Renesas Targets SoC with High-Speed, High-Reliability MRAM Technology

12/17/2004 - Renesas Technology Corp. announced the development of a high-speed, high-reliability MRAM (Magnetoresistive Random Access Memory) technology for SoC (system-on-a-chip) use. Using this technology, Renesas Technology fabricated a prototype 1-Mbit MRAM employing a 130 nm (nanometer) CMOS process. Investigation showed the prospect of high-speed operation with an operating frequency of 143 MHz or above at a 1.2 V operating voltage, and measurements in a one-trillion-rewrites experiment confirmed that there was no degradation.

Renesas Technology achieved these results through joint research with Mitsubishi Electric Corporation, and announced them on December 14 (local time) at the 2004 IEEE International Electron Device Meeting (IEDM) to be held in San Francisco from December 13.

The functions and performance of mobile devices and digital consumer appliances have improved remarkably in recent years, and this trend will continue in the future. As higher performance and functionality and lower power consumption are required in product development, there is a demand for technologies that will make this possible.

Memory elements used for data storage and others play an important role as a key technology supporting higher product functionality and performance, and various types of memory elements have been developed to date. To meet future needs, efforts are being made to improve various kinds of conventional volatile and nonvolatile memory elements on the one hand, at the same time as research is being conducted into new types of next-generation memory offering novel characteristics.

One such new kind of memory, MRAM, is nonvolatile memory that enables data to be retained when power is cut while also providing high-speed operation capability. This ability to implement functions provided by various kinds of conventional memory has led to high expectations of MRAM as next-generation memory.

Details of the Technology
Details of the newly developed technology are as follows.

  1. Establishment of an optimisation method for realising maximum performance
  2. Use of magnetic material enabling high speed plus tunnel layer optimisation

Use of the above approach gives a cell sensing time (data read time) of 5.2 ns, presenting the prospect of achieving a read cycle of approximately 7 ns and an operating frequency in excess of 143 MHz. Furthermore, an experiment in which one trillion write cycles were executed in a high-temperature environment of 150C showed almost no degradation. This confirmed that high reliability can be achieved despite reducing the thickness of the tunnel layer.

Effects of the New Technology
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 0.44 m2 and the world's smallest memory cell size of 0.81 m2 were achieved.

1. Magneto-resistance ratio: In MRAM, 0 and 1 are determined by a high and low resistance respectively. Magneto-resistance ratio is a ratio in which the low resistance value is the denominator and the resistance difference (high resistance value - low resistance value) is the numerator. As the magneto-resistance ratio increases, erroneous operations during reading decrease, enabling operating speed to be increased.
2. Electrical resistance: A quantity whereby the lower resistance is normalized for the MTJ area in the two MRAM states.

About Renesas Technology Corp.
Renesas Technology Corp. designs and manufactures highly integrated semiconductor system solutions for mobile, automotive and PC and Audio Visual markets. Established on April 1, 2003 as a joint venture between Hitachi, Ltd. (TSE:6501, NYSE:HIT) and Mitsubishi Electric Corporation (TSE:6503) and headquartered in Tokyo, Japan, Renesas Technology is one of the largest semiconductor companies in the world and the number one microcontroller supplier globally. Besides microcontrollers, Renesas Technology offers system-on-chip devices, Smart Card ICs, mixed-signal products, flash memories, SRAMs and more.

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