Powder for coating etching chambers

Abstract

A powder of particles, more than 95% by number of the particles having a circularity of 0.85 or greater, the powder comprising, as a percentage by mass based on the oxides, more than 99.8% of a rare earth metal oxide and / or hafnium oxide and / or aluminum oxide; The powder is Median particle size D is less than 15 μm 50 , the 90th percentile particle size D is less than 30 μm 90 , and a size dispersion index (D 90 -D 10 ) / D 10 , and Relative density above 90% The powder having the formula: [Selection diagram] None

Description

[Technical Field]

[0001] The present invention relates to powders suitable for plasma deposition, to a method for producing such powders, and to coatings obtained by plasma spraying of said powders, more particularly for use in semiconductor etching chamber coatings. [Background technology]

[0002] The interior surfaces of chambers used to process semiconductors, such as silicon wafers (e.g., by plasma etching), are conventionally protected with ceramic coatings applied by plasma spraying. This coating must be highly resistant to halogen-containing plasmas or highly corrosive environments. Plasma spraying requires a feed powder that exhibits high flowability and a particle morphology that allows adequate heating during spraying. More specifically, the particle size must be sufficient to allow the particles to penetrate the plasma and limit evaporation losses.

[0003] For example, very fine powders obtained directly from pyrolytic or chemical manufacturing processes are not suitable for plasma spraying without the additional step of densification to form larger (and porous) agglomerates, more specifically, sintered agglomerates. Because plasma spraying does not result in melting of all the agglomerates, the resulting coatings exhibit porosity. The total porosity of coatings obtained by spraying sintered agglomerates is typically 2-3%, making them unsuitable for protecting the interior surfaces of semiconductor etching chambers. More specifically, the sintered powders described in U.S. Pat. No. 6,916,534, U.S. Patent Application Publication No. 2007 / 077363, or U.S. Patent Application Publication No. 2008 / 0112873 cannot achieve very dense coatings by thermal spraying. Furthermore, coatings obtained from porous agglomerates result in particle shedding over time when exposed to corrosive environments.

[0004] U.S. Patent No. 7,931,836 or U.S. Patent Application Publication No. 2011 / 0129399 disclose particle powders resulting from plasma melting to form liquid droplets that solidify upon free fall. In some embodiments, more than 90% of the particles of the starting material can be fully or partially converted to a liquid form. The resulting powders have bulk densities of 1.2-2.2 g / cm. 3 is.

[0005] In the above cited application, powders obtained by grinding a molten mass are also unsuitable because impurities are added during the grinding process.

[0006] Rare earth metal oxides, hafnium oxide, and / or yttrium-aluminum oxide are known to exhibit uniquely high resistance to chemical attack. However, they have high melting temperatures and low thermal diffusivities. Therefore, it is difficult to obtain very dense coatings from these particles by plasma spraying.

[0007] In order to solve these problems, WO 2014 / 083544 describes a powder of particles in which more than 95% by number of the particles exhibit a circularity of 0.85 or more, the powder comprising more than 99.8% by mass, based on the oxides, of rare earth metal oxides, and / or hafnium oxide, and / or aluminum oxide, Median particle size D between 10 and 40 microns 50 , and less than 3, D 50 The size dispersion index (D 90 -D 10 ) / D 50 , a number percentage of particles having a size of 5 μm or less that is less than 5%, and Bulk density dispersion index (P) less than 0.2 <50 -P) / P and provided that the cumulative specific volume of pores having a radius of less than 1 μm is less than 10% of the bulk volume of the powder; Percentile D of the powdern is the particle size corresponding to the number percent, n%, based on the cumulative distribution curve of particle sizes in the powder, the particle sizes being sorted in ascending order; Density P <50 is D 50 is the bulk density of the fraction of particles having the following size, and density P is the bulk density of the powder: A powder of particles is described.

[0008] This powder can be efficiently sprayed with plasma with high productivity and produces very pure and very dense coatings.

[0009] Nevertheless, a need remains for semiconductor etch chamber coatings that exhibit improved erosion resistance and reduced defect counts.

[0010] It is an object of the present invention to meet this need while retaining the advantages of the powder of WO 2014 / 083544. Summary of the Invention

[0011] To this end, the present invention provides a powder (hereinafter "feed powder") of fused particles (hereinafter "feed particles"), wherein more than 95% by number of said particles exhibit a circularity of 0.85 or greater, said powder comprising, as a percentage by mass based on the oxides, more than 99.8% of a rare earth metal oxide, for example Yb2O3 or YO3 and / or hafnium oxide and / or aluminum oxide, Median particle size D is less than 15 μm 50 , the 90th percentile particle size D is less than 30 μm 90 , and the 10th percentile particle size D is less than 2 10 The size dispersion index (D 90 -D 10 ) / D 10 , and Relative density greater than 90%, preferably greater than 95% wherein the cumulative specific volume of pores having a radius of less than 1 μm is preferably less than 10% of the bulk volume of the powder.

