Patent Publication Number: US-2009229757-A1

Title: Plasma processing apparatus

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2008-061132, filed on Mar. 11, 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 plasma processing apparatus. 
     2. Description of the Related Art 
     A conventional plasma processing apparatus is disclosed, for example, in Japanese Laid-open Patent Publication No. 2002-184761. The conventional plasma processing apparatus disclosed in this publication includes a chamber in which a wafer is plasma processed, a matching box for supplying a radio frequency (RF) voltage to the chamber, and an elevation driving unit which elevates the matching box. In addition, terminals of the chamber and the matching box can be connected to each other for electrically connecting the chamber to the matching box. 
     In the plasma processing apparatus having the above structure, a gap between the terminals to be connected to each other needs to be reduced so as to guarantee an electrical connection. In this case, a resistance that occurs when the terminals are connected to each other increases. Thus, a large force is required for connecting the terminals. Thus, the plasma display apparatus disclosed in the above publication includes the elevation driving unit, which includes a ball screw, a guide rail, a rail, an operating handle, and an endless belt. 
     However, the elevation driving unit has a large and complicated structure. In addition, when the gap between the terminals is reduced, a contact portion may be damaged when connecting the terminals. 
     SUMMARY OF THE INVENTION 
     To solve the above and/or other problems, the present invention provides a plasma processing apparatus which includes a small-sized elevation driving unit for a matching box so that an electrical connection between a chamber and the matching box can be guaranteed. 
     According to an aspect of the present invention, there is provided a plasma processing apparatus including: an upper electrode and a lower electrode facing each other; a process container in which a substrate supported by the lower electrode is plasma processed; a matching box electrically connected to the lower electrode, wherein the matching box may be freely attached and detached with respect to the lower electrode and supplies a radio frequency (RF) power to the lower electrode; and a fluid pressure cylinder fixed at the process container and pulling up the matching box to a position where the matching box is connected to the lower electrode. The lower electrode and the matching box may be electrically connected to each other via a female terminal connected to one of the lower electrode and the matching box and a male terminal connected to other one of the lower electrode and the matching box and inserted in the female terminal, and at least one of the female terminal and the male terminal may include an elastic conductor covering a contact surface which contacts other one of the female terminal and the male terminal. 
     In the above structure, the female terminal and the male terminal are covered with the elastic conductor so that a predetermined gap between the male terminal and the female terminal can be formed. As such, a resistance that occurs when the female terminal and the male terminal are connected to each other can be reduced, and the female terminal and the male terminal can be prevented from being damaged during connection. In addition, due to a reduction in the resistance that occurs when the female terminal and the male terminal are connected to each other, a small-sized air cylinder can be used as an elevation driving unit for driving the matching box. 
     The elastic conductor may be a cylindrical member having a wrinkled hose structure. The wrinkled hose structure is elastically deformed, a mountain portion thereof contacts an inner diameter surface of the female terminal, and a valley portion thereof contacts an outer diameter surface of the male terminal so that, even though a predetermined gap between the male terminal and the female terminal is formed, the male terminal and the female terminal can be electrically connected to each other. 
     The fluid pressure cylinder may be disposed perpendicularly above the center of gravity of the matching box. As such, the matching box can be pulled up in a horizontal direction so that the male terminal and the female terminal can be properly electrically connected to each other. 
     The fluid pressure cylinder may be an air cylinder using air pressure. Also, a hydraulic cylinder using hydraulic pressure may be used. 
     The fluid pressure cylinder may be a double acting cylinder. Also, a single acting cylinder elastically supporting a piston toward one side may be used. 
    
    
     
       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 longitudinal cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a plan view schematically illustrating the plasma processing apparatus of  FIG. 1 ; 
         FIG. 3  is an expanded view illustrating a state where the lower electrode and the matching box are not connected to each other; 
         FIG. 4  is an expanded view illustrating a state where the lower electrode and the matching box are connected to each other; and 
         FIG. 5  illustrates a fluid pressure cylinder according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The attached drawings for illustrating exemplary embodiments of the present invention are referred to in order to gain a sufficient understanding of the present invention, the merits thereof, and the objectives accomplished by the implementation of the present 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. 
