Patent Publication Number: US-2009229753-A1

Title: Method for manufacturing shower plate, shower plate manufactured using the method, and plasma processing apparatus including the shower plate

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2008-063341 filed on Mar. 12, 2008, in the Japan Patent Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for manufacturing a shower plate, a shower plate manufactured using the method, and a plasma processing apparatus including the shower plate. 
     2. Description of the Related Art 
     Plasma technologies have been widely used for manufacturing many semiconductor devices such as integrated circuits, liquid crystal display devices, solar cells, and so on. Such plasma technologies are used in a deposition or etching of a thin film during a semiconductor manufacturing procedure, but a highly advanced plasma process, such as an ultra-fine process, is required for manufacturing high-performance and high-functional products. 
     Plasma is generated by microwaves or high frequency electromagnetic waves. Specifically, a plasma processing apparatus that generates high-density plasma excited by microwaves has been proposed. In order to generate stable plasma, it is desirable not only to uniformly radiate microwaves, but also to uniformly supply a gas for exciting plasma into a processing chamber. 
     Typically, a shower plate including a plurality of holes for a gas discharge is used in order to uniformly supply a gas for exciting plasma into a processing chamber. However, plasma formed directly beneath the shower plate flows reverse into the holes, and thus an abnormal discharge and accumulation of gas occur to deteriorate the yield of the products. 
     Japanese Patent Publication No. 2007-221116 (hereinafter, referred to as Reference 1) discloses a plasma processing apparatus which can introduce a predetermined gas from, for example, a top plate, and can generate plasma without an abnormal discharge. The plasma processing apparatus of the Reference 1 comprises a processing container, a top plate that is formed of a dielectric material and is hermetically or gas-tightly attached to an opening of the container so as to transmit electromagnetic waves into the container, an electromagnetic wave transfer means for transferring electromagnetic waves for generating plasma to the processing container, and a gas transfer means for transferring a predetermined gas to the processing container, wherein the gas transfer means includes gas ejection holes formed in the top plate so as to face inside the processing container, a porous dielectric substance placed in each of the gas ejection holes, and a gas supplying system for supplying the predetermined gas to the gas ejection holes. Thus, the top plate is also used as a shower plate. 
     In the conventional art, a porous dielectric substance is joined to gas ejection holes of the top plate directly or by using an adhesive. However, a gap may be generated between the top plate and the porous dielectric substance due to sintering shrinkage during sintering or firing the top plate, and thus gas may leak through the gap. Amounts of gas supplied from a plurality of gas ejection holes become non-uniform because some holes have such gap and some other holes do not have such gap. Thus, plasma becomes non-uniform. Moreover, due to repeated use of the gas ejection holes, thermal stress or heat distortion may be occurred, and thus the porous dielectric substance may be partially or entirely detached from the gas ejection holes. 
     SUMMARY OF THE INVENTION 
     To solve the above and/or other problems, the present invention provides a method for manufacturing a shower plate which can prevent generation of plasma reverse flow and can uniformly and stably supply a gas for exciting plasma. The present invention further provides a shower plate from which any part does not fall apart when used. The invention also provides a shower plate manufactured using such method, and a plasma processing apparatus comprising the shower plate. 
     According to an aspect of the present invention, there is provided a method for manufacturing a shower plate for introducing gas into a processing container in a plasma processing apparatus, the method comprising: forming a porous gas-communicating body having a pillar shape with a porous material; forming a dense member having a tube shape with a dense material that is not gas-permeable; forming a porous piece body by covering a lateral side of the porous gas-communicating body with the dense member so that the lateral side of the gas-communicating body and the dense member contact each other; performing a first sintering step by sintering the porous piece body at a first temperature; forming a concave portion on one of principal surfaces of a dielectric plate, which is to face plasma, wherein the dielectric plate is a main body of the shower plate; forming a gas flow path from the bottom face of the concave portion to the other of the principal surfaces of the dielectric plate; inserting the porous piece body into the concave portion; and performing a second sintering step by entirely sintering the dielectric plate after the inserting step, at a second temperature equal to or lower than the first temperature. 
     The method may further include pre-sintering step in which the porous gas-communicating body is sintered in advance, before the forming step of the porous piece body. 
     In the performing of the first sintering step, sintering conditions are selected such that a sintering shrinkage rate of the dense member is higher than a sintering shrinkage rate of the porous gas-communicating body. 
     The method may further include individually checking a gas-communicating amount of the porous piece body before the inserting step. 
