EP3746406A1

EP3746406A1 - Powder for coating an etch chamber

Info

Publication number: EP3746406A1
Application number: EP19701561.3A
Authority: EP
Inventors: Alain Allimant; Howard Wallar
Original assignee: Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Current assignee: Saint Gobain Centre de Recherche et dEtudes Europeen SAS
Priority date: 2018-01-31
Filing date: 2019-01-31
Publication date: 2020-12-09
Also published as: KR20240036112A; JP2021513001A; JP2024054107A; US20210115548A1; MX2020007729A; FR3077287A1; FR3077287B1; WO2019149854A1; CN111670164B; KR20200122310A; CN111670164A; SG11202006924QA; US11731883B2

Abstract

Particle powder, a number greater than 95% of the particles having a circularity greater than or equal to 0.85, the powder containing more than 99.8% of a rare earth oxide and/or a hafnium oxide and/or an aluminium oxide, as a percentage by weight on the basis of the oxides, and having: - a median particle size D₅₀ less than 15 μm, a 90th percentile of the particle sizes D₉₀ less than 30 μm, and a size dispersion index (D₉₀ - D₁₀)/D₁₀ less than 2; and - a relative density greater than 90%.

Description

POWDER FOR COATING OF ENGRAVING CHAMBER

Technical area

The invention relates to a plasma-deposited powder, a process for producing such a powder, and a coating obtained by plasma spraying said powder, in particular for a semiconductor etching chamber coating.

State of the art

The internal surfaces of the chambers used to treat (for example by plasma etching) semiconductors, for example silicon wafers, are conventionally protected with a ceramic coating applied by plasma spraying. This coating must be highly resistant to plasmas including halogens or highly corrosive environments. Plasma spraying requires, as a feed powder, a powder having a good fluidity and a particle morphology allowing a suitable heating during the projection. In particular, the size of the particles must be sufficient for the particles to enter the plasma and to limit losses by vaporization.

For example, very fine powders directly obtained by chemical or pyrolytic manufacturing processes are not suitable for plasma spraying without additional consolidation step to form larger (and porous) agglomerates, especially sintered agglomerates. Since plasma spraying does not lead to the melting of all agglomerates, the resulting coating has porosity. The total porosity of the sintered agglomerate coating is typically 2-3%, which would not be suitable for protecting the internal surfaces of a semiconductor etch chamber. In particular, the sintered powders described in US6,916,534, US2007 / 077363 or US2008 / 0112873 can not lead to a very dense coating by thermal spraying. In addition, coatings obtained from porous agglomerates lead, in time, to the release of particles when exposed to corrosive environments.

US 7,931,836 or US 2011/0129399 disclose a particle powder resulting from a plasma fusion to form liquid droplets that solidify in free fall. In some embodiments, more than 90% of the raw material particles may be wholly or partially converted to liquid form. The apparent density of the resulting powder is between 1.2 and 2.2 g / cm ³ . In the application mentioned above, the powders obtained by grinding a melt are not suitable either, because of the impurities that are added during the grinding step.

Rare earth oxides and / or hafnium oxide and / or yttrium aluminum oxides are known to have good intrinsic resistance to chemical attack. However, they have a high melting temperature and a low thermal diffusion. It is therefore difficult to obtain a very dense coating from these particles by plasma spraying.

To solve these problems, WO2014 / 083544 describes a powder of particles, more than 95% by number of said particles having a circularity greater than or equal to 0.85, said powder containing more than 99.8% of a rare earth oxide and and / or hafnium oxide and / or aluminum oxide, in percent by weight based on the oxides, and having:

a median particle size D50 ranging from 10 to 40 microns and a size dispersion index relative to D50 (D90 - D _I0) / D _50, less than 3;

a percentage by number of particles having a size less than or equal to 5 mhi which is less than 5%;

an apparent density dispersion index (P _< so-P) / P of less than 0.2, the cumulative specific volume of the pores having a radius of less than 1 mhi being less than 10% of the apparent volume of the powder,

powder in which the powder percentiles D _n of the powder are the particle sizes corresponding to the percentages, by number, of n%, on the cumulative distribution curve of the particle size of the powder, the particle sizes being ranked in ascending order ,

the density P _< n0 being the apparent density of the fraction of the particles having a size less than or equal to D50, and the density P being the apparent density of the powder.

This powder can be efficiently projected by plasma, with good productivity, and leads to a very pure and extremely dense coating.

There is, however, a continuing need for a coating for a semiconductor etch chamber having increased erosion resistance and having a reduced number of defects.

An object of the invention is to meet this need, while retaining the advantages of the powder of WO2014 / 083544.

