Technology
Theory
Downstream (remote) plasma cleaning, as used by Evactron®, removes hydrocarbon contamination using remotely generated neutral radicals—typically atomic oxygen—while avoiding the ion bombardment, ultraviolet exposure, and surface charging associated with direct plasma treatment. A process gas is dissociated by RF excitation in a remote plasma source, producing a flux dominated by long-lived neutral radicals that diffuse throughout the vacuum system. These radicals react with adsorbed hydrocarbons through hydrogen abstraction, carbon-bond cleavage, and successive oxidation, converting carbonaceous contamination into volatile products, primarily CO, CO₂, and H₂O, which are continuously removed by the vacuum pumping system. Because energetic ions and electrons are largely confined to the plasma source, downstream plasma cleaning is a chemically selective, low-damage process ideally suited for sensitive components, samples, and high-vacuum instrumentation.
THE CHEMISTRY
Inside the Plasma: RF Energy at Work
Radio Frequency (RF) excitation dissociates molecular oxygen into reactive atomic oxygen radicals (O•), which diffuse through the vacuum chamber and oxidize hydrocarbon contaminants via hydrogen abstraction, C–H and C–C bond cleavage, and successive oxidation reactions, ultimately converting carbonaceous deposits into volatile products such as CO, CO₂, and H₂O that are readily removed by the vacuum system.
HOW IT WORKS
RF Plasma vs. UV Ozone: Two Paths to a Clean Chamber
Unlike ozone cleaning, which relies on the slowly reacting O₃ species, RF plasma cleaning generates highly reactive atomic oxygen radicals, resulting in faster oxidation kinetics, greater cleaning efficiency for carbonaceous contamination, and more effective penetration into complex vacuum geometries.
Add space and another paragraph – Under typical operating conditions, RF downstream plasma removes hydrocarbon contamination in minutes, whereas ozone cleaning typically requires 30 minutes to several hours to achieve comparable carbon removal.
SEE THE PROBLEM
Contamination, As the Beam Sees It
Real scanning-electron-microscope footage of hydrocarbon buildup on a specimen surface — the haze that degrades imaging and analysis, and exactly what an Evactron plasma clean removes.