Patent Number: 
Section: claims

1. A wafer scanning device which causes a wafer to scan in a vacuum chamber, comprising:a holder which can hold a wafer;a linear translation structure which causes the holder to scan;a transmission mechanism and a motor which drive the linear translation structure; andan integrated support frame which supports them, wherein said holder and said linear translation structure are installed in a vacuum chamber;said transmission mechanism comprises a first transmission mechanism on a line of travel of the linear translation structure, which is installed in the vacuum chamber, and a second transmission mechanism offset from said line of travel; andsaid second transmission mechanism and said motor, which has a vacuum-tight cover, are located in the vacuum chamber, and both lead to the atmosphere, with vacuum sealing from the first transmission mechanism. 2. A wafer scanning device according to claim 1 wherein said support frame is supported on a side of the vacuum chamber in such a manner that the support frame can rotate about an axis in the vacuum chamber. 3. A wafer scanning device according to claim 1 wherein said support frame is positioned in the vacuum chamber together with the holder, the linear translation structure, the transmission mechanism and the motor; the support frame has a vacuum-tight cover which is open to the outside of the vacuum chamber via a ventilation pipe and provided with a vacuum seal member along the line of travel of the linear translation structure in order to isolate the interior of the vacuum chamber from the atmosphere; and the second transmission mechanism offset from the line of travel of the linear translation structure and said motor are placed in the vacuum-tight cover which is open to the atmosphere. 4. A wafer scanning device according to claim 3 wherein said support frame is supported by a wall of the vacuum chamber via a hollow rotation shaft including said ventilation pipe in it, and changes its angle by the rotation of said hollow rotation shaft. 5. A wafer scanning device according to claim 3 wherein said transmission mechanism includes a transmission belt which connects the first transmission mechanism on the line of travel of the linear translation structure and the second transmission mechanism offset from the line of travel, and said transmission belt is installed in said vacuum-tight cover. 6. A wafer scanning device according to claim 1 wherein a surface of a wafer held by said holder is parallel to the path of travel of the holder determined by the linear translation structure, said support frame is arranged in such a manner that it can change its angle and can cause the holder to tilt with keeping that condition, and the center line for changing the angle of the support frame is in a plane including the surface of the wafer held by the holder. 7. A wafer scanning device according to claim 1 wherein said support frame is provided with a belt and a pulley to transmit the drive power of the motor to the linear translation structure, and further provided with a linear guide member to guide the movement of the holder. 8. A wafer scanning device according to claim 1 wherein said seal to isolate the interior of the vacuum chamber from the atmosphere can be a magnetic fluid seal which is installed on a rotation shaft directly connected to the linear translation structure. 9. A wafer scanning device according to claim 1 wherein said linear translation structure and other components, having a rolling surface or a sliding surface and installed in the vacuum chamber, are assembled in such a manner that it is possible to exchange them as a unit. 10. A wafer scanning device according to claim 1 wherein the wafer fixed to the holder is caused to scan by means of the linear translation structure while an ion beam is irradiated to the wafer. 11. A wafer scanning device according to claim 1 wherein a first transmission coupling is connected between said transmission mechanism and said motor to drive the linear translation structure. 12. A wafer scanning device according to claim 1 wherein said linear translation structure, which causes the holder to scan, is a ball screw positioned in the vacuum chamber. 13. A wafer scanning device according to claim 12 wherein a rolling surface and a sliding surface of said ball screw are coated with a diamondlike carbon film and further covered by a baking film of fluorine oil. 14. A wafer scanning device according to claim 12 wherein said ball screw is a ball-retainer-embedded ball screw. 15. A wafer scanning device according to claim 12 wherein said ball screw is connected to the transmission mechanism via a second transmission coupling. 16. A wafer scanning device according to claim 12 wherein said ball screw is supported by the support frame via a radial bearing at its either end and further supported by the support frame via a preloaded thrust bearing at its end closer to the transmission mechanism. 17. A wafer scanning device according to claim 16 wherein a fluid passage which cools the ball screw is formed to run near said thrust bearing of the support frame.