Investigating block co-polymers
Argonne researchers in partnership with the University of Chicago’s Institute for Molecular Engineering are investigating the three dimensional structure of Block Co-Polymers (BCP). Understanding and controlling the three-dimensional structure of BCP thin films is critical for utilizing these materials for sub-20 nm nano-patterning in semiconductor devices, as well as in membranes and solar cell applications.
The interdisciplinary team from the Materials Science Division (MSD), Energy Systems Division (ES) and Center for Nanoscale Materials (CNM) are using the resources available at the CNM and the Laboratory Computing Resource Center (LCRC) for its research.
Combining an atomic layer deposition (ALD) based technique for enhancing the contrast of BCPs in transmission electron microscopy (TEM) together with scanning TEM (STEM) tomography reveals and characterizes the three-dimensional structures of poly(styrene-block-methylmethacrylate) (PS-b-PMMA) thin films with great clarity.
Sequential infiltration synthesis (SIS), a block-selective technique for growing inorganic materials in BCPs films in ALD tool, and an emerging tool for enhancing the etch contrast of BCPs, was harnessed to significantly enhance the high-angle scattering from the polar domains of BCP films in the TEM.
The power of combining SIS and STEM tomography for three dimensional (3D) characterization of BCPs films was demonstrated with the following cases: self-assembled cylindrical, lamellar, and sp herical PS-PMMA thin films. In all cases, STEM tomography has revealed 3D structures that were hidden underneath the surface, including: 1) the 3D structure of defects in cylindrical and lamellar phases, 2) nonperpendicular 3D surface of grain boundaries in the cylindrical phase, and 3) the 3D arrangement of spheres in body centered cubic (BCC) and hexagonal closed pack (HCP) morphologies in the spherical phase. The 3D data of the spherical morphologies wa s compared to coarsegrained simulations and assisted in validating the simulations’ parameters. STEM tomography of SIStreated BCP films enables the characterization of the exact structure used for pattern transfer, and can lead to better understating of the physics which is utilize d in BCP lithography.
Tamar Segal-Peretz, Jonathan Winterstein, Manolis Doxastakis, Abelardo Ramirez, Hernandez, Mahua Biswas, Jiaxing Ren, Hyo Seon Suh, Seth B Darling, J. Alexander, Liddle, Jeffrey W. Elam, Juan J. de Pablo, Nestor J. Zaluzec and Paul F Nealey, “Characterizing the Three-Dimensional Structure of Block Co-Polymers via Sequential Infiltration Synthesis and Scanning Transmission Electron Tomography,” ACS Nano, Just Accepted Manuscript. DOI: 10.1021/acsnano.5b01013. Published April 28, 2015.