Description
Extreme ultraviolet (EUV) lithography at 13.5 nm, driven by laser-produced tin (Sn) plasmas, has become the foundational technology in semiconductor manufacturing. A primary challenge is the control of plasma parameters: electron density, electron temperature, and ion charge state distribution, which define the spectral purity and conversion efficiency of the EUV source. Here, we present our experimental and modeling efforts on comprehensively characterizing laser-produced tin plasmas and the resulting EUV emission.
On the experimental side, we introduce ''SparkLight", a new platform for generating and characterizing laser-produced plasmas. Tin plasmas are generated by irradiating a continuously moving tin-coated wire with a 1064 nm Nd:YAG laser. The facility integrates three complementary diagnostics: EUV emission spectroscopy, laser interferometry, and coherent Thomson scattering.
We devote particular attention to Thomson scattering, which allows for space- and time-resolved characterization of laser-produced plasmas. To reject stray light and isolate Thomson signal from the plasma self-emission, we utilize a compact and cost-effective design based on a Wollaston prism, volume Bragg grating notch filters, and a single-grating spectrometer.
On the modeling side, we use the radiation hydrodynamics code FLASH to study how laser pulse shaping can be optimized to improve EUV source performance. We also develop the collisional Particle-in-Cell code PSC to simulate fast ion debris acceleration in current EUV sources and in future, shorter wavelength sources.
This work demonstrates an integrated and practical approach for experimental and modeling characterization of plasmas in EUV source development.