Full stress tensor measurement by photoelasticity in silicon

Photoelasticity offers a promising measurement tool for the in-line measurement of semiconductor materials such as silicon. Photoelasticity is a contactless, optical and full-field measurement method based on stress-induced birefringence. However, it is in principle only capable of measuring stress differences and therefore not able to determine the quantitative stress state inside a material. In this work a method is presented to separate this stress difference using modified equations of the mechanical equilibrium in conjunction with the Finite-Difference-Method. This method takes into account the anisotropic photoelastic law for mono-crystalline silicon and enables a full separation of the mechanical stresses with a single measurement.