Charged-particle-beam microlithography apparatus and methods including correction of aberrations caused by space-charge effects

In a method for performing charged-particle-beam microlithography in which an exposure region on a divided reticle is illuminated by an illumination beam, and a patterned beam propagating downstream of the illuminated region is imaged by a projection-optical system onto a surface of a sensitive substrate, a method for correcting a space-charge-effect (SCE)-based aberration arising while transferring an image of the illuminated region onto the substrate surface, the method comprising:

• (a) providing a calibration pattern;
• (b) computing an expected SCE-based aberration expected to occur if the image of the calibration pattern were transferred to the sensitive substrate;
• (c) illuminating the calibration pattern with the illumination beam and forming an image of the calibration pattern onto the sensitive substrate or onto a detection mark on a substrate stage;
• (d) measuring an actual SCE-based aberration exhibited by the transferred image of the calibration pattern;
• (e) computing a correction coefficient for correcting any difference between the expected SCE-based aberration and the actual SCE-based aberration of the transferred image of the calibration pattern;
• (f) determining correction data for correcting an SCE-based aberration of a transferred image of an exposure region of a reticle;
• (g) calibrating the correction data according to the correction coefficient;
• and
• (h) based on the calibrated correction data, correcting the exposure region and transferring an image of the exposure region to the sensitive substrate.

A charged-particle-beam microlithography apparatus for exposing a sensitive substrate using one or multiple charged particle beams, the apparatus comprising:

• a source configured to produce one or multiple charged particle beams;
• an optical system situated and configured to direct the one or multiple charged particle beams to respective selected exposure regions on the substrate so as to form respective transfer images;
• a beam-correction-optical system situated and configured to apply a correction to the one or multiple charged particle beams based on correction data for correcting a space-charge-effect (SCE)-based aberration;
• and
• a controller connected to the beam-correction-optical system, the controller being configured to control the beam-correction-optical system based on the correction data which are calculated from beam current, spread-angle distribution, and beam-accelerating voltage of the one or multiple charged particle beams, and from optical characteristics of the optical system.