Patent Abstract:
A transmission path of microwaves even after a temperature increases, is maintained in an appropriate state. A microwave plasma processing apparatus performs plasma processing on a substrate by exciting gas due to the electric field energy of microwaves emitted from a slot plate of a radial line slot antenna (RLSA). The microwave plasma processing apparatus includes: a processing container in which plasma processing is performed; a microwave source outputting microwaves; a rectangular waveguide transmitting the microwaves outputted from the microwave source; a coaxial converter converting a mode of the microwaves transmitted to the rectangular waveguide; a coaxial waveguide transmitting the microwaves of which the mode is converted by the coaxial converter; a taper-shaped connector attached to an inner conductor of the coaxial waveguide without contacting the slot plate; and an elastic body electrically connecting the taper-shaped connector and the slot plate.

Full Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of Japanese Patent Application No. 2008-159630, filed on Jun. 18, 2008, and Japanese Patent Application No. 2009-116336, filed on May 13, 2009, 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 microwave plasma processing apparatus and a method of supplying microwaves, and more particularly, to a microwave plasma processing apparatus that performs plasma-processing on an object to be processed by exciting gas due to the electric field energy of microwaves emitted from a radial line slot antenna (RLSA), and a method of supplying microwaves using the microwave plasma processing apparatus. 
     2. Description of the Related Art 
     Microwave plasma is generated by introducing microwaves into a processing container in a depressurized state and by exciting gas due to the electric field energy of the introduced microwaves. In microwave plasma processing apparatuses, when the electron density of plasma is higher than a cut-off density, microwaves cannot be absorbed into plasma and thus, are propagated between a dielectric plate and plasma, and some of the microwaves are absorbed into the plasma and are used to sustain the plasma. 
     According to the principle of generating plasma, since microwave plasma has a higher electron density (Ne) and a lower electron temperature (Te) than plasma that is generated by a capacitively coupled microwave plasma processing apparatus or an inductively coupled plasma processing apparatus, a high-quality device can be manufactured at high rate and with little damage by performing plasma processing. 
     A microwave plasma processing apparatus using a radial line slot antenna (RLSA) has been proposed (i.e., see Japanese Laid-Open Patent Publication No. hei 9-63793). The RLSA has a structure in which a wavelength-shortening plate having a disk shape is placed on a disk-shaped slot plate having a plurality of slots formed therein, and is disposed on a dielectric window formed in an opening of a ceiling part of a processing container. The middle part of the RLSA is connected to a coaxial waveguide. 
     In the above-described structure, microwaves of 2.45 GHz, for example, outputted from a microwave source, are transmitted to the wavelength-shortening plate of the RLSA via the coaxial waveguide so as to radiate in a radial direction of the wavelength-shortening plate. As such, microwaves can be emitted from the plurality of slots formed in the slot plate and can be radiated into the processing container. 
     However, during a plasma process, the processing container is maintained at a high temperature of 200° C. and more, and as a result, an RLSA 905, a cooling jacket  210 , an outer conductor  340  of the coaxial waveguide, a rectangular waveguide  305 , which are shown in  FIG. 8 , are thermally expanded. Thus, during the plasma process, even though a circumferential part of the RLSA 905 is cooled by the cooling jacket  210 , the temperature of the RLSA 905 increases about 150° C. to about 165° C. and the temperature of the cooling jacket  210  placed above the RLSA 905 increases about 80° C. to about 100° C. and the temperature of the external conductor  340  increases about 40° C. to about 60° C., and a temperature of 100° C. and more may be heated up even near the outer conductor  340  according to the plasma process. 
     Referring to  FIG. 8 , among these members, a wavelength-shortening plate  905   a  (see  FIG. 8 ) of the RLSA 905 is formed of a dielectric material such as alumina (Al 2 O 3 ). Meanwhile, the cooling jacket  210 , the outer conductor  340 , and the rectangular waveguide  305 , which are placed above the RLSA 905, are formed of metal such as copper (Cu) or aluminum (Al). The linear expansion coefficient of alumina is 7.0×10 −6 (/° C.). The linear expansion coefficient of copper is 16.7×10 −6 (/° C.) and the linear expansion coefficient of aluminum is 23.5×10 −6 (/° C.), which are more than twice that of alumina. Thus, when a temperature increases, the RLSA 905, the cooling jacket  210 , the outer conductor  340 , and the rectangular waveguide  305  are thermally expanded, and thus an upper part of the rectangular waveguide  305  is displaced to a higher location than that before the temperature increases. 
