Abstract
Amorphous In–Ga–Zn–O (a-IGZO)
thin-film transistors (TFTs) are employed in current flat-panel displays.
It is known that deposition conditions and post-deposition thermal
annealing affect structure and electrical properties of a-IGZO thin
films. It was previously reported that total pressure during sputter-deposition
deteriorates subthreshold swing, defect density and operation characteristics
of a-IGZO TFTs. Here, we provide comprehensive results on effects
of total pressure on film density, chemical composition, and TFT characteristics.
Rutherford backscattering measurements detected a small amount of
argon incorporated in all of the a-IGZO films. We found that increasing
the total pressure deteriorated TFT characteristics; i.e., saturation
mobility was dropped from 10 to 4
${{cm}}^{2}/({{V}}\cdot {{s}})$
, subthreshold swing was increased from 0.2 to 0.5 V/dec,
and threshold voltage was positive-shifted from 2 to 15 V. It is related
to increased oxygen concentration and decreased weight density of
the a-IGZO films. Thermal desorption spectra showed that amounts of
weakly-bonded oxygen increased as the total pressure increased, which
is considered to be related to the TFT deterioration.
© 2014 IEEE
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