Directed self-assembly of Di-Block copolymers for a new idea of length standards at the nanoscale

Di-Block Copolymers (DBCs) are materials composed of two different monomer subunits linked together. These blocks are able to self-assemble in different microphases with various morphologies (cylinders, lamellae, spheres, gyroids). For this reason, the DBCs are widely investigated as patterning and nanofabrication technique. In this work, the combination of conventional lithographic approaches with the Self-Assembly of DBCs is investigated, to develop a new generation of lateral length standards at the nanoscale (under 70 nm) with a low cost approach based on the natural constants of matter. The behavior of a cylinder forming Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) with Mn = 54 kg·mol-1 within SiO2 periodical trenches by a Rapid Thermal Processing (RTP) oven is studied. Although this material has been widely used as lithographic mask its application in metrology field was still unknown. The optimization and calibration of DBC thin film deposition processes as a function of geometrical and annealing parameters are performed and the characteristic dimensions (L0) of the cylindrical patterns are analyzed. A decoupling of the L0 along the two confinement directions is observed. The center-to-center distance in the direction parallel to the long side of the trenches (L0l) remains invariant as a function of process variability. Thus, the high stability of L0l makes it an intrinsic feature of the system usable as measurand for a new lateral length standard. Finally, the attempt to increase the chemical incompatibility between the two blocks within the PSb-PMMA system by copolymerization of a fluorine containing methacrylic monomer with the methyl methacrylate is performed. The aims are to understand how the fluorine-containing monomer influences the DBC segregation and the structure periodicity, and if this modification allows to obtain a smaller periodicity of the DBC features for potentially increasing the standard length size range.