LARGE AREA MULTI-COLUMN SCANNING ELECTRON MICROSCOPE OBJECTIVE LENS DESIGN

Abstract

Currently, there is an urgent need in the semiconductor industry for a high-resolution multi-column electron beam (e-beam) inspection system with throughput comparable to optical inspection system. To achieve such fast inspection speeds while detecting nanometer-scale defects, the objective lens needs to have a sub-centimeter inter-lens bore distance and produce a probe size smaller than 2 nm at a landing energy of 1 keV. This thesis presents three such objective lens layouts, suitable for large array e-beam wafer inspection. These lenses were designed, simulated, and tested as add-on attachments inside a SEM. All these objective lenses generate a magnetic field region for focusing an e-beam, but they have differing specimen layouts: the specimen lies outside the magnetic field region, partially immersed in it, or fully immersed within it. Depending on the specimen stage layout, spatial resolution, and throughput rates required, the objective lens designs presented will be of interest for the multi-column e-beam wafer inspection application.