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Detailed Program
Paper Number : TF-O01
Time Frame : 17:45~17:57
Presentation Date : Thurse day, 27, November
Session Name : Thin Films & Layers
Session Chair 1# : Jaeyeong Heo
Session Chair 2# : Hiromitsu Kozuka
Perovskite manganite based hetero-junction structure for cross-point arrays of ReRAM
Hong-Sub LEE
Yonsei University
Recently, the resistive switching (RS) phenomena of transition metal oxides (TMOs) have received a great deal of attention for next generation non-volatile memory (NVM) application.[1-2] Among the candidates of NVMs, the resistive RAM (ReRAM) using the RS phenomena has distinguishable merits as simple structure of metal/insulator/metal (MIM) and various RS characteristics of most TMOs. We can apply various materials with the RS characteristics to device fabrication with the various RS characteristics, and the MIM structure enables us to realize the highest density integration as a cross-point array (CPA) structure due to MIM simple structure which the CPA integration is operated by only bit line and word line without a cell selection transistor.[3] On the other hand, it has relatively weak point in endurance property because the RS characteristics in TMOs based on a redox. From the relatively fragile endurance property and a possibility of the highest density, the ReRAM is expected to substitute the position of present NAND flash memory. Therefore realization of the CPA structure of the highest density integration is most important issue of ReRAM for competitiveness. But cross-talk of CPA structure by sneak current should be overcome to realize ReRAM of the CPA structure and many studies noted the non-linearity characteristic of RS curve as one of the solutions of the sneak current issue. Figure 1 shows the sneak current of the worst condition in CPA circuit (N x N) which selected high resistance state (HRS) cell is surrounded by unselected selected low resistance state (LRS) cells. When we read the selected HRS cell (current path A) at Vread, the sneak current as much as current at 1/2Vread of RS element is induced through current path B and the sneak current increases as increasing of the number of ¡®N¡¯ in N x N circuit. In that case, the selected resistor and sneak path resistors are connected as parallel series and increasing of the number of ¡®N¡¯ increases sneak current. The result, sensing margin is reduced according to increasing ¡®N¡¯. Therefore the array size ¡®N¡¯ can be maximized from minimized sneak current which can be achieved from high non-linear characteristic of RS curve.[4] This study fabricated pnp bipolar hetero-structure using perovskite manganite family such as p-type R0.7A0.3MnO3 (R: rare-earth, A: alkaline-earth) (RAMO) and n-type AMnO3-¥ä (AMO) to obtain non-linear resistive switching (RS) curve. The pnp structure shows not only non-linear characteristic but also tunable characteristic with thickness of AMO layer. Basically, the non-linear characteristic could be obtained from potential barrier of AMO interlayer in hole transport and its tunable characteristic was induced by resistance change of AMO layer. From the results, this study demonstrated the systematically tunable non-linear characteristic.


Figure 1 A scheme of sneak current in cross-point array structure.

References:
[1] M. J. Rozenberg, Scholarpedia 6(4) (2011) 11414.
Acknowledgements :