Degas chamber particle shield

Abstract

A substrate processing chamber of the type adapted for processing a substrate having edges and a surface at a reduced pressure and elevated temperature relative to ambient. Typically, a combination of the elevated temperature and the reduced pressure tends to produce spallation of the substrate near the edges, which spallation produces chips that are redeposited across the surface of the substrate. Such chips inhibit proper operation of subsequent processing of the substrate. The improvement is a shield disposed in proximity to the surface of the substrate, but not touching the substrate. The shield forms a perimeter barrier at a circumference of the substrate that is interior to the edges of the substrate where the spallation occurs, and the shield prohibits the chips from redepositing across portions of the surface of the substrate that are interior to the perimeter barrier.

What is claimed is:  
     
         1 . In a substrate processing chamber of the type adapted for processing a substrate having edges and a surface at a reduced pressure and elevated temperature relative to ambient, where a combination of the elevated temperature and the reduced pressure tends to produce spallation of the substrate near the edges, which spallation produces chips that are redeposited across the surface of the substrate, and which chips inhibit proper operation of subsequent processing of the substrate, the improvement comprising a shield disposed in proximity to the surface of the substrate, and not touching the substrate, the shield forming a perimeter barrier at a circumference of the substrate that is interior to the edges of the substrate where the spallation occurs, the shield prohibiting the chips from redepositing across portions of the surface of the substrate that are interior to the perimeter barrier.  
     
     
         2 . The processing chamber of  claim 1 , wherein the processing chamber is a degas chamber.  
     
     
         3 . The processing chamber of  claim 1 , wherein the shield is disposed at a distance of between about zero millimeters and about five millimeters from the substrate.  
     
     
         4 . The processing chamber of  claim 1 , wherein the shield is formed of at least one of stainless steel, titanium, molybdenum, and quartz.  
     
     
         5 . The processing chamber of  claim 1 , wherein the shield has a thickness of between about one-half millimeter and about one and one-half millimeters.  
     
     
         6 . The processing chamber of  claim 1 , wherein the shield is held at an absolute bias voltage relative to the substrate of between about zero volts and about five thousand volts.  
     
     
         7 . The processing chamber of  claim 1 , wherein the shield is electrically insulated from the processing chamber at a location where the shield is electrically attached to the processing chamber.  
     
     
         8 . The processing chamber of  claim 1 , wherein the shield is adjustable as to the circumference of the substrate.  
     
     
         9 . The processing chamber of  claim 1 , wherein the shield is adjustable as to the proximity to the substrate.  
     
     
         10 . The processing chamber of  claim 1 , wherein the substrate is a semiconducting substrate.  
     
     
         11 . The processing chamber of  claim 1 , wherein the substrate is formed of at least one of silicon, germanium, and a III-V compound such as gallium arsenide.  
     
     
         12 . The processing chamber of  claim 1 , wherein the reduced pressure is less than about one millitorr.  
     
     
         13 . The processing chamber of  claim 1 , wherein the elevated temperature is at least about two hundred centigrade.  
     
     
         14 . The processing chamber of  claim 1 , wherein the shield is formed in a cylinder.  
     
     
         15 . The processing chamber of  claim 1 , wherein the shield is formed of a solid sheet.  
     
     
         16 . The processing chamber of  claim 1 , wherein the shield is formed of a mesh sheet.  
     
     
         17 . The processing chamber of  claim 1 , wherein the shield is formed of a ceramic material having a vitreous surface.  
     
     
         18 . The processing chamber of  claim 1 , wherein the shield is formed of a material having a thermal expansion that is less than that of the substrate.  
     
     
         19 . In a substrate processing chamber of the type adapted for processing a substrate having edges and a surface at a reduced pressure and elevated temperature relative to ambient, where a combination of the elevated temperature and the reduced pressure tends to produce spallation of the substrate near the edges, which spallation produces chips that are redeposited across the surface of the substrate, and which chips inhibit proper operation of subsequent processing of the substrate, the improvement comprising a shield disposed in proximity to the surface of the substrate, and not touching the substrate, the shield forming a perimeter barrier at a circumference of the substrate that is interior to the edges of the substrate where the spallation occurs, the shield disposed at a distance of between about zero millimeters and about five millimeters from the substrate, the shield formed of at least one of stainless steel, titanium, molybdenum, and quartz, and the shield prohibiting the chips from redepositing across portions of the surface of the substrate that are interior to the perimeter barrier.  
     
     
         20 . In a substrate processing chamber of the type adapted for processing a substrate having edges and a surface at a reduced pressure and elevated temperature relative to ambient, where a combination of the elevated temperature and the reduced pressure tends to produce spallation of the substrate near the edges, which spallation produces chips that are redeposited across the surface of the substrate, and which chips inhibit proper operation of subsequent processing of the substrate, the improvement comprising a shield disposed in proximity to the surface of the substrate, and not touching the substrate, the shield forming a perimeter barrier at a circumference of the substrate that is interior to the edges of the substrate where the spallation occurs, the shield held at an absolute bias voltage relative to the substrate of between about zero volts and about five thousand volts, the shield electrically insulated from the processing chamber at a location where the shield is electrically attached to the processing chamber, and the shield prohibiting the chips from redepositing across portions of the surface of the substrate that are interior to the perimeter barrier.