Erbium aluminum perovskite compositions, plasma chamber comprising the same, and related preparation and application methods

Abstract

The description pertains to aluminate compositions containing erbium aluminum oxide in a perovskite crystal structure; methods for preparing aluminate compositions containing erbium aluminum perovskite; articles containing erbium aluminum perovskite; and methods for preparing and using articles containing erbium aluminum perovskite.

Description

Technical Field

[0001] This specification relates to compositions containing erbium aluminum oxide in a perovskite crystal structure (or "crystalline phase"); methods for preparing compositions containing erbium aluminum perovskite; articles containing erbium aluminum perovskite; sintered bodies containing erbium aluminum perovskite; and methods for preparing and using compositions and articles containing erbium aluminum perovskite. Prior Technology

[0002] Ceramics, referring to room-temperature solid inorganic non-metallic materials, are known to have diverse chemical compositions and may possess a range of different crystalline and amorphous (non-crystalline) forms. Among known ceramic materials, a class encompassing a vast chemical diversity consists of aluminates, composed of aluminum, oxygen, and metal atoms. Aluminates cover materials with a wide range of chemical compositions, many of which can exist in multiple different crystalline phases. Even slight differences in stoichiometry or crystal composition within aluminates containing the same metallic element can produce significantly different mechanical, optical, and chemical properties, thus allowing the use of slightly different aluminates for various applications.

[0003] To cite just one example among many known aluminates, yttrium-containing aluminates can form ceramics with a highly unique and distinctive range of optical, chemical, and mechanical properties. For instance, high-purity cubic yttrium aluminum oxide, commonly known as garnet (YAG), is well-known for its chemical inertness and is used as a chemically resistant material in the presence of plasma and halogens, for example, as a coating within plasma chambers. YAG with a cubic crystal structure can also be doped with other rare-earth metal atoms for use in solid-state lasers such as Nd:YAG. Yttrium aluminum oxide exists in various crystal forms, including twisted cubic structures such as orthorhombic, perovskite (YAP), and monoclinic (YAM).

[0004] One type of ceramic that has not yet been studied is erbium aluminate (“erbium aluminum oxide”). This aluminate can exhibit a variety of different crystal forms (or “phases”) depending on its composition, including the erbium aluminum garnet phase Er3Al5O12 (“ErAG”), the erbium aluminum monoclinic phase Er4Al2O9 (“ErAM”), or the erbium aluminum perovskite phase ErAlO3 (“ErAP”).

[0005] The unique chemistry of rare-earth (lanthanide) aluminates makes them highly resistant to fluorine-based chemistry, particularly plasmas commonly used in semiconductor processing, such as those in etching chambers. In the semiconductor manufacturing industry, processing equipment such as plasma etching chambers and plasma deposition chambers (collectively referred to as "plasma chambers") maintains a high-purity environment as free of particulate contaminants as possible. The internal surfaces and components of plasma chambers are made of chemically inert materials resistant to degradation, as the chemical degradation of these materials within the plasma chamber generates particulate contaminants. Reducing the reaction between chamber materials and the plasma environment through the use of ceramic components is a highly sought-after area for improving yield and reducing uptime impacted by chamber material degradation.

[0006] US 2022 / 234959 A1 describes nanoparticles with thin-film coatings, wherein the thin-film coatings can be composed of different materials, such as erbium aluminum oxide. However, prior art references have not revealed the structure of erbium aluminum oxide, nor have they revealed that the material possesses a specific phase purity. Thin-film coatings can be prepared by atomic layer deposition, forming specific crystal forms.

[0007] US 10 730 798 B relates to a ceramic coating that can be formed by plasma spraying onto a substrate. Therefore, the coating may contain ErAlO3. Summary of the Invention

[0008] While many ceramic materials exhibit good resistance to chemical degradation and controlled erosion in the presence of reactive chemicals and plasma, there remains a sustained interest in materials with even better performance, such as ceramics with improved chemical inertness, which produce increasingly lower levels of particle contamination when used inside plasma chambers. Due to the complexity of semiconductor manufacturing processes and the diverse plasma chemistry and process conditions, a range of material solutions are required to achieve optimal performance.

[0009] This article describes a novel erbium aluminate composition, primarily comprising erbium aluminum perovskite. The crystalline perovskite phase is considered to have a stoichiometry defined by formula ABX3, where A is typically a positively charged ion, such as yttrium, or in this case, an erbium ion; B is a positively charged ion, such as an aluminum ion; and X is a negatively charged ion, such as an oxygen ion. In an ideal cubic structure, the B cation is 6-coordinated and surrounded by an anionic octahedron, and the A cation is 12-cubic-octahedral coordinated. According to this definition, erbium aluminum perovskite has the chemical formula ErAlO3, signifying a nominal stoichiometric ratio of 1 erbium atom to 1 aluminum atom to 3 oxygen atoms.

