Plasma-assisted chemical vapour deposition in a tunable microwave cavity

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Abstract
We describe a microwave plasma-assisted chemical vapour deposition facility with some novel features including the ability to adjust the microwave cavity tuning during operation, thereby maximizing the overall device efficiency. The initial application of the facility was for diamond thin film synthesis. Microwave power, generated by a magnetron obtained from a commercial microwave oven, enters the cylindrical resonant cavity from the top face, which can be adjusted to position the maximum electric field at the desired location within the cavity; this tuning can be done while the equipment is running, allowing fine adjustment of the field distribution when the cavity is plasma-loaded. The microwave power activates the reactant gases, which are at low pressure inside a quartz bell jar specimen chamber, and the cavity base plate has a window through which the rear face of the hot substrate can be viewed, allowing pyrometric temperature measurement. A moveable sample holder allows control of the sample position in relation to the plasma ball. The system is stable and the deposition rate is about 1.25 mu m h-1.