NEC, Toshiba Claim Memory Breakthrough

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NEC and Toshiba have made two advancements in developing a new type of memory that could eventually replace the standard memory used in mobile phones, MP3 players, and other portable electronic devices, the companies say.

Flash memory is currently favored for portable devices and memory cards because it retains data after a device is switched off. Several companies, including NEC and Toshiba, are developing a type of memory called MRAM (magnetorestitive RAM) that uses magnetic fields to store data. MRAM can retain data when switched off, and can also recall data faster, work longer, and potentially be produced at a lower cost than flash memory, according to its proponents.

MRAM could replace flash and DRAM (dynamic RAM) by as early as 2010, its backers say, but only if certain technical problems are solved first.

One issue involves the size of MRAM cells, which tend to be bigger than those of other memory types. Bigger cells result in higher production costs and can also use a lot of power when writing data. The developers must also determine how to control magnetic fields in each memory cell, to stop the fields from interfering with their neighbors and creating errors.

For these and other reasons, the capacity of MRAM chips developed so far has been limited to about 16 megabits, while flash memory is already available in gigabit densities.

Solving Problems

NEC and Toshiba developed two technologies that help solve some of the problems, allowing MRAM chips to store much more data and use less electricity, they say. The technologies could allow them to develop 256 megabit MRAMs by early 2006, they say.

One technology involves a new cell design that has arc-shaped bulges on its sides. The design reduces the amount of current required to write to the cells by about a half compared to current MRAM designs and also reduces errors, the companies say.

They also developed an alternative to the two basic MRAM cell designs produced to date. One of these existing designs couples each cell with a transistor, which improves "read times" but increases cell size. The other removes the transistor from each cell but results in read errors and longer read-access times.

NEC and Toshiba created a design that uses one transistor to control four cells, resulting in smaller cells that have a faster read time of about 250 nanoseconds. It has been used to design a 1 megabit chip that uses only about half the voltage of Toshiba's current 4 gigabit flash products, the companies say.

Despite the advances, Toshiba has not set a schedule for commercializing MRAM chips, says spokesperson Makoto Yasuda.

MRAM could one day be useful for flash or other memory applications, says Kim Soo-Kyoum, a program director for semiconductor research at IDC. However, its small memory capacities and future development work may mean MRAM takes a long time to replace other memory types, he says.

"MRAM is just in its infancy. Really, its future is as yet unknown," he says.

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