Effect of Top-Gate Dielectric Deposition on the Performance of Indium Tin Oxide Transistors
IEEE Electron Device Letters(2023)
摘要
We report ultrathin (
${\sim }4$
nm) channel indium tin oxide (ITO) transistors, comparing different precursors for atomic layer deposition (ALD) of the Al2O3 top-gate dielectric, and analyze the role of dielectric deposition on transistor performance and gate bias stress stability. Water-based ALD leads to very negative threshold voltage (
${V}_{\text {T}}$
), with devices remaining in the on-state. In contrast, both ozone and O2-plasma precursors yield devices that can turn off, but ozone-based ALD devices have less negative
${V}_{\text {T}}$
shift at short channel lengths, and relatively more positive
${V}_{\text {T}}$
at all channel lengths. We achieve maximum drive current,
${I}_{\text {max}} \approx 260 \mu \text{A}/\mu \text{m}$
at
${V}_{\text {DS}}=$
1 V, on/off current ratio of
$10^{{10}}$
(limited by the instrument’s noise floor) for
${L} \approx 700$
nm ozone-Al2O3 top-gated transistors. Across multiple devices, the effective mobility is
$\sim $
42 cm
$^{{2}}\text{V}^{-{1}}\text{s}^{-{1}}$
and contact resistance is
$\sim 376 \Omega \cdot \mu \text{m}$
. The transistors also show good gate bias stability with normalized
${V}_{\text {T}}$
shift of +0.12 V(MV/cm)
$^{-{1}}$
at gate stress field >3 MV/cm, a
$\sim 3\times $
improvement vs. our previous reports of uncapped ITO transistors.
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关键词
ITO,transistors,atomic layer deposition,effective mobility,contact resistance,bias stress stability
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