Abstract:
A charged particle separation apparatus that separates ionized gas clusters is disclosed. The charged particle separation apparatus includes an electric field applying part including two electrodes across which electric voltage is applied in order to generate electric field between the two electrodes thereby deflecting a trajectory of the ionized gas cluster, the electrodes including one of an opening and a void; and a plate opening that allows the ionized gas cluster whose trajectory is deflected by the electric field applying part to go therethrough.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application contains subject matter related to Japanese Patent Application No. 2009-146766 filed with the Japanese Patent Office on Jun. 19, 2009, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a charged particle separation apparatus and a charged particle bombardment apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    Gas clusters into which plural atoms and the like are condensed exhibit a unique physicochemical behavior, and attract attention for applications in various fields of technologies. Namely, gas cluster ion beams are thought to be applicable for processes such as ion-implantation, surface machining, and thin film deposition in a depth range of several nanometers from a surface of a solid material, while the processes in such a depth range have been considered difficult by conventional technologies. 
         [0006]    In a gas cluster generating apparatus, it is possible to generate gas clusters formed of several hundred through several thousand atoms from a compressed gas supplied from a gas supplying source. The number of the atoms in the gas cluster generated by the gas cluster generating apparatus is stochastically-distributed, and thus the gas clusters range in mass. The gas clusters need to be separated depending on the masses of the gas clusters in practical use. 
         [0007]    To this end, a method has been proposed in order to separate the gas clusters generated by the gas cluster generating apparatus depending on the masses (Patent Document 1). 
         [0008]    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2005-71642. 
         [0009]    The method of separating ionized gas clusters, which is described in Patent Document 1, employs two plate-like electrodes arranged in parallel with each other, and applies electric fields between the two plate-like electrodes in order to separate ionized gas clusters. 
         [0010]    When the gas clusters collide against the plate-like electrodes, they may be decomposed, which causes an increase in pressure between the plate-like electrodes. As a result, pressures become different in areas near the plate-like electrodes from areas away from the plate-like electrodes, which may affect separation performance of the ionized gas clusters. 
         [0011]    The present invention has been made in view of the above, and provides a charged particle separation apparatus and a charged particle bombardment apparatus that enable appropriate separation of ionized gas clusters depending on a mass or a valence of the ionized gas clusters. 
       SUMMARY OF THE INVENTION 
       [0012]    A first aspect of the present invention provides a charged particle separation apparatus that separates ionized gas clusters. The charged particle separation apparatus includes an electric field applying part including two electrodes across which an electric voltage may be applied in order to generate an electric field between the two electrodes thereby deflecting a trajectory of the ionized gas cluster, the electrodes including one of an opening and a void; and a plate opening that allows the ionized gas cluster whose trajectory is deflected by the electric field applying part to go therethrough. 
         [0013]    A second aspect of the present provides a charged particle separation apparatus according to the first aspect, wherein the one of the opening and the void is provided along a direction substantially orthogonal to a direction in which the ionized gas cluster moves. 
         [0014]    A third aspect of the present invention provides a charged particle separation apparatus according to the first aspect of the present invention, wherein each of the electrodes includes electrically conductive rods that extend in a direction substantially orthogonal to a direction in which the ionized gas cluster moves and are arranged along the substantially orthogonal direction. 
         [0015]    A fourth aspect of the present invention provides a charged particle separation apparatus according to the third aspect, wherein a value of D/P is one or more where P is a pitch of the electrically conductive rods constituting each of the electrodes and D is a distance between the electrodes. 
         [0016]    A fifth aspect of the present invention provides a charged particle separation apparatus according to the first or the second aspect, wherein the electrodes include mesh-like plates. 
         [0017]    A sixth aspect of the present invention provides a charged particle separation apparatus according to any one of the first through the fifth aspects, further comprising an additional one or more of the electric field applying part. 
         [0018]    A seventh aspect of the present invention provides a charged particle bombardment apparatus that includes a gas cluster generation part that generates a gas cluster; an ionizing electrode that ionizes the gas cluster generated by the gas cluster generation part; acceleration electrodes that accelerate the ionized gas cluster; a charged particle separation apparatus according to the first aspect that separates an ionized gas cluster having a desired valence number among the ionized gas clusters accelerated by the acceleration electrodes, wherein the ionized gas cluster emitted from the charged particle separation apparatus is bombarded onto an object. 
