WO2007148931A1

WO2007148931A1 - Ceramic coating material for thermal spray on the parts of semiconductor processing devices and fabrication method and coating method thereof

Info

Publication number: WO2007148931A1
Application number: PCT/KR2007/003017
Authority: WO
Inventors: Hyun-Kwang Seok; Hae-Won Lee; Kyeong-Ho Baik
Original assignee: Korea Institute Of Science And Technology
Priority date: 2006-06-21
Filing date: 2007-06-21
Publication date: 2007-12-27

Abstract

A thermal spray coating material for use in semiconductor equipment, its preparation method, and a coating method thereof are disclosed. The coating material may have a composition of (A1xY1-x)2O3 (x is within a range of 0.05 to 0.95), and be formed as a powder with a diameter of lμm~100μm. A coating film that is coated by using the powder according to the thermal spray method has an amorphous structure.

Description

[DESCRIPTION] [Title]

CERAMIC COATING MATERIAL FOR THERMAL SPRAY ON THE PARTS OF SEMICONDUCTOR PROCESSING DEVICES AND FABRICATION METHOD AND COATING METHOD THEREOF [Technical Field]

The present invention relates to a thermal spray coating material for use on components of semiconductor fabricating equipment, a method for preparing the material, and a coating method thereof. [Background Art]

Vacuum plasma equipment is commonly used in a processing field for implementing a semiconductor device or other ultra-fine configurations. The vacuum plasma equipment includes, for example, PECVD (plasma enhanced chemical vapor deposition) equipment for forming a deposition film on a substrate through a chemical deposition method using plasma, sputtering equipment for forming a deposition film through a physical method, dry etching equipment for etching a substrate or a material coated on the substrate into a desired pattern, etc.

The vacuum plasma equipment etches a semiconductor device or implements an ultra-fine configuration by using plasma at a high temperature. Thus, because the high temperature plasma is generated within the vacuum plasma equipment, a chamber and internal components thereof are inevitably damaged. In addition, particular elements or contaminant particles are generated from surfaces of the chamber and the components, so there is a high possibility for the interior of the chamber to be contaminated.

Especially, in the case of the plasma etching equipment, a reactive gas containing F and Cl is injected under a plasma atmosphere, causing inner walls of the chamber and the internal components to be exposed to a severely corrosive environment. Such corrosion primarily damages the chamber and the internal components and secondarily generates contaminants and particles, causing an increase in a defect rate and degradation of products generated through a process within the chamber. [Disclosure]

[Technical Problem]

The present invention has been made in an effort to provide a coating material for use in a chamber and internal components of vacuum plasma processing equipment having advantages of improving corrosion resistance by reducing internal defects of a protective coating film in a ceramic thermal spray coating unit and lengthening life span of the components. The present invention provides a method for preparing a coating material for use in semiconductor equipment.

In addition, the present invention provides a method for coating components for use in semiconductor fabricating equipment by using the above-described coating material. [Technical Solution]

An exemplary embodiment of the present invention provides a thermal spray coating material used for semiconductor fabricating equipment, having a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95) and an amorphous structure.

Here, x may be within a range of 0.5 to 0.95.

The thermal spray coating material may include a powder with a diameter of lμm to lOOμm. Another embodiment of the present invention provides a method for preparing a thermal spray coating material for use in semiconductor fabricating equipment, including: i) preparing a material with a composition of (Al_xYi-X)₂O₃ (x is within a range of 0.05 to 0.95) by mixing AI2O3 particles and Y₂O₃ particles each with a diameter of 0.1 μm ~30μm; ii) spraying and drying the prepared material to obtain a synthesized powder; and iii) calcining the synthesized powder at 800⁰C to 1500°C.

Here, the mixing of the materials may include applying static electricity that induces the AI2O3 particles and Y2O3 particles to assume static electric charges, each with a different polarity.

In addition, the applying of static electricity may include: i) adding Darvan C (poly-methyl metacrylic ammonium salt) to a solvent to allow the AI2O3 particles to assume a negative static electric charge; and ii) adding PI (polyethylene imide) to a solvent to allow the Y2O3 particles to assume a positive static electric charge.

Yet another embodiment of the present invention provides a method for coating a thermal spray coating material for use in semiconductor fabricating equipment, including: i) preparing a thermal spray coating material with a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95); ii) injecting the thermal spray coating material into a plasma flame to heat the material; and iii) stacking the thermal spray coating material in a completely molten or semi-solid state according to the heating on a surface of a component used for the semiconductor fabricating equipment to form a coating film with an amorphous structure. Here, the forming of the coating film may include forming a metal intermediate layer.

In addition, the forming of the coating film may include forming a gradient coating film by sequentially differentiating the composition of the thermal spray coating material. In addition, the gradient coating film may be formed by using a gradient coating method in which the composition of the thermal spray coating material is sequentially changed from a composition that is the same as or similar to a coated base material with a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95) while the coating proceeds. In addition, in forming the coating film, the component may be a chamber of a vacuum plasma apparatus or a component within the chamber. [Advantageous Effects]

As described above, because the coating material according to the exemplary embodiment of the present invention is made of powder of AI2O3 or Y2O3, it can be commonly used as a material for a component of the semiconductor fabricating equipment and is advantageous in that it is not expensive. In addition, because the coating film has been used, its stability has been verified, and thus it does not cause any problem in other semiconductor processes.

When the spray coating film is formed on the base material by using the coating material according to the exemplary embodiment of the present invention, the coating film is formed with amorphous phases. Thus, the volume of the coating film is not much changed when the amorphous phases are changed to solid phases, so an internal defect of the coating film can be reduced.

In addition, the reduction in the internal defect leads to an improvement of the corrosion resistance in the corrosive environment while maintaining high mechanical strength of the coating film. Moreover, the coating film formed on the chamber of the vacuum plasma process equipment and the internal components by using the coating powder and the coating method according to the exemplary embodiment of the present invention can have high mechanical strength and corrosion resistance. Accordingly, the life span of the components can be lengthened, and because there is no need to frequently repair the fabrication device, the efficiency of the semiconductor fabrication can be improved.

Furthermore, because the rate of contaminant particles in the semiconductor fabricating process can be lowered, quality of the final products can be improved. [Description of Drawings]

FIG. 1 is a vertical-sectional view of plasma etching equipment, which is one example of semiconductor fabricating equipment.

