatuses. Such parts or components can include, among other components, windows, nozzles, gas injectors, showerheads, (etching) chamber liners, mixing manifolds, wafer supports, electronic wafer chucks, and various rings such as focus rings and protection rings.

[0063] Using the materials and methods as disclosed herein, without using a sintering aid, for the ceramic sintered bodies as disclosed, high densities can be achieved, for example, 96%, 98%, and 99.5% or more of the theoretical density for phase-pure YAG. Thus, in a plurality of embodiments, the ceramic sintered body containing YAG substantially does not contain or does not contain a sintering aid (excluding zirconium compounds used as dopants as described herein). In some embodiments, the ceramic sintered body containing YAG also substantially does not contain a zirconium compound.

[0064] In a plurality of embodiments, a ceramic sintered body containing 90 vol% to 99.8 vol% of polycrystalline YAG may contain excess yttria and / or alumina that exceeds the stoichiometric amount of YAG, which may remain from the process or may be intentionally added during powder batch processing and preparation. Thus, excess yttria and / or alumina are not considered either a dopant or a sintering aid to the extent that they can remain in the ceramic sintered body.

[0065] In another embodiment, a ceramic sintered body containing 90 vol% to 99.8 vol% of polycrystalline YAG may contain excess alumina that exceeds the stoichiometric amount of YAG, which may remain from the process or may be intentionally added during powder batch processing and preparation. In this embodiment, since all yttria is consumed in the YAG formation reaction, there is no excess yttria. In yet another embodiment, since all alumina is consumed in the YAG formation reaction, yttria residues remain.

[0066] Step a) of the method disclosed herein is to combine yttria powder and alumina powder to produce a mixture, wherein i) the yttria powder is characterized by a particle size distribution in which at least 50% by volume of the particles are less than 15 microns in size and the remaining particles have a particle diameter in the range of 1 micron to 23 microns, and ii) the alumina powder is characterized by a particle size distribution in which 15% of the particles are less than 0.5 microns in size, 50% of the particles are less than 2 microns in size, and 100% of the particles are less than 15 microns in size. Accordingly, the first powder mixture may have a bimodal or trimodal particle size distribution.

[0067] Figure 2 shows the Gaussian particle size distribution of a typical commercially available yttria powder sample. In contrast, Figures 3 and 4 show the particle size distributions of mixtures of yttria powder and alumina powder, indicating that the above-described particle size distributions are optimal to ensure that all of the yttria is consumed (see the SEM micrograph of Figure 7). Here, if there are not enough alumina powder particles less than 1 micron, it can be seen that yttria is present in the resulting microstructure (see the SEM micrograph of Figure 8). If there are too many alumina particles of size less than 1 micron, large regions of alumina are present in the resulting microstructure (see the SEM micrograph of Figure 6). Figure 5 shows the particle size distribution of the sample of Figure 4, but expressed as volume % of particle size.

[0068] The starting powder materials of aluminum oxide and yttrium oxide for forming a corrosion-resistant ceramic sintered body and a component comprising at least one YAG layer as a result are preferably high-purity commercially available powders. d50 is defined as the median value, representing the value at which half of the population exists above this point and half exists below this point. Similarly, 90% of the distribution is below d90, and 10% of the population is below d10.

[0069] The d10 particle size of the yttrium oxide powder used as a starting material according to an embodiment of the present invention is preferably 1.5 to 8.8 μm, preferably 1.7 to 7.7 μm, preferably 2.0 to 6.7 μm, preferably 2.3 to 5.9 μm, preferably 2.6 to 5.1 μm, preferably 3.0 to 4.5 μm, preferably 3.4 to 3.9 μm.

[0070] The d50 particle size of the yttrium oxide powder used as a starting material according to an embodiment of the present invention is preferably 2.3 to 17.4 μm, preferably 2.6 to 15.2 μm, preferably 3 to 13.2 μm, preferably 3.4 to 11.6 μm, preferably 3.9 to 10.1 μm, preferably 4.5 to 8.8 μm, preferably 5.1 to 7.7 μm, preferably 5.9 to 6.7 μm.

[0071] The d90 particle size of the yttrium oxide powder used as a starting material according to an embodiment of the present invention is preferably 4.5 to 19.9 μm, preferably 5.1 to 17.4 μm, preferably 5.9 to 15.2 μm, preferably 6.7 to 13.2 μm, preferably 10 to 20 μm, preferably 7.7 to 11.6 μm, preferably 8.8 to 10.1 μm, preferably 10 to 18 μm.

[0072] The yttrium oxide powder preferably has a specific surface area (SSA) of 0.75 to 12 m 2 / g, preferably 0.75 to 10 m 2 / g, preferably 0.75 to 8 m 2 / g, preferably 0.75 to 6 m 2 / g, preferably 0.75 to 4 m 2 / g, preferably 0.75 to 2 m 2 / g, preferably 1 to 6 m 2 / g, preferably 1 to 4 m 2 / g, preferably 2 to 10 m 2 / g, preferably 4 to 10 m 2 / g, preferably 6 to 10 m 2 / g, preferably 1 to 4 m 2 / g.

[0073] The purity of the yttrium oxide starting material, measured by total acid decomposition powder and ICP-MS, is preferably over 99.99%, preferably over 99.995%, preferably over 99.999%, more preferably over 99.9995%, and even more preferably over 99.9999%. This corresponds to an impurity level of 100 ppm or less, preferably 50 ppm or less, preferably 25 ppm or less, preferably 10 ppm or less, more preferably about 1 ppm, preferably 1 - 100 ppm, preferably 1 - 50 ppm, preferably 1 - 25 ppm, preferably 1 - 10 ppm, preferably 1 - 5 ppm.

[0074] The d10 particle size of the aluminum oxide powder used as a starting material according to one embodiment of the present invention is preferably 0.05 - 3.0 μm, preferably 0.05 - 2.6 μm, preferably 0.05 - 2.3 μm, preferably 0.05 - 2 μm, preferably 0.05 - 0.75 μm, preferably 0.05 - 1.7 μm, preferably 0.12 - 1.5 μm, preferably 0.12 - 1.3 μm, preferably 0.12 - 1.2 μm, preferably 0.12 - 1 μm, preferably 0.13 - 0.88 μm, preferably 0.15 - 0.77 μm, preferably 0.17 - 0.67 μm, preferably 0.20 - 0.67 μm, preferably 0.23 - 0.58 μm, preferably 0.26 - 0.51 μm, preferably 0.30 - 0.45 μm, preferably 0.34 - 0.39 μm.

[0075] The d50 particle size of the aluminum oxide powder used as a starting material according to one embodiment is generally 0.39 - 11.6 μm, preferably 0.45 - 10.1 μm, preferably 0.51 - 8.8 μm, preferably 0.58 - 1 μm, preferably 0.67 - 6.7 μm, preferably 0.77 - 5.9 μm, preferably 0.88 - 5.1 μm, preferably 1.0 - 4.5 μm, preferably 1.2 - 3.9 μm, preferably 1.3 - 3.4 μm, preferably 1.5 - 3.0 μm, preferably 1.7 - 2.6 μm, preferably 2.0 - 2.3 μm.

[0076] The d90 particle size of the aluminum oxide powder used as a starting material according to an embodiment of the present invention is 0.58 to 67.5 μm, preferably 0.67 to 59.0 μm, preferably 0.77 to 51.5 μm, preferably 0.88 to 44.9 μm, preferably 1.0 to 39.2 μm, preferably 1.2 to 34.3 μm, preferably 1.3 to 29.9 μm, preferably 1.5 to 26.1 μm, preferably 1.7 to 22.8 μm, preferably 2.0 to 19.9 μm, preferably 2.3 to 17.4 μm, preferably 2.6 to 15.2 μm, preferably 3.0 to 13.2 μm, preferably 3.4 to 11.6 μm, preferably 3.9 to 10.1 μm, preferably 4.5 to 8.8 μm, preferably 5.1 to 7.7 μm, preferably 5.9 to 6.7 μm.

[0077] The aluminum oxide powder usually has a specific surface area of 3 to 18 m 2 / g, preferably 3 to 16 m 2 / g, preferably 3 to 14 m 2 / g, preferably 3 to 12 m 2 / g, preferably 3 to 10 m 2 / g, preferably 3 to 6 m 2 / g, preferably 6 to 18 m 2 / g, preferably 6 to 14 m 2 / g, preferably 8 to 18 m 2 / g, preferably 10 to 18 m 2 / g, preferably 8 to 10 m 2 / g, preferably 4 to 9 m 2 / g, preferably 5 to 10 m 2 / g, preferably 6 to 9 m 2 / g.

[0078] The purity of the aluminum oxide starting material is typically more than 99.99% as measured using the ICPMS method, preferably more than 99.995%, preferably more than 99.999%, preferably more than 99.9995%. Correspondingly, the impurity content of the alumina powder can be 100 ppm or less, preferably 50 ppm or less, preferably 25 ppm or less, preferably 10 ppm or less, more preferably 5 ppm or less.

[0079] In a plurality of embodiments, the aluminum oxide powder may include 80 to 100% by volume of an alpha-alumina crystal phase, preferably 90 to 100% by volume of an alpha-alumina crystal phase, preferably 95 to 100% by volume of an alpha-alumina crystal phase.