         [0019]    According to an embodiment of the present invention, a charged particle separation apparatus and a charged particle bombardment apparatus that enable appropriate separation of ionized gas clusters depending on a mass or a valence of the ionized gas clusters are provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a schematic view of a charged particle bombardment apparatus according to an embodiment of the present invention; 
           [0021]      FIG. 2  is a schematic view of a charged particle separation apparatus according to an embodiment of the present invention; 
           [0022]      FIG. 3  is a perspective view of electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0023]      FIG. 4  is a schematic view of the electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0024]      FIG. 5  illustrates a distribution of an electric field generated by the electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0025]      FIG. 6  illustrates another distribution of an electric field generated by the electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0026]      FIG. 7  illustrates yet another distribution of an electric field generated by the electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0027]      FIG. 8  illustrates still another distribution of an electric field generated by the electrodes in the charged particle separation apparatus according to the embodiment of the present invention; 
           [0028]      FIG. 9  is a perspective view of electrodes in a charged particle separation apparatus according to another embodiment of the present invention; 
           [0029]      FIG. 10  is a schematic view of a charged particle separation apparatus according to yet another embodiment of the present invention; 
           [0030]      FIG. 11  is a schematic view of a modified example of the charged particle separation apparatus according to the embodiment shown in  FIG. 10 ; and 
           [0031]      FIG. 12  is a schematic view of another modified example of the charged particle separation apparatus according to the embodiment shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0032]    Non-limiting, exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings, the same or corresponding reference symbols are given to the same or corresponding members or components. 
       First Embodiment 
       [0033]    Referring to  FIG. 1 , a charged particle bombardment apparatus according to a first embodiment of the present invention is explained in the following. A charged particle bombardment apparatus according to this embodiment includes a nozzle part  11 , ionization electrodes  12 , acceleration electrodes  13 , and a gas cluster separating part that corresponds to a charged particle separation apparatus according to this embodiment. 
         [0034]    The nozzle part  11  generates gas clusters from pressurized gas. Specifically, gas supplied at a high pressure to the nozzle part  11  is jetted out from the nozzle part  11 , and thus the gas clusters are generated. The gas used is a substance in gas phase at normal temperatures, and is preferably argon gas, oxygen gas, or the like. 
         [0035]    By supplying, for example, argon gas, the argon gas clusters are generated. These gas clusters do not have the same number of argon atoms, but have various numbers of the argon atoms. 
         [0036]    The generated gas clusters are ionized by the ionization electrodes  12 , and thus ionized gas clusters are generated. The ionized gas clusters do not have a constant valence number, but may be univalent, divalent, trivalent, or the like. 
         [0037]    Next, the ionized gas clusters are accelerated by the acceleration electrodes  13 . At this time, the ionized gas cluster is accelerated inversely proportional to a square root of the number of the atoms constituting the gas cluster or a square root of a mass of the gas cluster. In addition, the gas cluster is accelerated proportional to a square root of the valence number of the ionization. 
         [0038]    Next, the gas clusters are separated depending on the valence number of the gas clusters by the gas cluster separating part  14 . In this embodiment, only a univalent ionized gas cluster  15  can be separated. 
         [0039]    Incidentally, although a method of separating the ionized gas cluster  15  depending on the valence number is explained in this embodiment, the ionized gas cluster  15  obtained in the same apparatus configuration can be separated depending on the mass of the ionized gas cluster  15 , in other embodiments. 
         [0040]    The gas cluster separating part  14  is explained, with reference to  FIG. 2 , which schematically illustrates the gas cluster separating part  14 . 
         [0041]    The gas cluster separating part  14  in this embodiment includes an electric field applying part  21 , a plate  24 , and an electric power source  25 . 
         [0042]    The electric field applying part  21  includes electrodes  22 ,  23 . When an electric voltage is applied across the electrodes  22 ,  23 , an electric field is generated between the electrodes  22 ,  23 . 
         [0043]    In fact, alternating electric voltage is applied across the electrodes  22 ,  23  by the electric power source  25  in such a manner that electric potentials applied to the electrodes  22 ,  23  are opposite in phase or 180° phase-shifted. A frequency and an amplitude of the alternating electric voltage may be adjusted by the electric power source  25  so that the gas cluster whose trajectory is deflected can pass through an opening  24   a  (described later) of the plate  24 . 