FIG. 2 is a schematic sectional view of a plasma gun included in plasma spray equipment.

FIG. 3 is a SEM (scanning electron microscope) photograph of a section of a Y2O3 (yttria) coating film formed by using an external type of plasma gun.

FIG. 4 is a SEM photograph of a section of the Y2O3 (yttria) coating film formed by using an internal type of plasma gun.

FIG. 5 is a SEM photograph showing generation of cracks as molten ceramic particles in a liquid state are cooled.

FIG. 6 is a graph showing conditions in which crystallization occurs according to temperature over time as a material in a liquid state is cooled to be changed to a solid state.

FIG. 7 is a schematic view showing a process in which volume changes when the material in the liquid state is cooled to be changed to a solid state.

FIG. 8 is a schematic view showing a principle of formation of a defect occurring when a liquid phase is changed to a crystalline solid.

FIG. 9 is a graph showing conditions in which crystalline solid phases of materials are formed when the materials are cooled differently according to types of the materials.

FIG. 10 is a schematic view showing a process in which volume is contracted when a liquid material is cooled to be formed into an amorphous (glass) phase.

FIG. 11 is a schematic view showing a process in which formation of a defect such as a crack or the like is prevented when a liquid phase is formed as an amorphous (glass) phase. FIG. 12 is a schematic view showing a process in which heterogeneous powders are mixed to prepare a spray coating composite powder with a large particle size.

FIG. 13 is a SEM photograph of a thermal spray ceramic powder that is synthesized according to the exemplary embodiment of the present invention.

FIG. 14 is a graph showing an X-ray analysis result of pure AI2O3. (X=I)

FIG. 15 shows an X-ray analysis result of (AIxYi-X)₂O₃ (x = 0.9). (x=0.9)

FIG. 16 shows an X-ray analysis result of (Al_xYi-X)₂O₃ (x = 0.6). (x=0.6)

FIG. 17 shows an X-ray analysis result of (AlχYi_-x)₂θ3 (x = 0.1). (x=0.1) FIG. 18 shows an X-ray analysis result of pure Y2O3. (x⁼0)

FIG. 19 shows an X-ray analysis result of a coating film obtained by thermally spraying a powder of (Al_xYi_-x)2θ3 (x = 0.6) in an incompletely molten state. (x=0.6)

FIG. 20 is a low-magnification SEM photograph of an amorphous coating film made of an AI1.50Y0.44O3 material formed by spray coating. (X200)

FIG. 21 is a low-magnification SEM photograph of the amorphous coating film made of the AI1.50Y0.44O3 material formed by spray coating. (X650) FIG. 22 is a high-magnification TEM (transmission electron microscope) photograph of the amorphous coating film made of the AI1.56Y044O3 material formed by spray coating.

FIG. 23 is a low-magnification SEM photograph of an amorphous coating film made of an AI1.25Y0.75O3 material formed by spray coating. FIG. 24 is a low-magnification SEM photograph of an amorphous coating film made of the Ah.25Y0.75O3 material formed by an electrical mixture method.

FIG. 25 is a graph showing comparison results of hardness between Al₂O₃ and Y₂O₃ thermal spray coating films and the coating film according to the exemplary embodiment of the present invention.

FIG. 26 is a graph showing comparison results of scratch resistance between the Al₂O₃ and Y2O3 thermal spray coating films and the coating film according to the exemplary embodiment of the present invention. FIG. 27 is a graph showing comparison results of corrosion resistance with respect to hydrochloric acid (HCl) between the Y2O3 thermal spray coating film and the coating film according to the exemplary embodiment of the present invention.

FIG. 28 is a graph showing comparison results of resistance with respect to a corrosive environment (plasma) between the AI2O3 and Y2O3 thermal spray coating films and the coating film according to the exemplary embodiment of the present invention.

FIG. 29 is a graph showing X-ray analysis results of the coating film formed under the conditions of a fourth experimental example according to the exemplary embodiment of the present invention.

FIG. 30 is a graph showing X-ray analysis results of the coating film formed under the conditions of a fifth experimental example according to the exemplary embodiment of the present invention.

FIG. 31 is a graph showing X-ray analysis results of the coating film formed under the conditions of a sixth experimental example according to the exemplary embodiment of the present invention.

FIG. 32 is a SEM photograph of the coating film according to the exemplary embodiment of the present invention. FIG. 33 is a SEM photograph showing results obtained by etching the coating film for one hour under the conditions that SiO₂ is etched for 300nm/min.

[Best Mode] The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. A corrosion problem of a vacuum plasma chamber and its components will now be described in detail by using plasma dry etching equipment as shown in FIG. 1 as an example.

The plasma dry etching equipment is used to etch a substrate such as a semiconductor wafer or the like or a particular portion of a thin film formed on the substrate to thus implement a desired circuit or configuration.

The components of the equipment and its operational principle will now be described. An etching gas is introduced into a chamber through a hole 14 formed on a gas dispersion plate 13. When the etching gas flows in, an RF current is applied to upper and lower electrodes 2 and 9 to generate plasma to thereby increase reactivity of the introduced etching gas. The etching gas with the increased reactivity collides with a substrate 15 mounted on a substrate support 8 to etch a portion of a film coated on the substrate.

The etching gas may be, for example, one of a gas including fluorine

(F) such as C₄F₈, C₅H₈, CH₂F₂, CF, CF₂, CF₃, CF₄, SF₆, NF₃, F₂, CH₂F₂, CHF₃, C₂F₆, etc., a gas including chlorine (Cl) such as Cl₂, BCl₃, SiCi₄, and HCl, a gas including bromine (Br) such as HBr, Br₂, and CF3Br, and other gases such as

SiN₄, O₂, Ar, and H₂, and mixtures thereof.

In this respect, however, the etching gas may affect not only the substrate 15, which is the etching target, but also other portions. That is, the chamber of the etching equipment and internal components of the chamber may be chemically and physically damaged by an extreme atmosphere within the chamber during a fabrication process.

The etching process is a process in which a physical and chemical impact is applied to a portion or the entire surface of the substrate by using a corrosive gas, accelerated ions and plasma, etc., to damage it, and the damaged portion is removed, so internal wall surfaces and internal components of the chamber are inevitably damaged during the same process.

