A Presentation on

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A Presentation onOUM (OVONIC UNIFIED
MEMORY)Submitted byAakash Singh Chauhan
(CS 05101)
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• Memory-information retention
• Various forms of storage are
• Primary storage
• Secondary and off-line storage
• Tertiary and database storage
• Network storage
• Characteristics of storage are
• Volatility of information
• Ability to access non-contiguous information
• Ability to change information
• Classification of the Memory on the bases of
  Volatility of information is
• Volatile Memory
• Non-volatile Memory

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• Nonvolatile Memory
• Protection of data in the event of power loss
• Periodic refreshing
• Modern Approaches of Nonvolatile Memory
• FRAM Technique used- ferroelectricity
• MRAM Technique used-ferromagnetism
• OUM Technique used- phase changes in the
  thin-film
• 3DM Technique used- multiple layers of active
  circuitry on the silicon substrate

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• Comparison of Technologies

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• Phase Change Memory Technology
• Describes a class of non-volatile memory devices
• Exploits differences in the electrical
  resistivity of a material in different phases
  (solid, liquid, gas, condensate and plasma)
• Graphical representation of a basic PCM storage
  element

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• Relative to the amorphous state, the
  polycrystalline state shows a dramatic increase
  in free electron density, similar to a metal.

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OUM

• Ovonic Unified Memory

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• OUM
• Definition
• Phase Change Memory
• Changes the state
• stores information
• excellent solid-state memory properties.
• Ovonyx
• microelectronics memory technology
• developed by Mr. Stanford Ovshinsky
• Energy Conversion Devices (ECD) Inc.
• Ovonic unified memory
• derived from ''Ovshinsky'' and ''electronic''.
• known as phase change memory
• OUM allows the rewriting of CD DVDs .

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• Characteristics of OUM
• Essentially nondestructive use Can be read and
  write to trillionths of times
• The OUM solid-state memory
• Has cost advantages over conventional solid-state
  memories
• very small active storage media, and simple
  device structure.
• OUM requires fewer steps in an IC manufacturing
  process resulting in
• reduced cycle times,
• fewer defects, and
• greater manufacturing flexibility.

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• Chalogenide
• The PCM technology being developed by Intel uses
  a class of materials known as chalcogenides
  (kal-koj--uh-nyde).
• Basically, chalogenide alloy materials use one or
  more elements from column VI of the Periodic
  Table. OUM devices use an alloy system of GeSbTe
  (Germanium-Antimony-Tellurium).
• Chalcogenides are alloys that contain an element
  in the Oxygen/Sulphur family of the Periodic
  Table (Group 16 in the new style or Group VIa in
  the old style Periodic Table).

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• OUM Devices use the GeSbTe alloy system.
• Crystal Structures for GeSbTe Pseudobinary Alloys

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• Working
• Phase change memory also called ovonic unified
  memory (OUM),
• Phase states are programmed by the application of
  a current pulse through a Mosfet,
• heating a small volume of the material with a
  current pulse to make the transition.

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• thermally activated, rapid, reversible change
• chalcogenide alloy are an amorphous state and a
  polycrystalline state.

• polycrystalline state dramatic increase in free
  electron density, similar to a metal.

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• Depending upon the temperature profile applied,

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• Attributes of OUM
• Non volatile in nature
• High density ensures large storage of data within
  a small area
• Non destructive read-ensures that the data is
  not corrupted during a read cycle.
• Uses very low voltage and power from a single
  source.
• Write/erase cycles of 10e12 are demonstrated
• Poly crystalline
• This technology offers the potential of easy
  addition of non volatile memory to a standard
  cmos process.
• This is a highly scalable memory
• Low cost implementation is expected.

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Architecture of OUM

• resistance change is very large-more than a
  factor of 100.
• Thermal insulators are also attached to the
  memory structure in order to avoid data loss due
  to destruction of material at high temperatures.
• To write data into the cell, the chalcogenide is
  heated past its melting point and then rapidly
  cooled to make it amorphous.
• To make it crystalline, it is heated to just
  below its melting point and held there for
  approximately 50ns, giving the atoms time to
  position themselves in their crystal locations.

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• Ovonic materials
• The chalcogenide glasses (especially those based
  on Ge, Sb and Te) are key materials
• for the electrical switches,
• for erasable optical storage.
• The ground ovonic material is Ge15Te81S2Sb2.
• This is a memory material.
• It isanalogous of Ge15Te85
• it represents a eutectic composition in the
  binary system Te-Ge (eutectic temp. 375 oC).
• Addition of S and Sb changes the crystallization
  speed when the material is heated in the glassy
  state.

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• Data storage mechanism
• Devices store information through changes in
  their atomic structures
• Materials which are multi-element chalcogenide
  alloys
• exist in a stable fashion in amorphous and
  crystalline structures, and
• also in a range of intermediate structural
  states.
• These different atomic structures have
• different characteristic physical properties,
• including different values of electrical
  conductivity. The ability of a memory device to
  be programmed to stable intermediate structures
  allows storage of multiple bits of information
  in each memory cell location,

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• Advantages of OUM
• reversible structural phase change.
• Small active storage medium.
• Simple manufacturing process.
• Simple planar device structure.
• Low voltage single supply.
• Reduced assembly and test costs.
• Highly scalable- performance
• Multistates.
• High temperature resistance.
• base technology is not affected.

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Problems/Concerns of OUM

• OUM devices as devices decrease in size
• as the devices are scaled to smaller sizes,
• reducing programming current for lower voltage
  and lower power operation.

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• Application
• stored as a structural phase
• impervious to ionizing radiation effects.
• tolerance of the chalcogenide material
• A radiation hardened semiconductor technology
• OUM allows the rewriting of CD DVDs
• OUM has direct applications
• computers,
• cell phones,
• graphics-3D rendering,
• GPS,
• video conferencing,
• multi-media,
• Internet networking and interfacing,
• digital TV,
• telecom,
• PDA,
• digital voice recorders,
• modems,

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• Thank You!