Etching materials with an atmospheric-pressure plasma jet

A plasma jet has been developed for etching materials at atmospheric pressure and between 100 and 275 degrees C. Gas mixtures containing helium, oxygen and carbon tetrafluoride were passed between an outer, grounded electrode and a centre electrode, which was driven by 13.56 MHz radio frequency power at 50 to 500 W. At a flow rate of 51 l min(-1), a stable, are-free discharge was produced. This discharge extended out through a nozzle at the end of the electrodes, forming a plasma jet. Materials placed 0.5 cm downstream from the nozzle were etched at the following maximum rates: 8.0 mu m min(-1) for Kapton (O(2) and He only), 1.5 mu m min(-1) for silicon dioxide, 2.0 mu m min(-1) for tantalum and 1.0 mu m min(-1) for tungsten. Optical emission spectroscopy was used to identify the electronically excited species inside the plasma and outside in the jet effluent.