[0010] In one embodiment, this disclosure relates to an erbium aluminum oxide composition comprising erbium aluminum perovskite with a phase purity of at least 90% by weight.

[0011] In the context of this invention, phase purity refers to the weight percentage of a single crystalline species in a composition relative to all existing species.

[0012] In one embodiment, the erbium aluminum oxide composition contains no more than 1250 ppm of impurities.

[0013] More preferably, the erbium aluminum oxide composition contains no more than 250 ppm of impurities.

[0014] In the context of this invention, the amount of an impurity is defined as the amount of components other than erbium aluminum oxide present in the composition according to the invention. This is also referred to as a chemical impurity.

[0015] However, phase purity refers to the fact that all crystalline parts of a material have the same structure, such as a single type of crystal lattice. Overall purity is related to chemical composition. It is a measure of the amount of desired substances relative to impurities in a material, regardless of crystal structure. A material may be phase pure but still contain chemical impurities, or it may be chemically pure but still contain multiple crystalline phases.

[0016] Compositions containing (comprise, consist of, or substantially consist of) erbium aluminum perovskite can be in any useful form and can be prepared by any of a variety of useful methods. Examples of erbium aluminum perovskite compositions include: particles ("erbium aluminum perovskite particles"); aggregates of erbium aluminum perovskite particles in the form of powder compositions ("erbium aluminum perovskite powder"); coatings on substrates (e.g., "erbium aluminum perovskite coatings"); and solid materials, such as solids having low porosity (e.g., "erbium aluminum perovskite sintered bodies"). The example methods described herein for preparing these compositions produce compositions with non-zero porosity, that is, measurably greater than zero porosity, such as porosity in the range of 0.01 to 5 or 10 percent, for example, less than 1 percent.

[0017] In the literature, limited materials containing erbium aluminum perovskite have been created to develop phase diagrams supporting phase equilibrium science. Generally, melting techniques such as arc melting are used, resulting in highly contaminated material samples with uncontrolled microstructure and porosity. These techniques are used to study the correlations of material systems within a certain temperature and composition range, but due to poor control over material properties and the often severe contamination of arc electrodes or water-cooled sample holders, coupled with the small sample weights typically used, they are not suitable for producing monolithic components or as powder feedstocks.

[0018] Erbium aluminum perovskite particles and erbium aluminum perovskite powder containing erbium aluminum perovskite particles are preferably prepared by solid-state synthesis, also referred to herein as "heat treatment" or "calcination". By exemplary methods, alumina (alumina) particles and erbium oxide (erbium trioxide) particles can be combined in stoichiometric amounts of erbium and aluminum atoms (1 erbium atom: 1 aluminum atom), and the combination can be heated to a certain temperature to allow the alumina and erbium oxide to react, forming erbium aluminum perovskite powder composed of individual erbium aluminum perovskite crystalline particles. The particles formed by this method, and the powder containing the particles, can each primarily contain erbium aluminum perovskite. According to exemplary powders prepared by these methods, the erbium aluminum perovskite powder can contain at least 80, 90, 95, 98, or 99% by weight of erbium aluminum perovskite, which typically exists in the form of small, substantially non-porous crystals.

[0019] Erbium aluminum perovskite powder can be used to form ErAP compositions, such as coatings and sintered bodies. Erbium aluminum perovskite coatings can be formed on substrates using common techniques known in the art, such as plasma spraying or, more preferably, aerosol deposition coating. ErAP coatings can also be formed using other coating methods, such as deposition methods, including chemical vapor deposition (CVD), atomic layer deposition (ALD), and physical vapor deposition (PVD). These methods are typically used to produce very thin coatings that have lower durability against plasma etching or general handling of components to which such coatings are applied.

[0020] Erbium aluminum perovskite sintered bodies can be formed using sintering methods such as conventional sintering or reactive sintering. Conventional sintering typically begins with a pre-formed ErAP powder system, which is heated with or without pressure to reduce surface area and form a dense ceramic body. Reactive sintering involves heating a powder mixture containing erbium oxide and alumina particles, causing the erbium oxide and alumina in the powder mixture to react and form erbium oxide perovskite. The particles grow together without melting, forming an erbium aluminum perovskite sintered body by reducing the surface area of ​​the powder. The sintered body can have a range of porosity levels depending on the starting materials and the desired final form of the ceramic component.

[0021] In one embodiment, this disclosure relates to a method for preparing an erbium aluminum oxide composition comprising at least 90 weight percent of erbium aluminum perovskite. The method includes: preparing a powder mixture comprising erbium oxide particles and aluminum oxide particles; and heating the powder mixture, but without melting the particles, to cause the erbium oxide and aluminum oxide in the powder mixture to react and form erbium aluminum perovskite.

