Analysis of Residual Stress Effect on Out-of-Plane Deformation of Chemical-Vapor-Deposited Free-Standing Diamond Films

摘要

A theoretical model for the influence of residual stress on the out-of-plane deflection in a free-standing thick diamond films (the bowing phenomenon) is presented. The variation in residual stress with film thickness is believed to be a cause of the bowing. In this study, the stress variation is assumed to be produced by a gradual increase of substrate deformation resulting from the layer-by-layer deposition of the film. The model was developed using infinitesimal plate-bending theory, considering the two deformation modes of contraction or expansion and bending. To verify the suggested model, diamond films were fabricated on Si, Mo and W substrates of varying thicknesses using microwave plasma assisted chemical vapor deposition. The model's predictions on bowing, based on intrinsic stress value measured by the curvature method, were in good agreement with the bowing curvature of the as-released films measured by a profilometer. This confirms that the bowing of thick films depends on the intrinsic stress variation of the film associated with gradual increase in substrate deformation. Finally, a method of eliminating bowing by depositing multi-layers with different stresses was discussed.