Methods for detecting incidence orthogonality of a patterned beam in charged-particle-beam (CPB) microlithography, and CPB microlithography systems that perform same

In the context of charged-particle-beam (CPB) microlithography methods and systems, methods are disclosed for detecting the incidence orthogonality of a patterned beam on the lithographic substrate. In an embodiment, the position of reticle-fiducial-mark images, as formed on the substrate stage at a position Z1, are detected at two lateral positions of a corresponding reticle fiducial mark. A distance L1 between the images is determined. Then, the substrate stage is moved to a position Z2, at which the position of reticle-fiducial-mark images are detected at two lateral positions of the corresponding reticle fiducial mark. A distance L2 between the images is determined. The incidence-orthogonality error Deltatheta is calculated by substitution into Deltatheta=(L1-L2)/2DeltaH. The projection-optical system of the CPB microlithography apparatus is adjusted so that Deltatheta=0.