JP6706894B2 - Thermal spray material - Google Patents

Description

The present invention relates to a thermal spray material capable of forming a thermal spray coating having excellent corrosion resistance to plasma.

The thermal spray coating is formed by spraying a thermal spray material onto a substrate. Thermal spray coatings are used in various applications depending on the properties of the thermal spray material. For example, yttrium oxide (yttria) exhibits high plasma erosion resistance (etching resistance, corrosion resistance) when exposed to plasma. Therefore, the yttrium oxide sprayed coating formed of the yttrium oxide sprayed material is used as a protective coating for members in a semiconductor device manufacturing apparatus that is processed by plasma.

JP, 2002-302754, A JP, 2014-109066, A

By the way, as the degree of integration of semiconductor devices is improved, more precise management is required for contamination by particles (fine foreign matter) generated in a semiconductor device manufacturing apparatus. Therefore, for example, the yttrium oxide sprayed coating used as a protective coating has a problem that it can be a source of generation of finer particles, which has been a problem in the past. Therefore, in order to form a thermal spray coating excellent in plasma erosion resistance, a thermal spray material made of a compound containing a rare earth element has been proposed (see, for example, Patent Documents 1 and 2). However, even with the thermal spray materials disclosed in Patent Documents 1 and 2, it has been difficult to form a thermal spray coating having satisfactory plasma erosion resistance.

Therefore, it is an object of the present invention to provide a thermal spray material capable of forming a thermal spray coating having more excellent plasma erosion resistance.

As a solution to the above problems, the technology disclosed herein provides a thermal spray material that is a powder containing at least one of a fluoride of yttrium and an oxyfluoride. The powder is characterized in that it is composed of individual particles of a homogeneous matrix. According to such a structure, for example, a thermal spray coating containing a fluoride of yttrium and an oxyfluoride having excellent plasma erosion resistance against halogen-based plasma used in a semiconductor manufacturing apparatus can be formed. Further, when the thermal spray material is exposed to a high temperature by thermal spraying, it is possible to prevent the composition of the thermal spray material from changing excessively. As a result, it is possible to form a sprayed coating having a further excellent plasma erosion resistance.

In the technique disclosed herein, the halogen-based plasma is typically plasma generated using a plasma-generating gas containing a halogen-based gas (halogen compound gas). For example, specifically, a fluorine-based gas such as SF ₆ , CF ₄ , CHF ₃ , ClF ₃ , and HF, and chlorine such as Cl ₂ , BCl ₃ , and HCl, which are used in a dry etching step in manufacturing a semiconductor substrate. Typical examples are plasmas generated by using one type of bromine-based gas such as a system gas and HBr alone or by mixing two or more types. These gases may be a mixed gas with an inert gas such as argon (Ar).

In a preferred embodiment of the thermal spray material disclosed herein, the specific surface area measured by the BET method is less than 0.1 m ² /g. Since the specific surface area of the thermal spray material is small as described above, the deterioration of the thermal spray material due to thermal spray can be more reliably suppressed.

In a preferred aspect of the thermal spray material disclosed herein, the cumulative pore volume having a pore diameter of 3 μm or less is characterized by being 0.02 cm ³ /g or less. Also by this, deterioration of the thermal spray material during thermal spraying can be more reliably suppressed. Further, it is possible to form a dense spray coating with few pores.

In a preferred embodiment of the thermal spray material disclosed herein, the average particle diameter is 60 μm or less. Thereby, the handling property of the thermal spray material can be kept good. Further, by using the thermal spray material having a relatively large particle diameter, it is possible to suitably suppress the alteration of the thermal spray material during thermal spraying.

In a preferred embodiment of the thermal spray material disclosed herein, the total proportion of yttrium fluoride and oxyfluoride in the entire powder is 95% by mass or more. As a result, it is possible to form a sprayed coating that is more excellent in plasma erosion resistance.

In a preferred aspect of the thermal spray material disclosed herein, the average circularity is 0.5 or more and less than 1. As a result, it is possible to realize a thermal spray material having excellent supplyability to the thermal spray device.

It is a scanning electron microscope (SEM) image of the thermal spray material according to one embodiment. 2 is a cross-sectional SEM image of the thermal spray material of FIG. 1. 8 is an SEM image of a thermal spray material according to another embodiment. 4 is a cross-sectional SEM image of the thermal spray material of FIG. It is a SEM image of a comparative thermal spray material.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters particularly referred to in the present specification, which are necessary for carrying out the present invention, include teachings for carrying out the invention described in the present specification and common general technical knowledge at the time of application in this field. It can be understood and carried out by those skilled in the art on the basis of

The thermal spray material disclosed herein is a powder containing at least one of yttrium fluoride and oxyfluoride. Yttrium fluoride and yttrium oxyfluoride have excellent corrosion resistance to plasma (plasma erosion resistance). Particularly, it has excellent plasma erosion resistance against halogen-based plasma. By containing such a fluoride of yttrium and/or an oxyfluoride of yttrium, the thermal spray material disclosed herein can form a thermal spray coating having excellent plasma erosion resistance.

Here, it is preferable that the total ratio of the yttrium fluoride and the yttrium oxyfluoride in the thermal spray material is high because the generation amount of the component that can be a particle generation source when the thermal spray coating is formed is suppressed. For example, the total amount of yttrium fluoride and yttrium oxyfluoride is preferably 95% by mass or more, more preferably 97% by mass or more, and particularly preferably 98% by mass or more. For example, it is a particularly desirable mode that the content is substantially 100% by mass.

Here, yttrium fluoride can be oxidized by thermal spraying to form yttrium oxide in the thermal spray coating. Oxyfluoride of yttrium can also be oxidized by thermal spraying to form yttrium oxide in the thermal spray coating. According to the earnest studies by the present inventors, the yttrium oxide present in the thermal spray coating can be a source of generation of finer particles, which has not been a problem in the past, in an environment exposed to a halogen-based plasma. Therefore, it is more preferable that the yttrium fluoride and/or the yttrium oxyfluoride in the thermal spray material is in a form that is not transformed into yttrium oxide during thermal spraying. From this point of view, the thermal spray material disclosed herein has a form in which the thermal spray material is difficult to be oxidized in an unavoidable oxidizing environment due to thermal spraying.