Summary of the invention

For this purpose, the invention provides a powder (hereinafter "feed powder") of melted particles (hereinafter "feed particles"), more than 95% by number of said particles having a circularity greater than or equal to 0.85, said powder containing more than 99.8% of a rare earth oxide, for example Yb ₂ 0 ₃ or Y ₂ O ₃ , and / or hafnium oxide and / or an aluminum oxide as a percentage by mass based on the oxides, and having:

a median particle size D50 of less than 15 mHi, a 90 percentile of particle sizes D90 of less than 30 mHi, and a size dispersion index relative to the percentile of particle sizes D10, (D90-Dio) / Dio; less than 2;

a relative density greater than 90%, preferably greater than 95%,

the cumulative specific volume of the pores having a radius of less than 1 mhi being preferably less than 10% of the apparent volume of the powder.

A feed powder according to the invention is therefore a very pure powder, composed largely of spherical particles. This powder is remarkable, in particular, for the very small dispersion of particle size, with respect to D10, the small quantity of particles having a size greater than 30 mHi and a very high relative density.

This last characteristic implies a very small amount of hollow particles, or even substantially zero. The particle size distribution ensures a very homogeneous fusion during the projection.

Finally, a feed powder according to the invention has a high flowability, which allows to manufacture the coating without complex feeding device.

In the present invention, the term oxide may include single oxide but also a more complex oxide such as oxyfluoride, for example yttrium or ytterbium oxyfluoride.

A feed powder according to the invention may also include one or more of the following optional features:

More than 95%, preferably more than 99%, preferably more than 99.5% by number of said particles have a circularity greater than or equal to 0.87, preferably greater than or equal to 0.90;

The powder contains more than 99.9%, more than 99.950%, more than 99.990%, preferably more than 99.999% of a rare earth oxide and / or hafnium oxide and / or Aluminum, in particular YAG; The quantity of the other oxides is so small that it can not have a significant effect on the results obtained with a feed powder according to the invention;

Oxides account for 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 is selected from the group consisting of Scandium (Sc), Yttrium (Y), Lanthanum (La) and lanthanides; Preferably, the rare earth is selected from Yttrium (Y), Cerium (Ce), Neodymium (Nd), Samarium (Sm), Dysprosium (Dy), Gadolinium (Gd), Erbium ( Er), Ytterbium (Yb) and Lutetium (Lu); Preferably, said rare earth is Yttrium; The aluminum oxide is an yttrium-aluminum oxide composite, preferably YAG (Yttrium-Aluminum Gamet Y ₃ Al ₅ O ₁₂ , comprising about 58% by weight of yttrium oxide) and / or YAP (Yttrium aluminum perovskite comprising about 68.9% by weight of yttrium oxide);

The percentage by number of particles having a size of less than or equal to 5 μm is greater than 5%, preferably greater than 10%;

The percentage in number of particles having a size greater than or equal to 0.5 μm is greater than 10%;

The median particle size (D50) of the powder 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, and preferably less than 12 μm. at 10 pm or less than 8 pm;

The percentile (D10) of the particle sizes is greater than 0.1 μm, preferably greater than 0.5 μm, preferably greater than 1 μm, or greater than 2 μm;

The percentile 90 (D90) of the particle sizes is less than 25 μm, preferably less than 20 μm, preferably less than 15 μm;

The 99.5 percentile (D99, s) of the particle sizes is less than 40 μm, preferably less than 30 μm;

The size dispersion index (D9O-DIO) / DIO is preferably less than 1.5; This advantageously results in a higher coating density;

Preferably, the powder has a monomodal particle size dispersion type, i.e., a single main peak;

The powder contains, in percentage by mass on the oxide basis, more than 99.8% of Yb ₂ 0 ₃ and / or Y ₂ O ₃ and / or Y ₃ Al ₅ O ₁₂ and / or an oxyfluoride of yttrium, preferably according to the formula Y _a O _b L _c wherein a is 1, b is between 0.7 and 1.1 and c is between 1 and 1.5, preferably selected from an oxyfluoride YOL and Y ₅ O ₄ L ₇ or a mixture of these oxyfluorides;

The cumulative specific volume of the 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 apparent volume. powder;

The specific surface area of the feed powder is preferably less than 0.4 m ² / g, preferably less than 0.3 m ² / g. The invention also relates to a method for manufacturing a feed powder according to the invention comprising the following successive steps:

a) granulating a particulate filler so as to obtain a granule powder having a median median size of between 20 and 60 micron, the particulate filler comprising more than 99.8% of a rare earth oxide and / or hafnium oxide and / or aluminum oxide, in percent by weight based on the oxides;

b) injecting said granule powder, via a carrier gas, through at least one injection port to a plasma jet generated by a plasma gun, under conditions causing a burst before melting of more than 50% , preferably more than 60%, preferably more than 70%, preferably more than 80%, preferably more than 90% by number of the granules injected, in percentage by number, then a melting of the granules and pieces of granules so to obtain droplets,

c) cooling said droplets, so as to obtain a feed powder according to the invention;

d) optionally, granulometric selection, preferably by sieving or by pneumatic classification, of said feed powder.