     In this case, if a slot plate  905   b  of the RLSA 905 is screw-fixed to a taper-shaped connector part (hereinafter, referred to as a taper connector) attached to an inner conductor  315  of the coaxial waveguide, a coaxial converter  310 , the inner conductor  315 , and the taper connector, which are integrally formed as one body with one another, are displaced in a vertical upward direction of a processing container  100 , following the outward displacement of the position of the rectangular waveguide  305  in an outside direction of the processing container  100 . 
     In particular, the inner conductor  315  and the coaxial converter  310  allow a refrigerant to pass through to the outside of a refrigerant pipe  360  from the inside of the refrigerant pipe  360 , which is a double pipe installed within the inner conductor  315 , and thus are cooled even during the plasma process. Thus, the temperature of the inner conductor  315  and the temperature of the coaxial converter  310  during the process are lower than the temperature of the outer conductor  340  and the temperature of the rectangular waveguide  305 . Thus, the thermal expansion rate of the coaxial converter  310  and the inner conductor  315  during the plasma process is lower than the thermal expansion rate of the outer conductor  340  and the rectangular waveguide  305 . As such, in contrast with an ideal state shown in the upper drawing of  FIG. 9 , in the lower drawing of  FIG. 9 , when a temperature increases, a lower surface of a taper connector  320  connected to the inner conductor  315  is displaced in an upper direction away from a lower surface of the wavelength-shortening plate  905   a , and an air gap Ra between the taper connector  320  and thus the wavelength-shortening plate  905   a  varies. The air gap Ra is part of a transmission path of the microwaves and thus, it is important to maintain the air gap Ra so as to stabilize a mode of the microwaves. If the air gap Ra varies, the mode of the microwaves is unstable, and plasma is non-uniform. 
     In addition, if, when a temperature increases, the taper connector  320  is displaced in an upper direction away from the wavelength-shortening plate  905   a , the slot plate  905   b  screw-fixed to the lower surface of the taper connector  320  is also displaced upward and is distorted. Thus, the transmission path of the microwaves varies, and uniform plasma is not generated. 
     SUMMARY OF THE INVENTION 
     To solve the above and/or other problems, the present invention provides a plasma processing apparatus with Radial Line Slot Antenna or the plasma processing method which enables to suppress the variation of the microwave transmission path from the designed ideal microwave transmission path of elevated temperature when microwave is supplied and the apparatus is heated up and further to prevent the disturbance of the plasma. 
     According to an aspect of the present invention, there is provided a microwave plasma processing apparatus which performs plasma processing on an object to be processed due to plasma generated by using microwaves emitted from a slot plate of a radial line slot antenna (RLSA), the apparatus including: a processing container in which plasma processing is performed; a microwave source outputting microwaves; a rectangular waveguide transmitting the microwaves outputted from the microwave source; a coaxial converter converting a mode of the microwaves transmitted to the rectangular waveguide; a coaxial waveguide transmitting the microwaves of which the mode is converted by the coaxial converter; a taper-shaped connector attached to an inner conductor of the coaxial waveguide without contacting the slot plate; and an elastic body electrically connecting the taper-shaped connector and the slot plate. 
     According to this, the elastic body may electrically connect the taper-shaped connector and the slot plate that does not contact the taper-shaped connector. As such, referring to the lower portion of  FIG. 4 , the elastic body  330  may maintain electrical connection between the taper connector  320  and the slot plate  205   b  while absorbing the upward displacement of the taper connector  320  due to thermal expansion. Thus, when a temperature increases, the lower surface Sb of the taper connector  320  and the lower surface Sa of the wavelength-shortening plate  205   a  may be located at the same level. As such, the air gap Ra may not vary, and thus the mode of the microwaves may be stable and uniform plasma may be generated. 
     According to this, the slot plate  205   b  is not screw-fixed to the lower surface of the taper connector  320 , and thus is not displaced in an upper direction. As such, the mode of the microwaves may be stable, and uniform plasma may be generated. 
