Dynamic Properties of Electronic Trapping Centers at the Si-SiO2 Interface.

摘要

On unannealed, thermally oxidized silicon, electron spin resonance reveals an oriented interface defect which is termed the Pb center and identified as the trivalent silicon defect. Deep-level transient spectroscopy (DLTS) reveals two broad characteristic peaks in the interface-state distribution: one approximately 0.3 eV above the silicon valence-band maximum, and a second approximately 0.25 eV. below the conduction band. Isochronal anneals of oxidized silicon, coated with aluminum, show that the spin density and the densities of the two DLTS peaks have the same annealing kinetics. On large-area, A1-gated capacitors the spin density can be modulated with an applied voltage; sweeping the silicon bandgap at the interface through the Fermi level reveals that the spin density is approximately constant over the central region of the bandgap but decreases near the band edges. The variation of the spin density with gate voltage identifies an amphoteric center with both electronic transitions in the bandgap. Both the annealing behavior and the voltage dependence of the Pb center support the conclusion that these transitions correspond to the two characteristic peaks in the effective correlation energy of the dangling orbital on a trivalent silicon defect at the Si-Si02 interface. The similarity between the disordered interface and amorphous silicon and the effects of a correlation energy on deep-level measurements are discussed. (Author)