Abstract:
A plasma processing apparatus includes a processing chamber which has a dielectric wall partly formed of a dielectric substance and in which a to-be-processed substrate is subjected to a plasma process, an induction coil which is arranged to face the dielectric wall and generates an induction electric field to generate plasma in the processing chamber, a Faraday shield which is provided to partially have openings between the dielectric wall and the induction coil to shield an electrostatic field component and pass an electromagnetic field component, and a drive mechanism which moves the Faraday shield.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-132918, filed May 18, 2007, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to a plasma processing apparatus used for semiconductor etching and formation of thin films, and more particularly to a plasma processing apparatus having a Faraday shield, and further relates to a plasma processing method using the above apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    In a plasma processing apparatus used for semiconductor etching and formation of thin films, electromagnetic waves are applied to gas filled in a plasma processing chamber as one means for generating plasma in the plasma processing chamber. In this case, as representative means for generation of electromagnetic waves, an induction coil is used. 
         [0006]    In the plasma generation process using the induction coil, the inner wall of the processing chamber wall (dielectric wall) that faces the induction coil is exposed to a strong electromagnetic field. Such a strong electromagnetic field damages the dielectric wall surface. In order to reduce the damage, a measure of disposing a Faraday shield between the induction coil and the dielectric wall is taken. The Faraday shield is arranged not to cover the entire surface of the dielectric wall that faces the induction coil but to cover a portion thereof. Specifically, the Faraday shield is configured by arranging metal plates around the dielectric wall at regular intervals and alternately arranging areas (shielding portions) in which the metal plates are placed and areas (opening portions) in which the metal plates are not placed. This is because electromagnetic waves cannot be introduced into the plasma processing chamber if the entire surface of the dielectric wall that faces the induction coil is covered with the shielding portion. 
         [0007]    As documents in which the effect of the Faraday shield is explained, “IEEE Trans. Plasma Sci. PS-13 (1985) 569, 2” and “Study of Nuclear Fusion, Vol. 58, No. 1 (July, 1987), Plasma Wave Heating Antenna and Analysis of Electromagnetic Field, pp 13 to 25” are known. As given in the above documents, and also realized by the present invention, the following three effects are provided by a Faraday shield. 
         [0008]    (Effect 1): Component of electric field in antenna axial direction is smoothly distributed 
         [0009]    (Effect 2): Component of electric field perpendicular to antenna is shielded 
         [0010]    (Effect 3): Component of electrostatic field is shielded 
         [0011]    It is understood based on (Effect 1) that provision of the Faraday shield itself contributes to a reduction in the damage to the dielectric wall surface. However, (Effects 2 and 3) are different in the opening portion and shielding portion of the Faraday shield. The above difference results in the generation of local damage to the dielectric wall surface. When such local damage continues, particles are generated from the dielectric wall surface. 
         [0012]    Thus, in the conventional plasma processing apparatus, the dielectric wall surface is subjected to local damage due to the presence of the Faraday shield disposed between the induction coil and the dielectric wall, which causes a problem that particles may be generated. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    According to a first aspect of the present invention, there is provided a plasma processing apparatus including a processing chamber which has a dielectric wall partly formed of a dielectric substance and in which a to-be-processed substrate is subjected to a plasma process, an induction coil which is arranged to face the dielectric wall and generates an induction electric field to generate plasma in the processing chamber, a Faraday shield which is provided to partially have openings between the dielectric wall and the induction coil to shield an electrostatic field component and pass an electromagnetic field component, and a drive mechanism which moves the Faraday shield. 
         [0014]    According to a second aspect of the present invention, there is provided a plasma processing method which includes preparing a plasma processing apparatus having a dielectric wall formed of a dielectric substance and partly disposed in a processing chamber used for a plasma process and a Faraday shield that is provided to partially have openings between the dielectric wall and an induction coil to shield an electrostatic field component and pass an electromagnetic field component, generating plasma in the processing chamber by supplying gas into the processing chamber and generating an induction electric field in the processing chamber by use of the induction coil, and changing a positional relation of the openings of the Faraday shield with respect to the dielectric wall by moving the Faraday shield during the plasma process by use of the plasma or moving the Faraday shield after elapse of a preset processing period of time. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0015]      FIG. 1  is a schematic configuration view showing a plasma processing apparatus according to a first embodiment of this invention. 
           [0016]      FIG. 2  is a perspective view showing an installation example of a Faraday shield in the first embodiment. 
           [0017]      FIGS. 3A and 3B  are cross-sectional views each showing the Faraday shield as viewed from above, for illustrating the plasma processing apparatus according to the first embodiment. 
           [0018]      FIGS. 4A and 4B  are cross-sectional views each showing a Faraday shield as viewed from above, for illustrating a plasma processing apparatus according to a second embodiment of this invention. 
