Patent ID: 6855943

Claim:
A laser-plasma extreme ultraviolet (EUV) radiation source comprising: a nozzle including a source end and an exit end, said exit end including an orifice having a predetermined diameter, said nozzle emitting a stream of droplets of a target material from the orifice; a target material excitation source providing a pulsed excitation signal to the nozzle; and a laser source providing a pulsed laser beam, wherein the timing of the pulsed excitation source, the diameter of the orifice and the timing of the pulsed laser source are designed relative to each other so that the droplets emitted from the orifice of the nozzle have a predetermined speed and spacing therebetween and so that target droplets within the droplet stream are ionized by the pulses of the laser beam and a predetermined number of buffer droplets are provided between the target droplets that are not directly ionized by the pulsed laser beam, where the buffer droplets absorb radiated plasma energy from ionized target droplets so as to allow subsequent target droplets to be unaffected by preceding target droplet ionization.