First Commercial MRAM Technology Headlines Year of Innovations at Freescale Semiconductor

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Semiconductors

A Closer Look at a Potentially Disruptive Technology now in Volume Production

By Mark Shortt
Editorial Director, Design-2-Part Magazine

The year 2006 was a memorable one for Freescale Semiconductor, Inc., a company that was spun out of Motorola in 2004 and then acquired in what the company said was the largest private equity technology buyout in history last December. News of technology innovations and industry awards flowed from the company at a seemingly non-stop pace, highlighted by an announcement in November that it had become the first semiconductor company to receive a Supplier of the Year award from General Motors in two consecutive years. Along the way, the company produced the first commercially viable gallium arsenide (GaAs) MOSFET (metal-oxide semiconductor field effect transistor) device, a breakthrough that could enable development of new classes of power amplifier and low-power, ultra-fast semiconductors that significantly reduce the size and boost the performance of consumer electronics devices.

Freescale also unveiled a proprietary, redistributed chip-packaging (RCP) technique that addresses limitations associated with previous generations of packaging technologies by reducing packaged-die area and thickness by up to 30 percent. Reportedly, the RCP technology has the potential to replace ball grid array (BGA) and flip chip technology as the dominant packaging and assembly approach for advanced, highly integrated semiconductors. Freescale has already used the technique with package-on-package (PoP) technology to fabricate a radio-in-package that measures less than 25 x 25 mm, yet contains all of the electronics required for a 3G mobile phone, including memory, power management, baseband, transceiver, and RF front end modules.

Perhaps the biggest news involved memory chips, which some would say have been the "flagship" of the semiconductor industry for many years. Now, as the various chip technologies—memories, logic chips, microcontrollers (MCUs), analog/digital chips, signal processors, and RF devices—converge into smaller, more complex, and more useful systems, next-generation memory technologies have emerged as "perhaps the industry's most important technical and business issue," according to Matt Trumm, launch marketer for Freescale Semiconductor, Inc. (Austin, Tex.). One of the most publicized and highly anticipated of these technologies is magneto-resistive random access memory (MRAM), a non-volatile computer memory technology that uses magnetic storage elements, rather than electric charge or current flows, to store data.

Last July, Freescale Semiconductor became the first company to bring MRAM to market when it announced the commercialization and volume production of its four-megabit (4 Mbit) MRAM product, the MR2A16A memory chip. A fast, non-volatile memory device with "unlimited endurance," Freescale's MR2A16A is built on a foundation of technology protected by more than 100 Freescale patents, including toggle-bit switching. It combines magnetic materials with conventional silicon circuitry to deliver the speed of SRAM with the non-volatility of flash in a single, high-endurance device. According to Freescale, its successful commercialization of the technology could hasten new classes of electronic products that offer dramatic advances in size, cost, power consumption, and system performance.

"With the commercialization of MRAM, Freescale is the first-to-market with a technology of tremendous possibilities and profound implications," said Bob Merritt, Semico Research, in a statement announcing the milestone. "Competition to become the first company to market MRAM technology was fierce. This is a significant achievement that certainly confirms the dedication of Freescale's engineering team."

A System Designer's Dream

Manufactured at Freescale's 200 millimeter Chandler Fab in Arizona, the MR2A16A is a commercial temperature range, 3.3-volt device featuring 35-nanosecond read and write cycle times. It is an asynchronous memory organized as 256K words by 16 bits. An industry standard SRAM pin-out arrangement allows for system design flexibility without bus contention. The device is housed in a 400 mil TSOP type-II RoHS package.

According to Trumm, the advent of MRAM is a system designer's dream because the technology combines the best features of RAM and non-volatile memory. Freescale's MR2A16A device can perform unlimited, high-speed reading and writing of data, and it won't lose stored information when power is turned off. Its high-speed operation, unlimited cycling, and nonvolatility are said to be a unique combination of properties that can enhance performance and save costs by enabling a single MR2A16A device to replace multiple memories in numerous applications. For consumers, MRAM promises more reliable and faster networks, more reliable and cheaper machines in the office and home, and new capabilities in equipment that may be used in or out of the home.