     In addition, the elastic body may be a linear metal shield member. 
     The slot plate may include an opening that is larger than an area of an end surface of the taper-shaped connector, and the taper-shaped connector may be connected to a support member while penetrating the opening of the slot plate, and the elastic body may be disposed on the loading table. 
     The support member may include a flange part formed at an outer circumference of the loading table, and the elastic body may be disposed between the flange part and the slot plate. 
     The flange part of the support member may include a stepped part, and the elastic body may be disposed at an outer side than the innermost stepped part formed in the flange part. 
     A distance between the flange part of the support member and the slot plate may be set so that the elastic body absorbs the displacement of the taper-shaped connector due to an expansion and electrically connects the taper-shaped connector and the slot plate. 
     In addition, edges of the stepped part of the flange part may be rounded. According to this, the electric field energy of the microwaves may be prevented from being concentrated on the edges of the stepped part of the flange part, and occurrence of abnormal discharge may be prevented. 
     An insulating material may be coated on the surface of at least one of the group consisting of the wavelength-shortening plate and a cooling jacket that is disposed on the RLSA. 
     According to this, the insulating material may be coated on the wavelength-shortening plate or the cooling jacket so that a difference in electric potential generated between the cooling jacket and the slot plate may be reduced and thus occurrence of abnormal discharge can be suppressed. In addition, the insulating material may be polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether (PFA) copolymers, alumina (alumite processing, spraying), or the like. 
     According to another aspect of the present invention, there is provided a method of supplying microwaves to a microwave plasma processing apparatus which performs plasma processing on an object to be processed due to plasma generated by using microwaves emitted from a slot plate of a radial line slot antenna (RLSA), the method including: outputting microwaves from a microwave source; transmitting the microwaves outputted from the microwave source to a rectangular waveguide; converting a mode of the microwaves by using a coaxial converter; and electrically connecting a taper-shaped connector attached to an inner conductor of a coaxial waveguide and the slot plate by using an elastic body without contacting the slot plate. 
     According to this, the taper-shaped connector may be attached to the inner conductor without contacting the slot plate. The elastic body may electrically connect the taper-shaped connector with the slot plate while absorbing the upward displacement of the taper connector due to thermal expansion. Thus, when a temperature increases, the lower surface of the taper-shaped connector and the lower surface of the wavelength-shortening plate may be located at the same level. As such, the air gap Ra may not vary, and the mode of the microwaves may be stable, and uniform plasma may be generated. 
    
    
     
       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 microwave plasma processing apparatus according to an embodiment of the present invention; 
         FIG. 2  is a view of a path, in which microwaves are propagated, of the microwave plasma processing apparatus of  FIG. 1 ; 
         FIG. 3  is an enlarged view of a circumferential part of a taper connector of the microwave plasma processing apparatus of  FIG. 1 ; 
         FIG. 4  illustates a state of the microwave plasma processing apparatus of  FIG. 1  after a temperature of the microwave plasma processing apparatus of  FIG. 1  increases according to a design and a state of the microwave plasma processing apparatus of  FIG. 1  after the temperature thereof actually increases; 
         FIG. 5  is a longitudinal cross-sectional view of a microwave plasma processing apparatus including an engagement structure in which a rectangular waveguide and a coaxial converter are engaged with each other, according to another embodiment of the present invention; 
         FIGS. 6A and 6B  are a cross-sectional view and a graph of the result of simulation of the distribution of the electric field strengths near a gap, respectively; 
         FIG. 7  is a view of an engagement structure in which a rectangular waveguide and a coaxial converter are engaged with each other; 
         FIG. 8  is a longitudinal cross-sectional view of a general microwave plasma processing apparatus; and 
         FIG. 9  illustrates a state of the general microwave plasma processing apparatus of  FIG. 8  after a temperature of the general microwave plasma processing apparatus of  FIG. 8  increases according to a design and a state of the general microwave plasma processing apparatus of  FIG. 8  after the temperature thereof actually increases. 
     
    
    
     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. 