[0022] In another embodiment, this disclosure relates to a method for forming a coating on a substrate surface comprising at least 90 weight percent erbium aluminum perovskite. The method includes: providing a powder comprising particles containing at least 90 weight percent aluminum perovskite; forming an aerosol containing the particles; and, under vacuum conditions, directing the aerosol to the substrate surface such that the particles contact the surface and remain as a coating on the surface, the coating comprising at least 90 weight percent erbium aluminum perovskite. Simple Explanation of the Diagram

[0023] [Figure 1] shows the erosion data of the measured ceramic samples, including the erbium aluminum perovskite sample. Implementation

[0024] The following describes compositions containing erbium aluminum oxide in a perovskite crystal structure (or "crystalline phase"), referred to herein as "erbium aluminum perovskite" or ErAP. Methods for preparing compositions containing erbium aluminum perovskite, articles containing erbium aluminum perovskite (e.g., substrates having a coating containing erbium aluminum perovskite), methods for using articles including erbium aluminum perovskite, and sintered bodies containing erbium aluminum perovskite are also described.

[0025] Erbium aluminum oxide can exist in a variety of different crystal forms (or "phases"), including erbium aluminum garnet phase ("ErAG"), erbium aluminum monoclinic phase ("ErAM"), or erbium aluminum perovskite phase ("ErAP").

[0026] The example compositions (e.g., erbium aluminum perovskite powder compositions, erbium aluminum perovskite coatings, or erbium aluminum perovskite sintered bodies) may comprise, consist of, or be substantially composed of polycrystalline erbium aluminum oxide in the perovskite phase, for example, may contain at least 80, 85, 90, 95, 97, 98, 99, or 99.975% by weight of erbium aluminum oxide in perovskite form (“erbium aluminum perovskite”), rather than other crystalline forms of erbium oxide. The example compositions may contain other forms of erbium aluminum oxide, such as erbium aluminum garnet, or related materials (e.g., erbium oxide (Er₂O₃) or aluminum oxide (Al₂O₃)), in smaller amounts, for example, less than 5, 3, 2, or 1% by weight of such other materials. The amount of erbium aluminum perovskite in the compositions can be measured using known techniques and equipment, including inductively coupled plasma mass spectrometry (ICP-MS). Devices for measuring the amount of a substance in a composition include, for example, the Agilent 7900 ICP-MS (model G8403), which is commercially available from Agilent Technologies, Inc. (USA).

[0027] As used herein, an erbium aluminum perovskite composition (e.g., particles, combinations or aggregates of particles (i.e., "powders"), coating, or sintered body that "consists essentially of" erbium aluminum perovskite is a composition containing erbium aluminum perovskite and no more than a small amount of chemically different materials, such as no more than 5, 3, 2, or 1 weight percent of any other material, such as erbium aluminum oxide in the form of garnet, erbium oxide (Er2O3), aluminum oxide (Al2O3), or combinations thereof or other materials.

[0028] In other words, the composition may comprise, consist of, or consist substantially of erbium aluminum oxide having the chemical formula ErAlO3, meaning nominally having a stoichiometric ratio of 1 erbium atom to 1 aluminum atom to 3 oxygen atoms. Example compositions may have these atomic ratios, wherein the stoichiometric values ​​of the individual atoms in the composition fall within approximately equal to that stoichiometric value (e.g., within 1 percent of that stoichiometric value), as will be understood by one of ordinary skill in the fields of chemistry and materials. Such a composition comprising, or consisting primarily of, erbium aluminum perovskite having the chemical formula ErAlO3 may contain erbium, aluminum, and oxygen atoms in a stoichiometric ratio of one erbium atom to one aluminum atom to three oxygen atoms, with individual deviations in the stoichiometric values ​​of each atom not exceeding one percent. The example composition may contain an erbium atom to aluminum atom to oxygen atom ratio of 0.99 to 1.01 erbium atoms to 0.99 to 1.01 aluminum atoms to 2.97 to 3.03 oxygen atoms; or a ratio of 0.999 to 1.001 erbium atoms, 0.999 to 1.001 aluminum atoms, and 2.997 to 3.003 oxygen atoms.

[0029] The amount of erbium aluminum perovskite phase in the composition, expressed as a percentage, can be measured by surface analysis (i.e., by determining the surface area of ​​the erbium aluminum perovskite material, expressed as a percentage). The percentage amount of erbium aluminum perovskite surface area is considered to be the same as the percentage amount of erbium aluminum perovskite by weight in the composition. The amount of erbium aluminum perovskite in or on the surface of the composition can be determined using known methods such as scanning electron microscopy, X-ray diffraction, or atomic force microscopy (AFM).

[0030] Compositions containing erbium aluminum perovskite can be in any useful form. Examples include: "erbium aluminum perovskite particles," that is, an aggregate of erbium aluminum perovskite particles in the form of a "powder composition" (e.g., "erbium aluminum perovskite powder"); coatings on substrates (e.g., "erbium aluminum perovskite coatings"); or solid materials formed by sintering methods (e.g., reactive sintering), such as sintered bodies (e.g., "erbium aluminum perovskite sintered bodies").

