Methods and devices for evaluating beam blur in subfields projection-exposed by a charged-particle-beam microlithography apparatus

摘要

Methods and devices are disclosed for evaluating image performance in a charged-particle-beam (CPB) microlithography apparatus. In the disclosed method, multiple knife-edge reference marks are defined by a plate positioned at an image plane. The reference marks are illuminated by measurement beamlets formed by an upstream subfield. The beamlets are scanned over the reference marks to produce a series of beam-current transmissions. Each beam-current transmission corresponds to a single beamlet being scanned over a corresponding reference mark. The beam-current transmissions are exclusive of one another. The series of transmissions is then detected and analyzed. The knife-edge reference marks may be positioned on the plate so that the relative distance between the reference marks and the corresponding beamlets progressively increases for each successively scanned mark. A dummy beam also may be defined on the upstream subfield. The reference marks of the plate may be apertures or constructed of a charged-particle-reflecting material.