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Proceedings Paper

Unraveling the role of secondary electrons upon their interaction with photoresist during EUV exposure
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Paper Abstract

The interaction of 91.6eV EUV photons with photoresist is very different to that of optical lithography at DUV wavelength. The latter is understood quite well and it is known that photons interact with the resist in a molecular way through the photoacid generator (PAG) of the chemically amplified resist (CAR). In EUV however, the high energy photons interact with the matter on atomic scale, resulting in the generation of secondary electrons. It is believed that these secondary electrons in their turn are responsible in chemical modification and lead to switching reactions that enable resist local dissolution. However, details of the interaction are still unclear, e.g. which reaction an electron with a given energy can initiate.

In this work we have introduced a method to measure the chemical interaction of the secondary electrons with the EUV resist. The method is based on electron gun exposures of low energy electrons (range ~1eV to ~80eV) in the photoresist. The chemical interaction is then measured by Residual Gas Analysis (RGA), which can analyze out of the outgassing which and how much reaction products are generated. In this way a ‘chemical yield’ can be quantified as function of electron energy.

This method has been successfully applied to understand the interaction of secondary electrons on the traditional CAR materials. The understanding was facilitated by testing different compositions of an advanced EUV CAR, where resp. polymer only, polymer+PAG, and polymer+PAG+quencher are tested with the electron gun. It was found that low energy electrons down to ~3-4eV can activate PAG dissociation, which can lead to polymer deprotection. However it was observed too that energy electrons of ~12eV and higher can do direct deprotection even in absence of the PAG. In addition, testing suggests that electrons can generate also other chemical changes on the polymer chain that could lead to cross-linking.

Paper Details

Date Published: 16 October 2017
PDF: 7 pages
Proc. SPIE 10450, International Conference on Extreme Ultraviolet Lithography 2017, 104500H (16 October 2017); doi: 10.1117/12.2281449
Show Author Affiliations
Ivan Pollentier, IMEC (Belgium)
Yannick Vesters, IMEC (Belgium)
Jing Jiang, IMEC (Belgium)
Pieter Vanelderen, IMEC (Belgium)
Danilo de Simone, IMEC (Belgium)


Published in SPIE Proceedings Vol. 10450:
International Conference on Extreme Ultraviolet Lithography 2017
Paolo A. Gargini; Patrick P. Naulleau; Kurt G. Ronse; Toshiro Itani, Editor(s)

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