| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS-ThP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | M. Honda, Tokyo Electron Miyagi Ltd., Japan |
| Authors: | M. Honda, Tokyo Electron Miyagi Ltd., Japan T. Katsunuma, Tokyo Electron Miyagi Ltd., Japan K. Narishige, Tokyo Electron Miyagi Ltd., Japan K. Yatsuda, Tokyo Electron Limited, Japan |
| Correspondent: | Click to Email |
EUV lithography provides much bigger dry etch challenges than 193-nm lithography did. Its depth of focus (DOF) is
so small that the thickness of EUV resist is much thinner than that of 193-nm resist. Although EUV resist requires
higher etch selectivity than 193-nm resist does, UV/VUV cure, which has been used in 193-nm resist, is not an
effective technique to enhance etch selectivity and physical strength. This is because UV/VUV light is essentially
transparent in EUV resist. Etch selectivity normally attributes to polymer which prevents material from being etched.
In the case of EUV resist, line width roughness (LWR) is easily enhanced by polymer because its physical strength
is so low, and the resist width is so small that the resist cannot tolerate the stress of polymer. This is quite contrary
to the ideal reactive ion etch (RIE) which diminishes LWR. Therefore, an alternative curing technique for EUV resist
is required to improve the etch selectivity without increasing LWR.We introduced the e-beam curing technique for 193-nm resist utilizing a direct current superimposed (DCS) capacitively-coupled plasma (CCP) at the 55th AVS in 2008. Negative high DC voltage is applied in DCS CCP,
and positive ions collide with the upper electrode. Thus, secondary electrons are emitted from the upper electrode.
The applied negative high DC voltage also accelerates the emitted secondary electrons, which turn into ballistic
electrons. The curing mechanism of 193-nm resist is scission and cross-linking of polymer by e-beam which is a
consequence of ballistic electrons. Considering its mechanism, the e-beam curing should be available to any
polymer. Thus, we applied this technique to EUV resist, and investigated the effect of e-beam in EUV resist. In order
to identify the cured thickness and chemical structure change, the surface was analyzed with cross-sectional SEM
and ToF-SIMS, respectively. As a result, the curing effect was confirmed. In addition to the curing technique, we
also invented a coating technique with a silicon compound material by sputtering the upper electrode utilizing the
DCS technology. This coating technique increases the etch selectivity to EUV resist. In this technique, silane type
gases are not required, making it easily applicable to manufacturing.