Abstract:
A charged particle separation apparatus that separates ionized gas clusters is disclosed. The charged particle separation apparatus includes three or more electric field applying parts arranged in an incident direction of an ionized gas cluster, wherein each of the electric field applying parts includes a pair of electrodes; an electric power source configured to supply alternating-current electric voltages to the three or more electric field applying parts in such a manner that an alternating-current electric voltage applied across one pair of the electrodes of one of the three or more electric field applying parts is different in phase from an alternating-current voltage applied across another pair of the electrodes of an adjacent one of the three or more electric field applying parts; and a plate including an opening in an extension of the incident direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application contains subject matter related to Japanese Patent Application No. 2009-146765 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 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 from 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 in the gas cluster generating apparatus may be stochastically-distributed, and masses of the gas cluster vary in a certain range. Therefore, the gas clusters need to be separated depending on the masses of the gas clusters. 
         [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]    However, the ion clusters need to be separated depending on not only the masses but also valence numbers of the ion clusters. This is because intended use of the ion clusters greatly depends on the valence numbers, and more efficient and precise machining or the like can be realized when ion clusters having a desired valence number are separately used. According to experimental results obtained by the inventors of the inventions of the present application, ions can be traced even in a relatively deep area of a sample subject to ion cluster bombardment, which is deeper than a limited superficial layer of the sample. 
         [0010]    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 are capable of separating ionized gas clusters depending on a valence number of the ionized gas clusters. 
       SUMMARY OF THE INVENTION 
       [0011]    A first aspect of the present invention provides a charged particle separation apparatus that separates ionized gas clusters. The charged particle separation apparatus includes three or more electric field applying parts arranged in an incident direction of an ionized gas cluster, wherein each of the electric field applying parts includes a pair of electrodes; an electric power source configured to supply alternating-current electric voltages to the three or more electric field applying parts in such a manner that an alternating-current electric voltage applied across one pair of the electrodes of one of the three or more electric field applying parts is different in phase from an alternating-current voltage applied across another pair of the electrodes of an adjacent one of the three or more electric field applying parts; and a plate including an opening in an extension of the incident direction. 
         [0012]    A second aspect of the present invention provides a charged particle separation apparatus that separates ionized gas clusters. The charged particle separation apparatus includes three or more electric field applying parts arranged in an incident direction of an ionized gas cluster, wherein each of the electric field applying parts includes a pair of electrodes; an electric power source configured to supply alternating-current electric voltages to the three or more electric field applying parts in such a manner that an alternating-current electric voltage applied across one pair of the electrodes of one of the three or more electric field applying parts is different in phase from an alternating-current voltage applied across another pair of the electrodes of an adjacent one of the three or more electric field applying parts; and a plate including an opening through which an ionized gas cluster whose trajectory is deflected by the three or more electric field applying parts can pass. 
         [0013]    A third aspect of the present invention provides a charged particle separation apparatus that separates ionized gas clusters. The charged particle separation apparatus includes three or more electric field applying parts arranged in an incident direction of an ionized gas cluster, wherein each of the electric field applying parts includes a pair of electrodes; an electric power source configured to supply alternating-current electric voltages superposed with a direct-current voltage to the three or more electric field applying parts in such a manner that a superposed electric voltage applied across one pair of the electrodes of one of the three or more electric field applying parts is different in phase from a superposed voltage applied across another pair of the electrodes of an adjacent one of the three or more electric field applying parts; and a plate including an opening through which an ionized gas cluster whose trajectory is deflected by the three or more electric field applying parts can pass. 
         [0014]    A fourth aspect of the present invention provides a charged particle separation apparatus according to any one of the first through the third aspects, wherein a frequency of the alternating-current voltage is determined so that the ionized gas cluster having a predetermined valence number among ionized gas clusters having the same number of atoms can pass through the opening of the plate. 
         [0015]    A fifth aspect of the present invention provides a charged particle separation apparatus according to the fourth aspect, wherein the predetermined valence number is  1 . 
         [0016]    A sixth aspect of the present invention provides a charged particle separation apparatus according to any one of the first through the fourth aspects, wherein the difference in phase is 180°. 
         [0017]    A seventh aspect of the present invention provides a charged particle separation apparatus according to any one of the first through the sixth aspect, wherein the number of the three or more electric field applying parts is one of three and four. 
