Argon fluoride laser

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The argon fluoride laser (ArF laser) is a particular type of excimer laser, [1] which is sometimes (more correctly) called an exciplex laser. With its 193-nanometer wavelength, it is a deep ultraviolet laser, which is commonly used in the production of semiconductor integrated circuits, eye surgery, micromachining, and scientific research. "Excimer" is short for "excited dimer", while "exciplex" is short for "excited complex". An excimer laser typically uses a mixture of a noble gas (argon, krypton, or xenon) and a halogen gas (fluorine or chlorine), which under suitable conditions of electrical stimulation and high pressure, emits coherent stimulated radiation (laser light) in the ultraviolet range.

Contents

ArF (and KrF) excimer lasers are widely used in high-resolution photolithography machines, a critical technology for microelectronic chip manufacturing. Excimer laser lithography [2] [3] has enabled transistor feature sizes to shrink from 800 nanometers in 1990 to 7 nanometers in 2018. [4] [5] [6] Extreme ultraviolet lithography machines have replaced ArF photolithography machines in some cases as they enable even smaller feature sizes while increasing productivity, as EUV machines can provide sufficient resolution in fewer steps. [7]

The development of excimer laser lithography has been highlighted as one of the major milestones in the 50-year history of the laser. [8] [9]

Theory

An argon fluoride laser absorbs energy from a source, causing the argon gas to react with the fluorine gas producing argon monofluoride, a temporary complex, in an excited energy state:

2 Ar + F
2 → 2 ArF

The complex can undergo spontaneous or stimulated emission, reducing its energy state to a metastable, but highly repulsive ground state. The ground state complex quickly dissociates into unbound atoms:

2 ArF → 2 Ar + F
2

The result is an exciplex laser that radiates energy at 193 nm, which lies in the far ultraviolet portion of the spectrum, corresponding to an energy difference of 6.4 electron volts between the ground state and the excited state of the complex.

Applications

The most widespread industrial application of ArF excimer lasers has been in deep-ultraviolet photolithography [2] [3] for the manufacturing of microelectronic devices (i.e., semiconductor integrated circuits or "chips"). From the early 1960s through the mid-1980s, Hg-Xe lamps were used for lithography at 436, 405 and 365 nm wavelengths. However, with the semiconductor industry's need for both finer resolution (for denser and faster chips) and higher production throughput (for lower costs), the lamp-based lithography tools were no longer able to meet the industry's requirements.

This challenge was overcome when in a pioneering development in 1982, deep-UV excimer laser lithography was invented and demonstrated at IBM by K. Jain. [2] [3] [10] With advances made in equipment technology in the following two decades, semiconductor electronic devices fabricated using excimer laser lithography reached $400 billion in annual production. As a result, [5] excimer laser lithography (with both ArF and KrF lasers) has been a crucial factor in the continued advance of the so-called Moore's law. [6]

The UV light from an ArF laser is well absorbed by biological matter and organic compounds. Rather than burning or cutting material, the ArF laser dissociates the molecular bonds of the surface tissue, which disintegrates into the air in a tightly controlled manner through ablation rather than burning. Thus the ArF and other excimer lasers have the useful property that they can remove exceptionally fine layers of surface material with almost no heating or change to the remainder of the material which is left intact. These properties make such lasers well suited to precision micromachining organic materials (including certain polymers and plastics), and especially delicate surgeries such as eye surgery (e.g., LASIK, LASEK). [11]

Recently, through the use of a novel diffractive diffuse system composed of two microlens arrays, surface micromachining by ArF laser on fused silica has been performed with submicrometer accuracy. [12]

In 2021, the United States Naval Research Laboratory began work on an ArF for use in Inertial confinement fusion, providing up to 16% energy efficiency. [13]

Safety

The light emitted by the ArF is invisible to the human eye, so additional safety precautions are necessary when working with this laser to avoid stray beams. Gloves are needed to protect flesh from its potentially carcinogenic properties, and UV goggles are needed to protect the eyes.

See also

Related Research Articles

Photolithography is a process used in the manufacturing of integrated circuits. It involves using light to transfer a pattern onto a substrate, typically a silicon wafer.

<span class="mw-page-title-main">Ultraviolet</span> Form of electromagnetic radiation

Ultraviolet (UV) is a form of electromagnetic radiation with wavelength shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs; Cherenkov radiation; and specialized lights, such as mercury-vapor lamps, tanning lamps, and black lights.

<span class="mw-page-title-main">Excimer</span> Excited dimeric molecule containing a noble gas

An excimer is a short-lived polyatomic molecule formed from two species that do not form a stable molecule in the ground state. In this case, formation of molecules is possible only if such atom is in an electronic excited state. Heteronuclear molecules and molecules that have more than two species are also called exciplex molecules. Excimers are often diatomic and are composed of two atoms or molecules that would not bond if both were in the ground state. The lifetime of an excimer is very short, on the order of nanoseconds.

