Projection ion beam lithography

Abstract
Demagnifying mask-to-wafer projection with ion beams is a potential lithographic technique for high volume device production with large process latitudes. Sub-0.1 μm resolution is possible with more than 10 μm depth of focus. Furthermore, there is the possibility of an electronic alignment on-line during chip exposure with nanometer precision: ‘‘pattern lock’’ may be achieved in feedback control loops by controlling X and Y position, rotation, scale, difference in X–Y scale and trapezoidal distortion of the projected ion image by dipole, quadrupole, and hexapole fields induced in an electrostatic multipole, by axial magnetic fields generated in a solenoid, and by the fine adjustment of lens voltages. Results obtained with an advanced research type ‘‘Alpha Ion Projector’’ are presented with the focus on recent exposure latitude evaluations. Further developments of ion projection lithography are discussed concentrating on electrostatic lens optics for the realization of large exposure fields (20×20 mm2–35×35 mm2) with less than 20 nm distortion. Results of a cost of ownership model for ion projection steppers are presented.
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