Patent ID: 12203161

DETAILED DESCRIPTION

The structure of a component that forms the basis of a component for a plasma processing apparatus according to one or more embodiments of the present disclosure will be described. A plasma processing apparatus may include components to have high plasma resistance. Such a component may include a substrate and a film of yttrium oxide on the substrate.

As an example of such components for a plasma processing apparatus, Patent Literature 1 describes a component to be placed in a plasma processing compartment. The component includes a substrate with its surface coated with a Y2O3film having a purity of 95% or greater by mass formed by thermal spraying.

However, the Y2O3film with high purity formed by thermal spraying can have numeral pores per unit area. The film is to maintain high strength of bonding to the substrate over a long time for use in an environment involving repeated temperature rises and falls.

A component for a plasma processing apparatus according to one or more embodiments of the present disclosure will now be described in detail with reference to the drawings.

As shown inFIGS.1A to1C, a component10for a plasma processing apparatus according to one or more embodiments of the present disclosure includes a substrate5and a film3of an oxide, an fluoride, an oxyfluoride, or a nitride of a rare earth element formed on at least a part of the substrate5. In an example shown inFIG.1B, the substrate5has an upper surface5acoated with the film3. In another example shown inFIG.1C, the film3includes a first layer (lower layer)1located on the substrate5and a second layer (upper layer)2located on the first layer (lower layer)1. The ratio t1:t2of the thickness t1of the first layer1to the thickness t2of the second layer2is, for example, 4:6 to 6:4.

For the component10for a plasma processing apparatus, the surface of the film3to be exposed to plasma has a compressive stress σ11to occur across the surface and a compressive stress σ22to occur across the surface in the direction perpendicular to the compressive stress σ11. The ratio of σ22/σ11is 5 or less.

At the ratio of σ22/σ11within the above range, shrinkage and expansion across the surface cause no anisotropy in use in an environment involving repeated temperature rises and falls. This structure allows a longer period of use.

In particular, the ratio of σ22/σ11may be 0.1 to 1.5 inclusive, or 1.1 to 1.4 inclusive.

The arithmetic mean of the compressive stress σ11and the compressive stress σ22may be 200 to 1000 MPa inclusive. The film3having the arithmetic mean of 200 MPa or greater maintains hardness and thus can release fewer particles upon receiving impact from floating particles in a plasma processing apparatus. Thus, the plasma processing apparatus is less likely to be contaminated with such particles. The film3having the arithmetic mean of 1000 MPa or less withstands internal tensile stress occurring in the above environment. Thus, the film is less likely to break.

The coefficient of variation of each of the compressive stress σ11and the compressive stress σ22may be 0.5 or less. The film3having the coefficient of variation of 0.5 or less is less likely to detach from the substrate2, with less local strain occurring during use in the above environment.

In particular, the coefficient of variation may be 0.3 or less.

The values of the compressive stress σ11and the compressive stress σ22may be measured with a two-dimensional (2D) method using an X-ray diffractometer. The resulting values may be used to calculate the ratio of σ22/σ11, the arithmetic mean, and the coefficient of variation.

The surface of the film3to be exposed to plasma (the upper surface inFIGS.1B and1C, hereafter simply referred to as the surface) has an arithmetic mean roughness Ra of 0.01 to 0.1 μm inclusive. The surface also has multiple pores4.

FIG.1Ashows the structure with multiple pores4a,4b, . . . . The surface of the film3includes a surface portion newly exposed in response to the film being thinner after plasma exposure. The film3internally has multiple closed pores6.

The arithmetic mean roughness Ra may be measured in accordance with JIS B 0601-2013. More specifically, the arithmetic mean roughness Ra may be measured with a surface roughness measuring instrument (Surfcorder) SE500 (Kosaka Laboratory Ltd.), with the probe radius of 5 μm, the measurement length of 2.5 mm, and the cutoff value of 0.8 mm.

InFIGS.1B and1C, the film3is shown clearly for ease of explanation, but does not show the exact correlation between the thicknesses of the substrate5and the film3.

The film3is a film of an oxide, a fluoride, an oxyfluoride, or a nitride of a rare earth element (hereafter, an oxide, a fluoride, an oxyfluoride, and a nitride are collectively referred to as compounds). Examples of the rare earth element include yttrium (Y), cerium (Ce), samarium (Sm), gadolinium (Gd), dysprosium (Dy), erbium (Er), and ytterbium (Yb). The rare earth element being yttrium has high corrosion resistance and is less expensive than other rare earth elements, and is thus cost effective.

