ELECTRICAL STUDIES ON H-IMPLANTED SILICON

Electrical properties of high-dose (1.6 X 10(16) at./CM2 ) H+-implanted B-doped silicon have been investigated using transient capacitance spectroscopy, capacitance-voltage, and spreading resistance profiling. The role of hydrogen is twofold: to interact with the defects created by ion implantation, modifying their electrical properties, and to neutralize the shallow-acceptor dopants. The evolution of the defects responsible for the deep levels and the depth of the neutralized region have been investigated after isochronal annealing at various temperatures up to 800-degrees-C. Deep-level transient spectroscopy spectra show three hole traps; two of them, H(0.67), H(0.33), have been tentatively identified as vacancy-hydrogen complexes (VH2, VH3) while the attribution of the third, H(0.23), detected in the samples annealed at 400-450-degrees-C, is uncertain. As a function of the heat treatment, the total number of defects is strongly reduced at 300-degrees-C, it increases for T > 300-degrees-C and at the highest temperatures, namely 800-degrees-C, the defects disappear. The first decrease is attributed to the formation of neutral VH4 complexes and the disappearance to complete decoration of point defects or their agglomeration. The thickness of the passivated region has a minimum at 300-degrees-C, which corresponds to the formation of the stable VH4. At lower temperatures, the hydrogen necessary for the passivation is the unbonded one and presumably comes from the implantation process itself. At higher temperature, H comes from the,breaking of the VH, or H(n) complexes. These results are in good agreement with our previous studies concerning the role played by hydrogen in affecting the crystal properties of silicon.