Slotted electrostatic shield modification for improved etch and cvd process uniformity

Abstract

A more uniform plasma process is implemented for treating a treatment object using an inductively coupled plasma source which produces an asymmetric plasma density pattern at the treatment surface using a slotted electrostatic shield having uniformly spaced-apart slots. The slotted electrostatic shield is modified in a way which compensates for the asymmetric plasma density pattern to provide a modified plasma density pattern at the treatment surface. A more uniform radial plasma process is described in which an electrostatic shield arrangement is configured to replace a given electrostatic shield in a way which provides for producing a modified radial variation characteristic across the treatment surface. The inductively coupled plasma source defines an axis of symmetry and the electrostatic shield arrangement is configured to include a shape that extends through a range of radii relative to the axis of symmetry.

What is claimed is: 
     
         1 . A method for producing a more uniform plasma and process in a processing chamber for treating a treatment surface of a treatment object within the chamber using an inductively coupled plasma source which produces an asymmetric plasma density pattern at the treatment surface using a slotted electrostatic shield having uniformly spaced-apart slots, said method comprising:
 modifying said slotted electrostatic shield to include a modified slot pattern which compensates for said asymmetric plasma density pattern to provide a modified plasma density pattern at said treatment surface.   
     
     
         2 . The method of  claim 1  wherein the asymmetric plasma density pattern includes a first region having an unmodified plasma density which is different than an average plasma density of the asymmetric plasma density pattern and wherein modifying said shield includes forming said modified slot pattern in a modified shield such that a first portion of the modified slot pattern adjacent to said first region includes a modified effective aperture that is different than an average effective aperture of the overall modified slot pattern, to create a modified plasma density in said first region that is closer to the average plasma density than the unmodified plasma density. 
     
     
         3 . The method of  claim 2  wherein the unmodified plasma density in the first region is greater than the average plasma density and the modified effective aperture of the modified slot pattern adjacent to the first region is less than the average effective aperture of the overall modified slot pattern such that the modified plasma density is less than the unmodified plasma density. 
     
     
         4 . The method of  claim 2  wherein the modified plasma density in the first region is less than the average plasma density and the modified effective aperture of the modified slot pattern adjacent to the first region is greater than the average effective aperture of the overall modified slot pattern such that the modified plasma density is greater than the unmodified plasma density. 
     
     
         5 . The method of  claim 4  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot width and density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of equal area and wherein modifying said shield includes arranging a slot density of said slots adjacent to said first region that is greater than the uniform slot density. 
     
     
         6 . The method of  claim 4  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of an unmodified, equal area and wherein modifying said shield includes locating at least one modified slot with a modified slot opening to define a modified area, adjacent to said first region, that is greater than said unmodified area. 
     
     
         7 . The method of  claim 4  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of an unmodified, equal area based on an equal unmodified length and an equal unmodified width and wherein modifying said shield includes locating at least one modified slot with a modified slot length and said equal unmodified width to define a modified area, adjacent to said first region, with the modified slot length being longer than the equal unmodified length. 
     
     
         8 . In a processing system including a processing chamber, an apparatus for producing a more uniform plasma and process in said processing chamber for treating an object therein having a treatment surface using an inductively coupled plasma source which produces an asymmetric plasma density pattern at the treatment surface using a given electrostatic shield, said arrangement comprising:
 a modified electrostatic shield arrangement including a modified slot pattern, for replacing said given electrostatic shield, such that the modified electrostatic shield arrangement compensates for said asymmetric plasma density pattern to provide a modified plasma density pattern at said treatment surface.   
     
     
         9 . The apparatus of  claim 8  wherein the asymmetric plasma density pattern includes a first region having an unmodified plasma density, which is different than an average plasma density of the asymmetric plasma density pattern, and wherein said modified slot pattern includes a modified effective aperture adjacent to said first region that is different than an average effective aperture of the overall modified slot pattern, to create a modified plasma density in said first region which is closer to the average plasma density than the unmodified plasma density. 
     
     
         10 . The apparatus of  claim 9  wherein the unmodified plasma density in the first region is greater than the average plasma density and the modified effective aperture of the modified slot pattern adjacent to the first region is less than the average effective aperture of the overall modified slot pattern such that the modified plasma density is less than the unmodified plasma density. 
     
     
         11 . The apparatus of  claim 9  wherein the modified plasma density in the first region is less than the average plasma density and the modified effective aperture of the modified slot pattern adjacent to the first region is greater than the average effective aperture of the overall modified slot pattern such that the modified plasma density is greater than the unmodified plasma density. 
     