[0012] The feed powder according to the invention is therefore a very pure powder consisting mostly of spherical particles. 10 It is notable for its very low particle size distribution, the small number of particles having a size greater than 30 μm, and its very high relative density.

[0013] This latter characteristic implies that the amount of hollow particles is very low, or even virtually zero. The particle size distribution ensures that the melting during the spraying period is very uniform.

[0014] Finally, the feed powder according to the invention exhibits high flowability, thus allowing coatings to be produced without complex feed devices.

[0015] In the present invention, the term "oxide" may include simple oxides as well as more complex oxides, such as oxyfluorides, examples of which are yttrium oxyfluoride or ytterbium oxyfluoride.

[0016] Feed powders according to the present invention may also include one or more of the following optional features: More than 95% by number, preferably more than 99%, preferably more than 99.5%, of the particles have a circularity of 0.87 or greater, preferably 0.90 or greater; the powder comprises more than 99.9%, more than 99.950%, more than 99.990%, preferably more than 99.999%, of rare earth metal oxides and / or hafnium oxide and / or aluminum oxide, more particularly YAG; therefore, the amount of other oxides is too low to have a significant effect on the results obtained with the feed powder according to the invention, the oxide comprises more than 98%, more than 99%, more than 99.5%, more than 99.9%, more than 99.95%, more than 99.985%, or more than 99.99% of the mass of the powder; the rare earth metal is selected from the group consisting of scandium (Sc), yttrium (Y), lanthanum (La), and the lanthanides; Preferably, the rare earth metal is selected from yttrium (Y), cerium (Ce), neodymium (Nd), samarium (Sm), dysprosium (Dy), gadolinium (Gd), erbium (Er), ytterbium (Yb), and lutetium (Lu), and preferably, the rare earth metal is yttrium. The aluminum oxide is an yttrium-aluminum oxide composite, preferably YAG (yttrium-aluminum garnet YAlO 12 , containing approximately 58% by weight of yttrium oxide), and / or YAP (yttrium-aluminum perovskite, containing approximately 68.9% by weight of yttrium oxide); The percentage by number of particles having a size of 5 μm or less is greater than 5%, preferably greater than 10%; The number percentage of particles having a size of 0.5 μm or more is greater than 10%; The median particle size (D 50 ) is greater than 0.5 μm, preferably greater than 1 μm or even greater than 2 μm, and / or less than 13 μm, preferably less than 12 μm, preferably less than 10 μm or less than 8 μm; 10th percentile particle size (D 10 ) is greater than 0.1 μm, preferably greater than 0.5 μm, preferably greater than 1 μm, or greater than 2 μm; 90th percentile particle size (D 90 ) is less than 25 μm, preferably less than 20 μm, preferably less than 15 μm; 99.5th percentile particle size (D 99.5 ) is less than 40 μm, preferably less than 30 μm; Size dispersion index (D 90 -D 10 ) / D10 is preferably less than 1.5, which advantageously results in excellent coating density. Preferably, the powder exhibits a monomodal particle size distribution, in other words a single main peak. The powder is more than 99.8% by mass percent based on the oxides of Yb2O3 and / or Y2O3 and / or Y3Al5O 12 and / or yttrium oxyfluoride, preferably of formula Y a O b F c wherein a is equal to 1, b is between 0.7 and 1.1, and c is between 1 and 1.5, preferably comprising an oxyfluoride selected from YOF and Y5O4F7, or a mixture of these oxyfluorides, The cumulative specific volume of pores with a radius of less than 1 μm is less than 8%, preferably less than 6%, preferably less than 5%, preferably less than 4%, preferably less than 3.5% of the bulk volume of the powder; The specific surface area of ​​the feed powder is preferably 0.4 m 2 / g, preferably less than 0.3m 2 / g or less.

[0017] The present invention also relates to a method for producing a feed powder according to the invention, comprising the following successive steps: a) Granulating the particle feed to a median size D' of 20 to 60 microns 50 wherein the particle feed comprises more than 99.8% by mass percent based on the oxides of rare earth metal oxides, and / or hafnium oxide, and / or aluminum oxide; b) injecting said granule powder through at least one injection orifice via a carrier gas into a plasma jet generated by a plasma gun under conditions such that more than 50% by number, preferably more than 60% by number, preferably more than 70% by number, preferably more than 80% by number, preferably more than 90% by number of the injected granules burst before melting, and then melting the granules and granule fragments to obtain droplets; c) cooling said droplets to obtain a feed powder according to the invention; d) Optionally, performing particle size selection on the feed powder, preferably by sieving or by pneumatic classification.

