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Impact of device size and thickness of Al2O 3 film on the Cu pillar and resistive switching characteristics for 3D cross-point memory application.

Panja R, Roy S, Jana D, Maikap S - Nanoscale Res Lett (2014)

Bottom Line: The 8-μm devices show 100% yield of Cu pillars, whereas only 74% successful is observed for the 0.4-μm devices, because smaller size devices have higher Joule heating effect and larger size devices show long read endurance of 10(5) cycles at a high read voltage of -1.5 V.On the other hand, the resistive switching memory characteristics of the 0.4-μm devices with a 2-nm-thick Al2O3 film show superior as compared to those of both the larger device sizes and thicker (10 nm) Al2O3 film, owing to higher Cu diffusion rate for the larger size and thicker Al2O3 film.This conductive bridging resistive random access memory (CBRAM) device is forming free at a current compliance (CC) of 30 μA (even at a lowest CC of 0.1 μA) and operation voltage of ±3 V at a high resistance ratio of >10(4).

View Article: PubMed Central - PubMed

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

ABSTRACT
Impact of the device size and thickness of Al2O3 film on the Cu pillars and resistive switching memory characteristics of the Al/Cu/Al2O3/TiN structures have been investigated for the first time. The memory device size and thickness of Al2O3 of 18 nm are observed by transmission electron microscope image. The 20-nm-thick Al2O3 films have been used for the Cu pillar formation (i.e., stronger Cu filaments) in the Al/Cu/Al2O3/TiN structures, which can be used for three-dimensional (3D) cross-point architecture as reported previously Nanoscale Res. Lett.9:366, 2014. Fifty randomly picked devices with sizes ranging from 8 × 8 to 0.4 × 0.4 μm(2) have been measured. The 8-μm devices show 100% yield of Cu pillars, whereas only 74% successful is observed for the 0.4-μm devices, because smaller size devices have higher Joule heating effect and larger size devices show long read endurance of 10(5) cycles at a high read voltage of -1.5 V. On the other hand, the resistive switching memory characteristics of the 0.4-μm devices with a 2-nm-thick Al2O3 film show superior as compared to those of both the larger device sizes and thicker (10 nm) Al2O3 film, owing to higher Cu diffusion rate for the larger size and thicker Al2O3 film. In consequence, higher device-to-device uniformity of 88% and lower average RESET current of approximately 328 μA are observed for the 0.4-μm devices with a 2-nm-thick Al2O3 film. Data retention capability of our memory device of >48 h makes it a promising one for future nanoscale nonvolatile application. This conductive bridging resistive random access memory (CBRAM) device is forming free at a current compliance (CC) of 30 μA (even at a lowest CC of 0.1 μA) and operation voltage of ±3 V at a high resistance ratio of >10(4).

No MeSH data available.


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Read pulse endurance characteristics. (a) Read pulse endurance properties degraded at high negative voltage due to the Joule heating phenomena for the smallest size devices. The Cu pillar is broken during read endurance test, which is shown in schematic view. (b) For the large size devices, long endurance reveals the robustness of the Cu pillars inside the switching medium at a Vread of -1.5 V. Long read endurance of 105 cycles is obtained for the 8-μm devices. A stronger Cu pillar is formed into the Al2O3 films, which is shown in schematic view inside of figure.
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Fig4: Read pulse endurance characteristics. (a) Read pulse endurance properties degraded at high negative voltage due to the Joule heating phenomena for the smallest size devices. The Cu pillar is broken during read endurance test, which is shown in schematic view. (b) For the large size devices, long endurance reveals the robustness of the Cu pillars inside the switching medium at a Vread of -1.5 V. Long read endurance of 105 cycles is obtained for the 8-μm devices. A stronger Cu pillar is formed into the Al2O3 films, which is shown in schematic view inside of figure.

Mentions: Figure 4 shows the read endurance characteristics with different negative read voltages. As it is bipolar device, the negative bias makes the RESET. After formation, we have increased the negative bias sequentially as -1 and -1.5 V on the TE. The current compliances are 10 and 70 mA for the 0.4- and 8-μm devices, respectively. For the 0.4-μm devices, a value of LRS is approximately 32 Ω (Figure 4a), while the value is approximately 20 Ω for the 8-μm devices (Figure 4b). This indicates that the diameter of Cu pillar is larger for the 8-μm devices than the 0.4-μm devices, as shown schematic view in the inset. For the 0.4-μm devices, the LRS state is increased after approximately 40 and 30 k cycles for the read voltages of -1 and -1.5 V, respectively. The Cu pillar is broken easily after higher negative voltage on the TE, as shown schematically in the inset of Figure 4a. Robust read pulse endurances of >105 cycles are obtained for the 8-μm devices because larger diameter of the Cu pillars, as shown schematically in the inset of Figure 4b. So, after formation of the conducting path, the possibility of deterioration of the paths is less which indicates the ability of Cu pillar for 3D cross-point architecture in the future. Beside the Cu pillar investigation, the resistive switching characteristics of the Cu/Al2O3/TiN CBRAM devices with smaller thickness (<10 nm) of Al2O3 layer are also important, which have been investigated below.Figure 4


Impact of device size and thickness of Al2O 3 film on the Cu pillar and resistive switching characteristics for 3D cross-point memory application.

