Flash
Memory Chip Technology
The
Flash Memory Chip used to make thumbdrives, flash memory
cards and MP3 Players is called a NAND Flash Memory Chip.
In current designs of NAND flash memory chips, there is
a thin layer of silicon dioxide that coats the transistor
gates of flash chips which allows the flash memory chips
to retain memory even when power is cut off. This silicon
layer holds electrons within the transistor gate. Depending
on the nature of the electrons' charge, the device using
the flash memory reads the charge as "on" or
"off," creating the ones and zeroes necessary
for binary information.
This
silicon dioxide layer has been reduced down in size continually
as flash memory's production process has progressed over
time. For flash memory manufacturers, this shrinkage is
essential to increasing profits. A smaller chip allows
fabricators to make more chips from a single wafer. It
also allows a greater size-to-performance ratio.
NAND
Flash Memory Chip Capacity
NAND
Flash Memory Chips are the type used in thumbdrives, flash
memory cards and MP3 Players. NAND flash memory chips
are built into these USB memory products on which consumers
store images, video and music. These products are all
available with Gigabyte capacity.
NAND
Flash is a sequential access device appropriate for mass
storage applications, while NOR Flash is a random access
device appropriate for code storage applications. NAND
technology organizes cells serially to achieve higher
densities. This reduces the number of contacts needed
in the memory array. The trade-off between the two technologies
is NAND Flash data must be accessed sequentially compared
with NOR Flash which offers fast random
access.
Eight bits of memory chip
power are required to run one byte of storage capacity,
which is enough to store a single letter of the alphabet.
Eight Bits make one Byte and the chart below provides
the Gigabit and Megabit chip capacities required to make
Gigabyte Capacities on thumbdrives and FlashPoint ShareDrives.
Flash
Memory Capacity Composition of USB Flash Memory Drive
| USB
Thum Drive Capacity |
Flash
Memory Chip Used |
| 2
GB |
8G
(1G*8) chip * 2 pcs |
| 1
GB |
8
GB (1GB*8) chip* 1 pcs
or 4 GB (512MB*8) chip* 2 pcs |
| 512
MB |
512
MB 4G (512MB*8) Chip *1 pcs
or 2G (256MB*8) Chip*2 pcs |
| 256
MB |
2G
(256MB*8) chip* 1 pcs
or 1G (128MB*8) * 2 pcs |
| 128
MB |
1G
(128MB*8) * 1 |
The
Flash Memory Chip of the Future
One
of the first things experts like to point out about flash
is that, technically, it's contradictory. Flash chips
are electrical, meaning that they need electricity to
store data. Yet flash chips retain their data after the
host computer or cell phone is turned off.
The
trick lies in the fact that the gate in a flash transistor--the
microscopic on-off switch inside a flash chip--is wrapped
in a layer of silicon dioxide that prevents electrons
from escaping. Depending on what the charge inside is,
the computer reads the memory cell as a "1"
or "0".
The
silicon dioxide insulator is so effective that a floating
gate transistor (so-called because the gate "floats"
above the rest of the transistor) will retain data for
10 years. New data can be written to a flash chip a million
times before errors begin to occur.
While
the insulating layer is the secret layer in the flash
design, it also is the source of problems. The silicon
dioxide wrappers on flash chips today measure about 90
angstroms thick. An angstrom is one ten-billionth of a
meter, or less than the width of a hydrogen atom and can
probably be reduced in size to about 80 angstroms. Any
thinner, and the electrons begin to leak out, leading
to data corruption or loss.
In
its turn, the need for thickness makes power a problem.
About 10 volts must be applied to the floating gate to
get electrons through in the first place and far more
voltage than is used to animate microprocessor transistors.
In
addition, if the size of the chip is reduced, the voltage
intended for one cell might inadvertently zap a neighboring
cell which results in misrecorded data.
Consequently,
as existing technology nears its limits, manufacturers
are eager to develop new designs. For example, Texas Instruments
and Ramtron both have worked with ferroelectric RAM (FeRAM),
which uses moving atoms within a crystal. And Intel is
testing Ovionics Unified Memory, in which data is retained
in a heated material similar to that used in DVD discs.
Motorola is working with crystal materials in their research
and development. Sumsung is working with existing NAND
technology and they have released a NAND flash chip with
16 gigabits (which doubles the capacity of the existing
8 gigabit NAND flash chips).
To
increase capacity and to makel flash chips with an average
component size of 45 nanometers in the future is the goal
for the flash memory chip manufacturing process which
is set begin in 2007.
Worldwide
Demand
Worldwide
demand remains strong for flash memory chips, which are
used in everything from portable MP3 players to advanced
industrial equipment. Flash memory's ability to retain
data even when power is cut off makes it invaluable for
cell phones and digital organizers.
By
some estimates, the flash memory market could exceed US
$42 billion by 2007, compared with its current level of
approximately $13 billion.
Applicaiton
Note - Flash Memory Chip Technology
