| 摘要 |
PROBLEM TO BE SOLVED: To provide an improved scheme for generating shaped beam spots, having a desired geometric shape from rectangular, elliptical and semi-elliptical apertures having one sharp edge. SOLUTION: A sharper beam edge can be generated by offsetting a rectangular or elliptical aperture, in combination with under- or over-focus. In the spherical aberration limit, under-focused semicircular apertures provide a sharp, flat edge. The sharp edge can give sufficient resolution for precision milling applications, and at the same time, the spot can be made large enough with sufficient total current and current density, to efficiently mill away material in either a production or laboratory environment. Depending on the particular beam spot that is desired, combinations of techniques including defocusing, aperture offsetting, and stigmation adjustment, can be used in both spherical aberration dominant and chromatic aberration dominant environments, to achieve a desired beam for the desired application. COPYRIGHT: (C)2005,JPO&NCIPI
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