ANALYSIS OF STRESS GRADIENT IN CERAMIC FILM BY X-RAY-METHOD

The sin(2) psi diagram taken from a specimen with steep stress gradien ts beneath the surface shows nonlinearity, because the X-ray penetrati on 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 ha ve a significant effect on the nonlinearity of the sin(2) psi 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-mu m-thick silicon nitride film was prepared. The film specimen was polished carefully with diamond sl urry to obtain sharp profiles of the X-ray diffraction. To obtain a st eep stress gradient, the specimen was bent on a cylinder. The stress d istribution estimated by the present method agreed well with the appli ed bending stress. In conclusion, the stress gradient should be analyz ed 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 si x times larger than the effective X-ray penetration depth.