22 March 2016 Challenge toward breakage of RLS trade-off for EUV lithography by Photosensitized Chemically Amplified Resist (PSCAR) with flood exposure
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This paper proposes a promising approach to break the resolution (R), line-edge-roughness (LER), and sensitivity (S) trade-off (RLS trade-off) relationships that limit the ultimate lithographic performance of standard chemically amplified resists (CAR). This is accomplished in a process that uses a Photosensitized Chemically Amplified Resist (PSCAR) in combination with a flood-exposure in an in-line track connected to a pattern exposure tool. PSCAR is a modified CAR which contains a photosensitizer precursor (PP) in addition to other standard CAR components such as a protected polymer, a photo acid generator (PAG) and a quencher. In this paper, the PSCAR concept and the required conditions in resist formulation are carefully explained. In the PSCAR process, the sensitivity improvement is accomplished by PAG decomposition to selectively generate more acid at the pattern exposed areas during the flood exposure. The selective photosensitization happens through the excitation of the photosensitizer (PS) generated by the deprotection of the PP at the pattern exposed areas. A higher resist chemical gradient which leads to an improved resolution and lower LER values is also predicted using the PSCAR simulator. In the PSCAR process, the improved chemical gradient can be realized by dual acid quenching steps with the help of increased quencher concentration. Acid quenching first happens simultaneously with acid catalytic PP to PS reactions. As a result, a sharpened PS latent image is created in the PSCAR. This image is subsequently excited by the flood exposure creating additional acid products at the pattern exposed areas only. Much the same as in the standard CAR system, unnecessary acid present in the non-pattern exposed areas can be neutralized by the remaining quencher to therefore produce sharper acid latent images. EUV exposure results down to 15 nm half pitch (HP) line/space (L/S) patterns using a PSCAR resist indicate that the use of PSCAR has the potential to improve the sensitivity of the system while simultaneously improving the line-width-roughness (LWR) with added quencher and flood exposure doses. In addition, improved across-wafer critical dimension uniformity (CDU) is realized by the use of a PSCAR in combination with a flood exposure using pre α UV exposure module.
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Seiji Nagahara, Seiji Nagahara, Michael Carcasi, Michael Carcasi, Hisashi Nakagawa, Hisashi Nakagawa, Elizabeth Buitrago, Elizabeth Buitrago, Oktay Yildirim, Oktay Yildirim, Gosuke Shiraishi, Gosuke Shiraishi, Yuichi Terashita, Yuichi Terashita, Yukie Minekawa, Yukie Minekawa, Kosuke Yoshihara, Kosuke Yoshihara, Masaru Tomono, Masaru Tomono, Hironori Mizoguchi, Hironori Mizoguchi, Joel Estrella, Joel Estrella, Tomoki Nagai, Tomoki Nagai, Takehiko Naruoka, Takehiko Naruoka, Satoshi Dei, Satoshi Dei, Masafumi Hori, Masafumi Hori, Akihiro Oshima, Akihiro Oshima, Michaela Vockenhuber, Michaela Vockenhuber, Yasin Ekinci, Yasin Ekinci, Marieke Meeuwissen, Marieke Meeuwissen, Coen Verspaget, Coen Verspaget, Rik Hoefnagels, Rik Hoefnagels, Gijsbert Rispens, Gijsbert Rispens, Raymond Maas, Raymond Maas, Hideo Nakashima, Hideo Nakashima, Seiichi Tagawa, Seiichi Tagawa, } "Challenge toward breakage of RLS trade-off for EUV lithography by Photosensitized Chemically Amplified Resist (PSCAR) with flood exposure", Proc. SPIE 9776, Extreme Ultraviolet (EUV) Lithography VII, 977607 (22 March 2016); doi: 10.1117/12.2219433; https://doi.org/10.1117/12.2219433

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