US 4,225,378 A · Extrusion mold and method for growing monocrystalline structures

Abstract

An extrusion mold for growing crystalline silicon in any desired size at a very high purity level. The mold is formed of molybdenum with any desired width, length and depth. The major portion of its length is immersed in a temperature-controlled environment. A high temperature receiving end of the mold is located in a controlled atmosphere containing an inert gas such as nitrogen. Molten silicon is poured from a crucible into the open end of the mold in the controlled atmosphere. The extrusion mold is at an incline to permit the molten silicon to flow through the mold until it contacts a seed crystal of silicon. The seed crystal is located at the point where the silicon solidifies. The molten silicon begins to form a crystalline structure oriented according to the seed crystal. As crystallization takes place, the seed is slowly pulled out of the other end of the extrusion mold which is open to the atmosphere bringing the crystalline silicon structure with it.

Claims24

Dependent claims

A method of growing a monocrystalline body from a polycrystalline melt of the same material, the steps of said method comprising:

placing a seed crystal attached to a pull rod or web inside an enclosed extrusion mold made of material that is non-reactive to said melt from an end of said mold exposed to the atmosphere;
maintaining a fixed temperature gradient along the length of the mold from one end to the other which gradually decreases from a temperature slightly lower than the melt, but still above its melting point at one end to a temperature at the other end that would decrease the temperature of the exiting monocrystalline body sufficiently to expose it to the atmosphere, the seed crystal being located at the temperature within the mold at which said melt solidifies;
and
pouring the polycrystalline melt into the open hot end of said enclosed extrusion mold, said extrusion mold being at a slight downhill angle from its hot to its cool end;
and
forming said monocrystalline body by pulling the seed crystal out of said extrusion mold and into the atmosphere.

3 more elements

Dependencies are inferred from the claim text.

Extrusion mold and method for growing monocrystalline structures

Life of this patent

Extrusion mold and method for growing monocrystalline structures

Life of this patent

Abstract

Claims24