[0080] Table 1 describes the characteristics of the disclosed starting materials for forming the sintered body containing YAG. The particle sizes of the starting powder, powder mixture, and fired powder mixture were measured using a Horiba model LA-960 Laser Scattering Particle Size Distribution Analyzer capable of measuring particle sizes from 10 nm to 5 mm. The specific surface areas of the starting powder, powder mixture, and fired powder mixture were measured using a Horiba BET Surface Area Analyzer model SA-9601 with an accuracy of 10% or less over a specific surface area of 0.01 to 2000 m 2 / g.

[0081] [Table 1]

[0082] In one embodiment, a dopant containing a zirconium compound is added to yttria powder and alumina powder. Zirconia functions to impart red color to the YAG layer when formed and irradiated with UV light. Examples of the zirconium compound include zirconium oxide (zirconia), zirconium chloride, zirconium nitrate, or any other counter ion for zirconium. In a preferred embodiment, zirconium is added as oxide zirconia, and the zirconia may be stabilized with yttria, for example. The amount of the dopant zirconium compound should be sufficient to supply zirconium in amounts of 15 to 500 ppm, 15 ppm to 350 ppm, 15 ppm to 250 ppm, 15 ppm to 200 ppm, 15 ppm to 100 ppm, 15 ppm to 50 ppm, 50 ppm to 225 ppm, 50 ppm to 200 ppm, 50 ppm to 175 ppm, 50 ppm to 150 ppm, 50 ppm to 150 ppm, 50 ppm to 125 ppm, 50 ppm to 100 ppm, and 50 ppm to 75 ppm.

[0083] In the case of an embodiment where the zirconium dopant compound is zirconium oxide, the zirconia powder may have a particle size distribution having a d10 of 0.08 to 0.20 μm, a d50 of 0.3 to 0.7 μm, and a d90 of 0.9 to 5 μm. The average particle size of the zirconium oxide powder used as a starting material for the mixture according to an embodiment of the present invention can be 0.3 to 1 μm.

[0084] The zirconia powder typically has a specific surface area (SSA) of 1 to 16 m 2 / g, preferably 2 to 14 m 2 / g, preferably 4 to 12 m 2 / g, more preferably 5 to 9 m 2 / g, as measured according to ASTM C1274.

[0085] When used, the purity of the zirconia powder starting material is preferably over 99.8%, preferably over 99.9%, preferably over 99.95%, preferably over 99.975%, preferably over 99.99%, preferably over 99.995%. This corresponds to a total impurity content of 2000 ppm or less, preferably 1000 ppm or less, preferably 500 ppm or less, preferably 250 ppm or less, preferably 100 ppm or less, preferably 50 ppm or less, preferably 25 - 150 ppm, as measured using the ICPMS (Inductively Coupled Plasma Mass Spectrometry) method disclosed herein. The zirconia used in the embodiments disclosed herein typically contains a small amount of Hf of about 2 - 5 wt%, as is common in many commercially available zirconia powders.

[0086] In other embodiments, the powder mixture may preferably not contain a YAG phase having a specific surface area of about 2 m 2 / g or more to form at least one first layer of a multi-layer sintered ceramic body containing YAG by the in-situ reaction phase sintering process disclosed herein. All purity measurements disclosed herein were measured above the reporting limit of a particular element and were completed using an Agilent ICPMS, 7900 ICP-MS model G8403, quadrupole mass spectrometry system. The detection limit for using the ICP-MS method disclosed herein to identify the presence of lighter elements is higher than the reporting limit of heavier elements.

[0087] In a plurality of embodiments, a sintered ceramic body containing 90 vol% - 99.8 vol% of polycrystalline yttrium aluminum garnet (YAG) can be formed from a stoichiometric powder mixture of 37.5 mol% of yttrium oxide and 62.5 mol% of aluminum oxide. "Mechanisms of nonstoichiometry in Y3Al5O 12」The study reported in Patel et al, 2008, Appl. Phys. Lett. 93, 191902 (2008) showed that the dispersion can have a domain width of 0.1 mol% or less. Therefore, a deviation of 0.1 mol% or less from that of stoichiometric YAG (37.5% alumina / 62.5% yttria) can result in the formation of phase-pure yttrium aluminum garnet. Thus, in multiple embodiments, a ceramic sintered body containing more than 99 volume% of yttrium aluminum garnet (YAG) garnet cubic phase (Y3Al5O 12 ) can be formed from a starting powder combined with a powder mixture having a ratio of 37.4 - 37.6 mol% yttrium oxide and 62.6 and 62.4% mol aluminum oxide. By weight, the powder mixture can be formed from about 42.9 - 43.4% alumina and 57.1 - 56.6% yttria.

[0088] Combining the aforementioned starting powders containing yttrium oxide and aluminum oxide having the above particle size distribution can be carried out using wet or dry ball (axial rotation) milling, wet or dry tumbling (end over end or vertical) mixing, and powder preparation techniques that are combinations of these.

[0089] To maintain the purity of the starting powders during mixing, high purity (>99.99%) alumina media can be used to achieve ball milling or end over end tumbling mixing under dry conditions. The high purity alumina media used herein was tested using the ICPMS method and was found to have a purity of 99.997%. The media filling amount for dry ball or tumbling mixing can vary between about 50% media filling amount by powder weight for media elements of large dimensions (about 30 mm). Dry milling or mixing can be carried out for 12 - 48 hours, preferably 16 - 48 hours, preferably 24 - 48 hours, using RPMs of 50 - 200 RPM, preferably 75 - 150 RPM, preferably 100 - 125 RPM.

[0090] Wet ball milling or tumbling mixing can be carried out by suspending the starting powder in various solvents such as ethanol, methanol, and other alcohols, and / or water to form a slurry. The slurry may be formed such that the powder filling amount during milling or mixing is 5 - 50% by powder weight, preferably 10 - 40% by powder weight, preferably 20 - 40% by powder weight. Wet mixing or ball milling realizes the improvement of powder dispersion through the increase in mobility and results in a uniform mixing on a fine scale before heat treatment or firing. In certain embodiments, a dispersant can be optionally added to the slurry using any number of commercially available dispersants, such as polymethyl methacrylate (PMMA) and polyvinyl pyrrolidone (PVP). The dispersant can be optionally added in an amount of 0 (no dispersant) - 0.2% by powder weight, preferably 0 - 0.1% by powder weight. The medium filling amount can vary from not using the medium during ball milling to a medium filling amount of 50% or more by powder weight, preferably 40 - 100% by powder weight, preferably 60 - 100% by powder weight, preferably 50 - 80% by powder weight. Wet ball milling or tumbling mixing can be carried out over 8 - 48 hours, preferably 12 - 48 hours, preferably 16 - 48 hours, preferably 8 - 36 hours, preferably 8 - 24 hours, preferably 8 - 12 hours. For ball milling, an RPM of 50 - 200 RPM, preferably 75 - 150 RPM, preferably 100 - 125 RPM can be used for a container having a diameter of up to about 200 mm. End-over-end tumbling mixing can be carried out at 10 - 30 rpm, preferably at an RPM of about 20.

[0091] Jet milling processes known to those skilled in the art can also be used to completely mix powders to form powders, powder mixtures, or sintered powder mixtures having a narrow particle size distribution. Jet milling uses a high-speed jet of either an inert gas or air to cause the particles of the starting powder and / or powder mixture and / or sintered powder mixture to collide without using a milling or mixing medium, thus maintaining the initial purity of the powder being milled. The starting powders, powder mixtures, and / or sintered powder mixtures disclosed herein may be used alone or in combination with any or all of the disclosed powder milling / mixing processes, and may be subjected to jet milling at a pressure of about 100 psi. After jet milling, the powder or powder mixture may optionally be sieved and blended using any number of meshes, for example having openings in the range of 45 to 400 μm, without limitation as to the number of repetitions or order.

[0092] The use of wet ball milling, tumbling mixing, and / or jet milling is a high-energy process that can break down fine particles and aggregates, improve dispersion through increased particle mobility, provide fine-scale mixing, and provide a homogeneous powder mixture prior to sintering. Additional powder preparation procedures, such as attrition milling, high-shear mixing, planetary milling, and other procedures known to those skilled in the art, may also be applied. The slurry may be dried by rotary evaporation. In other embodiments, the slurry may be dried using spray drying techniques known in the art. Before or after drying, the powder mixture can be sieved using a mesh having openings, for example, in the range of 35 to 75 μm. The foregoing powder preparation techniques may be used alone or in any combination thereof.

[0093] After drying, the surface area of the powder mixture of step a) is 2 to 17 m 2 / g, 2 to 14 m 2 / g, 2 to 12 m 2 / g, 2 to 10 m 2 / g, 4 to 17 m 2 / g, 6 to 17 m 2 / g, 8 to 17 m 2 / g, 10 - 17 m 2 / g, 4 - 12 m 2 / g, 4 - 10 m 2 / g, and 5 - 8 m 2 It can be / g.

[0094] At this point in the process, if a multi - layer sintered ceramic body is formed, a second powder mixture can be formed. The second powder mixture can be, for example, a combination of alumina powder and zirconia powder, where the zirconia powder includes at least one of partially stabilized zirconia powder and stabilized zirconia powder, and may include producing the second powder mixture described in U.S. Provisional Patent Application No. 63 / 216,356, filed on June 29, 2021, the content of which is incorporated herein by reference.