     
         12 . The apparatus of  claim 11  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot width and density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of equal area and wherein said modified shield at least includes a slot density of said slots adjacent to said first region that is greater than the uniform slot density. 
     
     
         13 . The apparatus of  claim 11  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of an unmodified, equal area and wherein said modified shield includes a slot arrangement adjacent to said first region having at least one modified slot with a modified slot opening to define a modified area, adjacent to said first region, that is greater than said unmodified area. 
     
     
         14 . The apparatus of  claim 11  wherein said uniformly spaced-apart slots of said slotted electrostatic shield define a uniform slot density circumferentially around the slotted electrostatic shield with each slot defining a slot opening of an unmodified, equal area based on an equal unmodified length and an equal unmodified width and wherein modifying said shield includes locating at least one modified slot with a modified slot length and said equal unmodified width to define a modified area, adjacent to said first region, with the modified slot length being longer that the equal unmodified length. 
     
     
         15 . In a processing system including a processing chamber for plasma treatment of an object therein having a treatment surface, said processing chamber that is surrounded by a chamber sidewall, an apparatus comprising:
 an inductively coupled plasma source including an induction coil having one or more turns that surround the processing chamber sidewall such that the induction coil (i) defines a coil through-opening, (ii) is in a confronting, spaced apart relationship with the chamber sidewall, and (iii) defines a coil width; and   an electrostatic shield that is positioned between the induction coil and the processing chamber such that the electrostatic shield at least surrounds the processing chamber sidewall and extends through the induction coil through-opening, and said electrostatic shield defines a plurality of elongated slots each having an elongated length that extends through the induction coil through-opening to project outwardly beyond said coil width on each opposing side of the coil width and each slot having a width that varies along said elongated length.   
     
     
         16 . The apparatus of  claim 15  wherein the electrostatic shield includes an axis of symmetry and opposing major ends that are spaced apart along the axis of symmetry. 
     
     
         17 . The apparatus of  claim 15  wherein each slot includes a slot region that confronts the coil width of the induction coil with the slot region being shorter than the elongated length of each slot and each slot includes at least one width outside of the slot region that is different than any width of the slot within the slot region. 
     
     
         18 . The apparatus of  claim 17  wherein each slot includes at least one width outside of the slot region that is greater than any width of the slot within the slot region. 
     
     
         19 . The apparatus of  claim 18  wherein each slot includes opposing slot ends and a center position and each slot is widthwise symmetrical from each opposing slot end to the center position. 
     
     
         20 . The apparatus of  claim 17  wherein a slot region area for each slot that corresponds to said slot region is less than an area defined by each slot outside of the slot region. 
     
     
         21 . In a processing system including a processing chamber for plasma treatment of an object therein having a treatment surface, said processing chamber that is surrounded by a chamber sidewall, a method comprising:
 configuring an inductively coupled plasma source to include an induction coil having one or more turns that surround the processing chamber sidewall such that the induction coil (i) defines a coil through-opening, (ii) is in a confronting, spaced apart relationship with the chamber sidewall, and (iii) defines a coil width; and   positioning an electrostatic shield between the induction coil and the processing chamber such that the electrostatic shield at least surrounds the processing chamber sidewall and extends through the induction coil through-opening, and said electrostatic shield defines a plurality of elongated slots each having an elongated length that extends through the induction coil through-opening to project outwardly beyond said coil width on each opposing side of the coil width and each slot having a width that varies along said elongated length.   
     
     
         22 . The method of  claim 21  including forming the electrostatic shield to include an axis of symmetry and opposing major ends that are spaced apart along the axis of symmetry. 
     
     
         23 . The method of  claim 21  including forming each slot to include a slot region that confronts the coil width of the induction coil with the slot region being shorter than the elongated length of each slot and each slot is formed to include at least one width outside of the slot region that is different than any width of the slot within the slot region. 
     
     
         24 . The method of  claim 23  wherein each slot is formed to include at least one width outside of the slot region that is greater than any width of the slot within the slot region. 
     
     
         25 . The method of  claim 24  wherein each slot is formed to include opposing slot ends and a center position and each slot is widthwise symmetrical from each opposing slot end to the center position. 
     
     
         26 . The method of  claim 23  including defining a slot region area for each slot that corresponds to said slot region that is less than an area defined by each slot outside of the slot region.