Directed self-assembly of block copolymers and ternary block copolymer/homopolymer blends on chemically patterned surfaces into device-oriented geometries

The future of many applications at the nanoscale, for example in microelectronics, rests upon the ability to produce well-defined patterns with nanometer precision. The conventional method of patterning devices at these length scales involves photolithography, however, significant difficulties are encountered as the critical dimensions are reduced to sub-50 nm. An emerging approach to nanofabrication is the integration of self-assembling materials into existing manufacturing strategies so as to simultaneously achieve molecular-level process control and the ability to produce useful architectures. Diblock copolymers are promising self-assembling materials that in thin films form ordered nanostructures, including spheres, cylinders, and lamellae, whose shape and dimensions depend on the molecular weight and composition of the polymer. Prior application of block copolymer structures have been limited to the fabrication of devices that do not require perfect structure ordering and that are formed of periodic arrays of structures.; Our approach, in comparison, utilizes block copolymer lithography to achieve all the important characteristics of conventional photolithography including pattern perfection over macroscopic areas, dimensional control of features within exacting tolerances and margins, and registration and overlay. Recently we have found that the domains of block copolymer films could be directed to assemble perfectly over arbitrarily large areas and in registry with lithographically defined chemical surface patterns with tailored interfacial interactions. In addition, we have demonstrated that by directing the assembly of blends of block copolymers and homopolymers on chemically nanopatterned substrates, it is possible to pattern nonregular device-oriented structures such as sharp bends. The set of pattern geometries essential to the fabrication of integrated circuits, including arcs, T-junctions, jogs, contact hole arrays with hexagonal and square order, and isolated segments, also has been demonstrated to be feasible using directed assembly of block copolymers. Furthermore, three-dimensional network structures in thin films have been assembled on chemically patterned surfaces and may enable the fabrication of multiple device layers in a single process step. In the short term, the technological implication of this hybrid top-down bottom-up technique is that self-assembling block copolymer materials may be harnessed for applications that require two- and three-dimensional structures significantly more complex than simple periodic arrays.