In more detail, the chamber and its internal components are chemically attacked by the etching gas with high chemical reactivity. In addition, ionized gas particles are accelerated by an RF electromagnetic field while conducting ion bombardment on surfaces of the components, so the internal components are also physically attacked.

When the chamber and its internal components are thusly damaged, the damaged portions of the etching equipment should be replaced or cleaned and repaired, incurring an additional cost. In addition, because the processing line must be halted for the replacing or cleaning and repairing of the equipment, the processing time of the product is lengthened.

Moreover, a contaminant generated from the damaged chamber and the surfaces of the damaged internal components may contaminate the wafer or a liquid crystal display (LCD) glass substrate to be etched, so a defect rate of the semiconductor and the LCD increases.

Thus, various methods have been employed to increase the durability of the chamber and the internal components of the vacuum plasma processing equipment. Some commonly used methods for preventing corrosion of the vacuum plasma chamber and the internal components will now be described.

As a material of the general vacuum plasma chamber, a metallic material such as a stainless alloy, aluminum (or an alloy thereof), or titanium (or an alloy thereof), etc., or a ceramic material such as SiO₂, Si, Al₂θ3, etc., is used.

For components made of an Al alloy, a method in which an Al₂O₃ ceramic coating film is formed on a surface of a base material through an anodizing process is commonly employed. However, the ceramic coating film formed by this method has many defects therein, so it is difficult to form have high hardness and corrosion resistance and, in addition, there is high generation level of contaminant particles.

Meanwhile, for other various metallic materials or ceramic materials for which the anodizing process cannot be applied, a method in which a protective film is formed by using a material with a low contaminant particle generation rate is used.

Also, a coating technique for performing thermal spraying by solely using coating materials or by mixing them has been known, but coating these materials according to the above-described methods severely degrades the characteristics of the coating film with formation of internal defects.

Recently, for the Al alloy material for which the anodizing method may be used, a method for forming a protective film by using a heterogeneous ceramic material has been used. The typical method for forming the protective film by using the heterogeneous ceramic material is a thermal spray coating method.

Thermal spray coating is a technique in which a metal or ceramic powder is injected into a plasma flame at a high temperature so as to be heated, and a completely molten or semi-solid resultant material is formed on the surface of the base material to form a coating film.

FIG. 2 is a schematic sectional view of a plasma gun, a core part of the thermal spray coating equipment. The operational principle of the plasma gun 20 will be described as follows. First, a plasma gas of Ar, N₂, H₂, He, etc., is introduced through a gas injection hole 21, and while the plasma gas passes through a gap between a cathode 22 and an anode 24, to which high power (generally 30V to 100V, 400A to 1000 A) has been applied, a portion of the injected gas is dissociated to form a plasma flame 25 with a high temperature of about 5000°C to 15,000°C.

In order to prevent corrosion of an end portion, which is a plasma generated portion of the cathode 22, the cathode 22 is generally made of tungsten or a tungsten-tempered metallic material. The anode 24 is made of copper or a copper alloy and includes a cooling passage 23 therein to prevent the life span of the anode from being shortened by the high temperature plasma.

A homogeneous or heterogeneous material may be coated on surfaces of various materials such as metal or ceramic by using the plasma thermal spray method, and as the coating material, a metal or ceramic made of powder or wire may be used.

Next, a material to be coated is prepared in the form of powder, which is then injected into the plasma flame 25 through a powder injection hole 27.

The powder injection hole 27 may be fixed in the plasma gun 20 by means of a support 26 (referred to as "external type", hereinafter), or may be installed at the anode 24 (referred to as "internal type", hereinafter).

The powder injected through the powder injection hole 27 becomes completely molten or partially molten because of the high temperature plasma flame, and the completely molten or partially molten powder moves toward a coating target 30 at a high speed (200m/s to 1000m/s), to form a coating film 29.

In the case of an oxide ceramic material, it may be subjected to plasma thermal spray coating in the atmosphere, but in the case of a metallic material or a material such as a carbide or nitride, etc., which is oxide-reacted or readily decomposed at a high temperature, it is subjected to the plasma thermal spray coating within a vacuum/low pressure chamber.

However, the coating film according to such thermal spray is still not sufficient to solve problems arising in the actual semiconductor fabrication process.

FIGs. 3 and 4 are SEM (scanning electron microscope) photographs of a section of a Y2O3 (yttria) coating film formed by thermal spraying which is commonly used as a protective coating material of components of semiconductor fabricating process equipment. FIG. 3 is a SEM photograph of the section of the protective film coated by using the above-mentioned external type of plasma gun, which includes a plurality of irregular defects.

The coating film formed under such conditions has relatively good mechanical characteristics (e.g., hardness), but it is disadvantageous in that it is very sensitively changed depending on spray coating conditions such as distance between the plasma gun and the base material, an amount of injected gas , e.g., He, H₂, Ar, etc., applied power, etc. In addition, excessive power should be applied in the process of forming coating, so the energy efficiency is degraded. Also, in order to melt a material such as a ceramic having a high melting point, hydrogen or the like which is advantageous with respect to an increase in the plasma temperature should be used, but in this case, black spots are disadvantageously formed in the Y2O3 coating film.

FIG. 4 is a photograph of a section of the coating film formed by using the above-mentioned internal type of plasma gun. It is noted in FIG. 4 that a plurality of cracks are generated vertically within splats formed as separate slurries collide with the surface of the base material, and a gap is formed on the interface between the splats.

The coating film formed under such conditions has poor mechanical characteristics (e.g., hardness), and the cracks within the splats and the splat interface gaps act as diffusion paths of a reaction gas. Thus, the corrosive reaction of the coating film is promoted to accelerate formation of contaminant particles. In addition, the coating film is easily damaged by mechanical impact applied during the semiconductor fabrication process or cleaning.

Moreover, when the ceramic material is coated by the thermal spray, the cracks are formed in the splats and the splat interface gaps are formed. FIG. 5 shows defects. Specifically, FIG. 5 is a SEM photograph of the surface of the splat formed after a single ceramic particle is melted by the plasma flame and then formed on the surface of the base material. Such defects cause many problems in the actual semiconductor fabrication process in which the coating film is formed by the thermal spray.

