He plasma pretreatment of organic masking materials for performance improvement during pattern transfer by plasma etching

Previous work on 193 nm photoresist (PR) material has shown that a significant improvement of pattern transfer performance can be obtained by applying a helium plasma pretreatment (PPT) prior to the pattern transfer plasma etching step [Weilnboeck et al., Appl. Phys. Lett. 99, 261501 (2011)]. This work explores whether this PPT is applicable to other organic masking materials commonly employed in resist multilayer masking schemes. The materials investigated include an antireflection coating, a thermally activated hard mask, a near frictionless carbon similar to a 248 nm PR, and an extreme ultraviolet resist. These materials have substantially different ultraviolet/vacuum ultraviolet sensitivity among each other and relative to 193 nm PR. The authors find that the surface roughness seen after a combination of helium PPT and Ar plasma main etching step is either the same or increased slightly relative to a single Ar main etching step, in contrast to 193 nm PR materials. The fragile adamantane group removed during PPT from 193 nm PR is absent for these materials. This indicates that the He PPT efficacy and improved pattern transfer performance is specific to adamantane containing resists.