In step b), the injection conditions are contrary to those described in WO 2014/083544, which, on page 14, recommends a gentle injection to limit the risk of bursting.

The violent injection of the powder advantageously makes it possible simultaneously to reduce the median size of the feed powder and to reduce the proportion of hollow particles. It thus makes it possible to obtain a very high relative density.

Preferably, the plasma gun has a power greater than 40 kW, preferably greater than 50 kW and / or less than 65 kW, preferably less than 60 kW.

Preferably, the plasma gun has a power of between 40 and 65 KW and the ratio of the mass quantity of granules injected by injection orifice, preferably by each injection orifice, on the surface of said injection orifice is greater than 10, preferably greater than 15, preferably greater than 16, preferably greater than or equal to 17 g / min per mm ² of area of said injection port.

The injection orifice, preferably each injection orifice is preferably constituted by a channel whose length is greater than once, preferably twice or even 3 times the equivalent diameter of said injection port.

Preferably, the flow rate of the injected granule powder is less than 2.4, preferably less than 2.0 g / min per KW of power of the plasma gun. There is no intermediate sintering step, preferably no consolidation between steps a) and b). This lack of intermediate consolidation step advantageously improves the purity of the feed powder. It also facilitates the bursting of the granules in step b).

A method of manufacturing a powder according to the invention may also include one or more of the following optional features:

In step a), the granulation is preferably an atomization method or spray drying ("spray drying" in English) or pelletization (transformation into pellets); In step a), the mineral composition of the granule powder comprises more than 99.9%, more than 99.95%, more than 99.99%, preferably more than 99.999% of an oxide of rare earth and / or hafnium oxide and / or aluminum oxide, in weight percent based on the oxides;

The median circularity C 50 of the granule powder is preferably greater than 0.85, preferably greater than 0.90, preferably greater than 0.95, and even more preferably greater than 0.96;

The circularity percentile of the granule powder, C ₅ , is preferably greater than or equal to 0.85, preferably greater than or equal to 0.90;

The median aspect ratio A ₅₀ of the granule powder is preferably greater than 0.75, preferably greater than 0.8;

The specific surface area of the granule powder is preferably less than 15 m ² / g, preferably less than 10 m ² / g, preferably less than 8 m ² / g, preferably less than 7 m ² / g;

The cumulative pore volume having a radius less than 1 μm, measured by mercury porosimetry, of the granule powder 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;

The bulk density of the granule powder is preferably greater than 0.5 g / cm ³ , preferably greater than 0.7 g / cm ³ , preferably greater than 0.90 g / cm ³ , preferably greater than 0 , 95 g / cm ³ , preferably less than 1.5 g / cm ³ , preferably less than 1.3 g / cm ³ , preferably less than 1.1 g / cm ³ ;

The percentile (D'10) particle size of the granule powder is preferably greater than 10 μm, preferably greater than 15 μm, preferably greater than 20 μm;

The 90th percentile (90) particle size of the granule powder is preferably less than 90 μm, preferably less than 80 μm, preferably less than 70 μm, preferably less than 65 μm; The granule powder preferably has a median size of S n between 20 and 60 microns;

The granule powder preferably has a percent percentile of between 20 and 25 mhi and an D'9 _O of 60 to 65 mhi;

The 99.5 percentile (99.5) particle size of the granule powder is preferably less than 100 μm, preferably less than 80 μm, preferably less than 75 μm;

The size dispersion index with respect to the SO 2 (D'90-D'o) / D's, of the granule powder 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 orifice 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 the mass quantity of granules injected by an injection orifice , preferably by each injection orifice, in g / min and per mm ² of the surface of said injection orifice, is greater than 10 g / min per mm ² , preferably greater than 15 g / min per mm ² ; "equivalent" means "adapted so that the burst rate of the granules (number of granules burst on number of granules injected) is the same";

An injection port, preferably each injection port, defines an injection channel, preferably cylindrical, preferably of circular section, having a length at least once, preferably at least twice, or even three times greater the equivalent diameter of said injection port, the equivalent diameter being the diameter of a disc of the same surface as the injection port;

In step b), the flow rate of granule powder is less than 3 g / min, preferably less than 2 g / min, per kW of power of the plasma gun;