         [0018]    An eighth aspect of the present invention provides charged particle bombardment apparatus including 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 any one of the first through the seventh aspects 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 are capable of separating ionized gas clusters depending on a valence number 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 a first embodiment of the present invention; 
           [0022]      FIG. 3  illustrates a relationship between a deflection angle of ionized gas clusters and θ 1  when the charged particle separation apparatus is provided with one electric field applying part; 
           [0023]      FIG. 4  illustrates a relationship between a deflection angle of ionized gas clusters and θ 1  when the charged particle separation apparatus is provided with two electric field applying parts; 
           [0024]      FIG. 5  illustrates a relationship between a deflection angle of ionized gas clusters and θ 1  when the charged particle separation apparatus is provided with three electric field applying parts; 
           [0025]      FIG. 6  is a schematic view of a charged particle separation apparatus according to a second embodiment of the present invention; 
           [0026]      FIG. 7  is a schematic view of a charged particle separation apparatus according to a third embodiment of the present invention; 
           [0027]      FIG. 8  illustrates a relationship between a deflection angle of ionized gas clusters and θ 1  when the charged particle separation apparatus is provided with four electric field applying parts; 
           [0028]      FIG. 9  is a schematic view of a charged particle separation apparatus according to a fourth embodiment of the present invention; 
           [0029]      FIG. 10  is a schematic view of a charged particle separation apparatus according to a fifth embodiment of the present invention; 
           [0030]      FIG. 11  is a schematic view of a charged particle separation apparatus according to a sixth embodiment of the present invention; 
           [0031]      FIG. 12  is a schematic view of a charged particle separation apparatus according to a seventh embodiment of the present invention; and 
           [0032]      FIG. 13  is a schematic view of a charged particle separation apparatus according to an eighth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    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 
       [0034]    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. 
         [0035]    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. 
         [0036]    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. 
         [0037]    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. 
         [0038]    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. 
         [0039]    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. 
         [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 electric field applying parts  21 ,  22 ,  23 , a plate  24 , and an electric power source  25 . 
         [0042]    The electric field applying part  21  includes electrodes  21   a ,  21   b . When an electric voltage is applied across the electrodes  21   a ,  21   b , an electric field is generated between the electrodes  21   a ,  21   b . The electric field applying part  22  includes electrodes  22   a ,  22   b . When an electric voltage is applied across the electrodes  22   a ,  22   b , an electric field is generated between the electrodes  22   a ,  22   b . The electric field applying part  23  includes electrodes  23   a ,  23   b . When an electric voltage is applied across the electrodes  23   a ,  23   b , an electric field is generated between the electrodes  23   a ,  23   b.    
         [0043]    Alternating-current voltage is supplied from the electric power source  25  to the electric field applying parts  21 ,  22 ,  23 . The electrodes  21   b ,  22   a , and  23   b  are electrically connected, and the electrodes  21   a ,  22   b , and  23   a  are electrically connected. The electric power source  25  applies electric potential at the electrodes  21   a ,  22   b ,  23   a  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  21   b ,  22   a ,  23   b . A frequency and voltage value of the voltage supplied to the electric field applying parts  21 ,  22 ,  23  can be adjusted. 
         [0044]    In addition, the plate  24  has an opening  24   a  through which the ionized gas clusters that have proceeded straight, among the ionized gas clusters that have passed through the electric field applying parts  21 ,  22 ,  23 , can pass. Because an ionized gas cluster whose trajectory is deviated by the electric field applying parts  21 ,  22 ,  23  as shown by a dashed arrow in  FIG. 2  cannot pass through the opening  24   a  of the plate  24 , the ionized gas clusters can be separated. Namely, the ionized gas cluster proceeding straight as shown by a solid arrow in  FIG. 2  can be separated by the gas cluster separation part  14 . 
         [0045]    In this embodiment, an alternating-current voltage having a predetermined frequency is applied across the electrodes  21   a ,  22   b ,  23   a  and the electrodes  21   b ,  22   a ,  23   b , thereby separating the ionized gas clusters having a predetermined valence number. 
         [0046]    (Ion Gas Cluster Trajectory Deviation) 
         [0047]    Next, how a trajectory of the ionized gas cluster is deviated is explained. 
         [0048]    Specifically, a deflection angle of an ion gas cluster and θ 1  defined by the following expression (1) are explained. 
         [0000]      θ 1   =ωl/v   0   (1)
       where ω is an angular frequency of the voltage supplied from the electric power source  25 , while a frequency of the voltage is defined by       
 
         [0000]        f=ω/ 2π  (2),
       l is a length of a deflection system, namely a length of the electrodes in total along the moving direction of the ion gas clusters, and   v 0  is a speed of the ion gas cluster.       