[0031] The erbium aluminum perovskite powder composition may comprise, consist of, or substantially consist of erbium aluminum perovskite particles, i.e., particles comprising, consisting of, or substantially consisting of erbium aluminum perovskite. The erbium aluminum perovskite powder composition may be prepared by heating a powder mixture containing alumina particles (e.g., "alumina powder") and erbium oxide particles (e.g., "erbium oxide powder") to form erbium aluminum perovskite powder. Example methods include those referred to as "solid phase synthesis" or "solid state reaction," which may also be referred to as "heat treatment" or "calcination."

[0032] Erbium oxide powder is a powder containing (comprises, consists of, or substantially consists of) erbium oxide particles, wherein each erbium oxide particle contains (comprises, consists of, or substantially consists of) erbium oxide; for example, individual erbium oxide particles may contain at least 95, 98, 99, or 99.9% by weight of erbium oxide based on the total particle weight. Erbium oxide particles substantially composed of erbium oxide contain erbium oxide and particles of no more than 3, 2, 1, or 0.5% by weight of any other material. Erbium oxide powder may contain (comprises, consists of, or substantially consists of) erbium oxide particles and may contain at least 95, 98, 99, or 99.9% by weight of erbium oxide based on the total weight of the erbium oxide powder. Erbium oxide powder substantially composed of erbium oxide contains erbium oxide and powder of no more than 3, 2, 1, or 0.1% by weight of other material.

[0033] Alumina powder is a powder containing (comprises, consists of, or is substantially composed of) alumina particles, wherein each alumina particle contains (comprises, consists of, or is substantially composed of) alumina. For example, individual alumina particles may contain at least 99, 99.9, 99.99, or 99.999% by weight of alumina based on the total particle weight. Alumina particles substantially composed of alumina contain alumina and particles of any other material not exceeding 1, 0.1, 0.01, or 0.001% by weight. Alumina powder may contain (comprises, consists of, or is substantially composed of) alumina particles and may contain at least 99, 99.9, 99.99, or 99.999, or higher% by weight of alumina powder based on the total weight of the alumina powder. Alumina powder substantially composed of alumina contains alumina and particles of other material not exceeding 1, 0.1, 0.01, or 0.001% by weight.

[0034] According to one example, erbium aluminum perovskite powder can be prepared by a solid-state synthesis method. The example solid-state synthesis method includes the following steps: combining erbium oxide powder and alumina powder to form a powder mixture containing (comprises, consists of, or substantially consists of) erbium oxide particles and alumina particles; and heating the powder mixture, but without melting the particles, to allow the alumina and erbium oxide to react and form "erbium aluminum perovskite particles" containing a high weight percentage of erbium aluminum perovskite.

[0035] Powder mixtures can be prepared by combining erbium oxide powder and alumina powder in stoichiometric amounts of aluminum and erbium (meaning the amounts (atoms) of erbium and aluminum are equal or approximately equal). The powder mixture can be processed to adjust the size and size distribution of the powder particles to produce a highly homogeneous (well-mixed) powder mixture containing erbium oxide and alumina particles with particle sizes and distributions that allow for effective heating to react and form erbium-aluminum perovskite particles. Useful powder mixtures may contain erbium oxide and alumina particles with relatively small (fine) particle sizes, wherein the particle sizes and size distributions of the erbium oxide and alumina particles are similar. Heating erbium oxide and alumina particles with similar particle sizes and distributions facilitates the reaction of erbium oxide and alumina at high temperatures to form erbium-aluminum perovskite. In order to effectively react erbium oxide and aluminum oxide in the powder mixture to form a high amount of erbium aluminum perovskite, particles with relatively uniform size are required so that the particles can be closely packed and in high contact during heating.

[0036] Desired particle size and particle size distribution, as well as homogeneous mixtures, of powder mixtures can be achieved through useful mixing and particle size control methods (such as ball milling, particle separation (e.g., by sieving) or both). Powder mixtures can be ball-milled by combining the powder mixture with a liquid (e.g., an organic solvent such as ethanol) to form a slurry, and then wet-milling the slurry with ceramic or metallic media (e.g., alumina). Jet milling can be a useful alternative mixing technique to wet milling.

[0037] After processing the powder mixture to achieve the desired particle size and distribution, it can be further processed by solid-state synthesis (heat treatment or "calcination") to react erbium oxide and aluminum oxide to form erbium aluminum perovskite powder. According to the example method, the powder mixture can be heated under atmospheric pressure and an air atmosphere to form erbium aluminum oxide particles with the perovskite phase as the predominant form. By the example method, the powder mixture can be heated under ambient pressure and in air, and maintained at a temperature below the melting point of the components to effectively form erbium aluminum oxide predominantly in the perovskite phase rather than erbium aluminum garnet. Examples of useful temperatures are in the range of 1400 to 1700 degrees Celsius, for example, in the range of 1450 to 1650 degrees Celsius. Excessively high temperatures tend to form the erbium aluminum garnet phase (ErAG). The powder mixture can be held at this temperature for a period ranging from 2 to 6 hours.

