Determination of the Internal Morphology of Nanostructures Patterned by Directed Self Assembly

Abstract

The directed self-assembly (DSA) of block copolymers (BCP) is an emerging resolution enhancement tool that can multiply or subdivide the pitch of a lithographically defined chemical or topological pattern and is a resolution enhancement candidate to augment conventional lithography for patterning sub-20 nm features. Continuing the development of this technology will require an improved understanding of the polymer physics involved as well as experimental confirmation of the simulations used to guide the design process. Both of these endeavors would be greatly facilitated by a metrology, which is capable of probing the internal morphology of a DSA film. We have developed a new measurement technique, resonant critical-dimension small-angle X-ray scattering (res-CDSAXS), to evaluate the 3D buried features inside the film. This is an X-ray scattering measurement where the sample angle is varied to probe the 3D structure of the film, while resonant soft X-rays are used to enhance the scattering contrast. By measuring the same sample with both res-CDSAXS and traditional CDSAXS (with hard X-rays), we are able to demonstrate the dramatic improvement in scattering obtained through the use of resonant soft X-rays. Analysis of the reciprocal space map constructed from the res-CDSAXS measurements allowed us to reconstruct the complex buried features in DSA BCP films. We studied a series of DSA BCP films with varying template widths, and the internal morphologies for these samples were compared to the results of single chain in mean-field simulations. The measurements revealed a range of morphologies that occur with changing template width, including results that suggest the presence of mixed morphologies composed of both whole and necking lamella. The development of res-CDSAXS will enable a better understanding of the fundamental physics behind the formation of buried features in DSA BCP films.

Combining theory and experiment for X-ray absorption spectroscopy and resonant X-ray scattering characterization of polymers

“…This has been demonstrated for self-assembled block copolymer thin films, where resonant criticaldimension small angle X-ray scattering combined with thorough data fitting reveal the specific domain morphology of vertical lamella through the film thickness [98,99].…”

Strategies for Inorganic Incorporation using Neat Block Copolymer Thin Films for Etch Mask Function and Nanotechnological Application

“…For example, Sunday et al . [ 226,227 ] reported a technique using resonant critical dimension small angle x-ray scattering (res-CDSAXS) to three-dimensionally characterize buried features of PS-b -PMMA lamellar fi lms in DSA schemes. The methodology has also been utilized to examine pattern transfer of a Cr-evaporated mask versus SIS infused features of a lamellar forming PS-b -PMMA BCP.…”

Resonant soft X-ray scattering for polymer materials

“…Figure 6d is an example of resonant CD-SAXS (res-CDSAXS) to study the internal structure of self-assembled block copolymer thin films. 57 By taking transmission scattering measurements at variable angles, the 2-D or 3-D reciprocal space map from nanostructured scatters can be constructed, which can be further used to resolve the complex buried features in the phase separated block copolymer.…”