Patent ID: 6287876
Filing Date: 2001-09-11
Classification: H01J

Abstract:
In a charged-particle-beam (CPB) microlithography method for transfer-exposing a pattern, defined on a reticle mounted on a reticle stage, to a sensitive substrate made of a substrate material and mounted on a substrate stage, a method for determining an amount of relative rotation between the substrate or substrate stage and the reticle or reticle stage, the method comprising:(a) providing at least one index mark on the substrate or substrate stage, each index mark being configured to produce an amount of backscattered charged particles, whenever the index mark is irradiated by a charged particle beam, that is measurably different from a baseline amount of backscattered charged particles, the at least one index mark having a predetermined orientation relative to an alignment axis of the substrate or substrate stage;(b) providing at least one alignment mark on the reticle or reticle stage, each alignment mark having a configuration corresponding to the configuration of one or more respective index marks on the substrate, and having a predetermined orientation relative to an alignment axis of the reticle or reticle stage;(c) irradiating the at least one index mark with a charged particle beam that has passed through the corresponding alignment mark;(d) detecting amounts of backscattered charged particles produced by each irradiated index mark to produce a corresponding electrical signal; and(e) processing the electrical signal to determine the amount of relative orientation.