That is, the yttrium fluoride and/or yttrium oxyfluoride powders disclosed herein are characterized primarily by being composed of discrete particles of a homogeneous matrix. That is, the thermal spray material is in powder form. The particles which mainly constitute this powder can be present individually and independently. FIG. 1 is a scanning electron microscope (SEM, manufactured by Hitachi High-Technologies Corporation, S-3000N) of particles (hereinafter, also simply referred to as “spray particles”) constituting a spray material according to an embodiment. It is a statue. As shown in FIG. 1, the particles constituting the thermal spray material are essentially independent of each other. The individual particles have a smooth texture throughout and are composed of one homogeneous matrix. For example, the surface of the particles is almost smooth, and even when unevenness is present, it is only partially confirmed. The particles in FIG. 1 are particles having a substantially spherical outer shape. However, the outer shape of the spray particles is not particularly limited as long as the individual particles are independent particles composed of approximately one homogeneous matrix. For example, as shown in FIG. 3, the outer shape of the spray particles may be non-spherical. For example, it may be a square or amorphous particle having a corner.
In the present specification, the “matrix” can also be referred to as a matrix or a matrix, and the homogeneous matrix means a phase, a structure or the like which does not essentially include a heterogeneous phase or a structure or the like. Means

In the thermal spray material disclosed herein, it is acceptable that a small number of particles are integrated to form a composite particle. The small number referred to here is, for example, less than 10, typically about 5 or less, for example, 3 or less. The ratio of such composite particles can be 10% by mass or less of all particles constituting the powder. Further, it is permissible that extremely minute spray particle components adhere to the surfaces of the spray particles that mainly constitute the spray material. Such minute thermal spray particle components are components inevitably generated when the thermal spray material is manufactured or stored, and are, for example, about 1/50 or less of the spray particles attached. It refers to the volume. The proportion of this spray particle component can be, for example, 1% by weight or less of the total particles.

By forming the spray particles in such a form, the spray material disclosed herein is characterized in that it is difficult to be oxidized when subjected to spraying. As a result, when the thermal spray coating is formed, the thermal spray particles can be present in a larger proportion in the coating while maintaining the composition of yttrium fluoride or yttrium oxyfluoride. Thereby, the plasma erosion resistance of the thermal spray coating can be greatly improved.

In contrast, FIG. 5 is an SEM image showing, for comparison, spray particles different from the spray particles disclosed herein. In the particles of FIG. 5, a plurality of (for example, 10 or more, 100 or more in FIG. 5) fine particles are melt-integrated to form one spray particle (composite particle). In this composite particle, since each fine particle is sufficiently integrated at the time of melting, the boundary cannot be confirmed. That is, it can be said that the composite particles are single and exist independently. However, since the morphology (presence) of a large number of fine particles constituting the composite particles can be discriminated, the composite particles cannot be said to be composed of a homogeneous matrix with uneven tissue. In this regard, the composite particles of FIG. 5 are clearly distinguished from the thermal spray particles disclosed herein.

Although not specifically shown, for example, so-called granules are known in which a plurality of particles are integrated and formed (granulated) into a larger granular body. In this granular sprayed particle, individual particles constituting the granule are likely to be dissociated and collapsed, and it may not be said that they exist independently. Even if the individual particles that make up the granules are firmly bound to each other, the morphology (presence) of the numerous microparticles that make up the granules can be identified, as in the case of the composite particles described above, so that there is unevenness in the tissue. Yes, and cannot be said to consist of a homogeneous matrix. In this respect, granules are clearly distinguished from the thermal spray particles disclosed herein. The thermal spray particles in the thermal spray materials disclosed herein can be non-granular.

The thermal spray material disclosed herein contains at least one of yttrium fluoride and yttrium oxyfluoride, as described above. The thermal spray material may include only yttrium fluoride or only yttrium oxyfluoride. Further, it may be a mixture containing yttrium fluoride and yttrium oxyfluoride in an arbitrary ratio. Here, the yttrium (Y) fluoride is typically yttrium fluoride (YF ₃ ). The yttrium oxyfluoride may be a compound containing at least yttrium (Y), oxygen (O), and fluorine (F) as constituent elements. The yttrium oxyfluoride may contain any element other than yttrium (Y), oxygen (O) and fluorine (F) as long as the object of the present invention is not impaired. The ratio of yttrium (Y), oxygen (O), and fluorine (F) forming this yttrium oxyfluoride is not particularly limited.

For example, in yttrium oxyfluoride, the molar ratio of fluorine to oxygen (F/O) is not particularly limited. As a suitable example, the molar ratio (F/O) may be, for example, 1 and is preferably larger than 1. Specifically, for example, 1.2 or more is preferable, 1.3 or more is more preferable, and 1.4 or more is particularly preferable. The upper limit of the molar ratio (F/O) is not particularly limited and can be, for example, 3 or less. As a more preferable example of the molar ratio of fluorine to oxygen (F/O), for example, 1.3 or more and 1.53 or less (for example, 1.4 or more and 1.52 or less), 1.55 or more and 1.68 or less (for example, It is preferable that it is 1.58 or more and 1.65 or less) and 1.7 or more and 1.8 or less (for example, 1.72 or more and 1.78 or less) because thermal stability at the time of thermal spraying is enhanced. As described above, the ratio of fluorine to oxygen in the sprayed particles is increased, and thus the sprayed coating, which is a sprayed material of the sprayed material, can have excellent erosion resistance to halogen-based plasma.

Further, the molar ratio of yttrium to oxygen (Y/O) is not particularly limited. As a suitable example, the molar ratio (Y/O) may be 1, and is preferably larger than 1. Specifically, for example, 1.05 or more is preferable, 1.1 or more is more preferable, and 1.15 or more is particularly preferable. The upper limit of the molar ratio (Y/O) is not particularly limited and can be, for example, 1.5 or less. As a more preferable example of the yttrium molar ratio (Y/O) to oxygen, for example, 1.1 or more and 1.18 or less (for example, 1.12 or more and 1.17 or less), 1.18 or more and 1.22 or less (for example, 1.19 or more and 1.21 or less) and 1.22 or more and 1.3 or less (for example, 1.23 or more and 1.27 or less) are preferable because thermal stability at the time of thermal spraying is enhanced. As described above, the small ratio of the oxygen element to yttrium is preferable because the oxidative decomposition of the spray particles can be suppressed when the spray material is sprayed. For example, it is preferable because yttrium oxide (for example, Y ₂ O ₃ ) due to the oxidation of the yttrium component can be suppressed from being formed in the thermal spray coating which is a thermal spray material of this thermal spray material.

