Strategies for patterning silicon nanostructures with diblock copolymers, in view of application to microelectronics and optoelectronics

The use of diblock copolymers PS-b-PMMA self-assembly for patterning silicon nanopillars and nanowires is presented in this paper. In particular, formation of PMMA cylinders in a PS matrix is studied. After removal of the PMMA domains, a porous PS template is obtained. This PS template must then be transferred to a hard mask highly resistant to plasma etching. For this purpose, two strategies are investigated. The first strategy is based on the deposition of a thin metal layer by PVD on the PS mask followed by a lift-off. The second strategy is based on the selective ALD deposition of a thin Al₂O₃ layer in the mask pores. Both strategies allow for obtaining highly resistant etching mask through which high aspect ratio (>10) silicon nanopillars are patterned. These nanostructures could find applications in microelectronics and optoelectronics.