A Presentation on “OUM “ “(OVONIC UNIFIED MEMORY)” Submitted by: Aakash Singh Chauhan (CS 05101)

Memory-information retention Various forms of storage are: o Primary storage o Secondary and off-line storage o Tertiary and database storage o Network storage Characteristics of storage are: o Volatility of information o Ability to access non-contiguous information o 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 A AAKASH

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 A AAKASH

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

OUM Ovonic Unified Memory

OUM Definition: o Phase Change Memory o Changes the state o stores information o 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. A AAKASH

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 AAKASH

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 OUM o Non volatile in nature o High density ensures large storage of data within a small area o 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 demonstrated o Poly crystalline o 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. A AAKASH

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. A AAKASH

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. A AAKASH

Data storage mechanism Devices store information through changes in their atomic structures Materials which are multi-element chalcogenide alloys o 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, A AAKASH

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.

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.

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

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