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RESEARCH PRODUCT

Stress-induced dislocation generation in large FZ- and CZ-silicon single crystals—numerical model and qualitative considerations

subject

description

When growing silicon crystals with higher diameter (presently up to 300 mm) the thermal stresses and possible dislocation generation in single crystals become a serious problem for both FZ- and CZ-methods. A two-dimensional problem oriented code for the FEM-package ANSYS has been developed to calculate the temperature field in the growing crystal considering radiation exchange with reflectors and environment and thermal stresses. Comparing calculated stresses with critical stresses, the dislocated zone is determined. A qualitative concept for the occurrence of dislocations using the metastable state is developed. In a parametric study for different thermal boundary conditions and crystal geometries, the thermal stresses are calculated and are discussed. From this, some hints on how to reduce stress and avoid dislocation generation are deduced.