Mechanistic understanding of post-etch roughness in 193-nm photoresists

Abstract

Surface roughness of 193 nm resists after a dry etch process is one of the critical issues in the implementation of 193 nm lithography to sub-100 nm technology nodes. Compared to commercial 248 nm resists, 193 nm photoresists exhibit significant roughness especially under the etch conditions for dielectrics, such as silicon dioxide and silicon nitride. While AFM analysis of DUV resists exhibit the mean roughness (R a ) of ~1 nm after blanket oxide etch, R a 's of 193 nm resists were found to be in the range of 4 to 7 nm depending on the chemical structure of the resist backbone. In an effort to develop 193 nm resists with improved post-etch roughness (PER), we carried out exhaustive screening of the available 193 nm resist platforms using bulk oxide etch followed by AFM analysis of the resist surface. Benchmarking results indicated that cyclic olefin copolymers, prepared by vinyl addition copolymerization of norbornene derivatives, exhibit significantly better PER than (meth)acrylic copolymers, cyclic olefin/maleic anhydride (COMA) copolymers, or COMA/(meth)acrylic copolymers (COMA hybrid). In this paper, are addressed various factors that influence PER of 193 nm resists and presented solutions to overcome etch inferiority with 193 nm resists for the real device fabrication.

Ion and Vacuum Ultraviolet Photon Beam Effects in 193 nm Photoresist Surface Roughening: The Role of the Adamantyl Pendant Group

“…It is worth noting that the degree of surface roughening of 193 nm PR processed at 65 °C (Figure 3e) is comparable to that after argon plasma treatment with similar ion and VUV fluence, ∼3.5 nm 22. The severe roughening of p‐MAMA is also consistent with reports from plasma experiments 5, 15, 28. Moreover, VUV‐only or ion‐only exposures do not give the same degree of surface roughness.…”

“…While VUV photons can apparently play a role in both roughening and smoothing PRs, its synergism with other plasma‐generated species and the mechanisms associated with the resulting polymer texture are not well understood. Moreover, plasma experiments have shown that poly‐(2‐methyl‐2‐adamantyl methacrylate) (p‐MAMA), which is the leaving group in 193 nm PR, tends to roughen more compared to 193 nm PRs and associated model copolymers 5, 15, 28, 29. Surface roughening rate of adamantyl PR was correlated to deposited energy density during plasma processes 30.…”

Transistor gate line roughness formation and reduction in sub-30-nm gate patterning using multilayer hard mask structure

“…1 However, the photoresist (PR) for a shorter wavelength has to be thinner and softer with respect to the dry etch process because the shorter wavelength has a higher opacity and a lower depth of focus. [6][7][8] With aggressive scaling of complementary metal oxide semiconductor (CMOS) technology, line width roughness (LWR) is increasingly becoming a larger component of the total variation because it does not scale down with device dimensions. 3,4 With increasingly scaling line width, the PR height has to be thinner to maintain the AR at an appropriate value 5 so that a successful patterning can be expected for sub-30 nm and beyond nodes.…”