         [0044]    The plate  24  has the opening  24   a , so that the gas clusters whose trajectories are deflected by the electric field applying part  21 , among the gas clusters that have come into a space between the electrodes  22 ,  23 , can go through the opening  24   a . As shown by a dotted arrow in  FIG. 2 , a gas cluster that moves straight through the space between the electrodes  22 ,  23  is blocked by the plate  24  and cannot go through the opening  24   a . In other words, the gas clusters whose trajectories are appropriately deflected by the electric field applying part  21  as shown by a solid arrow in  FIG. 2  can be separated from other gas clusters. 
         [0045]    As shown in  FIG. 3 , the electrodes  22 ,  23  of the electric field applying part  21  are configured of plural electrically conductive rods, which are made of an electrically conductive material such as metal, arranged side by side. Specifically, the electrode  22  includes plural electrically conductive rods  22   a  arranged substantially in parallel with one another, and the electrode  23  includes plural electrically conductive rods  23   a  arranged substantially in parallel with one another. Each of the electrically conductive rods  22   a  extends in a direction substantially orthogonal to a direction along which an ionized gas cluster moves as shown by an arrow A in  FIG. 3 , and the electrically conductive rods  22   a  are arranged in the direction indicated by the arrow A. Similarly, each of the electrically conductive rods  23   a  extends in the direction substantially orthogonal to the direction along which an ionized gas cluster moves, and the electrically conductive rods  23   a  are arranged in the direction indicated by the arrow A. With such arrangements of the electrically conductive rods  22   a ,  23   a , the electric field is uniformly generated between the electrodes  22 ,  23  under predetermined conditions. 
         [0046]    Next, electric field distributions depending on the arrangements of the electrically conductive rods  22   a ,  23   a  are explained with reference to  FIG. 4 . It is assumed that the electrically conductive rods  22   a  of the electrode  22  are arranged at a pitch of P with one another as shown in subsections (a) and (b) of  FIG. 4 , and away from the corresponding electrically conductive rods  23   a  of electrode  23  with a distance D as shown in a subsection (a) of  FIG. 4 . In addition, it is assumed that the electrically conductive rods  23   a  of the electrode  23  are arranged at the same pitch of P. 
         [0047]      FIG. 5  illustrates a distribution of an electric field generated between the electrodes  22 ,  23 , wherein the electrically conductive rods  22   a ,  23   a  are arranged so that a ratio of D/P is 0.5, when a positive electric potential is applied to one of the electrodes  22 ,  23  and a negative electric potential is applied to the other one of the electrodes  22 ,  23 . As shown, the electric field is disturbed especially between the electrically conductive rods  22   a  and the corresponding electrically conductive rods  23   a . In this situation, it is thought that trajectories of the ionized gas clusters cannot be appropriately deflected by the electric field. 
         [0048]      FIG. 6  illustrates a distribution of an electric field generated between the electrodes  22 ,  23 , where the electrically conductive rods  22   a ,  23   a  are arranged so that a ratio of D/P is 1, when a positive electric potential is applied to one of the electrodes  22 ,  23  and a negative electric potential is applied to the other one of the electrodes  22 ,  23 . As shown, the electric field is relatively uniformly distributed between the electrodes  22 ,  23 , while being slightly disturbed around the electrically conductive rods  22   a ,  23   a . In this situation, it is thought that trajectories of the ionized gas clusters can be appropriately deflected by the electric field. 
         [0049]      FIG. 7  illustrates a distribution of an electric field generated between the electrodes  22 ,  23 , where the electrically conductive rods  22   a ,  23   a  are arranged so that a ratio of D/P is 2, when a positive electric potential is applied to one of the electrodes  22 ,  23  and a negative electric potential is applied to the other one of the electrodes  22 ,  23 . As shown, the electric field is substantially uniformly distributed between the electrodes  22 ,  23 . In this situation, it is thought that trajectories of the ionized gas clusters can be appropriately deflected by the electric field. 
         [0050]      FIG. 8  illustrates a distribution of an electric field generated between the electrodes  22 ,  23 , where the electrically conductive rods  22   a ,  23   a  are arranged so that a ratio of D/P is 2.5, when a positive electric potential is applied to one of the electrodes  22 ,  23  and a negative electric potential is applied to the other one of the electrodes  22 ,  23 . As shown, the electric field is more uniformly distributed between the electrodes  22 ,  23 . In this situation, it is thought that trajectories of the ionized gas clusters can be appropriately deflected by the electric field. 
