Page 177 - CW E-Magazine (20-2-2024)

Special Report Special Report

inerting and purging gas, protecting Oxygen local electrical properties of the semi- Table 1: Major semiconductor gases qualifi ed remote sources, as well as
sensitive silicon wafers from reactive Oxygen is used for the oxidation of conductor material. The list includes Atmospheric Silicon precursor Etchant gases Dopant gases liquid storage on-site equivalent to
oxygen and moisture in the air. silicon, one of the most critical processes arsine, boron trifl uoride, diborane, gases gases several days of production demand.
in all of semiconductor manufacturing. phosphine and trimethylboron.
To meet this demand, semiconductor Nitrogen Dichlorosilane Boron trichloride Arsine Market trends
manufacturing plants often install Silicon precursor gases Specifi cally, a dopant contributes Oxygen Disilane Chlorine Boron trifl uoride Growth in consumption of specia-
nitrogen generators onsite to ensure Silicon-precursor gases act as a either an electron defi ciency (p-dopant) Hydrogen Germane Halocarbons 116, Diborane lity gases (and other fab chemicals)
a cheap, effi cient, and always-ready source of silicon atoms for the deposi- or an electron (n-dopant) to the local 14, 218, 23, 32, is directly driven by the construction
supply of nitrogen gas. tion of polycrystalline silicon, epitaxial structure of the molecule’s crystal lat- RC318 of several new semiconductor fabs all
silicon, silicon dioxide, and silicon tice, which, in turn, alters the conduc- Argon Germanium tetrafl uoride Hydrogen bromide Phosphine over the world. Because modern chip
Helium nitride. The most common gases are tivity of the material. Dopants are avai- Helium Methylsilane Hydrogen chloride Trimethylboron fabs require huge investments, they are
Helium is particularly useful in silane, dichlorosilane, trichlorosilane, lable in liquid, solid and gaseous states. often supported by government poli-
semiconductor manufacturing, to and silicon tetrachloride. Dopants are used in epitaxial deposi- Silane Hydrogen fl uoride cies such as the US CHIPS and Science
effi ciently conduct heat away from tion, diffusion and ion implantation. Silicon tetrachloride Nitrogen trifl uoride Act, the European Chips Act, and other
energetic processes and help pro- Silane and dichlorosilane are used in Silicon tetrafl uoride Sulphur hexafl uoride incentive schemes such as those an-
tect them from thermal damage and epitaxial and chemical vapour deposi- A common gaseous p-dopant is Trichlorosilane nounced in India. Governmental sup-
unwanted chemical reactions. tion (CVD) processes to deposit layers diborane, while arsine is used for port has gained importance since the
of silicon or silicon compounds onto n-type doping. major factors that drive the supply of transportation is therefore the overall major global semiconductors supply
Hydrogen silicon substrates. Silicon epitaxial lay- bulk gases. cost driver; products are liquefi ed for shortage seen in 2021 and 2022.
In semiconductor production hydro- ers are formed in reactions based on the A major growth area for arsine and transportation and then vaporized on-
gen is used for: mechanisms of thermal decomposition phosphine use is the fabrication of Air separation is the primary set of demand for use. According to Linx Consulting, the
 Annealing: Silicon wafers are rou- or reduction by hydrogen, depending on wafers called ‘III-V devices,’ using a processes used to obtain nitrogen, oxy- semiconductor industry consumed $3-bn
tinely heated to high temperatures the silicon-precursor reactant gas used. vapour phase epitaxy (VPE) or, more gen, and argon from air. Moisture, car- Scale is the determiner for on-site worth of electronic specialty gases in
and slowly cooled in order to frequently, the metal organic chemical bon dioxide, and other impurities are production vs. truck delivery. For 2020 compared to $2.5-bn in 2019.
repair (anneal) the crystal structure. Each silicon-precursor gas has epi- vapour deposition (MOCVD) method. fi rstly removed from the air by chemi- nitrogen, almost all 300-mm fabs and
Hydrogen is used to transfer heat taxial processing advantages and dis- cal absorbers. The air is then cooled by new display fabs operate at scales that Major suppliers include global com-
uniformly to the wafer and assist advantages, including processing tem- Etchant gases successively compressing and expand- require on-site production of nitrogen: panies such as Air Liquide, Air Pro-
the reconstruction of the crystal perature range, degree of auto-doping Etchant gases include fl uorocarbons ing it until it turns into a liquid, which to reduce cost; to ensure robust supply; ducts, Iwatani, Linde, SK Materials and
structure. and growth rates. and other fl uorinated materials. The is then distilled into these three com- and to produce to the highest and most Versum. There is, however, an oppor-
 Epitaxy: Ultra-high purity hydro-  Silane is used throughout a fab in most important gases today are halo- ponents. Electronics-grade air separa- consistent purity standards. Often, the tunity in the market for smaller, more
gen is used as a reducing agent in numerous CVD processes to form carbon 14 (tetrafl uoromethane), halo- tion units can produce these gases to demand for ultra-high purity oxygen focused providers of high-purity appli-
the epitaxial deposition of semicon- oxide, nitride and polysilicon thin fi lms. carbon 23 (trifl uoromethane), halocarbon >99.999999% purity. Because argon requires an on-site plant to achieve cations and differentiated compression
ductor materials such as silicon and  Dichlorosilane, in a gaseous state 116 (hexafl uoroethane), and nitrogen makes up only 1% of air by volume, the required purity specifi cations. And capabilities. Diffi cult-to-source and

