Self-assembled block copolymer (BCP) thin films necessarily require a distinct chemical contrast between the blocks (or microdomain homogeneity) for the purpose of high-resolution pattern transfer applications. Despite its importance, however, there has been difficulty in measuring the chemical distribution associated with the self-assembling processes, i.e. solvent vapor annealing (SVA) or thermal annealing (TA). Herein, we present a simple yet effective method to probe the chemical distribution over polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films that underwent the SVA or SVA + TA processes. An IR nanospectroscopy using scattering-type scanning near-field optical microscopy (s-SNOM), in concert with X-ray scattering analyses, provides the relative chemical concentration of the perpendicular lamellar patterns. The chemical mapping for the components based on the s-SNOM reveals that the SVA process leaves a considerable portion of the intermixed zones of PS and PMMA blocks, whereas the subsequent TA process facilitates the chain segregation towards high-contrast chemical distribution. Interestingly, such a microdomain homogeneity critically affects the quality of the unidirectional Al2O3 lines that were substituted from topographically guided lamellae. Our results substantiate an important insight into understanding the chain redistribution behavior in the self-assembled BCP films using non-destructive s-SNOM technique.
|Publication status||Published - 2021 Dec|
Bibliographical noteFunding Information:
W. Lee and J. Kim contributed equally to this work. W.L. mainly wrote manuscript, prepared the BCP samples, and carried out X-ray scattering analyses. J.K. performed investigation on surface chemical distribution by s-SNOM and data post-processing. GISAXS (beamline 4C and 9A) and s-SNOM (beamline 12D IRS) were measured at Pohang Light Source-II, Korea. This work was supported by the NRF grants ( 2021R1A2C2006588 , 2020R1F1A1054198 ) funded by the Ministry of Science, ICT & Future Planning (MSIP), Korea .
© 2021 The Authors
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics