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Fluorine Use in the Electronics Industry By Dr. Paul Stockman

Fluorine (F2) is used in the high-tech thin absorb infrared radiation and convert it to film industries of semiconductor, display, heat energy, and therefore has zero global and photovoltaic manufacturing. Chemical warming potential (GWP) or contribute to vapor deposition (CVD) processes in this global warming. type of manufacturing require periodic For the largest use applications, fluorine cleaning — as often as once per deposition is a direct replacement for NF3 without the cycle or up to once per several days, need for further process development. On depending on the thickness of the film the same equipment, fluorine can clean deposited and the sensitivity of the devices three to five times faster. Compared with being made — to remove particles and films NF3, fluorine cleaning has a much lower from the surfaces of the vacuum chamber thermal effect on the chamber, meaning and process equipment. the overall cleaning cycle is significantly Cleaning gases comprise two-thirds of shorter. the GHGs (greenhouse gases) used in a Fluorine is the most electronegative typical semiconductor fab. Converting element from the periodic table so the risks Linde Generation-F™ on-site fluorine generators PECVD (plasma-enhanced chemical vapor associated with its reactivity and toxicity deposition) chamber cleaning to fluorine must be mitigated, like for any chemical. enables some mid-tier manufacturers to For small volumes, cylinders are available. Compared to NF3 and SF6, decrease their GHG below the reporting It can be transported in large volumes as a fluorine has been measured threshold and large manufacturers can cryogenic liquid or compressed gas, but it significantly reduce their compliance is safer to produce in on-demand volumes to do faster cleaning, use burden. on-site at low or atmospheric pressure, less gas, and consume Cost of compliance at large fabs can as its reactivity is directly related to its lower energy. be over $1 million. Manufacturers have pressure. Double containment and material to report the amount of GHGs used and selection are the keys to design for safety are substantially reduced and supply measure the gases at key steps in their and reliability. and reliability are increased as process processes. Fluorine is an alternative Incorporating fluorine has different demands scale. to greenhouse gases — which also project considerations for an on-site supply Linde Generation-F™ on-site fluorine have process inefficiencies — such as scheme compared to packaged material generators range in output production

CF4 (tetrafluoromethane), SF6 (sulfur supplies to ensure proper footprint, capacity from one ton a year to hundreds of hexafluoride), NF3 (nitrogen trifluoride), available utilities, and expansion capability. tons a year. There have been over 30 Linde and C2F6 (hexafluoroethane) for CVD With on-site production, chemical installations of fluorine generators in the cleaning. Unlike GHGs, fluorine does not inventory, safety risks, and pricing volatility last 20 years and they have operated without a single safety incident. Clean Gas Atmospheric Lifetime Global Warming Potential Compared to greenhouse gas producing alternatives such as NF3 and SF6, fluorine CF4 50,000 years 6,500 GWP100 has been measured to do faster cleaning, use less gas, and consume lower energy C2F6 10,000 years 9,200 GWP100 across all of the tested PECVD tools, and

C3F8 2,600 years 7,000 GWP100 is becoming more widely adopted in the electronics industry. SGR SF6 3,200 years 23,900 GWP100 About the Author NF3 740 years 17,200 GWP100 is Head of Market F 0 years 0 GWP Dr. Paul Stockman 2 100 Development at Linde Electronics. Figure 1 Source: Linde Electronics

28 Specialty Gas Report • Third Quarter 2016 www.specialtygasreport.com