GB1397338A - Impurity regions in semiconductors - Google Patents

Abstract

1397338 Manufacturing semi-conductors WESTERN ELECTRIC CO Inc 19 May 1972 [24 May 1971] 23584/72 Heading H1K A buried impurity region is formed in a semiconductor substrate by implanting ions of the impurity therein by bombardment, heating the substrate to diffuse the impurity ions further into the substrate and then removing surface substrate material damaged by the ion implantation, and growing an epitaxial layer on the substrate surface. The damaged surface material may be oxidized prior to its removal. The depth of the implanted region is from 300-3000 Š, preferably with an average depth of 1000 Š, which is sufficient to diffuse ahead of a growing oxide film. Simultaneously with the heating at 1200‹ C. in dry O 2 for 3¢ hrs. to diffuse in As implanted impurities into a Si substrate, a layer of SiO 2 is grown at the surface, which is subsequently removed by hydrofluoric acid. Residual disorder in the substrate after stripping the oxide is removed by etching an additional 5000 Š of substrate in the usual HF vapour etch cleaning process prior to epitaxial growth thereon. Alternatively the whole of the damaged region can be converted to oxide by heating at 1200‹ C. for 1 hour in dry O 2 to give a 2000 Š thick oxide layer and then heating at 1200‹ C. for 1 hour in steam to grow another 8000 Š of oxide. After removing the oxide an epitaxial N-type region is formed thereover to give a final transistor structure.