The composition of yttrium compound has the chemical formula Y2O3−x(0≤x≤1), YF3, YOF, Y5O4F7, Y5O6F7, Y6O5F8, Y7O6F9, Y17O14F23, or YN. The elements of the film3may be identified with a thin film X-ray diffractometer.

The film3may contain, in addition to a compound of a rare earth element, other elements such as fluorine (F), sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (CO, potassium (K), calcium (Ca), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and strontium (Sr), depending on the purity of a target used to form the film3and the configuration of a device used.

The substrate5may be formed from, for example, quartz, a translucent ceramic material, aluminum having a purity of 99.999% (5N) or greater, an aluminum alloy such as aluminum 6061 alloy, an aluminum nitride ceramic material, or an aluminum oxide ceramic material. An aluminum oxide ceramic material has an aluminum oxide content of 90% or greater by mass of the total mass (100%) of the elements contained in the substrate5. The content of aluminum oxide is the value obtained by converting Al to Al2O3. The same applies to an aluminum nitride ceramic material.

The aluminum oxide ceramic material may contain magnesium oxide, calcium oxide, silicon oxide, and other elements in addition to aluminum oxide. The substrate5formed from quartz or a translucent ceramic material has a content of 0.01 ppm or less by mass of each of lithium (Li), K, Na, Cr, Fe, Co, Ni, and Cu. The translucent ceramic material mainly contains, for example, aluminum oxide or yttrium aluminum complex oxide.

The film3has multiple pores4, for which a value A resulting from subtracting an average of circular equivalent diameters of the pores4from an average of distances between the centroids of neighboring pores4is 28 to 48 μm inclusive.

The value A being 28 to 48 μm inclusive indicates fewer, smaller pores4being dispersed. The component10for a plasma processing apparatus with the above structure thus produces fewer particle inside the pores4. In addition, the pores4are dispersed enough to prevent microcracks originating from any pores4nearby from extending, thus causing fewer particles from extended microcracks.

In the component10for a plasma processing apparatus according to one or more embodiments of the present disclosure, the film3may have multiple pores4constituting 1.5 to 6% inclusive of its total area. The pores4constituting 1.5 to 6% inclusive of the total area can prevent extension of any microcracks on the surface exposed to plasma (including a surface newly exposed in response to the film being thinner after plasma exposure), thus allowing the film3to have fewer particles resulting from microcracks. The area ratio of pores4on the surface exposed to plasma is low, with fewer particles produced inside the pores4.

In the component10for a plasma processing apparatus according to one or more embodiments of the present disclosure, the film3may have the pores4with an average sphericity of 60% or greater. With the sphericity of the pores4within this range, residual stress is less likely to accumulate around the pores4. The film3exposed to plasma is thus less likely to have particles around the pores4.

The sphericity of the pores4herein refers to the ratio defined by a graphite area method and is defined by Formula 1 below.
Sphericity of a pore (%)={(actual area of the pore)/(area of the smallest circumscribed circle of the pore)}×100  (1)

In particular, the average sphericity of the pores4may be 62% or greater.

The average of distances between the centroids of the pores4, the average of circular equivalent diameters of the pores4, the area ratio, and the sphericity can be determined as described below.

First, the surface of the film3is observed with a digital microscope at a magnification of 100×. For example, an observation image captured with a charge-coupled device (CCD) camera across an area of 7.68 mm2(with a lateral length of 3.2 mm and a vertical length of 2.4 mm) is analyzed. The average of distances between the centroids of the pores4can be obtained through dispersion measurement with image analysis software A-Zou Kun (ver. 2.52) (registered trademark, Asahi Kasei Engineering Corporation).

Using the same observation image as described above, the average of the circular equivalent diameters of the pores4, the area ratio, and the sphericity can be obtained through particle analysis with the image analysis software A-Zou Kun.

The setting conditions for dispersion measurement and particle analysis may include the threshold indicating the brightness of an image set to 140, the brightness set to dark, the small object removal area set to 1 μm2, and the noise reduction filter set to use. Although the threshold is set to 140 in the above measurement setting, the threshold may be adjusted depending on the brightness of the observation image. With the brightness set to dark, the binarization method set to manual, the small object removal area set to 1 μm2, and the noise reduction filter set to use, the threshold may be adjusted to cause the marked areas on the observation image to match the shapes of the pores4.