More specifically, the yttrium oxyfluoride may be a compound represented by YOF with a chemical composition in which the ratio of yttrium:oxygen:fluorine is 1:1:1. Further, thermodynamically relatively stable, the general _{formula; Y 5} (wherein, n, for example, satisfying 0.12 ≦ n ≦ 0.22.) Y 1 O 1-n F 1 + 2n represented by It may be O ₄ F ₇ , Y ₆ O ₅ F ₈ , Y ₇ O ₆ F ₉ , Y ₁₇ O ₁₄ F _23, or the like. In particular, the molar ratio (Y / O) and (F / O) is in the more preferable range of the _{Y 5 O 4 F 7, Y} 6 O 5 F 8, Y 7 O 6 F 9 , etc., a halogen gas plasma Is excellent in plasma erosion resistance, and is preferable because it is possible to form a denser and harder sprayed coating. Such yttrium oxyfluoride may be composed of a single phase of any one compound, or a mixed phase in which any two or more compounds are combined, a solid solution, a compound, or a combination thereof. It may be configured by mixing or the like.

Further, the thermal spray material disclosed herein may contain thermal spray particles made of other compounds in addition to the thermal spray particles made of yttrium oxyfluoride. However, for example, as a thermal spray material used for forming a thermal spray coating having excellent plasma erosion resistance, it is preferable that the thermal spray particles contain more yttrium oxyfluoride. Such yttrium oxyfluoride is preferably contained in the spray particles in a high proportion of 77% by mass or more. Yttrium oxyfluoride is more excellent in plasma erosion resistance than yttrium oxide (Y ₂ O ₃ ) which is conventionally known as a material having high plasma erosion resistance. Such yttrium oxyfluoride greatly contributes to the improvement of the plasma erosion resistance even if it is contained in a small amount, but it is preferable that it is contained in a large amount as described above because it can exhibit extremely good plasma resistance. The proportion of yttrium oxyfluoride is preferably 77% by mass or more, more preferably 80% by mass or more (exceeding 80% by mass), and further preferably 85% by mass or more (exceeding 85% by mass). It is more preferably 90% by mass or more (exceeding 90% by mass), and even more preferably 95% by mass or more (exceeding 95% by mass). For example, it is particularly preferable that it is substantially 100 mass% (all except unavoidable impurities). Note that the thermal spray particles are allowed to include other substances that are more likely to be a source of particles (fine particles, foreign matters) by including the yttrium oxyfluoride at such a high ratio.

Moreover, when yttrium oxyfluoride is contained in the spray particles, it can be a preferable aspect that all of the spray particles are yttrium oxyfluoride. However, among the yttrium oxyfluorides, for a composition that is relatively easily oxidized (for example, Y ₁ O ₁ F ₁ ), it is preferable that yttrium fluoride is simultaneously contained, for example. The ratio of the yttrium fluoride is not particularly limited, but it is preferably contained in a ratio of 23% by mass or less based on the total of the yttrium fluoride and the yttrium oxyfluoride. Yttrium fluoride contained in the spray particles can be oxidized by spraying to form an yttrium oxide in the spray coating. For example, as described above, yttrium fluoride and yttrium oxyfluoride can be oxidized by thermal spraying to form yttrium oxide in the thermal spray coating. However, when yttrium oxyfluoride and a small amount of yttrium fluoride coexist, the oxidation of yttrium oxyfluoride can be suppressed by the yttrium fluoride, which is preferable. However, an excessive content of yttrium fluoride leads to an increase in the number of particle sources as described above. Therefore, when it is contained in excess of 23 mass %, the plasma erosion resistance is deteriorated, which is not preferable. From this viewpoint, the content ratio of yttrium fluoride is preferably 20% by mass or less, more preferably 15% by mass or less, and further 10% by mass or less, for example, 5% by mass or less. preferable. A preferred embodiment of the thermal spray material disclosed herein may be substantially free of yttrium fluoride.

It should be noted that the thermal spray particles made of yttrium oxide (Y ₂ O ₃ ) are a preferable material for forming a white thermal spray coating, and a thermal spray coating having an environmental barrier property and general erosion resistance characteristics against plasma as compared with conventional ones. possible. However, the thermal spray material disclosed herein does not substantially contain the oxide of yttrium (yttrium oxide: Y ₂ O ₃ ) component in order to enhance the plasma resistance of the thermal spray coating which is a thermal spray material. It can also be configured. For example, it is preferable that this thermal spray material does not include thermal spray particles made of yttrium oxide. The yttrium oxide contained in the sprayed particles can exist as yttrium oxide in the sprayed coating as it is by spraying. As described above, this yttrium oxide has significantly lower plasma resistance than yttrium oxyfluoride or yttrium fluoride. Therefore, the portion containing this yttrium oxide is likely to form a brittle deteriorated layer when exposed to a plasma environment, and the deteriorated layer is likely to be detached as extremely fine particles. Then, the fine particles may be deposited as particles on the semiconductor substrate. Therefore, in the thermal spray material disclosed herein, it is preferable to exclude the inclusion of yttrium oxide, which can be a particle source.

In the present specification, "substantially free" means that the content ratio of the component (yttrium oxide here) is 5% by mass or less, preferably 3% by mass or less, for example, 1% by mass or less. means. Such a configuration can also be understood, for example, when a diffraction peak based on the component is not detected when the spray particles are subjected to X-ray diffraction analysis.

When the spray particles contain a plurality of yttrium oxyfluorides and/or yttrium fluorides having a composition (a is a natural number, a≧2), the content ratio of the compound of each composition is determined by the following method. Can be measured and calculated at. First, the composition of the compound constituting the spray particles is specified by X-ray diffraction analysis. At this time, yttrium oxyfluoride is identified up to its valence (element ratio).