The flow rate of the carrier gas (by injection orifice (that is to say by "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 granule powder is injected into the plasma jet at a feed rate greater than 20 g / min, preferably greater than 25 g / min, and / or less than 60 g / min, preferably less than 50 g / min. min, preferably less than 40 g / min, per injection port; The total granular feed rate (cumulative for all the injection orifices) is greater than 70 g / min, preferably greater than 80 g / min, and / or preferably less than 180 g / min, preferably less than at 140 g / min, preferably less than 120 g / min, preferably less than 100 g / min;

Preferably, in step c), the cooling of the melt droplets is such that, up to 500 ° C, the average cooling rate is between 50 000 and 200 000 ° C / s, preferably between 80 000 and 150 000 ° C / s.

The invention also relates to a thermal spraying method comprising a step of plasma spraying a feed powder according to the invention on a substrate in order to obtain a coating.

The invention also relates to a body comprising a substrate and a coating covering, at least partially, said substrate, said coating comprising more than 99.8% of a rare earth oxide and / or hafnium oxide and / or an aluminum oxide, in weight percent based on the oxides, and having a porosity less than or equal to 1.5%, said porosity being measured in a photograph of a polished section of said coating, as described hereinabove; below. Preferably, the porosity of the coating is less than 1%.

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 weight. rare earth oxide and / or hafnium oxide and / or aluminum oxide, in weight percent based on the oxides.

Such a coating can be manufactured with a thermal spraying method according to the invention.

The substrate may be a wall of an oven used in semiconductor processing, and in particular the wall of a plasma etching chamber.

The furnace may contain semiconductors, in particular silicon wafers. The furnace may be equipped with chemical vapor deposition (CVD) means or physical vapor deposition (PVD) means.

Definitions

"Impurities" are the inevitable constituents, involuntarily and necessarily introduced with the raw materials or resulting from reactions between the constituents. Impurities are not necessary constituents but only tolerated constituents. The level of purity is preferably measured by GDMS (Glow Discharge Mass Spectroscopy) which is more accurate than the AES-ICP (Coupled Inductively Coupled Plasma Atomic Emission Spectrometer).

The "circularity" of the particles of a powder is conventionally determined as follows: The powder is dispersed on a flat pane. The images of the individual particles are obtained by scanning the dispersed powder under an optical microscope, while keeping the particles in focus, the powder being illuminated by the underside of the glass. These images can be analyzed using a device of the type Morphologi ^® G3 marketed by the company Malvenu

As shown in FIG. 4, to evaluate the "circularity" C of a particle P ', the PD perimeter of the disk D having an area equal to the area A _p of the particle P' on an image of this particle is determined. . The perimeter P _p of this particle is also determined. The circularity is equal to the ratio of PD / P _p . So The longer the particle is elongated, the lower the circularity.

pp

The SYSMEX EPIA 3000 user manual also describes this procedure (see "detailed specification sheets" at www.malvem.co.uk).

To determine a circularity percentile (described below), the powder is poured onto a flat pane and observed as explained above. The number of particles counted should be greater than 250 so that the measured percentile is substantially the same, regardless of how the powder is poured onto the glass.

The shape ratio A of a particle is defined as the ratio of the width of the particle (its largest dimension perpendicular to the direction of its length) and its length (its largest dimension).

To determine a shape ratio percentile, the powder is poured onto a flat pane and observed as explained previously, to measure the lengths and widths of the particles. The number of particles counted should be greater than 250 so that the measured percentile is substantially the same, regardless of how the powder is poured onto the glass.

Percentiles or "percentiles" 10 (Mio), 50 (M ₅₀ ), 90 (M90) and 99.5 (M99, s), and more generally "n" M _n of a property M of particles of a powder of particles are the values of this property for the percentages, by number, of 10%, 50%, 90%, 99.5% and n%, respectively, on the cumulative distribution curve relating to this property of the particles of the powder, the values relating to this property being ranked in ascending order. In particular, the percentiles D _n (or D ' _n for the powder of granules), A _n , and C _n are relative to the size, the aspect ratio and the circularity, respectively.

For example, 10% by number of the particles of the powder have a size less than Dio and 90% of the particles in number have a size greater than or equal to Dio. The percentiles for size can be determined using a particle size distribution using a laser granulometer.

Similarly, 5% by number of particles of the powder have a circularity lower than the C ₅ percentile. In other words, 95% by number of particles of this powder have a circularity greater than or equal to C ₅ .

The percentile 50 is classically called the "median" percentile. For example, C50 is conventionally called "median circularity". Similarly, the percentile D50 is conventionally called "median size". The A50 percentile also conventionally refers to the "median form ratio".

