The Photo‐Elastic Constant of Silicon Reviewed in Experiment and Simulation

Results of experiments on single‐crystalline silicon wafers that allow for the determination of the degree of photo‐elastic anisotropy Ape are presented. Ape is introduced as an absolute value of (π11 − π12 − π44)/(π11 − π12 + π44), where π11, π12, and π44 are the piezo‐optical coefficients. These experiments are performed using the measurement system scanning infrared depolarization (SIRD) imager equipped with a special calibration set‐up that produces a defined diametrical loading of the wafer. The generated depolarization maps are compared with simulation results based on a classic 2D stress model, taking the crystallographic anisotropy of silicon into account, by applying the full tensor calculus. The best‐matching material constants used for simulation are compared with data being available from external publications. Ape is determined to be 0.21 ± 0.01 at a wavelength λ = 1.3 μm. Conclusions in view of current studies on other semiconductor material systems are discussed.