Device and process for producing poly-crystalline or multi-crystalline silicon; ingot as well as wafer of poly-crystalline or multi-crystalline silicon produced thereby, and use for the manufacture of solar cells

摘要

A process and a device for producing crystalline silicon, particularly poly- or multi-crystalline silicon are described, wherein a melt of a silicon starting material is formed and the silicon melt is subsequently solidified in a directed orientation. A phase or a material is provided in gaseous, fluid or solid form above the melt in such a manner, that a concentration of a foreign atom selected from oxygen, carbon and nitrogen in the silicon melt and thus in the solidified crystalline silicon is controllable, and/or that a partial pressure of a gaseous component in a gas phase above the silicon melt is adjustable and/or controllable, the gaseous component being selected from oxygen gas, carbon gas and nitrogen gas and gaseous species containing at least one element selected from oxygen, carbon and nitrogen. The formation of impurity compound precipitations or inclusions, in particular of silicon carbide affecting electric properties of solar cells, can be effectively inhibited and prevented according to the present invention.

主权项

1. Process for producing crystalline silicon, comprising the steps of:
forming a melt of a silicon starting material, performing directed solidification of the silicon melt, wherein at least one of the following steps is performed
a) a phase of a material in gaseous, fluid or solid form is provided above the melt such that a concentration of a foreign atom selected from the group consisting of oxygen, carbon and nitrogen in the silicon melt is controlled and thus a concentration of any one of such foreign oxygen, carbon or nitrogen atoms in the solidified crystalline silicon is controlled; orb) a partial pressure of a gaseous component in a gas phase above the silicon melt is controlled, the gaseous component being selected from the group consisting of oxygen gas, carbon gas and nitrogen gas and gaseous species comprising at least one element selected from oxygen, carbon or nitrogen; wherein at least during the entirety of the period of solidification steady-state equilibrium is established above the melt.