Sub-10 nm Silicon Nanopillar Fabrication Using Fast and Brushless Thermal Assembly of PS-b-PDMS Diblock Copolymer

Abstract

A new approach to obtaining spherical nanodomains using polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is proposed. To reduce drastically the process time, we blended a copolymer with cylindrical morphology with a PS homopolymer. Adding PS homopolymer into a low-molar-mass cylindrical morphology PS-b-PDMS system drives it toward a spherical morphology. Besides, by controlling the as-spun state, spherical PDMS nanodomains could be kept and thermally arranged. This PS-homopolymer addition allows not only an efficient, purely thermal arrangement process of spheres but also the ability to work directly on nontreated silicon substrates. Indeed, as shown by STEM measurements, no PS brush surface treatment was necessary in our study to avoid a PDMS wetting layer at the interface with the Si substrate. Our approach was compared to a sphere-forming diblock copolymer, which needs a longer thermal annealing. Furthermore, GISAXS measurements provided complete information on PDMS sphere features. Excellent long-range order spherical microdomains were therefore produced on flat surfaces and inside graphoepitaxy trenches with a period of 21 nm, as were in-plane spheres with a diameter of 8 nm with a 15 min thermal annealing. Finally, direct plasma-etching transfer into the silicon substrate was demonstrated, and 20 nm high silicon nanopillars were obtained, which are very promising results for various nanopatterning applications.

Au Nanospirals Transferred onto PDMS Film Exhibiting Circular Dichroism at Visible Wavelengths

“…The block copolymer PS-PDMS (P6194-SDMS Mn:47100-b-9000, Polymer Source Inc, Dorval, QC, Canada) and a hydroxy-terminated PS (P2996-SOH, Polymer Source Inc, Canada) were used for the fabrication of the nanodot template. The self-assembly of block copolymers is often used to fabricate nanosized large-area periodic nanostructures such as a nanodot array [ 29 , 30 , 31 , 32 ]. In particular, PS-PDMS is adopted in this work because it is advantageous for the fabrication of smaller dot patterns such as on the 10 nm scale [ 29 , 31 ].…”

“…After baking, the excess PS that did not form a covalent bond was removed by rinsing with PGMEA. Consequently, the surface of the Si substrate was coated with a thin layer of PS [ 29 ]. On this substrate, 1 wt % PS-PDMS dissolved in PGMEA was spin coated at 1500 rpm for 30 s ( Figure 3 (3)) and baked at 150 °C for 30 min in an oven.…”

“…The separated PDMS aggregated to form spheres. The size of the PDMS sphere depends on the ratio of PS and PDMS [ 29 , 31 ]. After the separation process, the surface of this film was covered by several nanometer-thick PDMS film because PDMS has the low surface energy [ 31 ], and the PDMS spheres were beneath this thin film ( Figure 3 (4)).…”

Thin film confinement reduces compatibility in symmetric ternary block copolymer/homopolymer blends

“…Blending the BCP with its constituent homopolymers provides a route to tuning BCP morphology and nanostructure domain size without changing f or N . In addition, blending has been shown to improve long‐range order and processing conditions of BCP nanostructures …”

“…11,12 The morphologies of linear diblock copolymers (diBCPs) at sufficiently high segregation strengths (χN, product of the Flory-Huggins interaction parameter and the number of repeating units) are dictated by the block volume fraction (f ) whereas the characteristic dimensions of the morphology are primarily governed by N. [13][14][15] Blending the BCP with its constituent homopolymers provides a route to tuning BCP morphology and nanostructure domain size without changing f or N. [16][17][18][19] In addition, blending has been shown to improve long-range order and processing conditions of BCP nanostructures. [20][21][22][23] The phase behavior of ternary blends consisting of a lamellaeforming symmetric diBCP and corresponding homopolymers is influenced by the ratio of homopolymer to BCP length (given by α = N H /N BCP ) and the overall volume fraction of homopolymer (Φ H ) in the blend. 24,25 The ternary blend system can be examined by adding homopolymer (Φ H ) into the BCP such that overall composition of the blend remains the same as that of the pristine BCP.…”