Charged-particle-beam optical systems and microlithography apparatus comprising a non-absorbing shaping aperture

摘要

Charged-particle-beam (CPB) optical systems, and CPB microlithography apparatus including CPB optical systems, are disclosed that include a “shaping aperture” that absorbs a very low percentage of incident charged particles and hence does not experience excessive temperature increases due to bombardment by and absorption of incident charged particles. Nevertheless, the shaping apertures are effective for trimming and shaping a charged particle beam to produce a downstream-propagating beam having a desired transverse profile. The aperture opening in the shaping aperture is defined in a conductive thin-film membrane. The membrane thickness is configured to cause charged particles incident on the membrane to experience scattering (e.g., forward-scattering). CPB optical systems including the shaping aperture also include a “screening aperture” downstream of the shaping aperture to block (absorb) scattered charged particles. The screening aperture is made from a relatively thick conductive sheet and is situated where the shaped beam forms a crossover downstream of the shaping aperture.