Analysis of Stress Gradient in Ceramic Film by X-ray Method

抄録

The sin² ψ diagram taken from a specimen with steep stress gradients beneath the surface shows nonlinearity, because the X-ray penetration depth changes depending on the tilt angle. Stress gradients can be determined from this nonlinearity. Since ceramic materials have deep X-ray penetration depth, the thickness of a ceramic thin film should have a significant effect on the nonlinearity of the sin² ψ method. In this paper, we propose a method of X-ray measurement of the stress gradient, which takes into account film thickness under the assumption of linear stress distributions. A 58-μm-thick silicon nitride film was prepared. The film specimen was polished carefully with diamond slurry to obtain sharp profiles of the X-ray diffraction. To obtain a steep stress gradient, the specimen was bent on a cylinder. The stress distribution estimated by the present method agreed well with the applied bending stress. In conclusion, the stress gradient should be analyzed by the weighted average stress on the basis of the intensity of the diffracted X-rays from the entire thin film, when the thickness is six times larger than the effective X-ray penetration depth.