In the component10for a plasma processing apparatus according to one or more embodiments of the present disclosure, the kurtosis Ku of circular equivalent diameters of the pores4on the film3may be 0.5 to 2 inclusive. When the kurtosis Ku of circular equivalent diameters of the pores4is within this range, the distribution of circular equivalent diameters of the pores4is narrower, and fewer pores4have abnormally large circular equivalent diameters. This reduces microcrack extension, produces fewer particles inside the pores4, and increases plasma resistance. After deposition, the film3with the above structure may be polished with less uneven abrasion and can have intended surface profiles with minimum polishing. In particular, the kurtosis Ku may be 1.3 to 1.9 inclusive.

Kurtosis Ku is an indicator (statistic) of differences in the peak and tails of a distribution from those of a normal distribution. The kurtosis Ku being Ku>0 indicates that the distribution has a sharper peak with longer and wider tails, Ku=0 indicates a normal distribution, and Ku<0 indicates a distribution having a rounded peak with shorter and narrower tails. The kurtosis Ku of the circular equivalent diameters of the pores4can be obtained using the function Kurt available with Excel (registered trademark, Microsoft Corporation).

In the component10for a plasma processing apparatus according to one or more embodiments of the present disclosure, the skewness Sk of circular equivalent diameters of the pores4on the film3may be 3 to 5.6 inclusive. When the skewness Sk of circular equivalent diameters of the pores4is within this range, the average of circular equivalent diameters of the pores4is smaller, and fewer pores4have abnormally large circular equivalent diameters. This reduces microcrack extension, produces fewer particles inside the pores4, and increases plasma resistance. After deposition, the film3with the above structure may be polished with less uneven abrasion and can have intended surface profiles with minimum polishing. In particular, the skewness Sk may be 3.2 to 5.3 inclusive.

Skewness Sk is an indicator (statistic) of the degree of a skewed distribution from a normal distribution, or the symmetry of the distribution. The skewness Sk being Sk>0 indicates the tail of the distribution extending to the right, and Sk=0 indicates a symmetrical distribution, and Sk<0 indicates the tail of the distribution extending to the left. The Skewness Sk of circular equivalent diameters of the pores can be obtained using the function SKEW available with Excel (registered trademark, Microsoft Corporation).

The relative density of the film may be 98% or greater, or more specifically, 99% or greater. The film3with the relative density within this range is dense and produces fewer particles when being exposed to plasma and becoming thinner. The relative density of the film3may be determined by obtaining its actual density with X-ray reflectometry (XRR) using a thin-film X-ray diffractometer and calculating the ratio of the actual density to the theoretical density.

The film3includes voids8extending in the thickness direction from recesses7on the surface of the substrate5facing the film3. The voids8may have closed tips inside the film3. The recesses7are either pores or void areas on the surface of the substrate5facing the film3. The recesses7are on surface of the substrate5before the film3is formed.

The film3with the voids8can undergo repeated temperature rises and falls with less residual stress accumulating. The voids8are not connected to the outside and thus have particles in the voids8without being out of the film3.

In the thickness direction of the film3in a cross section, each void8may be narrower in its part nearer the surface of the film3than in its part nearer the recess7on the substrate5. Compared with a void8wider in its part nearer the surface of the film3than in its part nearer the recess7on the substrate5, this structure can cause fewer particles in the voids8to be out of the film3, although any voids8are open at their tips after the film3is exposed to plasma and becomes thinner.

The substrate5may be formed from quartz or a translucent ceramic material. The substrate5and the film3may transmit visible light with a transmittance of 75 to 92% inclusive.

When the component for a plasma processing apparatus is a window component installable in a processing chamber, the visible light transmittance of 75% or greater provides improved visibility into the processing chamber, thus allowing observation of the state inside the processing chamber. This structure allows immediate response to any abnormal behavior in the processing chamber. The visible light transmittance of 92% or less reduces luster that can be proportional to visible light transmittance, thus providing high antiglare properties.

The wavelength of visible light in one or more embodiments of the present disclosure ranges from 380 to 780 nm.

The substrate5and the film3in one or more embodiments of the present disclosure may transmit near-infrared light with a transmittance of 80 to 92% inclusive.

When the component for a plasma processing apparatus is used as the above window component with the near-infrared light transmittance of 80% or greater, the manufacturing efficiency can be improved, for example, in forming a thin film on a substrate such as a semiconductor wafer by applying an infrared laser beam onto a target (a source material of the film) in the processing chamber through the window component. In contrast, the component with the near-infrared light transmittance of 92% or less can prevent malfunctions of components installed in the processing chamber and susceptible to infrared light.

