a presentation on “oum “ “(ovonic unified memory)” submitted by: aneesh.p.p

Memory-information retention

• Various forms of storage are:o Primary storageo Secondary and off-line storageo Tertiary and database storageo Network storage

• Characteristics of storage are:o Volatility of informationo Ability to access non-contiguous informationo Ability to change information

• Classification of the Memory on the bases of Volatility of information is:o Volatile Memory

• Non-volatile Memory

• 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

Comparison of Technologies

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• Phase Change Memory Technology o Describes a class of non-volatile memory devices o 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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Ovonic Unified Memory

OUM• Definition:

o Phase Change Memory o Changes the stateo stores informationo excellent solid-state memory properties.

• Ovonyx o microelectronics memory technology o developed by Mr. Stanford Ovshinsky o Energy Conversion Devices (ECD) Inc.

• Ovonic unified memory – o derived from ''Ovshinsky'' and ''electronic''. o known as phase change memory

• OUM allows the rewriting of CD & DVDs .

Characteristics of OUM• Essentially nondestructive use: Can be read and write

to trillionths of times• The OUM solid-state memory

o Has cost advantages over conventional solid-state memories

o very small active storage media, and simple device structure.

o 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).

A

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

Alloys:

• 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.

• 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.

• Depending upon the temperature profile applied,

• Attributes of OUMo Non volatile in natureo High density ensures large storage of data within a

small areao Non destructive read:-ensures that the data is not

corrupted during a read cycle.o Uses very low voltage and power from a single

source.o Write/erase cycles of 10e12 are demonstratedo Poly crystallineo This technology offers the potential of easy addition

of non volatile memory to a standard cmos process.o This is a highly scalable memory

• Low cost implementation is expected.

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• 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 o for the electrical switches,o for erasable optical storage.

• The ground ovonic material is Ge15Te81S2Sb2.• This is a memory material.

o It isanalogous of Ge15Te85 o it represents a eutectic composition in the binary system Te-Ge

(eutectic temp. 375 oC). o 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 alloyso exist in a stable fashion in amorphous and crystalline structures,

and o also in a range of “intermediate” structural states.

o These different atomic structures have o different characteristic physical properties, o 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.

• 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.

• 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

o computers, o cell phones, o graphics-3D rendering, o GPS, o video conferencing, o multi-media, o Internet networking and interfacing, o digital TV, o telecom, o PDA, o digital voice recorders, o modems, o DVD, o networking (ATM), o Ethernet, and pagers.

OUM offers a way to realize full system-on-a-chip

Thank You!