# US 6,723,998 B2 · Faraday system for ion implanters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,723,998 B2 - Document ID: US6723998B2 - Status: Granted - Kind: B2 - Application number: 09/950,940 - Filed: 2001-09-12 - Published: 2002-06-13 - Granted: 2004-04-20 - Earliest claimed: 2000-09-15 - Assignees: Varian Semiconductor Equipment Associates, Inc. - Inventors: Jack Bisson; Zhiyong Zhao; George Gammel; Daniel Alvarado; Craig Walker - Web page: https://patentgrep.com/patent/US6723998B2 ## CPC - H01J 37/244: Detectors; Associated components or circuits therefor - H01J 2237/24405: Faraday cages - H01J 2237/31703: Dosimetry - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A Faraday system for measuring ion beam current in an ion implanter or other ion beam treatment system includes a Faraday cup body defining a chamber which has an entrance aperture for receiving an ion beam, a suppression electrode positioned in proximity to the entrance aperture to produce electric fields for inhibiting escape of electrons from the chamber, and a magnet assembly positioned to produce magnetic fields for inhibiting escape of electrons from the chamber. The chamber may have a relatively small ratio of chamber depth to entrance aperture width. ## Claims ### Claim 1 A Faraday system for use in an ion beam treatment system, comprising: a Faraday cup body defining a chamber, said chamber having a defined depth and an entrance aperture for receiving an ion beam wherein an aspect ratio of said chamber depth and said entrance aperture is less than approximately 1.0; a suppression electrode positioned in proximity to the entrance aperture to produce electric fields for inhibiting escape of electrons from said chamber; and a magnet assembly positioned to produce magnetic fields for inhibiting escape of electrons from said chamber. ### Claim 2 (depends on 1) A Faraday system as defined in claim 1 wherein said magnet assembly comprises first and second magnets disposed on opposite sides of said Faraday cup body. ### Claim 3 (depends on 1) A Faraday system as defined in claim 1 wherein said suppression electrode comprises a suppression ring disposed around said entrance aperture. ### Claim 4 (depends on 3) A Faraday system as defined in claim 3 further comprising a suppression power supply for biasing said suppression electrode at a suppression voltage relative to said Faraday cup body. ### Claim 5 (depends on 3) A Faraday system as defined in claim 3 wherein said suppression ring has an aperture that is larger than said entrance aperture. ### Claim 6 (depends on 3) A Faraday system as defined in claim 3 wherein said suppression ring has an aperture and wherein said suppression ring is tapered toward the aperture in said suppression ring. ### Claim 7 (depends on 1) A Faraday system as defined in claim 1 wherein all or part of an interior surface of said Faraday cup body is coated with a material that exhibits relatively low secondary electron emission. ### Claim 8 (depends on 1) A Faraday system as defined in claim 1 wherein all or part of a interior surface of said Faraday cup body has a carbon coating. ### Claim 9 (depends on 1) A Faraday system as defined in claim 1 wherein said Faraday cup body is fabricated of graphite. ### Claim 10 (depends on 1) A Faraday system as defined in claim 1 wherein said Faraday cup body includes a plurality of holes facing said entrance aperture. ### Claim 11 (depends on 1) A Faraday system as defined in claim 1 further comprising a housing enclosing said Faraday cup body, said housing including a front plate having an opening which defines the entrance aperture of said chamber. ### Claim 12 A Faraday system for use in an ion beam treatment system, comprising: a Faraday cup body defining a chamber having an open side and a defined chamber depth; and a plate positioned in front of said open side, said plate having an opening that defines an entrance aperture of said chamber, wherein an aspect ratio of said chamber depth to entrance aperture width is less than approximately 1.0. ### Claim 13 A Faraday system for use in an ion beam treatment system, comprising: a Faraday cup body defining a chamber having an open side and a defined chamber depth; and a plate positioned in front of said open side, said plate having an opening that defines an entrance aperture for said chamber so that an aspect ratio of said chamber depth and said entrance aperture is less than approximately 1.0, wherein at least a portion of an inside surface of said Faraday cup body includes a plurality of holes facing said chamber. ### Claim 14 (depends on 13) A Faraday system as defined in claim 13 wherein said plurality of holes comprises a pattern of holes on an end wall of said Faraday cup body facing said entrance aperture. ### Claim 15 A method for measuring ion current in an ion beam treatment system, comprising steps of: providing a Faraday cup body which defines a chamber, said chamber having an entrance aperture and a defined chamber depth for receiving an ion beam wherein an aspect ratio of said chamber depth and said entrance aperture is less than approximately 1.0; positioning a suppression electrode in proximity to the entrance aperture to produce electric fields for inhibiting escape of electrons from said chamber; and positioning a magnet assembly to produce magnetic fields for inhibiting escape of electrons from said chamber. ### Claim 16 A Faraday system for use in an ion beam treatment system, comprising: a Faraday cup body defining a chamber, said chamber having an entrance aperture for receiving an ion beam; a suppression electrode positioned in proximity to the entrance aperture to produce electric fields for inhibiting escape of electrons from said chamber wherein said suppression electrode comprises a suppression ring disposed around said entrance aperture and wherein said suppression electrode has an aperture and said suppression ring is tapered toward the aperture in said suppression ring; and a magnet assembly positioned to produce magnetic fields for inhibiting escape of electrons from said chamber. ### Claim 17 A method for measuring ion current in an ion beam treatment system, comprising steps of: providing a Faraday cup body which defines a chamber, said chamber having an entrance aperture for receiving an ion beam; positioning a suppression electrode in proximity to the entrance aperture to produce electric fields for inhibiting escape of electrons from said chamber wherein said suppression electrode comprises a suppression ring disposed around said entrance aperture and wherein said suppression ring has an aperture and said suppression ring is tapered toward the aperture in said suppression ring; and positioning a magnet assembly to produce magnetic fields for inhibiting escape of electrons from said chamber.