24-06-2014, 10:55 AM
Polymer Memory
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ABSTRACT
Digital Memory is and has been a close comrade of each and every
technical advancement in Information Technology. The current memory
technologies have a lot of limitations. These memory technologies when
needed to expand will allow expansion only two dimensional space. Hence
area required will be increased.
Next Generation Memories satisfy all of the good attributes of
memory. The most important one among them is their ability to support
expansion in three dimensional spaces. They include MRAM, FeRAM,
Polymer Memory and Ovonics Unified Memory. Polymer memory is the
leading technology among them. It is mainly because of their expansion
capability in three dimensional spaces.
A polymer retains space
charges near a metal interface when there is a bias, or electrical current,
running across the surface. We can store space charges in a polymer layer,
and conveniently check the presence of the space charges to know the state
of the polymer layer. Space charges are essentially differences in electrical
charge in a given region. They can be read using an electrical pulse because
they change the way the devices conduct electricity
INTRODUCTION
Imagine a time when your mobile will be your virtual assistant and
will need far more than the 8k and 16k memory that it has today, or a world
where laptops require gigabytes of memory because of the impact of
convergence on the very nature of computing. How much space would your
laptop need to carry all that memory capacity? Not much, if Intel's project
with Thin Film Electronics ASA (TFE) of Sweden works according to plan.
TFE's idea is to use polymer memory modules rather than silicon-based
memory modules, and what's more it's going to use architecture that is quite
different from silicon-based modules.
While microchip makers continue to wring more and more from
silicon, the most dramatic improvements in the electronics industry could
come from an entirely different material plastic. Labs around the world are
working on integrated circuits, displays for handheld devices and even solar
cells that rely on electrically conducting polymers—not silicon—for cheap
and flexible electronic components. Now two of the world’s leading chip
makers are racing to develop new stock for this plastic microelectronic
arsenal: polymer memory. Advanced Micro Devices of Sunnyvale, CA, is
working with Coatue, a startup in Woburn, MA, to develop chips that store
data in polymers rather than silicon. The technology, according to Coatue
CEO Andrew Perlman, could lead to a cheaper and denser alternative to
flash memory chips—the type of memory used in digital cameras and MP3
players. Meanwhile, Intel is collaborating with Thin Film Technologies in
Linkping, Sweden, on a similar high capacity polymer memory.
PRESENT MEMORY TECHNOLOGY SCENARIO
Digital Memory is and has been a close comrade of each and every
technical advancement in Information Technology. The current memory
technologies have a lot of limitations. DRAM is volatile and difficult to
integrate. RAM is high cost and volatile. Flash has slower writes and lesser
number of write/erase cycles compared to others. These memory
technologies when needed to expand will allow expansion only two
dimensional space. Hence area required will be increased. They will not
allow stacking of one memory chip over the other. Also the storage capacities
are not enough to fulfill the exponentially increasing need. Hence industry is
searching for “Holy Grail” future memory technologies for portable devices
such as cell phones, mobile PC’s etc. Next generation memories are trying a
tradeoffs between size and cost .This make them good possibilities for
development.
NEXT GENERATION MEMORIES
As mentioned earlier microchip makers continue to wring more and
more from silicon, large number of memory technologies were emerged.
These memory technologies are referred as ‘Next Generation Memories’.
Next Generation Memories satisfy all of the good attributes of memory. The
most important one among them is their ability to support expansion in
three dimensional spaces. Intel, the biggest maker of computer processors, is
also the largest maker of flash-memory chips is trying to combine the
processing features and space requirements feature and several next
generation memories are being studied in this perspective. They include
MRAM, FeRAM, Polymer Memory and Ovonics Unified Memory
POLYMERS AS ELECTRONIC MATERIALS
Polymers are organic materials consisting of long chains of single
molecules. Polymers are highly adaptable materials, suitable for myriad
applications. Until the 1970s and the work of Nobel laureates Alan J. Heeger,
Alan G. MacDiarmid and Hideki Shirakawa, polymers were only considered
to be insulators. Heeger et al showed that polymers could be conductive.
Electrons were removed, or introduced, into a polymer consisting of
alternately single and double bonds between the carbon atoms. As these
POLYMER MEMORY ARCHITECTURE
The researchers made the storage device by spreading a 50-nanometer
layer of the polymer regioregularpoly on glass, then topping it with an
aluminum electrode. To write a space charge to the device, they applied a
positive 20-second, 3-volt pulse. To read the state, they used a 0.2-volt, one
minute pulse. Any kind of negative electrical pulse erased this high state, or
charge, replacing it with the default low state. In this process, a continuous
sheet of flexible polymer is unrolled from one spool, covered with circuitboard-
like patterns of silicon, and collected on another spool.
