UK researchers follow silicon-oxide ReRAM route

May 24, 2012 // By Peter Clarke
Researchers from University College London (UCL) have developed a silicon oxide based non-volatile resistive memory structure by following a promising line of research similar to that pursued by teams at Rice University and the University of Pennsylvania.

Resisitive RAM (ReRAM), sometimes called a memristor, is now being researched extensively as a potential replacement for flash memory which is not expected not to scale in plan much below 20-nm minimum dimensions. Some further memory capacity scaling may be achieved by stacking flash memory cells vertically but it is thought that resistive memory could displace flash memory if it can offer planar as well as z-directions scaling. Silicon oxide is now being researched as a potential alternative to metal-oxide types of ReRAM.

The UCL team has developed a silicon oxide memory, described in a recent paper in the Journal of Applied Physics, which they claim performs the switch in resistance much more efficiently than has been previously achieved.

The paper, entitled Resistive switching in silicon suboxide films, reports that the UCL team have worked with silcon-rich silicon dioxide. This differs from the work of Professor I-Wei Chen at the University of Pennsylvania who has reported the use of inclusions of atomically dispersed platinum in silicon oxide material. The UCL work appears to be closer to that of a team under James Tour at Rice University (see Making memory out of silicon oxide).

"The resistive switching phenomenon is an intrinsic property of the silicon-rich oxide layer and does not depend on the diffusion of metallic ions to form conductive paths. In contrast to other work in the literature, switching occurs in ambient conditions, and is not limited to the surface of the active material," the researchers state in the abstract to their paper.

They go on to propose a switch that is operated by field-driven formation and current-driven destruction of filamentary conductive pathways and report on/off resistence ratios of 10^4:1 and higher. The conductive pathways are 10-nanometers in diameter or smaller and programming currents can be as low as 2-microamps, with transition times on the order of nanoseconds.

"Our ReRAM memory chips need just a thousandth of the energy and