[0018] In step b), the injection conditions differ from those described on page 14 of WO 2014 / 083544, which recommends a gentle injection to limit the risk of bursting.

[0019] The intense injection of the powder has the advantageous effect of simultaneously reducing the median size of the feed powder and the proportion of hollow particles, thus making it possible to obtain very high relative densities.

[0020] Preferably, the plasma gun has a power of more than 40 kW, preferably more than 50 kW, and / or less than 65 kW, preferably less than 60 kW.

[0021] Preferably, the plasma gun has a power of 40 to 65 kW and the ratio of the mass of granules injected through the injection openings, preferably by each injection opening, to the surface area of ​​said injection opening is less than 1 mm2 of the surface area of ​​said injection opening. 2 per minute, preferably greater than 10 g / min, preferably greater than 15 g / min, preferably greater than 16 g / min, preferably 17 g / min or greater.

[0022] The injection opening, preferably each injection opening, preferably comprises a channel having a length greater than 1, preferably greater than 2 or even 3 times the equivalent diameter of the injection opening.

[0023] Preferably, the flow rate of the injected granular powder is less than 2.4 g / min, preferably less than 2.0 g / min per kW of power of the plasma gun.

[0024] Between steps a) and b) there is no intermediate sintering step, and preferably no densification. This absence of an intermediate densification step has the advantageous effect of improving the purity of the feed powder, which also facilitates bursting of the granules in step b).

[0025] The method for producing a powder according to the invention may also include one or more of the following optional features: In step a), the granulation is preferably a process of atomization or spray drying or pelletization (conversion into pellets), In step a), the mineral composition of the granular powder comprises, in mass percent based on the oxides, more than 99.9%, more than 99.95%, more than 99.99%, preferably more than 99.999%, of oxides of rare earth metals and / or hafnium oxide and / or aluminum oxide, The median circularity C of the granular powder 50 is preferably greater than 0.85, preferably greater than 0.90, preferably greater than 0.95, more preferably greater than 0.96; The 5th percentile C5 of the circularity of the granular powder is preferably 0.85 or more, preferably 0.90 or more. The median aspect ratio A of the granular powder 50 is preferably greater than 0.75, preferably greater than 0.8, The specific surface area of ​​the granular powder is preferably 15 m 2 / g, preferably less than 10m 2 / g, preferably less than 8m 2 / g, preferably less than 7m 2 / g or less, The cumulative volume of the pores of the granular powder having a radius of less than 1 μm, as measured by mercury porosimetry, is preferably less than 0.5 cm 3 / g, preferably less than 0.4 cm 3 / g or preferably less than 0.3 cm 3 / g or less, The bulk density of the granular powder is preferably 0.5 g / cm 3 and preferably 0.7 g / cm3 and preferably 0.90 g / cm 3 and preferably 0.95 g / cm 3 and preferably 1.5 g / cm 3 less than 1.3 g / cm 3 less than 1.1 g / cm 3 Less than, is, The 10th percentile particle size (D') of the granular powder 10 ) is preferably greater than 10 μm, preferably greater than 15 μm, preferably greater than 20 μm; The 90th percentile particle size (D') of the granular powder 90 ) is preferably less than 90 μm, preferably less than 80 μm, preferably less than 70 μm, preferably less than 65 μm; The granular powder preferably has a median size D' of 20 to 60 microns. 50 having The granular powder preferably has a percentile D' of 20 to 25 μm. 10 and D' of 60-65 μm. 90 having The 99.5th percentile particle size (D' 99.5 ) is preferably less than 100 μm, preferably less than 80 μm, preferably less than 75 μm; D' of the granular powder 50 The size dispersion index (D' 90 -D' 10 ) / D' 50 is preferably less than 2, preferably less than 1.5, preferably less than 1.2, more preferably less than 1.1; In step b), the diameter of each injection opening is less than 2 mm, preferably less than 1.8 mm, preferably less than 1.7 mm, preferably less than 1.6 mm; In step b), the injection conditions are equivalent to those of a plasma gun having a power of 40 to 65 kW and generating a plasma jet, in which case the mass of granules injected through the injection opening, preferably through each injection opening (within the surface area of ​​said injection opening per mm ) is 1000 MPa. 2 (expressed as g / min per mm)2 More than 10 g / min per mm, preferably 1 mm 2 and "equivalent" means "configured so that the granule burst ratio (number of burst granules relative to the number of injected granules) is the same." the injection opening, preferably each injection opening, defines an injection channel, preferably cylindrical, preferably circular in cross section, having a length at least one time, preferably at least two times or three times greater than the equivalent diameter of said injection opening, said equivalent diameter being the diameter of a disk having the same surface area as said injection opening; In step b), the flow rate of the granular powder is less than 3 g / min, preferably less than 2 g / min, per kW of power of the plasma gun; the carrier gas flow rate (per injection opening (i.e., per "powder line")) is greater than 5.5 L / min, preferably greater than 5.8 L / min, preferably greater than 6.0 L / min, preferably greater than 6.5 L / min, preferably greater than 6.8 L / min, preferably greater than 7.0 L / min; the granular powder is injected into the plasma jet at a feed rate per injection orifice of more than 20 g / min, preferably more than 25 g / min, and / or less than 60 g / min, preferably less than 50 g / min, preferably less than 40 g / min, the total feed rate of granules (cumulative for all injection openings) is greater than 70 g / min, preferably greater than 80 g / min, and / or preferably less than 180 g / min, preferably less than 140 g / min, preferably less than 120 g / min, preferably less than 100 g / min; and Preferably, in step c), the molten droplets are cooled to a maximum of 500° C., with an average cooling rate of 50,000 to 200,000° C. / s, preferably 80,000 to 150,000° C. / s.

