Patent ID: 8426829

Claim:
Ion implantation apparatus for implanting ions into planar substrate wafers, comprising: an implant wheel mounted for rotation about a wheel axis; a plurality of wafer carriers distributed about a periphery of said implant wheel; a respective heat sink in each said wafer carrier for removing heat from a wafer on said carrier during an ion implantation process by said wafer being thermally coupled with said heat sink; each of said wafer carriers having a wafer support surface in a respective wafer support plane canted inwards towards said wheel axis; and at least one fence located at a radially outer edge of each of said carriers to prevent wafers on said carriers from sliding outwards on said carriers during rotation of said implant wheel, whereby said wafers are pressed by centrifugal force against said support surfaces, wherein each said fence has a respective abutment surface to engage an outer edge of a wafer on said wafer carrier, wherein said abutment surface is movable transversely relative to said respective wafer support plane as said wafer is pressed by centrifugal force against said support surface, wherein said fence on each of said wafer carriers comprises a fence body mounted on said wafer carrier to provide said transversely movable abutment surface, said fence body being mounted to neutralize influence on said body of centrifugal force when said implant wheel is rotated, and wherein said fence body is cylindrical, mounted for rotation about an axis in a plane parallel to said wafer support plane.