Residual stress states are “fingerprints” that give an insight into the formation or use of a material or component. Their analysis is essential, for example in order to identify local stress states and defects on semiconductor substrates and component structures or to optimize production processes on the basis of information on stress states and defect distributions. This is made possible by the SIRD (Scanning InfraRed Depolarization) system from Metrology & Plasma Solutions that operate entirely without contact or destruction.
SIRD is a polariscope that can make visible stresses in materials that are transparent for the examination wavelength (e.g. silicon). The effect of stress-induced birefringence is used here: Defects and material inhomogeneities are often accompanied by stress fields whose spatial expansion is several times greater than that of the cause itself. If a material is exposed to shear stresses, its refractive index becomes anisotropic and the material becomes birefringent. Incident linear polarized light (laser) is therefore depolarized by the sample in transmission or reflection. Consequently, the obtained depolarization maps of SIRD can be interpreted as shear stress distributions.
Intelligent software solutions help the SIRD system to convert the obtained maps into interpretable results efficiently.