Our goal is to develop a facile process to create patterns of inorganic oxides and
metals on a substrate that can act as hard masks. These materials should have
high etch contrast (compared to silicon) and so allow high-aspect-ratio, highfidelity
pattern transfer whilst being readily integrable in modern semiconductor
fabrication (FAB friendly). Here, we show that ultra-small-dimension hard masks
can be used to develop large areas of densely packed vertically and horizontally
orientated Si nanowire arrays. The inorganic and metal hard masks (Ni, NiO, and
ZnO) of different morphologies and dimensions were formed using microphaseseparated
polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP)
thin films by varying the BCP molecular weight, annealing temperature, and
annealing solvent(s). The self-assembled polymer patterns were solvent-processed,
and metal ions were included into chosen domains via a selective inclusion
method. Inorganic oxide nanopatterns were subsequently developed using
standard techniques. High-resolution transmission electron microscopy studies
show that high-aspect-ratio pattern transfer could be affected by standard plasma
etch techniques. The masking ability of the different materials was compared
in order to create the highest quality uniform and smooth sidewall profiles of
the Si nanowire arrays. Notably good performance of the metal mask was seen,
and this could impact the use of these materials at small dimensions where
conventional methods are severely limited.