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AssigneeICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH
InventorJuergen Frosien
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An objective lens which is a component of a scanning electron microscope and wherein the electron source or the intermediate image of the electron source is reduced by condenser lenses is imaged onto a specimen (PR). The objective lens comprises an asymmetrical magnetic lens (ML), an electrostatic immersion lens (OE/UE) superimposed on the magnetic lens (ML), and electrode (ST) which is connected to a variable potential (U.sub.ST) so as to control the intensity of the current of secondary (SE) and back-scattered electrodes released from the specimen (PR), and a detector (DT) mounted immediately above the magnetic lens (ML). The electrodes (OE, UE) of the immersion lens are connected to potentials so that an electrical field which decelerates the primary electrons (PE) is formed inside the objective lens.
An objective lens for focusing charged particles on a specimen comprising, an electrostatic immersion lens which has a first electrode (OE) and a second electrode (UE) which are connected to potentials (U.sub.OE, U.sub.UE) so that the charged particles (PE) are decelerated in the field of the immersion lens from a first to a lower, second energy, a third electrode (ST) which is connected to a variable potential (U.sub.ST) so as to control the intensity of the current of secondary particles (SE) emanating from said specimen (PR) and which are accelerated in a direction toward a detector (DT).
Dependencies are inferred from the claim text.