Nitrogen trifluoride (NF3) is predominantly used to clean process equipment chambers used in manufacturing semiconductors, thin-film transistor liquid crystal display (TFT-LCD) and photovoltaic solar cells.

This safe, high-performance and cost effective gas is used throughout the world, and has been uniquely developed to replace other, more environmentally damaging materials for chamber cleans, like perfluorocarbons (PFC) and sulfur hexafluoride (SF6).

Dave Cooper, Global NF3 and F2 Product Manager at Air Products told gasworld, “NF3 has been shown to have enabled a substantial reduction in emissions of high global warming potential (GWP) gases to the atmosphere because of its higher rate of dissociation and higher destruction efficiency (and correspondingly decreased emissions).”

NF3 was introduced to the semiconductor market in the 1980s, Cooper added, “Working in conjunction with several major equipment and semiconductor manufacturers, Air Products participated in a substantial industry-wide development effort that resulted in the widespread adoption of NF3 as an alternative chamber cleaning gas to SF6 and the PFC gases that had previously been in use.”

A possible phase out?
Despite NF3’s environmental benefits compared to previous gases for chamber cleaning, there is another gas solution that’s threatening to steal its thunder.

Linde and Air Products have each developed state-of-the-art processes to replace NF3 with pure fluorine, which has a zero global warming potential.

While NF3 has received recent attention for its high global warming potential, Cooper noted, “Existing NF3 abatement procedures, equipment, and technology are available, proven, and affordable – allowing producers and users of NF3 to control emissions to very low levels. For this reason, along with the destruction efficiency of the molecule, recent legislation and regulation being discussed in the US Congress, US EPA, and UNFCC have all focused on controlling emissions of NF3 versus regulating production or future phase-out of the material.”

As well as fluorine’s potential environmental advantage, it may also improve performance and reduce costs in the chamber cleaning process, a critical step in the manufacturing of semiconductors, flat panels, and solar cells.

When asked if he considers that fluorine will take over from NF3, Cooper told gasworld, “While potentially offering cost-of-ownership benefits at the higher consumption levels associated with next-generation TFT-LCD and TF-PV facilities, elemental fluorine can pose higher safety and operability risks which must be taken into account – and, for this and economic cost-of-ownership reasons, F2 is not expected to ever fully replace NF3 applications. However, for some particular customers, F2 may be the best option.”

“Elemental fluorine is a powerfully reactive element, and it requires specific knowledge in system design, operation, and maintenance, expertise Air Products has developed through more than 35 years of safely handling and manufacturing large quantities of F2.”

“Whereas NF3 is safely transported around the globe in cylinders and ISO containers, transportation regulations prohibit the shipping of substantial quantities of fluorine – requiring it to be manufactured on-site at a customer’s facility.”

The market
In order to get accurate market data for this feature, gasworld usually enlists the help of at least one of the major gas companies. For nitrogen trifluoride however, it’s a very different story, as not one of the Tier 1 players was prepared to comment.

Cooper was able to discuss regions of potential; he told gasworld, “NF3 is still used as the predominant chamber cleaning gas-of-choice across all segments of the global electronics industry. In addition to the traditional semiconductor industry, Air Products is especially excited about the faster growth rates being experienced in the TFT-LCD and TF-PV markets.”

“As the emerging thin film Si PV market continues to expand, Air Products sees Asia continuing as a strong source for NF3 customer sales. Outside of the traditional regions of Korea, China, Taiwan, and Japan, PV customer growth in emerging regions of southeast Asia is anticipated.”

Supply options
Dave Cooper, Global NF3 and F2 Product Manager at Air Products, told gasworld, “Nitrogen trifluoride is shipped as a compressed gas to our global customers, either in cylinders of 20kg-195kg fill volume, or bulk ISO containers of up to 8000kg.”

“These NF3 containers are of steel construction and are designed in accordance with the DOT, UN, IMDG, and similar global compressed gas packaging standards.”

“These various national standards provide assurance that NF3 leakage does not occur during transport, and that the containers possess the required reliability to withstand a wide range of conditions during transportation.”