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RRAM characteristics using a new Cr/GdOx/TiN structure.

Jana D, Dutta M, Samanta S, Maikap S - Nanoscale Res Lett (2014)

Bottom Line: After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm.The GdOx film thickness dependence RRAM characteristics have been discussed also.Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

View Article: PubMed Central - PubMed

Affiliation: Thin Film Nano Technology Laboratory, Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan, 333, Taiwan, debanjan.jana@gmail.com.

ABSTRACT
Resistive random access memory (RRAM) characteristics using a new Cr/GdOx/TiN structure with different device sizes ranging from 0.4 × 0.4 to 8 × 8 μm(2) have been reported in this study. Polycrystalline GdOx film with a thickness of 17 nm and a small via-hole size of 0.4 μm are observed by a transmission electron microscope (TEM) image. All elements and GdOx film are confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. Repeatable resistive switching characteristics at a current compliance (CC) of 300 μA and low operating voltage of ±4 V are observed. The switching mechanism is based on the oxygen vacancy filament formation/rupture through GdOx grain boundaries under external bias. After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm. The GdOx film thickness dependence RRAM characteristics have been discussed also. Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

No MeSH data available.


Related in: MedlinePlus

RepeatableI-Vcharacteristics and cumulative probability of HRS and LRS. (a) Hundred I-V characteristics of the 0.4-μm devices. (b) Statistical distributions of HRS and LRS for the 8- and 0.4-μm devices are plotted. Fifty devices were measured randomly. The thicknesses of the GdOx film were 17 and 9 nm for the 8- and 0.4-μm devices, respectively. By considering resistance ratio of >2, successful devices are found to be 78% and 72% for the 8- and 0.4-μm devices, respectively.
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Fig7: RepeatableI-Vcharacteristics and cumulative probability of HRS and LRS. (a) Hundred I-V characteristics of the 0.4-μm devices. (b) Statistical distributions of HRS and LRS for the 8- and 0.4-μm devices are plotted. Fifty devices were measured randomly. The thicknesses of the GdOx film were 17 and 9 nm for the 8- and 0.4-μm devices, respectively. By considering resistance ratio of >2, successful devices are found to be 78% and 72% for the 8- and 0.4-μm devices, respectively.

Mentions: It is observed that the 0.4-μm devices with thicker a GdOx film of 17 nm do not show formation as well as resistive switching phenomena owing to thicker switching layer and smaller active area. By reducing thickness of the GdOx film up to 9 nm, the clear formation and SET operation could be observed even at a smallest size of 0.4 μm in our process. Figure 7a illustrates typical bipolar I-V characteristics for a device size of 0.4 × 0.4 μm2. The device performs consecutive 100 dc cycles with less distribution of LRS and HRS under a CC of 300 μA. The values of Vform, VSET, and VRESET are found to be 2 V, 0.7 V, and -0.7 V, respectively. The values of IRESET are found to be 1.8 mA and 375 μA for the first and second cycles, respectively. After measuring 100 RRAM devices, the values of Vform, VSET, VRESET, and IRESET (first/second cycle) at 50% probability are found to be 1.7 V, 0.9 V, and -0.7 V, and 1.07 mA/391 μA for the 8-μm devices, and those values are found to be 2.5 V, 0.7 V, and -0.8 V, and 1.35 mA/370 μA for the 0.4-μm devices, respectively (not shown here). Therefore, the 8-μm devices have lower formation voltage and smaller RESET current at the first cycle as compared to the 0.4-μm devices, which suggests that larger size devices have a better performance even with the thinner GdOx film of 9 nm. To check the uniformity of the resistance states, we have measured randomly >50 devices and studied statistical distribution of HRS and LRS of device-to-device with device sizes of 0.4 and 8 μm, as shown in Figure 7b. The thickness of the GdOx film is 17 nm for the 8-μm devices and 9 nm for the 0.4-μm devices. Except for few devices which have a small resistance ratio (HRS/LRS) of <2, it is found that the 8-μm device shows better device-to-device uniformity with a high yield >78% as compared to the 0.4-μm devices with a yield >72%. The 8-μm device with a 9-nm-thick GdOx film has also a high yield >88% (not shown here). Further, the 0.4-μm devices show SET failure (Figure 7b), which is reported similar in literature [42]. The values of HRS and LRS for the 8-μm devices at 50% probability are 471.6 and 6.6 kΩ, whereas those values are 126.58 and 4.52 kΩ for the 0.4-μm devices, respectively. The value of LRS is lower for the 0.4-μm devices than those of the 8-μm devices, which is due to higher IRESET. Therefore, it is observed that the 8-μm device exhibits better uniformity and resistance ratio as compared to the 0.4-μm device. This suggests that recombination rate of oxygen ion (O2-) with oxygen vacancy filament is less due to a smaller TE/GdOx interface area for the 0.4-μm devices. So dissolution of oxygen vacancy filament is less for the 0.4-μm devices resulting in higher RESET current, lower resistance ratio, and poor device-to-device uniformity. In the case of the 8-μm devices, recombination rate of oxygen ion (O2-) with oxygen vacancy filament is higher due to a larger TE/GdOx interface area, which results in lower RESET current, higher resistance ratio, and better device-to-device uniformity. Chen et al. [43] reported the oxygen recombination rate dependence improved resistive switching characteristics using HfOx-based RRAMs. The larger interface area has better switching characteristics because of a higher oxygen recombination rate. This implies that the TE/GdOx interface area in the Cr/GdOx/TiN structures plays an important role to have superior switching phenomena. Further study is also needed to unravel the effect of switching performance on different thicknesses of the GdOx layer.Figure 7


RRAM characteristics using a new Cr/GdOx/TiN structure.