     The method may further include chamfering an edge of a surface of the porous piece body contacting the bottom face of the concave portion and an edge of a lateral side of the porous piece body, before the inserting step. 
     The method may further include forming a gas passage connecting the gas flow path and a space of a portion cut off during the chamfering, before the inserting step. 
     According to another aspect of the present invention, there is provided a shower plate for a plasma processing apparatus forming plasma, the shower plate including: a dielectric plate formed of a dielectric material; a concave portion formed on one of principal surfaces of the dielectric plate facing the plasma; a gas flow path formed from the bottom face of the concave portion to the other of the principal surfaces of the dielectric plate; a porous gas-communicating body having a pillar shape, wherein the porous gas-communicating body is formed of a porous material; a dense member having a tube shape, wherein the dense member is formed of a dense material that is not gas-permeable; and a porous piece body installed in the concave portion wherein the dense member covers a side of the porous gas-communicating body being faced to the dense member so as to be integrated, wherein a gap between the porous gas-communicating body and the dense member, and a gap between the side of the concave portion and the porous piece body are smaller than a maximum pore size in the porous gas-communicating body. 
     The maximum pore size may be equal to or smaller than about  0 . 1  mm. 
     The porous gas-communicating body may not contact the concave portion. 
     According to another aspect of the present invention, there is provided a shower plate manufactured according to the method of above. 
     According to another aspect of the present invention, there is provided a plasma processing apparatus including the shower plate of above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a cross-sectional view illustrating a plasma processing apparatus including a shower plate, according to an embodiment of the present invention; 
         FIG. 2(   a ) is a plan view of a shower plate seen from a plasma processing container; 
         FIG. 2(   b ) is a cross-sectional view taken along a line M-M of  FIG. 2(   a ); 
         FIG. 3A  is a diagram illustrating the forming of a gas-communicating body in a method for manufacturing a shower plate according to an embodiment of the present invention; 
         FIG. 3B  is a diagram illustrating the forming of a dense member in the method for manufacturing a shower plate according to an embodiment of the present invention; 
         FIG. 3C  is a diagram illustrating the forming of a porous piece body in the method for manufacturing a shower plate according to an embodiment of the present invention; 
         FIG. 3D  is a diagram illustrating the processing (cutting) of a porous piece body in the method for manufacturing a shower plate according to an embodiment of the present invention; 
         FIG. 3E  is a diagram illustrating the processing (chamfering) of a porous piece body in the method for manufacturing a shower plate according to an embodiment of the present invention; 
         FIG. 3F  is a diagram illustrating the forming of the shower plate in the method for manufacturing a shower plate according to an embodiment of the present invention; and 
         FIG. 4(   a ) is a cross-section of a part of  FIG. 2(   b ), and  FIGS. 4(   b ) and  4 ( c ) are partially enlarged diagrams of a portion surrounded by a dotted line in  FIG. 4(   a ). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present invention will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. Like reference numerals in the drawings denote like elements, and thus descriptions thereof will not be repeated. 
       FIG. 1  is a cross-sectional view illustrating a microwave plasma processing apparatus  1  including a shower plate according to an embodiment of the present invention. The plasma processing apparatus  1  comprises a plasma processing container (chamber)  2 , the shower plate (dielectric substance)  3 , an antenna  4 , a waveguide  5 , and a substrate supporting stage  6 . The antenna  4  is comprised of a waveguide portion  4 A (shield member), a radial line slot antenna (RLSA)  4 B, and a wavelength-shortening plate  4 C (dielectric substance). The waveguide  5  is a coaxial waveguide including an external waveguide  5 A and an internal waveguide  5 B. 
       FIGS. 2(   a ) and  2 ( b ) are diagrams illustrating an example of the shower plate  3  in the plasma processing apparatus  1  of  FIG. 1 .  FIG. 2(   a ) is a plan view of the shower plate  3  seen from the plasma processing container  2 , and  FIG. 2(   b ) is a cross-sectional view taken along a line M-M of  FIG. 2(   a ). The shower plate  3  is provided with a plurality of porous piece bodies  13  respectively set in a plurality of concave portions  10  of a top plate  9  (formed of a dielectric substance) that is the base material of the shower plate  3 . Each of the porous piece bodies  13  is comprised of a gas-communicating body  11  and a dense member  12 . The pluralities of concave portions  10  and the porous piece bodies  13  of the shower plate  3  are scattered on the top plate  9 , and may be arranged in concentric circles or in alignment along a plurality of lines and it is desirable to be symmetrically arranged. Also, the shower plate  3  is provided with a gas flow path  14  penetrating the concave portion  10  from a side or top of the shower plate  3 , and is capable of introducing gas into the plasma processing container  2  via the gas flow path  14 . 