By "particle size" is meant the size of a particle conventionally given by a particle size distribution characterization performed with a laser granulometer. The laser granulometer used can be a Partica LA-950 from the company HORIBA.

The percentage or fraction by number of particles having a size smaller than or equal to a determined maximum size can be determined using a laser granulometer.

The cumulative specific volume of the pores of radius less than 1 mHi, expressed in cm ³ / g of powder, is conventionally measured by mercury porosimetry according to the ISO 15901-1 standard. It can be measured with a MICROMERITICS porosimeter.

The apparent volume of powder, expressed in cm ³ / g, is the inverse of the apparent density of the powder.

The "bulk density"("bulkdensity") of a particle powder is conventionally defined as the ratio of the mass of the powder divided by the sum of the apparent volumes of said particles. In practice, it can be measured with a MICROMERITICS porosimeter at a pressure of 200 MPa. The "relative density" of a powder is equal to its apparent density divided by its actual density. The actual density can be measured by helium pycnometry.

The "porosity" of a coating can be evaluated by image analysis of a polished cross-section of the coating. The coated substrate is sectioned using a laboratory cutting machine, for example using a Struers Discotom apparatus with an alumina cutting disc. The coating sample is then mounted in a resin, for example by using a Struvers Durocit type cold mounting resin. The mounted sample is then polished using polishing media of increasing fineness. Abrasive paper or, preferably, polishing discs can be used with a suitable polishing slurry. A typical polishing procedure begins with dressing the sample (for example with a Struers Piano 220 Abrasive Disc), then changing the polishing sheets associated with the abrasive suspensions. The size of abrasive grains is decreased at each fine polishing step, the size of the diamond abrasives starting for example at 9 microns, then at 3 microns, to finish at 1 micron (Struers DiaPro series). For each abrasive grain size, the polishing is stopped as soon as the porosity observed under optical microscope remains constant. The samples are thoroughly cleaned between the steps, for example with water. A final polishing step, after the 1 μm diamond polishing step, is performed using colloidal silica (OP-U Struers, 0.04pm) associated with a soft felt type sheet. After cleaning, the polished sample is ready for observation under the light microscope or SEM (Scanning Electron Microscope). Because of its superior resolution and outstanding contrast, SEM is preferred for producing images for analysis. The porosity can be determined from the images using image analysis software (eg ImageJ, NIH), adjusting the thresholding. The porosity is given as a percentage of the surface of the cross section of the coating.

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

The "granulation" operation is a process of agglomeration of particles using a binder, for example a binder polymer, to form agglomerated particles, which may optionally be granules. Granulation comprises, in In particular, atomization or spray drying and / or the use of a granulator or pelletizing apparatus is not limited to these processes. Conventionally, the binder comprises substantially no oxides.

A "granule" is an agglomerated particle having a circularity of 0.8 or more.

- A consolidation step is an operation to replace, in the granules, the links due to organic binders by diffusion links. It is generally carried out by a heat treatment, but without complete melting of the granules.

The "deposition efficiency" of a plasma spraying method is defined as the ratio, in percent by mass, of the amount of material deposited on the substrate divided by the amount of feed powder injected into the plasma jet.

"Projection productivity" is defined as the amount of material deposited per unit of time.

The flow rates in l / min are "standard", that is to say measured at a temperature of 20 ° C, under a pressure of 1 bar.

"Include" or "understand" must be understood in a non-limiting manner, unless otherwise indicated.

Unless otherwise indicated, all percentages of composition are percentages by weight based on the mass of the oxides.

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

Brief description of the figures

Other characteristics and advantages of the invention will emerge more clearly on reading the description which follows and on examining the appended drawings, in which:

FIG. 1 schematically represents step a) of a method according to the invention;

FIG. 2 diagrammatically represents a plasma torch for the manufacture of a feed powder according to the invention;

FIG. 3 schematically represents a method for manufacturing a feed powder according to the invention; Figure 4 illustrates the method that is used to evaluate the circularity of a particle.

detailed description

Method of manufacturing a feed powder

FIG. 1 illustrates an embodiment of step a) of a method for manufacturing a feed powder according to the invention.

Any known method of granulation can be used. In particular, those skilled in the art know how to prepare a slip suitable for granulation.

In one embodiment, a binder mixture is prepared by adding PVA (polyvinyl alcohol) 2 in deionized water 4. This binder mixture 6 is then filtered through a filter 5 of 5 mhi. A particulate filler consisting of powdered yttrium oxide (e.g., 99.99% purity), with a median size of 1 mhi, is mixed in the filtered binder mixture to form a slurry 12. The slurry may comprise mass, for example, 55% of yttrium oxide and 0.55% of PVA, the complement to 100% consisting of water. This slip is injected into an atomizer 14 to obtain a powder of granules 16. Those skilled in the art knows how to adapt the atomizer to obtain the desired particle size distribution.