           [0019]      FIG. 5  is a schematic configuration view showing a plasma processing apparatus according to a third embodiment of this invention. 
           [0020]      FIG. 6  is a plan view showing an installation example of a Faraday shield in the third embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Embodiments of the present invention will be described below with reference to the accompanying drawings. 
       First Embodiment 
       [0022]      FIG. 1  is a schematic configuration view showing a plasma processing apparatus according to a first embodiment of this invention. The apparatus is a cylinder type ICP (Inductive Coupling Plasma) etching apparatus having a Faraday shield. 
         [0023]    A reference symbol  10  in  FIG. 1  is a metal processing chamber and a conductive stage  21  on which a to-be-processed substrate  20  is placed, which is disposed in the processing chamber  10 . The stage  21  is fixed above a platform  11  that is fixed on the bottom portion of the processing chamber  21  with an insulating body  22  disposed therebetween. An RF power source  24  provided outside the processing chamber  21  is connected to the stage  21 . 
         [0024]    A gas inlet port  12  is formed in the upper wall portion of the processing chamber  10  and a vacuum pump drawing passage (gas outlet port)  13  is provided in a lower portion of the processing chamber  10 , lower than the stage  21 . Gas used for plasma etching is introduced via the gas inlet port  12  and discharged from the gas outlet port  13 . 
         [0025]    The upper portion of the processing chamber  10  is formed with a large inside diameter and a cylindrical dielectric wall  15  is provided in a portion in which the inside diameter of the processing chamber is increased. The dielectric wall  15  is formed of a dielectric substance such as ceramic or quartz and the inside diameter is set to be substantially the same as the inside diameter of the lower portion of the processing chamber  10 . 
         [0026]    An induction coil  31  is disposed on the upper portion in which the inside diameter of the processing chamber  10  is increased to surround the outer peripheral surface of the dielectric wall  15 . The induction coil  31  applies an induction electric field for plasma generation to an inside portion of the processing chamber  10  and is connected to an RF power source  32  provided outside the processing chamber  10 . Thus, plasma is generated in an area  34  shown in  FIG. 1  by supplying gas into the processing chamber  10  and applying the induction electric field by use of the induction coil  31 . 
         [0027]    A Faraday shield  41  that shields an electrostatic field component and permits an electromagnetic field component to pass therethrough is provided between the induction coil  31  and the dielectric wall  15 . The Faraday shield  41  has openings partly formed therein and arranged along the outer peripheral surface of the dielectric wall  15 . 
         [0028]      FIG. 2  is a perspective view showing the arrangement relation between the dielectric wall  15  and the Faraday shield  41 . Strip-form metal plates  41   a  (shielding portions) forming the Faraday shield  41  are arranged around the outer peripheral surface of the cylindrical dielectric wall  15  in a circumferential direction at regular intervals. The metal plate  41   a  has high conductivity and is formed by coating silver on the surface of a copper plate, for example. Further, the length of the metal plate  41   a  in the lengthwise direction is set to be equal to the height of the cylindrical dielectric wall  15 . 
         [0029]    The regular arrangement interval of the metal plates  41   a  makes a configuration in which areas (shielding portions)  41   a  in which the metal plates are present and areas (opening portions)  41   b  in which the metal plates are not present are alternately arranged in a circumferential direction of the dielectric wall  15 . That is, in the Faraday shield  41 , the shielding portions  41   a  and the opening portions  41   b  are alternately arranged in the circumferential direction of the dielectric wall  15 . In this case, the width of the shielding portion  41   a  (the length of the dielectric wall  15  in the circumferential direction) may be set to be the same as or different from the width of the opening portion  41   b . The shielding amount of the electrostatic field component and the passage amount of the electromagnetic field component can be adjusted by changing the dimensional relation between the width of the shielding portion  41   a  and the width of the opening portion  41   b.    
         [0030]    The bottom portion of the Faraday shield  41 , that is, the bottom portion of each metal plate  41   a  formed in a strip form is linked with a ring-form Faraday shield base  42 . The Faraday shield base  42  can be rotated by a motor or actuator (not shown) and the Faraday shield  41  can also be rotated by rotating the Faraday shield base  42 . The arrangement relation between the shielding portions  41   a  and the opening portions  41   b  of the Faraday shield  41  can be changed by rotating the Faraday shield base  42 . 
         [0031]    Next, the plasma processing method using the present apparatus is explained. First, the basic process of the plasma process by use of an ICP etching apparatus is explained. 
         [0032]    First, gas used for plasma etching is introduced into the processing chamber  10  via the gas inlet port  12  and filled in the plasma generation area  34 . Then, the pressure of the area  34  in which plasma is generated is controlled by controlling the cross-sectional area of the vacuum pump drawing passage  13 . 