     An opening of the plasma processing container  2  of the plasma processing apparatus  1  is gas-tightly closed by the shower plate  3 . Inside of the plasma processing container  2  is maintained in a vacuum state by using a vacuum pump. The antenna  4  is combined with the shower plate  3 , and the waveguide  5  is connected to the antenna  4 . The waveguide portion  4 A is connected to the external waveguide  5 A, and the RLSA  4 B is combined with the internal waveguide  5 B. The wavelength-shortening plate  4 C is disposed between the waveguide portion  4 A and the RLSA  4 B, and reduces a microwave wavelength. The wavelength-shortening plate  4 C may be formed of, for example, a dielectric substance such as quartz or alumina. 
     Microwaves are supplied from a microwave source via the waveguide  5 . The microwaves then propagate between the waveguide portion  4 A and the RLSA  4 B in a diameter direction, and are emitted from a slot of the RLSA  4 B. When plasma is formed as the microwaves are supplied inside the plasma processing container  2 , inert gases such as argon (Ar) or Xenon (Xe), and nitrogen (N 2 ), is introduced into the plasma processing container  2 . When required, a process gas, such as hydrogen, is also introduced into the plasma processing container  2 . 
     Gas is introduced from the side or top of the shower plate  3 , and is injected from the concave portion  10  via the gas flow path  14 . Since the porous piece body  13  is inserted into the concave portion  10 , which operates as a gas ejection hole, the gas is introduced into the plasma processing container  2  via the porous piece body  13 . 
     The gas-communicating body  11 , which is in the center of the porous piece body  13 , includes a plurality of pores that are connected in a gas-communicating direction so that the gas passes therethrough. Since the porous piece body  13  is inserted into the gas ejection hole, an abnormal discharge of plasma and reverse flow of plasma are prevented. In the conventional art, when plasma is abnormally discharged, the shower plate  3  is overheated, and thus deformation or distortion due to thermal stress is occurred. Accordingly, a part of the shower plate  3  may be damaged or may fall off. However, according to the present invention, by preventing an abnormal discharge of plasma, the shower plate  3  is prevented from being damaged, and reverse flow of plasma or accumulation of gas to or in the gas ejection hole does not occur. Accordingly, it is possible to effectively generate stable plasma  7 . 
     The dense member  12  on the circumference of the porous piece body  13  is formed of a material that is not gas-permeable. In the forming step of the porous piece body  13  by covering the side of the gas-communicating body  11  with the dense member  12 , a gas-communicating amount may be individually checked. By using the shower plate  3  that includes the porous piece body  13  allowing the equal gas-communicating amount, it is possible to uniformly transfer the gas into the plasma processing container  2 . 
     Also, by forming the dense member  12  in the porous piece body  13 , the concave portion  10  and the porous piece body  13  are closely combined with each other, and the gas-communicating body  11  and the dense member  12  are also closely combined with each other. Thus, since gaps between the concave portion  10  and the porous piece body  13  and between the gas-communicating body  11  and the dense member  12  are sufficiently small, an abnormal discharge of plasma, reverse flow of plasma, and accumulation of gas are prevented, and thus the stable plasma  7  is effectively generated. 
       FIGS. 3A through 3F  are diagrams illustrating a method for manufacturing a shower plate, according to an embodiment of the present invention. In the present embodiment, the shower plate  3  is identical to the shower plate  3  of the plasma processing apparatus  1  of  FIG. 1 . Specifically,  FIGS. 3A through 3E  illustrate processes of forming the porous piece body  13  included in the shower plate  3 . 
       FIG. 3A  is a diagram for describing forming of a gas-communicating body  11   a  that is made of a porous material. The gas-communicating body  11   a  has a pillar shape, is a member that transfers gas in a direction perpendicular to the cross-section of a circle, and has pores that are connected in a gas-communicating direction. The gas-communicating body  11   a  may be formed of porous quartz or porous ceramic. The maximum pore size of the pores is equal to or smaller than about 0.1 mm. When the maximum pore size is above 0.1 mm, an abnormal discharge of plasma due to microwaves may highly likely to be generated, and reverse flow of plasma may not be prevented. The pore size of the pores may be as small as possible without blocking of gas flow. 
