Improved reflectance and stability of Mo-Si multilayers
Improved reflectance and stability of Mo-Si multilayers
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DOI：
10.1117/1.1489426
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发表时间：
2002-08-01
影响因子：
1.3
通讯作者：
Spiller, EA
中科院分区：
文献类型：
--
作者：
Bajt, S;Alameda, JB;Spiller, EA
商业 EUV 光刻系统需要比迄今为止发布的多层膜具有更高的反射率和更好的稳定性。这项工作代表了我们为满足这些规范所做的努力。开发了界面设计的 Mo-Si 多层膜，在 13.5 nm 波长处具有 70% 反射率和 0.545 nm 带宽，在 12.7 nm 波长处具有 71% 反射率和 0.49 nm 带宽。这些结果是通过 50 个双层获得的。这些新的多层结构由交替的钼层和硅层组成，并由薄碳化硼层隔开。在界面上沉积碳化硼会减少Mo-on-Si界面上硅化钼的形成。双层收缩减少了 30%，这意味着 Mo 和 Si 混合形成硅化物的情况减少了。因此，界面设计多层膜中的 Mo-on-Si 界面比标准 Mo-Si 多层膜中的界面更清晰。最佳碳化硼厚度已确定，并且对于 Mo-on-Si 和 Si-on-Mo 界面似乎有所不同。使用 0.4 nm 厚的碳化硼层（Mo-on-Si 界面）和 0.25 nm 厚的碳化硼层（Si-on-Mo 界面）获得了最佳结果。反射率的增加与具有更清晰和更平滑界面的多层一致。钌端接的 Mo-Si 多层膜显着提高了 EUV 多层膜的抗氧化性。最佳的覆盖层设计由通过碳化硼扩散势垒与顶部硅层隔开的 Ru 层组成。该设计在水蒸气（氧化）环境中的 EUV 暴露过程中实现了高反射率和最佳的抗氧化性。在 5 x 10(-7)-Torr 水蒸气分压存在下，电子束暴露 4.5 小时（试图模拟顶层的 EUV 暴露扰动），显示没有可测量的反射率损失，并且 Ru 端接多层膜的氧化物厚度没有增加。 (C) 2002 年光电仪器工程师协会。
Commercial EUV lithographic systems require multilayers with higher reflectance and better stability than those published to date. This work represents our effort to meet these specifications. Interface-engineered Mo-Si multilayers with 70% reflectance and 0.545-nm bandwidth at 13.5-nm wavelength and 71% reflectance with 0.49-nm bandwidth at 12.7-nm wavelength were developed. These results were achieved with 50 bilayers. These new multilayers consist of alternating Mo and Si layers separated by thin boron carbide layers. Depositing boron carbide on the interfaces leads to reduction in molybdenum silicide formation of the Mo-on-Si interfaces. Bilayer contraction is reduced by 30%, implying that there is less intermixing of Mo and Si to form silicide. As a result, the Mo-on-Si interfaces are sharper in interface-engineered multilayers than in standard Mo-Si multilayers. The optimum boron carbide thicknesses have been determined and appear to be different for the Mo-on-Si and Si-on-Mo interfaces. The best results were obtained With 0.4-nm-thick boron carbide layers for the Mo-on-Si interfaces and 0.25-nm-thick boron carbide layers for the Si-on-Mo interfaces. The increase in reflectance is consistent with multilayers having sharper and smoother interfaces. A significant improvement in oxidation resistance of EUV multilayers has been achieved with ruthenium-terminated Mo-Si multilayers. The best capping-layer design consists of a Ru layer separated from the top Si layer by a boron carbide diffusion barrier. This design achieves high reflectance and the best oxidation resistance during EUV exposure in a water-vapor (oxidizing) environment. Electron-beam exposures of 4.5 h (in an effort to simulate EUV exposure perturbation of the top layers) in the presence of 5 x 10(-7)-Torr water-vapor partial pressure show no measurable reflectance loss and no increase in the oxide thickness of Ru-terminated multilayers. (C) 2002 Society of Photo-Optical Instrumentation Engineers.