Prism array for electron beam inspection and defect review

A beam separator for use in an electron beam inspection apparatus, the beam separator comprising:

• a central magnetic sector;
• inner magnetic sectors outside the central magnetic sector;
• and
• outer magnetic sectors outside the inner magnetic sectors;
• wherein the central magnetic sector generates a first magnetic field of a first field strength, each inner magnetic sector generates a second magnetic field of a second field strength, and each outer magnetic sector generates a third magnetic field of a third field strength.

A method of inspecting a substrate using charged particles, the method comprising:

• generating an incident charged-particle beam;
• bending the incident beam through a first outer magnetic sector, a first inner magnetic sector, a central magnetic sector, a second inner magnetic sector, and a second outer magnetic sector;
• focusing the incident beam to a substrate;
• retrieving a reflected charged-particle beam;
• bending the reflected beam through the second outer magnetic sector, the second inner magnetic sector, the central magnetic sector, a third inner magnetic sector, and a third outer magnetic sector;
• projecting the reflected beam to a detection system.

A low-energy electron beam inspection apparatus, the apparatus comprising:

• means for generating an incident charged-particle beam;
• means for decelerating and focusing the incident beam to a substrate;
• means for accelerating and refocusing a reflected charged-particle beam;
• means for projecting the reflected beam to a detection system to form a two-dimensional image;
• and
• a magnetic prism array configured to bend the incident beam through a first outer magnetic sector, a first inner magnetic sector, a central magnetic sector, a second inner magnetic sector, and a second outer magnetic sector, and further configured to bend the reflected beam through the second outer magnetic sector, the second inner magnetic sector, the central magnetic sector, a third inner magnetic sector, and a third outer magnetic sector.