Wi Seong Ju, Jang Yong Ju, Kim Haneul, Cho Kyeongjae, Ahn Jinho
Division of Materials Science and Engineering, Hanyang University, Seoul 04763, Korea.
EUV-IUCC (Industry University Cooperation Center), Hanuyang University, Seoul 04763, Korea.
Membranes (Basel). 2022 Mar 26;12(4):367. doi: 10.3390/membranes12040367.
A pellicle is a thin membrane structure that protects an extreme ultraviolet (EUV) mask from contamination during the exposure process. However, its limited transmittance induces unwanted heating owing to the absorption of EUV photons. The rupture of the EUV pellicle can be avoided by improving its thermal stability, which is achieved by improving the emissivity of the film. However, the emissivity data for thin films are not easily available in the literature, and its value is very sensitive to thickness. Therefore, we investigated the dependence of emissivity on structural parameters, such as thickness, surface roughness, and grain size. We found a correlation between resistivity and emissivity using theoretical and experimental approaches. By changing the grain size of the Ru thin film, the relationship between resistivity and emissivity was experimentally verified and confirmed using the Lorentz-Drude model. Finally, we present a method to develop an EUV pellicle with better thermal stability that can withstand high-power EUV light sources.
防护膜是一种薄膜结构，可在曝光过程中保护极紫外（EUV）掩模免受污染。然而，其有限的透射率会因EUV光子的吸收而导致不必要的发热。通过提高其热稳定性可以避免EUV防护膜的破裂，这可以通过提高薄膜的发射率来实现。然而，薄膜的发射率数据在文献中并不容易获得，并且其值对厚度非常敏感。因此，我们研究了发射率与结构参数（如厚度、表面粗糙度和晶粒尺寸）之间的关系。我们使用理论和实验方法发现了电阻率与发射率之间的相关性。通过改变Ru薄膜的晶粒尺寸，利用洛伦兹-德鲁德模型通过实验验证并确认了电阻率与发射率之间的关系。最后，我们提出了一种开发具有更好热稳定性的EUV防护膜的方法，该防护膜能够承受高功率EUV光源。