       FIG. 3B  is a diagram for describing forming of a dense member  12   a  covering a side of the gas-communicating body  11   a.  The dense member  12   a  has a tube shape and is formed of a material that is not gas-permeable. The dense member  12   a  may be formed of a ceramic material, such as SiO 2  or Al 2 O 3 . A tolerance between an inside diameter of a hollow portion of the dense member  12   a  and an external diameter of the gas-communicating body  11   a  may be referred to as a clearance fit or a transition fit. 
       FIG. 3C  is a diagram for describing forming of a porous piece body  13   a  by inserting the gas-communicating body  11   a  into the hollow portion of the dense member  12   a  and sintering it. In  FIG. 3C , thick arrows show portions where sintering-shrinkage is occurred in the dense member  12   a  during the sintering and pressure is applied from the circumference to the center of the circle. Only insertion of the dense member  12   a  into the gas-communicating body  11   a  results in generating a gap between the dense member  12   a  and the gas-communicating body  11   a.  Accordingly, by sintering a combination of the dense member  12   a  and the gas-communicating body  11   a,  the dense member  12   a  covering the lateral side of the gas-communicating body  11   a  is contracted towards the gas-communicating body  11   a,  and thus tightening stress is generated. As a result, the dense member  12   a  closely covers the lateral side of the gas-communicating body  11   a.    
     When a gas is flowed to the porous piece body  13 , if there is a gap between the gas-communicating body  11  and the dense member  12 , the gas flows from the gap instead of the gas-communicating body  11 , and thus gas ejection of the porous piece body  13  become non-uniform. Also, when a size of the gap is large, reverse flow or abnormal discharge of plasma may be generated, like when a pore size of the pores are large. Accordingly, the gap between the gas-communicating body  11  and the dense member  12  is set to be equal to or smaller than the maximum pore size, i.e. equal to or smaller than about 0.1 mm. 
     When the porous piece body  13   a  is sintered, the dense member  12   a  closely covers the lateral side of the gas-communicating body  11   a  if contraction of the external dense member  12   a  is stronger than contraction of the internal gas-communicating body  11   a.  The gas-communicating body  11   a  in  FIG. 3A  may be pre-sintered before the forming of the porous piece body  13   a  in  FIG. 3C . Since it is difficult to occur the sintering-shrinkage of the gas-communicating body  11   a  even when the gas-communicating body  11   a  is subjected to sintering step for forming the porous piece body  13   a,  it is easier to apply a contracting pressure toward the center of the dense member  12   a.  Accordingly, the dense member  12   a  closely covers the lateral side of the gas-communicating body  11   a.    
     A gas-communicating amount of the gas-communicating body  11  a of  FIG. 3A  and a gas-communicating amount of the porous piece body  13   a  of  FIG. 3C  are the same. The porous piece body  13   a  is formed by installing the dense member  12   a  on the gas-communicating body  11   a,  and thus non-uniformity of the external diameter remarkably decreases. Also, it becomes possible to more precisely combine the porous piece body  13  and the concave portion  10  in a post-process. Using only the gas-communicating body  11 , a part of gas may flow out from the lateral side of the gas-communicating body  11  and accumulate between the concave portion  10  and the gas-communicating body  11 . However by using the porous piece body  13 , the dense member  12  is not penetrated by gas, and thus the gas only flows in the gas-communicating direction. Accordingly, the gas does not accumulate between the concave portion  10  and the gas-communicating body  11 , and an abnormal discharge is not generated. 
       FIG. 3D  is a diagram illustrating the porous piece body  13 , wherein the integrally sintered porous piece body  13   a  is cut to a predetermined length. For example, when a height of the concave portion  10  is H 1 , the porous piece body  13  also needs to be cut to the height H 1 . When the porous piece body  13   a  is formed to have a height equal to or n times larger than H 1 , a plurality of porous piece bodies  13  may be formed. 
       FIG. 3E  is a diagram for describing chamfering of the dense member  12  on one side of the porous piece body  13 . An edge of a surface of the porous piece body  13  that is inserted on a lower surface of the concave portion  10  is chamfered. Actually, since the porous piece body  13  is not characterized by upper and lower directions, any side of the porous piece body  13  may be chamfered. A chamfered side is inserted into the lower surface of the concave portion  10 . A diameter R 1  is an external diameter of the dense member  12  and a diameter R 2  is an inside diameter of the dense member  12 . The height H 1  of the porous piece body  13  is divided into a height H 2  that is chamfered and a height H 3  that is not chamfered. Since a tightening stress is applied to a side of the height H 3  of the porous piece body  13  when the porous piece body  13  is installed in the concave portion  10 , it is sure that the height H 3  is not remarkably reduced. 