The cause of the formation of the cracks in the splat and the splat interface gaps generated when the ceramic material is coated by the thermal spray according to the related art will now be described with reference to FIGs. 5 to 11.

Referring to FIG. 5, it is noted that multiple cracks are formed in the splat. The splat is generated as the molten ceramic powder is deposited on the surface of the base material and cooled during the thermal spray coating. This will be described in more detail as follows.

In the liquid ceramic, its elements (e.g., Y and O of Y2O3) are bonded loosely and the arrangement order of the elements is maintained to be irregular. When the liquid ceramic is cooled to below its melting point Tm, it is changed to a solid state, namely, to a crystalline phase in which the bonding of elements is strong and the elements are arranged regularly.

In the thermal spray coating, when the molten ceramic powder is deposited on the surface of the base material and cooled, the molten ceramic powder is changed to the crystalline phase (phase transformation) which forms the cracks in the splat. FIG. 6 is a graph showing conditions in which the crystalline phase is formed according to temperature over time when the ceramic material is cooled to below the melting point.

Most of the ceramic material is quickly transformed to the crystalline phase near a particular temperature (Tm in FIG. 6). In this case, when the liquid phase is transformed to the solid phase, if the cooling speed is faster than time required for crystallization (indicated as to* in FIG. 6) in the temperature range, the crystalline phase cannot be formed. Then, the ceramic material remains in an amorphous state, which is a solid state in which the elements are arranged irregularly, like the liquid state.

FIG. 7 shows a change in volume when the liquid material is cooled to be transformed to the solid in the crystalline phase.

When the temperature is lowered, the ceramic material contracts as the distance between adjacent atoms of the elements is reduced, and when the crystalline phase in which the elements are arranged regularly is formed, the volume contraction abruptly occurs (ΔV in FIG. 7). The abrupt volume contraction causes formation of the cracks in the splat and the splat interface gaps in the thermal spray coating. FIG. 8 schematically shows how the defects are caused. In order for the liquid molten ceramic to be cooled and transformed into the crystalline phase solid, its elements should all be arranged in determined positions. Thus, the more diverse the kinds of elements, the more complicated the structure of the atomic arrangement of the crystalline phase becomes, and because many kinds of elements must move to each determined position, much time is taken for the arrangement.

Thus, when the types of elements increase, as shown in FIG. 9, that means amorphous materials (AmorM) are formed, rather than a general case, and in the case of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95), more time is taken to form the crystalline phase at the same temperature. Thus, in the case of the amorphous materials (AmorM), the amorphous phase is more easily formed.

The coating material according to the exemplary embodiment of the present invention includes the multi-elemental ceramic, and as shown in FIG. 9, much time is taken to form the crystalline phase. Thus, in the thermal spray coating, the amorphous phase can be easily formed.

In addition, the coating film according to the exemplary embodiment of the present invention is mostly formed with the amorphous phase by using the multi-elemental ceramic according to the exemplary embodiment of the present invention. In this case, preferably, the coating film is formed to include the amorphous phase at 50% or more, and more preferably the coating film is formed with a 100% amorphous phase.

When the coating film includes the amorphous phase at less than 50%, it means that the coating film includes the crystalline phase at more than 50%, so as stated above, as the liquid phase is transformed into the crystalline phase solid, the volume is significantly changed. Thus, the defects are generated at the coating film.

FIG. 10 shows the change in the volume when the liquid phase is transformed into the amorphous phase. Referring to FIG. 10, when the liquid phase is transformed into the amorphous phase, the volume is not sharply changed. This is because the atomic arrangement of the amorphous solid is almost the same as that of the liquid state. Thus, when the coating film is formed by using the multi-elemental ceramic coating material according to the present invention, because the solid with the amorphous structure is formed, the rapid volume contraction at a particular temperature does not occur. Therefore, such internal defects as the internal vertical cracks and the splat interface gaps caused by the volume contraction generated when the liquid phase is transformed into the crystalline phase solid are not generated. FIG. 11 schematically shows the process of phase transformation from the liquid phase to the amorphous solid phase.

The coating material for forming the coating film according to the exemplary embodiment of the present invention will now be described. In order to easily form the amorphous coating film, the coating material according to the exemplary embodiment of the present invention includes the multi-elemental ceramic material including three or more elements.

As the multi-elemental ceramic material, a multi-elemental ceramic material including Al, Y, and O, the elements of AI2O3 and Y2O3, may be used.

Preferably, the ratio of the elements of the multi-elemental ceramic material is (Al_x Yi-X)₂O₃ (x is within a range of 0.05 to 0.95). If the value x is smaller than 0.05 or exceeds 0.95, the coating film would not be formed with the 100% amorphous phase during its formation process. Then, the corrosion resistance and the physical or chemical characteristics of the coating film would be degraded. Here, the amount of oxygen may vary according to temperature of the frame and a spray distance in the thermal spray.

The method for preparing the multi-elemental ceramic material according to the exemplary embodiment of the present invention will now be described.

The multi-elemental ceramic material according to the exemplary embodiment of the present invention is prepared to have a powder state according to various ceramic synthesizing methods.

According to one example of the ceramic synthesizing method, a chemical material including Al and Y may be mixed and thermally processed to remove undesired elements and finally prepare a powder including Al, Y, and O. Here, the chemical material including Al may include Al(OH)₃, Al(C₃H₅Os)₃, Al(Ci₈H₃₃Oa)₃, Al(Ci₅H₃iCOO)₃, Ai₂(SO₄)₃, etc., and the chemical material including Y may include Y₂(COs)₃₃H₂O and Y₂(SO₄)₃ 8H₂O. The method for preparing the ceramic powder will now be described in more detail.

In a first method, first, the chemical material including Al and Y may be mixed to have a composition of (Al_xY_1-x)2θ3 (x is within a range of 0.05 to 0.95). Next, the mixture may be heated to a sufficiently high temperature so as to decompose unstable materials, except for Al-Y-O, to thus remove impurities such as C, H, and O.

In a second method, the chemical material may be dissolved in water or ethanol, etc., and then heated to prepare Al-Y-O powder having a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to.95).