[0038] Another example of an ErAP system is a coating (referred to as an "erbium aluminum perovskite coating" or "ErAP coating") formed on a substrate using a powder system. ErAP coatings can be formed on a substrate using any useful method, such as aerosol coating, plasma spraying, or any other useful coating deposition method, to achieve the desired coating thickness for the desired morphology.

[0039] Aerosol coating utilizes an aerosol containing ErAP particles dispersed in a gas stream, and optionally, the aerosol is heated. The aerosol is typically introduced into a low-pressure vacuum chamber and directed toward the substrate surface at high speeds sufficient to cause the ErAP particles to impact the surface, thus adhering the ErAP particles to the surface. This adsorption can accumulate over successive coating passes to form an ErAP coating. Examples of potential coating techniques include aerosol deposition, thermal spraying, or plasma spraying, as well as similar known particle spraying techniques. Example aerosol coating technologies can produce coatings on substrates with thicknesses ranging from 0.005 to 0.5 mm. Through process optimization, coating densities can exceed 99% of the theoretical density, also defined as less than 1% porosity.

[0040] For use as an inert coating inside a plasma chamber, the ErAP coating should have sufficient thickness to allow it to withstand erosion during its service life (generally referred to as its effective life) before replacement. To this end, aerosol coating methods can be optimized to produce ErAP coatings with a sufficiently useful thickness, greater than coatings prepared by certain deposition coating methods (CVD, ALD, PVD, etc.). In applications where a thicker anti-plasma coating is preferred or required, ErAP coatings can be prepared using aerosol coating methods.

[0041] Coatings can also be formed by deposition methods, such as chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), and other known physical, chemical, or atomic deposition coating methods. According to an example deposition method, an aluminum perovskite source can be dispersed in a vacuum to form a molecular vapor. The vapor can then be deposited onto the substrate surface as an ErAP coating.

[0042] Another example of ErAP composition is a sintered body formed from pre-reacted ErAP powder by sintering, or a sintered body formed from a suitable oxide system by reactive sintering. In reactive sintering, a powder mixture containing (comprises, is composed of, or is substantially composed of) erbium oxide and alumina particles is heated, and optionally pressure is applied to the powder mixture to cause the erbium oxide and alumina in the powder mixture to react and form ErAP, where the particles grow but do not melt, thereby forming a robust, dense, low-porosity erbium aluminum perovskite sintered body. To achieve stable performance in corrosive plasma environments, the ceramic should have high density (theoretical value >99%) and uniform pore and particle size distribution throughout the sintered body. This uniform ceramic body cannot be achieved through melting and cooling like metals because the cooling and crystallization rates of the entire ceramic body are not uniform, especially for larger components. Uneven grain size and porosity distribution can lead to localized damage to ceramic materials, resulting in rapid degradation. This generally leads to particle generation, affecting the quality of products being processed in the plasma chamber system.

[0043] According to the example reactive sintering process, the powder mixture is formed from alumina powder and erbium oxide powder in a ratio of one mole of alumina to one mole of erbium oxide. The alumina powder and erbium oxide powder can have high purity, for example, at least 99% or preferably up to 99.999% by weight of alumina or erbium oxide, respectively. The powder mixture may contain, consist substantially of, or be composed of erbium oxide powder and alumina powder.

[0044] Useful examples of reactive sintering methods include spark plasma sintering and hot pressing sintering. As used herein, the term "spark plasma sintering" ("SPS") refers to a method that binds individual particles of powder together to form a dense (low-porosity) sintered material (also known as a "sintered body") by applying pressure to the particles while simultaneously heating them in a die through an electric current passing through a graphite punch and die assembly. SPS is also known as field-assisted sintering ("FAST") or direct current sintering ("DCS"). The particles are heated to a temperature below their melting point, but high enough to allow the erbium oxide and alumina in the powder mixture to react and form erbium aluminum perovskite, while the individual particles are bonded together by atomic diffusion at the particle surface. Spark plasma sintering uses the heat generated by simultaneously applying uniaxial pressure and an electric current passing through the die to increase the temperature of the particles in the die. Spark plasma sintering differs from hot pressing, which uses an external heat source such as a radiant heating element, a furnace, or a resistance heating element to heat a mold containing powder to be sintered. SPS allows for a higher heating rate than hot pressing; however, when the different methods are operated in a similar manner, the resulting products are substantially similar.