     A diameter of a circumference P of a lateral side of the chamfered surface of the porous piece body  13  is identical to the diameter R 1 . When a diameter R 3  denotes a diameter of a circumference K of a lower surface of the chamfered surface of the porous piece body  13 , the following inequality may be satisfied R 1 &gt;R 3 &gt;R 2 . A surface KP between the circumference K and the circumference P may be a flat surface or a curved surface. 
     Due to the chamfering, the lateral side of the concave portion  10  and the edge of the porous piece unit  13  are not twisted when the porous piece body  13  is inserted into the concave portion  10 . Since the circumference of the lower surface of the concave portion  10  and the edge of the dense member  12  do not contact each other when the porous piece body  13  is inserted into the concave portion  10 , the porous piece body  13  is prevented from coming off or being tilted. This is because sometimes the circumference may become thinner than the center of the circle or have different depths, as it is difficult to parallelize the lower surface of the concave portion  10  while forming the concave portion  10  on the top plate  9 . Also, when the concave portion  10  is installed in the top plate  9 , an opening of the concave portion  10  is not widened. Thus, a gap between the concave portion  10  and the porous piece body  13  is not formed. 
     After chamfering the porous piece body  13 , a groove connecting a space S formed by chamfering and the gas flow path  14  may be formed. For example, the groove may be formed to cross the lower surface of the concave portion  10 , or may be formed in a diameter direction of the dense member  12 , i.e. toward the gas-communicating body  11 . When the porous piece body  13  is installed, it is possible to prevent the gas from accumulating in the space S and it is easier to install the porous piece body  13 . 
     While forming the porous piece body  13 , each of gas-communicating amounts may be individually checked. Accordingly, a defective product may be pre-removed, and thus the number of defective shower plates  3  may be substantially reduced. Also, by controlling the gas-communicating amounts of the porous piece body  13 , the shower plate  3  uniformly ejects gas. 
       FIG. 3F  is a diagram for describing forming of the shower plate  3  by inserting the porous piece body  13  into the concave portion  10  of the top plate  9  and then by sintering the combination of the porous piece body  13  and the top plate  9  into a unit body. The porous piece body  13  is inserted into the concave portion  10  such a way that the chamfered surface is adjusted on the lower surface of the concave portion  10 . Thick arrows in  FIG. 3F  show a pressure applied from the circumference of the concave portion  10  toward the center of the concave portion  10 , by sintering-contracting the top plate  9  during the sintering of the shower plate  3 . In other words, the pressure is applied from the top plate  9  to the porous piece body  13  inserted in the concave portion  10 . 
     A sintering temperature while entirely sintering the shower plate  3  is equal to or lower than a sintering temperature of the porous piece body  13   a  of  FIG. 3C . Accordingly, the porous piece body  13  is not sintering-contracted while entirely sintering the shower plate  3 , and thus the size of the shower plate  3  is constant. The concave portion  10  of the top plate  9  may be adjusted according to the size of the porous piece body  13 . Alternatively, the porous piece body  13  may be inserted into the concave portion  10  so that only a small gap is generated, before the sintering the shower plate  3 . Alternatively, by entirely sintering the shower plate  3 , the concave portion  10  tightly stresses the porous piece body  13 , and thus the porous piece body  13  and the concave portion  10  are closely adhered to each other without a gap. Accordingly, it is possible to integrally fix the porous piece body  13  to the shower plate  3 . 
     When a gap is generated between the concave portion  10  and the porous piece body  13 , the gas flows from the gap, instead of the gas-communicating body  11 , and thus gas ejection from the porous piece body  13  becomes non-uniform. Moreover, when the size of the gap is large, reverse flow or abnormal discharge of plasma may be generated. Accordingly, the gap between the concave portion  10  and the porous piece unit  13  may be equal to or smaller than the maximum pore size, i.e. equal to or smaller than about 0.1 mm. 