     &lt;Entire Structure of Microwave Plasma Processing Apparatus&gt; 
       FIG. 1  is a longitudinal cross-sectional view of a microwave plasma processing apparatus  10  according to an embodiment of the present invention. Referring to  FIG. 1 , the microwave plasma processing apparatus  10  according to the present embodiment includes a processing container  100 , a cover object  200 , a transmission path  300 , a cooling mechanism  400 , and a gas supply mechanism  500 . 
     The processing container  100  is a cylindrical container which is open at the top, and is formed of a metal such as aluminum (Al). A top plate  105  (which corresponds to a dielectric window) is fit into the opening of a ceiling of the processing container  100 , and is formed of a dielectric material. An extension is formed in the central part of a lower surface of the top plate  105 , and a middle part of the lower surface of the top plate  105  extends in a circumferential direction of the top plate  105 . An O-ring  110  is disposed at a point at which the processing container  100  and the top plate  105  contact each other. As such, a processing chamber U is sealed. 
     A susceptor (holding stage)  115 , on which a wafer W is held, is installed on a bottom of the processing container  100  using an insulator  120 , which is interposed between the susceptor  115  and the bottom of the processing container  100 . A radio frequency power supply source  125   b  is connected to the susceptor  115  via a matching device  125   a , and a predetermined bias voltage is applied to the processing container  100  due to a radio frequency power outputted from the radio frequency power supply source  125   b . Also, a high pressure direct current (DC) power supply source  130   b  is connected to the susceptor  115  via a coil  130   a , and the wafer W is electrostatically held due to a DC voltage outputted from the high pressure DC power supply source  130   b . Since a vacuum pump (not shown) is attached to the processing container  100 , gas in the processing container  100  is exhausted via a gas exhaust pipe  135 , and thus the processing chamber U is depressurized to a desired vacuum level. 
     The cover  200  includes a radial line slot antenna (RLSA)  205 , hereinafter simply referred to as an antenna  205 , and a cooling jacket  210 . The antenna  205  is disposed directly on the top plate  105 . The cooling jacket  210  is disposed on the antenna  205 . The cooling jacket  210  is formed of aluminum, and a refrigerant is circulated in a flow path formed in the cooling jacket  210  so that a temperature near the antenna  205  is adjusted. The cooling jacket  210  is grounded. 
       FIG. 2  is an enlarged longitudinal cross-sectional view of a left part of the antenna  205  of the microwave plasma processing apparatus  10  of  FIG. 1 . Referring to  FIG. 2 , the antenna  205  is a disk-shaped flat plate having a wavelength-shortening plate  205   a  and a slot plate  205   b.    
     The slot plate  205   b  is formed of a metal sheet and is inserted between the top plate  105  (dielectric window) and the wavelength-shortening plate  205   a .  FIG. 3  is an enlarged view of a circumferential part of a taper connector  320  of the microwave plasma processing apparatus  10  of  FIG. 1 . Referring to  FIG. 3 , a circular opening  205   b   1  that is larger than the area of a lower surface Sb of the taper connector  320  is formed in the middle of the slot plate  205   b . A support member  325  is screw-fixed to the lower surface Sb of the taper connector  320 , and passes through the opening  205   b   1  formed in the middle of the slot plate  205   b . A plurality of slots (not shown) that radiate microwaves are formed in the slot plate  205   b . The slot plate  205   b  is fixed to the cooling jacket  210  by a screw  215  shown in  FIG. 2 , in the outer circumference of the slot plate  205   b.    
     The wavelength-shortening plate  205   a  is formed of a dielectric material such as alumina or the like and transmits microwaves into the slots. Shield members  220 ,  225 ,  230 , and  235  prevent some of the microwaves, which through the slots, from leaking into a gap at sides of the cooling jacket  210  or a gap between the cover  200  and the processing container  100 . 
     The transmission path  300  mainly includes a rectangular waveguide  305 , a coaxial converter  310 , an inner conductor  315 , an outer conductor  340 , the taper connector  320 , and the antenna  205 . The microwaves are transmitted to a space (hereinafter, referred to as a transmission path R of the microwaves) that is defined by the transmission path  300 . In this regard, the microwaves are propagated within the wavelength-shortening plate  205   a  and are reflected from an end surface of the wavelength-shortening plate  205   a . Impedance of a discharge load and the transmission path  300  are matched by using a tuner (not shown), and standing waves are generated in the space of the transmission path  300  due to interference between progressive waves and reflective waves. 
