Apparatus and methods for improving treatment uniformity in a plasma process

Abstract

Apparatus and methods for improving treatment uniformity in a plasma process. The sacrificial body, which is extends about an outer peripheral edge of the workpiece during plasma processing, is composed of a plasma-removable material. The sacrificial body may include multiple sections that are arranged to define a circular geometrical shape. The sacrificial body functions to increase the effective outer diameter of the workpiece, which operates to alleviate detrimental edge effects intrinsic to plasma processing by effectively reducing the etch rate near the outer peripheral edge of the workpiece.

1 . An apparatus for use in plasma processing a workpiece having an outer peripheral edge, the apparatus comprising:
 a sacrificial body composed of a plasma-removable material, said sacrificial body adapted to be arranged about the outer peripheral edge of the workpiece so that an outer diameter of the workpiece is effectively increased.   
   
   
       2 . The apparatus of  claim 1  wherein said sacrificial body includes a plurality of sections arranged to have an annular geometrical shape when placed in a juxtaposed relationship, said plurality of sections configured to be arranged concentrically with the workpiece. 
   
   
       3 . The apparatus of  claim 1  wherein said sacrificial body is composed of an organic polymer. 
   
   
       4 . The apparatus of  claim 3  wherein said organic polymer is polyetheretherketone (PEEK), polyimide, or polyamide. 
   
   
       5 . The apparatus of  claim 1  wherein said sacrificial body is composed of a material similar in composition to a material constituting a portion of the workpiece exposed to the plasma. 
   
   
       6 . The apparatus of  claim 1  wherein said sacrificial body has an annular geometrical shape and an inner diameter approximately equal to an outer diameter of the outer peripheral edge of the workpiece. 
   
   
       7 . An apparatus for plasma processing a workpiece having an outer peripheral edge, a first surface, and a second surface connected by the outer peripheral edge, the apparatus comprising:
 a vacuum enclosure configured to contain a plasma, said vacuum enclosure including a support pedestal adapted to contact and support the second surface of the workpiece when the first surface of the workpiece is exposed to the plasma; and   a sacrificial body composed of a plasma-removable material, said sacrificial body extending about the outer peripheral edge of the workpiece supported on said pedestal so that an outer diameter of the workpiece is effectively increased.   
   
   
       8 . The apparatus of  claim 7  wherein said sacrificial body includes a plurality of sections arranged to have an annular geometrical shape when placed in a juxtaposed relationship, said plurality of sections configured to be arranged concentrically with the workpiece. 
   
   
       9 . The apparatus of  claim 8  further comprising:
 a wafer lift mechanism disposed inside said vacuum enclosure, said wafer lift mechanism including a wafer fixture movable between a first position in which said wafer fixture holds the workpiece in a non-contacting relationship with said support pedestal and a second position in which said wafer fixture places the second surface of the workpiece in a contacting relationship with said support pedestal, and said first section of said sacrificial body is carried by said wafer fixture.   
   
   
       10 . The apparatus of  claim 9  wherein said second section is mounted adjacent to said support pedestal, and said second section is stationary when said wafer fixture is moved between the first and second positions. 
   
   
       11 . The apparatus of  claim 7  wherein said sacrificial body is composed of an organic polymer. 
   
   
       12 . The apparatus of  claim 11  wherein said organic polymer is polyetheretherketone (PEEK), polyimide, or polyamide. 
   
   
       13 . The apparatus of  claim 7  wherein said sacrificial body is composed of a material similar in composition to a material constituting a portion of the workpiece exposed to the plasma. 
   
   
       14 . The apparatus of  claim 7  wherein said sacrificial body has an annular geometrical shape and an inner diameter approximately equal to an outer diameter of the outer peripheral edge of the workpiece. 
   
   
       15 . A method for plasma etching a workpiece having a first surface, a second surface, and an outer peripheral edge connecting the first and second surfaces, the method comprising:
 arranging a sacrificial body composed of a plasma-removable material about the outer peripheral edge of the workpiece;   exposing the first surface of the workpiece and the sacrificial body to a plasma; and   shifting a maximum etch rate from a location on the first surface of the workpiece to a different location on the sacrificial body.   
   
   
       16 . The method of  claim 15  further comprising:
 supporting the first surface of the workpiece on a support pedestal positioned inside a vacuum enclosure confining the plasma during the etching process.   
   
   
       17 . The method of  claim 15  wherein the sacrificial body is divided into a plurality of sections that, when aligned, define an annular geometrical shape, and further comprising:
 temporarily supporting the workpiece on a wafer lift mechanism disposed inside the vacuum enclosure;   moving the wafer lift mechanism to transfer the workpiece from the wafer lift mechanism to the support pedestal; and   when the workpiece is transferred, aligning at least one of the sections of the sacrificial body with at least another of the sections of the sacrificial body to define a substantially continuous annular geometrical shape.   
   
   
       18 . The method of  claim 17  further comprising:
 supporting the workpiece on the support pedestal while the first surface of the workpiece is etched.   
   
   
       19 . The method of  claim 15  further comprising:
 eroding the material of the sacrificial body with the exposure to the plasma; and   replacing the sacrificial body with another sacrificial body after sufficient erosion of the sacrificial body occurs.