Use of ion beam tails to manufacture a workpiece

Abstract

One method of implanting a workpiece involves implanting the workpiece with an n-type dopant in a first region with center and a periphery. The workpiece also is implanted with a p-type dopant in a second region complementary to the first region. This second region also has a center and a periphery. The periphery of the first region and the periphery of the second region at least partially overlap. A dose at the periphery of the first region or second region is less than a dose at the center of the first region or second region. The region of overlap may function as a junction where charge carriers cannot pass.

What is claimed is: 
     
         1 . A method of implanting a workpiece comprising:
 implanting an entire surface of said workpiece with a first dopant; and   implanting said workpiece with a second dopant in a second region that is a fraction of said surface, said second region having a center and a periphery, wherein said second region has a larger dose at said center than at said periphery.   
     
     
         2 . The method of  claim 9 , wherein said workpiece is a solar cell. 
     
     
         3 . The method of  claim 9 , wherein one of said first dopant and said second dopant is a p-type dopant and the other is an n-type dopant. 
     
     
         4 . The method of  claim 9 , further comprising implanting said surface of said workpiece with said first dopant in a first region that is a fraction of said surface, said first region having a center and a periphery, wherein said first region has a larger dose at said center than at said periphery, and wherein said periphery of said first region and said periphery of said second region at least partially overlap. 
     
     
         5 . The method of  claim 12 , wherein said first region and said second region extend to a depth deeper than a region formed by said implanting said entire surface of said workpiece with said first dopant. 
     
     
         6 . A solar cell comprising:
 a workpiece having a first surface;   a plurality of n-type regions in said first surface, each of said n-type regions having a center and a periphery, said center of said n-type region having a dose larger than in said periphery of said n-type region; and   a plurality of p-type regions in said first surface complementary to said plurality of said n-type regions, each of said p-type regions having a center and a periphery, said center of said p-type region having a dose larger than in said periphery of said p-type region, wherein said periphery of said p-type region and said periphery of said n-type region at least partially overlap.   
     
     
         7 . The solar cell of claim  14 , further comprising a junction at a location where said dose in said periphery of said n-type region and said dose in said periphery of said p-type region are equal. 
     
     
         8 . A solar cell comprising:
 a workpiece having a first surface, said first surface being doped to a first conductivity and to a first depth;   a plurality of second regions in said first surface, each of said second regions being doped to a second conductivity opposite said first conductivity, each of said second regions having a center and a periphery, said center of said second region having a dose larger than in said periphery of said second region; and   a space charge region between said plurality of said second regions.   
     
     
         9 . The solar cell of claim  16 , wherein an entirety of said first surface is doped evenly to said first conductivity and to said first depth. 
     
     
         10 . The solar cell of claim  16 , wherein said first conductivity and said second conductivity are selected from the group consisting of n-type and p-type. 
     
     
         11 . The solar cell of claim  16 , wherein a dopant profile of said periphery is configured to prevent shunting across said space charge region. 
     
     
         12 . The solar cell of claim  16 , further comprising a plurality of first regions in said first surface, each of said first regions being doped to said first conductivity, each of said first regions having a center and a periphery, said center of said first region having a dose larger than in said periphery of said first region, wherein said periphery of said first region and said periphery of said second region at least partially overlap, and wherein said first region and said second region extend to a depth deeper than said first depth.