Multiphysics modeling and simulations oflaser-sustained plasmas

Laser-sustained plasma (LSP), which can be utilized for a novel radiation light source, has advantages suchas high irradiance, broad spectral range, and stable emission, demonstrating significant applications in waferinspection in the field of the semiconductor industry. This paper revisits the historical development of LSPresearch and introduces fundamental physical processes in LSP. The mathematical description equations forLSP and methods of calculating plasma parameters are provided, thereby a time-dependent two-dimensionalfluid model is established by taking into consideration a laser-thermal-hydrodynamic coupling effect. Thepropagation of the laser in plasma is investigated based on the established model, and the fundamentalprocesses in LSP, including the initial evolution process, laser energy deposition, steady-state characteristics,and instability, are explored. The effectiveness of the simulation model is confirmed through comparing with theexperimental results of high-pressure Xe LSP. The findings indicate that the mode, power, F-number of incidentlasers, as well as parameters including components, pressure, and flow velocity of gas, can all affect the steady-state properties of LSPs. Under the identical power and F-number conditions, Gaussian mode laser and annularmode laser both produce LSPs with different shapes and positions. Notably, under the conditions of high-powerannular laser incidence, large laser F-number, and high flow velocity, the simulation results reveal temporal andspatial instability in LSP. These simulation results contribute significantly to a more in-depth understanding ofthe underlying physical mechanisms of the LSP. Furthermore, they provide a theoretical basis for designing thelight source system and optimizing the multiple parameters. The influence of laser parameters on LSPproperties elucidated in this study not only advances the fundamental understanding of LSP but also offerscrucial insights for designing and optimizing the light source systems in various applications, particularly in thefield of optical detection for semiconductor wafer inspection