<span class="mw-page-title-main">Excimer laser</span> Type of ultraviolet laser important in chip manufacturing and eye surgery

An excimer laser, sometimes more correctly called an exciplex laser, is a form of ultraviolet laser which is commonly used in the production of microelectronic devices, semiconductor based integrated circuits or "chips", eye surgery, and micromachining.

<span class="mw-page-title-main">Photomask</span> Photolithographic Tool

A photomask is an opaque plate with transparent areas that allow light to shine through in a defined pattern. Photomasks are commonly used in photolithography for the production of integrated circuits to produce a pattern on a thin wafer of material. In semiconductor manufacturing, a mask is sometimes called a reticle.

<span class="mw-page-title-main">Immersion lithography</span> Photolithography technique where there is a layer of water between a lens and a microchip

Immersion lithography is a technique used in semiconductor manufacturing to enhance the resolution and accuracy of the lithographic process. It involves using a liquid medium, typically water, between the lens and the wafer during exposure. By using a liquid with a higher refractive index than air, immersion lithography allows for smaller features to be created on the wafer.

<span class="mw-page-title-main">Gas laser</span> Laser in which electricity is discharged through gas

A gas laser is a laser in which an electric current is discharged through a gas to produce coherent light. The gas laser was the first continuous-light laser and the first laser to operate on the principle of converting electrical energy to a laser light output. The first gas laser, the Helium–neon laser (HeNe), was co-invented by Iranian engineer and scientist Ali Javan and American physicist William R. Bennett, Jr., in 1960. It produced a coherent light beam in the infrared region of the spectrum at 1.15 micrometres.

Nanolithography (NL) is a growing field of techniques within nanotechnology dealing with the engineering of nanometer-scale structures on various materials.

Next-generation lithography or NGL is a term used in integrated circuit manufacturing to describe the lithography technologies in development which are intended to replace current techniques. Driven by Moore's law in the semiconductor industries, the shrinking of the chip size and critical dimension continues. The term applies to any lithography method which uses a shorter-wavelength light or beam type than the current state of the art, such as X-ray lithography, electron beam lithography, focused ion beam lithography, and nanoimprint lithography. The term may also be used to describe techniques which achieve finer resolution features from an existing light wavelength.

<span class="mw-page-title-main">Krypton fluoride laser</span>

A krypton fluoride laser is a particular type of excimer laser, which is sometimes called an exciplex laser. With its 248 nanometer wavelength, it is a deep ultraviolet laser which is commonly used in the production of semiconductor integrated circuits, industrial micromachining, and scientific research. The term excimer is short for 'excited dimer', while exciplex is short for 'excited complex'. An excimer laser typically contains a mixture of: a noble gas such as argon, krypton, or xenon; and a halogen gas such as fluorine or chlorine. Under suitably intense conditions of electromagnetic stimulation and pressure, the mixture emits a beam of coherent stimulated radiation as laser light in the ultraviolet range.

<span class="mw-page-title-main">Stepper</span> Photolithographic Tool

A stepper is a device used in the manufacture of integrated circuits (ICs). It is an essential part of the process of photolithography, which creates millions of microscopic circuit elements on the surface of silicon wafers out of which chips are made. It is similar in operation to a slide projector or a photographic enlarger. The ICs that are made form the heart of computer processors, memory chips, and many other electronic devices.

<span class="mw-page-title-main">Nanoimprint lithography</span> Method of fabricating nanometer scale patterns using a special stamp

Nanoimprint lithography (NIL) is a method of fabricating nanometer-scale patterns. It is a simple nanolithography process with low cost, high throughput and high resolution. It creates patterns by mechanical deformation of imprint resist and subsequent processes. The imprint resist is typically a monomer or polymer formulation that is cured by heat or UV light during the imprinting. Adhesion between the resist and the template is controlled to allow proper release.

<span class="mw-page-title-main">ASML Holding</span> Dutch manufacturer of semiconductor production equipment

ASML Holding N.V. is a Dutch multinational corporation founded in 1984. ASML specializes in the development and manufacturing of photolithography machines which are used to produce computer chips.

<span class="mw-page-title-main">Microfabrication</span> Fabrication at micrometre scales and smaller

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" or "semiconductor device fabrication". In the last two decades microelectromechanical systems (MEMS), microsystems, micromachines and their subfields, microfluidics/lab-on-a-chip, optical MEMS, RF MEMS, PowerMEMS, BioMEMS and their extension into nanoscale have re-used, adapted or extended microfabrication methods. Flat-panel displays and solar cells are also using similar techniques.