[0045] According to the example of spark plasma sintering, a powder mixture can be placed inside a graphite mold in a controlled oxygen-free atmosphere (such as a vacuum or inert atmosphere). An oxygen-free atmosphere effectively prevents the graphite mold from reacting or burning. Pressure (“sintering pressure”), temperature rise rate (temperature profile), maximum temperature or temperature range (“sintering temperature”), type of current passing through the mold, and the amount of time the powder mixture is held at the sintering temperature (“sintering time”) are all factors in the sintering process. These factors can be controlled to produce erbium oxide sintered bodies primarily containing erbium aluminum perovskite.

[0046] Useful sintering pressures can reach up to approximately 140 MPa. Pressures exceeding 140 MPa generally damage graphite molds. Sintering pressures are typically no greater than 100 MPa, preferably at most 25 or 50 MPa, and more preferably in the range of 10 to 50 MPa.

[0047] Useful sintering temperatures can range up to 1700 degrees Celsius, such as 1400 to 1700 degrees Celsius, or 1450 to 1650 degrees Celsius. Excessively high temperatures may lead to the formation of the erbium aluminum garnet phase. For molds with diameters of 100 mm to 150 mm or smaller, useful sintering times can be up to 180 or 120 minutes, such as up to 90 minutes or up to 60 minutes. Different mold sizes may require different sintering times, especially for very large systems.

[0048] According to the example spark plasma sintering method, erbium aluminum perovskite sintered bodies may primarily contain erbium aluminum oxide in perovskite form, for example, at least 80, 90, 95, 96, 97, 98, or 99% by weight of erbium aluminum perovskite. For corrosion resistance in the plasma chamber, low porosity is required, preferably 1% or less (99% or higher relative density). Pores in the sintered body allow reactive gases or chemicals to enter, increasing the damaged surface and promoting basal etching, thereby generating particles.

[0049] Erbium aluminum perovskite compositions, either as an erbium aluminum perovskite coating or as erbium aluminum perovskite sintered bodies on a substrate, can be used as corrosion-resistant surfaces that resist degradation in the presence of reactive chemicals or plasma. Examples of erbium aluminum perovskite coatings and erbium aluminum perovskite sintered bodies include high erbium aluminum perovskite content, high purity, and relatively high density (including low porosity). These compositions can be particularly used as thermally stable, plasma-resistant internal surfaces within plasma chambers, especially for plasma deposition or plasma etching processes involving the introduction of a halogen-based process gas into the plasma processing chamber while an RF field is applied to the process gas to generate plasma.

[0050] Erbium aluminum oxide coatings and sintered bodies can be formed as inert (chemically resistant) surfaces for internal components of plasma chambers (such as those used in semiconductor manufacturing). Examples of such components include windows (RF windows or covers), nozzles, gas injectors, diffusers (e.g., nozzle diffusers), chamber liners, electronic wafer chucks, panels, spacers, isolator mixing manifolds, wafer supports, electronic wafer chucks, spikes, plasma source adapters, gas inlet adapters, and various rings (such as focusing rings and guard rings), and other components. Erbium aluminum perovskite surfaces can exhibit physical properties useful for these applications, including low RF transmission loss, as required in dielectrics or RF windows.

[0051] For use as an inert surface inside a plasma chamber, erbium aluminum perovskite sintered bodies or coatings can exhibit useful or advantageous inertness in the presence of active chemicals such as plasma, active halogens, or combinations thereof. Examples of erbium aluminum perovskite sintered bodies and coatings show measured erosion (etching) rates lower than those of other ceramics, such as yttrium aluminum garnet (YAG), a ceramic material known to be highly inert to reactive chemicals and plasma. [, , ] [Example] [1 --] [Erosion resistance of ceramic materials] [ ]

[0052] Figure 1 shows the erosion depth of the measured ceramic samples, including: 1.) yttrium aluminum garnet (YAG), 2.) erbium aluminum garnet (ErAG), and 3.) erbium aluminum perovskite (ErAP).

[0053] The corrosion resistance of ceramic samples was tested by exposing them to inductively coupled plasma (ICP). Argon, oxygen (O2), and carbon tetrafluoride (CF4) were used as plasma gases and supplied at rates of 5.0, 0.5, and 1.0 sccm, respectively (sccm - standard cubic centimeters per minute). The ICP power was 600 W, the programmed pressure was 0.01 mbar, the bias voltage was 250 V, and the exposure time was 120 minutes. Prior to plasma exposure, half of each sample was masked with plasma-resistant Kapton tape to induce a distinct etch step at the transition from the etched surface to the protective surface. The height of this etch step was measured using laser scanning microscopy, and the results are shown in Figure 1.

[0054] The compositions of the different ceramic samples are as follows: YAG -- High-purity single-phase yttrium aluminum garnet formed by spark plasma sintering. ErAG – High-purity dual-phase erbium aluminum oxide formed by spark plasma sintering, with the major component (>90%) being garnet and the minor component (<10%) being perovskite. (Results of Rietveld refinement: 93% ErAG and 7% ErAP). ErAP --- High-purity (>95% by weight) single-phase erbium aluminum perovskite formed by spark plasma sintering.

