$quot;You can mitigate something with a high global warming potential but if your alternative is a zero global warming potential, it is fundamentally better.”
Those are the words of Dean O’Connor, Head of Electronics Market Development and Technology at Linde, as he exclusively spoke to gasworld in October 2008.
Readers of our magazine will no doubt be aware of buzzwords like ‘onsite fluorine’ or simply ‘F2’ as this electronics gas solution continues to gain prominence throughout our industry and beyond. But what is onsite fluorine generation? And why is it becoming so important?
Put simply, high purity fluorine gas is the highest performance cleaning gas available, improving productivity in the electronics sector on CVD tools, reducing energy consumption and environmental impact, and boasting zero Global Warming Potential (GWP).
Linde Electronics has pioneered the use of molecular fluorine (F2) as a replacement for high GWP fluorinated cleaning gases, such as nitrogen trifluoride (NF3) and sulfur hexafluoride (SF6), which are currently used to clean CVD chambers in the manufacture of semiconductors, flat panel displays and thin film solar panels.
Of course, gasworld points out that Linde is not alone in its quest for sustainable solutions and the development of F2 supply systems & techniques.
However, for the purposes of this profile we will be referring to the technology from The Linde Group that is so often in the headlines.
Onsite and on-demand
Linde‘s proven technology for generating low pressure F2 onsite and on-demand eliminates the need for large volume/high pressure storage and ensures safe, reliable and high purity supply.
Anhydrous hydrofluoric acid (HF), supplied in either the gas or liquid phase, is the very low-cost feed material at the heart of the electrolytic process first used by Moissan in his isolation of elemental fluorine in 1886.
The working fluid, KF2HF, which is a liquid only above 70°C, is contained in a fluorine resistant alloy vessel that also serves as the cathode. Current applied through the proprietary anodes determines the rate of fluorine production, and the evolved fluorine and hydrogen are physically separated to prevent recombination. The H2 is diluted for direct disposal, or can be easily and completely abated in situ with proprietary passive catalytic oxidation.
Fluorine is filtered, purified of residual vapour-phase HF to levels below 20 ppm and can then be used at its nominally atmospheric production pressure, or compressed and buffered to a safe working pressure of up to around 20 psig.
To supply processes developed using diluted sources of fluorine, a near-zero pressure drop blender can supply on-demand blends of fluorine and inert gases, such as argon and nitrogen, in a 0-100% range of dilution.
Onsite fluorine generators are sized according to the total volume required, and all rely on the same simple low-pressure, low-temperature and low-inventory process design. The modular design is now available to supply all uses from evaluation/pilot production up to the largest TFT-LCD or PV production lines.
The logical choice
Onsite supply of F2 is widely regarded as the most logical choice of cleaning gas for the electronics industry in the future with the potential to replace all NF3 or SF6 based
chamber cleaning processes.
Generating high purity F2 onsite, at low pressure and on-demand has become a well proven solution, with more than 30 Linde installations worldwide across the semiconductor, TFT/LCD and now PV industries.
Recently activated PV production scale installations include Masdar PV and Malibu in Germany.