Panja R, Roy S, Jana D, Maikap S - Nanoscale Res Lett (2014)

Read pulse endurance characteristics. (a) Read pulse endurance properties degraded at high negative voltage due to the Joule heating phenomena for the smallest size devices. The Cu pillar is broken during read endurance test, which is shown in schematic view. (b) For the large size devices, long endurance reveals the robustness of the Cu pillars inside the switching medium at a Vread of -1.5 V. Long read endurance of 105 cycles is obtained for the 8-μm devices. A stronger Cu pillar is formed into the Al2O3 films, which is shown in schematic view inside of figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4494016&req=5

Fig4: Read pulse endurance characteristics. (a) Read pulse endurance properties degraded at high negative voltage due to the Joule heating phenomena for the smallest size devices. The Cu pillar is broken during read endurance test, which is shown in schematic view. (b) For the large size devices, long endurance reveals the robustness of the Cu pillars inside the switching medium at a Vread of -1.5 V. Long read endurance of 105 cycles is obtained for the 8-μm devices. A stronger Cu pillar is formed into the Al2O3 films, which is shown in schematic view inside of figure.
Mentions: Figure 4 shows the read endurance characteristics with different negative read voltages. As it is bipolar device, the negative bias makes the RESET. After formation, we have increased the negative bias sequentially as -1 and -1.5 V on the TE. The current compliances are 10 and 70 mA for the 0.4- and 8-μm devices, respectively. For the 0.4-μm devices, a value of LRS is approximately 32 Ω (Figure 4a), while the value is approximately 20 Ω for the 8-μm devices (Figure 4b). This indicates that the diameter of Cu pillar is larger for the 8-μm devices than the 0.4-μm devices, as shown schematic view in the inset. For the 0.4-μm devices, the LRS state is increased after approximately 40 and 30 k cycles for the read voltages of -1 and -1.5 V, respectively. The Cu pillar is broken easily after higher negative voltage on the TE, as shown schematically in the inset of Figure 4a. Robust read pulse endurances of >105 cycles are obtained for the 8-μm devices because larger diameter of the Cu pillars, as shown schematically in the inset of Figure 4b. So, after formation of the conducting path, the possibility of deterioration of the paths is less which indicates the ability of Cu pillar for 3D cross-point architecture in the future. Beside the Cu pillar investigation, the resistive switching characteristics of the Cu/Al2O3/TiN CBRAM devices with smaller thickness (<10 nm) of Al2O3 layer are also important, which have been investigated below.Figure 4

Bottom Line: The 8-μm devices show 100% yield of Cu pillars, whereas only 74% successful is observed for the 0.4-μm devices, because smaller size devices have higher Joule heating effect and larger size devices show long read endurance of 10(5) cycles at a high read voltage of -1.5 V.On the other hand, the resistive switching memory characteristics of the 0.4-μm devices with a 2-nm-thick Al2O3 film show superior as compared to those of both the larger device sizes and thicker (10 nm) Al2O3 film, owing to higher Cu diffusion rate for the larger size and thicker Al2O3 film.This conductive bridging resistive random access memory (CBRAM) device is forming free at a current compliance (CC) of 30 μA (even at a lowest CC of 0.1 μA) and operation voltage of ±3 V at a high resistance ratio of >10(4).

View Article: PubMed Central - PubMed

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

ABSTRACT
Impact of the device size and thickness of Al2O3 film on the Cu pillars and resistive switching memory characteristics of the Al/Cu/Al2O3/TiN structures have been investigated for the first time. The memory device size and thickness of Al2O3 of 18 nm are observed by transmission electron microscope image. The 20-nm-thick Al2O3 films have been used for the Cu pillar formation (i.e., stronger Cu filaments) in the Al/Cu/Al2O3/TiN structures, which can be used for three-dimensional (3D) cross-point architecture as reported previously Nanoscale Res. Lett.9:366, 2014. Fifty randomly picked devices with sizes ranging from 8 × 8 to 0.4 × 0.4 μm(2) have been measured. The 8-μm devices show 100% yield of Cu pillars, whereas only 74% successful is observed for the 0.4-μm devices, because smaller size devices have higher Joule heating effect and larger size devices show long read endurance of 10(5) cycles at a high read voltage of -1.5 V. On the other hand, the resistive switching memory characteristics of the 0.4-μm devices with a 2-nm-thick Al2O3 film show superior as compared to those of both the larger device sizes and thicker (10 nm) Al2O3 film, owing to higher Cu diffusion rate for the larger size and thicker Al2O3 film. In consequence, higher device-to-device uniformity of 88% and lower average RESET current of approximately 328 μA are observed for the 0.4-μm devices with a 2-nm-thick Al2O3 film. Data retention capability of our memory device of >48 h makes it a promising one for future nanoscale nonvolatile application. This conductive bridging resistive random access memory (CBRAM) device is forming free at a current compliance (CC) of 30 μA (even at a lowest CC of 0.1 μA) and operation voltage of ±3 V at a high resistance ratio of >10(4).

No MeSH data available.


Related in: MedlinePlus