Jana D, Dutta M, Samanta S, Maikap S - Nanoscale Res Lett (2014)

RepeatableI-Vcharacteristics and cumulative probability of HRS and LRS. (a) Hundred I-V characteristics of the 0.4-μm devices. (b) Statistical distributions of HRS and LRS for the 8- and 0.4-μm devices are plotted. Fifty devices were measured randomly. The thicknesses of the GdOx film were 17 and 9 nm for the 8- and 0.4-μm devices, respectively. By considering resistance ratio of >2, successful devices are found to be 78% and 72% for the 8- and 0.4-μm devices, respectively.
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Related In: Results  -  Collection

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Fig7: RepeatableI-Vcharacteristics and cumulative probability of HRS and LRS. (a) Hundred I-V characteristics of the 0.4-μm devices. (b) Statistical distributions of HRS and LRS for the 8- and 0.4-μm devices are plotted. Fifty devices were measured randomly. The thicknesses of the GdOx film were 17 and 9 nm for the 8- and 0.4-μm devices, respectively. By considering resistance ratio of >2, successful devices are found to be 78% and 72% for the 8- and 0.4-μm devices, respectively.
Mentions: It is observed that the 0.4-μm devices with thicker a GdOx film of 17 nm do not show formation as well as resistive switching phenomena owing to thicker switching layer and smaller active area. By reducing thickness of the GdOx film up to 9 nm, the clear formation and SET operation could be observed even at a smallest size of 0.4 μm in our process. Figure 7a illustrates typical bipolar I-V characteristics for a device size of 0.4 × 0.4 μm2. The device performs consecutive 100 dc cycles with less distribution of LRS and HRS under a CC of 300 μA. The values of Vform, VSET, and VRESET are found to be 2 V, 0.7 V, and -0.7 V, respectively. The values of IRESET are found to be 1.8 mA and 375 μA for the first and second cycles, respectively. After measuring 100 RRAM devices, the values of Vform, VSET, VRESET, and IRESET (first/second cycle) at 50% probability are found to be 1.7 V, 0.9 V, and -0.7 V, and 1.07 mA/391 μA for the 8-μm devices, and those values are found to be 2.5 V, 0.7 V, and -0.8 V, and 1.35 mA/370 μA for the 0.4-μm devices, respectively (not shown here). Therefore, the 8-μm devices have lower formation voltage and smaller RESET current at the first cycle as compared to the 0.4-μm devices, which suggests that larger size devices have a better performance even with the thinner GdOx film of 9 nm. To check the uniformity of the resistance states, we have measured randomly >50 devices and studied statistical distribution of HRS and LRS of device-to-device with device sizes of 0.4 and 8 μm, as shown in Figure 7b. The thickness of the GdOx film is 17 nm for the 8-μm devices and 9 nm for the 0.4-μm devices. Except for few devices which have a small resistance ratio (HRS/LRS) of <2, it is found that the 8-μm device shows better device-to-device uniformity with a high yield >78% as compared to the 0.4-μm devices with a yield >72%. The 8-μm device with a 9-nm-thick GdOx film has also a high yield >88% (not shown here). Further, the 0.4-μm devices show SET failure (Figure 7b), which is reported similar in literature [42]. The values of HRS and LRS for the 8-μm devices at 50% probability are 471.6 and 6.6 kΩ, whereas those values are 126.58 and 4.52 kΩ for the 0.4-μm devices, respectively. The value of LRS is lower for the 0.4-μm devices than those of the 8-μm devices, which is due to higher IRESET. Therefore, it is observed that the 8-μm device exhibits better uniformity and resistance ratio as compared to the 0.4-μm device. This suggests that recombination rate of oxygen ion (O2-) with oxygen vacancy filament is less due to a smaller TE/GdOx interface area for the 0.4-μm devices. So dissolution of oxygen vacancy filament is less for the 0.4-μm devices resulting in higher RESET current, lower resistance ratio, and poor device-to-device uniformity. In the case of the 8-μm devices, recombination rate of oxygen ion (O2-) with oxygen vacancy filament is higher due to a larger TE/GdOx interface area, which results in lower RESET current, higher resistance ratio, and better device-to-device uniformity. Chen et al. [43] reported the oxygen recombination rate dependence improved resistive switching characteristics using HfOx-based RRAMs. The larger interface area has better switching characteristics because of a higher oxygen recombination rate. This implies that the TE/GdOx interface area in the Cr/GdOx/TiN structures plays an important role to have superior switching phenomena. Further study is also needed to unravel the effect of switching performance on different thicknesses of the GdOx layer.Figure 7

Bottom Line: After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm.The GdOx film thickness dependence RRAM characteristics have been discussed also.Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

View Article: PubMed Central - PubMed

Affiliation: Thin Film Nano Technology Laboratory, Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan, 333, Taiwan, debanjan.jana@gmail.com.

ABSTRACT
Resistive random access memory (RRAM) characteristics using a new Cr/GdOx/TiN structure with different device sizes ranging from 0.4 × 0.4 to 8 × 8 μm(2) have been reported in this study. Polycrystalline GdOx film with a thickness of 17 nm and a small via-hole size of 0.4 μm are observed by a transmission electron microscope (TEM) image. All elements and GdOx film are confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. Repeatable resistive switching characteristics at a current compliance (CC) of 300 μA and low operating voltage of ±4 V are observed. The switching mechanism is based on the oxygen vacancy filament formation/rupture through GdOx grain boundaries under external bias. After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm. The GdOx film thickness dependence RRAM characteristics have been discussed also. Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

No MeSH data available.


Related in: MedlinePlus