Electron beam apparatus, foil or grid lens, and method of operating an electron beam apparatus

A method of operating an electron beam apparatus having a foil or grid lens, the foil or grid lens having a first foil or grid arranged adjacent to an electrode, the method comprising:

• applying an electrical potential between the first foil or grid and the electrode;
• directing a primary electron beam along an optical axis through a central opening provided in the first foil or grid;
• and
• focusing, using an objective lens, the primary electron beam on a sample for causing emission of a signal electron beam that propagates through the objective lens and through the foil or grid lens in an opposite direction as compared to the primary electron beam;
• wherein off-axial electrons of the signal electron beam propagate through the first foil or grid that surrounds the central opening and is substantially transparent to electrons;
• and
• wherein an electric potential of 2 kV or more is applied between the electrode and the first grid or foil.

An electron beam apparatus, comprising:

• an electron source configured to generate a primary electron beam propagating along an optical axis;
• a sample stage configured to support a sample;
• an objective lens configured to focus the primary electron beam on the sample for causing an emission of a signal electron beam;
• and
• a foil or grid lens for influencing the signal electron beam, comprising:
• an electrode that surrounds the optical axis;
• a first foil or grid adjacent to the electrode and perpendicular to the optical axis, the first foil or grid being substantially transparent to electrons, wherein a central opening configured to allow the primary electron beam to pass through the central opening is provided in the first foil or grid;
• and
• a second foil or grid adjacent to the electrode and perpendicular to the optical axis, the second foil or grid being substantially transparent to electrons, wherein a central opening configured to allow the primary electron beam to pass therethrough is provided in the second foil or grid;
• wherein the foil or grid lens is configured to apply at least one of negative spherical aberrations and negative chromatic aberrations on the signal electron beam.