LONDON — After seven years of R&D Unity Semiconductor Corp. has unveiled a nonvolatile memory based on a proprietary resistive RAM technology. The specification of the memory should allow it to be four times denser than NAND flash, with 5 to 10x the write speed, the company claimed.

If successfully brought to market " which Unity acknowledges may require some technology sharing and IP licensing " the so called CMOx memory could be a game-changer for the electronics industry, particularly at the high capacity end, in servers and personal computers, industry observers have said.

The company's technology, which it labels CMOx for conductive metal oxide, is based on the use of layered conductive metal oxides. With the technology, Unity claims to have devised a passive rewritable cross-point memory array that requires no transistor in a memory cell. This has obvious benefits for scalability in the lateral direction, allowing CMOx to go beyond 35-nm where flash and DRAM both start to hit problems. Indeed, the simplicity of the memory array is also allowing Unity to lay down multiple planes of memory on a chip, increasing density yet further.

Unity (Sunnyvale, Calif.) has been processing 64-kilobit circuits for two years, 64-megabit chips for one year, and is in design with a 64-gigabit product that is close to tape-out based on a 65-nm base wafer and slated for pilot production in the second half of 2010, with volume production in the second quarter of 2011.

The company's storage-class memory products will allow it to initially target the high-performance NAND flash replacement market. It is also designed to address emerging markets, such as solid-state drives (SSDs), mobile Internet devices (MIDs) and smart phones. "We're about two years away from being in volume production with our first product, a 64-gigabit storage class memory," said Unity chairman and CEO Darrell Rinerson.

The memory works because the CMOx structure has a variable resistance putting the device in the class of the much-touted memristor. However, Rinerson wanted to distance himself from the RRAM label. "We do not consider ourselves with the RRAM companies. In that technology the conducting path tends to be localized. It tends to be based on filamentary switching. Our technology is not filamentary and does not require a forming step. As a result it does not use heat-assisted switching " unlike phase-change memory."

Rinerson continued: "In these other technologies the write current is high because of the need to generate heat. We have a 1-microamp write because we are based on oxygen vacancy redistribution. Whereas the RRAM crowd tends to use binary metal oxides we use something more complex."

Rinerson is reluctant to say exactly what Unity uses, but reference to the company's applied-for patents reveals "The memory element includes a layer of a conductive metal oxide (CMOx) (e.g., a perovskite) in contact with an electrode that may comprise one or more layers of material. At least one of those layers of material can be a conductive oxide (e.g., a perovskite such as LaSrCoO₃ or LaNiO₃) that is in contact with the CMO.

The CMOx technology is said to yield products with 4 times the density and 5-to-10 times the write speed of today's NAND flash. Unity's CMOx-based designs use four physical layers of multi-level cell memory.

"The key here is the non-linearity which gives us a factor of 5 to 10x between the on and off state," said Rinerson. He is confident that the memory is capable of specifications to make it a drop-in replacement for NAND flash memory. "In terms of retention we have a 10 year, 85 C benchmark. We don't see any reason why we shouldn't reach that. And for endurance we see 10,000 to 100,000 cycles."

Unity also has closed its Series C round of financing of $22 million, taking the total invested to Unity to $75 million. The financing came primarily from Unity's three major venture capital organizations, August Capital, Lightspeed Venture Partners, and Morgenthaler Ventures, and an unnamed hard disk drive (HDD) manufacturer, also a repeat investor.

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