MEASUREMENT OF THE AMOUNT OF OXYGEN GENERATED BY QUARTZ SOURCE WALLS IN A SF6 DENSE-PLASMA - APPLICATION TO A HELICON REACTOR

The amount of oxygen generated in a SF6 dense plasma by the etching of the quartz tube walls surrounding the plasma source of the helicon re actor has been measured. Two complementary techniques have been used t o identify the wall etch products and the measurement of their equival ent flux: plasma induced emission spectroscopy of oxygen atoms (actino metry) and mass spectrometry by comparison with the amount of the isot opic oxygen (O-18(2)) introduced into the plasma. It appears that, wit h a 5 mm air gap between the antenna and quartz walls of the reactor, the equivalent oxygen outgassing flux ranges from 2 to 4 seem, dependi ng on the SF6 pressure and the radio frequency power applied. This cor responds to an oxygen concentration in the gas phase between 15% and 4 0%, depending on the operating conditions. This result should be consi dered for the development of future dense plasma reactors using quartz walls and for improvement of the performance of the present generatio n of inductively coupled and electron cyclotron resonance plasma react ors. (C) 1995 American Vacuum Society.