Impurity transport processes associated with interaction of reactive ambient gases and meniscus melt during growth of silicon ribbon by the edge-defined film-fed growth (EFG) technique have been investigated with the help of numerical solution of mass and momentum transport equations. The transport of oxygen and carbon is examined in detail. It is shown that oxygen transport from meniscus sources can account for the interstitial oxygen observed to be introduced into ribbon grown with CO2 in the meniscus ambient. Growth speed is the process parameter that has the most pronounced influence on ribbon impurity levels when a source or sink for the impurity is present on the meniscus surface. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.192.114.19 Downloaded on 2015-06-12 to IP
The effect of solid-liquid interface shape on lateral solute segregation during steady-state unidirectional solidification of a binary mixture is calculated under the assumption of no convection in the liquid. A finite element technique is employed to compute the concentration field in the liquid and the lateral segregation in the solid with a curved boundary between the liquid and solid phases. The computational model is constructed assuming knowledge of the solid-liquid interface shape; no attempt is made to relate this shape to the thermal field. The influence of interface curvature on the lateral compositional variation is investigated over a range of system parameters including diffusivity, growth speed, distribution coefficient, and geometric factors of the system. In the limiting case of a slightly non-planar interface, numerical results from the finite element technique are in good agreement with the analytical solutions of Coriell and Sekerka obtained by using linear theory. For the general case of highly non-planar interface shapes, the linear theory fails and the concentration field in the liquid as well as the lateral solute segregation in the solid can be calculated by using the finite element method.
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