Patent Publication Number: US-2015064358-A1

Title: Coating material for thermal spray coating, method for preparing the same, and method for coating with the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0102570 filed in the Korean Intellectual Property Office on Aug. 28, 2013, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a coating material for thermal spray coating, a method for preparing the same, and a method for coating with the same. More particularly, the present invention relates to a coating material for thermal spray coating having corrosion resistance and low activity, a method for preparing the same, and a method for coating with the same. 
     (b) Description of the Related Art 
     Vacuum plasma equipment is widely used in process fields for realizing semiconductor devices or other ultrafine patterns. Vacuum plasma equipment includes plasma enhanced chemical vapor deposition (PECVD) equipment, sputtering equipment, dry etching equipment, etc. Since the vacuum plasma equipment generates high-temperature plasma to etch semiconductor devices or realize ultrafine patterns, chambers and internal parts thereof are easily damaged. Particular elements and contaminating particles are generated from surfaces of the chambers and parts thereof, and thus are very likely to contaminate the inside of the chamber. 
     Particularly, since a reactive gas, such as a Cl or F species, is injected into the plasma etching equipment under the plasma atmosphere, the inside of the chamber or the internal parts thereof are exposed to a very corrosive environment. The corrosion primarily causes damage to the chamber and the internal parts thereof, and secondarily generates contaminating materials and particles, bringing about an increased failure rate of production goods and deteriorated product quality. The materials for the vacuum plasma chamber and the internal parts thereof are selected in consideration of many characteristics including corrosion resistance, processability, ease of manufacture, price, insulating properties, and the like. In general, metal materials, such as stainless alloys, aluminum and alloys thereof, and titanium and alloys thereof, and ceramic materials, such as SiO 2 , Si, and Al 2 O 3 , are used. 
     In thermal spray coating, hybrid ceramic materials are used to form a protection film. Thermal spray coating is a technique in which a metal or ceramic powder is injected to a high-temperature heat source and heated, and is then deposited in a completely molten or semi-solid phase on a surface of a base metal to form a coating film. Thermal spray coating techniques include plasma thermal spray coating, high velocity oxygen fuel (HVOF) coating, etc., depending on the kind of heat source. An Al 2 O 3  or Y 2 O 3  ceramic material is commercially used as a coating material for thermal spray coating. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     A coating material for thermal spray coating having advantages of improving corrosion resistance to plasma under a plasma atmosphere containing a reactive gas such as a Cl or F species, and suppressing and minimizing formation of ultrafine reaction products is provided. Also, a method for preparing the foregoing coating material for thermal spray coating is provided. Further, a method for coating with the foregoing coating material for thermal spray coating is provided. 
     An exemplary embodiment of the present invention provides a coating material for thermal spray coating having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99). More preferably, x may be 0.1 to 0.5. The coating material may include a powder having a diameter of 1 to 200 μm. 
     Another embodiment of the present invention provides a method for preparing a coating material for thermal spray coating, the method including: mixing a MgO powder having a diameter of 0.1 to 30 μm and a Y 2 O 3  powder having a diameter of 0.1 to 30 μm to prepare a material having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99); and spraying and drying the material to prepare a synthesized coating material for thermal spray coating. Here, x may be 0.1 to 0.5. The method may further include subjecting the coating material for thermal spray coating to a thermal treatment at 900 to 1500° C. 
     Yet another embodiment of the present invention provides a method for coating with a coating material for thermal spray coating, the method including: providing a coating material for thermal spray coating having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99); injecting the coating material for thermal spray coating toward a plasma jet, followed by heating; and depositing the coating material for thermal spray coating in a completely molten or semi-solid state on a surface of a base metal to form a coating film. More preferably, x may be 0.1 to 0.5. In the forming of the coating film, the base metal may be a chamber of vacuum plasma equipment or a part inside the chamber. 
     According to an embodiment of the present invention, a coating film having improved corrosion resistance can be formed on the internal parts of the semiconductor equipment, thereby improving the lifespan of the internal parts of the semiconductor equipment. In addition, a coating material having improved corrosion resistance under the plasma atmosphere containing a reactive gas such as a Cl or F species can be prepared. Further, unlike the conventional art, the present invention can prevent the formation of ultrafine reaction products in the plasma atmosphere containing a reactive gas such as a Cl or F species, thereby preventing damage to the inner wall of the semiconductor equipment or contamination of goods manufactured therefrom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic flowchart showing a method for preparing a coating material for thermal spray coating and a method for coating with a coating material for thermal spray according to an embodiment of the present invention. 
         FIG. 2  shows scanning electron microscopic images illustrating Mg—Y—O based materials for thermal spray coating prepared according to Experimental Examples 1 to 5 of the present invention. 
