Design and Optimization of Laser Produced Plasma Devices for Nanolithography

Laser Produced Plasma (LPP) devices with Sn targets are currently the leading design in the development of extreme ultraviolet (EUV) photon sources for the advanced lithography in future manufacturing of computer chips. The developments and optimizations of LPP sources for EUV lithography include research starting from simple planar targets to high frequency droplet targets. Investigation of Sn-doped materials for producing optically thin plasma was conducted to reduce EUV photons loss due to self-absorption and minimize tin debris. Recent utilization of small Sn droplets with pre-pulse technique promises achieving high volume manufacturing of this advanced nanolithography systems. Optimization of commercial devices using liquid droplets requires consideration of two major objectives: minimum debris production and maximum conversion efficiency (CE) and EUV power. We studied various laser beam parameters along with droplet sizes to determine conditions that influence EUV emission and absorption as well as debris development. The process of optimization included simulation and benchmarking of LPP devices with single and dual-beam pulses, producing enough volume of vapor/plasma mix that can be efficient source of EUV photons emission, optically thin for EUV photons collection and, at the same time, relatively dense to reduce energetic ions production. We used our comprehensive HEIGHTS package for modeling analysis, optimization, and LPP system design.