GB1020328A - Processing of semiconductor devices - Google Patents

Abstract

1,020,328. Semi-conductor devices. STANDARD TELEPHONES & CABLES Ltd. Dec. 11, 1964, No. 50522/64. Heading H1K. In a method of making a semi-conductor device a semi-conductor body is etched to remove surface contamination, and subsequently lifetime reducing impurity is applied to the surface of the body and diffused into the body. The semi-conductor body must be protected from the action of light between these two steps because the action of light gives rise to surface conditions which inhibit the introduction of lifetime reducing impurities. Resultant devices would have random variations in their switching properties. In the embodiment described silicon slices containing partially formed planar transistors are individually subjected to the following treatment which was carried out in subdued lighting. Each slice is cleaned in boiling concentrated sulphuric acid, washed in de-ionized water, etched in aqueous ammonium bifluoride to remove any oxide film, washed with de-ionized water, and blown dry with an air jet. (At this stage the slices may be stored in the dark in water or in a solution containing free hydrofluoric acid.) Still in subdued lighting the slices are loaded in a vacuum evaporator and gold deposited on one surface of each of the slices and diffused in. A similar treatment may be given to germanium devices but an alternative oxide-removing etchant to aqueous ammonium bifluoride may be needed.