Origins of the residual stress in CVD diamond films

Diamond films were deposited on (100) Si wafer, WC (5%Co) and quartz substrate materials by a microwave plasma chemical vapor deposition (CVD) system. The effects of deposition and substrate conditions on residual stress of the films were systematically investigated The films were characterized by scanning electron microscopy, X-ray diffraction, Raman and indentation adhesion testing. The him structure including its non-diamond carbon content, crystal size, texture coefficient, film thickness and surface roughness were examined. The results show that the residual stress of the films is a function of the surface pretreatment, in addition to the substrate material and deposition conditions. The origins of the residual stress are mainly the thermal stress and the intrinsic stress. The intrinsic stress is mainly from the effect of the non-diamond carbon content in the diamond crystals, not at the crystal boundaries. A greater non-diamond carbon content in diamond crystals results in a greater residual stress. The texture of the films has no significant effect on the residual stress. A low compressive residual stress on Si wafer is beneficial to the adhesion of the film.