In a third method, a mixed powder of an Al metallic powder and a Y metallic powder or an Al and Y alloy powder may be prepared to have a size of lμm to lOOμm and then oxidized to thus synthesize the powders. Here, although the surface of the Al metal may be oxidized when contacting with oxygen even at room temperature to form AI2O3 ceramic, in order to facilitate the oxidation, the temperature may be increased to accelerate the oxidation. In addition, the Al metal may be made into a powder so as to be prepared with a large reaction surface and used.

Besides the Al metallic powder, a Y metallic powder or an Al and Y alloy powder may also be oxidized according to the same method as the high temperature oxidation method of the Al metallic powder to prepare the (Al₂θ3)_x(Y2θ3)i-_x ceramic.

In a fourth method, the Al metal and the Y metal may be mixed and the mixed powder are oxidized to prepare a bulk type of ceramic, which is then crushed to prepare a powder of lOOμm or smaller. Also in this synthesizing method, the metallic elements are oxidized at a high temperature in the same manner as the high temperature oxidation method to form an oxide. Compared with the afore-mentioned high temperature oxidation method in which the powder is oxidized, in this method, masses with a diameter of a few mm or a few cm are oxidized.

The preparation of the metallic powder may have a problem in that the process is complicated and the unit cost is high. In this case, however, by oxidizing the metallic powder in a bulk state regardless of the size or the shape of the metallic alloy, the ceramic material can be prepared at a low cost.

In a fifth method, AI2O3 particles and Y₂θ3 particles may be mixed to have a composition of (Al_xYi-X)₂Cb (x is within a range of 0.05 to 0.95), and then sprayed and dried to prepare a dried synthetic powder with a diameter of lμm to lOOμm.

In the fifth method, the AI2O3 and Y2O3 particles may be prepared to have a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95) and then mixed with a solvent, a binder, a dispersion agent, etc. Thereafter, the resultant mixture may be sprayed with a gas such as air at a temperature of 7O⁰C to 8O⁰C or may be distributed through a fine hole formed on a disk that rotates at a high speed to thus prepare a powder with a diameter of lμm to 200μm.

The thusly prepared powder is weak in strength, so a heating process is additionally performed at a temperature range of 900⁰C to 1500⁰C. Through the heating process, the solvent, the binder, the dispersion agent, etc. are gasified, leaving only the ceramic powder, and the remaining ceramic powder is sintered to have improved strength.

A sixth method may include inducing Al₂O₃ particles and Y2O3 particles with a size of 0.1 μm to 30μm such that they assume respective static electric charges with different polarities, and mixing the charged particles to have a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95). If the AI2O3 powder and the Y2O3 powder are simply mechanically mixed, the mixture would not be uniform. However, in the sixth method as shown in FIG. 12, because the two particle types are formed into a mass electrostatically in a solvent of a particular acidity (e.g., Ph6), the AI2O3 powder and the Y2O3 powder can be mixed very uniformly. Accordingly, quality powder can be prepared.

Here, in charging the particles, Darvan C (poly-methyl metacrylic ammonium salt) may be added in the solvent to allow AI2O3 to assume a negative static electric charge, and PI (Poly-ethylene imide) may be added to the solvent to allow Y2O3 to assume a positive static electric charge.

The subsequent processes of this method are the same as the above- mentioned spray drying method, and only the powder preparing process for spray drying is different so a detailed description of the subsequent processes will be omitted.

The ceramic powder synthesized by the various methods as described above is calcined at a temperature range of 900°C to 1500⁰C to prepare a thermal spray powder with suitable strength. Meanwhile, in the ceramic powder synthesizing method according to the exemplary embodiment of the present invention, the solvent or the dispersion agent may be used in order to facilitate mixing of the AI2O3 particles and the Y2O3 particles and uniformly disperse the mixed particles. In addition, the binder may be used to maintain the shape in a post- processing procedure such as the calcining process.

In the ceramic synthesizing process, a mixture solution of one or more selected from the group consisting of water, acetone, and isoprophyl alcohol may be used as the solvent, a high molecular polymer may be used as the dispersion agent, and a high polymer (PVB 76) or benzyl butyl phthalate may be used as the binder.

FIG. 13 shows the resulting external appearance of the Al, Y, and O multi-elemental mixed powder prepared by using the powder preparing method according to the present invention, which is observed with a SEM. Next, the formation of the coating film by using the ceramic powder prepared according to the powder preparing method according to the exemplary embodiment of the present invention will be described.

The coating method according to the exemplary embodiment of the present invention includes the thermal spray coating method. The thermal spray coating method includes injecting the ceramic powder into the plasma flame to heat it, and forming completely molten powder or semi-solid powder on a surface of a component (referred to as "base material" hereinafter) used in the plasma chamber to form a coating film. First, the powder to be used for coating is prepared. As the ceramic powder to be used for thermal spray coating, a singlet powder with a size of lμm to lOOμm according to the exemplary embodiment of the present invention may be used. Alternatively, a primary fine powder of scores of nanometers to a few μm may be coagulated to have a size of lμm to lOOμm and used.

Next, the singlet powder or the coagulated powder is injected into the plasma flame. The injected powder is heated by the plasma flame, dissipated, and formed on the surface of the base material. When formed, the powder is rapidly cooled to form a coating film. Various operational conditions may be set to ensure a stable coating operation and improve characteristics of the coating material. The operational conditions may vary depending on the employed equipment and the size and type of the coating powder used. Experimental Examples The present invention will be described in detail through the experimental examples as follows. For the experimental examples of the present invention, the "PT-800" power application system manufactured by Plasma Tech, Switzerland, and the "F4-HBS" plasma gun manufactured by Sulzer-Metco. Co., U.S.A., were used. To form plasma, argon gas and hydrogen gas were used, and the amounts of the gases were controlled to be 36 1/min. and 4 1/min., respectively. Applied power was 36Kw (600A, 60V), and the injection speed of the coating powder was 10g/min. The distance between the plasma gun and the coating target material was about 120mm. In the experimental examples of the present invention, the "PT-800" power application system manufactured by Plasma Tech, Switzerland, and the "SG-100" plasma gun manufactured by Praxair Co., U.S.A., were used under the conditions that an amount of argon gas was 40 1/min., an amount of helium gas was 20 1/min., applied power was 25Kw, and the spray distance was 120mm.

