Method and apparatus for extracting ions from an ion source for use in ion implantation
Thermal control is provided for an extraction electrode of an ion-beam producing system that prevents formation of deposits and unstable operation and enables use with ions produced from condensable vapors and with ion sources capable of cold and hot operation. Electrical heating of the extraction electrode is employed for extracting decaborane or octadecaborane ions. Active cooling during use with a hot ion source prevents electrode destruction, permitting the extraction electrode to be of heat-conductive and fluorine-resistant aluminum composition. The service lifetime of the system is enhanced by provisions for in-situ etch cleaning of the ion source and extraction electrode, using reactive halogen gases, and by having features that extend the service duration between cleanings, including accurate vapor flow control and accurate focusing of the ion beam optics. A remote plasma source delivers F or Cl ions to the de-energized ion source for the purpose of cleaning deposits in the ion source and the extraction electrode. These techniques enable long equipment uptime when running condensable feed gases such as sublimated vapors, and are particularly applicable for use with so-called cold ion sources and universal 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 - 35 . (canceled)
36 . A heated cathode assembly for use in an ion source, the heated cathode assembly comprising:
a suppression cathode;
a ground cathode disposed adjacent to said suppression cathode and electrically insulated therefrom forming an extraction cathode; and
a heater for heating said extraction cathode.
37 . The heated cathode assembly as recited in claim 36 , wherein at least one of said suppression cathode and said ground cathode is formed from a fluorine resistant material.
38 . The heated cathode assembly as recited in claim 37 , wherein said fluorine resistant material is aluminum.
39 . The heated cathode assembly as recited in claim 37 , wherein said fluorine resistant material is a refractory material.
40 . The heated cathode assembly as recited in claim 39 , wherein said refractory material is molybdenum
41 . The heated cathode assembly as recited in claim 36 , wherein said heater is disposed in contact with said ground cathode.
42 . The heated cathode assembly as recited in claim 36 , wherein said assembly is configured so that said suppression cathode is heated by radiant heat energy.
43 . The heated cathode assembly as recited in claim 36 , further including a temperature sensing device for sensing the temperature of the extraction cathode.
44 . The heated cathode assembly as recited in claim 43 , wherein said temperature sensing device is a thermocouple.
45 . The heated cathode assembly as recited in claim 44 , further including a temperature controller for controlling the temperature of the cathode assembly.