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.

Abstract: The method of manufacture of the present invention provides a wafer that is better than a bulk monocrystalline silicon wafer and equivalent to silicon on sapphire (SOS) wafers for use as substrates for integrated circuits. The method comprises taking an inexpensive slab of silicon having <111> crystal orientation and by low pressure CVD, high pressure CVD, or plasma deposition techniques depositing a polycrystalline layer of sapphire on the <111> silicon base. The polycrystalline layer of sapphire is then annealed at an elevated temperature to form a monocrystalline layer having a <1101> orientation. A single crystalline layer of silicon having <111> crystal orientation is then epitaxially grown on the sapphire. The resultant multilayer wafer is equivalent in function and reliability to a silicon on sapphire wafer without the commensurate cost.