| 摘要 |
Exposure methods are disclosed for use in charged-particle-beam microlithography and that yield decreased blur and variation in blur within individual exposure fields (subfields) of a pattern. Blur at a location on the optical axis increases monotonically with increased shift in the focal point of a subfield image on the substrate. In contrast, blur at a subfield edge exhibits comparatively little change over a limited range in focal-point shift, and exhibits sharply increased change as the shift in focal point exceeds a threshold. Variation in blur within individual subfields decreases monotonically with increased shift in the focal point. Consequently, by changing the focal point during exposure, within a range in which maximum blur within the subfield is within an acceptable range, DELTAblur is decreased more than conventionally, thereby increasing the uniformity of blur within the projected subfield.
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