Low incident angle and classical x-ray diffraction analysis of residual stresses in diamond coated Si3N4

Abstract

The overall residual stresses and the stress distribution on chemical vapor deposition diamond coated silicon nitride (Si3N4) are investigated by x-ray diffraction using the classical sin2 ψ method and the low incident beam angle diffraction technique, respectively. The deposition time and the substrate surface roughness evidence a clear effect on the film texture and residual stress generation on the diamond coatings. For the roughest substrate, 15 μm polished diamond, as the deposition time increases from 2 to 6 h, a remarkable improvement of the (220) texture and compressive stress relaxation occur from −0.75 to −0.14 GPa. A change to less compressive and even to slight tensile stress takes place for the smoothest substrate, colloidal finished silica, giving stress values of −0.40 and 0.21 GPa for 2 and 6 h of deposition time, respectively. The stress profile along the film thickness for the 6 h grown diamond film on the 15 μm polished substrate exhibits a linear decrease, in absolute values, from a compressive residual stress of −3.7 GPa, in the upper layer of the film, to almost zero stress at the film/substrate interface.