[0095] In an optional step, the method disclosed herein can include heating the first powder mixture (and any additional powder mixtures) to a firing temperature and maintaining the firing temperature for a duration to form a first fired powder mixture (also referred to herein as the "fired powder mixture"). The firing disclosed herein may be carried out at ambient pressure in an oxygen - containing environment, although other pressures and firing environments may be used.

[0096] Firing may be carried out to remove moisture and ensure that the surface state of the powder mixture becomes uniform before sintering. In certain embodiments, firing can be carried out to reduce the surface area. In other embodiments, firing does not cause a reduction in the surface area of the starting powder.

[0097] Firing by the heat treatment process can be carried out at a temperature of 600°C to 1100°C, preferably 600 to 1000°C, preferably 600 to 900°C, preferably 700 to 1100°C, preferably 800 to 1100°C, preferably 800 to 1000°C, preferably 850 to 950°C. The firing can be carried out for 4 to 12 hours, preferably 4 to 10 hours, preferably 4 to 8 hours, preferably 6 to 12 hours, preferably 4 to 6 hours in an oxygen-containing environment. After firing, the fired powder mixture can be sieved through a mesh screen having an opening of, for example, 45 to 400 μm, and / or rolled and / or blended according to known methods to form the fired powder mixture.

[0098] The fired powder mixture for forming the YAG phase can preferably have a d10 particle size of 0.06 to 4 μm, preferably 0.08 to 4 μm, preferably 0.1 to 4 μm, preferably 0.2 to 4 μm, preferably 0.3 to 4 μm, preferably 0.4 to 4 μm, preferably 0.08 to 3 μm, preferably 0.08 to 2 μm, preferably 0.08 to 1 μm, preferably 0.5 to 3 μm, preferably 1 to 2 μm, preferably 1 to 3 μm.

[0099] The d50 particle size of the fired powder mixture can vary from 0.7 to 50 μm, preferably 1 to 40 μm, preferably 1 to 30 μm, preferably 1 to 20 μm, preferably 1 to 10 μm, preferably 1 to 5 μm, preferably 5 to 50 μm, preferably 10 to 50 μm, preferably 20 to 50 μm, preferably 30 to 50 μm, preferably 3 to 8 μm, preferably 5 to 10 μm, preferably 6 to 15 μm.

[0100] The d90 particle size of the fired powder mixture can preferably be 10 to 350 μm, preferably 10 to 300 μm, preferably 10 to 250 μm, preferably 10 to 200 μm, preferably 10 to 175 μm, preferably 10 to 150 μm, preferably 10 to 100 μm, preferably 10 to 75 μm, preferably 10 to 50 μm, preferably 10 to 40 μm, preferably 10 to 30 μm, preferably 15 to 45 μm, preferably 20 to 40 μm, preferably 20 to 350 μm, preferably 40 to 350 μm, preferably 60 to 350 μm, preferably 100 to 350 μm, preferably 150 to 350 μm, preferably 200 to 350 μm, preferably 12 to 330 μm, preferably 100 to 330 μm, preferably 100 to 250 μm.

[0101] In certain embodiments, the firing conditions disclosed herein result in the formation of one or more of the crystalline phases of YAP, YAM, and YAG and combinations thereof, and / or agglomeration of the powder mixture, thus resulting in a wide range of particle sizes or aggregate sizes. Thus, in multiple embodiments, the particle sizes referred to herein can include single particles, and in other embodiments, the particle sizes referred to herein can include aggregates of two or more particles or aggregates of multiple particles that can be measured as large single particles using the laser particle size detection method disclosed herein. Particles including either or both single particles or aggregates of multiple particles can include at least one crystalline phase selected from the group consisting of yttrium oxide, aluminum oxide, yttrium aluminum perovskite (YAP), yttrium aluminum monoclinic (YAM), and YAG (garnet) phases, and combinations thereof. In other embodiments, the lower temperature firing conditions disclosed herein may not affect the particle size distribution of the starting materials, and the particle size distribution is the same range as or similar to the starting powder material. Variations between lots during firing and maintenance of heat transfer can also contribute to broadening of the particle size distribution. The starting powders, powder mixtures, and / or fired powder mixtures disclosed herein can be subjected to any one or combination of the mixing / mill grinding processes disclosed herein. Thus, a wide range of particle size distributions can result from the firing conditions and processes as disclosed herein.

[0102] The fired powder mixture, when measured in accordance with ASTM C1274, is from about 1 m 2 / g to about 18 m 2 / g, preferably 1 m 2 / g to about 14 m 2 / g, preferably about 1 m 2 / g to about 10 m 2 / g, preferably about 1 m 2 / g to about 8 m 2 / g, preferably about 2 m 2 / g to about 18 m 2 / g, preferably about 2 m 2 / g to about 14 m 2 / g, preferably about 2 m 2 / g~about 10 m 2 / g, preferably about 3 m2 / g to about 9 m2 / g, preferably about 3 m 2 / g to about 6 m 2 / g and may have a specific surface area (SSA).

[0103] The fired powder mixture may have a total impurity content of 5 to 200 ppm, preferably 5 to 150 ppm, preferably less than 100 ppm, preferably less than 50 ppm, preferably less than 25 ppm, preferably less than 15 ppm, preferably 10 to 100 ppm, preferably 10 to 80 ppm, preferably 10 to 60 ppm, preferably 10 to 40 ppm, preferably 20 to 80 ppm, preferably 30 to 60 ppm, based on the mass of the fired powder mixture.

[0104] Table 2 shows the ICPMS purity results of a typical fired powder mixture before being formed into the polycrystalline YAG layer according to the present disclosure.

[0105]

Table 2

[0106] In one embodiment, the sintered ceramic body includes polycrystalline yttrium aluminum garnet having impurities of trace metals Na, Fe, and Mg of 50 ppm or less as determined by ICPMS. In another embodiment, the sintered ceramic body includes polycrystalline yttrium aluminum garnet having impurities of trace metals Na, Fe, and Mg of 5 ppm or less as determined by ICPMS. In yet another embodiment, the sintered ceramic body includes polycrystalline yttrium aluminum garnet having a purity of trace elements Li, Na, Mg, K, Ca, B, P, Fe, Cu, Cr, Zn, In, Sn, and Sb (in total) of 50 ppm or less as determined by ICPMS.

[0107] Step b) of the method disclosed herein involves placing a powder mixture (including a sintered powder mixture if the sintering step has been carried out) within a volume defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition within the volume. The spark plasma sintering (SPS) apparatus used in the process disclosed herein includes at least one graphite die, which is typically a cylindrical graphite die. In the graphite die, a first powder mixture (or a first sintered powder mixture) is disposed between two graphite punches. In embodiments where a multi-layer sintered ceramic body is formed, the sintered powder mixtures are sequentially added so as to correspond to the desired layers of the sintered material.

[0108] In some embodiments, the yttria powder and the alumina powder are combined in a molar ratio of yttria to alumina of less than 5:3 to form a mixture. This ratio, along with the particle size distribution, promotes the reaction during sintering, such that substantially all or all of the yttria reacts during sintering. Thus, further, a method of producing an alumina-rich YAG layer of less than 1% in a sintered ceramic body, wherein the YAG layer is substantially free of unreacted yttrium oxide, YAP or YAM, the method comprising: a) providing an alumina powder comprising alumina particles having a diameter of 10 microns or less, wherein less than 40% of the alumina particles have a diameter of less than 1 micron; b) providing a yttrium oxide powder; c) combining the yttrium oxide powder and the alumina powder in a molar ratio of yttrium oxide to alumina of less than 5:3 to form a mixture of yttrium oxide and alumina; d) performing non-reactive firing of the mixture of yttrium oxide and alumina by raising the temperature to a firing temperature and maintaining the firing temperature for a period of time to form a fired mixture; e) placing the fired mixture within a cylindrical volume having a diameter of greater than 100 mm defined by a tool set of a sintering apparatus, forming at least one layer of the fired mixture, and creating a vacuum condition within the volume; f) applying a uniaxial pressure to the fired mixture within the cylindrical volume while heating to a sintering temperature and performing sintering to form a sintered ceramic body comprising at least one layer in which yttrium oxide and alumina particles are combined with each other to form at least 99 volume% of polycrystalline yttrium aluminum garnet (YAG) in the at least one layer, is disclosed herein.

[0109] In a preferred embodiment, the SPS tool includes a die having side walls including an inner wall and an outer wall, the inner wall having a diameter that defines an internal volume capable of receiving at least one ceramic powder, a die, and an upper punch and a lower punch operably coupled to the die, each of the upper punch and the lower punch having an outer wall that defines a diameter smaller than the diameter of the inner wall of the die, such that when at least one of the upper punch and the lower punch moves within the internal volume of the die, a gap is defined between each of the upper punch and the lower punch and the inner wall of the die, and the gap has a width of 10 μm to 100 μm. In some embodiments, the gap has a width of 10 μm to 70 μm. Preferably, the die and the punches are made of graphite. Such an SPS tool is disclosed in U.S. Provisional Patent Application No. 63 / 087,204, filed on October 3, 2020, which is incorporated herein by reference.

