Multi-axis magnetic lens for focusing a plurality of charged particle beams

摘要

The present invention provides two ways to form a special permeability-discontinuity unit inside every sub-lens of a multi-axis magnetic lens, which either has a simpler configuration or has more flexibility in manufacturing such as material selection and mechanical structure. Accordingly several types of multi-axis magnetic lens are proposed for various applications. One type is for general application such as a multi-axis magnetic condenser lens or a multi-axis magnetic transfer lens, another type is a multi-axis magnetic non-immersion objective which can require a lower magnetomotive force, and one more type is a multi-axis magnetic immersion objective lens which can generate smaller aberrations. Due to using permeability-discontinuity units, every multi-axis magnetic lens in this invention can also be electrically excited to function as a multi-axis electromagnetic compound lens so as to further reduce aberrations thereof and/or realize electron beam retarding for low-voltage irradiation on specimen.

主权项

1. A multi-axis magnetic lens, comprising:
an upper magnetic conductor plate, comprising:
a first upper through round hole; anda second upper through round hole; a lower magnetic conductor plate, planar and parallel to said upper magnetic conductor plate, comprising:
a first lower through round hole, coaxial with said first upper through round hole; anda second lower through round hole, coaxial with said second upper through round hole; a first upper magnetic ring positioned inside and coaxial with said first upper through round hole, wherein a first upper radial gap is between said first upper magnetic ring and said upper magnetic conductor plate; a first lower magnetic ring, positioned inside and coaxial with said first lower through round hole, wherein a lower radial gap is between said first lower magnetic ring and said lower magnetic conductor plate; a second upper magnetic ring, positioned inside and coaxial with said second upper through round hole, wherein a second upper radial gap is between said upper magnetic conductor plate and said second upper magnetic ring; a second lower magnetic ring, positioned inside and coaxial with said second lower through round hole, wherein a second lower radial gap is between said lower magnetic conductor plate and said second lower magnetic ring; and a common excitation coil, located between said upper magnetic conductor plate and said lower magnetic conductor plate; wherein said first upper through round hole, said first upper magnetic ring, said first upper radial gap, said first lower round hole, said first lower magnetic ring and said first lower radial gap function as a first magnetic sub-lens module for focusing a first charged particle beam; wherein said second upper through round hole, said second upper magnetic ring, said second upper radial gap, said second lower round hole, said second lower magnetic ring and said second lower radial gap function as a second magnetic sub-lens module for focusing a second charged particle beam; wherein said common excitation coil provides magnetic flux to said first magnetic sub-lens module and said second magnetic sub-lens module; and wherein one of said first upper radial gap and said first lower radial gap is filled with weakly-magnetic material.