Patent GB-1002899-A (GB)
Title: Improvements in or relating to the preparation of monocrystalline semiconductor materials
IPC: C30B25/02
Filed: 1962-05-16
Abstract: A doped monocrystal of a silicon or germanium semi-conductor material is made by simultaneously depositing said semi-conductor material and one or more doping substances selected from the elements of Group III or V of the Periodic System from the gaseous phase on to a heated carrier or the semi-conductor material.  This is effected by passing a reaction gas comprising a gaseous halogen compound of the semi-conductor material, hydrogen, and a gaseous compound of one or more doping substances over the heated carrier. Hydrogen halide is added to the "reaction gas" during at least part of the deposition process.  The ratio of semi-conductor material deposited to doping substance deposited is controlled by varying the amount of hydrogen halide added and/or by varying the mole ratio of semiconductor compound to hydrogen in the reaction gas.  Specified doping substances are boron, phosphorus, and indium.  In an example, the "reaction gas" comprised SiCl4, H2, BCl3 and PCl5.  A p-conductive layer due to complete deposition of boron together with phosphorus was formed when no hydrogen halide was present in the reaction gas but when it was added thereto a n-conductive layer due solely to deposition of phosphorus was formed. Data for the deposition of consecutive layers of p, n, and p+ conductivity types on a silicon crystal are tabulated.  Specifications 926,807, 943,360 and 960,892 are referred to.ALSO:A doped mono crystal of a silicon or germanium semi-conductor material is made by simultaneously depositing said semi-conductor material and one or more doping substances selected from the elements of Group III or Group V of the Period System from the gaseous phase on to a heated carrier of the semi-conductor material.  This is effected by passing a "reaction gas" comprising a gaseous halogen compound of the semi-conductor material, hydrogen, and a gaseous compound of one or more doping substances over the heated carrier. Hydrogen halide is added to the "reaction gas" during at least part of the deposition process. The ratio of semi-conductor material deposited to doping substance deposited is controlled by varying the amount of hydrogen halide added and/or by varying the mole ratio of semi-conductor compound to hydrogen in the reaction gas. Specified doping substances are boron phosphorus, and indium. In an example, the "reaction gas" comprised silicon tetrachloride, hydrogen, boron trichloride, and phosphorus pentachloride.  The mole percentage ratios of the doping substance to semi-conductor material were 5 x 10-4 for BCl3/SiCl4 and 2.5 x 10-6\h for PCl5/SiCl4.  A p-conductive layer of resistivity 0.15 ohm./cm., due to complete deposition of boron together with phosphorus, was formed when no hydrogen halide was added to the "reaction gas"; but when 1 mole per cent HCl/H2 was added, a n-conductive layer of resistivity 4 ohm./cm. due solely to deposition of phosphorus was formed. Variation of the mole ratio of SiCl4/H2 in the "reaction gas" could also be made to produce the above effects. Data for the deposition of consecutive layers of p, n, and p+ conductivity types on a silicon crystal, using the abovementioned proportions of doping compounds, are tabulated. Diagrams (not shown) illustrate (a) the effect, at 1400 DEG  K., of change in the mole ratio of silicon compound to hydrogen (which may be brought about by hydrogen halide addition) upon the mole percentage ratio of boron halide to silicon compound in the "reaction gas" and on the atom percentage ratio of boron to silicon in the deposited layer; (b) the dependence of the deposited quantities of doping substance, boron, and semi-conductor material, silicon, on the surface temperature of the crystal and the mole percentage of hydrogen halide added to the reaction gas. Specifications 926,807, 943,360 and 960,892 are referred to.