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Statistical characteristics of reset switching in Cu/HfO2/Pt resistive switching memory.

Zhang M, Long S, Wang G, Liu R, Xu X, Li Y, Xu D, Liu Q, Lv H, Miranda E, Suñé J, Liu M - Nanoscale Res Lett (2014)

Bottom Line: The reset voltage increases and the current decreases with the on-state resistance, respectively, according to the scatter plots of the experimental data.The scale factor of the reset voltage increases with on-state resistance while that of the reset current decreases with it.Our work has provided an inspiration on effectively reducing the variation of the switching parameters of RRAM devices.

View Article: PubMed Central - PubMed

Affiliation: Lab of Nanofabrication and Novel Device Integration, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, China, zhangmeiyun@ime.ac.cn.

ABSTRACT
A major challenge of resistive switching memory (resistive random access memory (RRAM)) for future application is how to reduce the fluctuation of the resistive switching parameters. In this letter, with a statistical methodology, we have systematically analyzed the reset statistics of the conductive bridge random access memory (CBRAM) with a Cu/HfO2/Pt structure which displays bipolar switching property. The experimental observations show that the distributions of the reset voltage (V reset) and reset current (I reset) are greatly influenced by the initial on-state resistance (R on) which is closely related to the size of the conductive filament (CF) before the reset process. The reset voltage increases and the current decreases with the on-state resistance, respectively, according to the scatter plots of the experimental data. Using resistance screening method, the statistical data of the reset voltage and current are decomposed into several ranges and the distributions of them in each range are analyzed by the Weibull model. Both the Weibull slopes of the reset voltage and current are demonstrated to be independent of the on-state resistance which indicates that no CF dissolution occurs before the reset point. The scale factor of the reset voltage increases with on-state resistance while that of the reset current decreases with it. These behaviors are fully in consistency with the thermal dissolution model, which gives an insight on the physical mechanism of the reset switching. Our work has provided an inspiration on effectively reducing the variation of the switching parameters of RRAM devices.

No MeSH data available.


Related in: MedlinePlus

Scatter plots ofVresetandIresetand dependence of the calculatedRTHonRon. The dependence of the Vreset(a) and Ireset(b) as a function of Ron. Vreset increases and Ireset decreases with Ron, respectively, which are well fitted by the thermal dissolution model (blue lines) with Treset = 400 K, RTH,⟂ = 2.3 × 105 K/W. (c) The dependence of calculated thermal resistance on the CF resistance. RTH,⟂ is considered as being constant with a value of 2.3 × 105 K/W.
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Fig2: Scatter plots ofVresetandIresetand dependence of the calculatedRTHonRon. The dependence of the Vreset(a) and Ireset(b) as a function of Ron. Vreset increases and Ireset decreases with Ron, respectively, which are well fitted by the thermal dissolution model (blue lines) with Treset = 400 K, RTH,⟂ = 2.3 × 105 K/W. (c) The dependence of calculated thermal resistance on the CF resistance. RTH,⟂ is considered as being constant with a value of 2.3 × 105 K/W.

Mentions: The relationships of Vreset and Ireset with Ron are studied with a statistical method. Figure 2a,b shows the scatter plots of Vreset and Ireset as a function of Ron in the 4,000 continuous set and reset cycles. As can be seen, the spread of Vreset and Ireset is slightly wide and Vreset increases while Ireset decreases with Ron. These characteristics can be accounted for by the thermal dissolution model [21–23, 25–28] which assumes that reset is determined by the diffusion of the conductive defects. In Cu/HfO2/Pt RRAM device, the conductive defects are mainly the Cu metal atoms or ions. When the local CF temperature reaches a critical value Treset, the conductive defects begin to diffuse out of the CF and then reset occurs. Considering the balance between Joule dissipation and heat evacuation, the local temperature of the CF can be calculated by the basic equation where T0 is the operation temperature, Vreset is the voltage dropped on the CF at the reset point, and RTH is the thermal resistance describing heat dissipation from the CF to the environment. The thermal resistance RTH can be divided into two components in parallel, the parallel resistance (RTH,∥) and the perpendicular resistance (RTH,⟂). Their relation is described by RTH = RTH,∥RTH,⟂/(RTH,∥ + RTH,⟂), where RTH,∥ = Ron/(8LTreset) according to the Wiedemann-Franz (WF) law and L = 2.45 × 10- 8 WΩK- 2 is the Lorentz number [23]. The two components respectively describe the heat diffusion along the CF and from the CF surface to the surrounding oxide. Figure 2c shows the dependence of the calculated RTH on Ron. At the low-resistance region, the value of RTH/Ron is roughly constant and then when Ron increases, the ratio will not be constant anymore. Using the above relations, we can get the theoretical fittings for the experimental relationships between Vreset, Ireset, and Ron through choosing appropriate parameters of Treset and RTH,⟂. By the theoretical fitting, Vreset is proved to increase with Ron, which is consistent with our experimental results shown in Figure 2a. In this work, the on-state resistance is comparatively high, as compared with the reports in [21, 22], so Vreset increases with Ron. This increase trend is similar to the Vreset2 - Rreset2 relation reported in [23]. Since the CF behaves like a metallic conductor before the reset point [29], Ireset is inversely proportional to Ron as presented in Figure 2b.Figure 2


Statistical characteristics of reset switching in Cu/HfO2/Pt resistive switching memory.

