HITACHI'S MEMORY ELEMENT STRUCTURE OPENS DOOR TO GIGABIT MRAM

TOKYO, Dec 20, 2007 (AsiaPulse via COMTEX) -- HIT | charts | news | PowerRating -- Hitachi Ltd. (6501) and a group from Japan's Tohoku University have developed a new type of memory element structure for MRAM (magnetoresistive random access memory) that promises to eventually lead to gigabit-level versions of this next-generation memory technology.

MRAM is a type of nonvolatile memory that stores bits as changes in the polarity of the magnetic materials that make up each memory element.

For their MRAM memory element, Hitachi and the university group employed spin injection, a technology that is used for hard-drive magnetic heads and enables the structure around the element to be simplified. For the free layer where the bit is actually recorded, the element adopts the same laminated-ferri structure used in MRAM devices sold by U.S. firm Freescale Semiconductor Inc. This free layer has a double-layered composition made from cobalt-iron-boron and ruthenium.

Combining the spin injection method with the laminated-ferri structure enables data to be rewritten using a smaller current density, meaning that the transistors can be designed smaller so that the memory chip as a whole can store more bits.

In tests of a prototype, bits could be rewritten to the new memory element using a current density of 1 million amperes per sq. cm, and the structure also showed the kind of high thermal stability needed to enable bits to be stored longer than 10 years.

Using these technologies, if an MRAM chip were fabricated using a 45-nanometer process, it could store the same gigabit level of data as DRAM.

Hitachi and the university group still need to develop other essential technologies for the MRAM, but hope to have a high-capacity chip ready within several years.

(Nikkei)

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