|
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Another defect, found in
close to the
interface, is the
center oxide defect. The exact atomic configuration is still
debated [27,17,36,37,38] but possible
configurations of
centers involve an unpaired electron localized on a
silicon atom back-bonded to three oxygen atoms or two oxygen atoms and one
hydrogen atom, as shown in Figure 3.7. Variants proposed
include a second silicon atom impacting the defect as depicted in
Figure 3.8.
After very harsh negative bias temperature stressing conditions, those defects
can be detected using resonance measurements [22,18]. SDR
measurements are only capable of sensing near interface oxide defects, as only
those can interact with the interface traps and alter the recombination
current. Therefore it is not clear whether more
defects are located
deeper in the
.
centers have levels near the middle of the
band-gap where they
allow hole capture from the silicon inversion layer. It was shown
experimentally [36] that after hole capture an
center can
crack molecular hydrogen. This process might be important for the dissociation
of silicon-hydrogen bonds at the
interface and therefore for the
effect of NBTI.