Electron beam wafer inspection system and method of operation thereof

A multi-beam wafer imaging system, comprising

• a wafer imaging system comprising:
• an emitter for emitting an electron beam, wherein the emitter is a cold field emitter, a thermally assisted field emitter, or a Schottky emitter;
• a power supply for applying a voltage between the emitter and the column housing of at least 20 kV;
• an objective lens for focusing the electron beam on a wafer, wherein the objective lens has a magnetic lens component and an electrostatic lens component, wherein the magnetic lens component and the electrostatic lens component substantially overlap each other,
• wherein the electrostatic lens component has a first electrode, a second electrode and a third electrode;
• and
• a control electrode positioned along an optical axis from the position of the third electrode to the position of a specimen stage, wherein the control electrode is configured for control of signal electrons;
• a controller to switch between a first operational mode and a second operational mode, wherein the controller is connected to a further power supply for switching between the first operational mode and the second operational mode, where said first operational mode corresponds to moderate landing energies and said second operational mode corresponds to low landing energies;
• the multi-beam wafer imaging system further comprises:
• at least one further emitter for emitting an electron beam, wherein the at least one further emitter is a cold field emitter, a thermally assisted field emitter, or a Schottky emitter;
• wherein the objective lens comprises at least one further electrostatic lens component;
• wherein the at least one further electrostatic lens components has at least one further first electrode, at least one further second electrode and at least one further third electrode;
• and
• at least one further control electrode positioned along at least one further optical axis from the respective position of the respective third electrode to the position of a specimen stage, wherein the at least one further control electrode is configured for control of signal electrons.

A method of operating an electron beam wafer imaging system, comprising:

• emitting an electron beam having a brightness of 5×107 A/m2/sr/eV or above;
• guiding the electron beam through an electron beam column with an energy of 20 keV or above;
• focusing the electron beam on a wafer with a magnetic field and an electrostatic field, wherein the magnetic field and the electrostatic field substantially overlap each other, wherein the electrostatic field is provided by a first electrode, a second electrode and a third electrode, and wherein the electrostatic field is configured to be switched between a first operational mode and a second operational mode by varying the focal length of the electrostatic lens component, where said first operational mode corresponds to moderate landing energies and said second operational mode corresponds to low landing energies;
• and
• controlling the extraction field for signal electrons at the wafer with a control electrode.