The preparation of single-crystal silicon for the production of voltage-reference diodes

Silicon crystals with phosphorus concentrations up to 1.5×1019 atoms per cubic centimetre have been prepared by the Czochralski technique. The phosphorus was added either in the form of ammonium orthophosphate or by means of a silicon-phosphorus alloy containing approximately 1¿% phosphorus. It is shown that the use of such an alloy as the doping agent results in improved control of the phosphorus concentration compared with the results obtained with ammonium orthophosphate. Aluminium-wire-type alloyed diodes were prepared using silicon with phosphorus concentrations from 2×1016 to 1.5×1019 atoms per cubic centimetre. The breakdown voltage of these diodes was found to be dependent on the phosphorus concentration up to 3×1018 atoms per cubic centimetre. At concentrations greater than this, the breakdown voltage was found to be sensitive to the alloying conditions. The mechanism of the formation of the p-n junction in silicon with phosphorus concentrations greater than 3×1018 atoms per cubic centimetre is discussed.