Nanoscale silicon substrate patterns from self-assembly of cylinder forming poly(styrene)-block-poly(dimethylsiloxane) block copolymer on silane functionalized surfaces

Abstract

Poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) is an excellent block copolymer (BCP) system for self-assembly and inorganic template fabrication because of its high Flory-Huggins parameter (χ ∼ 0.26) at room temperature in comparison to other BCPs, and high selective etch contrast between PS and PDMS block for nanopatterning. In this work, self-assembly in PS-b-PDMS BCP is achieved by combining hydroxyl-terminated poly(dimethylsiloxane) (PDMS-OH) brush surfaces with solvent vapor annealing. As an alternative to standard brush chemistry, we report a simple method based on the use of surfaces functionalized with silane-based self-assembled monolayers (SAMs). A solution-based approach to SAM formation was adopted in this investigation. The influence of the SAM-modified surfaces upon BCP films was compared with polymer brush-based surfaces. The cylinder forming PS-b-PDMS BCP and PDMS-OH polymer brush were synthesized by sequential living anionic polymerization. It was observed that silane SAMs provided the appropriate surface chemistry which, when combined with solvent annealing, led to microphase segregation in the BCP. It was also demonstrated that orientation of the PDMS cylinders may be controlled by judicious choice of the appropriate silane. The PDMS patterns were successfully used as an on-chip etch mask to transfer the BCP pattern to underlying silicon substrate with sub-25 nm silicon nanoscale features. This alternative SAM/BCP approach to nanopattern formation shows promising results, pertinent in the field of nanotechnology, and with much potential for application, such as in the fabrication of nanoimprint lithography stamps, nanofluidic devices or in narrow and multilevel interconnected lines.

Review—Recent Advances in Block-Copolymer Nanostructured Subwavelength Antireflective Surfaces

“…(BCP) films deposited by solution-processing techniques 41 can selfassemble into microphase-separated arrays, providing well-defined periodic nanostructured surfaces over large areas and with a remarkable compatibility with both the substrate material and geometry. 46,47 The characteristics of each block composing the BCP, including their Flory-Huggins interaction parameter (χ), their degree of polymerization (N), and their volume fraction (f A ), enable a range of microphase separation regimes that can be observed both theoretically and experimentally. 49 Segregation of the different blocks composing the BCP into well-controlled microdomains may be influenced via a few parameters including the BCP-substrate interaction, the film thickness, the temperature and the solvent (Figure 2a).…”

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

“…The transfer of (flexible [237]) surface relief patterns on graphene [234,237] or other solid, often functionalized [239], substrates [206,240] can be done by employing additional etching or infiltration [233,238,241] procedures, which is followed by the controlled deposition of thin films of various materials [205,241,242], including metals [243] and metal oxides [244]. Examples of etching procedures include UV ozone [243], oxygen [241,243], nitrogen [241], or other types [239,241] of plasma etching, CO 2 and Cl 2 /O 2 reactive ion etching [205], etching in alkaline solutions [204]), etc.…”

“…The transfer of (flexible [237]) surface relief patterns on graphene [234,237] or other solid, often functionalized [239], substrates [206,240] can be done by employing additional etching or infiltration [233,238,241] procedures, which is followed by the controlled deposition of thin films of various materials [205,241,242], including metals [243] and metal oxides [244]. Examples of etching procedures include UV ozone [243], oxygen [241,243], nitrogen [241], or other types [239,241] of plasma etching, CO 2 and Cl 2 /O 2 reactive ion etching [205], etching in alkaline solutions [204]), etc. As a result, BCP templates made from materials such as poly(cyclohexylethylene)-b-poly(lactide) [242], polystyrene-b-poly(2vinyl pyridine) [233,245], polystyrene-b-polymethyl methacrylate [238,246], polystyreneb-polydimethylsiloxane [239,247,248], or others [205] lead to the fabrication of a large variety of versatile surface relief patterns of different material nature.…”

“…Examples of etching procedures include UV ozone [243], oxygen [241,243], nitrogen [241], or other types [239,241] of plasma etching, CO 2 and Cl 2 /O 2 reactive ion etching [205], etching in alkaline solutions [204]), etc. As a result, BCP templates made from materials such as poly(cyclohexylethylene)-b-poly(lactide) [242], polystyrene-b-poly(2vinyl pyridine) [233,245], polystyrene-b-polymethyl methacrylate [238,246], polystyreneb-polydimethylsiloxane [239,247,248], or others [205] lead to the fabrication of a large variety of versatile surface relief patterns of different material nature. Examples include (metal) nanodots [240,249,250], bimetallic NP arrays [251], perovskite cylinders, lamellae or cylindrical mesh [245], 2D metal/silicon nanowires [206,249], metal oxide arrays [242] of nanorods [244] or nanorings [243], and more [205,252].…”