 
         [0052]      FIGS. 3 through 5  illustrate a relationship between the deflection angles of the ion clusters and θ 1  when one electric field applying part, two electric field applying parts, and three electric field applying parts are provided, respectively. Incidentally, 1 is 0.1 m; a cluster size of the ion gas cluster concerned is 1000 atoms per ion gas cluster; and an acceleration voltage for the ion gas cluster is 10 kV. The gas clusters are formed of argon atoms. 
         [0053]    Referring to  FIG. 3 , the deflection angles of the ionized gas clusters are different depending on the valence number of  1 ,  2 , or  3  in the case of one electric field applying part. However, a range of θ 1  where a deflection angle is stabilized is very limited, regardless of the valence number. Therefore, it is rather difficult to separate the ionized gas clusters having the corresponding valence numbers of  1 ,  2  or  3  by adjusting the frequency of the voltage supplied to the electric field applying part. 
         [0054]    Referring to  FIG. 4 , the deflection angles of the ionized gas clusters are different depending on the valence numbers of  1 ,  2  or  3  in the case of two electric field applying parts, where the alternating-current voltages whose phases are opposite in phase or 180° shifted with each other are supplied to the two electric field applying parts, respectively. As shown, while there are certain ranges of θ 1  where the deflection angles are stabilized, these ranges are not overlapped. Therefore, it is rather difficult to separate the gas clusters depending on the valence numbers by changing the frequency. 
         [0055]    Incidentally, while when θ 1  is about 12 to 13, namely when the frequency is about 130 to 140 kHz, the deflection angle of the gas cluster having the valence number of  1  is about zero, the deflection angles of the gas clusters having the valence numbers of  2  or  3  are not stabilized. In addition, there are ranges where the deflection angle of the gas clusters having the valence numbers of  2  or  3  is not very different from the deflection angle of the gas cluster having the valence number of  1 . Namely, while the separation performance in the case of the two electric field applying parts is improved compared with the only one electric field applying part, it is still rather difficult in practical use. 
         [0056]    Referring to  FIG. 5 , the deflection angles of the ionized gas clusters are different depending on the valence numbers of  1 ,  2  or  3  in the case of three electric field applying parts, where the alternating-current voltages whose phases are opposite in phase or 180° shifted with one another are supplied to the three electric field applying parts, respectively. As shown, there are certain ranges of θ 1  where the deflection angles of the gas clusters having the valence numbers of  1 ,  2  or  3  are stabilized and overlapped with one another in the case of three electric field applying parts. 
         [0057]    For example, when θ 1  is about 16, namely when the frequency is about 170 kHz, the deflection angle of the gas cluster having the valence number of  1  is about zero, and the deflection angles of the gas clusters having the valence numbers of  2  or  3  are relatively large, which makes it possible to substantially completely separate the gas clusters by use of the deflection angle of the gas cluster having the valence number of  1 . Therefore, the separation performance is further improved in the case of the three electric field applying parts, compared to the one or two electric field applying parts, and the gas cluster separating part  14  ( FIG. 1 ) having the three electric field applying parts is preferable in practical use. 
         [0058]    As stated above, when the alternating-current voltage whose frequency is determined so that θ 1  is about 16 is applied by the electric power source  25 , the gas cluster having the valence number of  1  can proceed straight, and the gas clusters having the valence numbers of  2  and  3  are deflected in this embodiment. With this, the gas cluster having the valence number of  1  can pass through the opening  24   a  of the plate  24  and the gas clusters having the valence numbers of  2  or  3  are blocked by the plate  24 . Namely, the gas cluster having the valence number of  1  is selected. 
         [0059]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the electric power source  25 . 
       Second Embodiment 
       [0060]    Next, a second embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes three electric field applying parts, in the same manner as the first embodiment. 
         [0061]    A cluster separation part in this embodiment is explained based on  FIG. 6 . 
         [0062]    The gas cluster separation part in this embodiment includes three electric field applying parts  31 ,  32 ,  33 , a plate  34 , and an electric power source  35 . 
         [0063]    The electric field applying part  31  includes electrodes  31   a ,  31   b . When an electric voltage is applied across the electrodes  31   a ,  31   b , an electric field is generated between the electrodes  31   a ,  31   b . The electric field applying part  32  includes electrodes  32   a ,  32   b . When an electric voltage is applied across the electrodes  32   a ,  32   b , an electric field is generated between the electrodes  32   a ,  32   b . The electric field applying part  33  includes electrodes  33   a ,  33   b . When an electric voltage is applied across the electrodes  33   a ,  33   b , an electric field is generated between the electrodes  33   a ,  33   b.    
