Monday, July 10, 2006

A Better Memory Chip

Freescale's new product could outperform the competition and usher in a new breed of electronic devices.

By Kate Greene

Freescale Semiconductor has developed a new type of semiconductor memory, called magnetoresistive random-access memory (MRAM), that uses the magnetic properties of electrons to store information. Pictured are multiple four-megabit MRAM chips on a silicon wafer. (Courtesy of Freescale Semiconductor.)

Freescale Semiconductor, a Motorola spinoff, released today the first commercial semiconductor memory that uses magnetic properties to store data. This new type of chip will compete with other established forms of semiconductor memory, such as Flash and random-access memory (RAM). Most engineers believe that the technology, called magnetoresistive random-access memory -- or MRAM -- could reduce the cost and power consumption of electronics for cell phones, music players, laptops, and servers.

In fact, MRAM has the potential to transform the landscape of electronics devices, says Doug Burger, professor of computer sciences and electrical engineering at the University of Texas in Austin. The Freescale announcement shows that the materials and manufacturing processes are finally -- after decades of development -- technically and economically feasible. "Technology announcements are very often incremental but this is a big step," he says.

The fundamental feature that makes MRAM an alluring alternative to other forms of semiconductor memory is the way it stores data. Flash memory and RAM, for example, hold information as electric charge. In contrast, MRAM uses the magnetic orientation of electrons to represent bits.

An MRAM chip is made of hundreds of thousands of memory cells that contain two magnetic electrodes: one electrode's magnetic field is fixed in place; the other's can change polarization. The resistance between the electrodes can be high or low, depending on the polarization of the electrodes, and indicates which binary number the cell is storing, a 1 or a 0.

Using the magnetic properties of a material gives a "unique combination of characteristics that you can't get in any other semiconductor material," says Saied Tehrani, director of MRAM at Freescale. MRAM chips, he says, hold data without a power supply and can be written to and read from an unlimited number of times. Reading and writing data from MRAM is also fast, taking a matter of nanoseconds.

MRAM is able to hold data without power (a property called "nonvolatility"), because once the magnetic orientation of an electron is set, it doesn't need electricity to be maintained. This feature makes MRAM a candidate to replace RAM, the easy-access memory found in computers and other devices, says Tehrani. The electrons that hold data in RAM chips lose their place when a computer or cell phone is turned off, effectively erasing previously stored information. This is why more permanent data is stored in nonvolatile memory such as magnetic hard disks in computers and Flash memory in cell phones.