Anisotropic study of thermal stresses induced by diameter fluctuation during Czochralski silicon single crystal growth

Instabilities in the Czochralski crystal growth process result in deviation from the desired crystal diameter i.e. uneven crystal surface. The excessive thermoelastic stress induced by diameter perturbation is studied by mean of numerical simulations. A set of 3D simulation has been performed for an axisymmetric crystal. The crystal anisotropy is taken into account. The influence of crystal diameter fluctuation on stress field inside the crystal has been studied. The resolved shear stresses have been calculated for 12 slip systems for three crystal orientations. Accumulated excess stress from its critical value is calculated. Simulation results suggest that crystal surface undulation affects both thermal field and stress distribution inside the crystal. The crystal region with high risk of dislocation generation is discussed for three crystal orientation. The stress level in [111] crystal orientation is found to be lower than other orientations. •Effect of crystal diameter variation is studied by using an anisotropic model.•Excess stress from its critical value, τex, is calculated for set of wavelengths and amplitudes.•The stress field is found to be less sensitive for [111] crystal.•The length of non-zero τex region extends longer for [100] and [110] crystals.