極紫外光(Extreme ultraviolet, EUV)是目前半導體業界最關鍵的光源，這是因為極紫外光具有短波長的特性，可以為光刻技術提供較小的特徵尺寸(Feature size)，以持續縮小電晶體的大小。目前極紫外光光源已經投入商用，諸如ASML以及GIGAPHOTON都推出了自己的極紫外光光刻機，然而該項技術的轉換效率仍有尚待改進的地方，其中最重要的研究主題就是如何改善轉換效率。 極紫外光光刻使用雷射產生電漿(Laser-produced plasma)技術產生電漿，並使用錫作為靶材。由於靶材的選擇，光源的中心波長為13.5奈米附近的極紫外光。從實驗或模擬上可以發現，錫電漿輻射出來的極紫外光與所使用的幫浦雷射有著相近的脈衝長度，這代表電漿內部的物理過程達到了準平衡態(Quasi-steady state)，因此我們基於準平衡態假設提出了一維簡化模擬框架，該模擬框架能夠快速地計算極紫外光強度以及轉換效率等關鍵參數。 在本論文中，我們詳細描述了模擬框架的基本假設以及架構，並根據模擬框架的模擬結果，我們將電漿分為液體靶材區、雷射吸收區以及熱傳導區，並發現了不同區域的電漿特性對極紫外光的影響，並提出最大化轉換效率的條件。最後，我們根據最大化轉換效率的條件，得到了優化雷射條件的經驗公式。;Extreme Ultraviolet (EUV) light sources are currently the most critical light source in the semiconductor industry. The EUV light provides smaller feature sizes for photolithography to reduce the size of the transistor because of the feature of short wavelength. Right now, ASML and GIGAPHOTON have introduced their EUV lithography systems. However, there are still areas that can be improved. One of the most important research topics is the enhancement of conversion efficiency. EUV lithography applies the laser-produced plasma method to produce plasma, and tin as the target material. Because of the choice of target, the central wavelength of EUV light is 13.5 nm. Experiments and simulations show that the duration of EUV light emitted from tin plasma is similar to that of the pump laser used, which means that the physical processes inside the plasma have reached the quasi-steady state. Therefore, we propose a one-dimensional simplified simulation framework based on the quasi-steady state. Our simulation framework is capable of quickly calculating key parameters such as EUV light intensity and conversion efficiency. In this research, we will discuss in detail the assumptions as well as the structure of our simulation framework. Based on the result of our simulation framework, we divide the plasma into the liquid target region, the laser absorption region, and the thermal conduction region. Then, we find out the effects of the plasma properties on the extreme ultraviolet light in the different regions. Finally, we put forward the condition for maximizing the conversion efficiency and an empirical formula for optimizing the laser conditions.