         [0051]    From the foregoing explanations, the electric field can be uniformly distributed between the electrodes  22 ,  23  when the ratio of D/P is 1 or more, and thus the trajectories of the ionized gas clusters can be appropriately deflected. 
         [0052]    In addition, because the electrodes  22 ,  23  include the electrically conductive rods  22   a ,  23   a  arranged at predetermined pitches, respectively, in this embodiment, an area near the electrode  22  (or  23 ) can be evacuated through spaces (voids) between the electrically conductive rods  22   a  (or  23   a ), even if an evacuation mechanism is provided in a chamber where the electrodes  22 ,  23  are accommodated. Therefore, the electrodes  22 ,  23  do not affect the evacuation or impair smooth separation of ionized gas clusters. 
       Second Embodiment 
       [0053]    Next, a second embodiment of the present invention is explained. In this embodiment, an electric field applying part of the gas cluster separating part  14  includes mesh-like electrodes. 
         [0054]      FIG. 9  illustrates electrodes of the electric field applying part in this embodiment. The electric field applying part includes mesh-like electrodes  32 ,  33 , each of which is made of fine wires of copper or the like arranged in a matrix in a plane. By applying an electric voltage across the mesh-like electrodes  32 ,  33 , the electric field is generated between the mesh-like electrodes  32 ,  33 . 
         [0055]    Because the mesh-like electrodes  32 ,  33  have openings defined by the fine wires arranged in a matrix in a plane, the electrodes  32 ,  33  do not affect the evacuation or impair smooth separation of ionized gas clusters. 
         [0056]    The electric field applying part in this embodiment can be used in the same manner as the electric field applying part  21  in the first embodiment. With this, the charged particle separation apparatus that separates the ionized gas clusters and the charged particle bombardment apparatus can be obtained. 
       Third Embodiment 
       [0057]    Next, a third embodiment of the present invention is explained. A charged particle separation apparatus and a charged particle bombardment apparatus according to this embodiment include plural electric field applying parts having the electrodes in the first or the second embodiment. 
         [0058]      FIG. 10  illustrates the charged particle separation apparatus according to this embodiment. This charged particle separation apparatus includes two electric field applying parts  41 ,  42 , a plate  43 , and an electric power source  44 . 
         [0059]    The electric field applying part  41  includes electrodes  51 ,  52 . When an electric voltage is applied across the electrodes  51 ,  52 , an electric field is generated between the electrodes  51 ,  52 . The electric field applying part  42  includes electrodes  53 ,  54 . When an electric voltage is applied across the electrodes  53 ,  54 , an electric field is generated between the electrodes  53 ,  54 . 
         [0060]    Alternating electric voltage is supplied from the electric power source  44  to the electric field applying parts  41 ,  42 . The electrodes  51  and  54  are electrically connected, and the electrodes  52  and  53  are electrically connected. The electric power source  44  applies electric potential at the electrodes  52 ,  53  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  51 ,  54 . A frequency and an amplitude of the voltage supplied to the electric field applying parts  41 ,  42  can be adjusted. In addition, the plate  43  has an opening  43   a  through which the ionized gas clusters moving straight along the electrodes  51  through  54  can go through. 
         [0061]    In this charged particle separation apparatus, the electrodes  51 ,  52 ,  53 , and  54  may include the plural electrically conductive rods in the first embodiment, or may be configured of the mesh-like electrodes in the second embodiment. 
         [0062]    With such a configuration, an ionized gas cluster whose trajectory is deflected by the electric field applying parts  41 ,  42  as shown by a dotted line cannot go through the opening  43   a  of the plate  43  and is blocked by the plate  43  in  FIG. 10 . Therefore, the charged particle separation apparatus according to this embodiment can separate only the ionized gas clusters moving straight as shown by a solid line in  FIG. 10 . 
         [0063]    Another configuration of the charged particle separation apparatus according to this embodiment is illustrated in  FIG. 11 . This charged particle separation apparatus includes three electric field applying parts  61 ,  62 ,  63 , a plate  64 , and an electric power source  65 . 
         [0064]    The electric field applying part  61  includes electrodes  71 ,  72 , and an electric field is generated between the electrodes  71 ,  72  by applying a voltage across the electrodes  71 ,  72 . The electric field applying part  62  includes electrodes  73 ,  74 , and an electric field is generated between the electrodes  73 ,  74  by applying voltage across the electrodes  73 ,  74 . The electric field applying part  63  includes electrodes  75 ,  76 , and an electric field is generated between the electrodes  75 ,  76  by applying voltage across the electrodes  75 ,  76 . 