Then, for example, when one type of yttrium oxyfluoride is present in the thermal spray material and the rest is yttrium fluoride, the oxygen content of the thermal spray material is determined by, for example, an oxygen/nitrogen/hydrogen analyzer (for example, manufactured by LECO Co., The content of yttrium oxyfluoride can be quantified from the obtained oxygen concentration measured by ONH836).
When two or more types of yttrium oxyfluoride are present or a compound containing oxygen such as yttrium oxide is mixed, the ratio of each compound can be quantified by a calibration curve method. Specifically, several kinds of samples in which the content ratio of each compound was changed were prepared, X-ray diffraction analysis was performed on each sample, and a calibration curve showing the relationship between the main peak intensity and the content of each compound was created. To do. Then, based on this calibration curve, the content is quantified from the main peak intensity of the XRD yttrium oxyfluoride of the thermal spray material to be measured.

Regarding the molar ratio (F/O) and the molar ratio (Y/O) in the above yttrium oxyfluoride, the molar ratio (Fa/Oa) and the molar ratio (Ya/Oa) are calculated for each composition. , The molar ratio (Fa/Oa) and the molar ratio (Ya/Oa) are multiplied by the abundance ratio of the composition, respectively, and summed (a weighted sum is taken) to obtain the total mol of yttrium oxyfluoride in the thermal spray material. The ratio (F/O) and the molar ratio (Y/O) can be obtained. In addition, the above-mentioned material forming the spray particles may be introduced with an element other than those exemplified above for the purpose of enhancing functionality.

In the above thermal spray material, the average particle diameter of the thermal spray particles is not particularly limited. For example, the average particle size is preferably about 60 μm or less, and more preferably 55 μm, from the viewpoint that a relatively dense sprayed coating can be formed and oxidation during spraying can be suitably suppressed. It is below. For example, when the spray particles are made of yttrium fluoride, the average particle diameter is preferably 15 μm or more, more preferably 18 μm or more. Further, from the viewpoint that a denser sprayed coating can be formed, the average particle diameter is preferably 25 μm or less, more preferably 23 μm or less. On the other hand, yttrium oxyfluoride is particularly easily oxidized by thermal spraying, and therefore it is preferable to use a yttrium oxyfluoride having a relatively coarse particle size. From this point of view, the average particle diameter of the spray particles made of yttrium oxyfluoride is preferably 35 μm or more, more preferably 38 μm or more, and particularly preferably 40 μm or more. However, oversized spray particles can form bubbles in the spray coating. Therefore, the average particle diameter of the spray particles made of yttrium oxyfluoride is preferably 55 μm or less, more preferably 53 μm or less, and particularly preferably 50 μm or less.

In the present specification, the “average particle size” of the thermal spray material means the particle size at 50% integrated value in the particle size distribution based on volume measured by a particle size distribution measuring device based on the laser diffraction/scattering method (integrated value). 50% particle size; D50). At the same time as the measurement of the average particle diameter, the cumulative 3% particle diameter (D ₃ ) and the cumulative 97% particle diameter (D ₉₇ ) in the volume-based particle size distribution of the thermal spray material can be calculated.

Further, the specific surface area of the thermal spray material is preferably less than 0.1 m ² /g from the viewpoint of suitably suppressing oxidation during thermal spraying. The specific surface area is preferably at 0.098m ² / g or less, more preferably 0.095 ² / g or less, even more preferably at most 0.093m ² / g.
As the specific surface area of the thermal spray material, a value calculated based on the BET method can be adopted. Specifically, for the thermal spray material, the amount of gas adsorbed in the monolayer based on the BET method is obtained from the adsorption isotherm obtained by the gas adsorption method, and the specific surface is calculated based on the molecular size of the adsorbed gas. Is. The specific surface area of such a thermal spray material can be measured according to JIS Z 8830:2013 (ISO9277:2010) “Method for measuring specific surface area of powder (solid) by gas adsorption”. For example, the specific surface area of the sprayed particles can be measured using a surface area measuring device manufactured by Micromeritics Co., Ltd. under the trade name “FlowSorb II 2300”.

Similarly, from the viewpoint of suitably suppressing oxidation during thermal spraying, it is preferable that the surface of the thermal spray particles constituting the thermal spray material has no irregularities and is smooth. For example, the cumulative pore volume of the thermal spray material having a pore diameter of 3 μm or less is preferably 0.02 cm ³ /g or less. The cumulative pore volume, 0.01 cm ³ / g and more preferably less, particularly preferably 0.009 cm ³ / g or less, more preferably 0.005 cm ³ / g. In addition, since the cumulative pore volume of the thermal spray material having a pore diameter of 3 μm or less is small as described above, a dense thermal spray coating can be formed, which is preferable.
The cumulative pore volume of the thermal spray material can be calculated based on the mercury porosimetry method. The mercury injection method uses the fact that the surface tension of mercury is high, and the relationship between the pressure applied to infiltrate mercury into the fine pores of the powder and the amount of the injected mercury shows that the pores from the meso region to the macro region are large. This is a method of obtaining the distribution. The pore size distribution measurement based on the mercury porosimetry can be carried out, for example, according to JIS R1655:2003 (method for testing pore diameter distribution of molded body by mercury porosimetry of fine ceramics). For example, the cumulative pore volume of the thermal spray material can be measured by using a mercury press-in type porosimeter (manufactured by Shimadzu Corporation, Poisizer 9320).

Although not necessarily limited to this, the thermal spray particles contained in the thermal spray material preferably have an average circularity in plan view of 0.5 or more from the viewpoint of improving fluidity. The average circularity is more preferably 0.55 or more, particularly preferably 0.6 or more. The upper limit of the average circularity is not particularly limited, but since the thermal spraying material disclosed herein is composed of a uniform matrix, the average circularity is typically less than 1 (preferably 0.98 or less). , For example 0.95 or less).

