System for imaging a secondary charged particle beam with adaptive secondary charged particle optics

Abstract

A secondary charged particle imaging system for imaging a secondary charged particle beam emanating from a sample by impingement of a primary charged particle beam is provided. The system includes a detector arrangement, and an adaptive secondary charged particle optics. The detector arrangement comprises a first detection element for detecting a first secondary charged particle sub-beam of the secondary charged particle beam, and a second detection element for detecting a second secondary charged particle sub-beam of the secondary charged particle beam. The adaptive secondary charged particle optics comprises an aperture plate including a first opening for letting the first secondary charged particle sub-beam pass through and a second opening for letting the second secondary charged particle sub-beam pass through; a lens system for mapping the secondary charged particle beam onto the aperture plate, the lens system comprising a first lens and a second lens; and a controller for controlling the excitation of the first lens and the excitation of the second lens. The controller is configured to independently control the excitation of the first lens and of the second lens to map the secondary charged particle beam onto the aperture plate so that the first secondary charged particle sub-beam passes through the first opening and the second secondary charged particle sub-beam passes through the second opening independent of a variation of at least one first operating parameter selected from a group comprising: landing energy of the primary charged particle beam on the sample, extraction field strength for the secondary charged particle beam at the sample, magnetic field strength of an objective lens that focuses the primary charged particle beam onto the sample, and working distance of the objective lens from the sample.