EFFECT OF OXYGEN ADDITIVE ON MICROWAVE PLASMA FOR DIAMOND FILM SYNTHESIS STUDIED BY THE PLASMA IMPEDANCE MEASUREMENT

We have developed a new microwave-plasma-assisted chemical vapor depos ition (CVD) system for diamond film synthesis, which includes a real-t ime monitor of the plasma impedance in the microwave circuit. This imp edance measurement facilitated much the noncontact diagnosis of hydrog en-based CVD plasmas. It appeared that, with increasing the excitation energy, the impedance moved from capacitive to slightly reactive comp lexs. With high sensitivity and cleanliness, the impedance measurement s revealed that the addition of a small amount of oxygen to the hydrog en plasma increased the plasma density.