Numerical investigation of particle transport and deposition mechanisms driven by multiphase explosion coupling with buffer gas stream

Debris suppression and expulsion are among the key challenges in designing and optimizing the light source system of extreme ultraviolet lithography (EUVL). The mechanisms of debris transport and deposition still require further investigation. The study of this problem involves compressible gas-particle multiphase fluid dynamics. In this study, the transport, spatial distribution characteristics of debris particles, and the wall deposition mechanism within a rectangular cavity are investigated from the multiphase flow perspective by employing the compressible multiphase particle-in-cell (CMP-PIC) method. Our analysis reveals that particle transport encompasses the following processes: Firstly, multiple particle jets are induced due to shock-driven multiphase instability. Subsequently, the bending and coalescing process of particle jets are observed under the influence of vortex and buffer gas stream. Simultaneously, particles aggregate near the explosion center and are transported by the buffer gas stream. Furthermore, three distinct deposition mechanisms are identified for the first time, namely: (1) velocity-induced separation within the particle-buffer gas stream, (2) high-velocity particle jet impact, and (3) particle cluster transport driven by the buffer gas stream. Additionally, parametric study was conducted to evaluate the effect of particle diameter on the debris transport and deposition mechanism. Owing to variations of inertia and relaxation time, significant differences in the evolution, position distribution, and coalescing process are observed, which subsequently affect the deposition momentum of each wall and the emission ratio. Results indicate that smaller particles (d_p=0.2 μm and d_p=0.6 μm) exhibit shorter relaxation times, leading to enhanced expulsion by the buffer gas stream and reduced wall deposition momentum. Whereas larger particles (d_p=1.0 μm and d_p=2.0 μm) lag in evolution, weaken particle jet coalescing process, and increase wall deposition momentum due to its large inertia. Three-dimensional simulation results show that particle-buffer gas stream velocity separation and high-velocity particle impact mechanisms dominate particle distribution, while the influence of particle cluster formation and transport is significantly diminished. These findings on transport characteristics and deposition mechanism of particles provide valuable insights for optimizing EUVL source system.