Charged particle beam apparatuses are used in a plurality of industrial fields. Inspection of semiconductor devices during manufacturing, exposure systems for lithography, detecting devices and testing systems are only some of these fields.
In general, there is a high demand for structuring and inspecting specimens within the micrometer or nanometer scale. On such a small scale, process control, inspection or structuring is often done with charged particle beams, e.g. electron beams, which are generated and focused in charged particle beam devices such as electron microscopes or electron beam pattern generators. Charged particle beams offer superior spatial resolution compared to, e.g. photon beams due to their short wavelengths.
Thereby, throughput of devices for maskless lithography, inspection or defect review is a demanding task. To increase the throughput, multiple beam devices can be used. In order to integrate more charged particle beams, axis-free systems are proposed, whereby several charged particle beams are imaged within one charged particle optic. Such axis-free or distributed axis optical systems require specific conditions to be able to provide sufficient imaging quality. As these conditions limit other constructional and technical aspects, axis-free charged particle optical systems have to be further improved.