Sulfur Hexafluoride (SF6)

A colorless, odorless, nontoxic, nonflammable, liquefied gas

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Sulfur Hexafluoride is used by the semiconductor industry for plasma etching prior to chemical vapor deposition (CVD). These processes include Oxide etching, Nitride etching, and wafer cleaning. SF6 gas, which is itself inert, disassociates in the pressence of an RF field to form reactive Fluroide ions. These highly reactive ions are excellent for etching Tungsten and Tungsten Silicide films. Reaction products formed are gaseous Tungsten Hexafluoride and Silicon Tertafluoride. These volatile waste products are carried off in the exhaust gas stream. Oxygen can be injected into the SF6 inlet gas stream to react with the Sulfur in the plasma to form volatile Sulfur/Oxygen gases that will also exit the process equipment in the exhaust gas.

Critical Impurities:

Plasma etch selectivity and rate are maintained at required levels by precisely controlling process parameters. Purity control results in more precise process control.

Critical impurities include air, moisture, and other Fluorine species, notably CF4 and HF. Strict control of impurities improves the uniformity of the etch process.


Especiál Gas employs the recommended Allied Signal data in cylinder technologies for packaging Sulfur Hexafluoride. The treatments which comprise the preparation passivate and condition the internal cylinder surface to minimize the cylinder as a source of contamination.

In addition to the CGA 590, Especiál Gas offers the high integrity CGA 716 outlet connection. This outlet has a leak integrity of 1x10-9 cc/sec thus eliminating the incursion of atmospheric impurities at the cylinder valve connection.


Especiál Gas insures analysis of each cylinder using sophisticated gas chromatography and wet chemical analytical techniques to insure consistent product purity and adherence to specifications.


Limiting Characteristics Chemically Pure Instrument
Purity (Liquid Phase) 99.9% 99.99%
Water ppm <5.3 <5.3
Air as Nitrogen <400 ppm <50 ppm
Acidity <0.3 ppm <0.1 ppm
Tetrafluoromethane <400 ppm < 40 ppm
Oil <5 <2
Toxicity Non Toxic Non Toxic

Both grades exceed ASTM and IEC specifications for use as electrical insulating gas.

Pressure Chart | Periodic Table | Analytical Methods

Updated: 2/9/00