In the present specification, the average circularity may be the arithmetic average value of the circularity in plan view of the particles of 5000 or more of the thermal spray material obtained by the image analysis method. The circularity can be measured as follows. That is, specifically, first, a thermal spray material is dispersed in a measurement dispersion medium to prepare a measurement sample. The dispersion medium for measurement is not particularly limited as long as it can suppress aggregation of the spray particles in the spray material and can adjust the spray particles to a dispersed state. In this embodiment, ion-exchanged water to which polyoxyethylene sorbitan monolaurate, which is a surfactant, is added at a concentration of 0.1% by mass is used as the dispersion medium for measurement. Further, the ratio of the thermal spray material in the measurement sample was 30% by mass or less (30% by mass in the present embodiment). By pouring the measurement sample prepared in this way into a measurement container such as a glass cell, a flat sample flow in which overlapping of spray particles is suppressed is formed. By irradiating the sample flow with strobe light and capturing an image, a still image of the sprayed particles that are suspended and flowing in the measurement sample is acquired. The circularity is calculated by performing image analysis on the obtained still image of the spray particles. The circularity is defined by the following formula: (Circularity)=(perimeter of circle having the same area as the spray particle image)/(perimeter of spray particle); That is, the circularity is calculated from the projected area per spray particle and the perimeter. This circularity is obtained for 5000 or more sprayed particles, and the arithmetic mean value is taken as the average circularity. In the present specification, the above-mentioned average circularity adopts a value calculated using a flow-type particle image analyzer (FPIA-2100 manufactured by Sysmex Corporation).

The thermal spray material disclosed herein is also composed of discrete particles of a homogeneous matrix. Therefore, the fracture strength of such spray particles can be realized as, for example, higher than that of granular spray particles or spray particles composed of an inhomogeneous matrix. For example, the fracture strength of the thermal spray material is preferably 10 MPa or more, more preferably 50 MPa or more, and particularly preferably 80 MPa or more. The high fracture strength is preferable because the particles are less likely to collapse when the thermal spray material is supplied to the thermal spraying device and the fluidity is enhanced.
In the present specification, the fracture strength Nd is calculated by the following formula: Nd=2.8× from the compression load P measured by a micro compression tester (manufactured by Shimadzu Corporation, MCTE-500) and the particle diameter d of the spray particles. It is a value calculated based on P/(πd ² ); The average particle diameter can be used as the particle diameter d of the spray particles.

2 and 4 are SEM images of the cross sections of the spray particles shown in FIGS. 1 and 3, respectively. The thermal spray material disclosed herein is composed of discrete thermal spray particles that are composed of a homogeneous matrix. As a matter of course, not only the surface of the spray particles but also the inside thereof are constituted by a dense and homogeneous matrix. That is, not only is the surface morphology smooth, but the internal texture (eg, cross-sectional texture) can be homogeneous as well, as shown in these FIGS. 2 and 4. In the examples of FIGS. 2 and 4, the presence of a small number of pores inside the molten particles is recognized, but the morphology of the fine particles constituting the particles is not seen throughout the molten particles, and It can be seen that is composed of one homogeneous matrix.
The spray particles of such a form are produced by sufficiently melting the starting material of the yttrium fluoride and/or the yttrium oxyfluoride constituting the particles, and cooling and solidifying the melt in an independent state. can do. At this time, it is important to sufficiently melt the starting material and homogenize the structure so that the spray particles are composed of a homogeneous matrix.

As the starting material for this thermal spray material, various materials that can realize the desired composition by heating and melting can be used without particular limitation. As the starting material, for example, a compound or salt containing yttrium (Y), oxygen (O), and fluorine (F) is used so that the element (Y, O, F) can realize the composition of the target thermal spray material. Mixtures formulated in stoichiometric composition can be used. For example, specifically, at least one of yttrium oxide (Y ₂ O ₃ ), yttrium fluoride (YF ₃ ) and yttrium oxyfluoride is used in a stoichiometric amount so as to obtain yttrium oxyfluoride having a desired composition. The starting material may be a mixture that is mixed in the theoretical composition. For example, specifically, yttrium oxide (Y ₂ O ₃ ) and yttrium fluoride (YF ₃ ) are mixed in a predetermined stoichiometric composition to obtain a starting material of yttrium oxyfluoride having a desired composition. be able to. Further, for example, as a starting material, yttrium fluoride and/or yttrium oxyfluoride having a desired composition can be used as it is or as a mixture. This starting material is melted under the conditions that can achieve the desired composition and then cooled. Yttrium fluoride and yttrium oxyfluoride are easily oxidized. In particular, yttrium oxyfluoride has compounds of various compositions, but all of them are unstable and easily oxidized. Therefore, in order to obtain the yttrium fluoride and/or the yttrium oxyfluoride having the desired composition, it is preferable to heat in an inert atmosphere. As the inert atmosphere, an atmosphere of nitrogen or a rare gas such as helium (He), neon (Ne), or argon (Ar) can be used. The heating temperature is exemplified to be a temperature close to the melting point (Tm) of yttrium fluoride and/or yttrium oxyfluoride having a target composition (for example, about Tm±100° C.). In order to obtain a thermal spray material composed of spherical spray particles having good fluidity, it is preferable to melt and cool the starting material distributed in droplets by a method such as spray drying. The cooled thermal spray material may be used as it is as a thermal spray material, or may be used as a thermal spray material through means such as pulverization, classification, and crushing so as to have an appropriate average particle diameter. If pulverization is performed, impurities may be mixed into the thermal spray material from the pulverizer. From this point, it is preferable to use the spray dry method even when obtaining a thermal spray material composed of non-spherical thermal spray particles other than spherical. As a result, the thermal spray material disclosed herein can be suitably obtained.

A thermal spray coating can be formed by thermal spraying the thermal spray material disclosed herein. By being provided on the surface of the base material, this thermal spray coating can impart environmental barrier properties (typically, plasma erosion resistance) to the base material. The base material to be sprayed (material to be sprayed) is not particularly limited. For example, the material and shape of the base material are not particularly limited as long as the base material is made of a material that can have desired resistance when subjected to the thermal spraying of the thermal spray material. Examples of the material forming the base material include various metals or alloys. Specific examples include aluminum, aluminum alloys, iron, steel, copper, copper alloys, nickel, nickel alloys, gold, silver, bismuth, manganese, zinc, zinc alloys, and the like. Among them, among general-purpose metal materials, steels represented by various SUS materials (which may be so-called stainless steel) and the like having a relatively large thermal expansion coefficient, heat-resistant alloys represented by Inconel, Invar, Kovar, etc. Examples of the base material include a low expansion alloy typified by the above, a corrosion resistant alloy typified by Hastelloy, and an aluminum alloy typified by the 1000 series to 7000 series aluminum alloy useful as a lightweight structural material. The base material may be, for example, a member that constitutes a semiconductor device manufacturing apparatus and may be a member that is exposed to highly reactive oxygen gas plasma or halogen gas plasma.