Resolution enhancement technologies are methods used to modify the photomasks in the lithographic processes used to make integrated circuits to compensate for limitations in the optical resolution of the projection systems. These processes allow the creation of features well beyond the limit that would normally apply due to the Rayleigh criterion. Modern technologies allow the creation of features on the order of 5 nanometers (nm), far below the normal resolution possible using deep ultraviolet (DUV) light.

Computational lithography is the set of mathematical and algorithmic approaches designed to improve the resolution attainable through photolithography. Computational lithography came to the forefront of photolithography technologies in 2008 when the semiconductor industry faced challenges associated with the transition to a 22 nanometer CMOS microfabrication process and has become instrumental in further shrinking the design nodes and topology of semiconductor transistor manufacturing.

In semiconductor manufacturing, the International Technology Roadmap for Semiconductors defines the 7 nm process as the MOSFET technology node following the 10 nm node. It is based on FinFET technology, a type of multi-gate MOSFET technology.

An excimer lamp is a source of ultraviolet light based on spontaneous emission of excimer (exciplex) molecules.

<span class="mw-page-title-main">Foturan</span>

Foturan is a photosensitive glass by SCHOTT Corporation developed in 1984. It is a technical glass-ceramic which can be structured without photoresist when it is exposed to shortwave radiation such as ultraviolet light and subsequently etched.

Shanghai Micro Electronics Equipment (Group) Co., Ltd. (SMEE), is a manufacturer of semiconductor manufacturing equipment based in Shanghai, China. The company is involved in the research, development, manufacture and sale of lithography scanners and inspection tools to the semiconductor manufacturing industry; it also provides support services for its machines to its customers.

References

  1. ↑ Basting, D.; Marowsky, G. (2005). "Introductory Remarks". Excimer Laser Technology. Berlin: Springer-Verlag. pp. 1–7. Bibcode:2005elt..book....1B. doi:10.1007/3-540-26667-4_1. ISBN   3-540-20056-8.
  2. 1 2 3 Jain, K.; Willson, C.G.; Lin, B.J. (1982). "Ultrafast deep UV Lithography with excimer lasers". IEEE Electron Device Letters. 3 (3): 53–55. Bibcode:1982IEDL....3...53J. doi:10.1109/EDL.1982.25476. S2CID   43335574.
  3. 1 2 3 Jain, Kanti (1987-03-11). Luk, Ting-Shan (ed.). "Advances In Excimer Laser Lithography". Excimer Lasers and Optics. SPIE. 0710: 35. Bibcode:1987SPIE..710...35J. doi:10.1117/12.937294. S2CID   136477292.
  4. ↑ "Samsung Starts Industry's First Mass Production of System-on-Chip with 10-Nanometer FinFET Technology". news.samsung.com. Retrieved 2021-10-25.
  5. 1 2 "Lasers and Moore's Law". spie.org. Retrieved 2021-10-25.
  6. 1 2 "TSMC Kicks Off Volume Production of 7nm Chips". AnandTech. 2018-04-28. Retrieved 2018-10-20.
  7. ↑ "EUV Lithography Finally Ready for Chip Manufacturing". IEEE Spectrum. January 5, 2018.
  8. ↑ "SPIE / Advancing the Laser / 50 Years and into the Future" (PDF).
  9. ↑ "U.K. Engineering & Physical Sciences Research Council / Lasers in Our Lives / 50 Years of Impact" (PDF). Archived from the original (PDF) on September 13, 2011.
  10. ↑ Basting, D.; Djeu, N.; Jain, K. (2005). "Historical Review of Excimer Laser Development". In Basting, D.; Marowsky, G. (eds.). Excimer Laser Technology. Berlin: Springer-Verlag. pp. 8–21. Bibcode:2005elt..book....8B. doi:10.1007/3-540-26667-4_2. ISBN   3-540-20056-8.
  11. ↑ Kuryan J, Cheema A, Chuck RS (2017). "Laser-assisted subepithelial keratectomy (LASEK) versus laser-assisted in-situ keratomileusis (LASIK) for correcting myopia". Cochrane Database Syst Rev. 2017 (2): CD011080. doi:10.1002/14651858.CD011080.pub2. PMC   5408355 . PMID   28197998.
  12. ↑ Zhou, Andrew F. (2011). "UV Excimer Laser Beam homogenization for Micromachining Applications". Optics and Photonics Letters. 4 (2): 75–81. doi:10.1142/S1793528811000226.
  13. ↑ Szondy, David (2021-10-24). "Argon fluoride laser could lead to practical fusion reactors". New Atlas. Archived from the original on 2021-10-25. Retrieved 2021-10-25.
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