[0026] Likewise, the invention relates to a thermal spraying process comprising the step of plasma spraying a feed powder according to the invention onto a substrate to obtain a coating.

[0027] The present invention also relates to a body comprising a substrate and a coating at least partially covering the substrate, said coating comprising more than 99.8% by mass, based on the oxides, of a rare earth metal oxide and / or hafnium oxide and / or aluminum oxide, and exhibiting a porosity of 1.5% or less, said porosity being measured on a photograph of a polished cross-section of said coating, as described below. Preferably, the porosity of the coating is less than 1%.

[0028] Preferably, the coating comprises more than 99.9%, more than 99.95%, more than 99.97%, more than 99.98%, more than 99.99%, preferably more than 99.999%, by mass percent based on the oxide, of rare earth metal oxide and / or hafnium oxide and / or aluminum oxide.

[0029] This type of coating can be produced using a thermal spray process according to the present invention.

[0030] The substrate may be the wall of an oven used in semiconductor processing, more particularly the wall of a plasma etching chamber.

[0031] The oven may accommodate semiconductors, more particularly silicon wafers. The oven may comprise a chemical vapor deposition (CVD) tool or a physical vapor deposition (PVD) tool.

[0032] definition "Impurities" are unavoidable components that are unintentionally and necessarily introduced with the starting materials or that result from reactions between components. The impurities are not required components, but only tolerated components. The level of purity is preferably measured by GDMS (Glow Discharge Mass Spectrometry), which is more accurate than ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry).

[0033] The "roundness" of a powder particle is typically determined as follows: The powder is dispersed on a flat glass plate. Images of individual particles are obtained by scanning the dispersed powder under an optical microscope, keeping the particles in focus and shining a light on the powder from the underside of the glass. These images can be analyzed using a Morphologi® G3 instrument sold by Malvern.

[0034] As shown in Figure 4, to evaluate the "roundness" C of particle P', the area A of particle P' is calculated on the image of this particle. p The perimeter P of a disk D having an area equal to D The perimeter of this particle, P p The roundness is determined by the ratio P D / P p is equal to.

[0035]

number

[0036] To determine the percentile of circularity (described below), the powder is poured onto a flat glass and observed as described above. The particle count should be greater than 250 so that the measured percentile is substantially the same no matter how the powder is poured onto the glass.

[0037] The aspect ratio A of a particle is defined as the ratio of the particle's width (its largest dimension perpendicular to the length of the particle) to the particle's length (its largest dimension).

[0038] To determine the aspect ratio percentile, the powder is poured onto a flat glass and observed as described above to measure the length and width of the particles. The particle count should be above 250 so that it is substantially the same regardless of how the powder is poured onto the glass.

[0039] For particles of a powder, the percentile or "centile" of the characteristic M is 10(M 10 ), 50(M 50 ), 90(M 90 ), and 99.5(M 99.5 ), more generally "n"M n are the numerical values ​​of this property for 10%, 50%, 90%, 99.5%, and n% of the number percentiles based on the cumulative frequency distribution curve relating to this property of the particles in the powder, respectively, and the numerical values ​​relating to this property are sorted in ascending order. More specifically, percentile D n (or D' in the case of granular powder) n ), A n , and C n are related to size, aspect ratio, and circularity, respectively.

[0040] For example, 10% by number of particles in the powder are D 10 and 90% by number of the particles have a size less than D 10 The size-related percentiles can be determined from particle size distributions produced by a laser particle size analyzer.

[0041] Similarly, 5% by number of the particles in the powder have a circularity below the C5 percentile, in other words, 95% by number of the particles in the powder have a circularity of C5 or greater.

