Patent ID: 8309935

Claim:
An electrostatic lens assembly for use in an ion implanter, said assembly comprising: a terminal electrode defined by a top and bottom portion, each of said top and bottom portions having respective edges at an end, said terminal electrode configured to receive an ion beam traveling in z direction between said top and bottom portions of said terminal electrode, said ion beam is defined by a width in an x direction in a plane orthogonal to the z direction and a height in a y direction vertical to the x direction in the plane as the beam travels through the lens assembly in the z direction; a ground electrode defined by a top and bottom portion, said ground electrode configured to exit said ion beam from said assembly between said top and bottom portions of said ground electrode; a suppression electrode defined by a top and bottom portion wherein said ion beam travels between said top and bottom portions of said suppression electrode, said suppression electrode disposed between said terminal and ground electrodes, said suppression electrode having an associated electrostatic equipotential; and an end plate disposed between the respective edges of said top and bottom portions of said suppression electrode, said end plate having an hour-glass shape corresponding to the electrostatic equipotential of said beam associated with a region of said suppression electrode.