P+/N shallow junctions formation on Ge+ preamorphized silicon substrate

Ultra shallow P⁺/N junctions obtained by low energy boron implantation in a preamorphized silicon substrate are characterized. The preamorphization stage is accomplished by implanting high dose of germanium ions under well defined conditions of temperature and energy. As a result, the suppression of channelling tails, and the high degree of electrical activation of the boron after low temperature solid phase epitaxial (SPE) regrowth have been clearly demonstrated. Combining XTEM analysis, SIMS profiling, spreading resistance method and electrical noise measurements allowed us to characterize the preamorphization in terms of its effect on the structural and electrical properties of the P⁺/N junctions. Correlation between the preamorphization induced defects (End-Of-Range) and the junction leakage current has been established. We show that, when these defects are located in the space charge region, they act as generation-recombination centres and increase, by the way, the electrical noise on the forward current of the diodes