[0042] The 50th percentile is conventionally called the "median" percentile. For example, C 50 is commonly known as the "median circularity". Similarly, D 50 A percentile is colloquially known as a "median size." 50Percentile also commonly means "median aspect ratio."

[0043] "Particle size" refers to the size of a given particle according to conventional characterization of particle size distribution, which characterization is performed using a laser particle size analyzer. The laser particle size analyzer used may be a HORIBA Partica LA-950.

[0044] The number percentage or number fraction of particles having a size less than or equal to the determined maximum size can be determined by a laser particle size analyzer.

[0045] cm per 1g of powder 3 The cumulative specific volume of pores with a radius of less than 1 μm, expressed as ρ / μm, is typically measured by mercury porosimetry according to standard ISO 15901-1. The cumulative specific volume can be measured using a powder engineering porosimeter.

[0046] cm 3 The bulk volume of a powder, expressed as / g, is the reciprocal of the bulk density of the powder.

[0047] The "bulk density" P of a particle powder is typically defined as the ratio of the mass of the powder divided by the sum of the bulk volumes of the particles. In practice, P can be measured using a Micromeritics porosimeter at a pressure of 200 MPa.

[0048] The "relative density" of a powder is equal to its bulk density divided by its true density, which can be measured by Helium Pycnometry.

[0049] The "porosity" of a coating can be evaluated by analyzing the image of a polished cross section of the coating. The coated substrate is sectioned using a laboratory cutter, for example, a Struers Discotom device with an alumina-based cutting disc. Then, the coating sample is sealed in resin, for example, using a Struers Durocit-type low-temperature sealing resin. Then, the sealed sample is polished using abrasive media with increasing fineness. Abrasive paper, or preferably abrasive disc, is used with a suitable polishing suspension. The conventional polishing procedure begins by dressing the sample (for example, using a Struers Piano 220 abrasive disc), and then changing the polishing cloth with the abrasive suspension. The size of the abrasive grain decreases with each fine polishing step, for example, starting with 9 microns, then 3 microns, and ending with 1 micron (Struers DiaPro series). For each size of abrasive grain, polishing is stopped as soon as the porosity observed under an optical microscope remains constant. The sample is carefully washed between steps, for example with water. The final polishing step is performed with colloidal silica (OP-U Struers, 0.04 μm) combined with a soft felt cloth, followed by a 1 μm diamond polishing step. After cleaning, the polished sample can be immediately observed by optical microscope or SEM (scanning electron microscope). Due to its excellent resolution and outstanding contrast, SEM is preferred for obtaining images intended for analysis. The porosity can be determined from the image by using image analysis software (e.g., ImageJ, NIH) while adjusting the threshold. The porosity is given as a percentage of the surface area of ​​the coating cross section.

[0050] The "specific surface area" is conventionally measured by the BET (Brunauer Emmet Teller) method as described in Journal of the American Chemical Society 60 (1938), 309-316.

[0051] A "granulation" operation is a process for agglomerating particles with a binder, such as a binder polymer, to form agglomerated particles, which may possibly be granules. Granulation more particularly includes, but is not limited to, spray or spray drying and / or the use of granulators or pelletizers. Typically, the binder is substantially free of oxides.

[0052] "Granules" are agglomerated particles having a circularity of 0.8 or greater.

[0053] The densification process is an operation intended to replace the organic binder bonds with diffusion bonds within the granules, and is generally carried out by heat treatment, but without completely melting the granules.

[0054] The "deposition yield" of a plasma spray process is defined as the ratio of the amount of material deposited on the substrate divided by the amount of feed powder injected into the plasma jet, expressed as a mass percent.

[0055] "Thermal spray productivity" is defined as the amount of material deposited per unit time.

[0056] Flow rates expressed in L / min are "standard", meaning that the flow rates are measured at a pressure of 1 bar and a temperature of 20°C.

[0057] "Including" is to be understood as open ended unless expressly stated otherwise.

[0058] Unless otherwise specified, all composition percentages are weight percents based on the weight of the oxide.

[0059] The properties of the powder can be evaluated by the characterization methods used in the examples.

[0060] Other features and advantages of the present invention will become more apparent upon reading the following description and examining the accompanying drawings. [Brief explanation of the drawings]

[0061] [Figure 1] FIG. 1 is a diagrammatic representation of step a) of the method according to the invention. [Figure 2] FIG. 2 is a schematic representation of a plasma torch for producing a feed powder according to the present invention. [Figure 3] FIG. 3 is a schematic representation of a method for producing a feed powder according to the present invention. [Figure 4] FIG. 4 is a diagram illustrating the technique used to assess particle circularity. DETAILED DESCRIPTION OF THE INVENTION

[0062] Method for producing feed powder FIG. 1 illustrates one embodiment of step a) of the method for producing a feed powder according to the present invention.

