Patent ID: 7480030

Claim:
An extreme ultraviolet photolithography method in which: an object to be lithographed possesses a plane surface, placed orthogonally to the light radiation and having a photosensitive zone, this object being able to be moved transversely to this radiation; the radiation carrying out the etching operation includes at least one line in the extreme ultraviolet and consists of N successive current pulses whose energy per unit area through an irradiation window is measured; and these radiation pulses are produced by the impact, on a suitable target, of at least two laser beams output by pulsed laser sources chosen from a plurality thereof, each emitting at each triggering a quantum of energy of given duration Δt, these laser sources being focused at the same point on the target, this method comprising the following iterative steps, stated for an nth iteration: a) integration of the energy per unit area of extreme ultraviolet radiation that has passed through the irradiation window during the N−1 last pulses; b) during the time interval separating two successive radiation pulses, translation of the photosensitive object through a distance equal to a fraction 1/N of the width of the irradiation window along the axis of this translation; c) subtraction of the integral obtained in step a) from the quantity of energy needed for the photoetching process; d) determination of a quantity of energy remaining to be provided in order to reach this quantity of energy needed for the photoetching process; e) calculation of the number of pulse quanta remaining to be generated for an n th pulse; f) determination of the corresponding number of laser sources to be fired and selection of laser sources whose number is equal to the integer part of this number; and g) synchronous triggering of the lasers selected at step f), these steps a) to g) being repeated for the next iterative point and wherein the number of laser sources calculated at step f) is fractional and the quantity of energy less than one quantum, associated with this fractional part of the number of lasers, is provided by a laser source capable of delivering the quantum of energy common to the other laser sources and is triggered with a delay, of less than the duration Δt of a quantum, relative to the instant of synchronous triggering of the other laser sources that deliver the integer part of the number of quanta of the same current pulse.