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Abstract

A new method and apparatus is described for igniting a plasma from high vacuum. The ignition method uses a small, short term and quick rise in gas flow into plasma chamber while being excited by RF power to ignite the plasma and then drops the gas flow to fixed input flow rate to maintain the plasma. This plasma starting technique does not use electronic means for ignition. The associated apparatus has a gas buffer chamber in fluid communication with the gas source and the plasma chamber, the gas buffer chamber having a small volume gas that is refilled when the device is off. A flow restriction between the gas source and the gas buffer chamber has a maximum flow rate therethrough of 30 sccm (standard cubic centimeters per minute) or less. A valve between the plasma chamber and the gas buffer chamber permits flow between the gas chamber and the plasma chamber, wherein, upon opening the valve, gas is admitted into the plasma chamber and pressure in the plasma chamber rises temporarily causing plasma ignition if the plasma excitation device is energized. The flow restriction maintains the gas flow during plasma operation to maintain a pressure between approximately 0.5 Pa and approximately 6-7 Pa.

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First Claim