US Patent 7488938 Charge-control method and apparatus for electron beam imaging

One embodiment relates to a method of electron beam imaging of a target area of a substrate. During an imaging phase, an electron beam is controllably scanned over the target area of the substrate, and extracted secondary electrons are detected. An electric field at a surface of the substrate is changed from an original electric field after the imaging phase. During a charge control phase, the electron beam is controllably scanned over the target area of the substrate. The electric field at the surface of the substrate is reverted back to the original electric field after the charge control phase. The imaging and charge control frames are interleaved. Other embodiments and features are also disclosed.