Vaporiser for generating feed gas for an arc chamber

Abstract

A vaporiser generating feed gas for the arc chamber of an ion source has a crucible which is heated to a temperature at which material in the crucible sublimes to produce a vapor for use as the feed gas. In addition to the heating element for heating the crucible, there is a cooling element in the form of a cooling duct extending along the length of the crucible for receiving the cooling fluid. Forced cooling of the crucible when the heating element is switched off enables the crucible to be cooled more quickly so that the supply of a feed gas can be terminated sooner. This is important if an ion source is being switched from one feed gas to another. Also, the crucible may be forced cooled simultaneously while energising the heating element to enable the crucible to be accurately controlled at a lower operating temperature if desired.

1 . A vaporiser for generating feed gas for an arc chamber, the vaporiser comprising an elongate crucible arranged to contain a source of material, a heater to heat the source to generate the feed gas, and a cooling duct arranged to extend along substantially the entire length of the crucible to receive cooling fluid and cool the source of material.  
     
     
         2 . A vaporiser according to    claim 1   , wherein the cooling duct is wound around the crucible.  
     
     
         3 . A vaporiser according to    claim 2   , wherein the cooling duct is wound in a helical configuration.  
     
     
         4 . A vaporiser as claimed in    claim 3   , wherein the heater has a heating element helically wound around the crucible with the same helical pitch as the cooling duct but axially offset.  
     
     
         5 . Semi conductor implant apparatus having an ion source comprising an arc chamber and a vaporiser connected to supply a feed gas to the arc chamber, the vaporiser comprising an elongate crucible arranged to contain a source of material, a heater to heat the source to generate the feed gas, and a cooling duct arranged to extend along substantially the entire length of the crucible to receive cooling fluid and cool the source of material.  
     
     
         6 . A method of controlling the generation of a feed gas for the arc chamber of an ion source, comprising the steps of 
 a) providing in a crucible a quantity of non gaseous material which can be heated to generate a desired feed gas for the arc chamber,    b) heating the crucible to a temperature at which said desired feed gas is generated and supplying the generated feed gas to the arc chamber, and    c) stopping the supply of said desired feed gas by halting said heating and applying forced cooling to said crucible.    
     
     
         7 . A method of controlling the temperature of a crucible for generating, from non-gaseous material contained in the crucible, a feed gas for the arc chamber of an ion source, the method comprising the steps of 
 a) applying a heating current to a heating element to heat the crucible so as to generate said feed gas, and    b) simultaneously applying an amount of forced cooling to the crucible so that the crucible is heated by said heating current to a desired temperature.