Patent GB-1011254-A (GB)
Title: Improvements in and relating to the manufacture of semi-conductor bodies
Inventor: MILLETT ERIC JOHN
IPC: C30B25/02
Filed: 1961-11-15
Abstract: <PICT:1011254/C6-C7/1> A single crystal of an elemental semi-conductor (e.g. germanium) is grown epitaxially by the disproportionation of a halide of the semi-conductor material on a single-crystal seed, the halogen for combination with a source of elemental semi-conductor being provided in the form of a binary compound of a halogen and a semi-conductor or a metal (e.g. zirconium) which is insoluble in the semi-conductor material or is a significant impurity (e.g. gallium or indium) for the semi-conductor material.  As shown, a sealed and evacuated silica tube 2 contains three silica holders 4, 5 and 7 containing respectively a germanium semi-conductor wafer 3 on which it is desired to deposit an epitaxial layer, a quantity of germanium 6, and germanium tetra-iodide 8. The tube 2 is inserted into a silica furnace tube 1 and heated by a resistive winding 9, the end containing the holders 5 and 7 being heated more strongly (350-500  DEG C.) than that containing the holder 4 (350-450  DEG C.).  More than one wafer 3 may be provided in the tube 2, and the area of epitaxial deposition may be limited by a silica mask.  The sealed tube may be replaced by an open tube traversed by a desired gas.  The deposited material need not be chemically identical with that of the seed, and may contain significant impurity determining the conductivity type of the deposited material.  Halogen-containing compounds other than iodides may be used.ALSO:<PICT:1011254/C1/1> <PICT:1011254/C1/2> A single crystal of an elemental semi-conductor (e.g. silicon) is grown epitaxially by the disproportionation of a halide of the semi-conductor material on a single-crystal seed, the halogen for combination with a source of elemental semi-conductor being provided in the form of a binary compound of a halogen and a semi-conductor or a metal which is insoluble in the semi-conductor material or is a significant impurity for the semi-conductor material.  As shown in Fig. 1, a sealed and evacuated silica tube 2 contains three silica holders 4, 5 and 7 containing respectively a silicon semi-conductor wafer 3 on which it is desired to deposit an epitaxial layer, a quantity of silicon 6, and silicon tetra-iodide 8.  The tube 2 is inserted into a silica furnace tube 1 and heated by a resistive winding 9, the end containing the holders 5 and 7 being heated more strongly (1010 DEG  C.) than that containing the holder 4 (1000 DEG C.).  More than one wafer 3 may be provided in the tube 2, and the area of epitaxial deposition may be limited by a silica mask.  The sealed tube may be replaced by an open tube traversed by a desired gas.  The deposited material need not be chemically identical with that of the seed, and may contain significant impurity determining the conductivity type of the deposited material.  Silicon tetra-iodide may be placed in the tube 2 in a sealed glass container broken only after sealing the tube 2 or when the desired gas flow is established.  Halogen - containing compounds other than iodides may be used.  Germanium tetra-iodide is prepared by passing nitrogen or argon through a tube 10, Fig. 2, containing holders 18, 20 for pure iodine 19 and pure germanium 21, and heating so that the iodine 19 is at about 100 DEG  C., the germanium 21 is at about 360 DEG  C. and the tube 10 to the right of the constriction 11 is substantially at room temperature.  The tetra-iodide deposits on the tube walls between constrictions 11, 12, and at the end of the reaction, the tube 10 is sealed at constriction 11, the tetra-iodide is resumblimed on to the wall between constrictions 12, 13, and the tube is sealed at constriction 12, evacuated, and sealed at constriction 13.  The tetra-iodide may be further purefied by zone refining.  Silicon tetra-iodide is prepared by heating iodine to 100-130 DEG  C. in a current of nitrogen or argon in a silica bulb system, the iodine vapour being passed through a silica wool plug on which is deposited silicon in a divided state and heated to about 1000 DEG  C. The silicon tetra-iodide may be further purified by vacuum distillation or zone refining.