Patent ID: 6861187

Claim:
In a charged-particle-beam (CPB) microlithography method in which a pattern is transferred from a reticle to a lithographic substrate by projecting a charged particle beam, carrying an image of the pattern, through a CPB optical system to the substrate on which the beam is focused so as to imprint an image of the pattern on the substrate, a method for measuring beam blur, comprising the steps: disposing a reticle, defining a measurement opening, at an object plane of the CPB optical system, the measurement opening having a longitudinal dimension that, as the charged particle beam passes through the measurement opening, provides the beam with a longitudinal transverse dimension; disposing a knife-edged plate at an image plane of the CPB optical system, the knife-edged plate defining at least one of (a) at least one knife-edged opening having longitudinal edges dimensioned at least 2× the longitudinal dimension of the charged particle beam, wherein each longitudinal edge has a respective knife-edge, and (b) multiple knife-edged openings each having respective longitudinal edges dimensioned at least as long as the longitudinal dimension of the charged particle beam, wherein each longitudinal edge has a respective knife-edge; directing a charged particle beam through the measurement opening and through a selected region of the knife-edged opening, while scanning the beam across at least a portion of the respective longitudinal edges; detecting the charged particle beam propagating downstream of the knife-edged opening so as to obtain data concerning a blur characteristic of the beam; and before any significant radiation-induced contamination has accumulated on a just-scanned knife-edge, shifting the charged particle beam such that the beam (a) is scanned across a different portion of the respective longitudinal edges in a subsequent scan, or (b) is scanned across the respective longitudinal edges of a different knife-edged opening in a subsequent scan, respectively.