nitrogen trifluoride

Nitrogen trifluoride can be prepared from the elements in the presence of an electric discharge.{{cite book |first1 = P. A.|last2= Molochko |first2 =V. A.|last3= Andreeva |first3 =L. L.|script-title=ru:Химические свойства неорганических веществ|pages = 442–455|last1= Lidin |isbn = 978-1-56700-041-2|language=ru|year= 1995 }} In 1903, Otto Ruff prepared nitrogen trifluoride by the electrolysis of a molten mixture of ammonium fluoride and hydrogen fluoride.{{cite journal

| title = Das Stickstoff-3-fluorid

| author = Otto Ruff, Joseph Fischer, Fritz Luft

| journal = Zeitschrift für Anorganische und Allgemeine Chemie

| year = 1928

| volume = 172

| issue = 1

| pages = 417–425

| doi = 10.1002/zaac.19281720132

}} It is far less reactive than the other nitrogen trihalides nitrogen trichloride, nitrogen tribromide, and nitrogen triiodide, all of which are explosive. Alone among the nitrogen trihalides it has a negative enthalpy of formation. It is prepared in modern times both by direct reaction of ammonia and fluorine and by a variation of Ruff's method.Philip B. Henderson, Andrew J. Woytek "Fluorine Compounds, Inorganic, Nitrogen" in Kirk‑Othmer Encyclopedia of Chemical Technology, 1994, John Wiley & Sons, NY. {{doi|10.1002/0471238961.1409201808051404.a01}} Article Online Posting Date: December 4, 2000 It is supplied in pressurized cylinders.

{{chem|NF|3}} is slightly soluble in water without undergoing chemical reaction. It is nonbasic with a low dipole moment of 0.2340 D. By contrast, ammonia is basic and highly polar (1.47 D).{{cite journal | last1 = Klapötke | first1 = Thomas M. | author-link = Thomas M. Klapötke | year = 2006| title = Nitrogen–fluorine compounds | journal = Journal of Fluorine Chemistry | volume = 127 | issue = 6 | pages = 679–687 | doi = 10.1016/j.jfluchem.2006.03.001 }} This contrast reflects the differing electronegativities of H vs F.

Similar to dioxygen, NF₃ is a potent yet sluggish oxidizer. It oxidizes hydrogen chloride to chlorine:{{citation needed|date=January 2024}}

:2 NF₃ + 6 HCl → 6 HF + N₂ + 3 Cl₂

However, it only attacks (explosively) organic compounds at high temperatures. Consequently it is compatible under standard conditions with several plastics, as well as steel and Monel.

Above 200-300 °C, NF₃ reacts with metals, carbon, and other reagents to give tetrafluorohydrazine:{{cite journal |doi=10.1021/cr60250a004 |title=Derivatives of Nitrogen Fluorides |date=1967 |last1=Ruff |first1=John K. |journal=Chemical Reviews |volume=67 |issue=6 |pages=665–680 }}

:{{chem2|2NF3 + Cu -> N2F4 + CuF2}}

NF₃ reacts with fluorine and antimony pentafluoride to give the tetrafluoroammonium salt:

: NF₃ + F₂ + SbF₅ → NF{{su|b=4|p=+}}SbF{{su|b=6|p=−}}

NF₃ and B₂H₆ react vigorously even at cryogenic temperatures to give nitrogen gas, boron trifluoride, and hydrofluoric acid.Parry, Robert W., and Thomas C. Bissot. "The Preparation and Properties of Phosphorus Trifluoride-Borane and Phosphorus Trifluoride-Borane-d₃¹." Journal of the American Chemical Society 78, no. 8 (1956): 1524-1527.

