Polarity-switching photopatternable guidelines can be directly used to both orient and direct the self-assembly of block copolymers. We report the orientation and alignment of poly(styrene-block-4-trimethylsilylstyrene) (PS-b-PTMSS) with a domain periodicity, L0, of 44 nm on thin photopatternable grafting surface treatments (pGSTs) and cross-linkable surface treatments (pXSTs), containing acid-labile 4-tert-butoxystyrene monomer units. The surface treatment was exposed using electron beam lithography to create well-defined linear arrays of neutral and preferential regions. Directed self-assembly (DSA) of PS-b-PTMSS with much lower defectivity was observed on pXST than on pGST guidelines. The study of the effect of film thickness on photoacid diffusion by Fourier transform infrared spectroscopy and near-edge X-ray absorption fine structure spectroscopy suggested slower diffusion in thinner films, potentially enabling production of guidelines with sharper interfaces between the unexposed and exposed lines, and thus, the DSA of PS-b-PTMSS on thinner pXST guidelines resulted in better alignment control.
Bibliographical noteFunding Information:
The authors thank Nissan Chemical Industries, Lam Research, the ASTC, and the National Science Foundation Nanomanufacturing Systems for mobile Computing and Energy Technologies (NASCENT) (Grants EECS-1120823 and EEC-1160494) for financial support. P.L. thanks the National Science Foundation Graduate Research Fellowship for financial support. M.J.M. thanks the IBM Ph.D. Fellowship Program and the National Science Foundation Graduate Research Fellowship (Grant No. DGE-1110007) for financial support. G.B. thanks the Paul D. Meek Endowed Graduate Fellowship in Engineering for support. C.J.E. thanks the Welch Foundation (grant #F-1709) for partial financial support. C.R.B. thanks the Welch Foundation (grant #F-1891) and the National Science Foundation (CHE-1847199) for financial support. C.G.W. thanks the Rashid Engineering Regents Chair and the Welch Foundation (Grant #F-1830) for financial support. The authors also thank the Advanced Light Source, Lawrence Berkeley National Laboratory. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. R.J.K. and D.F.S. thank the National Institute of Standards and Technology for financial support. The authors thank Subhrangsu Mukherjee for assistance with the etching of the wafers for NEXAFS measurements and Eric Gullikson for assistance with setting up NEXAFS measurements. The authors also thank Drs. Dustin Janes, Lisa Lofano, Hoa Truong, Amy Bowers, and Christopher Soles for their insightful ideas, Alison Pawlick from Oak Ridge National Laboratory for initial AFM-IR measurements, and Ron Synockwicki from J. A. Woollam for initial ellipsometry patterning measurements.
- NEXAFS spectroscopy
- block copolymers
- directed self-assembly
- infrared spectroscopy
- photoacid diffusion
- thin films