         [0064]    Alternating-current voltage is supplied from the electric power source  35  to the electric field applying parts  31 ,  32 ,  33 . The electrodes  31   a ,  32   b , and  33   a  are electrically connected, and the electrodes  31   b ,  32   a  and  33   b  are electrically connected. The electric power source  35  applies electric potential at the electrodes  31   b ,  32   a ,  33   b  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  31   a ,  32   b ,  33   a . A frequency and voltage value of the voltage supplied to the electric field applying parts  31 ,  32 ,  33  can be adjusted by the electric power source  35 . 
         [0065]    The plate  34  is arranged so that the gas clusters whose trajectories are deflected at a predetermined deflection angle by the electric field applying parts  31 ,  32 ,  33 , among gas clusters that have passed through the electric field applying parts  31 ,  32 ,  33 , can pass through an opening  24   a  of the plate  24 , while gas clusters whose trajectories are not deflected at a predetermined deflection angle by the electric field applying parts  31 ,  32 ,  33  cannot pass through the opening  34   a . In other words, the gas clusters whose trajectories are deflected at the predetermined angle by the electric field applying parts  31 ,  32 ,  33  can be separated by the gas cluster separation part  14 . 
         [0066]    Namely, while the trajectories of the gas clusters having the valence numbers  2  or  3  are not deflected as much as possible, the trajectory of the gas cluster having the valence number of  1  is deflected at a large deflection angle by applying the alternating-current voltage from the electric power source  35  so that θ 1  become about 8, according to this embodiment. With this, when the plate  34  is arranged so that the gas cluster whose trajectory is deflected at a predetermined angle and is allowed to pass through the opening  34   a  of the silt  34 , the gas cluster having the valence number of  1  can pass through the opening  34   a  and the gas clusters having the valence numbers of  2  or  3  are blocked by the plate  34 . In addition, because the gas clusters moving straight cannot pass through the opening  34   a  of the plate  34 , neutral gas clusters, which have not been ionized, are blocked by the plate  34 . As a result, only the gas cluster having the valence number of  1  can be obtained. 
         [0067]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the electric power source  35 . 
         [0068]    The second embodiment is substantially the same as the first embodiment of the present invention except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the second embodiment. 
       Third Embodiment 
       [0069]    Next, a third embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes four electric field applying parts, where the ionized gas cluster having the valence number of  1  is separated. 
         [0070]    Referring to  FIG. 7 , a gas cluster separation part in this embodiment includes four electric field applying parts  41 ,  42 ,  43 ,  44 , a plate  45 , and an electric power source  46 . 
         [0071]    The electric field applying part  41  includes electrodes  41   a ,  41   b . When an electric voltage is applied across the electrodes  41   a ,  41   b , an electric field is generated between the electrodes  41   a ,  41   b . The electric field applying part  42  includes electrodes  42   a ,  42   b . When an electric voltage is applied across the electrodes  42   a ,  42   b , an electric field is generated between the electrodes  42   a ,  42   b . The electric field applying part  43  includes electrodes  43   a ,  43   b . When an electric voltage is applied across the electrodes  43   a ,  43   b , an electric field is generated between the electrodes  43   a ,  43   b . The electric field applying part  44  includes electrodes  44   a ,  44   b . When an electric voltage is applied across the electrodes  44   a ,  44   b , an electric field is generated between the electrodes  44   a ,  44   b.    
         [0072]    Alternating-current voltage is supplied from the electric power source  46  to the electric field applying parts  41 ,  42 ,  43 ,  44 . The electrodes  41   a ,  42   b ,  43   a , and  44   b  are electrically connected, and the electrodes  41   b ,  42   a ,  43   b , and  44   a  are electrically connected. The electric power source  46  applies electric potential at the electrodes  41   b ,  42   a ,  43   b ,  44   a  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  41   a ,  42   b ,  43   a , and  44   b . A frequency and voltage value of the voltage supplied to the electric field applying parts  41 ,  42 ,  43 ,  44  can be adjusted by the electric power source  46 . 