[0063] Any known granulation process can be used. More particularly, a person skilled in the art knows how to prepare a slip suitable for granulation.

[0064] In one embodiment, a binder mixture is prepared by adding PVA (polyvinyl alcohol) 2 to deionized water 4. This binder mixture 6 is then filtered through a 5 μm filter 8. A particle feed consisting of powdered yttrium oxide 10 (e.g., having a purity of 99.99%) having a median size of 1 μm is mixed with the filtered binder mixture to form a slip 12. The slip may contain, by weight, for example, 55% yttrium oxide and 0.55% PVA, with the remainder to 100% being water. The slip is injected into an atomizer 14 to obtain a granulated powder 16. Those skilled in the art will know how to adapt the atomizer to obtain the desired particle size distribution.

[0065] The granules are preferably agglomerates of particles made of oxide material exhibiting a median size of preferably less than 3 μm, preferably less than 2 μm, preferably less than 1.5 μm.

[0066] Preferably, to produce a feed powder in which the particles comprise a mixed oxide or oxyfluoride phase, for example an yttrium or ytterbium oxyfluoride, or a YAG or YAP phase, granules are used which preferably already comprise this phase; these are granules formed from particles of yttrium or ytterbium oxyfluoride, YAG or YAP, respectively.

[0067] The granular powder can be sieved (for example, through a 5 mm sieve 18) to remove any possible residue that has fallen off the walls of the atomizer.

[0068] The resulting powder 20 is a "spray dried only (SDO)" granular powder.

[0069] 2 and 3 illustrate one embodiment of the melting step b) of the method for producing a feed powder according to the invention.

[0070] 1 is injected by an injector 21 into a plasma jet 22 generated by a plasma gun 24, for example, of a Proplasma HP plasma torch. Conventional injection and plasma spray devices can be used, for example, to mix the SDO granular powder with a carrier gas and inject the resulting mixture into the center of the hot plasma.

[0071] However, the injected granular powder does not need to be compacted (SDO), and the injection into the plasma jet should be vigorous to promote the breakage of the granules. The intensity of the impact determines the burst strength of the granules and therefore the median size of the powder produced.

[0072] A person skilled in the art knows how to adjust the injection parameters for vigorously injecting the granules so that the feed powder obtained at the end of step c) or d) has a particle size distribution according to the invention.

[0073] More specifically, those skilled in the art will The injection angle θ between the injection axis Y of the granules and the axis X of the plasma jet should be close to 90°. Surface area of ​​injection opening: 1mm 2 increasing the powder flow rate per Decreasing the powder flow rate (g / min) per kW of gun power, and Increasing the flow rate of the plasma-forming gas It is recognized that this is a factor that promotes granule destruction.

[0074] More particularly, WO 2014 / 083544 does not disclose injection parameters that allow for the destruction of more than 50% by number of granules, as described in the examples below.

[0075] It is preferred that the particles be injected rapidly to disperse them in the very viscous plasma jet which flows at very high speeds.

[0076] When injected granules come into contact with the plasma jet, they are subjected to powerful impacts and may break into small pieces. To penetrate the plasma jet, the undensified, more particularly unsintered, granules to be dispersed are injected at a high enough speed to benefit from the high kinetic energy, however, this speed is limited to ensure a highly efficient burst. Without densification of the granules, their mechanical strength is reduced, and therefore their resistance to such impacts is reduced.

[0077] Those skilled in the art will recognize that the speed of the granules is determined by the flow rate of the carrier gas and the diameter of the injection orifice.

[0078] The speed of the plasma jet is also high. The flow rate of the plasma-forming gas is preferably above the median value recommended by the torch constructor for the selected anode diameter. Preferably, the flow rate of the plasma-forming gas is above 50 L / min, preferably above 55 L / min.

[0079] Those skilled in the art will recognize that the speed of the plasma jet can be increased by using a smaller diameter anode and / or by increasing the flow rate of the primary gas.

[0080] Preferably, the flow rate of the primary gas is greater than 40 L / min, preferably greater than 45 L / min.

[0081] Preferably, the ratio between the flow rate of the secondary gas, preferably dihydrogen (H2) gas, and the flow rate of the plasma-forming gas (composed of the primary and secondary gases) is 20% to 25%.

[0082] Of course, the energy of the plasma jet, which is particularly influenced by the flow rate of the secondary gas, must be high enough to cause the granules to melt.

[0083] The granular powder is preferably injected using a carrier gas without any liquid.

[0084] Within the plasma jet 22, the granules are melted into droplets 25. The plasma gun is preferably controlled so that melting is substantially complete.

