Method of implanting a substrate and an ion implanter for performing the method

A method of implanting a substrate wafer having an implant surface with a predetermined diameter, the method comprising:

• a) generating an implant beam having a predetermined beam direction,
• b) holding said substrate wafer aligned in an implant plane, normal to said beam direction,
• c) said beam having orthogonal cross-sectional dimensions in said implant plane each of which is less than said predetermined wafer diameter, and
• d) mechanically scanning said substrate wafer in two dimensions in said implant plane to provide a desired uniform total implant dose over the implant surface of the substrate wafer, said mechanically scanning comprising a first mechanically driven reciprocating movement of the wafer along a first translational direction, and a second mechanically driven reciprocating movement of the wafer along a second translational direction different from said first translational direction,
• wherein the substrate wafer is mechanically scanned so that the implant beam draws on the implant surface of the substrate wafer alternating first and second rasters of scan lines, each of said first and second rasters covering the whole of said implant surface,
• said first rasters are drawn with said substrate wafer held in a first constant orientation about a twist axis parallel to said predetermined beam direction, and
• said second rasters are drawn with the substrate wafer held in a second constant orientation at 180° to said first orientation about said twist axis.