[0110] In a plurality of embodiments, one or more (in the case of multi-layer embodiments) fired powder mixtures can be placed (sequentially in the case of multi-layer embodiments) within the graphite die. Vacuum conditions known to those skilled in the art are established within the powder between the punches surrounded by the die. Typical vacuum conditions include a pressure of 10 -2 ~10 -3 torr. The vacuum is applied primarily to remove air to protect the graphite from combustion and to remove most of the air from the powder mixture. In multi-layer embodiments, the order of placement of the powder mixtures may be reversed or repeated as necessary to achieve the desired structure of the multi-layer sintered ceramic body and the components formed therefrom. In such embodiments, the first and second layers of the fired powder mixture are adjacent when placed within the graphite die during sintering and are then sintered to form the first and second adjacent layers.

[0111] Step c) of the method disclosed herein includes applying pressure to at least one layer of the mixture while heating to the sintering temperature to perform sintering to form a sintered ceramic body including at least one layer containing 90% to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG). Step d) includes lowering the temperature of the sintered ceramic body, for example, by removing the heat source of the sintering apparatus or turning off the power supply to cool the ceramic sintered body.

[0112] Pressure can be applied to the powder mixture disposed between the graphite punches and increased to a pressure of 5 MPa to 100 MPa, preferably 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 to 40 MPa. The pressure is applied axially to the powder mixture in the die.

[0113] In a preferred embodiment, the powder mixture is directly heated by the punches and die of the sintering apparatus. The die can be composed of a conductive material such as graphite that promotes resistance / Joule heating. The temperature of the sintering apparatus according to the present disclosure is usually measured within the graphite die of the apparatus. Therefore, it is preferred that the temperature be measured as close as possible to the fired powder mixture being processed so that the indicated temperature is actually achieved in the fired powder mixture being sintered.

[0114] By applying heat to the fired powder mixture and / or the layered powder mixture provided to the die, a sintering temperature of 1000 to 1700 °C, preferably 1200 to 1700 °C, preferably 1400 to 1700 °C, preferably 1500 to 1700 °C, more preferably 1600 to 1700 °C, preferably 1200 to 1600 °C, preferably 1200 to 1400 °C, preferably 1400 to 1600 °C, preferably 1500 to 1600 °C is facilitated. Sintering is typically achieved with an isothermal holding time of 0.5 to 180 minutes, preferably 0.5 to 120 minutes, preferably 0.5 to 100 minutes, preferably 0.5 to 80 minutes, preferably 0.5 to 60 minutes, preferably 0.5 to 40 minutes, preferably 0.5 to 20 minutes, preferably 0.5 to 10 minutes, preferably 0.5 to 5 minutes, preferably 5 to 120 minutes, preferably 10 to 120 minutes, preferably 20 to 120 minutes, preferably 40 to 120 minutes, preferably 60 to 120 minutes, preferably 80 to 100 minutes, preferably 100 to 120 minutes, preferably 30 to 60 minutes, preferably 15 to 45 minutes. In certain embodiments, sintering can be achieved without an isothermal holding time, and once the sintering temperature is reached, the cooling rate disclosed herein is initiated. During sintering, typically a volume reduction occurs, and as a result, the ceramic sintered body can have a volume of about one-third of the volume of the starting powder mixture when placed in the tool set of the sintering apparatus. Polycrystalline YAG is preferably formed in-situ by reactive sintering during the sintering process by a combination of the particle size distribution, purity and / or surface area characteristics of the powder mixture disclosed herein.

[0115] In one embodiment, the order of application of pressure and temperature may be varied according to the present disclosure, which means that it is possible to apply the initially indicated pressure and then apply heat to reach the desired temperature. Further, in other embodiments, it is also possible to first apply the heat indicated to reach the desired temperature and then apply the indicated pressure. In a third embodiment according to the present disclosure, the temperature and pressure may be applied simultaneously to the fired powder mixture to be sintered and increased to the indicated values.

[0116] Induction heating or radiation heating methods can also be used to heat the sintering apparatus to indirectly heat the sintered powder mixture within the tool set.

[0117] In contrast to other sintering techniques, sintering aids are not required (although they may be used if desired). Further, high purity starting powders are desirable for optimal etching performance. The absence of sintering aids and the use of the high purity starting materials disclosed herein with purities from 99.99% to about 99.9999% enable the fabrication of high purity, high density / low porosity ceramic sintered bodies that provide improved etching resistance for use as ceramic sintered components within semiconductor etching chambers.

[0118] In one embodiment of the present invention, process step c) may further include a pre-sintering step having a specific heating gradient of from 0.1 °C / min to 100 °C / min, from 0.1 °C / min to 50 °C / min, from 0.1 °C / min to 25 °C / min, preferably from 0.5 °C / min to 50 °C / min, preferably from 0.5 to 25 °C / min, preferably from 0.5 to 10 °C / min, preferably from 0.5 °C / min to 5 °C / min, preferably from 0.75 to 25 °C / min, preferably from 1 to 10 °C / min, preferably from 1 to 5 °C / min until a specific pre-sintering time is reached.

[0119] In a further embodiment of the present invention, process step c) may further include a pre-sintering step having a specific pressure gradient of from 0.50 MPa / min to 30 MPa / min, preferably from 0.75 MPa / min to 20 MPa / min, more preferably from 1 to 10 MPa / min until a specific pre-sintering time is reached.

[0120] At the end of process step c), the method further includes step d) of lowering the temperature of the sintered ceramic body by natural cooling (non-forced cooling) of the process chamber under vacuum conditions, as is known to those skilled in the art. In a further embodiment by process step d), the ceramic sintered body can be cooled under the convection of an inert gas, for example, argon or nitrogen at 1 bar. Other gas pressures above or below 1 bar can also be used. In a further embodiment, the ceramic sintered body is cooled in an oxygen environment under forced convection conditions. To initiate the cooling process, at the end of sintering step d), except for the power applied to the sintering apparatus and the pressure applied to the ceramic sintered body, then cooling is performed by step d). The cooling rate of the ceramic sintered body disclosed in this specification can be 0.5 - 20 °C / min, 1 - 10 °C / min, preferably 1 - 8 °C / min, preferably 1 - 5 °C / min, preferably 2 - 10 °C / min, preferably 2 - 8 °C / min, preferably 2 - 5 °C / min.

[0121] Optionally, but preferably, the method disclosed herein includes a step of annealing the sintered ceramic body by heating to raise the temperature of the sintered ceramic body (or a component formed therefrom) to reach the annealing temperature and performing annealing, and a step of lowering the temperature of the annealed sintered ceramic body (or a component formed therefrom). In an optional annealing step according to the embodiment disclosed herein, the multi-layer sintered ceramic body may be subjected to a temperature of about 900 - about 1800 °C, preferably about 1250 - about 1700 °C, preferably about 1300 - about 1650 °C, and preferably about 1400 - about 1600 °C.

[0122] In multiple embodiments, optional annealing of the sintered ceramic body may be performed at a heating and / or cooling rate of 0.5 °C / min to 50 °C / min, preferably 0.5 °C / min to 25 °C / min, more preferably 0.5 °C / min to 10 °C / min, still more preferably 0.5 °C / min to 5 °C / min, still more preferably 1 °C / min to 50 °C / min, still more preferably 3 °C / min to 50 °C / min, still more preferably 5 °C / min to 50 °C / min, still more preferably 25 °C / min to 50 °C / min, preferably 1 °C / min to 10 °C / min, preferably 2 °C / min to 10 °C / min, preferably 2 °C / min to 5 °C / min.

[0123] The duration of the optional annealing process can be 1 to 24 hours, preferably 1 to 18 hours, preferably 1 to 16 hours, preferably 1 to 8 hours, preferably 4 to 24 hours, preferably 8 to 24 hours, preferably 12 to 24 hours, preferably 4 to 12 hours, preferably 6 to 10 hours.

[0124] In one embodiment, optional annealing according to the present disclosure can be performed in a sintering apparatus after the sintering process. The optional annealing process can preferably be performed under oxidation conditions such as forced convection or in air. Annealing results in an improvement in the chemical and physical properties of the sintered ceramic body or components fabricated therefrom through reduction of oxygen vacancies for stoichiometric correction and reduction of stress in the sintered body or components. The optional process step of annealing a sintered corrosion-resistant component is performed in an oxidizing atmosphere, whereby the annealing process can provide an increase in albedo, an improvement in mechanical handleability, and a reduction in porosity. After the optional process step of annealing a multi-layer sintered ceramic body is performed, the temperature of the sintered and optionally annealed multi-layer sintered ceramic body decreases to ambient temperature by removal of the heat source.

[0125] In an embodiment where a zirconium compound is added as a dopant to a first powder mixture to impart a uniform color to the layer, the method disclosed herein includes an optional step of exposing the sintered ceramic body to UV radiation for a period of 1 to 400 minutes. The purpose of the UV exposure step is to activate the doped zirconium to impart a red color to the sintered ceramic body. The length of the UV radiation exposure time should be determined by the uniformity and intensity of the red color imparted to the sintered ceramic body. The total exposure time depends on the intensity of the UV lamp used to irradiate the sintered ceramic body.

[0126] In a preferred embodiment, the UV radiation is delivered by a UV lamp, such as a Heraeus Noblelight Hammer Mark II LH10 Lamp System using an H + bulb and an R500 reflector, over an exposure time of about 6 hours at a distance of 3 inches from the sintered ceramic body.

