Lithography is often referred to as photo-engraving, and is the process of transferring a pattern into a reactive polymer film, termed as resist. This will subsequently be used to replicate that pattern into an underlying thin film. Many techniques of lithography have been developed in the last half a century.
?These processes use various lens systems and exposure radiation sources including photons, X-rays, electrons, ions and neutral atoms. In spite of different exposure radiation sources used in various lithographic methods and instrumental details, they all share the same general technical approaches and are based on similar fundamentals. Photolithography is the most widely used technique in microelectronic fabrication, particularly for mass production of integrated circuit.
As Compared to the general chemical fabrication and processing methods, physical fabrication techniques for producing nanostructures are derived mainly from the techniques applied for the fabrication of microstructures in semiconductor industry. Particularly the fundamentals and basic approaches are mostly based on micro fabrications.
The following techniques for the fabrication of nanostructures and nanopatterns are used in the industry.
(1)Lithographic techniques
(a) Photolithography
(b) Phase shifting optical lithography
(c) Electron beam lithography
(d) X-ray lithography
(e) Focused ion beam lithography
(f) Neutral atomic beam lithography
(2)Nanomanipulation and nanolithography
(a) Scanning tunneling microscopy (STM)
(b) Atomic force microscopy (AFM)
(c) Near-field scanning optical microscopy (NSOM)
(d) Nan manipulation
(e) Nanolithography
(3)Soft lithography
(a) Micro contact printing
(b) Molding
(c) Nanoimprint
(d) Dip-pen nanolithography
(4) Self-assembly of nanoparticles or nanowires
(a) Capillary force induced assembly
(b) Dispersion interaction assisted assembly
(c) Shear force assisted assembly
(d) Electric-field assisted assembly
(e) Covalently linked assembly
(f) Gravitational field assisted assembly
(g) Template assisted assembly
(5) Other methods for micro fabrication
(a) LIGA
(b) Laser direct writing
(c) Excimer laser micromachining
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