         [0065]    Alternating electric voltage is supplied from the electric power source  65  to the electric field applying parts  61 ,  62 ,  63 . The electrodes  71 ,  74 , and  75  are electrically connected, and the electrodes  72 ,  73 , and  76  are electrically connected. The electric power source  65  applies an electric potential at the electrodes  72 ,  73 ,  76  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  71 ,  74 ,  75 . A frequency and an amplitude of the voltage supplied to the electric field applying parts  61 ,  62 ,  63  can be adjusted. In addition, the plate  64  has an opening  64   a  through which the ionized gas clusters moving straight through the electric field applying parts  61 ,  62 ,  63  can go. 
         [0066]    In this charged particle separation apparatus, the electrodes  71 ,  72 ,  73 ,  74 ,  75 , and  76  may include the plural electrically conductive rods in the first embodiment, or may be configured of the mesh-like electrodes in the second embodiment. 
         [0067]    With such a configuration, an ionized gas cluster whose trajectory is deflected by the electric field applying parts  61 ,  62 ,  63  as shown by a dotted line cannot go through the opening  64   a  of the plate  64  and is blocked by the plate  64  in  FIG. 11 . Therefore, the charged particle separation apparatus according to this embodiment can separate only the ionized gas clusters moving straight as shown by a solid line in  FIG. 11 . 
         [0068]    Yet another configuration of the charged particle separation apparatus according to this embodiment is illustrated in  FIG. 12 . This charged particle separation apparatus includes four electric field applying parts  81 ,  82 ,  83 ,  84 , a plate  85 , and an electric power source  86 . 
         [0069]    The electric field applying part  81  includes electrodes  91 ,  92 , and an electric field is generated between the electrodes  91 ,  92  by applying a voltage across the electrodes  91 ,  92 . The electric field applying part  82  includes electrodes  93 ,  94 , and an electric field is generated between the electrodes  93 ,  94  by applying a voltage across the electrodes  93 ,  94 . The electric field applying part  83  includes electrodes  95 ,  96 , and an electric field is generated between the electrodes  95 ,  96  by applying a voltage across the electrodes  95 ,  96 . The electric field applying part  84  includes electrodes  97 ,  98 , and an electric field is generated between the electrodes  97 ,  98  by applying a voltage across the electrodes  97 ,  98 . 
         [0070]    Alternating electric voltage is supplied from the electric power source  65  to the electric field applying parts  81 ,  82 ,  83 ,  84 . The electrodes  91 ,  94 ,  95 , and  98  are electrically connected, and the electrodes  92 ,  93 ,  94 , and  97  are electrically connected. The electric power source  86  applies electric potential at the electrodes  92 ,  93 ,  94 ,  97  opposite in phase or 180° phase-shifted in relation to the electric potential at the electrodes  91 ,  94 ,  95 ,  98 . A frequency and an amplitude of the voltage supplied to the electric field applying parts  81 ,  82 ,  83 ,  84  can be adjusted. In addition, the plate  85  has an opening  85   a  through which the particles moving straight through the electric field applying parts  81 ,  82 ,  83 ,  84  can go. 
         [0071]    In this charged particle separation apparatus, the electrodes  91 ,  92 ,  93 ,  94 ,  95 ,  96 ,  97 ,  98  may include the plural electrically conductive rods in the first embodiment, or may be configured of the mesh-like electrodes in the second embodiment. 
         [0072]    With such a configuration, an ionized gas cluster whose trajectory is deflected by the electric field applying parts  81 ,  82 ,  83 ,  84  as shown by a dotted line cannot go through the opening  85   a  of the plate  85  and is blocked by the plate  85  in  FIG. 12 . Therefore, the charged particle separation apparatus according to this embodiment can separate only the gas clusters moving straight as shown by a solid line in  FIG. 12 . 
         [0073]    In this embodiment, even when the plural electric field applying parts are provided, or the number of the electrodes is increased, the electrodes do not affect the evacuation, and thus trajectories of the ionized gas clusters can be appropriately deflected. 
         [0074]    Although several embodiments according to the present invention have been explained, the present invention is not limited to the disclosed embodiments, but may be modified or altered within the scope of the accompanying claims.