         [0073]      FIG. 8  illustrates a relationship between the deflection angle of the gas cluster and θ 1  in the case of the four electric field applying parts. Incidentally, l is 0.1 m; a cluster size of the ion gas cluster concerned is 1000 atoms per ion gas cluster; and an acceleration voltage for the ion gas cluster is 10 kV. The gas clusters are formed of argon atoms. In this embodiment, the alternating-current voltages opposite in phase are supplied to every two adjacent electric field applying parts. 
         [0074]    In the case of the four electric field applying par, when θ 1  is about 18.5, namely when the frequency is about 200 kHz, the deflection angle of the gas cluster having the valence number of  1  is about zero, while the deflection angles of the gas clusters having the valence numbers of  2  or  3  are relatively large. Therefore, the gas cluster having the valence number of  1  can be separated. In addition, the separation performance of the ionized gas clusters is improved compared to a case where the three electric field applying parts are used. 
         [0075]    This embodiment is based on the above considerations, and the gas cluster having the valence number of  1  is allowed to move straight, while the trajectories of the gas clusters having the valence numbers of  2  or  3  are deflected, by applying the alternating-current voltage having a frequency that makes θ 1  about 18.5 by the electric power source  45 . 
         [0076]    The plate  45  is arranged so that the gas clusters moving straight, among the gas clusters that have passed through the electric field applying parts  41 ,  42 ,  43 ,  44 , can pass through the opening  45   a  of the plate  45 . On the other hand, gas clusters whose trajectories are deflected at a predetermined deflection angle by the electric field applying parts  41 ,  42 ,  43 ,  44  cannot pass through the opening  45   a . Namely, the gas clusters moving straight as shown by a solid arrow in  FIG. 7  are allowed to pass through the opening  45   a , while the gas clusters having the valence number of  2  or  3  whose trajectories are deflected as shown by a dashed arrow in  FIG. 7  are blocked by the plate  45 . Therefore, the gas cluster having the valence number of  1  can be separated by the gas cluster separation part  14 . 
         [0077]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the electric power source  46 . 
         [0078]    In addition, the third embodiment is substantially the same as the first embodiment of the present invention except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the third embodiment. 
       Fourth Embodiment 
       [0079]    Next, a fourth embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes four electric field applying parts, where the ionized gas cluster having the valence number of  1  is separated. 
         [0080]    Referring to  FIG. 9 , a gas cluster separation part in this embodiment includes four electric field applying parts  51 ,  52 ,  53 ,  54 , a plate  55 , and an electric power source  56 . 
         [0081]    The electric field applying part  51  includes electrodes  51   a ,  51   b . When an electric voltage is applied across the electrodes  51   a ,  51   b , an electric field is generated between the electrodes  51   a ,  51   b . The electric field applying part  52  includes electrodes  52   a ,  52   b . When an electric voltage is applied across the electrodes  52   a ,  52   b , an electric field is generated between the electrodes  52   a ,  52   b . The electric field applying part  53  includes electrodes  53   a ,  53   b . When an electric voltage is applied across the electrodes  53   a ,  53   b , an electric field is generated between the electrodes  53   a ,  53   b . The electric field applying part  54  includes electrodes  54   a ,  54   b . When an electric voltage is applied across the electrodes  54   a ,  54   b , an electric field is generated between the electrodes  54   a ,  54   b.    
         [0082]    Alternating-current voltage is supplied from the electric power source  56  to the electric field applying parts  51 ,  52 ,  53 ,  54 . The electrodes  51   a ,  52   b ,  53   a ,  54   b  are electrically connected, and the electrodes  51   b ,  52   a ,  53   b ,  54   a  are electrically connected. The electric power source  56  applies electric potential at the electrodes  51   b ,  52   a ,  53   b ,  54   a  opposite in phase or 180° phase-shifted in relation to the electric potential applied at the electrodes  51   a ,  52   b ,  53   a ,  54   b . A frequency and voltage value of the voltage supplied to the electric field applying parts  51 ,  52 ,  53 ,  54  can be adjusted by the electric power source  56 . 
         [0083]    The plate  55  is arranged so that the gas clusters whose trajectories are deflected at a predetermined angle, among the gas clusters that have passed through the electric field applying parts  51 ,  52 ,  53 ,  54 , can pass through an opening  55   a  of the plate  55 . On the other hand, gas clusters whose trajectories are not deflected at a predetermined deflection angle by the electric field applying parts  51 ,  52 ,  53 ,  54  cannot pass through the opening  55   a . Therefore, the gas cluster whose trajectory is deflected at a predetermined angle can be separated by the gas cluster separation part  14 . 