         FIG. 3  shows X-ray diffraction graphs illustrating Mg—Y—O based materials for thermal spray coating prepared according to Experimental Examples 1 to 5 of the present invention. 
         FIG. 4  shows scanning electron microscopic images obtained by observing polished surfaces of Mg—Y—O based coatings formed by a thermal spray coating process according to Experimental Examples 1 to 4 of the present invention. 
         FIG. 5  shows graphs obtained by analyzing a coating formed according to Experimental Example 1 of the present invention using an energy dispersive X-ray spectroscopy (EDX) system. 
         FIG. 6  shows X-ray diffraction graphs illustrating coatings formed according to Experimental Examples 1 to 4 of the present invention 
         FIG. 7  shows scanning electron microscopic images of etched surfaces before and after a corrosion resistance test on coatings formed according to Experimental Examples 1 to 4. 
         FIG. 8  is a graph illustrating etching rates of coatings formed according to Experimental Examples 1 to 4 and comparative examples 1 to 4 of the present invention. 
         FIG. 9  shows scanning electron microscopic images illustrating exposed surfaces of coatings formed according to Experimental Examples 1 to 4 of the present invention. 
         FIG. 10  is an image showing a state in which a large crude reaction product generated during a manufacturing process is dropped on a circuit. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on another element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements therebetween. 
     Terminologies used herein are provided to just mention specific exemplary embodiments and are not intended to limit the present invention. Singular expressions used herein include plurals unless they have definitely opposite meanings. The meaning of “including” used in this specification gives shape to specific characteristics, regions, integrals, steps, operations, elements, and/or component, and do not exclude existence or addition of other specific characteristics, regions, integrals, steps, operations, elements, components, and/or groups. 
     Spatially relative terms, such as “below” and “above” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the figures is turned over, elements described as “below” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. Apparatuses may be otherwise rotated 90 degrees or at other angles, and the spatially relative descriptors used herein are then interpreted accordingly. 
     If not defined differently, all the terminologies including technical terms and scientific terms used herein have the same meanings as those skilled in the art generally understand. Terms defined in common dictionaries are construed to have meanings corresponding to related technical documents and the present description, and they are not construed as ideal or overly official meanings, if not defined. 
     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. 
       FIG. 1  is a schematic flowchart showing a method for preparing a coating material for thermal spray coating and a method for coating with a coating material for thermal spray coating according to an embodiment of the present invention. The flowchart shown in  FIG. 1  is provided to merely exemplify the present invention, but the preset invention is not limited thereto. Therefore, the flowchart shown in  FIG. 1  may be changed into other forms. 
     As shown in  FIG. 1 , the method for preparing a coating material for thermal spray coating includes: mixing a MgO powder and a Y 2 O 3  powder to prepare a composite powder having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99) (S 10 ); and spraying and drying the composite powder to prepare a synthesized coating material for thermal spray coating (S 20 ). The method for coating a coating material for thermal spray coating may further include other steps. 
     The method for coating with a coating material for thermal spray coating further includes, in addition to the foregoing steps: injecting the coating material for thermal spray coating toward a plasma jet, followed by heating (S 30 ); and depositing the coating material for thermal spray coating in a completely molten or semi-solid state on a surface of a base metal to form a coating film (S 40 ). The method for coating with a coating material for thermal spray coating may further include other steps. Hereinafter, the foregoing steps will be described in more detail. 
     First, in the step S 10 , a MgO powder and a Y 2 O 3  powder are mixed to prepare a composite powder having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99). A Mg—Y—O based material has excellent plasma corrosion resistance when compared with Al 2 O 3  and Y 2 O 3  crystalline coating and Al—Y—O-based amorphous coating. In an embodiment of the present invention, the coating material for thermal spray coating is prepared by combining Mg and Y, which are verified to have no side effects when used in a semiconductor manufacturing process and generate no large crude reaction products when reacting with a reactive gas such as a Cl or F species. 
     As for the composite powder having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99), in the case where the value of x is too small, the amount of Y added is slight, causing a deterioration in the corrosion resistance of the composite powder. Further, when the value of x is too large, the amount of Y added is excessive, causing an increase in the preparation cost of the composite powder. Therefore, the value of x is controlled to the foregoing range. Preferably, x may be 0.1 to 0.5. Meanwhile, the value of x may be somewhat changed since the ceramic powder used is partially out of the compositional formulas of MgO and Y 2 O 3  as a chemically stable phase, or the composite powder is decomposed by high heat while passing through an ultrahigh-temperature plasma jet, and thus oxygen and the like vaporizes. When a coating is formed inside vacuum plasma equipment from a composite powder in which the value of x is controlled to the foregoing range, chlorides of Mg and Y, which are formed by a reaction of the coating with a reactive gas such as a Cl or F species, may easily volatilize, or ultrafine reaction products generated at the initial stage may be easily detached from a surface thereof and discharged out of a chamber. Therefore, the value of x is controlled to the foregoing range so that the reaction products are not generated, thereby removing bad influences on the process equipment and goods manufactured therefrom. 
