Patent ID: 6664551
Filing Date: 2003-12-16
Classification: H01J

Abstract:
In a charged-particle-beam (CPB) microlithography method, in which a pattern is defined on a segmented reticle divided into multiple subfields, the subfields are illuminated individually by an illumination beam to form a patterned beam, the patterned beam is projected to form corresponding subfield images on a lithographic substrate, and the subfield images are stitched together on the substrate to form a transferred pattern on the substrate, a method for determining an incidence orthogonality of the patterned beam on the substrate, the method comprising:(a) placing first and second reticle fiducial marks laterally spaced apart from each other at a reticle plane; (b) passing a charged particle beam individually through each of the first and second reticle fiducial marks to form respective laterally spaced-apart images of the first and second reticle fiducial marks at each of first and second locations situated near a substrate plane, wherein the first and second locations are separated from each other in an optical-axis direction by a distance (&Dgr;H); (c) measuring a lateral distance (L1, L2) between the respective images of the first and second reticle fiducial marks at each of the first and second locations, respectively; and (d) determining the incidence-orthogonality error (&Dgr;&thgr;) at the substrate surface by calculating &Dgr;&thgr;=(L1âˆ’L2)/2&Dgr;H for the first and second reticle fiducial marks.