Patent ID: 6965114

Claim:
A charged-particle-beam (CPB) pattern-transfer apparatus, comprising: a CPB source situated to irradiate a pattern defined on a mask retained by a mask stage; a CPB optical system having an optical axis and being configured to transfer the pattern from the mask to a substrate retained on a substrate stage; an optical position sensor fixed relative to the optical axis of the CPB optical system, the optical position sensor being configured to receive optical radiation from at least one optical reference mark on the mask or the mask stage and to indicate a displacement of the at least one optical reference mark, and thus of the mask or mask stage, with respect to the optical axis of the CPB optical system; and a CPB position sensor configured to receive CPB radiation that has propagated from at least one CPB reference mark on the mask or mask stage to a reference mark on the substrate or substrate stage and to indicate a displacement of the at least one CPB reference mark with respect to the optical axis of the CPB optical system.