Nitrogen Trifluoride: A Potent Greenhouse Gas?
Nitrogen Trifluoride (NF3) has received some sensational press of late, with the most eye catching claim being its potency as a greenhouse gas. It has been stated that NF3 is up to 17,200 times more potent a greenhouse gas than Carbon Dioxide and that it is used in the production of electronics and thin film solar panels. So does this gas pose a real threat? Uses of NF3 The primary use of this gas is for cleaning and for etching surfaces of Silicon, Titanium and Tungsten compounds. This is done primarily in the microelectronics industry but is also used to a far lesser extent in the production of flat panel TV and computer screens and thin film solar panels based on Titanium.
The function of the gas is to break down and supply Fluorine at the surface to be etched. It has been estimated that during use over 96% of NF3 is broken down, and that less than half of the remaining gas escapes into the atmosphere.NF3: The Preferred Option NF3 is already a vast improvement on the gases it has replaced. Sulfur Hexafluoride (SF6) was used previously for etching. This gas has a greenhouse effect 22,800 times greater than Carbon Dioxide, which is also more than 30% higher than the effect of Nitrogen Trifluoride. Also, SF6 does not break down during use, which meant that when it was being used industrially there was significant potential for it to escape into the atmosphere.
It is no surprise then that its use has grown over the last few decades. At present the concentrations of NF3 in the atmosphere is increasing at approximately 11% annually, in line with continuous growth in electronics manufacturing. While this sounds severe, it must be noted here that at the present levels NF3 is having less effect than one fifth of 1% of the Carbon Dioxide contributed by humans to the environment.NF3 And The Kyoto Protocol Sulfur Hexafluoride is listed in the Kyoto Protocol as one of the six greenhouse gases that signatory nations are required to take steps to control. NF3 does not feature on this list, though this does not yet need to be a matter of concern. Given that Sulfur Hexafluoride and Carbon Dioxide are such major contributors to potential human-caused climate change, the relatively small amount of NF3 in the atmosphere at present pales into insignificance. The Verdict for Nitrogen Trifluoride NF3 can and should be seen as a success rather than yet another problem. It breaks down when used, is less aggressive as a greenhouse gas than the Sulfur Hexafluoride it is replacing, and its current level in the atmosphere and rate of increase are not yet a significant issue. This gas surely does need to be monitored and will no doubt be included in some future climate treaty once its use becomes more widespread and if leakage of the gas during industrial processes cannot be fully halted. References: Hellriegel, R. et al. (2006) Remote plasma etching of titanium nitride using NF3/argon and chlorine mixtures for chamber clean applications. Microelectronic Engineering, Vol 84, Issue 1, Jan 2007, Pages 37-41 Forster, P., V. et al (2007): Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Borenstein, S. October 26, 2008. Sydney Morning Herald: TVs and old trees pose threat to climate. Return from Nitrogen Trifluoride to Solar Greenhouse Effect or return to the Green Planet home page for more Solar Power Facts.
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