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