A photo-stimulated spectroscopic method for spatially resolved stress analysis in hetero-epitaxial films

Abstract

In this paper, we have developed a laser-stimulated piezo-spectroscopic method for high-resolution stress analysis in ceramic thin films and coatings, with emphasis placed on correcting the convoluting effect arising from the finite size of the laser probe. A series of 3C–SiC/Si and Al2O3/Si3N4 samples were employed for this purpose, with various film thicknesses and substrate orientation as well. In-depth defocusing scans of selected spectral bands arising from both Raman scattering and fluorescence emission were collected. According to a quantitative measurement of the luminescence/Raman probe response function for each material investigated, a spatial probe deconvolution was carried out, from which the actual residual stress distributions could be retrieved by using a computer-aided data restoration procedure. The validity of the proposed methodology was confirmed by using different spectral stress sensors and by altering the collection configuration. The results show that with the aid of a probe deconvolution procedure, spatially resolved stress analyses can be experimentally carried out, thus greatly reducing the error involved in the averaging effect of the laser probe.