Synthesis of High Etch Contrast Poly(3-hydroxystyrene)-Based Triblock Copolymers and Self-Assembly of Sub-5 nm Features

Abstract

We demonstrate the successful synthesis of a series of poly­(3-hydroxystyrene)-block-poly­(dimethylsiloxane)-block-poly­(3-hydroxystyrene) (P3HS-b-PDMS-b-P3HS) triblock copolymers by atom transfer radical polymerization (ATRP). This system is a promising candidate for pattern transfer of single-digit nanometer features, due to its intrinsic high etch contrast, etch versatility, and the triblock architecture. Hydroxy-terminated PDMS polymers were directly functionalized to initiate the ATRP of an acetal-protected 3-hydroxystyrene monomer. The resulting triblocks have dispersity ranging from 1.10 to 1.26, and the synthesis provides robust control over molecular weights and volume fractions. The large chemical incompatibility between the blocks enabled the formation of ordered structures at low molecular weights, which yielded lamellar periodicities as small as 9.3 nm. This triblock hence permits access to sub-5 nm feature sizes. The phase diagram is asymmetric, with lamellar morphologies observed at lower volume fractions of the P3HS block, relative to the diblocks. This asymmetry is ascribed to the dispersity of the middle block relative to the end blocks.

Morphology Control of Perpendicularly Oriented Lamellar Films from Azobenzene-Containing Block Copolymers with Different Spacer Lengths

“…12 As is reported that the morphology of self-assembled lamellar domains is mainly sensitive to the BCP molecular structure and self-assembly process. 13 In addition, the BCP molecular structure is significantly affected by the Flory−Huggins interaction parameter (χ), 14 the volume fraction of the components ( f), 15 the degree of polymerization (N), 16 and the overall molecular weight. The relationship of the morphology, the BCP molecular structure, and the thin film self-assembly process gives an insight into pragmatic approaches for engineering the connectivity, etch selectivity, and orientation of lamellar domains.…”

Heterotelechelic homopolymers mimicking high χ – ultralow N block copolymers with sub-2 nm domain size

“…27 The movement towards using block copolymers to obtain the smallest domain spacings has established a class of "high  -low N" block copolymers in which N is minimised to reduce domain size, whilst  is maximised to retain a block interaction parameter capable of microphase separation despite the entropic penalty associated with demixing. Balancing these factors to maintain a sufficiently high value of N to enable self-assembly has led to sub-5 nm [28][29][30] and sub-3 nm 31,32 feature sizes. Low N block copolymers that maintain N ≥ 10.5 often contain a very hydrophobic part that can incorporate siliconised, fluorinated or styrenic groups (within the backbone [33][34][35] or side chain 30,[36][37][38] ) combined with a hydrophilic/ionic block.…”

“…Balancing these factors to maintain a sufficiently high value of χN to enable self-assembly has led to sub-5 nm (ref. 28–30) and sub-3 nm (ref. 31 and 32) feature sizes.…”

Fabrication of Ultrafine, Highly Ordered Nanostructures Using Carbohydrate-Inorganic Hybrid Block Copolymers

“…Organic–inorganic hybrid materials, which exhibit distinct properties due to the presence of both organic and inorganic components, have emerged as high-performance materials with a wide range of potential applications in a variety of fields [ 1 , 2 , 3 , 4 , 5 ]. Organic–inorganic hybrid block copolymers (BCPs) in particular have garnered considerable interest due to the fact that microphase separation enables the ordered periodic arrangement of organic and inorganic domains at the nanoscale [ 3 , 5 , 6 , 7 ]. Depending on the volume fraction of each block, it is possible to arrange not only alternating organic and inorganic layers in a lamellar (LAM) pattern but also in more complex patterns such as hexagonal cylinder, gyroid (GYR), and body-centered cubic sphere [ 8 ].…”

“…To overcome this constraint, the enhancement of χ is required, and indeed, numerous research groups have demonstrated microphase-separation from so-called “high χ /low N ” BCPs, resulting in ordered morphologies with d of less than 10 nm. Thus far, silicon-containing [ 3 , 5 , 6 , 7 , 10 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], metal-doped [ 31 , 32 , 33 ], and oligosaccharide-based BCPs [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] have been developed. The high χ /low N BCP strategy is now widely accepted as a standard method for obtaining smaller d , although several novel approaches have emerged recently [ 19 , 34 , 35 , 40 , 49 ,…”