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

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 CH4-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 CH4-H-2-O-2 gas mixture was 9.3 mum/h for a CH4 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, 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 profess 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/C-H (0.06) and CH4/H-2 (4%)], the growth rate increased by 50% from that without oxygen while the addition of a larger amount of oxygen [O-2/CH4 (0.06-0.5)] suppressed the growth rate to 3.8-2.8 mum/h, The I-(111)/I-(400) value increased from 25 to 10(3) with increasing O-2/CH4 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. (C) 2001 Elsevier Science B.V. All rights reserved.