         [0033]    After this, the RF power sources  24 ,  32  are activated to output RF powers so as to generate plasma in the processing chamber  10 . The to-be-processed substrate  20  on the stage  21  is etched by use of the thus generated plasma. In this way, the plasma process is performed by the ICP etching apparatus. 
         [0034]    Next, the arrangement relation and the operation of the Faraday shield  41 , which are the features of the preset embodiment, are explained. 
         [0035]      FIGS. 3A and 3B  are cross-sectional views each showing the Faraday shield  41  shown in  FIG. 2  as viewed from above. In  FIGS. 3A ,  3 B, the Faraday shield  41  is moved to rotate around the central axis of the cylindrical dielectric wall  15 . When the position shown in  FIG. 3A  is set as a reference, the Faraday shield  41  is moved to rotate by 15 degrees in  FIG. 3B . As a result, an opening area A of  FIG. 3A  becomes an opening area B in  FIG. 3B  and an area which is an opening area in  FIG. 3A  becomes a shield area in  FIG. 3B . When the Faraday shield base  42  is thus rotated, the arrangement of the shielding portions  41   a  and the opening portions  41   b  of the Faraday shield  41  can be shifted. As a result, damage to the dielectric wall  15  can be prevented, and generation of particles due to any irregularities in the dielectric wall  15  can be prevented. 
         [0036]    Specifically, any differences between the damage of the dielectric wall  15  that faces the opening portions  41   b  and the damage of the dielectric wall  15  that faces the shielding portions  41   a  can be controlled by changing the arrangement relation of the opening portions  41   b  of the Faraday shield  41  with respect to the dielectric wall  15 . In practice, when the damage difference has reached a certain reference level, the damage difference is gradually decreased by reversely setting the positions of the opening portions  41   b  and shielding portions  41   a . That is, it is understood that it is effective to change the arrangement of the opening portions  41   b  of the Faraday shield  41  in order to prevent occurrence of local damage of the dielectric wall  15  that is the problem of the Faraday shield  41 . 
         [0037]    The rotation operation of the Faraday shield  41  may be performed at the same time as the plasma process or may be performed a preset period of time after the plasma process was performed. When the rotation operation of the Faraday shield  41  is performed at the same time as the plasma process, the Faraday shield may be rotated at an extremely slow speed (for example, at a speed of one rotation/hour) during the plasma process. When the rotation operation of the Faraday shield  41  is periodically performed, for example, the relation between the plasma process accumulation time and a desired number of particles with respect to the processing chamber in which the plasma process is performed is previously acquired and time at which the arrangement of the opening portions is changed may be determined based on the thus acquired relation. That is, it is important to make uniform any local damage caused by the opening portions of the Faraday shield  41  without allowing any specific local damage to worsen. 
         [0038]    Thus, according to the present embodiment, irregularities in the damage to the dielectric wall  15  can be eliminated by rotating the Faraday shield  41  a preset period of time after the plasma process or during the process. Therefore, generation of particles due to irregularity in damage can be prevented. That is, generation of particles can be prevented by eliminating damage irregularities and controlling the damage amount. This leads to enhancement of the reliability of the plasma process and thus an extremely useful effect can be attained. 
       Second Embodiment 
       [0039]      FIGS. 4A and 4B  are cross-sectional views each showing a Faraday shield as viewed from above, for illustrating a plasma processing apparatus according to a second embodiment of this invention. Portions which are the same as those of  FIGS. 3A and 3B  are denoted by the same reference symbols and a detailed explanation thereof is omitted. 
         [0040]    The present embodiment also relates to a cylinder type ICP (Inductive Coupling Plasma) etching apparatus as in the first embodiment, and the basic apparatus configuration is substantially the same as that of the first embodiment. The differences are in the following three items. 
         [0041]    (1) Faraday shields are coaxially arranged in multiple stages (in two stages in this example). 
         [0042]    (2) Respective Faraday shield bases can be independently rotated. 
         [0043]    (3) The positional relation between the Faraday shield and the Faraday shield base can be changed. 
         [0044]    The present embodiment is an example in which the numerical aperture of the Faraday shield is controlled by using the function (3). Two-stage Faraday shields  51 ,  52  are provided to surround the outer peripheral surface of a dielectric wall  15 . The inner Faraday shield  51  is obtained by arranging strip-form metal plates (shielding portions)  51   a  at regular intervals in the circumferential direction of the dielectric wall  15 . In this case, however, unlike the first embodiment, two types of opening portions are provided, with small opening portions and large opening portions alternately arranged. The outer Faraday shield  52  is obtained by arranging strip-form metal plates  52   a  at regular intervals in the circumferential direction of the dielectric wall  15 . The size of the opening portions of the outer Faraday shield  52  is the same as that of the large opening portions of the inner Faraday shield  51  and the arrangement interval is set to twice that of the inner Faraday shield  51 . 
