Method and apparatus for multiple charged particle beams

A multi-source charged particle gun apparatus for generating a plurality of substantially parallel charged particle beams, comprising:

• a plurality of charged particle sources, each of the plurality of charged particle sources provided with at least one electrode energized by an adjustable voltage to extract a plurality of substantially parallel charged particle beams, one beam being from each of the plurality of charged particle sources;
• a magnetic coil energized by an adjustable electric current to generate a magnetic field;
• and a plurality of substantially cylindrically symmetric conical magnetic pole pieces excited by the electric current and disposed to control the focus of each of the multiple substantially parallel charged particle beams.

A charged particle multi-beam column apparatus for imaging with a plurality of substantially parallel focused charged particle beams, comprising:

• a plurality of charged particle sources, each of the plurality of charged particle sources being provided with at least one electrode energized by an adjustable voltage to extract a plurality of substantially parallel charged particle beams, one beam being from each of the plurality of charged particle sources;
• a magnetic coil energized by an adjustable electric current to generate a magnetic field;
• and a plurality of substantially cylindrically symmetric conical magnetic pole pieces excited by the electric current and disposed to focus the multiple substantially parallel charged particle beams approximately in a plane orthogonal to a direction of propagation of the multiple substantially parallel charged particle beams.

A multi-beam inspection system comprising:

• a stage for supporting a workpiece subject to inspection and mounted in a chamber;
• a multi-beam charged particle column, including substantially cylindrically symmetric conical magnetic pole pieces associated with each beam of the multi-beam charged particle column, that generates a plurality of substantially parallel charged particle beams, each of the plurality of charged particle beams being incident on portions of the workpiece thereby to produce a plurality of streams of image data;
• and an image processor coupled to process the plurality of image data streams, thereby to detect defects in the workpiece.