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Ion implanter with post mass selection deceleration

  • US 5,969,366 A
  • Filed: 09/08/1997
  • Issued: 10/19/1999
  • Est. Priority Date: 11/08/1995
  • Status: Expired due to Term
First Claim
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1. An ion implanter for implanting ions into a substrate comprising an ion beam generator for producing a beam of ions, a flight tube to transport said beam at a transport energy, a mass selection apparatus in the flight tube to select a desired mass of ions for transmission in the ion beam from the flight tube, a substrate holder for holding a substrate to be implanted with beam ions of said desired mass, neutralisation apparatus located in front of the substrate holder to provide a supply of low energy charged species of opposite polarity to the beam ions for neutralising surface charge build-up on the substrate during implantation, a deceleration potential generator connected to apply a deceleration potential between the flight tube and the substrate holder to decelerate beam ions to a desired implant energy, a deceleration lens assembly located between the flight tube and the neutralising apparatus and comprising a first apertured plate electrode connected to be substantially at the substrate potential, a second apertured plate electrode connected to be substantially at the flight tube potential and a field electrode located between and adjacent to each of said first and second apertured plate electrodes, and a potential bias supply connected to bias said field electrode to have the same polarity relative to each of said first and second electrodes the electrodes being arranged and a said bias being such as to provide a focusing field for beam ions passing through said first electrode, wherein for at least one direction normal to the beam direction the beam aperture of said first electrode is smaller than the beam aperture of said field electrode.

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