     A plasma processing apparatus  11  according to an embodiment of the present invention will now be described with reference to  FIGS. 1 through 4 .  FIG. 1  is a longitudinal cross-sectional view of the plasma processing apparatus  11 ,  FIG. 2  is a plan view schematically illustrating the plasma processing apparatus  11 , and  FIGS. 3 and 4  are expanded views illustrating states where a lower electrode  14  and a matching box  21  are not connected and respectively connected to each other. 
     First, referring to  FIG. 1 , the plasma processing apparatus  11  according to the present embodiment includes a chamber  12 , which is a process container having a process space S in which plasma processing is carried out, a matching box  21 , and an air cylinder  31  as a fluid pressure cylinder. 
     The chamber  12  is a cylindrical process container that is formed using a conductor. In the chamber  12 , an upper electrode  13  and the lower electrode  14  are arranged to face each other. Also, a gas supply source (not shown), which supplies a process gas, and an exhaust unit (not shown), which maintains the process space S at a predetermined pressure by exhausting the remaining process gas, are connected to the chamber  12 . Also, the process gas includes a gas for carrying out plasma ignition, such as argon (Ar) gas, and a gas for wafer processing, such as CFx gas. 
     The upper electrode  13  is disposed to close an upper opening of the chamber  12  and is connected to a radio frequency (RF) power source (not shown) via the matching box  21 . Also, a plurality of through holes  13   a  are formed in the upper electrode  13  by perpendicularly penetrating the upper electrode  13  and also act as a shower head that supplies the process gas into the process space S. 
     The lower electrode  14  faces the upper electrode  13  in a lower region of the chamber  12  and is connected to the RF power source (not shown) via the matching box  21 . Also, the lower electrode  14  also acts as a susceptor that supports on a top surface thereof a semiconductor wafer W as a substrate to be processed. Also, an RF pipe  15  extends to the matching box  21  from a bottom surface of the lower electrode  14  so that the lower electrode  14  and the matching box  21  can be electrically connected to each other. 
     An operation of the plasma processing apparatus  11  having the above structure will now be described. First, the semiconductor wafer W is put on the top surface of the lower electrode  14 , and the process space S is sealed. Next, as the process gas is supplied into the process space S from a process gas supply source (not shown) via the through holes  13   a  of the upper electrode  13 , the process space S is maintained at a predetermined pressure by an exhaust unit (not shown). 
     Next, an RF voltage is applied to each of the upper electrode  13  and the lower electrode  14 . For example, when a 60 MHz RF voltage is applied to the upper electrode  13  and a 2 MHz RF voltage is applied to the lower electrode  14 , the gas for plasma ignition is ionized and plasmatized in the process space S, and a bias electric potential is generated between the upper electrode  13  and the lower electrode  14 . Thus, the gas for wafer processing is activated, and plasma processing such as ion etching can be carried out on the surface of the semiconductor wafer W. 
     The matching box  21  is electrically connected to the upper electrode  13  and the lower electrode  14 , respectively, and supplies an RF power from the RF power source (not shown) to the electrodes. Specifically, a connection terminal  22 , which is disposed on the top surface of the matching box  21 , and the RF pipe  15  are electrically connected to each other so that an RF power is supplied to the lower electrode  14 . A description on a connection portion to the upper electrode  13  will be omitted herein. 
     The matching box  21  is moved to the lower portion of the chamber  12  along a rail  18  and is pulled up to a predetermined position by the air cylinder  31  so that the RF pipe  15  and the connection terminal  22  can be electrically connected to each other. 
     The air cylinder  31  is a double acting cylinder including: a cylinder case  32  including first and second cylinders  32   a  and  32   b ; a piston  33  separating the first and second cylinders  32   a  and  32   b  from each other and making a reciprocating motion in the cylinder case  32 ; a compressor (not shown) as a fluid supply unit supplying a fluid (“air” in the present embodiment) to the first and second cylinders  32   a  and  32   b ; a connection member  34  disposed outside the cylinder case  32  and connected to a member moved due to a fluid pressure (“matching box  21 ” in the present embodiment); and a connection rod  34   a  passing through the second cylinder  32   b  and connecting the piston  33  and the connection member  34 . Also, the connection member  34  may be an electrostatic chuck, an electromagnet, or the like. 
