Electron beam exposure system

An electron beam exposure apparatus for transferring a pattern onto the surface of a target, comprising:

• a beamlet generator for generating a plurality of electron beamlets;
• a modulation array for receiving said plurality of electron beamlets, comprising a plurality of modulators for modulating the intensity of an electron beamlet;
• a controller, operationally connected to the modulation array, for individually controlling the modulators using control signals;
• a focusing electron optical system comprising an array of electrostatic lenses wherein each lens focuses a corresponding individual beamlet, which is transmitted by said modulation array, to a cross section smaller than 300 nm, and
• a target holder for holding a target with its exposure surface onto which the pattern is to be transferred in the first focal plane of the focusing electron optical system,
• wherein said beamlet generator comprises at least one thermionic source, said source comprising at least one extractor electrode adapted for being operated in a space charge limited region, said source adapted for generating an electron beam, and said beamlet generator furthermore provided with a beamsplitter for splitting said electron beam up into a plurality of electron beamlets.