Studies on extreme ultraviolet (EUV) light sources for practical applications have attracted much attention. Although a laser-driven EUV source in conjunction with focusing mirrors enables the use of intense EUV radiation, mitigation of debris from the source plasma and focusing mirrors is a challenge to satisfy requirements for advanced material synthesis, because even a tiny amount of contamination in the processed materials such as micro-machined circuit patterns or thin film materials drastically changes the physical properties and consequently deteriorates the functions. In this study, we designed and validated two types of optical layout, namely a combination of a planar mirror and an ellipsoidal mirror (PT) and double ellipsoidal mirrors (TT), for the mitigation of debris, including neutral particles. The properties of these layouts were compared with those of a reference layout consisted with a single ellipsoidal mirror. Ray-trace calculations for EUV light showed that the PT and TT layouts can both transfer enough energy to process or ablate materials while preserving the EUV profile at the light source. Furthermore, simulations of the debris trajectory showed that the amount of debris arriving at the EUV ablation target position with the TT layout is reduced to 0.23% of that with the reference layout. Si thin film deposition experiments were conducted and the fraction of elements in the deposited film was characterized by x-ray fluorescence analysis. The proportions of elements other than Si in the thin films were 1.3% with the PT layout and 0.0% with the TT layout, which are significant reductions from that with the reference layout and thus show the feasibility of the proposed optical layouts.

实际应用中对极紫外（EUV）光源的研究引起了广泛关注。尽管将激光驱动的EUV源与聚焦镜结合使用可以使用强烈的EUV辐射，但要满足高级材料合成的要求，减轻源等离子体和聚焦镜中的碎屑仍然是一项挑战，因为即使是极少量的污染物也不能满足要求。诸如微机械电路图案的加工材料或薄膜材料会极大地改变其物理性能，从而使功能恶化。在这项研究中，我们设计并验证了两种光学布局，即平面镜和椭球镜（PT）以及双椭球镜（TT）的组合，用于减轻包括中性粒子在内的碎片。将这些布局的属性与由单个椭圆镜组成的参考布局的属性进行了比较。对EUV光线的光线跟踪计算表明，PT和TT布局都可以传递足够的能量来处理或烧蚀材料，同时保留光源处的EUV轮廓。此外，碎片轨迹的模拟显示，使用TT布局到达EUV烧蚀目标位置的碎片数量减少到使用参考布局的EUV消融目标位置的碎片数量的0.23％。进行了Si薄膜沉积实验，并通过X射线荧光分析表征了沉积膜中的元素比例。薄膜中Si以外的元素的比例在PT布局下为1.3％，在TT布局下为0.0％，