Patent ID: 8426834

Claim:
A method for generating EUV radiation from a gas discharge plasma, comprising the steps of: providing an emitter material in a discharge space between electrodes, the discharge space contains at least one buffer gas; providing a channel-generating beam of pulsed high-energy radiation, the channel-generating beam being formed by at least two partial beams; shaping, focusing and directing said at least two partial beams into a discharge space between the electrodes in such a way that respective foci of said at least two partial beams are superimposed in a pulse-synchronized manner in a superposition region along a spacing axis between the electrodes; generating an electrically conducting discharge channel along the superposition region due to an ionization of the at least one buffer gas present in the discharge space; vaporizing said emitter material in the discharge space by irradiation with pulsed high-energy radiation of a vaporizing beam; and converting the vaporized emitter material into a discharge plasma emitting EUV radiation by means of a pulsed discharge current generated between the electrodes; wherein the pulsed high-energy radiation of the channel-generating beam is triggered in such a way with the pulsed discharge current that the discharge channel is generated in each instance before a discharge current pulse has reached its maximum value, and wherein intensities of said at least two partial beams of the channel-generating beam are individually less than a threshold intensity for a breakdown of the buffer gas, and wherein a sum of the intensities of the partial beams is greater than the threshold intensity.