28 March 2014 Hydrogen plasma treatment: the evolution of roughness in frequency domain
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Roughness of lithographic lines is typically expressed as the absolute 3σ value variation of the resist lines. It was found that this 3σ value gives a good general indication of roughness across the wafer. However, it is important to have a full characterization of the roughness in the frequency domain. This necessity arises from the requirement to reduce different roughness frequencies for various lithographic levels. A power spectral density analysis is used to evaluate the effect of post-lithography plasma treatment processes on roughness evolution of 22 nm lines. It is found that the wafer to wafer roughness distribution after lithographic exposure is very stable for two types of extreme ultraviolet photoresists. Furthermore, by comparing various plasma processes, hydrogen based plasma was found to reduce mid and high frequency roughness contributions. However, the lithographic scaling towards smaller dimensions also causes the constriction of lithographic requirements which induces a limited roughness improvement. Nevertheless, power spectral density (PSD) analysis is found to give additional information.
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P. De Schepper, P. De Schepper, A. Vaglio Pret, A. Vaglio Pret, E. Altamirano-Sánchez, E. Altamirano-Sánchez, Z. el Otell, Z. el Otell, S. De Gendt, S. De Gendt, "Hydrogen plasma treatment: the evolution of roughness in frequency domain", Proc. SPIE 9054, Advanced Etch Technology for Nanopatterning III, 90540C (28 March 2014); doi: 10.1117/12.2046299; https://doi.org/10.1117/12.2046299

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