[0055] The data in Figure 1 show that YAG (a ceramic material commonly used as an inert material inside plasma chambers) has better corrosion resistance than ErAG, and high-purity ErAP has improved corrosion resistance compared to YAG. This is a surprising result, because garnet, especially YAG, is considered to be the material with the best corrosion resistance to the harsh environment of plasma chambers. [ ] [Example] [2 --] [Producing Erbium Aluminum Perovskite Sintered Bodies by Spark Plasma Sintering of Erbium Oxide and Aluminum Oxide] [ ]

[0056] By using spark plasma sintering, a powder mixture of erbium oxide powder and aluminum oxide powder with stoichiometry is processed to form a sintered erbium-aluminum perovskite body in the form of a disk with a diameter of 40 mm.

[0057] The powder mixture was formed by mixing 42.1 g of aluminum oxide and 157.9 g of erbium oxide. The powder mixture was ball-milled for 21 hours at 125 rpm in 400 ml of EtOH (ethanol) in the presence of 200 g of alumina grinding media. The ethanol was removed from the slurry by rotary evaporation (also known as rotary evaporation), followed by sieving. The resulting powder mixture was then used in a spark plasma sintering process to produce erbium aluminum perovskite ("ErAP") disks with a diameter of approximately 40 mm. Spark plasma sintering was performed under a vacuum of 25 MPa in a graphite mold lined with graphite foil, as follows:

[0058] Sample (i). The temperature of the powder mixture was increased from room temperature to 1600°C at a heating rate of 50°C per minute; then the temperature of the powder mixture was maintained at 1600°C for five minutes. The resulting disk-shaped sintered body was assessed as possibly not achieving complete densification (a failed example).

[0059] Sample (ii). The temperature of the powder mixture was increased from room temperature to 1625°C at a heating rate of 10°C per minute; then the temperature of the powder mixture was maintained at 1625°C for five minutes. The resulting disc-shaped sintered body was evaluated as successfully sintered.

[0060] Although XRD (X-ray diffraction) analysis was not performed, based on the softness of the sintered body obtained during the removal of the adhered graphite foil, it is estimated that the sintered body is at least 90% ErAP, and more likely about 95% ErAP. In contrast, ErAG is a harder phase, and the adhered graphite foil can be removed by sandblasting without damaging the sintered body. In this example, sandblasting produced many pits on the surface of the sintered body, indicating that the ErAP phase is softer.

[0061] Sample (iii). The temperature of the powder mixture was increased from room temperature to 1000°C at a heating rate of 25°C per minute, and then increased from 1000°C to 1450°C at a heating rate of 10°C per minute; the temperature of the powder mixture was then maintained at 1450°C for 30 minutes. The resulting disc-shaped sintered body was evaluated as successfully sintered. These parameters were used to press the ErAP sample shown in Figure 1. According to XRD analysis, the sintered body consisted of 99% by weight ErAP and 1% by weight Er₂O₃. [ ] [Example] [3]

[0062] A mixture of aluminum oxide powder and erbium oxide powder with equistoichiometric amounts of erbium oxide and aluminum oxide is processed by a solid-state synthesis method, using a heating (i.e. calcination) step, to form erbium aluminum perovskite powder ("ErAP powder") through the reaction of erbium oxide and aluminum oxide.

[0063] In the first procedure, a mixture of 157.9 g of Er₂O₃ powder and 42.1 g of aluminum oxide powder was ground together with 200 g of Al₂O₃ medium in 400 ml of EtOH at 125 rpm for 22 hours. After rotary evaporation and sieving, the ground powder mixture was calcined in air at a rate of 3° / min to 1500°C, and then held at 1500°C for four hours. According to XRD analysis, this produced powders containing 54 wt% ErAP (ErAlO₃), 25 wt% ErAG (Er₃Al₅O₁₂), and 20 wt% Er₂O₃. This first procedure is not in accordance with the present invention.

[0064] In the second process for producing ErAP powder, a mixture of 157.9 g of Er₂O₃ and 42.1 g of aluminum oxide was ground together with 200 g of Al₂O₃ medium in 400 ml of EtOH at a speed of 125 rpm for approximately 144 hours. After rotary evaporation, the mixture was calcined in air at a rate of 3° / min to 1500°C and held at 1500°C for four hours. XRD analysis showed that ErAP accounted for 89.3% by weight, ErAG for 3.7% by weight, and erbium oxide for 7% by weight. This second process is not in accordance with the present invention.

