Directed assembly of block copolymers using chemically and topographically patterned substrates to control and direct the order of various nanodomains

As an alternative to conventional photoresists, the morphologies of block copolymers have been studied for nanofabrication that can be applicable to the semiconductor industry. The microphase-separated domains of block copolymers provide well-ordered structures with nanometer length scales. Block copolymer lithography, referring to the use of these structures in the form of thin films as a template for pattern transfer, is able to be inexpensive, simple, and scalable for producing densely periodic arrays of nanostructures. Previous applications of block copolymer lithography have been limited to the fabrication of devices that do not require perfect ordering of block copolymer domains such as silicon capacitors, nanowires, and quantum dots. Recent advanced applications will require the control of the order and orientation of block copolymer domains to create desired structures. Here we demonstrate strategies to generate defect-free arrays of block copolymer domains using graphoepitaxial techniques and directed assembly on chemically nanopatterned surfaces.; Examples of our work include as below; A lamellae-forming poly(styrene- block-methyl methacrylate), (PS-b-PMMA) block copolymer that was directed to assemble parallel to topographic surfaces, consisting of grooves with gold sidewalls and polymer brush-coated bottoms that exhibited preferential and neutral wetting behavior towards the blocks of copolymer, respectively. These substrates directed the assembly of vertically oriented lamellae aligned to the groove edge. In order to explore the ultimately complex geometries that can be assembled, generation and replication of non-defined patterns were carried out using lamellae-forming block copolymers. This approach to generating a chemical pattern is combinatorial in the sense of generation of a large number and variety of pattern features in one sample. For quantitative assessment of block copolymer pattern replication, computer vision technique was used. Cylinder-forming PS-b-PMMA thin films were directed to assemble on chemically nanopatterned surfaces consisting of a hexagonal and square array of spots that were preferentially wet by the PMMA block. On this chemical pattern, cylindrical domains oriented perpendicular to the surfaces and formed a hexagonal and square array of vertical cylinders. Lastly, noble three-dimensional structures were demonstrated using sphere-forming diblock copolymer on chemically striped patterned surface.