[0127] The process described above is suitable for manufacturing the sintered ceramic bodies disclosed herein having a maximum dimension of, for example, 100 to about 625 mm, preferably 100 to 622 mm, preferably 200 to about 625 mm, preferably 300 to about 625 mm, preferably 400 to about 625 mm, preferably 500 to about 625 mm, preferably 300 to 622 mm, preferably 400 to 622 mm, preferably 500 to 622 mm. Despite their large size, the sintered ceramic bodies manufactured according to the method disclosed herein have a uniform density of about 99.5% of the theoretical value of YAG. The sintered ceramic body is formed, for example, in a disk shape where the diameter is the maximum dimension. The disclosed process provides rapid powder densification and high density, retains a maximum crystal grain size of about 10 μm or less in the sintered ceramic body, and achieves high density and low porosity within at least one first layer over the maximum dimension. This combination of fine crystal grain size, high density, and CTE match provides a high-strength sintered ceramic body of large dimensions suitable for machining, handling, and use as a component within a semiconductor plasma processing chamber.

[0128] The methods disclosed herein optionally include machining a sintered ceramic body (or an annealed sintered ceramic body) to produce window, lid, dielectric window, RF window, ring, focus ring, process ring, deposition ring, nozzle, injector, gas injector, showerhead, gas distribution plate, diffuser, ion suppressor element, chuck, electrostatic wafer chuck (ESC), and pack-shaped sintered ceramic components. Machining, drilling, punching, grinding, lapping, polishing, etc., known to those skilled in the art can be carried out as necessary to form the sintered ceramic body into a predetermined shape of the components for use in a plasma processing chamber. The use of the powder mixtures within the composition ranges disclosed herein can provide a sintered ceramic body with improved machinability by the use of layers with matched CTE, thereby reducing the stress during the machining step of the disclosed methods.

[0129] Optional surface preparation In one embodiment, at least one surface of the sintered ceramic body can be polished either before or after machining. Preferably, at least one surface is polished before machining as described above. Polishing at least one surface involves grinding the at least one surface until the surface has (i) a flatness of 25 microns or less on average over four quadrants of the at least one surface measured at angles of 0°, 90°, 180°, and 270° using a spherometer, (ii) an Ra of less than 14 microinches, and (iii) an Rz of less than 160 microinches, and after the grinding step, lapping the at least one surface with a lapping plate and a lapping media slurry, and after lapping, continuously polishing the at least one surface in a series of polishing steps until the at least one surface exhibits an Ra value of 2 microinches or less, an Rz of 2 microinches or less, and an absolute value of flatness exceeding 15 microns measured with a spherometer, wherein the polishing is performed in a typical manner known to those skilled in the art by lapping and continuous polishing using finer particles of a polishing abrasive having a controlled particle size such as aluminum oxide and diamond, and the process includes.

[0130] Such a polishing process is fully described in U.S. Patent Application No. 63 / 325956, filed on March 31, 2022, the disclosure of which is incorporated herein by reference.

[0131] YAG sintered ceramic body The sintered ceramic body includes at least one layer, and thus, in some embodiments, is a single-layer sintered ceramic body containing 90 to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG) and having the properties disclosed herein. In other embodiments, the sintered ceramic body is a multi-layer sintered ceramic body containing 90 to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG) and including at least one layer having the properties disclosed herein. In multi-layer embodiments, at least one layer containing 90 to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG) and having the properties disclosed herein is preferably an outer layer and can thus be the surface that is ultimately exposed to plasma within the plasma treatment chamber during use. The second layer can be any suitable material such as, for example, zirconia-reinforced alumina or yttrium oxide.

[0132] In multiple embodiments, the sintered ceramic body includes at least one layer containing a cubic crystal structure with 90 to 99.6% by volume, preferably 90 to 99.4% by volume, preferably 95 to 99.6% by volume, preferably 95 to 99.4% by volume of polycrystalline YAG through the use of the materials and methods disclosed herein. In certain embodiments, the sintered ceramic body disclosed herein can contain 95 to 99.6% by volume of the cubic crystal phase of YAG and 0.01 to 5% of an aluminum oxide phase. The volume measurements of the cubic crystal phase of YAG disclosed herein exclude any Al2O3 and zirconium-containing compounds. Embodiments of the sintered ceramic body disclosed herein are polycrystalline and thus, the sintered ceramic body can include, but is not limited to, two or more types of crystals. The sintered ceramic body includes a volume porosity in an amount of 0.1 to 4%, preferably 0.1 to 3%, preferably 0.1 to 2%, preferably 0.1 to 1%, preferably 0.1 to 0.5%, and the volume porosity is calculated from density measurements performed in accordance with ASTM B962-17 or, if the porosity is less than 2%, in accordance with ASTM B311-17.

[0133] In another embodiment, as used herein, a composition containing 90 to 99.8% by volume of cubic crystalline structure Y3Al5O 12 yttrium aluminum garnet (YAG) and at least one layer containing aluminum oxide in an amount of 0.2 to 10% by volume, preferably 0.2 to 8% by volume, preferably 0.2 to 5% by volume, preferably 0.2 to 3% by volume, preferably 0.2 to 2% by volume, preferably 0.2 to 1% by volume of aluminum oxide is disclosed for a sintered ceramic body.

[0134] In a plurality of embodiments, at least one layer of the sintered ceramic body contains at least one form of polycrystalline yttrium aluminum oxide having a volume percentage of 70 to 100% as determined by X-ray diffraction, a volume porosity of less than 0.1 to 5% calculated from density measurements performed according to ASTM B962-17, a purity of greater than 99.99% as measured by the ICPMS method, and a hardness of at least 1200 HV as measured according to ASTM standard C1327. In a plurality of embodiments, at least one layer of the sintered ceramic body contains at least one polycrystalline yttrium aluminum oxide phase or a combination of phases of yttrium aluminum oxide, and in certain embodiments, yttrium aluminum garnet Y3Al5O 12 (YAG) phase, yttrium aluminum perovskite YAlO3 (YAP), and yttrium aluminum monoclinic Y4Al2O9 (YAM) and combinations thereof. In a preferred embodiment, the sintered ceramic body contains 90% to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG).

[0135] In one embodiment, at least one layer of the sintered ceramic body disclosed herein may comprise approximately 100% single crystal phase of any one of yttrium aluminum oxides of YAG, YAP, or YAM. In other embodiments, the sintered ceramic body may comprise a matrix or composite structure of two or more discontinuous or continuous phases of yttrium aluminum oxide disclosed herein. In a further embodiment, the sintered ceramic body may comprise a minor phase of aluminum oxide and / or yttrium oxide, together with a multiphase of any one or combination of yttrium aluminum oxides YAG, YAP, and YAM.

[0136] For reference, FIG. 1 shows a binary phase diagram of yttrium oxide / aluminum oxide. The horizontal axis corresponds to the mixing ratio (mol %) of yttria and alumina, and the vertical axis is temperature (°C). The left side of the horizontal axis corresponds to 100% alumina, and the right side corresponds to 100% yttria. The phase diagram of FIG. 1 shows the regions where yttrium aluminum oxide phases of YAG, YAP, and YAM are formed, as well as the molar composition and temperature conditions required to produce these forms. The formation of YAG may require precise batch processing and careful handling of the powder to maintain stoichiometry and thus form a sintered ceramic body containing phase-pure YAG of 37.5 mol% yttrium oxide and 62.5 mol% aluminum oxide.

[0137] In a plurality of embodiments, at least one layer of the sintered ceramic body disclosed herein comprises zirconium at 15 ppm to 500 ppm as a dopant, and has an L value of 50 to 77, an a value of 6 to 12, and a b value of 3 to 6 when exposed to UV radiation. * value, an a value of 6 to 12 * value, and a b value of 3 to 6 *It has at least one surface that exhibits a value. The purpose of adding (i.e., doping) zirconium is to affect the uniform color change to red when the sintered ceramic body is exposed to UV radiation as detailed below. In a plurality of embodiments, zirconium can be present in amounts of 15 ppm to 500 ppm, 15 ppm to 100 ppm, 15 ppm to 250 ppm, 50 ppm to 250 ppm, 50 ppm to 225 ppm, 50 ppm to 200 ppm, 50 ppm to 175 ppm, 50 ppm to 150 ppm, 50 ppm to 150 ppm, 50 ppm to 125 ppm, 50 ppm to 100 ppm, and 50 ppm to 75 ppm.

[0138] The zirconium in the above amounts can be added as an oxide, chloride, nitrate, or any other counterion. Preferably, zirconium is added as an oxide.

[0139] At least one layer of the sintered ceramic body disclosed herein is very high density and, correspondingly, has a very small pore profile such that at least one surface contains pores with a pore diameter not exceeding 5 μm. In a plurality of embodiments, the pores have a maximum pore diameter of 1.5 μm for at least 95% of the pores.

