Methods and apparatus for scanning and focusing an ion beam

摘要

Methods and apparatus are provided for scanning and focusing a charged particle beam, such as an ion beam. The apparatus includes a charged particle source for generating a charged particle beam, scan electrodes disposed on opposite sides of the charged particle beam and a postscan electrode disposed adjacent to the charged particle beam and downstream of the scan electrodes. A postscan voltage is applied to the postscan electrode. A scan voltage generator applies to the scan electrodes scan voltages for scanning the charged particle beam in a first direction. The scan voltages have negative DC voltage offsets which are preferably more negative than the postscan voltage. The charged particle beam is focused in a second direction orthogonal to the first direction. The invention may be used in an ion implanter to increase the ion beam current delivered to a target.