Characterization of ultra-shallow p/sup +/-n junction diodes fabricated by 500-eV boron-ion implantation

Ultrashallow gated diodes have been fabricated using 500-eV boron-ion implantation into both Ge-preamorphized and crystalline silicon substrates. Junction depths following rapid thermal annealing (RTA) for 10 s at either 950 degrees C or 1050 degrees C were determined to be 60 and 80 nm, respectively. These are reportedly the shallowest junctions formed via ion implantation. Consideration of several parameters, e.g. reduced B/sup +/ channeling, increased activation, and reduced junction leakage current, lead to the selection of 15 keV as the optimal Ge preamorphization energy. Transmission electron microscope results indicated that an 850 degrees C/10-s RTA was sufficient to remove the majority of bulk defects resulting from the Ge implant. Resulting reverse leakage currents were as low as 1 nA/cm/sup 2/ for the 60-nm junctions and diode ideality factors for crystalline and preamorphized substrates ranged from 1.02 to 1.12. Even at RTA temperatures as low as 850 degrees C, the leakage current was only 11 nA/cm/sup 2/. The final junction depths were found to be approximately the same for both preamorphized and nonpreamorphized samples after annealing at 950 degrees C and 1050 degrees C. However, the preamorphized sample exhibited significantly improved dopant activation.<
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