Carlos Paz de Araujo, a professor at the University of Colorado and an expert in ferroelectric memory and materials, has revealed that his company Symetrix Corp. is preparing to launch a non-filamentary, non-volatile memory technology based on the metal-insulator Mott transition in nickel oxide.
The development was revealed on the web pages of EE Times in an online forum discussing non-volatile memory in which Professor Araujo said he was "sick and tired of these electrochemical approaches claiming to solve all problems when in fact the beauty of metal-insulator physics is not utilized."
There have been numerous R&D initiatives to try and develop a resistive RAM (ReRAM) replacement for flash memory, but most of these are based on the making and breaking of conductive filaments within an insulating sandwich between electrodes. Understanding and controlling the physical processes behind the forming, maintenance, and breaking of such filaments, which can be just one or a few atoms in diameter, has proved difficult.
Professor Araujo claimed his approach is different in that it is non-filamentary and does not depend on mass transport. Instead it uses a metal-insulator transition that occurs throughout the metal-oxide crystal structure and that is dependent on electron correlation. The metal-insulator transition is controlled by doping, with nickel carbonyl as the dopant, Professor Araujo said in his comments.
"We call our device CeRAM -- Correlated Electron RAM -- to separate ourselves from the filament crowd," Professor Araujo wrote on the EE Times website.
"We are introducing this technology in two months. It is fully compatible with lithography down to 20nm and can go lower. It is free of complicated contact materials such as platinum. It uses aluminum, cobalt silicide and nickel silicide. Anneals at 400 degrees C and is integratable in 3D using the same electrodes with an already proven diode. The storage temperature is 400 degrees C and the read/write is in the picoseconds. Blue Sky? Not really, it is common sense to try to dope nickel oxide instead of breaking it with filaments," Professor Araujo wrote.
Professor Araujo added that the technology reads at 0.2 volts, writes at 0.6 and 1.2 volts, and has a read endurance above 10^13 cycles, which is far in excess of the numbers quoted for flash memory at the leading-edge and for most alternative ReRAM technologies.
The end of scaling for the mainstream non-volatile memory technology, flash memory, which is based on electron storage, has been predicted for many years. Flash memory has just started to be implemented in multiple layers at relaxed minimum geometries to try and circumvent this issue. (See Samsung Confirms 24 Layers in 3D NAND.)
ReRAM memory, often based on layered metal-oxide materials, including transition metals, has yet to enter high-volume production and phase-change memory (PCM) although commercially deployed is only made at a lower storage density and features sizes much larger than flash memory.
Symetrix, based in Colorado Springs, Colo., was formed in 1986 by Professor Araujo to work on ferroelectric materials for use in non-volatile memory. Symetrix advocated the use of strontium barium titanate (SBT) as an alternative perovskite to lead zirconate titanate (PZT) for use in non-volatile ferroelectric random access memories (FeRAMs). Symetrix, which operates an IP-licensing business model, has licensed its technology to a number of semiconductor companies.
"We do not follow the capital-raising path and we are 27 years old with a portfolio of over 200 patents. We sold many licenses, and the royalty stream is enough to continue innovation," Professor Araujo wrote, but added that the company might be open to equity investment to accelerate the development of CeRAM.
EE Times wrote to Professor Araujo with supplementary questions about the nickel-oxide memory technology, but he declined to provide further information for publication at this time.