Aberration-corrected charged-particle optical apparatus

摘要

Aberration-corrected charged-particle optical apparatus improving the resolution of charged-particle optical systems by eliminating or minimizing optical aberrations. The apparatus comprises a source of charged particles and a plurality of charged-particle lenses including non-round lenses, energized in such manner so as to correct axial aberrations of orders up to and including fifth order. The non-round lenses comprise quadrupoles and octupoles disposed in such manner that fifth order combination aberrations are precisely controlled in addition to third order aberrations. The resultant apparatus very significantly improves on resolution attainable with non-aberration corrected charged-particle round lenses. It also improves on resolution attainable with correctors of third order aberrations only.