Method and apparatus for extending equipment uptime in ion implantation
The service lifetime of an ion source is enhanced or prolonged by the source having provisions for in-situ etch cleaning of the ion source and of an extraction electrode, using reactive halogen gases, and by having features that extend the service duration between cleanings. The latter include accurate vapor flow control, accurate focusing of the ion beam optics, and thermal control of the extraction electrode that prevents formation of deposits or prevents electrode destruction. An apparatus comprised of an ion source for generating dopant ions for semiconductor wafer processing is coupled to a remote plasma source which delivers F or Cl ions to the first ion source for the purpose of cleaning deposits in the first ion source and the extraction electrode. These methods and apparatus enable long equipment uptime when running condensable feed gases such as sublimated vapor sources, and are particularly applicable for use with so-called cold ion sources. Methods and apparatus are described which enable long equipment uptime when decaborane and octadecaborane are used as feed materials, as well as when vaporized elemental arsenic and phosphorus are used, and which serve to enhance beam stability during ion implantation.
1 . A system for generating an ion beam ( 475 or 240 ) comprising an ion source ( 400 or 10 ) in combination with an extraction electrode ( 405 or 220 ) and a reactive gas cleaning system ( 445 , 430 ),
the ion source comprising an ionization chamber ( 500 ) connected to a high voltage power supply and having an inlet ( 441 , 440 or 435 ) for gaseous or vaporized feed materials, and energizeable ionizing system for ionizing the feed material within the ionization chamber and an extraction aperture ( 304 ) that communicates with a vacuum housing ( 410 or 209 ), the vacuum housing evacuated by a vacuum pumping system ( 420 ),
the extraction electrode ( 405 or 220 ) disposed in the vacuum housing outside of the ionization chamber, aligned with the extraction aperture ( 504 ) of the ionization chamber and adapted to be maintained at a voltage below that of the ionization chamber to extract ions through the aperture from within the ionization chamber,
and the reactive gas cleaning system ( 455 , 430 ) operable when the ionization chamber and ionizing system are de-energized to provide a flow of reactive gas through the ionization chamber ( 500 ) and through the ion extraction aperture ( 504 ) to react with and remove deposits on at least some of the surfaces of the ion generating system.
2 - 69 . (canceled)