Charged-particle-beam projection apparatus and transfer methods

摘要

The present invention provides CPB projection apparatus and transfer methods for transferring a pattern from a mask onto a wafer with precise linear-distortion correction of transferred images without creating significant astigmatic blur of the image. A preferred embodiment of the projection apparatus includes an illumination-optical system and a projection-optical system. The illumination-optical system includes a CPB source for emitting a charged-particle beam, and first and second condenser lenses. A field-limiting aperture limits the field of the charged-particle flux. A first astigmatic-aberration correction coil is positioned at a principal plane of either the first or second projection lens and corrects linear distortion of a resulting projected image. A third condenser lens collimates the beam to form an image of the field-limiting aperture on a selected subfield of the mask. A projection-lens system demagnifies the image formed by the mask and projects the demagnified image on a wafer. A crossover aperture is positioned between the projection-lens system to further shape the CPB flux. A second astigmatic-aberration-correction coil is positioned parallel with the crossover aperture to correct astigmatic blur.