Preferably, the granules are agglomerates of particles of an oxide material having a median size of preferably less than 3 mhi, preferably less than 2 mhi, preferably less than 1.5 mhi.

Preferably, to manufacture a feed powder whose particles comprise a phase of the oxyfluoride type or of mixed oxides, for example of yttrium or ytterbium oxyfluoride, or of YAG or YAP type, granules comprising preferentially already this phase, namely respectively granules formed of yttrium or Ytterbium oxyfluoride grains, YAG, or YAP.

The granule powder can be sieved (5 mm sieve 18 for example) in order to eliminate the possible presence of residues fallen from the walls of the atomizer.

The resulting powder is a "spray-dried only" (SDO) granule powder.

Figures 2 and 3 illustrate an embodiment of step b) of melting a method of manufacturing a feed powder according to the invention.

An SDO granule powder 20, for example, as manufactured according to the method illustrated in FIG. 1, is injected by an injector 21 into a plasma jet 22 produced by a spray gun. plasma 24, for example an HP ProPlasma plasma torch. Conventional plasma injection and projection devices can be used to mix the SDO granule powder with a carrier gas and to inject the resulting mixture into the hot plasma core.

However, the injected granule powder must not be consolidated (SDO) and the injection into the plasma jet must be made brutally, to promote the breaking of granules. The shock force determines the intensity of the bursting of the granules, and therefore the median size of the powder manufactured.

Those skilled in the art know how to adapt the injection parameters for a sudden injection of the granules so that the feed powder obtained at the end of steps c) or d) has a particle size distribution according to the invention.

In particular, those skilled in the art know that:

a comparison of the injection angle θ between the injection axis of the Y granules and the X axis of the plasma jet by 90 °,

an increase in the powder flow rate per mm ² of surface area of the injection orifice,

a reduction in the powder flow, in g / min, per kW of power of the gun, and

an increase in the flow of plasma gas

are factors that promote breakage of the granules.

In particular, WO2014 / 083544 does not disclose injection parameters permitting the breaking of more than 50% in number of the granules, as described in the examples below.

It is preferable to inject the particles rapidly so as to disperse them in a very viscous plasma jet which flows at a very high speed.

When the injected granules come into contact with the plasma jet, they are subjected to violent shocks, which can break them into pieces. To penetrate the plasma jet, the unconsolidated, and in particular unsintered, granules to be dispersed are injected at a velocity sufficiently high to benefit from a high kinetic energy, but limited to ensure a good bursting efficiency. The lack of consolidation granules reduces their mechanical strength, and therefore their resistance to these shocks.

It is known to those skilled in the art that the speed of the granules is determined by the flow rate of the carrier gas and the diameter of the injection port.

The speed of the plasma jet is also high. Preferably, the plasma gas flow rate is greater than the median value recommended by the torch manufacturer for the anode diameter chosen. Preferably, the plasma gas flow rate is greater than 50 l / min, preferably greater than 55 l / min.

It is known to those skilled in the art that the plasma jet velocity can be increased by using a small diameter anode and / or by increasing the flow rate of the primary gas.

Preferably, the flow rate of the primary gas is greater than 40 l / min, preferably greater than 45 l / min.

Preferably, the ratio between the secondary gas flow rate, preferably the dihydrogen (¾) and the plasma gas flow (consisting of primary and secondary gases) is between 20% and 25%.

Of course, the energy of the plasma jet, influenced in particular by the flow rate of the secondary gas, must be high enough to melt the granules.

The granule powder is injected with a carrier gas, preferably without any liquid.

In the plasma jet 22, the granules are melted into droplets 25. Preferably, the plasma gun is set so that the melting is substantially complete.

Fusion advantageously reduces the level of impurities.

On leaving the hot zone of the plasma jet, the droplets are rapidly cooled by the surrounding cold air, but also by a forced circulation 26 of a cooling gas, preferably air. Air advantageously limits the reducing effect of hydrogen.

Preferably, the plasma torch comprises at least one nozzle arranged to inject a cooling fluid, preferably air, so as to cool the droplets resulting from the heating of the granule powder injected into the plasma jet. The cooling fluid is preferably injected downstream of the plasma jet (as shown in FIG. 2) and the angle g between the path of said droplets and the path of the cooling fluid is preferably less than or equal to 80 °. , preferably less than or equal to 60 ° and / or greater than or equal to 10 °, preferably greater than or equal to 20 °, preferably greater than or equal to 30 °. Preferably, the injection axis Y of any nozzle and the X axis of the plasma jet are secant.

