Silicon nanolithography

Fig. 8 Schematic representation of block copolymer nanolithography process, a Schematic cross-sectional view of a nanolithography template consisting of a uniform mono-layer of PB spherical microdomains on silicon nitride. PB wets the air and substrate interfaces, b Schematic of the processing flow when an ozonated copolymer film is used as a positive resist, which produces holes in silicon nitride, c Schematic of the processing flow when an osmium-stained copolymer film is used as a negative resist, which produces dots in silicon nitride, (taken from [44])...

Figure 13.19 The template-directed self-assembly of Au clusters on silicon substrate patterned by constructive nanolithography.

In [55] a large-area fabrication of hexagonally ordered metal dot arrays with an area density of 10u/cm2 was demonstrated. The metal dots were produced by an electron beam evaporation followed by a lift-off process. The dots size was 20 nm dots with a 40 nm period by combining block copolymer nanolithography and a trilayer resist technique. A self-assembled spherical-phase block copolymer top layer spontaneously generated the pattern, acting as a template. The pattern was first transferred to a silicon nitride middle layer by reactive ion etch, producing holes. The nitride layer was then used as a mask to further etch into a polyamide bottom layer. 

Dip-pen nanolithography has been employed to obtain magnetic nanopattems of y-Fe203 nanocrystals on mica and silicon substrates. The chemical and magnetic nature of the patterns have been characterized employing low-energy electron microscopy, x-ray photoemission electron microscopy, and magnetic force microscopy measurements. 2004 American Institute of Physics. 

Fontaine, P. A., et al. (1998), Characterization of scanning tunneling microscopy and atomic force microscopy-based techniques for nanolithography on hydrogen-passivated silicon, J. Appl. Phys., 84(1), 1776-1781. 

Block copolymers can be employed as templates to direct the deposition of inorganic nanostructures. Parket al. [82] used an Os04-stained microphase-separated thin film of poly(styrene-foZock-butadiene) that produced holes upon RIE in silicon nitride substrates. The etch ratio between the two phases, stained butadiene and styrene, was only about 1 2. MoUer et aL discussed the use of poly(styrene-fc/ock-2-vinylpyridine), to prepare masks for nanolithography by loading the PVP domains with gold particles [83] or by selective growth of Ti on top of the PS domains [84]. 

Fig. 2 Atomic force microscopy (AFM) friction images and schematic illustrations of the patterning processes of a microcontact printed SAMs (mercaptoethanol dots in oc-tadecanethiol matrix, scale bar 10 xm) b patterned molecular printboards fabricated by supramolecular dip-pen nanolithography (DPN) (reprinted with permission from [92] Copyright 2004. WUey VCH) e locally hydrolyzed tert-butyl acrylate-terminated polymer film on oxidized silicon (soft lithography scale bar 3 xm) (Feng CL, Vancso GJ, SchOn-herr H, manuscript submitted to Langmuir) d photopatterned bilayer of diacetylene lipid (scale bar 10 xm). Reprinted in part with permission from [93], copyright (1999), American Chemical Society...

Weinberger DA, Hong S, Mirkin CA, Wessels BW, Higgins TB (2000) Combinatorial generation and analysis of nanometer- and micrometer-scale silicon features via dip-pen nanolithography and wet chemical etching. Adv Mater 12 1600-1603... 

Colloidal nanolithography, deep silicon etching and nanomolding are the techniques used to achieve fibrillar polymer sfructures which mimic the gecko foot hairs these nanofibrils are densely packed, perpendicular and strongly adhesive to a synthetic surface, and due to these characteristics are promising materials for integration in flexible membranes and exploitation of new adhesives [169]. 

Examples of nanomaterials can be classified in different ways. Some of the common classes are based on application and consist of the following carbon nanotubes (fuUerenes), nanoparticles, nanorods, and nanoelectronic devices. Other more specific are, for example, medical applications, silicon solar cells, semiconductors, nanoelectromechanical systems (NEMS) or microelectromechanical systems (MEMS), and nanolithography. Another major potential application is in the medical field as nanorobotics. 

Figures 13.15 and 13.16 show two examples that underline the flexibility and robustness of this technique for nanofabrication. Figure 13.15a shows the steps to build molecular architectures by combining top-down nanolithography and self-assembled methods. In this case, single molecules of ferritin have been deposited on silicon surfaces with an accuracy similar to the size of the molecules (r IO nm. First, the silicon surface is covered with a self-assembled monolayer of aminopropyltriethoxysilane (APTES), and then a region is locally oxidized with the atomic force microscope tip. The oxidation process also removes the monolayer under the tip. The nanostripe before the deposition of ferritin molecules is shown in Fig. 13.15b, while Fig. 13.15c shows a densely packed distribution of proteins on the nanostripe. The...

Figure 13.15 Patterning of ferritin molecules by combining AFM oxidation nanolithography and silicon functionalization at low pH values, (a) Steps of the nanopatterning process, (b] AFM image of a local oxide pattern, (c) High-density packing of ferritin molecules on the nanopattern. The inset shows the distribution of the proteins in the marked region. (Data adapted from Ref 89.)...

J. Martinez, R. V. Martinez, and R. Garcia, Silicon nanowire transistors with a channel width of 4 nm fabricated by atomic force microscope nanolithography. Nano Lett, 8, 3636-3639 (2008). 

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