Process and apparatus for manufacturing polycrystalline silicon ingots

A process for producing polycrystalline silicon ingots, wherein the process comprises the following steps:

• placing a crucible in a process chamber, wherein the crucible is filled with solid silicon material or is filled with silicon material in the process chamber, wherein the crucible is arranged with respect to at least one diagonal heater in such a way that the diagonal heater is laterally offset and generally above the silicon ingot to be produced;
• heating the solid silicon material in the crucible above the melting temperature of the silicon material in order to form molten silicon in the crucible;
• cooling the silicon material in the crucible below the solidification temperature of the molten silicon, wherein a temperature distribution in the silicon material during the cooling step is controlled at least partially via the at least one diagonal heater;
• and
• blocking any direct gas flow from the crucible (6) to the diagonal heater (9a, 9b) by means of at least one foil curtain (14) which is provided adjacent to the side of the at least one diagonal heater (9a, 9b) which faces the crucible.