Preferably, the injection angle θ between the injection axis Y and the X axis of the plasma jet is greater than 85 °, preferably about 90 °. Preferably, the forced cooling is generated by a set of nozzles 28 disposed about the X-axis of the plasma jet 22, so as to create a substantially conical or annular flow of cooling gas.

The plasma gun 24 is oriented vertically towards the ground. Preferably, the angle α between the vertical and the X axis of the plasma jet is less than 30 °, less than 20 °, less than 10 °, preferably less than 5 °, preferably substantially zero. Advantageously, the flow of cooling gas is perfectly centered with respect to the axis X of the plasma jet.

Preferably, the minimum distance d between the external 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. mm.

Advantageously, the forced cooling limits the generation of satellites, resulting from the contact between very large hot particles and small particles in suspension in the densification chamber 32. Moreover, such a cooling operation makes it possible to reduce the overall size of the treatment equipment, especially the size of the collection chamber.

The cooling of the droplets 25 makes it possible to obtain feed particles 30, which can be extracted in the lower part of the densification chamber 32.

The densification chamber may be connected to a cyclone 34, whose exhaust gas is directed to a dust collector 36, so as to separate very fine particles 40. According to the configuration, certain feed particles conform to The invention may also be collected in the cyclone. Preferably, these feed particles can be separated, in particular with an air separator.

Optionally, the collected feed particles 38 can be filtered, so that the median size D50 is less than 15 microns.

The following Table 1 provides the preferred parameters for making a feed powder according to the invention.

The characteristics of a column are preferably, but not necessarily, combined. The characteristics of the two columns can also be combined.

The plasma torch "ProPlasmaHP" is sold by Saint-Gobain Coating Solutions. This torch corresponds to the torch T1 described in WO2010 / 103497.

Table 1

Examples

The following examples are provided for illustrative purposes and do not limit the scope of

The invention. Feeding powders H1, II (comparative) and C1 (comparative) were made with a plasma torch similar to the plasma torch shown in Figure 2 of WO2014 / 083544, from a Y ₂ powder. 0 ₃ pure having a median size D50 of 1.2 micron, measured with a Horiba laser particle analyzer, and a chemical purity of 99.999% of Y ₂ 0 ₃ .

In step a), a binder mixture is prepared by adding PVA (polyvinyl alcohol) binder 2 (see Figure 1) in deionized water 4. This binder mixture is then filtered through a filter of 5 mhi 8. The powdered yttrium oxide is mixed in the filtered binder mixture to form a slurry 12. The slurry is prepared to comprise, in percent by weight, 55% yttrium oxide and 0.55% PVA, the 100% complement being deionized water. The slurry is mixed intensively using a high shear mixer.

The granules G3 are then obtained by atomizing the slip, using an atomizer 14. In particular, the slip is atomized in the chamber of a GEA Niro SD 6.3 R atomizer, the slip being introduced at a flow rate of about 0.38 l / min.

The speed of the rotary atomizing wheel, driven by a Niro FS1 engine, is adjusted to obtain the sizes of the targeted granules (G3).

The air flow rate is adjusted to maintain the inlet temperature at 295 ° C and the outlet temperature near 125 ° C so that the residual moisture of the granules is between 0.5% and 1%.

The granule powder is then screened with a sieve 18 in order to extract the residues and obtain a powder of SDO 20 granules.

In step b), the granules of step a) are injected into a plasma jet 22 (see FIG. 2) produced with a plasma gun 24. The injection and melting parameters are given in table 2 following.

In step c), to cool the droplets, 7 Silvent 2021L nozzles 28, sold by Silvent, were attached to a Silvent 463 annular nozzle holder, sold by Silvent. The nozzles 28 are evenly spaced along the annular nozzle holder, so as to generate a substantially conical airflow.

The collection efficiency of the collected feed particles 38 is the ratio between the amount of feed particles collected and the total amount of pellets injected into the plasma jet.

Table 2 The cumulative specific volume of the pores having a radius of less than 1 mHi in the granules was 260 × 10 ³ cm ³ / g.

The invention thus provides a feed powder having a size distribution and a relative density imparting a very high density to the coating. In addition, this feed powder can be efficiently projected by plasma and with good productivity.

The feed powder according to the invention thus makes it possible to produce coatings with a lower concentration of defects. Moreover, it has improved flowability compared to plasma unmelted powder of the same size, which allows an injection without complex feed means.

Of course, the invention is not limited to the embodiments described and shown.

