@article{Self-Assembly:1987,
      recid = {1987},
      author = {Dolejsi, Moshe},
      title = {New Methods and Materials for Directed Self-Assembly of  Block Copolymers},
      publisher = {University of Chicago},
      school = {Ph.D.},
      address = {2019-08},
      pages = {148},
      abstract = {Directed Self-Assembly (DSA) is a promising strategy for  quickly and cheaply manufacturing nanoscale features. DSA  leverages the natural nanoscale phase separation of  materials, which are guided by lithographically defined  precise chemical cues. Polystyrene block  polymethylmethacrylate (PS-b-PMMA) is ubiquitous for DSA,  as the blocks possess equal surface free energy, and a  random copolymer brush of the two blocks presents a  balanced substrate surface both of which are a necessary  prerequisite for achieving through film structures. In a  standard process, PS guide stripes at pitches of 70-90 nm,  are backfilled with a brush to direct PS-b-PMMA to form  features down to ~24 nm pitch (3x density multiplication).  In chapter 2, we show how metal – polymer interactions can  be used in place of polymer – polymer interactions to  provide the necessary chemical cues for DSA. This enables a  new kind of self-aligned process in which a patterning  layer is thermodynamically driven to align precisely not  with a lithographically defined guide or mandrel, but  instead with an existing metal – dielectric pattern on an  underlying layer. Next in chapter 3, we turn to the DSA  hole shrink process, where great effort has been expended  to use various wet processes to selectively modify the  sidewall and bottoms of lithographically defined template  holes to provide the proper chemical cues. Here we  demonstrate that ultraconformal initiated chemical vapor  deposition (iCVD) can be used as a drop in replacement to  conventional wet processes. Finally we turn towards the  material itself. The repulsion between PS and PMMA,  quantified by the Flory Huggins parameter χ, is too low to  achieve sub 24 nm pitch features. Increasing the χ often  goes hand in hand with increasing differences in surface  free energy, which can be ameliorated only by additional  complex processing involving top coats or solvent  atmospheres. A further complication is that if the product  of χ and the polymer size, N, is too high, defects become  trapped. Thus for each pitch desired, there exists a range  of acceptable χ. One method to sidestep these limitations  is by engineering the polymer microstructure such that  these fundamental relationships might be changed. Chapter  4, studies the fundamental physics underlying graft polymer  architecture in thin film confinement. Here we discovered  substrate interactions can shift materials from perfectly  symmetric lamella to cylindrical morphologies. A second  method is the use of A-b-(B-r-C) architectures. Chapter 5,  outlines a high throughput process to use click chemistry  to modify a common platform polystyrene block  polybutadiene, to rapidly achieve multiple materials with  differing χ, each of which has equal surface energies and  is fully compatible with DSA flows. Second we expand to a  new platform polystyrene block polyglyicdyl methacrylate  which we demonstrate is suitable not just for DSA of 16 nm  full pitch features, but can also serve as its own  non-preferential brush enabling new self-brushing DSA  processes, and can even be modified with etch resistance  through the incorporation of silicon. As a result DSA is no  longer material limited, and is now enabled for a near  infinite diversity of chemistry, providing the potential  for further optimization.},
      url = {http://knowledge.uchicago.edu/record/1987},
      doi = {https://doi.org/10.6082/uchicago.1987},
}