As the thermal spraying method for thermal spraying the thermal spraying material, various known thermal spraying methods can be adopted. For example, preferably, a plasma spraying method, a high-speed flame spraying method, a flame spraying method, an explosive spraying method, an aerosol deposition method or the like is adopted.
The plasma spraying method is a thermal spraying method that uses a plasma flame as a thermal spraying heat source for softening or melting the thermal spraying material. When an arc is generated between the electrodes and the working gas is turned into plasma by the arc, the plasma flow is ejected from the nozzle as a high-temperature and high-speed plasma jet. The plasma spraying method generally includes a coating method in which a sprayed material is put into this plasma jet, heated and accelerated to be deposited on a substrate to obtain a sprayed coating. The plasma spraying method includes atmospheric plasma spraying (APS) performed in the atmosphere, low-pressure plasma spraying (LPS) performing spraying at a pressure lower than atmospheric pressure, and pressure higher than atmospheric pressure. It may be a mode such as high pressure plasma spraying in which plasma spraying is performed in a pressure vessel. According to such plasma spraying, for example, by melting and accelerating the spraying material with a plasma jet of about 5000° C. to 10000° C., the spraying material collides with the base material at a speed of about 300 m/s to 600 m/s. And can be deposited.

Further, as the high-speed flame spraying method, for example, an oxygen-supporting high-speed flame (HVOF) spraying method, a warm spray spraying method, an air-supporting (HVAF) high-speed flame spraying method, or the like can be considered.
The HVOF spraying method is a type of flame spraying method in which a combustion flame obtained by mixing fuel and oxygen and burning at high pressure is used as a heat source for spraying. By increasing the pressure in the combustion chamber, a high-speed (possibly supersonic) high-temperature gas flow is ejected from the nozzle despite the continuous combustion flame. The HVOF thermal spraying method generally includes a coating method in which a thermal spraying material is introduced into this gas flow, heated and accelerated to be deposited on a substrate to obtain a thermal sprayed coating. According to the HVOF thermal spraying method, for example, by supplying the thermal spraying material to a jet of a supersonic combustion flame at 2000° C. to 3000° C., the thermal spraying material is softened or melted to a high value of 500 m/s to 1000 m/s. It can be impinged and deposited on the substrate at a velocity. The fuel used in the high-velocity flame spraying may be a hydrocarbon gas fuel such as acetylene, ethylene, propane or propylene, or a liquid fuel such as kerosene or ethanol. Further, the higher the melting point of the thermal spray material, the higher the temperature of the supersonic combustion flame. From this viewpoint, it is preferable to use gas fuel.

Further, a so-called warm spray spraying method, which is an application of the above HVOF spraying method, may be employed. The warm spray spraying method is typically the HVOF spraying method described above, in which the temperature of the combustion flame is lowered by mixing the combustion flame with a cooling gas such as nitrogen having a temperature of about room temperature. This is a method of forming a thermal spray coating. The thermal spray material is not limited to a completely melted state, and for example, a partially melted state or a softened state below the melting point can be sprayed. According to this warm spray thermal spraying method, for example, by supplying the thermal spraying material to a jet of a supersonic combustion flame at 1000° C. to 2000° C., the thermal spraying material is softened or melted, and 500 m/s to 1000 m/s. Can be collided and deposited on the substrate at a high speed.

The HVAF thermal spraying method is a thermal spraying method in which air is used instead of oxygen as a combustion supporting gas in the above HVOF thermal spraying method. According to the HVAF spraying method, the spraying temperature can be lower than that of the HVOF spraying method. For example, as an example, by supplying the thermal spray material to a jet of a supersonic combustion flame at 1600° C. to 2000° C., the thermal spray material is softened or melted, so that the thermal spray particles have a high velocity of 500 m/s to 1000 m/s. Can be collided with the substrate and deposited.

The thermal spray material disclosed herein is a powder containing at least one of yttrium fluoride and oxyfluoride, but is composed of independent particles composed of a homogeneous matrix. Therefore, for example, this thermal spray material is not easily oxidized even when subjected to thermal spraying. Therefore, the thermal spray coating obtained by thermal spraying of this thermal spray material can be mainly composed of, for example, yttrium fluoride and oxyfluoride. For example, the main component may be yttrium fluoride or oxyfluoride. The oxyfluoride may have the same composition as the thermal spray material, or may be an oxyfluoride in which a part or the whole thereof is oxidized (a large proportion of oxygen). Here, the main component means that the component has the largest content among the components constituting the thermal spray coating. Specifically, for example, it means that the component accounts for 50% by mass or more of the entire thermal spray coating, preferably 75% by mass or more, for example 80% by mass or more. Yttrium oxyfluoride is excellent in plasma erosion resistance, particularly in erosion resistance to halogen-based plasma. Therefore, the thermal spray coating containing yttrium oxyfluoride as a main component can be extremely excellent in plasma erosion resistance.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to the examples.

(Example)
Powdery thermal spray materials having the compositions shown in Examples 1 to 11 of Table 1 below were prepared. Specifically, yttrium oxide (Y ₂ O ₃ ) and yttrium fluoride (YF ₃ ) were used as starting materials by mixing the yttrium oxide (Y ₂ O ₃ ) as it is or in a stoichiometric composition of the target compound. .. Then, this starting material was dispersed in an appropriate dispersion medium to prepare a spray liquid, and then sprayed by an ultrasonic sprayer or the like to form droplets containing the starting material. Such droplets were placed on an air stream, passed through a continuous furnace, dried, and then heated at a predetermined temperature in an Ar atmosphere for about 2 hours. This produced the thermal spray material of Examples 1-11.

During the production of the thermal spray materials of Examples 1 to 9, the heating temperature was set near the melting point temperature of the target compound. On the other hand, in manufacturing the thermal spray materials of Examples 10 to 11, the heating temperature was set to a temperature about 200° C. lower than the melting point of the target compound.

The details of the obtained thermal spray materials of Examples 1 to 11 are shown in Table 1.
In the column of “composition” in Table 1, the composition of the spray particles (target compound) constituting each spray material is shown.
In the "XRD main peak ratio" column in Table 1, the ratio of the heights of the main peaks of the crystal phases detected as a result of the X-ray diffraction analysis of each thermal spray material is shown as a percentage. In the column, “Y ₂ O ₃ ”is yttrium oxide, “YF ₃ ” is yttrium fluoride, and “YOF” is yttrium oxyfluoride whose chemical composition is represented by YOF (Y ₁ O ₁ F ₁ ). , “Y ₅ O ₄ F ₇ ”indicates that each phase of the yttrium oxyfluoride whose chemical composition is represented by Y ₅ O ₄ F ₇ has been identified.