[0065] In the third process of producing ErAP powder, 355.3 g of Er₂O₃ powder was combined with 94.7 g of alumina powder and worn-milled for 2 hours in 400 ml EtOH with 1446.6 g of 3 mm alumina grinding media. After rotary evaporation and sieving, the milled powder mixture was calcined to 1500 °C at a rate of 1 °C / min and held at 1500 °C for 4 hours. XRD analysis showed that the phase purity of ErAP was 95.9 wt%, ErAG was 3.6 wt%, and erbium trioxide was 0.5 wt%. The overall purity of the calcined powder mixture was also analyzed using ICP-MS. The calcined powder mixture was analyzed using an Agilent 7900 ICP-MS (model G8403) commercially available from Agilent Technologies, Inc. (USA). According to ICP-MS analysis, the total purity of the powder was 99.975%. That is, the amount of impurities in the composition is 0.025% or 250 ppm by weight. The third procedure is according to the present invention.

[0066] Regarding the first to third procedures described above, the following points must be noted: The difference between the third procedure and other procedures for achieving high phase purity lies in the mixing and grinding steps. In the first procedure, mixing lasted 22 hours, resulting in low phase purity of only 54 wt% ErAP. In the second procedure, mixing lasted 144 hours, increasing the phase purity to 89.3 wt% ErAP. However, 144 hours is a long mixing time. Therefore, in the third procedure, abrasive grinding was used, which imparts more energy and requires only 2 hours of grinding to achieve a phase purity of 99.975 wt%.

[0067] The first and second procedures used end-to-end barrel tumbling, while the third procedure used abrasive grinding. Thorough mixing is required to achieve high phase purity and ensure all erbium oxide reacts with aluminum oxide. In this embodiment, either prolonged barrel tumbling or abrasive grinding can be used to achieve the same result in a shorter time during the mixing step. As an alternative to abrasive grinding, other high-energy methods known in the art, such as high-shear mixing, high-energy ball milling, planetary ball milling, or ultrasonic dispersion, can be employed to achieve thorough mixing and reduce the time required for the mixing step, for example, high-shear mixing, high-energy ball milling, planetary ball milling, or dispersion.

[0068] The foregoing description is presented for purposes of illustration and description. It is not intended to be exhaustive or limited to the precise forms or examples disclosed. Modifications and variations are possible given the foregoing teachings and may be obtained through experimentation. The embodiments and examples were chosen and described to explain the principles and practical applications of the various embodiments and to make various modifications to suit a particular purpose. It is intended that the scope of the invention be defined by the appended claims and their equivalents.

[0069] none

Claims

1. An erbium aluminum oxide composition comprising erbium aluminum perovskite with a phase purity of at least 90% by weight, wherein the erbium aluminum oxide composition contains no more than 250 ppm of impurities.

2. The erbium aluminum oxide composition of claim 1 is in the form of a sintered body.

3. The erbium aluminum oxide composition of claim 2, wherein the porosity of the sintered body is in the range of 0.01 to 10 percent.

4. The erbium aluminum oxide composition of claim 1 is in powder form, the powder comprising particles comprising at least 90% by weight of erbium aluminum perovskite.

5. The erbium aluminum oxide composition of claim 1 is in the form of a coating.

6. The erbium aluminum oxide composition of claim 1 has a greater tolerance to plasma etching than yttrium aluminum garnet.

7. A plasma chamber comprising an interior and an erbium-aluminum oxide composition as claimed in claim 6, which serves as a plasma-facing surface within the interior.

8. A method for preparing an erbium aluminum oxide composition comprising at least 90% by weight of erbium aluminum perovskite, the method comprising: preparing a powder mixture comprising erbium oxide particles and aluminum oxide particles, and heating the powder mixture without melting the erbium oxide particles and aluminum oxide particles, so that the erbium oxide and aluminum oxide in the powder mixture react to form erbium aluminum perovskite.

9. The method of claim 8, wherein the powder mixture is prepared by abrasive grinding of the powder mixture for at least 2 hours.

10. The method of claim 9, comprising heating the powder mixture at or below atmospheric pressure to form a powder containing particles comprising erbium aluminum perovskite with a phase purity of at least 90% by weight.

11. The method of claim 9, comprising: placing the powder mixture inside a mold, removing gaseous oxygen from inside the mold, applying unidirectional pressure to the powder mixture in the mold, and increasing the temperature of the powder mixture to cause the erbium oxide and alumina in the powder mixture to react to form erbium aluminum perovskite, and fusing the erbium oxide particles and alumina particles together without melting to form a sintered body comprising at least 90% by weight of erbium aluminum perovskite.

12. The method of claim 11, wherein the pressure does not exceed 50 MPa and the temperature does not exceed 1700 degrees Celsius.

13. A method for forming a coating on a substrate surface, the coating comprising at least 90 weight percent of erbium aluminum perovskite, the method comprising: providing a powder comprising particles comprising erbium aluminum perovskite with a phase purity of at least 90 weight percent; forming an aerosol containing the particles; and, under vacuum conditions, directing the aerosol to a substrate surface such that the particles contact the surface and remain as a coating on the surface, the coating comprising at least 90 weight percent of erbium aluminum perovskite.

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