21 July 2000 Smooth low-stress sputtered tantalum and tantalum alloy films for the absorber material of reflective-type EUVL
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Tantalum (Ta) and Ta-alloy films were evaluated for use as the absorber material of masks for extreme ultraviolet lithography (EUVL). It was found that Ta film with a stress below 100 MPa, a surface roughness of less than 1 nm rms, a film density of over 14 g/cm3, and a deposition rate of more than 50 nm/min could be obtained by DC sputtering with Ar gas. Experiments on delineating mask patterns in this film by using dry etching revealed that 250-nm line-and-space patterns could be formed. The alloys evaluated were TaGe and TaN. These films were found to have some better properties than Ta film, for example, less stress, a smaller change in stress, and a smoother surface. This is confirmed to be due to the fact that the alloy films are amorphous. Of particular note is that TaN film has a lower deep ultraviolet (DUV) reflectivity than either Ta or TaGe, thus providing higher contrast between the underlying multilayer and the absorber patterns of an EUVL mask during DUV inspection. However, TaN has a lower density than the other two films. So, our current results indicate that using Ta or TaGe for the bulk absorber material and covering that with a thin layer of TaN is a promising way to obtain the film properties required for EUVL mask patterns, including film density and DUV inspection capability.
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Masashi Takahashi, Masashi Takahashi, Taro Ogawa, Taro Ogawa, Hiromasa Hoko, Hiromasa Hoko, Eiichi Hoshino, Eiichi Hoshino, Hiromasa Yamanashi, Hiromasa Yamanashi, Naoya Hirano, Naoya Hirano, Akira Chiba, Akira Chiba, Shinji Okazaki, Shinji Okazaki, } "Smooth low-stress sputtered tantalum and tantalum alloy films for the absorber material of reflective-type EUVL", Proc. SPIE 3997, Emerging Lithographic Technologies IV, (21 July 2000); doi: 10.1117/12.390087; https://doi.org/10.1117/12.390087

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