         [0084]    Namely, the gas cluster having the valence number of  1  is deflected at a relatively large angle, while the gas clusters having the valence numbers of  2  or  3  are not deflected, by applying the alternating-current voltage having a frequency that makes θ 1  about 11.5 (see  FIG. 8 ) by the electric power source  56 . Therefore, when the plate  55  is arranged so that the gas cluster having the valence number of  1  whose trajectories are deflected at a predetermined relatively large deflection angle are allowed to pass through the opening  55   a  of the plate  55 , the gas cluster having the valence number of  1  can pass through the opening  55   a , while the gas clusters having the valence numbers of  2  or  3  are blocked by the plate  55 . With this, the gas cluster having the valence number of  1  can be separated. In addition, because the gas clusters moving straight cannot pass through the opening  55   a  of the plate  55 , neutral gas clusters can be blocked by the plate  55 . Therefore, only the gas cluster having the valence number of  1  can be separated. 
         [0085]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the electric power source  56 . 
         [0086]    The fourth embodiment is substantially the same as the first or the third embodiment of the present invention except for the configuration of the plate  55  and the frequency of the alternating-current voltage of the electric power source  56 . Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the fourth embodiment. 
         [0087]    As stated above, the ionized gas clusters can be efficiently separated depending on the valence number with the three or more electric field applying parts. In addition, the separation performance of the ionized gas clusters depending on the valence number can be improved by increasing the number of the electric field applying parts. 
       Fifth Embodiment 
       [0088]    Next, a fifth embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes an additional electric power source that outputs a direct-current voltage. 
         [0089]    Referring to  FIG. 10 , the gas cluster separation part according to this embodiment includes an electric field applying part  61 , a plate  66 , an alternating-current power source  66 , and a direct-current power source  67 . 
         [0090]    The electric field applying part  61  includes electrodes  61   a ,  61   b . When an electric voltage is applied across the electrodes  61   a ,  61   b , an electric field is generated between the electrodes  61   a ,  61   b.    
         [0091]    The electric voltage is applied by the alternating-current power source  66  and the direct-current power source  67 . Namely, alternating-current voltage biased by (or superposed with) direct-current voltage is applied to the electrodes  61   a ,  61   b . An electric potential at the electrode  61   b  is opposite in phase or 180° phase-shifted in relation to an electric potential at the electrode  61   a . A frequency and voltage applied to the electrodes  61   a ,  61   b  can be adjusted by the alternating-current power source  66  and/or the direct-current power source  67 . 
         [0092]    In addition, the plate  65  is arranged so that the gas clusters whose trajectories are deflected by the electric field applying part  61 , among gas clusters that have passed through the electric field applying part  61 , can pass through an opening  65   a  of the plate  65 . The gas clusters whose trajectories are not deflected by the electric field applying part  61  cannot pass through the opening  65   a  of the plate  65 . Therefore, the gas clusters whose trajectories are deflected can be separated in the gas cluster separation part of this embodiment. 
         [0093]    Namely, because the alternating-current voltage having a frequency that makes θ 1  about 6.3 (see FIG.  3 ), i.e., about 70 kHz, from the alternating-current power source  66  and the direct-current voltage from the direct-current power source  67  are superposed and supplied to the electric field applying part  61 , the gas cluster having the valence number of  1  is deflected at a predetermined angle and is allowed to pass through the opening  65   a  of the plate  65 , while neutral gas clusters are blocked by the plate  65 . Therefore, only the gas cluster having the valence number of  1  can be separated, excluding the neutral gas clusters. 
         [0094]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the alternating-current power source  66  and the direct-current power source  67 . 
         [0095]    The fifth embodiment is substantially the same as the first or the like except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the fifth embodiment. 
       Sixth Embodiment 
       [0096]    Next, a sixth embodiment of the present invention is explained with reference to  FIG. 11 . A charged particle separation apparatus according to this embodiment includes an additional electric power source that outputs a direct-current voltage. 
         [0097]    The gas cluster separation part  14  according to this embodiment includes two electric field applying parts  71 ,  73 , a plate  75 , an alternating-current power source  76 , and a direct-current power source  77 . 
         [0098]    The electric field applying part  71  includes electrodes  71   a ,  71   b . When an electric voltage is applied across the electrodes  71   a ,  71   b , an electric field is generated between the electrodes  71   a ,  71   b . The electric field applying part  72  includes electrodes  72   a ,  72   b . When an electric voltage is applied across the electrodes  72   a ,  72   b , an electric field is generated between the electrodes  72   a ,  72   b.    
