High resolution deep level transient spectroscopy and process-induced defects in silicon

Abstract

High resolution, or Laplace, deep level transient spectroscopy (LDLTS) enables the identification of very closely spaced energetic levels in a semiconductor bandgap. DLTS may resolve peaks with a separation of tens of electron volts, but LDLTS can resolve defect energy separations as low as a few MeV. In this paper, we present results from LDLTS applied to ion implantation-induced defects in silicon, with particular emphasis on characterisation of end-of-range interstitial type defects. Silicon was implanted with a variety of ions from mass 28 to 166. A combination of LDLTS and direct capture cross-section measurements was employed to show that electrically active small extended defects were present in the as-implanted samples. Larger dislocations were then generated in Si by oxygenation to act as a control sample. These stacking faults had typical lengths of microns, and their electrical activity was subsequently characterised by LDLTS. This was to establish the sensitivity of LDLTS to defects whose carrier capture is characterised by a non-exponential filling process and an evolving band structure as carrier capture proceeds. The LDLTS spectra show several components in capacitance transients originating from both the end-of-range defects, and the stacking faults, and also clearly show that the carrier emission rates reduce as these extended defects fill with carriers. The end-of-range defects and the stacking faults are shown to have the same electrical behaviour.