Cleaning gas for the use in plasma, ion beam or sputter etching in semiconductor devices manufacturing
Sifren® 46 (C4F6 or Hexafluorobutadiene) C4F6 has a GWP=0 and it is the most advanced etching gas for critical applications. Its low C/F ratio and its insaturations allow achieving the highest aspect ratios in etching.
Sifren® 46 (C4F6 or Hexafluoro-1,3-butadiene) is an unsaturated fluorocarbon with an alternating double bond. It is a colorless, odorless, toxic, flammable gas showing very high performance for plasma, ion beam, or sputter etching in semiconductor devices manufacturing with Xenon (Xe) and Argon (Ar) as carrier or dilution gas. Due to the short atmospheric lifetime (< 1day), the negligible global warming potential, and the inertness to the stratospheric ozone layer, Sifren® 46 is an environmentally compatible gas.
As long as using plasma dielectric etching it is essential to control the plasma. Chemicals such as C4F6 are able to balance etching deposition species, by which superior results are achieved compared to other gases used to produce vertical profiles.
In the C4F6 molecule the C:F ratio is high enough to control the amount of polymer on the chamber surface and wafer surface with regard to F etching radicals. More important is, that the intrinsic characteristic allows high selectivity to substrates or photo resists and wider process windows compared to e.g. C4F8 (Octafluorobutane). This behavior is particularly beneficial to address the need for sub 0.25 µm requirements.
In using Argon as carrier gas nitride selectivity can result in a decreasing function. Xenon as the other possible carrier gas has an increased selectivity. Therefore mixtures from Ar/Xe are a good compromise.
Markets & Applications
Sifren® 46 is suggested for the use in plasma, ion beam or sputter etching in semiconductor devices manufacturing.
Particularly outstanding results have been observed in plasma dielectric etching with Xe and Ar as carrier gas and dilutants. In plasma dielectric etching it is important to control the plasma chemistries in order to balance etching and deposition species. C:F ratio in C4F6 molecule is high enough to control the amount of polymer on the chamber surface and wafer surface with respect to F etching radicals so achieving superior results over other gases to produce vertical profile. More important, its intrinsic characteristics allow high selectivity to substrate or photoresist and wider process window compared to C4F8. This behaviour is particularly beneficial to address the need for sub 0.25 µm requirements. Ar is being used as a carrier gas but nitride selectivity results a decreasing function for Ar. On the opposite side, Xe increases selectivity in such a way the mixtures Ar/Xe are a good compromise. Normalised global warming emissions result in a reduction greater than 80% compared to a typical C3F8 based process emissions.
Around 20°C Sifren® 46 is a stable gas and is compatible with the most carbon- or stainless-steel types. The chemical behaviour in presence of other metals e.g. copper, tin, brass, zinc it is not completely studied. In contact with magnesium or alloys with high magnesium (> 2%) content, reactions are possible, contact must be avoided. The compatibility with plastics and elastomers depends on the temperature employed and additional additives in the plastics materials. Fluoro-rubbers, PVC and Nylon are suitable plastics for Sifren® 46. Material compatibility tests with Sifren® 46 are recommended.
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