High-volume applications such as DRAM computer memory production, the manufacturing of flat panel displays and the large-scale production of thin-film solar cells use {{chem|NF|3}}.{{cite journal | last=Tsai | first= W.-T. | year=2008 | title=Environmental and health risk analysis of nitrogen trifluoride ({{chem|NF|3}}), a toxic and potent greenhouse gas | journal=J. Hazard. Mater. | volume= 159| doi=10.1016/j.jhazmat.2008.02.023 | pages=257–63 | pmid=18378075 | issue=2–3}}

{{Main|Etching (microfabrication)}}

Nitrogen trifluoride is primarily used to remove silicon and silicon-compounds during the manufacturing of semiconductor devices such as LCD displays, some thin-film solar cells, and other microelectronics. In these applications {{chem|NF|3}} is initially broken down within a plasma. The resulting fluorine radicals are the active agents that attack polysilicon, silicon nitride and silicon oxide. They can be used as well to remove tungsten silicide, tungsten, and certain other metals. In addition to serving as an etchant in device fabrication, {{chem|NF|3}} is also widely used to clean PECVD chambers.

{{chem|NF|3}} dissociates more readily within a low-pressure discharge in comparison to perfluorinated compounds (PFCs) and sulfur hexafluoride ({{chem|SF|6}}). The greater abundance of negatively-charged free radicals thus generated can yield higher silicon removal rates, and provide other process benefits such as less residual contamination and a lower net charge stress on the device being fabricated. As a somewhat more thoroughly consumed etching and cleaning agent, NF₃ has also been promoted as an environmentally preferable substitute for {{chem|SF|6}} or PFCs such as hexafluoroethane.{{cite journal

| title = Environmentally friendly wafer production: {{chem|NF|3}} remote microwave plasma for chamber cleaning

| author = H. Reichardt, A. Frenzel and K. Schober

| doi = 10.1016/S0167-9317(00)00505-0

| journal = Microelectronic Engineering

| volume = 56

| year = 2001

| pages = 73–76

| issue = 1–2}}

The utilization efficiency of the chemicals applied in plasma processes varies widely between equipment and applications. A sizeable fraction of the reactants are wasted into the exhaust stream and can ultimately be emitted into Earth's atmosphere. Modern abatement systems can substantially decrease atmospheric emissions.{{cite web |url=https://www.epa.gov/sites/production/files/2016-09/documents/fpd_full_supplier_profiles_2016_508compliant.pdf |title=F-GHG Emissions Reduction Efforts: Flat Panel Display Supplier Profiles |publisher=U.S. EPA |date=2016-09-30}} {{chem|NF|3}} has not been subject to significant use restrictions. The annual reporting of {{chem|NF|3}} production, consumption, and waste emissions by large manufacturers has been required in many industrialized countries as a response to the observed atmospheric growth and the international Kyoto Protocol.{{cite web |url=https://www.epa.gov/ghgreporting/fluorinated-greenhouse-gas-emissions-and-supplies-reported-ghgrp |title=Fluorinated Greenhouse Gas Emissions and Supplies Reported to the Greenhouse Gas Reporting Program (GHGRP) |date=27 September 2015 |publisher=U.S. Environmental Protection Agency |access-date=2021-03-05}}

Highly toxic fluorine gas (F₂, diatomic fluorine) is a climate neutral replacement for nitrogen trifluoride in some manufacturing applications. It requires more stringent handling and safety precautions, especially to protect manufacturing personnel.{{cite journal

| title = Etch performance of Ar/N₂/F₂ for CVD/ALD chamber clean

|author1=J. Oshinowo |author2=A. Riva |author3=M Pittroff |author4=T. Schwarze |author5=R. Wieland | journal = Solid State Technology

| volume = 52

| year = 2009

| pages = 20–24

| issue = 2}}

Nitrogen trifluoride is also used in hydrogen fluoride and deuterium fluoride lasers, which are types of chemical lasers. There it is also preferred to fluorine gas due to its more convenient handling properties

File:Halogenated gas concentrations 1978-present.png

The GWP of {{chem|NF|3}} is second only to Sulfur hexafluoride in the group of Kyoto-recognised greenhouse gases, and {{chem|NF|3}} was included in that grouping with effect from 2013 and the commencement of the second commitment period of the Kyoto Protocol. It has an estimated atmospheric lifetime of 740 years, although other work suggests a slightly shorter lifetime of 550 years (and a corresponding GWP of 16,800).