     Here, the diameter of the MgO powder may be 0.1 to 30 μm. A MgO powder having too small a diameter may be partially lost in a subsequent spraying process. Alternatively, a MgO powder having too large a diameter may be somewhat unsuitable for thermal spray coating. Therefore, the diameter of the MgO powder is controlled to the foregoing range. Meanwhile, the diameter of the Y 2 O 3  powder may be 0.1 to 30 μm. A Y 2 O 3  powder having too small a diameter may be partially lost in a subsequent spraying process. Alternatively, a Y 2 O 3  powder having too large a diameter may be somewhat unsuitable for thermal spray coating. Therefore, the diameter of the Y 2 O 3  powder is controlled to the foregoing range. 
     When the MgO powder and the Y 2 O 3  powder are mixed, static electricity that induces the powders to have static electric charges with different polarities may be applied. That is, when the MgO powder and the Y 2 O 3  powder are simply mechanically mixed, the powders may not be homogeneously mixed. However, since two particles have static electric charges with different polarities in a solvent of for example pH 6, hybrid powders can be homogeneously mixed. 
     In the step S 20 , the composite powder is sprayed and dried to prepare a synthesized coating material for thermal spray coating. That is, a coating material for thermal spray coating is prepared by spraying and drying a composite powder having a composition of Mg 1−x Y 2x O 2x+1  (where x is 0.01 to 0.99). At the time of spraying or drying, a single powder is used or powders of at least two kinds are mixed at a particular mixing ratio. In addition, the powder is mixed with a solvent, a binder, a dispersant, and the like to prepare a mixture. Here, a mixed liquid of water, acetone, and isopropyl alcohol may be used as the solvent; a polymer (PVB76), benzyl butyl phthalate, or the like may be used as the binder; and a polymer may be used as the dispersant. As necessary, the binder and the dispersant may not be added. 
     After the mixture is prepared, a powder having a diameter of 1 to 200 μm is prepared by spraying the mixture in a gas, such as air, at 70 to 80° C., or spraying the mixture onto fine grooves formed in a disc rotating at a high rate. Here, when the diameter of the powder is too small, the powder may be partially lost at the time of subsequent thermal spray coating. Alternatively, when the diameter of the powder is too large, subsequent thermal spray coating may not be done well. Therefore, the diameter of the powder is controlled to the foregoing range. 
     Meanwhile, since the coating material for thermal spray coating synthesized by spraying and drying has low hardness, the coating material for thermal spray coating may be subjected to a thermal treatment at 900 to 1500° C. When the thermal treatment temperature for the coating material for thermal spray coating is too low, the hardness of the coating material for thermal spray coating is low. Alternatively, when the thermal treatment temperature for the coating material for thermal spray coating is too high, the coating material for thermal spray coating may deteriorate. Therefore, the thermal treatment temperature of the coating material for thermal spray coating is controlled to the foregoing range. 
     In the step S 30 , the coating material for thermal spray coating is injected toward a plasma jet, followed by heating. In this case, the injected coating material for thermal spray coating is heated by the plasma jet and is thus volatilized, and is then deposited on a surface of the base metal. The deposited powder is rapidly cooled to form a coating film. Here, the base metal may be a chamber of the vacuum plasma equipment or a part inside the chamber. Therefore, the coating film is formed on the chamber of the vacuum plasma equipment, thereby improving the corrosion resistance to plasma. Since the heating by the plasma jet can be easily understood by those skilled in the art, detailed descriptions thereof are omitted. 
     Finally, in the step S 40 , the coating material for thermal spray coating in a completely molten or semi-solid state is deposited on a surface of the base metal to form a coating film. Separately, a raw material powder may be homogeneously dispersed to improve characteristics of the coating, or a post-treatment may be performed to enhance the hardness of the sprayed and dried composite powder. Since the detailed preparation method besides the foregoing descriptions can be easily understood by those skilled in the art, detailed descriptions thereof are omitted. 
     Meanwhile, the Mg—Y—O coating film formed according to an embodiment of the present invention may be placed inside the vacuum plasma equipment. In general, when the plasma atmosphere is formed in the vacuum plasma equipment, atoms and molecules in the plasma are excited, dissociated, or ionized to generate etchant species. In this case, neutral particles are adsorbed on a surface of an inner wall of the vacuum plasma equipment, and the ions may collide therewith. As a result, the reaction products may be formed on and desorbed from the coating film on the surface of the inner wall due to the dissociation by the ions. Therefore, the reaction products may contaminate the vacuum plasma equipment and even an object inside the vacuum plasma equipment. Table 1 below shows the foregoing materials to be etched, reactive gases, and reaction products generated therefrom. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Material to be etched 
                   
