激光维持等离子体多物理场耦合模型与仿真

Multiphysics modeling and simulations of laser-sustained plasmas

激光维持等离子体作为一种光照强度高、光谱范围宽、发光稳定的新型辐射光源,在光学检测(半导体晶圆检测)等领域具有重要的应用价值.本文回顾了激光维持等离子体研究的发展历程,介绍了其基本物理过程及数学描述方程,建立了基于多物理场耦合的二维流体模型.利用该模型研究了激光在等离子体中的传播过程,探讨了激光维持等离子体的初始演化过程、能量注入机制、稳态特性及不稳定性等关键问题.通过与高气压氙气等离子体实验结果对比,确定了仿真模型的有效性.相关仿真结果有助于深入理解激光维持等离子体的底层物理机制,为实现光源系统设计、多参数优化提供理论依据.

Laser-sustained plasma(LSP),which can be utilized for a novel radiation light source,has advantages such as high irradiance,broad spectral range,and stable emission,demonstrating significant applications in wafer inspection in the field of the semiconductor industry.This paper revisits the historical development of LSP research and introduces fundamental physical processes in LSP.The mathematical description equations for LSP and methods of calculating plasma parameters are provided,thereby a time-dependent two-dimensional fluid model is established by taking into consideration a laser-thermal-hydrodynamic coupling effect.The propagation of the laser in plasma is investigated based on the established model,and the fundamental processes 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 the experimental results of high-pressure Xe LSP.The findings indicate that the mode,power,F-number of incident lasers,as well as parameters including components,pressure,and flow velocity of gas,can all affect the steadystate properties of LSPs.Under the identical power and F-number conditions,Gaussian mode laser and annular mode laser both produce LSPs with different shapes and positions.Notably,under the conditions of high-power annular laser incidence,large laser F-number,and high flow velocity,the simulation results reveal temporal and spatial instability in LSP.These simulation results contribute significantly to a more in-depth understanding of the underlying physical mechanisms of the LSP.Furthermore,they provide a theoretical basis for designing the light source system and optimizing the multiple parameters.The influence of laser parameters on LSP properties elucidated in this study not only advances the fundamental understanding of LSP but also offers crucial insights for designing and optimizing the light source systems in various applications,particularly in the field of optical detection for semiconductor wafer inspection.