Focusing electrode for cathode arrangement, electron gun, and lithography system comprising such electron gun

摘要

The invention relates to a cathode arrangement comprising:a thermionic cathode comprising an emission portion provided with an emission surface for emitting electrons, and a reservoir for holding a material, wherein the material, when heated, releases work function lowering particles that diffuse towards the emission portion and emanate at the emission surface at a first evaporation rate;a focusing electrode comprising a focusing surface for focusing the electrons emitted from the emission surface of the cathode; andan adjustable heat source configured for keeping the focusing surface at a temperature at which accumulation of work function lowering particles on the focusing surface is prevented.