Fabrication of Vertical Silicon Nanotube Array Using Spacer Patterning Technique and Metal-Assisted Chemical Etching

Large-Area Fabrication of Vertical Silicon Nanotube Arrays via Toroidal Micelle Self-Assembly

“…Block copolymer (BCP) self-assembly provides an avenue for the formation of a myriad of nano-scale morphologies, with applications such as optoelectronics, biosensing, filtration, bioactive surfaces, surface coatings, and magnetic applications, among others. − More usual microphase separated self-assembled architectures include lamellar, cylindrical, spherical, and gyroidal structures as well as various micellar-based morphologies such as helices, tubes, disks, and toroids. − Micelle formation is defined as the self-assembly of an amphiphilic BCP in a solvent medium to form a structure typically with a core and corona. , Of the myriad of available micellar structures, toroidal micelles, in particular, have garnered interest owing to their proven applicability in synthesizing unique nanostructured materials with unique plasmonic and magnetic properties. , Such structures are typically fabricated via incorporating various metals and metal oxides, which upon removal of the polymer matrix produce metallic toroidal or nanoring structures . These metal/metal oxide structures have also been utilized as hard masks for patterning underlying silicon substrates, yielding high aspect ratio nanotube arrays. , Nonetheless, one notable drawback of toroidal micelles obtained via BCP or triblock copolymer self-assembly is that the size distributions of the structure are often too small for optoelectronic applications …”

“…We use the term array to describe a densely packed arrangement of structures with little periodicity as no single self-assembled entities are observed. Traditional methods for silicon nanotube growth often include extensive chemical steps or require toxic chemicals such as silanes, acidic conditions, and high processing temperatures. − Therefore, our methods are relatively facile compared to existent methods of production of metallic nanorings and vertical silicon nanotube vertical arrays, which usually involve complicated multistep synthesis and top-down approaches such as wet chemistry synthesis, chemical vapor deposition, various lithographic approaches, and use of multiple resist layers and materials. ,− Additionally, WVA treatment is a low-cost and environmentally friendly fabrication method. One of the critical advantages of our approach is the formation of large feature size patterns by advantaging a highly controlled micelle approach to compliment smaller feature sizes produced by microphase separation of the systems.…”

“…17 These metal/metal oxide structures have also been utilized as hard masks for patterning underlying silicon substrates, yielding high aspect ratio nanotube arrays. 18,19 Nonetheless, one notable drawback of toroidal micelles obtained via BCP or triblock copolymer self-assembly is that the size distributions of the structure are often too small for optoelectronic applications. 13 In this work, we describe a novel strategy to address this issue by controlling the formation of large toroidal structures via water vapor annealing (WVA) of a polystyrene-bpoly(ethylene oxide) (PS-b-PEO) diblock copolymer system atop a PS-modified substrate.…”

Silicon Nanotubes Fabricated by Wet Chemical Etching of ZnO/Si Core–Shell Nanowires

“…A Si shell layer is deposited on a template such as ZnO [ 2 , 5 ], Ge [ 9 , 11 ], or MgO [ 12 ] nanowires, followed by selectively etching away the templates to form the SiNTs. Top-down techniques using lithography [ 13 , 14 , 15 ] and self-assembled nanosphere bead templates [ 16 , 17 , 18 ] have more recently been developed to fabricate SiNTs, but they require a complex manufacturing process, long processing time, or the use of noble metals. Other methods such as chemical etching [ 19 ] and electrochemical formation [ 20 ] cannot produce vertically aligned SiNTs, so they have limited applications.…”

Integrated in situ self-aligned double patterning process with fluorocarbon as spacer layer

“…Specifically, chemical vapor deposition (CVD) is normally employed for a conformal deposition of the spacer layer, which is typically a dielectric material such as silicon nitride. 9,10 With a uniform step coverage and accurate thickness control of the spacer layer, atomic layer deposition (ALD) has shown its advantages for SADP processing, 11,12 while highly purified precursors and the slow deposition rate can set limitations for certain applications. Apart from these techniques, thermal oxidation 13 and direct coating of organic spacer films 14 are also alternative options to reduce equipment costs.…”