Method and apparatus for reducing charge density on a dielectric coated substrate after exposure to large area electron beam

Abstract

Embodiments in accordance with the present invention relate to a number of techniques, which may be applied alone or in combination, to reduce charge damage of substrates exposed to electron beam radiation. In one embodiment, charge damage is reduced by establishing a robust electrical connection between the exposed substrate and ground. In another embodiment, charge damage is reduced by modifying the sequence of steps for activating and deactivating the electron beam source to reduce the accumulation of charge on the substrate. In still another embodiment, a plasma is struck in the chamber containing the e-beam treated substrate, thereby removing accumulated charge from the substrate. In a further embodiment of the present invention, the voltage of the anode of the e-beam source is reduced in magnitude to account for differences in electron conversion efficiency exhibited by different cathode materials.

1 . A method of irradiating a substrate with an electron beam, the method comprising: 
 disposing a substrate within a chamber proximate to a source anode of an electron beam source;    placing the substrate into electrical contact with ground through a supporting pin; and    exposing the substrate to radiation from the electron beam.    
   
   
       2 . The method of  claim 1  wherein the supporting pin is provided in threaded engagement with a grounded chamber body.  
   
   
       3 . The method of  claim 1  wherein the supporting pin is provided in physical contact with a metal gasket of the chamber.  
   
   
       4 . The method of  claim 1  wherein: 
 exposing the surface of the substrate to electron beam radiation comprises delaying application of a bias voltage to the source anode until a process gas has flowed into the chamber for a predetermined time; and    the method further comprises delaying regulation of a chamber throttle valve to adjust a current of the electron beam until a high voltage has been applied to a source cathode for a second predetermined time.    
   
   
       5 . The method of  claim 1  further comprising introducing a plasma into the chamber following exposure of the substrate to the electron beam.  
   
   
       6 . The method of  claim 5  wherein the plasma is intentionally struck in the chamber.  
   
   
       7 . The method of  claim 5  wherein the plasma is residual from a delay between deactivation of the high voltage to the source cathode, and deactivation of the bias voltage to the source anode, while processing gas is flowed into the chamber.  
   
   
       8 . The method of  claim 1  wherein exposing the substrate to radiation from the electron beam comprises applying a voltage difference of about 3.05 KeV or less between the source anode comprising aluminum and a source cathode comprising aluminum.  
   
   
       9 . The method of  claim 1  wherein exposing the substrate to radiation from the electron beam comprises applying a voltage difference of about 2.95 KeV or less between the source anode comprising aluminum and a source cathode comprising aluminum.  
   
   
       10 . The method of  claim 8  wherein a high voltage of about +3 KeV is applied to the source cathode, and a bias voltage of about −50 V is applied to the source anode.  
   
   
       11 . The method of  claim 8  wherein a high voltage of about −3 KeV is applied to the source cathode, and a bias voltage of about −50 V is applied to the source anode.  
   
   
       12 . A method of irradiating a substrate with an electron beam, the method comprising: 
 disposing a substrate within a chamber proximate to an anode of an electron beam source;    flowing a processing gas into the chamber for a predetermined time;    applying a bias voltage to the anode after the predetermined time; and    exposing the substrate to an electron beam emitted from a cathode of the electron beam source, by applying a high voltage to the cathode, and delaying regulation of a chamber throttle valve to adjust a current of the electron beam until after the high voltage has been applied to the cathode for a second predetermined time.    
   
   
       13 . The method of  claim 12  further comprising introducing a plasma into the chamber following exposure of the substrate to the electron beam.  
   
   
       14 . The method of  claim 13  wherein the plasma is intentionally struck in the chamber.  
   
   
       15 . The method of  claim 13  wherein the plasma is residual from a delay between deactivation of the high voltage to the cathode, and deactivation of the bias voltage to the anode, while the processing gas is continued to be flowed into the chamber.  
   
   
       16 . The method of  claim 12  wherein exposing the substrate to radiation from the electron beam comprises applying a voltage difference of about 3.05 KeV or less between the anode comprising aluminum and the cathode comprising aluminum.  
   
   
       17 . The method of  claim 12  wherein exposing the substrate to radiation from the electron beam comprises applying a voltage difference of about 2.95 KeV or less between the anode comprising aluminum and the cathode comprising aluminum.  
   
   
       18 . The method of  claim 16  wherein a high voltage of about +3 KeV is applied to the cathode, and a bias voltage of about −50 V is applied to the anode.  
   
   
       19 . The method of  claim 16  wherein the high voltage of about −3 KeV is applied to the cathode, and the bias voltage of about −50 V is applied to the anode.  
   
   
       20 . A method of treating a substrate with an electron beam, the method comprising: 
 disposing a substrate within a chamber proximate to an anode of an electron beam source;    applying a bias voltage to the anode of the electron beam source;    exposing the substrate to an electron beam emitted from a cathode of the electron beam source; and    introducing a plasma into the chamber following exposure of the substrate to the electron beam.    
   
   
       21 . The method of  claim 20  wherein the plasma is intentionally struck in the chamber.  
   
   
       22 . The method of  claim 20  wherein the plasma is a low density plasma residual from a delay between deactivation of a high voltage to the cathode of the electron beam source, and deactivation of the bias voltage to the anode of the electron beam source, while a processing gas is continued to be flowed into the chamber.  
   
   
       23 . A method of irradiating a substrate with an electron beam, the method comprising: 
 disposing a substrate within a chamber proximate to an aluminum anode of an electron beam source;    applying a bias voltage to the aluminum anode; and    applying a high voltage to an aluminum cathode of the electron beam source, such that a voltage difference between the aluminum anode and the aluminum cathode is between about 1-30 keV.    
   
   
       24 . The method of  claim 23  wherein the bias voltage of about −50 eV is applied to the aluminum anode, and the high voltage of about +3 KeV is applied to the aluminum cathode.  
   
   
       25 . The method of  claim 23  wherein the bias voltage of about −50 V is applied to the aluminum anode, and the high voltage of about −3 KeV is applied to the aluminum cathode.  
   
   
       26 . The method of  claim 23  wherein the bias voltage is less than 125 V.  
   
   
       27 . An apparatus for treating a substrate with electron beam radiation, the apparatus comprising: 
 a processing chamber enclosing a substrate support;    an electron beam source comprising an anode proximate to the substrate support and a cathode distal from the substrate support; and    a ground pin configured to be in electrical communication with an underside of a supported substrate, and in electrical communication with ground.    
   
   
       28 . The apparatus of  claim 27  wherein the ground pin is in physical contact with a chamber ground.  
   
   
       29 . The apparatus of  claim 27  wherein the substrate support is grounded, and the ground pin is in threaded engagement with the substrate support.  
   
   
       30 . The apparatus of  claim 27  wherein the ground pin is in electrical communication with a grounded metal gasket located on an exterior of the chamber.