Patent GB-778383-A (GB)
Title: Improvements in or relating to the production of material for semi-conductors
Inventor: SCOTT THOMAS ROBERTSON
IPC: C01B25/06
Filed: 1953-10-02
Abstract: The manufacture of a coherent body of pure elements other than silicon, for a semi-conductor comprises flowing a stream of a hydride of that element on to a surface located in an enclosure, heating the said surface to a temperature above the decomposition temperature of the hydride and adjusting the rate of flow of the hydride and the pressure in the enclosure to ensure decomposition of the hydrides substantially wholly on said surface.  Pure elements which may be produced are germanium, boron, phosphoros, arsenic, antimony, bismuth, selenium, tellurium.  Germanium hydride for use in the above process, may be prepared by reacting lithium aluminium hydride with germanium tetrachloride in a solvent such as tetrahydrofuran.  Sodium borohydride may be used instead of lithium aluminium hydride. Diborane or stibine, for use in the above method, may be produced by reacting lithium aluminium hydride with the trichloride in diethyl ether.  Preferably the lithium aluminium hydride solution should be added to the chloride.  Phosphine and Arsine are prepared by reaction in tetrahydrofuran.  Hydrogn telluride and hydrogen selenide are prepared by addition of the tetrachloride to lithium aluminium hydride in ether solution at low temperatures e.g. -78 DEG C. Hydrogen selenide may also be produced by reacting aluminium selenide with hydrochloric acid.  Lead telluride or lead selenide may be produced according to the invention by decomposing a mixture of lead tetra-ethyl and tellurium hydride or selenium hydride.  Cadmium selenide may be produced by decomposing a mixture of cadmium diethyl and selenium hydride when the cadmium and selenium react to form the cadmium selenide.  Specification 745,698 describes a similar process for the production of silicon from silane.ALSO:A process of manufacture of a coherent body of pure element (other than silicon) for a semi-conductor comprises flowing a stream of a hydride of that element on to a surface located in an enclosure, heating the said surface to a temperature above the composition temperature of the hydride and adjusting the rate of flow of the hydride and the pressure in the enclosure to ensure decomposition of the hydride substantially wholly on said surface. Modifications of the process are (a) the manufacture of a semi-conductor element containing a minor amount of a significant impurity by using a stream containing hydrides of the elements in the desired proportions and decomposing both hydrides on, for example, the surface of a seed of semi-conductor material, (b) the manufacture of N-P-N (or P-N-P) junction devices by flowing on to the surface of a body containing the N (or P) impurity a stream of mixed hydrides of the main and P (or N) impurity elements to form a layer of P (or N) type material and thereafter flowing a second stream of mixed hydrides of the main and N (or P) impurity elements to form a layer of N (or P) type material, and (c) the manufacture of a semi-conducting alloy by using a mixed stream of gaseous compounds comprising a hydride of one element and a hydride, carboxyl or lower alkyl of the other element. Pure elements which may be produced are Ge, B, P, As, Sb, Bi, Se, and Te.  For Ge or Si, suitable hydride-forming impurity elements are B, Ga, P, As, Sb and Bi.  Examples of the manufacture of semiconducting alloys are (a) germanium-silicon using the mixed hydrides and (b) alloys of an element of Group IIIB with an element of Group VB such as (i) indium antimonide, using a mixture of indium triethyl with stibine, (ii) lead telluride (or selenide) using a mixture of lead tetraethyl with tellurim (or selenium) hydride, and (iii) cadmium selenide, using a mixture of cadmium diethyl and selenium hydride (the cadmium selenide may be utilized as an intermediate layer in a selenium rectifier between selenium and a counter-electrode of cadimium, in which case it is deposited upon selenium, and the cadimum counter-electrode deposited thereover by stopping the supply of selenium hydride but continuing the flow of cadmium diethyl). The preparation of specific hydrides is described as also in apparatus (Fig. 7, not shown) suitable for depositing semi-conductor material upon a surface, which surface may be, apart from a seed, and another semi-conductor material, a metal, e.g. steel, plate, or a glass or mica plate.  Specification 745,698 is referred to.