30 December 1999 Damage control during dry etching of EUV mask: I. Control of surface roughness
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Abstract
To obtain good optical properties in an EUVL mask, the substrate should not suffer any damage either during mask fabrication or during use. As one step in ensuring that this is the case, the surface roughness of patterns etched on a mask substrate was examined, since it reduces the reflectance of the substrate. The experiments involved coating a Mo/Si multilayer with a SiO2 buffer layer and a Ta absorber layer. After the absorber was dry etched with a mixture of Cl2 and BCl3 gases, dry etching was used to over-etch the buffer layer. It was found that dry etching with Cl2 + BCl3 provides both a smooth Ta surface (roughness: less than 1 nm rms) and good control of the etching depth, even though the Ta etching rate was very high (389.6 nm/min.). The results indicate that the process used in this study is quite suitable for making absorber patterns.
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Eiichi Hoshino, Taro Ogawa, Masashi Takahashi, Hiromasa Hoko, Hiromasa Yamanashi, Naoya Hirano, Shinji Okazaki, "Damage control during dry etching of EUV mask: I. Control of surface roughness", Proc. SPIE 3873, 19th Annual Symposium on Photomask Technology, (30 December 1999); doi: 10.1117/12.373372; https://doi.org/10.1117/12.373372
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