Block copolymers resist self-assembly

Block co-polymers Self-assembled mask Parallel, fast, small size, no resist, solvents, etc. Material constraints, no long-range order, cleanliness New amphiphilic, diblock copolymers, multifunctional structures... 

In [55] a large-area fabrication of hexagonally ordered metal dot arrays with an area density of 10u/cm2 was demonstrated. The metal dots were produced by an electron beam evaporation followed by a lift-off process. The dots size was 20 nm dots with a 40 nm period by combining block copolymer nanolithography and a trilayer resist technique. A self-assembled spherical-phase block copolymer top layer spontaneously generated the pattern, acting as a template. The pattern was first transferred to a silicon nitride middle layer by reactive ion etch, producing holes. The nitride layer was then used as a mask to further etch into a polyamide bottom layer. 

Block copolymer self-assembly provides an elegant, cheap, and environmentally sustainable way to produce mesoporous templates. After adoption of an appropriate nanomorphology during phase separation the selective removal of one block yields the desired mesoporous template. In the past few years, a number of experimental protocols on the selective degradation of one copolymer component have been reported, see Table 1.1. Of particular interest are systems containing poly(styrene), since it is cheap, cross-linkable, chemically resistant against most bases and acids. 

A chemical pattern with precise surface chemistry and well-defined lateral dimension is a necessary platform to further advance the understanding of the self-assembly of block copolymer on the chemical patterns as well as improve the self-assembly quality. Nealey and his group developed a technique to generate chemical prepattems based on a lithographically defined resist strucmre and subsequent plasma surface modification. For example, a well-defined chemical prepattem was accomplished by first grafting PS-r-PMMA bmshes to a silicon substrate, covering it with an EUV resist (PMMA), and then creating a stripe pattern in the photoresist by EUV interference... 

Alternatively, ID brush-like templates for the synthesis of organic-inorganic hybrids have been fabricated by self-assembly of amphiphilic block copolymers in selective solvent and subsequent cross-linking. The cross-linking procedure is necessary to convert the block copolymer assemblies into permanent structures resistant to either disassembly or morphological transitions. These structures have the... 

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