First, a difference between a case where the composition of the coating material according to the exemplary embodiment of the present invention and a case where pure metallic oxide (here, Al and Y oxide is used) powder is used will now be described with reference to FIGs. 13 to 17. In order to check an amorphous formation degree of the coating film according to the composition of powder, powder were prepared by controlling a value x of (Al_xYi_-x)2θ3 powder, and the generated coating powder was used to form the coating film on a base material for the vacuum plasma chamber. FIG. 14 shows an X-ray diffraction value of the coating film formed by coating the pure Al₂O₃ powder according to the plasma thermal spray method. In order to compare it with the ceramic powder according to the exemplary embodiment of the present invention, the pure AI2O3 powder was coated according to the plasma thermal spray method and then X-ray diffraction measurements were taken.

With reference to FIG. 14, when the pure AI2O3 powder was used, peaks with high strength were observed at particular diffraction angles (indicated by V in FIG. 14). Such peaks with high strength appear in a certain repeated structure, so it can be understood that the coating film formed by using the pure AI2O3 powder includes crystalline phases therein.

FIG. 15 shows the analysis result of the coating film formed by coating (Al_xYi -x)2U3 coating powder in which x had a value of 0.9 according to the thermal spray method.

With reference to FIG. 15, unlike the comparison case as shown in FIG.

13, it is noted that there is no peak with high strength at a particular diffraction angle. Accordingly, it is noted that the composition of the

(Alo.9Yo.i)2θ3 powder is suitable for forming the amorphous coating film according to the exemplary embodiment of the present invention.

Next, a coating powder with a composition of (Alo.₆Yo.₄)2θ3 by changing the value x to 0.6 was prepared and subjected to plasma spray coating to form a coating film, and the coating film was analyzed by X-ray.

FIG. 16 shows the X-ray analysis results of the coating film with the composition of (Alo.όYo.φOs, in which it is noted that the coating film includes amorphous phases even when the value x is 0.6.

Next, a coating powder with a composition of (Alo.iYo.9)2θ3 in which the value x is 0.1 was used for thermal spray coating.

FIG. 17 shows the X-ray analysis results of the coating film with the composition of (Alo.iYo.φCb. With reference to FIG. 17, it is noted that values of X-axis angles (2 theta) are observed with weak peaks (indicated by V) between 30°and 40°. Thus, it can be known that the coating film formed with the composition of (Alo.iYo.9)2θ3 includes amorphous phases at most portions and also crystalline phases at some portions. Meanwhile, FIG. 18 is a graph showing an X-ray diffraction value of a coating film formed by coating pure Y2O3 powder according to the plasma thermal spray method. In order to compare it with the ceramic powder according to the exemplary embodiment of the present invention, the Y2O3 powder was coated according to the plasma thermal spray method and then its diffraction aspect was measured by using X-ray analyzing equipment.

With reference to FIG. 18, it is noted that strong peaks appear at particular angles. Thus, as described above, also in the case of coating by using the pure Y₂O₃ powder, the coating film mostly includes the crystalline phases.

In comparing the X-ray diffraction result of the coating film made of the pure AI2O3 and that of the coating film made of the pure Y2O3, it is noted that the positions of the peaks of the crystalline phases are different, and in the case of the coating film made of the pure AI2O3, the strength of the diffraction peaks is low overall while in the case of the coating film made of the pure Y2O3, higher values were measured between 30° to 40°.

This means that even in the case of the pure AI2O3 coating film, it is not completely formed with the crystalline phases but includes some amorphous phases. Thus, it can be noted that compared with Y2O3, amorphous phases can be easily formed with AI2O3. Namely, in order to easily form the amorphous phases, a composition having the value of x within a range of 0.5 to 0.9 in which there is more Al than Y is preferably used.

Through the above-described experimental examples, it can be noted that when the value x has a composition range of 0.1 to 0.9 in (AlχYi-_x)2θ3, a good amorphous coating film is formed.

Next, FIG. 19 shows defects that may be generated according to coating conditions in the thermal spray coating.

FIG. 19 shows the X-ray analysis result of the coating film formed by coating the coating powder according to the plasma thermal spray coating according to the exemplary embodiment of the present invention. The composition used is (Alo.6Yo.4)2θ₃, which corresponds to the present invention but shows a result when plasma temperature in the thermal spray coating is low or a result when the powder is not completely molten. With reference to FIG. 19, it is noted that peaks are formed at some angles overall. Thus, it is noted that some crystalline phases coexist with the amorphous phases. This is because the plasma temperature in the thermal spray coating was low or the powder was not completely melted, so the crystalline phases were transferred as is to the coating film.

Alternatively, when the temperature of the base material or the surface of coating material is maintained at such a high level so as to make the amorphous phase transform into the crystalline phase during the coating process, some amorphous phases may be transformed into the crystalline phases to form the amorphous/ crystalline complex phases.

The coating film formed under such conditions mainly includes the amorphous phases and partially dispersed crystalline phases, without having air pores in the coating material or the splat interface gas. Thus, although the conditions are not sufficient for forming the coating film, the coating film exhibits good characteristics compared with the coating film that uses the pure Al or Y oxide.

A coating film according to the first experimental example according to the present invention will now be described with reference to FIGs. 20 to 22. In the first experimental examples, a multi-elemental powder with a composition of (AIo 7δYo 22)203 was prepared, and an amorphous coating film was formed by using the internal type of plasma gun. Hereinbelow, the amorphous coating film according to the first experimental examples of the present invention will be referred to as "AmorMl".

FIGs. 20 and 21 are SEM photographs of sections of the AmorMl coating film after the sections were hard-faced. With reference to FIGs. 20 and 21, the coating film includes a few cracks but does not have such vertical cracks within the splat or splat interface gaps observed in the general crystalline phase spray coating tissues. FIG. 22 is a high-magnification TEM (transmission electron microscope) photograph of the AmorMl amorphous coating film. With reference to FIG. 22, it can be confirmed that the AmorMl coating film has an amorphous phase structure. Next, a coating film according to a second experimental example of the present invention will now be described with reference to FIG. 23.

In the second experimental example, a multi-elemental powder with a composition of (Alo.62sYo.375)2θ3 was prepared and an amorphous coating film was formed by using the internal type of plasma gun. Hereinbelow, the amorphous coating film according to the second experimental example of the present invention will be referred to as "AmorM2".