[0085] A beneficial effect of the melting is to reduce the level of impurities.

[0086] Upon exiting the hot zone of the plasma jet, the droplets are rapidly cooled by the surrounding cool air as well as by the forced circulation 26 of a cooling gas, preferably air, which advantageously limits the reducing effect of hydrogen.

[0087] The plasma torch preferably comprises at least one nozzle configured to inject a cooling fluid, preferably air, to heat the granular powder injected into the plasma jet and to cool the resulting droplets. The cooling fluid is preferably injected downstream of the plasma jet (as shown in FIG. 2), and the angle γ between the path of the droplets and the path of the cooling fluid is preferably 80° or less, preferably 60° or less, and / or 10° or more, preferably 20° or more, preferably 30° or more. Preferably, the axis Y of any nozzle injection and the axis X of the plasma jet intersect.

[0088] Preferably, the angle of injection θ between the axis of injection Y and the axis X of the plasma jet is greater than 85°, preferably approximately 90°.

[0089] Preferably, the forced cooling is produced by a series of nozzles 28 arranged around the axis X of the plasma jet 22 to create, for example, a substantially conical or annular flow of cooling gas.

[0090] The plasma gun 24 is arranged perpendicular to the ground. Preferably, the angle α between the perpendicular and the axis X of the plasma jet is less than 30°, less than 20°, less than 10°, preferably less than 5°, preferably substantially zero. Advantageously, therefore, the flow of cooling gas is perfectly centered with respect to the axis X of the plasma jet.

[0091] Preferably, the minimum distance d between the outer surface of the anode and the cooling zone (where the droplets come into contact with the injected cooling fluid) is between 50 mm and 400 mm, preferably between 100 mm and 300 mm.

[0092] Advantageously, the forced cooling limits the generation of secondary particles resulting from contact between very large, hot particles and small particles in suspension within the densifying chamber 32. Furthermore, this type of cooling operation allows for a reduction in the overall size of the processing equipment, and more particularly, the size of the collection chamber.

[0093] Cooling of the droplets 25 makes it possible to obtain feed particles 30 which can be extracted in the lower part of the sintering chamber 32 .

[0094] The sintering chamber may be connected to a cyclone 34, the exhaust gases of which are directed to a dust collector 36 to separate out very fine particles 40. Depending on the configuration, some feed particles according to the invention may also be collected in the cyclone. Preferably, these feed particles can be separated out, more particularly using an air separator.

[0095] Optionally, the collected feed particles 38 have a median size D 50 can be filtered to be less than 15 microns.

[0096] Table 1 below provides preferred parameters for producing a feed powder according to the present invention.

[0097] The properties of the columns are preferably, but not necessarily, combined. The properties of the two columns can also be combined.

[0098] The "ProplasmaHP" plasma torch is sold by Saint-Gobain Coating Solutions and corresponds to the torch T1 described in WO 2010 / 103497.

[0099] [Table 1] [Example]

[0100] The following examples are provided for illustrative purposes and do not limit the scope of the present invention.

[0101] Feed powders H1, I1 (comparative) and C1 (comparative) had a median particle size D of 1.2 microns as measured using a Horiba laser particle analyzer. 50 , and Y2O 3の It was produced from pure Y2O3 powder with a chemical purity of 99.999% using a plasma torch similar to the one shown in Figure 2 of WO 2014 / 083544.

[0102] In step a), a binder mixture is prepared by adding PVA (polyvinyl alcohol) binder 2 (see FIG. 1) to deionized water 4. This binder mixture is then filtered through a 5 μm filter 8. Yttrium oxide powder 10 is mixed with the filtered binder mixture to form a slip 12. The slip is prepared to contain, by weight, 55% yttrium oxide and 0.55% PVA, with the remainder to 100% being deionized water. The slip is thoroughly mixed using a high-shear speed mixer.

[0103] Granules G3 are then obtained by atomization of the slip using an atomizer 14. More specifically, the slip is atomized in the chamber of a GEA Niro SD6.3R atomizer, the slip being introduced at a flow rate of approximately 0.38 l / min.

[0104] The speed of the rotary atomizing wheel, driven by a Niro FS1 motor, is controlled to obtain the target size of granules 16 (G3).

[0105] The air flow rate is adjusted to maintain an inlet temperature of 295°C and an outlet temperature around 125°C so that the residual moisture content of the granules is between 0.5% and 1%.

[0106] The granular powder is then sieved using a sieve 18 to extract residue from the granular powder and obtain an SDO granular powder 20 .

[0107] In step b), the granules from step a) are injected into a plasma jet 22 (see FIG. 2) generated using a plasma gun 24. The injection and melting parameters are given in Table 2 below.

