Study of diamond films grown at low temperatures and pressures by ECR-assisted CVD

We have studied a set of diamond films grown at low temperatures and pressures by electron cyclotron resonance (ECR)-assisted chemical vapor deposition (CVD). These films were grown on Si (100) substrates at temperatures ranging between 550 and 710 °C and pressures ranging between 1 and 2 Torr. Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were employed to investigate the crystalline quality, diamond yield, and stresses developed in these films. Our Raman lineshape analysis indicates that most of the diamond films exhibit a net compressive stress. An estimate of the net stresses developed in these films was made by adding the thermal interfacial stress component to the calculated stress developed at the grain boundaries from the X-ray analysis. It was found that the residual stress is compressive in nature, but less compressive than that calculated from the Raman shift. The net stress exhibits a strong correlation with the relative amount of non-sp³ phase, thus implying that the non-sp³ phase is causing the measured excess compressive stress. However, the crystalline quality of the diamond phase improves as the overall non-sp³ component increases, thus indicating a process analogous to phase segregation within the films. These results indicate that the source of the excess compressive stress is non-sp³-bonded carbon accumulated at the grain boundaries.