FIG. 23 is a SEM photograph of the section of the AmorM2 coating film after the coating film was hard-faced. With reference to FIG. 23, the AmorM2 coating film has a similar shape to the AmorMl coating film. Namely, there is no vertical crack in the splat and no splat interface gap.

Meanwhile, a coating film according to a third experimental example of the present invention was formed by applying a method in which AI2O3 powder and Y2O3 powder, each having the same composition as AmorM2, were allowed to assume negative (-) and positive (+) static electric charges, respectively, so as to be uniformly distributed, and then mixed.

FIG. 24 is a SEM photograph of the section of the coating film according to the third experimental example. Because the compositions of the spray powder were maintained to be uniform at every portion by applying the electrostatic mixing method, it is noted that there is no splat interface and thus favorable coating was obtained.

In addition, it is noted in FIG. 24 that some crystalline phase particles are distributed at the bottom (at the lower portion of the photograph) of the coating material. This is because the crystalline phases existing in the powder were not completely molten because the temperature of the plasma flame was low or the temperature of the surface of the coating material or the base material was maintained at such an excessively high level that the amorphous phases were transformed into the crystalline phases.

Mechanical and chemical characteristics of the MorMl and MorM2 coating films will now be described with reference to FIGs. 25 to 28. FIGs. 25 to 28 show a comparison between the mechanical and chemical characteristics of the AmorMl and AmorM2 coating films and the characteristics of the existing coating film using Y2O3 and AI2O3 powder.

FIG. 25 shows a result obtained by measuring the mechanical strength of the coating film according to the exemplary embodiment of the present invention and the coating film formed by using the Al and Y oxide. Hereinbelow, the coating film formed by using the Al oxide will be referred to as Comparative Example 1 and the coating film formed by using the Y oxide will be referred to as Comparative Example 2. With reference to FIG. 25, it is noted that the AmorMl and AmorM2 amorphous coating films have a 50% to 100%-improved hardness value compared with Comparative Example 2, and have a similar hardness value to that of Comparative Example 1 with good mechanical strength.

FIG. 26 shows a comparison result obtained by measuring scratch resistance of the coating films according to the exemplary embodiment of the present invention and the comparative examples.

With reference to FIG. 26, the AmorMl and the AmorM2 amorphous coating films exhibit high scratch resistance of more than 10 times compared with Comparative Example 2. The measurement of the scratch resistance was performed such that the surface of the coating films were scratched by applying a force of 3ON with a pointed diamond tip, and depths of the scratched portions were measured. FIG. 27 shows a comparison result obtained by measuring corrosion resistance between the coating films according to the exemplary embodiment of the present invention and Comparative Example 2.

With reference to FIG. 27, it is noted that the AmorMl and AmorM2 amorphous coating films have very high corrosion resistance to an acid chemical material such as HCl. The Y axis of the graph indicates a reduction in mass after corrosion. The mass of the coating films according to the exemplary embodiment of the present invention were reduced by one-fifth compared with Comparative Example 2 for the same time period. Thus, it can be noted that the speed of corrosion reaction of the coating films according to the exemplary embodiment of the present invention is one-fifth compared with Comparative Example 2. The resistance to corrosion was measured such that the coating materials were put in an HCl solution of 2N concentration at room temperature for 24 hours, and then taken out to measure the amount of reduction in the mass.

FIG. 28 shows results obtained by measuring durability of the plasma vacuum chamber according to the exemplary embodiment of the present invention.

With reference to FIG. 28, the coating films according to the exemplary embodiment of the present invention have excellent durability with respect to a plasma atmosphere by more than five times compared with the coating film of Comparative Example 1. The evaluation of the durability was performed such that the coating materials were etched with a CF₄+O₂ gas by using plasma etching equipment, which is semiconductor fabricating equipment, and then the etched depth was measured.

The durability measurement conditions will be described in more detail as follows.

It was based on the conditions that SiO₂ is etched at lOOnm per minute. That is, CF₄ gas injection speed was set as 30sccm (standard cubic centimeters per minute), O₂ injection speed was set at βsccm, main electrode input power was set at 900W, bias power was set at 9OW, and etching chamber pressure was set at δmtorr. The internal temperature of the chamber was set to be maintained at 25⁰C.

The following Table 1 shows comparisons between the characteristics of the coating films of Comparative Examples 1 and 2 and the coating film according to the exemplary embodiment of the present invention. The results in Table 1 were measured by applying the above-described durability measurement conditions.

[Table 1]

As shown in Table 1, the coating film according to the exemplary embodiment of the present invention has similar hardness to that of Comparative Example 1 and corrosion resistance similar to or superior to that of Comparative Example 2. That is, the coating film according to the exemplary embodiment of the present invention has the advantages of the existing coating material but does not have the disadvantages. Therefore, the coating film according to the exemplary embodiment of the present invention exhibits excellent physical and chemical characteristics compared with the comparative examples.

In order to effectively describe the excellent characteristics of the present invention, the durability of the plasma vacuum chamber was tested under more corrosive conditions in experimentation.

[Table 2]

The compositions used for the experimentation were the same as those of AmorM2, and powder was prepared with a diameter of lOμm to 60μm. Coating films were fabricated under the conditions of the comparative examples and experimental examples in Table 2.

FIG. 29 is a graph showing X-ray analysis results of the coating film according to Experimental Example 3 of the exemplary embodiment of the present invention. With reference to FIG. 29, with multiple peaks observed, it is noted that the coating film was formed with amorphous phases overall but also with some crystalline phases.

FIGs. 30 and 31 show the X-ray analysis results of coating films fabricated under the conditions of Experimental Examples 4 and 5 of the exemplary embodiment of the present invention. With reference to FIGs. 30 and 31, it is noted that the coating films were formed with nearly 100% amorphous phases under the conditions of Experimental Examples 4 and 5, unlike Experimental Example 3.

Before measuring resistance to corrosion, hardness of each of the coating films according to respective experimental examples was measured. The hardness of the coating films were measured by Vickers hardness set with a load of 20Og. The measurement results are as shown in Table 3 below.

[Table 3]

According to the results shown in Table 3, in the case of Experimental Example 4 in which some crystalline phases are generated, it has a hardness value similar to those of Experimental Examples 5 and 6. That is, when the coating film is mostly formed with the amorphous phases, even though it includes some crystalline phases, its hardness is not much affected.