[0108] In step c), seven Silvent 2021L nozzles 28, also sold by Silvent, were fixed onto a Silvent 463 annular nozzle holder, also sold by Silvent, to cool the droplets, the nozzles 28 being regularly spaced along the annular nozzle holder to generate a substantially conical air flow.

[0109] The yield of collected feed particles 38 is the ratio of the amount of collected feed particles to the total amount of granules injected into the plasma jet.

[0110] [Table 2-1]

[0111] [Table 2-2]

[0112] The cumulative specific volume of pores having a radius of less than 1 μm in the granule is 260×10 -3 cm 3 / g.

[0113] Thus, the present invention provides a feed powder with a size distribution and relative density that results in a very dense coating, which can be efficiently sprayed by plasma with high productivity.

[0114] Thus, the feed powder according to the present invention allows for the production of coatings with fewer defect concentrations. Furthermore, the powder exhibits enhanced flowability relative to powders of the same size that have not been plasma fused, thus allowing for pouring without complex feed means.

[0115] Of course, the present invention is not limited to the embodiments described and shown.

Claims

1. A powder of fused particles, more than 95% by number of the particles having a circularity of 0.85 or greater, the powder comprising, as a percentage by mass based on the oxides, more than 99.8% of a rare earth metal oxide and / or hafnium oxide and / or aluminum oxide; The powder is A median particle size D of less than 15 μm ５０ , the 90th percentile particle size D being less than 30 μm ９０ , and a size dispersion index (D ９０ -D １０ ) / D １０ , and Relative density above 90% and the powder has a percentile D ｎ is the particle size corresponding to the number percent, n%, in the cumulative distribution curve of particle sizes in the powder, the particle sizes being sorted in ascending order.

2. a number percentage of particles having a size of 5 μm or less that is greater than 5%, and / or A median particle size (D) of less than 10 μm ５０ ), and / or The 90th percentile particle size (D) is less than 25 μm. ９０ ), and / or The 99.5th percentile particle size (D) is less than 40 μm. ９９．５ ), and / or A size dispersion index (D) of less than 1.5 ９０ -D １０ ) / D １０ 2. The powder of claim 1, having

3. The median particle size of the powder (D ５０ 3. The powder of claim 1, wherein the particle size is less than 8 μm.

4. More than 99.8% Yb as a mass percent based on the oxide ２ O ３ and / or Y ２ O ３ and / or Y ３ Al ５ O １２ and / or formula Y ａ O ｂ F ｃ 4. The powder of claim 1, comprising yttrium oxyfluoride of the formula: wherein a is 1, b is 0.7 to 1.1, and c is 1 to 1.

5.

5. A method for producing the powder according to any one of claims 1 to 4, comprising the steps of: a) Granulating the particle feed to a median size D' of 20-60 μm ５０ wherein the particle feed comprises more than 99.8% by mass percent on an oxide basis of rare earth metal oxides and / or hafnium oxide and / or aluminum oxide. b) injecting the granular powder via a carrier gas through at least one injection opening in an injection device into a plasma jet generated by a plasma gun under injection conditions; The injection conditions are: bursting more than 50% by number of the injected granules to obtain molten droplets, The flow rate of the injected granular powder is less than 3 g / min per kW of power of the plasma gun; and The ratio of the mass of granules injected through the injection opening to the area of ​​the injection opening is 1 mm2 or less. ２ the process is more than 10 g / min per minute c) cooling the molten droplets to obtain the powder of any one of claims 1 to 4, and d) Optionally, subjecting said powder to particle size selection.

6. The method of claim 5, wherein the injection conditions are determined to cause more than 70% (by number percent) of the injected granules to burst.

7. The method of claim 6, wherein the injection conditions are determined to cause more than 90% (by number percent) of the injected granules to burst.

8. In step b), the injection conditions include a power of 40-65 kW and a mass of granules injected through each injection opening that is less than 1 mm2 of the area of ​​the injection opening. ２ 8. The method of claim 5, adapted to provide a rate of bursting granules equal to that of a plasma gun generating a plasma jet of more than 15 g / min per granule.

9. The mass of granules injected through each injection opening is equal to the area of ​​said injection opening 1 mm ２ The method of claim 8, wherein the flow rate is greater than 16 g / min.

10. The method according to any one of claims 5 to 9, wherein in step b) the flow rate of the granular powder is less than 2 g / min per kW of plasma gun power.

11. The method of any one of claims 5 to 10, wherein the granulation comprises spraying.

12. A thermal spraying process comprising the step of thermally spraying a powder according to any one of claims 1 to 4 or a powder produced according to any one of claims 5 to 11.

13. The thermal spray process of claim 12, wherein the powder is thermally sprayed onto the walls of a semiconductor processing chamber.

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