Zhang M, Long S, Wang G, Liu R, Xu X, Li Y, Xu D, Liu Q, Lv H, Miranda E, Suñé J, Liu M - Nanoscale Res Lett (2014)

Scatter plots ofVresetandIresetand dependence of the calculatedRTHonRon. The dependence of the Vreset(a) and Ireset(b) as a function of Ron. Vreset increases and Ireset decreases with Ron, respectively, which are well fitted by the thermal dissolution model (blue lines) with Treset = 400 K, RTH,⟂ = 2.3 × 105 K/W. (c) The dependence of calculated thermal resistance on the CF resistance. RTH,⟂ is considered as being constant with a value of 2.3 × 105 K/W.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Fig2: Scatter plots ofVresetandIresetand dependence of the calculatedRTHonRon. The dependence of the Vreset(a) and Ireset(b) as a function of Ron. Vreset increases and Ireset decreases with Ron, respectively, which are well fitted by the thermal dissolution model (blue lines) with Treset = 400 K, RTH,⟂ = 2.3 × 105 K/W. (c) The dependence of calculated thermal resistance on the CF resistance. RTH,⟂ is considered as being constant with a value of 2.3 × 105 K/W.
Mentions: The relationships of Vreset and Ireset with Ron are studied with a statistical method. Figure 2a,b shows the scatter plots of Vreset and Ireset as a function of Ron in the 4,000 continuous set and reset cycles. As can be seen, the spread of Vreset and Ireset is slightly wide and Vreset increases while Ireset decreases with Ron. These characteristics can be accounted for by the thermal dissolution model [21–23, 25–28] which assumes that reset is determined by the diffusion of the conductive defects. In Cu/HfO2/Pt RRAM device, the conductive defects are mainly the Cu metal atoms or ions. When the local CF temperature reaches a critical value Treset, the conductive defects begin to diffuse out of the CF and then reset occurs. Considering the balance between Joule dissipation and heat evacuation, the local temperature of the CF can be calculated by the basic equation where T0 is the operation temperature, Vreset is the voltage dropped on the CF at the reset point, and RTH is the thermal resistance describing heat dissipation from the CF to the environment. The thermal resistance RTH can be divided into two components in parallel, the parallel resistance (RTH,∥) and the perpendicular resistance (RTH,⟂). Their relation is described by RTH = RTH,∥RTH,⟂/(RTH,∥ + RTH,⟂), where RTH,∥ = Ron/(8LTreset) according to the Wiedemann-Franz (WF) law and L = 2.45 × 10- 8 WΩK- 2 is the Lorentz number [23]. The two components respectively describe the heat diffusion along the CF and from the CF surface to the surrounding oxide. Figure 2c shows the dependence of the calculated RTH on Ron. At the low-resistance region, the value of RTH/Ron is roughly constant and then when Ron increases, the ratio will not be constant anymore. Using the above relations, we can get the theoretical fittings for the experimental relationships between Vreset, Ireset, and Ron through choosing appropriate parameters of Treset and RTH,⟂. By the theoretical fitting, Vreset is proved to increase with Ron, which is consistent with our experimental results shown in Figure 2a. In this work, the on-state resistance is comparatively high, as compared with the reports in [21, 22], so Vreset increases with Ron. This increase trend is similar to the Vreset2 - Rreset2 relation reported in [23]. Since the CF behaves like a metallic conductor before the reset point [29], Ireset is inversely proportional to Ron as presented in Figure 2b.Figure 2

Bottom Line: The reset voltage increases and the current decreases with the on-state resistance, respectively, according to the scatter plots of the experimental data.The scale factor of the reset voltage increases with on-state resistance while that of the reset current decreases with it.Our work has provided an inspiration on effectively reducing the variation of the switching parameters of RRAM devices.

View Article: PubMed Central - PubMed

Affiliation: Lab of Nanofabrication and Novel Device Integration, Institute of Microelectronics, Chinese Academy of Sciences, Beijing, 100029, China, zhangmeiyun@ime.ac.cn.

ABSTRACT
A major challenge of resistive switching memory (resistive random access memory (RRAM)) for future application is how to reduce the fluctuation of the resistive switching parameters. In this letter, with a statistical methodology, we have systematically analyzed the reset statistics of the conductive bridge random access memory (CBRAM) with a Cu/HfO2/Pt structure which displays bipolar switching property. The experimental observations show that the distributions of the reset voltage (V reset) and reset current (I reset) are greatly influenced by the initial on-state resistance (R on) which is closely related to the size of the conductive filament (CF) before the reset process. The reset voltage increases and the current decreases with the on-state resistance, respectively, according to the scatter plots of the experimental data. Using resistance screening method, the statistical data of the reset voltage and current are decomposed into several ranges and the distributions of them in each range are analyzed by the Weibull model. Both the Weibull slopes of the reset voltage and current are demonstrated to be independent of the on-state resistance which indicates that no CF dissolution occurs before the reset point. The scale factor of the reset voltage increases with on-state resistance while that of the reset current decreases with it. These behaviors are fully in consistency with the thermal dissolution model, which gives an insight on the physical mechanism of the reset switching. Our work has provided an inspiration on effectively reducing the variation of the switching parameters of RRAM devices.

No MeSH data available.


Related in: MedlinePlus