                   
               
               
                   
                 (substrate, inner wall, 
                 Reaction gas 
               
               
                 NO 
                 parts, etc.) 
                 (etchant gas) 
                 Reaction product 
               
               
                   
               
             
            
               
                 1 
                 Si, SiO 2 , SiN 4   
                 CF 4 , SF 6 , CHF 3 , NF 3   
                 SiF 4   
               
               
                 2 
                 Si 
                 CF 4 , CCl 2 F 2 , F 113,   
                 SiCl 2 , SiF 4 , SiCl 4   
               
               
                   
                   
                 F 115   
               
               
                 3 
                 Al 
                 BCl 3 , CCl 4 , Cl 2   
                 AlCl 4 , AlCl 3   
               
               
                 4 
                 photoresist 
                 O 2 , O 2  + CF 4   
                 CO, CO 2 , H 2 O, 
               
               
                   
                   
                   
                 HF 
               
               
                 5 
                 refractory metal and 
                 CF 4 , CCl 2 F 2   
                 WF 4   
               
               
                   
                 silicon compound 
               
               
                   
                 thereof 
               
               
                   
                 W: WSi 2   
               
               
                   
                 Ta: TaSi 2   
               
               
                   
                 Mo: MoSi 2   
               
               
                   
               
            
           
         
       
     