     Regarding a contacted portion of the concave portion  10  and the porous piece body  13 , only the dense member  12  of the porous piece body  13  may contact the concave portion  10 , and the gas-communicating body  11  may not contact the concave portion  10 . When the gas-communicating body  11  and the concave portion  10  contact each other, a gas-communicating amount in the contacted portion may change, and thus an amount of gas that is different from a gas-communicating amount that was checked after forming the porous piece body  13  may be communicated from the porous piece body  13  inserted into the concave portion  10 . Accordingly, the shower plate  3  is not able to uniformly eject the gas. 
       FIG. 4(   a ) is a cross-section of a part of the shower plate  3  of  FIG. 2(   b ), and  FIGS. 4(   b ) and  4 ( c ) are partially enlarged diagrams of a portion W surrounded by a dotted line in  FIG. 4(   a ). 
       FIG. 4(   a ) is a partially enlarged diagram of  FIG. 2(   b ). Referring to  FIG. 4(   a ), a surface of the porous piece body  13  is chamfered, and the chamfered surface is installed on the lower surface of the concave portion  10 . Gas transferred from the gas flow path  14  is diffused via the gas-communicating body  11 . When a flow path diameter of the gas flow path  14  is large, a microwave distribution changes as the electric field density changes, which causes a plasma mode to change, and thus the flow path diameter of the gas flow path  14  may become small. 
     A cross section of the gas flow path  14  is very small compared to a cross section of the gas-communicating body  11 , and the gas flow path  14  transfers the gas only to a part of the gas-communicating body  11 . Since the gas-communicating body  11  transfers the gas only in a predetermined direction, the gas is not ejected from the entire gas-communicating body  11 , and thus gas ejection becomes non-uniform. Accordingly, a groove is formed in the lower surface of the concave portion  10  in order to serve as a gas diffusing space  15 . A cross section of the gas diffusing space  15  is larger than the cross section of the gas-communicating body  11 , and has a size that allows the lower surface of the concave portion  10  to sufficiently contact the dense member  12 . When a diameter of the gas diffusing space  15  is G, the following inequality may be satisfied diameter R 3  (diameter of the circumference K)&gt;G&gt;diameter R 2  (the inner diameter of the dense member  12 ). The gas transferred via the gas diffusing space  15  is communicated from the entire gas-communicating body  11 , and thus is uniformly ejected from the porous piece body  13 . Since the gas is ejected from the plurality of the porous piece body  13 , the gas is uniformly diffused just below the shower plate  3 . 
       FIGS. 4(   b ) and  FIG. 4(   c ) are enlarged diagrams of the portion W and illustrate examples of grooves  16   a  and  16   b  for preventing gas from accumulating in the space S when the porous piece body  13  is chamfered. Referring to  FIG. 4(   b ), the groove  16   a  is formed to cross the lower surface of the concave portion  10 . The gas accumulated in the space S flows to the gas diffusing space  15  via the groove  16   a,  and thus flows to the gas flow path  14 . Referring to  FIG. 4(   c ), the groove  16   b  is formed in a diameter direction of the dense member  12  of the porous piece body  13 . The groove  16   b  connects the space S and the gas diffusing space  15 , and transfers the gas accumulated in the space S to the gas flow path  14 . The space S and the gas flow path  14  may be connected to each other via the groove  16   a,  the groove  16   b,  or any other hole for transferring the gas. 
     By using a shower plate manufactured using the above method, a plasma processing apparatus, which can prevent reverse flow of plasma, can uniformly and stably supply gas for exciting plasma, and prevents a part of the shower plate from falling off, may be obtained. 
     Materials of a top plate, a gas-communicating body, and a dense member that constitute the shower plate are not limited to the materials described above. In the embodiments of the present invention, the top plate that gas-tightly closes the plasma processing apparatus and the shower plate for introducing plasma gas are integrally formed, but the top plate and the shower plate may be separately formed. For example, a closed gas flow path is formed by combining a shower plate, in the upper surface of which a groove of a gas flow path is formed, with a top plate. A method of manufacturing a gas ejection hole has been described above. Also, a location of a porous piece body and a shape of the gas flow path of the shower plate are not limited to the above embodiments, and may have various patterns. 
     The plasma processing apparatus may be applied for all plasma processes, such as a plasma CVD process, an etching process, a sputtering process, and an ashing process. The plasma gas for forming plasma may be selected based on conditions such as processing methods, and a substrate for performing a plasma process is not limited to a semiconductor substrate. 
     By using the method of the present invention, a shower plate which can prevent reverse flow of plasma, can uniformly and stably supply gas for exciting plasma, and prevents a part thereof from falling off, is obtained. 
     While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.