CHARACTERIZATION OF ULTRA-SHALLOW P+-N JUNCTION DIODES FABRICATED BY 500-EV BORON-ION IMPLANTATION

Ultra-shallow 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 either 950°C or 1050°C were determined to be 60 and 80 nm, respectively. These are the shallowest junctions formed via ion implantation reported in the literature. Consideration of several parameters, e.g., reduced B+ 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°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/cm2 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°C, the leakage current was only 11 nA/cm2. The final junction depths were found to be approximately the same for both preamorphized and nonpreamorphized samples after annealing at 950°C and 1050°C. However, the preamorphized sample exhibited significantly improved dopant activation. © 1991 IEEE