File:Nitrogen Trifluoride concentration.jpg

Image:NF3 mm.png) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion.]]

Since 1992, when less than 100 tons were produced, production grew to an estimated 4000 tons in 2007 and is projected to increase significantly.{{cite journal | last=Prather | first=M.J. |author2=Hsu, J. | year=2008 | title={{chem|NF|3}}, the greenhouse gas missing from Kyoto | journal=Geophys. Res. Lett. | volume=35 | doi=10.1029/2008GL034542 | issue=12 | url=http://www.agu.org/journals/gl/gl0812/2008GL034542/ | pages=L12810 | bibcode=2008GeoRL..3512810P| doi-access=free }} World production of NF₃ is expected to reach 8000 tons a year by 2010. By far the world's largest producer of {{chem|NF|3}} is the US industrial gas and chemical company Air Products & Chemicals. An estimated 2% of produced {{chem|NF|3}} is released into the atmosphere.{{cite news | url = http://www.latimes.com/news/nationworld/nation/la-na-climate8-2008jul08,0,7460950.story | title = A climate threat from flat TVs, microchips | date = 2008-07-08 | author = M. Roosevelt | work=Los Angeles Times}}{{cite news |last= Hoag |first= Hannah |title= The Missing Greenhouse Gas |work= Nature Reports Climate Change |publisher= Nature News |date= 2008-07-10 |volume= 1 |issue= 808 |pages= 99–100 |url= http://www.nature.com/climate/2008/0808/full/climate.2008.72.html |doi= 10.1038/climate.2008.72 }} Robson projected that the maximum atmospheric concentration is less than 0.16 parts per trillion (ppt) by volume, which will provide less than 0.001 Wm⁻² of IR forcing.{{Cite journal|last=Robson |first=Jon |title=Nitrogen trifluoride (NF₃) |url=http://www.rmets.org/activities/awards/scholarships/sch_2.php |publisher=Royal Meteorological Society |access-date=2008-10-27 |url-status=dead |archive-url=https://web.archive.org/web/20080516180731/http://www.rmets.org/activities/awards/scholarships/sch_2.php |archive-date=May 16, 2008 }}

The mean global tropospheric concentration of NF₃ has risen from about 0.02 ppt (parts per trillion, dry air mole fraction) in 1980, to 0.86 ppt in 2011, with a rate of increase of 0.095 ppt yr⁻¹, or about 11% per year, and an interhemispheric gradient that is consistent with emissions occurring overwhelmingly in the Northern Hemisphere, as expected. This rise rate in 2011 corresponds to about 1200 metric tons/y NF₃ emissions globally, or about 10% of the NF₃ global production estimates. This is a significantly higher percentage than has been estimated by industry, and thus strengthens the case for inventorying NF₃ production and for regulating its emissions.{{cite journal|first1 = Tim| last1 = Arnold| first2 = C. M.| last2 = Harth| first3 = J. | last3 = Mühle| first4 = A. J.| last4 = Manning| first5 = P. K.| last5 = Salameh| first6 = J.| last6 = Kim| first7 = D. J.| last7 = Ivy| first8 = L. P.| last8 = Steele| first9 = V. V.| last9 = Petrenko| first10 = J. P.| last10 = Severinghaus| first11 = D.| last11 = Baggenstos| first12 = R. F. | last12 = Weiss| title = Nitrogen trifluoride global emissions estimated from updated atmospheric measurements| journal = Proc. Natl. Acad. Sci. USA| volume = 110| issue = 6| pages = 2029–2034| date = 2013-02-05| doi = 10.1073/pnas.1212346110| pmid = 23341630|bibcode = 2013PNAS..110.2029A | pmc = 3568375| doi-access = free}}