[0140] To evaluate the crystal grain size of at least one first layer containing polycrystalline YAG, linear intercept crystal grain size measurements were performed in accordance with the Heyn Linear Intercept Procedure described in ASTM Standard E112-2010, "Standard Test Method for Determining Average Grain Size". (As described in Table 3) Crystal grain size measurements were carried out, and an average crystal grain size of 1.1 to 6.3 μm was measured over 25 repetitions. The maximum and minimum crystal grain sizes of 2 to 7.7 μm were also measured on the surface of at least one first layer containing YAG. A single multi-layer sintered ceramic body can have, for example, a surface with a crystal grain size having a maximum crystal grain size of about 8 μm or less, preferably a maximum crystal grain size of 6 μm or less. In a plurality of embodiments, a single multi-layer sintered ceramic body can have a surface with an average crystal grain size of 0.4 to 6.5 μm, preferably 0.4 to 5 μm, preferably 0.4 to 3 μm, preferably 0.8 to 6.5 μm, preferably 0.8 to 5 μm, preferably 0.8 to 3 μm, preferably 1 to 7 μm, preferably 1 to 6.5 μm.

[0141]

Table 3

[0142] Density measurements were performed using the Archimedes buoyancy method in accordance with ASTM B962-17 and ASTM B311-17 (when the porosity level is 2% or less). The reported density values and standard deviations are the average values over 5 or more measurements. Commercial single crystal samples of YAG were measured for density using the methods disclosed herein. Commercial single crystal samples of bulk YAG were measured for density using the methods disclosed herein. An Archimedes density of 4.56 g / cc was obtained over 5 measurements, and this value is taken as the theoretical density of YAG used herein. Sintered ceramic bodies containing at least one layer of phase-pure YAG and additional phase-pure YAG containing up to 1 wt% excess alumina disclosed in the embodiments herein can have a YAG theoretical density of, for example, 4.374-4.556 g / cc, 4.419-4.556 g / cc, 4.465-4.556 g / cc, 4.510-4.556 g / cc, and 4.533-4.556 g / cc, or as a percentage, 96-99.999%, 97-99.999%, 98-99.999%, 99-99.999%, and 99.5-99.999%. The corresponding volume porosity (Vp) can be calculated from density measurements performed as disclosed herein to be less than 0.010-5%, 0.010-4%, 0.010-3%, 0.010-3%, 0.010-2%, 0.010-1%, preferably less than 1%, preferably less than 0.5%. In embodiments where the ceramic sintered body contains at least one second layer containing at least one of about 16 vol% stabilized zirconia and partially stabilized zirconia (and the remaining alumina), the density was measured under similar conditions and a density of about 4.32 g / cc was calculated. Using the volume mixing rule, the theoretical density of ZTA containing about 16 vol% zirconia was calculated, a density of 4.32 was measured, and it was adopted as the theoretical density of at least one second layer containing about 16 vol% zirconia. Thus, at least one second layer of a multi-layer sintered ceramic body containing about 16 vol% zirconia has a theoretical density percentage of 99-100%, preferably 99.5-100%, preferably about 100%.The disclosed multi-layer sintered ceramic body according to this embodiment has a relative density (RD), expressed as a percentage of the theoretical density of a single multi-layer sintered ceramic body including at least one first and second layer, of greater than 99%, preferably 99 - 100%, preferably 99.5 - 100%, preferably approximately 100%.

[0143] The relative density (RD) of a given material is defined as the ratio of the measured density of a sample to the reported theoretical density of the same material, as shown in the following equation. The volume porosity (Vp) is calculated from the density measurements as follows:

[0144]

Equation

[0145] These density, purity, and porosity levels can provide improved resistance to the effects of erosion and corrosion resulting from plasma etching and deposition processes. The disclosed methods and materials are particularly useful for the preparation of ceramic sintered bodies having large dimensions, e.g., a maximum dimension of 200 to about 625 mm. The high density of the ceramic sintered body and thereby its high mechanical strength also provide improved handleability, particularly at large dimensions. The success of fabricating a sintered yttrium aluminum oxide body, particularly an object comprising a layer formed from relatively pure YAG within the ranges disclosed herein over the longest dimension (about 200 to about 625 mm), can be enabled by controlling the density variation over at least one longest dimension. An average density of 96% or greater is desirable, and the density variation is 0.2 to 5% or less, preferably 4% or less, preferably 3% or less, preferably 2% or less, preferably 1% or less, as measured over the maximum dimension, where the maximum dimension can be, for example, 100 to 625 mm, preferably 100 to 622 mm, preferably 100 to 575 mm, preferably 200 to 625 mm, preferably 200 to 510 mm, preferably 400 to 625 mm, preferably 500 to 625 mm. The thickness, i.e., the dimension perpendicular to the longest dimension, can range from 12 mm to 40 mm, preferably 16 mm to 36 mm, more preferably 20 mm to 32 mm, even more preferably 24 mm to 28 mm, and still more preferably 25 mm to 27 mm. A low density of less than 95% of the theoretical density of YAG can have lower strength and thereby a higher porosity of greater than 5%, which results in breakage and poor handleability.

[0146] In addition to high density, the density variation over the maximum dimension of the disclosed ceramic sintered bodies can affect whether they can be handled, machined, and used as ceramic sintered components, particularly at large (>100 mm) dimensions. The density was measured over the maximum dimension for several examples of the ceramic sintered bodies disclosed herein.

[0147] In addition to high density, high hardness values can further provide improved resistance to erosion during use as plasma chamber components. Therefore, Vickers hardness measurements were performed in accordance with ASTM standard C1327, "Standard Test Method for Vickers Indentation Hardness of Advanced Ceramics". The test equipment used for all hardness measurements was a Wilson Micro Hardness Tester Model VH1202. For the ceramic sintered body disclosed herein, hardness values of at least 1200 HV, preferably at least 1400 HV, preferably at least 1800 HV, preferably at least 2000 HV, 1300 - 1600 HV, 1300 - 1500 HV, 1300 - 1450 HV, 1300 - 1400 HV, 1400 - 1600 HV, 1450 - 1600 HV, 1450 - 1550 HV can be obtained. Measured values can be obtained using the Vickers hardness method known in the art and converted to SI units of GPa. For the ceramic sintered body disclosed herein, hardness values of 12.75 - 15.69 GPa, 12.75 - 14.71 GPa, 12.75 - 14.22 GPa, 12.75 - 13.73 GPa, 13.73 - 15.69 GPa, 14.22 - 15.69 GPa, preferably 14.22 - 15.20 GPa can be obtained. These high hardness values can contribute to improved resistance to ion bombardment during semiconductor etching processes and reduced erosion during use, providing extended life when the ceramic sintered body is machined into ceramic sintered components having microscale features.

[0148] In one embodiment, the sintered ceramic body disclosed herein has an average hardness of 13.0 - 15.0 GPa as measured in accordance with ASTM standard C1327 for eight samples using an applied load of 0.2 kgf. In another embodiment, the ceramic sintered body disclosed herein has an average hardness of about 13.5 - 14.5 GPa as measured in accordance with ASTM standard C1327 for eight samples using an applied load of 0.2 kgf.

[0149] Mechanical strength characteristics are known to improve with a decrease in crystal grain size. To evaluate the grain size, linear intercept grain size measurements were performed according to the Heyn Linear Intercept Procedure described in ASTM Standard E112-2010, "Standard Test Method for Determining Average Grain Size". The crystal grain size can also be measured by SEM. To meet the requirements of high flexural strength and rigidity for use in a reaction chamber as a large component of 200 to 625 mm, the ceramic sintered body may have, for example, a maximum crystal grain size of about 10 μm or less, preferably 8 μm or less, preferably an average crystal grain size of 5 μm or less, preferably 3 μm or less, preferably 2 μm or less, preferably 1.5 μm or less, preferably 1.0 μm or less, preferably 0.5 to 8 μm, preferably 1 to 5 μm.

[0150] At least one layer containing 90 vol% to 99.8 vol% of polycrystalline yttrium aluminum garnet (YAG) has a total impurity content of less than 100 ppm, preferably less than 75 ppm, 50 ppm, preferably less than 25 ppm, preferably less than 15 ppm, preferably less than 10 ppm, preferably less than 8 ppm, preferably less than 5 ppm, preferably 5 to 30 ppm, preferably 5 to 20 ppm, as measured using the ICPMS method, based on the total mass of at least one first layer containing polycrystalline YAG. The total impurity content disclosed herein does not include Si in the form of silica.

[0151] The detection limit using the ICP-MS method disclosed herein to identify the presence of lighter elements is higher than the reporting limit for heavier elements. In other words, heavier elements, such as elements above Sc, are detected with a higher precision, such as a lower precision of about 0.06 ppm, than lighter elements, such as elements from Li to Al (which are detected with a lower precision of about 0.7 ppm). Therefore, the impurity content of the powder containing lighter elements such as from Li to Al can be determined to be about 0.7 ppm or more, and the impurity content of heavier elements from Sc (scandium) to U (uranium) can be determined to be about 0.06 ppm or more. Using the ICPMS method disclosed herein, silica can be detected in a relatively low amount of about 14 ppm, while K (potassium) and Ca (calcium) can be identified in an amount of 1.4 ppm or more. Iron can be detected with a precision of a relatively low amount of 0.14 ppm.

[0152] A sintered ceramic body comprising at least one layer containing 90 to 99.8 volume% of polycrystalline yttrium aluminum garnet (YAG), wherein the at least one layer comprises at least one surface, and the at least one surface comprises pores having a pore diameter of 5 μm or less and a maximum pore diameter of 1.5 μm for at least 95% of the pores disclosed herein. The sintered ceramic body may be a single-layer sintered ceramic body or a layer of a multi-layer sintered ceramic body.

