Abstract: The invention relates to a compound objective lens for a Scanning Electron Microscope having a conventional magnetic lens excited by a first lens coil, an immersion magnetic lens excited by a second lens coil, and an immersion electrostatic lens excited by the voltage difference between the sample and the electrostatic lens electrode. For a predetermined excitation of the lens, the electron beam can be focused on the sample using combinations of excitations of the two lens coils. More BSE information can be obtained when the detector distinguishes between BSE's (202) that strike the detector close to the axis and BSE's (204) that strike the detector further removed from the axis. By tuning the ratio of the excitation of the two lens coils, the distance from the axis that the BSE's impinge on the detector can be changed, and the compound lens can be used as an energy selective detector.

Abstract: The invention relates to an in-column back-scattered electron detector, the detector placed in a combined electrostatic/magnetic objective lens for a SEM. The detector is formed as a charged particle sensitive surface, preferably a scintillator disk that acts as one of the electrode faces forming the electrostatic focusing field. The photons generated in the scintillator are detected by a photon detector, such as a photo-diode or a multi-pixel photon detector. The objective lens may be equipped with another electron detector for detecting secondary electrons that are kept closer to the axis. A light guide may be used to offer electrical insulation between the photon detector and the scintillator.

Abstract: The invention relates to a dual beam apparatus equipped with an ion beam column and an electron beam column having an electrostatic immersion lens. When tilting the sample, the electrostatic immersion field is distorted and the symmetry round the electron optical axis is lost. As a consequence tilting introduces detrimental effects such as traverse chromatic aberration and beam displacement. Also in-column detectors, detecting either secondary electrons or backscattered electrons in the non-tilted position of the sample, will, due to the loss of the symmetry of the immersion field, show a mix of these electrons when tilting the sample. The invention shows how, by biasing the stage with respect to the grounded electrodes closest to the sample, these disadvantages are eliminated, or at least reduced.