Patent DE-102006017622-A1 (DE)
Title: Manufacturing multi-crystalline silicon comprises placing detachable upper section at an upper edge of crucible furnace to build container structure, filling the container structure with silicon filling, and heating the container structure
Inventor: MUELLER MATTHIAS
IPC: C30B29/06
Filed: 2006-04-12
Abstract: The manufacturing multi-crystalline silicon by vertical-gradient-freeze procedure, comprises placing a detachable upper section at an upper edge of a crucible furnace to build a container structure, filling the container structure with silicon filling made of particulate or granular silicon up to a predetermined height, that is larger than the height of the crucible furnace, heating the container structure for melting up the silicon filling to liquid silicon, and cooling the container structure and solidifying the liquid silicon. The manufacturing multi-crystalline silicon by vertical-gradient-freeze procedure, comprises placing a detachable upper section at an upper edge of a crucible furnace to build a container structure, filling the container structure with silicon filling made of particulate or granular silicon up to a predetermined height, that is larger than the height of the crucible furnace, heating the container structure for melting up the silicon filling to liquid silicon, and cooling the container structure and solidifying the liquid silicon. The predetermined height is selected in such a manner that the molten liquid silicon is completely taken up within the crucible furnace. The upper section has contour, which coincides with that of the crucible furnace. A lid consists of a back-flushing gas inlet (14) and -outlet (15) placed on the removable upper section to isolate the interior of the container structure from the exterior atmosphere. Over the back-flushing gas inlet, back-flushing gas is flowed into the container structure to clean the interior of the container structure. The crucible furnace and the removable upper section are provided with perpendicularly stretching interior walls. The removable upper section is placed flushing with the upper edge of the crucible furnace. An interior circumferential edge of the removable upper section protrudes from or lies at a plane with an interior circumferential wall of the crucible furnace. The crucible furnace and the removable upper section are made from quartz. The removable upper section is supported by a fixing clamp (12) to prevent it from falling into the interior of the container. A heat insulator is placed on the upper edge of the crucible furnace between the crucible furnace and the removable upper section. The particulate or granular silicon is melted up from the upper edge of the container structure by means of a lid heater (5), so that the molten liquid silicon flows down through the silicon filling. The particulate or granular silicon is additionally melted up by means of a jacket heater (6) without heating from the bottom of the container structure. The jacket heater builds a temperature gradient from the top to the bottom of the container structure. For the filling of the container structure, firstly silicon sheets, which are sliced off from the sides of a previously manufactured silicon ingot, are arranged on the bottom of the crucible furnace and along the inner walls of the crucible furnace to partly cover the bottom and the interior walls, and then medium or fine grain are fed. After the addition of a thin layer of granular silicon, firstly large silicon structures are brought along the horizontal direction, so that they span from the middle of the crucible furnace to more or less to the interior walls of the crucible furnace and/or along the vertical direction, so that they span from the proximity to the bottom of the crucible furnace to more or less up to the upper edge of the container structure. The large silicon sheets are covered by further silicon granules. The silicon filling is covered finally by smaller pieces of silicon. The smaller silicon pieces are originate from a recycling process or cleaning process of waste materials, or are silicon fractions from previous batches or silicon wafer fractions. The crucible furnace is provided with a polygonal cross-section/rectangular or square cross-section. The back-flushing gas is free from carbon monoxide and/or carbon dioxide and pure argon. An independent claim is included for a device for manufacturing multi-crystalline silicon.