     A current of the microwaves flows through the surface of a metal member that defines the transmission path R of the microwaves. The microwaves propagate within the wavelength-shortening plate  205   a  and are radiated into the processing container  100  from the slots formed in the slot plate  205   b  that is adjacent to the wavelength-shortening plate  205   a.    
     When the microwave plasma processing apparatus  10  is manufactured, an air gap occurs between the members due to a limit in processing accuracy. For example, an air gap Ra occurs between the wavelength-shortening plate  205   a  and the cooling jacket  210  and between the wavelength-shortening plate  205   a  and the taper connector  320  due to a limit in processing accuracy. The air gap Ra is part of the transmission path of the microwaves and thus, it is important to maintain the air gap Ra so as to stabilize a mode of the microwaves. 
     The rectangular waveguide  305  is connected to a microwave source  335 . The coaxial converter  310  is formed to have a cone shape and converts a TE(transverse electric) mode of the microwaves into a mixed mode of the TE mode and a TM(transverse magnetic) mode. The mode-converted microwaves are transmitted to a coaxial waveguide (the inner conductor  315  and the outer conductor  340 ). The inner conductor  315  and the outer conductor  340  are formed of silver-plated copper. 
     The taper connector  320  is taper-shaped and is screw-fixed to the internal conductor  315  at a lower surface of the inner conductor  315 , as illustrated in  FIG. 3 . 
     The support member  325  is screw-fixed to the taper connector  320  at a plurality of places of the lower surface Sb of the taper connector  320 . The taper connector  320  and the support member  325  are formed of gold-plated copper. The support member  325  includes a flange part  325   a  at its outer circumferential part. The flange part  325   a  is stepped. 
     An elastic body  330  is disposed between the flange part  325   a  and the slot plate  205   b , and electrically connects the taper connector  320  and the slot plate  205   b.    
     An upper portion of the outer conductor  340  shown in  FIG. 2  is screw-fixed to the rectangular waveguide  305 , and a lower portion of the outer conductor  340  is screw-fixed to the cooling jacket  210 . The air gap Ra occurs between the cooling jacket  210  and the wavelength-shortening plate  205   a  and between the taper connector  320  and the wavelength-shortening plate  205   a  due to a limit in processing accuracy. 
     The coaxial converter  310  is inserted in an opening formed in the rectangular waveguide  305 , and when the rectangular waveguide  305  and the coaxial converter  310  are assembled, a spiral shield  370  for preventing the microwaves from leaking is formed in a gap G that is occurred between surfaces of the rectangular waveguide  305  and the coaxial converter  310 , which face each other. 
     A refrigerant pipe  360  is inserted in the inner conductor  315  of  FIG. 1 . The refrigerant pipe  360  is a double pipe. In the cooling mechanism  400  of  FIG. 1 , a refrigerant supply source  405  and the refrigerant pipe  360  are connected to each other, and the refrigerant supply source  405  and the cooling jacket  210  are connected to each other. A refrigerant supplied from the refrigerant supply source  405  passes through an outside of the refrigerant pipe  360  from an inside of the refrigerant pipe  360 , and thus the temperature of the inner conductor  315  is adjusted. Also, the refrigerant supplied from the refrigerant supply source  405  is circulated in the flow path of the cooling jacket  210  so that the temperature near the cooling jacket  210  is adjusted. 
     In the gas supply mechanism  500  of  FIG. 1 , a gas supply source  505  and a plurality of upper gas supply lines  510  are connected to each other, and the gas supply source  505  and a shower plate  515  are connected to each other. A plurality of gas supply holes are uniformly formed in the shower plate  515  to face the wafer W. A plasma excitation gas from the gas supply source  505  is supplied in a lateral direction toward the inner space of the processing chamber U through the plurality of upper gas supply lines  510  formed to penetrate a side wall of the processing container  100 . A process gas from the gas supply source  505  is supplied to the shower plate  515  in the lateral direction and then supplied in a downward direction from the plurality of gas supply holes formed in the shower plate  515  having a lattice shape. 