germanium. at 0.5 atmosphere, is also a primary trifl uoride. These etchant gases react it is often not economically sensible to at leading-edge semiconductor plants, diffi cult-to-handle materials can also
 Deposition: Hydrogen can be source for polysilicon deposition. with silicon, silicon dioxide and silicon produce with smaller plants. the use of epitaxial processes and the provide a major point of differentiation
incorporated into thin silicon fi lms  Trichlorosilane and silicon tetra- nitride. adoption of EUV lithography are twin for specialty gas providers.

to make their atomic structure more chloride are both corrosive liquids It takes about three times as much drivers affecting consideration of
disordered and help increase their at room temperature and pressure. Halocarbons are used typically to electricity to produce these products as on-site hydrogen production. In March 2023, the Semiconductor
electrical resistivity.  Methylsilane is used for deposition etch silicon compounds, whereas the liquids compared to the gas phase. For Solutions business Merck KGaA, started
 Plasma cleaning: Hydrogen plasma of silicon carbide fi lms. other chlorine and fl uorine compounds gases made on-site, it is therefore most In certain locations, fabs are co- construction of a new manufacturing
is particularly effective at removing  Germane is used for silicon-germanium are usually required for etching metal- economical to produce most as gases, located into clusters. This allows for site in Kaohsiung, Taiwan. This project

tin contamination from light sources epitaxy for bandgap modifi cation. lic interconnects. which are supplied on-demand imme- even greater economies of scale, as a will manufacture speciality gases and
used in UV photolithography. diately to the fab, with a small portion pipeline can network the supply from semiconductor materials for thin fi lm
There is increasing use of dichloro- The choice of gas strongly depends liquefi ed for storage and redundant larger gas plants to multiple customers. and patterning starting 2025.
Argon silane over the high-deposition tem- on the ability of a given mixture of supply.
Because argon is comparatively perature trichlorosilane and silicon gases to selectively etch one fi lm in the Regardless of the primary supply, In April 2023, EMD Electronics,
easy to ionise, it is commonly used as tetrachloride. presence of another with a suffi cient However, because gases are much electronics production requires the electronics subsidiary of Merck,
a primary plasma gas for etching and degree of profi le control. less dense than liquids, it takes fi ve extremely high guarantees of supply; announced it will spend $300-mn to
deposition reactions in semiconductor Dopant gases trucks to deliver the same amount therefore, redundant sources and sup- expand its specialty gas production
fabrication. In addition, argon is used Dopant gases are a source of con- Supply chains of gas-phase product as one truck ply schemes are put in place. Most facility in eastern Pennsylvania (USA).
in excimer lasers for UV lithography. trollable impurities used to modify the Scale, purity, reliability and cost are of liquid-phase product. The cost of often, this means having one or more The expansion will create the world’s

176 Chemical Weekly February 20, 2024 Chemical Weekly February 20, 2024 177

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