The effects of tin droplets on the EUV emission after laser-triggered discharge for EUVL

This paper reports the effects of an interaction between tin droplets and a subsequent trigger laser on the Extreme Ultra Violet (EUV) emission after Laser-Triggered Discharge (LTD). Two Nd: YAG lasers were focused on the high-voltage tin cathode surface to trigger the discharges with various delay time. The experiments are based on the observations of the visible light emissions and emitted EUV spectrum by using a high speed camera and Transmission Grating Spectrometer (TGS) with a zirconium filter, respectively. Experimental results of visible light emission suggested that the subsequent trigger laser evaporate both of irradiated cathode surface and the droplets produced by the first discharge. Moreover, these interactions affected the intensity and distributions of the EUV emission. The effects of the tin droplets under various conditions were investigated and discussed.