For the XRD analysis, an X-ray diffraction analyzer (Ultima IV, manufactured by RIGAKU) was used, CuKα rays (voltage 20 kV, current 10 mA) were used as the X-ray source, the scanning range was 2θ=10° to 70°, and the scanning speed was : 10°/min, sampling width: 0.01°, divergence slit: 1°, divergence vertical limit slit: 10 mm, scattering slit: 1/6°, light receiving slit: 0.15 mm, offset angle: 0° went.
For reference, the main peak of each crystal phase is around 29.157° for Y ₂ O ₃ , around 27.881° for YF ₃ , and around 28.064° for YOF, and Y ₅ O ₄ F ₇ is detected near 28.114°.

In the "Sintering temperature" column in Table 1, the heating temperature at the time of manufacturing the thermal spray material of each example is shown.
In the column of "Average particle size" in Table 1, the results of measuring the average particle size of each thermal spray material are shown. The "particle size distribution width" column, the D ₃ particle size and D ₉₇ results of the particle size was measured for the thermal spraying material, a particle size distribution width represented by D ₃ particles size value to D ₉₇ particle size value Indicated.
In the "Specific surface area" column of Table 1, the result of measuring the specific surface area of each thermal spray material based on the BET method is shown.
In the "Circularity" column in Table 1, the results of measuring the average circularity of each thermal spray material are shown.
The "breaking strength" column in Table 1 shows the results of measuring the breaking strength of each thermal spray material.
In the column of "cumulative pore volume" in Table 1, the results of measuring the cumulative pore volume in which the pore diameter of each thermal spray material is 3 μm or less are shown.
The column of "Particle morphology" in Table 1 shows the morphology of the spray particles when each spray material was observed by SEM. For reference, SEM images of the spray particles of Example 2 are shown in FIGS. 1 and 2, SEM images of the spray particles of Example 3 are shown in FIGS. 3 and 4, and SEM images of the spray particles of Example 10 are shown in FIG.

Next, plasma spraying was performed using the thermal spraying materials of Examples 1 to 11 prepared above, the supply properties of the thermal spraying material at the time of thermal spraying, and the characteristics of the thermal spray coating formed by thermal spraying were examined, and the results are shown in Table 2. Indicated. The thermal spraying conditions were as follows.
That is, first, a plate material (70 mm x 50 mm x 2.3 mm) made of an aluminum alloy (Al6061) was prepared as a base material which was a material to be sprayed, and was subjected to a blasting treatment with a brown alumina abrasive (A#40). Using. The plasma spraying was performed using a commercially available plasma spraying device (SG-100, manufactured by Praxair Surface Technologies). As plasma generation conditions, argon gas of 50 psi (0.34 MPa) and helium gas of 50 psi (0.34 MPa) were used as plasma working gas, and plasma was generated under the conditions of a voltage of 37.0 V and a current of 900 A. A powder feeder (Model 1264, manufactured by Praxair Surface Technologies) was used to supply the thermal spray material to the thermal spray apparatus, and the thermal spray material was supplied to the thermal spray apparatus at a rate of 20 g/min to obtain a thermal spray having a thickness of 200 μm. A film was formed. The moving speed of the spray gun was 24 m/min, and the spray distance was 90 mm.

The column "Supplyability" in Table 2 shows the supplyability when each thermal spray material was supplied to the thermal spraying apparatus. The evaluation result “⊚” indicates that the thermal spray material could be supplied to the thermal spray flame at a constant flow rate during the thermal spraying without being clogged in the powder feeder and the thermal spray apparatus. “Δ” indicates that during spraying, pulsation and unevenness were confirmed in the transport of the sprayed powder in the powder feeder and the spraying device. The evaluation result "x" indicates the case where the thermal spray material could not be sprayed because the thermal spray material was clogged in the powder feeder and the thermal spray device, but no thermal spray material was evaluated as x in the present embodiment.
The column "Porosity" in Table 2 shows the results of measuring the porosity of the obtained thermal spray coating.

The porosity of the thermal spray coating was measured by the following procedure. That is, a 2000-fold plan view image obtained by observing an arbitrary cross-sectional structure of the thermal spray coating with SEM (Hitachi High-Technologies Corporation, S-3000N) was analyzed by image analysis software (MUNTECH Co., Ltd., Mac. -View) was used to perform binarization to separate the pore portion and the solid phase portion, and by analyzing this, the ratio of the area of the pore portion in the cross section of the thermal spray coating was calculated. As the analysis image, it is preferable to use an image having a resolution such that the thickness of the sprayed coating is 30 pixels or more.

In the "plasma erosion resistance" column in Table 2, the rate at which the thermal spray coating was etched was calculated based on the amount of reduction in the thickness of the thermal spray coating when the following plasma exposure test was performed on the obtained thermal spray coating. The calculated results are shown.
In the column of "plasma erosion resistance" in Table 2, "◎ (excellent)" when the plasma erosion resistance is less than 40 nm/min, "○ (good)" when 40 nm/min or more and less than 50 nm/min. , And the case of 50 nm/min or more was shown as “× (defective)”.

<Plasma exposure test>
The plasma exposure of the thermal spray coating was performed as follows. That is, first, a 20 mm×20 mm sprayed coating was formed on the substrate as described above, the surface was mirror-polished until the thickness became 2 mm, and then the four corners of the sprayed coating were masked with masking tape to give a test piece. I prepared. Then, this test piece was placed on a silicon wafer having a diameter of 300 mm installed on a stage in a chamber of a parallel plate type semiconductor device manufacturing apparatus (ULVAC, NLD-800). Then, under the conditions shown in Table 3 below, fluorine-based plasma and chlorine-based plasma were alternately and repeatedly generated in a predetermined cycle to plasma-etch the central portion of the silicon wafer and the sprayed coating. The plasma exposure time was set to 0.9 hours including the interval (cooling time). Then, the etching rate of the thermal spray coating was calculated from the amount of decrease in the thickness of the thermal spray coating. The amount of decrease in the thickness of the sprayed coating was determined by measuring the level difference between the masked portion and the plasma exposed surface with a surface roughness measuring device (SV-3000CNC manufactured by Mitutoyo).

