Enhancing the performance of LPP sources for EUV and BEUV lithography

Abstract

Photon sources for extreme ultraviolet Lithography (EUVL) are still facing challenges in required performance for high volume manufacture. Currently EUVL community has focused the research and developments on the dual-pulse laser produced plasma (LPP) devices with mass-limited targets. Such complex systems require extensive optimization to enhance the conversion efficiency (CE) and components lifetime and such optimization requires significant experimental and costly efforts. <br/> We continued to enhance our state-of-the art HEIGHTS package to analyze and optimize LPP sources and to make projections and realistic predictions of near future powerful devices. HEIGHTS package includes full 3-D detail description of all integrated physical processes involved in LPP devices. The models continued to be upgraded and well benchmarked in each interaction physics phase of plasma evolution for EUV and BEUV production. <br/> We simulated LPP sources using small droplets as the targets and evaluated the requirements for optimization of these sources in dependence on laser wavelength. We also simulated the targets as distributed fragments resulting from the intense pre-pulse laser energy deposition. Additionally, we simulated vapor/plasma mixture created by pre-pulse laser with comparatively low intensity. We studied mass dependence, laser parameters efficiency, optimization of EUV (13.5 nm) and BEUV (6.7 nm) radiation output, and atomic and ionic debris generation to predict potential damage to the optical collection system from energetic debris and the requirements for mitigating systems to reduce debris fluence. Our modeling and simulation included all phases of laser target evolution: from laser/droplet interaction, energy deposition, target vaporization and fragmentation, ionization, plasma hydrodynamic expansion, thermal and radiation energy redistribution, and EUV/BEUV photons collection as well as detail mapping of photons source location and size. Modeling results were benchmarked against recent experimental studies for the in-band photons production and for debris and ions generation for both EUV and BEUV systems.