Claims

1. powder of melted particles, more than 95% by number of said particles having a circularity greater than or equal to 0.85, said powder containing more than 99.8% of a rare earth oxide and / or oxide of hafnium and / or aluminum oxide, in percentage by weight on the basis of the oxides, and having:

a median particle size D50 of less than 15 mHi, a 90 percentile of particle sizes, D 90, of less than 30 mHi, and a size dispersion index (D 90 -Dio) / D 10 of less than 2;

a relative density greater than 90%,

the percentiles D _n of the powder being the particle sizes corresponding to the percentages, by number, of n%, on the cumulative distribution curve of the particle size of the powder, the particle sizes being ranked in ascending order.

2. Powder according to the immediately preceding claim, having:

a percentage by number of particles having a size less than or equal to 5 mhi which is greater than 5%, and / or

a median particle size D50 of less than 10 mhi, and / or

a 90th percentile of particle sizes D90 of less than 25 mh, and / or a 99.5 percentile of particle sizes Ü99.5 of less than 40 mh, and / or - a size dispersion index (D9 _O -D ₁₀ ) / D _IO less than 1.5.

A powder according to any one of the preceding claims, wherein the median size of the D50 particles is less than 8 mhi.

4. Powder according to any one of the preceding claims, containing, in percentage by mass on the oxide basis, more than 99.8% of Yb ₂ 0 ₃ and / or Y ₂ O ₃ and / or Y ₃ Al ₅ O ₁₂ and / or an yttrium oxyfluoride, preferably according to the formula Y _a O _b F _c in which a is equal to 1, b is between 0.7 and 1.1 and c is between 1 and 1 , 5, preferably an oxyfluoride selected from YOF and Y ₅ O ₄ F ₇ or a mixture of these oxyfluorides.

5. A method of manufacturing a powder according to any one of the preceding claims, said method comprising the following steps: a) granulating a particulate filler so as to obtain a granule powder having a median median size of between 20 and 60 micron, the particulate filler comprising more than 99.8% of a rare earth oxide and / or hafnium oxide and / or aluminum oxide, in weight percent based on the oxides;

b) injecting said granule powder, via a carrier gas, through at least one injection port to a plasma jet generated by a plasma gun, under injection conditions causing a burst of more than 50 % of the injected granules, in percentage by number, so as to obtain molten droplets, the flow rate of the injected granule powder being less than 2 g / min per KW of power of the plasma gun and the ratio of the mass quantity of granules injected by said injection orifice, preferably by each injection orifice, on the surface of said injection orifice being greater than 16 g / min per mm ² of surface of said injection orifice;

c) cooling said melt droplets so as to obtain a feed powder according to any one of the preceding claims;

d) optionally, granulometric selection of said feed powder.

6. Method according to the immediately preceding claim, wherein the injection conditions are determined so as to cause bursting of more than 70% of the injected granules, in percentage by number.

7. Method according to the immediately preceding claim, wherein the injection conditions are determined so as to cause bursting of more than 90% of the injected granules, in percentage by number.

8. A method of manufacturing a powder according to any one of claims 5 to 7, wherein, in step b), the injection conditions are adapted to cause a burst rate granules identical to a gun with a plasma power having a power of 40 to 65 kW and generating a plasma jet in which the mass quantity of granules injected by each injection orifice, in g / min and per mm ² of the surface of said injection orifice is greater than 10 g / min per mm ² .

9. A method according to the immediately preceding claim, wherein the mass quantity of granules injected by each injection port, in g / min and per mm ² of the surface of said injection port is greater than 15 g / min per mm ^2. .

10. A method of manufacturing a powder according to any one of claims 5 to 9, wherein said injection port defines an injection channel having a length at least one greater than the equivalent diameter of said injection port.

The method of the immediately preceding claim, wherein said length is at least two times greater than said equivalent diameter.

12. A method of manufacturing a powder according to any one of claims 5 to 11, wherein, in step b), the flow rate of granules powder is less than 3 g / min per kW of power of the gun to plasma.

13. The method of one of claims 5 to 12, wherein the granulation comprises an atomization.

14. Thermal spraying method comprising a step of thermal spraying a powder according to any one of claims 1 to 4 or manufactured according to any one of claims 5 to 13.

15. Semiconductor processing chamber, said chamber comprising a wall protected by a coating, said coating comprising more than 99.8% of a rare earth oxide and / or hafnium oxide and / or an oxide of aluminum, in percentage by mass on the oxide basis, and having a porosity of less than or equal to 1.5%, said coating being obtained by thermal spraying of a powder according to any one of claims 1 to 4 or manufactured according to a process according to any one of claims 5 to 13.