The Thin Film memory design is solid state, with no mechanical or
moving parts involved. It uses a passively addressed, cross point matrix. An
ultra thin layer of the TFE polymer is sandwiched between two sets of
electrodes. A typical array may consist of several thousand such electrically
conducting lines and hence millions of electrode crossings. Memory cells are
defined by the physical overlap of the electrode crossings and selected by
applying voltage. Each electrode crossing represents one bit of information
in a true 4f² (4-Lampda square) cell structure, the smallest possible physical
Manufacture
With Thin Film’s memory technology, polymer solutions can be
deposited on flexible substrates with industry standard processes like spin
coating in ultra thin layers. Using an all-organic architecture, the Thin Film
Polymer Memory
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memory system is suitable for roll-to-roll manufacture. This is a continuous
production method where a substrate is wound from one reel to another
while being processed. The basic premise is to exploit the fact that polymers
can be handled as liquids and, at a later stage, printed directly with the cross
matrices of electrodes, thus allowing square meters of memory and
processing devices to be produced by the second. This can be taken even
further by the use of simple ink-jet printers. Such printers, with modified
printer heads, will have the capability to print complete memory chips at the
desktop in the future. With the Thin Film technology, there are no individual
components that must be assembled in a purpose-built factory, nor is the
technology limited to a particular substrate.
EXPANDING MEMORY CAPABILITY- STACKED MEMORY
Expanding memory capability is simply a matter of coating a new
layer on top of an existing one. The footprint remains the same even after
expansion because each new layer adds the same capacity as the first one.
This stacking is a fundamental strength of the Thin Film technology. A layer
may include a self-contained active memory structure with on-layer TFT
circuitry, or share circuitry with all other layers. Both approaches offer true
3D memory architecture. This means that the new technology is not just for
saving space, but also the option of using different, and optimized software
architectures
NUMBER OF TRANSISTORS, SPEED, COST ETC
1 Number of transistors
The stacking also means that a lesser number of transistors can be
used for the circuitry in the chip. The Thin Film system requires about 0.5
million transistors per gigabit of memory compared to 1.5 to 6.5 billion
transistors required by traditional silicon-based systems for one gigabit.
While the illustrations on advantages regarding the size were based on RAM
for matters of convenience, the fact is that the new polymer-based
technology can offer total storage solutions
ADVANTAGES OF POLYMER MEMORY
1. Polymer memory layers can be stacked This enable to achieve very
high storage capacity.
2. Memory is Nonvolatile
3. Fast read and write speeds
4. Very low cost/bit, high capacity per dollar
5. Low power consumption
Polymer Memory
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6. Easy manufacture use ink-jet printers to spray liquid-polymer
circuits onto a surface
7. Thin Film system requires about 0.5 million transistors per gigabit of
memory. Traditional silicon-based system would require between 1.5
to 6.5 billion transistors for that same gigabit.
LIMITATIONS OF POLYMER MEMORY
But turning polymer memory into a commercial product won’t be
easy. Memory technologies compete not only on storage capacity but on
speed, energy consumption and reliability. The difficulty is in meeting all the
requirements of current silicon memory chips. Until new memory materials
are able to compete with the high performance of silicon, their notes, they
are likely to be limited to niche applications. One likely use is in disposable
electronics, where cost, rather than performance, is the deciding factor.
Researchers at Lucent Technologies’ Bell Laboratories are working on
polymer memory devices for use in identification tags. The polymer memory
made at Bell Labs is still relatively slow by silicon standards, and anticipated
capacity is only on the order of a kilobit. But, says Bell Labs chemist Howard
Katz, the flexible and low-cost polymer memory devices could be “very
attractive” for, say, identification tags meant to be thrown away after a few
uses.
CONCLUSION
The fundamental strength, i.e. The stacking of memory layers which
yields maximum storage capacity in a given footprint is the main reason why
Polymer memory is highly preferred. The nonvolatileness and other features
are in built in molecular level and offers very high advantages in terms of
cost. Polymers ,which are once considered to be the main reason for
pollution and refered to be removed from the earth, has found a new area of
utilization