     &lt;Circumference of Taper Connector&gt; 
     Next, a circumferential part of the taper connector  320  will be described with reference to  FIGS. 3 and 4  in detail. In the present embodiment, the slot plate  205   b  is not fixed to the taper connector  320  and does not contact the taper connector  320 , and the slot plate  205   b  and the taper connector  320  are electrically connected to each other via the elastic body  330 . In order to describe the reason why the slot plate  205   b  is not fixed to the taper connector  320 , the microwave plasma processing apparatus  10  of  FIG. 1  will be compared with a general microwave plasma processing apparatus shown in  FIGS. 8 and 9 , in which a slot plate is fixed to a taper connector. 
       FIG. 8  is a longitudinal cross-sectional view of the general microwave plasma processing apparatus, and  FIG. 9  illustrates a state of the general microwave plasma processing apparatus of  FIG. 8  after a temperature of the general microwave plasma processing apparatus of  FIG. 8  increases according to a design and a state of the general microwave plasma processing apparatus of  FIG. 8  after the temperature thereof actually increases. Referring to  FIGS. 8 and 9 , in the conventional microwave plasma processing apparatus using an RLSA 905, a slot plate  905   b  is fixed to the cooling jacket  210  by a screw  910  in an outer circumference of the slot plate  905   b  and the middle part of the slot plate  905   b  is screw-fixed between the taper connector  320  and a fixing plate  915 . 
     The amount of expansion of each of the members depends on a material used to form each of the members of the conventional microwave plasma processing apparatus or a temperature of a processing container  100  during a plasma process. In particular, an inner conductor  315  and a coaxial converter  310  are cooled even during the plasma process, as described above, and thus, the temperature of the inner conductor  315  and the temperature of the coaxial converter  310  are lower than the temperature of an outer conductor  340  and the temperature of a rectangular waveguide  305 . Thus, the thermal expansion rate of the inner conductor  315  and the coaxial converter  310  during the plasma process is lower than the thermal expansion rate of the outer conductor  340  and the rectangular waveguide  305 . As such, after a temperature increases, it is not easy to displace a lower surface Sb of the taper connector  320  and a lower surface Sa of the wavelength-shortening plate  905   a  at a same level as in the upper drawing of  FIG. 9 . In other words, referring to the lower drawing of  FIG. 9 , the lower surface Sb of the taper connector  320  is located at a higher position than the lower surface Sa of the wavelength-shortening plate  905   a . Thus, the air gap Ra varies, a mode of the microwaves is unstable, and thus plasma is non-uniform. 
     Also, if the taper connector  320  is displaced in an upper direction from the wavelength-shortening plate  905   a , the slot plate  905   b  that is screw-fixed to the lower surface Sb of the taper connector  320  is also displaced in the upper direction and thus is distorted. As such, the transmission path of the microwaves varies due to deviation of the position of the slot plate  905   b , and plasma is non-uniformly generated. 
     Variation of the transmission path of the microwaves described above affects stability and reliability of a microwave plasma processing apparatus during the plasma process. Thus, as illustrated in  FIG. 3 , in the microwave plasma processing apparatus  10  according to the present embodiment, the opening  205   b   1  that is larger than the area of the lower surface Sb of the taper connector  320  is formed in the center of the slot plate  205   b.    
     The taper connector  320  and the support member  325  are connected to the slot plate  205   b  in a non-contact way while penetrating the opening  205   b   1  of the slot plate  205   b . The flange part  325   a  is formed at an outer circumference of the support member  325 . The elastic body  330  is disposed between the flange part  325   a  and the slot plate  205   b  and electrically connects the taper connector  320  and the slot plate  205   b.    
     The elastic body  330  is formed of a linear metal shield member. The reaction force of the metal shield member is less than that of the spiral shield member, and thus, an electrical connection between the slot plate  205   b  and the support member  325  may be smoothly performed without applying an excessive load to the slot plate  205   b  or the support member  325 . 
     The elastic body  330  is formed at an outer side than the innermost stepped part formed in the flange part  325   a . In addition, edges of the stepped part of the flange part  325   a  are rounded. Thus, electric field energy of the microwaves may be prevented from being concentrated on an inside or edges of the flange part  325   a  and occurrence of abnormal discharge may be prevented. 
