Method and apparatus for plasma surface treatment of the interior of hollow forms

Plasma processing apparatus for treating the interior of a hollow dielectric form having a mouth opening comprising:

• (a) an enclosure having walls defining a vacuum chamber, a gate in the enclosure which can be opened to allow a hollow form to be introduced into the vacuum chamber, a form port in the enclosure for communication with the hollow form, and another port in the enclosure for evacuating gas from the vacuum chamber;
• (b) means for selectively sealing a hollow form to the enclosure to provide communication between the mouth opening of the form and the form port in the vacuum chamber while sealing the interior of the hollow form from the vacuum chamber;
• (c) a pump in communication with the form port in the enclosure and a pump in communication with the other port in the enclosure to draw the pressure within the vacuum chamber enclosure and the form to low levels;
• (d) means for introducing gas to be ionized into the interior of the hollow form to provide pressure within the hollow form higher than the pressure within the vacuum chamber outside the hollow form;
• (e) an electrically conductive radio frequency coil mounted within the vacuum chamber to define a working volume which conforms to the hollow form and adapted to allow at least a portion of the hollow form to be inserted in the working volume when the form is within the vacuum chamber;
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• (f) a radio frequency power supply connected to provide radio frequency electrical power to the coil to induce an electric field within the working volume to excite a plasma in the gas contained within the hollow form without breaking down the gas in the vacuum chamber outside the hollow form.

A method for plasma treating the interior surface of a hollow dielectric form within a vacuum chamber enclosure, the form having inner and outer surfaces and a mouth opening, comprising the steps of:

• (a) providing an electrically conductive radio frequency coil within the vacuum chamber which defines a working volume substantially conforming to the hollow form and which is closely spaced to the hollow form such that the hollow form is within at least a portion of the working volume of the coil;
• (b) sealing the mouth opening of the hollow form to seal off the interior of the hollow form from the vacuum chamber outside the hollow form, evacuating the vacuum chamber and the hollow form, and introducing a gas to be ionized into the hollow form such that the pressure within the hollow form is higher than the pressure outside the hollow form within the vacuum chamber;
• and
• (c) providing radio frequency power to the coil to induce a radio frequency electric field in the working volume to excite the gas in the hollow form to produce a plasma within the hollow form at the pressure of the gas within the hollow form while not breaking down the gas in the vacuum chamber outside the hollow form.