Effects of low temperatures, low pressures and seeding over the crystalline quality, yield and stress of diamond films grown by ECR-assisted chemical vapor deposition

We have studied diamond films grown by electron cyclotron resonance (ECR)-assisted chemical vapor deposition (CVD) on Si (100) substrates seeded with diamond, boron nitride and unseeded. Relatively low temperatures (550-710 °C) and low pressures (1-2 Torr) were employed. Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterize the crystalline quality, diamond yield, and stresses developed in these films. Most of the diamond films exhibit a Raman blue-shift with respect to natural diamond, indicating that the net stress is compressive. However, this net stress is significantly more compressive than the one estimated by taking into account the thermal interfacial stress and the stress developed at the grain boundaries. In addition, this net stress exhibits an inverse correlation with diamond yield, and a direct correlation with crystalline quality. These results were interpreted in terms of the critical interplay between the supply of precursor species to the growing surface and the surface mobility of adsorbed species. The excess (or intrinsic) compressive stress shows an inverse correlation with diamond crystalline quality, indicating that the creation of point defects serves as a stress-relieving mechanism. Seeding effects, in general, are deleterious to diamond quality, in this temperature and pressure regime studied. Seeding with boron nitride had the effect of reversing the net stress from compressive into tensile, but this effect was rapidly lost as the diamond yield increased.