When the coating film is formed with 100% amorphous phases and when the coating film is densely formed without any air pores, the hardness value increases. Thus, in the case of the coating films formed with 100% amorphous phases as in Experimental Examples 5 and 6, the hardness value may change according to coating conditions.

Next, as mentioned above, corrosion resistance of respective coating films was measured under conditions in which corrosion occurs easily.

The testing was performed under conditions in which SiO₂ was etched for 300nm/min. Specifically, CF₄ gas injection speed was set at 40 seem, O₂ injection speed was set at lOsccm, main electrode input power was set at 100OW, bias power was set at 150W, etching chamber pressure was set at 5 mtorr, and temperature within the chamber was maintained at 25⁰C. Plasma exposure time was set as one hour.

FIGs. 32 and 33 are resultant SEM photographs showing sections of the coating films before and after the etching testing. FIG. 32 shows the surface of the coating film before etching and FIG. 33 shows the surface of the coating film after etching. The results are shown in Table 4.

[Table 4]

In Table 4, it is noted that the average etching speeds of the coating films according to the experimental examples of the present invention are much lower than those of the comparative examples. Thus, it can be understood that the coating films according to the exemplary embodiment of the present invention have high resistance even in a strong oxidation condition. In case of Experimental Example 4, the coating film includes some crystalline phases and has a high etching (corrosion) speed compared with Experimental Examples 5 and 6 of the coating films formed with 100% amorphous phases. Accordingly, it can be said that when the coating film is formed with 100% amorphous phases, it can prevent corrosion most effectively. In addition, in comparing the results of Table 1 and Table 4, in the gentle corrosion environment (100 nm/min. based on SiO₂), the coating film according to the exemplary embodiment of the present invention does not show much difference from that of Comparative Example 2 in etching speed, but in the strong corrosion environment (300 nm/min. based on SiO₂), the coating film according to the exemplary embodiment of the prevent invention has the drastically lower etching speed compared with that of Comparative Example 2. Thus, it is noted that the coating film according to the exemplary embodiment of the present invention has excellent resistance in a strong corrosion environment.

Meanwhile, in the present invention, a process of forming a metal intermediate layer may be added in order to improve bonding strength of the spray coating film, and a process of forming several coating layers according to a method (gradient coating technique) for sequentially changing the composition of the base material and the coating material may be additionally performed.

By forming a metallic intermediate layer on the base material, even when a material having different physical and chemical characteristics from those of the base material is coated, a problem that the coating film is easily separated because of a weak interface can be solved.

As for the coating films and the components according to the exemplary embodiment of the present invention, 1) When ZrO₂ is coated on an aluminum base material, a method for forming an intermediate layer with a material such as NiCrAIY having a small thermal expansion coefficient may be used in the middle. 2) In addition, a method for forming a FeCr-based amorphous metal having high strength and good corrosion resistance as an intermediate layer may be used with respect to an aluminum metal. 3) Further, a method for forming an intermediate layer with Cr, Ni, Fe, or an alloy including them on a metal base material may be used. 4) Still further, a method for forming an intermediate layer with the same material as a base material such as AI2O3, Si, or SiO₂, etc. on the base material and coating an amorphous material according to the exemplary embodiment of the present invention thereon may be used. By forming such a metal intermediate layer according to the exemplary embodiment of the present invention_/ the coated coating film can be prevented from being separated and its corrosion resistance can be further increased. Meanwhile, for the coating film and the components according to the exemplary embodiment of the present invention, a gradient coating method in which powder is prepared the same as or similar to a base material, rather than forming the intermittent second coating film (intermediate layer), and a fraction of amorphous coating according to the present invention is sequentially increased while coating is proceeding, can also be used. With this method, durability of the coating film can be increased.

In addition, modified techniques may be used such that a different coating film formation technique may be associated to be used or the amorphous coating film proposed in the present invention may be applied to a portion of the spray coating film.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A thermal spray coating material that is used for semiconductor fabricating equipment having a composition of (Al_xYi-_x)2θ3 (x is within a range of 0.05 to 0.95) and an amorphous structure.

2. The material of claim 1, wherein x is within a range of 0.5 to 0.95.

3. The material of claim 1, wherein the thermal spray coating material comprises a powder with a diameter of lμm to lOOμm.

4. A method for preparing a thermal spray coating material for use in a semiconductor fabricating equipment, comprising: preparing a material with a composition of (Al_x Yi-X)₂O₃ (x is within a range of 0.05 to 0.95) by mixing Al₂O₃ particles and Y₂O₃ particles each with diameter of 0.1 μm ~30μm; spraying and drying the prepared material to obtain a synthesized powder; and calcining the powder at 800°C to 1500°C.

5. The method of claim 4, wherein the mixing of the materials comprises applying static electricity that induces the A12O3 particles and Y2O3 particles to respectively assume a static electric charge with different polarities.

6. The method of claim 5, wherein the applying of static electricity comprises: adding Darvan C (Poly-methyl metacrylic ammonium salt) to a solvent to allow the AI2O3 particles to assume a negative static electric charge; and adding PI (polyethylene imide) to the solvent to allow the Y2O3 particles to assume a positive static electric charge.

7. A method for coating a thermal spray coating material for use in semiconductor fabricating equipment, comprising: preparing a thermal spray coating material with a composition of (Al_xYi-X)₂O₃ (x is within a range of 0.05 to 0.95); injecting the thermal spray coating material into a plasma flame to heat the material; and forming the thermal spray coating material in a completely molten or semi-solid state according to the heating on a surface of a component used for the semiconductor fabricating equipment to form a coating film with an amorphous structure.

8. The method of claim 7, wherein the forming of the coating film comprises forming a metal intermediate layer.

9. The method of claim 7, wherein the forming of the coating film comprises forming a gradient coating film by sequentially differentiating the composition of the thermal spray coating material.

10. The method of claim 9, wherein the composition of the thermal spray coating material is sequentially changed from a composition that is the same as or similar to a coated base material to a composition of (Al_xYi_-x)2θ3 (x is within a range of 0.05 to 0.95) while the coating proceeds.

11. The method of claim 7, wherein in forming the coating film, the component is a chamber of a vacuum plasma apparatus or a component within the chamber.