Electron paramagnetic resonance investigation of charge trapping centers in amorphous silicon nitride films

Abstract

We have explored the nature of the silicon dangling-bond center in amorphous hydrogenated silicon nitride (a-SiNx:H) thin films, and its relationship to the charge trapping centers using electron paramagnetic resonance (EPR) and capacitance-voltage (C-V) measurements. We have investigated the quantitative relationship between the concentration of silicon dangling bonds using EPR and the concentration of charge traps, measured by C-V measurements, for both UV-illuminated and unilluminated a-SiNx:H thin films subjected to both electron and hole injection sequences. A theoretical framework for our results is also discussed. These results continue to support a model in which the Si dangling bond is a negative-U defect in silicon nitride, and that a change in charge state of preexisting positively and negatively charged Si sites is responsible for the trapping phenomena observed in these thin film dielectrics.

Effect of topological disorder on structural, mechanical, and electronic properties of amorphous silicon nitride: An atomistic study

“…However, our simulations show that defect density is not a strong function of structure density in the 2.7-3.1 g/cm 3 range. While EPR experiments strongly suggest the existence of undercoordinated atoms (III-Si and II-N), 21 there is no direct experimental evidence for overcoordination defects in a-Si 3 N 4 . Similar observations for structural defects have been reported in previous studies.…”

“…33,34 The slow anneals we use lead to a concentration of defects lower than in prior simulations and closer to the experimental values obtained from EPR and electrical conduction in a-Si 3 N 4 . 17,21 We obtain 0.6% undercoordinated Si atoms, 1.1% undercoordinated N atoms and 2.0% overcoordinated atoms in average for the amorphous and semi-crystalline structures. While this is still higher than the experimental values of 10 18 -10 20 cm -3 17, 21 our samples have lower defect concentrations than those reported in simulations to date, from 1% in Ref.…”

“…These results are in very good agreement with spectroscopic measurements and prior theoretical models. 21,23,24,34 However, our ensemble approach enables us to characterize the distribution of energy levels and compare the theoretical predictions with reported by TSICS measured trap ranges. Figure 11 shows the distribution of trap levels in the bandgap contributed by every defect type.…”

“…Extensive experimental studies based on electron paramagnetic resonance (EPR) investigations have associated the charge trapping centers to the existence Si and N dangling bonds. [19][20][21][22][23][24] A combination of optical absorption spectra and EPR measurements indicate that the Si dangling bond contributes to trap energy level at approximately 2.8eV below the conduction band (CB). 23,24 Analyzing the electrical conduction measurements using Poole-Frenkel mechanism models to determine trap depths showed the existence of two different slopes in the same sample indicating existence of two different trap depths.…”

Effective passivation of Si surfaces by plasma deposited SiOx/a-SiNx:H stacks

“…5 The positive charges in SiN x originate from the so-called K centers, which are dangling bonds of Si atoms that are backbonded to three N atoms. [6][7][8] Therefore, Si-rich SiN x films generally exhibit a lower Q f than ͑nearly͒stoichiometric N-rich films. 8 Consequently, Si-rich SiN x leads to high sheet resistances or the absence of an inversion layer.…”