The wavelength of near-infrared light in one or more embodiments of the present disclosure ranges from 780 to 2500 nm.

The transmittance of visible light and that of the near-infrared light through the substrate5and the film3may be measured using a Fourier transform infrared spectrophotometer (FTIR) such as IRPrestige-21 (Shimadzu Corporation).

The measurement is performed under the conditions below.Resolution: 4 cm−1Number of integrations: 50 timesMode: Transmission methodDetector: DLATGS detectorBackground atmosphere: Air

A method for manufacturing the component for a plasma processing apparatus according to one or more embodiments of the present disclosure will now be described.

A method for manufacturing the substrate will be described first.

An aluminum oxide (Al2O3) powder A with a mean particle size of 0.4 to 0.6 μm and an aluminum oxide powder B with a mean particle size of about 1.2 to 1.8 μm are prepared. A silicon oxide (SiO2) powder as a Si source and a calcium carbonate (CaCO3) powder as a Ca source are prepared. The silicon oxide powder is a fine powder with a mean particle size of 0.5 μm or smaller. To obtain an alumina ceramic material containing Mg, a magnesium hydroxide powder is used. Hereafter, powders other than the aluminum oxide powder A and the aluminum oxide powder B are collectively referred to as first subelement powders.

A predetermined amount of each first subelement powder is weighed out. Subsequently, the aluminum oxide powder A and the aluminum oxide powder B are weighed to have a mass ratio of 40:60 to 60:40 to obtain an aluminum oxide powder mixture. The mixture is prepared to form an alumina ceramic material with an Al2O3(converted from Al) content of 99.4% or greater by mass of the total mass (100%) of the elements contained in the alumina ceramic material. To prepare the first subelement powders, the amount of Na in the aluminum oxide powder mixture may be determined first. The amount of Na is then converted to Na2O to form an alumina ceramic material. The first subelement powders are weighed to have the ratio of 1.1 or less as the ratio of the converted Na2O value to a value of oxides from converting the elements contained in the first subelement powders (in this example, Si and Ca) to oxides.

With respect to 100 parts by mass in total of the alumina powder mixture and the first subelement powders, 1 to 1.5 parts by mass of a binder such as polyvinyl alcohol (PVA), 100 parts by mass of a solvent, and 0.1 to 0.55 parts by mass of a dispersant are placed into a stirrer together with the alumina powder mixture and the first subelement powders. These are then mixed and stirred to obtain slurry.

The slurry is spray-granulated, and the resulting granules are molded with, for example, a powder press molding device or a hydrostatic press molding device into a predetermined shape, which is cut as appropriate into a plate-like molded body.

The resulting molded body is then fired at a firing temperature of 1500 to 1700° C. inclusive for 4 to 6 hours inclusive. The surface of the resultant body on which the film is to be formed is then polished with diamond abrasive grains having a mean grain size of 1 to 5 μm inclusive and an abrasive disc of tin. This completes the substrate.

A method for forming the film will now be described with reference toFIG.2.FIG.2is a schematic diagram of a sputtering apparatus20. The sputtering apparatus20includes a chamber15, a gas supply source13connected to the chamber15, an anode14and a cathode12located in the chamber15, and a target11connected adjacent to the cathode12.

To form the film, the substrate5obtained by the method described above is placed adjacent to the anode14in the chamber15. At the opposite position in the chamber15, the target11formed mainly from a rare earth element, yttrium metal in this example, is placed adjacent to the cathode12. The chamber15is then decompressed using a vacuum pump, and argon and oxygen are supplied as gas G from the gas supply source13. The pressure of the argon gas to be supplied is 0.1 to 2 Pa inclusive, and the pressure of the oxygen gas is 1 to 5 Pa inclusive.

The component for a plasma processing apparatus having the arithmetic mean of the compressive stress σ11and the compressive stress σ22of 200 to 1000 MPa inclusive may be obtained by using argon gas supplied at a pressure of 0.1 to 1 Pa inclusive and oxygen gas at a pressure of 1 to 5 Pa inclusive.

The component for a plasma processing apparatus with the coefficient of variation of each of the compressive stress σ11and the compressive stress σ22being 0.5 or less may be obtained by using argon gas supplied at a pressure of 0.1 to 0.5 Pa inclusive and oxygen gas at a pressure of 1 to 5 Pa inclusive.