     Meanwhile, when the Mg—Y—O coating film according to an embodiment of the present invention is used on the inner wall of the vacuum plasma equipment, the foregoing reaction products may not be generated. That is, the inner wall of the vacuum plasma equipment needs to have corrosion resistance, and even though the reaction products are generated, lump types of products should not be generated due to high volatility thereof. The Mg—Y—O coating film according to an embodiment of the present invention has corrosion resistance to a reactive gas such as a Cl or F species, and also does not generate lump types of reaction products. Therefore, a coating film that has completely new characteristics while not generating reaction products causing failures of goods at the time of processing can be formed. 
     Hereinafter, the present invention will be described in detail through experimental examples. These experimental examples are given to merely exemplify the present invention, but the preset invention is not limited thereto. 
     EXPERIMENTAL EXAMPLES 
     A MgO fine powder and a Y 2 O 3  fine powder were sprayed and dried depending on the mixing ratio thereof, to prepare a Mg—Y—O based coating material for thermal spray coating. At the time of spraying and drying, the forming and drying of droplets are simultaneously performed to prepare a spherical powder. For atomization, a co-current type of chamber that supplies high-temperature air was used, and the temperature at an inlet and the temperature at an outlet, which are basic process parameters, were set to 108° C. and 120° C., respectively. Delivery rate of a slurry in which the micro-sized ceramic powder, binder, and dispersant were mixed was controlled to be 25 liters/hour. In addition, the powder was sprayed and dried while the rotation rate of a disc was set to 15,000 rpm, thereby preparing the coating material for thermal spray coating. 
     Meanwhile, the coating material for thermal spray coating was coated using an SG-100 plasma gun manufactured by Praxair, USA. In this case, power was supplied to the plasma gun using a “PT-800” power application system manufactured by Plasma Tech, Switzerland. In addition, for plasma formation, argon gas and hydrogen gas were used, and the amounts of the gases were controlled to be 36 L/min and 20 to 40 L/min, respectively. Meanwhile, the current and voltage were controlled to 850 A and 45 V, respectively, and thus the applied power was controlled to 30 to 38 kW, and the injection rate of the coating power was controlled to about 15 g/min. The distance between the plasma gun and the material to be coated was controlled to about 120 mm. 
     Experimental Example 1 
     A MgO fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 10:90 to prepare an Mg—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Experimental Example 2 
     A MgO fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 30:70 to prepare an Mg—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Experimental Example 3 
     A MgO fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 50:50 to prepare an Mg—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Experimental Example 4 
     A MgO fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 70:30 to prepare an Mg—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Experimental Example 5 
     A MgO fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 90:10 to prepare an Mg—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Comparative Example 1 
     For forming an amorphous based coating, an Al 2 O 3  fine powder and a Y 2 O 3  fine powder were mixed at a weight ratio of 50:50 to prepare an Al—Y—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Comparative Example 2 
     A MgO fine powder and a ZrO 2  fine powder were mixed at a weight ratio of 10:90 to prepare an Mg—Zr—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing comparative example. 
     Comparative Example 3 
     A MgO fine powder and a ZrO 2  fine powder were mixed at a weight ratio of 30:70 to prepare an Mg—Zr—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Comparative Example 4 
     A MgO fine powder and a ZrO 2  fine powder were mixed at a weight ratio of 50:50 to prepare an Mg—Zr—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Comparative Example 5 
     A MgO fine powder and a ZrO 2  fine powder were mixed at a weight ratio of 70:30 to prepare an Mg—Zr—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Comparative Example 6 
     A MgO fine powder and a ZrO 2  fine powder were mixed at a weight ratio of 90:10 to prepare an Mg—Zr—O based coating material for thermal spray coating. The remaining experimental procedure was the same as that of the foregoing experimental example. 
     Observation of Structure of Coating Material for Thermal Spray Coating 
     Experimental Results of Experimental Example 1 
       FIG. 2  shows scanning electron microscopic images illustrating Mg—Y—O based materials for thermal spray coating prepared according to Experimental Examples 1 to 5 of the present invention. As shown in  FIG. 2 , it could be confirmed that the MgO finer powder and the Y 2 O 3  fine powder were homogeneously mixed to prepare a Mg—Y—O based coating material for thermal spray coating. 
     X-Ray Diffraction Analysis of Coating Material for Thermal Spray Coating 
     Experimental Results of Experimental Examples 1 to 5 
