Theoretical Study on Acid Diffusion Length in Chemically Amplified Resists Used for Extreme Ultraviolet Lithography

Acid diffusion length has been regarded as the most important factor in the development of chemically amplified resists used for ultrafine patterning. In this study, the acid diffusion length in chemically amplified extreme ultraviolet (EUV) resists was investigated by a Monte Carlo method in the pr...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 52; no. 1; pp. 016501 - 016501-5
Main Author Kozawa, Takahiro
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.01.2013
Subjects
Amplification
Diffusion length
Exposure
Generators
Lithography
Optimization
Resists
Ultraviolet
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Summary:Acid diffusion length has been regarded as the most important factor in the development of chemically amplified resists used for ultrafine patterning. In this study, the acid diffusion length in chemically amplified extreme ultraviolet (EUV) resists was investigated by a Monte Carlo method in the presence of quenchers. The acid diffusion length corresponding to the highest chemical gradient, which results in the lowest line edge roughness, was investigated by varying the exposure dose, the acid generator concentration, and the effective reaction radius for deprotection. Although the optimum acid diffusion length was decreased with the increase of effective reaction radius for deprotection, it did not depend on the exposure dose or acid generator concentration.
Bibliography:Latent images at the half-depth of resist film calculated by Monte Carlo method: (a) exposure dose dependence, (b) acid generator concentration dependence, and (c) effective reaction radius dependence. The exposure dose was changed from 10 to 30 mJ cm -2 with steps of 10 mJ cm -2 . The acid generator concentration was changed from 10 to 30 wt % with steps of 10 wt %. The effective reaction radius was changed from 0.1 to 0.5 nm with steps of 0.1 nm. (a) Dependence of acid diffusion length (three-dimensional) and lifetime on the initial position ($x$-direction) of acid molecules and (b) $x$-, $y$-, and $z$-components of acid diffusion. ADL in the graph denotes acid diffusion length. The acid diffusion length calculated from the acid lifetime, $\sqrt{6Dt}$, is shown in (a) for comparison. PEB time is also shown. The dashed lines in (b) represent the average value of each component of acid diffusion length. The exposure dose was 10 mJ cm -2 . The acid generator concentration was 10 wt %. The effective reaction radius was 0.1 nm. The quencher concentration was 0.0211 nm -3 . Histogram of acid diffusion length distributions. The $x$-component of the diffusion length of acid molecules initially generated at $|x| = 0 \pm 0.5$, $5 \pm 0.5$, $10 \pm 0.5$, and $15 \pm 0.5$ nm is shown. The exposure dose was 10 mJ cm -2 . The acid generator concentration was 10 wt %. The effective reaction radius was 0.1 nm. The quencher concentration was 0.0211 nm -3 . PEB time was 56.1 s. Dependence of $x$-component of acid diffusion length on exposure dose. The acid generator concentration was 10 wt %. The effective reaction radius was 0.1 nm. The quencher concentrations for 10, 20, and 30 mJ cm -2 exposure doses were 0.0211, 0.0440, and 0.0646 nm -3 , respectively. PEB times for 10, 20, and 30 mJ cm -2 exposure doses were 56.1, 54.4, and 55.9 s, respectively. Dependence of $x$-component of acid diffusion length on acid generator concentration. The exposure dose was 10 mJ cm -2 . The effective reaction radius was 0.1 nm. The quencher concentrations for 10, 20, and 30 wt % acid generator concentrations were 0.0211, 0.0262, and 0.0291 nm -3 , respectively. PEB times for 10, 20, and 30 wt % acid generator concentrations were 56.1, 51.9, and 51.5 s, respectively. Dependence of $x$-component of acid diffusion length on effective reaction radius for deprotection. The effective reaction radius was changed from 0.1 to 0.5 nm with steps of 0.1 nm. The exposure dose was 10 mJ cm -2 . The acid generator concentration was 10 wt %. The quencher concentrations for 0.1, 0.2, 0.3, 0.4, and 0.5 nm effective reaction radii were 0.0211, 0.0246, 0.0261, 0.0279, and 0.0293 nm -3 , respectively. PEB times for 0.1, 0.2, 0.3, 0.4, and 0.5 nm effective reaction radii were 56.1, 51.3, 44.1, 42.0, and 40.0 s, respectively.
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0021-4922
1347-4065
DOI:10.7567/JJAP.52.016501