Objective lenses, charged particle microscopes including the same, and associated methods
AssigneeFEI Company
InventorsRadovan Vašina, Bohuslav Sed'a, Marek Uncovský, Magdalena Špoková
Life of this patent
Estimating the term…
Abstract
Objective lenses, charged particle microscopes including the same, and associated methods are disclosed herein. An objective lens can include a lens body, a shielding electrode, and a steering electrode. The objective lens is configured such that varying a steering electrode voltage adjusts a location of a main objective plane of the objective lens to vary a focal working distance of the objective lens. A method can include positioning a sample relative to an objective lens and operating the objective lens to focus a charged particle beam to a focus location.
Claims20
An apparatus, comprising:
- an objective lens, comprising:
- a lens body extending circumferentially around a lens central axis of the objective lens;
- a shielding electrode disposed within a downstream end region of the lens body and configured to at least partially shield a test region downstream of the objective lens from a lens electrostatic field generated within the objective lens;
- and
- a steering electrode disposed within the downstream end region of the lens body and upstream of the shielding electrode,
- wherein the objective lens is configured such that varying a steering electrode voltage that is applied to the steering electrode adjusts a location of a main objective plane of the objective lens in a downstream direction to increase a focal working distance of the objective lens.
An objective lens, comprising:
- a shielding electrode;
- and
- a steering electrode,
- wherein the objective lens is configured to generate a lens electrostatic field to at least partially direct a charged particle beam along an optical axis to a focus location with a landing energy, as measured at the focus location, that is at most 100 eV,
- wherein the shielding electrode is configured to at least partially shield a test region downstream of the objective lens such that the lens electrostatic field has an axial electric field strength, as measured at the focus location in a direction parallel to the optical axis, that is at most 150 volts per millimeter (V/mm), and
- wherein the steering electrode is configured to generate at least a portion of the lens electrostatic field such that the objective lens operates with a focal working distance, as measured between the objective lens and the focus location along a direction parallel to a lens central axis of the objective lens, that is 1-3 millimeters (mm).
A method, comprising:
- positioning a sample relative to an objective lens that is configured to focus a charged particle beam to a focus location;
- and
- operating the objective lens,
- wherein the objective lens comprises:
- a lens body extending circumferentially around a lens central axis of the objective lens;
- a shielding electrode disposed within a downstream end region of the lens body and configured to at least partially shield a test region downstream of the objective lens from a lens electrostatic field generated within the objective lens;
- and
- a steering electrode disposed within the downstream end region of the lens body and upstream of the shielding electrode, and
- wherein the operating the objective lens comprises controlling a focal working distance between the objective lens and the focus location by applying a steering electrode voltage to the steering electrode.
Dependencies are inferred from the claim text.