Development of a facile block copolymer method for creating hard mask patterns integrated into semiconductor manufacturing

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, high-fidelity 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 microphase-separated 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.