Use of computer modeling for defect engineering in Czochralski silicon growth

The yield and quality of silicon wafers are mostly determined by defects, including grain boundaries, dislocations, vacancies, interstitials, and vacancy and oxygen clusters. Active generation and multiplication of dislocations during Czochralski monosilicon crystal growth is almost always followed by a transition to multicrystalline material and is called structure loss. Possible factors in structure loss are related to high thermal stresses, fluctuations of local crystallization rate caused by melt flow turbulence, melt undercooling and incorporation of solid particles from the melt into the crystal. Experimental analysis of dislocation density distributions in grown crystals contributes to an understanding of the key reasons for structure loss: particle incorporation at the crystallization front and strong fluctuations of crystallization rate with temporal remelting. Comparison of experimental dislocation density measurements and modeling results calculated using the Alexander-Haasen model showed good agreement for silicon samples. The Alexander-Haasen model provides reasonably accurate results for dislocation density accompanying structure loss phenomena and can be used to predict dislocation density and residual stresses in multicrystalline Czochralski silicon ingots, which are grown for the purpose of manufacturing polysilicon rods for Siemens reactors and silicon construction elements.