Tohoku University - Page 3

Hitachi, Ltd. and Prof. Hideo Ohno of The Research Institute of Electrical Communication, Tohoku University have jointly prototyped a 2 Mbit nonvolatile RAM chip based on the spin torque transfer writing technology. When a 1.8 V voltage is supplied, the write and read times are 100 and 40 ns, respectively. TMR elements used in the chip were produced by the Tohoku Univ. lab while the chip designed with a 0.2 ?m rule process technology was manufactured by Hitachi. The details were presented at the ISSCC 2007 event being held in San Francisco on February 14 (US time).

The nonvolatile RAM based on spin torque transfer is designed to eliminate write lines for magnetic field generation used in a magnetoresistive RAM (MRAM). Instead, data rewriting is performed by the current flown through memory elements (TMR elements). In this way, the spin torque transfer RAM can solve a problem of the write current in MRAM which increases as miniaturization accelerates. Thus far, Hitachi and Tohoku Univ. have jointly examined the principles of this method at the element level.

Professor Hideo Ohno at the Tohoku University Research Institute of Electrical Communication and a research group of Hitachi's Advanced Research Laboratory have jointly developed a tunnel magneto-resistance (TMR) element with a reluctivity of 287%, the highest room temperature value ever measured.

The high reluctivity TMR element is necessary to speed up and reduce power consumption of MRAM, a nonvolatile memory that is regarded as a future super-gigabit memory candidate.
The new device also achieved 403% at low temperature.