DIAGNOSIS OF MICROWAVE PLASMA CVD FOR DIAMOND GROWTH BY PLASMA IMPEDANCE MEASUREMENT

We have attempted to set up a new diamond CVD apparatus equipped with a plasma impedance monitor in the microwave circuit. The advantages of this apparatus are: (1) the remote sensing of CVD plasma, (2) real-ti me sensing, (3) high sensitivity and (4) monitoring of reactor contami nation. Since our microwave impedance monitor responds only to electro n motion, we could obtain information on plasma electrons separately f rom ionic motion. As a result, we confirmed the change in plasma imped ance under the variations of microwave power, total gas (H,) pressure and oxygen addition. The particular importance of this experiment was the new finding that a small amount of oxygen enhances plasma excitati on. Highly reproducible diamond CVD was obtained by in situ oxygen ash ing of the reactor tube under impedance monitoring.