         [0099]    The electric voltage is supplied by the alternating-current power source  76  and the direct-current power source  77 . Namely, alternating-current voltage biased by (or superposed with) direct-current voltage is supplied to the electric field applying parts  71 ,  72 . The electrodes  71   a ,  72   b  are electrically connected, and the electrodes  71   b ,  72   a  are electrically connected. Electric potentials at the electrodes  71   b ,  72   a  are opposite in phase or 180° phase-shifted in relation to electric potentials at the electrodes  71   a ,  72   b . A frequency and voltage supplied to the electric field applying parts  71 ,  72  can be adjusted by the alternating-current power source  76  and/or the direct-current power source  77 . 
         [0100]    The plate  75  is arranged so that the gas clusters whose trajectories are deflected at a predetermined angle, among gas clusters that has passed through the two electric field applying parts  71 ,  72 , can pass through an opening  75   a  of the plate  75 . On the other hand, the gas clusters whose trajectories are not deflected at a predetermined angle by the electric field applying parts  71 ,  72  cannot pass through the opening  75   a . Therefore, only the gas clusters whose trajectories are deflected at a predetermined angle can be separated by the gas cluster separation part. 
         [0101]    Namely, because the alternating-current voltage having a frequency that makes θ 1  about 12 through about 13 (see  FIG. 4 ), i.e., about 130 through 140 kHz, from the alternating-current power source  76  and the direct-current voltage from the direct-current power source  77  are superposed and supplied to the electric field applying parts  71 ,  72 , the gas cluster having the valence number of  1  is deflected at a predetermined angle and is allowed to pass through the opening  75   a  of the plate  75 , while neutral gas clusters are blocked by the plate  75 . Therefore, only the gas cluster having the valence number of  1  can be separated, excluding the neutral gas clusters. 
         [0102]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the alternating-current power source  76  and the direct-current power source  77 . 
         [0103]    The sixth embodiment is substantially the same as the first or the like except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the sixth embodiment. 
       Seventh Embodiment 
       [0104]    Next, a seventh embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes an additional electric power source that outputs a direct-current voltage. 
         [0105]    Referring to  FIG. 12 , a gas cluster separation part according to this embodiment includes three electric field applying parts  81 ,  82 ,  83 , a plate  85 , an alternating-current power source  86 , and a direct-current power source  87 . 
         [0106]    The electric field applying part  81  includes electrodes  81   a ,  81   b . When an electric voltage is applied across the electrodes  81   a ,  81   b , an electric field is generated between the electrodes  81   a ,  81   b . The electric field applying part  82  includes electrodes  82   a ,  82   b . When an electric voltage is applied across the electrodes  82   a ,  82   b , an electric field is generated between the electrodes  82   a ,  82   b . The electric field applying part  83  includes electrodes  83   a ,  83   b . When an electric voltage is applied across the electrodes  83   a ,  83   b , an electric field is generated between the electrodes  83   a ,  83   b.    
         [0107]    The electric voltage is supplied by the alternating-current power source  86  and the direct-current power source  87 . Namely, alternating-current voltage biased by (or superposed with) direct-current voltage is supplied to the electric field applying parts  81 ,  82 . The electrodes  81   a ,  82   b ,  83   a  are electrically connected, and the electrodes  81   b ,  82   a ,  83   b  are electrically connected. Electric potentials at the electrodes  81   b ,  82   a ,  83   b  are opposite in phase or 180° phase-shifted in relation to electric potentials at the electrodes  81   a ,  82   b ,  83   a . A frequency and voltage supplied to the electric field applying parts  81 ,  82 ,  83  can be adjusted by the alternating-current power source  86  and/or the direct-current power source  87 . 
         [0108]    The plate  85  is arranged so that the gas clusters whose trajectories are deflected at a predetermined angle, among gas clusters that has passed through the two electric field applying parts  81 ,  82 ,  83 , can pass through an opening  85   a  of the plate  85 . On the other hand, the gas clusters whose trajectories are not deflected at a predetermined angle by the electric field applying parts  81 ,  82 ,  83  cannot pass through the opening  75   a . Therefore, only the gas clusters whose trajectories are deflected at a predetermined angle can be separated by the gas cluster separation part. 
