@article{Nanostructures:1792,
      recid = {1792},
      author = {Zhou, Chun},
      title = {Self-Assembly of Block Copolymer Thin Films for  Fabricating Tailored Nanostructures},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2019-06},
      pages = {142},
      abstract = {Block copolymers (BCPs) self-assemble into periodic arrays  of lamella, cylinders, spheres and gyroids with  characteristic feature sizes of 3-100nm, making them ideal  for fabrication of nanostructured materials. For many  applications including separation membranes and  nanopatterning, it is necessary to use block copolymer in  thin film geometries and with domain orientations  perpendicular to substrates. Chapter 2 discusses the  effects of surface and interfacial energy on the  self-assembly of PS-cylinder forming PS-b-PMMA thin films.  These are less studied than the standard PMMA-cylinder  forming BCPs. We explore using this BCP as a sacrificial  template for the formation of nanoporous metal oxide films  with tunable pore sizes. The fabricated nanoporous membrane  is transferred onto a macroporous support for protein  separation studies.  

Directed self-assembly (DSA) of BCPs  utilizes topographic or chemical contrast guide patterns to  provide long-range orientational order. DSA has great  potential for next generation lithography as it enables low  processing cost and feature density multiplication.  Defectivity is the biggest challenge for moving DSA into  high-volume manufacturing. Current defectivity studies  reply on surface or cross-sectional 2D metrologies. These  data are not enough to describe the 3D nature of DSA  morphologies and probe hidden defects under the surface. In  chapter 3, we describe a 3D metrology for graphoepitaxial  DSA contact-hole shrink process (to make vias) using the  post-DSA membrane fabrication technique and STEM  tomography. The 3D reconstruction results reveal  relationships between guide patterns of different surface  chemistry and geometry and types of defects in DSA  morphologies.

In addition to patterning contacts using  graphoepitaxial patterns, DSA using chemoepitaxial patterns  is a very effective technology for line/space patterning  over large area. It is of particularly interest in bit  patterned media (BPM) applications. In BPM, an areal  density of 5 Tb/in¬2 corresponds to an 11 nm bit pitch  size, which is a huge challenge for any existing  lithography techniques. Chapter 4 investigates the  combination of two commonly used pitch splitting  techniques: DSA and self-aligned double patterning (SADP)  to reach a total density multiplication factor of 8.  Starting from guiding lines with 84 nm pitch, a final  line/space pattern with pitch as small as 10.5 nm is  demonstrated. This combined DSA and SADP strategy could  avoid many sacrificial layers and etch/deposition steps to  reach the same aggressive pitch scaling compared to  self-aligned octuplet patterning (SAOP).

While DSA is  approaching maturity for use in the semiconductor industry,  researchers can develop high-resolution nanofabrication  using DSA technology to solve problems in the condensed  matter physics community. One revolutionary idea is to  control the thermal transport by periodic nanostructures,  or phononic crystal patterning. Chapter 5 describes the  approach to fabricate DSA templated phononic crystal  devices which have well-defined hexagonal packed holes with  38 nm pitch in suspended silicon nitride bridges. A great  reduction in thermal conductivity is observed from  thermoreflectance measurements. This work has applications  into novel thermoelectric devices and highly sensitive  bolometric radiation detectors.},
      url = {http://knowledge.uchicago.edu/record/1792},
      doi = {https://doi.org/10.6082/uchicago.1792},
}