High-performance droplet-triggered laser shooting accuracy evaluation system for LPP-EUV light sources

Extreme ultraviolet (EUV) light sources with a central wavelength of 13.5 nm have become a foundational technology for advanced semiconductor manufacturing. In laser-produced plasma EUV (LPP-EUV) light sources, achieving the precise spatial-temporal synchronization between tin droplets and laser pulses is of paramount importance. To address this need, we have developed a droplet-triggered laser shooting accuracy evaluation (DLSAE) system specifically designed for LPP-EUV applications. The DLSAE system generates synchronized, tunable delay trigger signals with sub-nanosecond precision for the narrow-pulse laser and the droplet imaging camera based on real-time droplet detection. By analyzing the positional fluctuations of droplets captured via high-speed imaging, the DLSAE system quantitatively assesses shooting accuracy of the droplet-triggered laser shooting system. Under experimental conditions involving droplets with a diameter of approximately 75 μm, a velocity of ~15 m/s, and a repetition rate of 25 kHz, through the DLSAE system, the shooting error of a droplet-triggered laser shooting control system is evaluated about 3.325 μm (3σ) in the target space, compared to 60.002 μm (3σ) in the non-target space—corresponding to an 18.05× improvement.