One study co-authored by industry representatives suggests that the contribution of the NF₃ emissions to the overall greenhouse gas budget of thin-film Si-solar cell manufacturing is clear.{{cite journal| author1 = V. Fthenakis| author2=D. O. Clark |author3=M. Moalem |author4=M. P. Chandler |author5=R. G. Ridgeway |author6=F. E. Hulbert |author7=D. B. Cooper |author8=P. J. Maroulis| title = Life-Cycle Nitrogen Trifluoride Emissions from Photovoltaics| journal = Environ. Sci. Technol.| volume = 44| issue = 22| pages = 8750–7| publisher = American Chemical Society| date = 2010-10-25| doi = 10.1021/es100401y| pmid = 21067246|bibcode = 2010EnST...44.8750F }}

The UNFCCC, within the context of the Kyoto Protocol, decided to include nitrogen trifluoride in the second Kyoto Protocol compliance period, which begins in 2012 and ends in either 2017 or 2020. Following suit, the WBCSD/WRI GHG Protocol is amending all of its standards (corporate, product and Scope 3) to also cover NF₃.{{cite news |last= Rivers |first= Ali |title= Nitrogen trifluoride: the new mandatory Kyoto Protocol greenhouse gas |work= Ecometrica.com |publisher= www.ecometrica.com |date= 2012-08-15 |url= http://ecometrica.com/blog/nitrogen-trifluoride-the-7th-mandatory-kyoto-protocol-greenhouse-gas}}

Skin contact with {{chem|NF|3}} is not hazardous, and it is a relatively minor irritant to mucous membranes and eyes. It is a pulmonary irritant with a toxicity considerably lower than nitrogen oxides, and overexposure via inhalation causes the conversion of hemoglobin in blood to methemoglobin, which can lead to the condition methemoglobinemia.{{cite web | url=http://www.gasworld.com/news.php?a=2896 | title=Nitrogen trifluoride – Cleaning up in electronic applications | last=Malik | first=Yogender | publisher=Gasworld | date=2008-07-03 | access-date=2008-07-15 | url-status=dead | archive-url=https://web.archive.org/web/20080804170411/http://www.gasworld.com/news.php?a=2896 | archive-date=2008-08-04 }} The National Institute for Occupational Safety and Health (NIOSH) specifies that the concentration that is immediately dangerous to life or health (IDLH value) is 1,000 ppm.{{cite web | url = https://www.cdc.gov/niosh/idlh/7783542.html | publisher = National Institute for Occupational Safety and Health | title = Immediately Dangerous to Life or Health Concentrations (IDLH): Nitrogen Trifluoride | date = 2 November 2018 }}

• IPCC list of greenhouse gases
• Nitrogen pentafluoride
• Tetrafluorohydrazine

{{notelist}}

{{reflist|30em}}

• {{webarchive |url=https://web.archive.org/web/20031222093109/http://www.npi.gov.au/database/substance-info/profiles/44.html |date=December 22, 2003 |title=National Pollutant Inventory – Fluoride and compounds fact sheet }}
• [https://www.eiga.eu/index.php?eID=dumpFile&t=f&f=3086&token=9b75311deb73cbe57d664ea166a3e4b6dfa34386 NF₃] Code of Practice (European Industrial Gas Association)]
• [http://webbook.nist.gov/cgi/cbook.cgi?ID=C7783542 WebBook page for NF₃]
• [https://www.cdc.gov/niosh/npg/npgd0455.html CDC - NIOSH Pocket Guide to Chemical Hazards]

{{Nitrogen compounds}}

{{fluorine compounds}}

{{Nitrides}}

{{DEFAULTSORT:Nitrogen Trifluoride}}

Category:Inorganic amines

Category:Nitrogen fluorides

Category:Greenhouse gases

Category:Industrial gases

Category:Nitrogen(III) compounds