Commercialization of the edge-defined film-fed growth (EFG) process for growth of silicon ribbon crystals in the form of hollow tubes has directed the development of EFG furnaces toward increasing tube diameters in order to maximize productivity in manufacture of wafers for solar cells. The current state-of-the-art EFG production is based on thin-walled octagon tubes with 12.5 cm faces, where tube diameter is of the order of 38 cm. We describe here the challenges faced in bringing EFG technology into large-scale manufacturing, and ongoing development of furnace designs for growth of tubes for larger wafer production using hexagons with 15 cm face widths, and wall thicknesses in the range 250-300 mu m. (c) 2005 Elsevier B.V. All rights reserved.