Effect of a Radiation Shield on Thermal Stress Field during Czochralski Crystal Growth of Silicon

Abstract

For silicon CZ crystal growth, the effect of a radiation shield inserted in a furnace on the thermal stress field was studied theoretically by the finite-element method based on thermoelastic analysis.
It is found that a radiation shield lowers the maximum (thermally induced) shear stress, since it reduces the temperature gradient, especially in the radial direction, in a crystal. There is an optimum location for placement of the radiation shield so as to realize the smallest shear stress. From the viewpoint of thermal stress, a radiation shield can allow a higher pull rate of defect-free crystal.