Ion projection: the successor to optical lithography

Abstract

Ion projection lithography (IPL) is analogous to an optical wafer stepper except the exposing photons have been replaced by high energy, light ions. In the IPL machine being developed by the Advanced Lithography Group (ALG), a silicon stencil mask is `illuminated' by a broad area beam of hydrogen or helium ions. The ions pass through stencil mask openings and enter a multi-electrode electrostatic lens system which projects a demagnified image of the stencil mask onto a resist coated wafer substrate. Demonstrated IPL performance is covered. Independent calculations of the novel ion-optical column of the ALG prototype tool show less than 15 nm distortion over a 20 mm X 20 mm field, and indicate that even larger fields are possible. This machine will utilize standard optical, off-axis, wafer alignment and a precision laser interferometer controlled X-Y-stage. This combined `pattern lock' will enable the ALG prototype to achieve overlay requirements necessary for 0.15 micrometers geometries. The Advanced Lithography Group project for constructing the prototype ion projector is discussed.