LOW-TEMPERATURE EPITAXIAL GROWTH OF DOPED SILICON FILMS AND JUNCTIONS

Studies of the structural and electrical properties of homo-epitaxial silicon films and junctions deposited at low temperatures by ultra-high vacuum sublimation have been made. Spreading resistance measurements of epitaxial layers sublimed from boron- and phosphorus-doped silicon sources have shown that films of known and uniform impurity concentrations could be deposited. Fault-free epitaxial layers have been grown on (111) at temperatures above 650°C, and on (100) at temperatures down to 500°C. Excellent silicon junction structures have been achieved at temperatures far lower than heretofore reported as demonstrated by junctions comprising 0.05 Ω-cm, P-type silicon epitaxial layers on 1.5 Ω-cm N-type, (100) substrates. These junctions, which in general show abrupt impurity profiles, are characterized by low reverse leakage currents and sharp voltage breakdowns close to the theoretical breakdown voltage anticipated from measured resistivity data. Minority carrier lifetimes ranging from 4 to 8 μsec have been measured by the carrier decay technique. The detrimental effects of substrate out-diffusion (resulting from the elevated temperatures used for cleaning the substrate surface prior to deposition) can be avoided by the sequential deposition of all-epitaxial junction structures. P+N- on N epitaxial structures with good junction properties have successfully been formed from highly P- and lightly N-doped sources. © 1969.