[0153] In the case of a multi-layer sintered ceramic body comprising one or more additional layers, the one or more additional layers may be, for example, (i) alumina containing at least one of stabilized zirconia and partially stabilized zirconia; (ii) an additional YAG layer; (iii) yttria; and (iv) alumina, among others.

[0154] In some embodiments, at least one first layer containing YAG, as measured using the ICPMS method disclosed herein, may have a purity of 99.99% or more, preferably 99.995% or more (excluding Al2O3 and zirconium-containing compounds) for a material having 100% purity.

[0155] The above-described properties of the corrosion-resistant component formed from the ceramic sintered body are achieved by adapting the purity of the yttrium oxide and aluminum oxide powders, the combination of the powders, the firing of the powders, the pressure applied to the yttrium oxide and aluminum oxide powders, the temperature of the yttrium oxide and aluminum oxide powders, the duration of the sintering of the powders, the temperature of the ceramic sintered body / ceramic sintered component during an optional annealing step, and the duration of an optional annealing step. The method disclosed herein is suitable for manufacturing ceramic sintered bodies, particularly ceramic sintered bodies of large dimensions, using a scalable manufacturing process.

[0156] It should be understood that the methods and compositions disclosed herein are described in more detail with reference to the following examples, but are not to be considered limited thereby.

Examples

[0157] To more clearly show the overall nature of the present disclosure, the following examples are given. These examples illustrate the present disclosure and are not limiting.

[0158] Measurements for all examples were performed using the disclosed apparatus and methods. Purity measurements were performed using ICP-MS of an Agilent 7900 ICP-MS model G8403. The specific surface area (SSA) of the powders and powder mixtures was measured using a Horiba BET Surface Area Analyzer model SA-9601. Specific surface area measurements were performed in accordance with ASTM C1274. The particle size was measured using a Horiba model LA-960 Laser Scattering Particle Size Distribution Analyzer capable of measuring particle sizes from 10 nm to 5 mm. For all examples, considering the need to minimize impurities, the total concentration of undesirable elements in the raw materials used is at most 1 atomic %.

[0159] The sintered ceramic body produced in the following examples was circular and had a diameter of 622.3 mm.

[0160] Example 1 YAG 4.5 - 6 m 2 / g specific surface area, 2.0 - 3.5 μm d10 particle size, 4.0 - 6.5 μm d50 particle size, and 6.5 - 10 μm d90 particle size of yttria (purity 99.9984%, about 16 ppm impurities by mass), and 6 - 8 m 2 / g specific surface area, 0.075 - 0.2 μm d10 particle size, 2.5 - 5.5 μm d50 particle size, and 15 - 22 μm d90 particle size of alumina (purity about 99.9995%, about 5 ppm impurities by mass) were combined in a molar ratio to form a powder mixture, which reacted during sintering to form a ceramic sintered body containing a cubic yttrium aluminum garnet (YAG) phase. A high-purity alumina medium (more than 99.9% measured by ICPMS) was added at a filling amount of about 60% based on the powder weight, and ethanol was added in an amount of about 35% based on the combined weight of ethanol and powder to form a slurry. Tumbling mixing or end-over-end mixing known to those skilled in the art was performed for 20 hours, and then ethanol was extracted from the powder mixture using rotary evaporation according to a known method. When fired at 1050 °C in air for 6 hours, the fired powder mixture had a specific surface area of 4 - 6 m 2It was measured to have a specific surface area of / g. The powder, powder mixture and / or sintered powder mixture can be sieved, for example, using an aperture diameter of 45 - 400 um, and can be sintered, blended and / or milled in various process steps according to methods known to those skilled in the art. The purity was measured using the ICPMS method disclosed herein, and the total impurity content of the sintered powder mixture was measured to be about 5 ppm with respect to the total mass of the oxides calculated from all the constituents, which corresponded to a purity of about 99.9995%. The starting powders of yttria and alumina, as well as the purity limits and impurity contents of the sintered powder mixtures disclosed herein, do not contain Si. For Si, the detection limit using the ICPMS method for measuring the purity disclosed herein is about 14 ppm, and thus the starting powders of yttria and alumina and the sintered powder mixtures can contain Si in the form of silica at a detection level of about 14 ppm. The sintered powder mixture was placed into the volume defined by the tool set of the sintering apparatus disclosed herein, and a vacuum condition of 10 -2 ~10 -3 torr was created inside the volume. A pressure of 5 MPa was applied, and the sintered powder mixture inside the volume was heated from ambient temperature to 800 °C at about 10 °C / min, and then the pressure was increased at a rate of about 0.4 - about 0.6 MPa / min and the temperature gradient was continued as before to reach the sintering conditions of 1600 °C and 15 MPa over 60 minutes, forming a disk-shaped polycrystalline YAG sintered ceramic body having a maximum dimension of 150 mm. Density measurements were performed on the as-sintered samples and annealed samples according to ASTM B962-17. Averaged over 5 measurements, a density of 4.549 g / cc was obtained. This corresponded to 99.854% of the theoretical density of YAG (reported herein as 4.556 g / cc) calculated from the density measurement and a corresponding volume porosity of 0.146% respectively. The treated sample has a slightly transparent dark gray ceramic appearance when ground thin for light transmission. The sample was then oxidized at 1400 °C for 8 hours using a heating rate of 1 - 5 °C / min up to 1400 °C to obtain a translucent white material.

[0161] Example 2: Non-optimal particle size distribution Lot #21307 of alumina had the particle size distribution shown in FIG. 9. The BET and numerical values in FIG. 9 are listed below.

[0162] BET (surface area) 7.74 d10 (micron) 0.9626 d50 (micron) 2.6778 d90 (micron) 5.9797

[0163] 4.775 kg of alumina was mixed with 6.282 kg of yttrium oxide in 9 liters of ethanol in a 5 - gallon jug, tumbled in a bucket using alumina milling media, treated in a rotary evaporator at 60 °C for 60 minutes and then at 75 °C for 120 minutes, and dried in an oven at 120 °C for 8 hours. Thereafter, the mixture was sintered.

[0164] 5 kg of the sintered powder was placed in a 622.3 - mm circular die and sintered at 1625 °C by field - assisted sintering under a pressure of several tons under vacuum conditions. Specifically, the sintered powder was placed within the volume defined by the tool set of the sintering apparatus disclosed herein, and a vacuum condition of 10 -2 ~10 -3 torr was created within the volume. A pressure of 5 MPa was applied, and the sintered powder mixture within the volume was heated from ambient temperature to 800 °C at a rate of about 10 °C / min, and then the pressure was increased at a rate of about 0.4 - about 0.6 MPa / min, continuing such that the temperature gradient reached the sintering conditions of 1625 °C and 15 MPa over 60 minutes as before, to form a disk - shaped polycrystalline YAG sintered ceramic body having a maximum dimension of 622.3 mm. The thickness of the YAG was 4 - 5 mm. The thickness could be 5 mm - 30 mm, or more. Alumina and yttria reacted to form YAG, but as shown in the SEM image of FIG. 10, it contained regions of unreacted yttria and alumina (the white regions are unreacted yttrium oxide and the dark regions are unreacted alumina).

[0165] Example 3: Optimal Particle Size Distribution Lot #21182 of alumina had the particle size distribution shown in Figure 11. The BET and numerical values in Figure 11 are listed below.

[0166] BET (surface area) 9.89 d10 (micron) 0.5007 d50 (micron) 2.4601 d90 (micron) 6.7047

[0167] 4.775 kg of alumina was mixed with 6.282 kg of yttrium oxide in 9 liters of ethanol in a 5-gallon jug, tumbled in a bucket using alumina milling media, treated in a rotary evaporator at 60 °C for 60 minutes and then at 75 °C for 120 minutes, and dried in an oven at 120 °C for 8 hours. The mixture was then sintered.

[0168] 5 kg of the sintered powder mixture was placed in a 650-mm circular die and sintered at 1625 °C by field-assisted sintering under a pressure of several tons under vacuum conditions. Specifically, the sintered powder was placed within the volume defined by the tool set of the sintering apparatus disclosed herein, and a vacuum condition of 10 -2 ~10 -3 torr was created within the volume. A pressure of 5 MPa was applied, and the sintered powder mixture within the volume was heated from ambient temperature to 800 °C at approximately 10 °C / min, and then the pressure was increased at a rate of approximately 0.4 to approximately 0.6 MPa / min, and the temperature gradient was continued at the aforementioned rate for 60 minutes to reach the sintering conditions of 1625 °C and 15 MPa, forming a disk-shaped polycrystalline YAG sintered ceramic body having a maximum dimension of 622.3 mm. Alumina and yttrium reacted to form YAG. As shown in Figure 12, in the SEM image of YAG, unreacted yttrium oxide was not seen. Only the region of unreacted alumina was visible, which was expected since the ratio of alumina to yttrium oxide was alumina-rich and resulted in the desired microstructure as shown in Figure 12.

