Self-Assembly of Block Copolymers for Nanopatterning

The impressive developments in the semiconductor industry over the past five decades have largely been dependent on the ability to continually reduce the dimensions of devices on a chip. However, as critical dimension requirements for these devices approach the limits of photolithography, new fabrication strategies must be introduced for these remarkable advances to continue. One technology listed by the International Technology Roadmap for Semiconductors as a candidate for next-generation nanostructure fabrication is the directed self-assembly of block copolymers. Block copolymers have received significant attention of late for their ability to template large regular arrays of nanostructures with dimensions ranging from 10 to 50 nm. The production of denser sub-10 nm nanostructures is also possible by reducing the size of these polymers, but a reduction of the polymer size also compromises the quality of nanostructures, making small polymers extremely difficult to use.;Besides using bilayer films, dense arrays of nanostructures may also be patterned using a multi-step patterning approach. In this approach, multiple layers of block copolymer films are subsequently deposited onto the substrate to template nanostructures. Because nanostructures from previous layers contribute to the surface topography, they influence the self-assembly of successive layers and more dense and complex patterns may be produced as a result.;In this thesis, two different patterning approaches are introduced to push the nanostructure density limits possible for a given polymer. In the first, a novel patterning approach involving thin films of bilayer block copolymer domains is used to effectively double the nanostructure density patterned by a given polymer. The technique is successfully applied to different types and sizes of polymer, and can also form highly controlled arrays of patterns with the help of surface topography. By varying different process parameters during the self-assembly or subsequent plasma steps, the dimensions of these density-doubled patterns may be finely-tuned to the desired width and pitch. The surface coverage of these density-doubled nanostructures is also maximized through adjusting the film thickness and parameters in the self-assembly process.