Patent Number: 
Section: claims

1. Multiple beam lithography system comprising:a beam source for providing a multitude of beams,a blanker array comprising a blanker for each beam out of the multitude of beams, said array adapted for substantially allowing a plurality of beams to pass through,a control device for providing the blanker array with a temporal blanking pattern indicating for each beam when it should be blanked and when not, thereby modulating each beam with an unique temporal blanking pattern, anda measuring device arranged downstream of the blanker array, comprising a sensor having a sensor area arranged for directly and simultaneously sensing the plurality of individually modulated beams for providing an aggregated signal of the plurality of beams as a function of time. 2. Multiple beam lithography system according to claim 1, further comprising a demodulator adapted for demodulating said aggregated signal into an intensity value for each individual beam. 3. Multiple beam lithography system according to claim 2, wherein the demodulator comprises an electronic data processor adapted providing the control device with said temporal blanking patterns and for calculating a measure of the intensity of individual beams based on their corresponding temporal blanking patterns and the aggregated signal of the plurality of beams as a function of time. 4. System according claim 1, wherein the sensor area is arranged for simultaneously sensing all beams of the multitude of beams of the system. 5. System according to claim 1 or 4, in which the sensor area is a contiguous area. 6. System according to claim 1, wherein the multitude of beams comprises a multitude of charged particle beams, and the measuring device comprises a current measuring sensor arranged for measuring an aggregated current generated by the plurality of beams. 7. System according to claim 6, wherein the current measuring sensor comprises one or more than one Faraday cup, current clamp and/or scintillating material and photon counter. 8. System according to claim 1, further comprising a target positioning system comprising a stage for carrying and moving a target to be exposed to the beams, wherein the measuring device is mounted on the stage. 9. System according to claim 1, further comprising a converging element for directing the plurality of beams onto the sensor area. 10. System according to claim 1, in which the measuring device further comprises a knife edge or knife edge array placed in front of the sensor area. 11. System according to claim 10, in which the knife edge or knife edge array is placed substantially in an image plane of the system. 12. Method for simultaneous measurement of a multitude of beams in a system according to claim 1,said method comprising the steps of:i) providing a multitude of temporal blanking patterns comprising a temporal blanking pattern for each blanker, each temporal blanking pattern representing a modulation of an associated beam over a time interval,ii) modulating the multitude of beams during the time interval by streaming to each blanker associated with a beam an associated temporal blanking pattern, sensing an aggregated beam intensity signal of all unblanked beams, and measuring said signal during the streaming of the temporal patterns as a function of time,iii) calculating a measure of the intensity of individual beams based on their associated temporal blanking patterns and the signal as a function of time. 13. Method according to claim 12, wherein step iii) comprises demodulating said signal by calculating a measure of the intensity of individual beams based on their associated temporal blanking patterns and the signal as a function of time. 14. Method according to claim 12, wherein the temporal blanking patterns of said multitude of beams are substantially orthogonal with respect to each other. 15. Method according to claim 12, wherein during steps i) and ii) substantially only half of the multitude of beams is switched on. 16. Method according to claim 14, wherein the multitude of temporal blanking patterns is generated using pseudo random numbers. 17. Method according to claim 12, wherein the temporal blanking patterns are chosen such that each temporal blanking pattern contains a large number of on-off transitions. 18. Method according to claim 12, wherein the temporal blanking patterns are arranged such that at substantially any time the total amount of unblanked beams is substantially constant. 19. Method according to claim 12, wherein the measuring device comprises a current measuring sensor arranged for measuring an aggregated current generated by the plurality of beams as a function of time, in which the measuring device further comprises a variable gain amplifier which can be switched betweena first setting comprising a high gain and low noise setting, anda second setting comprising a low gain and high noise setting,wherein said method comprises the step of setting the variable gain amplifier to the first setting when the aggregate current is expected to be small, or setting the variable gain amplifier to the second setting when the aggregate current is expected to be large. 20. Measuring device suitable for use in a system according to claim 1, said device comprising a sensor having a sensor area arranged for simultaneously sensing a plurality of beams for providing an aggregated signal of the plurality of beams, further comprising a knife edge or knife edge array placed in front of the sensor area. 21. Multiple beam lithography system comprising a multiple beam column for projecting multiple beams onto a target, wherein the column comprises:a beam source for providing a multitude of beams,a blanker array arranged between the beam source and the target, comprising a blanker for each beam out of the multitude of beams, wherein said array is adapted for substantially allowing a plurality of beams to pass through,a control device for providing the blanker array with a blanking pattern indicating for each beam when it should be blanked and when not,projection means for projecting the plurality of beams onto the target,a sensor arranged downstream of the multiple beam column for examining the throughput of the multiple beam column, wherein the sensor comprises a sensor area which is adapted for sensing all beams of the multitude of beams simultaneously, and wherein the sensor is arranged for providing an aggregated signal of the plurality of beams as a function of time, anda demodulator adapted for demodulating said aggregated signal by calculating a measure of the intensity of individual beams based on their corresponding temporal blanking patterns and the aggregated signal of the plurality of beams as a function of time. 22. Method according to claim 12, wherein several beams are left unblanked at any time.