近年來半導體產業為了維持摩爾定律，全力研發由13.5 奈米中心波長在2％的頻寬範圍內的帶內極紫外光，作為先進光蝕刻技術的光源。運用高強度奈秒脈衝雷射轟擊錫靶材產生錫電漿，使其激發極紫外光，是目前產生所需光源的有效方法，而上述過程可統稱為雷射引發電漿光譜學。 本論文著重在以模擬方法探討高功率脈衝雷射引起的電漿光譜學，從雷射脈衝的生成、雷射電漿交互作用、電漿內部的碰撞、解離和輻射效應分別建立可靠的數值模型，發展出一套完整的模擬架構，搭配解析理論與實驗數據進行雷射電漿生成的極紫外光源之研究探討，未來可以應用在不同雷射引起電漿光譜學的相關研究上。論文內容可主要分為三個部份。 第一部份，我們針對高功率掺鐿光纖雷射系統中的各種訊號動態行為，發展一套模擬不同條件和特性下的光纖雷射放大器之數值模型。基於此模型，我們探討了在光纖內各種訊號的動態行為，包含自發性輻射、寬頻寄生受激放大過程和非線性拉曼散射。模擬結果與實驗量測相當吻合，進而優化實驗參數使得由光纖放大器串聯的奈秒光纖主從式放大器系統輸出的雷射強度達成雷射產生錫電漿生成極紫外光源的需求。 第二部分著重在完成一套穩態輻射電漿模型，並用來研究在各種實驗條 件下極紫外光生成過程。此數值模型包含電漿流體動力學、碰撞輻射解離模型和輻射在電漿中的傳遞。我們運用此模型定量計算考慮電漿再吸收狀態下的極紫外光輻射量並探討雷射脈衝寬度和雙脈衝機制對極紫外光轉換效率的影響。 論文的最後一部份，為了正確模擬碰撞性電漿行為，我們針對了碰撞性粒子模擬法裡固有的粒子離散效應引發的數值熱化現象進行研究。當外加碰撞加入一維模擬時，導致電漿熱化時間大幅縮短並與德拜長度內模擬粒子數目的一次方成正比，此現象可以由Balescu-Lenard-Landau 理論說明。此外，我們研究了粒子分散效應對於逆軔致輻射的影響，並基於粒子模擬法建立了研究電漿極紫外光光譜學的動態模型。;In order to keep Moore′s Law alive, an extreme ultraviolet (EUV) light of a 13.5-nm wavelength within 2% bandwidth as an appropriate light source for lithography has attracted considerable attention. Laser produced plasma (LPP) is an effective method to generate the required EUV light, where the Sn target is heated by a nanosecond laser pulse to produce the high-temperature plasma to generate EUV radiation. These processes can be called a LPP spectroscopy. This dissertation aims to develop an integrated model to numerically investigate several physical properties within a LPP spectroscopy respectively. Studied topics include generation of an intense laser pulse, laser-plasma interaction, radiation transfer in a hot-dense plasma, and kinetic behavior of the particle. The work consists of three parts. The first part includes a numerical study and a systematical analysis of the spectral dynamics in a high-power fiber laser amplifier, e.g., amplified spontaneous emission, parasitic amplification, stimulated Raman scattering, etc. The simulation results agree well with experiments and optimize the experimental conditions to achieve the irradiance requirements in order to generate the laser-produced plasma. In the second part, we have constructed an integrated model to investigate the laser-produced plasma light source. The model includes plasma hydrodynamic processes, radiative-collisional ionization and radiation transfer in a plasma. Using the model, the quantitative estimation of in-band EUV emission from optically thick plasma can be achieved. According to the simulation results, we present the effect of pulse duration on the conversion efficiency of the EUV light and the enhancement of the EUV emission energy by using a dual-pulse scheme. In the last part, we have investigated numerical thermalization due to the discrete-particle effect in collisional simulations in order to accurately simulate particle collisions in a plasma. The scaling law of the thermal relaxation time with the particle number in a Debye length in a one-dimensional collisional PIC simulation has been purposed. The discrete-particle noise thus can be described using Balescu-Lenard-Landau kinetic theory. As a result, using a collisional particle-in-cell (PIC) method, we investigate the discrete-particle effect on inverse-bremsstrahlung absorption rate and present the preliminary simulation results of the LPP EUV light source instead of the hydrodynamic model in order to study the particle kinetic behavior.