Automotive, Industrial Seen as First Markets

Freescale Semiconductor has established a major presence in the design and manufacture of embedded semiconductors for the automotive, consumer, industrial, networking, and wireless markets. It's not surprising that the company sees big things ahead for MRAM in its target markets.

"There are significant applications in networking and data storage where MRAM's unique attributes provide capability and performance advantages," says Trumm. "The first markets for MRAM chips are likely to be in automotive and industrial settings, where durability is critical. They will also be suited for data-logging devices, such as airline black boxes that store data on aircraft performance and must be recoverable after a crash."

The MR2A16A is appropriate for a variety of commercial applications in addition to networking and data storage, including security, gaming, and printers. Engineered to be a reliable, economical, single-component replacement for battery-backed SRAM units, the part can also be used in cache buffers, configuration storage memories, and other applications that require the speed, endurance, and non-volatility of MRAM. Specific applications are reported to include data streaming, RAID disk controllers, POS terminals, industrial controllers, fire alarms, routers/switches, and copiers.

"MRAM is the only memory that has all the major desirable attributes for memory—speed, nonvolatility, and unlimited endurance," says Trumm. "From that point of view, MRAM is disruptive. However, for applications that favor one or two particular attributes, a memory that sacrifices something else to be good in those attributes has an advantage. Time will tell how much of the overall memory market can be covered by MRAM."

The Uncharted Territory of Magnetic Storage Elements

Trumm said that it's taken a number of years to bring high-level MRAM to market because convergence of the technical and business conditions required for a new memory technology is an extremely difficult proposition. Freescale was faced with the overarching problem of controlling the properties of the magnetic elements used for storage of information, and integrating these elements with the underlying CMOS structures. The challenge is huge, he said, because millions of elements must perform similarly on each chip and maintain that performance during usage across a broad commercial temperature range. And because the technology was just emerging from the research phase, it quickly became clear to the members of the design team that their greatest challenge would be to track and accommodate the continuing discoveries about the characteristics of the storage elements.

"The members of this circuit design team joined to design a 256k x 16 stand-alone MRAM with SRAM-like functionality, and quickly realized that many aspects of the architecture and circuitry would be unlike other memories," said Trumm. "Among the first challenges were the need for large, regulated, short-duration write currents running through on-pitch circuitry, a small differential read signal less than half a micro-amp, a 'Catch-22' initialization problem setting the state of reference-bits used in the data sensing scheme, and modeling the electrical behavior of the tunnel junctions.

"In the course of the design, new knowledge about the storage element parameters occasionally required complete scrapping and rethinking of individual circuits and of the chip architecture, especially as switching statistics and sensitivity to temperature became known," he continued. "These features accelerated learning and reduced time to market. For instance, innovative circuitry allows closely-controlled stress voltage levels to be applied to each tunnel junction in the array in a reasonable amount of time in spite of the fact that each cell conducts current under this stress condition. Tests were developed to reveal the presence of any low incidence extraneous failure mechanisms, and have shown none."

Trumm expects that MRAM will eventually be suitable for use in portable digital devices, giving users the benefit of faster write speeds, quick performance, and lower power consumption in digital cameras and music players. As MRAM technology continues to mature, he reasons, it will be produced with fabrication processes smaller than the current 0.18 micron process. The resulting higher densities should allow MRAM to be used in applications that replace Flash without many of its drawbacks, such as limited read-write cycles and slow write time.

The future may also hold yet another intriguing possibility: MRAM, embedded on processor chips, could allow for a unified memory that replaces electrically erasable, programmable read-only memory (EEPROM), Flash, and RAM. By reducing power consumption and enabling infinite read/writes, the technology could extend the battery life and product longevity of portable applications like PDAs, digital music players, and laptops, Trumm says.

"The commercial launch of the industry's first MRAM product is a major milestone made possible by the pioneering research of Freescale technologists," said Sumit Sadana, senior vice president, strategy and business development, and chief technology officer, Freescale. "It underscores our commitment to deliver breakthrough technology to our customers to address real-world challenges."

One of the 10 largest chip makers in the world, Freescale Semiconductor posted revenues of $6.4 billion in 2006. The company is said to invest $1.2 billion (U.S. dollars) annually in research and development.

For more information about Freescale Semiconductor, visit www.freescale.com.

Material from Business Wire was used in this report.

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