Verfahren zur Oberflaechenbehandlung von Halbleiterbauelementen mit einem stroemenden AEtzmittel

911,676. Semi-conductor devices. SIEMENS-SCHUCKERTWERKE A.G. June 5, 1959 [June 18, 1958], No. 19325/59. Class 37. In a method of treating the surface of an element consisting of a slab comprising at least one PN junction emerging on a flat face of the slab a jet of chemical etchant is directed on to said face and the slab rotated about a vertical axis perpendicular to said flat face so that the etchant is removed by centrifugal force after etching the exposed junction. In the embodiment (Figs. 1 and 2) a transistor comprising a wafer 45 of P-type silicon to which have been alloyed antimony gold alloy foils to form collector 46 and emitter 47, and circular and annular aluminium foils to form base contacts 48, 49 is etched in this way. The transistor is fixed via plate 4 on a hollow copper stud 5 and the whole assembly rotated by motor 36 in a chamber comprising a channelled " Teflon " (Trade Mark) plate 39 and polymethylmethacrylate cover 42. Initially, the emitter PN junction is etched in a 1 : 1 mixture of hydrofluoric and nitric acids supplied by eccentrically mounted jet 50. At the same time distilled water is fed via jet 51 to dilute the acid before it reaches the base contact 49. After washing in water supplied by jet 50 the collector junction is etched by fluid from jet 52. During the etching steps the copper stud is protected by a flow of water from jet 53. In alternative methods a plurality of elements are placed on the face of a single rotating disc.