Growth of diamond films by a 5-kW microwave plasma CVD reactor

Abstract

Diamond films were grown by a 5-kW microwave plasma CVD reactor with an input microwave power of 2.0–4.5 kW at a gas pressure of 100–120 torr using CH 4–H 2–O 2 gas mixtures, and the growth rate, surface morphology, film texture as well as the quality of the films, were examined. The highest growth rate achieved using a CH 4–H 2 gas mixture was 9.3 μm/h for a CH 4 concentration of 2–4%, an input power of 4.5 kW and gas pressure of 120 torr. The films are either 〈100〉- or 〈111〉-textured, which was determined from the X-ray diffraction peak height ratio between (111) and (400), I (111)/ I (400). It was concluded that the dependence of film texture on CH 4 concentration and substrate temperature for the 5-kW CVD reactor was significantly different for that of 1.5-kW CVD reactors. Thus, a new map of surface morphology and film texture was proposed for the process parameters examined in the present work by the 5-kW CVD reactor. The effects of adding oxygen to the process gas were also examined. By adding a small fraction of oxygen [O 2/CH 4 (0.06) and CH 4/H 2 (4%)], the growth rate increased by 50% from that without oxygen, while the addition of a larger amount of oxygen [O 2/CH 4 (0.06–0.5)] suppressed the growth rate to 3.8–2.8 μm/h. The I (111)/ I (400) value increased from 25 to 10 3 with increasing O 2/CH 4 from 0.06 to 0.56. The surface morphology of the diamond films observed by SEM was consistent with the film texture represented by the change in the I (111)/ I (400) values. It was concluded that the addition of oxygen is an important and useful parameter for controlling surface morphology.