       FIG. 3  shows X-ray diffraction graphs illustrating Mg—Y—O based materials for thermal spray coating prepared according to Experimental Examples 1 to 5 of the present invention. That is,  FIG. 3  shows X-ray diffraction analysis results of Mg—Y—O based coating materials for thermal spray coating prepared by spraying and drying the MgO fine powder and the Y 2 O 3  fine powder of different mixing ratios according to Experimental Examples 1 to 5. 
     As shown in  FIG. 3 , crystalline peaks corresponding to cubic MgO and cubic Y 2 O 3  were observed at all the mixing ratios of MgO:Y 2 O 3  for the Mg—Y—O based coating materials for thermal spray coating. Therefore, it could be confirmed that MgO and Y 2 O 3  were incorporated into the coating material for thermal spray coating. 
     Analysis Results of Structure of Coating Material for Thermal Spray Coating 
     A coating for thermal spray coating according to Comparative Example 1 was formed in known optimum thermal spray coating conditions. In addition, coatings for thermal spray coating according to Comparative Examples 2 to 6 and Experimental Examples 1 to 5 were formed in the same thermal spray coating conditions. 
       FIG. 4  shows scanning electron microscopic images obtained by observing polished surfaces of Mg—Y—O-based coatings formed by a thermal spray coating process according to Experimental Examples 1 to 4 of the present invention. As shown in  FIG. 4 , normal coatings were formed in Experimental Examples 1 to 4. As for the coatings formed according to Experimental Examples 1 to 4, white, gray, and black areas were shown to be mixed, and the higher the proportion of MgO in a mixing ratio of MgO and Y 2 O 3 , the larger the black area. 
     The coating for thermal spray coating according to Experimental Example 5 was not deposited and thus not formed on the surface of the base metal. In Experimental Example 5, the coating was not completely molten and thus was very vulnerable, and normal coating was impossible due to large crude pores and inside cracks. Meanwhile, the coatings formed according to Comparative Examples 2 to 6 showed similar tends to the coatings formed according to Experimental Examples 1 to 4, and thus illustrations thereof will be omitted. 
     EDX Analysis Results of Coating Material for Thermal Spray Coating 
     The white, gray, and black areas shown in the coatings in  FIG. 4  were analyzed in more detail using EDX. That is, in order to check the difference in shading among the white, gray, and black areas, composition analysis thereof was conducted using EDX. 
       FIG. 5  shows graphs obtained by analyzing a coating formed according to Experimental Example 1 of the present invention using an EDX system. 
     As shown in  FIG. 5 , Mg, Y, and O elements corresponding to MgO particles and Y 2 O 3  particles are mixed in the coating of Experimental Example 1. Particularly, since the amount of Y was relatively greater than the amount of Mg in the white area, it could be confirmed that the white area was composed of more Y 2 O 3  particles than MgO particles. Meanwhile, since the amount of Mg was more increased than the amount of Y toward the black area, it could be confirmed that the black area was composed of more MgO particles than Y 2 O 3  particles. 
     X-Ray Diffraction Experiment on Coatings Formed Through Thermal Spray Coating and Experimental Results 
       FIG. 6  shows X-ray diffraction graphs illustrating coatings formed according to Experimental Examples 1 to 4 of the present invention. 
     In Experimental Examples 2 to 4, crystalline peaks corresponding to cubic MgO and cubic Y 2 O 3  were observed even after thermal spray coating. However, it could be confirmed that an amorphous peak was shown in Experimental Example 1. This was the same as a crystallized structure of a general amorphous coating. 
     Corrosion Resistance Test on Coatings Formed Through Thermal Spray Coating and Test Results 
     A corrosion resistance test on coatings was conducted under the plasma atmosphere containing a corrosive gas of a Cl species. That is, the corrosion resistance of the coating was measured for 900 seconds under conditions of plasma power of 800 W, bias power of 300 W, 100 seem of BCl 3 , 100 seem of Cl 2 , and pressure of 20 mTorr. 
       FIG. 7  shows scanning electron microscopic images of etched surfaces before and after a corrosion resistance test of coatings formed according to Experimental Examples 1 to 4. That is, upper panels of  FIG. 7  show scanning electron microscopic images before the corrosion resistance test of the coatings, and lower panels of  FIG. 7  show scanning electron microscopic images after the corrosion resistance test of the coatings. 
     As shown in  FIG. 7 , the coatings of Experimental Examples 1 to 3 were shown to have almost the same coating surfaces that were hardly etched. However, the coating of Experimental Example 4 was shown to have a coating surface that was remarkably etched along large crude pores as well as interfaces of droplets. 
     Etching Rate Test on Coatings Formed Through Thermal Spray Coating and Test Results 
     The etching rates of the coatings were measured under the plasma atmosphere containing a corrosive gas of a Cl species. The plasma etching rate was calculated by measuring the step difference between a region etched with plasma containing a reactive gas of a Cl species and a region not etched with the plasma while the surface of the coating was masked, and then dividing the step difference by the etching time. 
       FIG. 8  is a graph illustrating etching rates in coatings formed according to Experimental Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention. 
