Patent Number: 
Section: claims

1. A beam deflector for scanning and deflecting a charged particle beam, the charged particle beam having a regular trajectory in a vacuum, the deflector comprising:a pair of deflection electrodes, wherein each of the electrodes includes an inner surface having a generally symmetrical concave shape relative to each other;the inner surfaces of the electrodes being oriented toward one another so as to form an opening, the opening having an axis generally aligned with a direction of a beam trajectory, wherein the beam deflector generates only an electric field to periodically change the trajectory of the charged particle beam. 2. A beam deflector according to claim 1, wherein a cross-sectional shape of said concave shape is a substantially circular-arc concave shape or a polygonal concave shape. 3. A beam deflector according to claim 2, wherein the cross-sectional shape of said concave shape changes linearly or in steps along a center axis of the beam trajectory. 4. A beam deflector according to claim 2, wherein said inner electrode surfaces in said pair of deflection electrodes curve along maximum scan trajectories of a center axis of the beam trajectory so as to be substantially parallel to said maximum scan trajectories. 5. A beam deflector according to claim 1, wherein AC signals having the same phase and reverse polarity are applied to the pair of deflection electrodes, the AC signals being generally in the form of triangular waves having the same phase and reverse polarity. 6. A beam deflector according to claim 1, wherein said pair of deflection electrodes are applied with AC signals having the same values, the same phase, and reverse polarity. 7. A beam deflector according to claim 5 or 6, wherein DC signals are superimposed on said AC signals. 8. A beam deflector according to any one of claims 1 to 4, wherein each of said pair of deflection electrodes is formed by a plurality of individual members that are divided in the direction of a center axis of the beam trajectory. 9. An ion implantation system comprising the beam deflector for scanning according to any one of claims 1 to 6. 10. A beam deflecting method for scanning and deflecting a charged particle beam the charged particle beam having a regular trajectory in a vacuum, said beam deflecting method comprising the steps of:preparing, as said beam deflection means for scanning, a pair of deflection electrodes, wherein each of the electrodes includes an inner surface having a generally symmetrical concave shape; the inner surfaces of the electrodes being oriented toward one another so as to form an opening, the opening having an axis generally aligned with a direction of a beam trajectory; andapplying a generally uniform electric field generated by said pair of deflection electrodes to the charged particle beam passing through the opening defined between said pair of deflection electrodes, thereby performing the deflection for scanning wherein the beam deflection means generate only an electric field to periodically change the trajectory of the charged particle beam. 11. A beam deflecting method for scanning according to claim 10, wherein said pair of deflection electrodes have shapes that form a generally uniform electric field such that a horizontal-width direction of the beam remains generally uniform throughout passage between said pair of deflection electrodes. 12. A beam deflecting method for scanning and deflecting a charged particle beam, the charged particle beam having a regular trajectory in a vacuum, said beam deflecting method far-scanning comprising the steps of:preparing a pair of deflection electrodes, wherein each of the electrodes includes an inner surface having a generally symmetrical concave shape; the inner surfaces of the electrodes being oriented toward one another so as to form an opening, the opening having an axis generally aligned with a direction of a beam trajectory; andcausing the charged particle beam having an oval cross-sectional shape in which a horizontal width of said oval beam parallel to a confronting direction of said pair of deflection electrodes is greater than a vertical width of said oval beam perpendicular to said confronting direction, and said oval beam being incident upon an inlet side of said pair of deflection electrodes; andapplying a periodic deflection action for scanning in said confronting direction of said deflection electrode to change the trajectory of the charged particle beam, wherein the pair of deflection electrodes generate only an electric field. 13. A beam deflecting method according to claim 12, wherein the electric field generated by said pair of deflection electrodes is generally uniform, such that the charged particle beam having the oval cross-sectional shape is deflected at substantially the same deflection angle throughout passage between the pair of deflecting electrodes. 14. A beam deflecting method according to claim 13, wherein, in the opening formed between said pair of deflection electrodes, a change in beam profile is made as small as possible and orderly with respect to the deflection angle. 15. A beam deflecting method for scanning and deflecting a charged particle beam, the charged particle beam having a regular trajectory in a vacuum, said beam deflecting method comprising the steps of:deflecting the charged particle beam for scanning in one scanning direction by the use of a pair of deflection electrodes, wherein each of the electrodes includes an inner surface having a generally symmetrical concave shape; the inner surfaces of the electrodes being oriented toward one another so as to form an opening, the opening having an axis generally aligned with a direction of a beam trajectory;generating only an electric field to periodically change the trajectory of the charged particle beam; andmechanically moving a substrate, implanted with said charged particle beam, in a direction perpendicular to said one scanning direction to thereby perform ion implantation. 16. An ion implantation method using the beam deflecting method to any one of claims 10 to 15. 17. A beam deflector for scanning and deflecting a charged particle beam, the charged particle beam having a regular trajectory in a vacuum, said beam deflector comprising:a pair of deflection electrodes, wherein each of the electrodes includes an inner electrode-surface having a generally symmetrical concave shape; the inner surfaces of the electrodes being oriented toward one another so as to form an opening, the opening having an axis generally aligned with a direction of a beam trajectory;wherein, in order to generate a uniform electric field zone by said deflection electrodes an inlet side of said pair of deflection electrodes are separated at the innermost ends of the inner surface of said deflection electrodes by a width much greater than the horizontal width of the charged particle beam, andwherein the beam deflector generates only an electric field to periodically change the trajectory of the charged particle beam. 18. A beam deflector according to claim 17, wherein a plurality of shield electrodes each have an opening through which the charged particles beam passes are disposed adjacent to said pair of deflection electrodes, least one shield electrode is located upstream of the pair defection electrodes and at least one shield electrode is located downstream of the pair of defection electrodes. 