20 March 2015 Advanced patterning approaches based on negative-tone development (NTD) process for further extension of 193nm immersion lithography
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Two approaches which achieve the further evolution of NTD (Negative Tone Development) process are shown in this article. One is ACCEL (Advanced Chemical Contrast Enhancement Layer) process that can improve the lithography performance and the other is DTD (Dual Tone Development) process that can shrink patterning pitch below the limit of single exposure process. ACCEL is an additionally provided layer which is coated on a surface of NTD resist film before exposure and removed by NTD developer. ACCEL can enhance the acid distribution and dissolution contrast of the NTD resist. In fact, lithography performances such as exposure latitude (EL) and DOF improved dramatically by applying ACCEL compared to the NTD resist without ACCEL. We consider that suppression of excessive acid diffusion and material transfer between the resist layer and the ACCEL layer are the causes of the contrast enhancement. DTD process is one of the simplest pitch shrink method which is achieved by repeating PTD and NTD process. Feasibility study of DTD patterning has been demonstrated so far. However, Exposure latitude margin and CDU performance were not sufficient for applying DTD to HVM. We developed the novel DTD specific resist under a new concept, and 32 nm half pitch (hp) contact hole (CH) pattern was successfully formed with enough margins. DTD line and space (L/S) patterning are also demonstrated and 24 nm hp L/S pattern can be resolved. k1 factors of DTD CH and L/S patterns reach to 0.20 and 0.15, respectively.
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Michihiro Shirakawa, Michihiro Shirakawa, Naoki Inoue, Naoki Inoue, Hajime Furutani, Hajime Furutani, Kei Yamamoto, Kei Yamamoto, Akiyoshi Goto, Akiyoshi Goto, Mitsuhiro Fujita, Mitsuhiro Fujita, "Advanced patterning approaches based on negative-tone development (NTD) process for further extension of 193nm immersion lithography", Proc. SPIE 9425, Advances in Patterning Materials and Processes XXXII, 942509 (20 March 2015); doi: 10.1117/12.2085744; https://doi.org/10.1117/12.2085744

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