Patent GB-961161-A (GB)
Title: Improvements in semiconductor devices
IPC: C04B37/02
Filed: 1960-07-11
Abstract: 961,161. Semi-conductor devices. MINNESOTA MINING & MANUFACTURING CO. July 11, 1960 [July 13, 1959], No. 24103/60. Heading H1K. Semi-conductor elements, e.g. of alloys of lead with tellurium, selenium, or sulphur, are bonded to ceramic bodies, by contacting the surface of the bodies with molten semi-conductor material under at least slightly oxidizing conditions and allowing the semi-conductor material to solidify. The ceramic is, for example, silicate based e.g. Al 2 O 3 .4SiO 2 .H 2 O ; 2MgO.SiO 2 ; or MgO.SiO 2 . Semi-conductor material in the molten state wets the ceramic and fills and clings to concavities of small cross-section therein. A resistor, Fig. 2, having a high positive temperature coefficient of resistance, comprises a cylindrical insulating ceramic body 10 in the periphery of which a helical groove 13 of small V-shaped cross-section is formed. The body 10 is dipped into a melt of selected semi-conductor material, e.g. lead telluride, under oxidizing conditions, and then withdrawn, the semi-conductor material clinging within the groove 13 solidifying to form a filamentary element 14. The assembly is annealed in hydrogen below the melting point of the semi-conductor, after which insulated lead wires 15, 16, which pass through an axial bore in the body 10, are connected to the ends of the element 14. Finally the assembly is coated, as by dipping, with insulating material 19. The oxidizing conditions are secured by dipping under a partial pressure of oxygen, or by firing a thin coating of an oxidation product of the semi-conductor on to the ceramic before dipping in an inert atmosphere. Fig. 3 shows in end view a thermo-pile comprising two similar elongated rectangular insulating support members 21, 22 having spaced parallel grooves 23, 24 extending along their entire lengths. The grooves 23 accommodate elements 25 of P-type semiconductor material, and the grooves 24 accommodate elements 26 of N-type semi-conductor material, the grooves being filled by dipping into semi-conductor melts under oxidizing conditions. The ceramic supports and elements are next annealed and supplied with cold junction members 27, hot junction members 29, and terminal members 28 as by spraying; for elements of lead telluride, iron and tin are suitable for junction members. The thermopile shown in Fig. 4 comprises an outer ceramic cylinder 31, having N-type semi-conductor elements 33 bonded within grooves 32 in its inner surface, and an inner ceramic cylinder 36 having P-type semi-conductor elements 35 bonded within grooves 34 in its outer surface. The Fig. 5 embodiment consists of a plurality of ceramic sectors 43, 44 each having grooves 45, 46, 47 in its periphery. The grooves in sectors 43 are filled with P-type material 48 while those in sectors 44 are filled with N-type material 49. Sectors 43 and 44 are then disposed alternately, the elements 48, 49 being connected in series, as shown, by junction elements 50, 51, 52. In Fig. 6 (not shown) rods of N- and P-type material are placed alternately in grooves in the outer surface of a single ceramic tube; the assembly is enclosed in a mica tube and heated under oxidizing conditions to melt the semi-conductor material and bond it to the ceramic. The ceramic members should have a thermal expansion coefficient substantially matching that of the semiconductor elements.