Abstract: A laser plasma X-ray source for use in photolithography is disclosed wherein an electro-optical shutter is used to trim the output pulse from a master oscillator to a desired duration. The pulse is then split into several pieces which travel along various optical delay paths so that the pieces pass sequentially through a laser power amplifier. After amplification, the pieces are reassembled and then focussed at the plasma target. In a first embodiment, polarization and angle coding methods are used to distinguish each pulse piece at it travels along the delay paths. In a second embodiment, polarization coding is replaced by additional angle coding transverse to the plane of the angles of the first embodiment. An expander/reducer lens assembly is used in both embodiments to reduce the angles between the beam paths and allow more beams to fit closely to the laser amplifier gain region.

Abstract: A laser plasma X-ray source for use in photolithography is disclosed wherein an electro-optical shutter is used to trim the output pulse from a master oscillator to a desired duration. The pulse is then split into several pieces which travel along various optical delay paths so that the pieces pass sequentially through a laser power amplifier. After amplification, the pieces are reassembled and then focussed at the plasma target. In a first embodiment, polarization and angle coding methods are used to distinguish each pulse piece as it travels along the delay paths. In a second embodiment, polarization coding is replaced by additional angle coding transverse to the plane of the angles of the first embodiment. An expander/reducer lens assembly is used in both embodiments to reduce the angles between the beam paths and allow more beams to fit closely to the laser amplifier gain region.