         [0109]    Namely, because the alternating-current voltage having a frequency that makes θ 1  about 16 (see  FIG. 5 ), i.e., about 170 kHz, from the alternating-current power source  86  and the direct-current voltage from the direct-current power source  87  are superposed and supplied to the electric field applying parts  81 ,  82 ,  83 , the gas cluster having the valence number of  1  is deflected at a predetermined angle and is allowed to pass through the opening  85   a  of the plate  85 , while neutral gas clusters are blocked by the plate  85 . Therefore, only the gas cluster having the valence number of  1  can be separated, excluding the neutral gas clusters. 
         [0110]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the alternating-current power source  86  and the direct-current power source  87 . 
         [0111]    The seventh embodiment is substantially the same as the first or the like except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the seventh embodiment. 
       Eighth Embodiment 
       [0112]    Next, an eighth embodiment of the present invention is explained. A charged particle separation apparatus according to this embodiment includes an additional electric power source that outputs a direct-current voltage. 
         [0113]    Referring to  FIG. 13 , a gas cluster separation part according to this embodiment includes four electric field applying parts  91 ,  92 ,  93 ,  94 , a plate  95 , an alternating-current power source  96 , and a direct-current power source  97 . 
         [0114]    The electric field applying part  91  includes electrodes  91   a ,  91   b . When an electric voltage is applied across the electrodes  91   a ,  91   b , an electric field is generated between the electrodes  91   a ,  91   b . The electric field applying part  92  includes electrodes  92   a ,  92   b . When an electric voltage is applied across the electrodes  92   a ,  92   b , an electric field is generated between the electrodes  92   a ,  92   b . The electric field applying part  93  includes electrodes  93   a ,  93   b . When an electric voltage is applied across the electrodes  93   a ,  93   b , an electric field is generated between the electrodes  93   a ,  93   b . The electric field applying part  94  includes electrodes  94   a ,  94   b . When an electric voltage is applied across the electrodes  94   a ,  94   b , an electric field is generated between the electrodes  94   a ,  94   b.    
         [0115]    The electric voltage is supplied by the alternating-current power source  96  and the direct-current power source  97 . Namely, alternating-current voltage biased by (or superposed with) direct-current voltage is supplied to the electric field applying parts  91 ,  92 . The electrodes  91   a ,  92   b ,  93   a  are electrically connected, and the electrodes  91   b ,  92   a ,  93   b  are electrically connected. Electric potentials at the electrodes  91   b ,  92   a ,  93   b  are opposite in phase or 180° phase-shifted in relation to electric potentials at the electrodes  91   a ,  92   b ,  93   a . A frequency and voltage supplied to the electric field applying parts  91 ,  92 ,  93  can be adjusted by the alternating-current power source  96  and/or the direct-current power source  97 . 
         [0116]    The plate  95  is arranged so that the gas clusters whose trajectories are deflected at a predetermined angle, among gas clusters that has passed through the two electric field applying parts  91 ,  92 ,  93 ,  94 , can pass through an opening  95   a  of the plate  95 . On the other hand, the gas clusters whose trajectories are not deflected at a predetermined angle by the electric field applying parts  91 ,  92 ,  93 ,  94  cannot pass through the opening  95   a . Therefore, only the gas clusters whose trajectories are deflected at a predetermined angle can be separated by the gas cluster separation part. 
         [0117]    Namely, because the alternating-current voltage having a frequency that makes θ 1  about 18.5 (see  FIG. 8 ), i.e., about 200 kHz, from the alternating-current power source  76  and the direct-current voltage from the direct-current power source  77  are superposed and supplied to the electric field applying parts  91 ,  92 ,  93 ,  94  the gas cluster having the valence number of  1  is deflected at a predetermined angle and is allowed to pass through the opening  95   a  of the plate  95 , while neutral gas clusters are blocked by the plate  95 . Therefore, only the gas cluster having the valence number of  1  can be separated, excluding the neutral gas clusters. 
         [0118]    Incidentally, while the above explanation is made about a case where the gas cluster having the valence number of  1  is separated, the gas cluster having the valence number of  2  or  3  can be separated, if necessary, by adjusting the frequency of the alternating-current voltage of the alternating-current power source  96  and the direct-current power source  97 . 
         [0119]    The eighth embodiment is substantially the same as the first or the like except for the configuration explained above. Therefore, the same charged particle bombardment apparatus as explained in the first embodiment can be obtained by employing the charged particle separation apparatus according to the eighth embodiment. 
         [0120]    Although several embodiments according to the present invention have been explained, the present invention is not limited to the foregoing embodiments, but may be modified or altered within the scope of the accompanying claims.