     The air cylinder  31  fixes the cylinder case  32  at the bottom surface of the chamber  12  and the connection member  34  at the top surface of the matching box  21  with the first cylinder  32   a  placed above the piston  33 . Also, the air cylinder  31  supplies compressed air to one of the first and second cylinders  32   a  and  32   b  so that the piston  33  can be moved upwards and downwards in a vertical direction. 
     In other words, when the compressed air is supplied to the second cylinder  32   b , the piston  33  is pushed upwards. As a result, the matching box  21  connected to the piston  33  is pushed upwards so that the RF pipe  15  and the connection terminal  22  are connected to each other. Meanwhile, when the compressed air is supplied to the first cylinder  32   a , the piston  33  is pushed downwards. As a result, the matching box  21  connected to the piston  33  is pushed downwards so that the RF pipe  15  and the connection terminal  22  are disconnected from each other. 
     Next, the relationship between a position of the chamber  12  and a position of the matching box  21  will be described with reference to  FIG. 2 . First, the RF pipe  15  extends downwards from the center of the chamber  12 . Meanwhile, the air cylinder  31  is placed out of the center of the chamber  12  and is also disposed perpendicularly above the center of gravity G of the matching box  21 . 
     In other words, since the connection member  34  is pulled up while being fixed perpendicularly above the center of gravity G of the matching box  21 , the matching box  21  may be pulled up horizontally. As a result, the RF pipe  15  and the connection terminal  22  can be properly connected to each other. 
     The air cylinder  31  having the above structure has a small and simple structure as compared to the conventional elevation driving unit including a ball screw, etc. On the other hand, the air cylinder  31  generates a weak force for pulling up the matching box  21 . However, as the portion where the RF pipe  15  and the connection terminal  22  are connected to each other is constituted below, the RF pipe  15  and the connection terminal  22  can be properly connected to each other. 
     Next, details of the portion where the RF pipe  15  and the connection terminal  22  are connected to each other will be described with reference to  FIGS. 3 and 4 . First, referring to  FIG. 3 , the RF pipe  15  includes a ground pipe  16  and an RF feeding rod  17  disposed inside the ground pipe  16 . Meanwhile, the connection terminal  22  includes a terminal  23  for electric potential of the ground pipe  16  and an RF power terminal  24  disposed inside the terminal  23 . 
     The ground pipe  16  is a female terminal that accommodates the terminal  23  for electric potential of the ground pipe  16  in a cylindrical inner diameter surface, and the terminal  23  for electric potential of the ground pipe  16  is a male terminal that is inserted in the inner diameter surface of the ground pipe  16 . The ground pipe  16  and the terminal  23  for electric potential of the ground pipe  16  are connected to each other so that electric potential of the ground pipe  16  can be obtained simultaneously. 
     Similarly, the RF feeding rod  17  is a female terminal that accommodates the RF power terminal  24 , and the RF power terminal  24  is a male terminal that is inserted in an inner diameter surface of the RF feeding rod  17 . The RF feeding rod  17  and the RF power terminal  24  are connected to each other so that the lower electrode  14  can be connected to the RF power source (not shown). 
     Contact surfaces where the male terminals  23  and  24  contact the female terminals  16  and  17 , that is, the outer diameter surface of the terminal  23  for electric potential of the ground pipe  16  and the outer diameter surface of the RF power terminal  24  are covered with elastic conductors  23   a  and  24   a , respectively. The elastic conductor  23   a  is a cylindrical member formed of high-conductivity metal such as aluminum, copper, or the like. Also, the elastic conductor  23   a  has a wrinkled hose structure which is repeatedly bent forming a mountain portion and a valley portion alternately. An elastic deformation capability of the elastic conductor  23   a  in a diameter direction is high. In addition, the elastic conductor  24   a  has the same configuration as the elastic conductor  23   a , and thus, description thereof will be omitted. 
     Since the outer diameter surfaces of the male terminals  23  and  24  are covered with the elastic conductors  23   a  and  24   a , even though the outer diameter surfaces of the male terminals  23  and  24  and the inner diameter surfaces of the female terminals  16  and  17  do not directly contact each other, the male terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, can be electrically connected to each other. Specifically, the inner diameter of the ground pipe  16  may be set to be larger than the outer diameter of the terminal  23  for electric potential of the ground pipe  16  and smaller than the diameter of the mountain portion of the elastic conductor  23   a . Similarly, the inner diameter of the RF feeding rod  17  may be set to be larger than the outer diameter of the RF power terminal  24  and smaller than the diameter of the mountain portion of the elastic conductor  24   a.    