         [0045]    The Faraday shields  51 ,  52  are connected to a Faraday shield base (not shown) and rotated by rotating the Faraday shield base. Further, the positional relations of the Faraday shields  51 ,  52  with respect to the Faraday shield base can be independently changed. 
         [0046]    As shown in  FIG. 4A , in the initial condition, it is supposed that the large opening portions of the inner Faraday shield  51  are overlapped with the opening portions of the outer Faraday shield  52 . At this time, if the large opening portion of the inner Faraday shield  51  is set to the same size as the opening portion  41   b  of the Faraday shield  41  of  FIG. 3A , the numerical aperture in the initial state is set to the same value as that of  FIG. 3A . Therefore, the arrangement relation of the opening portions with respect to the dielectric wall  15  can be changed, as in the first embodiment, by rotating both of the Faraday shields  51 ,  52  in the same direction by driving the Faraday shield base in this state. 
         [0047]    Next, as shown in  FIG. 4B , the outer Faraday shield  52  is rotated in the circumferential direction to set and overlap the small opening portions of the inner Faraday shield  51  with the opening portions of the outer Faraday shield  52  by using the function (3). As a result, for example, the numerical aperture of 33% in the case of  FIG. 4A  can be reduced to 11% in the case of  FIG. 4B . Thus, the arrangement relation of the opening portions with respect to the dielectric wall  15  can be changed, as in the first embodiment, by rotating both of the Faraday shields  51 ,  52  in the same direction by driving the Faraday shield base in this state. Additionally, the state of the small numerical aperture can be maintained. 
         [0048]    According to this embodiment, the Faraday shields are provided in two stages and the sizes of the opening portions determined by overlapping of the two Faraday shields  51 ,  52  can be changed. Therefore, it is of course possible to attain the same effect as that of the first embodiment and freely adjust the passage amount of the electromagnetic field component and the shielding amount of the electrostatic field component determined by the numerical aperture of the Faraday shield. This means that the optimum numerical aperture of the Faraday shield can be selected based on a combination of the damage to the dielectric wall  15  and the strength of the electromagnetic field applied within the processing chamber  10 . 
       Third Embodiment 
       [0049]      FIG. 5  is a schematic configuration view showing a plasma processing apparatus according to a third embodiment of this invention. Portions which are the same as those of  FIG. 1  are denoted by the same reference symbols and a detailed explanation thereof is omitted. 
         [0050]    The present embodiment is different from the first embodiment explained before in that the induction coil  31  is not disposed on the side wall surface of the processing chamber  10  but arranged above the processing chamber  10 . 
         [0051]    The upper wall portion of the processing chamber  10  is formed of a disk-like dielectric wall  17  and the induction coil  31  is arranged above the dielectric wall  17 . A Faraday shield  61  is movably provided between the induction coil  31  and the dielectric wall  17 . As shown in  FIG. 6 , the Faraday shield  61  is formed by radially arranging fan-shaped metal plates (shielding portions)  61   a  at regular intervals. That is, the Faraday shield  61  is formed by alternately arranging the shielding portions  61   a  and opening portions  61   b  in the circumferential direction. 
         [0052]    The outer peripheral portion of the Faraday shield  61 , that is, the outer peripheral surface of each metal plate  61   a  is connected to a ring-form Faraday shield base  62 . The Faraday shield base  62  can be rotated by use of a motor or actuator (not shown). Therefore, the Faraday shield  61  is rotated by rotating the Faraday shield base  62  to change the position of the opening portions of the Faraday shield  61 . 
         [0053]    With the above configuration, any irregularities in the damage of the dielectric wall  15  can be eliminated by rotating the Faraday shield base  62  to rotate the Faraday shield  61  a preset period of time after the plasma process or during the process. Therefore, the same effect as that of the first embodiment can be attained. 
       Modification 
       [0054]    This invention is not limited to the above embodiments. In the first and second embodiments, the Faraday shield is configured by a plurality of strip-form metal plates and the shielding portions and opening portions are alternately arranged. However, this invention is not limited to this case and the Faraday shield can be configured by forming openings in a cylindrical metal plate at regular intervals. Further, the material and numerical aperture of the Faraday shield can be appropriately changed according to the specification. Also, the driving mechanism of the Faraday shield is not limited to the motor or actuator and can be provided by use of a hydraulic or pneumatic apparatus. In addition, the rotation direction of the Faraday shield is not limited to one direction and may be within a range of preset angles. 
         [0055]    Further, the apparatus of the embodiments is explained as an example of the etching apparatus, but the apparatus can be used as a film formation apparatus by replacing the introduced gas. In addition, the apparatus is not limited to the etching apparatus or film formation apparatus and can be applied to various types of plasma processing apparatuses. 
         [0056]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.