Verfahren zur Herstellung von Halbleiterstueckchen kleiner raeumlicher Abmessungen

1,006,174. Coating semi-conductor chips. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 2, 1964 [July 3, 1963], No. 27309/64. Heading H1K. An insulating coating is produced on a semiconductor chip made from a semi-conductor blank by joining one side of the blank to a larger supporting surface so that a selected surface is masked, applying a masking overlay to the opposite side of the blank, dividing the blank into a plurality of separate masked chips each joined to the supporting surface and applying the insulating coating solely to the unmasked surfaces of the chips along the dividing line between the chips. In a specific embodiment, Fig. 4, an uncut semi-conductor blank is joined to a stainless steel or platinum cathode 36 by a silver epoxy adhesive 34, thus ensuring good electrical contact therewith. Next the upper surface of the blank is coated with a masking material 38, e.g. black wax. An ultrasonic cutter using an oil base abrasive grit is used to divide the blank into a plurality of chips. After washing, the chip-bearing cathode 36 is immersed in an electrophoretic bath 32, e.g. of finely divided glass dispersed in ethyl acetate or A1 or Mg oxide dispersed in water or methanol. A D.C. voltage is applied between cathode 36 and electrode 44 and an insulating coating is built up on the exposed surfaces. After removal of the chips 39 and cathode 36 from the bath, the masking material 38 is removed and then the adhesive 34. The glass coating may be hardened by firing it in air. The Specification discloses the modification of the coated chips by doping the lower surface thereof with material to give an oppossite conductivity type. This semi-conductor junction device is then soldered on to a printed circuit.