     A distance between the flange part  325   a  of the support member  325  and the slot plate  205   b  is set so that the elastic body  330  absorbs the displacement of the taper connector  320  due to expansion and electrically connects the taper connector  320  and the slot plate  205   b.    
     In the above structure, the elastic body  330  is disposed so that the taper connector  320  and the slot plate  205   b  that does not contact the taper connector  320  are electrically connected to each other.  FIG. 4  illustates a state of the microwave plasma processing apparatus of  FIG. 1  after a temperature of the microwave plasma processing apparatus of  FIG. 1  increases according to a design and a state of the microwave plasma processing apparatus of  FIG. 1  after the temperature thereof actually increases. As such, referring to the lower drawing of  FIG. 4 , the elastic body  330  absorbs the upward displacement of the taper connector  320  due to thermal expansion and transmits the microwaves between the taper connector  320  and the slot plate  205   b . Thus, after a temperature increases, the lower surface Sb of the taper connector  320  and the lower surface Sa of the wavelength-shortening plate  205   a  are located at the same level. As such, the air gap Ra does not vary, the mode of the microwaves is stable, and uniform plasma may be generated. 
     Also, the slot plate  205   b  is not screw-fixed to the lower surface Sb of the taper connector  320 , and thus is not displaced in an upper direction. As such, the transmission path R of the microwaves does not vary, the mode of the microwaves is stable, and uniform plasma may be generated. 
     In addition, the support member  325  and the elastic body  330  may be integrally formed as one body. In this case, a protrusion (for example, ring-shaped protrusion) is formed at the top surface of the flange part  325   a  of the support member  325 , and is formed of a material having the same function as that of the elastic body  330 . Thus, the protrusion that replaces the elastic body  330  absorbs the displacement of the taper connector  320  and electrically connects the taper connector  320  and the slot plate  205   b.    
     &lt;Gap G&gt; 
       FIG. 5  is a longitudinal cross-sectional view of a microwave plasma processing apparatus including an engagement structure F in which a rectangular waveguide  305  and a coaxial converter  310  are engaged with each other, according to another embodiment of the present invention. Referring to  FIG. 5 , when a path in which the mode of the microwaves transmitted to the rectangular waveguide  305  is converted and the microwaves are transmitted is defined by inserting the coaxial converter  310  into the opening of the rectangular waveguide  305 , a gap G is occurred between a lateral sidewall of the rectangular waveguide  305  and a lateral sidewall of the coaxial converter  310  that faces the lateral sidewall of the rectangular waveguide  305 , due to tolerance. 
     The gap G exists in a position in which the mode of the microwaves is converted into a mixed mode of a TE mode and a TM mode from the TE mode. In addition, near the gap G, the microwaves are reflected from a reflective end  305   a  of the rectangular waveguide  305  and thus, the electric field of the microwaves is prone to be disturbed. 
     In an experiment, even though a distance between the reflective end  305   a  and the gap G was designed as λg/2 so that node of the microwaves is placed in the reflective end  305   a  of the rectangular waveguide  305  and the gap G, abnormal discharge was not suppressed. Thus, in addition to controlling the distance between the reflective end  305   a  of the rectangular waveguide  305  and the gap G, the engagement structure F is formed in the rectangular waveguide  305  and the coaxial converter  310  so as to control the gap G uniformly. 
     &lt;Control of Gap&gt; 
     First, in order to specifically determine proper ranges of the engagement structure F and the gap G, the distribution of the electric field strengths of the microwaves near the gap G was obtained by simulation. 
       FIGS. 6A and 6B  are a cross-sectional view and a graph of the result of simulation of the distribution of the electric field strengths near the gap G, respectively. Referring to  FIGS. 6A and 6B , the electric field strengths at positions P 1  through P 4  shown in  FIG. 6A  were calculated by simulation, and the results are shown in  FIG. 6B . Referring to the results illustrated in  FIG. 6B , the electric field strengths of the microwaves at the positions P 1  and P 3  are higher than the electric field strengths of the microwaves at the positions P 2  and P 4 . In addition, as the gap (leak path thickness) G increases, the electric field strengths increase, and if the gap G is uniform, even if the size of the gap G varies by 0.1 mm, the electric field strengths do not increase. 
