| 摘要 |
922, 583. Semi-onductor devices. RADIO CORPORATION OF AMERICA. July 15, 1959 [July 25, 1958], No. 24388/59. Class 37. A thin sheet of semi-conductor material is diced by forming a metallic film on at least one surface of the slice in a pattern of spaced areas, dipping the sheet into molten metal to plate the metallic film and immersing the slice in an etch which dissolves the semi-conductor material between the coated areas. The semi-conductor material may be for example silicon, germanium-silicon alloys, silicon carbide, phosphides, arsenides and antimonides of aluminium, gallium and indium and the sulphides, selenides and tellurides of zinc, cadmium and mercury. The metal film may be of copper, cobalt, nickel, rhodium, palladium, silver, iridium, platinum or gold. In a first example silicon sheet is masked to expose the separated areas on one side and the opposite face completely covered. A rhodium pellet is then evaporated by tungsten wire so as to form a thin film on the unmasked portion. The slice is then dipped in the molten lead, tin or a lead tin alloy which coats the rhodium thickly but not the silicon. The sheet is then coated with wax on the face opposite the masked face and immersed for about five minutes in hydrofluoric acid nitric acid mixture which dissolves the unmasked silicon so that the sheet is diced. Connections may be soldered to the lead coating. In a further example silicon diodes made by diffusing phosphorus into P-type material, boron into N- type or boron and phosphorus into opposite faces of an intrinsic sheet is first coated with nickel by a known electric process in a solution described in detail. Adherence of the nickel coating thus formed may be improved by sintering and recoating. The slice is then placed in a masking jig and sprayed with an acid wax resist so as to cover a series of spaced hexagonal areas. The slice is then placed in an etch to dissolve the nickel between the hexagons not protected by the resist. The wax resist is then dissolved and the slice dipped in a lead-tin solder which adheres to the nickel. Finally the slice is inserted in a beaker of etchant to dissolve the silicon between the hexagonal areas. The solder may be used for mounting the separated hexagons on a base. In a still further example a slice to be divided into gallium arsenide diodes is coated with silver and then sprayed with a photo resist. The slice is then placed in the masking jigs so as to expose registering light patterns on opposite faces, the photo resist is then developed and the unexposed portion removed. The portions of the silver film not covered by the resist are then washed away in a nitric acid hydrochloric acid solution and the rest of the plate resist removed. The slice is then dipped in a 99% lead 1% tin solder which coats the silver areas so that when the slice is inserted for five minutes in an etch consisting of equal volumes of nitrogen hydrofluoric acid and distilled water it breaks up into square areas. The wafers are then washed, mounted and encapsulated. |
