Development of Green NF3™: Lowering the Cost and Environmental Impact of NF3 through the use of Additives
(Matheson, Longmont, CO)
Authors: Glenn Mitchell, Robert Torres, Adam Seymour, Ramkumar Subramanian, and Carrie Wyse Matheson, Advanced Technology Center, Longmont CO 80501, USA Nitrogen trifluoride (NF3) is traditionally used in CVD chamber cleaning processes, most notably for thin film transistor (TFT) flat panel displays (FPD), and is used in very large quantities. As the semiconductor industry moves to more stringent regulations regarding high global warming potential (GWP) gases, NF3 usage and emissions are coming under scrutiny. Recent estimates (1) indicate that an optimized process can have greater than 98% destruction efficiency (DE), leaving 2% of the NF3 to be present in the process effluent. A recent report (2) estimates that NF3 has a GWP impact of 17,000 CO2 equivalents, which make the molecule a very high potential contributor to global warming over other gases used in the semiconductor industry. Matheson has developed Green NF3TM technology, with the objective of reducing the amount of NF3 used in a cleaning process as well as to improve the utilization of NF3 in the process. This is achieved by introducing a carefully selected additive into the NF3 process which forms new in-situ cleaning species. These cleaning species are formed in a plasma environment from the reaction of radicals and fragments from both the NF3 and additive and are easily abated species. Using this approach Matheson has demonstrated reduction in the amount of NF3 used in standard process recipes since the created in-situ molecules can maintain or increase the cleaning efficiency over pure NF3. Experiments conducted on-site with OEM FDP tools show up to a 10% reduction in NF3 usage and up to a 40% reduction in million metric tons carbon dioxide equivalent emissions directly exiting the tool. Further experiments conducted at Matheson’s Advanced Technology Center have established even higher levels of NF3 usage and emission reduction through process optimization and additive tuning. References (1) L. Brindley, “Nitrogen trifluoride (NF3): Calls to monitor potent greenhouse gas” RSC Chemistry World, July 2008. (2) M. J. Prather et al., “NF3, the greenhouse gas missing from Kyoto” Geophysical Research Letters, 35, June 2008.