METHOD AND APPARATUS FOR PRODUCING HIGH PURITY SILICON FROM FLAMES OF SODIUM AND SILICON TETRACHLORIDE

摘要

METHOD AND APPARATUS FOR PRODUCING HIGH PURITY SILICON FROM FLAMES OF SODIUM AND SILICON TETRACHLORIDE Vaporized silicon tetrachloride is mixed with vaporized sodium in an exothermic reaction producing liquid silicon droplets and gaseous sodium chloride which are subsequently separated in an efficient manner. Separation of the silicon from the salt by-products is performed by a jet impaction separation technique wherein the products of the complete reaction between sodium and silicon tetrachloride are made to exit from a small hole in the reactor into a region held at a pressure less than half of the reactor pressure. A supersonic jet is thus formed which impinges upon a surface so that the direction of flow of the gas changes abruptly. The silicon droplets, however, are carried by their large forward momentum onto the surface where they are deposited. The salt vapor is then made to flow away from the depositing area and is passed over cooled surfaces where it is made to condense. Modifications of the basic technique allow the silicon to be collected in a variety of physical configurations including pellet form, crystal form, sheet form and ingot form.