As shown in the results of the XRD main peak ratio shown in Table 1, it was confirmed that, as the thermal spraying materials of Examples 1 to 11, thermal spraying materials having the target stoichiometric composition were obtained. In particular, it was confirmed that each thermal spray material does not contain Y ₂ O _{3 and} has a single phase of Y ₅ O ₄ F ₇ , YOF or YF ₃ .

As a result of SEM observation, it was confirmed that the thermal spray materials of Examples 1 to 9 were composed of independent particles, and each particle had a smooth surface and was composed of a homogeneous matrix. These thermal spray materials are manufactured by sufficiently heating them to near the melting point temperature of the materials constituting the thermal spray material. Therefore, the starting material is sufficiently melted, and as shown in, for example, FIG. 1 (Example 2) and FIG. 3 (Example 3), the morphology of the original raw material powder is completely lost to form a single particle. It was confirmed that Therefore, the term "molten powder" is used in the column of particle morphology in Table 1. It was also confirmed that the raw material powder was completely melted, for example, by observing the cross section of the spray particles. That is, as shown in FIG. 2 and FIG. 4, the thermal spray particles of Examples 2 and 3 completely lost the morphology of the raw material powder even in the inside thereof, and the entire particles had a uniform structure, It was confirmed that it was composed of various matrices.

On the other hand, as shown in Table 1, the thermal spray materials of Examples 10 and 11 were produced by heating to a temperature lower than the melting point of the material constituting the thermal spray material (for example, 1000° C. or less). Therefore, as a result of SEM observation, it was confirmed that the thermal spray materials of Example 10 and Example 11 were in the form of granular particles (or composite particles) in which a large number of particles were bonded. Therefore, in the column of the particle morphology in Table 1, "granule" is used. For example, as shown in FIG. 5, in the sprayed particles of Example 10, the morphology of the raw material powder was mostly left, and irregularities based on the particle diameter of the raw material particles were clearly confirmed on the surface of the particles. Thus, it was confirmed that the particles formed without being sufficiently melted had an inhomogeneous structure.

Further, the thermal spray materials of Examples 1 to 9 formed by being completely melted have an average particle diameter of 15 μm or more, and each has a small specific surface property of less than 0.1 m ² /g, and has a cumulative pore size. The volume is 0.01 cm ³ /g or less, and although the circularity is not 1, it can be said that the particle surface is extremely smooth. It can be said that this is the first mode that is realized by sufficiently melting the molten material.

It was confirmed that the thermal spray coating formed from such a thermal spray material is relatively dense and has high resistance to etching by fluorine plasma and chlorine plasma. The thermal spray materials of Examples 6 to 9 are all composed of thermal spray particles having a composition of YF ₃ and are controlled so that the average particle diameters thereof are different from each other. It has been found that in the thermal spray coating formed from these thermal spray materials, the smaller the average particle diameter of the thermal spray material is, for example, about 15 to 25 μm, the denser thermal spray coating is formed and the plasma erosion resistance is also excellent. This is in agreement with the conventional knowledge that a denser spray coating can be formed as the particle diameter of the spray particles is smaller.

On the other hand, the thermal spray materials of Example 6 and Example 11 are both powders having an average particle diameter of 30 μm and composed of thermal spray particles having a composition of YF ₃ . These thermal spray materials differ in that the thermal spray material of Example 6 is in the form of molten powder, whereas the thermal spray material of Example 11 is in the form of granules. Although the thermal spray coatings formed from these thermal spray materials all have a porosity of 5%, the thermal spray coating of Example 6 has extremely high plasma erosion resistance as compared with the thermal spray coating of Example 11. It is considered that this is because YF ₃ was oxidized to Y ₂ O ₃ during thermal spraying because the thermal spray particles of Example 11 were in the form of granules, and a thermal spray coating vulnerable to plasma was formed. Be done.

On the other hand, the thermal spray materials of Examples 2, 3 and 5 are all composed of thermal spray particles having a composition of Y ₅ O ₄ F ₇ and are controlled so that the average particle diameters thereof are different from each other. It has been found that in the thermal spray coating formed from these thermal spray materials, the larger the average particle diameter of the thermal spray material is, for example, about 40 to 50 μm, the denser thermal spray coating is formed and the plasma erosion resistance is also excellent. That is, in the thermal spraying technique, it was a result contrary to the conventional knowledge that a denser thermal spray coating can be formed by using the thermal spray particles having a smaller particle size. Although the reason for this is not certain, yttrium oxyfluoride typified by Y ₅ O ₄ F ₇ is very likely to be oxidized during thermal spraying, and fluorine is easily released as a gas. Therefore, it is considered that the thermal spraying material having a relatively coarse particle size is less likely to be oxidized during thermal spraying, has less change in composition when the thermal spray coating is formed, and contributes to the improvement of plasma erosion resistance.

As described above, the spray particles of yttrium fluoride or yttrium oxyfluoride have high plasma erosion resistance, but are easily oxidized and deteriorated during spraying. Therefore, as disclosed herein, the thermal spray material composed of yttrium fluoride or yttrium oxyfluoride is in the form of a molten powder that is sufficiently melted, so that the plasma erosion resistance utilizing the properties of the thermal spray material is utilized. It is preferable because a sprayed coating having high property can be formed.
Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (5)

A powder in which the content of any one of YF ₃ , YOF and Y ₅ O ₄ F ₇ is substantially 100% by mass ,
The powder is composed of independent particles consisting of a matrix,
The thermal spray material, wherein the cumulative pore volume having a pore diameter of 3 μm or less is 0.02 cm ³ /g or less. The thermal spray material according to claim 1, wherein the specific surface area measured based on the BET method is less than 0.1 m ² /g. The thermal spray material according to claim 1 or 2, wherein substantially 100% by mass of the powder is composed of any one of YF ₃ , YOF and Y ₅ O ₄ F ₇ . The thermal spray material according to claim 1, wherein the average particle diameter is 60 μm or less. The average circularity is 1 less than 0.5 or more, the spray material according to any one of claims 1-4.