Abstract
In an effort to develop block copolymer lithography to create high aspect vertical pore arrangements in a substrate surface we have used a microphase separated poly(ethylene oxide) -b- polystyrene (PEO-b-PS) block copolymer (BCP) thin film where (and most unusually) PS not PEO is the cylinder forming phase and PEO is the majority block. Compared to previous work, we can amplify etch contrast by inclusion of hard mask material into the matrix block allowing the cylinder polymer to be removed and the exposed substrate subject to deep etching thereby generating uniform, arranged, sub-25 nm cylindrical nanopore arrays. Briefly, selective metal ion inclusion into the PEO matrix and subsequent processing (etch/modification) was applied for creating iron oxide nanohole arrays. The oxide nanoholes (22 nm diameter) were cylindrical, uniform diameter and mimics the original BCP nanopatterns. The oxide nanohole network is demonstrated as a resistant mask to fabricate ultra dense, well ordered, good sidewall profile silicon nanopore arrays on substrate surface through the pattern transfer approach. The Si nanopores have uniform diameter and smooth sidewalls throughout their depth. The depth of the porous structure can be controlled via the etch process.
Highlights
Context, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) has been the greatest system of interest extensively studied because of its accessibility, ease of production, and well-established processing technologies[17,18,19]
We have developed a simple solution mediated metal ion (Fe, Ni, Zn etc.) insertion by using PS-PEO block copolymer (BCP) where chemical co-ordination between metal ion and PEO microdomains produces inorganic patterns that can act as ‘hard’ masks to allow facile and efficient, high aspect ratio pattern transfer into Si substrate[27,28,29,30,31,32,33,34]
Prepared BCP thin films have been placed in the annealing chamber with different annealing solvents, time and temperature in order to achieve long range ordered nanopatterns
Summary
Context, polystyrene-b-polymethylmethacrylate (PS-b-PMMA) has been the greatest system of interest extensively studied because of its accessibility, ease of production, and well-established processing technologies[17,18,19]. This is used to create an inorganic etch mask to form good sidewall profile, uniform well ordered Si nanopore network through a plasma based pattern transfer process. The BCP nanopatterned templates can be used to generate good sidewall profile Si nanopore arrays through the hard mask pattern transfer process.
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