Process for producing multicrystalline silicon ingots by the induction method and apparatus for carrying out the same

Abstract

This invention is related to obtaining multicrystalline silicon using induction method. The method comprises melting and casting of a pool in the form of a melting space, crystallization of a multicrystalline silicon ingot, and its controlled cooling by means of a heating equipment set. After the pool melting and casting is terminated, crystallization of the remaining part of the multicrystalline silicon ingot is finished along with the controlled cooling of the whole ingot; the ingot is then removed together with a movable bottom and the heating equipment set; and its controlled cooling continues. At the same time, another heating equipment set is supplied to the vacated place with another movable bottom; then the new movable bottom is moved into the water-cooled crucible; and the process steps are repeated in order to produce the next ingot. The method is implemented using an apparatus that additionally includes a platform installed in the controlled cooling compartment and designed to revolve on its axis. This platform holds at least two heating equipment sets. The proposed invention ensures increased output of multicrystalline silicon suitable for production of solar cells.

1 . A process for producing multicrystalline silicon ingots by the induction method, comprising charging and start-up heating a lump silicon charge material in a controlled atmosphere on a movable bottom within the melting space of a water-cooled crucible, creating a bath of molten silicon, and subsequently melting and casting the molten silicon to the shape of the melting space, crystallizing a multicrystalline silicon ingot, and controllably cooling the silicon ingot using a heating equipment set, terminating the steps of melting and casting when the content of impurities in the molten silicon becomes critical, and repeating the process steps starting from the steps of charging and start-up heating the lump silicon charge material, characterized in that upon terminating the steps of melting and casting, the step of crystallizing the remaining part of the multicrystalline silicon ingot is finished as the whole ingot is controllably cooled; upon completion of crystallization, the multicrystalline silicon ingot is removed together with the movable bottom and the heating equipment set and further cooled in a controllable manner; and at the same time, another heating equipment set including another movable bottom is supplied to the vacated space; then said another movable bottom is moved into the water-cooled crucible; and the process steps are repeated in order to produce the next ingot. 
     
     
         2 . The process according to  claim 1 , characterized in that simultaneous removal of the multicrystalline silicon ingot with the heating equipment set and the supply of another heating equipment set together with another movable bottom is done by a 180-degree rotary turn. 
     
     
         3 . An apparatus for producing multicrystalline silicon ingots by the induction method, comprising a chamber connected to a charge bin, the chamber including a water-cooled crucible enveloped by an inductor, a device for start-up heating a lump silicon charge material, and a movable bottom with a rod connected to a movement means, as well as a controlled cooling compartment arranged underneath the water-cooled crucible and including a heating equipment set, the movable bottom being movable up and down along the heating equipment set, characterized by further comprising a platform installed in the controlled cooling compartment and capable of rotation about the axis whereon said heating equipment set is mounted; and the apparatus further comprising at least one more heating equipment set installed on the platform and another movable bottom arranged in said another heating equipment set together with a rod connected to a suitable movement means therefor. 
     
     
         4 . The apparatus according to  claim 3 , characterized in that it contains two heating equipment sets installed on the platform symmetrical around an axis of rotation.