     When the male terminals  23  and  24  having the above configuration are inserted in the inner diameter surfaces of the female terminals  16  and  17 , the elastic conductors  23   a  and  24   a  are elastically deformed so that the mountain portions thereof contact the inner diameter surfaces of the female terminals  16  and  17  and the valley portions thereof contact the outer diameter surfaces of the male terminals  23  and  24 . Thus, even though a gap between the male terminals  23  and  24  and the female terminals  16  and  17  is formed to a degree, the male terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, can be electrically connected. In addition, in  FIG. 4 , the male terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, overlap with each other so as to make a portion where each of the female terminals  16  and  17  and each of the elastic conductors  23   a  and  24   a  firmly overlap with each other. 
     As a result of the above configuration, a resistance that occurs when the male terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, are connected to each other can be reduced, and the terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, can be prevented from being damaged when connected to each other. Also, due to a reduction in the resistance that occurs when the male terminal  23  and the female terminal  16  and the male terminal  24  and the female terminal  17 , respectively, are connected to each other, the above-described, small-sized air cylinder  31  can be used as the elevation driving unit for the matching box  21 . 
     Also, in the present embodiment, the elastic conductors  23   a  and  24   a  are adhered to the terminal  23  for electric potential of the ground pipe  16  and the RF power terminal  24 , which are the male terminals. However, the present invention is not limited to this structure, and the inner diameter surfaces of the ground pipe  16  and the RF feeding rod  17 , which are the female terminals, may be covered with the elastic conductors  23   a  and  24   a , or the elastic conductors  23   a  and  24   a  may be adhered to both of the male terminals  23  and  24  and the female terminals  16  and  17 . 
     Also, in the present embodiment, the elastic conductors  23   a  and  24   a  having the wrinkled hose structure have been described. However, the present invention is not limited to this structure, and any elastic conductor having a high elastic deformation capability may be used. 
     Next, an air cylinder  41  as a fluid pressure cylinder according to another embodiment of the present invention will be described with reference to  FIG. 5 . Also, the same elements as those of the air cylinder  32  of  FIG. 1  are indicated by the same reference numerals, and detailed descriptions thereof will be omitted. 
     The air cylinder  41  is a single acting cylinder in which an elastic member  35  elastically supporting the piston  33  toward the first cylinder  32   a  (“coil spring” in the present embodiment) is disposed in the second cylinder  32   b , instead of connecting the second cylinder  32   b  to the compressor. The air cylinder  41  is disposed at the bottom surface of the chamber  12  with the first cylinder  32   a  placed above the second cylinder  32   b.    
     In the air cylinder  41  having the above configuration, in an initial state (“a state where the compressed air is not supplied to the first cylinder  32   a ”), the elastic member  35  pushes up the piston  33  in a vertical, upward direction. As a result, the matching box  21  connected to the piston  33  is pushed upwards so that the RF pipe  15  and the connection terminal  22  can be electrically connected to each other. Meanwhile, when the compressed air is supplied to the first cylinder  32   a , the piston  33  is pushed downwards against the elastic member  35 . As a result, the matching box  21  connected to the piston  33  is pushed downwards so that the RF pipe  15  and the connection terminal  22  can be disconnected from each other. 
     In the air cylinder  41  having the above configuration, the elastic member  35  always elastically supports the piston  33  towards the first cylinder  32   a . Thus, even when the compressed air cannot be supplied to the first cylinder  32   a  due to breakdown of the compressor, the RF pipe  15  and the connection terminal  22  are not disconnected from each other. As such, the plasma processing apparatus  11  has high reliability. 
     In addition, in the present embodiment, the air cylinder  31  or  41  is used as a fluid pressure cylinder. However, the present invention is not limited to this structure, and any configuration capable of elevating the matching box  21  using a fluid pressure may be used. For example, a hydraulic cylinder using oil instead of air may be used. 
     As described above, in the plasma processing apparatus according to the present invention, an elastic conductor is disposed at a portion where a lower electrode and a matching box are connected to each other, and a fluid pressure cylinder is used as an elevation driving unit for the matching box such that the plasma processing apparatus can be miniaturized and the lower electrode and the matching box can be electrically connected to each other. 
     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.