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Polycrystallization effects on the nanoscale electrical properties of high-k dielectrics.

Lanza M, Iglesias V, Porti M, Nafria M, Aymerich X - Nanoscale Res Lett (2011)

Bottom Line: In this study, atomic force microscopy-related techniques have been used to investigate, at the nanoscale, how the polycrystallization of an Al2O3-based gate stack, after a thermal annealing process, affects the variability of its electrical properties.The impact of an electrical stress on the electrical conduction and the charge trapping of amorphous and polycrystalline Al2O3 layers have been also analyzed.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept, Eng, Electrònica, Edifici Q, Campus UAB, 08193 Bellaterra, Spain. mario.lanza@uab.cat.

ABSTRACT
In this study, atomic force microscopy-related techniques have been used to investigate, at the nanoscale, how the polycrystallization of an Al2O3-based gate stack, after a thermal annealing process, affects the variability of its electrical properties. The impact of an electrical stress on the electrical conduction and the charge trapping of amorphous and polycrystalline Al2O3 layers have been also analyzed.

No MeSH data available.


Related in: MedlinePlus

Current images obtained on an amorphous (c) and polycrystalline (d) sample where previously, four RVS where applied to induce BD. The voltage applied during the scan was, in both cases, -8.6 V. (a, b) correspond to typical I-V curves measured on those positions. The maximum current and area of the BD spots can be found in the table.
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Figure 4: Current images obtained on an amorphous (c) and polycrystalline (d) sample where previously, four RVS where applied to induce BD. The voltage applied during the scan was, in both cases, -8.6 V. (a, b) correspond to typical I-V curves measured on those positions. The maximum current and area of the BD spots can be found in the table.

Mentions: Finally, the impact of breakdown (BD) was also investigated on polycrystalline and amorphous oxides. Toward this aim, first, ramped voltage stresses (RVS) with a current limit of 100 pA and with the same ending voltage have been applied on different oxide locations until BD. Figure 4a,b shows an example of two consecutive I-V curves measured on an amorphous and a polycrystalline structure, respectively. Note that, in the second RVS, current can be measured at much lower voltages in both cases, which is an indication that BD has been triggered. Moreover, the voltage at which current is measured in the polycrystalline structure is lower, pointing out a harder BD. After the measurement of the I-V curves, current images of the areas that contain the stressed locations have been collected. Figure 4c,d shows the current images obtained on a 1 μm × 1 μm area of the amorphous (c) and the polycrystalline (d) sample where four RVS had been previously applied until BD at different locations. Regions with larger currents are observed, which correspond to the BD spots. The table in the figure shows the maximum current and area of the BD spots generated on each sample. Note that, for the amorphous sample, the BD areas are smaller and the post-BD electrical conduction is lower, suggesting softer BD events, in agreement with the post-BD I-V curves. From these results and those obtained during the degradation stage, it seems reasonable to speculate that, in polycrystalline structures (with harder BD), BD takes place at the weaker regions, that is, the grain boundaries. Therefore, the presence of grain boundaries on Al2O3 layers could reduce significantly the reliability of MOS devices due to their lower robustness.


Polycrystallization effects on the nanoscale electrical properties of high-k dielectrics.

Lanza M, Iglesias V, Porti M, Nafria M, Aymerich X - Nanoscale Res Lett (2011)

Current images obtained on an amorphous (c) and polycrystalline (d) sample where previously, four RVS where applied to induce BD. The voltage applied during the scan was, in both cases, -8.6 V. (a, b) correspond to typical I-V curves measured on those positions. The maximum current and area of the BD spots can be found in the table.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211152&req=5

Figure 4: Current images obtained on an amorphous (c) and polycrystalline (d) sample where previously, four RVS where applied to induce BD. The voltage applied during the scan was, in both cases, -8.6 V. (a, b) correspond to typical I-V curves measured on those positions. The maximum current and area of the BD spots can be found in the table.
Mentions: Finally, the impact of breakdown (BD) was also investigated on polycrystalline and amorphous oxides. Toward this aim, first, ramped voltage stresses (RVS) with a current limit of 100 pA and with the same ending voltage have been applied on different oxide locations until BD. Figure 4a,b shows an example of two consecutive I-V curves measured on an amorphous and a polycrystalline structure, respectively. Note that, in the second RVS, current can be measured at much lower voltages in both cases, which is an indication that BD has been triggered. Moreover, the voltage at which current is measured in the polycrystalline structure is lower, pointing out a harder BD. After the measurement of the I-V curves, current images of the areas that contain the stressed locations have been collected. Figure 4c,d shows the current images obtained on a 1 μm × 1 μm area of the amorphous (c) and the polycrystalline (d) sample where four RVS had been previously applied until BD at different locations. Regions with larger currents are observed, which correspond to the BD spots. The table in the figure shows the maximum current and area of the BD spots generated on each sample. Note that, for the amorphous sample, the BD areas are smaller and the post-BD electrical conduction is lower, suggesting softer BD events, in agreement with the post-BD I-V curves. From these results and those obtained during the degradation stage, it seems reasonable to speculate that, in polycrystalline structures (with harder BD), BD takes place at the weaker regions, that is, the grain boundaries. Therefore, the presence of grain boundaries on Al2O3 layers could reduce significantly the reliability of MOS devices due to their lower robustness.

Bottom Line: In this study, atomic force microscopy-related techniques have been used to investigate, at the nanoscale, how the polycrystallization of an Al2O3-based gate stack, after a thermal annealing process, affects the variability of its electrical properties.The impact of an electrical stress on the electrical conduction and the charge trapping of amorphous and polycrystalline Al2O3 layers have been also analyzed.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept, Eng, Electrònica, Edifici Q, Campus UAB, 08193 Bellaterra, Spain. mario.lanza@uab.cat.

ABSTRACT
In this study, atomic force microscopy-related techniques have been used to investigate, at the nanoscale, how the polycrystallization of an Al2O3-based gate stack, after a thermal annealing process, affects the variability of its electrical properties. The impact of an electrical stress on the electrical conduction and the charge trapping of amorphous and polycrystalline Al2O3 layers have been also analyzed.

No MeSH data available.


Related in: MedlinePlus