     As shown in  FIG. 8 , the etching rates of the coatings in Experimental Examples 1 to 3 were significantly improved when compared to the etching rates of the coatings in Comparative Examples 1 to 5. In particular, the etching rate of the coating in Experimental Example 1 was about 11 nm/min, which was the lowest value. That is, the etching rate in Experimental Example 1 was improved so as to be merely about 27% of 40 nm/min, which is an approximate etching rate of the coatings in Comparative Examples 1 to 5. More specifically, as a result of etching the coatings in Comparative Examples 2 to 5 under the plasma atmosphere containing a gas of a Cl species, the coatings showed significantly high etching rates, which were higher compared with the coating in Comparative Example 1. 
     Experiment on Formation of Ultrafine Reaction Products of Coatings Formed Through Thermal Spray Coating and Experimental Results 
     The experiment on the formation of ultrafine reaction products of the coatings was conducted under the plasma atmosphere containing a corrosive gas of a Cl species. That is, the experiment on the formation of ultrafine reaction products of the coatings was conducted for 900 seconds under conditions of plasma power of 800 W, 100 seem of BCl 3 , 100 seem of Cl 2 , and pressure of 20 mTorr. 
       FIG. 9  shows scanning electron microscopic images illustrating exposed surfaces of coatings formed according to Experimental Examples 1 to 4 of the present invention. Here, upper panels of  FIG. 9  show scanning electron microscopic images before the experiment on the formation of ultrafine reaction products of the coatings, and lower panels of  FIG. 9  show scanning electron microscopic images after the experiment on the formation of ultrafine reaction products of the coatings. 
     As shown in  FIG. 9 , the coatings in Experimental Examples 1 to 4 of the present invention, which were exposed to the plasma atmosphere containing a corrosive gas of a Cl species, showed smooth surfaces without ultrafine reaction products. That is, the formation of the ultrafine reaction products were remarkably suppressed and thus minimized in the coatings in Experimental Examples 1 to 4 compared to the coatings in Comparative Examples 1 to 5. 
     In the conventional art, a multi-component based ceramic material having three or more elements was thermal spray coated, so that the coating film was mostly formed in an amorphous phase. For example, the Al 2 O 3  fine powder and the Y 2 O 3  powder were mixed to prepare a composite powder having a size of 40 to 60 μm, and then the composite powder was thermal spray coated, thereby forming a coating in an amorphous phase. Through this method, Al—Y—O coatings, Al—Zr—O coatings, and Y—Zr—O coatings, which had greatly improved corrosion resistance to plasma compared with coatings composed of Y 2 O 3 , were formed. However, although the Al—Y—O coatings and the Al—Zr—O coatings showed excellent corrosion resistance under the reactive gas atmosphere containing a reactive gas, such as a Cl or F species, the corrosion resistance was largely changed due to the thermal spray coating, and thus it was not easy to secure reproducibility. Moreover, since the surface of the coating reacted with a reactive gas such as a Cl or F species, a large amount of ultrafine reaction products were generated. Meanwhile, the Y—Zr—O coatings were proposed to overcome the limitations of the foregoing amorphous coatings, but showed problems, like the Al—Zr—O based coatings, in that they have low chemical corrosion resistance to a reactive gas such as a Cl or F species under the plasma atmosphere containing the reactive gas such as the Cl or F species. Moreover, the Y—Zr—O coatings had a problem in which the etching of surfaces of the Y—Zr—O coatings caused ultrafine reaction products, similarly to the Al—Zr—O based coatings. 
       FIG. 10  is an image showing a state in which a large crude reaction product generated during a manufacturing procedure is dropped on a circuit. 
     As shown in  FIG. 10 , the use of the foregoing Al—Y—O coating, Al—Zr—O coating, Y—Zr—O coating, and Y—Zr—O coating caused the formation of large crude reaction products, which contaminated processing equipment and goods manufactured in the processing equipment. In contrast, the coatings formed according to experimental examples of the present invention had very high physical corrosion resistance under the plasma atmosphere containing a corrosive gas of a Cl species when compared with the conventional coatings formed according to the comparative examples. That is, in the case where the coatings formed according to experimental examples of the present invention are used, the lifespan of the parts of the semiconductor equipment can be extended to significantly improve the process efficiency, and the failure rate of goods due to contamination caused by the reaction products can be minimized. 
     The physical corrosion resistance and chemical corrosion resistance of the coatings formed according to the experimental examples of the present invention were improved by about 500% or higher when compared with the coatings formed according to the comparative examples. Therefore, the Mg—Y—O alloy can be used as a protective coating agent useful for equipment and internal parts thereof, which are used under the corrosive atmosphere in a poor state. 
     While the present invention has been described above with respect to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the spirit and scope of the appended claims.