Method and apparatus for etching a workpiece

Abstract

An XeF 2 source includes an XeF 2 source chamber having a tray or ampoule for XeF 2 crystals, a reservoir coupled to the XeF 2 source chamber via a valve, a flow controller fed by the reservoir and a valve between the reservoir and the flow controller. Pressure sources are provided respectively to maintain the reservoir and the source chamber at the sublimation pressure of XeF 2 . The arrangement allows for a steady supply of XeF 2 to an etching chamber.

1 . A method of etching a workpiece using XeF 2 , comprising allowing solid XeF 2  to subliminate into its gaseous state into a reservoir of sufficient volume to provide gas at a pre-determined flow rate for a pre-determined etch period, supplying the gas at the desired flow rate to an etching chamber containing the workpiece and etching the workpiece.  
     
     
         2 . A method as claimed in  claim 1  wherein XeF 2  gas is mixed with an inert carrier gas prior to its introduction into the etch chamber.  
     
     
         3 . A method as claimed in  claim 1  or  claim 2  wherein the XeF 2  source continues to subliminate going outward flow from the reservoir.  
     
     
         4 . A method as claimed in any one of  claims 1  to  3  including recharging the reservoir between etches.  
     
     
         5 . A method as claimed in any one of the preceding claims wherein the flow rate is controlled on a pressure basis.  
     
     
         6 . Apparatus for etching a workpiece comprising an etch chamber, a XeF 2  source, a reservoir, valve means for connecting the source to the reservoir to allow sublimination of the source into XeF 2  gas, a flow control of the feeding of the etch chamber and valve means for connecting the reservoir to the flow controller.  
     
     
         7 . Apparatus as claimed in  claim 6  further including pressure control means for maintaining the reservoir at approximately sublimination pressure of XeF 2  when there is no outward flow from the reservoir.  
     
     
         8 . Apparatus as claimed in  claim 6  or  claim 7  further comprising means for mixing the XeF 2  gas with an inert carrier gas prior to its introduction into the process.  
     
     
         9 . Apparatus as claimed in any one  claim 6  to  8  when the flow controller is a pressure based flow controller.