Droplet target delivery method for high pulse-rate laser-plasma extreme ultraviolet light source

摘要

A laser-plasma, EUV radiation source (10) that controls the target droplet delivery rate so that successive target droplets (66, 72) are not affected by the ionization of a preceding target droplet. A source nozzle (50) of the source (10) has an orifice (56) of a predetermined size that allows the droplets (54) to be emitted at a rate set by the target materials natural Rayleigh instability break-up frequency as generated by a piezoelectric transducer (58). The rate of the droplet generation is determined by these factors in connection with the pulse frequency of the excitation laser (14) so that buffer droplets (70) are delivered between the target droplets (66, 72). The buffer droplets (70) act to absorb radiation generated from the ionized target droplet (66) so that the next target droplet (72) is not affected.