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Effect of ion implantation energy for the synthesis of Ge nanocrystals in SiN films with HfO2/SiO2 stack tunnel dielectrics for memory application.

Sahu BS, Gloux F, Slaoui A, Carrada M, Muller D, Groenen J, Bonafos C, Lhostis S - Nanoscale Res Lett (2011)

Bottom Line: No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV) sample for the same implanted dose.The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor.A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: InESS, UDS-CNRS, 23 rue du Loess, 67037 Strasbourg, France. sahu.bhabani@iness.c-strasbourg.fr.

ABSTRACT
Ge nanocrystals (Ge-NCs) embedded in SiN dielectrics with HfO2/SiO2 stack tunnel dielectrics were synthesized by utilizing low-energy (≤5 keV) ion implantation method followed by conventional thermal annealing at 800°C, the key variable being Ge+ ion implantation energy. Two different energies (3 and 5 keV) have been chosen for the evolution of Ge-NCs, which have been found to possess significant changes in structural and chemical properties of the Ge+-implanted dielectric films, and well reflected in the charge storage properties of the Al/SiN/Ge-NC + SiN/HfO2/SiO2/Si metal-insulator-semiconductor (MIS) memory structures. No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV) sample for the same implanted dose. The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor. A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

No MeSH data available.


Related in: MedlinePlus

Evolution of flat-band voltage as a function of waiting time for the MIS structures after Ge+ ion implantation at 5 keV followed by thermal annealing at 800°C and subjected to a stress voltages of +6 V for electron charging, and -6 V for hole charging for 3s. The constant-capacitance method at flat-band point was used for this measurement.
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Figure 5: Evolution of flat-band voltage as a function of waiting time for the MIS structures after Ge+ ion implantation at 5 keV followed by thermal annealing at 800°C and subjected to a stress voltages of +6 V for electron charging, and -6 V for hole charging for 3s. The constant-capacitance method at flat-band point was used for this measurement.

Mentions: In the investigation of this study, an implantation energy of 5 keV seems to be the optimum parameter for a particular dose of 1.5 × 1016 cm-2 and SiN/HfO2/SiO2 stack for the evolution of Ge-NCs and obtaining significant memory properties. In this regard, sample A5 has been chosen for charge retention measurement to have a better insight for its utility in low power-consuming NVM devices. Figure 5 shows the charge retention characteristics of sample A5 by stressing the samples with voltage pulses of ± 6 V (positive for electron charging and negative for hole charging) for 3s. The retention curves exhibit a logarithmic dependence on the waiting time. A faster charge loss rate was observed after applying a positive stress, indicating higher electron loss rate due to the higher conductance band edge of Ge-NCs [30]. A significant memory window of 2.36 V has been achieved through a waiting time of 104 s with a possible trend of stabilization indicating charge confinement in Ge-NCs. With further extrapolation of the retention curves, a memory window of 1.06 V has been estimated after a waiting time of 10 years. This enhanced charge retention should be attributed to charge confinement in Ge-NCs, immunity of Ge-NCs to local defects in the dielectric, and interface traps.


Effect of ion implantation energy for the synthesis of Ge nanocrystals in SiN films with HfO2/SiO2 stack tunnel dielectrics for memory application.

Sahu BS, Gloux F, Slaoui A, Carrada M, Muller D, Groenen J, Bonafos C, Lhostis S - Nanoscale Res Lett (2011)

Evolution of flat-band voltage as a function of waiting time for the MIS structures after Ge+ ion implantation at 5 keV followed by thermal annealing at 800°C and subjected to a stress voltages of +6 V for electron charging, and -6 V for hole charging for 3s. The constant-capacitance method at flat-band point was used for this measurement.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211230&req=5

Figure 5: Evolution of flat-band voltage as a function of waiting time for the MIS structures after Ge+ ion implantation at 5 keV followed by thermal annealing at 800°C and subjected to a stress voltages of +6 V for electron charging, and -6 V for hole charging for 3s. The constant-capacitance method at flat-band point was used for this measurement.
Mentions: In the investigation of this study, an implantation energy of 5 keV seems to be the optimum parameter for a particular dose of 1.5 × 1016 cm-2 and SiN/HfO2/SiO2 stack for the evolution of Ge-NCs and obtaining significant memory properties. In this regard, sample A5 has been chosen for charge retention measurement to have a better insight for its utility in low power-consuming NVM devices. Figure 5 shows the charge retention characteristics of sample A5 by stressing the samples with voltage pulses of ± 6 V (positive for electron charging and negative for hole charging) for 3s. The retention curves exhibit a logarithmic dependence on the waiting time. A faster charge loss rate was observed after applying a positive stress, indicating higher electron loss rate due to the higher conductance band edge of Ge-NCs [30]. A significant memory window of 2.36 V has been achieved through a waiting time of 104 s with a possible trend of stabilization indicating charge confinement in Ge-NCs. With further extrapolation of the retention curves, a memory window of 1.06 V has been estimated after a waiting time of 10 years. This enhanced charge retention should be attributed to charge confinement in Ge-NCs, immunity of Ge-NCs to local defects in the dielectric, and interface traps.

Bottom Line: No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV) sample for the same implanted dose.The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor.A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

View Article: PubMed Central - HTML - PubMed

Affiliation: InESS, UDS-CNRS, 23 rue du Loess, 67037 Strasbourg, France. sahu.bhabani@iness.c-strasbourg.fr.

ABSTRACT
Ge nanocrystals (Ge-NCs) embedded in SiN dielectrics with HfO2/SiO2 stack tunnel dielectrics were synthesized by utilizing low-energy (≤5 keV) ion implantation method followed by conventional thermal annealing at 800°C, the key variable being Ge+ ion implantation energy. Two different energies (3 and 5 keV) have been chosen for the evolution of Ge-NCs, which have been found to possess significant changes in structural and chemical properties of the Ge+-implanted dielectric films, and well reflected in the charge storage properties of the Al/SiN/Ge-NC + SiN/HfO2/SiO2/Si metal-insulator-semiconductor (MIS) memory structures. No Ge-NC was detected with a lower implantation energy of 3 keV at a dose of 1.5 × 1016 cm-2, whereas a well-defined 2D-array of nearly spherical and well-separated Ge-NCs within the SiN matrix was observed for the higher-energy-implanted (5 keV) sample for the same implanted dose. The MIS memory structures implanted with 5 keV exhibits better charge storage and retention characteristics compared to the low-energy-implanted sample, indicating that the charge storage is predominantly in Ge-NCs in the memory capacitor. A significant memory window of 3.95 V has been observed under the low operating voltage of ± 6 V with good retention properties, indicating the feasibility of these stack structures for low operating voltage, non-volatile memory devices.

No MeSH data available.


Related in: MedlinePlus