     According to Paschen&#39;s Law, as defined by the formula V=f(pd), a discharge firing voltage V between parallel electrodes is expressed as a function of a product of gas pressure (p) and a distance (d) between the electrodes. Since the amount of variation of the electric field strengths with respect to variation of the position of the gap G or variation of a uniform leak path thickness is small, it is considered that an effect caused by the concentration of an electric field on a narrow position is large. Thus, the gap G is set in the range of (k±n)(n≦0.1) mm with respect to a predetermined reference distance kmm (k≧0.3) so that discharge does not occur easily and the electric field strengths are not easily biased, and thus occurrence of abnormal discharge may be prevented. 
     Thus, even though the ring-shaped gap G is formed in any facing position, the high-degree engagement structure F (see  FIGS. 5 and 7 ) is formed at the rectangular waveguide  305  and the coaxial converter  310  at an outer circumferential side from the gap G so that the gap G is formed within a predetermined range. Specifically, the engagement structure F is formed so that the reference distance k of the gap G is set to 0.3 mm and, even if the ring-shaped gap G is formed in any facing position, the gap G is adjusted within a range of (k±n)mm (n≦0.1). A gap (i.e., within about 20% of a maximum of the gap G) that is sufficiently smaller than the gap G is allowed in the engagement structure F in consideration of tolerance that occurs during assembling so that any manufacturer may easily assemble the microwave plasma processing apparatus while maintaining the gap G within the gap allowed for a design of the microwave plasma processing apparatus. As such, occurrence of abnormal discharge in the gap G between the rectangular waveguide  305  and the coaxial converter  310  may be avoided. 
     &lt;Coating With Insulating Material&gt; 
     The rectangular waveguide  305  and the coaxial converter  310  near the gap G are coated with an insulating material. The insulating material may be polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether (PFA) copolymers, alumina (alumite processing, spraying), or the like. As such, a potential difference in the gap G may be reduced so that occurrence of abnormal discharge may be more easily suppressed. 
     As described above, in the microwave plasma processing apparatus  10  according to the present embodiment, the air gap Ra during a temperature increase does not vary. Thus, the mode of the microwaves is stable, and uniform plasma may be generated. As such, the stability and reliability of the microwave plasma processing apparatus  10  may be improved. 
     In addition, the insulating material may be coated on the surface of at least one of the wavelength-shortening plate  205   a  and the cooling jacket  210 . As such, the insulating material is coated on the wavelength-shortening plate  205   a  or the cooling jacket  210  so that a difference in electric potential generated in the air gap Ra between the cooling jacket  210  and the slot plate  205   b  may be reduced and thus occurrence of abnormal discharge may be suppressed. 
     In addition, a material that has a low friction coefficient and does not stir up dust even when sliding, such as PTFE or PFA, may be used as the insulating material to be coated on a circumference of the wavelength-shortening plate  205   a  or the cooling jacket  210 . 
     In the above embodiment, operations of the elements are related to each other and may be substituted as a series of operations in consideration of the relation. By substituting the operations of the elements in this way, the embodiment of the microwave plasma processing apparatus may be used as an embodiment of a method of supplying the microwaves using the microwave plasma processing apparatus. 
     While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill 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. 
     For example, the engagement structure F may be included in the microwave plasma processing apparatus  10  according to the present invention but is not an essential construction of the microwave plasma processing apparatus  10 . 
     In addition, the stepped part of the flange part  325   a  of the support member  325  may have two or more steps. However, in any case, in order to prevent abnormal discharge, the elastic body  330  is not disposed in the innermost stepped part of the flange part  325   a  of the support member  325 . 
     In addition, gas may be supplied only from the upper gas supply lines  510  or only from the shower plate  515 . Also, instead of the gas supply mechanism  500  or in addition to the gas supply mechanism  500 , a gas path is formed in the top plate  105 , and the top plate  105  may be used as a shower plate. 
     As described above, according to the present invention, when microwaves are supplied into a processing container by using an RLSA, variation of a transmission path of the microwaves, during an actual temperature increase, from the transmission path of the microwaves during a temperature increase set in a design of the microwave plasma processing apparatus, may be suppressed, and disturbance of plasma may be prevented.

Technology Classification (CPC): 7