Controlled solvent vapor annealing of a high χ block copolymer thin film

Abstract

Molecular self-assembling block copolymers (BCPs) have shown promise as a next generation bottom-up lithography technology. However, a critical step in advancing this approach is the elimination of polymer dewetting due to bulk solvent nucleation and thermodynamically driven film rupture that can occur during the solvent vapor annealing process. We report on the pattern formation via phase segregation of spin coated diblock copolymer films through the investigation of annealing parameters in the limit of high solvent vapor saturation conditions that results in wafer-scale patterning without observing polymer dewetting defects. Specifically, the work addresses polymer dewetting in diblock copolymer nanodot templates through the use of a "neutral" functionalization layer and the development of a custom-built solvent vapor annealing chamber to precisely control saturation conditions. Furthermore, the long anneal times (4 h) using a standard static solvent vapor annealing procedure were reduced to ∼15-30 minutes with our dynamic solvent vapor annealing system for the high χ, cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) [PS-b-P4VP] diblock copolymer system. We discuss the kinetic mechanism governing the phase segregation process that highlights the small processing window bounded by long phase segregation timescales (≳1 min) on one side and the initiation of polymer film dewetting on the other. These results demonstrate a key step towards realizing a high fidelity, low cost BCP patterning technique for large-scale "bottom-up" feature definition at nanometer length scales.

Design and Testing of a Bending‐Resistant Transparent Nanocoating for Optoacoustic Cochlear Implants

“…The sample consistently displayed grooves with a depth of approximately two nanometers, and a general reduction of surface roughness (Figure i). Interestingly, similar patterns are often observed after exposing block copolymer films to solvents or vapours with significantly different affinity for the various blocks . It could be hypothesized then that the structure observed here arises from the surface microphase separation of hydrophilic PEO and hydrophobic PDMS domains in the top layer of the material, covalently bound but still retaining significant mobility.…”

“…Interestingly, similar patterns are often observed after exposing block copolymer films to solvents or vapours with significantly different affinity for the various blocks. [35][36][37] It could be hypothesized then that the structure observed here arises 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 from the surface microphase separation of hydrophilic PEO and hydrophobic PDMS domains in the top layer of the material, covalently bound but still retaining significant mobility. It should also be noted that the flattening observed for the aged coating could be beneficial to its antifouling performance, since surface roughness has been sometimes associated with improved cell adhesion.…”

Polymer porous thin films obtained by direct spin coating

“…For complete control of rapid and efficient methods for ordering block copolymers, the present work represents an effort to obtain nanoporous thin films (and other nanostructures) in a simple way. These results seem particularly interesting considering that there are defect‐tolerant applications of block copolymer films …”

Perpendicularly aligned nanodomains on versatile substrates via rapid thermal annealing assisted by liquid crystalline ordering in block copolymer films

“…[16][17][18][19] Solvent or thermal annealing as a posttreatment is necessary to determine the orientation and alignment of BCP microdomains. [20][21][22][23][24] In industry, thermal annealing is preferred because it avoids the use of solvents and the associated problems, such as dewetting and corrosion. 25 Moreover, the thermal annealing time is relatively shorter, so it can match the requirements of industrial processes.…”