Microlithography is a general name for any manufacturing process that can create a minutely patterned
thin film of protective materials over a substrate, such as a
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...
wafer
A wafer is a crisp, often sweet, very thin, flat, light and dry biscuit, often used to decorate ice cream, and also used as a garnish on some sweet dishes. Wafers can also be made into cookies with cream flavoring sandwiched between them. They ...
, in order to protect selected areas of it during subsequent
etching
Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. In modern manufacturing, other chemicals may be used on other types ...
,
deposition, or
implantation operations.
[
The term is normally used for processes that can reliably produce features of microscopic size, such as 10 ]micrometre
The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer (American spelling), also commonly known as a micron, is a unit of length in the International System of Unit ...
s or less. The term nanolithography may be used to designate processes that can produce nanoscale
The nanoscopic scale (or nanoscale) usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is (roughly speaking) a lo ...
features, such as less than 100 nanometres.
Microlithography is a microfabrication
Microfabrication is the process of fabricating miniature structures of micrometre scales and smaller. Historically, the earliest microfabrication processes were used for integrated circuit fabrication, also known as "semiconductor manufacturing" ...
process that is extensively used in the semiconductor industry and also manufacture microelectromechanical systems.
Processes
Specific microlithography processes include:
* Photolithography using light projected on a photosensitive Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicit ...
metarial film (photoresist
A photoresist (also known simply as a resist) is a light-sensitive material used in several processes, such as photolithography and photoengraving, to form a patterned coating on a surface. This process is crucial in the electronic industry.
...
).
* Electron beam lithography
Electron-beam lithography (often abbreviated as e-beam lithography, EBL) is the practice of scanning a focused beam of electrons to draw custom shapes on a surface covered with an electron-sensitive film called a resist (exposing). The electron ...
, using a steerable electron beam.
* Nanoimprinting
* Interference lithography
Interference lithography (or holographic lithography) is a technique for patterning regular arrays of fine features, without the use of complex optical systems or photomasks.
Basic principle
The basic principle is the same as in interferometry o ...
* Magnetolithography
* Scanning probe lithography
* Surface-charge lithography[
* Diffraction lithography][
These processes differ in speed and cost, as well as in the material they can be applied to and the range of feature sizes they can produce. For instance, while the size of features achievable with photolithography is limited by the wavelength of the light used, the technique it is considerably faster and simpler than electron beam lithography, that can achieve much smaller ones.
]
Applications
The main application for microlithography is fabrication of integrated circuits ("electronic chips"), such as solid-state memories and microprocessor
A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...
s. They can also be used to create diffraction grating
In optics, a diffraction grating is an optical component with a periodic structure that diffracts light into several beams travelling in different directions (i.e., different diffraction angles). The emerging coloration is a form of structur ...
s, microscope calibration grids, and other flat structures with microscopic details.
See also
* Printed circuit board
References
[John N Helbert (2001), ''Handbook of VLSI Microlithography''. Elsevier Science, 1022 pages. ]
[Bruce W. Smith and Kazuaki Suzuki (2007): ''Microlithography: Science and Technology'', 2nd Edition. CRC Press, 864 pages. ]
[S. Grilli, V. Vespini, P. Ferraro (2008): "Surface-charge lithography for direct PDMS micro-patterning". ''Langmuir'', volume 24, pages 13262–13265. ]
[M. Paturzo, S. Grilli, S. Mailis, G. Coppola, M. Iodice, M. Gioffré, P. Ferraro (2008): "Flexible coherent diffraction lithography by tunable phase arrays in lithium niobate crystals". ''Optics Communications'', volume 281, pages 1950–1953. ]
Integrated circuits
Lithography (microfabrication)
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