An electric field is then applied between the anode14and the cathode12from a power supply to generate plasma P, and a metal yttrium film is deposited on the surface of the substrate5by sputtering. A film with a thickness of subnanometers forms per deposition. The metal yttrium film is then oxidized. Through repeated deposition and oxidation of the metal yttrium film, the film forms with a total thickness of 10 to 200 μm inclusive. The resultant component for a plasma processing apparatus according to one or more embodiments of the present disclosure includes a film of yttrium oxide.

The component for a plasma processing apparatus having the pores with the area ratio of 1.5 to 6% inclusive may be obtained with a substrate having pores with an area ratio of 1 to 5% inclusive in the surface facing the film.

The component for a plasma processing apparatus having the pores with the average sphericity of 60% or greater may be obtained with a substrate having pores with an average sphericity of 62% or greater in the surface facing the film.

The component for a plasma processing apparatus having the pores with the kurtosis Ku of circular equivalent diameters of 0.5 to 2 inclusive may be obtained with a substrate having pores with a kurtosis Ku of circular equivalent diameters of 0.6 to 1.8 inclusive in the surface facing the film.

The component for a plasma processing apparatus having the pores with the skewness Sk of circular equivalent diameters of 3 to 5.6 inclusive may be obtained with a substrate having pores with a skewness Sk of circular equivalent diameters of 3.1 to 5.4 inclusive in the surface facing the film.

The component for a plasma processing apparatus having the voids with closed tips inside the film is obtained by first forming an yttrium oxide film, or a first layer, on a substrate with the procedure described above. The substrate with the first layer is then removed from a chamber, and the film surface of the first layer undergoes smoothing. The smoothing includes polishing of the film surface of the first layer with diamond abrasive grains having a mean grain size of 1 to 5 μm inclusive and an abrasive disc of tin to obtain a processed surface (polished surface).

The component for a plasma processing apparatus having the voids extending in the thickness direction from the recesses on the surface of the substrate facing the film and with closed tips inside the film may be obtained by preparing a substrate with pores with an average diameter of 1 to 8 μm inclusive in the surface facing the film and polishing the film surface of the first layer1to have the average diameter of pores of 0.1 to 5 μm inclusive.

When the sputtering apparatus20forms a film on a substrate having pores with an average diameter of 1 to 8 μm inclusive in the surface facing the film, each void is narrower in its part nearer the film surface than in its part nearer the recess on the substrate in the thickness direction of the film in a cross section. The film surface of the first layer is polished to have the average diameter of pores of 0.1 to 5 μm inclusive, and the second layer (described below) is formed to have the closed voids inside the film.

The second layer having yttrium oxide as a main component is formed on the processed surface of the first layer with the same procedure as for the first layer. This completes the component for a plasma processing apparatus.

The component for a plasma processing apparatus with the substrate and the film with the transmittance of visible light of 75 to 92% inclusive may be obtained with a substrate having the transmittance of visible light of 87 to 99% inclusive.

The component for a plasma processing apparatus with the substrate and the film having the transmittance of near-infrared light of 80 to 92% inclusive may be obtained with a substrate having the transmittance of near-infrared light of 83 to 95% inclusive.

A film of yttrium fluoride may also be formed with the same process as described above except the oxidation being replaced by fluorination.

A film of yttrium oxyfluoride may be formed through repeated deposition, oxidation, and fluorination of a metal yttrium film in this order to form the film.

A film of yttrium nitride may be formed with the same process as described above except oxidation being replaced by nitridation.

The power supply may supply either radio frequency power or direct current power.

The component for a plasma processing apparatus according to one or more embodiments of the present disclosure produces fewer particles both inside the pores and from microcrack extension. The component may be a window component for transmitting radio frequency that generates plasma, a shower plate for distributing gas for generating plasma, or a susceptor for placement of a semiconductor wafer.

The component for a plasma processing apparatus according to one or more embodiments of the present disclosure has high strength of bonding to the substrate over a long period of time.

The plasma processing apparatus according to one or more embodiments of the present disclosure is highly reliable.

The present disclosure may be embodied in various forms without departing from the spirit or the main features of the present disclosure. The embodiments described above are thus merely illustrative in all respects. The scope of the present disclosure is defined not by the description given above but by the claims. Any modifications and alterations contained in the claims fall within the scope of the present disclosure.

REFERENCE SIGNS LIST

1first layer2second layer3film4pore5substrate6pore (closed pore)7recess8void10component for plasma processing apparatus11target12cathode13gas supply source14anode15chamber20sputtering apparatus