Thermal stability of defect complexes due to high dose MeV implantation in silicon

The nature of electrically active defects created by high dose MeV Ar+ implantation in epitaxial silicon and thermal stability of these defects have been investigated using capacitance–voltage (C–V) and deep level transient spectroscopy (DLTS) measurements. Unusual C–V characteristics in as-implanted Schottky devices is interpreted taking into account migration and clustering of ion beam generated defects. Using DLTS, a compensating midgap trap of large concentration has been detected in as-implanted deep buried layers of both n-type and p-type silicon. Due to low temperature (160°C) oven annealing of implanted n-Si, the dominant defect related peak in DLTS shifts towards higher temperature indicating deepening of emission energy and increased concentration of electrically active species with annealing time. Furnace annealing of damaged silicon at 400 and 600°C reveals gradual annealing of defects with changes in defect spectra. In n-type silicon the majority of the electrically active defects were annealed after 30 min annealing at 600°C, while a stable defect with high concentration was found in p-type silicon upon annealing. The results indicate that due to annealing, stable defects clusters were formed which introduce energy level in the lower half of the band-gap of silicon and the presence of both majority carrier and minority carrier traps are detected due to possible inversion in the damaged layer. The observed major defects in both n-type and p-type silicon are of common origin, which we attribute to interstitial cluster related, and their size changes with low temperature annealing.