[0169] Example 4: Balanced Stoichiometry 300 grams of a stoichiometrically balanced fired powder mixture of alumina and yttrium oxide for forming YAG was placed in a 100 mm circular die and sintered at 1550 °C by electric field assisted sintering under a pressure of several tons under vacuum conditions. The alumina in this fired powder mixture had a particle size distribution as shown in FIG. 13. The fired powder was placed in a volume defined by the tool set of the sintering apparatus disclosed herein, and 10 -2 ~10 -3 torr of vacuum conditions were created within the volume. A pressure of 5 MPa was applied, and the fired powder mixture within the volume was heated from ambient temperature to 800 °C at about 10 °C / min, and then the pressure was increased at a rate of about 0.4 to about 0.6 MPa / min, and the temperature gradient was continued at that rate for 30 minutes to reach the sintering conditions of 1550 °C and 30 MPa, forming a disk-shaped polycrystalline YAG sintered ceramic body having a maximum dimension of 100 mm and a thickness of 7 mm. Alumina and yttrium reacted to form YAG. As shown in FIG. 14, in the SEM image of YAG, unreacted yttrium oxide was not seen. Only a small area of unreacted alumina was visible. Based on the amount of unreacted alumina visible in the SEM image, the microstructure was 99.905% crystalline YAG.

[0170] Example 5: Alumina-rich Stoichiometry 200 grams of an alumina-rich fired powder mixture of alumina and yttrium oxide for forming YAG was placed in a 100 mm circular die and sintered at 1625 °C by electric field assisted sintering under a pressure of several tons under vacuum conditions. In particular, 219.3 grams of alumina was mixed with 282.93 grams of yttrium oxide in 700 ml of ethanol, and 200 grams of alumina-rich fired powder was obtained by milling and pulverizing at 200 rpm for 16 hours using 500 grams of 10 mm alumina media. Then, the mixture was rotary evaporated, sieved through -40 mesh, and fired. The alumina powder used to form the mixture had a particle distribution as shown in FIG. 15. After firing, the powder mixture was placed in a volume defined by the tool set of the sintering apparatus disclosed herein, and 10 -1 ~10 -3A vacuum condition of toluene was created inside the volume. A pressure of 15 MPa was applied, and the sintered powder mixture inside the volume was heated from the ambient temperature to 800 °C at about 10 °C / min. Then, the pressure was increased at a rate of about 0.4 to about 0.6 MPa / min, and the temperature gradient was continued at that rate for 90 minutes to reach the sintering conditions of 1625 °C and 15 MPa, forming a disk-shaped polycrystalline YAG sintered ceramic body having a maximum dimension of 100 mm. Alumina and yttria reacted to form YAG. As shown in FIG. 14, in the SEM image of YAG, unreacted yttrium oxide was not seen. Only the region of unreacted alumina was seen, which was expected since the powder was only 0.5 mol% alumina rich in alumina.

[0171] Based on the foregoing examples and the data shown in the drawings, it has been shown that alumina powder should have a range of particle sizes for reacting with yttrium having a particle size distribution as shown in FIG. 2, thereby forming YAG substantially free of unreacted yttrium. In particular, alumina containing mostly fine particle sizes (the curves marked with circles in FIGS. 4 and 5) leaves unreacted yttrium. The fine alumina particles react too rapidly with yttrium during sintering, surrounding some regions of yttrium with YAG and preventing the surrounded yttrium regions from reacting. When alumina contains a mixture of fine and larger particles, the larger particles of alumina are thought to slow down the reaction during sintering and allow more yttrium to react with alumina (the curves marked with diamonds, squares, and dashed lines in FIGS. 4 and 5). However, as shown by the curves marked with triangles in FIGS. 4 and 5, there cannot be too many larger particles relative to the smaller particle sizes.

[0172] Some embodiments have been described as disclosed herein. However, it will be understood that various modifications can be made without departing from the spirit and scope of the embodiments disclosed herein. Accordingly, other embodiments are also within the scope of the following claims.

Claims

1. A method for preparing a sintered ceramic body, comprising: a. Combining yttria powder and alumina powder to produce a mixture, wherein: i. The yttria powder is characterized by a particle size distribution in which at least 50% by volume of the particles have a size of less than 15 microns, and the remaining particles have a particle diameter in the range of 1 micron to 23 microns; ii. The alumina powder is characterized by a multimodal particle size distribution including first and second maxima of particle size across the particle size distribution by percent amount of particle size, wherein one of the first and second maxima is in the particle size range of 0.75 micron to 1.35 microns, and the one of the first and second maxima has a particle size greater than the particle size of the other maximum; b. Placing the mixture within a volume defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition within the volume; c. Applying pressure to the at least one layer of the mixture while heating to a sintering temperature to perform sintering to form a sintered ceramic body including the at least one layer and containing 90% to 99.8% by volume of polycrystalline yttrium aluminum garnet (YAG); d. Lowering the temperature of the sintered ceramic body.

2. The method according to claim 1, wherein 15% of the particles of the alumina powder have a size of less than 0.5 micron, 50% of the particles of the alumina powder have a size of less than 2 microns, and 100% of the particles of the alumina powder have a size of less than 15 microns.

3. The method according to claim 2, wherein the first and second maxima are expressed as a percentage of the amount of particles, and the ratio of the first maximum to the second maximum is greater than 3.

4. The method according to claim 2, wherein the first maximum has a particle size of 3 to 5.5 microns.

5. The method according to claim 2, wherein the second maximum has a particle size of less than 0.0004 micron.

6. The method according to claim 2, wherein the multimodal particle size distribution includes a third maximum.

7. The method according to claim 1, wherein the ratio of the first maximum to the third maximum is from 2:3 to 9:

1.

8. A method for producing an alumina-rich YAG layer of less than 1% in a sintered ceramic body, wherein the YAG layer is substantially free of unreacted yttrium oxide, YAP or YAM, and the method comprises: a) providing an alumina powder containing alumina particles having a diameter of 23 microns or less, wherein 5% to 40% of the alumina particles have a diameter of less than 1 micron; b) providing yttrium oxide powder; c) combining the yttrium oxide powder and the alumina powder in a molar ratio of yttrium oxide to alumina of less than 3:5 to form a mixture of yttrium oxide and alumina; d) placing the mixture into a cylindrical volume having a diameter of more than 100 mm defined by a tool set of a sintering apparatus, forming at least one layer of the mixture, and creating a vacuum condition within the volume; e) applying a uniaxial pressure to the fired mixture within the cylindrical volume while heating to a sintering temperature, performing sintering, and combining yttrium oxide and alumina particles to form at least one layer containing 99% by volume or more of polycrystalline yttrium aluminum garnet (YAG) in the at least one layer, thereby forming a sintered ceramic body. A method comprising:

9. Before placing the mixture into the cylindrical volume, raising the temperature to the sintering temperature and maintaining the sintering temperature for a certain period of time to perform non-reactive sintering of the mixture of yttrium oxide and alumina, and further comprising sintering the mixture. The method according to claim 8.

10. The method according to claim 8, wherein providing the alumina powder comprises providing an alumina powder having a multimodal particle size distribution including at least two maximum particle sizes.

11. Providing the alumina powder comprises: providing a first alumina powder having a particle diameter of less than 7 microns, wherein the first alumina powder particles include a first distribution of diameters, the distribution consisting of a single maximum value expressed as a percentage of the amount of the first alumina powder particles, and the single maximum value being in the range of 0.2 to 0.4 microns. Providing a second alumina powder having a particle diameter of less than 11 microns, wherein the second alumina powder particles include a second distribution of diameters, the distribution includes an absolute maximum value represented as a percentage of the amount of the second alumina powder particles, and the absolute maximum value is in the range of 3.4 to 4.4 microns, and mixing the first alumina powder and the second alumina powder together at a weight ratio of 4:1, the method according to claim 8, comprising.

12. The method according to claim 8, wherein providing the alumina powder includes providing an alumina powder having a multimodal particle size distribution including at least three maxima of particle diameters.

13. The method according to claim 9, wherein the first maximum value is a particle diameter in the range of 3 to 5.5 microns.

14. The method according to claim 13, wherein the first maximum value is an absolute maximum value represented as a percentage of the amount of particles.

15. The method according to claim 9, wherein the second maximum value is in the range of 0.7 to 1.5 microns.

16. The method according to claim 9, wherein the ratio of the first maximum value to the second maximum value is in the range of 2:3 to 9:

1.

17. A composition for sintering YAG, the composition including a mixture of yttria powder and alumina powder, i. the yttria powder includes particles falling within a size range of 0 microns to 23 microns, ii. the alumina powder includes particles falling within a size range of 0 microns to 12 microns, iii. each of the alumina powder and the yttria powder includes a particle size distribution including d50, d10, and d90, and the ratio of the d50 of the yttria powder to the d50 of the alumina powder falls within a range of 2.64:1 to 6.89:1, the ratio of the d90 of the yttria powder to the d90 of the alumina powder falls within a range of 3.4:1 to 17:1, and the ratio of the d10 of the yttria powder to the d10 of the alumina powder falls within a range of 1.7:1 to 5:1, a composition.

18. The composition according to claim 17, wherein the alumina powder further includes first and second maxima of particle diameters across an alumina particle size distribution by percentage amount of particle diameter.

19. The composition according to claim 17, wherein the yttria powder and the alumina powder are present in a molar ratio of yttria to alumina of less than 3:

5.

20. The composition according to claim 17, wherein the yttria powder and the alumina powder are present in a molar ratio of yttria to alumina of 3:5 to 3:5.025.

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