Sn droplet target development for laser produced plasma EUV light source

We are developing a Sn droplet generator for a LPP HVM EUV light source. Droplet trains with frequencies up to 500kHz and droplet diameters below 20um are generated via the continuous jet method. Charging single droplets and using deflector electrodes these charged droplets are selected from the droplet train and irradiated by the drive laser. Due to the small droplet diameter, the drive laser otherwise irradiates several droplets inside the droplet train thus increasing the Sn debris as is experimentally shown. In addition, the paper outlines that a 30um droplet size is the mass limit for up to 180W EUV generation based on the assumption that each Sn atom emits on average a single in-band photon.