Influence of the microwave plasma CVD reactor parameters on substrate thermal management for growing large area diamond coatings inside a 915 MHz and moderately low power unit

Abstract

The tuning (optimization) of the reactor parameters is very important in order to achieve spatial temperature uniformity across the large area substrate for growing high quality and uniformly thick diamond coatings. It is also important to minimize the thermal stress, arising from temperature non-uniformity, for producing crack free large area diamond coatings. So by varying different process parameters, such as chamber pressure, microwave power, gas flow rate and cavity lengths (by changing the probe, short and stage positions), the resultant variation of substrate surface temperature can be measured. By tuning these parameters the geometry as well as the density of the plasma discharge which directly influences substrate surface temperature may be controlled. It has been shown that by suitable manipulation of the reactor parameters one could achieve at best 80°C variation in temperature uniformity over 100mm diameter, which indeed has resulted in a very uniformly thick (±12.8%) high quality polycrystalline diamond (PCD) coating.