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Department of Electronics Advanced Information Storage 15 Atsufumi Hirohata 16:00 21/November/2013 Thursday (V 120)

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Presentation on theme: "Department of Electronics Advanced Information Storage 15 Atsufumi Hirohata 16:00 21/November/2013 Thursday (V 120)"— Presentation transcript:

1 Department of Electronics Advanced Information Storage 15 Atsufumi Hirohata 16:00 21/November/2013 Thursday (V 120)

2 Quick Review over the Last Lecture MRAM read-out : Bit line Sensing current Word line Parallel magnetisation Low resistant state 0 Magnetic free layer Magnetic pin layer Antiparallel magnetisation High resistant state 1 Selection transistor (MOSFET) Insulator / nonmagnet Magnetic tunnel / spin-valve junctions * ** M. Oogane and T. Miyazaki, Magnetic Random Access Memory, in Epitaxial Ferromagnetic Films and Spintronic Applications, A. Hirohata and Y. Otani (Eds.) (Research Signpost, Kerala, 2009) p. 335; MRAM STT write-in : *** Perpendicularly magnetised MRAM :

3 15 Ferroelectric / Phase Change Random Access Memory FeRAM PRAM ReRAM

4 Memory Types * Rewritable Read only Read majority (Writable) Volatile Non-volatile Dynamic Static DRAM SRAM MRAM FeRAM PRAM PROM Mask ROM Flash EPROM

5 Comparison between Next-Generation Memories *

6 Ferroelectric Random Access Memory (FeRAM) * In 1952, Dudley A. Buck invented ferroelectric RAM in his masters thesis : ** Utilise ferroelectric polarisations Very fast latency : < 1 ns CMOS process compatible ×Relatively large cell size : 15 F 2 ×Destructive read-out

7 FeRAM Cells 1 * 1-transistor 1-capacitor type : 1-transistor type :

8 FeRAM Cells 2 * 2-transistor 2-capacitor type : Bit line 1 Bit line 2 Word line Plate line Ferroelectric capacitor 1 Ferroelectric capacitor 2 Bit line 1 Bit line 2 Word line Plate line Capacitor V 1 Capacitor V 2 FeRAM Writing operation Reading operation Prevent destructive read-out

9 Requirements for Ferroelectric Materials FeRAM cell structure : Large residual polarisation High recording density Small dielectric constant Read-out error reduction Small coercive electric field Low power consumption High fatigue endurance 10-year usage (> polarisation reversal) High remanence 10-year tolerance for data Small imprint High recording density

10 Ferroelectric Materials * ABO 3 type materials :

11 Polarisation Hysteresis * For example, BaTiO 3 :

12 Applications 2-Mb FeRAM introduced by Fujitsu : *

13 Comparison between Next-Generation Memories *

14 Phase Change In 1960s, Stanford R. Ovshinsky studied phase-change properties of chalcogenide ** In 1969, Charles Sie demonstrated the feasibility for memory applications. In 1999, Ovonyx was established for memory realisation : 512 Mbit (Samsung, 2006) 1 Gbit (Numonyx, 2009) 1.8 Gbit (Samsung, 2011) *

15 Phase Change Random Access Memory (PRAM) Required writing currents for several techniques dependent upon cell size : * Utilise phase change Low resistivity : crystalline phase High resistivity : amorphous phase CMOS process compatible ×Rewritability : 1,000 ~ 100,000 times ×Destructive read-out

16 PRAM Properties PRAM properties as compared with NOR-flash memory : **

17 PRAM Operation PRAM operation : * * memory-performance

18 PRAM Architecture PRAM architecture : * * memory-performance

19 Resistive Random Access Memory (ReRAM) In 1997, Yoshinori Tokura found colossal magnetoresistance (CMR) : * In 2002, Sharp demonstrated 64-bit ReRAM with Pr 0.7 Ca 0.3 MnO 3 : ** Utilise large resistivity change High endurance : ~ Fast switching speed : < 1 ns CMOS process compatible

20 ReRAM Operation Unipolar / bipolar operations : * **

21 ReRAM Operation Cycle Oxygen vacancy can be repaired during the operation cycle : * **

22 ReRAM Demonstration Samsung (2004) : * Stanford (2011) : * **


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