Center for Functional Nanomaterials Seminar

Directed self-assembly (DSA) of block copolymers (bcp) is a leading strategy to pattern at sub-lithographic resolution in the technology roadmap for semiconductors, and is the only known solution to fabricate nano-imprint templates for the production of bit pattern media. Integration of DSA with traditional top-down processes is a principal challenge, particularly with respect to the process used to anneal the polymer thin films. Thermal annealing is the most developed method, resembling track processing of photoresists on hotplates, and has been used in demonstrations of DSA closest to commercial applications. Solvent annealing is a more complicated process and is less manufacturing friendly, but offers advantages in terms of diversity of materials and domain structures that can be assembled, and has resulted in the DSA of the highest resolution features demonstrated to date. Here we report a DSA process based on lithographically defined chemical templates and solvent annealing to pattern and pattern transfer 8 nm features on a 16 nm pitch with precise controllable variation in pattern dimensions (± 5 percent) required for arranging bits of patterned media in circular tracks. Key innovations include: 1) implementing a quasi-equilibrium process using solvents in which the polymer assembles in the solvated state, 2) delineating and taking advantage of the thermodynamic properties of tri-block copolymer/solvent mixtures to allow for sub 10 nm features, and 3) optimizing a pattern transfer technology using reactive vapor phase precursors to selectively transform block copolymer domains into inorganic hard masks.