Method for manufacturing a silicon cylinder by growth on seeds in a directed solidification furnace

A process for manufacturing a silicon ingot by seeded regrowth in a directional solidification furnace, comprising at least the steps consisting of:

• (i) providing a crucible of longitudinal axis (Z), the bottom of which comprises a tiling of monocrystalline silicon seeds of straight prism shape;
• and
• (ii) carrying out the directional solidification of silicon by seeded regrowth, in a growth direction collinear to the axis (Z) and with a spatially or temporally concave solidification front;
• wherein the tiling in step (i) is formed:
• from one or more central seeds Gc;
• and
• from one or more peripheral seeds Gp, adjacent to the seed(s) Gc,
• a seed Gp having a crystal lattice symmetrical to the crystal lattice of the adjacent seed Gc, relative to the plane P defined by the boundary between said seeds Gp and Gc;
• said seed(s) Gp having, in a vertical cutting plane, a width (lp) strictly smaller than the total width (lu) of said central seed(s);
• and
• the peripheral seeds Gp being sized so that:
• lp=d−b
• with:
• d satisfying:
• d≧H.tan θmax, wherein θmax is the maximum value of the angle of the solidification front of the furnace used, and H is the desired height, measured along the axis (Z), of the silicon ingot;
• and
• b=0 for a crucible with right angles, and b=Rinternal crucible, wherein Rinternal crucible is the size of the bevel for a crucible with rounded edges.