Patent Number: 
Section: claims

1. A particle-beam projection processing apparatus for irradiating a target by means of a beam of energetic electrically charged particles, comprising:an illumination system for generating and forming said energetic particles into an illuminating beam,a pattern definition means located after the illumination system as seen along the direction of the beam, said pattern definition means being adapted to position an aperture pattern composed of apertures transparent to the energetic particles in the path of the illuminating beam, thus forming a patterned beam emerging from the aperture pattern, anda projection system positioned after the pattern definition means and adapted to project the patterned beam onto a target to be positioned after the projection system, the projection system comprising at least two consecutive projector stages, namely, at least one non-final projector stage forming an intermediate stage and one final projector stage,further comprising at least one foil located across the path of the patterned beam, said at least one foil being positioned between the pattern definition means and the position of the target at a location close to a respective image of the aperture pattern formed by the projection system, a first foil of the at least one foil being located before a consecutive projector stage of the projection system. 2. The apparatus of claim 1, wherein a second foil of the at least one foil is located in front of the position of the target as seen along the direction of the beam. 3. The apparatus of claim 2, wherein the at least one foil is adapted to be held at an electrical potential, thus forming a final electrode of the projection system. 4. The apparatus of claim 3, wherein the at least one foil is sufficiently thin to allow unimpeded propagation of a fraction of the irradiating beam through the at least one foil. 5. The apparatus of claim 2, wherein the at least one foil is sufficiently thin to allow unimpeded propagation of a fraction of the irradiating beam through the at least one foil. 6. The apparatus of claim 1, further comprising an aperture diaphragm located after the at least one foil as seen along the direction of the beam, said diaphragm having an aperture limiting the lateral extension of the beam. 7. The apparatus of claim 6, wherein the at least one foil is sufficiently thin to allow unimpeded propagation of a fraction of the irradiating beam through the at least one foil. 8. The apparatus of claim 1, wherein the at least one foil is sufficiently thin to allow unimpeded propagation of a fraction of the irradiating beam through the foil. 9. The apparatus of claim 1, wherein the at least one foil separates two adjacent recipients held at different gas pressures. 10. The apparatus of claim 1, wherein the at least one foil is continuous across the area of the respective image of the aperture pattern. 11. The apparatus of claim 1, wherein the at least one foil is made from an electrically conductive material. 12. The apparatus of claim 1, wherein the at least one foil is made from a semiconductor material. 13. The apparatus of claim 12, wherein the semiconductor material is silicon or diamond-like carbon. 14. The apparatus of claim 1, comprising a sensor means adapted to monitor the integrity of the at least one foil and a mechanical shutter means located near an opening for the patterned beam within the apparatus and being adapted to close said opening upon detection of a damage to the at least one foil by said sensor means. 15. The apparatus of claim 1, wherein the at least one foil is sufficiently thin to allow unimpeded propagation of a fraction of the irradiating beam through the at least one foil.