Patent ID: 6831282
Filing Date: 2004-12-14
Classification: B82Y,H01J

Abstract:
In a charged-particle-beam (CPB) micro lithography method in which a reticle, defining a pattern to be transferred to a sensitive substrate, is irradiated with a charged-particle illumination beam, and a charged-particle patterned beam, formed by passage of the illumination beam through an illuminated portion of the reticle and carrying an aerial image of the illuminated portion of the reticle, is projected onto a sensitive surface of a substrate to imprint the sensitive surface with the aerial image, a method for evaluating imaging performance, comprising:defining a beam-transmitting measurement mark at an object plane; defining a knife-edged reference mark, at an image plane, as a corresponding through-hole in a charged-particle-scattering membrane; illuminating the measurement mark with a charged particle beam to form a charged-particle beamlet propagating downstream of the measurement mark toward the reference mark; projecting the beamlet onto the reference mark while scanning the beamlet over a knife-edge of the reference mark to produce non-scattered charged particles transmitted through the through-hole and forward-scattered charged particles transmitted through the membrane, the non-scattered and forward-scattered charged particles propagating downstream of the reference mark; disposing a beam-limiting diaphragm downstream of the reference mark, the beam-limiting diaphragm comprising a diaphragm plate defining a beam-limiting aperture having a diameter sufficient to block most of the forward-scattered charged particles while not blocking the non-scattered charged particles from reaching a detector, wherein an axial distance from the knife-edged reference mark to the beam-limiting diaphragm is such that an axial angle of the beam-limiting aperture as measured at the knife-edge is slightly greater than a convergence angle of the beamlet at the substrate; and detecting beam current of charged particles passing through the beam-limiting aperture.