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Renesas develops MRAM technology

Posted: 20 Dec 2004 ?? ?Print Version ?Bookmark and Share

Keywords:mram? magnetoresistive random access memory? system-on-a-chip? cmos? 1mbit mram?

Renesas Technology Corp. has developed a high-speed, high-reliability MRAM (magnetoresistive random access memory) technology for SoC (system-on-a-chip) use. Using the technology, Renesas fabricated a prototype 1Mb MRAM employing a 130nm CMOS process. Investigation showed the prospect of high-speed operation with an operating frequency of 143MHz or above at a 1.2V operating voltage and measurements in a one-trillion-rewrites experiment confirmed that there was no degradation.

Renesas achieved these results through joint research with Mitsubishi Electric Corp. The joint development team looked at the relationship between the magneto-resistance (MR) ratio and resistance-area (RA) in the MTJ (magnetic tunnel junction), and by further applying correlativity with read speed, the team established an original method of finding the optimal conditions for achieving high speed.

The MTJ structure comprises a free layer, tunnel layer, and pin layer. With conventional Renesas MRAM, CoFe (ferrocobalt: magnetic material), AlOx (alumina), and CoFe are used respectively, and high-speed operation with an operating frequency exceeding 100MHz has been confirmed in trial production.

Using the technology, a prototype MRAM was fabricated using 4-layer Cu wiring, and its effects were studied. Using a 1T-1MTJ structure comprising one transistor and one MTJ for the memory cells, a TMR (tunnel magneto-resistance) element size of 0.26 by-0.44 um2 and the world's smallest memory cell size of 0.81 um2 were achieved.

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