Patent ID: 8829477

Claim:
A device comprising: a system producing a laser beam directed to an irradiation region; and a droplet source comprising a fluid exiting an orifice and a sub-system having an electro-actuatable element producing a disturbance in the fluid, the electro-actuatable element driven by a first-waveform to produce droplets for irradiation to generate EUV radiation, the droplets produced by said first waveform having differing initial velocities causing at least some adjacent droplets to coalesce as the droplets travel to the irradiation region, the first waveform being formed from a series of pulse waveforms with at least one of rise-time and fail-time of pulses of said series of pulse waveforms shorter than a period of said first waveform so as to generate a fundamental frequency within an operable response range of said electro-actuable element and at least one harmonic of the fundamental frequency.