Electron source designs are disclosed. The emitter structure, which may be silicon, has a layer on it. The layer may be graphene or a photoemissive material, such as an alkali halide. An additional layer between the emitter structure and the layer or a protective layer on the layer can be included. Methods of operation and methods of manufacturing also are disclosed.

An apparatus for monitoring of an ion beam. The apparatus may include a processor; and a memory unit coupled to the processor, including a display routine, where the display routine operative on the processor to manage monitoring of the ion beam. The display routine may include a measurement processor to receive a plurality of spot beam profiles of the ion beam, the spot beam profiles collected during a fast scan of the ion beam and a slow mechanical scan of a detector, conducted simultaneously with the fast scan. The fast scan may comprise a plurality of scan cycles having a frequency of 10 Hz or greater along a fast scan direction, and the slow mechanical scan being performed in a direction parallel to the fast scan direction. The measurement processor may also send a display signal to display at least one set of information, derived from the plurality of spot beam profiles.

A photocathode can include a body fabricated of a wide bandgap semiconductor material, a metal layer, and an alkali halide photocathode emitter. The body may have a thickness of less than 100 nm and the alkali halide photocathode may have a thickness less than 10 nm. The photocathode can be illuminated with a dual wavelength scheme.

Multi-beam effects which reduce the accuracy, or the speed of a wafer inspection are corrected dependent on an inspection position using an improved multi-beam system and a wafer inspection method using the multi-beam system. The multi-beam system comprises a mechanism for influencing and homogenising an extraction field dependent on the inspection position, for example dependent on a distance from a wafer edge.

An aperture system of an electron beam apparatus includes a plurality of apertures each including a first area including at least one through hole allowing an electron beam to pass therethrough and a second area disposed outside the first area and including first and second alignment keys, wherein two apertures, among the plurality of apertures, include the first alignment keys arranged in mutually overlapping positions and having the same size, and an aperture, excluding the two apertures, among the plurality of apertures, includes the second alignment keys arranged to overlap the first alignment keys and having an area larger than an area of the first alignment keys.

An apparatus for monitoring of an ion beam. The apparatus may include a processor; and a memory unit coupled to the processor, including a display routine, where the display routine operative on the processor to manage monitoring of the ion beam. The display routine may include a measurement processor to receive a plurality of spot beam profiles of the ion beam, the spot beam profiles collected during a fast scan of the ion beam and a slow mechanical scan of a detector, conducted simultaneously with the fast scan. The fast scan may comprise a plurality of scan cycles having a frequency of 10 Hz or greater along a fast scan direction, and the slow mechanical scan being performed in a direction parallel to the fast scan direction. The measurement processor may also send a display signal to display at least one set of information, derived from the plurality of spot beam profiles.

A photocathode structure, which can include an alkali halide, has a protective film on an exterior surface of the photocathode structure. The protective film includes ruthenium. This protective film can be, for example, ruthenium or an alloy of ruthenium and platinum. The protective film can have a thickness from 1 nm to 20 nm. The photocathode structure can be used in an electron beam tool like a scanning electron microscope.

An aperture system of an electron beam apparatus includes a plurality of apertures each including a first area including at least one through hole allowing an electron beam to pass therethrough and a second area disposed outside the first area and including first and second alignment keys, wherein two apertures, among the plurality of apertures, include the first alignment keys arranged in mutually overlapping positions and having the same size, and an aperture, excluding the two apertures, among the plurality of apertures, includes the second alignment keys arranged to overlap the first alignment keys and having an area larger than an area of the first alignment keys.

An apparatus for monitoring of an ion beam. The apparatus may include a processor; and a memory unit coupled to the processor, including a display routine, where the display routine operative on the processor to manage monitoring of the ion beam. The display routine may include a measurement processor to receive a plurality of spot beam profiles of the ion beam, the spot beam profiles collected during a fast scan of the ion beam and a slow mechanical scan of a detector, conducted simultaneously with the fast scan. The fast scan may comprise a plurality of scan cycles having a frequency of 10 Hz or greater along a fast scan direction, and the slow mechanical scan being performed in a direction parallel to the fast scan direction. The measurement processor may also send a display signal to display at least one set of information, derived from the plurality of spot beam profiles.

A photocathode structure, which can include an alkali halide, has a protective film on an exterior surface of the photocathode structure. The protective film includes ruthenium. This protective film can be, for example, ruthenium or an alloy of ruthenium and platinum. The protective film can have a thickness from 1 nm to 20 nm. The photocathode structure can be used in an electron beam tool like a scanning electron microscope.