In situ surface contaminant removal for ion implanting

Abstract

Methods and apparatus that introduce, within the ion implant chamber or an isolated chamber in communication therewith, the capability to remove contaminants and oxide surface layers on a wafer surface prior to ion implantation, are disclosed. The mechanisms for removal of contaminants include conducting: a low energy plasma etch, heating the wafer and application of ultraviolet illumination, either in combination or individually. As a result, implantation can occur immediately after the cleaning/preparation process without the contamination potential of exposure of the wafer to an external environment. The preparation allows for the removal of surface contaminants, such as water vapor, organic materials and surface oxides.

1 . An ion implanting apparatus comprising: 
 an implant chamber;    means for generating ions for implanting a wafer in the chamber; and    means for removing contaminants from a surface of the wafer in situ within the implant chamber.    
   
   
       2 . The apparatus of  claim 1 , wherein the contaminant removing means includes means for exposing the surface to ultraviolet (UV) illumination.  
   
   
       3 . The apparatus of  claim 2 , wherein the exposing means is mounted externally of the implant chamber and includes a UV illumination device to transmit UV light through a window of the implant chamber.  
   
   
       4 . The apparatus of  claim 2 , wherein the exposing means includes one of an internally-mounted UV illumination device and means for producing an ion plasma configured to emit UV light.  
   
   
       5 . The apparatus of  claim 4 , wherein the producing means includes one of: 
 a) a radio frequency (RF) source configured to resonate radio frequency currents in a radio frequency antenna to pass into the implant chamber and excite and ionize a process gas to generate plasma within the implant chamber; and    b) a direct current (DC) pulse generator for generating a pulsed DC voltage in a wafer cathode to excite and ionize the process gas to generate plasma within the implant chamber.    
   
   
       6 . The apparatus of  claim 2 , wherein the exposing means further includes means for exposing the wafer to a vacuum of better than 1×10 −5  Torr.  
   
   
       7 . The apparatus of  claim 1 , wherein the contaminant removing means includes a heater for heating the wafer.  
   
   
       8 . The apparatus of  claim 7 , further comprising a temperature controller for the heater.  
   
   
       9 . The apparatus of  claim 7 , further comprising a gas portal for introducing a gas between a platen that holds the wafer and the wafer to improve heat transfer.  
   
   
       10 . The apparatus of  claim 1 , wherein the contaminant removing means includes means for conducting a low energy plasma etch.  
   
   
       11 . The apparatus of  claim 10 , wherein the low energy plasma etch uses no greater than −1000 V of wafer bias.  
   
   
       12 . The apparatus of  claim 10 , wherein the low energy plasma etch includes using one of: 
 BF 3 , NF 3  and F 2  as a plasma for a subsequent BF 3  plasma implantation.    
   
   
       13 . The apparatus of  claim 10 , wherein the ion generating means includes at least one of: 
 a) a radio frequency (RF) source configured to resonate radio frequency currents in a radio frequency antenna to pass into the implant chamber and excite and ionize a process gas to generate plasma within the implant chamber; and    b) a direct current (DC) pulse generator for generating a pulsed DC voltage in a wafer cathode to excite and ionize the process gas to generate plasma within the implant chamber.    
   
   
       14 . A method of removing contaminants from a surface of a wafer in situ of an ion implant apparatus, the method comprising: 
 placing the wafer in an isolated chamber that is in communication with an implant chamber; and    removing contaminants from a surface of the wafer in situ within one of the isolated chamber and the implant chamber.    
   
   
       15 . The method of  claim 14 , wherein the contaminant removing step includes exposing the surface to ultraviolet (UV) illumination.  
   
   
       16 . The method of  claim 15 , wherein the exposing step includes exposing the surface to UV light through a window of one of the isolated chamber and the implant chamber.  
   
   
       17 . The method of  claim 15 , wherein the exposing step includes exposing the surface to one of an internally-mounted UV illumination device and means for producing a UV light emitting plasma.  
   
   
       18 . The method of  claim 17 , wherein the producing means includes one of: 
 a) a radio frequency (RF) source configured to resonate radio frequency currents in a radio frequency antenna to pass into the implant chamber and excite and ionize a process gas to generate plasma within the implant chamber; and    b) a direct current (DC) pulse generator for generating a pulsed DC voltage in a wafer cathode to excite and ionize the process gas to generate plasma within the implant chamber.    
   
   
       19 . The method of  claim 15 , wherein the exposing step further includes exposing the wafer to a vacuum of better than 1×10 −5  Torr.  
   
   
       20 . The method of  claim 14 , wherein the contaminant removing step includes heating the wafer.  
   
   
       21 . The method of  claim 20 , wherein the heating step includes heating a platen that holds the wafer in the implant chamber, and further comprising controlling a temperature of the heating.  
   
   
       22 . The method of  claim 20 , further comprising introducing a gas between the platen and the wafer to improve heat transfer.  
   
   
       23 . The method of  claim 14 , wherein the contaminant removing step includes controlling a radio frequency (RF) source of the implant chamber to conduct a low energy plasma etch.  
   
   
       24 . The method of  claim 23 , wherein the low energy plasma etch uses no greater than −1000 V wafer bias.  
   
   
       25 . The method of  claim 23 , wherein the low energy plasma etch includes using one of: BF 3 , NF 3  or F 2  as a plasma for a subsequent BF 3  plasma implantation.  
   
   
       26 . A method of removing contaminants from a surface of a wafer, the method comprising: 
 placing the wafer in an isolated chamber that is in communication with an implant chamber; and    removing contaminants from a surface of the wafer in situ within one of the isolated chamber and the implant chamber by conducting at least one of:    exposing the surface to ultraviolet (UV) illumination;    heating a platen that holds the wafer in the implant chamber; and    controlling a radio frequency (RF) source of the implant chamber to conduct a low energy plasma etch.    
   
   
       27 . The method of  claim 26 , wherein the exposing step includes exposing the surface to UV light through a window of one of the isolated chamber and the process chamber.  
   
   
       28 . The method of  claim 26 , wherein the exposing step includes exposing the surface to one of an internally-mounted UV illumination device and means for producing UV light emitting plasma.  
   
   
       29 . The method of  claim 28 , wherein the producing means includes one of: 
 a) a radio frequency (RF) source configured to resonate radio frequency currents in a radio frequency antenna to pass into the implant chamber and excite and ionize a process gas to generate plasma within the implant chamber; and    b) a direct current (DC) pulse generator for generating a pulsed DC voltage in a wafer cathode to excite and ionize the process gas to generate plasma within the implant chamber.    
   
   
       30 . The method of  claim 26 , wherein the heating step further includes controlling a temperature of the heating.  
   
   
       31 . The method of  claim 26 , wherein the heating step further includes introducing a gas between the platen and the wafer to improve heat transfer.  
   
   
       32 . The method of  claim 26 , wherein the controlling step includes using no greater than 0.1 V.  
   
   
       33 . The method of  claim 26 , wherein the controlling step includes using one of: BF 3 , NF 3  or F 2  as a source gas for a subsequent BF 3  plasma implantation.