19. A beam deflector according to claim 18, wherein said shield electrodes which are disposed on each of said upstream and downstream sides have plural electrodes, respectively. 20. A beam deflector according to claim 19, wherein each of said shield electrodes is independently applied with one of a fixed voltage and a variable voltage. 21. A beam deflector according to claim 18, wherein a single shield electrode is disposed on each of the upstream and downstream sides of said pair of deflection electrodes and each of the shield electrodes is grounded. 22. A beam deflector according to claim 19, wherein two shield electrodes are disposed on each of the upstream and downstream sides of said pair of deflection electrodes,one of said two shield electrodes on the upstream side, which is located closer to said pair of deflection electrodes, and one of said two shield electrodes on the downstream side, which is located closer to said pair of deflection electrodes, are applied with a voltage of about −1 kV to −2 kV so as to serve as electron suppression electrodes, andthe other of said two shield electrodes on the upstream side and the other of said two shield electrodes on the downstream side are grounded so as to serve as ground electrodes. 23. A beam deflector according to claim 22, wherein each of the openings of said suppression and ground electrodes is formed into a rectangular shape with an opening width which is large in a direction of a horizontal beam width and an opening height in a direction of the vertical beam width which is substantially equal to the vertical width of the charged particle beam so as to suppress the electric field from leaking to the outside of the deflector. 24. A beam deflector according to claim 23, wherein said suppression and ground electrodes cause the electrical field to be weak in the direction of the horizontal beam width and have no effect on the trajectory (deflection angle) of the charged particle beam. 25. A beam deflector according to any one of claims 18 to 24, wherein the opening of each of said shield electrodes on the upstream and downstream sides is configured such that the width thereof in a direction of a horizontal beam width is sufficiently greater than the horizontal beam width to thereby prevent the charged particle beam from passing near edges of the opening in the direction of the horizontal beam width. 26. A beam deflector according to claim 18, wherein dimensions of each of the concave shapes of said pair of deflection electrodes are determined such that electric fields in a direction perpendicular to a beam deflection plane near said shield electrodes and the electrical fields in the direction perpendicular to said beam deflection plane within said beam deflector cancel each other, making a focus/defocus and a trajectory declination of the charged particle beam in the direction perpendicular to said beam deflection plane before and after passing through said beam deflector small. 27. A beam deflector according to claim 18, wherein, the electric field in a direction perpendicular to a beam deflection plane at a center portion in said beam deflector is slightly stronger than the electric field outside the center path. 28. A beam deflector according to any one of claims 17 to 24, 26, and 27, wherein each of said pair of deflection electrodes is formed by a plurality of individual members that are divided in the direction of the center axis of the beam trajectory. 29. An ion implantation system comprising the beam deflector according to any one of claims 17 to 24, 26, and 27. 30. An ion implantation system according to claim 9, whereinsaid pair of deflection electrodes are disposed in a housing having openings for beam passing; andsaid housing is configured to be freely put on and taken off of a beam line in generally the middle of said beam line. 31. An ion implantation system according to claim 30, whereina rack is arranged generally in the middle of said beam line,a beam guide box having beam passing openings and being larger than said housing is mounted on said rack; andsaid housing is movable along a rail disposed in said beam guide box so that said housing is allowed to be received into and taken out from said beam guide box. 32. An ion implantation system according to claim 31, wherein said rail extends in a direction perpendicular to an extending direction of the beam line and a door for allowing said housing to be received into and taken out of said beam guide box is provided on one side of said beam guide box near one end of said rail. 33. An ion implantation system according to claim 32, wherein said housing is provided with a plurality of terminals having a feedthrough structure for establishing connection between at least said pair of deflection electrodes and a power supply. 34. An ion implantation system according to claim 30, wherein an outlet connected to an evacuator is provided in said housing. 35. An ion implantation system according to claim 29, whereinsaid pair of deflection electrodes are disposed in a housing having openings for beam passing; andsaid housing is configured to be freely put on and taken off of a beam line generally in a middle of said beam line. 36. An ion implantation system according to claim 35, whereina rack is arranged in the midway of said beam line,a beam guide box having beam passing openings and being larger than said housing is mounted on said rack; andsaid housing is movable along a rail disposed in said beam guide box so that said housing is allowed to be received into and taken out from said beam guide box. 37. An ion implantation system according to claim 36, wherein said rail extends in a direction perpendicular to an extending direction of the beam line and a door for allowing said housing to be received into and taken out of said beam guide box is provided on one side of said beam guide box near one end of said rail. 38. An ion implantation system according to claim 37, wherein said housing is provided with a plurality of terminals having a feedthrough structure for establishing connection between at least said pair of deflection electrodes and a power supply. 39. An ion implantation system according to claim 35, wherein an outlet connected to an evacuator is provided in said housing.